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It's crucial to make inexpensive, effective palladium catalysts employing α-alumina in the realms of pollution remediation and drug synthesis. The α-alumina foam ceramics prepared by the template approach were modified by adding a thin coating of γ-alumina containing Ce and P elements to further prepare the palladium catalyst. γ-Alumina significantly raised the foam's specific surface area, multiplied the number of acidic sites, decreased the Pd–O bond strength in palladium oxide, and brought the active phase content closer to the ideal value. Phosphate radicals were adsorbed onto the alumina surface, reducing the proportion of strongly acidic sites on the surface, and facilitating the desorption of oxygen species adsorbed by surface defects. As P and Ce elements interacted, the Ce4+/Ce3+ ratio decreased, increasing the number of oxygen vacancies in cerium oxide to improve the oxygen storage capacity of cerium oxide. In addition to acting as an oxygen storage material, the Ce elements increased the electron density of Pd and weakened the binding strength of the oxygen species bound to the individual metal Pd. There was a strong interaction between cerium and palladium, resulting in a mixed state of Pd0, PdO, and Pd2+ after the reaction. On the other hand, the surface of the foam was rough enough to facilitate the adhesion of the thin coating, while the thin coating, with a thickness of less than 8 μm, improved its mechanical properties. The CO full conversion temperature was reduced by 135 °C in the Pd/CeP(γ/α-A) compared to the uncoated foam catalyst. [ABSTRACT FROM AUTHOR]

Owing to the good physicochemical compatibility and complementary mechanical properties of Ti 3 SiC 2 and Al 2 O 3 , Ti 3 SiC 2 /Al 2 O 3 composites are considered as ideal structural materials. However, TiC and TiSi 2 typically coexist during the synthesis of Ti 3 SiC 2 /Al 2 O 3 composites through an in-situ reaction, which adversely affects the mechanical properties of the resulting composites. In this study, Ti 3 SiC 2 /Al 2 O 3 composites were prepared via in-situ hot pressing sintering at 1450 °C. Ge, which was used as a sintering aid, improved the purity and mechanical properties of the Ti 3 SiC 2 /Al 2 O 3 composites. This is because Ge replaced some of the Si atoms to compensate the evaporation loss of Si to form Ti 3 (Si 1-x Ge x)C 2 , which showed a crystal structure similar to that of Ti 3 SiC 2. Furthermore, the molten Ge accelerated the diffusion reaction of the raw materials, increasing the overall density of the Ti 3 SiC 2 /Al 2 O 3 composites. The optimum Ge amount for improving the mechanical properties of the composites was found to be 0.3 mol. The flexural strength, fracture toughness, and microhardness of the composite with the optimum Ge amount were 640.2 MPa, 6.57 MPa m1/2, and 16.21 GPa, respectively. The formation of Ti 3 (Si 1-x Ge x)C 2 was confirmed by carrying out X-ray diffraction, energy dispersive spectroscopy, and transmission electron microscopy analyses. A model crystal structure of Ti 3 (Si 1-x Ge x)C 2 doped with 0.3 mol Ge was established by calculating the solid solubility of Ge. [ABSTRACT FROM AUTHOR]

In this work, the Al2O3/Ti3SiC2 composites with different Nb doping amounts (0–5 vol%) were prepared by vacuum hot pressing sintering (30 MPa, 1450 for 1 h). Various tests and characterization had been performed on samples to investigate the dependence of Nb doping on the mechanical properties and microstructure of Al2O3/Ti3SiC2 composites. Nb doping can optimize the microstructure of Al2O3/Ti3SiC2 composites. Scanning electron microscopy (SEM) images showed that with the increase in Nb doping, the pores of the composites gradually decreased and the microstructure became denser. Based on X-ray diffraction (XRD) pattern analysis, it was found that Ti3SiC2 may react with Nb to form the enhanced phases Ti5Si3, TiC and Nb3Si. Therefore, with the continuous doping of Nb, more toughening phase Ti3SiC2 will be converted to the strengthening phases, leading to the sacrifice of partial fracture toughness to improve the bending strength and hardness of Al2O3/Ti3SiC2 composites. [ABSTRACT FROM AUTHOR]

