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Abstract

Nickel-cobalt ferrite spinels are ferrimagnetic ceramic materials that possess a great potential for application in highdensity magnetic media, recording, color imaging, ferrofluids, and high-frequency devices. A change of their structure from micro- to nano- improves their properties drastically, therefore many methods have been investigated to fabricate nanopowder of these spinels. Gel combustion method is one of them. In this research, Ni0.5Co0.5Fe2O4 nanoparticles were fabricated via gel combustion method using metallic nitrates as an oxidant and citric acid, glycine and urea as fuels and the effects of fuel type on the reaction behavior, structure and morphology of Ni0.5Co0.5Fe2O4 nanoparticles were investigated. The reaction behavior was studied by thermal analysis method (TGA-DTA), crystallite size of powders was characterized by X-ray diffraction (XRD) and their morphology was studied by FE-SEM. The results revealed that the reaction was initiated in urea, glycine and citric at 219 °C, 197 °C, 212 °C, respectively. Samples fabricated from glycine and citric acid had a pure spinel structure but the others fabricated with urea fuel had iron oxide impurity. The crystallite size of nickel cobalt ferrite nanoparticles was in the range of 58 nm to 64 nm and the nanoparticles were agglomerated.

Abstract

Nanoparticles of Li2MnO3 were fabricated by sol-gel method using precursors of lithium acetate and manganese acetate, and citric acid as chelating agent in the stoichiometric ratio. TGA/DTA measurements of the sample in the regions of 30 °C to 176 °C, 176 °C to 422 °C and 422 °C to 462 °C were taken to identify the decomposition temperature and weight loss. The XRD analysis of the sample indicates that the synthesized material is monoclinic crystalline in nature and the calculated lattice parameters are 4.928 Å (a), 8.533 Å (b), and 9.604 Å (c). The surface morphology, particle size and elemental analysis of the samples were observed using SEM and EDAX techniques and the results confirmed the agglomeration of nanoparticles and, as expected, Li2MnO3 composition. Half cells of Li2MnO3 were assembled and tested at C/10 rate and the maximum capacity of 27 mAh/g was obtained. Charging and discharging processes that occurred at 3 V and 4 V were clearly observed from the cyclic voltammetric experiments. Stability of the electrodes was confirmed by the perfect reversibility of the anodic and cathodic peak positions observed in the cyclic voltammogram of the sample. The Li2MnO3 nanoparticles exhibit excellent properties and they are suitable for cathode materials in lithium ion batteries.

Abstract

Single crystals of L-Valinium Picrate (LVP), 0.1 mol% Ni2+ doped L-Valinium Picrate, and 0.2 mol% Ni2+ doped L-Valinium Picrate were grown by low temperature solution growth method, especially by solvent evaporation technique at ambient temperature. Function groups and modes of vibration were identified by FT-IR studies. The grown crystals belong to monoclinic system which has been revealed by powder XRD. The estimated band gaps were found to be 3.86 eV for LVP, 3.72 eV for 0.1 mol% Ni2+ doped LVP, and 3.70 eV for 0.2 mol% Ni2+ doped LVP crystals, respectively. The PL excitation wavelength of the grown materials is 370 nm. All the elements (C, N, O, Ni, and Cl) as per molecular formula were present in the EDAX spectrum of the grown materials. The 0.2 mol% Ni2+ ion doped LVP materials had higher thermal stability (208 °C) than LVP and 0.1 mol% Ni2+ doped LVP.

Abstract

For evolving a surface layer on the X40CrMoV5-1 steel, a plasma-nitridation and PVD coating process was applied. In our experiments, the samples were heat-treated (high-temperature hardening, annealed three times) and surface treatments (plasma-nitridation, PVD coating by TiAlN, duplex surface treating by plasma nitridation and after that, PVD coating TiAlN). After the heat treatments, we performed hardness tests and surface abrasion wear tests. The abrasion wear resistance of the specimens was studied in order to understand the heat treatment effects on abrasion behaviour. It was observed that the heat treatment and surface treatment process greatly influence the tool steel surface hardness and abrasion resistance behaviour. By plasma-nitridation the surface hardness doubled compared to the quenched surface hardness while the PVD coated TiAlN surface layer hardness is more than five times that of the hardened one. There was no relevant difference between the PVD coated (TiAlN) surface hardness and the duplex surface-treated hardness. On the basis of the results of the comparative abrasive wear tests, it can be concluded that the duplex surface treatment resulted in the greatest wear resistance..

