Fabrication of Yttria-Stabilized Zirconia Coatings Using Electrophoretic Deposition: Packing Mechanism During Deposition

Electrophoretic deposition (EPD) of yttria-stabilized zirconia (YSZ) particles on metal substrates has been examined as a function of EPD conditions and suspension properties. The packing density of particles, i.e., volume occupation of particles in a wet deposit, depends on the deposition time, applied voltage, and the electrical conductivity and solid concentration of the suspension. In addition, the packing density of particles in a wet deposit further increased when the deposit was immersed in a pure acetylacetone solvent with application of a constant electric field. The packing mechanism of YSZ particles in the wet deposit was discussed based on the electro-osmotic flow mechanism of YSZ particles during EPD.     

Effect of Dispersants on the Electrophoretic Deposition of Hydroxyapatite‐Carbon Nanotubes Nanocomposite Coatings

Isopropanolic Suspensions of HA nanoparticles (20 g/L) plus various concentrations of carbon nanotubes (CNTs) were prepared using Tris and triethanolamine as dispersant. The positively charged HA nanoparticles were heterocoagulated on the negatively charged CNTs and generated the HA‐CNT composite particles with net positive surface charge. The heterocoagulation was more intensive in dispersant‐containing suspensions (DCS) due to the higher zeta potential of HA nanoparticles in them. HA‐CNTs particles can be rotated and aligned parallel to electric field as a result of torque exerted on them due to the generation of a dipole moment in CNTs during electrophoretic deposition (EPD). The mobility of HA‐CNTs particles aligned parallel to electric field is ≈50% higher than that of HA nanoparticles leading to the faster EPD from DCS when CNTs are added into them. CNTs more efficiently reinforced the coatings deposited from DCS due to the stronger electrostatic bonding between CNTs and HA nanoparticles in them.     

钛白粉粒径分布对粉末涂料性能的影响研究

粉末涂料具有优异的涂装效果和良好的环保特性。就钛白粉粒径分布对粉末涂料遮盖力和光泽度的影响进行研究。     

A New Alternative for Obtaining Nanocrystalline Bioactive Coatings: Study of Hydroxyapatite Deposition Mechanisms by Cold Gas Spraying

The present article is intended to study the deposition mechanisms of bioactive hydroxyapatite (HA) particles by means of Cold Gas Spraying (CGS). A comparison of the deposition on two different substrates (Ti6Al4V and Al7075T6) and different particle sizes is presented. Although this is a more specific deposition technique for ductile materials, it is here shown that, in certain conditions, ceramic deposition is possible despite the inherent low ductility. The resulting internal structure and the features at the particle–substrate interface are discussed in view of Transmission Electron Microscopy examinations of a Focused Ion Beam lift‐out prepared sample. Mainly, under shock compressive loading, the porous sintered powder proceeds through pore collapse, fragmentation and densification as well as grain refinement. The process is described through different plastic mechanisms in ceramics. This opens a new alternative route to produce nanocrystalline HA coatings through a cost‐effective process.     

水性聚氨酯乳液的粒径影响研究

采用预聚体法,以聚酯多元醇、甲苯二异氰酸酯、二羟甲基丙酸(DMPA)制备了聚酯型水性聚氨酯乳液。考察了NCO/OH比、亲水扩链剂DMPA用量、中和度、乙二胺用量对水性聚氨酯乳液粒径的影响。结果表明,随着NCO/OH比的增大,乳液粒径增大;随着DMPA用量和中和度的增加,乳液的粒径减小;随着乙二胺用量的增大,乳液的粒径先减小后增大。     

基于粒径分布的静电粉末喷涂上粉率研究

为研究粉末粒径分布对静电粉末喷涂上粉率的影响,采用不同目数标准检验筛将商用粉末涂料进行人工筛选.通过测量铝合金试样单位面积增质量来表征静电粉末喷涂一次上粉率,研究粉末涂料粒径分布对静电粉末喷涂一次上粉率的影响.此外,通过设计矩形凹槽模拟喷涂死角区,采用槽内试样单位面积增质量与槽外单位面积增质量的比值表征静电粉末喷涂死角...     

