水基SiC浆料的喷雾造粒特性

以水为液体介质,制备分散稳定的水基SiC料浆,并利用喷雾造粒技术对水基SiC浆料进行造粒,研究了碳化硅浆料固含量及喷雾干燥工艺对造粒粉特性的影响。研究结果表明:浆料固相含量对造粒粉体粒径分布影响明显,粉体粒径随固含量的增加而增大。在最佳的干燥工艺条件下,碳化硅粉体流动性得到较大改善,素坯密度增加,陶瓷力学性能提高。     

铁封玻璃造粒粉的制备与性能研究

研究了3种铁封玻璃浆料体系与不同压力式喷雾干燥工艺参数对造粒粉基本性能(颗粒度、流动性、松装密度)的影响,并且研究了由造粒粉压制而成的坯体的密度和强度,以及坯体的排胶率、烧结收缩率和烧结密度等。结果表明,通过选取适当的粘结剂,采用60%~70%(质量分数)的固含量,0.7 mm直径的喷嘴和2~3 MPa的喷雾压力,可以使铁封玻璃造粒粉获得理想的工艺性能,如适当的粘合强度、可压性、可脱模性和可排胶性。     

喷雾造粒因素对粉体颗粒形成的影响

通过研究BaTiO3浆料的造粒干燥过程,雾化条件、固含量、粘结剂的比例对PTC粉体是形成致密颗粒还是空心颗粒或絮状颗粒起决定性作用,实验证实,高固体物含量、适量的粘结剂和较高泵压是形成实心颗粒、松装密度大的粉体的重要条件,并从理论上给出了初步分析结果。     

3D打印氧化硅陶瓷的制备及性能研究

随着陶瓷3D打印技术的发展,3D打印高性能陶瓷越来越受关注,在航空航天领域得到快速应用.通过研究分散剂、浆料pH、氧化硅粉体粒径和固相含量对浆料粘度和流动性的影响,可制备出粘度低、固相含量高、流动性好的陶瓷浆料.测试了不同固相含量对SiO2陶瓷的弯曲强度、烧成收缩率、气孔率和致密度的影响.结果表明:在68vol%的固相含量条件下,烧结后SiO2陶瓷的致密度达到74.32%,烧成收缩率为0.95%.     

喷雾造粒工艺因素对PTC热敏陶瓷粉体性能的影响

采用小型喷雾干燥造粒机制备PTC热敏电阻粉体,分析了浆料的粘度、粘合剂含量、固含量和干燥温度、泵压、喷嘴等因素对粉体性能的影响,得到了性能较好的粉体。     

喷雾造粒对固相烧结SiC陶瓷的影响

采用离心式喷雾造粒技术对SiC浆料进行造粒,研究了喷雾造粒对SiC粉体的流动特性、成型行为、烧结性能、力学性能及显微结构的影响机制。研究结果表明:喷雾造粒后,碳化硅粉体流动性得到较大改善,素坯密度增加,微观结构致密;固相烧结后,碳化硅陶瓷的烧结性能提高,陶瓷显微结构得到改善。     

流延法制备铌酸钾钠无铅压电陶瓷的工艺研究

以Na2CO3,K2CO3,Nb2O5等为原料,采用固相法合成了K0.5Na0.5NbO3的粉体,并以此粉体为主要原料,添加适量的分散剂、粘结剂及除泡剂制备浆料,采用流延法制备K0.5Na0.5NbO3膜片,研究了K0.5Na0.5NbO3固相含量、分散剂、粘结剂及除泡剂的种类及含量对流延浆料流延性能和对K0.5Na0.5NbO3陶瓷的影响。实验结果表明:流延膜的厚度在0.3mm时,选用三乙醇胺作分散剂效果最好,当固相含量在55wt%时,分散剂用量在2%时浆料的粘度为2000mPa.s,适合于流延工艺;粘结剂PVB的含量在8%时膜片强度较高。     

Cr2O3料浆固含量对其喷雾造粒料性能的影响

以Cr2O3料浆为对象,研究三聚磷酸钠、六偏磷酸钠和柠檬酸等减水剂对料浆ζ电位、粘度和固含量的影响,并采用SEM等方法观察分析了料浆固含量对Cr2O3喷雾造粒料松装密度、粒径分布和颗粒形状的影响.结果表明由三聚磷酸钠和水玻璃复合的减水剂对Cr2O3料浆的分散效果最好;在保证喷雾造粒要求的粘度下,加入0.2%复合减水剂可将Cr2O3料浆的固含量由不添加时的58%(w,下同)提高到79%;Cr2O3料浆固含量为75%的喷雾造粒料松装和摇实密度大,粒径分布合理,空心、破损和梨形颗粒少.     

