耐高温压铸镁合金的发展及研究现状

综述了耐高温压铸镁合金的发展及研究现状.指出适用于150 ℃以上使用的压铸镁合金品种少, 而且存在着压铸工艺性能差的问题, 因此, 研究开发新型实用的耐高温压铸镁合金具有重要实际意义.     

铈对压铸镁合金AZ91组织和高温性能的影响

采用Olympus—PMG3型光学显微镜、D／Max 2500PC型X射线衍射仪(XRD)、带有EDAX—Falcon能谱仪(EDS)的JSM-5500LV型扫描电子显微镜(SEM)及AG-10TA型电子万能实验机，研究了Ce对压铸镁合金AZ91显微组织、常温性能及高温(150℃)性能的影响。结果表明：AZ91合金中加入Ce后，形成了新的Al4Ce相，使Mg17Al12(γ)相尺寸减小、数量减少、并由网状分布变得离散分布。Ce对AZ91合金常温性能的影响不大，但显著提高了高温性能。加入1．0％Ce的合金具有最好的显微组织和性能，但是Ce的加入量过高，反而使合金的性能降低。     

含锌镁合金的研究现状与应用及其LPSO相对合金性能的影响

Zn元素添加到镁合金中能提高合金的流动性、力学性能和抗蠕变性能,使得含Zn镁合金成为该领域的研究热点之一.本文系统综述了含Zn镁合金的研究现状,包括Zn元素对镁合金微观组织、拉伸力学性能和耐蚀性影响等研究成果,介绍了含Zn镁合金在变形镁合金和铸造镁合金上的应用情况.在此基础上,进一步概述了含Zn镁合金中的LPSO相提高...     

预处理对镁合金镧转化膜及耐腐蚀性能的影响

为了提高镁合金镧转化膜的耐腐蚀性能,通过容量法和电化学方法研究了预处理对镁合金AX91D镧转化膜在5%NaCl溶液中腐蚀行为的影响.利用扫描电子显微镜(SEM)和能量色散谱仪(EDS)研究了膜层表面形貌及其组成,通过电极电位的跟踪测试研究了镧转化膜的成膜过程.结果表明:预处理不改变镧转化成膜过程的基本规律,但有助于镧的氧化物沉积;提高了镁合金镧转化膜的耐腐蚀性能,浸泡30 h其耐腐蚀性能与传统的封闭的铬酸盐转化膜相当.     

AZ91D镁合金上钼改性锌系磷化膜的制备、 结构及性能

采用在磷化液中添加钼酸钠及腐蚀抑制剂的方法, 在AZ91D 镁合金表面上制备了均匀细致的锌系复合磷化膜. 用XRD对膜层的化学组成及结构进行了表征,用SEM和EDS对膜层的形貌和组分含量进行分析. 结果表明, 磷化膜主要由Zn3(PO4)2·4H2O和单质Zn组成. 在磷化液中加入钼酸钠使磷化膜组织更加细致而且无裂纹. 磷化液中的钼酸钠含量为1.5 g/L时, 磷化膜的结晶最致密, 单质锌的含量最高, 耐蚀性最好. 还提出了一种快速测量镁合金表面膜层耐蚀性的试验方法, 同时对镁合金上的磷化反应的机理进行了探讨.     

变形镁合金的研究、开发及应用

采用操作简单的基体匹配法和内标法校正基体,建立了一套完整的电感耦合等离子体质谱（ICP-MS）法检测镁合金中的铜、钴、银、铅、锑、铍、铬、铟、钇、镉、锰、钛、钽、镧、铈15种痕量元素. 检出限、加标回收、精密度的相关试验表明,各元素的检出限范围为0.003 9~1.6 μg/L,加标回收率为95.1%~109.2%,精密度为0.2%~2.3%. 方法简单、快速、高效,可满足市场上对镁合金中痕量元素的检测需求.     

AZ91镁合金表面稀土转化膜的制备及耐蚀性能研究

采用在镁合金表面形成无毒、无污染的稀土铈转化膜的方法解决AZ91镁合金表面的腐蚀问题。确定了最佳成膜工艺参数，讨论了处理液的浓度、成膜温度和成膜时间等因素对转化膜耐蚀性的影响。利用湿热实验、阳极极化曲线的测定等实验方法评价了转化膜对镁合金表面的防护作用。结果表明，在潮湿温热条件下稀土铈转化膜试样仍能保持膜层的完整性并具有较高的覆盖度，腐蚀现象不明显。腐蚀电势升高，出现钝化现象，腐蚀电流密度下降，稀土铈转化膜可以提高AZ91镁合金的耐蚀性能。用扫描电镜观察了膜的微观形貌，稀土铈转化膜是由基膜和附着的细小颗粒组成，最佳工艺形成的铈转化膜无破碎现象，对AZ91镁合金表面的腐蚀过程的发生有明显的抑制作用。     

新型脱氧核糖核酸光纤生物传感器的研制及其性能评价

研制了一种新型脱氧核糖核酸(DNA)光纤生物传感器,以带尾纤的脉冲半导体激光器为激发光源,结合流动进样系统,能够快速方便地对光纤传感器表面发生的DNA杂交反应进行测定.研究表明:通过链霉亲和素/生物素作用修饰到传感器表面的DNA探针对Dylight 680荧光标记的完全互补DNA有良好的响应,而对非互补的DNA基本没有响应.系统检测灵敏度可达到4.5×10-10 mol/L;线性范围为1×10-9～3×10-8 mol/L.光纤传感器具有良好的再生性能.     

