In situ multi‐axial loading frame to probe elastomers using X‐ray scattering

An in situ tensile–shear loading device has been designed to study elastomer crystallization using synchrotron X‐ray scattering at the Synchrotron Soleil on the DiffAbs beamline. Elastomer tape specimens of thickness 2 mm can be elongated by up to 500% in the longitudinal direction and sheared by up to 200% in the transverse direction. The device is fully automated and plugged into the TANGO control system of the beamline allowing synchronization between acquisition and loading sequences. Experimental results revealing the evolution of crystallization peaks under load are presented for several tension/shear loading sequences.     

Cu functionalized nano crystalline ZSM-5 as efficient catalyst for selective oxidation of toluene

Nano crystalline ZSM-5 (NZ) functionalized with Cu has been explored for the selective oxidation of toluene to benzoic acid for the first time, where a comparison is made with the traditional microcrystalline ZSM-5 (MZ) based catalyst having similar framework Si/Al ratios at organic solvent-less reaction conditions in presence of H₂O₂ as a green oxidant. The ZSM-5 catalysts exhibited oxidation property even in the absence of any Cu species, but with low toluene conversions and benzoic acid yields. Functionalization with Cu greatly enhanced the benzoic acid formation, especially on NZ loaded with 0.4 wt% of Cu (Cu-NZ) to produce 92 wt% of benzoic acid, by virtue of the presence of highly dispersed nano particles of CuO along with Cu⁺² ions on the high surface area, mesopore possessing NZ support, revealed from XRD, N₂ adsorption-desorption, XPS, SEM, TEM, FITR, TPR and TPD analysis.     

Dynamic response of glass panels subjected to shock loading

A controlled study has been performed to understand fracture and damage in glass panels subjected to air blast. A shock tube apparatus has been utilized to obtain the controlled blast loading. Five different panels, namely plain glass, sandwiched glass, wired glass, tempered glass and sandwiched glass with film on both the faces are used in the experiments. Fully clamped boundary conditions are applied to replicate the actual loading conditions in windows. Real-time measurements of the pressure pulses affecting the panels are recorded. A post-mortem study of the specimens was also performed to evaluate the effectiveness of the materials to withstand these shock loads. The real time full-field in-plane strain and out-of-plane deformation data on the back face of the glass panel is obtained using 3D Digital Image Correlation (DIC) technique. The experimental results show that the sandwich glass with two layers of glass joined with a polyvinyl butyral (PVB) interlayer and protective film on both the front and back faces maintains structural integrity and outperforms the other four types of glass tested.     

Application of split Hopkinson tension bar technique to the study of dynamic fracture properties of materials

A novel approach is proposed in determining dynamic fracture toughness(DFT) of high strength steel,using the split Hopkinson tension bar(SHTB) apparatus,combined with a hybrid experimental-numerical method.The center-cracked tension specimen is connected between the bars with a specially designed fixture device.The fracture initiation time is measured by the strain gage method,and dynamic stress intensity factors(DSIF) are obtained with the aid of 3D finite element analysis(FEA).In this approach,the dimensions of the specimen are not restricted by the connection strength or the stress-state equilibrium conditions,and hence plane strain state can be attained conveniently at the crack tip.Through comparison between the obtained results and those in open publication,it is concluded that the experimental data are valid,and the method proposed here is reliable.The validity of the obtained DFT is checked with the ASTM criteria,and fracture surfaces are examined at the end of paper.     

Li含量对Li/MgO丙烷氧化脱氢制烯烃反应催化性能的影响

采用浸渍法制备了不同Li含量的Li/MgO催化剂,并通过TG-DTA、N_2吸附及XRD等手段对其进行了表征;对丙烷在Li/MgO催化剂表面的两种吸附状态所占据的空间体积大小进行了计算,研究了Li含量对其丙烷氧化脱氢制烯烃反应催化性能的影响。结果表明,随着Li/MgO催化剂中Li含量的增加,丙烷转化率与乙烯、甲烷、乙烷和COx的选择性均先增加,在Li物质的量分数为3%时达到最高,然后随Li含量增加而降低,而丙烯选择性则出现相反的变化趋势。丙烷在Li/MgO催化剂上的吸附和反应同时受动力学和热力学两个因素的制约;Li负载量不同,反应活性位Li+O-分散状态也不同,导致产物分布发生变化。活性位分散度高时受热力学因素影响,有利于生成丙烯;活性位分散度低时受吸附动力学影响,更趋向于生成乙烯等其他产物。     

