浅论土钉墙支护施工在市政边坡工程中的应用

土钉墙支护设计在市政工程的山体边坡稳定及建筑工程的地下室基坑支护中得到广泛应用,适用于粉质、砂质粘土等地质情况。本文介绍了某市政道路的山体边坡稳固支护采用土钉墙施工的过程及取得的良好效果。     

Microstructure and mechanical properties of dissimilar joint between aluminum and aluminum-coated steel by cold metal transfer process

Two dissimilar materials, aluminum alloy and aluminum-coated steel, were joined by cold metal transfer process using AlSi₅ filler wire. To this end, the steel was coated with Al-Si. The steel did not melt and aluminum was melt to form the joint during the process, it was actually cold metal transfer welding-brazing. The macrostructure, microstructure, alloy element distribution, and inter-metallic compounds were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. It was found that the Al-Si coating dissolved into the weld metal. The pre-existing thin Fe-Al-Si ternary inter-metallic compounds in the interface between the Al-Si coating layer and base metal steel also partially dissolved into the weld zone, tending to reduce the thickness of inter-metallic compounds. Approximate 3 μm thick undissolved inter-metallic compound was found at the interface after welding which could guarantee sound bonding strength in dissimilar materials joining. The sample was fractured at the fusion zone near the aluminum side in the tensile test. The ultimate tensile strength was about 156 MPa, and the fracture mode is ductile failure in nature according to its morphology.     

ZSM-5的合成及其在甲醇转化方面的应用

用C_2—C_4烷基季铵盐(或碱)为有机铵阳离子合成了一系列ZSM-5型沸石分子筛,并对其有关物化性质进行了测定,结果与文献数据基本一致,其中以四丙基季铵合成者为最佳;由四丙基氢氧化铵合成的ZSM-5分子筛以不同方法改性制成的催化剂,可以使甲醇转化朝不同方向进行,分别适用于制备高辛烷值汽油、烯烃或与甲苯进行烷基化制对二甲苯等。     

磷镁改质Pentasil型沸石催化剂上甲苯乙基化反应的研究

以高硅Pentasil型沸石为基质,添加磷和镁的氧化物,再辅以其它改质手段,对沸石的酸性等表面性能进行词变,并采用程脱、能谱、红外以及烃类流动态吸附等方法进行跟踪表征,考察了影响沸石形状选择性的诸因素及反应工艺条件变化的影响。催化剂单程操作周期可达370小时,失活后的催化剂可以烧焦再生。     

Microstructures and wear resistance of high boron and low carbon ferroalloy using hybrid powder/ wire overlaying method

The high boron alloy surfacing layer was easily cracked due to its insufficient toughness by using hybrid powder/wire overlaying method. In order to explore the cracked mechanism, the microstructures and the wear resistance of the samples with different boron contents were studied. Further, phases analysis, microhardness, macrohardness and wear test were also carried out. The boron content depended microstructures were observed. The precipitation of the Fe ₂ B, Fe ₃ ( C, B) , Fe ₂₃ ( C, B) ₆ were increased with the increase of boron content. It was found that the wear resistance was independent of the macrohardness as the macrohardness increased firstly and then remained steady at ~ 62 HRC. However, the wear resistance was depended on the boron contents, and which increased with the increase of the boron contents. The abrasive loss mechanism changed from plastic deformation removal to fracture removal.