热喷涂用纳米结构Al_2O_3/TiO_2/SiO_2团聚体粉末的研究

对喷雾干燥和不同温度热处理后Al2O3/TiO2/SiO2纳米团聚体粉末的流动性、松装密度及振实密度进行了测试,对喷雾干燥后的粉末进行了热重-差热分析,通过扫描电镜观察了粉末颗粒形貌和大小,采用X射线衍射分析了不同温度热处理后粉末的相组成,并对粉末的综合性能进行了比较。实验结果表明:在1000～1450℃热处理后的Al2O3/TiO2/SiO2纳米团聚体粉末颗粒仍近似球形,粒径在10～100μm之间。随着热处理温度升高,纳米团聚体大颗粒表面发生塌陷,大颗粒之间发生连接,大颗粒内部纳米颗粒明显长大。低于1250℃热处理后的粉末流动性好,振实密度高,适于等离子体喷涂制备纳米结构涂层。     

热处理对喷雾干燥制备的Al2O3纳米团聚体粉末的影响

对喷雾干燥和经不同温度热处理后的Al2O3纳米团聚体粉末的松装密度及振实密度进行了测试,通过扫描电镜观察分析了团聚体粉末颗粒的大小和形貌以及纳米晶颗粒的大小,采用X射线衍射分析了热处理后粉末的相组成.实验结果表明,在1050～1250℃热处理后的Al2O3纳米团聚体粉末颗粒仍近似球形,粒径在10～90μm之间.随着热处理温度升高,纳米团聚体大颗粒表面发生塌陷,大颗粒之间发生连接,大颗粒内部纳米颗粒明显长大.低于1250℃热处理后的粉末流动性好,振实密度高,适于等离子体喷涂制备纳米结构涂层.     

喷雾干燥YPSZ纳米结构热喷涂粉末材料制备及表征

YPSZ纳米结构粉末材料的研究是热喷涂制备YPSZ纳米结构涂层必须首先进行研究的问题。本文采用喷雾干燥方法制备适合于热等离子体喷涂的YPSZ纳米结构粉末原料,同时采用等离子体喷涂制备涂层。利用扫描电子显微镜分析晶粒大小、颗粒形貌,X射线衍射分析相组成,对喷雾干燥后粉末进行热重-差热分析,测定粉末的松装密度、振实密度及流动性。结果表明制备的YPSZ粉末材料具有实心、流动性好、松装密度高、振实密度高、球形度高、单斜相少等优点,采用热等离子体喷涂沉积制备YPSZ纳米结构涂层。     

形貌可控的Cr_2O_3纳米颗粒的制备与表征

室温下,将三氧化铬(CrO_3)和聚乙烯醇(PVA)在水溶液中反应合成聚合物前驱体,退火处理得到不同形貌的Cr_2O_3纳米颗粒。采用热重-差热分析仪(TG-DTA)、傅里叶红外光谱仪(FT-IR)、粉末X射线衍射仪(XRD)和扫描电镜(SEM)对所得样品进行了分析。结果表明,750℃退火后获得纯的单相Cr_2O_2纳米颗粒;通过控制PVA和CrO_3的初始反应比例,得到了球形和片状的Cr_2O_3纳米颗粒。     

YPSZ纳米结构热喷涂粉末材料工艺优化研究

热等离子体喷涂制备YPSZ纳米结构涂层必须首先进行YPSZ纳米结构粉末材料的研究.本文采用浆料分散、喷雾干燥、热处理的方法制备适于热等离子体喷涂纳米结构涂层的球形、致密YPSZ纳米结构粉末材料.测定浆料的粘度、沉降高度曲线表征浆料的均匀性和稳定性,利用扫描电子显微镜、x射线衍射分析对粉末材料的微观组织及相结构进行分析,利用热重/差热分析对热处理工艺过程进行分析.结果表明:采用优化的工艺成功制备出球形、结构均匀、致密的YPSZ纳米结构粉末材料,适于热喷涂制备YPSZ纳米结构涂层.     

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。     

选区激光熔化用Inconel625合金粉末的特性

为了研究适用于选区激光熔化技术(SLM)用Inconel625合金粉末的性能特征,测定其粒径大小和分布、颗粒形貌特征以及粉末的流动性和松装密度,分析粉末不同特性相互之间的影响关系并对粉末进行SLM成形验证。结果表明:用于SLM的Inconel625合金粉末粒径范围是20~60μm,平均粒径约为35μm;粉末颗粒基本呈球形,平均球形度大于0.7;流动性每50g低于20 s,松装密度高于4.0 g/cm~3;SLM成形件的拉伸强度、延伸率均超过ASTM标准规定的Inconel625合金SLM成形件最低力学性能要求。     

