Papers by Keyword: Powder

Abstract: This study addressed the evolution of microstructure across some duplex stainless steel joints welded by laser beam without and with applying additional materials. The chemical composition and the thickness of the parent material modify the welded joints profile also. Similar technological parameter results different macrostructure and ferrite content at different type of additional material. Pitting corrosion resistance were also studied.

Abstract: In the present work, the molten-salt method was applied to synthesize 0.948K_0.5Na_0.5NbO₃–0.052LiSbO₃ powder for the first time. Characteristics of the powder were investigated. Based on X-ray diffraction technique, pure perovskite phase was observed at a calcination temperature of 700 oC which is lower than that required by the conventional solid-state reaction technique for ∼200 oC. Raman spectroscopy technique showed that the powder had an orthorhombic symmetry which consistent with the X-ray diffraction results. The powder exhibited very fine grain with narrow size distribution. Particle size of the obtained powders increased with increasing calcination temperature. Therefore, the molten-salt method is a simple and effective method to synthesize 0.948K_0.5Na_0.5NbO₃ – 0.052LiSbO₃ powder.

Abstract: Micro-particle composites can find application in the area of bonded joints. Adhesive bonds rank among progressively developing technologies of material joining. Its usage is found in various industry branches, where they compete the conventional methods of material joining. Optimization of adhesive bonds is discussed topic with respect to mechanical properties as well as its price. This work describes the optimization of adhesives by way of particle micro fillers – glass powder, iron powder and aluminium powder. Shear strength of steel adherents, such as one of key mechanical properties of adhesives, was used for description of effect of inclusion of particles on adhesive. This paper evaluates filled adhesives from the mechanical properties point of view. Image analysis of adhesive bonds and fracture areas were made on stereoscopic microscope and on electron microscope.

Abstract: The structural and electrochemical properties of lanthanum manganate (LaMnO₃) powder prepared by the sol-gel method are researched in this article. The powder calcined at 600 °C showed amorphous, and the powder calcined at 700-800 °C showed the pure phase of the LaMnO₃. The grains with the size of about 80-120 nm were agglomerating together. Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical properties in alkaline environment. The electrochemical properties calcined at 700 °C showed a specific capacitance of 73 F/g at the current density of 0.5 A/g. The raw materials for preparing the LaMnO₃ powder are cheap, and the operation method is simple.

Abstract: The effect of Ni or Zr addition to Ti-Cu alloy was studied on the microstructure evolution during mechanical milling regarding to dependence of the amorphous transformation on the various composition elements. The microstructure of initial crystalline alloys and the remained phases after few hours of milling were investigated. The milling process lasted to the full amorphization of the powders. The results show that amorphous Ti₄₈Cu₄₂Ni₁₀ and Ti₄₈Cu₄₂Zr₁₀ powders are obtained after 13 h and 14 h of milling.

Abstract: “Art is everywhere” to quote Ben, a renowned French contemporary artist. However, there are some areas in which art is more prevalent. Thermal spray is one of them, as this presentation seeks to demonstrate. For this, each of the arts (according to their official classification) is shown to correspond to a specific key point of the thermal spray process for coating: e.g., coating build-up, additive manufacturing, deposition onto brittle and/or temperature sensitive materials (glass, wood, fabrics, polymers), powder optimization, and adhesion. Both modeling and experimental aspects are discussed, focusing on the study of particle-to-particle or particle-to-substrate interfaces, shock phenomena and advanced investigation techniques such as X-ray microtomography or high-speed instrumentation. Plasma spray and cold spray provide the relevant examples that this contribution elaborates. They relate to different industrial sectors such as aircraft-aerospace, luxury, biomedical and the automotive industry. Beyond anecdotal evidence, the discussion aims to show that an artistic approach to thermal spray does help to understand better this powerful coating process.

Abstract: Influence of Fe-Si-Al-C alloy cooling rate on its phase composition, structure and microhardness is shown based on metallographic investigations, electron microscopy and x-ray diffraction analysis. It was determined that the structure will change from dendrite to grained, size of structure elements will decrease, quantity and size of secondary phases precipitations will decrease when cooling rate changes from 103 to 107 K/s. The metastable phases such as primary ferrite, austenite and complex carbides are formed in cooling rate range. The volume ratio of main phases changes in favor of primary ferrite with cooling rate increasing. Hardening of the material occurs more than twice. Hardening is due to the interaction of solid-solution hardening, grain boundary hardening and dispersive hardening by secondary phases particles. The maximum hardening is achieved during formation of the alloy in molten pool at electron-beam melting. The alloy in this case contains 80 vol. % of austenite with dendrite similar structure and precipitations of carbide and silicocarbide phases. It can be assumed than such structure will be formed from the alloy with investigated composition at additive manufacturing.

Abstract: The results of X-ray microanalysis of powder obtained by the electroerosion dispersing of solid alloy waste VK8 in kerosene are presented. It is established that the basic elements in the powder, obtained by the electroerosion dispersing of waste, are tungsten, cobalt, carbon and oxygen.

Abstract: Ceramic materials of (La_0.5Sm_0.5)₂(Zr_0.7Ce_0.3)₂O₇ composition powder was synthesized by chemical coprecipitation method using Sm₂O₃, La₂O₃, Ce (NO₃)₃·6H₂O and ZrOCl₂·8H₂O powders as raw materials. Microstructure and phases of (La_0.5Sm_0.5)₂(Zr_0.7Ce_0.3)₂O₇ (LSZCO) powder was examined by Transmission Electron Microscope (TEM) and X-ray diffraction (XRD). The specific surface area of powders were determined by BET specific surface area test. The structure of LSZCO powder remained in pyrochlore with the increase of temperature more than 1200 °C. According to the impact on the specific surface area of LSZCO powder, the factors of the process is ordered in descending sequence as follows: pH value, dispersant content, concentration of reactants, the reaction temperature.

Abstract: A precursor was obtained after dissolution, drying and cooling using MgSO₄·7H₂O and NH₄Al (SO₄)₂·12H₂O as raw materials. Then the high-purity magnesium aluminate (MgAl₂O₄) spinel powder was synthesized via the thermal decomposition process of the precursor calcined at different temperatures. The phase, morphology and particle size of the powder obtained at different calcining temperatures were characterized by X-ray diffraction, scanning electron microscopy and laser particle size analyzer. And also the purity of the powder was tested by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results show that the powder exhibits better crystalline shape and bigger crystalline size with the calcining temperature increasing. The calculated grain size is below 30 nm according to Scherrer formula. The particle size of the powder is below 35μm, the particle size distribution is relatively wide and some particles reunite to be bigger ones with the calcining temperature rising. The powder appears to be plate-shaped and the morphology of the grain is irregular particle. The purity of the powder is relatively high. Especially, the purity of the powder obtained at 1150 °C is 98.88%.