不同取样方向AZ31B镁合金应变率效应

采用分离式Hopkinson压杆获得了冲击压缩方向与热轧态A231B镁合金板材法向分别成90°、45°及0°的动态应力一应变曲线,利用光学显微镜及透射电子显微镜对微观组织演化过程进行了分析。结果表明：应变率约为1 200 s-1,压缩方向与板面法向成90°时,孪晶的面积分数随应变量的增大逐渐增加,孪生是主要变形机制,其曲线为凹型;压缩方向与板面法向成45°及0°时,其塑性变形以位错滑移为主,曲线形状分别为近似线型和凸型;应变率约为2 800 s-1,压缩方向与板面法向成90°时,孪晶面积分数迅速增加,大多数晶粒取向发生7改变,有利于滑移,其曲线由较低应变率的凹形变为凸型。     

超支化聚合物的合成及其在涂料中应用研究进展

首先介绍了超支化聚合物(HBP)的化学性质,并与传统线性聚合物的优缺点进行比较,接着对HBP的AB2单体缩聚、自缩合乙烯基聚合、自缩合开环聚合等合成方式进行了介绍,并对将来HBP的合成发展方向进行了推测.对现有HBP合成方法和末端官能团改性对比发现,在不同涂料体系中对HBP进行相应的改性是需要解决的首要问题.功能化改性HBP可作为涂料添加剂或主要成膜物质,有效地改善了涂料的流动性,降低了涂料中有机溶剂的挥发.重点结合HBP对涂料领域研究进行了概述,并介绍了近年涌现的HBP制备新策略、新方法.通过对HBP合成方法的探讨和众多末端官能团的不同修饰进行分析、对比和总结,介绍了HBP在UV固化涂料、高固体分涂料、有机-无机杂化涂料中的应用现状.结合相关研究,分析了HBP增强涂膜性能机理.最后基于HBP在涂料领域的应用现状,对今后研究侧重点提出相关建议和展望.     

Composition and Structure of Single Cell Oil Produced by Schizochytrium limacinum SR31

Schizochytrium limacinum sp. was commercially utilized to produce single cell oil (SCO), but its detailed lipid profile remains unknown. In order to analyze the composition and structure of SCO produced by Schizochytrium limacinum SR31, the SCO extracted at stationary growth phase was separated into neutral lipids (NL), polar lipids and glycolipids by using silica gel column chromatography. The result of lipid classes in NL revealed that triacylglycerol (TAG) was the primary glyceride (93.81 %). Fatty acid (FA) analysis by gas chromatography–mass spectrometer (GC–MS) proved that palmitic acid (29.78 %) and docosahexaenoic acid (25.64 %) were the major FA. Quadrupole time of flight mass spectrometry in electrospray ionization mode coupled with ultra‐performance liquid chromatography was carried out to investigate TAG structures. More than 80 species were identified. Positional distribution of FA in TAG might contribute to further study of the FA shifts during the lipid turnover stage and nutritional evaluation of the SCO.     

三倍体毛白杨KP法蒸煮中木素结构的变化

以三倍体毛白杨为研究对象,进行了常规硫酸盐法蒸煮。采用酶-弱酸解两段法分别从原料和KP纸浆中分离出原料木素和纸浆残余木素。采用酸析法从KP蒸煮黑液中分离出溶出木素样品,经过弱酸水解得到纯木素试样。通过凝胶渗透色谱分析(GPC),对所有试样分别进行了分子质量的检测,得出各种木素样品的分子质量及其分布,分析了木素溶出过程中的分子质量的变化。通过磷谱核磁共振31P-NMR技术得出木素结构谱图,对原料木素、纸浆残余木素和黑液溶出木素结构中各官能团进行了定量分析对比,研究了木素结构在KP蒸煮过程中的变化规律。     

