四针状氧化锌晶须应用研究进展

四针状氧化锌晶须是唯一具有三维四针状结构的晶须。综述了四针状氧化锌晶须的性质和其在增强材料、抗菌、抗静电、吸波减震方面的应用研究进展,最后讨论了以后的研究方向。     

四针状氧化锌晶须的研究进展

四针状氧化锌晶须是唯一具有三维空间结构的晶须。作为复合材料的一种特殊组份,它不仅显著地提高了材料的力学性能,而且赋予材料导电、吸波、光电等特殊的物理性能,使之成为有特殊功能的复合材料。本文综述四针状氧化锌晶须的制备,侧重讨论其生长机理方面的研究进展,并指出了存在的问题和进一步研究的方向。     

PLC在氧化锌晶须加工中的应用

针对氧化锌晶须加工的工艺要求,结合生产实际设计了一套以西门子S7-300 PLC为控制器、带死区的增量式PID为控制算法的自动控制系统,实现了氧化锌晶须加工的自动监控与管理。实际生产的四针状晶须针长较长,针与针之间的空间角度接近理论值,产品质量为上等。     

氧化锌晶须的制备及杂质元素的行为

针对制备四针状氧化锌晶须(T-ZnO)均采用高纯锌粉为原料的现状，研究了直接以热镀锌渣制备T-ZnO的方法和原料中杂质元素的行为。XPD和SEM等分析检测表明，产物为六方纤锌矿结构的高纯T-ZnO，产物尺寸均匀，中心体边长3-5μm，针状体长60～110μm。杂质元素在氧化过程中的不同行为对产品质量产生不同的影响。通过控制恰当的温度、氧含量和残渣率，可以实现将原料提纯和晶须制备整合在同一过程中完成。实验为用热镀锌渣替代高纯锌粉制备T-ZnO提供了可行的途径，这对降低T-ZnO的生产成本具有非常重要的意义。     

锌精馏塔生产高级氧化锌

我国历来在化工部门生产间接法氧化锌,但是由于冶炼厂在锌精馏塔上直接氧化锌具有很多优点,继1982年2月在葫芦岛锌厂试验成功并投入生产以来,同年5月水口山矿务局四厂投入了生产,1983年8月韶关冶炼厂也形成年产5000吨的能力,至此,我国冶炼厂形成了年产两万吨氧化锌的生产能力,约占全国生产能力的一半以上。     

我国的氧化锌工业

氧化锌是用途广泛的冶金化工产品。冶金与化工行业均可提供这种产品,並已形成了我国氧化锌工业体系。冶炼厂主要以锌矿砂为原料直接生产氧化锌(直接法)。而化工厂则以商品锌为原料生产氧化锌(间接法)。随着生产工艺技术的发展,自1982年起精馏法氧化锌在我国主要火法炼锌厂相继建成投产,短短三年时间已形成13000吨/年能力。精馏法氧化锌以其纯变高、能耗低、经济效益好等优势,突破了氧化锌生产的传统格局。     

高频等离子法制取活性超细氧化锌粉

中国科学院化工冶金研究所近日向社会推出高频等离子法制取活性超细氧化锌粉生产技术。据介绍 ,活性超细氧化锌粉即超细锌白粉 ,是橡胶、油漆、造纸、涂料等工业中广泛应用的添加剂 ,而超细球状锌白粉则是橡胶工业必不可少的原料。传统的低温和长周期焙烧碱式碳酸锌制取活性氧化锌的工艺产率低 ,有污染。高频等离子超高温瞬间焙烧新工艺制取活性超细氧化锌粉是在高频等离子反应器中将碱式碳酸锌直接分解成针状或多孔海绵球状活性超细氧化锌粉 ,产率高 ,无污染 ,产品质量 (氧化锌含量和粒度 )明显提高 ,纯度高于 95 %～ 98% ,平均粒度小于 0 …     

