Yaxiang Zhang

Preparation and properties of ceramic facing brick from East-lake sediment

In order to utilize solid wastes, ceramic facing brick was made form East-lake sediment and some additives. The strength and freeze-thaw resistance of the samples were tested, and the crystal phases and microstructures were studied by XRD and SEM. The results indicate that the samples have a wide firing temperature range. The main crystal phases are CaAl2Si2O8, α-Al2O3, Fe2O3, which distribute uniformly in the samples. The sample have the best properties in the series ‘Ca-Al-Si’, and water absorption (Wa), porosity (Pa), bulk density (D), bending strength and compressive strength are 7.24%, 15.82%, 2.19 g·cm−3, 45.57 MPa and 56.81 MPa respectively, when the addition amount of East-lake sediment is 80% and the firing temperature is 1 100 °C. In the series ‘K-Al-Si’, the sample with the best properties was obtained when addition amount of East-lake sediment was 70% and firing temperature was 1 060 °C. The water absorption, porosity, bulk density, bending strength and compressive strength are 7.62%, 16.37%, 2.15 g·cm−3, 39.26 MPa, and 50.81 MPa respectively. They all come up to the national standardization, and meet the needs of manufacturing production.

Cordierite Ceramics Prepared from Poor Quality Kaolin for Electric Heater Supports: Sintering Process, Phase Transformation, Microstructure Evolution and Properties

To efficiently utilize the kaolin, an economical way of preparing cordierite ceramic with high performance for electric heater supports was put forward. In this study, sintering process, phase transformation, microstructure evolutions were systematically studied by heating microscope, X-ray diffraction, scanning electronic microscope and thermal analysis. Properties (physical properties, electrical properties and coefficient of thermal expansion (CTE)) were tested for comprehensive performance evaluation. The results showed that the utilization of poor quality kaolin broadened the firing range of cordierite ceramic which was from 1 200 to 1 380 °C. Microstructure becomes loose with increasing of the pore size, which had significant influence on bending strength and electrical properties. High content of K2O in poor quality kaolin was the reason for liquid phase generation in sintering process, which further leads to microstructural changes. The cordierite ceramic sintered at 1 320 °C had the properties as follows: CTE of 1.98×10-6 °C-1 (500 °C), bending strength of 90 MPa, apparent porosity of 15.1%, dielectric constant of 7.5 (100 Hz), and volume resistivity of 1.05×109 Ω·cm (100 Hz). The comprehensive properties are very suitable for use as electric heater supports.

Effect of MnO2 on properties of SiC-mullite composite ceramics for solar sensible thermal storage

For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO2 was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, andalusite, α-Al2O3 as the starting materials with non-contact graphite-buried sintering method. Phase composition and microstructure of the composites were investigated by XRD and SEM, and the effect of MnO2 on the properties of SiC composites was studied. Results indicated that samples SM1 with 0.2 wt% MnO2 addition achieved the optimum properties: bending strength of 70.96 MPa, heat capacity of 1.02 J·(g·K)-1, thermal conductivity of 9.05 W·(m·K)-1. Proper addition of MnO2 was found to weaken the volume effect of the composites and improve the thermal shock resistance with an increased rate of 27.84% for bending strength after 30 cycles of thermal shock (air cooling from 1 100 °C to RT).

Research and development of cadmium sulphoselenide red pigment

Cadmium sulphoselenide was synthesized continuous substitution solid solution and the only known pigment to yield bright red color on ceramic decoration. Encapsulated cadmium sulphoselenide pigments could yield abundant hues from yellow to red with high opacity at high temperature. The color generation has a linear function relation with the substitution rate. The encapsulation formation process of zirconium silicate encapsulated cadmium sulphoselenide was shown. Insufficient encapsulation efficiency and potential hazard to human and environment had limited the industrial application of cadmium sulphoselenide red pigment. Ink-jet printing decoration required fine size cadmium sulphoselenide red pigment on ceramic decoration. The review mainly focused on the synthesis techniques and industrial application of cadmium sulphoselenide red pigment.