The changes on microstructure and electrical properties of Bi:2223/Ag composite as a function of the granulation and the content of the added silver powder

The Bi-Sr-Ca-Cu-O system has been one of the most studied superconducting ceramic materials for industry applications. The most of the studies with this aim are on silver/ceramic composites, due to the benefits and great compatibility of this metal with the oxide. In this paper we describe a systematic and comparative study on Ag/BSCCO composite, made by the citrate route, in which the ceramic pellets are sintered in the presence of silver powder using several proportions and having several granulations. It was observed that the introduction of fine (0.5 and 2 μm) silver powder in the proportions of 5 wt. % always implies in a better critical current density compared to the no silver pellet. According to the results, the silver powder in excess of 5 wt.% may not promote best electrical properties, depending on the size of the silver particles.

Recycling leather waste: preparing and studying on the microstructure, mechanical, and rheological properties of leather waste/rubber composite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Recycling leather waste: preparing and studying on the microstructure, mechanical, and rheological properties of leather waste/rubber composite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structure, microstructure, and selected mechanical properties of Ti-Zr-Mo alloys for biomedical applications

New titanium alloys for biomedical applications have been developed primarily with the addition of Nb, Ta, Mo, and Zr, because those elements stabilize the β phase and they don’t cause cytotoxicity in the organism. The objective of this paper is to analyze the effect of molybdenum on the structure, microstructure, and selected mechanical properties of Ti-15Zr-xMo (x = 5, 10, 15, and 20 wt%) alloys. The samples were produced in an arc-melting furnace with inert argon atmosphere, and they were hot-rolled and homogenized. The samples were characterized using chemical, structural, and microstructural analysis. The mechanical analysis was made using Vickers microhardness and Young’s modulus measurements. The compositions of the alloys were sensitive to the molybdenum concentration, indicating the presence of α’+α”+β phases in the Ti-15Zr-5Mo alloy, α”+β in the Ti-15Zr-10Mo alloy, and β phase in the Ti-15Zr-15Mo and Ti-15Zr-20Mo alloys. The mechanical properties showed favorable values for biomedical application in the alloys presenting high hardness and low Young’s modulus compared with CP-Ti.

Effect of heat treatment on microstructure and mechanical properties of Ti-5wt-%Ni alloys for use as biomaterial

Titanium alloys are among the most important and frequently used class of biomaterials. In addition to biocompatibility, it is important that an implant material present satisfactory mechanical properties that allow long term use in the body. To improve such properties, different heat treatments are used, as well as doping with oxygen. The presence of interstitial oxygen in the crystal lattice causes deformation, increases the hardness, and causes modifications in anelasticity, thereby decreasing the elastic modulus. In this study, an alloy was prepared by arc melting precursor metals, heat and mechanically treated, and doped with oxygen, resulting in samples with different processing conditions. In each condition, the alloy was characterised in terms of amount of oxygen, X-ray diffraction, and optical microscopy. In addition, properties of the alloy, such as hardness and elastic modulus, were analysed.

The influence of heat treatment on the structure and microstructure of Ti-15Mo-xNb system alloys for biomedical applications

The Ti-15Mo-xNb system integrates a new class of titanium alloys without the presence of aluminum and vanadium, which exhibit cytotoxicity, and that have low elasticity modulus values (below 100 GPa). This occurs because these alloys have a beta structure, which is very attractive for use as biomaterials. In addition, Brazil has about 90% of the world’s resources of niobium, which is very important economically. It strategically invests in research on the development and processing of alloys containing this element. In this paper, a study of the influence of heat treatments on the structure and microstructure of the alloys of a Ti-15Mo-xNb system is presented. The results showed grain grown with heat treatment and elongated and irregular grains after lamination due to this processing. After quenching, there were no changes in the microstructure in relation to heat-treated and laminated conditions. These results corroborate the x-ray diffraction results, which showed the predominance of the β phase.

Effect of the substitutional elements on the microstructure of the Ti-15Mo-Zr and Ti-15Zr-Mo systems alloys

Titanium alloys have excellent biocompatibility, and combined with their low elastic modulus, become more efficient when applied in orthopedic prostheses. Samples of Ti-15Mo-Zr and Ti-15Zr-Mo system alloys were prepared using an arc-melting furnace with argon atmosphere. The chemical quantitative analysis was performed using an optical emission spectrometer with inductively coupled plasma and thermal conductivity difference. The X-ray diffractograms, allied with optical microscopy, revealed the structure and microstructure of the samples. The mechanical analysis was evaluated by Vickers microhardness measurements. The structure and microstructure of alloys were sensitive to molybdenum and zirconium concentration, presenting α′, α″ and β phases. Molybdenum proved to have greater β-stabilizer action than zirconium. Microhardness was changed with addition of molybdenum and zirconium, having Ti-15Zr-10Mo (436 ± 2 HV) and Ti-15Mo-10Zr (378 ± 4 HV) the highest values in each system.