Journal of the Australian Ceramic Society最新文献

Mullite ceramics were fabricated by reaction sintering using bauxite and kaolin as raw materials and Al(OH)₃ as an additive. Enhanced mullite ceramic performance was achieved by optimizing sintering temperature and amount of added Al(OH)₃. Results show that higher amount of Al(OH)₃ led to increased mullite content. Furthermore, scanning electron microscopy results revealed better interfacial bonding due to interlocking structures of columnar mullite at high sintering temperatures (≥ 1500 °C) in samples prepared with the addition of Al(OH)₃. This led to significant improvement in bulk density and mechanical strength of mullite ceramics. Thus, compared with samples prepared without Al(OH)₃, the addition of Al(OH)₃ was beneficial to formation, growth, and development of mullite. The optimum bulk density of 2.75 g/cm³ was achieved with apparent porosity of 0.79%, and the highest flexural strength of 129.25 MPa was achieved in samples with 12 wt.% Al(OH)₃ after sintering at 1550 °C for 3 h.

Ce/Sb/Mn different borate glass systems based PbO in concentrations of 50, 35, and 15 mol%, respectively, were prepared by the melting–annealing method. Wide chemical, structural, and radiation shielding characterizations were studied before and after 120 kGy of gamma radiation to test the possible use of glasses for immobilizing radioactive wastes. The results showed suitable density values ranging from 3.34 to 5.30 g/cm³ increased by irradiation. FTIR spectra revealed high structural stability against irradiation correlated to the trigonal BO₃, tetrahedral BO₄ groups, high polarizable Pb²⁺ ions, and the doped metal ions. Unexpectedly, the chemical durability after in situ leaching process in H₂O, 0.1 N HCl, and 0.1 N NaOH for ~ 3 months revealed clear improving after irradiation e.g., enhanced by ~ 25% for Ce-lead borate glass. Scanning electron microscope (SEM) images of the glass surfaces revealed more smooth and homogenous surfaces after irradiation. Shielding parameters by Monte Carlo code (MCNP5) and Phy-X/PSD software were studied, e.g., mass and linear attenuation coefficients (MAC and LAC), effective atomic number (Z_eff), radiation protection efficiency (RPE%), half and tenth value layers (HVL and TVL), and heaviness%. Comparing the shielding behavior of the three glasses revealed that Ce-lead borate glass has the highest values of LAC, MAC, Z_eff, heaviness%, and RPE% and the lowest values of HVL, TVL, and MFP, referring to the best shielding efficiency. The whole study indicates the desired properties of glasses as immobilizers or containers for radioactive wastes, e.g., nuclear medicine units in hospitals, especially lead borate glass doped Ce ions.

Graphical Abstract

MFI zeolite was synthesized using TPABr (Tetrapropylammonium bromide) and TBABr (Tetrabutylammonium bromide) templates to investigate the zeolite-template interaction and obtain the mesoporous structure of this zeolite. To achieve the lowest amount of required template, the zeolite was synthesized with TPABr with several molar compositions. The synthesized zeolite with TPABr at a temperature of 170 °C and a molar ratio of 0.2 has better crystallinity with smaller particle size. However, the zeolite synthesis with TBABr at similar condition is not successful due to the high zeolite-template interaction. Investigating the temperature effect (125–185 °C) on the zeolite-template interaction within the hydrothermal synthesis shows that the synthesis with TBABr at 140 °C reduced the zeolite-template interaction and led to successful synthesis of MFI zeolite. These crystals are less sharp, longer, and thinner than the crystals synthesized with TPABr. It has more mesoporous crystalline structure (15%) and larger pore diameter (30%) with narrow slit-like pores.

