Vibrational study of TlH2AsO4, TlH2-PO4 and their deuterated analogues

The Raman and infrared spectra of polycrystalline samples TlH₂AsO₄, TlD₂AsO₄, TlH₂PO₄ and TlD₂PO₄ have been investigated at 300 K in the frequency ranges 0 to 4000 and 200 to 4000cm^–1 respectively. The assignment of lattice, internal, and OH group vibrations has been approximated in terms of symmetry species. Although all the vibrations follow more or less the space group symmetry, the internal vibrations do not completely fulfill the requirements of the symmetry rule. The isotope effect was observed prominently on both compounds in Raman and infrared spectra. An attempt has been made to assign and explain the results.     

Investigation on the failure of air compressor

The cause for the failure of an air compressor has been investigated. It was found that a pre-existing fatigue crack was present at the root of the impeller blade. Transients and unsteady operation of the equipment prior to the accident are thought to have grown the fatigue crack to its critical size, thereby causing an imbalance in the impeller rotation and leading to failure.     

Influence of uniaxial ratchetting on low cycle fatigue behviour of SA 333 Gr. 6 C–Mn steel

Ratchetting behaviour and its influence on the subsequent low cycle fatigue behaviour of a plain carbon steel (SA 333 Gr. 6) has been evaluated. Uniaxial stress controlled ratchetting experiments have been carried out at various combinations of mean stress and stress amplitudes. It is noted that the ratchetting strain increased with increasing mean stress and stress amplitude. Maximum strain accumulation was observed for the highest value of the peak stress, irrespective of the stress ratio. Further, post ratchetting-low cycle fatigue (LCF) tests have been carried out and compared with non-ratchetted base LCF behaviour. The comparison showed that the fatigue life decreased in proportion to the accumulated ratchetting strain. This indicates that accumulation of significant ratchetting strain can be detrimental to the fatigue life and must be avoided. Mean stress induced due to pre-ratchetting is found to be responsible for the decrease in LCF fatigue life.     

Mechanical Properties and Dry Sliding Wear Behaviour of Molybdenum Disulphide Reinforced Zinc–Aluminium Alloy Composites

ZA-27 alloy is a lightest alloy which offers excellent bearing and mechanical properties in automobile and industrial applications. In this study, the MoS₂ particles with 0.5, 1 and 1.5 (wt%) weight percentages were reinforced in ZA-27 alloy to form composites, which were fabricated by using ultrasonic assisted stir casting method. The ZA-27/MoS₂ composite specimens were examined for chemical composition with the aid of XRD technique and EDS. Microstructure analysis of the ZA-27/MoS₂ composites was studied using SEM. Tests were conducted for mechanical properties such as tensile strength and hardness on ZA-27/MoS₂ composites samples as per ASTM standards. Dry sliding wear behavior of the composites was tested at various operating conditions by using pin-on-disc apparatus. Microstructural images of the ZA-27 composites reveal that there is a uniform dispersion of the MoS₂ particles in the base material. From the results it is observed that the mechanical properties increases with ZA-27 reinforced with 0.5 wt% MoS₂ composite and further decreases with increase in the filler content. The enhanced wear resistance is observed in ZA-27 reinforced MoS₂ composites as compared to the unreinforced alloy. The wear rate of the ZA-27 composites decreases with the increase in filler content, further the worn surfaces as examined using SEM reveals the wear mechanism explaining the improved wear resistance of the particulate composites.     

Low Cycle and Ratchetting Fatigue Behavior of High UTS/YS Ratio Reinforcing Steel Bars

Cyclic deformation behavior of high UTS/YS rebars has been studied employing both symmetric strain-controlled and asymmetric stress-controlled cycles in an attempt to understand the influence of UTS/YS ratio on fatigue life. While strain-controlled cyclic deformation did not exhibit a pronounced influence of UTS/YS ratio, a substantial life enhancement is noted for the asymmetric stress-controlled cycle. Reasons for life enhancement were found to be due to the ratchetting strain development and the associated hardening behavior. An equivalent stress-based model has been used to predict both the symmetric and asymmetric fatigue lives of rebars.     