粘结剂对喷雾造粒ZrO2(Y2O3)粉末特性的影响

采用喷雾造粒工艺对及ZrO2(Y2O3)粉体进行造粒，研究喷雾造粒过程中粘结剂含量对粉料流动性、填充性、造粒团聚体强度的影响，并对坯体成形过程中团聚体的破碎行为进行了分析。结果表明：喷雾造粒过程中粘结剂含量较高时，造粒团聚体粒子具有良好的填充性，但粒子强度高，在成形过程中不易破碎，将阻碍致密化烧结。     

封接玻璃密度与粘结剂含量对造粒粉性能的影响

选用不同种类玻璃粉末进行喷雾造粒实验,研究了密度与粘结剂含量对玻璃造粒性能与烧结性能的影响。结果表明,相同工艺条件下,玻璃粉密度增大,所得造粒粉平均粒径增加、球形度降低,保持相同流动性需要更高的粘结剂含量;造粒粉中的粘结剂含量影响封接玻璃的排胶温度与保温时间,对封接性能无明显影响。     

Effect of ball-milling parameters on the rheological properties of mold powder slurry

In this study, mold powder slurries with high solid loading and low viscosity were prepared during the ball-milling process for improving the homogeneity and mechanical properties of granules after spray-drying. The effect of ball-milling parameters, such as solid loading, binder/dispersant content, and ball-milling time, on the flowability, dispersibility, stability, and rheological behavior of mold powder slurries was systematically investigated by rheology observation and sedimentation tests. As these parameters varied, the slurry exhibited the shear-thinning behavior of a non-Newtonian fluid with a shear rate range of 0–50 s^?1, which was adequately described by the Herschel-Bulkley model. The optimal parameters that optimized the flowability, dispersibility, and stability of the slurry, along with its rheological behavior, were chosen as follows: solid loading, 60 wt%; modified sodium carboxymethyl cellulose binder content, 1.0 wt%; sodium tripolyphosphate dispersant content, 0.5 wt%; ball-milling time, 60 min.     

The preparation of SiCP/Ag–Cu–Ti hybrid tapes and application in the joining of silicon carbide ceramics

Abstract

A novel method of tape casting to fabricate ceramic-particulate-reinforced composite filler alloy tapes with low organics (no more than 6?wt.%) was developed, with which SiC_P/Ag–Cu–Ti hybrid tapes were successfully prepared and used in joining of sintered silicon carbide ceramics. The stress rheometer, scanning electron microscopy and energy dispersive spectrometer were used to characterize the rheological properties of slurry and microstructure of green tapes and joints. The slurry for tape casting consists of dispersant, binder, solvent, a mixture of ceramics particulates and metal powders, and no plasticizer was added. Castor oil phosphate was proven the suitable dispersant for the slurry, and the content of dispersant, binder, solid loading was optimized as 3?wt.%, 2.6?wt.% and 26?vol.%, respectively. The fabricated hybrid tapes possess good ductility and uniform thickness. The SiC particulates were homogeneously distributed in the metal powders matrix in both sides of the green tapes, and the distribution was retained in the SiC/SiC joints.     

石墨凝胶注模工艺研究

采用凝胶注模成型工艺制备了石墨浆料,研究了石墨粉体类型、pH值、分散剂加入量和固相含量对浆料粘度的影响,浆料温度对凝胶固化时间的影响,以及乙酰丙酮对素坯强度的影响.实验结果表明:当采用等静压石墨粉,pH值为7,分散剂加入量为4wt%,固相含量为50vol%时,可制备流动性良好的石墨浆料;浆料温度为3 ℃时,凝胶固化时间为5.6 min;当乙酰丙酮加入量为0.6wt%时,素坯强度达到15.8 MPa.     

Novel structure of ceramic tape for multilayer devices

To reduce the content of binders surrounding ceramic powders in a ceramic tape and the residual pore after burnout to a minimum, a ceramic tape with double layers was manufactured. One layer was comprised of only organic binder, which imparted sufficient strength and strong adhesive property to the green tape. The other one was a ceramic layer with a very small amount of binder. The binder content of the slurry for ceramic layer was less than 2 wt%, which could lower the viscosity, make the slurry well dispersed and considerably increase solid loading in the slurry. This higher solid loading led to higher green tape density, higher fired density of the product. The two-layer ceramic tape showed much better qualities than a common (or conventional) green tape especially in microstructure, laminatablilty, and tape density. In the multilayer structure made of the two-layer ceramic tape, the binder layer completely disappeared after binder-burnout and no defects from the two-layer structure were observed.     