Abstract In this work, Ti 3 SiC 2 /Al 2 O 3 composites with various volume contents of Ti 3 SiC 2 were fabricated under different orthogonal processes by vacuum hot pressing sintering. optimized comprehensive mechanical properties and relative density (＞97%) were obtained (the microhardness, flexural strength and fracture toughness reached the values of 16.25 GPa, 536.31 MPa and 9.3 MPa m1/2, respectively.) when the Al 2 O 3 (60.0 vol %) and Ti 3 SiC 2 (40.0 vol %) were sintered at 1500 °C for 0.5 h at 30 MPa, which basically correspond to the best level of after orthogonal calculation. The orientational growth behavior of Ti 3 SiC 2 was further confirmed by EBSD, and temperature was found to play a prominent role in the growth of Ti 3 SiC 2 to some extents, fewer columnar Ti 3 SiC 2 grains were observed at lower temperature and weak decomposition of Ti 3 SiC 2 was observed at 1500 °C. Meanwhile, high volume Ti 3 SiC 2 was beneficial to the improvement of mechanical properties for the intrinsical layered structure. [ABSTRACT FROM AUTHOR]

Abstract A novel laminar B 4 C/Al composite was fabricated by vacuum hot-press sintering at a temperature of 680 °C, dwell time of 120 min, and pressure of 30 MPa. The measured Vickers hardness reached maximum and minimum values of 114.29 ± 4.85 HV and 48.59 ± 5.42 HV in the outermost and innermost layers, respectively. The specific “hard-soft-hard” laminar structure was capable of bearing high a load because of the excellent harmony between the different layers. Consequently, the laminar B 4 C/Al composite was endowed with remarkable mechanical properties, such as bending strength of 767.50 ± 9.52 MPa and flexural toughness of 11.73 ± 0.15 MPa m1/2, which were better than those of a homogeneous B 4 C/Al composite with the same B 4 C volume content. The EBSD results showed that the orientation of the Al particles in the laminar composite was random. The stress and strain in the deformed sample were evenly dispersed because of the great coordination of the lamellar structure. [ABSTRACT FROM AUTHOR]

New type of structural functional materials, Ti/Al 2 O 3 composites, were successfully fabricated by vacuum hot-pressing sintering at 1350 °C, 1400 °C, 1450 °C, and 1500 °C under a pressure of 30 MPa with a holding time of 90 min. The brittle TiAl and Ti 3 Al phases, which were regarded as detrimental to the mechanical performance, were present in the reaction products, as observed in X-ray diffraction patterns. Therefore, metallic Nb was introduced into the system to explore its inhibitory effect between Ti and Al 2 O 3 . The EDS and EPMA results illustrated that Nb played an active role in inhibiting interfacial reactions. Moreover, the mechanical properties and microstructure of the composites were improved owing to Nb doping. [ABSTRACT FROM AUTHOR]

The Ti/Al 2 O 3 composites are fabricated by hot pressing sintering, and the effect of Y 2 O 3 on the microstructure and mechanical property of Ti/Al 2 O 3 composites has been studied by means of SEM, EDS and XRD. The results show that the Al 2 O 3 decomposition to Al and O first, and then Al diffusion to Ti formed the intermetallics such as Ti 3 Al and TiAl phases in the composites. Thermodynamics calculation shows us the Gibbs free energy are −120.23 kJ/mol and −73.44 kJ/mol for Ti 3 Al phase and TiAl phase, respectively. The addition of yttria to the composites makes enthalpy changes, reduces the amount of Ti 3 Al phase. The effect of Y 2 O 3 addition on the microstructures and mechanical properties of the Ti/Al 2 O 3 composite was characterized. When the Y 2 O 3 content is 1.0 vol%, the flexural strength, fracture toughness, Vickers hardness and relative density of the composite reach the maximum values of 302.73 MPa, 6.45 MPa m −1/2 , 16.78 GPa and 98.63%, respectively, and the fracture mode changes from intergranular to transgranular. [ABSTRACT FROM AUTHOR]

