The rheological behavior of concentrated ZnO-Al 2 O 3 aqueous suspensions has been studied in order to obtain an ultrahighdensity ZnO-Al 2 O 3 composite ceramic target by slip casting. The influence of the mass fraction of polyacrylic acid (PAA) on the fluidity of slurries and the density and strength of the green and sintered bodies was investigated. The slurries exhibited a near-Newtonian flow behavior and had a lower viscosity with 0.3 wt% PAA. The excess of PAA enhanced the green strength and the density and strength of the sintered bodies. An ultrahigh density sintered body (499.7% theoretical density) could be obtained after pressureless sintering at 14001C. The Al species were well distributed in the sintered bodies, which showed a homogeneous, defect-free microstructure with no abnormal grain growth.

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Investment casting, which is almost independent of part size, shape, and quality, enables the production of castings that are lightweight, thin-walled, and complex in shape. 1 It is one of the main techniques for the production of high-temperature precision alloy castings such as aero-engine turbine blades, turbine disks, guide belts, and combustion chambers. During the investment casting process, the ceramic molds 2 (shell and core) are used, and molten metal may be gravity poured or forced by applying positive air pressure. The fabrication of ceramics molds with the current method usually involves the shaping of the wax pattern, impregnation of the wax pattern into the slurry, and sandblasting, dewax, and burnout. This process is faced with the problems of high-cost, time-consuming, and low yield rate, especially for ceramics mold with

ZTM ceramics comprising of 0.75ZnAl 2 O 4 -0.25TiO 2 and MgTiO 3 at a ratio of 90:10 wt.% are widely used in the field of communication as filters and resonators owing to their excellent microwave dielectric properties. However, the development of such dielectrics with complex structures, as required by microwave devices, is difficult using traditional fabrication methods. In this study, ZTM microwave dielectric ceramics were prepared using the digital light processing (DLP) technology. The influence of the sintering temperature on the phase composition, microstructure, and microwave dielectric properties of ZTM ceramics was investigated. Results showed that with an increase in the sintering temperature, the dielectric constant (ε r ) and quality factor (Q × f) of ZTM ceramics initially increased owing to the increase in the density and diffusion of ions.However, when the sintering temperature was excessively high, the abnormal growth of crystal grains and micropores led to a decrease in ε r and Q × f. The ZTM ceramics sintered at 1450 • C exhibited the optimum microwave dielectric properties (ε r = 12.99, Q × f = 69 245 GHz, τ f = −9.50 ppm/ • C) owing to the uniform microstructure and a high relative density of 95.02%. These results indicate that DLP is a promising method for preparing high-performance microwave dielectric ceramics with complex structures.

Existing wetting theories have difficulty accurately describing advancing/receding processes on micro-structured surfaces. A strategy is proposed to solve this problem by recognizing it as a liquid–vapor interface geometrical question. The wetting chip method is proposed to realize the microscopic observation of liquid–vapor interface variations. A wetting model based on the liquid–vapor interface shape (LVIS model) is established to describe the analytical relationships between the apparent contact angles, liquid–vapor interface radius, substrate geometry, and chemical nature of liquid. The LVIS model is divided into four typical time points and three transition stages, and its predictions agree with the experimental measurements. In contrast to traditional theories, the apparent contact angles in a quasi-equilibrium state should be separated into advancing and receding processes, and in this state, apparent contact angles vary with changes in the parameters of micro-pillar width and spacing. This strategy has the potential to accurately describe the wetting process on micro-structure surfaces.