Modeling Electrophoretic Deposition on Porous Non-Conducting Substrates Using Statistical Design of Experiments

Statistical design of experiments was used to model electrophoretic deposition of yittria-stabilized zirconia (YSZ) particles on porous, non-conducting NiO–YSZ substrates. A 2³–full-factorial matrix with three repetitions of the centerpoint was augmented with six axial runs and two additional centerpoints to form an inscribed central composite design. Fixed ranges of substrate firing temperature (1100°–1300°C), deposition voltage (50–300 V), and deposition time (1–5 min) were used as the independent design variables to model responses of YSZ deposition thickness, area-specific interfacial resistance (ASR), and power density. Regression equations were determined, which were used to optimize deposition parameters based on the desired responses of low interfacial polarization resistance and high-power density. Low substrate firing temperature (1100°C) combined with a low voltage (50 V) and minimal deposition time (1 min) resulted in a 6 μm-thick YSZ film, a power density of 628 mW/cm², and an ASR of 0.21 Ω·cm². Increasing the substrate firing temperature, voltage, and time to 1174°C, 215 V, and 3 minutes, respectively, reduced the ASR to 0.19 Ω·cm², increased YSZ film thickness to 25 μm, but had only a negligible effect on power density (600 mW/cm²).     

浅谈粉末涂料中的粒度理论及粒度仪的选择

介绍了粒度测量基础理论、基本概念以及常用的粒度仪,提出了涂料企业如何选择粒度仪的建议,并说明了粉末涂料粒度控制的重要性。     

Centrifugal Settling of Polydisperse Suspensions with a Continuous Particle Size Distribution: A Generalized Kinetic Description

The settling of a polydisperse suspension with a continuous particle size distribution (PSD) can be modeled by an equation of the generalized kinetic theory, which represents the limit case of a system of conservation laws for a finite number of size classes. A previous model of gravity settling of such a mixture is extended to settling in a rotating tube or basket centrifuge. A numerical scheme to approximate solutions of the generalized kinetic equation is defined and simulations are presented, illustrating the formation of sediment and the effect of various centrifuge geometries. In particular, the model predicts the radial variation of the composition of the sediment forming at the outer wall.     

粉末涂料粒径对涂装产品质量的影响

介绍了用激光粒度分布仪检测粉末涂料粒径的原理,分析了粉末涂料的粒径对涂料的流平性、上粉率、稳定性、回收率及涂装产品质量外观等的影响,结合实际生产经验,根据涂装产品质量的要求,提出了控制粉末涂料粒径的生产工艺参数。     

The Effect of Particle Size on the Mechanical and Microstructural Properties of Freeze‐Casted Macroporous Hydroxyapatite Scaffolds

Two different hydroxyapatites with the particle sizes of 3.9 and 1.69 μm were chosen. Slurries with initial hydroxyapatite concentration of 15 vol% were prepared. Different cooling rates from 2 to 14°C/min were utilized. The specimens were sintered at different temperatures of 1250–1350°C. The phase composition (by X‐Ray Diffraction), microstructure (by Scanning Electron Microscopy), mechanical characteristics, and the porosity of sintered samples were assessed. The porosity of the sintered samples was in range of ~57–83%, and the compressive strength varied from ~1.7 to 15 MPa. The mechanical strength of the scaffolds increased as a function of cooling rate and sintering temperature.     

团聚对亚微米5A分子筛粒度分析的影响

为了考察小晶粒分子筛团聚对亚微米级5A分子筛粒度分布结果的影响以及适宜的测定条件,实验以水为分散介质,六偏磷酸钠为分散剂,在超声波辅助作用下,用电位/粒度分析仪测定研究了试样浓度、分散剂用量和超声时间对亚微米级5A分子筛分散性的影响。结果表明,当分子筛含量大于5 g/L时,晶粒团聚现象严重,粒度分布呈现单峰(假象),导致粒度测量结果偏大;加入少量(0.005~0.195 g/L)的六偏磷酸钠,有缓解晶粒团聚作用,可将较大团聚粒子(大于2.8μm)分散为较小粒子(1.3μm左右),少量团聚粒子分散成单个晶粒,可测得较小晶粒粒径;超声作用可使较大团聚粒子(0.85~2.80μm)分布峰强度降低,相对较小粒子(0.30~0.85μm)分布峰强度增加。超声时间不宜太长,否则将加剧粒子间团聚,使得测定粒径偏大。当试样中5A分子筛含量为5 g/L,六偏磷酸钠浓度0.195 g/L、超声时间4 min条件下,测得5A分子筛试样粒径分布0.25~0.80μm,峰顶对应粒径为0.473μm,中位径(d50)为0.784μm,与电镜分析结果一致,说明是较为准确的粒度分析方法。     