Building energy consumption and industrial solid wastes have attracted great concerns in recent years. A novel thermal insulation composite (NTIC) is prepared by combining industrial solid wastes with expanded polystyrene (EPS) beads for non-structural applications of building energy conservation. Industrial solid waste containing flue gas desulfurization (FGD) gypsum improves the fire resistance of NTIC samples and reduces the carbon footprint of the material as compared with similar insulation composites based on portland cement. In order to substantially reduce the density and thermal conductivity of NTIC samples, the proportion of industrial solid wastes should be decreased. However, significant quantities of large voids appear in the samples which leads to the difficulty of the shaping and sharp decrease of mechanical properties. Compression method was used to solve the above problem in this paper. The morphological characterization, physico-mechanical properties, water absorption, thermal conductivity and fire behavior of the NTIC samples with different compression ratios were studied. The results showed that density, mechanical properties, water absorption and thermal conductivity of the NTIC samples gradually decreased with the increase of EPS beads content. The samples with a compression ratio of 1.8 possessed preferable mechanical properties and lower water absorption than those with a compression ratio of 1.4 in the case of approximately same density due to many voids inside the latter. The thermal conductivity of samples was mainly determined by their density. There is no fire combustion for all the samples under the flame, which illustrated the NTICs in this paper possessed superior fire safety. • A novel thermal insulation composite was prepared by using a compression method. • An environmentally friendly cementitious composite was used. • The mechanical strength and thermal conductivity were positively linear with density. • The water absorption of NTIC samples could be reduced by adjusting compression ratio. • Flue gas desulfurization gypsum was beneficial to fire resistance. [ABSTRACT FROM AUTHOR]

Proton-conductor solid oxide fuel cells (PC–SOFCs) have demonstrated innovative capabilities in energy applications, particularly for the efficient transformation of biomass fuels into hydrogen for power generation. Methanol, a readily available and economical biomass fuel with a high hydrogen content, has shown significant potential for waste utilization and energy recovery. Consequently, this study employed methanol as a fuel for PC-SOFCs and investigated the optimal operating conditions through meticulously designed experiments. This study also enhanced the cell performance through the co-reforming of steam and methanol, demonstrating that the introduction of steam during the methanol-reforming process significantly improved cell efficiency. At a 30 % methanol fuel concentration and a 700 °C operating temperature, co-reforming increased the maximum power density (MPD) from 0.269 to 0.352 W cm−2. Additionally, integrating Ru-GDC nanofiber catalysts into the anodic dendritic microchannels enabled the creation of an in-situ catalytic cracking reactor, further boosting MPD to 0.412 W cm−2. The catalyst-equipped cell demonstrated stable operation for continuous 102 h at a current density of 0.6 A cm−2, with no performance decline, thereby confirming the exceptional long-term stability of the system. [Display omitted] [ABSTRACT FROM AUTHOR]

Converting CO 2 to highly demanded fuels or chemicals is able to achieve substantial economic and environmental benefits. Herein, a series of Pd/P–CeO 2 –Al 2 O 3 coatings on foam ceramics with particular morphologies including mesh, rod, plate, as well as mixed mesh and plate, are successfully prepared. The mesh Pd/P–CeO 2 –Al 2 O 3 coatings (MC) supported on ceramic displayed much higher catalytic activity and better selectivity than those of catalysts with other morphological Pd/P–CeO 2 –Al 2 O 3 coatings. The CO 2 conversion and CH 4 selectivity of MC were up to 85.9% and 100%, respectively. The superior catalytic performance was ascribed to the strong MSI effect, high hydrogen storage capacity, abundant oxygen vacancies, and metal sites, as well as moderately basic sites, which were characterized by TEM, XPS, CO 2 -TPD, and H 2 -TPD. More importantly, the intermediates and possible reaction pathways were systematically investigated by in situ FTIR. And the high performance of MC mainly comes from the accelerated conversion of carbonate and the hydrogenation of the generated monodentate formate. Overall, the catalytic performance of Pd/P–CeO 2 –Al 2 O 3 coatings supported on ceramic can be facilely regulated and optimized by accurately devising the morphology of the Pd/P–CeO 2 –Al 2 O 3 coatings, which offers a novel perspective for high-performance CO 2 methanation. [ABSTRACT FROM AUTHOR]

