The Chinese Journal of Process Engineering

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Preparation and electrochemical performance investigation of molybdenum dioxide nanorods

Zengli GAO Shouzhi YI Haiyan TANG Hongbin XU

The Chinese Journal of Process Engineering 2021, 21 (11): 1338-1345. DOI: 10.12034/j.issn.1009-606X.220355

Abstract （464）

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With high conductivity, high melting point and large specific capacity, molybdenum dioxide (MoO2) nanorods have a wide application prospect in the field of electrode materials for supercapacitors. Although there are many methods to prepare MoO2 nanorods, most of them have disadvantages of a complicated process, low yield, high production cost and easy to introduce impurities. Moreover, the prepared MoO2 products have the characteristics of non-uniform morphology, poor dispersibility and inferior electrochemical performances. In this work, the precursor of peroxymolybdic acid prepared by hydrogen peroxide and molybdenum powder was used as the source of molybdenum, and PEG (8000) was used as the template. The molybdenum-containing hybrid with a band structure was prepared by mixing the precursor and template with stirring and thermal insulation. The nano-rod-shaped MoO2 was prepared through a two-stage hydrometallurgical process using the hybrid compound as raw material. X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), X-ray energy spectrometer (EDS) and scanning electron microscope (SEM) were used to analyze the phase, surface composition and morphology of the obtained MoO2 nanorods. The electrochemical capacitance behavior of MoO2 nanorods was studied using a three-electrode system and two-electrode system, and the performance of MoO2 nanorods as electrode assembly capacitors was also investigated. The results showed that the prepared MoO2 had a rod-like structure with 500 to 800 nm in length and with 100 to 200 nm in width. The MoO2 had uniform morphology and size with good dispersion and high purity. The specific capacitance of MoO2 nanorods was 366.7 F/g for the three-electrode system at the current density of 1 A/g, and the specific capacitance for the two-electrode system was 290.4 F/g, and the capacitance retention rate was higher than 72% after 2000 cycles of charging and discharging at 5 A/g current density, both showing the good electrochemical performance of MoO2 nanorods. The research results of this study can provide a new method for the preparation of other nano metal oxides.

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Preparation and characterization of temperature/pH dual response nitrifying bacteria gel spheres

Qiong WAN Yingchun REN Zhixiao ZHAO Xinyan ZHANG Wenjing WANG Jingyu HAO Xuan LI Kai JÜ

The Chinese Journal of Process Engineering 2021, 21 (11): 1346-1354. DOI: 10.12034/j.issn.1009-606X.220385

Abstract （262）

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Calcium alginate (CA) nitrifying bacterial gel spheres with uniform particle size were drop-produced by the embedding method, and the effect of different concentrations of NaCl on the diffusion and mass transfer properties and mechanical strength of CA nitrifying bacterial gel spheres was investigated using the controlled variable method. The temperature-sensitive material N-isopropylacrylamide (NIPAAm) and the pH-sensitive material acrylic acid (AA) were combined onto the surface of NaCl-modified CA nitrifying bacteria gel spheres by stepwise polymerisation to form a temperature/pH-responsive layer on the surface of the spheres. A new type of temperature/pH dual response nitrifying bacterial gel spheres was prepared. NH4+?N was used as an indicator to investigate the ammonia nitrogen removal performance of nitrobacterial gel spheres and their sensitivity to temperature and pH under different preparation conditions, and the prepared temperature/pH dual response nitrifying bacterial gel spheres were applied to the actual nitrogen removal treatment of wastewater. The results showed that the CA nitrifying bacterial gel spheres modified with a concentration of 0.3% NaCl solution had the best diffusive mass transfer performance. The best ammonia removal performance of temperature/pH dual response nitrifying bacterial gel spheres was achieved at 200 mg of NIPAAm and 4 mg of MBA in 15 mL of temperature?response solution and at 200 mg of AA and 4 mg of MBA in 10 mL of pH?response solution. When the temperature was as low as 4℃, the ammonia nitrogen removal rate could reach 29.45%, when the pH was 9, the ammonia nitrogen removal rate could still reach 35.48%. Temperature/pH dual response nitrifying bacterial gel spheres have good temperature and pH sensitivity, and also have good effect on the removal of ammonia nitrogen in the actual wastewater, which is conducive to improve the nitrification effect of nitrifying bacteria under low temperature and alkaline conditions.

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Processing and characterization of Fe-(9~11)Cr-Y ₂ O ₃ as ITER structural material

Zhenzhen WANG Yi′na HUANG Yucheng WU Laima LUO

The Chinese Journal of Process Engineering 2021, 21 (10): 1207-1215. DOI: 10.12034/j.issn.1009-606X.220271

Abstract （312）

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Oxide dispersion strengthened (ODS) steel has excellent radiation properties and is considered a candidate for the first wall structure of fusion reactors. Adding Y element to the material can improve thermal stability, and Cr element can improve corrosion resistance, because the high oxide density inside will cause needle-like dislocations, the material has higher strength and lower toughness to brittle transition temperature. The nano-precipitation phase can trap helium and make it in the form of nano-scale helium bubbles, avoiding the production of large helium bubbles to reduce possibility of expansion. Reducing helium embrittlement can make the material have a longer service life in the fusion reactor. In this work, based on mechanical alloying (MA) and spark plasma sintering (SPS), binary alloys with Fe(9~11)Cr content and ODS alloys were prepared successfully. The morphology and phase analysis of MA powders were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), micro Vickers-hardness tester and energy dispersive spectrum (EDS), and the precipitation phase of the alloy sample was observed by transmission electron microscope (TEM). The results showed that the fine grain size enabled the material to have good tensile and creep properties at high temperatures. The MA powder was continuously refined after being crushed and deformed under a rotational speed of 300 r/min and the ball-to-powder mass ratio was 10:1. The MA powder reached the cold welding-crushing balance at 40 h. The powder grain size decreased to about 16.1 nm and tended to be stable with the increase of ball grinding time. After spark plasma sintering and solidification of the MA powder for 40 h, the grain size did not increase significantly, and the trace elements were uniformly distributed in the matrix. The Vickers-hardness of binary alloy samples increased with the addition of Cr content. The grain boundaries of ODS alloy samples proved to be fine and uniform after being eroded by corrosive liquid.

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Effect of pressurized carbonization system on the particle size and dispersion of nano calcium carbonate

Xixi LIU Xiaopeng CHEN Chenmin LIU Liubin SHI Dankui LIAO Cui LIU Zhangfa TONG

The Chinese Journal of Process Engineering 2021, 21 (10): 1216-1224. DOI: 10.12034/j.issn.1009-606X.220278

Abstract （343）

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Nano calcium carbonate with uniform particle size and high dispersion was prepared by pressurized carbonization system. The effects of calcium hydroxide concentration, surfactant addition amount, reaction temperature and CO2 pressure on the size and dispersion degree of prepared nano CaCO3 particles were investigated. X-ray diffraction (XRD), scanning electron microscope (SEM), Zeta potential and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the prepared nano CaCO3 particles. The results showed that the optimum conditions for pressure carbonization are Ca(OH)2 mass concentration of 2%, surfactant dosage of 3% (percentage of theoretical production of calcium carbonate), reaction temperature of 40℃ and CO2 pressure of 6 MPa, the average particle size of the cubed calcium carbonate was 117 nm, and the crystal type was calcite calcium carbonate. The addition of surfactant cetyl trimethyl ammonium bromide (CTAB) to the carbonization reaction increased the positive charge formed on the surface of CaCO3 to +37.7 mV and higher than the standard value of 30 mV, indicating that the prepared CaCO3 product has good dispersibility and stability. FT-IR and Zeta potential were used to characterize CaCO3 nanoparticles before and after the modification of CTAB, and the influence mechanism of CTAB on the dispersion of synthetic CaCO3 nanoparticles was discussed, providing a new method for the preparation of nano CaCO3 .

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Preparation of UiO-66 based catalyst and its performance for CO methanation

Yong YANG Yong XU Guangjin ZHANG

The Chinese Journal of Process Engineering 2021, 21 (9): 1074-1081. DOI: 10.12034/j.issn.1009-606X.220314

Abstract （431）

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Converting coal-based gas to natural gas has great economic and environmental benefits. As coal gasification technology matures, the CO methanation process acts as an important role. MOFs materials have shown excellent performance in many fields and have attracted more and more attention. Compared with conventional catalysts, UiO-66 is a Zr-based MOFs material with high specific surface area and good thermal and chemical stability, the active metal Ni has low cost and is equivalent to the catalytic hydrogenation ability of precious metals. In present study, a series of UiO-66 catalysts with Ni loading were prepared via ultrasonic impregnation method. Plenty of characterizations including XRD, BET, TG, SEM, TEM and XPS were used to study the structure, textual properties, thermal stability and morphology of the UiO-66 supported Ni-based catalysts. The catalytic performance of different catalysts was also evaluated in the fixed-bed reactor. The results showed that the Ni was reduced to metallic state in the prepared catalyst, the Ni metal was highly dispersed on the UiO-66 support and exhibited no significant effect on the framework structure and crystal morphology of the MOF material. The structure of the carrier did not change below 400℃. In the CO methanation reaction, the activation temperature of the Ni/UiO-66 catalysts gradually decreased with the increase of Ni loading content. At the same reaction temperature (320℃), the Ni content on different catalysts increased from 10% to 30%, the CO conversion increased from 10.7% to 89.7%.When the Ni content was 20%, the catalyst showed good stability during the reaction process. Meanwhile, the CO conversion on the Ni-based catalyst was much higher than that of the Fe-based and Co-based catalysts with the same metal content, indicating that Ni as an active metal had excellent catalytic performance in the synthesis gas to methane reaction process.

