Sharif Digital Repository

The hydrogen diffusivity and subsurface concentration (C app) were evaluated by fitting a series expansion of the diffusion equation to the permeation data. The hydrogen diffusivity in the steel was found to be approximately in a order of magnitude 10 -7 cm 2 s -1. The influence of the passive layer on the hydrogen permeation and its influence on the evaluation of diffusion and trapping characteristics were discussed. Hydrogen diffusion experiments in A106 GRB carbon steel pipeline were performed electrochemically at 25°C in NACE B, solution in various amount of sulphide ion concentrations. In this case the effect of concentration of sulphide ion evaluated by study the electrochemical... 

Hydrogen diffusion experiments in A106GR B carbon steel pipeline were performed electrochemically at 25°C in NACE,B, solution in various amount of sulfide ion concentration for a thin sample. In this case the effect of concentration of sulfide ion evaluated by study the electrochemical behavior of sample by the galvanostatic way. Generally, sulfur components were found to increase the hydrogen permeation rate. Presence of sulfide layer helped to absorption of hydrogen reduction and exacerbates the amount of hydrogen absorption in steel. this phenomena can be noted that as regard to analysis of corrosion products which formed in the surface sample, the high amount of FeS, The sulfide ion are... 

Silica composite membranes and BaCe0.9Y0.1O3-δ (BCY) perovskite membranes were successfully synthesized to separate hydrogen in an equimolar mixture of H2, CH4, CO, and CO2 at temperature range of 500–900 °C and pressure difference of 1 bar. The phase structure of both membranes was characterized by X-ray diffraction (XRD). Thermogravimetric analysis (TGA) was used to evaluate phase stability of perovskite membrane. FESEM images confirmed graded structure of silica membrane and uniform, dense structure of perovskite membrane. H2 permeation in semi-dense silica layer deposited on alumina substrate indicated that permeation in top selective layer follows a diffusion mechanism which is based on... 

Hydrogen permeation through ACe0.9Y0.1O3-δ (A = Sr, Ba, La, and BaSr) perovskite-type membranes was studied at high temperatures. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to characterize phase structure and phase stability of the membrane. The XRD results showed the formation of a single phase of perovskite structure with configuration orthorhombic for BCY and BSCY membranes. Based on the TGA results, it was found that the phase stability increases in the order of LCY < SCY < BCY < BSCY. The microstructure examinations of the synthesized membranes studied by scanning electron microscopy (SEM) showed the formation of a dense-like... 

The BaCe0.9Y0.1O3-δ (BCY) perovskite membrane was successfully synthesized by liquid citrate method. The phase structure of the powder was characterized by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to characterize microstructures of the membrane sintered under various conditions. Sintering temperatures and dwell time during sintering influence the final microstructure of the ceramic. Results showed that increasing sintering temperature resulted in a dense membrane with clear grains. An increase of dwell time was favorable to produce membranes with larger grains in the sintered ceramics. A density of 5.87 g/cm3 was reached for the membrane after sintering at 1200 °C... 

The hydrogen-induced cracking (HIC) behavior of X70 pipeline steel was studied by means of Linear Polarization Resistance (LPR), hydrogen permeation tests, weight loss and Scanning Electron Microscopy (SEM). In this study, the dissolved HZS was created by chemical reactions in solution. The specimens were immersed into synthetic sea water saturated with HZS. The experimental results showed that the increase of exposure time and HZS concentration leads to an increase of the hydrogen content in X70 steel, which plays a key role in the initiation and propagation of HIC  

La0.3Sr0.7FeO3-δ (LSF) perovskite was prepared according to two methods: (1) applying new phenolic derivative of serine amino acid (L) as chelating agent, and (2) in absence of L as ligand-free perovskite (LFP). The newly prepared aminophenolic ligand L was fully characterized by 1H and 13C NMR, IR as well as elemental analysis while the LSF perovskite samples were characterized using the IR spectra, powder x-ray diffraction (PXRD) patterns, and SEM micrographs. The PXRD pattern obtained for the perovskite prepared by L (PPP) indicated on the presence of pure perovskite phase. The hydrogen permeation through PPP and LFP membranes with thickness of 1.0mm were measured as a function of... 

Tubular ceramic membranes were synthesized by depositing a dense layer of silica-alumina on top of a multilayer substrate using co-current chemical vapor deposition (CVD) method. The multilayer substrate was prepared by coating with a series of bohemite sols with certain particle sizes. Cross-sectional and surface images obtained from high resolution FESEM showed that the intermediate layer had a thickness of about 1μm and the top selective layer was uniform and dense with a thickness of less than 100nm. Permeance tests, which were carried out with H 2, CO 2, N 2 and CH 4 at a high temperature range of 923-1073K, indicated that gas permeation took place via different mechanisms through...