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World’s growing energy need is mostly reliant upon fossil fuels. Fossil fuels are considered to be non-renewable energy sources because it needs million years to form and reserves are being depleted much more faster than new reserves are being made. Usage of fossil fuels comes with harmful consequences. It is responsible for 20 % of global warming pollution. To avoid these harmful effects, new energy sources must be discovered. As an alternative to fossil fuels, hydrogen can be used for energy needs and it has a lot of benefits over fossil fuels such as being environmentally friendly, carrying high energy content and being renewable. To use hydrogen as an energy source instead of fossil fuels, some challenging problems must be solved. One of them is hydrogen storage. Hydrogen can be stored as gas or liquid but these types of storage are not so efficient for widespread use. A more convenient way is to store hydrogen in the form of solid. For this purpose, metal borohydrides and ammines can be used due to their high gravimetric and volumetric densities. To decompose hydrogen, metal borohydrides requires very high temperatures and this situation can be moderated by mixing them with ammines. To achieve this goal, in this study we designed dual-cation ammine metal borohydrides (AMBs) in the form of LiSc(BH4)4(NH3)x (x = 2, 3) using an approach which combines crystal structure prediction with density functional theory computations.

Hydrogen is one of the promising alternatives for the replacement of fossil-fuels. One of the major bottlenecks preventing its widespread commercialization for on-board applications is to find the most suitable storage medium. Metal borohydrides are one of the classes of solid materials studied intensively to store hydrogen due to their high theoretical hydrogen capacities. However, their high thermodynamic stability is one of the major problems limiting their usage. The requirement of high decomposition temperature can be lowered by the inclusion of ammonia. The resulting new complex containing both borohydrides and ammines is called as Ammine Metal Borohydrides (AMBs). However, some of the AMBs have insuppressible release of ammonia during the dehydrogenation. This can be solved by the inclusion of a second metal atom into AMBs leading to dual-cation AMBs with a general formula of M1M2(BH4)y(NH3)x. Experimental studies about one dual-cation AMBs (LiMg(BH4)3(NH3)2) indicate desired properties e.g., decomposition occurs below 200 °C and no release of ammonia. In this study, a computational screening using periodic density functional theory was performed to find promising dual-cation AMBs (M1M2(BH4)y(NH3)x with M1 = Li, Na, K, M2 = Mg, Ca, Sr, Zn, Mn, Ni, y = 3, x = 2, 3, 4, 5, 6). The screening has been accomplished using template crystal structures generated by Crystal Structure Prediction via Simulated Annealing (CASPESA) method. Formation, alloying and simple decomposition reactions were employed for the evaluation of the complexes.

Metal matrix composites, prepared by pressure infiltration casting of copper base alloy into 2 types of microporous carbon preforms, one with 100% amorphous carbon and the other containing 40 wt pct. graphite and 60 wt pct. amorphous carbon, have been examined for their wear and friction behavior under ambient conditions using a pin-on-plate reciprocating wear tester. Micro-structural characterization of tribo-surfaces has been carried out. The thin carbon films formed on the tribo-surface reduced the friction coefficient and wear for the composites, especially at low loads on the pin. Adhesive wear observed on the tribo-surface promoted wear and friction at high loads. The wear and friction were observed to be very sensitive to the size and distribution of the microstructural constituents.

Refractory metals belonging to the Group IV-VIB of the periodic table are conventionally produced from their natural sources by a sequence of pyro and hydro-metallurgical process first to produce a pure chemical intermediate which is then reduced to crude metal. The physical, chemical and mechanical properties of the metal are very sensitive to the presence of metallic and interstitial impurities. The reduced crude metal is usually subjected to post reduction purification treatment to obtain pure metals. For certain specific applications it is further necessary to purify the metals to still higher purity. This paper briefly reviews the present status on purification of refractory metals such as titanium, zirconium, hafnium, niobium, tantalum, vanadium, molybdenum and tungsten and also presents directions for future research in the field of these metals.

The technique of explosive consolidation was used to prepare cermets of boron carbide with aluminium and 7075 aluminium alloy. Compacts were produced by application of 10–12 GPa pressure which was induced by explosive detonation. The compacts obtained exhibit high hardness-increasing with an increase in the boron-carbide content, integrity and close to theorical density. Hardness, fracture toughness and flexural strengths of the composites produced indicate extensive shock hardening of the metal (or alloy) matrix during consolidation.

