竹原纤维和亚麻纤维鉴别分析方法研究

竹原纤维和亚麻纤维理化性质极其相似，常规方法中难以找到合适的鉴别方法，文章采用纤维投影法、密度法、溶解法、傅立叶红外法等多种方法分析研究，根据亚麻和竹原纤维分子结构中-CH、-CH2、-CH3个数（聚合度）的差异，利用红外光谱仪测其光谱图，发现在2900cm^-1和2850cm^-1处存在较为明显的差异，经多次测量完成竹原纤维的标准红外光谱图，利用此光谱图可以定性鉴别亚麻和竹原纤维。     

Manganese oxide embedded graphene nanohybrid for pH-universal electrochemical overall water splitting

Efficient non-noble metal bifunctional electrocatalysts for overall water splitting in pH universal is highly desired in application. Herein, MnO₂/graphene composition are applied as efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in pH-universal electrolytes with the help of plasma dc arc method. The couple of MnO₂ and graphene highly benefits to the H₂O, H⁺ and OH⁻ absorption respectively. The defects and stable Mn³⁺ contribute to the transfer of electron and charge. The low overpotentials and small Tafel slopes reveal attractive activities of HER and OER. The good electrocatalytic performances are attributed to the synergistic effect and abundant heterogeneous interfaces in MnO₂/graphene. These can offer rich electroactive sites and accelerate electron transfer. Thus, it may provide facile route for developing nonprecious electrocatalysts of water splitting.     

EGR对生物柴油颗粒物氧化活性及微观结构的影响

为研究废气再循环(EGR)及燃用调合生物柴油(B0,B20)对柴油机排放颗粒物(PM)氧化活性与微观结构的影响,通过一台4缸共轨柴油机进行试验,并采集燃烧颗粒物,使用热重分析仪(TGA)、高倍透射电镜(HRTEM)和拉曼光谱(RS)对颗粒物进行研究.结果表明:燃用同种燃料时,随着EGR率增加,颗粒中干碳烟含量增加,起始氧化温度T_i上升,表观氧化活化能E逐渐增强,氧化活性降低;相比B0颗粒,B20颗粒中干碳烟含量略有减少,起始氧化温度T_i略有下降,E减弱,氧化活性增加.随着EGR率增加,颗粒物核-壳结构更为明显,当EGR率从0增至25%时,B0和B20颗粒初级碳粒子的平均微晶尺寸分别增加20%和25%,平均微晶曲率分别降低10%和7%,平均碳层间距分别降低5.8%和6.0%.同时,B0和B20颗粒的I_G/I_D增加,石墨化程度提高.     

超疏水材料应用于文物表面封护研究进展EI北大核心CSCD

文物是人类宝贵的历史文化遗产,具有非常丰富的文化内涵,但在水汽、微生物等因素作用下受损严重,对文物保护就显得极为重要。仿生超疏水材料具有优异的疏水性及自清洁性能,可以有效防止水汽、微生物等对于文物的侵害,开始应用于文物保护。综述超疏水材料在文物保护领域的研究进展。介绍我国文物保护的基本原则及面临的问题,并且对超疏水表面的润湿机理进行阐述,归纳总结当前超疏水材料在不同类型文物保护方面的应用实例及存在的问题。最后分析影响涂层透光性、耐久性的关键技术问题,提出超疏水封护材料的发展前景,填补了超疏水材料应用于文物保护领域的综述空白。     

液罐车流-固耦合分析及优化设计

在液罐车转向的过程中,罐体内液体的晃动会对液罐车产生侧向冲击力和侧倾力矩。以非满载液罐体为研究对象,采用流体体积法(Volume of fluid,VOF)对转向工况下的液体晃动进行数值分析,获得了侧向加速度和充液比对液晃的影响规律。建立液罐车侧向动力学模型,仿真结果表明,充液比为50%~70%时液罐车侧翻阈值较小。对罐体内部结构进行优化设计,设计一种倒V型防波板装置来降低液体对罐壁冲击。研究了9种倒V型防波板在不同充液比时的减晃效果,结果表明,安装三块夹角为150°的V型防波板防晃效果最好。搭建缩比液罐车侧倾台架,利用电动液压缸举升整个钢板平面和滑台以模拟罐车侧倾状态,同时滑台带动罐体向反方向平移,实现质心位置纠正,从而减小液体侧向晃动力与侧倾力矩,提高了液罐车的侧向稳定性。     

