Academia Revista Latinoamericana de Administracion

High mobility of ITO films for solar cells is enhanced by decreasing SnO2 content in ITO gargets. However, the sintering densification of ITO targets becomes difficult. The density of ITO targets with low SnO2 content is enhanced by TiO2, SiO2 and cold sintering. The green bodies of ITO are first compacted by cold sintering and then further fully densified by microwave sintering. Three types of ITO targets exhibit single cubic bixbyite structure, dense microstructure and transgranular fracture. ITO targets sintered at a microwave temperature of 1450 °C have a high relative density of over 99% and low resistivity of below 4.87 × 10−4 Ω·cm. The fine grains have a size of less than 2.0 μm. Therefore, the synergistic effect of additives and the sintering process can resolve the difficulty of sintering densification of ITO targets with low doping content.

Using solution-gelation and the auto-combustion process, calcium (Ca)-doped cobalt ferrite (CoFe2O4) nanoparticles were synthesised. The synthesised nanomaterials were characterised by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, field-effect scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), UV–Vis spectroscopy, and vibrating sample magnetometer (VSM) techniques. The PXRD analysis shows that the crystallite size reduces from 39 to 27 nm with increasing calcium content. UV–Vis spectroscopy reveals that the band gap is enhanced with calcium content. The VSM illustrates that coercivity and saturation magnetisation decrease with the concentration of calcium. The synthesised nanomaterials were first time applied to humidity sensing, and different sensing parameters were determined. The response and recovery times were 44.95 and 53.52 s, respectively. The designed sensor has a repeatability of 97% and a minute ageing effect.

The brittleness of silicon carbide restricts its wide application. Graphene as a superior second-phase material can improve the toughness and brittleness of silicon carbide. In this article, a graphene/β-SiC ceramic material was prepared with 1–3 wt.% graphene added in β-SiC matrix via pressure-free sintering at 2120°C for 60 min. The effect of the graphene addition on the phase composition, bulk density, porosity, and mechanical properties of ceramic material was investigated. The results show that the bulk density of graphene/β-SiC ceramic material decreases, the porosity of openings increases, and the bending strength, hardness, as well as fracture toughness firstly increase and then decrease as graphene addition increases. Compared with β-SiC ceramic without graphene, the optimum properties of graphene/β-SiC ceramic with graphene addition of 1 wt.% (i.e. a fracture toughness of 5.07 MPa m1/2, bending strength of 410.84 MPa and hardness of 27.72 HV) can be obtained, which are increased by 35.56%, 13.35%, and 3.8%, respectively. The fracture morphology indicates that the crack deflection is the main mechanism of toughening β-SiC ceramic with graphene.

Calcium silicate–based materials have been a long-time favourite in thermal insulation applications. This work emphasises synthesising calcium silicate–based thermal insulating material via solid-state reaction using silica, calcium carbonate and fly ash as binding material. The calcium silicate formulations were mixed into a ratio of 1:1:1 (CaO:SiO2:FA) and sintered at temperatures 800–1100°C for 2 h. The developed tailored powder and the sample with calcium silicate formulations were characterised by X-ray diffraction, IR, thermagravimetric analysis, scanning electron microscopy (SEM)-EDS and thermophysical properties (thermal diffusivity, heat capacity per unit volume and thermal conductivity). The synthesised samples are composed mainly of calcium silicate phases, that is, wollastonite with minor larnite and rankinite. The microstructure was evaluated by SEM. It was found that the developed calcium silicate material reached low thermal conductivity values, that is, 0.29 and 0.42 W/mK (for 2P1000 and 2P1100, respectively). The thermal constant analysis of the material shows the stability of the material at high temperatures. Thus, the present results suggest that in-situ calcium silicate–based material prepared is a good thermal insulation ceramic material.

The ceramic composite electrolytes in the NaTi2(PO4)3–NaF system were characterised by thermal analysis, X-ray diffraction, Fourier infrared absorption spectroscopy, scanning electron microscope, and impedance spectroscopy. X-ray diffraction confirmed that the ceramic composites have a Na Super Ionic Conductor (NASICON) structure. The scanning electron images showed that the addition of NaF significantly improved the microscopic morphology of the NaTi2(PO4)3 crystals and made the packing of crystal grains closer. The addition of NaF in a certain proportion is beneficial to the growth of crystals, making the crystal grains more compact and improving the density of the solid electrolytes. The ionic conductivity analysis was carried out by alternating current (AC) impedance spectroscopy. The conductivity can be effectively improved when a certain proportion of NaF is added to the ceramic composites. The maximum total conductivity is about 1.50 × 10−5 S·cm−1 obtained when the molar ratio of NaF to NaTi2(PO4)3 reaches 0.4.