Ce–P/γ-Al 2 O 3 coatings applied with the freeze-drying technique were deposited on foam ceramics before being further prepared as Pd catalysts. According to the research, phosphoric acid replaced the hydroxyl on the surface of γ-Al 2 O 3 to produce polyhydroxy P-containing sites that readily attracted cerium oxide. The palladium oxide was then embedded into the cerium oxide vacancy. The impacts of the drying technique on the catalysts were investigated, and the results indicated that freeze drying created a special coating with a large specific surface area and uniform mesoporous structure by inhibiting nanoparticle agglomeration. H 3 PO 4 's altering action was augmented to boost the number of active sites and the percentage of weakly acidic sites. Due to better P–Ce interactions, more Ce3+ was added into CeO 2 , which created numerous oxygen vacancies. By adjusting the P-containing sites, the dispersion of cerium oxide and the active phase could be controlled, which aided the activation and spillover of hydrogen. Furthermore, the capacity for oxygen adsorption and desorption was enhanced, and the amount of adsorbed oxygen species increased. As a result, the freeze-drying technique improved the advantages of the Ce–P/γ-Al 2 O 3 coating, increasing the conversion and selectivity of CO 2 methanation to 81% and 94%, respectively, and lowering the complete conversion temperature of CO oxidation to 116 °C. This research has a guiding influence on the development of foam ceramic-loaded palladium catalysts in the fields of energy and the environment. [ABSTRACT FROM AUTHOR]

Ti 3 SiC 2 /Al 2 O 3 composites attract attention because Ti 3 SiC 2 and Al 2 O 3 have complementary advantages in mechanical properties. However, the high temperatures (≥1400 °C) required for densification of the Al 2 O 3 lead to the decomposition of Ti 3 SiC 2. To address this issue, Ti 3 (Al 1-x Si x)C 2 /Al 2 O 3 composites were fabricated via current-assisted sintering of Ti 3 AlC 2 /SiO (TM sample) and Ti 3 AlC 2 /SiO 2 (TD sample) at 1100–1300 °C. After sintering, most Al atoms in Ti 3 AlC 2 were substituted by Si atoms, forming Ti 3 (Al 1-x Si x)C 2 with values of x greater than 0.85. However, the morphologies of Al 2 O 3 produced from Ti 3 AlC 2 /SiO and Ti 3 AlC 2 /SiO 2 were different. Spherical Al 2 O 3 produced by Al–Si substitution in SiO 2 was difficult to densify at low temperatures, whereas the reaction between Ti 3 AlC 2 and SiO disintegrated the matrix of SiO and produced dense Al 2 O 3. As a result, the relative densities and mechanical properties of TM samples were less affected by a reduction in sintering temperature than those of TD samples. As sintering temperature declined from 1300 °C to 1100 °C, flexural strength, hardness, and fracture toughness of TM samples decreased by 35.9% (from 546.2 MPa to 350.0 MPa), 27.4% (from 4.56 GPa to 3.31 GPa), and 33.4% (from 7.45 MPa m0.5–4.96 MPa m0.5), respectively. Meanwhile, the flexural strength, hardness, and fracture toughness of TD samples were reduced by 81.2% (from 466.1 MPa to 87.6 MPa), 85.4% (from 6.50 GPa to 0.95 GPa), and 68.6% (from 6.94 MPa m0.5–2.18 MPa m0.5), respectively. Therefore, Ti 3 AlC 2 /SiO is more suitable for fabricating Ti 3 (Al 1-x Si x)C 2 /Al 2 O 3 composites at low temperatures. [ABSTRACT FROM AUTHOR]

Ti3SiC2/Al2O3 multilayered composites were prepared by the combination of tape casting and hot pressing sintering. The slurry was produced by adjusting the amounts of each organic material, including triethyl phosphate (TEP) as a dispersion, polyvinyl butyrate (PVB) as a binder, dioctyl phthalate (DOP) as a plasticizer, and anhydrous ethanol as an organic solvent. When TEP content was 3 wt.%, PVB content was 4.5 wt.%, R‐value (DOP/PVB) was 1.4, and solid content was 38 wt.%; the cast film with a smooth surface, good flexibility, and uniform thickness was obtained after defoaming, tape casting, and drying. Three samples were prepared, namely, S1–S3. The S1 was monolithic Ti3SiC2/Al2O3 (mass ratio is 1:1) composites. S2 and S3 were Ti3SiC2/Al2O3 multilayered composites, which matrix layers were Ti3SiC2/Al2O3 composites (mass ratio is 1:1) and Al2O3, respectively, and their interface layer was Ti3SiC2. S1–S3 were also sintered at 1550°C. The bending strength of multilayered materials were lower than that of monolithic material, but the fracture toughness of multilayered materials significantly increased. Due to the introduction of Ti3SiC2 interface layer, the friction coefficient and wear rate of Ti3SiC2/Al2O3 multilayered composites were reduced by 30.7% and 33.8%, respectively, compared with monolithic material. [ABSTRACT FROM AUTHOR]

