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This letter details the design and validation of a legged terrestrial locomotion system integrated onto a hummingbird-scale flapping wing robot. Two pairs of legs powered by the flight actuators allow forward, reverse, and steering motions while on the ground. Through controlled sinusoidal drive signals, this mechanically simple locomotion system allows the robot to crawl through small gaps about half the height of spaces through which it could fly thanks to the robot's transition from a vertical to horizontal orientation when crawling. On smooth hard surfaces, the robot is capable of crawling at 100 mm/s. Gaining a terrestrial mode of movement not only expands its locomotion strategies and environmental adaptability, but it also improves the endurance of the robot in particular missions due to the low power consumption. A unique design principle is that the flight components of the robot are unchanged from the original aerial robot design, and terrestrial locomotion is realized with the addition of two capstan-interlinked pairs of legs constructed from 3D printed plastic and carbon fiber rods. Based on the dual use of the flight actuators, the robot experimentally demonstrated sustained hybrid aerial-terrestrial locomotion as well as smooth crawl-to-fly transition.

Generating oxygen vacancies is an effective way to improve the lithium-ion storage performance of V2O5. However, the mechanism has not been theoretically investigated. In this study, first-principle calculations were performed to study the effect of oxygen vacancy on electrochemical properties of γ-V2O5 as cathode material for lithium-ion batteries. γ-V2O5 with oxygen vacancy mole fraction of 1.67% shows an open circuit voltage about 0.1 V lower than that of the perfect γ-V2O5. Oxygen vacancies generates gap states, which is beneficial to the electronic conductivity of γ-V2O5 and γ-LiV2O5. In addition, the activation energies for lithium-ion diffusion along [010] in both γ-V2O5 and γ-LiV2O5 are increased by oxygen vacancy, which might lead to the decrease of diffusion coefficient. Our results will provide guidance for further improving the lithium-ion storage performance of γ-V2O5.

Insects wings are subject to wear and tear from collisions and environmental disturbances during flight. They can tolerate both symmetrical and asymmetrical wing damages while maintaining flight capability to some extent. Drawing inspiration from nature's adaptation capabilities, we investigated the consequences of wing damage on a flapping wing micro air vehicle by quantifying the changes in wing kinematics, lift generation, control torque offset, and aerodynamic damping variations in flight tests with intact and damaged wings. For the proposed vehicle, the wing damage affected the lift generation significantly. Compared to the intact wings, the damaged ones result in increased stroke angle amplitude in order to compensate for lift loss and torque imbalance, which causes an increase in power consumption accordingly. Furthermore, asymmetric damages usually require a larger amount of additional control effort for flight stabilization compared to symmetric cases. In addition, aerodynamic damping varies as the wing areas change. All these aspects pose challenges in flight control. An adaptive controller is proposed to cope with the wing damage induced detrimental effects on flight capacity. Flight tests were conducted to validate the control performance. As a result, the robot can effectively overcome such challenges even in the case of a maximum unilateral lift loss of up to $\approx$ 22%. Such a result matches the performance of hovering hawkmoths, which can handle torque asymmetry up to 22.3 $\pm$ 7.8%. To the best of our knowledge, this is the first demonstration of FWMAVs to handle significant wing asymmetry in hover flight.

Samples in Si–Al-R-O-N (R = Y, Gd, Yb) systems were prepared by solid-state reactions using R2O3, Al2O3, SiO2 and Si3N4 powders as starting materials. X-ray diffraction was done to investigate RAM-J(R) solid solutions [RAM = R4Al2O9, J(R) = R4Si2N2O7] formation and their equilibrium with RSO (R4Si2O10). Phase relations between RAM, J(R) and RSO at 1700 °C were summarized in a phase diagram. It was determined that a limited solid solution of RAM and RSO could be formed along RAM-RSO tie-line, while RAM and J(R) form a continuous solid solution along RAM-J(R) tie-line. In RAM-J(R)-RSO ternary systems, the RAM-J(R) tie-lines were extended towards the RSO corner to form a continuous solid solution area of JRAMss (R = Y, Gd, Yb). The established phase relations in the Si–Al-R-O-N (R = Y, Gd, Yb) systems may facilitate compositional selections for developing JRAMss as monolithic ceramics or for SiC/Si3N4 based composites using the solid-solutions as a second refractory phase.

