Cd-ZSM-5沸石催化剂的制备、表征和芳构化催化性能

采用离子交换、浸渍和混合三种方法制备镉改性ZSM-5沸石催化剂,考察了改性方法和镉含量对催化剂的表面酸性和Cd状态以及芳构化性能的影响。结果表明,加入镉降低了B酸性,Cd~(2+)与沸石结合形成了L_(1612)酸中心,其生成量取决于改性方法和Cd含量,并与芳构化活性提高有直接关系。     

SHS/PHIP制备TiC-Al2O3/Fe复合材料的性能

对 SHS/ PHIP技术制备出的 Ti C- Al2 O3/ Fe复合材料的性能进行了测试和分析。结果表明 ,Ti C- Al2 O3/Fe复合材料具有良好的综合力学性能。材料具有很高的比刚度。金属 Fe相的加入 ,较大地提高了材料的抗弯强度和断裂韧性。 Ti C- Al2 O3复相陶瓷为典型的脆性断裂 ;随着 Fe含量的增加 ,材料具有明显韧性断裂的特征     

Composition dependence of structural and optical properties of Ba(Zrx,Ti1-x)O3 thin films grown on MgO substrates by pulsed laser deposition

Ba(Zr_x,Ti_1-x)O₃ (BZT) films with Zr concentration ranging from 0 to 40% were grown on MgO single crystal substrates by pulsed laser deposition, and their optical properties in the visible range were systematically characterized. A linear increase in the out-of-plane lattice constant of BZT unit cell with increasing Zr content was detected by X-ray diffraction. The surface morphology was observed by atomic force microscopy and the grain size was shown to increase with Zr concentration. Prism coupling and UV-visible transmission spectroscopy techniques were used to analyze the optical properties of the films. Refractive index between 2.15 and 2.3 was observed at 633 and 1547 nm respectively, which decreased with rising Zr content. The BZT films also possessed large optical band gap energy up to 3.92 eV, which increased with rising Zr content. Quadratic electro-optic effect was observed with electro-optic coefficients between 0.11 and 0.81 × 10^− 18 m²/V², which decreased with Zr concentration. Optical loss was estimated from scattering and absorption, and the absorption coefficient dropped with increasing Zr content at near band gap. The obtained results provide information for the design of BZT thin film-based optical devices.     

微量Zr对Al-5.8Cu-0.3Mn合金焊接接头组织与性能的影响

采用4047焊丝对Al-5．8Cu-0．3Mn铝合金进行熔化极惰性气体保护焊，利用金相显微镜、透射电镜、显微硬度等检测分析手段研究了Zr对Al-5．8Cu-0．3Mn母材及焊接接头的力学性能和显微组织的影响。结果表明，Al-5．8Cu-0．3Mn合金中添加适量Zr元素可使母材强度提高30MPa，焊接接头强度提高50MPa，同时，细化了母材的再结晶组织和焊缝组织。焊接接头的强度低于母材强度，焊缝区是合金的薄弱处，热影响区强度降低是θ‘相粒子受热粗化所致。     

织物树脂层压复合材料抗弹性能研究

针对防弹织物树脂层压复合材料的研制，考察了层压复合材料面密度，纤维类型，树脂体系，铺层混杂方式及纤维混杂分数，织物铺层，预置分层等因素对层压复合材料靶板弹道冲击性能的影响。     

加卸载条件下原煤渗透率与有效应力的规律

为研究采动过程中有效应力的变化对渗透率的动态演化的影响,基于自行研制的"含瓦斯煤热流固耦合三轴伺服渗流实验装置",进行了单调加载和不同初始应力状态加卸载条件下原煤渗流特性的试验研究。考虑瓦斯力学作用和瓦斯吸附作用两个方面对有效应力系数的影响,得到了加卸载条件下原煤的有效应力计算公式及渗透率与有效应力关系的公式,根据初始孔隙率、吸附常数等试验数据和不同条件下渗流试验数据对建立的渗透率与有效应力表达式进行验证。研究结果表明,理论计算值和试验结果吻合度比较高,单调加载与加卸载条件下原煤的渗透率随着有效应力的增加呈负指数关系下降。     

Effects of cold metal transfer mode on the reaction layer of wire and arc additive-manufactured Ti-6Al-4V/Al-6.25Cu dissimilar alloys

Components of Ti and Al dissimilar alloys were obtained by wire and arc additive manufacturing using two cold metal transfer (CMT) modes.Direct current CMT (DC-CMT) mode was used for Ti alloy deposition,and DC-CMT or CMT plus pulse (CMT + P) mode was used for the Al alloy deposition.During deposition of the first Al alloy layer,little and a significant amount of Ti alloy were melted using DC-CMT and CMT +P mode,respectively.TiAl3 formed in the reaction layer when DC-CMT mode was used,while TiAl3,TiAl,and Ti3Al formed in the reaction layer when CMT + P mode was used.Compared to using DC-CMT mode,more cracks occurred when using CMT + P.The nanohardness of the reaction layer was between that of the Al and Ti alloys,irrespective of the CMT modes.The average tensile strengths of the samples us ingDC-CMT and CMT + P mode were 108 MPa and 24 MPa,respectively.DC-CMT mode was more suitable for the wire and arc additive manufacturing of Ti/Al dissimilar alloys.     

Mechanical behavior of C/SiC T-section under pulling load

For the C/SiC T-section structures, fabrication defects such as pores and local delaminations can be easily formed in the intersection zone which significantly affect the load bearing capacity. In this work, the mechanical behavior of C/SiC T-section under pulling load was investigated, and especially the delamination behavior was studied by introducing the cohesive zone model into the finite element modeling. It was found that for C/SiC T-section under pulling load, the maximum critical delamination load was about 1075 N in the present work, and the interface delamination was the main failure mode. It was verified that the effective interfacial strength influenced the critical delamination load, and the strain energy release affected the delamination behavior of the T-section specimen. The failure mechanisms of C/SiC T-section under pulling load depend on the interface bonding states. When the interface is well bonded, the failure mechanisms mainly include matrix stripping, matrix fracture and fiber breakage. Otherwise, only the matrix stripping can be found at the interface of the C/SiC T-section specimen.     

Revisiting the procedure for characterising mechanical properties in welded joints through nanoindentation

Owing to the microstructural inhomogeneities and residual stresses that are generated during welding, welded joints are the weakest parts of structures. Nanoindentation, a non-destructive technique, is commonly used to analyse the local mechanical properties and residual stresses in welded joints. However, the pile-up effect is often neglected during the nanoindentation procedure, which results in inaccurate measurements. In this study, an alternative procedure, based on a previous study, was used to measure the local mechanical properties and residual stresses in metal inert gas (MIG) welded joints. Moreover, a new equation is proposed for estimating the residual stresses.