Application of face centred cubic TiB powder as conductive filler for electrically conductive adhesives

Face centred cubic（FCC） TiB ceramic powder synthesized by Ti-boronizing method was used as conductive filler to make ceramic electrically conductive adhesives（ECAs） with the polymer matrix.Electrically conductive properties of the ceramic ECAs were studied.The bulk electrical resistivity varied with the powder content of the FCC-TiB in ECAs.The FCC-TiB filled ECAs also showed the percolation behavior that usually occurred for the metal-filled ECAs,the percolation threshold was located at the content of 60%FCC-TiB.A minimum value of 0.1 Ω·cm was obtained at a content of 75%FCC-TiB.In order to check the reliability of mechanical property,tensile test was done to measure the shear strength,and the shear strength dropped with increasing the content of FCC-TiB powders.It is about 12.26 MPa at the content of 70%TiB powders.The Cu filled ECAs were also prepared for comparison.The properties of the oxidation resistance of the two ECAs were evaluated.The results show that the ceramic ECAs have excellent oxidation resistance and better stability compared with the Cu filled ECAs.

Preparation of PbTiO_3 Conductive Powders and Coatings

La2O3 and Ce2O3 were penetrated into PbTiO3 to obtain conductive powders, and then they were mixed with polyurethane and butyl acetate to prepare conductive coatings. The results showed that the electric property of modified PbTiO3 powders was improved by penetration of La2O3 and Ce2O3. XRD patterns showed that some new compounds such as La2Ti6O15, CeTi21O38 and Pb0.634La0.209Ti0.948O2.284 were formed, which led to the rapid increase of conductivity. The resistivity of modified PbTiO3 powders decreased to 3.88 Ω·m. The coatings using modified PbTiO3 powders as fillings also had a good conductivity. When the PbTiO3 powders were 10% and antisettle agent (bentonite) content was 0.50%, and mass ratio between polyurethane and butyl acetate was 1.05, the surface resistivity of the coatings fell down to 1.3×108 Ω·m. This kind of conductive coatings could be used in electromagnetic shielding.

Preparation of rare-earth-modified medical stone powders and their application as conductive fillers

Traditional metal conductive fillers are expensive and prone to oxidation. Thus, the development of new conductive powders as fillers is urgently needed. A novel gaseous penetration technology was adopted to prepare La-doped medical stone powders(La-MSPs), which are inexpensive mesoporous materials, as a new kind of conductive filler material. The prepared La-MSPs attained a resistivity of 450 ?·m and were used as a filler to prepare conductive coatings with epoxy resin as the resin matrix. The influence of the La-MSPs dosage on the resistance and hardness of the coatings was also determined. The resistance and the hardness both decreased with increasing filler dosage. Finally, the optimum recipe of the conductive coatings with the most suitable fillers dosage(55 wt%) was obtained. The hardness and resistance of the coatings with 55 wt% La-MSPs were HV 4 and 5.5 × 10~7 ?, respectively.

Effect of Curing Procedure on the Properties of Copper-Powder-Filled Conductive Adhesives

By means of testing the shear strength with single lap joint, measuring electrical resistivity for cured products and the curing strain with strain gauges, the effect of cure parameters on the properties of HT1012 conductive adhesive filled with copper powder was investigated, and the residual stress in the conductive adhesives was also estimated. The experimental results show that the properties such as shear strength of the adhesives, electrical resistivity of products as well as the residual stress of cured HT 1012 copperfitted conductive adhesive were evidently affected by curing temperature and time. The diagrams of scanning electron microscopy （SEM） and Fourier transform infrared （FT-IR） were also used to determine the properties. The higher mechanical property was achieved under the condition of curing the adhesive 3 h at 60 ℃ as the density of the hydrogen links or linkages existed in the adhesive was relatively higher and the lower electrical resistivity occurred at 80 ℃.

