Advanced Materials Research Vols. 11-12

Abstract: EIS is used in this paper to study the effects of anodic oxidation parameters on the film’s ability, and multi-layer equivalent circuits are proposed. The oxidation time has great effect on porous layer, the porous layer’s impedance increases as the anodic oxidation time prolong; anodic current density has effect on both barrier layer and porous layer, higher current density gets higher impedance values in both barrier layer and porous layer; anodic oxidation temperature has great effect on barrier layer, when the temperature decreases, the barrier layer’s impedance increases.

Abstract: Nanosized silica powders were synthesized via w/o emulsion method using sodium silicate as SiO2 source under ultrasonic process. The powders were prepared under conventional process and ultrasonic process using the same reactants at ambient temperature for 1h varying the concentration of Na2SiO3 solution while fixing the concentration of surfactant in cyclohexane. The particle size of the silica powder decreased with decreasing the concentration of sodium silicate solution under both conditions, with and without ultrasounds. However, the particle size and size distribution of the silica powder with ultrasounds were smaller and narrower than those without ultrasounds, establishing that ultrasound treatments decrease the particle size and become narrow in particle size distribution.

Abstract: The feasibility of bubble templating method to prepare hollow particles was tested in this paper by passing a bubble into a silica sol. The silica sol was prepared by mixing TEOS, water, alcohol and hydrochloric acid. To control the gel point, the reactants and their concentrations were varied in each experiment. After the sol was prepared, an ammonia bubble was introduced into the prepared sol through a capillary tube. With the catalysis of ammonia, the silica sol gelled on the surface of bubble and formed a hollow gel particle. The nucleation of silica gel on the surface of bubble was discussed in this paper.

Abstract: Hollow calcium carbonate (CaCO3) particles were synthesized by bubbling CO2 in the solution of calcium chloride (CaCl2) with the presence of ammonia at room temperature. Hollow calcium carbonate is a potential component to be used as pharmaceuticals, agrochemicals, and catalysis. This paper investigated the effect of additive on the hollow structure. In this study was used vanadate ion as additive agent. Physical characteristics of precipitate were evaluated using scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Abstract: The control of particle dispersion is essential to the fabrication of highly designed ceramics. In this study, a direct observation technique was employed to characterize the heterocoagulation of particles in two-component slurry. TEM observation of solidified slurry composed of alumina and silica particles was attempted to evaluate heterocoagulation. At 10 mass% solid loading, the TEM showed the aggregation of silica with dispersed alumina particles at acidic region. A large scale of aggregation caused by attractive force among alumina and silica particles was observed on the TEM images at neutral region. At basic region, the aggregation of alumina with dispersed silica particles was observed. The measurements of zeta potential and viscosity were conducted to explain the results of the TEM observations.

Abstract: Centrifugal sintering is a novel process for the preparation of thick films. In this process, high gravity such as 104g is applied at high temperatures. Because of the distinctive measure of pressing by the centrifugal force, gradient of pressure arises in the specimen, resulting in the graded porous structure during the progress of sintering. After the sintering, highly densified thick films are obtained. Furthermore, crack formation was suppressed by this process.

Abstract: This paper shows a very promising approach for developing the structure of grain orientation through weak magnetic interaction of ceramics particles in a high magnetic field. Grain oriented bismuth titanate ceramics was successfully developed through a processing in a high magnetic field. XRD and SEM show that c-axes of particles were oriented perpendicular to the applied magnetic field. The orientation structure developed by sintering, and the orientation factor achieved 0.85 as determined using the Lotgering method.

Abstract: Magnesium oxide (MgO) films are utilized for the anti-plasma sputtering coating with excellent ability of secondary electron emission in plasma display panels (PDP). These properties are degraded by the impurities adsorbed on the film surface. Therefore, we should obtain impurity-free surface during the PDP manufacturing process. We have synthesized whisker and continuous film types of metal oxide using a chemical vapor deposition (CVD) method operated under atmosphere. In this study, a temperature programmed desorption method has been applied to detect residual species adsorbed on the surface of the present films in the ultra-high vacuum atmosphere. The amount of water adsorption was determined by this method.

Abstract: The amount of melted slag has substantially increased due to the rapidly expanding Chinese industry in the recent years. The exiting methods to dispose such slag bring about some problems which hinders its utilization. In the paper, a new method, realized by high pressure jet, is put forward to simultaneously producing fine powder and increasing cementitious activity, and the method would be useful to a benign recycle of resources, energy and environment.

Abstract: Filtration medium is one of the most important parts of air-filtration. A Micro-filtration membrane made by expanded poly-tetra-fluoric-ethylene (ePTFE) was introduced in the dust removal process in our previous work. Compared with conventional fabric media, ePTFE membrane has many advantages, such as low residual pressure drop and high efficiency of dust removal, etc., because of its characteristics of micro-porous structure and slippery surface. More importantly, the useful life of ePTFE membrane is longer and the operating costs are lower during the surface-filtration process. In this paper, the residual pressure drop of the ePTFE micro-filtration membrane and conventional needle-felts fabric filtration medium were compared. The results clearly show that the residual pressure drop of the conventional filter medium increases after several filtration cycles, but that of the ePTFE membrane remains constant.