THE USE OF (Mg0.9Zn0.1)TiO3+2wt.% Bi2O3 CERAMICS AS A DIELECTRIC RESONATOR OSCILLATOR MATERIAL AND CHARACTERISATION OF STRUCTURE, MICROSTRUCTURE, AND DENSITY

Magnesium titanate (MgTiO3)-based ceramics have the potential for use in the telecommunications industry at microwave frequencies, including as a resonator in dielectric resonator oscillator (DRO) circuit. This research is intended to study the application of (Mg0.9Z0.1)TiO3+2wt.% Bi2O3 (abbreviated MZT01-2) ceramics as DRO material and characterize the structure, microstructure, and bulk density. Fabrication was carried out by ball milling between (Mg0.9Z0.1)TiO3 crystalline powder and 2wt.% Bi2O3 powder. The milled powder was compacted at certain pressure using a die press to become pellets. All pellets were sintered at 1000, 1100, 1200°C for 4 h to obtain ceramics. The structural characterization using XRD showed that the three ceramics contained the main MgTiO3 phase, each 93.63, 93.83, and 90.78% molar, the rest was the MgTi2O5 phase. The increase in sinter temperature causes the lattice parameter and the unit cell volume to decrease. The Archimedes bulk density was 2.928; 2.832 and 2.736 g/cm3. The microstructure is solid surfaces with a grain diameter of 1.9-2.3 μm accompanied by pores. As DRO materials, the three ceramics exhibited a resonant frequency at 5.11, 5.08, and 5.12 GHz which shows that the ceramics can be applied as DRO materials at microwave frequencies. The sinter temperature variation tends not to affect the resonant frequency position.

Densification process of silica microspheres by multi-step sintering

Dense silica microspheres were fabricated by spray drying and multi-step sintering. The effect of sinter temperatures on densification, dispersibility and inner morphology of silica spheres was analyzed by SEM, and the densification process was deeply discussed. The results showed that single-step sintering at 1100 °C made silica spheres seriously coherent each other and spherical morphology irregular. However, a multi-step process made the sinter temperature increase to 1190 °C, while silica spheres still kept uniformly spherical and dispersed. The increased temperature resulted in that the silica particles obtained dense inner morphology, and their density reached 2.18 g · cm–3, corresponding to a relative density of 98.6% (in comparison with the density of 2.21 g · cm–3 for noncrystal silica).

Preparation and Properties of Aluminum Boron Composite

Al/B composite is a new structural-functional integration material, which has a promising potential in future application due to their good combination of neutron shielding property and mechanical property. In order to obtain sintering process parameters of Al/B composite, the mold pressure, sintering temperature and the composition of powders were investigated and the physical properties of Al/B composite also systematically studied. In addition, the surface morphology of Al/B composite was analyzed. The experimental results indicate that the relative density will be higher when the mold pressure was bigger in appropriate pressure intervals, and when the mold pressure was more than 144MPa, the composites was difficult for molding because of the great internal stress. From the analysis of morphology, it shows that the best sinter temperature interval is 550-580°C. From the studies of composition of powders, it has been found that the percentage of Al affect the density and hardness. The density will be higher if the percentage of Al is higher.

Influence of Reaction Temperature on the Densification Behavior of the SiC/B4C Composites

In this investigation, the rare-earth oxide La2O3 combined with Al2O3 served as sintering additives and commercial α-SiC and B4C powder were applied to fabricate SiC/B4C composites by pressureless sintering. The results proved that combination of Al2O3 and La2O3 sinter additives were effective for densification of SiC/B4C composites. The influence of sinter temperature on the phase constitution, micro-structure and densification behavior of SiC/B4C composites was investigated.

The Preparation of CaO:Dy3+, Na+ Rare Phosphor by High Sofid-State Method

The CaO:xDy3+, yNa+ phosphors, were synthesized by high solidstate method, and the starting materials are CaCO3Na2CO3 and Dy2O3. The effects of the Dy3+,Na+doping concentration on luminescent properties were studied by TG/DSC,XRD and PL spectra.The results indicated that when the sinter temperature of precursors over 950 °C,the main phase of the phosphor is CaO, and when x=0.02,y=0.15 we obtained the best luminescent properties of CaO:xDy3+, yNa+phosphors;Na+effectively enhances the luminescent properties of phosphors;The maximum emission wavelength is about 480 nm (blue),corresponding to 4F9 /26H15 /2 of Dy3+; There are a series of spectral lines in the 240-420 nm range of excitation spectrum,and the strong excitation peak located at 360 and 375 nm.

Influence of Sinter Temperature on the Hardness of Fly Ash Based Glass Ceramics

The glass ceramics bricks were prepared by the method of isostatic pressing and one time sintering using fly ash and glass powder as raw materials. X-ray diffraction experiment was performed to identify the main crystal phase. The influence of sinter temperature on the hardness was studied. It was concluded that the main phase were anorthite and albite. The hardness of sample which contains 60% of fly ash attains 766.79MPa when the sintering temperature was 1110°C .The hardness of sample which contains 50% of fly ash attains 780MPa when the sintering temperature was 1075°C.

Study on Preparation and the Noise Suppression Effect of Co2Z Ferrite Films

The Co2Z ferrites noise suppression sheet was prepared by tape casting. Its microstructural characterization was performed by electron microscopy and noise suppression effect was measured by a microstrip line method. Results indicate that as the sinter temperature increases, the imaginary permeability increases leading to the enhancement of the suppression capability, and the thickness of noise suppression sheets also contribute to the noise suppression capability.

The DC-Bias-Superposition Characteristics of Low Sinter Temperature NiCuZn Ferrite

The DC-bias superposition characteristics of NiCuZn ferrite with different amount of Bi2O3 have been investigated. The microstructure depends much on the amount of Bi2O3. The DC-bias-superposition characteristics have great relationship with the microstructure. The permeability of materials composed of tiny grains decreases more slowly with the increase of DC-bias superposition due to the absence of the domain walls in the grain. The nonmagnetic phase in the grain boundary can reduce the actual DC-bias superposition in the grains when the sample was subject to DC-bias superposition. In short, a microstructure with relatively small average grain size and thick nonmagnetic phase in the grain boundary, which is favorable for obtaining better DC-bias superposition characteristics.

On Effect of Microstructure about Bi for AgSnO2 Compositions by Reaction Synthesis

This paper adopted XRD, SEM and DTA/TGA methods to discuss the microstructure of sinter AgSnO2 compositions with bismuth and without bismuth. The results showed that microstructures AgSnO2 compositions are different whether or not include bismuth. The introduction of Bi does not produce the expected SnO2 and Bi2O3 phase, but generated SnO2 and Sn2Bi2O7 phase. The reason with different microstructure has relation with early melting of Bi-rich alloys having low melting point and silver oxide decomposition rate and sinter temperature. Therefore, bring third element should be cautious for preparation composite metal oxide increase silver matrix electrical contact materials.