In previous works, it was found hard to synthesize “phase pure” ζ-Ta4C3-z at relatively low temperatures even by prolonged heating, though ζ-Ta4C3-z was believed stable till decomposition at ~2130°C. When the samples were subjected to TEM, vast richness of locally disordered structures in close relation with stacking of the close-pacted Ta-atom planes was observed. Although kinetic factors including diffusion of C atoms/vacancies and re-stacking of the Ta-atom planes explain the densely disordered structures, the richness of local disorders is a scenario that shows cohabitant of the cubic, rhombohedral, and hexagonal structures in a single grain, i.e. formation of a “hybrid grain” consisted of the three symmetries, indicating a transitional or intermediate stage before complete formation of the final phase of rhombohedral ζ-Ta4C3-z. This time tantalum carbide ceramics TaCx with C:Ta atomic ratios x = 0.66 and 0.7 were prepared by reaction hot pressing of TaC and Ta powder mixtures. 5–30 mol% Cu/Ag additives and heat treatments were used to reproduce “hybrid grains” to facilitate further TEM and HRTEM observations on the disordered hybrid grains to argue for the transitional/intermediate stage. The cohabitant cubic, rhombohedral, and hexagonal structures in single grains may also help explain the difficulty in identification of the various phases by XRD in the transitional/intermediate stage of ζ-Ta4C3-z reaction. Microstructural evolution and fracture toughness of the composites were also investigated.

TaC ceramics with 0-0.237 wt% B addition were prepared by hot pressing. The effect of B addition on the phase constitution, interfacial chemistry/bonding and mechanical properties of the TaC ceramics were investigated. Upon B addition, the elimination of O impurity and segregation of B at grain boundaries were evidenced, accompanied by an increase in bonding strength of the TaC grains, to result in a fracture mode change from intergranular to transgranular and a reduced fracture toughness. Addition of excessive B resulted in the formation of TaB2 and C within TaC ceramics. Further, TaC-TaB2-SiC composites were prepared by Si addition. Coherent bonding between TaB2 and TaC was preserved in the TaC-TaB2-SiC composites, and residual stresses due to thermal expansion mismatch of the different phases increased flexural strength and fracture toughness of the composites.

Relation extraction is a popular topic in natural language processing. This survey will introduce several major relation extraction methods, from feature and kernel-based to neural networks. We will discuss the basic idea and the performance of these methods and hope that this article will give readers a general concept of relation extraction.

With the advance of technology, radical innovation plays an increasing essential role in gaining competitive advantages by leveraging the brandy new technologies such as internet of things (IoT) in product or services innovations. Although its importance is widely recognized, the mechanism of radical innovation is still poorly understood due to high level of uncertainty about its prospects. This paper aims to evaluate the radicality of design ideas from their technological changes that are the obvious and measurable characteristics of radical innovation at very beginning of their developments. To do so, a radicality evaluation method is formulated after a systematic review of studies on radical innovation and integrating of ideas evaluations methods in relevant domains. Afterwards, two radicality computing formulas are regressed through a statistical analysis of known design cases. The feasibility of the formulas is verified by a serial of recognized radical innovations followed by a case study that is related to additive manufacturing. Its application in new product development is demonstrated by a design project of adhering devices. The proposed method has potential to fertilize studies on radical innovation and knowledge-based innovation.

