ABSTRACT Carbide-derived carbon (CDC) was previously proposed as a surface modification method for hip implant applications since it showed excellent tribocorrosion performance under open-circuit potential (OCP) conditions. Nonetheless, a systematic evaluation of the CDC’s tribocorrosion properties was still missing. Therefore, our objective is to test CDC’s tribocorrosion performance under various electrochemical conditions and to identify the synergism between wear and corrosion. Based on the findings, the variations in OCP for CDC (0.626 mV) are smaller than Ti6Al4V (1.91 mV), and CDC showed lower induced current than T6Al4V for all potentials, suggesting CDC is more stable than Ti6Al4V under tribocorrosive conditions. Eventually, the weight loss of Ti6Al4V (50.662 ± 5.19 μg) was found to be significantly higher than that of CDC (4.965 ± 5.19 μg), which agrees with the electrochemical results. In summary, CDC showed better tribocorrosion performance than Ti6Al4V and was determined as an Antagonism regime.

ABSTRACT The major objective of the work is to explore the mechanical properties of biphasic calcium phosphates (BCP), a biomaterial derived from marine resources like prawn (Fenneropenaeus Indicus) shell biowaste through wet chemical treatment of CaO. We report the BCP, a mixture of hydroxyapatite and octa calcium phosphate from prawn shell biowaste using wet chemical synthesis at 80°C under pH 10. XRD of BCP revealed the coexistence of secondary phases like β-TCP and α-TCP along with HA upon sintering at different temperatures. Furthermore, the SEM and EDS opened well-sintered uniaxial grains and the presence of trace elements like Fe, Mg, Si, and Na. The specimens sintered at 1100°C showed the highest compression strength of 56.8 MPa due to MgO at the grain boundaries, which plays an important role in grain boundary diffusion. Therefore, the prawn shell biowaste-derived BCP has good mechanical properties, making them suitable materials for high-strength bone substitutes.

ABSTRACT Using a conventional sintering (CS) process, it is difficult to eliminate pore distribution across ceramic composites, resulting in mechanical properties destruction. In this study, 90%–95% of pores were reduced with the same sintering parameters by replacing CS with the cutting-edge Alumina-Graphite Powder Bath (AGPB) sintering method. Alumina-Zirconia-CNT(AZC) composites were fabricated using both AGPB and CS methods. The ceramic samples were surrounded by alumina-graphite powder particles in the AGPB method, which provided indirect homogeneous heating to the samples. This powder bath setup changed convection-radiation heat to conduction heat and produced sintered product with pore-free microstructures. The hardness of the AGPB-AZC composite was 43% higher than the CS-AZC, demonstrating the exponential property enhancement caused by cutting-edge AGPB sintering. The AGPB-AZC FESEM investigation revealed the formation of a homogenous microstructure with minimum pores, which eventually increased the hardness.

ABSTRACT Lanthanum-doped strontium titanate powder, La0.05Sr0.95TiO3+δ, was fabricated by peroxide-based route and calcination of freshly prepared precipitate and precipitate after ageing was carried out. The starting titanium precursor was titanium nitride, which underwent the reaction to form titanium peroxohydroxide and then compound containing strontium and lanthanum. A perovskite structure of strontium titanate with 5 mol-% doped lanthanum was obtained after calcination of the freshly-prepared precipitate at 500°C. However, the ageing powder revealed the presence of the second phase of strontium carbonate after calcination at the same condition. Thermogravimetric results showed that the decomposition of ammonia promoted a reaction to form the pure phase of ceramic oxide only in the freshly calcined sample.

ABSTRACT In this paper, the oxidation resistance of magnesia carbon bricks with different compositions was evaluated and the influencing factors were obtained, the influence of oxidation resistance on the performance of magnesia carbon bricks was investigated. The test results showed that for low-carbon MgO-C refractories, the influence of holding time was greater than that of oxidation temperature; for medium and high carbon MgO-C refractories, the influence of oxidation temperature was greater than that of holding times. The oxidation resistance of refractories, especially that of low-carbon MgO-C refractories, improved with the increase of the content of metallic additives. The oxidation resistance improved with the increase of graphite purity, especially in the low-temperature region. It is expected that this study can contribute to the optimal selection of magnesia carbon bricks in the trunnion area of furnace lining and provide a reference for the design of refractories with long overall service life.