氧化锆喷雾造粒料浆的制备

为了制备出流动性和稳定性好的喷雾造粒料浆,研究了分散剂三聚磷酸钠、六偏磷酸钠、聚丙烯酸铵和PEG2000对氧化锆喷雾造粒料浆流变特性的影响,认为聚丙烯酸铵对于氧化锆料浆具有较好的分散效果。在此基础上采用正交试验设计,以料浆的平均黏度和沉降度为评价指标,对料浆固含量、结合剂PVA和分散剂聚丙烯酸铵加入比例进行了优选,选用料浆固含量(w)为85%、结合剂PVA加入量(w)为8%、分散剂聚丙烯酸铵加入量(w)为0.5%,制备了综合性能较好的氧化锆料浆,利用此料浆获得了较好的喷雾造粒效果。     

Aqueous processing of Ce0.8Sm0.2O1.9 green tapes

An aqueous tape casting of Ce_0.8Sm_0.2O_1.9 (SDC) ceramics was developed using poly(acrylic acid) (PAA) as dispersant, poly(vinyl alcohol) (PVA) as binder, poly(ethylene glycol) (PEG) as plasticizer, and deionized water as solvent. Surface properties of SDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The rheology of the SDC slurries was evaluated with a rotary viscometer. The zeta potential measurement showed that the isoelectric point (IEP) for SDC powders in the absence of dispersant corresponds to a pH value of 3.66. The experimental results showed that the pH value greatly affects the rheology of the slurry. The optimum content to get a stable dispersed slurry is 2 wt% PAA in pH value range of 9–10. In presence of 2 wt% PAA dispersant, 55 wt% SDC powders exhibited shear thinning behavior, indicating that SDC slurry was homogenous and well stabilized. Homogeneous, smooth, and defect-free green tapes were successfully obtained by an appropriate slurry formula.     

Fabrication and performance of dielectric tape based on CaO-B2O3-SiO2 glass/Al2O3 for LTCC applications

A non-aqueous tape-casting process for fabricating CaO-B₂O₃-SiO₂ glass/Al₂O₃ dielectric tape for LTCC applications was investigated. An isopropanol/ethanol/xylene ternary solvent-based slurry was developed by using castor oil, poly(vinyl butyral), and dibutyl phthalate as dispersant, binder, and plasticizer, respectively. The effects of dispersant concentration, binder content, plasticizer/binder ratio, and solid loading, on the properties of the casting slurry and resultant tape were systematically investigated. The results showed that the optimal values for the dispersant and binder contents, plasticizer/binder ratio, and solid loading were 2.0 wt%, 7.5 wt%, 0.6, and 62 wt%, respectively. The resultant flexible and uniform, 120-μm-thick CaO-B₂O₃-SiO₂ glass/Al₂O₃ tape had a density of 1.90 g/cm^?3, tensile strength of 1.66 MPa, and average surface roughness of 310 nm. Laminated tapes sintered at 875 °C for 15 min exhibited excellent properties: relative density of 97.3%, ε_r of 7.98, tan δ of 1.3 × 10^?3 (10 MHz), flexural strength of 205 MPa, and thermal expansion coefficient of 5.47 ppm/°C. The material demonstrated good chemical compatibility with Ag electrodes, indicating a significant potential in LTCC applications.     

ZTA陶瓷注凝成型工艺中浆料性能的研究

对ZTA陶瓷注凝成型工艺中分散剂、pH值、氧化锆含量、固相体积分数、有机单体含量对浆料流变性的影响进行了研究.研究表明:合适的分散剂加入量可使浆料粘度降低;pH值的改变对浆料粘度有较大影响;随氧化锆含量、固相体积分数、有机单体含量增大,浆料粘度也会增大.     

Optimization of spray freeze drying parameters for spark plasma sintering of transparent MgAl2O4 spinel

Magnesium aluminate spinel (MgAl₂O₄) is considered as one of the most important spinels possessing desirable mechanical properties, with a wide range of applications at high temperatures. Powder granulation by spray freeze drying can lead to better powder flow and distribution in the mold, resulting in a specimen with high green density and strength. Accordingly, this study aimed at investigating the influential parameters on the granulation process of spinel powders via the spray freezing drying method. At first, spinel powders with various weight percents of 20, 25, 30, 35 and 50, and PVA binders with 0, 1, 2 and 8 wt% were investigated to prepare the optimal solution. Finally, the granules were sintered using the SPS method. The obtained bodies were tested by X-ray diffraction, SEM, FE-SEM, Viscosity and UV–Vis. The results showed that the optimal amount of the binder to obtain uniform granules in this process was 3%. Also, 35 wt% of solid loads represented the optimum amount for slurries, forming granules with the size range of 10–50 μm. By powder granulation, density experienced an increase of about 20%, leading to the growth of more than 15% in the in-line transmission for the IR range.