TaC ceramics with 0.03–0.60 wt% of boron additions were prepared by hot pressing at 2100 °C for 1 h under a pressure of 40 MPa. Effects of boron content on densification, phase composition, microstructure, mechanical properties and oxidation resistance of the TaC ceramics were investigated. When the boron content was 0.12 wt% and above, full density was obtained due to reactions between boron and oxygen impurity at presence of TaC. Minor phases of TaB2 and C were formed in the 0.24 and 0.60 wt% B compositions after gas-out of the oxygen impurity. Microstructure of the TaC ceramics was refined with increasing in boron content. The TaC ceramic with 0.24 wt% of boron showed the best mechanical properties with a Vickers hardness, flexural strength and fracture toughness of 17.7 GPa, 534 MPa and 4.6 MPa m1/2, respectively. When more boron was added, interfacial bonding of the TaC grains was strengthened causing a decrease in fracture toughness. Oxidation resistance of the TaC ceramics increased with boron content. Particularly, the 0.60 wt% B composition showed a weight gain of 0.0018 g/cm2 after oxidization at 800 °C in air for 3 h.

Tantalum carbide ceramics with an overall composition of TaC 0.6 were prepared by hot pressing at 1700 °C for 1 h under 30 MPa pressure with fcc TaC and bcc Ta powder as starting materials. Effects of adding 0–30 mol% Cu on densification, phase formation, microstructural evolution, mechanical properties and electrical conductivity of the obtained composite ceramics were investigated. Full density could be reached at 20 mol% Cu addition and above. Reactions between TaC and Ta resulted in the final phases of hexagonal Ta 2 C and rhombohedral ζ-Ta 4 C 3-x . Plate-shaped ζ laminate grew in both TaC and Ta 2 C and consequently had their sizes confined by the parental grains. Addition of 20–30 mol% Cu could significantly grow the intermediate Ta 2 C grains, hence controlling length of the ζ laminates precipitated in them to form bimodal microstructures consisting of large grains. The 20 mol% Cu composition had a better flexural strength (706 ± 46 MPa) and fracture toughness (9.2 ± 1.7 MPa m 1/2 ). Electrical resistivity at room temperature of the composites decreased with Cu content from 1.03 μΩ m at 0 mol% addition to 0.12 μΩ m at 30 mol% Cu.

The electrochemical properties of VPO4O as a cathode for Mg batteries were studied by performing first principles calculations. Mg insertion features a plateau at about 2.8 V up to Mg0.5VPO4O and then another plateau at around 2.2 V up to MgVPO4O, with a theoretical capacity of about 154 mA h g−1 and 144 mA h g−1, respectively. MgVPO4O is found to be dynamically stable with the absence of negative frequencies in the phonon density of states. The insertion of one Mg reduced two VO6 units instead of reducing only one VO6 unit. In addition, MgVPO4O shows an energy barrier of about 0.58 eV for Mg-ion vacancy migration along the [111] direction, which is comparable to that of many other cathode materials. Our results indicated that MgVPO4O has the potential to be a promising candidate as a cathode material for Mg batteries.

TaC-Al2O3 composites were prepared by hot pressing. Influence of Al2O3 content ranging from 10 to 40 vol. % on densification, phase composition, microstructure, mechanical properties and oxidation behavior of the TaC-Al2O3 composites was investigated. With 30 and 40 vol. % Al2O3 addition a closed porosity was achieved. The Al2O3 particles were uniformly distributed among TaC grains retarding grain growth and resulting in refined microstructures with grains below 2 μm in size. The most densified composite with 40 vol. % Al2O3 addition exhibited good mechanical properties with a Vickers’ hardness of 17.8 GPa, a flexural strength of 485 MPa and a fracture toughness of 5.4 MPa·m1/2. After holding at 700°C for 3 h in air, the dense 30 and 40 vol. % Al2O3 compositions showed hardly noticeable and mainly surface oxidation, whereas less densified TaC-Al2O3 composites with 10 and 20 vol. % Al2O3 content and with open porosity were disintegrated to powders.

