不同结晶状态的聚丙烯材料的声发射研究

用MISTRAS2001声发射监测系统对加入一定量成核剂（0－2.0%）的聚丙烯材料进行冲击过程声发射研究,研究记录了冲击过程的应力－时间曲线。结果表明,在成核剂加入量为0.4％时,冲击强度出现极大值,与之相对应,其声发射信号最为丰富,声发射振铃计数最高,裂纹扩展阶段的声发射信号占主导地位,随成核剂含量增大,材料冲击断裂过程中裂纹萌生阶段AE计数呈上升趋势,而裂纹扩展阶段的AE计数呈先上升后下降的趋势,同时裂纹萌生功和裂纹扩展功也呈现相同的变化趋势,与断面特征区特征参量的变化相对应。     

低磷化学镀镍层性能的研究

低磷镀层（ＬＰ）在碱性和中性盐水条件下的耐蚀性较高磷镀层好，当ＬＰ镀层在３５０℃下热处理１ｈ后，镀层在显微硬度从４５４Ｈｖ增加到８９０Ｈｖ。差热分析研究发现，在３４１．６℃和４０６．２℃有两个放热峰，分别对应于新相Ｎｉ５Ｐ２和Ｎｉ３Ｐ的形成，利用Ｘ射线衍射对镀层的结构进行分析，发现该镀层由非常细的微晶构成。     

基于SEM的MLCC端电极焊接失效分析

针对多层陶瓷电容器端电极锡镀层的可焊性失效问题,运用扫描电子显微镜(SEM)分析了锡镀层的微观结构,并用能谱仪对其进行成分分析,找出了失效的主要原因:可焊性变差样品的端电极表面锡镀层出现因氧化产生的异常区域,以至于器件的可焊性变差.并通过后期的可焊性实验验证了分析的结果,找出了端电极焊接失效的原因,并提出了应对端电极氧化问题的改进措施.根据分析提出了改进意见,较好地解决了器件的焊接失效问题.     

高聚物声发射的一些观察

对高聚物的声发射做了进一步的实验观察。玻璃态高聚物在拉伸屈服以前的声发射有Kaiser效应,但在高弹态则不然。非晶态高聚物从玻璃态到高弹态的转变,玻璃态拉伸时在屈服附近出现声发射,高弹态时声发射要少而弱得多,只在高弹拉伸的断裂前出现声发射。非晶态、晶态高聚物或共混高聚物在突然升温到100℃时有声发射,但在突然降温到-60℃时却不出现声发射,这可能也说明声发射与高聚物试样内形成空洞有关。一种聚丙烯树脂在不同注射成形工艺条件下所得试件,在拉伸时的声发射行为可反映加工成形的好坏,成形好的声发射少得多。     

高聚物拉伸形变中的声发射

对一系列高聚物进行了单轴拉伸过程中声发射的观察,包括玻璃态高聚物、结晶高聚物、共聚物、共混高聚物和一种交联橡胶。非晶态高聚物拉伸时声发射次数很少,伴随银纹和微裂缝的产生而出现。结晶高聚物在屈服成颈时出现强的声发射,在颈部拉伸的初期声发射较少或不出现,拉伸到接近试件断裂前声发射强烈,次数急剧增多。相同高聚物但试件加工成形历史不同会在声发射上得到反映。交联的顺丁橡胶拉伸时声发射很弱,但可以观察到,在拉力-形变曲线开始偏离线性后出现,没有Kaiser效应。共混高聚物拉伸时声发射很多。高耐冲击共混接枝塑料在断裂前不出现强烈的声发射。如试样和试件加工成形条件相同,声发射现象的重演性是相当好的。     

Al－Mn合金镀层的组成结构及其耐蚀性

研究了在低温熔盐中（低于２００℃）电沉积Ａｌ－Ｍｎ合金镀层成分的控制,镀层化学组成与结构之间的关系以及镀层的耐蚀性能．提出影响镀层锰含量的主要因素是熔盐中锰离子的浓度．镀层含锰量在２５～４０（ｗｔ）％之间可形成非晶态结构．实验表明,Ａｌ－Ｍｎ合金镀层在０．５ｍｏｌ／ＬＨ＿２ＳＯ＿４熔液及ＮａＣｌ溶液中具有优良的耐蚀性,非晶态结构的Ａｌ－Ｍｎ合金镀层的耐蚀性更为优异．     