多聚磷酸盐在鸡腿肉中水解的~(31)P核磁共振研究

利用31P核磁共振(NMR)对添加到鸡腿肉中的焦磷酸四钠(TSPP)和三聚磷酸钠(STPP)所发生的水解进行了研究。三组新鲜鸡腿肉样品,按照200ml腌制液/kg的比例分别注入新配制的腌制液5%NaCl、5%NaCl+6%TSPP、5%NaCl+6%STPP。结果表明,TSPP和STPP在肉中均发生水解。TSPP水解成正磷酸钠,STPP水解成焦磷酸钠和正磷酸钠,生成的焦磷酸钠随即水解成正磷酸钠。STPP水解速率大于TSPP。     

AZ31镁合金无氰化学镀镍工艺的研究

研究了在AZ31镁合金表面二次浸锌后直接进行化学镀镍的工艺。分析了pH、温度、镍离子质量浓度和次磷酸钠质量浓度对镀速的影响,并测试了镀层的结合力、表面形貌、成分含量和耐蚀性。结果表明,以二次浸锌法进行预处理,无需氰化镀铜打底;在pH为7,碱式碳酸镍质量浓度25g/L,次磷酸钠质量浓度30g/L时,镀速有最大值;AZ31镁合金化学镀镍后耐蚀性明显提高,腐蚀电位从-1.52V提高到-0.55V;化学镀镍的优化参数为15g/L碱式碳酸镍,25g/L次磷酸钠,pH为6,温度82℃。     

溶质离子在镁合金微弧氧化膜形成过程中的作用

利用交流脉冲微弧氧化电源在NaF、NaCl和NaI三种电解液中对AZ31镁合金样品进行处理,采用SEM、XPD和XPS观察分析溶质离子对镁合金样品表面形貌、相组成及起弧前后微弧氧化膜层成分的变化。结果表明:微弧氧化现象只发生于NaF电解液中,起弧前样品表面的沉积膜为MgF2,起弧后膜层由MgF2和MgO两相组成;NaCl和NaI电解液中的两组样品既无微弧氧化现象发生,又未发现任何沉积膜层;微弧氧化初期阳极放电产生的金属阳离子与溶液中的阴离子形成沉积于样品表面的高阻抗膜层是微弧氧化过程进行的必要条件。     

AZ31镁合金铸坯均匀化退火

研究了一种新的均匀化退火工艺对AZ31镁合金铸坯组织转变和成分均匀化的影响,保温温度为530、540和550 ℃以及保温时间为30、60和90 min.结果表明,AZ31镁合金在固相线温度以下应尽可能提高退火温度,同时缩短退火时间可使铸坯达到较好的均匀化效果,消除大部分枝晶偏析,γ-Mg_(17)Al_(12)相在α-Mg基体上呈细小的颗粒状分布; AZ31镁合金铸锭的优化退火工艺为540 ℃保温60 min.     

Plastic deformation mechanisms ofAZ31 magnesium alloy under high strain rate compression

The twinning and slip activities of AZ31 magnesium alloy sheet at a strain rate of 1 200 s^-1 were investigated. Dynamically mechanical properties of various oriented samples were measured using Split Hopkinson Pressure Bar（SHPB）. Optical microscope observations reveal that the dominant deformation mechanism is twinning for 90° oriented sample, and is slip for 45° and 0° oriented samples. TEM analysis for samples at a strain of 0.3% shows that the main deformation mechanisms for 90°, 45° and 0° oriented sample are {1012} 〈 1011 〉 and {1011} 〈 1012 〉 twinning, basal slip and non basal slip, respectively. The main features of the true stress--true strain curves can be explained based on deformation mechanism analysis.     

Analysis on flow stress of magnesium alloys during high temperature deformation

The flow stress of magnesium alloys during hot compression at different temperatures and strain rates was studied by experiments.Materials used were AZ91D alloys in as-cast,homogeneous treatment states,AZ31 and ZK60 alloys in as-cast state. The results show that the thermal simulation curves of different alloys differ from one another at the same deforming condition.The general curves of AZ31 and AZ91D alloys have the character of dynamic recrystallization.There are increase of true stress,drastic fallin...