TaCx (x = 0.5, 0.55, 0.6, 0.7) ceramics with 20 mol% Fe, Co or Ni addition were prepared by hot pressing TaC and Ta powder mixtures at 1800 °C. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, X-ray energy dispersive spectroscopy and selected area electron diffraction were used to investigate the constituent phases and microstructures of the composites. Vickers hardness, flexural strength and fracture toughness were measured. Intermetallic compounds Fe7Ta3, Co2Ta and Ni3Ta were formed due to reactions of Fe, Co and Ni with Ta. The remaining TaC and Ta reacted to form hexagonal Ta2C, rhombohedral ζ-Ta4C3-z or cubic TaCy depending on the overall C:Ta ratios. The microstructure of the TaC0.5–20 mol% Fe, Co, Ni compositions (where C:Ta = 0.5) were composed of intermetallics and fine anisotropic Ta2C and ζ-Ta4C3-z grains. As the C:Ta ratio increased to 0.55–0.7, the ζ-Ta4C3-z and TaCy grains were enlarged in size and equiaxed in the TaC0.55-, TaC0.6-, and TaC0.7–20 mol% Fe, Co, Ni compositions. Addition of Ni instead of Fe and Co benefitted to refine microstructures of the composites. The TaC0.5–20 mol% Fe, Co, Ni compositions had good flexural strength (580-650 MPa) and fracture toughness (9.3–9.5 MPa·m1/2) due to growth of fine lamellar grains, despite the high Ta2C content.

Surfactants possess the ability to reduce surface tension at low concentrations, resulting in emulsification, foaming, wetting, and solubilizing. As a versatile industrial material, surfactants can be widely used as additives in the industrial field as different as textile, metal processing, mineral processing, new materials, industrial cleaning, construction, and pharmaceuticals. The most extensive application of surfactants perhaps is in the household and cosmetic industries, such as laundry detergents, dishwashing detergents, facial and body cleansers, and preparation of emulsions and creams. However, the extensive use of detergents, cleaners, and cleansers on skin may cause itching, redness, and dryness termed as surfactant-induced irritation, which is at least, partially due to surfactant penetration into skin. To understand how surfactants penetrate into skin, this review summarizes the penetration models proposed by researchers in the past two decades, including the surfactant monomer penetration model, the surfactant micelle and submicelle penetration model, and the recently proposed surfactant charge density and penetration correlation model that demonstrates the correlation between the surfactant charge density and skin penetration.

Tantalum carbide ceramics containing 0.25–3.40 wt% Al as densifying aid were prepared by hot pressing at 1900 °C under 30 MPa for 60 min. Effects of Al addition on densification, phase composition, microstructure and mechanical properties of the TaC-Al ceramics were investigated. Al was an effective oxygen getter which reacted with volatile oxygen impurities such as Ta2O5 on surfaces of TaC particles to form non-volatile minor phase of Al2O3, thus slowed TaC grain growth via inhibiting the non-densifying matter transport by evaporation-condensation. When Al content was larger than the value that was needed for complete impurity reaction of 10Al + 3Ta2O5 = 6Ta + 5Al2O3, presence of Al liquid at high temperatures improved densification of the TaC-Al ceramics because Al liquid spread along the grain boundaries and wet the TaC grains. The TaC ceramic with 0.75, 1.50 and 3.40 wt% Al addition reached a relative density value of 91.6, 97.5 and 100%, respectively, with a similar average grain size of 3.5–4.8 μm. Fe impurity dissolved in Al and formed Al6Fe; slight reaction of Al with TaC formed a thin layer of Ta-Al-C compound around TaC grains. The TaC ceramic with 1.50–3.40 wt% Al additions showed good Vickers hardness, Young's modulus and flexural strength in the range of 12.4–13.2 GPa, 413–479 GPa and 532–673 MPa, respectively. Increase in oxidation resistance of TaC ceramics was observed at 600 °C in air with a few percentages of Al additions.

Subsolidus relations and liquidus boundaries in the Ta 2 O 3 -WO 3 -SiO 2 system at temperatures ranging from 1200 °C to 1500 °C were investigated. Phase diagrams were constructed. Compounds with stoichiometries of Ta 22 W 4 O 67 , Ta 2 WO 8 and Ta 16 W 18 O 94 formed in the Ta 2 O 5 -WO 3 subsystem at 1200 °C. SiO 2 was compatible with each of the compounds. A solid solution with a formula of (1 − x) Ta 2 O 5 ·xWO 3 formed on the Ta 2 O 5 -WO 3 line in the compositional range of Ta 2 O 5 :WO 3 > 11:4. SiO 2 had a maximum solubility of 25% SiO 2 in the solid solution. Liquid phase first appeared in the WO 3 -rich corner at 1300 °C. As the temperature was increased up to 1500 °C, the liquidus area boundary gradually expanded towards the SiO 2 - and the Ta 2 O 5 -rich corners.