单边裂纹聚苯乙烯样品拉伸断裂过程的声发射

本文测定了单边裂纹聚苯乙烯(PS)样品在拉伸加载时的声发射以及声发射事件按幅度、脉宽、计数和位置的分布,实验证实,单边裂纹PS样品拉伸时的声发射来源于裂纹端部银纹区的变形、断裂和扩展,大部分总振铃计数由裂纹亚临界和失稳扩展引起,在重复加载时观察到PS声发射的Kaiser效应。     

化学镀非晶态Ni—P层的初期沉积过程研究

化学镀非晶态Ｎｉ－Ｐ镀层初期沉积过程和沉积层状态是影响结合强度的决定性因素．对不同基体材料初期沉积的观察发现，有些非晶态镀层的初期沉积中含有微晶．微晶的产生与否与基体材料以及镀层材料晶格的错配度有关，当镀层与基体材料点阵常数相差不大，镀层的初期沉积沿基体晶格外延生长出现微晶层，反之，点阵常数相差较大时，初期沉积物中未发现微晶．     

钨含量对Ni-W合金镀层结构的影响

对于用电镀方法获得的非晶态合金镀层,普遍认为合金元素的加入破坏了原基体金属晶格的规则排列,形成非晶．而且只有合金镀层的组成达到临界限度时,才能非晶化,镀层的合金组成是其能否形成非晶态的决定性因素［１］．但镀层的合金组成与镀层结构的关系未见详细报道．本文用Ｘ射线衍射法和扫描电镜对ＮｉＷ镀层的结构进行了初步探讨．所用仪器：日本理学Ｄ／ｍａｘＲＢ型Ｘ射线衍射仪（ＣｕＫα靶,λ＝０－１５４１８ｎｍ,管流２０ｍＡ,管压２５ｋＶ,扫速２°／ｍｉｎ）;日本ＥＤＡＸ９１００型扫描电镜．基础镀液：Ｎａ２ＷＯ…     

ZnO荧光粉中的紫外发射和绿色发射之间的关系

通过在低氧分压和真空中热处理ZnO粉末, 获得了ZnO荧光粉. ZnO荧光粉有两个发射谱带, 分别位于380 nm(紫外)和510 nm(绿色). 紫外谱带对应于ZnO中的激子发射, 是一个单中心发光过程；绿色谱带是一个复合发光过程, 与ZnO中的本征缺陷相关, 如氧空位、锌空位等. 实验表明, 高密度的激发条件有利于紫外发射, 而低氧分压下的热处理有利于提高绿色发射谱带的强度. 研究结果还表明, 与紫外发射相联系的激子可向与本征缺陷相联系的绿色发光中心传递能量, 这种传递可能是通过激子扩散实现的.     

Graphite felt modified with electroless Co-Ni-P alloy as an electrode material for electrochemical oxidation and reduction of polysulfide species

Electroless deposition of a Co?Ni?P alloy on the surface of graphite felt filaments was performed in a low-temperature pyrophosphate solution under flow-through conditions. The loading, composition, morphology, and structure of electroless the Co?Ni?P alloy deposit on the filaments of the modified graphite felt were investigated by gravimetric analysis, energy-dispersive X-ray spectroscopy, scanning electron microscopy and X-ray diffraction, respectively. Electrochemical characterization of a graphite felt electrode modified with electroless Co?Ni?P alloy was performed by cyclic voltammetry, chrono-techniques, and the electrochemical impedance spectroscopy test in an aqueous solution of polysulfide composed of the mixture of 1 M Na₂S, 1 M NaOH and 1 M S. It was found that the electroless Co?Ni?P alloy deposit on graphite felt has good cycling stability and high electrocatalytic activity toward reversible electrochemical redox reactions of polysulfide species. In comparison with the bare graphite felt electrode, the electrode modified with the electroless Co?Ni?P alloy showed five to seven times lower values of anodic and cathodic overpotentials in the aqueous solution of polysulfide. It is very likely that the good electrochemical performance of the modified graphite felt electrode is related to the high surface area of the electroless Co?Ni?P alloy deposit.     

