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Abstract SiC ceramics are important high-temperature structural materials with excellent chemical and physical properties. However, the different impurities are usually introduced into the raw materials in the preparation of SiC powders, especially Fe 2 O 3 impurity. The current work aims to investigate the effect of Fe 2 O 3 contents (0–0.8 wt%) on the sintering behaviour and mechanical properties of SiC ceramics. Fe 2 O 3 -containing SiC ceramics were prepared by pressureless sintering using carbon and boron carbide as sintering additives. The X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, scanning electron microscope, and mechanical testing were used to understand the effect of Fe 2 O 3 on a few key properties of sintered samples. The results indicated that the hardness (from 24.4 ± 1.0 GPa to 27.2 ± 1.3 GPa) and flexural strength (from 360 ± 38 MPa to 394 ± 18 MPa) can be increased by 10% upon a gentle introduction of only 0.02 wt% of Fe 2 O 3 , due to the formation of fine gains and homogenous microstructures. However, the further increase of Fe 2 O 3 contents above 0.4 wt% is found to be detrimental to sintering of SiC ceramics. It is suggested that excessive Fe 2 O 3 reacts with C leading to the formation of more volatile species (CO, Fe), and increasing the porosity of SiC matrix, which hampers the densification process and is harmful to mechanical properties of sintered SiC. Highlights • Hardness and flexural strength can be increased by 10% upon a gentle introduction of only 0.02 wt% of Fe 2 O 3. • The abnormal growth of grains can be controlled to some extent by adding Fe 2 O 3. • The content of Fe 2 O 3 should be controlled within 0.4 wt% in the preparation of SiC powders. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) has been broadly employed for bone treatment applications. In the present research, HA was extracted from hen, goat and cattle bone. Samples were prepared by cold isostatic pressing method (CIP) and sintered at 1100, 1200 and 1300 °C. In order to evaluate the characteristics of the produced HA, X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier Transform spectroscopy (FTIR), scanning electron microcopy (SEM) and energy dispersive spectroscopy (EDS) analyses were carried out on it. Hardness and compression tests were examined before and after sintering. Also, the morphology of the samples at different sintering temperatures was studied by SEM imaging. The obtained experimental results ascertained that with increasing the sintering temperature up to 1300 °C, relative density and hardness of the samples increased. Finally, compressive strength of the sintered sample at 1200 °C was determined as maximum value. [ABSTRACT FROM AUTHOR]

Cu-1 wt%Al 2 O 3 composite powder, prepared by mechanical milling and consolidated by spark plasma sintering to have about 98–99% of theoretical density, were characterized by scanning electron microscope, focused ion beam microscope, X-ray diffraction, nanoindentation and transmission electron microscope. The mechanically milled powders, upon consolidation, exhibited a finer grain size of 2 μm. Tensile deformation behavior of this composite, at ambient temperature but over the strain rates of 10 −4 s −1 to 5 × 10 −2 s −1 , exhibited typical manifestations of dynamic strain ageing in the form of serrations and negative strain rate dependence of flow stress. The yield and ultimate tensile strengths, and so also the elongation decrease gradually with increase in strain rate. Such variation was also shown by nanoindentation hardness as a function of loading rate over 1–100 mN/s. The observed results are explained by the dislocation structure evolved from its interaction with Al 2 O 3 dispersoids and impurity atoms like Fe, C and O coming from the powder processing. [ABSTRACT FROM AUTHOR]

A suitable sintering method is important to obtain the Ti(C,N)-based cermets with superior properties. In this paper, Ti(C,N)-based cermets were fabricated by hot-pressing sintering (HP) and conventional pressureless sintering (PLS) technology, respectively, to investigate the influence of different sintering methods on the microstructure and mechanical properties of cermets materials. The microstructure, fracture morphology, indention cracks and phase composition were observed and detected using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The transverse rupture strength (TRS), Vickers hardness ( HV ) and fracture toughness ( K IC ) were also measured. The results reveal that all of the Ti(C,N)-based cermets exhibit core–rim microstructures with black cores, white cores and grey rims embedded into metal binder phases. The grain size of the samples fabricated by HP is much finer and the structure is more compact than those fabricated by PLS, while there exist pores in the HP sintered samples. The sintering process has no influence on the phase composition of cermets, but affects the phase content and crystallinity. The samples fabricated by PLS present higher transverse rupture strength, fracture toughness and density than samples fabricated by HP. However, the HP sintered samples possess a higher hardness. [ABSTRACT FROM AUTHOR]