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Alumina substrates are increasingly used for high-power integrated circuits due to their high thermal conductivity, low thermal expansion coefficient, and excellent insulation properties. However, pores in the green tape from the tape casting process reduce the thermal conductivity and permittivity of the sintered ceramic substrate. Researchers have attempted to minimize ceramic porosity with chemical additives or by sintering pure alumina at temperatures above 1650 °C, but these methods often degrade thermal conductivity or quality of substrate evenness. This study proposes a low-cost casting-warm pressing process to densify pure alumina ceramic substrates using micro–nano-mixed alumina powders and sintering at relatively low temperatures. The results indicate that the relative density of the pure alumina ceramic substrate prepared at 1500 °C is 93%, a 4.4% improvement over the tape casting process. Additionally, the thermal conductivity of the alumina substrate from the casting-warm pressing process reaches 15.89 W/(m K), which is 1.4 times higher than that of the tape casting process. Microstructure analysis shows that the casting-warm pressing process with micro- and nano-multi-scale mixed alumina powders forms a novel thermal conduction enhancement mechanism. Large particles in the green tape overlap, while small particles fill the spaces between the large particles. The connected micrometer-sized particle skeletons form high thermal conduction net channels in the substrate, improving the thermal conductivity for heat transfer. [ABSTRACT FROM AUTHOR]

Multi-criteria optimization is used for developing molecular models for ethylene carbonate (EC) and propylene carbonate (PC), organic solvents commonly used in Li-ion batteries. The molecular geometry and partial charges of the solvents are obtained from quantum mechanical calculations. Using a novel optimization strategy that combines systematic variations of the Lennard-Jones parameters with a reduced units approach, the models are fitted to experimental data on the liquid density, vapor pressure, relative permittivity, and self-diffusion coefficient. Since no experimental data for the self-diffusion coefficient of pure EC were available in the literature, they are measured in this work using a gradient-based nuclear magnetic resonance technique. For all pure component properties, excellent agreement between experiment and simulation is obtained. Moreover, the predictive capabilities of the new solvent models are assessed by comparison to experimental data for the liquid density and relative permittivity of mixtures of EC and PC. In addition, molecular models for the anions P F 6 − , B F 4 − , and C l O 4 − in solutions of their lithium electrolytes in PC are developed using experimental data on the solution densities. Finally, the self-diffusion coefficients of LiPF6 in PC and in aqueous solution are predicted and compared, showing that diffusion is much slower in the organic solution due to the formation of larger solvent shells around the ions. Furthermore, an analysis of the radial distribution functions in these solutions suggests that the ions have much less impact on the structure of the solvent PC than on water. [ABSTRACT FROM AUTHOR]

Quantum memories facilitate the storage and retrieval of quantum information for on-chip and long-distance quantum communications. Thus, they play a critical role in quantum information processing and have diverse applications ranging from aerospace to medical imaging fields. Bulk acoustic wave (BAW) phonons are attractive candidates for quantum memories because of their long lifetimes and high operating frequencies. In this study, we establish a modeling approach to design hybrid magnonic high-overtone bulk acoustic wave resonator (HBAR) structures for high-density, long-lasting quantum memories, and efficient quantum transduction devices. We illustrate the approach by investigating a hybrid magnonic system, consisting of a gadolinium iron garnet (GGG) thick film and a patterned yttrium iron garnet (YIG) thin film. The BAW phonons are excited in GGG thick film via coupling with magnons in the YIG thin film. We present theoretical and numerical analyses of the diffraction-limited BAW phonon lifetimes, modeshapes, and magnon–phonon coupling strengths in YIG/GGG planar and confocal HBAR (CHBAR) structures. We utilize Fourier beam propagation and Hankel transform eigenvalue problem methods and compare the two methods. We discuss strategies to improve the phonon lifetimes in the diffraction-limited regime, since increased lifetimes have direct implications on the storage times of quantum states for quantum memory applications. We find that ultra-high cooperativities and phonon lifetimes on the order of ∼ 10 5 and ∼ 10 milliseconds, respectively, could be achieved using a CHBAR structure with 10 μ m YIG lateral area. Additionally, high integration density of on-chip memory or transduction centers is naturally desired for high-density memory or transduction devices. The proposed CHBAR structure will offer more than 100-fold improvement of integration density relative to a recently demonstrated YIG/GGG device. Our results will have direct applicability for devices operating in the cryogenic or milliKelvin regimes. For example, our study will inform the design of HBAR devices that could couple with superconducting qubits for promising quantum information platforms. [ABSTRACT FROM AUTHOR]

We examined the sweat characteristics and fluid balance of elite female field hockey players during two heat training camps. Fourteen elite female field hockey players from the Australian national squad participated in two heat training camps held ∼6 months apart, following winter- (Camp 1) and summer-based training (Camp 2). Daily waking body mass (BM) and urine specific gravity (USG) were collected, along with several markers of sweat and fluid balance across two matches per camp. There was a 19% mean reduction in estimated whole-body sweat sodium concentration from Camp 1 (45.8 ± 6.5 mmol/L) to Camp 2 (37.0 ± 5.0 mmol/L; p <.001). Waking urine specific gravity ≥ 1.020 was observed in 31% of samples, with no significant differences in mean urine specific gravity or BM between camps (p >.05), but with substantial interindividual variation. Intramatch sweat rates were high (1.2–1.8 L/hr), with greater BM losses in Camp 1 (p =.030), resulting in fewer players losing ≥2% BM in Camp 2 (0%–8%), as compared with Camp 1 (36%–43%; p =.017). Our field data suggest that elite female field hockey players experience substantial sweat losses during competition in the heat regardless of the season. In agreement with previous findings, we observed substantial interindividual variation in sweat and hydration indices, supporting the use of individualized athlete hydration strategies. [ABSTRACT FROM AUTHOR]