Stoichiometric Tantalum carbide (TaC) ceramics were prepared by reaction spark plasma sintering using 0.333–2.50 mol% Si 3 N 4 as sintering aid. Effects of the Si 3 N 4 addition on densification, microstructure and mechanical properties of the TaC ceramics were investigated. Si 3 N 4 reacted with TaC and tantalum oxides such as Ta 2 O 5 to form a small concentration of tantalum silicides, SiC and SiO 2 , with significant decrease in oxygen content in the consolidated TaC ceramics. Dense TaC ceramics having relative densities >97% could be obtained at 0.667% Si 3 N 4 addition and above. Average grain size in the consolidated TaC ceramics decreased from 11 µm at 0.333 mol% Si 3 N 4 to 4 µm at 2.50 mol% Si 3 N 4 addition. The Young's modulus, Vickers hardness and flexural strength at room temperature of the TaC ceramic with 2.50 mol% Si 3 N 4 addition was 508 GPa, 15.5 GPa and 605 MPa, respectively. A slight decrease in bending strength was observed at 1200 °C due to oxidation of the samples.

Metallic Si as sintering aid was effective in densifying tantalum carbide ceramic (TaC) by spark plasma sintering (SPS) at 1700°C. Full density was reached at 5.0 mol% Si addition (equivalent to 1.088% Si in weight) and above. Enhanced densification of TaC ceramic with Si was associated with decrease in oxygen content from ~0.24 wt% in TaC powder to ~0.03 wt% in consolidated specimen. Rest of the oxygen species was collected at multigrain conjunctions to form SiO2-based liquid at high temperatures. Upon cooling, Ta, Si, O, and C dissolving in the liquid precipitated minor phases of TaSix and SiC of low concentrations. Microstructure of TaC ceramics was refined by the Si addition, with average grain size decreasing from 11±8 μm at 1.0 mol% Si to 3±2 μm at 7.5 mol% Si addition. Ta solute in SiC and Si solute in TaC were evidenced. TaC ceramic containing 7.5 mol% Si had a relatively good flexural strength and fracture toughness of 646±51 MPa and 5.0 MPa·m1/2, respectively.

The present work determined the phase relations in Si-Al-M-O-C (M = Zr, Mg) systems, involving SiC-Al2O3-ZrO2, SiC-Al2O3-MgO, SiC-SiO2-Al2O3-ZrO2 and SiC-SiO2-Al2O3-MgO systems by XRD phase analyses of the solid-state reacted samples from powder mixtures of SiC, Al2O3, ZrO2, MgO and SiO2. Within these systems, SiC was respectively compatible with other neighboring phases, forming a set of four-phase compatibility tetrahedrons. The subsolidus phase diagrams of the SiC-SiO2-Al2O3-ZrO2 and SiC-SiO2-Al2O3-MgO quaternary systems were presented.

The electrochemical properties of VPO4O as a cathode for Mg batteries were studied by performing first principles calculations. Mg insertion features a plateau at about 2.8 V up to Mg0.5VPO4O and then another plateau at around 2.2 V up to MgVPO4O, with a theoretical capacity of about 154 mA h g-1 and 144 mA h g-1, respectively. MgVPO4O is found to be dynamically stable with the absence of negative frequencies in the phonon density of states. The insertion of one Mg reduced two VO6 units instead of reducing only one VO6 unit. In addition, MgVPO4O shows an energy barrier of about 0.58 eV for Mg-ion vacancy migration along the [111] direction, which is comparable to that of many other cathode materials. Our results indicated that MgVPO4O has the potential to be a promising candidate as a cathode material for Mg batteries.

