几种间苯二酚甲醛粘合剂的应用比较

间苯二酚甲醛树脂是橡胶轮胎工业常用的钢丝帘线和聚酯帘线与橡胶之间的粘合剂,间苯二酚甲醛粘合剂树脂完全可以替代间苯二酚单体。本文选取了国外知名品牌的进口树脂和两个国内品牌的树脂,在实验室进行了树脂的化学组成、胶料性能以及和钢丝的粘合力等研究。结果表明,虽然国产树脂的化学成分与进口树脂不完全一样,但是基本上,可以满足粘合的要求,代替进口产品。     

不同硅烷偶联剂对填充胶料硫化反应的影响

研究了硅烷偶联剂对白炭黑填充胶料的硫化反应的影响,探讨了硅烷偶联剂种类和用量对胶料性能的影响。结果表明,在使用白炭黑的SBR胶料配方中加入硅烷偶联剂,可以促进胶料的硫化反应,缩短硫化时间,提高生产效率。在本文所采用的硅烷偶联剂中,Si69对胶料的硫化反应具有最大的促进作用,并促进胶料和填料之间形成了最强的相互作用。     

自蔓延高温技术制备ZrC粉体(英文)

采用自蔓延高温合成(self-propagating high-temperature synthesis,SHS)技术,以 Zr+C 为反应体系合成了 ZrC 粉末。研究了实验参数对 SHS过程中点火电流、燃烧温度的影响。采用了 3 种碳源,研究了其对最终产物形貌及化学组成的影响。通过添加不同含量的 NaCl 作为 SHS 稀释剂,控制产物粒径及形貌。结果表明:炭黑是高温自蔓延法制备 ZrC 粉体的最佳碳源。由该体系制备的 ZrC 粉末粒径在 0.5～1 μm之间,氧含量为 0.38%。随稀释剂 NaCl 含量增加,体系燃烧温度降低,产物粒径减小。当 NaCl 含量为 30% (质量分数)时,体系燃烧温度下降至 1 810 K,产物 ZrC 粉末的粒径减小至 50 nm。     

Influence of tool plunge depth and welding distance on friction stir lap welding of AA5454-O aluminum alloy plates with different thicknesses

AA5454-O aluminum alloy plates with thicknesses of 1.4 and 1.0 mm were friction-stir-lap-welded (FSLWed).The influences of the tool plunge depth and welding distance on surface appearance,macrostructure and mechanical properties of the FSLWed plates were experimentally investigated.The tensile shear load of the FSLWed plates was compared with that of the adhesive-bonded plates.Defect-free FSLWed zones were successfully obtained in all the tool plunge depths and the welding distances.The FSLWed zones exhibited the relatively smooth surface morphologies.Under all the FSLWed conditions,the FSLWed zone exhibited higher average hardness than the base metal.In addition,the upper plate exhibited a higher average hardness than the lower plate,although there was no special tendency in spite of the change in the tool plunge depth and the welding distance.The maximum tensile shear load of the FSLWed plates was much higher than that of the adhesive-bonded aluminum alloy plate.Especially,under the FSLW condition of the plunge depth of 1.8 mm and the welding distance of 40 mm,the tensile shear load of the FSLWed plate reached a level about 41% greater than that of the adhesive-bonded aluminum alloy plate.In addition,the maximum tensile shear load of the FSLWed plate was increased with the increase of the welding distance.     

Thermal stability and mechanical properties of thick thermal barrier coatings with vertical type cracks

The thermal stability and failure mechanism of thick thermal barrier coatings (TBCs) with and without vertical type cracks were investigated through the cyclic thermal exposure and thermal-shock tests. The TBC systems with thickness of about 2000 µm in the top coat were prepared by an air plasma spray (APS) on the bond coat of about 150 µm in thickness prepared by APS. The adhesive strength values of the as-prepared TBCs with and without vertical type cracks were determined to be 24.7 and 11.0 MPa, respectively, indicating the better interface stability in the TBC with vertical type cracks. The TBC with vertical type cracks shows a better thermal durability than that without vertical type cracks in the thermal cyclic exposure and thermal-shock tests. The hardness values of the as-prepared TBCs with and without vertical type cracks were found to be 6.6 and 5.3 GPa, respectively, which were increased to 9.5 and 5.5 GPa, respectively, after the cyclic thermal exposure tests. These results indicate that the vertical type cracks developed in the top coat are important in improving the lifetime performance of thick TBC in high temperature environment.     

