A new approach for stabilizing a predesigned Co gradient in the microstructure of nano WC–Co thinning structure via graphene additions is presented. For this purpose, laminated specimens of green WC–Co functionally graded material, having three layers structured, with and without graphene additions in the intermediate layer were sintered at solid and liquid sintering temperatures of 1290 and 1400°C, respectively, using the hot isostatic pressing technique (HIP). With graphene additions, the mean average grain size of WC matrix phase is reduced, a new inter-phase layer is created and the amplitude of predesigned Co gradient, which had lost during liquid phase sintering of graphene-free WC–Co composite, is maintained through the cross section of the predesigned structure. As a consequence, the liquid state sintered specimens containing graphene show better hardness to toughness relationships compared to the graphene-free specimens fabricated under the same processing conditions. Such improvements are attributed to the extraordinary thermo-mechanical properties of graphene, and its beneficial role in grain refinement and creation of inter-phase layer that enables the stabilization of the predesigned Co-gradient.
Zinc, magnesium and silicon ions are known as bioactive ions that promote the hard and soft tissue regeneration. We hypothesized that Zn-smectite consisting of zinc and silicon ions provide a more potential biomaterial in regenerative medicine field. Zn-smectite powder was thus synthesized in this study and used for wound healing. The aim of the present work was to evaluate the effect of Zn-smectite on wound healing in rats. An aqueous solution was prepared by dissolving zinc chloride (ZnCl2) and water glass in distilled water, and then refluxed at 90°C for 12 h; after which crystalline Zn-smectite powder was obtained. The amount of Zn2+ and Si4+ ions releasing from Zn-smectite in physiological saline was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). It was observed that the amount of the Zn2+ ion released from the Zn-smectite powder increased with the soaking time, but the released amount of Si4+ ion decreased with the soaking time. To evaluate the biofunctional ability, Zn-smectite was applied to a full thickness surgical wound created in the rat’s abdomen. In the results for skin regeneration, there was no significant difference in wound size between the control and Zn-smectite group at 1 and 2 weeks. However, it was observed that Zn-smectite promoted greater vascular regeneration and more skin appendages in comparison with the control. Zn-smectite can be expected to stimulate wound healing and heal the tissue close to the native tissue by releasing Zn2+ and Si4+ ions, suggesting that this newly formed material could offer greater potentiality in the field of regenerative medicine.
One-dimensional nanostructures of gamma alumina exhibiting excellent properties such as a large surface area and high porosity are widely used as catalysts and adsorbents and in other applications. Here, we report the effect of ultrasound treatment on infra-red spectrum, mineral phase, morphology, and textural properties of gamma alumina nanorods, which were successfully synthesized from salt-starch precursors through a facile precipitation method. We used aluminum ammonium carbonate hydroxide-starch derived from aluminum nitrate at pH 9 and a 2% (w/v) starch slurry, under normal conditions with ultrasound treatment as a precursor. The as-synthesized alumina were then calcined at 600°C. We observed the infra-red spectrum of the as-synthesized alumina treated by ultrasound show typical absorption bands of functional that groups. Ultrasonically treated as-synthesized alumina at 600°C consist of a pure gamma alumina phase with higher intensity and a microstructure of nanorod-like shapes with aspect ratios of 2–17.5, indicating a mesoporous material, and exhibit a higher specific surface area and pore volume than that of alumina synthesized under normal conditions.
Hydroxyapatite (HA) can be used for removing F−. Materials containing HA for removing F− can be obtained from biological wastes, and these HA might contain carbonate ions. The dissolution behavior of HA should affect the F− removal as fluorapatite (FA) formation at HA surface by the dissolution of HA and subsequent precipitation of FA results in the removal of F−. In this study, we examined the relationship between the dissolution and F− removal rates of carbonated HA (CHA). CHA samples with different carbonate contents were prepared by a hydrothermal process. The dissolution and F− removal rates were investigated by immersing the samples in pH 5 and 7 buffer solutions in the absence and presence of F−, respectively. The dissolution and F− removal rates were increased with an increase of carbonate-ion content in the samples. Dissolution and F− removal rates at pH 5 were larger than that at pH 7. The pseudo-second order kinetic model provides a good fit for the F− removal process. An increase in the kinetic constant of dissolution decreases the kinetic constant of the F− removal process for samples with high carbonate contents at pH 5.
For the first time, mullite fibers were successfully prepared using non-hydrolytic sol–gel as the precursor solution and electrospun polyvinyl pyrrolidone fibers as the template. The mullite fibers were investigated using thermogravimetric and differential thermal analyses, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Results showed that most of the organic molecules were removed and the pure mullite fibers were obtained successfully after calcination at 1200°C. The average diameter of the fibers was 270 nm. This method can be potentially used to synthesize other 1D materials.
Electronic structure of amorphous niobium oxide prepared by a sputtering method was investigated based on optical absorption and photoelectron spectroscopies. In the valence band photoelectron spectra, broad peaks without any characteristic components were observed. Then, theoretical calculations based on a density functional theory were performed to interpret the experimental spectra by using three Nb2O5 polymorphs. Among the polymorphs, M-phase with tetragonal structure showed better reproducibility than the other B- and R-phases with monoclinic structure. It was finally concluded that the amorphous niobium oxide had a similar electronic structure to M-Nb2O5, and it was supposed that the broad feature in the photoelectron spectra was due to the broad distribution of Nb–O bonds in NbO6 polyhedra, which was characteristic in M-Nb2O5.
Porous titania particles were prepared by partial dissolution of hydrous titania and subsequent heat treatment. Uniform and spherical particles of hydrous titania were prepared by hydrolysis of titanium alkoxide at different hydrolysis conditions. The as-prepared hydrous titania particles were soaked in ethanol to dissolve the weakly polycondensed part of the particles. As a result, meso- and macroporous structures were formed on the surface of the hydrous titania particles that were prepared by mild hydrolysis. The porous structure was retained even after heat treatment at 400°C while the particles crystallized into the anatase phase. The specific surface area of the porous titania particles prepared by heat treatment of hydrous titania at 400°C for 15 min was 121 m2/g.