Acoustic emission study of the TDCB test of microcapsules filled self-healing polymer

The failure process of self-healing microcapsule filled epoxy composites was investigated with Acoustic Emission (AE) measurement during tapered double cantilever beam (TDCB) tests. Unfilled, epoxy microcapsule filled and self-healing microcapsule (dual-microcapsules consisting of epoxy capsules and trifluoromethanesulfonic acid (TfOH) capsules) filled epoxy matrix specimens were compared. It was found that, with acoustic emission measurements, reliable data can be retrieved about the nature and progress of crack propagation and failure. Comparing the unfilled and the microcapsule filled specimens, considerably more AE hits were detected in the latter case due to the cracking of capsules and capsule-matrix debonding, which was confirmed by scanning electron microscopy investigations. Also, key differences were observed in the shape of the sum of AE hits curves and amplitude ranges of detected AE hits. Uniform distribution of the healing agent was demonstrated by energy-dispersive X-ray spectroscopy.     

热处理对化学沉积Ni-Fe-P合金性能的影响

采用DSC和XRD研究了化学镀Ni-Fe-P合金的晶化行为和结构.结果表明,镀态合金呈非晶结构, 367.6 ℃下热处理出现亚稳态Ni5P2(P3)和Fe-Ni(Im3m), 499.2 ℃下热处理进一步晶化为稳定的Ni3P(I-4)和FeNi3(Pm3m).采用磁性能实验和在w=3.5％氯化钠溶液浸泡实验以及阳极极化实验研究了热处理对镀层磁性能和耐腐蚀性的影响.结果表明,该镀层在镀态时几乎没有磁性,随着退火温度的升高,磁性能不断提高. 400 ℃以后,镀层的饱和磁化强度和矫顽力随着退火温度升高而急剧上升.浸泡实验和阳极极化实验结果均表明镀态镀层比经热处理后的镀层在w=3.5％氯化钠溶液中具有更好的耐腐蚀性,但是它们的阳极极化行为不同.     

Thermoanalytical Study of Baryte Decrepitation

The decrepitation results of mineral baryte BaSO₄ (Rudňany, Slovakia) of various quality obtained by completed Acoustic Emission (AE)-TG-DTA measurements are presented in this paper. The overall effect of decrepitation ability of major component BaSO₄ is not hindered by accompanying mineral siderite FeCO₃. This fact confirms decrepitation study of pure minerals by the thermovacuum impulse method, too. This revised version was published online in August 2006 with corrections to the Cover Date.     

Process aspects of electroless deposition for nickel–zinc–phosphorous alloys

Electroless deposition of Ni–Zn–P thin film was considered as a barrier film on a galvanic Zn or Ni–Zn sacrificial layer in a multicomponent corrosion protective coating on steel. The incorporation of zinc on the chemical composition of electroless Ni–Zn–P coating was studied. The effect of operating conditions such as temperature, pH value and concentration of zinc sulphate was investigated. Some physical characteristics such as morphology, structure, corrosion properties of Ni–Zn–P coatings were assessed in parallel with those of Ni–P. Inclusion of Zn to Ni–P is accompanied by the transformation of the coating structure from amorphous to crystalline. The effect of adding nonionic surfactant to the plating solution on the composition and surface morphologies was also investigated. The results indicate that nonionic surfactant has no effect on the Zn % in the deposit layer, but it affects the surface morphology and improves the corrosion resistance of Ni–Zn–P layers. Copyright © 2005 John Wiley & Sons, Ltd.     