Perovskite layered materials with A2B2O7 structure such as Ca2Nb2O7, Sr2Nb2O7, Nd2Ti2O7, La2Ti2O7, Sm2Ti2O7 and Pr2Ti2O7 possess very high Curie temperature (Tc > 1000°C). The above materials in powder form were synthesised using mixed oxide method by calcining well-mixed constituent powders between 1000°C and 1300°C for 2 h. Circular disc samples of 12 mm diameter were prepared and sintered at 1200–1450°C, with a soaking duration of 2 h. The sintered density, X-ray diffractometer, scanning electron microscope and electrical resistivity were measured for all samples. The samples experience a linear decrease in electrical resistivity from 1013 to 105 Ω.cm as temperature increases between 100 and 900°C. In this paper, a comparative study on electrical resistivity for the above materials was carried out to determine their suitability for sensing applications at high temperatures.

Rare-earth hexaborides (RB6) are promising materials for photonic and electronic applications in modern technology. However, the known methods of synthesis of RB6s are challenging due to their complexities and nuances, usually requiring high temperatures, long synthesis durations and complicated by the use of complex precursors. This paper reports the development of an energy-efficient and straightforward microwave-assisted synthesis (MS) method. The series of rare-earth metal hexaboride powders RB6 (R = La, Ce, Nd and Sm) have been prepared by the MS method in a dramatically short times (synthesis duration is 10 minutes). For the synthesis, easily available raw materials (lanthanide oxides and boron) were used, although the reactions R2O3/B → RB6 are thermodynamically prohibited (except CeO2/B system). The x-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis show that all hexaborides are cubic phases with high crystallinity. Although the shapes are similar, the sizes are in the range of 1 to 10 μm. being different for each of the formulations.

In this study, lead magnesium niobate–aluminium bismuthate ((1 −  x) PMN–( x) AB) solid solution ceramics with composition of x = 0.1, 0.2 and 0.3 were prepared by solid state reaction method to study temperature and frequency dependency of its dielectric properties. Dielectric properties were studied using the complex impedance spectroscopic method. The temperature dependence of dielectric constant ([Formula: see text]) for compositions with x = 0.1, 0.2 and 0.3 is ≈ 109.75, 112.56 and 115, respectively. The imaginary dielectric constant is also ≈ 0.030, 0.033 and 0.035 for the composition 0.1, 0.2 and 0.3, respectively, for frequency of 10 kHz. The temperature at maximum of dielectric constant of (1 −  x) PMN–( x) AB ceramics was seen to increase with increasing AlBiO3 content. Temperature of maximum dielectric constant ( Tm) of 86 °C was obtained at 10 kHz for the composition x = 0.3.

Alumina-based tungsten carbide composites reinforced by different weight percentages of graphene platelets (GPLs) were successfully sintered by latest spark plasma sintering (SPS) technique. The WC-Al2O3-GPLs composites were fabricated to design advanced tool materials to acquire an optimum set of mechanical, thermal and anti-wear properties for high-temperature cutting tool applications. This study has the novelty that such composites have not been developed using SPS. The addition of GPLs to composites enhanced the microstructure, however the optimum mechanical and thermal properties were exhibited with the composite having lesser addition of GPLs. At higher levels of GPLs addition, the microstructures and properties of composites were degraded on account of stacking/agglomeration of GPLs. It was observed that SPS delivered better densification and microstructures as compared to other conventional sintering. The mechanical properties were best revealed by the sample with 0.6 wt. % of GPLs with hardness of 20.71 GPa and fracture toughness of 11.84 MPa.m1/2. The improved toughening and strengthening results of WC-Al2O3-GPLs composites were essentially acquired by inhibiting grain growth during sintering, bridging of GPLs between matrix components, and improved dispersion of composite constituents (EPMA/WDS), particle hardening and phase toughening (Al2O3, GPLs). A thermal study was conducted to investigate the thermal stability of sintered composites at higher temperatures while providing the maximum thermal conductivity and thermal diffusivity of 166 Wm−1K−1 and 0.276 × 10−4 m2s−1 at room temperatures. The tribological testing revealed that the composites with lesser GPLs reinforcement attributed lower coefficients of friction, better surface finish and least wear of the materials.

Corals, crucial for ocean ecosystems, face threats such as ocean acidification from global warming and pollution, which weaken their skeletons. This study focuses on Acropora cervicornis, known for its hard but fragile structure, requiring strength and flexibility to withstand the forces from climate-driven atmospheric events. An experiment using uniaxial mechanical loading from the initial stage to complete failure at a very low strain rate (1.2821 × 10−5 s−1) was conducted to ascertain the mechanical properties of corals. The geometric properties and Young's modulus were analysed based on various levels of micro-architectural details from micro-CT data, with resolution values influencing the measurements. The highest resolution model showed a Young's modulus approaching 22.265 GPa and porosity at 40.448%. Calibration of finite element models incorporating micro-architectural details enabled a precise comparison of parameter effects and more accurate results, highlighting the significance of resolution in modelling coral mechanical properties.