In this study, the effects of red volcanic tuff, which has different uses in automobile brake pads, on the friction performance of brake pads were investigated in a brake pad testing device. Brake pad containing red volcanic tuff was produced using the hot-pressing method at 150 °C temperature, 15 MPa pressing pressure, and 15 min of pressing time at four different mixing ratios. Nine different materials were used in the production of the samples. The developed samples’ friction coefficient, mass wear rate and hardness were determined. Optimum friction coefficient and wear rate performance were obtained in brake pad samples produced with red volcanic tuff. The friction coefficient increased with the increase of the red volcanic tuff ratio. The microscopic analysis of the worn surfaces of the brake pad samples, the friction coefficient of which was determined, was examined by scanning electron microscopy. The hardness of the brake pad sample decreased with the increase in the use of red volcanic tuff in the sample content. The decrease in the hardness of the sample caused the wear rate to be within the standard limits but high in the sample using the highest rate of red volcanic tuff. As a result, the performance of brake pad containing red volcanic tuff is similar to the studies in the literature, and it has been determined that this material can be used in the content of brake pads.

The hydroxyapatite (HA) powder has been successfully prepared by using calcined Indian clam seashells through the hydrothermal technique. Initially, the clam seashell is calcined at 900 ℃ to achieve calcium oxide (CaO). The obtained seashell-based calcium oxide is mixed properly with pre-determined tri-calcium phosphate in demineralized water. Further, the colloidal solution is heat-treated at a temperature of 1000 ℃ for various time durations (1 h, 1:30 h, 1:45 h, 2 h, 2:30 h, and 3 h) to perform the hydrothermal reactions. Quantification of HA and different phases present in the synthesized powders is carried out with the help of the Rietveld refinement method. The phases, crystallite size, and crystallinity of synthesized powder are evaluated by the X-ray diffraction (XRD) technique. The microstructure of the powder is analyzed through Field Emission Scanning Electron Microscopy (FESEM). The Ca/P ratio and particle size of the prepared powder are estimated by energy-dispersive X-ray spectroscopy (EDS) and the image analysis technique, respectively. The results indicate that the heating duration of the hydrothermal reaction is a crucial parameter in modifying the various properties, specifically the phase quantity of prepared HA. All six synthesized powders show the presence of the HA phase, along with a few secondary phases in those. Spherical and cylindrical nano-crystals of HA are observed to form. With an increase in time duration, coarsening of crystallite is observed. The average particle size and crystallinity of HA are also noticed to be increased with increased time duration.

Hydroxyapatite (HAp) is observed as a mineral deposition on bones and in teeth enamel and hence serves as an ideal model or as a component for orthopaedic and dental implants. Synthetic HAp has been synthesized on a lab scale for several decades to mimic the naturally occurring HAp based on its chemical and crystallographic nature. There are several methods for synthesis of HAp available in the literature, amongst which the following are a few examples: dry methods which include the solid-state method and mechano-chemical method, wet methods which include chemical precipitation and sol–gel method, and methods which use high-temperature such as combustion method and pyrolysis method. However, more economical and better yield-giving methods produce HAp with controlled morphology for its potential use in biomedical applications. One such method that exploits Schiff base ligands to form chelating complexes with calcium and phosphate precursors and protect generated HAp nuclei is recent ongoing research for the preparation of HAp. This review presents the synthesis of HAp using a wide array of methods, with the recent HAp using novel methods compared to the traditional synthesis of HAp.

The first time machine learning-based refractive index model proposed based on the density parameter using a glass dataset of 2000 oxide glass samples to predict refractive index of the xZnF₂-(20-x)ZnO-40As₂O340TeO₂. The study uses various machine learning techniques such as gradient decent, artificial neural network, and random forest regression to predict the refractive index and density of glasses. The random forest regression (RFR) model is found to be the most effective with a maximum R² value of 0.950 in the case of refractive index prediction and 0.926 for density prediction. The study also investigates the effects of nitrogen ion implantation on the glasses, finding that increased nitrogen dose causes a reduction in density and an increase in refractive index. The glass transition temperature decreases with increased nitrogen dose, possibly due to implantation defects. However, the glass stability increases with increasing implantation dose for low and high fluorine content glasses, likely due to the development of band gap defect levels and an increase in carrier concentration.

