摘要：
Electrokinetic and gel behavior of Si3N4 aqueous suspension for gel casting were investigated in this study. The zeta potential of dilute and concentrated suspension with organic binder was evaluated innovatively. The influence of the binder composition and solid loading on the gel time and viscosity of the slurry was studied. The result showed that absolute value of zeta potential would be lower in the concentrated suspension or suspension with organic binder. The release of NH3 during ball milling would increase the pH value, while the dissociation of the soluble SiO2 would increase it during setting. The gel time of the suspension was significantly affected by the organic binder addition. Higher pH value and lower solid loading was conductive to obtain slurry with lower viscosity.
摘要：
A fused deposition modeling(FDM)system via screw extrusion suitable for feeding granular feedstocks with high solid loading was developed. Key parameters included aspect ratio of the screw, the compression ratio and pitch etc. In order to get constant extruded mass flow and wire diameter a processing window was determined by optimizing the barrel temperature, the nozzle diameter and the screwing speed. Microstructural characterization coupled with flexural strength measurement revealed that a higher printing temperature was beneficial to the inter layer bonding. The sintered zirconia ceramic samples with 99% of theoretical density of the 3 mol% yttria stabilized tetragonal zirconia polycrystal (3Y-TZP) and flexural strength of 890 +/- 60 MPa was obtained. A set of zirconia ceramic parts with complex geometries and controllable dimensional accuracy was also successfully prepared for demonstrating the potential of the technique.
摘要：
In this paper, the dynamic process of thermal debinding was analyzed. The critical thickness of debinding was defined as the thickness at which the steps to control dynamics change from diffusion of gas products in liquid binder to diffusion or permeation in pores. Subsequently, the equation of critical thickness was deduced. The results show that the critical thickness of debinding is independent of the thickness of the green body, but mainly depends on the particle size, solid content, and binder composition. Moreover, larger particle diameter and higher solid loading will contribute to a greater critical thickness, which means that higher heating rate can be used in the initial stage of debinding. The prediction is in agreement with the experimental results. In addition, the effect of binder composition on the formation of cracks during thermal debinding was investigated by thermogravimetry combined with FTIR spectrometry (TG-FTIR) analysis of binders and thermogravimetric curves of feedstocks. It suggests that the feedstock containing polystyrene and acrylic resin is helpful for rapid and safe thermal debinding.
摘要：
Ca3Dy3Ti7Ta2O26.5 and Ca3Er3Ti7Ta2O26.5 oxides were synthesized using a high-temperature solid-state fritting technique, and the thermophysical performances of these two oxides were investigated. Both Ca3Dy3Ti7Ta2O26.5 and Ca3Er3Ti7Ta2O26.5 show a monophasic pyrochlore-type lattice. The thermal conductivity of Ca3Er3Ti7Ta2O26.5 is lower than that of Ca3Dy3Ti7Ta2O26.5. The oxides exhibit lower thermal conductivities than YSZ owing to their complex elemental compositions, large number of ions, and high oxygen vacancy concentrations. The thermal expansion coefficients of the obtained oxides are similar to that of YSZ.
摘要：
Abstract: Filament is always used in traditional fused deposition molding, which is not suitable for 3D printing of engineering ceramics. A fused deposition modeling method with screw extrusion suit-able for granular feedstock with high solid loading was developed in this study. The key parameters of the extrusion screw were optimized and Polyflow software was used to simulate the screw extrusion process. A uniform and stable extrusion wire was obtained based on the key printing parameters. The reliability of the printed material was analyzed by Weibull modulus. A ceramic material with dense structure and uniform grains was obtained and ceramic components with complex geometry were prepared.#@#@#摘要: 传统的熔融沉积成型一般采用线材供料，不适合特种陶瓷的3D打印，本研究开发了一种采用螺杆挤出供料的熔融沉积成型方法，适用于高固相含量的颗粒状耗材混合料。本研究优化设计了挤出螺杆的关键参数，采用Polyflow软件对螺杆挤出过程进行模拟，结合实验结果确定了关键打印参数，得到了均匀稳定的挤出线材。采用韦布尔模量分析了打印材料的可靠性，得到了结构致密、晶粒均匀的陶瓷材料，并制备了复杂形状陶瓷部件。
通讯机构：
[Guo Yi] C;Chongqing Water Resources & Elect Engn Coll, Intelligent Manufacture Inst, Chongqing 402160, Peoples R China.
关键词：
rare earth oxides;heat properties;solid state reaction;phonon scattering
摘要：
In this present manuscript, the (Sm1-xLax)(2)Ce2O7 solid solutions were obtained adopting solid state fritting method at high-temperature. The micro-structure, phase structure and thermal-properties were investigated. Results show that the synthesized (Sm1-xLax)(2)Ce2O7 ceramics exhibit a pure have a fluorite-type structure, the heat conductivity of (Sm1-xLax)(2)Ce2O7 solid solutions decreases with increasing La2O3 fraction, which is between 1.09-1.69Wm(-1) K-1 at 1273 K. The coefficients of thermal expansion for the prepared samples are also raised due to the increasing ionic radius at sites A, which are greater than those of YSZ. The synthesized compounds also show outstanding phase-structure-stability between room-temperature and 1273 K.
摘要：
Calcination was used for surface modification of ultrafine silicon nitride powders, which improved the flowability and dispersion stability of their slurries. Surface characteristics of the powder were investigated by X‐ray photoelectron spectroscopy (XPS), which showed the generation of an oxide layer and partial elimination of amine groups on the particle surfaces. Ion analysis results suggested a drop in both ion conductivity and supernatant concentration after calcination. For the as‐received powder, poor flowability and dispersion stability was caused by high‐valence cations, which were detrimental to colloidal processing according to the Schulze‐Hardy rule, and surface amine groups were also present; both of these were partly removed by calcination. The oxide layer formed on the particle surfaces hydrolyzes into silanol groups when the powder is dispersed in aqueous solutions, which was favorable for surface charging and formation of higher diffuse layer potential on the particles. These factors contributed to the improved flowability and dispersion stability of the slurries. This article is protected by copyright. All rights reserved.
