Preparation and toughening mechanism of Mo2NiB2-based cermets with SiC whiskers

Mo₂NiB₂ is a kind of cermet with excellent mechanical properties, stable chemical properties, and excellent corrosion resistance and is often used in wear-resistant application fields, such as injection molding machine parts, can making tools and hot copper extruding dies. The brittleness of Mo₂NiB₂-based cermets limits their wide application. Mo₂NiB₂-based cermets were prepared by the vacuum sintering method, the effect of SiC whiskers (SiCw) on the microstructure and mechanical properties of cermets was investigated, and the toughening mechanism of SiCw on cermets was further discussed. The results indicate that with increasing SiCw content, the indentation fracture toughness (K_IC), transverse fracture strength (TRS), and Vickers hardness (HV) of the cermets first increase and then decrease. The HV, TRS, and indentation fracture toughness of Mo₂NiB₂-based cermets with 0.5 wt% SiCw are 1 113 HV, 1 620 MPa, and 27.97 MPa·m^1/2, respectively, which are 16.8%, 22.7%, and 25% higher than those without SiCw. In the sliding friction tests, Mo₂NiB₂-based cermets with 0.5 wt% SiCw have the smallest friction coefficient, low wear rate, and high wear resistance. SEM observation and analysis of the crack path and fracture surface showed that the toughening mechanism is whisker bridging, crack deflection, microcrack toughening, and whisker pull-out. The results indicate that the addition of 0.5 wt% SiCw can effectively improve the mechanical properties of Mo₂NiB₂-based cermets and further expand the application space of Mo₂NiB₂-based cermets.     

浸胶帆布经向刚度影响因素分析

综合分析各方面因素对浸胶帆布经向刚度的影响。结果表明纤维材料的种类、线密度和捻度,帆布织物的材质和结构,浸胶工艺中的附胶量、温度、浸胶速度、循环风机频率、浸渍张力和柔化器,测试中的实验室外部环境、放置时间和操作方法均会对浸胶帆布的经向刚度产生影响。实际生产中可以采取相应措施来控制经向刚度的大小,以满足客户需求。     

高效煤粉锅炉负荷提升优化实践

本文对金川集团东部贫矿锅炉房高效煤粉锅炉运行中负荷不能达产达标的问题进行了调查分析,探讨提出了负荷提升优化途径,并组织实施,取得了可观的经济效益和环保效果。     

Research on Effects of Groove Shape Optimization on Cavitation and Lubricating Characteristics for Microgroove Rotary Seal

This article studies the effects of groove shape optimization on cavitation and lubricating characteristics of microgroove rotary seals (MGRS). A lubrication model considering cavitation effects for MGRS is established to obtain the variation in cavitation and lubricating characteristics with operating conditions. Furthermore, an optimization model of groove shape based on the lubrication cavitation model is developed and an optimal groove is obtained by co-designing the parameters of both groove shape structures and molded lines. The effects of optimal grooves and ordinary spiral grooves on cavitation and lubricating characteristics are compared and validation tests are carried out. Theoretical and experimental results indicate that the lubrication cavitation model based on the mass conservation boundary condition for MGRS could accurately predict the cavitation region of ordinary spiral grooves. Optimal grooves improve the pressure distribution of the groove area and restrain the generation of a cavitation region; therefore, the fluid bearing capacity and dynamic stiffness of optimal grooves are much larger than those of ordinary spiral grooves.     

The Nitrolysis Mechanism of 3,7‐Dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane

Two intermediates, 1,5‐dinitroso‐3,7‐dinitro‐1,3,5,7‐tetraazacyclooctane (DNDS) and 1‐nitroso‐3,5,7‐trinitro‐1,3,5,7‐tetraazacyclooctane (MNX), were isolated and characterized in the synthesis of 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) from the nitrolysis of 3,7‐dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane (DPT) for the first time. When the nitrolysis of DPT was slowed down, two intermediates were detected with HPLC. It was proposed that electrophilic NO₂⁺ and NO⁺ from HNO₃ and N₂O₄ might attack nitrogen atoms at positions 3 and 7 of DPT to form the cations of the intermediates, then nucleophilic H₂O attacked the bridge carbon atoms of DPT to produce the intermediates, which were oxidized to form HMX.     

离子色谱法测定硫酸根离子的不确定度评定

对离子色谱法测定烟气脱硫吸收液中的硫酸根离子浓度进行了不确定度评定。通过对标准溶液、标准工作曲线拟合、样品稀释和测定过程重复性等影响测定结果的不确定度分量进行分析,计算出测定结果的扩展不确定度,并找出影响该不确定度的主要因素。     

大黄中蒽醌类成分的药代动力学研究近况

蒽醌类成分是大黄的主要药效成分,具有广泛的药理作用。研究其药代动力学过程,对指导其临床用药具有现实意义。而药动学研究的顺利开展有赖于选取恰当的样本前处理方法,建立合适的分析方法。分类介绍了大黄中蒽醌类成分的体内分析方法,并探讨其药代动力学的影响因素。     

催化裂化装置柴油系统腐蚀原因分析

陕西延长石油延安炼油厂现有一套1.0MMTA催化裂化装置,主要处理常压渣油。在装置运行过程中,发现分馏塔柴油系统出现了较为严重的腐蚀现象,其中柴油系统工艺管线、冷却设备因腐蚀穿孔多次出现泄露情况,对装置的安全平稳运行带来了严重影响。本文主要根据装置的腐蚀情况,分析了装置产生腐蚀的主要原因,初步探讨了腐蚀产生的机理,并根据实际生产过程中的经验,提出了一些可行性的预防措施。     

煤化工废水设备沉积物清洗剂的研制

针对煤化工废水流经设备中的沉积物,研发出一种具有良好清洗能力的清洗剂。该清洗剂以水作为主要溶剂,添加适量的表面活性剂(AEO-9:1%,AES:3%,OP-10:4%)、高沸点有机溶剂(乙二醇丁醚:20%)、清洗助剂(三聚磷酸钠:3%,硅酸钠:0.5%,适量氢氧化钠)。通过性能评价实验,测得沉积物溶解度能达到约75%。初步的工业试验结果表明,该清洗剂除垢能力较强。采用在线清洗装置,经过5 h的清洗,可较彻底地去除设备中的沉积物。