An effect of Cu-doped Ni-Zn nanoferrite particles synthesized through the citrate gel auto-combustion method on structural dielectric and magnetic properties was investigated. The structural characterization of synthesized powder is investigated using XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), EDXS (energy-dispersive X-ray spectroscopy), AFM (atomic force microscope), and TEM (transmission electron microscope). All prepared samples were established to have a single-phase spinel structure and fine grain size with an Fd-3 m space group. The lattice parameter, volume, and crystallite size decrease with increasing copper substitution. By adding copper ions, the surface area rises from 123.9 to 187.4 m² g⁻¹. The surface roughness is increased by AFM examination from 7.6 to 11 nm. From the AFM samples, it is shown that they are soft to hard in nature due to the Cu doping. The real imaginary impedance and the complex electric modulus were studied within the frequency range of 20 Hz to 1 kHz at room temperature, respectively. In the Cole–Cole plots studied for dielectric constant, it was observed that all samples had single semi-circles and continuously decreased with increasing copper content. This shows that the prepared material is good for high-resistance applications and the fabrication of multilayer inductor chips. The magnetic characteristics of hysteresis loops were studied at room temperature using a VSM (vibration sample magnetometer) for nanoferrites. The prepared ferrites samples were examined; copper doping increased the width of the loops, which confirms the change from soft to hard magnetic material. They are utilized in data processing, telecommunications, and the automobile industries. At low temperatures, the prepared samples showed superparamagnetic behavior. It is used in medical and electrical device applications.

Owing to the importance of hydrogen metallurgy for the low-carbon and green iron and steel industries, the reduction behavior and microstructure evolution of two iron oxides (hematite and magnetite) at various temperatures were investigated in a pure hydrogen environment (99.999%). The weight loss ratio, total oxygen content, reduction degree, and phase composition of the iron oxides were also discussed. The hematite shows a better reducibility compared to magnetite. It is indicated that hematite and magnetite transform into iron metal with total oxygen contents below 6790 and 25,200 ppm, respectively, when the reduction temperature exceeds 800 °C. Simultaneously, a porous iron skeleton was formed at 800 °C, and the densification of the porous iron occurred with increasing temperature. The impurities in iron oxides significantly affect the microstructure evolution, weight loss ratio, and total oxygen content.

Fabrication of Ti₃SiC₂ from elemental powder compacts was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS). Samples were formulated with three atomic ratios of Ti:Si:C = 3:1:2, Ti:Si:C = 3:1.2:2 (with excess Si by 20 mol.%), and Ti:Si:C:Al = 3:1.2:2:0.1 (a Si-rich and Al-added composition). Combustion reaction was highly exothermic and combustion wave velocity (from 4.1 to 8.8 mm/s) and temperature (from 1340 to 1610 °C) increased significantly with sample compact density varied in the range of 45% to 57.5% TMD (theoretical maximum density). In addition to the sample density, excess Si and a small amount of Al contributed greatly to the formation of Ti₃SiC₂. For the powder compacts of 57.5% TMD, the product synthesized from the sample of Ti:Si:C = 3:1:2 was composed of Ti₃SiC₂, TiC, and Ti₅Si₃ at 64 wt.%, 28 wt.%, and 8 wt.%, respectively. The sample with excess Si by 20 mol.% yielded a product with a weight proportion of Ti₃SiC₂:TiC:Ti₅Si₃ = 70:27:3. The product having the highest yield of Ti₃SiC₂ was obtained from the Si-rich/Al-added sample, which produced Ti₃SiC of 83 wt.%, TiC of 13 wt.% and Ti₅Si₃ of 4 wt.%. As-synthesized Ti₃SiC₂ grains were in a thin plate-like shape with 0.5–1.5 µm in thickness and 5–10 µm in length. Ti₃SiC₂ platelets were stacked closely into a layered structure.