In order to improve the quality of Hunyuan inferior Ca-based bentonite(Ca-Bent),semidry process was used to modify Ca-Bent into superior Na-based bentonite(Na-Bent).The factors affecting sodium-modification were inves...In order to improve the quality of Hunyuan inferior Ca-based bentonite(Ca-Bent),semidry process was used to modify Ca-Bent into superior Na-based bentonite(Na-Bent).The factors affecting sodium-modification were investigated.The optimized experimental parameters are obtained as follows:Na2CO3 dosage 4.0%,ageing time 25 d,briquetting pressure 25 MPa and briquetting moisture 20%.Under the optimization conditions,the modified Na-Bent has a colloid value of 73.6 mL/(3g),dilation of 38 mL/g and water absorption in 2 h(2HWA) of 465%,respectively.The balling results indicate that the modified Na-Bent pellets have higher drop strength and compression strength than the Ca-Bent pellets.展开更多
The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte...The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.展开更多
In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2...In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.展开更多
金属氯化物-石墨插层化合物具有导电性优异,石墨层间距大等特点,可用作钠离子电池负极材料。然而,在传统金属氯化物插层石墨过程中,不可避免地用到氯气,既增加了实验操作的风险,也对实验设备提出更高要求。基于上述原因,本文创新性地使...金属氯化物-石墨插层化合物具有导电性优异,石墨层间距大等特点,可用作钠离子电池负极材料。然而,在传统金属氯化物插层石墨过程中,不可避免地用到氯气,既增加了实验操作的风险,也对实验设备提出更高要求。基于上述原因,本文创新性地使用SO_(2)Cl_(2)作为氯源来促进BiCl_(3)插层石墨。该方法不仅有效提高了BiCl_(3)插层效率,也避免了直接使用氯气带来的安全性风险。采用该方法所合成的三氯化铋-石墨插层化合物(BiCl_(3)-GICs)的层间距为1.26 nm,BiCl_(3)插层含量高达42%。以其为负极材料,组装的钠离子电池具有高的比容量(213 mAh g^(-1)at 1 A g^(-1))和优异的倍率性能(170 mAh g^(-1)at 5 A g^(-1))。此外,原位拉曼光谱测试结果表明,首圈放电后石墨与插层的BiCl_(3)相互作用减弱,该过程有效促进了钠离子在石墨层内的存储。采用该方法可成功制备多种类型金属氯化物-石墨插层化合物,为开发高性能储能材料提供了可行思路。展开更多
Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investig...Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investigated by laboratory experiments under simulated industrial conditions.The results show that at higher temperature the variation period of particle size is shortened,while prolongs with more solid content.Particle size fluctuation amplitude reduces with the temperature rising but increases with the solid content increasing.Particle size distribution becomes more uniform by replenishing fine seeds,enabling the periodical fluctuation of Al(OH)3 particle size to be attenuated.Combining properly the additives with controlling the seed size is able to reduce the amplitude of periodical fluctuation and shorten the attenuation time.With unbalance of particle size distribution,the particles gradually become bigger,even inducing the decrease of the specific surface area of seeds,which is the major reason causing explosive attenuation of Al(OH)3 particles in seed precipitation process.展开更多
基金Project(50725416) supported by the National Science Fund for Distinguished Young Scholars Project(50804059) supported by the National Natural Science Foundation of China+1 种基金 Project(2008BAB32B06) supported by the Key Project in the National Science and Technology Pillar Program during the 11th Five-Year Plan PeriodProject(200805331080) supported by the Specialized Research Fund for the Doctoral Program of Higher Education
文摘In order to improve the quality of Hunyuan inferior Ca-based bentonite(Ca-Bent),semidry process was used to modify Ca-Bent into superior Na-based bentonite(Na-Bent).The factors affecting sodium-modification were investigated.The optimized experimental parameters are obtained as follows:Na2CO3 dosage 4.0%,ageing time 25 d,briquetting pressure 25 MPa and briquetting moisture 20%.Under the optimization conditions,the modified Na-Bent has a colloid value of 73.6 mL/(3g),dilation of 38 mL/g and water absorption in 2 h(2HWA) of 465%,respectively.The balling results indicate that the modified Na-Bent pellets have higher drop strength and compression strength than the Ca-Bent pellets.
基金The project was supported by the FAPESP(2014/09087-4,2014/50279-4).
文摘The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
基金financially supported by the National Natural Science foundation of China (Nos. 51234008 and 51174230)the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-11-0515)
文摘In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.
基金the financial supports from the National Key R&D Program of China(No.2022YFC2904401)the National Natural Science Foundation of China(Nos.22078055,52074083,51774079)the Fundamental Research Funds for the Central Universities,China(No.N2225002)。
文摘金属氯化物-石墨插层化合物具有导电性优异,石墨层间距大等特点,可用作钠离子电池负极材料。然而,在传统金属氯化物插层石墨过程中,不可避免地用到氯气,既增加了实验操作的风险,也对实验设备提出更高要求。基于上述原因,本文创新性地使用SO_(2)Cl_(2)作为氯源来促进BiCl_(3)插层石墨。该方法不仅有效提高了BiCl_(3)插层效率,也避免了直接使用氯气带来的安全性风险。采用该方法所合成的三氯化铋-石墨插层化合物(BiCl_(3)-GICs)的层间距为1.26 nm,BiCl_(3)插层含量高达42%。以其为负极材料,组装的钠离子电池具有高的比容量(213 mAh g^(-1)at 1 A g^(-1))和优异的倍率性能(170 mAh g^(-1)at 5 A g^(-1))。此外,原位拉曼光谱测试结果表明,首圈放电后石墨与插层的BiCl_(3)相互作用减弱,该过程有效促进了钠离子在石墨层内的存储。采用该方法可成功制备多种类型金属氯化物-石墨插层化合物,为开发高性能储能材料提供了可行思路。
基金Project(50804031) supported by the National Natural Science Foundation of China
文摘Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investigated by laboratory experiments under simulated industrial conditions.The results show that at higher temperature the variation period of particle size is shortened,while prolongs with more solid content.Particle size fluctuation amplitude reduces with the temperature rising but increases with the solid content increasing.Particle size distribution becomes more uniform by replenishing fine seeds,enabling the periodical fluctuation of Al(OH)3 particle size to be attenuated.Combining properly the additives with controlling the seed size is able to reduce the amplitude of periodical fluctuation and shorten the attenuation time.With unbalance of particle size distribution,the particles gradually become bigger,even inducing the decrease of the specific surface area of seeds,which is the major reason causing explosive attenuation of Al(OH)3 particles in seed precipitation process.