(Ti,Ta) 3 SiC 2 /Al 2 O 3 composite ceramics were prepared by hot-pressing sintering using TaC as Ta source. X-ray diffraction analysis showed that the maximum of solid solubility of Ta in Ti 3 SiC 2 were determined to be from 7.5 to 10 at%. With the increase of TaC contents, the grain size of Ti 3 SiC 2 reduced obviously. Combined Wulff theorem and first-principle calculations, the probable mechanism of this refinement phenomenon was revealed. When Ta atoms substitute Ti in surface atomic layers, the surface energy of (001) plane increased significantly compared to those of (100) plane, which restricted the growth of (001) facets. As it is the largest exposed surface, the lower growth rate of (001) facets lead to the grains refinement. The results will provide theoretical guidance for surface modification and morphological transformation of Ti 3 SiC 2 -based ceramics. [ABSTRACT FROM AUTHOR]

(Ti,Nb) 3 SiC 2 /60 vol%-Al 2 O 3 composite ceramic samples with different Ti/Nb atomic ratios were prepared by hot-pressing sintering using Ti/Si/Al/TiC/NbC/Al 2 O 3 powders as starting materials. X-ray diffraction analysis showed that the solid solubility of Nb is approximately 7.5 at%. Excessive NbC powder addition can lead to the generation of an impurity phase. Scanning transmission electron microscopy and X-ray photoelectron spectroscopy images reveal that most of the Nb-doped atoms aggregate at 2a -sites, as this configuration exhibits the lowest system energy. The optimized hardness, flexural strength and fracture toughness of (Ti,Nb) 3 SiC 2 /Al 2 O 3 were determined to be 16.0 GPa, 672 MPa and 6.9 MPa m1/2, which corresponds to an increase of 15.9%, 18.7% and 25.4% respectively, compared with Ti 3 SiC 2 /Al 2 O 3 composite ceramics. By means of first-principle calculations, the strengthening mechanism is derived from both intragranular improvement in (Ti,Nb) 3 SiC 2 solid solutions and intergranular enhancement of (Ti,Nb) 3 SiC 2 /Al 2 O 3 grains interfaces. [ABSTRACT FROM AUTHOR]

Hydrazine hydrate, characterized by its high hydrogen content and eco-friendliness, garners extensive attention in the field of fuels. Its high energy density and rapid decomposition capabilities render it a promising fuel option for Proton-Conductor Solid Oxide Fuel Cells (PCFCs). Given the unique properties of hydrazine hydrate, this study employs a dendritic porous anode structure to facilitate faster fuel transport. Additionally, the influence of operational temperature and concentration of hydrazine hydrate as fuel on cell performance is analyzed. An effective vapor management strategy is implemented to address its decomposition into water vapor, resulting in a significant 23.17 % increase in the maximum power density (MPD) of the cell. To further enhance the performance of hydrazine hydrate fuel in PCFCs, a Pt–Al spherical catalyst is integrated within the anode structure of the cell. This approach notably improves the cell performance, yielding an additional 14.98 % increase in MPD. This design not only augments the electrical output but also effectively mitigates the degradation of the interface between the anode and the electrolyte. These optimization measures significantly improve the lifespan and reliability of the cell. The outcomes of this study demonstrate the practical feasibility of using hydrazine hydrate as a fuel in PCFCs. • Explored the application of hydrazine hydrate as a novel fuel in PCFCs. • Boosted hydrazine hydrate mass transfer with dendritic anode. • Studied hydrazine hydrate's effect on PCFCs' temperature and vapor management. • Enhanced hydrazine hydrate conversion with Pt–Al in dendritic anodes. [ABSTRACT FROM AUTHOR]