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Preparation of styrene acrylic resin composite with high thermal conductivity

Fuhua JIA Bin GONG Qianyu WANG Duoyin ZHU Yanbin CUI

The Chinese Journal of Process Engineering 2021, 21 (9): 1082-1090. DOI: 10.12034/j.issn.1009-606X.220263

Abstract （452）

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Styrene acrylic resin is the main component of toner. The thermal conductivity of toner could be improved significantly by increasing the thermal conductivity of styrene acrylic resin. Then, the life of printer and copier could be extended. By adding single or hybrid high thermal conductivity fillers of carbon nanotubes and graphene into styrene acrylic resin, a connected thermal conductivity network was constructed in styrene acrylic resin to improve the thermal conductivity. When 0.75wt% multi-walled carbon nanotubes (MWCNTs) were added into styrene acrylic resin, the thermal conductivity of styrene acrylic resin composite was increased from 0.1252 W/(m?K) to 0.1644 W/(m?K) with an increasing of 31.31%. When 1.0wt% MWCNTs-COOH was added into styrene acrylic resin, the thermal conductivity of styrene acrylic resin composites was increased to 0.1751 W/(m?K) with an increasing of 39.86%. When MWCNTs-COOH and graphene were added into styrene acrylic resin, the thermal conductivity of styrene acrylic resin composites was increased to 0.2093 W/(m?K) with increasing of 67.17%, which indicated the hybrid fillers (MWCNTs-COOH and graphene) formed connected thermal conductivity network in styrene acrylic resin. Thus, the thermal conductivity of styrene acrylic resin composite was improved significantly.

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Preparation of MgMn ₂O ₄ cathode material for aqueous magnesium ion batteries

Wanquan LI Doudou ZHANG Shuqing DENG Mengting YUAN Yunlan CHANG Bing QIAN Yaxin SUN

The Chinese Journal of Process Engineering 2021, 21 (9): 1091-1098. DOI: 10.12034/j.issn.1009-606X.220218

Abstract （495）

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Rechargeable magnesium ion batteries (MIB) as next-generation secondary battery systems have attracted increasing attention due to the high theoretical volumetric capacities, low cost and safety of Mg metal anodes. One of the key challenges in MIB is to develop cathode materials with higher specific capacity. Tetragonal spinel structure MgMn2O4 can be as MIB cathode material in aqueous electrolyte environments. However,the strong polarization and low kinetics diffusion of Mg2+ ion results a sluggish Mg migration in MgMn2O4. Herein, nanostructured MgMn2O4 samples were prepared via a simple sol-gel route followed by annealing using magnesium nitrate, manganese nitrate and critic acid as raw materials. The crystal structures and the morphologies of the products were analyzed by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Electrochemical measurements of the products were carried out in a three-electrode breaker cell. The results showed that the samples annealed at 550℃ (MMO550) exhibited the maximum discharge specific capacity of 54.0 mAh/g at a current density of 40 mA/g, which was almost twice that of 750℃ samples (MMO750). The average grain size of MMO550 was about 30 nm analyzed by XRD and TEM, respectively. The MMO550 samples comprise microaggregated with channels and pores on the surface observed by FESEM, which were favorable for the effective contact between the electrolyte and particles. Further, nanocomposites of MgMn2O4 and carbon nanotube (MMO/CNT) obtained by annealing MMO550 with adding 5wt% CNT at a temperature of 400℃ for 2 h, exhibited the first discharge specific capacity of 118.0 mAh/g and capacity retention of 75% after 30 cycles. The Coulombic efficiency of MMO/CNT was very stable and above 95%. This outcome could be attributed to the improvement of conductivity provided by CNTs. FESEM and TEM results confirmed that CNTs can be acted as conductive grid connecting the MgMn2O4 particles effectively.

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Properties and application of coal-based high purity graphite in polysilicon preparation

Qili WANG Fengtao ZHANG Xiaofeng GAO Jianwen HU

Chin. J. Process Eng. 2021, 21 (3): 323-331. DOI: 10.12034/j.issn.1009-606X.220030

Abstract （445）

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High-purity graphite was prepared from coal coke particles and high-temperature coal pitch, and its micro-structure characteristics and physical properties were measured and analyzed. High-purity graphite was used in the reduction furnace of the polysilicon preparation, which played the role of clamping the silicon rods, conducting electricity and transferring heat. Measures to improve production reliability and reuse rate of the graphite assembly in the reduction furnace were discussed. The results showed that the structure of the high-purity graphite samples was relatively smooth in general, and exhibited good similarity overall structure at different scales. The prepared high-purity graphite materials had outstanding physical properties: the bulk density of 1.84~1.88 g/cm3, the shore hardness of 55.2~62.4 Hs, the flexural strength of 33.9~45.6 MPa, the compressive strength of 66.3~78.8 MPa, the thermal expansion coefficient of 3.76×10–6/℃~4.08×10–6/℃, the electrical resistivity of 8.92~11.98 μΩ?m, and the ash content of 133~202 mg/kg, respectively. All the parameters of the samples were excellent. From the analysis of elemental composition, carbon element is the absolute main body, its weight content was between 88.71wt%~90.57wt%, and its atomic content was between 92.09at%~93.25at%. In addition to the matrix carbon, other elements are mainly O, S, Si, and Al. The weight content of O was between 7.15wt% and 9.79wt%, and the atom content was between 5.61at% and 7.57at%. Except for C and O, the content of other elements was lower, and the atomic content was lower than 1at%. In addition, the phenomenon of “bright spot” and “collapse of the silicon rod” in reduction furnace applications due to heterogeneous conductivity and heat concentration in the silicon cores was analyzed. By optimizing the structure of the graphite assembly, the reuse rate of the graphite cap was increased from 5.85% to 7.28%, the reuse rate of the graphite seat was increased from 7.95% to 9.01%, and the collapse rate of silicon rods was reduced from 14.22% to 4.43%. Consequently, the safe production in the reduction furnace was more effectively improved, the reject rate and the production cost of silicon rods were reduced, which demonstrated good application prospects of the coal-based high purity graphite in the field of the preparation of polysilicon.

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Fabrication and characterization of form-stable solar salt/steel slag composite phase change material for thermal energy storage

Yan WANG Yun HUANG Hua YAO Xianggui XU Qiao HUANG Junlei WANG Pusheng MA Junsheng WANG

Chin. J. Process Eng. 2021, 21 (3): 332-340. DOI: 10.12034/j.issn.1009-606X.220096

Abstract （490）

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Renewable energy has been actively developed due to the global energy shortage and environmental pollution. The technology of thermal energy storage (TES) is the key to deal with the instability of new energy. Because of its advantages of high heat storage density and wide operating temperature range, molten salts have attracted extensive attention in the medium and high temperature ranges. A form-stable solar salt/steel slag composite phase change material (PCM) was developed in this work for solving the problems of leakage, poor heat transfer performance and high cost of molten salts. The optimum mass ratio of steel slag and molten salt (solar salt) was obtained as 5:5. The microstructure, thermal property and chemical compatibility of the composites were characterized subsequently by scanning electron microscope (SEM), thermogravimetric–differential scanning calorimeter (TG–DSC), laser flash analysis (LFA) and X-ray diffraction (XRD), respectively. The results showed that there was no leakage as the composite material keeps good shape and compact microstructure. The composite material showed good chemical compatibility between molten salt and steel slag. The latent heat was 64.0 kJ/kg, the thermal energy storage density was 945 kJ/kg (100~500℃) and the thermal conductivity was up to 2.23 W/(m?K). Thus, the developed solar salt/steel slag composite PCM is not only of interest to the large-scale application of thermal energy storage, but also provide an excellent option for waste recycling in steel industry.

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DEM modeling of mechanical behavior of partially sintered ceramics

Zengxu ZHANG Yongchang WANG Yin YU Xiaoxing LIU

Chin. J. Process Eng. 2021, 21 (3): 341-352. DOI: 10.12034/j.issn.1009-606X.220116

Abstract （353）

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In this work, the mechanical behavior of partially sintered ceramics under both tensile and compressive loadings was investigated by performing 3D discrete element method (DEM) simulations. The simulation results indicated that the failure of samples under tensile loading was dictated by the nucleation of crack, whereas for compressive loading it was linked to the coalescence of cracks. By monitoring the time sequence of bond breakage and its failure mode, it was found that for tensile loading the dominate failure mode of bond was tensile fracture, whereas for compressive loading it was shear fracture. The fracture strength of sample was closely related to the critical tensile (?c,t) and shear (?c,s) fracture strengths of bond. As to the partially sintered alumina ceramics considered in this work, it was found that the predicted tensile and compressive fracture strengths can both be in quantitative agreement with experimental data. The simulation results indicated that the influence of the distribution of bond strength on the compressive fracture strength of sample was minor. While for tensile fracture strength, it depended on the type of distribution: for Gaussian distribution, the strength of sample only weakly depends on the distribution width, whereas for uniform distribution, the strength of sample decreases notably with the increase of distribution width.

