Modelling and characterisation of Mo2C precipitation and cementite dissolution during tempering of Fe–C–Mo martensitic steel

Abstract

The precipitation and Ostwald ripening behaviour of needle shaped Mo₂C particles during the tempering of a ternary Fe-C-Mo martensitic steel have been characterised and modelled, taking account of local equilibrium, the capillarity effect, and the simultaneous enrichment and dissolution of cementite. Particles of Mo₂C are represented as paraboloids of revolution, with the tip radius chosen to yield the maximum lengthening rate. Transmission electron microscopy has been used to validate the theory; measurements of the average length, volume fraction, and number density of particles showed good agreement with experimental observations.     

28—THE SPECIFIC HEAT OF WOOL CONTAINING AN ADDITIVE AND THE HEAT OF FUSION OF THE ABSORBED WATER

Specific-heat values are presented, in the temperature range from ?70 to 100°C, for a modified wool at various water contents. The modification was analogous to a dyeing process and involved the uptake of 14% of an additive by the wool. As for untreated wool, an endothermic peak resulting from the fusion of absorbed water was found in the range from ?30 to 0°C. The absorbed water exhibits a sub-division into freezable and non-freezable fractions. Heats of fusion of freezable absorbed water are given and compared with corresponding results for untreated wool. The integral heat of fusion at saturation water content is much less for treated than for untreated wool, as is the amount of freezable water. It appears that the treatment causes the exclusion of a considerable quantity of loosely held water. This is in accord with the concept, derived from Flory–Huggins solution theory, that one effect of the additive is to swell the wool fibres and thereby cause a greater resistance to further swelling at a given water content.     

Functionalisation of polypropylene by solid phase graft polymerisation and its effect on the mechanical properties of silica nanocomposites

Abstract

To prepare macromolecular compatibiliser for grafted nano-SiO₂/polypropylene (PP) composites, solid phase graft copolymers of PP with styrene and ethyl acrylate were synthesised, respectively. It was found that both percentage grafting and grafting efficiency can be adjusted by changing initiator concentration, reaction temperature and reaction time. Due to partial chain scission and deterioration of the ordered structure of PP during the graft polymerisation, the grafted PP exhibits worse thermal stability and crystallisability than the unmodified PP. Mechanical tests of grafted nano-SiO₂/PP composites indicated that the addition of PP copolymer with the same species of grafting polymer as that on the nanoparticles further improves the ductility of the composites. Molecular rigidity of the grafting polymers, presence of the homopolymer produced during the graft polymerisation, and strain rate of the load applied have important influences on the toughening effect of the functionalised PP.     

High-Throughput Measurement of Drug pKa Values for ADME Screening

Combinatorial chemistry is now widely used to synthesize large numbers of new chemical entities. New methods have been developed for early-stage pharmacokinetic tests, to help decide which molecules have the properties required to make them efficacious and successful in the marketplace. Of the various physicochemical tests that are used to assess ADME, pK_a (aqueous ionization constant) is the key to understanding how other properties will be affected by pH. A new method is described for rapid measurement of pK_a of samples drawn from 96 well DMSO stock solutions.     

Superconducting Bi(2223) thick film on Ba2HoNbO6: a new perovskite ceramic substrate

Abstract

Barium holmium niobate Ba₂HoNbO₆ (BHNO) has been developed as a new substrate for (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (Bi(2223)) superconductor film. Ba₂HoNbO₆ has a cubic perovskite structure with lattice constant a = 8·26 Å. The dielectric constant and loss factor of this material are in a range suitable for its use as a substrate for microwave applications. The Bi(2223) superconductor shows no detectable chemical reaction with BHNO, even under extreme processing conditions. Dip coated Bi(2223) thick film on Ba₂HoNbO₆ substrate had T _c(0) of 109 K and current density of around 4 × 10³ A cm ^{- 2} at 77 K and in zero magnetic field.     

