等离子喷涂氧化锆纳米涂层显微结构研究

利用大气等离子喷涂（APS）技术,在不锈钢基体上制备了氧化锆纳米结构涂层.运用XRD、SEM与TEM等分析手段对喷涂用粉末原料和涂层的显微结构、物相组成进行了观察和确定.实验结果表明,纳米氧化锆粉末经喷雾造粒后的颗粒粒径主要分布在15～40μm之间,流动性好,适合于等离子喷涂用.等离子喷涂氧化锆纳米涂层颗粒分布在60～120nm之间,晶粒发育良好.涂层物相由四方和立方相氧化锆所组成.氧化锆纳米涂层的气孔率约为7％,结合强度为45MPa。     

氧化锆空心球形粉末的粒度分布对流动性的影响

采用喷雾造粒和高温球化工艺制备空心球形氧化锆(YSZ-1型)喷涂粉末.研究了各种粒度区间的粉末流动性,将各种粒度区间的粉末进行适当配比,找出了粒度分布在产品标准规定的范围内流动性较好的配比方案,并进一步研究了超细粉末(粒径＜5μm)含量对粉末流动性的影响.     

SiC喷雾造粒粉的影响因素研究

通过SiC喷雾造粒试验,分析了影响SiC造粒粉性能的因素,如进出口温度、浆料的固含量、喷雾压力及进料速度等;同时总结出了喷雾造粒时的合理工艺,制备出了松装密度为0.91 g/cm3,流动性为20 s(样品量为30 g),且粒形较好、适于成型的SiC粉体。     

BSAS喷涂粉体制备工艺及其对涂层性能的影响

采用不同工艺制备BSAS(BaO-SrO-Al_2O_3-SiO_2)喷涂粉体。研究喷涂粉体特性及其对等离子喷涂工艺制备的环境障涂层结构和性能的影响。结果表明:粉体造粒工艺制备的BSAS喷涂粉体颗粒不均匀,流动性差。制备的涂层粗糙,孔隙率高,结合强度为24.1MPa;造粒烧结工艺制备的BSAS喷涂粉体表面圆滑,流动性好,沉积效率高。制备的涂层结构均匀,少孔隙,无裂纹,结合强度达到29.8MPa,涂层中BSAS相保留率最高,达到53.2%;熔融破碎工艺制备的BSAS粉体呈致密不规则块状,虽然流动性好沉积效率高,制备的涂层光滑且孔隙极少,但微裂纹较多,结合强度仅为14.2MPa,粉体经喷涂后发生相结构重组,BSAS相保留率为20.5%,对涂层的高温性能不利。分析认为,造粒烧结工艺制备BSAS粉体具有工艺过程简化、粉体质量好、相稳定性高等优点,更适合于等离子喷涂的要求。     

Ti-Co-B4C复合粉体喷雾造粒浆料的流变特性研究

研究了分散剂(A15)、粘结剂(PVA)及固相含量等流变学因素对Ti-Co-B4C复合粉体喷雾造粒粉体流动性和松装密度的影响.结果表明:A15的加入,增大了浆料zeta电位的绝对值,能够有效的分散浆料.在相同的剪切速率下,浆料的粘度随着A15的添加先增大再减小,过低A15的添加起不到分散浆料的目的,而过量添加A15会提高浆料的pH值,对浆料的稳定性和喷雾造粒粉末成型不利;在一定的剪切速率下,浆料的粘度随着PVA的添加先增大再减小然后又增大,过低PVA的添加会降低喷雾造粒粉末的流动性,而PVA的过量添加导致浆料的粘度出现失稳状态,影响浆料的流动性.相反,在一定的剪切速率下,浆料的粘度随着固相含量的增加而增大,而过低的固相含量不利于浆料的稳定性和喷雾造粒粉末的成型性,过高的固相含量有害于浆料的流动性和喷雾造粒的顺利进行.但是所有复合粉体的浆料都具有剪切变稀的特性,有利于其喷雾造粒.综合分析得出:当固相含量为浆料质量的35%,A15和PVA为固相粉末质量的0.5%和2.5%时,浆料具有合适的粘度和良好的分散稳定性.所获喷雾造粒粉末为球形或近似球形,具有较高的松装密度和良好的流动性,满足后续反应喷涂的要求.     

液相烧结碳化硅喷雾造粒工艺控制

阐述了液相烧结SiC陶瓷喷雾造粒过程中的相关制备工艺,研究了浆料的特性、干燥温度、喷雾压力等因素对粉体性能的影响.并通过实验总结出一套合理的工艺参数,制备出球形实心颗粒粉料.粉料的松装密度0.88 g/cm3、休止角33.5°、平均粒径50μm,具有良好的流动性及快速填充性,可直接用于干压成型.     

