Papers by Author: Hong Wen Ma

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Authors: Shuang Qing Su, Hong Wen Ma
Abstract: Zeolite A was successfully synthesized via convenient hydrothermal process using potassium-extracted residue of potassium feldspar as a combined source for silica and alumina. Optimization studies on the molar ratios of Na2O/SiO2 and H2O/SiO2, and aging time have been conducted. The results were that pure zeolite A with high crystallinity could be synthesized when the reaction mixture with molar ratios of Na2O/SiO2 and H2O/SiO2 of 2.0 and of 85, respectively, were crystallized at 100°C for 3h. Aging was found to be not prerequisite for the formation of zeolite A in the system. The product was characterized by XRD, FTIR, SEM and calcium exchange capacity. Finally, a comparative study of the zeolite A formation from the potassium-extracted residue and other industrial waste or natural silicate minerals was also carried out.
Authors: Jian Xiong Ye, Xin Gang Yu, Wen Yue Bi, De Jun Li, Hong Wen Ma, Hui Feng Zhao, Guo Hong Qiu, Li Wang
Abstract: ZrO2-CeO2 thin film was successfully prepared on 316L stainless steel by sol-gel process and the corrosion characteristics of the substrate coated with ZrO2-CeO2 thin film were evaluated through potentiodynamic polarization curve obtained in deaerated 15% H2SO4. The results show that, with the increase of CeO2 content, the corrosion rate of 316L stainless steel substrates coated with ZrO2-CeO2 thin film decreases. The surface morphology of the coating was observed by field scanning electron microscopy and the elements in the surface of coated substrate analyzed by FEM-EDX.
Authors: Yan Hong Liu, Hong Wen Ma, Mei Tang Liu
Abstract: The morphology and particle size of boehmite play a decisive role on the application of alumina that derived from it. In this paper, we employed pseudoboehmite that produced from Al2 (SO4)3•18H2O and NH3•H2O at 70 °C, pH 7.5 as precursor to synthesize boehmite, and utilized different seeding when preparing pseudoboehmite and boehmite. To identify the influence of seeding on the microstructure of pseudoboehmite and boehmite, the products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and BET. The results indicate that the pseudoboehmite seeding has a significant influence on the morphology and particle size of pseudoboehmite to which we should pay high attention. However, the boehmite seeding does not play the role of crystal nucleus as expected. The further intrinsic mechanism study is ongoing.
Authors: Peng Deng, Yu Qin Liu, Da Jian Ma, Hong Wen Ma
Abstract: The present paper focuses on the experimental investigation of the aluminothermic reduction of magnesia under vacuum condition with the fixed magnesia to aluminum molar ratio of 11:6. The influences of reaction temperature and time on the reduction ratio of magnesia were studied. The chemical composition, phase constitution and morphology of the condensed magnesium and the briquettes after thermal reduction were investigated by X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectrometry. The reduction ratio of magnesia increases with the increase in the reaction temperature and time. The briquettes after thermal reduction at 1050°C-1150°C are mainly composed of the spinel, unreacted magnesia and aluminum. The briquette after 1 hrs thermal reduction at 1200°C contains corundum, magnesium aluminium oxide, trace amount of spinel, unreacted MgO and aluminium.
Authors: Yun Jiang, Hong Wen Ma, Yu Qin Liu
Abstract: The structure and composition of carbon materials affect obviously the result of carbothermic reduction of magnesia. Coke, charcoal and graphite were used in reduction experiments under the same conditions. The reactivity ratio of magnesia and XRD pattern of residues were analyzed and compared. The reactivity ratio of magnesia by coke was similar to the one by charcoal. The amorphous carbon in coke graphitized partly in reduction experiments of 1673K. The results show that the effective composition in coke is the amorphous carbon. It also suggests that the temperature of reaction should be control less than 1700K to avoid the amorphous carbon’s graphitization.
