四针状氧化锌晶须的开发研究

提出了新的四针状氧化锌晶须的生产工艺及流程,设计了专门的研究装置。在该装置中将锌锭挥发形成锌蒸气,然后进入晶须反应炉氧化形成四针状氧化锌晶须;分析了空气量和锌浓度对形成四针状的氧化锌晶须的影响。     

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。     

刺状氧化锌晶须的特点、应用和制备

刺状氧化锌是一种特殊形貌的晶须，本文介绍了近年来国内外对刺状氧化锌的性质、应用及制备方面的研究成果。     

四针状氧化锌晶须的生产和市场

综述了氧化锌晶须的性能特征、主要用途和制备方法,分析了市场前景。     

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     

四脚状氧化锌晶须-特性、应用和制备

简要介绍了四脚状氧化锌晶须的特性、应用前景和制备方法。     

四针状氧化锌晶须的生产和市场

综述了氧化锌晶须的性能特征、主要用途和制备方法，分析了市场前景。     

直接法生产氧化锌产品灰份控制的探讨

结合维氏炉直接法生产氧化锌的生产实际,对影响氧化锌产品灰份的因素进行了分析,讨论了控制产品灰份的方法。     

直接法生产氧化锌产品灰份控制的探讨

结合维氏炉直接法生产氧化锌的生产实际，对影响氧化锌产品灰份的因素进行了分析，讨论了控制产品灰份的方法。     

锌精矿制备氧化锌晶须工艺的研究

以锌矿为原料,硫酸为浸出剂,经过焙烧浸取、净化除杂质、制备硫酸锌,再将制得的硫酸锌以离子交换树脂为沉淀剂,通过化学沉淀法合成了前驱体氢氧化锌,进一步灼烧制备了纯度达99%的氧化锌晶须。研究结果表明:浸出工艺条件为反应温度60℃,固液比1∶8,硫酸1.3 mol/L,反应时间2.5 h,锌的浸出率在98%以上。以高锰酸钾氧化除铁、锰,以锌粉置换去除重金属,去除效果较好。     

Experience-dependent plasticity in adult rat barrel cortex

This study tested the hypothesis that the receptive fields (RFs) of neurons in the adult sensory cortex are shaped by the recent history of sensory experience. Sensory experience was altered by a brief period of "whisker pairing": whiskers D2 and either D1 or D3 were left intact, while all other whiskers on the right side of the face were trimmed close to the fur. The animals were anesthetized 64-66 h later and the responses of single neurons in contralateral cortical barrel D2 to stimulation of whisker D2 (the center RF) and the four neighboring whiskers (D1, D3, C2, and E2; the excitatory surround RF) were measured. Data from 79 cells in four rats with whiskers paired were compared to data from 52 cells in four rats with untrimmed whiskers (control cases). During the period of whisker pairing, the RFs of cells in barrel D2 changed in three ways: (i) the response to the center RF, whisker D2, increased by 39%, (ii) the response to the paired surround RF whisker increased by 85-100%, and (iii) the response to all clipped (unpaired) surround RF whiskers decreased by 9-42%. In the control condition, the response of barrel D2 cells to the two neighboring whiskers, D1 and D3, was equal. After whisker pairing, the response to the paired neighbor of D2 was more than twice as large as the response to the cut neighbor of D2. These findings indicate that a brief change in the pattern of sensory activity can alter the configuration of cortical RFs, even in adult animals.     

热轧低碳钢氧化铁皮厚度的数值模拟及微观形貌的研究

利用热重法研究了低碳钢在500～900℃恒温氧化动力学,利用扫描电镜和金相显微镜对氧化铁皮的表面和断面形貌进行了观察.在试验基础上建立了恒温氧化动力学模型,并推导变温条件下氧化动力学模型用于氧化铁皮厚度演变计算,并研究了氧化铁皮中三种铁的氧化物的生长方式.结果表明:数值模拟出的铁皮厚度与实测结果十分接近.这种模拟方法解...     

Whisker growth in reduction of oxides

Cobalt ferrite (CoFe₂O₄) was reduced in CO-CO₂ gas mixtures at 1173 K at total pressure between 6.6 × 10³ and 3.3 × 10⁴ Pa, and at CO/CO₂ ratios between 2.9 and 11.8. The reduction led to the formation of metal whiskers. The experiments and analysis emphasized the behavior of the whisker diameter during reduction. Impurities such as calcium and potassium stimulate metal nucleation but appear to inhibit catalysis of gas reactions at the metal/gas/oxide triple junction. The steady state whisker diameter was found to be inversely proportional to the total gas pressure at constant CO/CO₂ ratio. A new model is proposed to explain whisker development. It considers metal/oxide interface diffusion coupled with a metal/oxide/gas triple junction reaction at the whisker base as the process determining the whisker diameter.     

Morphology and Growth Kinetics of Straight and Kinked Tin Whiskers

Time-lapse SEM studies of Sn whiskers were conducted to estimate growth kinetics and document whisker morphologies. For straight whiskers, growth rates of 3 to 4 microns per day were measured at room temperature. Two types of kinked whiskers were observed. For Type A kinks, the original growth segment spatial orientation remains unchanged, there are no other changes in morphology or diameter, and growth continues. For Type B kinks, the spatial orientation of the original segment changes and it appears that the whisker bends over. Whiskers with Type B kinks show changes in morphology and diameter at the base, indicating grain boundary motion in the film, which eliminates the conditions suitable for long-term whisker growth. To estimate the errors in the whisker growth measurements, a technique is presented to correct for SEM projection effects. With this technique, the actual growth angles and lengths of a large number of whiskers were collected. It was found that most whiskers grow at moderate or shallow angles with respect to the surface; few straight whiskers grow nearly normal to the surface. In addition, there is no simple correlation between growth angles and lengths for whiskers observed over an approximate 2-year period.     

Effect of Substrate Composition on Sn Whisker Growth in Pure Sn Films

Pure Sn films deposited on Cu and Cu alloys are prone to spontaneous whisker formation. One way of preventing whisker formation is to alloy Pb into Sn coatings. However, restriction on the use of Pb demands the development of alternative methods for preventing whisker growth. The present work reports the effect of substrate composition on whisker formation and morphology. Despite employing identical plating conditions, long filament-like whiskers grew only on Sn-plated Cu samples and not on brass. The presence or lack of Sn whiskers has been explained via the thermodynamic stability of various intermetallic compounds at the Sn/substrate interface.