The Chinese Journal of Process Engineering

Select

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 （503）

PDF （1936KB）（180）

Save

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.

Related Articles | Metrics

Select

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 （467）

PDF （986KB）（317）

Save

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.

Related Articles | Metrics

Select

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 （453）

PDF （11921KB）（123）

Save

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.

Related Articles | Metrics

Select

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）

PDF （2432KB）（143）

Save

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.

Related Articles | Metrics

Select

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 （352）

PDF （1720KB）（163）

Save

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 .

Related Articles | Metrics

Select

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）

PDF （3102KB）（170）

Save

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.

Related Articles | Metrics

Select

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）

PDF （2380KB）（126）

Save

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.

Related Articles | Metrics

Content of Materials Engineering in our journal