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Preparation and physicochemical properties of cyclopropyl methyl ketazine

Wenzhao ZHAO Peng ZHAO Long LIU Yangfeng XIA, Yanqiang ZHANG

Chin. J. Process Eng. 2021, 21 (2): 183-192. DOI: 10.12034/j.issn.1009-606X.220091

Abstract （517）

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Ketazines as useful intermediates have been extensively applied in many industrial fields, including dyes, pharmaceuticals, aviation fuels, photosensitive materials, as well as polymerizable monomers. In this work, a new ketazine derivative (cyclopropyl methyl ketazine, C10N2H16) was prepared from cyclopropyl methyl ketone and hydrazine hydrate. Under the atmospheric pressure, the reaction was studied under different mole ratios of cyclopropyl methyl ketone to hydrazine, reaction temperatures, and reaction times. With the optimized reaction conditions of 2.0:1, 363.2 K, 101.3 kPa and 7 h, the yield of cyclopropyl methyl ketazine was up to 93.6% through the chromatograph measurements. The structure of cyclopropyl methyl ketazine was characterized by IR and NMR spectra after it was purified through distillation. In order to prove the existence of isomers, Gaussian 09 program to optimize the structures was used and the energy values (single point energy) of cyclopropyl methyl ketazine was calculated. Furthermore, a comprehensive set of the physicochemical parameters for cyclopropyl methyl ketazine was provided, including density [ρ=0.884~0.947 g/cm3], dynamic viscosity (η=1.39~2.88 mPa?s), liquid heat capacity [Cp=2.03~2.32 J/(g?K)] and surface tension (σ=22.1~25.0 mN/m) in temperature range (280?400 K). The data of ρ, η and σ exhibited the negative correlations with temperature, while Vm, α and Cp showed the positive correlations with temperature, which all had a good fitting degree for equations. Considering the cyclopropyl methyl ketazine reaction systems, the vapor?liquid equilibria (VLE) of binary system (cyclopropyl methyl ketone?cyclopropyl methyl ketazine) was measured and correlated with NRTL model to acquire the binary interaction parameters. The obtained data and correlations are valuable for industrial processes, and could be the good references for industrial design.

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Catalytic wet peroxide oxidation of methyl orange in a fixed bed with Fe ⁰-NaA-SSFSF

Jian LIU Yini HUANG Xi CHEN Zhengji YI

Chin. J. Process Eng. 2021, 21 (2): 193-201. DOI: 10.12034/j.issn.1009-606X.220066

Abstract （337）

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Stainless steel fiber sintered felt supported Fe0-NaA molecular sieve membrane (Fe0-NaA-SSFSF) was prepared by the secondary growth and liquid-phase reduction method. The catalytic wet peroxide oxidation performance of methyl orange in a fixed bed with Fe0-NaA-SSFSF was studied. The effects of pH, bed height, temperature and inlet concentration on the conversion rate of methyl orange, COD removal rate and iron leaching concentration were investigated. The stability of Fe0-NaA-SSFSF catalyst was determined. The results showed that when the pH of the solution was 2.5, the conversion of methyl orange fluctuated in the experimental time range. With the decrease of pH to 2.0, the conversion of methyl orange tended to be stable. When the pH continued to decrease to 1.5, the conversion of methyl orange remained basically unchanged. With the increase of bed height from 0.45 cm to 0.90 cm, the conversion rate of methyl orange remained almost the same and the COD removal rate increased from 21.2% to 85.0%. With the decrease of reaction temperature from 70℃ to 50℃, the conversion rate of methyl orange remained almost unchanged and the COD removal rate decreased from 85.0% to 42.4%. Both the conversion rate of methyl orange and COD removal rate had no obvious change with the increase of inlet methyl orange concentration. Under the conditions of pH=2.0, bed height of 0.90 cm, reaction temperature of 70℃, methyl orange concentration of 50~200 mg/L, the conversion rate of methyl orange was greater than 97% in the experimental time range, the maximum iron leaching concentration was lower than 10.2 mg/L, and the COD removal rate was above 85% when the fixed bed was running continuously for 240 min. When the Fe0-NaA-SSFSF catalyst was reused three times, the conversion rate of methyl orange kept basically the same.

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Preparation and characterization of graphene oxide modified n-dodecanol phase change microcapsules

Jinli LU Li WU Yafang HAN Yang LI

Chin. J. Process Eng. 2021, 21 (2): 202-209. DOI: 10.12034/j.issn.1009-606X.220022

Abstract （354）

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With the characteristics of high energy storage density, constant temperature in phase change process and convenient storage/transportation, the microencapsulated phase change material (MPCM) has a broad application prospect in the fields of thermal storage, transportation and utilization such as solar energy thermal utilization, waste heat recovery and utilization, refrigeration and air conditioning, and so on. However, the traditional MPCM particles use formaldehyde as the shell material, which releases harmful substances during application process. In addition, the MPCM application fields is restricted because of low thermal conductivity of polymer shell. Therefore, it is necessary to develop a new type of formaldehyde-free MPCM. In this work, the MPCM particles of n-dodecanol as core material and acrylic resin copolymers as shell were prepared employing the method of suspension polymerization under the condition of ultrasound exposure. Furthermore, in order to enhance the thermal performance of MPCM particles, the graphene oxide (GO) was introduced to modify the MPCM. Then the characteristics of MPCM and GO-MPCM were tested by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR), differential scanning calorimetry (DSC), thermal gravimetric analyzer (TG–DTA). The results showed that there was no effect on basic chemical organization of MPCM with introduce the graphene oxide nano-particles. However, under the same preparation conditions, the introduction of graphene oxide nano-particles increased the MPCM particles size and greatly affected their appearance and morphology. The thermal conductivity of MPCM particles was improved. The encapsulation rate increased to 62%, and the latent heat of phase change was 135.6 kJ/kg, which was 45% higher than that of unmodified phase change microcapsules. The study results in this work can provide data support for the preparation and performance improvement of MPCM particles, and also provide theoretical basis for its engineering application.

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Giant dielectric properties and mechanism of Ca and Ta co-doped TiO ₂ ceramics

Bing CUI Ji CHEN Zaizhi YANG Weiyu ZHAO Yujun DENG Qian YU Juan LIU Dong XU

Chin. J. Process Eng. 2021, 21 (2): 210-218. DOI: 10.12034/j.issn.1009-606X.220023

Abstract （372）

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With the rapid development of the society, ceramic materials are being studied more and more. Recently, most of the studies on co-doping TiO2 ceramics are about trivalent acceptor and pentavalent elements which exhibit good dielectric properties, while the studies on divalent elements are relatively few. However, the mechanism, preparation process and the effects of different doped ion combinations on the dielectric properties are still unclear. Further research on the microstructure, dielectric properties and mechanism of co-doped TiO2 ceramics is of great significance. In this work, (Ca, Ta) co-doped TiO2 ceramics were prepared by a solid state reaction process. The effects of different components on their morphology, crystal structure and dielectric properties were studied. The sample with high viscosity needs to be sintered at 1400℃ for a minimum of about 4 h. When (Ca1/3Ta2/3)xTi1?xO2 ceramic with x≥7%, the second phase appeared in the (Ca1/3Ta2/3)xTi1?xO2 ceramic sample. Compared with pure TiO2, (Ca1/3Ta2/3)xTi1?xO2 ceramics all had giant dielectric constant, which roughly increased by two orders of magnitude. With the continuous increase of doping, the dielectric constant increased first and then decreased, while the dielectric loss was completely opposite. (Ca1/3Ta2/3)xTi1?xO2 ceramic with x=3% showed better dielectric and pressure-sensitive properties of ceramics. Ta doping led to the generation of electrons in the material, but Ca doping can produce vacancy and the defective dipole cluster can improve the dielectric performance.

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Preparation and performance of the 1,2,3-triazolium-based membranes with high ionic conductivity and CO ₂ permeability

Chao FU Xiuyun WANG Liqiang WAN Xinyue HAN Linxiao WANG Jianwei FANG Farong HUANG

Chin. J. Process Eng. 2021, 21 (1): 100-107. DOI: 10.12034/j.issn.1009-606X.220054

Abstract （395）

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The 1,2,3-triazole ring can be transformed into a 1,2,3-triazolium through the alkylation or protonation reaction. The research on the application of this novel poly(ionic liquid)s has only been valued recently even though 1,2,3-triazolium have been found long ago. 1,2,3-triazolium can be used in various fields. Compared with the linear triazolium cross-linked triazolium have rarely been reported. The special cross-linked structure makes the mechanical properties of cross-linked triazolium, better than linear triazolium. A series of novel cross-linked 1,2,3-triazolium-based membranes were prepared via 1,3-dipolar cycloaddition reaction between azides and alkynes along with N-alkylation and anion substitution reaction. Firstly, an alkynyl-terminated polytetramethylene ether glycol (DPPTMEG) was synthesized, and reacting with biphenyl dibenzyl azide (DAMDB) and bisphenol A dipropargyl ether (BADPE) along with alkylation and anion substitution reaction, the new kind of membranes were prepared. The structure of the cross-linked polytriazolium membranes were characterized by nuclear magnetic resonance (NMR). The thermal properties and mechanical properties of the cross-linked polytriazolium membranes were studied by dynamic mechanical thermal analysis (DMA), thermogravimetric analysis (TGA), and electronic universal testing machine. While the ionic conductivity and CO2/N2 permeability of the cross-linked polytriazolium membranes were measured by broadband dielectric spectroscopy (BDS) and isochoric gas permeation system. The results showed that the membranes had excellent ionic conductivity, the direct current conductivity at 30℃ up to 2.94×105 S/cm and CO2 permeability of up to 550.4 barrer. The Td10 of the 1,2,3-triazolium-based membranes with different formulations did not change significantly while the glass transition temperature (Tg) increased with the increase of the proportion of bisphenol A dipropargyl ether. The membranes showed great mechanical properties, the tensile strength would reach to 1.70 MPa and the elongation at break up to 136.8%.