新技术

一种包覆有金属层的氧化锌晶须,其表面至少包覆有一种纯金属或合金层。纯金属或合金层的厚度根据需要确定,一般为10纳米-10微米。此种晶须与金属基体形成复合材料时,相容性好,能有效地提     

有色冶金动态

锌精馏塔制取间接氧化锌在橡胶、涂料、电子、医药、陶瓷等工业中广为应用的间接氧化锌,目前国内均采用圆型“花瓶”炉生产。该工艺是将锌块熔化,液体锌进入“花瓶”炉蒸发,制得的锌蒸气,再经空气氧化而获得氧化锌。水口山四厂自1980年开始,参考国外资料,设计了一座B~#锌精馏塔,并在该精馏塔旁装设一套设施,将塔内锌蒸气引入其中,以制得纯度为99.8%的氧化     

低度复杂氧化锌矿直接法生产等级氧化锌工业试验

以低度复杂氧化锌矿为原料直接生产等级氧化锌。确定了物料的配比,解决了高铁高硅低锌氧化矿(含锌低于30%)直接生产等级氧化锌的一系列技术难题,并形成规模化生产。     

Ag Whisker Formation in Ag-In-Se Alloys

Whiskers of pure Ag as long as 10 cm are found in Ag-In-Se alloys. Striations and faceted microstructures are observed, and a [200] preferred growth orientation has been determined. The compositional regime of whisker growth is about 15 to 30 at. pct Se, and is within the miscibility gap. For these alloys at higher temperatures, two liquids are formed, with the more Ag-rich liquid at the bottom. Stress is developed during solidification, and whisker formation is a result of stress release.     

Fracture mechanisms of a 2124 aluminum

This study was aimed at investigating the effects of microstructure on the fracture behavior of a 2124 aluminum composite reinforced with SiC whiskers. Particular emphasis was placed on the role of matrix intermetallic particles, inhomogeneous distribution of whiskers, and whisker breakage in the fracture process. Various tests were conducted on the composite to identify the micromechanical processes that were involved in microvoid or microcrack formation. Detailed microstructural analyses showed that the aluminum matrix contained a significant amount of coarse manganese-containing particles of various sizes which could have been formed during composite processing.In situ scanning electron microscope (SEM) fracture study of the crack initiation and propagation processes clearly showed that these coarse particles fractured prior to matrix/whisker decohesion or whisker breakage, suggesting that the manganese-containing par- ticles significantly accelerated crack initiation in the 2124 Al-SiC_w composite. For a better ma- trix alloy for use in the composite, it is suggested that microalloying elements must be monitored to prevent the formation of the coarse intermetallic particles.     

基于有限元的锌锅升降装置结构分析

基于AnsysWorkbench工作平台对冷轧连续镀锌线上的锌锅升降装置整体进行三维有限元分析,全面掌握结构的应力和变形情况。通过验证计算结果的合理性,并对锌锅升降装置的结构安全性做出可靠性分析。     

硼酸镁晶须的制备及其中子辐射屏蔽性能

采用高温固相法制备硼酸镁晶须的最佳工艺条件为:焙烧温度大于900℃,焙烧时间为8.0h.制得的晶须粗细均匀,晶型完美,直径约为1.5μm,长度约35μm,长径比约为24.经XRD、SEM和FT-IR分析确定为硼酸镁晶须.以酚醛树脂为基体,添加硼酸镁晶须制备硼酸镁晶须/酚醛树脂复合材料,探讨了硼酸镁晶须添加量和材料厚度对热中子屏蔽率的影响;当硼酸镁晶须添加量为40份时,热中子屏蔽率为73.64％,继续增加添加量,热中子屏蔽率增幅不大;材料厚度为1.0 cm时,热中子屏蔽率为85.01％,继续增加厚度,热中子屏蔽率增加不明显.实验结果表明,以硼酸镁晶须制备聚合物中子屏蔽材料不仅可行,而且对热中子辐射具有较好的屏蔽性能.     