Zeolite encapsulated Ru(III), Cu(II) and Zn(II) complexes as effective catalysts for the oxidation of ethylbenzene

Ru(III), Cu(II) and Zn(II) complexes of imidazole (ImzlH) have been synthesized in the supercages of zeolite-Y by flexible ligand method and characterized by spectroscopic (IR and UV?CVis) studies, XRD and thermogravimetric analysis, surface area, and pore volume measurements. These complexes were screened for their catalytic study towards the oxidation of ethylbenzene to a mixture of acetophenone, benzaldehyde and styrene using tert-butylhydroperoxide (TBHP) as an oxidant. A best-suited reaction condition has been optimized for these catalysts by varying the amount of the oxidant and catalyst, reaction time and volume of solvent for maximum transformation of ethylbenzene. Under the optimized reaction conditions, [Cu(ImzlH)]-Y gave 79.3% conversion after 1?h of reaction time. All these catalysts were more selective towards acetophenone formation. Among the prepared catalysts, zeolite encapsulated Cu(II) complex was found to be more active than the corresponding Ru(III) and Zn(II) complexes and all the complexes were stable enough to be reused. The catalytic activities of the neat complexes and metal exchanged zeolites were also compared with the zeolite encapsulated metal complexes.     

INFLUENCE OF MICROSTRUCTURE ON WEAR RESISTANCE PARAMETER OF CERAMIC CUTTING TOOLS

This report examines the role of microstructure of a new type of cutting tool material on an existing relationship between its abrasion wear resistance, fracture toughness (K_IC), and hardness (H). Three alumina-silver composites with different amounts of metal particles have been prepared, and their hardness and fracture toughness properties have been determined together with the assessment of their microstructural features such as volume fraction of the second phase, porosity, etc. The mechanical wear on the flanks of cutting tool inserts, made from the developed composites, has also been estimated by machining experiments against 0.45% carbon steel. The results indicate that flank wear resistance of these silver toughened ceramic cutting tool inserts is not proportional to an existing wear resistance parameter K_IC^3/4H^1/2. A modified relation between flank wear resistance, hardness, and fracture toughness has been suggested here for these cutting tool materials. The modification incorporates consideration of the volume fraction of the second phase and the porosity in the developed metal toughened ceramics.     

Synthesis of gold nanoparticles by cotton peels aqueous extract and their catalytic efficiency for the degradation of dyes and antioxidant activity

In this study, the authors synthesised gold nanoparticles (Au NPs) by a green approach using an aqueous extract of empty cotton boll peels (ECBPs) which was rapid, simple and inexpensive eco‐friendly method compared to chemical and physical methods. The ECBP aqueous extract played a vital role in the reduction of Au⁺³ ions into Au NPs which was further confirmed by analytical characterisation. The phase purity and crystallinity of Au NPs were confirmed by X‐ray diffraction analysis. The characteristic functional groups of synthesised Au NPs were identified by Fourier transform infrared analysis. The surface morphology and topography of Au NPs were studied by scanning electron microscopy and transmission electron microscopy analysis. Size with dispersion stability of Au NPs was determined by dynamic light scattering and zeta potential studies. In this study, the authors performed a catalytic activity of Au NPs using different pollutant organic dyes such as methylene blue and methyl orange. It also showed good antioxidant activity compared to standard ascorbic acid by using the standard 1,1‐diphenyl‐2‐picryl‐hydrazil method. Hence, this study concluded that ECBP mediated Au NPs could act as a promising material for degradation of dyes and antioxidant activity.Inspec keywords: gold, dyes, nanoparticles, nanofabrication, X‐ray diffraction, Fourier transform infrared spectra, surface morphology, surface topography, scanning electron microscopy, transmission electron microscopy, electrokinetic effectsOther keywords: gold nanoparticles, cotton peels aqueous extract, catalytic efficiency, antioxidant activity, green approach, empty cotton boll peels, analytical characterisation, phase purity, crystallinity, X‐ray diffraction, functional groups, Fourier transform infrared analysis, surface morphology, surface topography, scanning electron microscopy, transmission electron microscopy, dispersion stability, dynamic light scattering, zeta potential, pollutant organic dyes, methylene blue, methyl orange, Au     

Experimental investigation on cyclic deformation behaviour of primary heat transport piping materials: Masing analysis of hysteresis loops

In this work, the hysteresis loops of 304LN stainless steel at various strain amplitudes obtained via multi specimen, incremental and decremental load schemes were analysed for their Masing behaviour. In all the loading schemes, the material showed a non-Masing behaviour. A probabilistic density approach is used to examine the variation of yield during cyclic deformation. It is noted that yield level increased with increasing strain amplitude in all the test methods. The change in yield level is attributed to the microstructural changes in the material. Variation in microstructure and yield are thought to be responsible for the non-Masing behaviour of 304LN stainless steel.