Electrochemical migration behavior of Ag-plated Cu-filled electrically conductive adhesives

The electrochemical migration (ECM) behavior of the electrically conductive adhesives (ECAs) filled with pure Ag powder or Ag-plated Cu composite powder with varied Ag:Cu ratios was investigated under the condition of applying constant voltage and distilled water environment.ECM resistance was determined from the current-time curves.The microstructure and composition of ECM dendrite products were analyzed by SEM/EDS and XRD.It was found that the ECM resistance of Ag-plated Cu composite powder-filled ECAs was evidently higher than that of pure Ag powder-filled ECAs.The Ag:Cu ratio of composite powder in ECAs had notable influence on ECM resistance,which was enhanced with the decrease of Ag:Cu ratios.The composition of dendrites formed between cathode and anode during ECM process was not uniform for Ag-plated Cu-filled ECAs.An ECM inhibiting mechanism of Ag-plated Cu composite powder was proposed according to analysis of the electrochemical impedance spectroscopy,Tafel plot and dendrite composition.

A Prediction Model of Effective Thermal Conductivity for Metal Powder Bed in Additive Manufacturing

In current research,many researchers propose analytical expressions for calculating the packing structure of spherical particles such as DN Model,Compact Model and NLS criterion et al.However,there is still a question that has not been well explained yet.That is:What is the core factors affecting the thermal conductivity of particles?In this paper,based on the coupled discrete element-finite difference(DE-FD)method and spherical aluminum powder,the relationship between the parameters and the thermal conductivity of the powder(ETC_(p))is studied.It is found that the key factor that can described the change trend of ETC_(p) more accurately is not the materials of the powder but the average contact area between particles(a_(ave))which also have a close nonlinear relationship with the average particle size d_(50).Based on this results,the expression for calculating the ETC_(p) of the sphere metal powder is successfully reduced to only one main parameter d_(50)and an efficient calculation model is proposed which can applicate both in room and high temperature and the corresponding error is less than 20.9%in room temperature.Therefore,in this study,based on the core factors analyzation,a fast calculation model of ETC_(p) is proposed,which has a certain guiding significance in the field of thermal field simulation.

Effect of processing parameters on the microstructure and thermal conductivity of diamond/Ag composites fabricated by spark plasma sintering

Diamond/metal composites with 50 vol.% diamond have been produced by spark plasma sintering（SPS） using pure Ag as a matrix and diamond particles as reinforcement.Three kinds of powder mixing processes were used to prepare the mixture of diamond/Ag powders：dry mixing without milling medium,wet mixing and magnetic blending.Subsequently,they were all consolidated by SPS at various processing parameters to produce bulk diamond/Ag composites.Then samples were heat treated in order to obtain a higher thermal conductivity.The effect of processing parameters on the morphologies of the mixed powders,the microstructure and the thermal conductivity of the composites were investigated by comparing the experimental data.It reveals that particles were easy to agglomerate and the distribution of mixed powders was inhomogeneous by dry mixing method,and wet mixing method is too complex.The most favorable mixing process is magnetic blending by which the powders can be homogenously mixed and the composites prepared by optimized SPS processing parameters can obtain the highest relative density and the best thermal conductivity among the composites prepared by different processes.The magnetic blending diamond/Ag composites even have a 23% increase in thermal conductivity compared with pure silver sintered by SPS.

Relation between powder size and electrolyte properties in nano YSZ system

YSZ (yttria stabilized zirconia) electrolyte properties made from different sizes of nano powders were investigated. As a result, the sample marked KD with the smallest size (10 nm) of first particles and the sample marked TH with narrow distribution and the smallest median diameter Mmed of 0.49μm have the best sintering properties and the highest electrical conductivity. There is a very well correlation between the density and the electrical conductivity of YSZ, that is, the samples with a higher density have a higher electrical conductivity. The area resistance of YSZ electrolyte made in the experiment, such as TH of 0.483 Ω·cm2, is much lower than that of the sample D of 1.300 Ω·cm2 made in Germany at 850℃. The complex resistance of YSZ electrolyte made in the experiment at the grain, grain boundary and electrode in the range of 300-750℃ decreases greatly compared to the sample made in Germany by shown in the complex impedance plot.