• Methanol fuel's advantages over hydrogen include its liquid state storage at ambient conditions, higher energy density, compatibility with existing fuel infrastructure, and comparatively lower production and conversion costs. Consequently, this study explores the potential of methanol as an alternative fuel to hydrogen in fuel cells. • An anode with a novel branched porous design has been crafted to enable the integration of efficient reforming catalysts, facilitating methanol decomposition and conversion at the anode, while also improving carbon poisoning resistance. • A strategically selected Ru-GDC fiber catalyst has been incorporated within the built-in cracking reformer, paired with a porous anode, to elevate fuel cell performance, fuel utilization efficiency, and cell stability. Methanol, as an indirect hydrogen storage medium rich in hydrogen, is considered an ideal fuel for fuel cells. Oxygen-ion conducting solid oxide fuel cells (O-SOFCs) powered by methanol are renowned for their high energy conversion efficiency and minimal environmental impact, offering broad application prospects. However, challenges to their stable power generation arise from the rate of hydrogen production through methanol decomposition at the anode and carbon deposition on nickel-based anodes. To address these issues, this study explores the optimal operating temperature and concentration of methanol as an O-SOFCs fuel, while also developing a novel cell design. In this design, an in-situ cracking reactor for internal conversion of methanol is constructed by loading Ru-GDC high-efficiency nanofiber catalysts on dendritic anode microchannels, significantly enhancing the cell's power generation performance. Experimental results demonstrate that at 800 °C and a 30 % methanol concentration, the system increases the maximum power density (MPD) from 0.622 W cm−2 to 0.893 W cm−2, exhibiting a 43.57 % increase in power density and a 13.03 % improvement in methanol utilization. Additionally, the system effectively mitigates carbon deposition and nickel anode deactivation, thereby enhancing the cell's operational stability. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and first-principles calculations of Ti 3 SiC 2 /Al 2 O 3 ceramics were reported. X-ray diffraction measurements showed that the composite ceramics were highly pure. Scanning electron microscopy and transmission electron microscopy were used to characterize the interface information for Ti 3 SiC 2 and Al 2 O 3 crystals. Surface energies and interface properties were calculated using the first-principles method. The results suggested that Ti 3 SiC 2 with Ti terminations and Al 2 O 3 with O terminations are more stable than other terminations crystals. Thus powerful attraction between the coordinatively unsaturated Ti and O atoms on the Ti 3 SiC 2 ∥Al 2 O 3 interface would result in higher work of adhesion (Wad) and shorter boundary distance, demonstrating the intercrystalline strengthening of Ti 3 SiC 2 /Al 2 O 3 composite ceramics. [ABSTRACT FROM AUTHOR]

Multi-component solid solution composite ceramics (Ti 0.9 Nb 0.03 Ta 0.03 W 0.03) 3 SiC 2 /Al 2 O 3 were fabricated with a high yield by doping NbC, TaC and WC powders via in-suit synthesis, which demonstrated that using metallic carbide as dopants is more efficient than using metal powders to synthesize the desired products. The optimized hardness and flexural strength of (Ti 0.9 Nb 0.03 Ta 0.03 W 0.03) 3 SiC 2 /Al 2 O 3 were measured to be 16.6 ± 0.5 GPa and 695 ± 29 MPa, respectively, which represents significant improvements compared to Ti 3 SiC 2 /Al 2 O 3 composite ceramics. To deeply understand the influence of dopants, the crystal structure of multi-component solid solutions and interface modeling of composite ceramics were built and evaluated by first-principle calculations. The results indicated that the strengthening effects derived from both intragranular improvements in solid solutions and intergranular enhancement of crystal interfaces. • (Ti 0.9 Nb 0.03 Ta 0.03 W 0.03) 3 SiC 2 /Al 2 O 3 composite ceramics are synthesized by doping metal carbide. • The multi-component solid solution modeling were constructed. • The doped elements enhance both intragranular and intergranular strength in (Ti 0.9 Nb 0.03 Ta 0.03 W 0.03) 3 SiC 2 /Al 2 O 3 composite ceramics. [ABSTRACT FROM AUTHOR]

Abstract Si 3 N 4 ceramics with constant proportion of sintering aids and different mass percentages of tetra-needle-like ZnO whisker (T-ZnO w) added were prepared by gas pressure sintering process at 1700 °C under an applied pressure of 4 MPa for 2 h. The microstructure, mechanical and antibacterial properties of Si 3 N 4 ceramics were characterized and investigated. The results indicated that T-ZnO w could be well- dispersed in the sintered ceramic matrix and grain size of Si 3 N 4 ceramics became larger with the addition of T-ZnO w. Moreover, the mechanical properties of Si 3 N 4 ceramics with T-ZnO w added were slightly lower than those of samples without T-ZnO w added for the unnoticeable negative effects of T-ZnO w. Additionally, Si 3 N 4 ceramics with T-ZnO w added possessed superior antibacterial rate against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) compared with samples without T-ZnO w added owing to generation and release of reactive oxygen and Zn2+ ions that could inhibit the growth of bacteria. [ABSTRACT FROM AUTHOR]