Effect of sintering temperature on structure,magnetic and magnetocaloric properties of La0.6Ca0.4MnO3 manganite

The effect of sintering temperature on the structure, magnetic transition and magnetic entropy of La_0.6Ca_0.4MnO₃ manganite was studied. It was observed that this compound belongs to the orthorhombic structure with the Pnma space group without any impurity phase. The effect of sintering temperature on the Curie temperature (T_C) was studied. The small increment in T_C is found with increasing the sintering temperature. The magnetocaloric study exposes a quite large change of the magnetic entropy, which varies with sintering temperature. For an applied magnetic field of 3 T and sintering temperature of 1300 °C, the relative cooling power (RCP) is 89 J/kg. As a result, the studied compound can be considered as potential material for magnetic refrigeration near and below room temperature.     

Competition Growth of α and β Phases in Ti-50 at.%Al Peritectic Alloy during the Rapid Solidification by Laser Melting Technique

Rapid solidification of Ti-50 at.%Al peritectic alloy is realized by laser melting technique at diferent conditions of laser power and scanning speed.The temperature field and the cooling rate under the corresponding conditions are derived from the finite element simulation.Comparing the measured pool size with the simulated result,the laser absorptivity of Ti-50 at.%Al peritectic alloy at diferent conditions can be deduced to establish the relationships between the laser absorptivity,the laser power and the scanning speed.The morphology evolution and the phase selection of Ti-50 at.%Al peritectic alloy are described by the temperature gradient and the cooling rate.With the increase of temperature gradient and cooling rate,βphase replacesαphase to become the leading growth phase.And the growth ofαphase experiences the transition from facet to non-facet manner,whileβphase is refined.To understand the underlying mechanism of the competition growth can bring benefit to the industrial application of Ti-Al alloy.     

制备方法对ZK60变形镁合金组织与变形能力的影响(英文)

通过微观组织和固有内在缺陷观察,研究了加工方法对ZK60A变形镁合金加工性能的影响。利用半连续铸造、半连续铸造后挤压及模具铸造方法制备了3种合金,并在2种变形速率下进行高温压缩,研究合金的变形能力。利用EBSD和TEM研究了合金的晶粒结构,采用X射线扫描仪检测了合金的内部缺陷。与传统模具铸造合金相比,半连续铸造合金具有更好的变形能力,且后续的挤压工艺可以提高合金的变形能力。     

高温、中应变速率下预测四道次连续轧制力的流变应力方程(英文)

为了计算在应变速率100～400s-1、温度900～1050℃条件下四道次连续线材轧制过程中的轧制力,提出了一个流变应力方程。基本概念是对Shida模型和Misaka模型进行改进。通常用这2种模型建立的流变应力本构方程来描述高温材料在不同应变率下的变形行为。将改进模型与有限元方法相结合来计算应变速率100～400s-1、温度900～1050℃条件下的四道次连续轧制过程中的轧制力。测量材料在每个道次的轧制力和表面温度,并与预测值进行比较。结果表明,在高温、中应变速率条件下,Misaka模型比Shida模型更好。在900℃时,采用Misaka模型的轧制力误差为-5.7%。在1050℃时,采用Misaka模型的轧制力误差为-15.2%,而采用改进的Misaka模型的轧制力误差降低到1.8%。由此可以得出,对于高温、中应变速率的线材轧制过程,改进的Misaka模型能用来预测高温材料的变形行为。     

Post‐thinning using Ar ion‐milling system for transmission electron microscopy specimens prepared by focused ion beam system

We investigate Ar ion‐milling rates and Ga‐ion induced damage on sample surfaces of Si and GaAs single crystals prepared by focused ion beam (FIB) method for transmission electron microscopy observation. The convergent beam electron diffraction technique with Bloch simulation is used to measure the thickness of the Ar‐ion milled samples to calculate the milling rates of Si and GaAs single crystals. The measurement shows that an amorphous layer is formed on the sample surface and can be removed by further Ar‐ion milling. In addition, the local symmetry breaking induced by FIB is investigated using quantitative symmetry measurement. The FIBed‐GaAs sample shows local symmetry breaking after FIB milling, although the FIBed‐Si sample has no considerable symmetry breaking.