The possibility of producing aluminium matrixed aluminium nitrideboron carbide composites by pressureless wetting assisted infiltration has been shown. Cold isostatically pressed cup-shaped preforms of boron carbide (1–10 wt%) aluminium nitride mixtures were sintered at 1400–1600 °C in nitrogen atmosphere and then infiltrated with aluminium under 6.5 kPa argon at 1250 °C. Pore diameter in the preforms increased with increase in sintering temperature. Infiltrated samples which were sectioned and polished showed no infiltration front. Higher B 4 C contents (4–10%) and sintering temperature (1600 °C) resulted in full infiltration. In the sintered preforms AlN was the only phase observed. However, in the infiltrated materials both AlN and Al were observed.

The formation and separation of metal nitrides from a variety of materials including ferroalloys, oxides, natural materials and minerals is an important component in current materials processing practice. Ferroalloys like ferroniobium and ferrovanadium undergo nitridation by ammonia yielding a mixture of iron nitrides and the refractory metal nitride. Acid leaching effectively separates the iron nitride from the mixture. Niobium nitride thus obtained is used to produce niobium metal by pyrovacuum treatment. Vanadium nitride converts to metal when pyrovacuum treatment is followed by electrorefining. Nitride suitable for decomposition to metal can be obtained from niobium pentoxide by reacting ammonia or by reacting a mixture of carbon and nitrogen. Rice husk is a ready-made intimate mixture of silica and carbon. It can be converted to silicon nitride or to a mixture of silicon carbide and silicon nitride by carbonitrothermic reduction. β sialon can be directly prepared from kaolinite by carbonitrothermic reduction. Ilmenite is another mineral amenable to nitridation processing. It yields after reaction with nitrogen in presence of carbon, a separable titanium nitride-iron mixture. All these attractive features of nitridation have been discussed in this paper. The possibility of incorporating nitridation into the process flowsheets has been highlighted.

The processes for the production of ferroboron and ferrovanadium from indigenous resources by open aluminothermic reduction have been described. The influence of process parameters such as charge composition, particle size, and the use of fluxes on the yield and composition of the ferroalloys obtained are discussed. In the case of ferroboron, it has been possible to obtain a recovery of 60% of boron as Fe-15B while restricting the residual aluminium content in the product to approximately 2% by using 90% of stoichiometric aluminium in the charge. In the case of ferrovanadium, it has been possible to achieve a recovery of 70% of vanadium as Fe-75V by using 5% excess aluminium in the charge, with the same percentage remaining as residual aluminium in the product.

Carbothermic reduction of boric acid has scientific and economic advantages over other methods of boron carbide production. The strongly endothermic reaction which has a favourable free energy change only at high temperatures is best carried out in a specially designed graphite resistance furnace at temperatures above 2000 degrees C, using boric acid and petroleum coke as starting materials. The composition of the charge has a strong influence on the quality of boron carbide obtained and also on the yield. The use of boron anhydride in place of boric acid decreases the yield. The yield is also affected by the heating conditions prevailing in the furnace. The yield of boron carbide can be substantially improved and thus the specific energy consumption in boron carbide production can be significantly decreased by adding an optimum quantity of salt to the boric acid-petroleum coke mixture. The various factors that influence the quality and yield of boron carbide product and hence the economy of boron carbide production by the carbothermic reduction route have been discussed in this paper.

The microstructure of a semi-continuously cast AA 6063 alloy was investigated and the transformation of insoluble intermetallic phases by applied heat treatment was studied by selective dissolution of the matrix. Residual intermetallics were characterized using energy-dispersive X-ray analysis, X-ray and electron diffraction techniques. Transformation of β-AlFeSi phase, which is known to have detrimental effects on the surface finish of the extrudates, to more favourable α-AlFeSi phase by heat treatment was determined.

Studies on roasting of sheelite concentrate have been carried out in fluidized bed to reduce its sulphur content to

An approximate amount of 2 million tons of copper slag has been lying on the northern part of Turkey from ancient time. This slag contains 0.43% cobalt and 1% copper. This paper reports work carried out to process this slag for recovery of cobalt and copper.

Metal-matrix composites have been prepared by pressure-infiltration casting of copper-base alloy melts into microporous carbon preforms. The carbon preforms contained varying proportions of amorphous carbon and graphite. Load dependence of the wear and friction behavior of the composite pins has been examined under ambient conditions against cast-iron plates, using a pin-on-plate reciprocating wear tester. The wear resistance of the composite is significantly improved, as compared with the base alloy. Contrary to the normally expected behavior, the addition of graphite to the amorphous carbon does not reduce the friction coefficient, especially at high loads. The wear and friction behavior of the composites is very sensitive to the size and distribution of the microstructural constituents.