Papers by Keyword: Nitrogen

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Authors: Walter Lengauer, Marcel Bohn
Abstract: A common and straightforward method for the standardisation in electron-probe microanalysis (EPMA) is the use of homogeneous reference materials prepared by various techniques such as by melting, sintering, high-temperature annealing and hot-pressing. The reference materials have to be analysed by independent methods accurately in order to define their “true” composition. For some compounds the preparation techniques are difficult because of their specific thermo-chemical properties (e.g. low diffusivities, high equilibrium nitrogen pressure, incongruent melting). In addition, many compounds show large homogeneity ranges with an a priori existing uncertainty in composition, contrary to what is generally preferred: to use compounds with a narrow homogeneity range (“line compounds”). For the latter, diffusional preparation techniques can be applied to yield diffusion layers instead of massive samples for standardisation. However, also single-phase samples with narrow homogeneity ranges can be prepared by diffusion, depending on the phase equilibria in the corresponding system. The presentation summarises efforts that have been made in order to prepare various reference materials for carbon and nitrogen standardisation of EPMA by various techniques. The boundary conditions such as phase stabilities, phase compositions and diffusion kinetics, which are important for their preparation to obtain well-defined reference samples are discussed. These samples were applied to various WDS/EPMA-based studies of phase diagrams and diffusion kinetics by means of Cameca SX 50 and SX 100 microprobes.
Authors: Meltem Ipekci, Fared Seahjani, Huseyin Cimenoglu
Abstract: Commercial purity titanium samples were gas nitrided for 3, 5, 7 and 12 h at 1250°C. TiN layers with nitrogen diffusion zones were formed on the surfaces, which caused an increase in the surface hardness with respect to the processing time. In addition, nitriding provided a reduction in friction coefficient and an enhancement in wear resistance against an alumina ball under dry sliding conditions.
Authors: Vera Prokoshkina, Liudmila M. Kaputkina, Yu.I. Lojnikov
Authors: Jin Mu Fu, Wei Gong, Xiao Yin Chen, Gang Fang
Abstract: For understanding the temporal variation of nitrogen and phosphorus concentrations in Huihe River, Suzhou, the observed data (including NH4+-N、 TN、TP, the temple and quantity of the water) from 2007 to 2010 were analyzed by statistical analysis including correlation, cluster and factor analysis. The results imply that the variations of concentrations of NH4+-N, TN and TP in Huihe River were significant, their concentrations are 0.05-4.22mg/L, 0.11-15.14mg/L and 0.01-1.41mg/L, respectively. Correlation and factor analysis suggest that NH4+-N、TN and TP are well correlated with water temperature, whereas there is no significant between them and water quantity. Comparative study and cluster analysis, as well as factor analysis imply that the temporal variations of nitrogen and phosphorus concentrations in Huihe River are significant, and coincide with the seasonal variation of climatic variation of the study area. The results show that either dredging project or climate factors (seasonal changes) had dramatically affected the pollution of NH4+-N, TN and TP. Moreover, the study also confirmed that NH4+-N, TN pollution is mainly anthropogenic, different with TP pollution, who is more likely to be controlled by natural factors.
Authors: Toshimi Yamane, Koji Hisayuki, Yoshimi Kawazu, Yasuro Kimura, Shin-ichi Tsukuda, Toshiomi Itatani
Authors: Gian Ricardo Corrêa Silva
Abstract: Protetive atmospheres are used in powder metallurgy to prevent oxidation and to reduce oxides, to control carbon contents of iron and iron alloys, and to flush volatilized lubrificants from the furnace. Another important function of the atmosphere during sintering is to burn and remove the hydrocarbon lubrificants used to compact the powdered metal. However, one of the most important services that the Air Products "industrial gas company" can provide to its heat treat customers is assistance in troubleshooting their furnace(s) when there are problems. To be able to troubleshoot a furnace, it is important to know what the typical problems are that arise, what causes them and how to fix or minimize to problem. This work should aid in finding the source of the problem with analysis equipment, and, by using your knowledge of the furnace and the process, solve the problem. Summarizing, (1) ensure system integrity, (2) Know the required safety interlocks, and (3) Verify their operation.
Authors: A. Hara, M. Aoki, T. Fukuda, A. Ohsawa
Authors: Yu Li, T.N. Baker
Abstract: Vanadium microalloyed steels with high yield strength (»600MPa), good toughness and ductility have been successfully produced in commercial thin slab casting plants employing direct rolling after casting. Because of the high solubility of VN and VC, most of the vanadium is likely to remain in solution during casting, equalisation and rolling. While some vanadium is precipitated in austenite as cuboids and pins the grain boundaries, a major fraction is available for dispersion strengthening of ferrite. Despite a coarse as-cast grain size, significant grain refinement can be achieved by repeated recrystallisation during hot rolling. Consequently, a fine and uniform ferrite grain structure is produced in the final strip. Increasing the V and N levels increases dispersion strengthening which occurs together with a finer ferrite grain size. The addition of titanium to a vanadium containing steel, decreases the yield strength due to the formation of V-Ti(N) particles in austenite during both casting and equalisation. These large particles reduced the amount of V and N available for subsequent precipitation of fine (~5nm) V rich dispersion strengthening particles in ferrite.
Authors: Henri Buscail, Y.P. Jacob, M.F. Stroosnijder, Eric Caudron, Régis Cueff, F. Rabaste, Sébastien Perrier
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