Group V–VI binary sulfides are semiconductors, and find application in a number of commercial devices. Synthesis of these metal sulfides is problematic, and traditional synthesis techniques utilizing ...thermal and chemical means have disadvantages such as a long process time, contamination, and the use of toxic substances. In this work, the novel synthesis technique of electric discharge assisted mechanical milling (EDAMM) has been used to rapidly synthesize Bi
2S
3 and Sb
2S
3 powders from elemental S and Sb/Bi powders. This technique is shown to be both rapid and successful, and produces crystalline metal sulfide powders with a particle size of approximately 2
μm.
The abrasion resistance of WC-4Ovol%(FeAl-B), WC-4Ovol%(Ni3Al-B), and WC-4Ovol%Co, prepared from ultra fine precursor powders and processed by uniaxial hot pressing, has been investigated using a ...pin-on-drum tester. Intermetallic binders, with different amount of boron including 0, 250, 500, 750, and 1000 ppm B, were prepared in ultrafine form under controlled atmosphere using ring grinding, blended with submicron (0.8 mm) WC powder and then uniaxially hot pressed at 1500 DGC under a pressure of 20 MPa for 4 min in 10-2 MPa argon atmosphere. In an additional investigation, wear results were compared with that of commercial H1OF (WC-lOwt%Co, WC particle size of 0.7 mm). It was found that the wear resistance of WC-FeAl-B and WC-Ni3Al-B increased with the increasing amount of boron. WC-4Ovol%FeAl-B showed the highest abrasion resistance, close to that for WC-lOwt%Co (H1OF) composite, followed by WC-40vol%Ni3Al-B and WC-4Ovol%Co.
When magnesium powder containing small additions of certain multiple valence transition metal oxides (TMOs) is ball milled in hydrogen, the hydrogenated Mg-based product can show remarkable ...improvements in hydrogen absorption/desorption properties. Using a magnetically controlled Uni-Ball-Mill, small amounts of the iron oxides, Fe
2O
3 and Fe
3O
4, were ball milled with Mg powder in a hydrogen atmosphere (Mg to Fe atomic ratio; 20:1). Milling products as well as samples used in hydrogen absorption/desorption experiments were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis.
TG analysis combined with DSC revealed a higher hydrogen storage capacity for the Mg
+
Fe
2O
3
+
H
2-milled product (6
wt% H) compared with 5
wt% H for Mg
+
Fe
3O
4
+
H
2. XRD revealed that during heating, both iron oxides were reduced to pure Fe, a result not previously reported for similar materials milled using different milling devices. For both samples, there was little difference found in the decomposition temperature of the as-prepared MgH
2 and rehydrogenated composites. However, storage capacity degradations were observed for the rehydrogenated composites (4
wt% H storage capacity for MgH
2
+
Fe
2O
3 and 4.4
wt% H for MgH
2
+
Fe
3O
4). The higher capacity degradation of rehydrogenated MgH
2
+
Fe
2O
3 composite is also believed to be a result of the reduction reaction, during which more magnesium was consumed than was consumed by the same amount of Fe
3O
4. The results also were related to the particular ball-milling equipment and low-energy shearing milling mode employed, which promoted the development of a nanostructural hydride product which subsequently changed structure significantly during the first desorption cycle.
Mechanical alloying of magnesium metal powders with hydrogen in specialized hydrogen ball mills can be used as a direct route for mechanochemical synthesis of emerging chemical hydrides and hydride ...mixtures for advanced solid-state hydrogen storage. In the 2Mg–Fe system, we have successfully synthesized the ternary complex hydride Mg
2FeH
6 in a mixture with nanometric Fe particles. The mixture of complex magnesium-iron hydride and nano-iron released 3–4
wt.%H
2 in a thermally programmed desorption experiment at the range 285–295
°C. Milling of the Mg–2Al powder mixture revealed a strong competition between formation of the Al(Mg) solid solution and the β-MgH
2 hydride. The former decomposes upon longer milling as the Mg atoms react with hydrogen to form the hydride phase, and drive the Al out of the solid solution. The mixture of magnesium dihydride and nano-aluminum released 2.1
wt.%H
2 in the temperature range 329–340
°C in the differential scanning calorimetry experiment. The formation of MgH
2 was suppressed in the Mg–B system; instead, a hydrogenated amorphous phase (Mg,B)H
x
, was formed in a mixture with nanometric MgB
2. Annealing of the hydrogen-stabilized amorphous mixture produced crystalline MgB
2.