Purpose: We examined fluid intake, the relation between body mass (BM) loss and performance, and core temperature in young triathletes during a competition in tropical climate. Methods: Fluid intake and pre and post BM were measured in 35 adolescent athletes, and core temperature was measured in one female and one male. Results: Mean urine specific gravity (1.024 [0.007]) indicated that athletes were in suboptimal state of hydration upon waking. Race time was 73.2 (8.0) minutes. BM decreased by 0.6 (0.3) kg (P <.05). Fluid intake (528.5 [221.6] mL) replaced 47% of the fluid loss (1184.9 [256.4] mL) and was higher during run (11.5 [6.6] mL·min−1) compared to bike (7.3 [3.1] mL·min−1), P <.01. Loss in BM was ≥1.0% in 66% and ≥1.5% in 29% of the athletes. Males showed a moderate association between percentage loss in BM and finishing time (r = −.52), higher sweat rates (1.0 [0.3] L·h−1), and faster times (69.4 [7.5] min; P <.05). Core temperature rose to 40.1 °C in the female and 39.6 °C in the male. Conclusion: Young triathletes competing in a hot/humid climate became mildly to moderately dehydrated and hyperthermic even when water and sports drinks were available but did not show symptoms of heat illness. [ABSTRACT FROM AUTHOR]

First morning urine (FMU) assessment would be a practical and convenient solution for clinically acceptable detection of underhydration prior to competition/training, and for the general public. Thus, we thus sought to determine the diagnostic accuracy of FMU as a valid indicator of recent (previous 24 hr, 5 days average) hydration practices. For 5 consecutive days and one final morning, 67 healthy women (n = 38) and men (n = 29; age: 20 [1] years, body mass index: 25.9 [5.5]) completed 24-hr diet logs for total water intake (from beverages and foods, absolute and relative to body mass), 24-hr urine and FMU collection (last morning only) for osmolality (Osm), specific gravity (SG), and color (Col), and morning blood sampling for plasma osmolality and copeptin. Correlations determined significance and relationship strength among FMU and all other variables. Area under the receiver operating characteristic curves, sensitivity, specificity, and positive likelihood ratios were employed using previously reported values to indicate underhydration (total water intake < 30 ml/kg, osmolality > 500, and >800 mOsm/kg, specific gravity > 1.017, and copeptin > 6.93 pmol/L). FMU_Osm and FMU_SG were significantly correlated (p <.05) to all variables except the previous 5-day plasma osmolality. FMU_Col was only significantly correlated with other color time intervals and total water intake per gram. FMU_Osm held greatest utility (area under the receiver operating characteristic curve, sensitivity, and specificity >80%) overall, with the best outcome being FMU_Osm indicating a previous 24-hr osmolality threshold of 500 mOsm/kg (FMU_Osm criterion >710 mOsm/kg and positive likelihood ratio = 5.9). With less effort and cost restriction, FMU is a viable metric to assess underhydration. [ABSTRACT FROM AUTHOR]

Radioisotope thermoelectric generators (RTGs) are deal energy supply devices for deep space and deep-sea exploration, and it is also the energy core of the operation of the working equipment. Except for 238Pu (Plutonium), 241Am (Americium) was also used as a nuclide in the radioactive energy system for future space exploration missions. In this work, neodymium oxide (Nd 2 O 3) was used as analogues for Am 2 O 3. Cold-press-and-sinter methods was used. Different particle parameters (morphology, size, and crystal structure) and synthesized parameters of Nd 2 O 3 were investigated. The synthesized powders contained lath-shaped particles, and batches with different particle sizes and microscopic topography were made and sintered. The results show that the optimal precipitation temperature of Nd 2 O 3 is 25 °C. The optimal thermal decomposition temperature range is 900 °C to 1100 °C, and the optimal thermal decomposition heating rate is 10 °C min−1. The samples of Nd 2 O 3 pellets without cracking is obtained with relative density of 85%–90 %. The Vickers hardness of Nd 2 O 3 pellets was also studied. This paper provides an important scientific guiding significance for the cold-press-and-sinter of radioisotope 241Am batteries in the future. [ABSTRACT FROM AUTHOR]

The temperature coefficient of dielectric constant (τ ε) is a crucial parameter for assessing the performance stability of microwave devices operating under varying temperature conditions. In this study, polyphenylene oxide (PPO) resin was utilized as the matrix and six types of ceramics with distinct temperature coefficients of dielectric constant were employed as fillers. Six PPO-based composites were fabricated through twin-screw extrusion combined with hot pressing route. The dielectric properties of the ceramics and their influence on the dielectric properties of the composites, particularly the τ ε , were systematically investigated. The results revealed that all six types of composites exhibited dense structures and uniform filler distribution, with a relative density exceeding 98.0 % and a water absorption below 0.1 %. The dielectric constant and its temperature coefficient of the fillers had a more pronounced effect on the dielectric properties of the composites, compared to dielectric loss. The dielectric constants of the six types of composites aligned well with the theoretical values predicted by the effective medium theory. Reaching up to 9.7 (at 10 GHz). The dielectric loss ranged from 1.0 × 10−3 to 3.0 × 10−3. Notably, the PPO/Mg 0.95 Ca 0.05 TiO 3 composite substrate with a filler ratio of 40 vol% exhibited exceptional dielectric properties: ε r = 6.8, tg δ = 1.4 × 10−3, τ ε = −8.6 ppm/°C, highlighting its significant advantages for communication applications under varying temperature conditions. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of nanostructured composite powders (WC-Ni), nickel binder content, and sintering techniques on the morphology and mechanical properties of tungsten carbide. An alternative low-temperature gas-solid reaction route with a short reaction time was employed to produce nanostructured composite powders with 5 and 15 wt% Ni. The powders were consolidated using spark plasma sintering (SPS) and conventional vacuum furnace sintering at temperatures of 1350 °C and 1450 °C. The composite powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and particle size measurements. The expansion/contraction of the compacted nanocomposite powders was studied through dilatometric analysis. The composite powders exhibited a uniform distribution of Ni, in both compositions. For the WC-5 wt% Ni nanocomposite powders, the average crystallite sizes for WC and Ni were 41.6 nm and 46.2 nm, respectively. While, for the WC-15 wt% Ni nanocomposite, the crystallite sizes for WC and Ni were 45.6 and 38.4 nm. The sintered composites were evaluated through XRD, SEM, measurements of density and Vickers hardness. The enhanced sinterability of the nanostructured powders enabled their consolidation into (WC-Ni) hard metal with densities approaching the theoretical relative density of 96.07 %, even with low binder content (5 wt% Ni). This is attributed to the uniform distribution of Ni and an extensive Ni-WC interface present prior to sintering. The SPS process at 1350 °C produced sintered bodies (WC-5 wt% Ni and WC-15 wt% Ni) with higher Vickers hardness (2322 HV and 1512 HV, respectively) and superior microstructural quality compared to samples produced by conventional vacuum furnace techniques. These results demonstrated that the mechanical properties of the system WC-Ni processed by SPS are superior to those obtained by vacuum furnace. Therefore, WC-Ni hard metals processed by this approach is a promising alternative to conventional hard metals (WC-Co) for a wide range of applications. [Display omitted] • Impact of the preparation technique on the characteristics of WC-Ni composite powders. • WC-Ni nanocomposite prepared by gas-solid reaction at low temperature and short reaction time. • WC-Ni composites with relative density of 97.67 % and Vickers hardness of 2322 HV. [ABSTRACT FROM AUTHOR]

