Papers by Keyword: Sintering

Abstract: The structural, physical and mechanical properties of alumina composites reinforced with various zirconia contents were studied. Zirconia with specific stress-induced toughness mechanisms (from tetragonal to monoclinic) can improve its mechanical properties. The raw materials were commercial products of alumina (Al₂O₃) and zirconia (ZrO₂) with gamma alumina (γ-Al₂O₃) and monoclinic zirconia (m-ZrO₂) phases, respectively. In this study, alumina and zirconia powders containing 0, 10, 20, 30, and 40 wt% were mechanically activated and sintered at 1400°C for 3 h. Fourier transform infrared spectroscopy (FTIR) characterization was used to confirm the functional groups in the sample. Phase analysis of the sintered samples was carried out via X-ray diffraction (XRD). Composite characterization includes diameter shrinkage, density, and Vickers hardness. Corundum (α-Al₂O₃), monoclinic zirconia (m-ZrO₂) and tetragonal zirconia (t-ZrO₂) phases were the observed phases in the sintered sample. The Al₂O₃/ZrO₂ 60:40 sample had the largest shrinkage in pellet diameter, apparent density, and Vickers hardness, at 8%, 4.35 g/cm³, and 1.33 HVN, respectively.

Abstract: This paper is aimed at investigating the mechanical properties of spark plasma sintered alumina (Al₂O₃) reinforced with tungsten-carbide-cobalt (WC-12wt%Co). Pure Al₂O₃ and admixed-Al₂O₃ powders were sintered using spark plasma sintering (SPS) technique at a temperature of 1800°C, heating and cooling rates of 100 °C/min and 200 °C/min, a pressure of 48 MPa in an argon atmosphere. The density, hardness (HV) and indentation fracture toughness (K_IC) of the sintered samples were measured and compared. Between 9 and 17% increase was observed in the HV values of the additives, while the K_IC value recorded an increase between 17 and 63% for all the additive as compared to pure Al. Phase analysis and identification was carried out with X-ray diffraction and microstructure was taken with scanning electron microscope. The results obtained showed the samples potential for cutting tool applications.

Abstract: The volumetric changes and variable porosity due to the concentration expansion of the solid phase in the synthesis of zirconium nitride (ZrN) are studied. The model of two-stage reactor based on spark plasma sintering (SPS) is proposed. At the first stage the synthesis for the given kinetics is simulated. At the second stage the densification of ZrN using the Olevsky’s sintering model [1-5] is applied. The synthesis and densification processes using the prescribed heat sources, at the given positions inside the reactor is simulated. The generalization of the two-temperature model [6] and the formula of the porosity in the densification using calculation of the solid concentration expansion and thermal dispersion is proposed. The concentration expansion coefficients in the process of zirconium nitrogenating at a given initial density values and coefficients of expansion of reagents .is studied The temperature at the stage of ZrN synthesis and porosity variation at the stage of densification are in satisfactory agreement with experimental results [2,7,8]

Abstract: This study aims to determine the magnetic properties and structural properties of zinc ferrite (ZnFe₂O₄) material with the sonochemichal synthesis method. The sonochemichal method was obtained by sonication lasting for 30 minutes with the addition of 100 ml of 10 M NaOH. ZnFe₂O₄ material was sintered with temperature variations of 950°C, 1050°C, and 1150°C with a holding time of 2 hours. Phase identification revealed that the cubic phase structure of zinc ferrite is franklinite and also obtained crystal size results with values ​​of 70.58 – 84.71 nm. Morphological identification revealed that the ZnFe₂O₄ material had an irregular cubic shape and the highest agglomeration was at ZnFe₂O₄ temperature of 950°C. Identification of functional groups using FTIR characterization resulted in the wavelength range of 400-600cm^-1 having basic lattices of Fe-O and Zn-O which occupy tetrahedral and octahedral positions, respectively. Magnetic identification uses VSM characterization which results that the sample is softmagnetic and gets several Mr, Ms, and Hc values. ZnFe₂O₄ with a sintering temperature of 1150°C in this study has the potential to be used as a microwave device.

Abstract: The pressing and sintering processes of copper powders produced by different methods are studied in the paper. The main research is based on PMS-1 powders, obtained by electrolysis. To find the easiest and the most reasonable sintering mode, the process is carried out in the open air and dissociated ammonia atmosphere. The samples parameters after each processing procedure were calculated, compression tests were carried out. Basing on preliminary experiments the masses and sintering modes of rectangular shape forms used for equal channel angular pressing were figured out. The possibility in principle to carry out the process of equal channel angular pressing of porous sintered samples without metal damage was shown.