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Influence of spraying power on mechanical and resistance to aluminum–silicon melt corrosion properties of YSZ coating

Wen HUANG Zhaolu XUE Xia LIU Zhenhang NI Chaojun WU Shihong ZHANG

Chin. J. Process Eng. 2020, 20 (12): 1463-1471. DOI: 10.12034/j.issn.1009-606X.220005

Abstract （406）

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Hot-dip Al–Si alloy coating is an effective corrosion resistant coating for modern steel. However, the molten Al–Si alloy corrosion has become one of the problems to be urgently solved for sink rollers and their spare parts in the hot-dip Al–Si alloy production line. In this work, yttria partially stabilized zirconia (YSZ)/NiCrAlY protective coating was fabricated by air plasma spraying. The influence of spraying power on the microstructure and mechanical properties of the YSZ coating, and its corrosion behavior in Al–Si melt at 700℃ was also investigated. The results showed that YSZ coating presented a typical layered structure with lath-shaped and interlayer columnar grains. The interlayer columnar grains tended to grow up with the increase of spraying power from 37 kW to 46 kW. YSZ coating was mainly composed of t-ZrO2 phase and small amount of m-ZrO2 phase, and spraying power had no obvious influence on the phase compositions. The YSZ coating with 40 kW spraying power had relatively high microhardness and adherence strength values (642.4 HV0.3 and 62 MPa). Additionally, no reaction layer was formed at the interface between YSZ coating and Al–Si melt at 700℃ for 240 h, and the Si and Al elements in the molten Al–Si alloy also did not infiltrate into the YSZ coating, suggesting that YSZ/NiCrAlY protective coating could effectively prevent Al–Si alloy melt on the surface of coating.

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Preparation of nano Co/rGO magnetic materials and the adsorption properties to Cu ²⁺ ions

Jingjing ZHANG Jian LI Qinggui XIAO Hui ZHANG Xuan DU Tianyan XUE Tao QI

Chin. J. Process Eng. 2020, 20 (12): 1472-1482. DOI: 10.12034/j.issn.1009-606X.220006

Abstract （395）

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Flaky graphene oxide (GO) prepared by the improved Hummer method was used as a carrier and template to load cobalt ions. Then, nano-metal Co/graphene magnetic composite adsorption material (Co/rGO) was prepared using in situ reduction method and was applied to adsorb and remove Cu2+ to provide the guidance for the synthesis and application of remover with efficient and reusable copper ion. The experimental results showed that Co/rGO composite materials had super paramagnetism, and could be easily separated by magnets as well as be oscillating dispersed without magnetic field. Co/rGO composite materials had stable adsorption and desorption properties for Cu2+. The maximum adsorption capacity for Cu2+ could reach 117.5 mg/g under experimental conditions and the adsorption balance could be achieved within 5 min, which was far superior to its raw material GO with the adsorption capacity of 27.6 mg/g in 60 min. In this work, the key factors including the amount of NaOH addition, the type of complexant, and the type of solvent on the morphology and distribution characteristics of Co particles on rGO carrier were systematically investigated. The adsorption effects for Cu2+ of composite materials under different synthesis conditions were compared. The properties of Co/rGO composite materials prepared in preferred conditions were characterized by FT-IR, XRD and SEM. The results showed that the adsorption process of Cu2+ by nano-Co/rGO magnetic materials was more consistent with Freundlich model and belonged to multilayer adsorption. The adsorption enthalpy ΔH was 17.81 kJ/mol, and the equilibrium constant of adsorption reaction Kθ was 3.65 at room temperature. When the initial concentration of Cu2+ was 39.22 mg/L, the desorption rate exceeded 93%, and initial value of adsorption capacity remained at 94% after five adsorption/desorption cycles. The residual concentration of Cu2+ in the solution after each adsorption always met the requirements of cobalt electrolyte for the removal of impurity copper ions (5 mg/L) or GB 8978-1996 level 3 (2 mg/L) of comprehensive sewage discharge, which was expected to play a role in related fields.

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Evolution process of FeSi ₅Cr _5.5/SiO ₂ core-shell structure during fluidized bed chemical vapor deposition

Zhaoyang WU Chen XIAN Jixiang JIA Xi'an FAN Xiangwei LIAO Mingya ZHANG

Chin. J. Process Eng. 2020, 20 (11): 1321-1328. DOI: 10.12034/j.issn.1009-606X.219371

Abstract （405）

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The formation time and evolution process of FeSi5Cr5.5/SiO2 core-shell structure during the fluidized bed chemical vapor deposition were studied with tetraethoxysilane as the precursor of SiO2 insulation and FeSi5Cr5.5 spherical particles as the substrate. The microscopic characteristics of particle samples before and after deposition were characterized by X-ray diffraction, field-emission scanning electron microscopy and X-ray photoelectron spectroscopy. The magnetic hysteresis loops and resistivity of particle samples before and after deposition were measured using vibrating sample magnetometer and four point probe instrument. The results showed that it took 30 minutes at a minimum to completely convert from FeSi5Cr5.5 particles to FeSi5Cr5.5/SiO2 core-shell structure particles according to the three-dimensional island nucleation model during the fluidized bed chemical vapor deposition. There were four and five categories of silicon and oxygen electron structure in the FeSi5Cr5.5/SiO2 core-shell structure. The resistivity of FeSi5Cr5.5/SiO2 core-shell structure particles increased three and four orders of magnitude than that of FeSi5Cr5.5 particles, while the values of saturation flux density declined slightly.

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Simulation analysis of flow field and thermally induced damage mechanism in ceramic membrane filter

Kaikai SI Yunfa CHEN Qingzhu LIU Rui XIONG Guangchao SUN Kaiqi LIU

Chin. J. Process Eng. 2020, 20 (11): 1329-1335. DOI: 10.12034/j.issn.1009-606X.220010

Abstract （322）

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Thermal stability of ceramic membranes for high-temperature gas purification is the key to long-term stable operation of ceramic membrane filters. Based on the standard k?? turbulence model and porous media model, the gas flow in the ceramic membrane filter was numerically simulated. The distribution characteristics of the gas velocity field, pressure field and temperature field in the device during the steady-state filtration phase were studied. The temperature field changes in the device before and after the non-steady-pulse cleaning were compared, and the mechanism of the ceramic filter material damage caused by thermal-mechanical coupling during pulse cleaning was studied by quantitative analyses. The results showed that the model established by the simulation can more realistically reflect the field distribution characteristics of the gas in the whole process of hot gas filtration and pulse cleaning. During the steady-state filtration stage of the hot gas, the gas velocity was higher at the inlet and outlet pipes compared to those in the dust-containing chamber and the clean air chamber. The gas velocity in the filter tube gradually increased along the axis of the tube, while the gas pressure gradually decreased. The filter temperature did not change with the change of position. During the non-steady-state pulse cleaning stage, the temperature field of the gas near the blowback inlet formed a low-temperature region, which was distributed in an almost elliptical shape in the axial section of the tube. It should be emphasized that the temperature at the inner wall of the tube first decreased and then rose along the axial direction. However, the temperature of the gas in the tube gradually increased and the temperature in dust-containing chamber was almost unchanged. At a distance of 0.0664 m from the top of the ceramic tube, the material was subjected to the greatest thermal stress of 2.8 MPa, which was the most vulnerable position during the pulse cleaning process.

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Study on the preparation and performance of Mn-doped ultra-low density proppants

Junmei FAN Dan LIU Xianguang WANG Bingzhong SHI Fangli YUAN

Chin. J. Process Eng. 2020, 20 (11): 1336-1343. DOI: 10.12034/j.issn.1009-606X.220180

Abstract （333）

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Under the condition of ensuring the high strength of the proppant, reducing the apparent density of the proppant as much as possible is the key to the development of shale gas clean water fracturing technology. In this work, low-grade bauxite and micro-SiO2 were used as the main raw materials, and water glass, nano-SiO2 and manganese oxide were used as auxiliary materials. The ultra-low density proppants were prepared by plasma dynamic sintering and later high-temperature sintering methods. The effects of different manganese oxide doping and different sintering time on phase composition, bulk density, apparent density and crushing rate at 69 MPa of proppants were discussed. And based on the classic PKN fracturing model, the settlement and migration of ultra-low density proppant in simulated fractures were studied. The results showed that an ultra-light proppant with an apparent density of 1.639 g/cm3 and a breakage ratio of 8.91% under 69 MPa was successfully prepared. The optimal manganese oxide doping content was 7.5wt%, and the optimal sintering temperature and sintering time were 950℃ and 2 h. Ultra-low density proppant migrated a longer distance in the horizontal direction than conventional proppants, and the distribution of proppant inside the fracture was relatively more uniform, which can meet the requirements of clean water fracturing for medium and deep oil wells.