Abstract

Tattooing is becoming more and more accepted at different levels of society today. A contributor to this is that besides body decoration, the cosmetics industry is increasingly using it for make-up tattoos and to hide skin imperfections and surgical scars. Tattoo needles, despite being in direct contact with human tissues and even with blood, are not subject to current Medical Device Regulation, so they do not require a number of material and biocompatibility tests in order to be placed on the market. The focus of our research was on how the needle and the soldering of the needles are damaged during tattooing, and how this develops over time, as a worn needle tip can not only degrade the quality of the tattoo, but also increase skin breakdown and the amount of dissolving allergenic substances.

Abstract

This paper deals with the development of equipment that can accurately determine the magnetic properties of small volume thin plate samples. The alloys to be tested are sheets of amorphous structure, such as Finemet alloy, which has excellent high frequency magnetic properties, making it a good candidate for the construction of high efficiency electric motors. This article discusses the components and operation of the equipment under development, whilst giving a brief overview of the efficiency classification of electric motors and the importance of the emerging efficiency class.

Abstract

Earing of deep drawn cups is an effective measure of plastic anisotropy. It is the result of crystallographic anisotropy, i.e. texture. There are several methods to predict earing, but all of these methods are rather complex. Furthermore, above a certain sheet thickness, deep drawing cannot be performed, and prediction methods fail since they are usually valid within a certain sheet thickness range. A new, simple method has been proposed to predict earing. Besides simplicity, another major benefit of the method is that it can be applied to a wide range of sheet thicknesses. The method has been previously applied for unidirectionally rolled and recrystallized and cross-rolled Al sheets. In the present manuscript, the proposed method is applied on the AW-5056 type, unidirectionally and cross-rolled, then annealed Al sheets having very weak (close to random) structure. It is shown that for such samples, the method predicts negligible earing. It is also revealed that for the 5056 type Al alloy, the differences in texture and earing between unidirectionally and cross-rolled samples become so small after annealing, that the benefit of cross rolling is negligible.

Abstract

Nowadays, quality development is a growing challenge, which places a heavy burden on economic operators, especially on smaller companies. ISD Dunaferr Zrt is the largest steel company in Hungary with its annual steel production of about 2 million tons, but it is small on a global scale. Taking advantage of the opportunities, locating the hidden problems, qualitative development and productivity enhancement can be realized without major investment. This study points out the steel production and casting parameters that have the greatest impact on the quality of the hot rolled product (sheet and coil) and touches upon the effect of rolled product final thickness on the ratio of downgrading. As a result the examination of overheating shows correlation with the ratio of downgrading, but the age of the mould does not. Regarding the thickness of the rolled product, it can be stated that in the case of thicker products (above 9 mm) the ratio of downgrading increases.

Abstract

Four lattice structures based on well-known crystal structures were evaluated in this study using the finite element method. Simple cubic, face-centered cubic, body-centered cubic, and diamond structural alignments were used to build up lattices from the body volume. Modern-day implant development trends are shifting towards additive manufacturing technologies, which have the advantage of creating structures that can improve the biological stability of implants that have integrated scaffolds. Such scaffolds can be trabecular structures that mimic bone tissue and facilitate tissue penetration into the porous parts of the implant. The final purpose of our study is to create an implant system that promotes the process of osseointegration. Evaluations have been carried out using finite element analysis.

Abstract

In the present work the comparison of the effect of traditional, pulse and stress annealing is made by monitoring the important mechanical and magnetic properties of FINEMET type amorphous precursor alloy. The magnetic properties were determined from the shape of magnetization curve (coercive force, anisotropy) during various heat treatments and the mechanical properties were measured using brittleness test. The traditional heat treatments were performed in resistance furnace and the magnetic measurements were performed in astatic magnetometer. The pulse and stress annealing (as well as their combinations) were carried out inside in the magnetometer. The temperature of pulse heat treatments is regulated with the length of current pulse flowing through the sample. After each pulses the magnetization curves were measured in-situ, in the magnetometer.