Application of the gel casting process in iron powder metallurgy

The effects of various gel casting process parameters such as the dispersant and solid loading on the rheology of Fe slurries, molding, and sintering behaviors were studied. The relationship between solid loading and viscidity in the process of iron base powder metallurgy was researched to obtain better microstructure and properties. The results showed that the viscosity of Fe slurries is obviously reduced with the increase of the dispersant. The suitable parameters are as follows： the solid loading is 61% and sintering temperature is 1180℃. Iron parts with relatively high density and better properties were obtained by the gel casting process.

Gel Casting of 316L Stainless Steel Powder Through Mold DIS Process

This paper presents the gel casting of metal powder by agar gelation through mold decomposed injection sculpture (DIS) process:verifying the feasibility and improving the processing parameters to prepare stable metal slurry and strong green body. The optimal processing parameters were achieved after investigating the effects of these parameters such as temperature, agar content, dispersant concentration, and solid volume loading. The rheological behavior of metal slurry and the character of formed green body were also investigated. The mixture and dispersion mechanism of metal slurry as well as the consolidation forming and sintering technology of green body were studied based on analysis of experimental results. The results show that the optimal pH range is 8.5-9.5 with the grain size distribution of 2-30 μm and 55% solid suspension, which can be prepared by adding proper dispersant (Polyvinyl Alcohol). The agar and dispersant content has great effect on the properties of slurry. When 1.0 wt.% dispersant and 0.7 wt.% agar content (referred to dry solid) are adopted, stable metal slurry with viscosity less than 1 Pa·s and green body with bending strength of 2.7 MPa are obtained. The sintered bodies with uniform structure, relative density of 90%, and yield strength of 150 MPa are prepared at 1300℃/30min in vacuum. This process can be applied in rapid prototyping of complex shape metal products such as rotor blades.

Samaria-doped Ceria Modified Ni/YSZ Anode for Direct Methane Fuel in Tubular Solid Oxide Fuel Cells by Impregnation Method

A porous NiO/yttria-stabilized zirconia was prepared by gel casting technique. anode substrate for tubular solid oxide fuel cells Nano-scale samaria-doped ceria （SDC） particles were formed onto the anode substrate to modify the anode microstructure by the impregnation of solution of Sm（NO3）3 and Ce（NO3）3. Electrochemical impedance spectroscopy, current-voltage and current-powder curves of the cells were measured using an electrochemical workstation. Scanning electron microcopy was used to observe the microstructure. The results indicate that the stability of the performance of the cell operated on humidified methane can be significantly improved by incorporating the nano-structured SDC particles, compared with the unmodified cell. This verifies that the coated SDC electrodes are very effective in suppressing catalytic carbon formation by blocking methane from approaching the Ni, which is catalytically active towards methane pyrolysis. In addition, it was found that a small amount of deposited carbon is beneficial to the performance of the anode. The cell showed a peak power density of 225 mW/cm^2 when it was fed with H2 fuel at 700 ℃, but the power density increased to 400 mW/cm^2 when the fuel was switched from hydrogen to methane at the same flow rate. Methane conversion achieved about 90%, measured by gas chromatogram with a 10.0 mL/min flow rate of fuel at 700 ℃. Although the carbon deposition was not suppressed absolutely, some deposited carbon was beneficial for performance improvement.

Three-dimensional graphitic carbon sphere foams as sorbents for cleaning oil spills

Frequent offshore oil spill accidents, industrial oily sewage, and the indiscriminate disposal of urban oily sewage have caused seri- ous impacts on the human living environment and health. The traditional oil-water separation methods not only cause easily environmental secondary pollution but also a waste of limited resources. Therefore, in this work, three-dimensional (3D) graphitic carbon sphere (GCS) foams (collectively referred hereafter as 3D foams) with a 3D porous structure, pore size distribution of 25-200 μm, and high porosity of 62vol% were prepared for oil adsorption via gel casting using GCS as the starting materials. The results indicate that the water contact angle (WCA) of the as-prepared 3D foams is 130°. The contents of GCS greatly influenced the hydrophobicity, WCA, and microstructure of the as-prepared samples. The adsorption capacities of the as-prepared 3D foams for paraffin oil, vegetable oil, and vacuum pump oil were approximately 12-15 g/g, which were 10 times that of GCS powder. The as-prepared foams are desirable characteristics of a good sorbent and could be widely used in oil spill accidents.