负极材料Li4Ti5O12的制备与性能研究

利用纳米二氧化钛(P25)粉为钛源,Li2CO3为锂源,采用固相法及高能球磨法制备亚微米级尖晶石Li4Ti5O12.将Li4Ti5O12与碳纳米管(CNTs)制备成复合电极作为工作电极与锂片组成电池进行电化学性能测试.通过SEM,XRD等表征材料形貌、结构及粒径分布,通过充放电测试表征其电化学性能.结果表明,在800℃合成温度及8h合成时间制备条件下可以得到小尺寸且颗粒均匀的亚微米晶体Li4Ti5O12,且合成的产物电化学性能最佳.在800℃及8h合成条件下,产物首次充放电容量分别为188.0 mAh/g和189.1 mAh/g,首次充放效率为99.4％,且具有良好的可逆性.     

Chromatographic behaviour of metal ions on tin(IV) and titanium(IV) antimonate papers

Summary The chromatographic behaviour of 49 metal ions has been studied on papers impregnated with Sn(IV) and Ti(IV) antimonates in aqueous HNO₃ and mixed solvent systems containing dimethyl sulphoxide. Numerous separations have been achieved and the Alberti equation, for Sn(IV) and Ti(IV) antimonate papers, in the modified form: –nloga K⁺=R_M + constant (a K⁺=activity of K⁺), has been verified. The effect of the concentration of impregnating reagents on these papers has been determined and compared with other papers. The effect of pH on R_f, R_i, log R_f and R_M values of metal ions has also been examined in aqueous systems.     

小分子吸附调控Ti掺杂石墨烯电子结构和磁性的密度泛函理论研究

本文采用基于密度泛函理论的第一性原理方法,研究了气体分子CO、NO、NO_2和SO_2吸附对Ti掺杂石墨烯(Ti G)电子结构和磁性的调制.研究表明:Ti G对CO、NO、NO_2和SO_2分子的吸附作用较强,各分子与Ti原子键合并形成Ti-X键(X代表C、O、N原子);各分子的吸附可导致Gas@Ti G体系电磁性质明显改变:CO分子吸附基底后,虽未能引起CO@Ti G体系电子性质改变和磁性的产生,却能够有效调控该体系的带隙宽度;不同于CO分子,NO、NO_2和SO_2分子的吸附使得半导体性的Ti G基底转变为金属特性,但各体系磁性表征不同:NO@Ti G发生完全自旋极化,即NO分子与基底上均有自旋分布,且二者的自旋方向相同;顺磁性的NO_2分子吸附于Ti G基底时磁性消失;SO_2分子吸附于Ti G基底后自身产生磁性,但基底几乎未发生自旋极化,SO_2@Ti G呈现自旋极化的局域分布特征.由此,依据分子吸附后体系电磁性质特征的不同,可辨识被测气体分子.此项研究结果为高灵敏度和高选择性的石墨烯基气体传感器的设计提供理论参考.     

Si基Bi3.25La0.75Ti3O12铁电薄膜的制备与特性研究

采用Sol-Gel工艺低温制备了Si基Bi3.25La0.75Ti3O12铁电薄膜.研究了退火温度对薄膜微观结构、介电特性与铁电性能的影响.500℃退火处理的Bi3.25La0.75Ti3O12薄膜未能充分晶化,晶粒细小且有非晶团聚,介电与铁电性能均较差.高于550℃退火处理的Bi3.25La0.75Ti3O12薄膜表面平整无裂纹,晶粒均匀,无焦碌石相或其他杂相,薄膜为多晶生长,具有较好的介电与铁电性能,4V电压下的漏电流密度低于2×10-8A/cm2.随退火温度升高,晶化程度的提升和晶粒尺寸的增大使薄膜的剩余极化增大而矫顽电场降低.600℃退火处理的Bi3.25La0.75Ti3O12薄膜显示了优于Bi4Ti3O12薄膜的铁电性能,其剩余极化Pr和矫顽电场Ec分别达到17.5μC/cm2和102kV/cm.     

Density functional theory study of NO2-sensing mechanisms of pure and Ti-dopedWO3 （002） surfaces

Density functional theory (DFT) calculations are employed to explore the NO₂-sensing mechanisms of pure and Ti-doped WO₃ (002) surfaces. When Ti is doped into the WO₃ surface, two substitution models are considered: substitution of Ti for W_6c and substitution of Ti for W_5c. The results reveal that substitution of Ti for 5-fold W forms a stable doping structure, and doping induces some new electronic states in the band gap, which may lead to changes in the surface properties. Four top adsorption models of NO₂ on pure and Ti-doped WO₃ (002) surfaces are investigated: adsorptions on 5-fold W (Ti), on 6-fold W, on bridging oxygen, and on plane oxygen. The most stable and likely NO₂ adsorption structures are both N-end oriented to the surface bridge oxygen O_1c site. By comparing the adsorption energy and the electronic population, it is found that Ti doping can enhance the adsorption of NO₂, which theoretically proves the experimental observation that Ti doping can greatly increase the WO₃ gas sensor sensitivity to NO₂ gas.     