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Preparation of ceramic ultrafiltration membrane with high performance from dense ultrafine spherical Al2O3 powders

Pan LUO Yuge OUYANG Fei DING Junmei FAN Fangli YUAN

Chin. J. Process Eng. 2020, 20 (10): 1218-1226. DOI: 10.12034/j.issn.1009-606X.219378

Abstract （512）

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Ceramic membranes with the advantages of excellent thermal, chemical and higher permeable properties have attracted more attention and have been applied in turbidity removal, sanitary wastewater and other important industries. However, the ceramic membrane required “coating-drying-sintering” process, in which the process inevitably leads to cracks and wide pore size distribution. In this study, ceramic ultrafiltration membranes with narrow pore size distribution and high permeability were prepared by the dip?coating method using ultrafine spherical alumina powders with high density and smooth surface synthesized by thermal plasma. The microstructure evolution of prepared membranes could be controlled by adjusting the sintering temperature, and the ceramic membranes with a narrow pore size distribution of 25?65 nm and a high pure water permeability of 986.4 L/(m2?h) were sintered at 1250℃. The sintering mechanism of the ceramic membrane was fully investigated and it was found that the narrow pore size distribution of membranes came from the spherical Al2O3 powders with the narrow particle size distribution and high density synthesized by thermal plasma, and the homogeneous sintering necks formed at 1250℃. The result indicated that the pure water flux of the membranes decreased as the sintering temperature increased. It can be explained that the surface of ceramic membranes became denser with the increase of the sintering temperature, resulting in the decrease in porosity and the average pore size. In addition, the prepared membranes were employed to filter the nano-silicon dispersion slurry to evaluate the performance of the membranes sintered under different temperatures. The result indicated that the membrane sintered at 1250℃ showed a higher removal rate of turbidity (99.96%), and the turbidity of the permeate was 0.231 NTU. Finally, the reduction of the permeate flux of the nano-silicon dispersion slurry were analyzed using pore blocking models, and it was found that the cake filtration model was suitable to the prepared membranes.

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Effect of nano-Nb addition on microstructure and wear resistance of Fe-based alloy coatings by plasma transferred arc welding

Lulu XU Wenxu ZHANG Longsheng ZHAN Mingxi LI

Chin. J. Process Eng. 2020, 20 (10): 1227-1233. DOI: 10.12034/j.issn.1009-606X.219359

Abstract （460）

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Plasma transferred arc welding is a kind of surface modification technology. Plasma transferred arc is used as a heat source and alloy powder is sprayed on the surface of metal materials to prepare a wear-resistant coating with excellent performance. In order to further improve the wear resistance of Fe-based alloy, hard particles are often used as the reinforcements of composite materials. At present, there are few researches on in-situ formed NbC reinforcements in Fe-based alloy coatings, and the density of NbC is very close to that of Fe-based alloy, which can be very evenly distributed in the coatings. In this work, Fe-based alloy coatings without nano-Nb and with mass fraction of 1wt%, 3wt% and 5wt% nano-Nb powder were prepared on Q235 surface by plasma transferred arc welding. The phase composition, microstructure, microanalysis and worn surface observation of the coatings were investigated by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. The microhardness and wear resistance of the coatings were tested using microhardness tester and pin-on-disc wear machine. The results showed that the main phases of Fe-based alloy coatings were composed of α-Fe, γ-Fe and Cr7C3. NbC phase was identified in the coating by adding nano-Nb powder, and Cr23C6 phase appeared with addition of 5wt% nano-Nb. The untransformed γ-Fe increased and the microstructure changed from approximately equiaxed microstructure to dendrite with addition of nano powder, and the greatly refined microstructure was obtained by adding 5wt% additive. The microhardness of coatings was improved, which was about 766 HV0.3 increased by about 250 HV0.3 with 1wt% and 3wt% nano-Nb. The wear resistance of coatings was also improved. The minimum friction coefficient of 0.48 was obtained by adding 3wt% nano-Nb. The wear mechanism changed from adhesive wear to abrasive wear.

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Preparation of ultrafine copper powder by high frequency hydrogen plasma enhanced reduction

Huacheng JIN Liuyang BAI Junmei FAN Guolin HOU Fei DING Fangli YUAN

Chin. J. Process Eng. 2020, 20 (8): 979-988. DOI: 10.12034/j.issn.1009-606X.219302

Abstract （381）

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Ultrafine copper powder is widely used in the fields of electronics, lubrication, catalysts, due to its large specific surface area, excellent thermal conductivity and high surface activity. The ultrafine copper powder?s application performance is determined by the control technology of spherical, uniform particle size, monodisperse and high purity. The ultrafine copper powder was prepared by high frequency hydrogen plasma enhanced reduction with characteristics of simple operation, high purity, controllable atmosphere and less environmental pollution. The free radicals produced by hydrogen plasma arc was helpful to control the morphology and the particle size of copper powder. The feeding rate, reducing hydrogen flow rate, hydrogen distribution position, reaction zone space, cooling temperature, and the optimal process conditions were determined, and more uniform and well dispersed ultrafine spherical particles were prepared with particle size mainly between 100 and 200 nm. The oxygen content was under 1%, bulk density was 0.502 g/cm3.

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Influence of surface hydrophobicity of epoxy resin coatings on microalgae adhesion property

Guoqiang DAI Jing TANG Wen LIU Shujun TAN Bin LIU Wenqing WANG Tianzhong LIU, Ge SU

Chin. J. Process Eng. 2020, 20 (7): 832-842. DOI: 10.12034/j.issn.1009-606X.220033

Abstract （498）

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Formation of bio?lm on solid surfaces is a common feature of microalgae, which is tightly associated with the properties of microalgae and substratum material. Increasing interests on microalgae biofilm attached cultivation or antifouling require to determine the effect of material surface physico-chemical characteristics on algal adhesion. However, reference researches are usually inconclusive and do not work well. This work is to evaluate the influence of hydrophobicity/hydrophilicity of substratum on microalgae adhesion. First, this work reported a novel method for surface hydrophobic modification of bisphenol-A Epoxy (EP) resin by adding hydrophilic diethanolamine (DEA) or hydrophobic polymethylhydrosiloxane (PMHS). The results showed that the water contact angles of the modified EP resin coatings were regulated in the range from 36.80? to 98.34?. With the increase of DEA, the water contact angle linearly declined. While, with the increase of PMHS, the water contact angle linearly increased. However, little difference between the two kinds of modified EP materials was observed through the characteristics of morphology, surface texture and roughness. Then, the static adhesion of microalgae C. vulgaris and S. dimorphus was investigated. The results showed that both C. vulgaris and S. dimorphus could adhere on all the coating surfaces with different wettabilities, but preferred to adhere more and faster on the hydrophilic ones. The linear relationships of two microalgae between their maximum adhering capacities and the water contact angles of the modified EP coatings were existed respectively. Hydrophobic surface had less adhered algal cells. The adhesion amount of S. dimorphus was larger than that of C. vulgaris.

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Research on vertical flame spread characteristics over flame retardant rigid polyurethane polymer

Xinjie HUANG Chunjie WANG Jinda GAO Cheng CHEN Gang TANG Changlong WANG

Chin. J. Process Eng. 2020, 20 (7): 843-851. DOI: 10.12034/j.issn.1009-606X.219257

Abstract （478）

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Based on the frequent occurrence of fire accidents on insulation materials rigid polyurethane (RPUF), which can cause great economic loss and casualties, RPUF was prepared by one-step water-blown method and hope to reduce the fire hazards in reality. A small and medium-scale insulation flame spread experimental platform was built, which was used to reveal the flame spread characteristics over RPUF and flame retardant RPUF. The flame structure, flame spread speed, flame temperature and mass loss rate etc. characteristics were analyzed. The results showed that the surface of all the samples was charred during flame spread. The non-flame retardant RPUF showed the largest combustion intensity, while the flame retardant expanded graphite (EG), aluminum hypophosphite (AHP) and aluminum diethylhypophosphite (ADP) resisted the flame spread in some degree, respectively, which was shown in the reduced flame spread speed, mass loss rate, and flame temperature parameters etc. It was also found that RPUF/AHP5 flame spread could sustain a period, while after 20 s the extinguishment was formed. It was because that, the flame retardant RPUF/AHP5 released non-combustion gas when heated, and AHP decomposed into the phosphorus-containing compound, which promoted the formation of charcoal in the polyurethane molecular chain. At the same time, flame retardant RPUF/ADP5 samples distinguished during flame spread, however, the distinguish degree was lower than that of flame retardant RPUF/AHP5. Meanwhile, the surface temperature had two peaks during the flame spread over RPUF/EG5, which were attributed to the instability of the char layer. When the temperature was higher than 400℃, the char layer was oxidized immediately and the heat penetrated the char layer, and unburned material continued to pyrolysis, therefore, the second temperature peak was formed.