Abstract: A new method for obtaining submicron hard alloys based on sintered tungsten carbide with cobalt by joint low-temperature carbothermic synthesis in vacuum has been developed. The compositions of the initial components for the synthesis of powders of the composition WC-6%Co and WC-10%Co are calculated. The main component for the synthesis of submicron tungsten carbide powders is tungsten oxide WO_2.9, obtained by reducing α-tungsten oxide WO₃ in a hydrogen medium at a temperature of 500-550 °C. The powders obtained by synthesis are characterized by high hardness values (up to 94 HRA). Cutting tests of replaceable polyhedral plates made from the obtained powders for processing a heat-resistant alloy have shown satisfactory results. The microstructure of the alloys was analyzed using scanning electron microscopy.

Abstract: The Magnesium and its alloys are majorly utilized in automotive, aerospace, and biomedical applications because of their extensive properties. The approach for the preparation of the Magnesium materials is done by modern powder metallurgy. This method allows us to study the structural, mechanical, and controlled corrosion resistance. In the present paper, the effect of cold compaction on magnesium AZ31B alloy are studied, were Ultra-Fined Grained (UFG) Magnesium AZ31B alloys of particle size 60 nm were obtained by 8hrs of Ball milling followed by cold compaction at the pressure of 40Mpa at laboratory temperatures. Sintering process for 8hrs were done for cold compacted specimens at temperatures of 425°C,450°C and 475°C in a Horizontal tubular vacuum furnace. Influence of compacting pressure and sintering were investigated for properties of microstructural, mechanical and corrosion resistance. It was observed that, during cold compaction process for Magnesium AZ31B alloys the product grains are distributed uniformly with less pores and particle boundaries. Homogenization were attended by sintering process and Microstructural, Mechanical properties strength, were shown extensive results of hardness and compressive strength of 516Mpa and 123Mpa, as the sintering temperatures were increased from 425°C to 475°C. The lowest corrosion resistance of 0.35 mm.y^-1 is obtained for compacted AZ31B alloy as the temperature of sintering temperature raised to 475°C.

Abstract: In this work, hydroxyapatite ceramics were prepared from hydroxyapatite micropowder and nanopowder. The hydroxyapatite nanopowder was obtained from natural buffalo bone by using a high speed vibro-milling machine for 2 hour. The green compacted pellets of all HA powders were subsequently sintered at 1200, 1250, 1300 and 1350°C for 3 hour and then the physical and mechanical characterizations as well as microstructural evaluation have been carried out. It was found that the optimum sintering temperature were 1250°C by fabricated from nanopowder which gave the HA nanoceramic with the maximum bending strength of 78.6±2.6 MPa. This is about 200% higher than that of the sample which fabricated from HA micropowder.

Abstract: The integration of local metal structures into polymer components using Laser Powder Bed Fusion (PBF-LB/M) offers great potential regarding multifunctional lightweight structures. However, such process hybridization involves huge challenges. In order to reduce the temperature input into the less temperature-resistant materials, the use of lower laser powers in the interfacial region is essential. The resulting local sintering of the metal powder affects the thermal properties in the interfacial region, leading to a change in heat dissipation in the temperature-unstable material. A modeling approach oriented to selective laser sintering is presented for predicting the degree of sintering and associated thermal properties in the context of PBF-LB/M process simulation.

Abstract: Titanium is a high-performance material with relatively high specific mechanical strength, high fracture toughness, low elastic modulus, and high corrosion resistance with important applications in aerospace, medical, and chemical industries. Nowadays, developing and fabrication of titanium-based structures by means of additive manufacturing technologies, especially robotic assisted deposition, is exceptionally attractive and challenging. The study was aimed to evaluate the effects of sintering conditions on microstructure and mechanical behaviour of complex robotic deposited porous titanium structures. The results demonstrated that the mechanical behaviour of such structures can be determined not only by their macrodesign, but also microstructural features, such microporosity and grain size controlled by sintering conditions, have an effect on it. The stiffest titanium structure with the densest filaments and with elastic modulus in a range of that of human trabecular bone was obtained by sintering at 1400 °C for 10 h.