Recent progress on biosorption of heavy metals from liquids using low cost biosorbents : characterization, biosorption parameters and mechanism studies

A significant number of biosorption studies on the removal of heavy metal from aqueous solutions have been conducted worldwide. Nearly all of them have been directed towards optimizing biosorption parameters to obtain the highest removal efficiency while the rest of them are concerned with the biosorption mechanism. Combinations of FTIR, SEM-EDX, TEM as well as classical methods such as titrations are extremely useful in determining the main processes on the surfaces of biosorbents. Diverse functional groups represented by carboxyl, hydroxyl, sulfate and amino groups play significant roles in the biosorption process. Solution pH normally has a large impact on biosorption performance. In brief, ion exchange and complexation can be pointed out as the most prevalent mechanisms for the biosorption of most heavy metals.

Influence of trace-metals on the colour and photostability of wool

This study expands the knowledge of the mechanisms that cause wool to yellow. It established that metals in wool influence the production of free radicals and the extent of degradation and yellowing of photo-irradiated wool. It also examined the relationship between the colour and trace metal content of fleece wool.

Effects of replication on measured S-N curves of metals

Replication, or repeated tests at the same stress amplitude, is used to provide statistical confidence in life data during the development of S-N curves. This paper discusses the effects of replication on the measurement of S-N curves and presents an alternative to traditional replication methods for the determination of S-N curves, particularly for the development of preliminary S-N curves. Using specimens made out of the extruded bars of a magnesium alloy, it is demonstrated that the S-N curve estimated using the data from non-replication tests is almost same as that from replication tests. The advantage of using non-replication fatigue tests is that it uses fewer specimens, in this instance, only half of that required for 50% replication fatigue test, to achieve the same estimation as that of the replication fatigue tests. Another advantage of using non-replication fatigue tests is that it can detect the non-linearity using limited specimens.

Crystal orientation characterisation of electrodeposited nanocrystalline nickel alloy

The collection contains EBSD maps of annealed nanocrystalline Ni and Ni-Fe alloys. The maps show the variation of crystallographic texture across mesoscale colonies within these alloys.

Modelling the combined effect of grain size and grain shape on plastic anisotropy of metals

Within each columnar grain of a metallic film, the resistance to dislocation glide varies in function of the orientation of the slip plane with regard to the grain long axis. Plastic slip is impeded across grain boundaries and this contributes to the anisotropy of the overall mechanical response. A simplified (Taylor-type) crystal plasticity model is proposed that accounts for such effect of grain shape on the slip system selection. Assuming that dislocation density gradients are normal to the grain boundaries, backstresses developed at the onset of plasticity are estimated based on two definitions of the effective grain boundary spacing ‘‘seen’’ by individual slip systems. The first one reduces to the mean area-to-perimeter ratio of cross-sections of the grain cut parallel to the slip plane. Closed-form expressions of the average backstresses developed inside grains with spheroidal shapes are introduced in the crystal hardening law. The model reproduces the very high plastic anisotropy of electro-deposited pure iron with a strong c-fiber and a refined columnar grain structure [Yoshinaga, N., Sugiura, N., Hiwatashi, S., Ushioda, K., Kada, O., 2008. Deep drawability of electro-deposited pure iron having an extremely sharp h111i//ND texture. ISIJ Int. 48, 667–670]. It also provides valid estimates of the texture development and the influence of grain size on the yield strength.

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.