Synthesis and characterization of biomorphic CeO2 obtained by using egg shell membrane as template

A new technology based on bio-templating approach was proposed in this paper. Egg-shell membrane (ESM) has been employed as a natural biotemplate. Fibrous oxide ceramics was prepared by wet impregnation of biological template with water solution of cerium nitrate. The template was derived from membranes of fresh chicken eggs. Repeated impregnation, pyrolysis and final calcination in the range of 600 to 1200 °C in air resulted in template burnout and consolidation of the oxide layers. At low temperatures, the obtained products had structure which corresponded to the negative replication of biological templates. Unique bio-morphic CeO2 microstructures with interwoven networks were synthesized and characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), whereas low-temperature nitrogen adsorption (BET) method was used in order to characterize porous properties

Применение модифицирования при электрошлаковой сварке жаропрочных сплавов

Предложено для изготовления кольцевых заготовок, используемых в авиационном двигателестроении, применять электрошлаковую сварку комбинированным электродом с модифицированием металла шва дисперсными частицами карбонитрида титана. Приведены результаты исследований металла шва при сварке сплава ХН77ТЮР. Показаны преимущества новой технологии сварки.It is offered for manufacturing of the ring preparations used in aviation engine-building, to apply electroslag welding by the combined electrode with modifying of metal of a seam by disperse particles the carbonitrid titan. Results of researches of metal of a seam are given when welding alloy KhN77TYR. Advantages of new technology of welding are shown

Energy Consumption During Nanoparticle Production: How Economic is Dry Synthesis?

The production of oxide nanoparticles by selected wet-chemistry or dry processes is compared in terms of energy requirements. Clear differences arise for production using electricity-intensive plasma processes, organic- or chloride-derived flame synthesis and liquid based precipitation processes. In spite of short process chains and elegant reactor design, many dry methods inherently require vastly bigger energy consumption than the multi-step wet processes. Product composition strongly influences the selection of the preferred method of manufacturing in terms of energy requirement: Metal oxide nanoparticles of light elements with high valency, e.g. titania demand high volumes of organic precursors and traditional processes excel in terms of efficiency. Products with heavier elements, more complex composition and preferably lower valency such as doped ceria, zirconia, and most mixed oxide ceramics may be readily manufactured by recently developed dry processe

A Thermodynamic and experimental study of low-alloy steels after carbonitriding in a low-pressure atmosphere

The effect of the composition of two steels (B and 6MnCr5) on precipitation of undesirable phases (carbides, nitrides and carbonitrides) under thermochemical treatment (low-pressure or vacuum carbonitriding) is investigated. Metallographic and x-ray diffraction studies and thermodynamic computations are performed.BMI Fours Industriels, St. Quentin Fallavier, Franc

Rola obróbki plazmą MV na odporność korozyjną stali stopowych

Obróbkę powierzchni wysokostopowych stali chromowo-niklowej typu duplex S32404 i austenitycznej S32615 przeprowa- dzono poprzez węgloazotowanie przy użyciu techniki próżniowej z mikrofalowym wspomaganiem plazmowym o częstotliwości 2.45GHz i mocy generatora 350W. Zastosowano reaktywną mieszaninę gazową zawierającą CH4 i N2 w warunkach niskiego ciśnienia 0.2 Tr. przy niskiej temperaturze 400°C. Oceniono wpływ składu chemicznego i struktury stopów na tworzącą się war- stwę wierzchnią podczas obróbki. Strukturę powierzchni analizowano za pomocą rentgenowskiej spektroskopii fotoelektronów (XPS). Odporność korozyjną próbek określano na podstawie krzywych polaryzacyjnych LSV w 3% roztworze chlorku sodu przy temperaturze 37°C. Powierzchnie stali poddane obróbce wykazały wyższą skłonność do pasywacji w oraz podwyższały odporność na korozję wżerową w porównaniu z powierzchniami niemodyfikowanymi.Two stainless steels (S32404 duplex and S32615 austenitic) were subject to the carbon/nitrogen plasma treatment to examine the role of alloy composition and structure in the behavior of surface during modification. The modification process was performed in the electron cyclotron resonance (ECR) micro wave plasma system, with the frequency of 2.45 GHz and the generator power of 350 W, and with the use of reactive gas mixtures containing CH4 and N2, at the low temperature of 400°C and under pressure of 0.2Tr. The treated surface was analyzed by means of X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the samples was determined on the basis of LSV polarization curves in 3% sodium chloride solution at 37°C. The treated steel surfaces showed a higher tendency for passivation and higher pitting corrosion resistance compared to the non-modified surfaces

Implications of carbon, nitrogen and porosity on the γ→α′ martensite phase transformation and resulting hardness in PM-steel Astaloy 85Mo

This study aims at a thorough characterization of the relationship of interstitially solved carbon and nitrogen on the γ → α′ transformation in PM steels, the accompanied volume change and the resulting hardness. Furthermore, the investigations include multiple porosity levels of 6.9, 7.2 and 7.35 g/cm$^{3}$ to characterize porosity effects. Dilatometric samples were carburized and carbonitrided to seven distinct compositions to account for common compositions in the process of thermochemical case hardening heat treatment. The dilatometric samples were rapidly austenitized and quenched and the dilatometric response was evaluated. To fully characterize the martensitic transformation of PM steels, X-ray diffractometry evaluated the amount of retained austenite after quenching. Conclusive results of iterative quenching procedures along with elemental analysis after heat treatment give distinct evidence that PM steels underlie rapid decarburization. This effect ultimately leads to an erroneous evaluation of the martensite transformation kinetics, especially the often proposed effect of porosity on M$_{S}$. However, a distinct effect on the accompanied volume change from austenite to martensite is proposed. To account for an interplay of solved carbon and nitrogen, an effective nitrogen contribution of 25% based on carbon equivalent is proposed. Utilizing the effective content, the impact of nitrogen can be projected on carbon within the range of common carbon and nitrogen contents, and a good predictability of the martensite transformation can be achieved. Regarding the resulting hardness, a dependency solely on carbon is suggested. The overall hardness shows a typical maximum at approximately 0.6–0.7 wt%, irrespective of the solved amount of nitrogen