This paper studied the densification, phase composition, microstructure and properties of polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulks prepared by SPS. The dense specimen (98.9 % in relative density) with the average grain size of 15.46 μm has been determined to be a CsCl-type single-phase substitutional solid solution without any impurities or other secondary phases. The homogenous elemental distributions of La, Ce and Pr have been confirmed by both microscale and nanoscale. The room temperature (RT) Vickers hardness (H v), indentation fracture toughness (K IC) and flexure strength of the dense specimen have been measured to be 23.0 GPa, 2.04 MPa m1/2 and 305.1 MPa, respectively. The Berkovich hardness (H B) and elastic modulus (E) of the dense specimen have been measured to be 30.0 GPa and 376.0 GPa, respectively, by nanoindentation tests at a maximum load of 40 mN. In comparison with the polycrystalline LaB 6 bulk, the lower work function Φ of 2.64 eV evaluated by UPS and the larger thermionic emission current densities measured at the same operating condition suggest that the polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulk is a superior-performance thermionic cathode material. [ABSTRACT FROM AUTHOR]

Binary aluminosilicate glasses containing 20–50 wt% Al 2 O 3 were successfully densified through a cold sintering process (CSP) using 1–10 M NaOH solutions. The investigation focused on densification and structural unit changes in the cold-sintered binary aluminosilicate glasses. Specifically, the binary aluminosilicate glass with 40 wt% Al 2 O 3 , cold-sintered at 180 °C using 1–10 M NaOH solutions, achieved a relative density of up to 90 % at 10 M NaOH. This was attributed to an enhanced dissolution-precipitation process facilitated by an increased concentration of the NaOH solution. In aluminosilicate glasses with 20–50 wt% Al 2 O 3 , the relative densities approached 90 % after CSP at 180 °C using a 10 M NaOH solution. Al(OH) 3 formation in the cold-sintered glasses was confirmed, particularly at higher concentrations of NaOH solution (>10 M) and higher contents of Al 2 O 3 (>40 wt%). Changes in Si structural units were observed during CSP, with Al-rich Si units becoming dominant as the concentration of the NaOH solution increased. The higher substitution of Si-O-Si bonds by Si-O-Al bonds led to the precipitation of Al(OH) 3 , as well as an increased Vickers hardness and biaxial flexural strength of the cold-sintered glasses. These findings demonstrate that the Al 2 O 3 content and NaOH concentration play important roles in the densification and enhancement of the mechanical property in the cold-sintered alumina-rich binary aluminosilicate glasses and offer insights into the optimal conditions for obtaining desirable aluminosilicate materials through CSP. [ABSTRACT FROM AUTHOR]

We report new class of natural nacre-like alumina toughened by zirconia fabricated by the simple two-step approach of unidirectional freeze-casting and spark plasma sintering. The biomimetic alumina-zirconia with a relative density of more than 98 % was achieved by consolidating at temperature of 1300–1425 °C with 50 MPa pressure. The resultant microstructure consists of two levels of structural hierarchy, i.e. level-1: bulk lamellar brick phase (alumina platelets) and level-2: mortar phase (yttria stabilized tetragonal zirconia polycrystals). The increase in volume fraction of zirconia (in tetragonal form) from 0 to 15 vol% was effective in progressively reducing the size of alumina platelets from 12 to 9 μm, and significantly improved the flexural strength of the composite by 60 % (from 172 to 270 MPa). By optimizing the hierarchical architecture from micro to macroscopic level, the structural performance of our synthetic nacre, where strength and toughness of 270 MPa and 13.5 MPa √ m respectively are superior to that of natural nacre and many other engineering materials (illustrated in the form of Ashby map). The exceptional damage resistance is rationalized by both intrinsic (stress induced tetragonal to monoclinic phase transformation of zirconia) and extrinsic (crack deflection, crack branching and bridging, multiple cracking, platelets interlocking) toughening mechanisms. For 15 vol% ZrO 2 composition, the contribution of intrinsic and extrinsic toughness was quantitatively evaluated as 0.9 ± 0.03 and 4.3 ± 0.07 MPa√m respectively (with experimentally measured toughness at crack initiation as 5.2 ± 0.2 MPa√m). [ABSTRACT FROM AUTHOR]

