石墨烯/SnO2/Si@PPy复合材料制备及电化学性能

以氧化石墨烯和SnCl2为原料，通过微波水热法合成了石墨烯/SnO2复合材料(GS)，以过硫酸铵为引发剂，通过吡咯在Si粉表面原位氧化聚合制备了Si@PPy包覆结构(SP)，最后通过微波水热组装法制备了石墨烯/SnO2/Si@PPy复合材料(GSSP)。采用SEM、TEM、XRD、Raman和BET对GS、SP和GSSP材料的形貌和结构进行表征，并以GSSP复合材料为负极组装半电池进行倍率、循环、CV和EIS等电化学性能测试。结果表明：GSSP复合材料具有优异的倍率性能，在100 mA/g电流密度下，放电和充电的平均比容量分别为948.44和869.63 mAh/g。1000 mA/g电流密度下，经过400次循环放电和充电的比容量保持率高达90.69%和89.34%。     

SnO_2/石墨烯基锂离子电池负极材料的多级可控制备及其电化学性能研究

分别使用不同种类的表面活性剂对SnO_2在二维石墨烯片表面的生长和所得到的复合片层材料的三维自组装进行多级调控,制备了具有取向大孔结构的SnO_2和石墨烯复合气凝胶材料(SnO_2-CTAB/GM)。SEM和TEM等测试表明了SnO_2-CTAB/GM中取向大孔结构的存在,且SnO_2纳米颗粒以2~3nm的尺寸均匀分布在石墨烯片层表面。电化学测试表明了SnO_2-CTAB/GM复合材料具有高可逆容量和循环稳定性:当电流密度为100mA/g时,首次可逆容量高达1125mAh/g,循环60次后,可逆容量稳定在945.6 mAh/g;当电流密度为100、500、2000 mA/g时,SnO_2-CTAB/GM复合负极材料的放电容量分别为1 180、786.5、566mAh/g,具有优异的的倍率性能。     

碳@硒化钴/还原氧化石墨烯锂离子电池负极材料的制备及性能研究

以葡萄糖和石墨烯为碳源,通过简便的水热工艺成功制备了一系列具有多孔结构的C@CoSe/rGO复合材料。电化学测试结果表明,在200 mA/g电流密度下进行150圈循环测试后,C@CoSe/rGO-2复合材料的可逆比容量为751 mAh/g;在1 000 mA/g和2 000 mA/g大电流密度下进行150圈循环测试,其比容量仍可达525 mAh/g和285 mAh/g。该工作提供了一种简单的方法用于制备比容量高、倍率性能好且循环稳定的锂离子电池负极材料。     

石墨烯负载纳米二硫化钴的制备及其在锂离子电池方面的应用研究

采用二次水热法将纳米二硫化钴负载于石墨烯上,并通过结构表征和电化学性能测试,探讨了纳米二硫化钴/石墨烯材料作为锂离子电池负极的性能。电容量测试结果表明：在电流密度为100 mA/g条件下,二硫化钴/石墨烯复合材料的首周充放电容量分别为1 610 mA·h/g和774 mA·h/g,测算出的库伦效率为48.1%;循环性能测试结果表明：经过50次循环测算后的复合材料的放电比容量为302 mA·h/g,容量保持率为33.4%;倍率性能测试结果表明：当电流密度回复到100 mA/g时,复合材料的比容量恢复至550 mA·h/g。实验制备的纳米二硫化钴/石墨烯复合材料在锂电池负极的应用上表现出了优异的循环性能和倍率性能。     

SnO_2纳米粒子/氮掺杂石墨烯复合材料的制备和储锂性能

本文以SnC_2O_4、GO、柠檬酸和尿素为原料,通过溶剂热和热处理相结合的方法制备出SnO_2纳米粒子/氮掺杂石墨烯复合材料(SnO_2NPs/NG)。用作锂电负极时,SnO_2NPs/NG复合材料在100 mA·g~(-1)的电流密度下循环100次后,其容量为1238 mAh·g~(-1),即使在8 A·g~(-1)的大电流密度下,其容量仍高达206 mAh·g~(-1),显示出了较好的循环和倍率性能。     

TiO_2/C/BP复合负极材料的制备及其储锂性能研究

为了提高TiO_2负极材料的电化学性能,采用球磨-超声-水热法制备了TiO_2/C/BP复合负极材料,测定了材料的循环放电比容量、倍率性能、循环伏安曲线和交流阻抗。结果表明,二氧化钛掺杂石墨、黑磷后,二氧化钛晶型不受影响,TiO_2/C/BP复合材料颗粒分散性得到改善、交流阻抗减小、导电性明显增强,与纯TiO_2相比,电流密度为100 mA/g,首圈放电比容量由320 mA·h/g提高到502 mA·h/g,第3圈放电比容量由175 mA·h/g提高到335 mA·h/g,经过100次循环后,纯TiO_2的放电比容量降至98 mA·h/g,而TiO_2/C/BP的放电比容量仍维持在255 mA·h/g,放电比容量保持率明显提高,库伦效率的稳定性也得到显著提高。     

