共查询到19条相似文献,搜索用时 84 毫秒
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泡沫表面吸附钯浓度的测定及其对镀层质量的影响 总被引:3,自引:0,他引:3
通过比色分析方法的应用,测定了活化后泡沫表面吸附钯原子的浓度,其结果与SEM照片对比,可看出,3mm厚、孔率90%的聚氨酯泡沫得到良好镀层所需最低的表面吸附钯原子浓度为0.5mg/dm^2。 相似文献
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泡沫镍基镍硫合金涂层形貌、结构和析氢性能研究 总被引:4,自引:0,他引:4
在含有柠檬酸、硫脲和少许糖精的Watt镀液中,用电沉积的方法在镍泡沫基体上制备了镍硫合金涂层.各层涂层的形貌用SEM分析,各层硫量的分布用EDX测量.第1层涂层的结构用XRD测定.对各种电极包括镍泡沫基、镍网基上镍硫涂层电极,空白镍泡沫、镍网电极等的极氢电位进行了测量,研究了不同温度下镍泡沫基镍硫涂层电极的析氢活性.结果表明,镍泡沫基Ni-S涂层电极的析氢活性比镍网基Ni-S涂层电极活性高得多.镍泡沫各层硫量呈梯度的分布规律,由表及里硫含量逐步降低,中心层硫含量最低.各层表面微细颗粒大小及其均一性不相同,第1层的颗粒尺寸大于其它层的颗粒,其大小均一性也较其它层差.镍硫涂层是镍和Ni3S2组成的非晶态,使涂层具有丰富的表面积和氢气析出反应的活性中心.在加热的电解液中,在60℃以下和60℃以上的温区内电极析氢反应的机制不完全一样,受温度影响的程度也不一样.4000A/m2、90℃时,这种电极的析氢电位比15℃时析氢电位低180mV. 相似文献
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分别采用纤维强伸度仪、乌氏粘度计、X射线衍射仪等测定了4种不同PAN纤维的抗拉强度、分子量、结晶度以及沸水收缩率.结果表明,拉伸速率对4种纤维的强度测试方法的准确性都有影响.在低速拉伸时,由于拉伸速率的增加使分子链段的松弛时间缩短,测试强度随拉伸速率的增加而升高;而在高速拉伸情况下,缺陷成为导致纤维断裂的主要因素,测试强度又随拉伸速率的增加而逐渐降低.在一定范围内,分子量越大、结晶度越高,PAN纤维的强度就越高;作为表征纤维中非晶含量的一项指标,沸水收缩率越大,说明非晶区的比例越大.因此应控制PAN纤维的分子量,提高纤维结晶度,降低纤维的沸水收缩率,从而为制备高性能的碳纤维提供优质原丝. 相似文献
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相较于铆接、螺接、焊接等连接方式,板状粘结构件具有质量轻、应力分布均匀等特点,广泛运用于航空航天、车辆制造等工业领域。板状粘结构件在服役过程中出现的粘结强度退化、弱粘结等会影响其服役可靠性及安全性,因此对粘结强度进行检测十分必要。非线性超声导波对材料微观结构特征变化比较敏感,可用于粘结构件的粘结强度检测。采用非线性超声导波对铝合金-环氧树脂-铝合金板状构件进行检测,通过不同的固化工艺制备粘结结构件模拟不同粘结强度,检测结构件中传播的非线性超声导波,计算超声非线性参量,获得超声非线性参量在不同固化工艺下的变化趋势。通过拉伸实验测得粘结强度,进而构建超声非线性参量与粘结强度的关系。实验结果显示,粘结强度越大,超声导波的非线性参量越小。该研究表明,非线性超声导波可有效检测板状构件的粘结强度,为工业检测板状结构粘结强度提供了有效方法。 相似文献
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通过有关计算公式的应用分析,找到了较合适的发泡镍电阻率用孔率计算的方法,从而为高性能电极基体材料和发泡镍电阻率的生产控制提供便利。 相似文献
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The relationships between fatigue strength and ultimate tensile strength as well as hardness have been studied in high-strength NZK alloys (Mg–yNd–zZn–xZr) and other magnesium alloys. In the absence of casting defects, clear linear relationships have been found between the fatigue strength and the ultimate tensile strength and the hardness values in these magnesium alloys in both T4 (solutionized) and T6 (solutionized and aged) conditions. The fatigue strength models developed in this work alloys can be directly applied to other defect-free magnesium alloys. 相似文献
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《Materials Science & Technology》2013,29(5):669-672
AbstractThe effect of preparation conditions on the relative elongation of nickel foams prepared by electrodeposition technology has been studied. The relative elongation is hardly influenced by sintering in NH3 decomposition atmosphere at 980°C for 40 min, by burning in air at 600°C for 4 min beforehand, or by lowering the sintering temperature to 850°C. With regard to conductive treatment, the relative elongation is significantly higher for chemically plated Ni than for coating by graphite base conductive colloid. 相似文献
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C.R. Chiang 《Composites Science and Technology》1994,50(4):479-482
This paper is concerned with the prediction of the tensile strength of short-fiber-reinforced composites by following the statistical theory of the strength of fiber bundles. Unidirectional, misaligned, and random-fiber directions are all treated. Depending on the fiber length, two failure modes can be distinguished. When the fiber length is smaller than 2Lc, where Lc is the critical transfer length, the composite should fail by direct fiber pull-out. By contrast, it the fiber length is longer than 2Lc, most fibers break first and are then pulled out. At small fiber lengths, the prediction of the present theory is one-half the value predicted by the conventional model. However, the prediction of the present theory is in close agreement with that of the conventional approach if the fiber length is long. 相似文献