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Physical properties test of a composite porous wick based on foam metal

Dongdong WANG Pengjie LIU Huaqiang CHU Jinxin WANG Houyang LU

Chin. J. Process Eng. 2020, 20 (7): 852-859. DOI: 10.12034/j.issn.1009-606X.219310

Abstract （449）

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In order to improve the heat and mass transfer performance of porous wicks, a composite porous wick was prepared by using copper or nickel foam as the skeleton and filling with the dendritic copper or nickel powders in this work. The foam metal can provide reliable porous framework and good heat transfer performance. And the dendritic metal powders can regulate the pore structure and pore size distribution inside the foam metal. The physical properties of the composite porous wick, including the porosity, capillary pumping capacity, effective thermal conductivity and evaporating rate, were studied experimentally. The prepared composite porous wicks had high porosity and low effective thermal conductivity in the range of 4.1?9.8 W/(m?K). According to the filling amount of metal powders and the microstructure of samples, the foam nickel and dendritic nickel powder were the most suitable combination for loose sintering of composite porous wick. Porosity had little effect on capillary pumping capacity of the composite porous wicks, but the porous structure and pore size distribution of porous wicks can cause the obvious effect. Due to the use of metal foam as skeleton, partial evaporation can be formed locally on the surface of composite porous wicks, and heat transfer equilibrium can be achieved by surface evaporation at low heat load of 30 W. Increase the heat load to 50 W or 70 W, local temperature on composite porous wick was over 100℃, and heat transfer entered the meniscus evaporation inside composite porous wick. Based on capillary pumping characteristics, effective thermal conductivities and evaporating rates in these porous samples, the composite porous wick with nickel foam as the skeleton and the mass ratio of dendritic nickel powder to the pore former of 5:5 had the best performance. The simple preparing method for the composite porous wick was proposed, and it was expected to be used for further practical application in loop heat pipe.

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Preparation and high-efficiency hydrogen evolution performance of iron-boron-based sponge catalytic electrode

Qiuyu XU Chenfeng WANG Lincai WANG Chenglong ZHANG Weiju HAO

Chin. J. Process Eng. 2020, 20 (5): 599-608. DOI: 10.12034/j.issn.1009-606X.219250

Abstract （440）

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Developing a high efficiency, stability and low cost catalytic electrode is of great practical significance to reduce the overpotential of hydrogen evolution. For this reason, NiB@Fe–B/PU catalytic electrode on non-conductive base material polyurethane sponge (PU) was prepared by a mild electroless plating method in this work. NiB@Fe–Co–B/PU, NiB@Fe–Mo–B/PU catalytic electrode were successfully prepared by doping a small amount of the third element, such as cobalt, molybdenum and other metal elements to improve its hydrogen evolution performance in neutral electrolyte solution. The results showed that the performance of NiB@Fe–B/PU catalytic electrode had significant improvement by doping of cobalt and molybdenum, and the performance of doping cobalt was better. The overpotential was only 161 mV(current density, j=50 mA/cm2) and the Tafel slope was 68.24 mV/dec for NiB@Fe–Co–B/PU catalytic electrode to hydrogen evolution reaction (HER) in 0.5 mol/L phosphate buffered saline (PBS). At the same time, the electrode showed good stability, which can work stably for more than 24 h under the overpotential of 61 mV.

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Properties analysis of steel slag compound replaced mineral powder, sand and stone as concrete admixture and aggregate

Hao ZHANG Xiankun YU Hongming LONG

Chin. J. Process Eng. 2020, 20 (4): 432-439. DOI: 10.12034/j.issn.1009-606X.219230

Abstract （765）

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With steel slag as the research object, concrete was prepared by using wind slag powder replaced mineral powder, electric furnace slag sand replaced mixed sand and electric furnace slag stone replaced crushed stone. Internal exposure index, external exposure index, content of f-CaO, boiling expansion value, specific surface area, density, moisture content, bulk density, contents of mud and soil, slump and compressive strength of concrete were tested. The chemical component, mineral composition and microstructure of concrete were analyzed. The safety and stability of steel slag, effects of wind slag powder replaced mineral powder, electric furnace slag sand replaced mixed sand, electric furnace slag stone replaced crushed stone and steel slag compound replaced mineral powder, sand and stone on the properties of concrete were studied. The results showed that the safety and stability of wind slag powder, electric furnace slag sand and electric furnace slag stone met the standard requirements and could be used in concrete. When wind slag powder replaced 20wt% of mineral powder, electric furnace slag sand replaced 10wt% of mixed sand and electric furnace slag stone replaced 20wt% of crushed stone, the properties of concrete were the best. Reasonable proportion of steel slag compound replaced mineral powder, sand and stone could improve the interface structure compactness of concrete, especially the late age strength of concrete.

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Preparation and properties characterization of 4-nitrophenol imprinted materials by surface imprinting coupled with sol-gel method

Gang XUE Lei DING Yang GAO Meiying ZHONG

Chin. J. Process Eng. 2020, 20 (4): 440-448. DOI: 10.12034/j.issn.1009-606X.219248

Abstract （619）

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The 4-nitrophenol imprinted materials that can selectively identify and remove 4-nitrophenol pollutants were prepared by surface imprinting and sol?gel methods using 4-nitrophenol as template molecule, α-methacrylic acid (α-MAA) as functional monomer, three hydroxymethyl propane three methacrylate (TRIM) as crosslinking agent, 2-methylpropionitrile (AIBN) as initiator. The effects of mole ratios of 4-nitrophenol to α-MAA and 4-nitrophenol to TRIM, types of pore formation agents and extracting solutions on the adsorption properties of surface molecularly imprinted materials were investigated. The preparation conditions of imprinted materials were further optimized by orthogonal experiments. The imprinted materials synthesized under the optimum conditions were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, specific surface analyzer, thermo-gravimetric analyzer and nanometer particle size analyzer. The results showed that the imprinted material had the best removal efficiency to 4-nitrophenol when the molar ratio of 4-nitrophenol to α-MAA and 4-nitrophenol to TRIM were 1:8 and 1:10, respectively, the pore formation agent was ethanol and the extracting solution was methanol/acetic acid (7:3, volume ratio), the value was 6.23 μmol/g. 4-nitrophenol was successfully imprinted on the surface of silica gel and the imprinted materials could specifically adsorb 4-nitrophenol.

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Regulation of properties and characterization of strontium titanate nanoparticles synthesis by oleic acid-assisted hydrothermal process

Na ZHANG Li ZHONG Dongping DUAN

Chin. J. Process Eng. 2019, 19 (6): 1212-1219. DOI: 10.12034/j.issn.1009-606X.219122

Abstract （615）

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Due to its excellent photocatalytic activity and piezoelectricity properties, SrTiO3 has attracted much attention in environmental photocatalysis, electronic and ceramic industries. SrTiO3 nanoparticles were synthesized by one-step oleic acid-assisted hydrothermal process using anatase TiO2 and Sr(OH)2?8H2O in this work. SrTiO3 nanoparticles were analyzed. The effects of oleic acid concentration, reaction time and Sr/Ti molar ratio on the properties of SrTiO3 nanoparticles were researched, photocatalytic property of the prepared SrTiO3 catalyst was investigated by the degradation of methylene blue. The results showed that perovskite phase cubic SrTiO3 nanoparticles with uniform size and regular morphology. The grain size of SrTiO3 nanoparticles increased with the increase of reaction time and Sr/Ti molar ratio, while decreased with the increase of oleic acid concentration. The agglomerate phenomenon of SrTiO3 nanoparticles became weaken and perovskite phase cubic SrTiO3 nanoparticles with regular morphology were obtained with the addition of oleic acid. When the Sr/Ti molar ratio was 0.75, the purity of the product was high. The influence of oleic acid concentration, reaction time and Sr/Ti molar ratio on microstructures of SrTiO3 nanoparticles could be explained by interparticle force, Ostwald ripening and crystal nucleation theory, respectively.

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Preparation of Pickering emulsion based on alumina hydroxide nanoparticles

Nan WU Jie WU Chunyu MIAO Guanghui MA Wenqi AN

Chin. J. Process Eng. 2019, 19 (6): 1220-1227. DOI: 10.12034/j.issn.1009-606X.219138

Abstract （659）

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Pickering emulsion is a new type of emulsion stabilized by solid particles instead of traditional organic surfactants. Compared to the traditional surfactant-stabilized emulsion, Pickering emulsion has the advantages of strong interfacial stability, regeneration, low toxicity and low cost, and has broad application value in the fields of food, medicine and cosmetics. The size of solid particle for stabilizing Pickering emulsion is in the nanometer range. The particles used to prepare Pickering emulsion are generally inorganic particles and polymer particles, most of which are not biocompatible or easily degradable. It is important to choose materials that have both good biocompatibility and stability. In this work, the boehmite-type aluminium hydroxide nanoparticles were prepared from aluminum isopropoxide by hydrolysis?hydrothermal method. Pickering emulsion was prepared by using boehmite-type aluminium hydroxide nanoparticles as stabilizer and squalene as oil phase. The effects of preparation conditions on size distribution and stability of Pickering emulsion were examined, including the concentration of nanoparticles, aqueous phase and dispersion condition. The results showed that two main factors affected the formation of nanoparticles were hydrothermal temperature and time. When the hydrothermal temperature was set to 200℃ for 2 h, the boehmite-type aluminium hydroxide nanoparticles were spherical with good dispersibility, uniform size distribution and high crystallinity. The average size of boehmite-type aluminium hydroxide nanoparticles was 55.70?9.20 nm and the polydispersity index was 0.187?0.011. The average size of Pickering emulsion was 1870?55 nm and the polydispersity index was 0.120?0.010. The Pickering emulsion could be stored stably at room temperature for more than 120 d. Based on this study, Pickering emulsion with uniform size distribution and good dispersibility was prepared, which provided a new material for biomedical area.