镁合金化学转化膜的制备及其性能研究

在磷酸钠-磷酸二氢铵-高锰酸钾体系中对镁合金进行化学转化处理.研究了磷酸钠、磷酸二氢铵、高锰酸钾、温度、时间和添加剂对转化膜性能的影响.通过对转化膜结构、成分及性能的测试评价,得到了性能较好的化学转化溶液配方:Na3PO4为5g·L-1,NH4H2PO4为15 g· L-1,KMnO4为1g· L-1,添加剂(NH4)6 Mo7O24为0.5g·L-1.由SEM可观察到转化膜的表面成“干枯河床”状.XRD和EDS检测表明,膜层的主要成分是Mg,Al12 Mg17和无定形相,膜层表面主要有Mn,Mg,K,O和Al等元素组成.腐蚀实验和电化学测试表明,添加剂能够降低转化膜的腐蚀率,转化膜较基体的腐蚀电位正移了0.73 V,提高了镁合金的耐蚀性.     

Corrosion behavior of AZ91D magnesium alloy in distilled water

The corrosion of AZ91D magnesium alloy has received extensive attention due to the continuous expansion of its application field in recent years. However, the corrosion of AZ91D magnesium alloy in distilled water is relatively few. In this paper, the corrosion behavior of AZ91D magnesium alloy was studied in distilled water by electrochemical tests in combination with weight loss and surface analysis methods. The results indicated that the corrosion rate of AZ91D magnesium alloy increased with the increase of temperature and immersion time. The increase of the corrosion rate of AZ91D magnesium alloy with the increase of immersion time might be attributed to the damage of the structure of corrosion product film by hydrogen evolution, significantly accelerating the anodic process of AZ91D magnesium alloy. It was interesting that, in distilled water, the EIS of AZ91D magnesium alloy excluded an inductive arc in the low frequency region, which indicated that there was no the adsorption and desorption of aggressive ions or the damage and repair of film. The corrosion product film of AZ91D magnesium alloy in distilled water was composed of a compact inner corrosion product film and a loose outer corrosion product film.     

Surface evaluation and electrochemical behavior of cerium conversion coating modified with silane on magnesium alloy

A new cerium conversion coating modified with the hydrolysis silane is designed for AZ31 magnesium alloy, which aims at assessing the surface characterizations and electrochemical behaviors between the cerium conversion coating with and without the silane modified. The effect of the silane addictive is studied by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The adhesion of the coatings is undertaken according to the American Society for Testing and Materials (ASTM) standard D3359‐08 cross tape test. The electrochemical behavior is evacuated by polarization experiment and electrochemical impedance spectroscopy (EIS) in NaCl electrolyte. The results show that the addition of bis‐[triethoxysilylpropyl] tetrasulfide (BTESPT) to loosen and porous cerium conversion coating leads to the formation of a more compact and homogenous film, higher resistance to water uptake and better adhesion to substrate. Electrochemical measurements show that, compared with the non‐modified cerium conversion coating, the coating modified with the silane exhibits better anticorrosion properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Fabrication of tragacanth and water soluble tragacanth nanoparticles through electrospraying

This work reports the fabrication of tragacanth and water soluble tragacanth (WST) through electrospraying technique. Tragacanth is a biocompatible and biodegradable carbohydrate with a wide range of applications. Suspensions of tragacanth in water and water‐ethanol (70:30) were electrosprayed successfully. Moreover, deesterified tragacanth (WST), which is highly water soluble, was also successfully electrosprayed. The results showed that electrospraying technique is capable of producing tragacanth nanoparticles with an average size in the range of 30 to 50 nm, depending on the electrospraying conditions. Water soluble tragacanth gave rise to even smaller nanoparticles. It was also found that lowering feed rate, increasing nozzle‐ collector distance, and increasing voltage decrease the average size of the electrosprayed tragacanth nanoparticles. The molecular weight of tragacanth and WST was measured to be 610 and 301 KDa, respectively. The electrosprayed tragacanth and WST nanoparticles showed moisture regain of 50% and 75%, respectively. These values are much higher than that of their normal powder form. Fourier transform infrared proved the absence of ester groups in the WST as a result of deesterification. X‐ray diffraction studies showed an amorphous microstructure for both tragacanth and WST before electrospraying. After electrospraying, the amorphous structure of the 2 showed some orientation.     

