Effects of laser heat treatment on the fracture morphologies of X80 pipeline steel welded joints by stress corrosion

The surfaces of X80 pipeline steel welded joints were processed with a CO2 laser, and the effects of laser heat treatment （LHT） on H2S stress corrosion in the National Association of Corrosion Engineers （NACE） solution were analyzed by a slow strain rate test. The fracture morphologies and chemical components of corrosive products before and after LHT were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively, and the mechanism of LHT on stress corrosion cracking was discussed. Results showed that the fracture for welded joints was brittle in its original state, while it was transformed to a ductile fracture after LHT. The tendencies of hydrogen-induced corrosion were reduced, and the stress corrosion sensitivity index decreased from 35.2% to 25.3%, indicating that the stress corrosion resistance of X80 pipeline steel welded joints has been improved by LHT.     

锥度量空间中四个自映射的公共不动点定理

在完备的锥度量空间中讨论了4个自映射的公共不动点定理,其存在性和唯一性得到证明。所得主要结果将锥度量空间中的公共不动点定理进行了推广。     

生态敏感性评价研究进展

生态敏感性评价不仅为分析和预测区域生态系统失衡和环境问题提供依据,而且是生态环境影响分析和城市生态系统建设调控的重要内容和环节。文章总结了生态敏感性评价的内涵,从生态敏感性评价对象、评价方法和步骤、评价体系建立的方法、评价权重确定和评价模型选择的方法等方面,阐述了当前生态敏感性评价的研究进展,分析了生态敏感性研究存在的不足,并对生态敏感性的应用前景做出了展望。     

Separation of propylene and propane with a microporous metal–organic framework via equilibrium-kinetic synergetic effect

Adsorption separation of olefin and paraffin can greatly lower the energy consumption associated with the currently utilized distillation technique but remains a great challenge. Herein, we report the efficient separation of propylene (C₃H₆) and propane (C₃H₈) in a phosphate anion-functionalized metal–organic framework (MOF) ZnAtzPO₄ by synergetic effect of equilibrium and kinetics. The material features periodically expanded and contracted apertures decorated with electronegative groups, offering eligible pore shape and pore chemistry to effectively trap C₃H₆ under moderate isosteric heat of adsorption (27.5 kJ mol⁻¹) while obstruct the diffusion of C₃H₈. It simultaneously combines excellent thermodynamic selectivity (uptake ratio of 1.71) and kinetic selectivity (~31) for C₃H₆/C₃H₈ separation, meanwhile can be easily regenerated. Breakthrough experiment for C₃H₆/C₃H₈ gas mixture was conducted and confirmed the outstanding separation capability of ZnAtzPO₄. The equilibrium and kinetics cooperative C₃H₆/C₃H₈ adsorption separation was for the first time found in anion-functionalized MOFs, and further confirmed by computational studies.     

Oxidation resistance and thermal stability of the SiC-ZrB2 composite ceramic fibers

In this study, continuous SiC-ZrB₂ composite ceramic fibers were synthesized from a novel pre-ceramic polymer of polyzirconocenecarbosilane (PZCS) via melt spinning, electron beam cross-linking, pyrolysis, and finally sintering at 1800°C under argon. The ZrB₂ particles with an average grain size of 30.7 nm were found to be uniformly dispersed in the SiC with a mean size of 59.7 nm, as calculated using the Scherrer equation. The polycrystalline fibers exhibit dense morphologies without any obvious holes or cracks. The tensile strength of the fibers was greater than 2.0 GPa, and their elastic modulus was ~380 GPa. After oxidation at 1200°C for 1 hour, the strength of the fibers did not decrease despite a small loss of elastic modulus. Compared to the advanced commercial SiC fibers of Tyranno SA, the fibers exhibited improved high-temperature creep resistance in the temperature range 1300-1500°C.     

SURFACE CARBURIZATION OF TiAl BASED ALLOY

ＳＵＲＦＡＣＥＣＡＲＢＵＲＩＺＡＴＩＯＮＯＦＴｉＡｌＢＡＳＥＤＡＬＬＯＹ￥Ｈｕａｎｇ，Ｂａｉｙｕｎ；Ｈｅ，Ｙｕｅｈｕｉ；Ｑｕ，Ｘｕａｎｈｕｉ；Ｋｏｎｇ，Ｇａｏｎｉｎｇ（ＰｏｗｄｅｒＭｅｔａｌｌｕｒｇｙＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，Ｃｅｎｔｒａｌ...     

稀土和镁对热浸镀铝液和镀层组织的影响

研究了热浸镀铝液中添加微量稀土和镁对铝液质量和镀铝层厚度的影响及镀铝层的表面和第二相的形貌。结果表明，微量稀土改善了铝液的质量和镀层的组织，而微量镁有损铝液质量和镀层组织。     

碳热法合成具有蓝光发射特性的氧化镓纳米线、纳米带和纳米片

利用碳纳米管通过碳热法合成了氧化镓纳米线、纳米带和纳米片。采用扫描电镜和透射电镜对其进行了形态和结构表征。合成的氧化镓纳米结构是单晶体。室温光致发光谱分析发现，氧化镓纳米晶在蓝光区域487nm处产生明显的发射峰。     

W18Cr4V高速钢激光相变强化层的残余应力

利用Ｘ射线衍射法对Ｗ１８Ｃｒ４Ｖ高速钢激光相变强化层的残余应力进行了测定和分析。试验结果表明，相变强化层表面的残余应力为压应力，内部为拉应力，近似按正弦函数分布。其大小和分布状态随工艺参数的变化而改变。当改变工艺参数使表面熔化时，表面为拉应力。     

EFFECTS OF TWO－STEP HEAT－TREATMENT ON MICROSTRUCTURE AND PROPERTIES OF TiAl INTERMETALLICS

ＥＦＦＥＣＴＳＯＦＴＷＯ－ＳＴＥＰＨＥＡＴ－ＴＲＥＡＴＭＥＮＴＯＮＭＩＣＲＯＳＴＲＵＣＴＵＲＥＡＮＤＰＲＯＰＥＲＴＩＥＳＯＦＴｉＡｌＩＮＴＥＲＭＥＴＡＬＬＩＣＳ￥Ｋｏｎｇ，Ｇａｏｎｉｎｇ；Ｈｕａｎｇ，Ｂａｉｙｕｎ；Ｑｕ，Ｘｕａｎｈｕｉ；Ｌｅｉ，Ｃｈａ...