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Preparation of steel slag modified activated carbon and its formaldehyde degradation performance

Hao ZHANG Yuandi XU Lei ZHANG Xiuyu LIU

Chin. J. Process Eng. 2019, 19 (6): 1228-1233. DOI: 10.12034/j.issn.1009-606X.219132

Abstract （499）

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Steel slag ultrafine powder was prepared with steel slag and grinding aid, it was used to modify activated carbon to obtain steel slag modified activated carbon. The influences of types of steel slag, amount of grinding aid and amount of steel slag ultrafine powder on formaldehyde degradation performance of steel slag modified activated carbon were studied. Chemical composition of steel slag, particle size distribution and structure of steel slag ultrafine powder, and microstructure of steel slag modified activated carbon were characterized by XRF, LPSA, FT-IR, BET and SEM, respectively. The results showed that the steel slag modified activated carbon prepared under the conditions of steel slag was hot braised slag, amount of grinding aid (ethylene glycol, triethanolamine and absolute ethyl alcohol mixed with volume ratio 1:1:1) was 6 g, amount of steel slag ultrafine powder was 10 g, amount of activated carbon was 30 g and amount of absolute ethyl alcohol was 50 g had good formaldehyde degradation performance, degradation rate of formaldehyde after 12 h was 60.9%. The high contents of Fe2O3 and MnO in hot braised slag were conducive to formaldehyde enrichment and catalytic degradation in activated carbon with porous structure. Appropriate amount of grinding aid could significantly reduce the particle size and improve the particle size distribution uniformity of steel slag ultrafine powder, which was beneficial to increase the contact area of steel slag ultrafine powder, activated carbon and formaldehyde. Appropriate amount of steel slag ultrafine powder could offset activated carbon adsorption performance decline due to the decrease of porosity and specific surface area, improve the formaldehyde degradation performance of steel slag modified activated carbon.

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Preparation of a novel polytriazole resin based on silicon-containing multi-aromatic acetylene compounds

Wenmei LUO Liqiang WAN Shuaishuai ZHU Chao FU Xinyue HAN Farong HUANG

Chin. J. Process Eng. 2019, 19 (5): 1022-1029. DOI: 10.12034/j.issn.1009-606X.219119

Abstract （575）

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In recent years, the rapid development of aerospace vehicles urgently needs materials with high temperature resistance, light weight and high strength, which provides a good opportunity for the development of high temperature resistant polymer matrix resins. The polytriazole resin prepared by the 1,3-dipolar cycloaddition of an azide group and an alkynyl group has excellent heat resistance due to a rigid triazole ring in the main chain. The thermal properties of the polytriazole resin can be further improved by increasing the functionality of the polytriazole resin and the crosslinking density of the cured resin. In this work, a novel polytriazole resins Si-PTA3 were synthesized from silicon-containing multi-aromatic acetylene compounds (PSA) and 1,3,5-triazidemethyl-2,4,6-trimethylbenzene (TAMTMB) via 1,3-dipolar cycloaddition. The rheological properties of the Si-PTA3 resins were studied by rotating rheometer, the curing behaviors of the resins were traced by infrared spectra analysis and differential scanning calorimetry, the thermal properties and the effect of mole ratio of monomer on thermal properties were studied by dynamic mechanical analysis and thermogravimetric analysis. T700 carbon fiber-reinforced Si-PTA3 composites T700/Si-PTA3 were prepared by compression molding, and the mechanical properties of the composites were characterized by a tensile machine. The results showed that Si-PTA3 resins had good processing properties and can be cured at 80℃. The cured resin had excellent thermal properties, the best molar ratio of alkynyl group to azide group was 1.1:1.0, the glass transition temperature (Tg) and 5% weight loss temperature (Td5) reached 334 and 351℃, respectively. With the increase of the alkyne ratio, Tg decreased gradually, and Td5 reached more than 341℃. Composites T700/Si-PTA3 had good mechanical and thermal properties, the flexural strength at ambient temperature was higher than 1670 MPa and their retention rate at 250℃ was more than 67%. The Si-PTA3 resins can be used as a matrix of high temperature resistant resin composites.

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Synthesis and crystal conversion processes of nonlinear optical crystal 3BiCl ₃.7SC(NH ₂) ₂

Yunhe BAI Tiezhu PEI Liang ZHANG Ning ZHANG Dejia MA Qiuxiang YIN Chuang XIE

Chin. J. Process Eng. 2019, 19 (5): 1030-1036. DOI: 10.12034/j.issn.1009-606X.219125

Abstract （622）

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Semi-organic nonlinear optical (NLO) materials attract growing attention due to its balanced properties and potential applications in various fields. Thiourea-coordinating metal-organic NLO material is one of the famous semi-organic systems. In our previous work, new 3BiCl3?7SC(NH2)2 (DCBPB) NLO crystals which exhibits excellent fluorescence properties and better optical transmission properties than other reported complexes of thiourea and bismuth(Ⅲ) chloride were synthesized. However, during the synthesis of DCBPB, the coexistence of BiCl3?3SC(NH2)2 (β-BTC) was found to be difficult to avoid. In order to improve the quality of the synthesized DCBPB crystals, the effects of solvent ratio, reaction temperature, and reagent ratio on the purity of DCBPB using thiourea and bismuth(III) chloride as reagents in formic acid?water solvent system were investigated. The results showed that formic acid not only depressed the hydrolysis of bismuth(III) chloride, but also improved the selectivity of DCBPB. A high selectivity of DCBPB could be achieved when the molar ratio of bismuth(III) chloride to thiourea was larger than 1:3. The reaction temperature shouldn′t exceed 50℃ to avoid side reactions. The optimization of the synthesis indicated that the hydrolysis of bismuth(III) chloride was inevitable and the highest purity of DCBPB was 89.91wt%. A two-step mechanism of DCBPB synthesis was found which included the formation of β-BTC and the conversion of β-BTC to DCBPB. Furthermore, the conversion between β-BTC and DCBPB in formic acid aqueous solution was investigated based on XRD characteristic peak area correlation. The results showed that β-BTC almost completely converted to DCBPB and no hydrolysis of bismuth(III) was detected during the conversion, a high purity of more than 98wt% was achieved via conversion of β-BTC to DCBPB in formic acid.

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Synthesis and tribological properties of lubricant oil with highly dispersed and stable nanodiamond

Chuan LI Kai WU Bo WU Weimin FENG Xianguo HU

Chin. J. Process Eng. 2019, 19 (4): 809-816. DOI: 10.12034/j.issn.1009-606X.218327

Abstract （630）

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In mechanical systems, high-efficiency and environmentally friendly lubricant oil is demanded for extension of the equipment service life and energy saving demand highly efficient and environmentally friendly lubricating oil. Over last few decades, more attention have been paid to the addition of carbon nanoparticles, such as graphite, graphene and carbon nanotubes etc., in order to reduce the friction and wear in lubricating oil. At present, nanodiamond particles (NDPs) have been considered to be one of the most promising candidates for enhancing the friction reduction and anti-wear properties of lubricating oil effectively and economically due to its excellent properties of hardness, chemical stability, thermal stability and high thermal conductivity. Although NDPs as lubricant additives in lubricating oil have been reported, its dispersity in lubricating oil has not been well investigated. NDPs are easy to agglomerate in many media and have poor dispersive capacity in lubricating oil. In this work, in order to improve the dispersity of NDPs in anti-wear hydraulic oil (AHO), acidified and heat-treated NDPs (T-NDPs) were prepared and mixed with a variety of additives [oleylamine, polyisobutylene succinimide (T154) and high alkaline calcium sulfonate (T106)], then the mixture was added into AHO to prepare AHO containing T-NDPs. The materials and dispersity were characterized by FESEM, a Zeta potentiostat, FT-IR and static sedimentation experiment. The tribological property of AHO with T-NDPs and worn surfaces were investigated by the four-ball tribometer, 3D laser scanning microscopy and SEM/EDS. The results showed that the average diameter of NDPs decreased from 270.2 nm to 153.5 nm after acidified and heat-treatment. The average diameter of T-NDPs after adsorption additives was 101.5 nm. Additives could increase oil solubility of T-NDPs and imped their aggregation. Hence, AHO with T-NDPs possessed good dispersion stability. Particularly, the friction coefficient and wear scar diameter of AHO containing 0.04wt% of T-NDPs were reduced 13.2% and 17.8% compared with AHO without T-NDPs. We can analysed the friction reduction and anti-wear mechanism of T-NDPs as lubricant additives from two aspects, one is that the T-NDPs could support the load and act as roll bearing between the friction interfaces, and the other one is that the T-NDPs participated in the lubricating film formation between the friction surfaces.