Ceramic injection molding (CIM) is a near-net-shape technology for the rapid manufacture of complex-shaped small parts. Preparation of thick-walled parts remains a challenge owing to the difficulty in debinding process for green body based on micron and irregular ceramic powders. In this study, spherical metal-ceramic composite powders with different particle sizes were prepared using a wet granulation method. NiFe 2 O 4 -based cermets with a thickness of 20 mm were fabricated using both spherical (SP) and non-spherical (NSP) powders as raw materials. Roles of the powder shapes in catalytic debinding and sintering behaviour were investigated. Compared with that of NSP, green body with SP exhibited improved debinding efficiency, due to the well developed pore channels. A new perspective was proposed to explain the mass transfer mechanism during the debinding process. The adoption of spherical composite powders significantly enhanced the debinding rate without affecting the sintering performance. After sintering, sound cermet parts with uniform microstructure and the highest relative density of 98.62 % were achieved. This provides an important reference for the fabrication of large and thick-walled parts by CIM via controlling the powders. [ABSTRACT FROM AUTHOR]

Ceramics or refractories prepared in the Al 2 O 3 -rich corner of the Al 2 O 3 -MgO-CaO system show excellent high-temperature mechanical properties and chemical stability because of the presence of spinel (MgAl 2 O 4) and calcium hexaluminate (CaAl 12 O 19). However, the densification of these two crystals usually requires high firing temperatures due to their poor sinterability. To address this issue, La 2 O 3 -doped MgAl 2 O 4 -CaAl 4 O 7 -CaAl 12 O 19 refractory composites were designed, and the influence of the doping level on the densification, microstructure, and mechanical properties of the composite was investigated. It was found that the doped La3+ was predominantly dissolved in the CA 6 grains by replacing Ca2+, forming uniform solid solutions regardless of doping concentration. This reaction significantly accelerates ion diffusion and CA 2 grain growth. Besides, it reduces the aspect ratio of CA 6 crystals, weakening the negative effect of the elongated grains on mass transfer and sintering. As a result, the relative density increases from 79.5 % to 95.1 % after sintering at 1600 °C with doping only 0.5 wt% La 2 O 3 into the composite, producing a uniform and dense microstructure with regular angular grains. The above effects result in a significant improvement in flexural strength and fracture toughness (increasing by 61 % and 57 %, respectively). Moreover, the La 2 O 3 -doped refractory composite achieves a decline of the high-temperature creep rate by one order of magnitude at 1600 °C. [ABSTRACT FROM AUTHOR]

Monazite ceramic is one of the potential waste forms to incorporate actinides in planned nuclear waste repositories. Inspired by recent progress on the low-temperature sintering and enriching radionuclides by wet-chemistry, the sintering processes of monazite ceramic with/without pre-sintering are investigated by spark plasma sintering and pressureless sintering using La 0.8 Sr 0.1 Th 0.1 PO 4 ·nH 2 O rhabdophane as raw materials. Some specific issues such as the behavior of dissociation, structural evolution, and physicochemical properties affected by SPS and PLS are discussed in detail. The results reveal that a low-temperature appears to be a prevailing factor for SPS under 40 MPa with a suggested 1050 °C for 15 min process to prepare La 0.8 Sr 0.1 Th 0.1 PO 4 monazite ceramic without forming Th(PO 3) 4 phase, and the relative density and Vickers hardness of ceramic are more than 98 % and 600 (HV10). The dissolution experiment based on the ASTM-1220 method indicates that La 0.8 Sr 0.1 Th 0.1 PO 4 monazite ceramics is a typical example of an incongruent reaction, associated with Sr2+ is more likely to be dissolved out form monazite lattice compared with Th4+ and La3+. [ABSTRACT FROM AUTHOR]

A CO 2 -stable, easily sintered proton-conducting oxide electrolytes based on solid solution Ba 7 In 6 Al 2– x Zn x O 19-0.5 x with hexagonal structure has been synthesized for the first time. Within the homogeneity region (0 ≤ x ≤ 0.10), there is an increase in unit cell parameters, cell volumes and free cell volumes. The addition of Zn2+ markedly improved the sinterability of the material. The relative density of the ceramics of the doped samples reached 95 % at lower sintering temperatures than the parent phase. The electrical conductivity was studied using electrochemical impedance spectroscopy. Upon doping the oxygen-ion conductivity increased by 0.25 orders of magnitude at 800 °C. Proton transport was predominant below 500 °C for a wet atmosphere (pH 2 O = 1.92·10−2 atm). The investigated phases Ba 7 In 6 Al 2– x Zn x O 19-0.5 x are capable of hydration and incorporate up to 1.45 mol H 2 O vs 0.41 mol H 2 O for the parent phase. The studied phases exhibit chemical resistance to CO 2 under heat treatment at 600 °C. It was shown that solid solution Ba 7 In 6 Al 2– x Zn x O 19-0.5 x is a promising electrolyte material for intermediate-temperature fuel cells. [Display omitted] • The Zn-doping in solid solution Ba 7 In 6 Al 2– x Zn x O 19-0.5 x markedly improved the sinterability of the material and well-sintered ceramics were obtained with relative density 95 %. • The water uptake increased with increasing Zn-concentration. • Ba 7 In 6 Al 2– x Zn x O 19-0.5 x phases were protonic conductors at T < 500 °C in wet air. • Ba 7 In 6 Al 2– x Zn x O 19-0.5 x phases exhibited chemical resistance to pure CO 2. [ABSTRACT FROM AUTHOR]

Poor machinability and limited electrical conductivity present significant challenges for silicon carbide (SiC) composites used in the semiconductor industry. In this study, Ti-Si/SiC composites were synthesized by liquid infiltration of a Ti-Si eutectic alloy, using SiC and Carbon black as raw materials. The reactive sintering mechanism and properties of Ti-Si/SiC composites were investigated using the reactive infiltration sintering process. The relative density of Ti-Si/SiC composites reached 98.43 % at 1600 °C. The results indicate that continuous infiltration of the Ti-Si eutectic alloy and dissolution-reprecipitation are critical for synthesizing Ti-Si/SiC composites. The coefficient of thermal expansion for the composites is 5.16 × 10−6 °C−1. Remarkably, the exponential increase in electrical conductivity with rising temperature strongly supports the enhanced conductive properties of this composite semiconductor. The Ti-Si/SiC composites exhibit maximum flexural strength, indentation modulus, and hardness values of 310.4 MPa, 434.1 GPa, and 29.4 GPa, respectively. This research aims to advance the application of high-performance Ti-Si/SiC materials in semiconductor technology. [ABSTRACT FROM AUTHOR]