TaCx (x = 0.5, 0.55, 0.6 and 0.7) ceramics with 20 mol% Al addition were prepared by hot pressing TaC, Ta and Al powder mixtures. Effects of the overall C:Ta ratios and the Al addition on constituent phases, microstructures and mechanical properties of the consolidated materials were examined. Results showed that O impurity contained in the starting powders was collected in form of Al2O3 due to strong affinity of O with Al. The TaCx-Al composites were easy to densify due to presence of molten Al at its melting point (Tm = 660 °C) and a transient Al–Ta eutectic liquid at higher temperatures. After densification, the metallic liquids were eliminated ultimately by formation of refractory Ta4AlC3 via reaction of Al, Ta and TaC. Reactions between the remnant Ta and TaC after Ta4AlC3 formation resulted in ζ-Ta4C3-z or h-Ta2C depending on the initial C:Ta ratio. The Ta4AlC3 compound was compatible with the tantalum carbides. Microstructures of the TaCx-Al (x = 0.5–0.7) composites were consisted of ζ-Ta4C3-z and Ta4AlC3 fine lamellar grains to benefit the mechanical properties of the composites. The TaC0.7–20mol% Al composition had satisfying mechanical properties (flexural strength 613 ± 28 MPa and fracture toughness 11.2 ± 0.8 MPa m1/2). TG-DSC evidenced an increase in oxidation resistance of the TaCx ceramics by the addition of 20 mol% Al.

ZrB2-20%volSiC composites were hot pressed with ZrB2 and SiC powders and the effect of temperature and friction couples (WC or Al2O3) on the tribological properties of these composites was investigated. The results show that the coefficient of friction (CoF) of ZrB2–SiC composites coupled with WC or Al2O3 was almost constant with respect to temperature (0.5–0.6). Meanwhile, their wear rates (WRs) were of the order of 10−4 mm3 N−1 m−1. Either discontinuous (with WC) or continuous (with Al2O3) tribo-layers were found to have been formed on the worn surfaces of the composites and these tribo-layers did not exhibit any lubricious or anti-wear effects. At temperatures of 25–400 °C, the wear mechanism of the composites coupled with WC and Al2O3 included abrasion, tribo-oxidation, and adhesion. At higher temperatures (600–800 °C), the wear mechanism of both tribo-pairs included tribo-oxidation and adhesion.

(Ti,Ta)(B,C)–(Ta,Ti)C composites were synthesized by reactive hot pressing using commercial TaB2 and TiC powders as starting materials. The reaction process and effects of TiC contents in the starting batches on the microstructure and mechanical properties of the resultant composites were reported. The microstructure of the composites was refined due to reaction and solid solution coupling effect. A core-rim structure was observed in the (Ti,Ta)(B,C) grains. Vickers hardness, flexural strength and fracture toughness of the composites increased with increasing the TiC content. The TaB2–70 mol.% TiC sample (starting batch composition) prepared by hot pressing at 2000 °C for 1 h had a super high Vickers hardness value of 30.5 GPa (indented under 9.8 N, 15 s) approaching that of B4C-based composites. Good flexural strength (714 MPa) and fracture toughness (5.4 MPa m1/2) were also found.

TaC ceramics were prepared by hot pressing at 1900 °C for 30 min under 30 MPa mechanical pressure. Effects of the addition of 20 mol% ZrC or 5–20 mol% ZrC plus 5 mol% Cu as sintering aids on densification, phase composition, microstructure and mechanical properties of the consolidated materials were investigated. The results showed the pure TaC had a relative density of 86%of the theoretical value. Densities >97% theoretical were reached in the materials when the sintering aids were used. ZrC and TaC reacted to form solid solutions. The grain average size decreased from 18 µm in the pure TaC to 6 µm at 20 mol% addition. Addition of 5 mol% Cu further refined the microstructures. The 20 mol% ZrC+5 mol% Cu and the 10 mol% ZrC+5 mol% Cu composition had good flexural strength of 608 MPa and fracture toughness of 5.4 MPa m 1/2 , respectively.