La(Mg1/2Ti1/2)O3–La2/3TiO3 microwave dielectric ceramics

Structure and microwave dielectric properties were studied in the (1−x)La(Mg_1/2Ti_1/2)O₃–xLa_2/3TiO₃ system. Ceramics with this composition in the 0⩽x⩽0.5 range were processed from powders obtained by a citrate-based chemical route. Structure of these perovskite solid solutions changed from orthorhombic for x=0.1 and 0.3 to pseudocubic for x=0.5. Microwave and radio frequency measurements revealed increase in permittivity and temperature coefficient of the resonant frequency τ_f with increasing of La_2/3TiO₃ content. Close to zero τ_f value was found near to x=0.5 composition of (1−x)La(Mg_1/2Ti_1/2)O₃–x La_2/3TiO₃.     

Reducing the thermal expansion anisotropy in Mo5Si3 by Nb and V additions: theory and experiment

Mo₅Si₃ exhibits a high anisotropy of its coefficients of thermal expansion (CTEs) in the a and c directions, i.e., CTE(c)/CTE(a)=2.0. The high CTE anisotropy is due to the existence of prominent atom chains along the c-axis. Ternary alloying additions that effectively stretch the atom chains are likely to reduce the bonding directionality/strength and CTE anisotropy. First-principles local-density-functional calculations were carried out for two alloy systems, MoNb₄Si₃ and Mo₄VSi₃. Indeed, we find a significant reduction of the CTE ratio to a value of 1.5 for MoNb₄Si₃ and a value close to 1.0 for Mo₄VSi₃. The decrease in the CTE anisotropy mainly comes from the reduction in CTE in the c-direction. While a conventional approach to reduce the CTE would involve an increase in lattice rigidity by increasing the bond strength, our strategy focuses on the reduction of driving force for thermal expansion by decreasing the bond directionality.     

Phase equilibria among α (hcp), β (bcc) and γ (L10) phases in Ti–Al base ternary alloys

Phase equilibria between the α(A3), α₂ (D0₁₉), β(A2 or B2) and the γ(L1₀) phases in the Ti–Al base ternary systems were investigated over the temperature range 1000–1300°C. The tie lines and the phase boundaries were determined by electron probe microanalysis using multiphase alloys. It was established that almost all the elements except Zr tended to partition into the β phase rather than into the α, α₂ or the γ phase, while Zr mostly partitioned into the γ phase. At 1000°C, in the equilibrium state between the α₂ and the γ phases, V, Cr, Mo, Ta and W partitioned to the α₂ phase rather than to the γ phase, whereas Mn, Fe, Co, Ni, Cu and Zr tended to concentrate into the γ phase. The partition coefficients for the alloying elements were only slightly dependent on their concentration. Based on these data, the relative stabilizing effects of alloying elements on the α, α₂, β and γ phases are discussed.     

Influence of particle size and bed thickness on the screening process

Screening involves two processes, stratification and passage of fine particles through the apertures. The stratification produces a bottom layer of fine material. This paper deals with the influence of distribution and bed thickness on the rates of stratification and passage.The initial proportion of fine particles in the bottom layer is determined by the feed rate and the initial share of fine material. The rates of stratification and passage are determined by two rate parameters. The stratification parameter is determined here by the proportion of fine particles, the size of the particles in relation to the surrounding material, and the thickness of the upper material layer. The passage parameter for a given screen depends on the size of the particles relative to that of the apertures and the thickness of the material layer on the screen.Here, the particles of different sizes are divided into fractions. This makes possible a prediction of the grading curve of the material at any point along the screen. It is also possible to determine the influence of the feed rate and varying proportions of fine material. For a given screen, bed thickness is directly related to the feed rate.The model has been implemented in a calculation program. The calculations are in general accord with Svedala's experimental results.     

A new class of approach for hybrid inorganic/organic materials containing semiconductor ZnO

A new route has been developed to prepare ZnO of various shapes using different thiophene acids and ZnO at suitable reaction. Nanosized hybrid materials have a diversity of well-defined morphologies, such as rod-like, star-like sample and particle. The structure and morphology changes of the as-prepared product were investigated by means of transmission electron microscopy (TEM), X-ray powder diffractometry (XRD), infrared spectrum (IR). The required thiophene acids have been prepared by using organometallic synthetic route and characterized by EI, ¹H NMR and photoluminescence (PL). The ZnO nanomaterials are expected to present special optical and electrical properties, and facilitate future nanoscale device application.