Caesium tungsten bronze materials are widely used in various applications, such as architectural glass, medicine, insulation coating and textile fibre, owing to their excellent mechanical, optical and thermal properties. In this study, a caesium tungsten bronze (Cs x WO 3 , x = 0.3–0.32) target with a relative density of 99.63 % and uniform microstructure was successfully prepared via hot-pressing sintering. Cs x WO 3 films were deposited on a quartz glass substrate via magnetron sputtering, and the mechanisms and effects of the substrate temperature and oxygen flow rate on the phase structure, microstructure and optical properties of Cs x WO 3 films were investigated. When the substrate temperature increased, the crystallinity and oxygen vacancy concentration of the Cs x WO 3 film improved. Consequently, the visible light transmittance of the film decreased, whereas the infrared blocking rate considerably increased, reaching up to 93.877 %. With the increase in the oxygen flow rate, the visible light transmittance exhibited an increasing trend, reaching a maximum value of 84.319 %, whereas the infrared blocking rate remained relatively stable. We successfully fabricated Cs x WO 3 films possessing a visible light transmittance of 66 % and infrared blocking rate of 94.97 % under the conditions of a substrate temperature of 300 °C and an oxygen flow rate of 2.5 sccm. Our study offers a method for the large-scale production of Cs x WO 3 films, which are excellent infrared shielding materials, rendering a substantial contribution to global energy conservation and emission reduction. [ABSTRACT FROM AUTHOR]

BaIn 2 O 4 ceramics with the monoclinic crystal system of the P 2 1 / c space group were synthesized using a solid-state reaction method. The sample sintered at 1250 °C exhibits a relative density (94.3 %) and the following microwave dielectric properties: ε r = 16.3, Q × f = 49,500 GHz, τ f = −73.1 ppm/°C. The bond valence results shows that the deviation of permittivity (24.9 %) between the experimental (ε r = 16.3) and calculated values (ε r C-M = 13.05) obtained using the Clausius−Mosotti equation may be ascribed to the rattling effect of Ba2+ and In3+. Compared with orthorhombic CaIn 2 O 4 and SrIn 2 O 4 ceramics, BaIn 2 O 4 ceramics have lower Q × f values possibly because of the intrinsic loss caused by nonharmonic lattice vibration. The E dc value (0.43 eV) of BaIn 2 O 4 demonstrates that the defects are caused by the single ionized oxygen vacancies. The intrinsic ε r (14.7) and Q × f (105,600 GHz) values of the BaIn 2 O 4 ceramic was inferred through infrared reflectivity spectroscopy. All results demonstrate that the dielectric properties are affected not only by density, ionic polarizability, and rattling effect of cations, but also by the crystal system, and particularly the intrinsic factors. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of the microstructure for the zinc silicate ceramics with different Zn/Si ratios was revealed, and the factors influencing their dielectric properties were discussed. Our results demonstrate that Zn volatilization plays an important role on the defect structure of the samples. Low relative density, high conductivity loss caused by volatilization, and the presence of ZnO phase collectively result in low quality factor (Qf) of Zn 2.0 SiO 4.0. By using the powder embedded sintering method, the loss could be reduced owing to the suppression of volatilization. As the Zn/Si ratio decreases, the ZnO disappears, while the Si-rich phase emerges and increases. The formation of a liquid phase results in a dense microstructure of the non-stoichiometric samples. Moreover, these samples exhibit a minor degree of Zn loss, probably because the presence of liquid phase constraints the volatilization during sintering. The samples with x = 1.8 display desirable properties, including a relative dielectric constant (ε r) of 6.5, a Qf of 100,800 GHz, and a temperature coefficient of resonant frequency (τ f) of −21.3 ppm/°C, due to their high degree of densification, slight zinc loss, and the elimination of the ZnO phase. [ABSTRACT FROM AUTHOR]

Samples of alumina – 3 % yttria-stabilized zirconia (YSZ) composites were sintered in rapid processing regimes using 24 GHz microwave heating at rates of up to 200 °C/min and zero hold time. The final relative density was 96–99 % for the samples containing 1.5 and 7.5 wt % YSZ and 98–99 % for the samples containing 13 wt % YSZ. The microwave sintering kinetics were compared for the processes carried out by direct and susceptor-assisted microwave heating. Under direct microwave heating, the effect of an intense microwave electromagnetic field with an estimated absorbed power density of up to 130 W/cm3 resulted in a shift of the shrinkage curves by about 100 °C towards lower temperatures compared to the case of susceptor-assisted heating. The grain size of the samples sintered by direct microwave heating decreased with an increasing heating rate. The mechanical properties were slightly higher for the materials sintered under susceptor-assisted microwave heating. The samples containing 13 wt % YSZ exhibited a microhardness of about 20 GPa and a fracture toughness of about 7 MPa m1/2. [ABSTRACT FROM AUTHOR]

In this paper, Ce 2 [Zr 1− x (Cd 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1− x (CS) x M, x = 0.01–0.1) were prepared via the conventional solid-state method. XRD and Rietveld refinement analyses confirmed the formation of a single-phase CZ 1− x (CS) x M solid solution with a space group of R -3c(167). The sintering behavior of the samples were investigated using SEM and relative density, which showed that optimal densification for CZ 0.98 (CS) 0.02 M ceramics were achieved at 675 °C with an average grain size of 1.70 μm. The P-V-L theory revealed the significant influence of the Zr(Cd/Sb)-O bond on the dielectric properties of CZ 1− x (CS) x M ceramics. Furthermore, far-IR reflectance spectra indicated that the measured dielectric loss value (1.04 × 10−4) is in line with the calculated value (1.60 × 10−4), suggesting a substantial impact of phonon oscillation absorption on the dielectric properties. Notably, CZ 0.98 (CS) 0.02 M ceramics demonstrated superior performance at 675 °C, with ε r = 10.44, Q × f = 93,152 GHz (at 12.96 GHz), and τ f = −17.73 ppm/°C. [ABSTRACT FROM AUTHOR]

