Papers by Keyword: Low Temperature Sintering

Abstract: Manufacturing a porous ceramic specimen from natural zeolite materials mined in Malang, Indonesia was conducted by using a low temperature sintering. In this study, a porous ceramic property with rectangular shaped and prism shaped fillets at each end were sintered at 800-900°C and finally were investigated. Density and porosity measurements were performed using Archimedes method. The microstructure photos were used to measure the neck diameter and the contact angle between the two grains particles and two-dimensional porosity. The result of the zeolite ceramic measurement shows that the higher the sintering temperature the higher the density value and the smaller the open porosity. While from the microstructure photo it is shown that the neck diameter was larger the contact angle was wider. This phenomenon was happened because of the flux diffusion on the grain boundaries. This diffusion flow condition would influence the specimen surface, volume and grain boundary so that the porous ceramic density increases.

Abstract: Influence of Ca substitution on structural, magnetic and dielectric properties of Ba₃Co_2-xCa_xFe₂₄O₄₁ (where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba₃Co_2-xCa_xFe₂₄O₄₁ powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper

Abstract: Uranium dioxide powders were surface pre-oxidation treated. Phases and properties of the powders after pre-oxidation treatment were investigated by DSC-TG、XRD、BET and Dilatometer. The results show that there is a little of U₃O₇ in uranium dioxide powders by pre-oxidation treatment at 240°C for 8h in air, UO₂ powders will transform into U₃O₈ at 382°C for 8h in air. The shrinkage temperature of the uranium dioxide pellets after pre-oxidation treatment decreased from 1200°C to 580°C, densification rate (ΔL/L) increased also from 1.52×10^-4/K to 3.08×10^-4/K. The mechanism of low temperature sintering to pre-oxidation UO_2+x pellets was explained by simplified point defect model and densification equation. The UO_2+x diffusion coefficient, , is much higher than which of UO₂. The densification equation is expressed by , and the factor A is according to , a=16.23658, b=0.04247 and c=-2.18802×10^-5.

Abstract: With sugar as an addition, the active carbon released from sugar can lead to the effective carbon doping in MgB2 superconductors only under the condition of high temperature sintering. However, this kind of carbon doping cannot occur at low temperature sintering condition. The reason is that the carbon released from the decomposition reaction of the sugar added in MgB2 has very low chemical activity during low temperature sintering process, which is similar with the results of elemental carbon or graphite doping directly. Thus, only the sintering temperature reaches a certain temperature or more (generally greater than 700oC), the carbon can possess sufficiently high chemical activity and go into the lattice of MgB2 to replace the B. In the condition of low temperature, it is difficult to form an effective carbon-doped.

Abstract: (Bi_1.5Zn_0.5)(Zn_0.5Nb_1.5)O₇ (BZN) ceramic samples were prepared by solid state reaction. B₂O₃ was introduced by liquid coating technology with H₃BO₃ solution in the BZN ceramic specimen to reduce its sintering temperature. The sintering behavior, phase composition and dielectric properties of ceramics were investigated by X-ray diffraction, scanning electron microscopy and vector network analyzer. The (Bi_1.5Zn_0.5)(Zn_0.5Nb_1.5)O₇ ceramic composite could be sintered well at 900°C for 3h when 0.9M/l H₃BO₃ was added and showed good dielectric properties of ε_r=150,Q×f=228,τ_f=-362ppm/°C.

Abstract: The sintering temperature of 8YSZ (8mol% yttrium stabilized zirconia) is very high, usually above 1500°C. BAS (BaO-Al2O3-SiO2) microcrystalline glass can be used as sintering aids to reduce the sintering temperature of 8YSZ. In this research, large proportion (30-50wt%) BAS was added in 8YSZ to observe the influence of the sintering aids. The change rules of mechanical properties such as density test, bending strength and toughness in different material component and sintering process were researched. The results show that physical and mechanical performance improvement with the increase of sintering temperature and sintering time, density and bending strength decreases with the increase of BAS mass fraction. The optimal mechanical properties are obtained by sintering temperature 1300°C, sintering time 0.5h and 30wt% BAS.

Abstract: The effects of CuO-B₂O₃ (CBO) additive on densification, microstructure, and electrical properties of (Ba_0.98Ca_0.02)(Sn_0.04Ti_0.96)O₃ (BCST) cermaics were investigated. The phase compositions, microstructure, dielectric, ferroelectric and piezoelectric properties of BCST ceramics were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), precision impedance analyzer, ferroelectric tester and quasi-static piezoelectric constant testing meter, respectively. The results show that CuO-B₂O₃ (CBO) frit can improve the densification and promote low-temperature sintering of BCST ceramics prepared by a conventional solid-state reaction method. Dense BCST ceramics with CBO can be sintered at temperatures as low as 1175 °C, which is approximately 275 °C less than the sintering temperature of pure BCST. When sintered at 1200 °C, the optimized properties of the BCST ceramics with 0.5 wt% CBO were obtain as ε = 1206, d₃₃ = 346 pC/N, k_P = 0.39, tgδ = 0.009.

Abstract: Low temperature sintering of TiO₂-base varistor was systematically investigated through doing with V₂O₅ and B-Si glass. Pellets prepared could be densely sintered from 1273 to 1473K. The highest relative density, 94.6%, was found in the sample sintered at 1433K. According to I-V plots of ceramic pellets, the nonlinear coefficient α and breakdown voltage V_1mA were obtained and found to be α=2~5 and V_1mA=15~30V. The room temperature dielectric constant was very large, high as to about 20000. Powder XRD analysis has shown the desirable macro-structural characteristics of these compacts.

Abstract: The effects of B2O3 on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.95Zr0.05]O3−δ−0.04TiO2 (CLNZ−0.04TiO2) ceramics were investigated . B2O3 doping can effectively reduce sintering temperatue by 150~200°C. The temperature coefficient of resonator frequency τf increased with an increase of B2O3 content and sintering temperatue. When B2O3 of 2wt% were added, the optimum microwave dielectric properties: εr =31.8,Qf =17240GHz and τf = − 5.9×10−6/°C were obtained at the sintering temperature of 950°C.

Abstract: Ba₂Ti₉O₂0 ceramics were prepared with different additives of B₂O₃ by liquid coating method and solid phase mix method. The sintering behavior, phase structure and dielectric properties of ceramics were investigated by X-ray diffraction, scanning electron microscopy and inductance-capacitance resistance analysis. The liquid coating method can reduce the amount of sintering aid and minimized the negative impact of sintering aid on dielectric properties. A ceramic composite which could be sintered well at 900°C for 3h and showed good dielectric properties of εr=42,tanδ=0.002 and TCF=-4ppm/°C（1MHz）was obtained when 1.0mol/l H₃BO₃ was added to the Ba₂Ti₉O₂₀ ceramic.