By using industrial sodium silicate solution as raw material,high purity SiO2 powder was successfully synthesized by the split-step carbonation method.The relations between pH value of end point and the removal percen...By using industrial sodium silicate solution as raw material,high purity SiO2 powder was successfully synthesized by the split-step carbonation method.The relations between pH value of end point and the removal percentage of impurity at the first carbonation and the purity and yield of product SiO2 powder at the second carbonation were studied.The SiO2 powder was characterized by using XRD,SEM,IR and composition analysis.The results showed that when the pH value of end point at the first carbonation was 10.9,the purity of SiO2 prepared was up to 99.9%.The SiO2 powder synthesized was amorphous with regular sphere shape,uniform size and no reunion.The reaction mechanism was also discussed.展开更多
To obtain the appropriate conditions for eliminating Fe3＋from NiSO4 solution, the digestion solution of the clinker was used as raw material, which was obtained from roasting the nickel oxide ore with （NH4）2SO4. Th...To obtain the appropriate conditions for eliminating Fe3＋from NiSO4 solution, the digestion solution of the clinker was used as raw material, which was obtained from roasting the nickel oxide ore with （NH4）2SO4. The ammonium jarosite was successfully synthesized from the solution with analytic grade NH4HCO3. The effects of reaction temperature, reaction time, end pH value of reaction on the removal rate of iron were investigated, and the effect of the initial concentration of Fe3＋was also discussed. All of those factors had significant effects on the removal rate of Fe3＋, among which the reaction temperature was the most prominent. The appropriate reaction conditions were concluded as follows： reaction temperature 95 ℃ reaction time 3.5 h, end pH value of reaction 2.5 at initial concentration of Fe3＋19.36 g/L. The physical aspect of （NH4）2Fe6（SO4）4（OH）12 was cluster figure composed of sheet or prismatic particles with smooth surface.展开更多
锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研...锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研究针对高镍三元材料阳离子无序排列严重和循环稳定性差的问题,通过共沉淀法在前驱体合成过程中将Mg掺杂进入晶体,得到Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)(Mg1.0)活性材料,进一步利用液相法在材料表面包覆Al_(2)O_(3),成功制备Al_(2)O_(3)涂覆的Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)复合材料(Mg1.0@Al)。X射线衍射(XRD)结果表明,Mg掺杂能够有效扩大材料层间距,抑制阳离子混排;扫描电子显微镜(SEM)结合透射电子显微镜(TEM)结果表明,改性未对NCM811材料整体形貌造成影响,同时能够明显地观察到通过液相法在材料表面包覆的Al_(2)O_(3)涂层。电化学测试结果表明,镁铝协同改性可以稳定NCM811材料结构,减少阴极的界面极化,遏制材料与电解液发生副反应,使得材料表现出优越的电化学性能。Mg1.0@Al在1 C循环100次后表现出稳定的放电电压(ΔV=5.2 m V)、较低的电荷转移阻抗(R_(ct)=51.66Ω)和卓越的锂离子扩散系数(D_(Li)=4.05×10^(-14)cm^(2)/s)。同时,Mg1.0@Al材料在2.8~4.3V电压范围下,展现出卓越的循环性能和倍率性能:1 C下循环100次和400次后仍有188.58 m Ah/g和147.47 m Ah/g的放电比容量,容量保持率分别为95.18%和74.54%;5 C大倍率电流下,放电比容量高达146.3 m Ah/g。展开更多
文摘By using industrial sodium silicate solution as raw material,high purity SiO2 powder was successfully synthesized by the split-step carbonation method.The relations between pH value of end point and the removal percentage of impurity at the first carbonation and the purity and yield of product SiO2 powder at the second carbonation were studied.The SiO2 powder was characterized by using XRD,SEM,IR and composition analysis.The results showed that when the pH value of end point at the first carbonation was 10.9,the purity of SiO2 prepared was up to 99.9%.The SiO2 powder synthesized was amorphous with regular sphere shape,uniform size and no reunion.The reaction mechanism was also discussed.
基金Project(51204054)supported by the National Natural Science Foundation of ChinaProject(N110402012)supported by Fundamental Research Funds for the Central Universities,ChinaProject(2007CB613603)supported by the National Basic Research Program of China
文摘To obtain the appropriate conditions for eliminating Fe3＋from NiSO4 solution, the digestion solution of the clinker was used as raw material, which was obtained from roasting the nickel oxide ore with （NH4）2SO4. The ammonium jarosite was successfully synthesized from the solution with analytic grade NH4HCO3. The effects of reaction temperature, reaction time, end pH value of reaction on the removal rate of iron were investigated, and the effect of the initial concentration of Fe3＋was also discussed. All of those factors had significant effects on the removal rate of Fe3＋, among which the reaction temperature was the most prominent. The appropriate reaction conditions were concluded as follows： reaction temperature 95 ℃ reaction time 3.5 h, end pH value of reaction 2.5 at initial concentration of Fe3＋19.36 g/L. The physical aspect of （NH4）2Fe6（SO4）4（OH）12 was cluster figure composed of sheet or prismatic particles with smooth surface.
文摘锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研究针对高镍三元材料阳离子无序排列严重和循环稳定性差的问题,通过共沉淀法在前驱体合成过程中将Mg掺杂进入晶体,得到Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)(Mg1.0)活性材料,进一步利用液相法在材料表面包覆Al_(2)O_(3),成功制备Al_(2)O_(3)涂覆的Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)复合材料(Mg1.0@Al)。X射线衍射(XRD)结果表明,Mg掺杂能够有效扩大材料层间距,抑制阳离子混排;扫描电子显微镜(SEM)结合透射电子显微镜(TEM)结果表明,改性未对NCM811材料整体形貌造成影响,同时能够明显地观察到通过液相法在材料表面包覆的Al_(2)O_(3)涂层。电化学测试结果表明,镁铝协同改性可以稳定NCM811材料结构,减少阴极的界面极化,遏制材料与电解液发生副反应,使得材料表现出优越的电化学性能。Mg1.0@Al在1 C循环100次后表现出稳定的放电电压(ΔV=5.2 m V)、较低的电荷转移阻抗(R_(ct)=51.66Ω)和卓越的锂离子扩散系数(D_(Li)=4.05×10^(-14)cm^(2)/s)。同时,Mg1.0@Al材料在2.8~4.3V电压范围下,展现出卓越的循环性能和倍率性能:1 C下循环100次和400次后仍有188.58 m Ah/g和147.47 m Ah/g的放电比容量,容量保持率分别为95.18%和74.54%;5 C大倍率电流下,放电比容量高达146.3 m Ah/g。