V2O5/Graphene复合电极材料的制备与储锂性能

采用简便的溶胶凝胶法制备了V2O5/石墨烯复合电极材料。利用SEM、XRD、Raman和TGA表征了样品的微观结构,以V2O5/石墨烯复合材料和Li4Ti5O12分别作为正极和负极组装了V2O5/石墨烯 // Li4Ti5O12全电池。结果表明,该复合电极材料是含有0.55%（质量分数）石墨烯的片状正交相V2O5。电化学测试表明,与未复合石墨烯的纯V2O5样品相比,V2O5/石墨烯复合材料具有更高的储锂活性和优异的大电流放电性能。在200 mA/g的电流密度下,V2O5/石墨烯复合材料和纯V2O5样品的放电比容量分别为283 mAh/g和253 mAh/g;当电流密度增加到5 A/g时,V2O5/石墨烯复合材料依然保持有150 mAh/g的放电比容量,而纯V2O5样品的放电比容量仅为114 mAh/g;V2O5/石墨烯和纯V2O5电极的电荷传递电阻分别为142 Ω和293 Ω。V2O5/石墨烯 // Li4Ti5O12全电池测试结果表明,在1.0 ~2.5 V电压范围内,循环初期全电池正极材料的放电比容量从110 mAh/g衰减到96 mAh/g,随后又出现上升,循环100次后正极材料的放电比容量稳定在102 mAh/g,库伦效率接近100%,这表明该V2O5/石墨烯复合电极材料是一种非常有应用前景的锂离子电池电极活性材料。     

球磨法制备SnO_2/石墨复合材料及其电化学性能

利用球磨法制备了氧化锡（SnO2）/石墨复合材料,采用场发射扫面电镜、X射线衍射和比表面积对样品进行表征,结果显示,SnO2颗粒包裹在石墨片层上,SnO2/石墨复合材料的比表面积为83.90 m2/g。电化学测试结果表明,球磨法制备的SnO2/石墨复合材料首次放、充电容量分别为1 749mA h/g和1 346 mA h/g,在50 mA/g,100 mA/g和500 mA/g电流密度下,循环40次后,该电极可逆放电容量仍然高达432 mA h/g。     

基于表面改性纳米硅复合负极材料的制备及其性能EI北大核心CSCD

基于简单易操作的湿法包覆制备了以纳米硅粉体和石墨(G)为主要原料,添加表面活性剂脂肪醇聚氧乙烯醚和石墨烯(GR)的Si/C@GR/G复合材料。研究了不同组分配比对复合材料的成分、形貌及电化学性能的影响。结果表明:制得的复合材料具有良好的循环稳定性,体积膨胀得到缓解。当复合材料中硅质量分数为10%,首次放电比容量约为730 mA·h/g,在电流密度为100 mA/g经100次循环后,其放电比容量稳定维持在500 mA·h/g左右,也展现了良好的倍率性能,首次Coulombic效率达到87.27%,相比纯硅不足70%的效率有了大幅度提高。     

SnO_2纳米球的制备及其电化学性能

以Na_2SnO_3·4H_2O为原料,CO(NH_2)_2为沉淀剂,采用水热法制备了SnO_2纳米球。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面积测试仪(BET)及电化学测试仪测试材料的结构、形貌、比表面积及电化学性能。结果表明,所制备的纳米SnO_2材料具有规整的球体形貌,颗粒分散均匀,半径约为400nm,呈典型的金红石相结构。在电压为0.01~3V、电流密度200mA/g的条件下进行充放电测试,首次放电比容量为2206.6mA·h/g,50次循环后,放电比容量保持在440mA·h/g,具有较好的循环性能。     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

The System Si3N4-SiO2-Y2O3

Subsolidus phase relations were established in the system Si₃N₄-SiO₂-Y₂O₃. Four ternary compounds were confirmed, with compositions of Y₄Si₂O₇N₂, Y₂Si₃O₃N₄, YSiO₂N, and Y₁₀(SiO₄)₆N₂. The eutectic in the triangle Si₃N₄-Y₂Si₂O₇-Y₁₀(SiO₄)₆N₂ melts at 1500°C and that in the triangle Si₂N₂O-SiO₂-Y₂Si₂O₇ at 1550°C. The eutectic temperature of the Si₃N₄-Y₂Si₂O₇ join was ∼ 1520°C.     

Phase Relations in the Pseudobinary System Na2TiSi4O11-Na2Ti2Si2O9

The quenching technique was used to study subliquidus and subsolidus phase relations in the pseudobinary system Na₂ Ti₂Si₂ O₁₁-Na₂ Ti₂ Si₂ O₉. Both narsarukite (Na₂TiSi₄O₁₁) and lorenzenite (Na₂Ti₂Si₂O₉) melt incongruently. Narsarsukite melts at 911°±°C to SiO₂+liquid, with the liquidus at 1016°C. Lorenzenite melts at 910°±5°C to Na₂ Ti₆ O₁₃+liquid; Na₂ Ti₆ O₁₃ reacts with liquid to form TiO₂ and is thus consumed by 985°±5°C. The liquidus occurs at 1252°C.