No description available.

In many manufacturing and service industries, a need exists for a nondestructive test to determine the presence of hydrogen in a material system. The feasibility of such a system is examined here. Acoustic emission activity resulting from a microhardness indentation is employed to detect hydrogen in A106 and 4340 steel bars following cathodic, gaseous, and chemical charging. These tests show a large increase in emission energy after charging followed by a drop to precharge levels with time. These activity levels are used to calculate hydrogen diffusivity and binding energy of hydrogen to traps in the steel. A mechanism of acoustic emission generation is proposed involving the breakaway of dislocations from Cottrell-like hydrogen atmospheres. The effects of surface roughness and microstructure are also evaluated. Testing of various surfaces indicates that limited surface preparation is necessary prior to implementing the test procedure. Low activity levels before and after charging in 4340, and in martensitic and bainitic A106 indicate possible difficulties in applying the test to harder, more dispersed structures. Despite this limitation and a large amount of scatter in the acquired data, the results indicate that acoustic emission monitoring of microhardness indentations may be of value in detecting the presence of hydrogen in metals and as a research tool in the study of hydrogen transport and embrittlement mechanisms. / M.S.

No description available.

No description available.

Torsional fatigue tests were conducted on 4370 steel oil quenched and tempered at 1000° F in (l) the uncharged state, (2) the hydrogen charged state, and (3) in a hydrogen environment. The tests were conducted on both smooth (K_t = l.l) and V-notch (K_t = 3.8) test specimens. A statistical analysis conducted at the 99% confidence limit for the smooth test specimens indicated that precharging with hydrogen increased the fatigue life of the material and also the fracture surface of the test specimens changed from a circumferential crack to a 45° diagonal crack. At a 90% confidence limit, charging with hydrogen did not affect the fatigue life of the V-notched specimens. At a 99% confidence limit for both the smooth and V-notched test specimens, testing in a hydrogen environment increased the fatigue life of the material. Bending fatigue tests were also conducted on the same material and the results indicated that charging with hydrogen decreased fatigue life of smooth test specimens (K_t = l.l) but increased the fatigue life for V-notched specimens (K_t = 2.4 and 3.8). / Ph. D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Subramanian Suresh. / Sc.D.

M. Tech. Hydrogen storage modeling. / In this dissertation, a 2D dynamic simulation for a portion of metal hydride based hydrogen storage tank was performed using computational software COMSOL 4.0a Multiphysics. The software is used to simulate the diffusion and heating of hydrogen in both radial and axial directions. The model consists of a system of partial differential equations (PDE) describing two dimensional heat and mass transfer of hydrogen in a porous matrix. This work provides an important insight to the fundamental understanding of multi-physics coupling phenomena during hydrogen absorption/ desorption process. The simulation results could be applied to the on-board hydrogen storage technology, in particular for the hydrogen supply of a fuel cell for powering of a hydrogen fuel cell vehicle.

No description available.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / The Water Gas Shift (WGS) reaction describes the reaction between carbon monoxide and water vapour to produce carbon monoxide and hydrogen. This work describes the application of a Palladium-Silver (Pd-Ag)-based membrane film reactor, wherein the Pd-Ag film was supported by porous stainless steel (PSS), for the potential replacement of the current multi-stage WGS reaction. The objective of this work was to develop a better understanding of impediments which are relevant to the application of Pd-Ag membrane reactor for the WGSR. The long term behaviour (hydrogen permeability and selectivity) of Pd-Ag membrane under hydrogen exposure was studied, and the use of the Pd-Ag membrane reactor to produce hydrogen through the WGSR was also performed. A detailed literature review was conducted, based on the information gathered from literature. A Permeability and WGS reaction testing stations was designed and built. A thin (20μm) 77%wtPd-23%wtAg film was purchased from Takanaka Company in Japan. The membrane film was enclosed between two stainless steel plates to form a membrane reactor. The membrane reactor was fitted at the two different testing stations.

Hydrogen causes defects, for which aluminiurn alloy products are rejected. The behaviour of hydrogen in aluminium-magnesium-silicon alloy extrusion ingots, has been studied throughout the course of manufacture from freshly reduced aluminium. It is shown that hydrogen in the liquid metal is produced by temperature-dependent reaction between the metal and water vapour in the atmosphere. As the metal is received from the reduction cells, its temperature is -850 'C and its hydrogen content, >0.4 cm3/100 g, is too high for casting sound ingots. The metal is transferred first to a so-called melting furnace, where it is alloyed and stirred, thence to a holding furnace, where the composition is adjusted, the metal is degassed by gas sparging and allowed to settle before casting. The metal cools throughout these operations and as the temperature falls, the calculated value for the hydrogen content in equilibrium with the atmosphere falls in response to the reduced hydrogen solubility. The actual hydrogen content of the metal exhibited marked hysteresis in following the equilibrium value. Significant reduction of the hydrogen content occurred only when the metal was agitated. The hydrogen content never fell below the equilibrium value even during the nominal degassing operation, leading to the conclusion that gas sparging in a furnace does not positively remove hydrogen but only assists the equilibration. The hot-top DC casting process yielded a 8 m x 0.18 m diameter ingot with a virtually uniform hydrogen content. When this ingot was homogenised by heating it to 590˚C in a 7h cycle, a significant proportion of the hydrogen content was lost from the surface zone. By matching the loss to a theoretical model assuming diffusion control, it was shown that the loss of hydrogen is attenuated by trapping in micropores. The effects of simulated industrial atmospheres on the loss or absorption of hydrogen by the solid alloy were investigated in an extended series of laboratory heat-treatments. The interaction of the metal with these atmospheres was found to be determined by the nature of the oxide films formed and therefore the films were investigated by XPS and SIMS surface analysis techniques. In clean atmospheres the absorption or loss of hydrogen was determined by the balance between inward migration of protons and outward diffusion of hydrogen atoms through the oxide. Pollution of the air by chlorine or especially sulphur stimulated hydrogen absorption to a degree which seriously damaged the metal by pore growth. These effects are explained by modified compositions and structures in the surface oxide.