单分散球形YAG透明陶瓷粉体的喷雾造粒制备及其性能表征

采用无水乙醇基浆料结合喷雾造粒工艺制备YAG透明陶瓷粉体, 通过扫描电子显微镜、压汞仪、能谱仪及紫外–可见–红外透过光谱系统研究了不同PVB粘结剂添加量下YAG造粒颗粒的形貌、尺寸、成型性能及其破碎行为, 对成型素坯的孔分布及烧制透明陶瓷的显微结构及光学性能进行了详细表征。在优化PVB添加量为1.0wt%时, 造粒粉体为实心单分散颗粒, 球形度高、化学均匀性好, 其平均粒径约为40 μm, 成型性能优异; 在75 MPa压力下, 造粒颗粒完全破碎形成密实均一的坯体结构。烧结后的YAG透明陶瓷显微结构均一, 无气孔及其他缺陷, 光学质量优异。     

纳米YSZ热喷涂粉末的制备及其性能

基于纳米涂层的优异性能,研究了纳米YSZ热喷涂粉末的制备工艺。喷雾干燥造粒后,分别用霍尔漏斗法和电子扫描显微镜对团聚体粉末的流动性、松装密度及微观形貌进行了测试与分析。研究发现,固含量越高,粉末的流动性及松装密度性能越好,但过高的固含量反而会影响造粒效果;在固含量一定的情况下,黏结剂含量适中的浆料造粒后团聚体粉末的流动性更好。为了得到性能更好的团聚体粉末,合理的后续处理方法是在电流300A,电压40V条件下进行等离子致密化。     

化工产品熔融造粒技术及其应用

与粉状、片状和块状形式相比,球形颗粒具有外形美观、不易结块、流动性好、便于计量、使用方便等优点而倍受青睐,是固体化工产品最理想的形式.塔式振动喷流造粒技术、喷雾造粒技术和流化床冷却造粒技术是天津大学化工学院造粒工程技术中心近年来开发的适用于制备球形颗粒的化工产品熔融造粒技术,并在烧碱、硝酸钾、硝酸钠、氯化钙、橡胶防老剂RD的生产中得到成功应用.本文对这三种造粒技术的机理、工艺特点及工程应用情况进行了简单介绍.     

昆山元成机械有限公司流动层造粒干燥机

昆山元成机械有限公司生产的流动层造粒干燥机功能包括粉末或颗粒的干燥．速度为一般烘箱的10～20倍；在流动的细粉末上喷上黏合剂或主成份．使得细颗粒完成造粒后．即溶性及流动性都非常好。     

用内凝胶法制备球形Y2O3-ZrO2等离子喷涂粉料

以无机物为前驱物,用内凝胶法制备了适合于等离子喷涂的、粒径在10～50μm范围内的、用氧化钇稳定的氧化锆（YSZ）球形粉末,实验结果表明,通过改变乳化条件可以控制这种粉末的形貌、粒径和粒度分布．利用SEM和光学显微镜观察发现,用该方法得到的粉末主要是球形的,并且符合粒径分布的要求（5～50μm）．致密的球形粉末显示出良好的流动性．差热分析表明,用47mol％氧化钇稳定的氧化锆（YSZ）粉末在468℃有一放热峰,是YSZ粉末的相转变温度．XRD分析表明,上述粉末在800℃条件下煅烧可以得到100％非平衡四方相（t’）的YSZ粉末,没有单斜相存在．     

Dry mixing of cathode composite powder for all-solid-state batteries using a high-shear mixer

All-solid-state lithium-ion batteries (ASSLIBs) are promising candidates for next-generation batteries because of their various attractive properties. The uniform mixing of active materials (AMs) and solid electrolytes (SEs) is important for high-performance ASSLIBs. However, most AMs and SEs have poor flowability owing to their small particle size, which makes it difficult to uniformly mix the AM and SE particles. This study is focused on a high-shear mixer (HSM) as a scalable method to uniformly mix the AM and SE particles. The objective of this study is to determine the optimal operating conditions for HSM and its effectiveness in AM-SE mixing. The higher rotating speed of the chopper caused uniform SE dispersion by deagglomerating the SE particles and improving the adhesion of SE onto the AM particles, affording an electrode with well-balanced electrical/ionic conductivity and lower internal resistance. The ASSLIB with this electrode exhibited lower electrode polarization and excellent rate and cycle performance. Additionally, it has been demonstrated that the HSM could lead to a more uniform SE dispersion than conventional lab-scale mixing methods, resulting in significantly improved battery performance. Moreover, insights into the process-homogeneity-performance relations have been obtained.     

等离子喷涂用Y2O3稳定ZrO2空心球形粉末制备技术及涂层性能的研究现状

原始粉末是影响等离子喷涂热障涂层组织结构和性能的主要因素之一。Y_2O_3稳定ZrO_2(Yttria stabilized zirconia,YSZ)空心球形粉末综合了熔融破碎粉末的预合金化效果好和团聚烧结粉末的流动性好的优点。采用该粉末制备的YSZ热障涂层的隔热性能、抗热震性能以及抗烧结性能等均显著提高,是目前综合性能最为优异的热障涂层之一。结合国内外研究情况,文章主要介绍了喷雾干燥法、等离子球化法以及模板法制备等离子喷涂用YSZ空心球形粉末的原理和优缺点;同时,对等离子喷涂过程中YSZ空心球形粉末熔滴的飞行特性、铺展凝固行为以及YSZ空心球形粉末制备涂层组织结构及性能的研究进行了概述;最后,指出了目前研究中存在的问题并对其未来的研究方向进行了展望。     