Bimetallic Sulfide/Sulfur Doped T3C2Tx MXene Nanocomposites as High-performance Anode Materials for Sodium-ion Batteries

The application of transition metal dichalcogenides(TMDs) as anode materials in sodium-ion batteries (SIBs) has been hindered by low conductivity and poor cyclability. Herein, we report the synthesis of Co_xFe_1-xS₂ bimetallic sulfide/sulfur-doped Ti₃C₂ MXene nanocomposites(Co_xFe_1-xS₂@S-Ti₃C₂) by a facile co-precipitation process and thermal-sulfurization reaction. The interconnected 3D frameworks consisting of MXene nanosheets can effectively buffer the volume change and enhance the charge transfer. In particular, sulfur-doped MXene nanosheets provide rich active sites for sodium storage and restrain sulfur loss during charging/discharging processes, leading the increase of specific capacity and cycling the stability of anode materials. As a result, Co_xFe_1-xS₂@S-Ti₃C₂ anodes exhibited high capacity, high rate capability and long cycle life(399 mA·h/g at 5 A/g with an 94% capacity retention after 600 cycles).     

Interaction of common cocatalysts in Ziegler–Natta-catalyzed olefin polymerization

In this study, density functional theory (DFT) molecular modeling studies were performed to explore mechanisms underlying the interactions of cocatalysts in Ziegler–Natta olefin polymerization using a range of commercially available cocatalysts, namely, trimethylaluminum (in monomeric and dimeric form, Al₂Me₆), dimethylaluminum chloride (in monomeric and dimeric form, Al₂Me₄Cl₂), and triisobutylaluminum. In this regard, after exploring structural and electronic features of cocatalysts, by steric maps and conceptual DFT, their interaction with possible impurities in hydrocarbon solvents and monomer feeds such as NH₃, CH₃OH, H₂O, H₂S, CO₂, and O₂ was considered. Then, activation of Ti species, adsorbed on the (110) and (104) surfaces, with the assistance of cocatalysts was studied as well. In this aspect, two possible reactions were investigated: (i) formation of first vacancy on Ti center and (ii) formation of first Ti–C bond by transalkylation reaction with cocatalysts. Finally, the effect of cocatalysts on the stereospecificity of Ti center adsorbed on the (110) surface was also taken into account by DFT calculations.     

Titanium Carbide (Ti3C2Tx) MXene Ornamented with Palladium Nanoparticles for Electrochemical CO Oxidation

Titanium carbide (Ti₃C₂T_x) MXene possesses various unique physicochemical and catalytic properties. However, the electrochemical CO oxidation performance is not yet addressed experimentally. Herein, Ti₃C₂T_x (T_X=OH, O, and F) ordered and exfoliated two-dimensional nanosheets ornamented with semi-spherical palladium nanoparticles (2.5 Wt. %) with an average diameter of (10±1 nm) (denoted as Pd/Ti₃C₂T_x) is rationally designed for the electrochemical CO oxidation. The fabrication process is based on the selective chemical etching of Ti₃AlC₂ and delamination under sonication to form Ti₃C₂Tx nanosheets that are used as a substrate and reducing agent for supporting in situ growth of Pd nanoparticles via impregnation with Pd salt. Interestingly, Pd-free Ti₃C₂T_x displayed inferior CO oxidation activity, while Pd/Ti₃C₂T_x enhanced the CO oxidation activity substantially. This is attributed to the combination of outstanding physicochemical properties of Ti₃C₂T_x and the catalytic merits of Pd nanoparticles.     

钝化处理1Cr18Ni9Ti不锈钢在H2O2 水溶液中的摩擦学性能初探

为研究1Cr18Ni9Ti不锈钢钝化膜在H2O2水溶液中的摩擦学性能,对1Cr18Ni9Ti不锈钢表面进行了酸洗钝化处理,利用CS300电化学测试系统和XPS对不锈钢表面钝化膜的电化学行为、元素组成和化学状态进行了分析;用SST销-盘式摩擦磨损试验机研究了1Cr18Ni9Ti不锈钢盘与GCr15钢球摩擦副在不同浓度H2O2水溶液中配副时的摩擦学性能;用TR240形貌轮廓仪和扫描电子显微镜(SEM)观察分析了盘试样磨损处的轮廓形貌、磨痕面积和微区结构.结果表明,1Cr18Ni9Ti不锈钢经钝化工艺处理后,耐腐蚀性能显著提高,且表面形成一层富氧、富铬、贫铁的钝化膜,其主要成分是Cr2O3;钝化后的1Cr18Ni9Ti不锈钢在过氧化氢溶液中的摩擦系数较钝化前均出现不同程度的降低,耐磨性提高;钝化或未钝化的1Cr18Ni9Ti不锈钢在过氧化氢溶液中的磨损机理均表现为黏着磨损、磨粒磨损和腐蚀磨损,但在90%H2O2水溶液中,盘磨损表面的黏着作用明显减轻.     

微织构刀具正交切削Ti6Al4V的试验研究

仿生摩擦学的出现,为刀具减摩技术提出了新的研究方向,通过钛合金的正交切削试验研究了表面微织构刀具在微量润滑和无润滑剂条件下的减摩性能.结果表明：表面微沟槽在润滑剂条件下可以有效地改善刀屑之间的摩擦,降低切削力与切削温度,同时表面微沟槽还可以改善钛合金的粘结现象;在无润滑剂条件下,微沟槽依然具有一定的＂润滑＂作用.