Mössbauer Study of the Influence of Fe-Si-N Liquid in the Synthesis of β-Si3N4 from Silica

Mössbauer spectra of the products obtained by carbothermal reduction and distribution of silica in the presence of iron in the temperatures range 1200^o to 1540^o were studied. The preponderance of β- Si₃N₄ over the α form at a higher reaction temperature were assumed to be related to the formation of an Fe-Si-N liquid. The liquid did not alter its composition with the variation of reduction-temprature, Iron had no effect on the reaction mechanism below 1300^oC.     

Phenotypic identification and technological properties of lactic acid bacteria isolated from traditionally processed fish products of the Eastern Himalayas

Sukako maacha, gnuchi, sidra and sukuti are traditional smoked and sun-dried fish products of the Eastern Himalayan regions of Nepal and India. A total of 40 samples of sukako maacha (14), gnuchi (6), sidra (10) and sukuti (10) were collected and were analysed for microbial load. Population of lactic acid bacteria (LAB) as well as aerobic mesophilic counts ranged from 4.7-8.3 to 5.1-8.5 log cfu g(-1), respectively. A total of 189 strains of LAB were isolated from sukako maacha, gnuchi, sidra and sukuti samples, out of which 171 strains were cocci and 15 strains, were heterofermentative lactobacilli. LAB were identified on the basis of phenotypic characters including API system as Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, Lactococcus plantarum, Leuconostoc mesenteroides, Enterococcus faecium, Enterococcus faecalis, Pediococcus pentosaceus and Weissella confusa. LAB strains produced a wide spectrum of enzymes. Some strains of LAB showed antagonistic properties against pathogenic strains. None of the strains produced biogenic amines in the method applied. This paper is the first report on the microbial composition, mostly lactic acid bacteria, of traditionally processed fish products of Eastern Himalayas.     

Effect of Heat Treatment, Pre-stress and Surface Hardening on Fracture Toughness of Micro-Alloyed Steel

Micro-alloyed steels are being increasingly accepted by industry in various fields of application and are available with a wide variety of microstructures. Extensive literature is available on their microstructure-property relationships. The superior mechanical properties of micro-alloyed steels are caused by fine-grained microstructures and precipitation of micro-alloying elements such as V, Ti and Nb that led to an improvement in yield strength, in the product of tensile strength and total elongation and in Charpy V-notch impact energy as well. The microstructural changes caused by heat treatment or residual stress state caused by surface hardening or mechanical means may influence the fracture toughness of these micro-alloyed steels. It is in this context that the present work begins with experimental determination of quasi-static initiation fracture toughness (J _1c) of low carbon (0.19%) micro-alloyed steel in as-rolled condition without any heat treatment. The study further explores the effect of normalizing, shot-peening and cyaniding followed by shot-peening on fracture toughness of as-rolled steel under study. The normalizing heat treatment, shot-peening and cyaniding followed by shot-peening—each indicates a positive influence on initiation fracture toughness. Results, when compared, show that cyaniding followed by shot-peening have led to a 2.7 times increase in J _1c. Cyaniding followed by shot-peening may therefore be considered as having the most positive influence on initiation fracture toughness in as-rolled condition for the type of micro-alloyed steel under study. Although initiation fracture toughness is in general known to decrease with increase in yield strength in LEFM arena, the micro-alloyed steel under study when normalized displayed simultaneous improvement in yield strength and J _1c. All these observed effects of normalizing, shot-peening and cyaniding on initiation fracture toughness (elastic-plastic fracture mechanics) were explained on the basis of microstructural study and stress depth profiles.     

Stabilization of Cubic Zirconia by Aluminum Nitride

Cubic ZrO₂ is stabilized at room temperature by the addition of AIN. The percentage of c-ZrO₂ in the mixture of c-ZrO₂ and m-ZrO₂ increases linearly with the addition of up to 20 mol% AIN and decreases thereafter. Stabilization becomes complete at 50 mol% AIN. The lattice spacing of the cubic phase gradually expands up to 20 mol% AIN. A displacement reaction ZrO₂+ AIN → ZrN+Al₂O₃ occurs above 20 mol% AIN and is completed at 50 mol% AIN.     

Field between two unequal opposite and displaced slots electricmachines

The problem of Laplacian field distribution in the space enclosed by two rectangular slots in an electric machine is solved by using the method of separation of variables. The effects of placing exciting sources deep inside the slots are also accounted for. Though the analysis is mainly concerned with slots with infinite depths, the modifications needed to deal with finite slot depths are also indicated. The numerical results yielded by the mathematical model are compared with those available in the literature and with experimental plots     

The Adsorption of CO on the Stepped Pt{211} Surface: A Comparison of Theory and Experiment

Experimental measurements and DFT calculations reveal that, as expected, CO adsorbs most strongly at the step edge of Pt{211}, with similar adsorption energies for bridged and atop CO on the step. Terrace sites are significantly less stable. In the light of our results, we attempt to provide explanations for previous disagreement between experiment and theory.