Factors affecting mechanical properties of resistance spot welds

Abstract

The present paper addresses the factors governing the mechanical performance of low carbon resistance spot welds. Correlations among the process parameters (welding current, welding time, electrode force and holding time), physical spot weld attributes and mechanical performance are analysed. Peak load and energy absorption of spot welds during the tensile shear test are used to describe spot welds performance. It is shown that weld nugget size, electrode indentation, failure mode and strength/ductility of the failure location are the main factors affecting peak load and energy absorption of spot welds.     

21—THE WIRA SHOWER TESTER: A NEW INSTRUMENT FOR THE QUALITY CONTROL OF FABRICS

A new instrument for measuring the absorption and penetration-resistance of fabrics is described. It is based on a novel method of drop propagation, and it is shown that the dynamical properties of the drops lie within the wide range of values provided by natural rain. The test procedure, which is intended to form the basis of a draft British Standard method of test, is described. Results of tests on a variety of apparel fabrics are given, and these include comparative tests on unproofed and treated cloth and tests on fabrics of known wear performance.     

Investigation of surface molecular orientation of poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) films using dynamic contact angle measurements,NEXAFS and XPS

Since poly(dimethylsiloxane)-modified poly(amic acid) was not wetted by the photoresist, poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) was synthesized to improve the wettability of photoresist. From a study on dynamic contact angles of water, the initial advancing contact angles on poly(dimethylsiloxane)-modified poly(amic acid) and those on poly(dimethylsiloxane-co-diphenyl-siloxane)-modified poly(amic acid) are almost the same, but the equilibrium advancing contact angles on poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) are much smaller than those on poly(dimethylsiloxane)-modified poly(amic acid). The decrease in equilibrium advancing contact angles on poly(dimethylsiloxane-co-diphenylsiloxane) appears to indicate migration of phenyl groups to the surface in the polar environment. Thus, photoresist could be wetted on the poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) film. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS) were used to investigate the orientation and surface migration of molecules in poly(dimethylsiloxane-co-diphenylsiloxane).     

14—REVERSIBLE AND IRREVERSIBLE DIMENSIONAL CHANGES IN WOOL FABRICS

An account is given of experiments made with an apparatus constructed for recording, simultaneously and continuously, weight and length changes during the drying and steaming of fabrics. Hot air at a temperature of 100 or 115°C was used in the drying experiments. Steaming was done under the same conditions. The maximum level to which the moisture regain could be increased with steam varied with the fabric construction. Below this maximum level, absorption and desorption experiments with relaxed fabrics gave reproducible and identical hygral-expansion curves. Moisture-regain changes below saturation caused by steaming and drying did not completely release the strain in fabrics cohesively set. The difference resulting from the use of saturated and superheated steam was negligible. The lower the temperature during cohesive setting, the less resistant was the set towards moisture-regain changes.     

Change in microstructure of Al–Si–Cu casting alloys during high temperature solution treatment

Abstract

The solution treatment in Al–Si system casting alloys is usually performed to obtain supersaturated solid solution and spheroidising Si particles. It can be inferred that a high temperature solution treatment enhances mechanical properties without any special apparatuses or techniques. However, it is well known that the solution treatment close to an eutectic temperature causes local melting. In this study, the change in microstructure of Al–Si–Cu casting alloys, which have been solution treated at temperatures ranging from 773 to 824 K, have been investigated from a viewpoint of Cu concentration and the distributions of micropores and locally melt regions due to eutectic reaction. Tensile and hardness tests were carried out to discuss the relationship between mechanical properties and microstructures. In addition to a surface observation, an internal microstructural observation was carried out using the high resolution X-ray computed tomography. The burnt regions during the high temperature solution treatment were identified to be Cu rich. Porosity increased with increasing the solution treatment temperature. The porosity in the sample solution treated above a binary eutectic temperature was confirmed to be >0˙2 vol.-%. The Cu concentration in the α-phase increased below the binary eutectic temperature.