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Synthesis of magnesium oxysulfate whiskers from bittern and post-sequence separation process

Xue BAI Hongfei GUO Xueqing CHEN Bin ZHAO Jilin CAO

Chin. J. Process Eng. 2019, 19 (4): 817-825. DOI: 10.12034/j.issn.1009-606X.218328

Abstract （625）

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Based on the comprehensive utilization of bittern resources, the synthesis of magnesium oxysulfate whiskers from bittern and the separation of potassium salt and sodium salt in the subsequent process were studied. Magnesium oxysulfate whiskers were synthesized by hydrothermal reaction of bittern with NaOH. The effects of raw material ratio, reaction temperature, concentration of liquid alkali and reaction time on liquid phase composition and product morphology were investigated. The products were characterized by XRD and SEM. The optimum conditions were determined as follows: the raw material molar ratio of Mg2+ to OH? was 1:1.5, the concentration of liquid alkali was 4 mol/L, the reaction temperature was 200℃ and the reaction time was 7 h. The Mg2+ in the mother liquid was completely converted into magnesium hydroxide crystals with the theoretical molar ratio of Mg2+ to OH? of 1:2. According to the phase diagrams of Na+, K+//Cl?, SO42??H2O system at 0 and 25℃ and NaCl?KCl?H2O ternary system at 25 and 100℃, NaCl, Na2SO4?10H2O and KCl were separated from the remaining mother liquor by evaporation concentration crystallization and freezing crystallization.

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Oxidation processes of MoSi ₂ and (Mo,W)Si ₂ coatings in wide temperature range

Shaobao MAO Ying YANG Haiqing LI Shihong ZHANG

Chin. J. Process Eng. 2019, 19 (4): 826-835. DOI: 10.12034/j.issn.1009-606X.218310

Abstract （585）

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MoSi2 and (Mo,W)Si2 coatings were prepared on Mo and Mo?W substrates respectively by means of pack cementation, and the effects and mechanisms of W element doping on the oxidation resistances of MoSi2 coating were investigated systematically. XRD, SEM and EDS were used to determine the phase structure, morphology and composition of the coatings. The results showed that W element was dissolved in MoSi2 coating in the form of (Mo,W)Si2 solid solution, and the microstructure of (Mo,W)Si2 coating was denser compared with that of MoSi2 coating as a result of W element doping. After static oxidation at 1600℃, the antioxidant life of (Mo,W)Si2 coating reached 70 h, while MoSi2 coating was failed after 25 h oxidation due to severe weight loss. Moreover, (Mo,W)Si2 coating exhibited excellent high-temperature protection performance after oxidation at 1200℃ for 1000 h. At the initial stage of the oxidation, the oxidation rate of (Mo,W)Si2 coating was higher than that of MoSi2 coating owing to W element doping, which led to lower formation velocity of dense oxide layer on the surface of (Mo,W)Si2 coating. After the dense SiO2 covering the surface completely, the oxidation rate of (Mo,W)Si2 coating decreased dramatically. The diffusion reaction between the Si element and the substrate was hindered by the addition of W element, the consumption rate of Si element in the coating was reduced remarkably, and the high-temperature oxidation resistance of (Mo,W)Si2 coating was enhanced significantly. After static oxidation at 500℃, comparing with MoSi2 coating, (Mo,W)Si2 coating exhibited a typical “Pest” phenomenon after oxidation for 50 h, and the coating failed in the form of disintegration. The addition of W element reduced the diffusion rate of Si element in the coating, therefore, a dense oxide layer could not be formed on the coating surface at low-temperature, which caused the rapid oxidation of the coating.

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Preparation and properties characterization of microencapsulated phase change materials using acrylic resin copolymers/n-dodecanol

Jinli LU Yang LI Yafang HAN Fuping QIAN

Chin. J. Process Eng. 2019, 19 (3): 617-622. DOI: 10.12034/j.issn.1009-606X.218282

Abstract （767）

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With the characteristics of high energy storage density, approximate constant temperature of phase change and convenient to storage or transport, the microencapsulated phase change materials (MEPCM) have wide application prospect in the fields of energy storage, transport and utilization. However, the traditional MEPCM particles use formaldehyde as the shell material, which would release harmful substances during application process. Therefore, it is necessary to develop a new type of formaldehyde-free MEPCM. A novel MEPCM particles with n-dodecanol as core material and acrylic resin copolymers as shell material using suspension polymerization under ultrasound irradiation condition were prepared in this work. The scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermo-gravimetric analyzer (TGA) and laser particle size analyzer (LPSA) were employed to characterize the performance of MEPCM particles. The results indicated that the MCPM particles were almost regular and had a uniform particle size. The particle sizes of MEPCM were 638.14~1478.65 nm, and the median diameter d50 was 933.91 nm which reaches nanometer scale. Two types of crystals were formed in core materials of all MEPCM particle during crystallization. The melting latent heat and the encapsulation efficiency of MEPCM reached to the maximum value of 93.31 kJ/kg and 86%, respectively. The melting temperature of MEPCM was 22.26℃, and the degree of supercooling reduced from 4.61℃ to 2.13℃. The proportion of core was 43%, it was closed to the design value of 50%. The shell material did not react with the core material. The mass reduce starting temperature of MEPCM was slightly higher than that of pure n-dodecanol, indicating that the thermal stability of the phase change material can be improved after encapsulation. In summary, the MEPCM had a good potential for energy storage and high response speed when face to temperature fluctuation.

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Pyrolysis of an organic polymeric precursor of zirconium carbide ceramics

Weijia KONG Shouquan YU Min GE Weigang ZHANG Lingzhong DU

Chin. J. Process Eng. 2019, 19 (3): 623-630. DOI: 10.12034/j.issn.1009-606X.218299

Abstract （879）

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To meet the requirement of rapid development in near spacecraft, continuous research efforts have been focused on the anti-oxidation materials which can be applied in very harsh environmental conditions. Carbon fiber reinforced SiC matrix (C/SiC) composites have overall advantages including lower density, good mechanical performance, and strong anti-oxidation capability, etc. Therefore, it can be used as various aerospace structural materials. However, C/SiC composites can only endure the short-time use (1000 s) when the temperature is lower than 1800℃, and longer-time use below 1600℃ in oxidizing environment. In this case, ZrC has been considered as a good candidate, owing to its melting point of 3540℃. Adding ZrC could increase the anti-oxidation capability of C/SiC composites, and besides, preceramic polymer processing is a good way to obtain ceramic matrix composites at a relatively low temperature. Various precursors of ceramic have been synthesized, but very little systematic work has been done regarding to the pyrolysis mechanism of polymeric precursor to zirconium carbide ceramics. In this work, pyrolysis process of an organic polymeric precursor of zirconium carbide (PZC) was investigated, the conversion mechanism of the precursor to ceramics was studied in detail as well. The methodology involved the microstructure analysis and phase composition of products by FT-IR, XRF, TG?DSC, MS-online, XRD and SEM. Furthermore, thermodynamics of carbothermal reduction reaction was calculated as well. The results showed that there was the decomposition of PZC with the temperature up to 600℃, including the release of small-molecule gases, such as water vapor, carbon monoxide, carbon dioxide, methane, acetone, and tetrahydrofuran, which were formed from the rearrangement of pyrolysis species. Then the solid inorganic products of amorphous-free carbon and m-ZrO2 were formed with the temperature range from 600℃ to 1200℃. Cubic ZrC crystalline in nano size can be formed above 1300℃, via the carbothermal reduction reaction between carbon and m-ZrO2, and this temperature was lower than the temperature from thermodynamic calculations. The ceramization of PZC could be completed with temperature at 1500℃, and the yield of ceramic was 33.45%.

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Optimization of activated carbon preparation from sawdust and plastics using response surface method

Peiyong MA Tian WANG Jinzhou WU Xianjun XING Xianwen ZHANG

Chin. J. Process Eng. 2019, 19 (2): 377-386. DOI: 10.12034/j.issn.1009-606X.218186

Abstract （601）

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Activated carbon was prepared from the mix of sycamore tree sawdust and polypropylene plastics by activation of K2CO3. Based on the central composite design (CCD) of response surface method (RSM), the preparation process was optimized, for the purpose of the highest methylene blue adsorption with higher iodine number. The optimum conditions were plastic content of 19wt%, K2CO3/sawdust mass ratio of 1.73, activation temperature of 958℃, and activation time of 91 min. The adsorption capacities of iodine and methylene blue were 1320.97 and 471.95 mg/g, with the predictive errors of 1.64% and 8.56%, respectively, which proves the high credibility of second-order model. The analysis of variance showed that the salt/sawdust ratio, activation temperature, and activation time were significant factors influencing the iodine adsorption capacity of activated carbon, which had a promoting effect, while plastic percentage had an inhibitory effect on the iodine adsorption capacity of activated carbon. The activation temperature and activation time had significant effects on the adsorption capacity of methylene blue on activated carbon, and had a promoting effect on the percentege of plastic. The salt/sowdust was a non-significant factor and had an inhibitory effect. The specific surface area, total pore volume and average pore size of the optimum sample were 1916.10 m2/g, 1.12 cm3/g, and 2.63 nm. Among them, the mesopore volume was 0.75 cm3/g, and the mesoporosity reached 70.10%. Compared with the activated carbon prepared by single factor optimization experiments, the specific surface area was increased by 454.11 m2/g. FT-IR analysis showed that the functional groups of the activated carbon prepared by the two optimization experiments did not change basically, and the increase of the activated carbon methylene blue adsorption was mainly due to the increase in specific surface area. The results suggested that the activated carbon optimized by response surface method has good absorptive property of macromolecules.

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