Increasing gas sorption onto carbon by milling with alumina

Graphite milled alone for 50 h shows an increase in gas sorption of a factor of three over unmilled powder. When graphite is milled in the presence of a much harder phase, aluminium oxide, the increase in sorption is much greater with a seven fold increase achieved after 5 h milling. Extending the milling time resulted in increased capacity; an estimated capacity of 2.5 g/ g carbon was achieved after 50 h milling

Comparative study of mechanical activation of molybdenite (MoS2) with and without magnesium (Mg) addition

Molybdenite concentrate was mechanically activated in the presence of magnesium metal using a planetary mill in order to try to form elemental molybdenum. A sample milled for 90 min in planetary mill showed almost the same structural distortion as after 50 h in a tumbling mill, neither showed the presence of molybdenum metal. However, molybdenite milled together with magnesium showed more amorphization than separately milled molybdenite. Despite the apparent lack of reaction, molybdenite showed higher solubility in dilute HCl after milling with magnesium than without.Mongolian Journal of Chemistry 16 (42), 2015, 30-3

Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

No abstract available

Effect of milling in oxygen on sphalerite-bearing materials

A sphalerite concentrate and two flotation rougher tails have been milled in an oxygen atmosphere for up to 10 h. Pressure measurements on the mills indicated that the concentrate had an induction time of < 2 h before significant reaction occurred whereas one of the tailings showed reaction within 1 h. The second tailings sample showed a slow pressure loss with time. All three samples showed a similar rate of pressure loss between 2 h and 10 h of milling indicating they were probably all reacting at a similar rate. Leaching of the milled powders in water showed significant increases which coincided with the pressure drops indicating that the oxidation products were water soluble; similar increases were also evident in acid

Formation of an alumina–silicon carbide nanocomposite

The high intensity ball milling of a mixture of silicon dioxide, aluminum and graphite powders was investigated to determine the formation of a composite of alumina and silicon carbide. Differential thermal analysis (DTA) was performed on milled powders. The products were analyzed by x-ray diffraction using monochromatic Cokα radiation using acount time of 1 s per 0.03 °step. The results show that for shorter milling time the reaction was two stage with elemental silicon appearing as an intermediate prior to carburization to silicon carbide

Highly adsorbent carbon formed by ball milling

The adsorption capacity of activated carbon formed by ball milling from alumina and synthetic graphite was investigated. It was observed that ball milling graphite with a harder phase led to a greater adsorption capacity for a shorter milling time. The mass loss of the sample was found to be a function of temperature. The mass losses during leaching were 9.75% and 25.2% for graphite milled for 50 h without and with alumina respectively. Compared with graphite milled alone, the sample milled with alumina has a capacity of 3.7 time greater

Carbonitridation of mechanically activated mixtures of zircon and carbon

Two different stoichiometries of zircon (ZrSiO4) and activated carbon (C:zircon molar ratios of 3:1 and 6:1) were milled together at for 5 h and subjected to thermo-gravimetric analysis (TGA). TGA runs were performed under argon and nitrogen atmospheres. The main mass loss reaction started at around 1200 °C in all samples, but the mass loss was greater in the 6:1 C:zircon ratio samples in nitrogen. X-ray diffraction (XRD) of the residues showed the decomposition of zircon was nearly complete. Traces of ZrN along with monoclinic and tetragonal forms of zirconia were observed in the nitrogen atmosphere, however only zirconia was present after heating in argon. Heating the 6:1 C:zircon molar ratio sample for 1 h at 1400 °C in argon resulted in the formation of ZrC and SiC, in nitrogen ZrN was formed

Ball milling induced reduction of SrSO4 by Al

The reduction of celestite concentrate to SrS using Al has been shown to be induced by mechanical activation. A thermodynamic appraisal showed that the reaction between SrSO4 and Al is highly exothermic and should be self-sustaining. XRD analyses showed that reaction started only after milling for an induction time of 30-35 min, after induction only product peaks were present. Increasing milling time up to 60 min had no significant effect other than refining the crystallite size. The aluminium product was not Al 2O3 as expected but mixed phases such as Sr 3Al32O51, SrAl4O7 and SrAl2O4 which were thought to be formed by an adventitious oxidation process. © 2010 Elsevier B.V. All rights reserved

Mechanochemical reduction of SrSO 4 by Mg

Mixtures of celestite concentrate (98% purity) and magnesium powders (97% purity) with a molar ratio of 1:4 were milled for increasing times. The temperature-time profile indicated a sudden increase in vial temperature between 10 and 11 min for the stoichiometric mixture of SrSO 4-Mg, whilst only 8-9 min were required with a 25% excess of magnesium. X-ray diffraction showed that the reaction produced SrS and MgO, increasing the milling time beyond that necessary for ignition did not have any major effect on the products. The results showed the mechanochemical reaction was highly exothermic and initiated as mechanically induced self sustaining reaction (MSR). After milling, the products were washed with hot water (T = 80 °C) for 2 h to separate the soluble SrS from the insoluble MgO. © 2011 Elsevier B.V. All rights reserved

Production of titanium nitride by carbothermic reduction of the anatase and rutile forms of titanium dioxide

Two types of titanium oxide were used, rutile (>99.9% TiO2) and anatase (>99% TiO2). Both samples were mixed with graphite in accordance with the required stoichiometry, and then milled in a tumbling mill for 50 hours in an argon atmosphere to ensure thorough mixing. The mill vial was loaded with five 25.4 mm diameter stainless steel balls giving a powder to ball mass ratio of 1:43. After milling, samples were heated to 1400°C in an alumina crucible at 20°C min-1 under a flowing nitrogen (100 mL min-1) atmosphere in a thermogravimetric analyser (TGA). Srilankite was detected in the as-milled anatase sample but the anatase to rutile transformation was not completed during milling. After heating to 800°C most of the anatase had transformed to rutile. Reduction of anatase started just below 900°C whilst rutile underwent reduction below 800°C. TGA results showed that the anatase reduction was more complex than the rutile reduction with several stages evident between 880 and 1000°C in the anatase sample whilst only two steps were observed for rutile. The initial identified products were Ti5O 9 and Ti4O7 prior to TiN in anatase sample but in rutile sample only Ti4O7 was detected. Reduction was completed in rutile sample before 1180°C whilst in anatase completed at 1230°C. TiN was the final product in both systems after heating to 1400°C. These results are discussed in light of recent work demonstrating the different reductions paths of rutile and anatase