Flash sintering (FS) is of great interest today, as it allows the production of high-density ceramics in seconds at lower temperatures than conventional sintering. In this study, the effects of conventional sintering at 1250°C for 4 h and FS at various electric fields (12.5, 25, 50 and 75 V/mm) on copper smelting slag (CSS), which is a multiphase material system, are investigated. The results show that FS occurs at substantially lower temperatures with much shorter times than conventional sintering, in conjunction with improved density and hardness values for CSS. The optimum condition for better densification is observed for the sample applied the 25 V/mm electric field in 554 s, and the maximum power density of about 76.49 mW/mm3. On the other hand, the shortest FS duration is achieved with the sample applied 75 V/mm in 114 s. Flash sintering at lower temperatures also stabilizedthe magnetite-hematite the phase transition, which arouses at higher temperatures. Overall, FS has made a huge contribution to reducing sintering time and temperature while providing better microstructure integrity and mechanical properties in multiphase materials systems.

The accuracy of computer-aided design/computer-aided manufacturing (CAD/CAM) methods plays an important role in the clinical success of ceramic veneers. This study aimed to evaluate the impact of different CAD/CAM methods, including subtractive, hybrid, and additive manufacturing, on the trueness and precision of ceramic veneers. A typodont central incisor was prepared for a laminate veneer, followed by the design of a veneer with CAD software. Ceramic veneers were fabricated with four different CAD/CAM methods, including milled lithium disilicate, pressed lithium disilicate with three-dimensional (3D) printed wax patterns, milled zirconia, and 3D-printed zirconia. All veneers were scanned and imported to 3D inspection software for trueness and precision evaluation. Laminate veneers fabricated with all investigated methods exhibited clinically acceptable trueness and precision. Pressed lithium disilicate veneers from 3D-printed wax patterns and 3D-printed zirconia veneers showed lower precision of the fitting surfaces compared to their milled counterparts.

Three types of alumina powders and a polymer electrolyte Isobam system were used to fabricate translucent alumina ceramics via gelcasting, and each powder had the highest attainable solid loading. The effects of alumina particle size on slurry dispersion, microstructures and properties of green bodies and ceramics were investigated. All of the high-solid loading slurries contained strong aggregates, which could bridge with each other to form weak agglomerates. The smaller the initial particle size was, the more the contained particle number per aggregate. In addition, the smaller the aggregate size was, the lower the sintering activation energy of the ceramic and, finally, the higher the relative density. The initial particle size of the powder may not be the critical factor determining ceramic sintering, but the aggregate size and effective volume fraction of the aggregates may be the critical factors. Finally, the in-line transmittance of the ceramic with a higher density reached 22% at a wavelength of 650 nm and a thickness of 0.8 mm.

Hydroxyapatite (HAp) is an essential material in the biomedical field because of its chemical composition, similar to the apatites found in bones. The lack of bactericidal properties of HAp-based materials cannot prevent the adhesion and growth of bacteria. However, it can develop composite biomaterials using nanoparticles (NPs) such as silver (Ag) and zinc (Zn), which exhibit biocidal behaviours to control resistant microorganisms. This study aimed to prepareHAp–AgNPs and HAp–Ag@ZnNPs nanocomposite and evaluate their antimicrobial properties against Gram-positive and Gram-negative bacteria. HAp powders were produced from sheep bone. An aqueous extract of Marrubium astracanicum was used as a reducing and stabilising agent for the synthesis of NPs. The composites were characterized by XRD, SEM–EDX, SEM and FTIR. In vitro biocompatibility assessment was determined by agar well diffusion tests. The HAp–Ag@ZnNPs nanocomposites showed stronger antimicrobial activity than HAp–AgNPs against bacteria and fungi, while pure HAp did not show any effect.

Magnesium oxide (MgO) porous ceramics with high porosity, compressive strength and low thermal conductivity were prepared by Organic Foam Template Method. The effects of the sintering temperature, polycarboxylic acid (PCE) dispersant and pore size of organic foam template on the properties of MgO porous ceramics were investigated. The experiment results showed that with the increase of sintering temperature, the MgO porous ceramic shrinkage, skeleton density and compressive strength increased. PCE could increase the fluidity of slurry and make the framework clearer, as well as reduce the cracks formed in the process of drying effectively. When the content of PCE was 0.5 wt-%, the porosity, compressive strength and thermal conductivity of MgO porous ceramics were 88.5%, 1.6 MPa and 0.045 W/(m·K), respectively. In addition, as the pore size of the organic foam template decreased, the porosity decreased, and the resistance increased and the thermal conductivity increased.