Effects of heat treatment on the properties of powder injection molded AlN ceramics

The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride（AlN） ceramics were investigated.The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis（SHS） and compacts were fabricated by employing powder injection molding technique.The polymer-wax binder consisted of 60 wt.% paraffin wax（PW）,35 wt.% polypropylene（PP）,and 5 wt.% stearic acid（SA）.After the removal of binder,specimens were sintered at 1850°С in nitrogen atmosphere under atmospheric pressure.To improve the thermal conductivity,sintered samples were reheated.The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics.The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m^-1·K^-1 and 3.28 g·cm^-3 and the secondary phase is yttrium aluminate.For the sample reheated in reducing nitrogen atmosphere with carbon,the thermal conductivity and density are 173 W·m^-1·K^-1 and 3.23 g·cm^-3,respectively,and the secondary phase is YN.

Influences of dehydrating process on properties of ATO nano-powders

Sb-doped SnO2 （ATO） nanometer powders were synthesized by hydrolysis of alkoxides, using SnCl4·5H2O and SbCl3 as raw materials. Some dehydrating processes, such as n-butanol/xylene mixed solvent heterogeneous azeotropic distillation, organic dehydrating agent and other dehydrating processes, were used to treat the wet colloids for preparing nonagglomerated ATO nanoparticles. The influences of dehydrating processes on the particle size, agglomeration and resistance were investigated using X-ray diffraction （XRD）, transmission electron microscopy （TEM） and Brunauer-Emmet-Teller （BET）. It is indicated that the dehydrating methods have great influences on the products properties, and that n-butanol/xylene mixed solvent heterogeneous azeotropic distillation processing and organic dehydrating agent can effectively remove the residual H2O molecules in wet colloids, and be used to prepare powders with high surface areas, about 85.32 m2/g, low agglomeration and good conductivity.

Development of Powder Metallurgy （PM） Compacted Cu-TaC Electrodes for EDM

The main aim of this paper is to investigate the properties of Cu-TaC electrodes produced by Powder Metallurgy （PM） method. The design of Experiment （DOE） method was used to plan the investigation. Two different compositions of the powders （Cu-TaC with 30 and 55 % wt TaC） were used. The major properties which determine suitability of electrodes for Electro Discharge Machining （EDM） are electrical conductivity, therrnal conductivity and to some extent density. These properties were measured for the green compacted electrodes, analyzed and compared with their sintered counterparts. This is the initial stage to determine the suitability or otherwise of the compacted electrodes. The results showed that the compacted electrodes in green form can be suitable for EDM, since the electrical conductivities are very high （94.96-189.92Ω^-1m^-1）. The thermal conductivity is good （29.70-33.20W/m K）. The density ranges between 6.13 and 9.80 g/cm3. The sintered electrodes were found to be unsuitable at the specified conditions, because they became non-conductive electrically after sintering. Current efforts are geared towards improving these properties for the sintered ones and also determining their optimum levels.

Synthesis of LaF_3 superfine powder by microwave heating method

LaF3 superfine powder was synthesized from La（CH3COO）3 and NH4F by micro wave heating method,using ethanol or pure water as dispersants respectively. Th e results of XRD and SEM indicate that the superfine powder has high purity,reg ular particle shape and narrow distribution of granularity. The granularity of t he best sample is in the range of 100200 nm.The influence of different dispersants on the crystal degree and microstructure was discussed. After the su perfine powder was formed into a slice at pressure of 2560 MPa,its ele ctrochemical impedance spectroscopy was tested by electrochemical impedance spec troscopy（EIS） measurement. The result shows that the grain refining of LaF3 po wder increases its ionic conductivity. Compared with traditional preparation met hods of LaF3 powder,the advantages of microwave heating method were summarize d.

