Microtexture characterisation of electrodeposited nanocrystalline nickel

This data includes transmission electron microscopy orientation maps of the received electrodeposited nanocrystalline nickel. The data was obtained using the Nanomegas Digitstar System which is currently the only equipment of this type available in Australia. The data has been acquired with steps in nanometre scale and enables the determination of local microtexture of the specimens.

Synthesis and characterization of nanocrystalline hexagonal boron carbo-nitride under high temperature and high pressure

A study of the synthesis of hexagonal boron carbo-nitride (h-BCN) compounds via a two-step high-temperature and high-pressure (HTHP) technique using melamine (C 3N 6H 6) and boron oxide (B 2O 3) as raw materials is presented. An amorphous BCN precursor was prepared at 1000K under vacuum in a resistance furnace and then single-phase h-BCN nanocrystalline was synthesized at 1600K and 5.1GPa in a multi-anvil apparatus. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the final products were pure h-BCN crystals with the lattice constants a ≤ 0.2510nm and c ≤ 0.6690nm. The average grain size was about 150nm. X-ray photoelectron spectroscopy (XPS) results confirmed the occurrence of bonding between C-C, C-N, C-B and N-B atoms. Raman scattering analysis suggested that there were three strong Raman bands centered at 1359, 1596 and 1617cm -1, respectively. The band at 1617cm -1 was considered to be consistent with the characteristic Raman peak of h-BCN.

The implied convenience yield of precious metals: safe haven versus industrial usage

During a financial crisis, investors find it convenient to hold gold (Gd) as a safe haven. But during good economic times, manufacturing firms find it convenient to stockpile platinum (Pl), palladium (Pd) and especially silver (Si), for industrial usages. We have three related objectives. First, we examine the nature of cross-market interactions among the convenience yields (cy_it) of {Gd, Pl, Pd, Si}, which are implied from cost-of-carry relations. Second, we test if the more influential cy_it of certain precious metals are also affecting the return, volatility and/or volume dynamics of other precious metals. Third, we analyze if the cy_it of gold is enhanced (diluted) during (after) the Asian and Global financial crises. We find, consistent with our propositions, that during crisis period, gold’s cy_it provides incremental information to the volatility series of {Gd, Pl, Pd, Si}. But during good economic times, it is silver’s cy_it that has the most influence on the return series across {Gd, Pl, Pd, Si}. This is not surprising given that Si has the largest proportion of industrial usage among the four metals.

Influence of hydrogen peroxide in the preparation of nanocrystalline ceria

The influence of H2O2 in the preparation of nanocrystalline CeO2 has been investigated by treating solutions of Ce(III) with NaOH in the presence of different concentrations of H2O2. The resulting precipitated material was then examined by a range of techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). A decrease in CeO2 crystallite size with increasing H2O2 concentration was observed. This was found to be associated with the formation of an amorphous material containing an η2-peroxide (O22-) species.

Temperature variations at nano-scale level in phase transformed nanocrystalline NiTi shape memory alloys adjacent to graphene layers

The detection and control of the temperature variation at the nano-scale level of thermo-mechanical materials during a compression process have been challenging issues. In this paper, an empirical method is proposed to predict the temperature at the nano-scale level during the solid-state phase transition phenomenon in NiTi shape memory alloys. Isothermal data was used as a reference to determine the temperature change at different loading rates. The temperature of the phase transformed zone underneath the tip increased by _3 to 40 _C as the loading rate increased. The temperature approached a constant with further increase in indentation depth. A few layers of graphene were used to enhance the cooling process at different loading rates. Due to the presence of graphene layers the temperature beneath the tip decreased by a further _3 to 10 _C depending on the loading rate. Compared with highly polished NiTi, deeper indentation depths were also observed during the solidstate phase transition, especially at the rate dependent zones. Larger superelastic deformations confirmed that the latent heat transfer through the deposited graphene layers allowed a larger phase transition volume and, therefore, more stress relaxation and penetration depth.

Effect of nanocrystalline structure on the corrosion of a Fe20Cr alloy

The corrosion behaviour of nanocrystalline and microcrystalline Fe20Cr alloys, prepared by high energy ball milling followed by compaction and sintering, was studied in 0.05M H2SO4 and 0.05M H2SO4 + 0.5M NaCl by potentiodynamic polarization. The nanocrystalline alloy exhibited improved passivating ability and pitting resistance as described by passivation potential, critical current density, passive current density and breakdown potential. XPS and SIMS analysis revealed greater Cr content in the passive film formed on the nanocrystalline form of the alloy. The enhanced passivating ability of the nanocrystalline alloy was attributed to the formation of the passive film with higher Cr content.

Resistance of nanocrystalline vis-à-vis microcrystalline Fe–Cr alloys to environmental degradation and challenges to their synthesis

This paper presents a hypothesis and its experimental validation that a nanostructure can bring about dramatic improvements in the oxidation/corrosion resistance of iron–chromium alloys. More specifically, a nanocrystalline Fe–10 wt% Cr alloy was found to undergo oxidation at a rate that was an order of magnitude lower than its microcrystalline counterpart. Importantly, the oxidation resistance of nanocrystalline Fe–10 wt% Cr alloy was comparable with that of the common corrosion-resistant microcrystalline stainless steels (having 18–20 wt% chromium). The findings have the potential of leading to the next generation of oxidation-resistant alloys. However, due to poor thermal stability of nanocrystalline structure, synthesis/processing of such alloys is a challenge. Discs of nanocrystalline Fe–10% Cr alloy were produced by ball-milling of Fe and Cr powders and compaction of the powder without considerable grain growth by processing within a suitable time–temperature window. The paper also presents a theoretical treatise to arrive at the minimum chromium content required for establishing a protective layer of chromium oxide in an Fe–Cr alloy of a given nanometric grain size.