In this work, SiC–AlN–TiB 2 –VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 °C-2100 °C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y 2 O 3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al 2 O 3 (on the surface of AlN) and Y 2 O 3 , which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB 2 , and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB 2 , and between TiB 2 and VC. Al 5 C 3 N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B 2 O 3 on the surface of TiB 2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 °C, SiC multiphase ceramics with added Y 2 O 3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa. [ABSTRACT FROM AUTHOR]

The rapid preparation of high-performance microwave dielectric ceramics has always been a technical challenge in the field of electronic ceramics. In this investigation, we rapidly fabricate MgTiO 3 –CaTiO 3 microwave ceramics with homogenous microstructure and high quality factor Q by microwave-assisted sintering, highlighting the efficiency gains and sintering time reductions. As the sintering time increases from 15 min to 45 min, the bulk density and relative density of MT-CT ceramic rapidly increase. The relative density of samples sintered for 30 min exceeds 97 %, which is difficult to achieve through conventional sintering methods. Combined with Rietveld refinement and Raman spectra, it is confirmed that the cell volume of MT-CT ceramics shrinks with the extension of sintering time, resulting in the weaken of Ti–O bond strength. More refined grain size distribution and uniform microstructure obtained by microwave-assisted sintering are likely to be pivotal factors in enhancing the microwave dielectric properties of MT-CT ceramics. MT-CT ceramics sintered at 1300 °C for only 45 min by microwave-assisted sintering exhibit excellent dielectric properties: Q×f = 87, 300 GHz, ε r = 20.42, and τ f = 2.11 ppm/°C, thereby demonstrating the potential of achieving rapid densification of microwave ceramics through microwave-assisted sintering. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP) technology shows promise in addressing the challenges of preparing high-strength, precise, and complex SiC ceramic structural parts. However, the low strength of DLP-printed SiC ceramic parts remains a persistent issue. To address this, a nano-ZrO 2 particle enhancement strategy is proposed. This study systematically investigates the effects of ZrO 2 content on slurry viscosity, curing depth, microscopic morphology, and the mechanical properties of SiC ceramics. The results indicate that increasing the ZrO 2 content raises the viscosity of the SiC slurry and decreases the curing depth, which can adversely affect the printing quality of SiC ceramic green bodies. However, a higher ZrO 2 content significantly reduces pore defects in the sintered parts, improving densification and mechanical properties. This underscores the importance of optimizing ZrO 2 content. The SiC sintered parts reinforced with ZrO 2 particles exhibited outstanding properties, including a relative density of 91.1 ± 3.2 %, Vickers hardness of 996.4 ± 93.8 HV, and a flexural strength of 201.5 ± 11.4 MPa. This study provides a straightforward and effective method for producing high-strength SiC ceramics via DLP. [ABSTRACT FROM AUTHOR]

Solid-state electrolytes (SSE) are one of the fundamental components of the upcoming generation of batteries since they increase the operational safety and efficiency. In this work, composite solid electrolytes (CSE) based on Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 and a (PEO 2 -LiTFSI) polymer matrix are obtained via the pioneering Cold Sintering Process (CSP), with a drastic reduction of the conventional sintering temperature. The CSP is performed at only 150 °C and 700 MPa, for 90 min of sintering time, by using a 3 m acetic acid solution as the transient liquid phase (TLP). Here, the effect of the LATP particle size (d 50) is studied to tailor the final microstructure, which enables the fine-tuning of the ultimate electrical properties of the electrolyte. An optimum d 50 of 0.415 μm produces CSEs with 91 % of relative density, an ionic conductivity of 0.169 mS/cm, activation energy of 0.293 eV and electrical stability under 0.1 mA/cm2, thus leading to competitive properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Binder jetting (BJ) additive manufacturing of zirconia (ZrO 2) ceramics presently encounters the challenges of achieving high relative density, dimensional precision, and superior mechanical properties of the prepared ceramics. This study extensively investigates the impacts of BJ processing parameters—namely, binder saturation, layer thickness, roller speed, and printing layout—on the dimensional accuracy, density, and mechanical strength of the resulting green parts. The identification of optimal BJ processing parameters is pivotal in the fabrication of ZrO 2 ceramic green bodies with superior dimensional precision and mechanical strength. The study shows that while solid-phase sintering alone can result in a relative density of 50.99%–54.27 % for BJ-processed ZrO 2 ceramics, glass infiltration after sintering substantially elevates the relative density and flexural strength. Specifically, infiltration at an optimal temperature of 800 °C increases the relative density of the sintered ceramic to 94.49 % and flexural strength to 76.48 ± 3.25 MPa, which represent a significant improvement of 40.22 % in density and a 35-fold increase in strength of the sintered ZrO 2 ceramics, respectively. These findings underscore the potential of BJ printing and subsequent glass infiltration as a synergistic approach to achieve high-performance ZrO 2 ceramics through additive manufacturing. [ABSTRACT FROM AUTHOR]

Lattice materials are an emerging family of advanced engineering materials with unique advantages for lightweight applications. However, the mechanical behaviors of lattice materials at ultra‐low relative densities are still not well understood, and this severely limits their lightweighting potential. Here, a high‐precision micro‐laser powder bed fusion technique is dveloped that enables the fabrication of metallic lattices with a relative density range much wider than existing studies. This technique allows to confirm that cubic lattices in compression undergo a yielding‐to‐buckling failure mode transition at low relative densities, and this transition fundamentally changes the usual strength ranking from plate > shell > truss at high relative densities to shell > plate > truss or shell > truss > plate at low relative densities. More importantly, it is shown that increasing bending energy ratio in the lattice through imperfections such as slightly‐corrugated geometries can significantly enhance the stability and strength of lattice materials at ultra‐low relative densities. This counterintuitive result suggests a new way for designing ultra‐lightweight lattice materials at ultra‐low relative densities. [ABSTRACT FROM AUTHOR]