一种从无机锆盐水溶胶制备球形氧化锆颗粒的方法及其原理

以氧氯化锆为前驱体 ,通过加入氨水升高溶液的 pH值 ,形成锆的水溶胶。将丙醇逐渐加入锆的水溶液中 ,由于醇的介电常数比水小 ,加醇的结果将降低溶胶介质的介电常数 ,由DLVO理论可知减小介质的介电常数会使胶体颗粒之间的静电斥力下降 ,引起溶胶失稳 ,胶粒互相聚集 ,形成大的球形粒子同液体介质分离。从溶胶中析出的是非晶态的Zr4 O2 (OH) 8Cl4 ,经过 6 5 0℃下煅烧转变成单斜型氧化锆。胶体凝聚过程的动力学方程可写成 :( 1-Y ) -1.5=kt ,其中Y为相对产率 ,该过程的反应活化能为 115 .79kJ/mol     

Preparation and properties of uniform mixed and coated colloidal particles

Colloidal dispersions of uniform spherical particles of zirconium basic sulphate and zirconium oxy-basic carbonate were prepared by ageing zirconium sulphate solutions at elevated temperatures in the presence of urea. Different chemical compositions of the above products resulted when the ageing temperature was altered. Depending on the nature of the original solids, calcination at 800° C resulted in the formation of tetragonal or monoclinic zirconia. Under certain conditions a mixed phase, including cubic zirconia, has also been identified. The particle morphology was retained during these transformations. Coprecipitation in mixed solutions of zirconium and yttrium salts aged at 80° C yielded composite spherical particles of basic carbonate with a zirconium to yttrium ratio of the solid similar to that used in the initial solution. Zirconium basic sulphate particles coated with yttrium basic carbonate were prepared by ageing, in the presence of urea, a Zr₂(OH)₆SO₄ dispersion containing yttrium nitrate.     

微纳米金属颗粒复合与整形技术

介绍了微纳米颗粒复合化系统的工作原理。采用颗粒复合化系统对HDH钛粉和还原铁粉进行球化处理,可使钛粉和铁粉由原来的不规则形状变为近球形,改善流动性。球形钛粉的烧结密度高达99%、临界装载量为66%,比原始钛粉高3%。利用机械分散和颗粒复合化系统联合工艺制备的复合球形Al2O3/Cu颗粒,烧结后,Al2O3在铜基体中得到了良好的分散。结果表明:颗粒复合化系统能实现不规则颗粒的整形以及两种或两种以上不同粒径粉体的均质化复合。     

Bottom‐Up Design of Composite Supraparticles for Powder‐Based Additive Manufacturing

Additive manufacturing promises high flexibility and customized product design. Powder bed fusion processes use a laser to melt a polymer powder at predefined locations and iterate the scheme to build 3D objects. The design of flowable powders is a critical parameter for a successful fabrication process that currently limits the choice of available materials. Here, a bottom‐up process is introduced to fabricate tailored polymer‐ and composite supraparticles for powder‐based additive manufacturing processes by controlled aggregation of colloidal primary particles. These supraparticles exhibit a near‐spherical shape and tailored composition, morphology, and surface roughness. These parameters can be precisely controlled by the mixing and size ratio of the primary particles. Polystyrene/silica composite particles are chosen as a model system to establish structure–property relations connecting shape, morphology, and surface roughness to the adhesion within the powder, which is accessed by tensile strength measurements. The adhesive properties are then connected to powder flowability and it is shown that the resulting powders allow the formation of dense powder films with uniform coverage. Finally, successful powder bed fusion is demonstrated by producing macroscopic single layer specimens with uniform distribution of nanoscale silica additives.     

Structural study of zirconia nanoclusters by high-resolution transmission electron microscopy

Monodisperse and uniformly spherical ZrO₂ nanostructured clusters have been synthesized by microwave-assisted sol–gel processing. The techniques used produced molecular-structured precipitates from which zirconia nanometric particles were easily obtained. These particles retained their stability during the subsequent separation process. The microwave treatment was proven to be highly beneficial for assisting the sol–gel processing, mainly because of its contribution to the mixed dispersion and thermal effects. The zirconia nanoclusters thus formed were subsequently characterized by high-resolution electron microscopy to study the nanostructural morphology and transformation defects.     

DEM simulation analysis of the improvement in particle discharge flowability using adhesive force distribution models based on admixed particle coating

Particle flowability can be improved by admixing particles smaller than the original particles (main particles). However, the details of the mechanism of this improvement are not yet fully understood. In this study, we used a discrete element method simulation to investigate the effects on the particle flowability of the adhesive force distribution at each contact point based on the admixed particle coating. We used the non-uniform, random, and uniform surface adhesive force distribution models and calculated the discharge flow rates. The non-uniform models had a larger discharge flow rate compared with the other models because the non-uniform adhesive force distribution destabilized the force balance in the bed, and thus destabilized the particle arching structure, which generated discontinuous layers more frequently and improved the flowability. Consequently, in a smaller particle admixing system, the adhesive force distribution at each contact point would help to improve the flowability.