Search results for "Mechanical engineering"
showing 10 items of 4245 documents
Recent progress in understanding the persistent luminescence in SrAl 2 O 4 :Eu,Dy
2019
Ever since the discovery of SrAl2O4:Eu,Dy persistent afterglow material, that can intensively glow up to 20 h, the mechanism of long-lasting luminescence has been a popular area of research. The re...
Characteristics of Sintered Materials Obtained from Ferrite Nanopowders Synthesised with Different Methods
2018
Ferrite materials, especially those containing nickel and cobalt, are popular due to their unique mechanical and magnetic properties. Single phase NiFe2O4 and CoFe2O4 nanopowders obtained by different methods were used for sintering studies. Chemical sol-gel self-propagating combustion method, co-precipitation technology combined with hydrothermal synthesis or spray-drying method, and high frequency plasma chemical synthesis have been used to synthesize ferrite nanopowders. Relatively dense (95-99%) materials with high saturation magnetization (MS = 80-84 emu/g for CoFe2O4 and MS = 46-48 emu/g for NiFe2O4) were obtained at 1100-1200 °C temperatures.
The Matrix Effect and Application of the Multi-Parameter Optimization Method for X-Ray Spectrometric Determination of the Quantitative Composition of…
2018
Determining the quantitative composition of clay samples with X-ray fluorescent spectrometry is complicated because of the matrix effect, in which any element can increase or decrease the analytical signals of other elements. In order to predict the properties of clays, it is essential to know their precise chemical composition. Therefore, using the standard addition method was determined calibration and empirical influence coefficients, as well as the true composition of the elements. Farther, these coefficients were used to correct the matrix effect and develop a multi-parameter optimization method. It was determined that in clay samples, consisting of Si, Al, Fe, K, Mg, Ca, Na and Ti oxi…
Preparation and Characterization of Nanocrystalline Gadolinium Oxide Powders and Films
2020
Due to its magnetic, electrical, absorption, and emission properties, nanoscale gadolinium oxide is widely used in various fields. In this research, nanocrystalline Gd2O3 powders and films on glass substrates have been produced by the extraction-pyrolytic method. X-ray diffraction analysis revealed the formation of single phase Gd2O3 with cubic crystal structure and the mean crystallite size from 9 to 25 nm in all produced materials. The morphology of samples has been characterized by scanning electron microscopy and transmission electron microscopy.
Validation of mathematical model for CZ process using small-scale laboratory crystal growth furnace
2018
The present material is focused on the modelling of small-scale laboratory NaCl-RbCl crystal growth furnace. First steps towards fully transient simulations are taken in the form of stationary simulations that deal with the optimization of material properties to match the model to experimental conditions. For this purpose, simulation software primarily used for the modelling of industrial-scale silicon crystal growth process was successfully applied. Finally, transient simulations of the crystal growth are presented, giving a sufficient agreement to experimental results.
Reactive Sintering of molybdenum disilicide by Spark Plasma Sintering from mechanically activated powder mixtures: Processing parameters and properti…
2008
Abstract Dense molybdenum disilicide with a nano-organized microstructure was synthesized by mechanical activation, by producing nanostructured agglomerates of a 1:2 mixture of Mo and Si, followed by the synthesis/consolidation in one step using SPS technology. In order to synthesize a dense molybdenum disilicide with a perfectly controlled microstructure, an investigation of the influence of Spark Plasma Sintering processing parameters (temperature, heating rate, mechanical pressure and holding time) on the chemical composition and the microstructure characteristics has been performed. The present work shows also that the so-obtained materials present better oxidation resistance in compari…
Evaluation of nano/submicro pores in suspension plasma sprayed YSZ coatings
2019
Abstract Nano-submicro pores could considerably influence the coating performances and thus should be properly designed for the intended applications. However, it is challenging to characterize accurately such small pores in coatings. In this study, YSZ coatings were firstly manufactured by suspension plasma spray (SPS) and the nano-submicro pores in as-prepared coatings were investigated using Ultra-small-angle X-ray scattering (USAXS). Afterwards, a multivariate analysis on the effect of five different process parameters was carried out. The two main results showed that: 1) the nano-submicro pores content in coatings has a negative correlation with suspension mass load and powder size, an…
Choice of the detectors for light impurities plasma studies at W7-X using ‘CO Monitor’ system
2019
Abstarct The ‘CO Monitor’ is a new spectrometer system dedicated for the continuous measurements of line intensities of carbon, oxygen, boron and nitrogen at the fusion plasma experiment Wendelstein 7-X (W7-X). Its main purpose is to deliver constant information about indicated elements with high time resolution (better than 1 ms), but low spatial resolution since the line shapes are not going to be investigated. The system consists of four independent channels, each equipped with dispersive element dedicated for measurement of selected line of interest. In order to perform the highest efficiency of the ‘CO Monitor’ system, it is essential to choose the proper detector type for this task. T…
SiC Power Switches Evaluation for Space Applications Requirements
2016
We have evaluated several SiC power switches available on the market, by defining and performing a global test campaign oriented to Space applications requirements, in order to define their main benefits but also the limits of current SiC technology. This allowed to identify a number of target applications where SiC could be used as a technology push for a new generation of space electronics units. Silicon devices qualified for space systems above 600V for the switches and 1200V for the rectifiers are not available due to performances limitations of Si. Among the typical static and dynamic characterization, we have performed temperature and power stress and HTRB tests. More remarkably, we h…
Cold gas dynamic spray technology: A comprehensive review of processing conditions for various technological developments till to date
2018
Abstract Today, cold gas dynamic spray (CGDS) technology has thrived with considerable capabilities for manufacturing various technological depositions. The deposition conditions have been developed through many years and that have led to produce ample experimental data which is available in the literature. But, recent research and development activities also reveal innovative findings regarding various deposition conditions. This paper contains a review of experimental deposition procedures for the cold spray additive manufacturing. Details of processing conditions are reported and classified into various categories of baseline working conditions, specific processing including deposition o…