ABSTRACT Cadmium (Cd) contamination in agricultural soil brings severe health risks through the dietary intake of Cd‐polluted crops. The comprehensive role of pectin in lowering Cd accumulation is investigated through low Cd accumulated (L) and high Cd accumulated (H) cultivars of L. sativa. The significantly different Cd contents in the edible parts of two L. sativa cultivars are accomplished by different Cd transportations. The pectin is the dominant responsive cell wall component according to significantly increased uronic acid contents and the differential Cd absorption between unmodified and modified cell wall. The chemical structure characterization revealed the decreased methyl esterification in pectin under Cd treatment compared with control. Significantly brighter LM19 relative fluorescence density and 40.82% decreased methanol in the root pectin of L cultivar under Cd treatment (p < 0.05) supported that the de‐methyl esterification of root pectin is more significant in L cultivar than in H cultivar. The pectin de‐methyl esterification of L cultivar is achieved by the upregulation of pectin esterases and the downregulation of pectin esterase inhibitors under Cd treatments, which has facilitated the higher Cd‐binding of pectin. Our findings provide deep insight into the differential Cd accumulation of L. sativa cultivars and contribute to the understanding the pollutant behaviors in plants. [ABSTRACT FROM AUTHOR]

To enhance the density of SiC and improve the purity of the SiC, carbon is frequently used as a sintering additive. SiC ceramics were prepared in this study by using various carbon sources (graphitic carbon microsphere, carbon black, and flake graphite) combined with B 4 C through spark plasma sintering (SPS) at temperatures ranging from 1800 °C to 1900 °C. Among the above carbon sources, the graphitic carbon microspheres were created by hydrothermal carbonization combined with catalytic graphitization. The influence of the carbon sources on the phase compositions, microstructure, physical properties, and oxidation resistance of the SiC specimens was investigated. The findings revealed that the SiC specimens prepared with graphitic carbon microsphere had a smaller crystallite size than those prepared with other kinds of carbon. The SiC specimens prepared with graphitic carbon microsphere displayed high relative density, hardness, fracture toughness, and remarkable oxidation resistance. This was attributed to the lower oxygen content, better dispersion, and higher chemical reactivity of graphitic carbon spheres. In terms of the oxidation resistance of SiC specimens, factors such as purity (residual carbon) and porosity were found to have a more significant impact than grain size. In general, the use of carbon sources with high reactivity and good dispersion is an effective method in preparing SiC ceramics. [ABSTRACT FROM AUTHOR]

Calcium hexaaluminate (CaAl 12 O 19 , CA 6) has great potential for application in high-temperature industries. However, owing to its intrinsic hexagonal lamellar crystal structure, it is difficult to obtain calcium hexaaluminate materials with high densification. In this study, using a two-stage sintering method and TiO 2 sintering aid, the densification of calcium hexaaluminate materials (relative density >95 %) was achieved. The evolution behaviors of the phase composition and microstructure and the intrinsic sintering kinetics were investigated in detail. The results showed that the addition of TiO 2 promoted the formation of CA 6 grains with a more homogeneous morphology and an increased-density equiaxial morphology. The elevation of the sintering temperature the sintering temperature also facilitated the densification of CA 6 , as the growth rate of the CA 6 grains along the C-axis raised significantly with the sintering temperature. When 1 wt% of TiO 2 was added and the sintering temperature was 1750 °C, a CA 6 material with a bulk density of 3.61 g/cm3 (relative density over 95 %) could be fabricated. [ABSTRACT FROM AUTHOR]

Mask stereolithography 3D printing for zirconia ceramics has attracted increasing attention in the industrial manufacturing due to their advantages of complex shapes, precisely controlled internal structures and fine surface effects. However, high refractive index and expensive equipment cost have always affected its development. Herein, we combine liquid crystal display (LCD) light curing 3D printing with zirconia molding, which is free from environmental and price limitations. In the conventional method of operation, the cured layer is bonded to the bottom and cannot be manufactured. We put forward a strategy for optimizing separation process and investigate the mechanism of the separation process in depth for high-quality zirconia ceramics LCD 3D printing. The results show that the controlled adjustment of the surface free energy can achieve a great reduction in the separation force, which enabled the successful printing of zirconia ceramics based on LCD. The effect of physical properties of the separation membrane on the separation process was studied and the solid content and 3D printing parameters of ceramic paste were optimized. When the solid content is 72.5 wt%, high quality zirconia ceramic parts with flexural strength of 255 MPa and relative density of 98.1 % can be obtained. This work provides new ideas for the convenient customization of zirconia ceramics in many fields. [ABSTRACT FROM AUTHOR]

High entropy (Y 0.2 Gd 0.2 Lu 0.2 Sc 0.2 Tm 0.2) 2 O 3 transparent ceramics with a single phase of cubic structure were prepared for the first time via vacuum sintering using ZrO 2 as sintering aid. In addition, the content of ZrO 2 was optimized and the investigated systematically. The Zr4+ ions in sintering aid replaced RE3+ sites and produced interstitial oxygen, promoted densification of the ceramics, and inhibited growth of grains. The relative density was increased to 99.79 % from 96.91 %. The grain size reduced from 34.25 μm to 5.68 μm. Due to the higher relative density and smaller grain size, (Y 0.2 Gd 0.2 Lu 0.2 Sc 0.2 Tm 0.2) 2 O 3 transparent ceramics with 1 wt% ZrO 2 had better optical and mechanical properties. The transmittance is better than 75 % at the region of 2–7 μm and reached 80.9 % at 5.43 μm, and the hardness and fracture toughness were 9.179 ± 0.062 GPa and 0.805 ± 0.024 MPa m1/2, respectively. This high-entropy transparent ceramics has potential applications in medium wave atmospheric windows (3–5 μm). [ABSTRACT FROM AUTHOR]