TiN–Ti/Al 2 O 3 composites of varying TiN content (0–20 vol%) were prepared by vacuum hot-pressing sintering at different temperatures (1400 °C and 1500 °C) to investigate how TiN affected the mechanical properties and electrical conductivity of the composites. Sintered samples with added TiN exhibited better performance than those without it. The sample with 20 vol% TiN sintered 1500 °C had an optimal relative density of 99.49, Vickers hardness of 14.94 GPa, flexural strength of 321.55 MPa, and electrical resistivity of 1474.7 μΩ cm. However, this increased temperature did not improve the best sample resistivity of 930.3 μΩ cm, which was obtained at 1400 °C. Form SEM images and XRD patterns, the positive effect of TiN on composite mechanical properties may be ascribed to its good performance of high hardness and strength, a decrease of the brittle intermetallic phase, the form of AlTi 3 N, and the impact of the fine-grained strength of the TiN phase. [ABSTRACT FROM AUTHOR]

Al/B 4 C composites with various volume contents of B 4 C (5%, 10%, 15%, 20%, and 25%) reinforcing the Al matrix, have been fabricated by vacuum hot press sintering at 680 °C, with a soaking time of 90 min and external pressure of 30 MPa. Mechanical properties, phase composition, and microstructure of the Al/B 4 C composites are discussed to reveal the physical properties of the composites. Field emission transmission electron microscopy and selected area electron diffraction have been employed to verify the interior structure and crystal growth direction, respectively. The Vickers hardness, fracture strength, tensile strength, and maximum force attained the optimal values of 108.45 ± 4.02 HV, 585.70 ± 23.26 MPa, 196.18 ± 2.48 MPa, and 4.44 ± 0.17 kN, respectively, for 25 vol% B 4 C/Al composites. The static compression strength increased before the 15 vol% B 4 C addition and then decreased, acquiring the highest value of 292.15 ± 2.09 MPa for 15 vol% B 4 C/Al composites. In general, the relative density and ductility of these composites consistently increased, with an increase in the volume content of Al, achieving a maximum of 99.22% and 54.63 ± 7.34%, respectively, for 5 vol% B 4 C/Al composites. [ABSTRACT FROM AUTHOR]

Graphene has been successfully fabricated by a novel method, using graphite powder and NMP (N-Methyl Pyrrolidone) as the raw materials based on the principles of liquidoid exfoliation and mechanical milling. SEM, TEM and Raman spectrum were utilized to characterize the morphology of the homemade graphene, illustrating the few defects and rare layers were endowed in this study. Afterwards, the homemade and commercial graphene were doped into Al 2 O 3 powder with the mass ratio of 0%, 1%, 2%, and 3% to reinforce the mechanical properties of the matrix. The composites were processed at 1600 °C, pressure of 30 MPa and soaking time of 1 h by vacuum hot pressing. The test results illustrated the bending strength and fracture toughness tended to be intensive at first and subdued afterwards, achieving the optimal performance of 625.4±18.2 MPa and 6.07±0.22 MPa m 1/2 at 2 wt% prepared graphene additive, and the commercial grapheme owned the best heighten effect in 3 wt% graphene/Al 2 O 3 composites. Compared to the blank Al 2 O 3 sintered samples, the graphene/Al 2 O 3 specimens (both prepared and commercial additive) behaved evident increase in mechanical properties, even upon 30% enhanced in fracture toughness and bending strength generally by the prepared grapheme. Moreover, the prepared graphene had better improvement effect than commercial graphene in enhancing mechanical properties of Al 2 O 3 ceramic. [ABSTRACT FROM AUTHOR]