新型喷雾干燥法制备LiFePO_4/C复合材料及其性能研究

通过新型喷雾干燥技术及热处理制备出具有球形二次形貌结构的纳米LiFePO4/C复合材料。首先合成了纳米FePO4颗粒(约20nm),并与Li2CO3和一定量的蔗糖均匀混合,对材料前驱体进行碳包覆,通过喷雾干燥获得了前驱体二次颗粒;经过热处理获得了由一次颗粒组成的二次颗粒。详细研究了碳含量对一次颗粒粒径及复合材料性能及形貌的影响,发现当LiFePO4/C复合材料中碳含量为5.3%(质量分数),样品拥有良好的形貌结构和最佳的性能,0.1,1和5C下的比容量分别为162,145和116mAh/g。     

热喷涂粉末的制备技术

热喷涂粉末占热喷涂材料总用量的70%以上,热喷涂粉末的成分、分布、形貌和粒度因粉末制备方法而异.雾化法、熔融+破碎法、研磨+烧结法、球磨法、喷雾干燥法、包覆法和等离子体雾化法可用于制备热喷涂粉末,为了获得致密的球形热喷涂粉末,等离子体球化技术得到迅速发展.综述了热喷涂粉末的常用制备方法,重点介绍了先进的等离子体球化技术.     

热障涂层用La2O3、Y2O3共掺杂ZrO2陶瓷粉末的制备及其相稳定性

采用反向化学共沉淀法制备了热障涂层用La₂O₃-Y₂O₃-ZrO₂（LaYSZ）原始复合粉末, 将原始粉末团聚造粒和热处理后得到适于等离子喷涂的团聚粉末. 采用电感耦合等离子体原子发射光谱（ICP-AES）、扫描电子显微镜（SEM）、霍尔流速计、X射线衍射（XRD）等方法分别对LaYSZ的化学组成、微观形貌、流动性和松装密度、高温相稳定性进行了研究. 结果表明: LaYSZ团聚粉末室温呈四方ZrO₂结构, 在1150℃热处理2h后为致密的球形或近球形颗粒, 粉末流动性较好, 适于等离子喷涂. LaYSZ团聚粉末在1300℃热处理100h后仍保持单一的四方ZrO₂晶型, 而8YSZ中有12mol%的四方相转变为单斜相; LaYSZ在1400℃热处理100h后, 单斜相含量为2mol%, 而8YSZ中单斜相含量达到47mol%, 表明La₂O₃、 Y₂O₃共掺杂稳定ZrO₂较单一Y₂O₃ 稳定ZrO₂具有更好的高温相稳定性.     

利用离心喷雾干燥制备球形粉体的工艺因素研究

研究了铝矾土料浆的离心喷雾造粒过程,考察了料浆固含量、粘度、喷雾头的旋转速度对粉体干燥的影响.从颗粒内部水分迁移的距离、空气进出口温度两方面,分析了蘑菇头颗粒、变形颗粒、球形颗粒和破裂颗粒等颗粒形貌的形成原因,并优化了一组工艺参数:喷雾头转速为12000r/min,料浆固含量为50%,热风入口温度为300℃,废气出口温度为115℃,塔内负压为-350Pa,料浆流速为4L/h,料浆的粘度为14s,在此条件下能制备出球形度高、颗粒粒径集中分布在55μm左右的粉体.     

SiC/纳米TiN水基复合料浆特性及喷雾干燥

以四甲基氢氧化铵(TMAH)为分散剂, 纳米TiN、亚微米SiC粉体为原料, 分别制备单组分水基料浆及复合料浆, 分析了SiC/纳米TiN复合料浆的分散稳定机制以及喷雾干燥行为. 研究结果表明, TMAH在纳米TiN、SiC颗粒表面形成特征吸附, 通过静电作用和空间位阻协同作用提高颗粒的分散性; 当pH=8、TMAH加入量为0.75wt%时, 复合浆料分散稳定, 喷雾干燥制备的SiC/纳米TiN复合粉体流动性好, 且分布均匀.     

Deagglomeration of spray-dried submicron particles by low-power aqueous sonication

The resistance to deagglomeration of spray-dried agglomerated particles of submicron size was investigated using an ultrasonication system in water. Submicron agglomerates consisting of water-insoluble primary particles with size of 10 or 100 nm were prepared in different shapes by varying the heating profile during spray drying. Deagglomeration experiments were performed using a low-power sonication device. Spherical agglomerates were found to be more resistant to ultrasonic forces, while dent- or doughnut-shaped agglomerates tended to break down. The results show that the shape of the agglomerate plays an important role in the energy balance of the ultrasound operation. The energy produced from the collapse of cavitation bubbles in the ultrasound vessel may be used to promote motion of the agglomerates and deagglomeration.     

