A novel process for sulfidation of ZnO by co-grinding with sulfur and reductive additives （P, Fe, A1, and Mg） was developed. The sulfidation extent of ZnO with the addition of P, Fe, A1 or Mg can reach 85.2%, 81.6%,...A novel process for sulfidation of ZnO by co-grinding with sulfur and reductive additives （P, Fe, A1, and Mg） was developed. The sulfidation extent of ZnO with the addition of P, Fe, A1 or Mg can reach 85.2%, 81.6%, 96.7% and 92.6% after grinding for 4, 6, 1 and 1 h, respectively. Based on the chemical phase composition analysis and morphological characteristics of sulfidized products by XRD, SEM and TEM, a possible reaction mechanism, mechanically induced self-propagating reaction （MSR）, was proposed to explain the sulfidization reaction. In addition, the floatability of sulfidized products was investigated for the recovery of metal sulfide and ZnS can be concentrated with a high concentration ratio and concentrate grade. By using the sulfidizing process, it is expected that the recovery of zinc from the wastes or purification of heavy-metal-containing hazardous residues is technically feasible.展开更多
Combustion synthesis involving metallothermic reduction of Fe2O3 and TiO2 was conducted in the mode of self-propagating high-temperature synthesis(SHS)to fabricate FeAl-based composites with dual ceramic phases,TiB2/A...Combustion synthesis involving metallothermic reduction of Fe2O3 and TiO2 was conducted in the mode of self-propagating high-temperature synthesis(SHS)to fabricate FeAl-based composites with dual ceramic phases,TiB2/Al2O3 and TiC/Al2O3.The reactant mixture included thermite reagents of 0.6Fe2O3+0.6TiO2+2Al,and elemental Fe,Al,boron,and carbon powders.The formation of xFeAl−0.6TiB2−Al2O3 composites with x=2.0−3.6 and yFeAl−0.6TiC−Al2O3 composites with y=1.8−2.75 was studied.The increase of FeAl causes a decrease in the reaction exothermicity,thus resulting in the existence of flammability limits of x=3.6 and y=2.75 for the SHS reactions.Based on combustion wave kinetics,the activation energies of Ea=97.1 and 101.1 kJ/mol are deduced for the metallothermic SHS reactions.XRD analyses confirm in situ formation of FeAl/TiB2/Al2O3 and FeAl/TiC/Al2O3 composites.SEM micrographs exhibit that FeAl is formed with a dense polycrystalline structure,and the ceramic phases,TiB2,TiC,and Al2O3,are micro-sized discrete particles.The synthesized FeAl−TiB2−Al2O3 and FeAl−TiC−Al2O3 composites exhibit the hardness ranging from 12.8 to 16.6 GPa and fracture toughness from 7.93 to 9.84 MPa·m1/2.展开更多
Designing highly selective and efficient singleatom electrocatalysts is essential for ammonia production under ambient conditions. This paper describes a density functional theory study on exploring the performance tr...Designing highly selective and efficient singleatom electrocatalysts is essential for ammonia production under ambient conditions. This paper describes a density functional theory study on exploring the performance trends of transition metal complexes with P-based ligands in nitrogen reduction reaction(NRR) and further develops a design principle for high-performance single-atom catalysts(SACs)of NRR. Among the explored catalysts, W@BP(0.40 eV),Ta@BP(0.47 eV), and Nb@BP(0.53 eV) are identified as remarkable candidates with low free energy change in the potential-limiting step, high stability and high electrical conductivity for NRR. It is worth noting that almost all SACs with P-based ligands exhibit high NRR selectivity, due to the fact that they adsorb *N_(2) more strongly than *H. The adsorption free energy of *N_(2) H can be considered as a descriptor for the intrinsic activity trends in NRR. Furthermore, by constructing a volcano plot of the activity against the electronic charge on metal centers, it is demonstrated that the metal center with a moderate amount of positive charge can promote the catalytic performance of NRR.展开更多
基金Project(50925417) supported by the China National Funds for Distinguished Young ScientistsProject(50830301) supported by the National Natural Science Foundation of China+1 种基金Projects(2010AA065203,2011AA061001) supported by the National High-tech Research Program of ChinaProject(NCET-10-0840) supported by the Program for New Century Excellent Talents in University,China
文摘A novel process for sulfidation of ZnO by co-grinding with sulfur and reductive additives （P, Fe, A1, and Mg） was developed. The sulfidation extent of ZnO with the addition of P, Fe, A1 or Mg can reach 85.2%, 81.6%, 96.7% and 92.6% after grinding for 4, 6, 1 and 1 h, respectively. Based on the chemical phase composition analysis and morphological characteristics of sulfidized products by XRD, SEM and TEM, a possible reaction mechanism, mechanically induced self-propagating reaction （MSR）, was proposed to explain the sulfidization reaction. In addition, the floatability of sulfidized products was investigated for the recovery of metal sulfide and ZnS can be concentrated with a high concentration ratio and concentrate grade. By using the sulfidizing process, it is expected that the recovery of zinc from the wastes or purification of heavy-metal-containing hazardous residues is technically feasible.
文摘Combustion synthesis involving metallothermic reduction of Fe2O3 and TiO2 was conducted in the mode of self-propagating high-temperature synthesis(SHS)to fabricate FeAl-based composites with dual ceramic phases,TiB2/Al2O3 and TiC/Al2O3.The reactant mixture included thermite reagents of 0.6Fe2O3+0.6TiO2+2Al,and elemental Fe,Al,boron,and carbon powders.The formation of xFeAl−0.6TiB2−Al2O3 composites with x=2.0−3.6 and yFeAl−0.6TiC−Al2O3 composites with y=1.8−2.75 was studied.The increase of FeAl causes a decrease in the reaction exothermicity,thus resulting in the existence of flammability limits of x=3.6 and y=2.75 for the SHS reactions.Based on combustion wave kinetics,the activation energies of Ea=97.1 and 101.1 kJ/mol are deduced for the metallothermic SHS reactions.XRD analyses confirm in situ formation of FeAl/TiB2/Al2O3 and FeAl/TiC/Al2O3 composites.SEM micrographs exhibit that FeAl is formed with a dense polycrystalline structure,and the ceramic phases,TiB2,TiC,and Al2O3,are micro-sized discrete particles.The synthesized FeAl−TiB2−Al2O3 and FeAl−TiC−Al2O3 composites exhibit the hardness ranging from 12.8 to 16.6 GPa and fracture toughness from 7.93 to 9.84 MPa·m1/2.
基金supported by the National Natural Science Foundation of China (21525626 and 21761132023)the Program of Introducing Talents of Discipline to Universities (BP0618007)。
文摘Designing highly selective and efficient singleatom electrocatalysts is essential for ammonia production under ambient conditions. This paper describes a density functional theory study on exploring the performance trends of transition metal complexes with P-based ligands in nitrogen reduction reaction(NRR) and further develops a design principle for high-performance single-atom catalysts(SACs)of NRR. Among the explored catalysts, W@BP(0.40 eV),Ta@BP(0.47 eV), and Nb@BP(0.53 eV) are identified as remarkable candidates with low free energy change in the potential-limiting step, high stability and high electrical conductivity for NRR. It is worth noting that almost all SACs with P-based ligands exhibit high NRR selectivity, due to the fact that they adsorb *N_(2) more strongly than *H. The adsorption free energy of *N_(2) H can be considered as a descriptor for the intrinsic activity trends in NRR. Furthermore, by constructing a volcano plot of the activity against the electronic charge on metal centers, it is demonstrated that the metal center with a moderate amount of positive charge can promote the catalytic performance of NRR.