The aim of this work was to investigate nitrogen uptake and nitridation characteristics of titanium metal powder during processing by electrical discharge assisted mechanical milling under flowing ...nitrogen. Samples were prepared using an in-house reactor with an AC high voltage transformer, generating impulses within kV/mA range. The structures of reaction products were characterized by X-ray diffractometry, nitrogen contents by CHN combustion analysis and powder morphologies by SEM. An extremely rapid nitridation reaction was found to take place during milling under an electrical discharge and within 3–5
min titanium nitride (TiN) particles were directly synthesized from titanium powder. In contrast, under the same milling conditions without a discharge no TiN was detected after 30
min milling. The nitrogen uptake rate was extremely fast for milling under both low and high energy electrical discharges, however, the total nitrogen content of the product was higher in samples milled under a high energy discharge. The formation of TiN during milling was believed to occur via a complex process, involving rapid particle fracturing due to the combined effects of milling and an electrical discharge, interaction of the fine particles with hot nitrogen gas and free radicals generated by the electrical discharges, and thermally activated local diffusion of the nitrogen into the powder particles.
The newly developed synthesis technique of electrical discharge assisted mechanical milling (EDAMM) is used to reduce Pb and Sb sulfides using Fe and Mg as reduction agents. It is demonstrated that ...both Fe and Mg can successfully be used to fully reduce PbS and Sb2S3 in only 5 min using EDAMM. This is the fastest sulfide reduction technique so far developed, and has the added advantage of not requiring external heating of the reactants during processing. The reaction products are a solid mixture of larger crystal sizes than would be achieved through conventional milling.
Carbo-thermic reduction of ilmenite (FeTiO3) to TiO2 and/or TiC is traditionally carried out by a high temperature annealing treatment at 1500 deg C. In this work, electric discharge assisted ...mechanical milling (EDAMM) has been used to synthesise TiC + Fe3C from FeTiO3 in 5 min. In this study we report of the reduction of FeTiO3 with C that does not require an additional high temperature annealing treatment.
Controlled reactive mechanical milling (CRMM) of Mg powder under “
shearing” mode in hydrogen gas for 26.5, 50, 70 and 100
h results in the formation of nanostructured β-MgH
2 hydride. Based on the ...comparison of integrated X-ray diffraction (XRD) intensities of Mg and β-MgH
2 peaks, it is postulated that during reactive milling up to 50
h the crystalline Mg is mostly consumed to form β-MgH
2. However, from 50 to 100
h the crystalline Mg mostly forms an
amorphous phase with only a small fraction of it being consumed for the β-MgH
2 creation. The formation of amorphous Mg was also observed in the 2Mg–Fe mixture subjected to controlled reactive mechanical alloying (CRMA) in hydrogen. A massive formation of Mg(OH)
2 hydroxide is observed by XRD in the powders reactively milled in hydrogen and subsequently exposed to the ambient environment for about 4 months. The formation of Mg(OH)
2 occurs due to hydrolysis of nanostructured β-MgH
2. Abnormally high weight losses on the order of ∼16–24
wt.% are observed during thermogravimetric analysis (TGA) of powders containing Mg(OH)
2 which confirm the release of water from Mg(OH)
2 upon heating. Also, differential scanning calorimetry (DSC) curves show endothermic peaks corresponding to the release of water from Mg(OH)
2 which are in excellent agreement with DSC peaks corresponding to the release of water from Mg(OH)
2 in the 2Mg–Fe 10
h reactively milled and “aged” mixture.
MgH2/graphite composite was fabricated by mechanically milling elemental ingredients in hydrogen using a special low-energy ball-particle shearing milling. Rehydrogenated MgH2/graphite composite ...exhibits a desorption temperature that is lower by about 35 deg C compared with that of the as-prepared composite. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), differential scanning calorimeter (DSC), and Raman and IR spectroscopy were used to investigate the possible origins of the noticeable enhancement in the desorption temperature. It is found that gamma-MgH2, a by-product of ball milling, does not contribute to the enhancement of the hydrogen desorption. Carbon hydrogen bonding is not detected and it seems that the formation of classical C-H bonding is not feasible with this kind of milling mode. It is believed that the structural change in hydrogenated carbon clusters and/or charge-transfer reactions upon hydrogen cycling are likely to be responsible for the enhancement in the hydrogen desorption temperature.
The abrasive wear behavior of tungsten-carbide iron-aluminide composite materials was investigated using a pin-on-drum wear-testing machine. Samples were prepared by uniaxially hot pressing blended ...powders. The wear rates of specimens containing 40
vol.% matrix of atomic composition, Fe
60Al
40, were measured and results compared with those of conventional WC–10
vol.% Co hardmetal. They were found to be comparable to those of WC–10% Co hardmetal, when abraded by 120
μm SiC papers under identical conditions. The wear resistance of WC–Fe
60Al
40 composites increased with reduction in WC-grain size and associated with increase in composite hardness. Scanning electron microscopy revealed that the wear surfaces of WC–40% Fe
60Al
40 composites and WC–Co hardmetal were similar in appearance. The higher hardness and work hardening ability of Fe
60Al
40 binder, as compared to Co metal, are believed to be responsible for the excellent abrasive wear resistance of WC composites containing iron aluminide binder.