Authors: Ming Wei Wang, Jing Yang, Hong Wen Ma, Jie Shen, Jin Hong Li, Feng Guo
Abstract: Using coal fly ash from one thermal power plant in Ningxia, China as the raw material, aluminum hydroxide powder was successfully extracted by pre-desilication , calcination, dissolution and carbonation precipitation processes. The research results indicated that the mullite, Quartz and glass phase in the coal fly ash could be changed into NaSiO3, NaAlO2 and Na2CaSiO4 after the coal fly ash was treated by desilication and calcination. The SiO2and Al2O3 components in the coal fly ash were mainly separated by dissolving the calcined sample using water. The dissolution rate of Al2O3 from the calcined sample is 91%. The aluminum hydroxide powder extracted from the coal fly ash is bayerite with the particle size of more than 50m. The extraction rate of the aluminum hydroxide from the coal fly ash can be up to 83%.
Authors: Bi Ya Cai, Jin Hong Li, Hong Wen Ma, Xiao Qian Jiang
Abstract: The hydration heat of aluminate cement containing magnesium aluminate spinel (MA-spinel) and Commercial Lafarge cement are studied. The results show that five stages exist in the hydration processes of both cements, e.g. pre-induction, induction, acceleration, deceleration and stabilization stage. The N values of the two cements are both lower than 1 in acceleration stage, on the contary higher than 1 in stabilization stage. As a result, the hydration is mainly controlled by nucleation reaction and diffusion process in acceleration stage and stabilization stage respectively. The hydration heat of aluminate cement containing MA-spinel is lower than Lafarge cement. Accordingly, the hydration rate of aluminate cement containing MA-spinel is slower than that of Lafarge cement.
Authors: Xin Gang Yu, Lan Yun Liu, Yan Bin Zuo, Lin Jiang Wang, Hong Wen Ma, Wen Yue Bi, Hui Feng Zhao, Li Wang, Fei Long, Wu Wen Luo
Abstract: X-ray diffraction (XRD) method to measure the residual stress existing in the metal substrate surface layer was introduced and the sol-gel ZrO2-CeO2 thin film was successfully prepared on SUS304 stainless steel substrate by dip-coating process. The macro residual stress existing in metal substrate was analyzed by XRD. It turns out that the compressive stress existing in the metal substrate surface layer increases with the increase of heat-treated temperature. Based on the above study, colored stainless steels of high quality were prepared by sol-gel process.
Authors: Yi Miao Nie, Hong Wen Ma, Shu Xian Liu, Fu Sheng Niu
Abstract: Products of mineral polymer were prepared from meta-kaolin in this research. The mechanism of polymerization was deduced from the analytical data of XRD, IR, SEM and MAS-NMR. Several stages were produced during the solidification of meta-kaolin-based mineral polymer, that is, firstly, the Si-O-Si, Al-O-Si bonds of the meta-kaolin were broken in the high molar alkaline solution; Parallel to this process, complexes and polymerized species (-Si-O-Na, Al(OH)4-, Al(OH)52-, Al(OH)63-) formed; secondly, aluminosilicate zeolite precursors or precipitates formed; finally, by dehydration, the precursors turned into the non-crystaline phase, in which Q4(2Al) were the main forms of Si element, and tetrahedral aluminum were the main form of Al element in the mineral polymer products cured for 28 days. The experimental results provided a good basis for understanding the formation of mineral polymer.
Authors: Xiao Qian Jiang, Hong Wen Ma, Ge Li, Wen Gui Yao
Abstract: Pure magnesium hydroxide (Mg(OH)2) nanoparticles were synthesized successfully from dolomite-talc ore via chemical precipitation. Carbonate minerals in dolomite-talc ore were dissolved with hydrochloric acid, and Fe2+ was oxidized to Fe3+, then Fe3+ and Al3+ were removed by adding ammonia to adjust pH to reach 6. Magnesium hydroxide (Mg(OH)2) nanoparticles with about 20nm thickness and lamella shape were obtained successfully when pH>10 in the presence of a nonionic surfactant polyethyleneglycol (PEG) with 3wt %, which reached by adding more ammonia. The XRD results show that the amorphous precipitate with 87% Fe2O3 generates at pH=6. However, CaMg2Cl6 (H2O)12 generates when pH = 7, then disappears with the increasing of pH. Mg(OH)2 appears at pH= 9 and pure Mg(OH)2 particle is obtained at pH > 10. Meanwhile, PEG plays an important role in the growth of Mg(OH)2 nanoparticles.
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