Effect of Albumin on the Growth Characteristics of Hydroxyapatite Coatings on Alumina Substrates

A potent biomolecule, egg albumin (EA), has been used in the biomimetic coating of hydroxyapatite (HAp) on α-Al₂O₃ substrate. The same experiment was repeated without using EA and the results have been compared. In both cases, the substrates were incubated up to 6 days in SBF (simulated body fluid) at 37°C with a periodic replacement by freshly prepared SBF at 48-h intervals. The presence of EA influenced the growth and morphology of HAp crystals. Without EA, the HAp coating comprises irregular-shaped, serrated-edged plates whereas with EA, thick and regular-edged HAp crystal plates were observed on the α-Al₂O₃ substrate.     

不同溶剂中表面活性剂对氧化铝电泳沉积的影响

本文系统研究了不同溶剂体系下,添加不同表面活性剂对氧化铝悬浮液及其电泳沉积行为的影响.结果表明,溶剂和表面活性剂的不同搭配对氧化铝悬浮液的导电性、Zeta电势、悬浮性和电泳沉积产率都有显著的影响.同时,聚合物型表面活性剂PEG会改变悬浮液体系的粘度,也会大大影响氧化铝的电泳沉积.     

正丁胺对氧化铝悬浮液及其电泳沉积的影响

悬浮液的悬浮性和颗粒带电性是决定氧化铝电泳沉积的关键因素.本文研究了正丁胺的添加对不同溶剂和表面活性剂体系下氧化铝悬浮液的悬浮性能和电泳沉积的影响.结果表明,正丁胺的加入不利于以水为溶剂的悬浮液体系的悬浮性,同时造成沉积产率下降.而在醇类溶剂中,正丁胺的加入对非离子型表面活性剂的体系的表面带电性影响较大,而对醇类为溶剂的悬浮液沉积产率并无明显影响.以PEI为表面活性剂的醇类悬浮液中加入正丁胺能有效提高悬浮性和沉积产率.     

丙烯酸阳极电泳涂料的电泳涂装工艺研究

针对铝型材丙烯酸阳极电泳涂料,探讨了槽液固体含量、电泳电压、电泳时间、槽液pH等因素对漆膜外观和厚度的影响,确定了电泳涂装的最佳工艺参数:固体分5%～6%,电压120 V,电泳时间80～100 s,电泳槽液pH 7.6～8.1。     

Effect of Particle Shape on Inline Particle Size Measurement Techniques

The influence of the particle shape on the results of different measuring techniques was investigated. Considered were single‐frequency ultrasound technique, 3D optical reflectance measurement (advanced particle analyzing system with multi capture signal technology), and focused‐beam reflectance measurement probes as techniques which are usable inline and in suspension density ranges usually present in industrial crystallization processes. Advantages and shortcomings of these techniques are compared and discussed.     

Synthesis of Pure Hydroxyapatite and the Effect of Synthesis Conditions on its Yield,Crystallinity, Morphology and Mean Particle Size

Abstract

Hydroxyapatite (HAP) is a calcium phosphate compound with the chemical formula Ca₅(PO₄)₃OH. This compound is especially significant in biomedical applications since it resembles the mineral constituents of the hard tissue in the human body. Its biocompatibility, castability, and sinterability make it a very attractive material for simulating bones and therefore for implantations. The objective of this study was to produce HAP with a high purity and to determine quantitatively the exact percentage of HAP in the synthesized powder. Hydrothermal methods have been used to produce HAP. In the present work, Hydroxyapatite powder was produced using the chemical precipitation method in a batch and semi‐batch modes of operation. The effect of temperature, pH, and reactant addition rates on the mean particle size was studied. Results showed a maximum in the mean particle size at pH 9, while a minimum was observed at around 45°C. As the reactant addition rate increased the mean particle size increased as well. The purity of the obtained powder was characterized using both quantitative and qualitative techniques. The quantitative results were performed using the powerful Rietveld refinement method. The quantitative results were obtained for three samples. Results showed that pure HAP was produced at a temperature of 85°C, pH 9 and reactant addition rate of 1.3 mL/min.     

乙氧基镁催化剂粉末粒度及粒度分布测定的研究

用乙醇做分散介质,用激光粒度测定仪测定四个乙氧基镁催化剂粉末试样的粒度及粒度分布,测试快速、准确。试验结果显示乙氧基镁（德国）催化剂粉末粒度最小,粒度分布集中,在四个样品中质量最好,试验结果令人满意。