Using developed creep constitutive model for optimum design of HDPE pipes

Unlike metal pipes, high density polyethylene (HDPE) pipes are not susceptible to erosion and corrosion. However, the most important mechanical feature of the HDPE pipes is that this material creeps even at room temperature. Therefore, it is essential to study the creep behavior of this material in order to develop a model. In this paper, creep behavior of HDPE at different temperature and stress levels has been experimentally studied to obtain the creep constitutive parameters of the material. These parameters are used to predict the creep behavior of different structures such as HDPE pipes. For this purpose, a number of specimens have been machined from industrial manufactured pipe walls. Uniaxial creep tests have been carried out and creep strain curves with time for each test were recorded. Then, a constitutive model is proposed for HDPE based on the experimental data and optimization methods. The results of this model have been compared with the test data and good agreement is observed. The developed constitutive model and reference stress method (RSM) were used to produce graphs which provide optimum creep lifetime and design conditions for HDPE pipes that are subjected to combined internal pressure and rotation. These graphs can facilitate the design process of HDPE pipes.     

水热合成一锅法制备FePO4-SBA-15及其水热稳定性能

通过两种水热处理方式,即800 oC水汽条件和100 oC沸水处理,考察了一锅法制备的FePO4–SBA-15(OP)的水热稳定性.水热处理前后样品的结构变化通过小角X射线衍射和N2物理吸附表征.研究发现,经水热条件下原位生成FePO4修饰后的OP样品具有良好的水热稳定性,并且FePO4的担载量(5%和40%)对OP样品的水热稳定性几乎没有影响.这与文献报道的金属担载量会影响介孔材料水热稳定性的结果不同.此外,还对比研究了浸渍法制备的FePO4/SBA-15(IMP)和商品SBA-15的水热稳定性.结果表明,各样品水热稳定性由强到弱的顺序是OP>IMP>>SBA-15. OP和IMP样品水热稳定性优于纯硅分子筛SBA-15的原因可能是FePO4保护层能抑制介孔材料在水热环境下的结构塌陷. OP样品水热稳定性较IMP样品好的原因可能主要是由于OP样品中存在稳定的Si–O–Fe键和较多的微孔.     

Correlation between Dispersion Stability of Concentrated Ceramic Suspension and Capillary Suction Time

Dispersion stability of highly concentrated ceramic suspensions using different dispersants required for colloidal processing can be assessed by measuring capillary suction time (CST). A systematic evaluation of dispersibility characteristics of colloidal alumina suspension is reported in the presence of three commonly used dispersants, namely, Dispex N 100, Darvan C, and Aluminon by employing the CST technique. The correlation between dispersibility of ceramic suspension and capillary suction time has been established. It has been found that higher the CST value of a suspension, the greater is the stability of the suspension and viceversa. In this investigation, this technique is employed both to choose suitable dispersant and to characterize the suspension. It has been concluded that higher the dispersion ratio (DR) of a suspension above unity the better is the stability and the lower the DR value below unity, the better is the aggregation tendency of the suspension. Quantitative estimation of dispersibility of an aqueous suspension is reported in terms of dispersion ratio. The CST technique has been found to be very useful and suitable for obtaining information for assessing stability of ceramic suspensions and characterizing concentrated ceramic slurry.     

WO3对MnOx/TiO2低温脱硝SCR催化剂的改性研究

以醋酸锰为前驱物通过浸渍法制备了MnO_x/TiO₂催化剂,用WO₃对载体进行改性制得一系列MnO_x-WO₃/ TiO₂催化剂,采用X射线衍射（XRD）、比表面积测定(BET)、拉曼光谱(LRS)、原位红外(FT-IR)光谱等表征技术进行相关的微观表征分析,同时在模拟氨气选择性催化还原NO_x（NH₃-SCR）的反应条件下对催化剂的脱硝反应活性进行了考察。研究表明,添加5%的WO₃拓展了载体的比表面积,提高了催化剂的抗热性,增加了催化剂表面的Brnsted酸位,拓宽其选择性催化还原脱硝活性温度窗口,对MnO_x/TiO₂催化剂有很好的改性作用;先钨后锰的负载顺序优于先锰后钨;随着温度的升高,化学催化反应速率提高,催化剂表面NH₃吸附峰呈减弱或消失趋势,故催化剂脱硝活性温度曲线呈中间高、两头低。