ABSTRACT The paper studies the structural features, phase composition and complex mechanical properties of two-layer composite ceramics based on alumina-toughened zirconia with silica added (Ca-ATZ/Ca-ATZ+SiO2). The ceramics under study were manufactured using a cost-effective technology involving grinding and mixing powders, layering of powder mixtures (different compositions), uniaxial pressing and two-stage sintering. It was found that at the interface of the compositions, there is an abrupt increase in fracture toughness (by 33%) and a decrease in hardness and Young’s modulus (by 8% and 7%, respectively). The possibility of manufacturing composite ceramics Ca-ATZ+SiO2 (with a thin surface layer, not containing SiO2) with a high ratio of hardness (not lower than 14 GPa) and fracture toughness (not lower than 12 MPa m1/2) was shown. Given the increased resistance to low-temperature degradation of the developed ceramics, this will increase the service life of products operated under high mechanical loads in a humid atmosphere.

ABSTRACT Uniform-sized amorphous hydrous titania particles (HTPs) with nonporous or porous surface were prepared and subjected to hot-water or hydrothermal treatment to induce crystallisation of the titania phase for preparing porous titania particles with high specific surface area (SSA) and outer diameter in a micron order. Porous HTPs were crystallised under milder treatment conditions than those required to crystallise nonporous spherical HTPs. This difference was attributed to the difference in the polycondensation states of hydrous titania. The SSA of the porous titania particles crystallised by hot-water treatment at 80°C for 24 h was 216 m2 g−1, despite their micron-order particle size. This simple method can synthesise highly functional titania particles at low temperatures and is a general-purpose method for preparing porous particles for use as adsorbents, catalysts and catalyst supports.

ABSTRACT In this study, aluminosilicate fiber-embedded SiBOC matrix composite foams are realised by a simple, cost-effective and easily scalable method. Aluminosilicate wool is transformed into a compressible preform using polyvinyl alcohol as a binder. The preforms are impregnated with methylvinylborosiloxane (MVBS), followed by heat treatment at 1400°C in an inert atmosphere. The composite foam’s density, compressive strength and thermal conductivity are modulated in the ranges 0.71–0.46 g/cc, 0.79–0.39 MPa and 0.21–0.13 Wm−1K−1, respectively, by varying MVBS concentration from 29 to 54 wt.%. While the incorporation of aluminosilicate fibers was observed to lower the thermal conductivity of the composite foams, it did not contribute to their compressive strength. Exposure of the foams to air at 1300°C for 90 min didn’t change their density, while it increased the compressive strength by up to 46% due to improved fiber-matrix adhesion and rounding of cracks.

ABSTRACT SiC-reinforced SiC ceramic matrix composites (SiC/SiC CMCs) are considered promising candidates to replace their super alloy counterparts due to higher temperature capabilities and lower densities. However, high-temperature and high-pressure water vapour sourced from the hydrocarbons’ combustion reactions inhibit the potential of SiC/SiC CMCs by leading to rapid surface recession. In order to address this challenge, environmental barrier coatings (EBCs) have been developed. The emphasis of this review is on the materials and processing techniques for the development of EBC systems. In the first part of the review, the characteristics of the SiC/SiC CMCs and the most common EBC materials are summarised. Then, the interrelationship between processing methods, microstructures and the resulting properties is reviewed. Finally, an overview of the future directions is outlined to assist developments in advanced and novel EBCs for next generation gas turbines.

ABSTRACT The binder jetting (BJ) process shows significant superiority in manufacturing ceramic parts with a complex structure. The performance of the green part is highly reliant on the features of raw materials. A kind of grading zirconia powder M0 was designed, its intrinsic characteristics including microstructure, size and size distribution, bulk density, porosity, hall velocity and spread performance were systematically evaluated. The design principles of M0 were illustrated in detail. Meanwhile, a kind of organic epoxy binder was prepared and its properties including density, viscosity and surface tension were estimated. The jet ability of binder was evaluated quantitatively. The compatibility and bonding strength between binder and powder were assessed through contact angle, infiltration time and microstructure of M0. As a result, M0 and epoxy binder can be successfully applied in the printer, the zirconia structure with good dimensional accuracy (shrinkage rate ≤ ±2%) and flexible strength (1.74 ± 0.28 MPa) were achieved.