ATO-TiO_(2)浅色导电粉体的可控制备及性能研究

浅色导电材料因其较低的电阻率,优异的装饰特质迅速发展,运用在传感、电子信息、机械制造、通讯、电磁屏蔽等诸多领域。锑掺杂二氧化锡和二氧化钛(ATO-TiO_(2))纳米复合材料不仅具有半导体性质,并且颜色浅、可染性好,同时具有优异的化学稳定性和热稳定性。然而其制备过程中容易团聚,导致导电性能较差。因此,制备过程中均匀分散,同时兼具优异的导电性能是目前研究需要迫切解决的科学问题。采用共沉淀的方法,制备了ATO-TiO_(2)浅色导电材料,分析了包覆复合过程中不同改性剂、Sb_(x)Sn_(1-x)O_(2)∶TiO_(2)复合比和干燥方式对ATO-TiO_(2)浅色导电材料的物相组成、微观形貌、电学性能等微观结构形貌及宏观理化性能的影响,实现了可控制备并得到了最佳制备的工艺路线。

碳纤维和EPS颗粒对RPC性能的影响

研究了不同掺量(0、0.2%、0.3%、0.4%、0.5%、1.0%)的碳纤维(CF)全取代钢纤维(SF)对活性粉末混凝土(RPC)工作性的影响,优选出了适宜CF掺量;在此基础上,研究了EPS颗粒掺量(10%、20%、30%、40%、50%)对掺CF的RPC(CF-RPC)工作性、力学性能、干表观密度和导热系数的影响,并与同EPS颗粒掺量条件下掺SF的RPC(SF-RPC)性能进行了对比。结果表明:CF的适宜掺量为0.3%;随着EPS颗粒掺量的增加,CF-RPC试件的扩展度先增大后减小,抗压强度、抗折强度、干表观密度和导热系数均降低,韧性提升;与掺EPS的SF-RPC试件相比,掺EPS的CF-RPC试件的抗压强度较低,但韧性较好,干表观密度和导热系数均较低。

直流电下导电沥青混凝土非线性导电行为研究

导电沥青混凝土中非线性导电行为的导电机制尚不明确。基于实验室制备的碳纤维(CF)–碳纤维粉(CFP)导电沥青混凝土,通过测试外力场对导电沥青混凝土电阻率的关系,结合线性随机电阻网络模型、动态随机电阻网络模型和非线性随机动态电阻器模型,研究导电沥青混凝土非线性导电行为,明确非线性导电行为的导电机制。结果表明:随着碳纤维掺量、油石比和压力的增加,电阻率呈现明显且相似的非线性下降趋势,其中,碳纤维粉掺量的增加导致电阻率先下降后上升;不同掺量的导电沥青混凝土伏安特性曲线均呈现非线性特征;在强电场作用下,导电相材料本身的非线性导电行为和绝缘态部分载流子通道导通引起的非线性导电行为共同导致了碳纤维–碳纤维粉导电沥青混凝土的非线性导电行为,并证明在电场作用下导电沥青混凝土存在隧道效应。

俄歇电子能谱测试中非导电粉末样品的荷电效应及消除方法

俄歇电子能谱在分析绝缘样品时,要得到正确的谱图,荷电效应是一个重要的影响因素。本文选取Al_(2)0_(3)粉末为例,提出了俄歇电子能谱分析Al_(2)0_(3)粉末样品的制样方法,通过对比几种减少荷电效应的实验,选取了以覆盖铝导电膜的方法进行实验。此方法流程简便、高效,降低了因荷电效应的影响,通过对Al203的标准摩尔比进行匹配,得到了比较好的匹配度。此方法检测结果较好。

