The role of abrasion and corrosion in grinding media wear

A range of ferrous grinding media compositions was subjected to laboratory marked ball wear tests in an ongoing research program at the Mineral Resources Research Center which was aimed at elucidating the responsible wear mechanisms during the grinding of minerals. Most of the wear data in this paper were obtained using a model quartz-pyrrhotite mineral slurry but these have been supplemented, where appropriate, with a small amount of data from wear tests on taconite ore and a Cu-Ni gabbroic ore. The role of abrasive and/or corrosive wear was determined by comparing the wear rates which result under a range of grinding atmospheres, i.e. O₂, N₂ or compressed air, flushing through a laboratory mill of 8 in diameter coupled with examination of ball surfaces after grinding using scanning electron microscopy.     

pI-dependent isolation of antibody isoforms by semipreparative isoelectric focusing

Polyclonal antibodies were raised against peptides corresponding to residues 1-15, 469-483 and 933-951 of the rabbit skeletal muscle L-type calcium channel alpha 2/delta primary translation product, for use as topological probes. Immunocytochemical comparison of the abilities of the antibodies to bind to the alpha 2 and delta subunits in intact and detergent-permeabilised rat dorsal root ganglion cells enabled the membrane orientation of these regions to be established. The resultant data indicate that the regions containing residues 1-15 and 469-483 of the alpha 2 subunit, and residues 1-17 of the delta subunit, are exposed on the extracellular surface of the membrane, findings consistent with a model that proposes alpha 2 to be entirely extracellular.     

Friction and wear of tribofilms formed by zinc dialkyl dithiophosphate antiwear additive in low viscosity engine oils

Friction and wear characteristics of low viscosity SAE 5W-20 engine oils containing different amounts of phosphorus were studied using two different test devices. One was a laboratory high frequency reciprocating rig (HFRR) testing new and used oils at low and elevated temperatures. A direct acting mechanical bucket (DAMB) sliding valvetrain bench test apparatus was used to measure the friction and wear performances of fresh engine oils containing 0, 0.05 and 0.1 wt% phosphorus for a cam lobe rubbing against a tappet insert. The tester was coupled with a radioactive tracer machine (RTM). The results show that in the region of low phosphorus concentration, friction is inversely correlated to temperature. The friction coefficient slightly drops with increasing temperature and increases with increased phosphorus concentration at elevated temperatures. Significant wear is produced at phosphorus concentrations lower than 0.02 wt% at most temperatures. Friction and wear are reduced with the addition of supplemental antiwear additives. MoDTC reduces wear more effectively than ZnDTC in the presence of ZDDP.     

Enhanced Combustion Characteristics of Bismuth Trioxide‐Aluminum Nanocomposites Prepared through Graphene Oxide Directed Self‐Assembly

We present a facile, spontaneous, and surfactant‐free method to controllably self‐assemble aluminum and bismuth trioxide nanoparticles through the introduction of graphene oxide as a self‐assembly directing agent. The self‐assembled nanocomposites demonstrate significant combustion performance improvements in comparison to randomly mixed aluminum and bismuth trioxide nanoparticles with enhanced pressure generation from 60 to 200 MPa, pressurization rate from 3 to 16 MPa μs⁻¹, burning rate from 1.15 to 1.55 km s⁻¹, and specific impulse from 41 to 71 s. The sensitivity of the self‐assembled aluminum and bismuth trioxide to electrostatic discharge was reduced by four orders of magnitude, without decreasing the combustion performance. Graphene oxide directed self‐assembly can be used to synthesize nanocomposites with diverse combustion properties and controlled ignition sensitivity, which lays the foundation for preparing multi‐functional, highly‐reactive, combustion systems in the future.     

X-ray study of weak interactions in two flavonoids

X-ray diffraction studies were carried out on single crystals of two flavonoids, viz. 5-hydroxy-6,7,4′-trimethoxyflavone, C₁₈H₁₆O₆, (I) and 5-hydroxy-3,7,4′-trimethoxyflavone, C₁₈H₁₆O₆, (II). Crystal structures of both the flavonoids were solved by direct methods and refined by full-matrix least-squares procedures. In both the molecules, the benzopyran moiety is planar. The dihedral angle between the phenyl ring and the benzopyran portion is 5.50(4)° in (I) and 29.11(5)° in (II). In (I), the crystal packing is influenced by O-H…O hydrogen bonds, and weak C-H…O and π…π interactions whereas in (II) the crystal structure is stabilized by the presence of four intermolecular short contacts of the type C-H…O. There is also one C-H…π hydrogen bond with H… centroid distance of <2.7 Å. The molecules are further stabilized by π-π interactions.     

Enhanced plumbagin production in elicited Plumbago indica hairy root cultures

Elicitation of Plumbago indica hairy roots with yeast carbohydrate fraction, chitosan, manganese chloride, copper chloride and methyl jasmonate exhibited significant elevation (~1.2 to 2 fold) of plumbagin production in shake flask culture as compared with control. Chitosan and methyl jasmonate elicitation also caused simultaneous plumbagin leaching into culture media. Three days' exposure of chitosan (200 mg l(-1)) and methyl jasmonate (80 μM) together synergized total plumbagin yield to its maximum 11.96 ± 0.76 mg g(-l) DW in shake flask culture. In bioreactor cultivation, a significant raise in fresh root biomass was recorded on day 20 as compared with control shake flask culture. Three days' exposure of chitosan (200 mg l(-1)) and methyl jasmonate (80 μM) with 20 days old bioreactor-culture significantly improved total plumbagin production to 13.16 ± 1.72 mg g(-l) DW with simultaneous plumbagin leaching into bioreactor media.     

Role of hydrazine monohydrate during texturization of large-area crystalline silicon solar cell fabrication

Reduction of optical losses in monocrystalline silicon solar cells by surface texturing is one of the important issues of modern silicon photovoltaic. For texturization during commercial monocrystalline silicon solar cell fabrication, a mixture of NaOH or KOH and isopropyl alcohol (IPA) is generally used in order to achieve good uniformity of pyramidal structure on the silicon surface. The interfacial energy between silicon and electrolyte should be reduced in order to achieve sufficient wettability for the silicon surface which in turn will enhance the pyramid nucleation. In this work, we have investigated the role of hydrazine monohydrate as a surface-active additive, which supplies OH⁻ ions after dissociation. This cuts down the IPA consumption during texturing without any loss of uniformity of textured pyramid. We are probably the first group to report such a novel idea of using hydrazine monohydrate addition in NaOH solution for texturization of solar cell. We were able to fabricate monocrystalline silicon solar cells with more than 85% yield in the range of 14–15% efficiency.     

Soot–additive interactions in engine oils

Soot is known to cause engine wear. In this work, we focus on how engine oil formulation affects soot‐related wear, and how the lubricant‐derived anti‐wear film changes when soot is present. Friction and wear experiments of fully and partially formulated diesel engine oils (containing basestock, dispersants and viscosity modifiers) are conducted with a ball‐on‐disk rig in the presence of carbon black (CB) as a soot surrogate. The friction coefficient was largely unaffected by CB dispersed in the oils, but electrically insulating film formation, an indication of the formation of anti‐wear films, was decreased. Wear on the disk was found to either remain the same or decrease when CB was present, depending on the oil formulation. An examination of the lubricant‐derived films using Raman and Auger electron spectroscopies found that the presence of more abundant amorphous carbon and lesser amounts of anti‐wear film components on the surface was associated with higher wear. Copyright © 2009 John Wiley & Sons, Ltd.