Fabrication and characterization of heat and plasma treated SiC/Al2O3-YSZ feedstocks used for plasma spraying

The SiC/Al₂O₃-YSZ (ZrO₂ + 8 wt.% Y₂O₃) powders with different SiC particle sizes were fabricated and treated from spray drying, heat treatment, and plasma spraying. The morphology, phase composition, flowability and density of powders were analyzed. The sphericity and flowability of powders treated by plasma flame are increased greatly, and the particle surface is very smooth. The flowability and density of powder with nano SiC were evident better than those of powder with submicron SiC. The optimum flowability and compactness of powder with submicron SiC is obtained when the critical plasma spray parameter is 341 and 325, respectively. For nano size SiC, the optimum flowability and the maximum compactness of powders are obtained with critical plasma spray parameter of 341. The grain size of powders is increased after heat treatment and plasma spraying. The SiC is oxidized to SiO₂ in the powders after heat treatment and plasma spraying. The Y₂O₃ dissolved from 8YSZ solid solution at higher critical plasma spray parameter. Besides, there is no phase transformation of ZrO₂ for powders. The metastable phase of Al₂O₃ appeared in feedstocks with submicron SiC, but no metastable phase was formed in feedstocks with nano SiC particles, which nano SiC can hinder the formation of Al₂O₃ metastable phase. The densification process and mechanism of reconstituted particles used for plasma spraying were analyzed from surface morphology, cross section and simulation.     

Neue Technologie zur Herstellung von Wolframschmelzkarbid

New Manufacturing Technologies of Two Phase Tungsten Carbide A promising application of the inductively coupeld RF Plasma technology is the one‐step spheroidization and solidification of porous, agglomerated particles. The acclomerated particles are produced by spray drying in a solution of binder and agent. The feedstock consists of WC/W₂C with a dispersity of 90 – 120 μm and a carbon concentration of 4.8 mass%. It is the aim of the project to obtain dense spheroidzed particles with definite carbon content in the region of 3.8 – 4.3 mass%.     

CFD simulations of droplet and particle agglomeration in an industrial counter-current spray dryer

In this study, CFD simulations of particle and droplet agglomeration in an industrial counter-current spray dryer are presented. For this purpose, a modified form of the stochastic collision agglomeration model is proposed. This model takes into account droplet–droplet collision as well as wet and dry particle interaction. These events are coupled with heat, mass and momentum transfer. A comprehensive moisture evaporation model based on the concept of characteristic drying curve (CDC) was applied to predict the drying kinetics of the detergent slurry. Due to high instability in air flow inside the drying chamber, simulations were carried out under transient condition. A comparison between time-averaged simulation results and measurements, which were performed on an industrial spray drying installation, shows a good agreement. This finding proves the correctness of the developed agglomeration and drying models. The presented methodology of CFD simulations of agglomeration can be used to design or optimise spray-drying installations and to predict the final particle size distribution of the product.     

Chromaticity,brightness and aging of silica spray coated zinc sulfide silver phosphor particles

A spray drying approach was used to coat 15 nm SiO₂ continuous films onto ZnS:Ag phosphor particles. The coating was deposited on the particles by simultaneously spraying a slurry consisting of a solution of TEOS and ethanol with the solid phosphor particles into a heated drying column. The cathodoluminescent spectra of silica coated phosphor has CIE 1931 chromaticity coordinates of X ∼ 0.055, Y ∼ 0.085, brightness that is 90% of the uncoated phosphor brightness, and improved aging behavior under laboratory testing conditions.     

Preparing of nanostructured Al2O3–TiO2–ZrO2 composite powders and plasma spraying nanostructured composite coating

Nanostructured Al₂O₃–TiO₂–ZrO₂ composite powders for plasma spraying were prepared by spray drying granulation technology. The effects of processing parameters on the microstructure and properties of composite powders were investigated. The results show that with increasing the slurry solid content, the particle size of powders increases, and the bulk density of powders increases, and the flowability of powders increases firstly and then decreases. With increasing the binder content, the particle size of powders increases, and the bulk density of powders increases, and the flowability of powders increases firstly and then decreases. With increasing the spray drying temperature, the particle size of powders increases, and the bulk density and flowability of powders increases firstly and then decreases. The most appropriate spray drying parameters are the slurry solid content of 40 wt.%, the binder content of 2.0 wt.% and the spray drying temperature of 250 °C. The nanostructured composite coating was successfully prepared by using the as-prepared nanostructured Al₂O₃–TiO₂–ZrO₂ composite powders as feedstocks. The nanostructured coating possessed higher hardness and toughness compared with the conventional microstructured one, which was attributed to the use of the nanostructured composite powders feedstocks.