石化储罐水性导静电防腐涂料制备及性能研究

为解决石化储罐在储存、运输过程可能由于积聚电荷产生的安全隐患,以及水性导静电涂料耐腐蚀性差的问题,以环氧类乳液及导电云母粉为主要原料制备导静电涂层,通过水热法制备了碳纳米点,将其以不同比例添加,增强涂层的防腐性能。并对涂层进行耐化学浸泡实验、耐盐雾实验以及力学性能测试。结果表明选用浙江安邦新材料发展有限公司的环氧乳液A与固化剂A作为成膜物,导电云母粉质量含量为15%,碳纳米点质量含量为1%的涂层表现最为良好。

基于骨架结构设计的高性能W10Cu材料制备及表征

用商用不规则W粉和球形W粉压制W骨架坯,经1800~2000℃真空烧结制备W骨架,在H_(2)气氛1350℃下熔渗Cu获得高致密W10Cu复合材料。结果表明:等离子球化W粉团聚消失,流动性更好,松装密度提升82%,相同压力下压坯密度提升15%。用球形W粉制备的W骨架可保持低的W-W连接度及良好的通孔率,为熔渗提供高品质骨架材料。W骨架经熔渗4h后获得W10Cu块体材料,其室温拉伸强度为680MPa,电导率为1.856S/m,比商用W10Cu的拉伸强度、电导率分别提升了41%、28%,可归因于低W-W连接度、Cu相良好的网状结构、Cu对W颗粒的包覆协同作用结果。本研究中新型低W-W连接度骨架结构设计可为高比重W、高通孔率W-Cu材料设计与开发提供思路。

间歇超声搅拌辅助化学镀制备核壳型镍包铜粉

[目的]通过优化化学镀配方和工艺,提升镍包铜粉的分散均匀性和镀层品质,以增强其作为导电填料在电子浆料中的抗氧化和导电性能。[方法]先采用Pd Cl_(2)体系活化铜粉,然后在间歇超声搅拌辅助下,采用酸性体系进行化学镀镍,制备出核壳型镍包铜粉。利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析了Ni镀层的微观形貌和晶体结构,研究了活化液组分、镀液配方和搅拌方式对化学镀的影响。通过扫描电镜观察、能谱面扫分析和热重分析,检验了在较优条件下制备的镍包铜粉的镍层包覆效果和抗氧化性能。[结果]铜粉活化的较优配方为:Pd Cl_(2)0.50 mmol/L,盐酸2.40 mol/L,聚氧乙烯20油醚2.0 g/L。铜粉化学镀镍的较优配方为:硫酸镍0.037 5 mol/L,乙酸钠0.15 mol/L,乙酸0.27 mol/L,聚氧乙烯20油醚2.0 g/L,聚乙烯吡咯烷酮1.5 g/L,还原剂溶液(次磷酸钠3.367 mol/L)滴加速率2.5 mL/h。化学镀过程中采用30 s超声振荡和30 s机械搅拌交替进行的间歇超声搅拌方式有利于制备出镀层均匀致密和颗粒分散性良好的镍包铜粉。[结论]在较优条件下制备的镍包铜粉具有镀覆率高、镍层致密、颗粒分散均匀、抗氧化性能好等优点。

基于正交试验的免蒸压加气混凝土的制备与性能优化

【目的】制备轻质高强、节能保温的免蒸压加气混凝土,寻找最优制备配合比,提高固体废弃物的利用率。【方法】基于正交试验采用极差分析和矩阵关联分析的方法确定免蒸压加气混凝土的基础最优配比,优化玻璃粉的掺入量来实现加气混凝土性能的提升。【结果】各因素对免蒸压加气混凝土的表观干密度和抗压强度的影响程度由大到小为铝粉掺量(质量分数,下同)、水泥掺量、水料比、聚丙烯纤维(PP纤维)掺量,加气混凝土的基础最优配比为水泥掺量为24%,水料比为0.44,铝粉掺量为0.13%,PP纤维掺量为0.4%;当玻璃粉质量替代率达到25%时,混凝土的综合性能达到最优。【结论】玻璃粉作为粉煤灰的替代材料,在改善免蒸压加气混凝土干密度、抗压强度、导热系数方面效果显著。