SiC晶须含量对镁基复合材料性能影响的研究

采用加压烧结法制备镁基复合材料,研究不同含量的SiC晶须对镁基复合材料密度、硬度、抗拉强度、抗压强度、摩擦磨损等性能的影响。结果表明:镁基复合材料的致密度并不随SiC晶须质量分数的改变而发生规律性变化;材料的硬度随着晶须质量分数的增加而增大;与基体材料ZK60相比,添加SiC晶须的镁基复合材料的抗拉强度、抗压强度、弹性模量、压缩模量和伸长率都有一定提高,当SiC晶须的质量分数为20.0%时,复合材料烧结体的常温力学性能最好;通过对烧结材料磨损量变化的分析,发现当SiC晶须质量分数为10.0%时,摩擦磨损性能最好。综合比较分析,SiC晶须的质量分数为15.0%时,增韧增强效果最佳。     

Working with avoidant children: a clinical challenge

We examined axon-target interactions in cocultures of embryonic rat trigeminal, dorsal root, nodose, superior cervical ganglia or retina with a variety of native or foreign peripheral targets such as the whisker pad, forepaw, and heart explants. Axon growth into these peripheral target tissues was analyzed by the use of lipophilic tracer DiI. Embryonic day 15 dorsal root and trigeminal axons grew into isochronic normal and foreign cutaneous targets. Both axon populations avoided the same age heart tissue, but grew profusely into younger (embryonic day 13) or older (postnatal) heart explants. In contrast, embryonic day 15 superior cervical or nodose ganglion axons grew heavily into the same age heart and forepaw explants and to a lesser extent into the whisker pad explants. Embryonic day 15 retinal axons grew into all three peripheral targets used in this study. Primary sensory and sympathetic axons, but not retinal axons, formed target-specific patterns in the whisker pad and forepaw explants. DiI-labeling and immunostaining of primary sensory neurons in coculture revealed that these neurons retain their bipolar characteristics, and express class-specific markers such as parvalbumin, calcitonin gene-related peptide and TrkA receptors. In the whisker pad explants, axons positive for all three markers were seen to form patterns around the follicles. Our results indicate that developing peripheral targets can attract and support axon growth from a variety of sources. Whereas neurotrophins play a major role in attracting and supporting survival of subpopulations of sensory neurons, other substrate-bound or locally released molecules must regulate sensory neurite growth into specific peripheral and central targets.     

Nickel and cobalt eutectic alloys reinforced by refractory metal carbides

Eutectiferous behavior was observed within pseudobinary joins between the monocarbides of the group IVa and Va metals with nickel and cobalt. Coupled two phase growth normal to a macroscopically planar liquid-solid interface was noted even though the various carbide phases grew in a faceted manner. The composite structures formed by unidirectional freezing consisted of either a cobalt or nickel matrix with an aligned whisker-like or three-sided lamellar carbide dispersion. The nickel-niobium monocarbide system was examined in greatest detail and found to be stronger than TD nickel in tension from room temperature to 2100°F. Repeated fracture along the length of individual carbide whiskers was observed during tensile straining. This behavior, which is nontypical of previous eutectic whisker composites, was interpreted in terms of the distribution in whisker strengths. The strength of extracted NbC whiskers measured in bending was found to approach the theoretical failure stress. Creep rupture tests further indicated that reinforcement of a weak nickel or cobalt matrix with aligned monocarbide whiskers provides a new type of material for use at elevated temperatures.     

利用热镀锌渣制备超细锌粉的试验研究

利用冷轧厂热镀锌渣为原料,采用蒸发-冷凝法直接制备出超细锌粉。采用新型蒸发装置、冷却装置,考察了最大蒸发温度、恒温时间、保护气体通入量、蒸发物料量、冷却强度等对锌粉收得率及粒度分布的影响。对所得超细锌粉的化学成分、粒度分布、XRD和微观结构进行测试,并讨论了锌粉团聚的原因及对策。