Glass formation in Fe-Cr-Zr-B-Mo alloys by tuning Nb addition

Fe-based bulk metallic glasses (BMGs) with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal. The high glass forming ability (GFA) and large supercooled liquid region are therefore required for such Fe-based BMGs in either the glassy powder fabrication or the subsequent coating spraying. In order to meet these requirements, the influence of Nb content on the GFA of Fe₅₇Cr₁₀Zr₈B₁₈Mo_7−xNb_x (x=1–5, at.%) alloys was investigated, as Nb has positive roles in GFA and thermal stability of BMGs. The results indicate that a fully amorphous phase in the as-cast samples with 3 mm in diameter is obtained for both the Fe₅₇Cr₁₀Zr₈B₁₈Mo₅Nb₂ and Fe₅₇Cr₁₀Zr₈B₁₈Mo₄Nb₃ alloys. The corresponding supercooled liquid regions of the two BMGs are 78 K and 71 K, respectively. The mechanism for improving their GFA was analyzed based on the principle of metal solidification, the parameters for glass formation and thermal properties of the alloys. The compression strength and Vicker’s hardness of the two BMGs are 1,950 MPa and 1,310 HV, 2,062 MPa and 1,180 HV, respectively. The developed BMGs with high B content, good GFA, and very high hardness can be used as coating materials to the framework for spent nuclear fuels.

     

32Cr3MoVE钢的气体渗氮工艺

为提高32Cr3MoVE钢工件的硬度和耐磨性,对其渗氮工艺进行了研究.结果表明:渗氮过程中采取较低的渗氮温度及较低的氮势,可以有效控制白亮层深度及避免产生粗大的合金氮化物,但渗氮速度较慢;通过氮势门槛值控制的渗氮方法,在渗氮前期可以适当提高氮势,随着渗氮时间的增加,逐步多段地降低氮势,使实际氮势始终维持在氮势门槛值的附...     

Ti-Zr-Cu-Fe非晶合金制备及生物相容性研究

采用单辊快淬法制备了厚40μm,宽3 mm的四元Ti50Zr16Cu31Fe3非晶合金条带。使用扫描电镜(SEM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)分析了合金的组织、相结构以及热稳定性;同时将合金在模拟体液(SBF)中培养15 d,分析了合金的组织相容性,利用动态凝血时间以及溶血率分析非晶合金的血液相容性。结果表明,Ti50Zr16Cu31Fe3非晶条带具有较高的热稳定性,过冷液相区ΔTx可达80 K;在模拟体液(SBF)中浸泡15 d后,羟基磷灰石(HA)沉积在合金表面,厚度可以达到5μm,HA团絮状生长,且Ca/P值约为1.65,与人骨的Ca/P值1.67接近;溶血率低,仅为1.08%,表明合金具有良好的生物相容性。     

温度及加载速率对U-5.7%Nb合金变形行为的影响

研究了淬火和时效2种状态的U-5.7%Nb合金,从室温(20℃)~800℃温度范围的准静态拉伸性能,及合金的变形和断裂行为。结果表明,不论淬火或时效状态的U-5.7%Nb合金,当温度高于200℃后,合金在室温下表现出的二次屈服现象将完全消失,并在400℃温度附近发生脆化,在700℃温度附近表现出明显的超塑性,其中淬火态合金性能的变化尤为明显。并对准静态拉伸、Hopkinson拉伸及爆炸膨胀环3种加载速率下,时效态U-5.7%Nb合金的组织结构进行了对比分析。结果表明,以不同应变速率断裂的时效态U-5.7%Nb合金,断口中心部位的韧窝比边缘部位相对明显,Hopkinson拉伸断口的晶粒大于准静态拉伸断口的晶粒,爆炸速率断裂的合金断口有剪切断裂、边缘开裂及局部夹杂脱落的现象。     

Manufacture of Nano-Sized Particle-Reinforced Metal Matrix Composites:A Review

Compared to the micro-sized particle-reinforced metal matrix composites, the nano-sized particle-reinforced metal matrix composites possess superior strength, ductility, and wear resistance, and they also exhibit good elevated temperature properties. Therefore, the nano-sized particle-reinforced metal matrix composites are the new potential material which could be applied in many industry fields. At present, the nano-sized particle-reinforced metal matrix composites could be manufactured by many methods. Different kinds of metals, predominantly A1, Mg, and Cu, have been employed for the production of composites reinforced by nano-sized ceramic particles such as carbides, nitrides, and oxides. The main drawbacks of these synthesis methods are the agglomeration of the nano-sized particles and the poor interface between the particles and the metal matrix. This work is aimed at reviewing the ex situ and in situ manufacturing techniques. Moreover, the distinction between the two methods is discussed in some detail. It was agreed that the in situ manufacturing technique is a promising method to fabricate the nano-sized particle-reinforced metal matrix composites.     

压制参数对TATB基PBX膨胀特性的影响

对采用不同工艺参数(压力、药温)压制成型的TATB基PBX药柱进行了热循环试验。研究了压制参数对TATB基PBX药柱膨胀特性的影响,并对其影响机理进行了分析。结果表明,在药温恒定(110℃)条件下,增加压制压力,药柱轴向高度的不可逆膨胀增大,而药柱体积的不可逆膨胀却减小;压力恒定(170M Pa)时,降低药温,药柱轴向高度和整体体积的不可逆膨胀都有所减小。分析认为这是由于不同压制参数导致成型过程晶体取向度不同和晶体破碎程度不同所引起的。     

硝基苯催化加氢制苯胺的热力学分析

用基团估算法计算了硝基苯的热力学数据。对硝基苯催化加氢制苯胺进行了比较详细的热力学分析,首次建立了该反应的反应焓变、Gihbs自由能以及反应平衡常数的变化与反应温度的关系。得出该反应为自发放热反应,反应温度越高,趋于热力学平衡程度越低。     

低压化学气相沉积制备ZrC涂层：原位溴化工艺

本研究设计了一种溴化装置,用于合成并稳定控制ZrBr4蒸汽的流量。采用低压化学沉积技术,以Zr-Br2-C3H6-H2-Ar为体系,1200°C在石墨基底上制备了ZrC涂层。研究了气体组分(源气C/Zr比)对ZrC涂层微观形貌及生长机制的影响。源气C/Zr比为1.5时,涂层的沉积过程为由表面反应机制为主,ZrC涂层较为疏松。源气C/Zr比为0.5~1时,扩散动力学是涂层的主要生长机制,所制备的ZrC涂层具有致密均匀ZrC涂层,并沿(200)晶面择优取向。同时,源气C/Zr比为0.5时,制备的ZrC涂层无自由碳存在并具有近化学计量比。     

精细化工工艺学课程教学的改革与实践

围绕地方工科院校应用化学专业人才的培养目标,从教学文件建设、教学内容选择、教学方法改革及考核方式改革等四方面介绍了开展精细化工工艺学课程教学的改革与实践。文章指出：完善教学文件,有利于规范教学管理;教学内容的取舍与补充应遵循时代性、实践性和地方特色的原则;改革教学方法,以激发学生的学习兴趣,提高学生的学习能力,培养学生的科学素质和创新精神。     

聚合物共混体系中分散相在物理老化过程的尺寸变化

文章研究了退火过程对乙烯-辛烯共聚物/热塑性聚氨酯不相容共混物的相聚集现象的影响,利用扫描电子显微镜分析分散相的粒径,结果表明,随着退火温度的提高和时间的延长,分散相的粒径变大、分布变宽,聚集长大机理起关键作用。