During investigation of the phase relations in the SiC–ZrO 2 –CaO ternary system, it was revealed that ZrO 2 reacted with SiC and CaO to form ZrC and calcium silicate via a series of solid-state reactions. Because these reactions may provide a new route to reaction-sintering of ZrC ceramics, ZrC/SiC and ZrC/salt composites, the formation process of the ZrC phase was analyzed. Subsolidus phase diagram of the related SiC–SiO 2 –ZrC–ZrO 2 –CaO (Si–Zr–Ca–O–C) quinary system at 1400 °C was presented.

Present work determined the phase relations of the SiC-Al2O3-Nd2O3, SiC-Nd2O3-SiO2 and SiC-Al2O3-Nd2O3-SiO2 subsystems in the Si-Al-Nd-O-C system by XRD phase analysis of samples which were prepared via the solid-state reaction using SiC, Al2O3, Nd2O3 and SiO2 as the starting materials. The phase diagrams of the subsystems were presented. SiC was compatible with each of the two Nd-aluminates of NdAlO3 and NdAl11O18 in the system. Nd4Al2O9 was stable at temperatures >1720 °C and compatible with SiC. Six four-phase coexistent regions were established in the quaternary SiC-Al2O3-Nd2O3-SiO2 system at 1250 °C. Possible effects of the SiO2 on sintering of the SiC ceramics were discussed.

Phase formation sequence of the yttrium aluminates in the Y2O3-Al2O3-SiC ternary system as temperature increases were investigated via x-ray diffraction (XRD). Results showed that YAM (monoclinic), YAP (perovskite) and YAG (garnet) were the yttrium aluminates presented in the solid-state reacted samples at a fixed Al2O3:SiC ratio of 1:1. Formation of the yttrium aluminates depended on the temperature. The YAM, YAP and YAG started to form below 1150 °C, at 1300 °C, and at 1450 °C, respectively. Accordingly, two behavior phase diagrams of the Y2O3-Al2O3-SiC ternary system were recognized, one is in the temperature range of 1150-1300 °C and the other is in 1300-1450 °C, respectively. Thereafter, the phase equilibrium was reached in the temperature range of 1450-1700 °C. Effects of SiC on the phase formation processes in the ternary system were discussed.

Gradient porous and homogeneous porous β-SiAlON ( Z = 2) ceramics were successfully fabricated through the unidirectional freezing of camphene-based suspensions at 0 °C and −196 °C, respectively. The dielectric constant of the porous β-SiAlON ceramics was investigated as a function of the pore shape and porosity. The dielectric constant decreased with increasing porosity, and the gradient porous β-SiAlON ceramics with channel and dendritic pores exhibited lower dielectric constants than homogeneous samples with irregular pores. The dielectric constants of the gradient porous β-SiAlON ceramics were found to be in good agreement with the prediction of the modified cubes model. The dielectric constant of the porous β-SiAlON ceramics was associated not only with porosity and pore shape, but also with pore anisotropy. The value of dielectric loss was not sensitive to porosity. These results have practical value for fabricating and optimizing porous ceramics on specific applications.

TaC0.6-Cu composites were fabricated by hot pressing of TaC, Ta and Cu powder mixtures. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, scanning-transmission microscopy, X-ray energy-dispersive spectroscopy, and selected area electron diffraction were used to investigate formation process and growth behavior of the ζ-Ta4C3-x lamellae. Cu addition did not change the reaction sequence of TaC + Ta → Ta2C + TaCy → ζ-Ta4C3-x to form the targeted ζ-Ta4C3-x phase, but enhanced growth of ζ-Ta4C3-x lamellae by introducing a dissolution-reprecipitation mechanism due to presence of Cu liquid at high temperatures. ζ-Ta4C3-x could directly nucleate and grow on h-Ta2C grain surface, meanwhile C immediately reacted with Ta solutes in Cu liquid after the C atoms diffusing along the {111}TaCy stacking faults out of parental γ-TaCy grains to initiate extension of ζ-Ta4C3-x lamella outside the γ-TaCy grains, thus grew large ζ-Ta4C3-x lamellae with a uniform thickness in the microstructure of the TaC0.6-Cu composites. The TaC0.6-Cu composites with large ζ-Ta4C3-x lamellae in the microstructures showed increase in fracture toughness.