Study of the nature of the crystallization water in some magnesium hydrates by thermal methods

The nature of the crystallization water in MgSO₄·7H₂O, Mg(NO₃)₂·6H₂O and MgCl₂·6H₂O has been studied with the nonisothermal methods of thermogravimetry (TG), derived thermogravimetry (DTG) and differential thermal analysis (DTA). Analysis of the characteristic thermogravimetric data (T _M,W _∞) and the kinetic parameters (n, E _a), together with the DTA results, with CuSO₄·5H₂O as control sample, provided evidence of the existence of coordinated water and of the nature of the anions in these hydrates. The results are confirmed by the observation of a real compensation effect. For the compensation effect, the following equation is proposed: InA=0.220E-0.8 Structures explaining the presence of the coordinated water and the nature of the anions in these hydrates are also proposed.     

Effect of internal mold release agent on flexural and inter laminar shear properties of carbon and glass fabric reinforced thermoset composites

The study is focused on thermoset composites reinforced with carbon and glass woven fabrics. Two types of thermoset resins, for example, epoxy and vinyl ester were used as the matrix. Varying concentrations of internal mold releasing (IMR) agent was used in the resin. The composites were cured both at room temperature and at 80°C. The flexural properties were studied using 3‐point bending test method. Further theinter‐laminar shear strength (ILSS) was investigated using the short beam shear strength test based on 3‐point bending. The flexural modulus of room temperature cured epoxy resin is higher than that of high temperature cured epoxy resin and cured vinyl ester resin. The flexural modulus is lowest for 1% IMR sample in epoxy system and the modulus for 0% and 2% epoxy are not significantly different. Lowest flexural strength and modulus can be observed for the combination of reinforcement and curing conditions for samples containing 1% IMR for the epoxy systems. Carbon fiber is found to be less compatible with the vinyl ester resin system and the addition of IMR to the resin degraded the properties further. Inter‐laminar shear strength for epoxy‐based composites is not much affected by presence of IMR, but in case of vinyl ester based composites there is a decrease in ILSS on addition of IMR agent. The study explains variation in flexural properties on addition of IMR and change of curing conditions. These results can be used for ascertaining variation in mechanical properties in real use.     

Synthesis of water soluble Pd-Piperidoimidazolin-2-ylidene complexes and their catalytic activities in neat water

Through the strategy of water soluble N-heterocyclic carbene (NHC) ligand, Pd-catalyzed reactions were developed in aqueous media. Therefore, four new piperidoimidazolinium salts ( 1a-d ) consisting of sulfonate ( a ), esther ( b , c ) and carboxylic acid ( d ) functionalities and their water-soluble Pd-NHC complexes ( 2a - d ) were synthesized. The new compounds were characterized by elemental analysis, FTIR, TGA, UV–vis and NMR spectroscopy. The catalytic activities of water soluble Pd-NHC complexes ( 2a - d ) were investigated using the Suzuki-Miyaura (S-M) reaction and the reduction of nitroarenes. We found that the water-soluble polar or ionic groups on piperidoimidazolin-2-ylidine had an effect on the catalytic activity. The water-soluble catalyst can be recycled efficiently and reused six times with only a very slight loss of catalytic activity.     

镁及镁合金中微量磷的测定方法研究

磷与钼酸铵形成磷钼杂多酸络幌物,用乙酸丁酯萃取分离,用SnCl2还原反萃取后借磷钼蓝光度法测定镁及镁合金中微量磷。在波长700 nm处工作曲线线性范围0~1.5μg/mL,相关系数为0.9995,络合物表观摩尔吸光系数ε=1.45×104L.mol-1.cm-1,相对标准偏差在1.40%~3.10%之间,加标回收率在99.3%~101.0%之间,本法与ICP法相对照结果比较满意。     

Monochromatized x‐ray photoelectron spectroscopy of the AM60 magnesium alloy surface after treatments in fluoride‐based Ti and Zr solutions

The behaviour of the 6% aluminium–magnesium alloy (AM60) surface in zirconium or titanium fluoride aqueous acid solutions was studied. X‐ray photoelectron spectroscopy was used to investigate modifications in the surface chemistry with respect to the composition of the surface treatment solution. The surface film is composed of magnesium hydroxide and hydroxyfluoride, zirconium oxide, oxyhydroxide or oxyfluoride, titanium oxide and structural and adsorbed water. Optimal parameters leading to the formation of a zirconium‐ or titanium‐rich film were determined. A mechanism is proposed for the formation of zirconium‐ or titanium‐based films. Copyright © 2005 John Wiley & Sons, Ltd.     

Aggregation of water soluble octaanionic phthalocyanines and their photoinactivation antimicrobial effect in vitro

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