Titanium hydride formation

The theoretical hmit of 5.4% (NaAlH4+2 mol% TiN) for the two subsequent decomposition reactions is in both cases only observed in the first cycle. The reason for the decrease in capacity is stiU unknown and litde is known about the mechanism of alanate activation via titanium dopants in the sohd state. Certainly, the ease of titanium hydride formation and decomposition plays a key role in this process, but whether titanium substitution in the alanate or the formation of a titanium aluminum alloys, i.e., finely dispersed titanium species in the decomposition products is crucial, is stiU under debate [41]. 

Cathodic currents causing titanium hydride formation and embrittlement. 

A cathodic current is in principle possible, but in case of hydrogen evolution, titanium will be destroyed by hydride formation. 

Analogous to the DSA manufacture, a pure htanium dioxide coating can be prepared, which shows a high activity and stabihty (also against titanium hydride formation), for electroorganic cathodic reductions (e.g. [40], see Chapter 7). 

For hydride-forming alloys, such as titanium alloys, the crack growth response may exhibit strong temperature and frequency dependence that is also a function of K level. This dependence reflects the influence of strain, strain rate, and temperature on hydride formation and rupture [7,8]. Support for this response is provided by the early fatigue crack growth data on Ti-6Al-4V(Ti64) alloy in 0.6 M NaCl... 

Boodey, J. B., Gao, M., and Wei, R. P., Hydrogen Solubility and Hydride Formation in a Thermally Charged Gamma-Based Titanium Aluminide, in Environmental Effects on Advanced Materials, R. H. Jones and R. E. Ricker, eds., The Minerals, Metals and Materials Society, Warrendale, PA (1991), 57-65. 

M is the analyte and m may be equal to n or not (for example, As and As are both reduced to AsHs). Hydrides were collected in U-tubes in a nitrogen trap or in rubber balloons. Titanium(iii) chloride—hydrochloric acid and magnesium-zinc reductants were used to extend the hydride method to bismuth, antimony, and tellurium. For some elements, especially tin, lead, and tellurium, the hydride formation reaction is relatively slow and hence the collection vessel is necessary. In addition, arsenic(v) must be reduced to arsenic(iii) by tin(ii) chloride or potassium iodide before the actual hydride generation when a metal-acid reduction is employed. 

Titaniuni is also prone to hydrogen adsorption leading to the possibility of hydride formation this limits the use of titanium as a cathode material in electrochemical reactors involving addic electrolytes. Such conditions may not allow a stable passive filni to be retained on the electrode surface. 

The other mode of failure for titanium alloys in the presence of hydrogen predominates rmder slow strain rate loading. The low strain rate embrittlement is related to hydride formation caused by strain-enhanced precipitation, but embrittlement imder impact is caused by hydride-phase formation after fabrication or heat treatment. Unlike many hydrideforming systems, titanium forms a stable hydride, but the kinetics of precipitation are slow compared to the Group Vb metals. Therefore, embrittlement is more prone to occur at low strain rates at which precipitation can proceed at a rate that is sufficient to provide a brittle crack path. 

Current on cathode dissolution, particularly due to combination of electroreduction of protective surface films and active generation of hydrogen. This may be especially marked in the case of titanium, due to facile hydride formation. The result may be pitting, embrittlement or exfoliation of the electrode surface. Electrode corrosion may significantly alter electrocatalytic properties (resulting in a reduced selectivity) contaminate electrolytes (and, hence, products) block cells, dividers or manifolds cause electrical shorting, or provide parasitic redox couples (e.g. Fe /Fe ) which decrease current efficiency or promote deposit or bimetallic corrosion efficiency elsewhere. 

Hydrogen embrittlement The ductility of a metal is reduced and it cracks due to absorption of hydrogen. Hydride formation The degradation of mechanical properties and cracking of metals, such as titanium, resulting from hydride formation due to pick-up of hydrogen. 

In general, however, for titanium immersed in acid solutions, potentials above zero on the saturated calomel scale are conducive to the formation of protective oxide, while at certain negative potentials hydride films, which also confer some protection, can be formed. Between the potential at which a continuous hydride film is formed and that at which protective oxide films appear, soluble titanium ions are produced and rapid corrosion ensues. 

Also the titanium hydride can react with PhSiH3 to form 63, followed by the extrusion of silylene again with formation of the hydride. 

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