The evolution of growth morphology and corrosion behavior of electrodeposited Ni–P coatings on alumina borate whisker‐reinforced pure aluminum composite

The Ni–P alloy coatings were obtained on alumina borate whisker‐reinforced pure aluminum composite by electro‐deposition. The initial electro‐deposition behavior of the Ni–P alloys on the composite and pure aluminum was studied, respectively. It was found that the composition and the morphology of materials had a distinct effect on the initial electro‐deposition behavior of the Ni–P alloys. The Ni–P alloy coatings preferred to nucleate at the composite as compared with the pure aluminum. Moreover, the Ni–P particles were prone to deposit at the whisker/Al interface in the composite. The Ni–P coatings were barely depositing upon the surface of whisker during the plating process. As the deposition time increased, the Ni–P particles that were deposited on the surface of the composite grew gradually. These Ni–P particles linked to each other and eventually covered the whisker surface. Moreover, it can be found that the surfaces of the composite were gradually covered by Ni–P coatings and the anticorrosion performance of the coated composite increased remarkably with the increase in the deposition time. When the deposition time is 60 min, only the Ni–P diffraction peak could be detected. In this case, the coated composite had significantly better corrosion resistant, which is attributed to the surface of composite was perfectly covered by the Ni–P coatings. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Heat Treatment on Structure and Magnetic Performance of Ni-Fe-P Alloy Obtained by Electroless Plating

The electroless deposition of Ni68-Fe10.5-P21.5 alloy has been investigated. The crystallization behavior of the deposit was comparatively studied by using differential scanning calorimetry and X-ray diffractometry. The deposit transforms into a square Ni3P phase at 380. 0 ℃, then changes into a cubic FeNi3 phase at 490. 0 ℃. The microhardness, the size of the formed grains and the magnetic performance of the deposit increase with the increase of the heat treatment temperature below 500 ℃, then they decrease after this temperature. The effect of heat treatment time at 500 ℃ on the surface micromorphology, the structure and the magnetic performance of the deposit were also studied. The resuits show that with the increase of heat treatment time, the extent of crystallization of the deposit increases and the size of the formed grains becomes uniform. The results also show that the magnetic performance of the deposit under heat treatment for 40 min is maximal and then decreases with the increase of heat treatment time. The property change of the deposit is related to the crystal structure and the size of the formed grains of the deposit.     

Mechanical and corrosion behavior of amorphous and crystalline electroless Ni–W–P coatings

Two types of electroless Ni–W–P coatings: nanocrystalline with low P and amorphous with higher P content are investigated. Scanning probe microscopy is applied to study their morphology. Textured nanocrystalline coatings consist of coarse pyramids built of nanometer thick lamellas. The surface morphology of amorphous coatings is much finer and uniform. Nanohardness of all coatings depends on W content. Microhardness is increasing during the heat treatment up to 350 °C due to nickel phosphide precipitation affected by tungsten also. The wear resistance of nanocrystalline Ni–W–P coatings is much higher than that of amorphous in spite of the similar tungsten content in both. Lower corrosion resistance of amorphous Ni–W–P coatings is found by weight loss method during long-term immersion in 5 % NaCl. Electrochemical tests by potentiodynamic polarization curves in two model corrosion media—solutions of 0.5 M H₂SO₄ and 5 % NaCl—are performed. The corrosion of bi-layered Ni–W–P/Ni–P and Ni–W–P/Ni–Cu–P deposits on mild steel is also investigated. The results prove that an electroless Ni–W–P coating on mild steel extremely improves its mechanical and corrosion behavior. It is demonstrated that in addition to deposit’s structure and composition, the distribution and chemical state of alloy ingredients are also responsible for its properties.     

纳米晶镍—钼合金电沉积层的结构与性能

通过控电流沉积制备出纳米晶镍钼合金沉积层,沉积层的ＸＲＤ、ＸＰＳ结果表明,纳米晶镍钼合金沉积层存在较大的晶格畸变,其微晶尺寸为１７ｎｍ,纳米合金各元素的结合能发生了不同程度的位移．在３０％的ＫＯＨ溶液中纳米晶镍钼合金电极对析氢反应表现出较高的电催化活性．电化学交流阻抗谱表明,析氢过程按ＶｏｌｍｅｒＨｅｙｒｏｖｓｋｙ机理进行．     

纳米晶Ni-Mo-Co合金镀层的结构与析氢行为

电沉积;结构;纳米晶Ni-Mo-Co合金镀层的结构与析氢行为