The composites with CeO 2 addition varied from 0 vol.% to 5 vol.% were sintered at 1420 °C under an applied pressure of 30 MPa for 60 min. The results of mechanical tests showed that CeO 2 is useful for improving mechanical properties, but excessive addition (>3 vol.%) will deteriorate the composite; The highest values of relative density, Vickers harness, flexural strength and fracture toughness were recorded for the sample with 3 vol.% addition, which produced 97.6%, 15.7 MPa, 406.5 MPa and 6.36 MPa m 1/2 . It can been seen from the SEM images and EDX analysis that the abnormal rod-like crystals appeared among Al 2 O 3 grains. These unusual grains were confirmed as the solid solution of Ce–Al–O. The XRD revealed the crystalline phase and the transformation of grain growth trend of Ti/Al 2 O 3 cermet composite. Moreover, the relationship of microstructure evolution and mechanical properties for the composite were illustrated. [ABSTRACT FROM AUTHOR]

The isothermal oxidation resistance of Al 2 O 3 –TiC composites with 3 wt.% and 5 wt.% cobalt is investigated at 800–1000 °C in air for 25 h. The oxidation resistance of Al 2 O 3 –TiC composites with 5 wt.% cobalt is better than that of ones with 3 wt.% cobalt. The general rate constant k and oxidation exponent n depend on the cobalt content and oxidation temperature. The oxidation kinetics of Al 2 O 3 –TiC composites with 3 wt.% and 5 wt.% cobalt both followed a rate that is slightly faster than the parabolic-rate law at 800–1000 °C. The activation energy of the Al 2 O 3 –TiC composites with 5 wt.% cobalt is larger than that of ones with 3 wt.% cobalt at 800–1000 °C. [ABSTRACT FROM AUTHOR]

The ablation property of a three-dimensional 4-directional Cf/ZrC–SiC composite was determined by using a plasma wind tunnel facility. The composite exhibited excellent configurational stability with surface temperature of 2400K for 600s. After ablation, the composite showed a mass loss rate of 7.0×10−4 g/s and a linear recession rate of 9.0×10−4 mm/s. The viscous binary glass mixture of ZrO2 and SiO2 on the surface of the composite mainly contributed to the improvement in the ablation property. After ablation, the composite showed three different zones, namely, the ablation center region, ablation transition region, and unablation region, because of the temperature and pressure gradients. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional needled Cf/ZrC–SiC composites were successfully fabricated via in-situ reaction using zirconium powders, silicon powders, and phenolic resin as raw materials. ZrC–SiC matrix is formed through the crystallization at relatively low temperature. The microstructures and mechanical properties of the composites were studied using X-ray diffraction, scanning electron microscopy, and three-point bending test. Their high-temperature oxidation resistance and anti-ablation properties were evaluated using a muffle furnace and the plasma wind tunnel test. The experimental results show that the composites have good mechanical and excellent ablative properties. [Copyright &y& Elsevier]

Highlights: [•] Three-dimensional 4-directional Cf/ZrC–SiC composites fabricated by polymer infiltration and pyrolysis. [•] The microstructure and mechanical properties of the composites were studied. [•] High-temperature oxidation resistance and anti-ablation properties were evaluated. [•] Results show the composites have good mechanical and excellent ablative properties. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional needled Cf/ZrB2–ZrC–SiC composites were successfully fabricated via polymer infiltration and pyrolysis (PIP) using ZrB2 powder, polycarbosilane, and ZrC precursor as raw materials. The microstructures and mechanical properties of the composites were studied using X-ray diffraction, scanning electron microscopy and the three-point bending test. Their high-temperature oxidation resistance and anti-ablation properties were evaluated using a muffle furnace and plasma wind tunnel test. Results show that the composites have good mechanical and excellent ablative properties. [Copyright &y& Elsevier]

Abstract: Three-dimensional needled Cf/ZrC–SiC composites were successfully fabricated by the vapor silicon infiltration process. The bulk density, open porosity, and flexural strength of the composite with PyC/SiC interphases were 2.25g/cm3, 6%, and 301MPa, respectively. All composites exhibited a non-brittle failure behavior due to propagation and deflection of cracks, as well as fracture and pullout of fibers. The mass loss and linear recession rate of the three-dimensional needled Cf/ZrC–SiC composite exposed to oxyacetylene torch were 0.013g/s and 0.004mm/s, respectively. The formation of ZrSiO4 melt on the surface of the composite contributed mainly to the excellent high-temperature property of the composite. [Copyright &y& Elsevier]