In the present study, the boron carbide ceramics reinforced with silicon carbide fibers (B 4 C-SiC f) were fabricated by incorporating various contents of SiC f ranging from 2.5 to 10 wt%. The B 4 C-SiC f powder mixtures were sintered using the Field Assisted Sintering Technique (FAST), also known as Spark Plasma Sintering (SPS), at temperatures of 1800 °C and 2000 °C for 5 min by applying a pressure of 70 MPa in argon atmosphere, while heating and cooling rates were maintained at 100 °C/min and 50 °C/min, respectively. The influence of the initial powder ratio on the sintering behavior, relative density, microstructural development, and mechanical properties of the obtained B 4 C-SiC f composites was investigated. The results indicated that the sintered ceramic materials contained only the initial compounds, i.e. B 4 C and SiC phases. Scanning Electron Microscopy (SEM) showed that the sintered composites consisted of densely compacted B 4 C grains. The highest relative density (>99 %) was achieved for the sample with 95 wt%B 4 C and 5 wt%SiC f , sintered at 2000 °C. Depending on the constituent content and the densification temperature the obtained composites demonstrated hardness values ranging from 29 to 43 GPa. The maximal hardness was attained in the composite with 95 wt%B 4 C sintered at 2000 °C. To assess the performance of the composites under extreme conditions, the ablation resistance was evaluated using a flowing oxyacetylene torch test. The material containing 5 wt%SiC f exhibited superior ablation resistance when compared to the other compositions. The attained results of this study showed that the SPS technique is a highly effective method for the densification of additive-free B 4 C-SiC f ceramic composites, showcasing promising properties for applications in extreme environments. [ABSTRACT FROM AUTHOR]

The coefficient of earth pressure at rest (K0) is a crucial parameter in geotechnical design. In this study, coral sands with various initial relative densities were subjected to K0 consolidation tests and consolidated-drained triaxial compression tests to investigate the impact of the relative density, stress level, and particle breakage on K0. Based on the Mohr–Coulomb failure law and experimental data, a formula for estimating K0 related to the effective stress and effective friction angle was proposed. The results revealed that the K0 of coral sand decreased with an increase in effective stresses, while the impact of the initial relative density on K0 was more obvious. At the same effective stress, the smaller the initial relative density was, the larger the K0 can be. In the tested stress range, minimal particle breakage was observed during the K0 consolidation, whereas a greater degree of particle breakage occurred during triaxial shear. This particle breakage has the potential to undermine the stress-dilatancy and interparticle locking characteristics in coral sands, leading to a diminished effective friction angle and potentially affecting K0. The proposed formula for estimating K0 can be expressed as a function of the effective stresses and effective friction angle, and the effect of initial relative density on K0 can be reflected by the function parameters. This formula provides a reasonable estimate of the K0 value for coral sand within a certain range of relative densities and stress levels. Furthermore, it demonstrates favorable applicability to other types of granular soils, such as quartz sand and rockfills. [ABSTRACT FROM AUTHOR]

Predicting how nature's contributions to people (NCP) vary spatially remains a challenge. For NCP provided by mobile species, it is unclear how predictions need to account for the influence of multiple habitat types that act as sources, sinks and potential distractors of the NCP‐providing species. Existing approaches that do not account for these effects may inaccurately predict outcomes in real landscapes.To move beyond these limitations, we transfer quantitative inference approaches from movement ecology to explore how spatial habitat patterns determine the negative NCP of the invasive common brushtail possum Trichosurus vulpecula in New Zealand. We used a Bayesian model to investigate how the size of, and distance from, grassland and indigenous and exotic forest patches together contribute to relative possum density (measured by capture probability across a trapping network) in a heterogeneous 11,000‐ha landscape.We found that indigenous and exotic forest area were the most important factors in determining possum density. Although capture probability declined with increasing grassland area, the addition of grassland did not improve the relative model fit above one with indigenous forest as the only habitat.We expected differences in predicted possum density at habitat boundaries, for example, due to preferential foraging at edges. We found that indigenous and exotic forests contributed to capture probability interactively, such that capture probability at the between‐habitat edge was lower than expected, given the habitat area. We also found that models allowing for non‐linear habitat effects of exotic forests or grasslands, but not indigenous forests, were significantly better at predicting possum density than simpler models.Synthesis and applications. Our novel approach for spatial prediction can be applied to any of nature's contributions to people (NCP), and extended to identify trade‐offs and synergies among multiple NCP. For example, the negative NCP of possum density trades off with multiple known positive NCP from indigenous forests, including culturally significant non‐material NCP, and material NCP produced by exotic forests. We recommend that landscape management plans to maximise these positive NCP in future scenarios also consider how the risk of possum density may dampen net NCP provision. To minimise this negative NCP, our results support trap deployment in both indigenous and exotic forest. [ABSTRACT FROM AUTHOR]

Sandwich structures with ceramic honeycomb cores are extensively employed in thermal protection systems owing to their exceptional ability to resist high temperatures. This work aims at exploring the effect of cracking on the transient thermal process of the sandwich panel subject to impulsive and cyclic thermal loadings. Both the conventional and re-entrant hexagonal alumina honeycombs are considered for the core material. By the integral transform method, combined with singular integral equations, the transient temperatures of the whole sandwich panel are determined from the semi-analytical solution. The straightforward temperature difference of the crack face's midpoints is exploited to characterize the heat intensification near the crack. Parametric investigations are carried out for the internal cell angle, the relative density, crack length, crack position, and thickness of face sheets, which provides a better understanding of the honeycomb materials working in thermal protection systems. [ABSTRACT FROM AUTHOR]

The sensation of dry mouth is a clinical illness known as xerostomia. Treatment is necessary for alleviating symptoms in patients who experience either transient or persistent dry mouth. It is essential to develop artificial saliva for this purpose. The fruit of the Phoenix dactylifera is edible and has been used in food. Its mucilage from dried fruits was extracted by soaking in distilled water and precipitated with 90% v/v ethanol. The mucilage of P. dactylifera was used for producing artificial saliva and was combined with other components including proteins and electrolytes. The translucent light brown gel solution was seen in the artificial saliva using P. dactylifera mucilage. The measured relative density ranged from 1.02 to 1.15 g/mL. Artificial saliva had to become more viscous with the addition of P. dactylifera mucilage and its concentration. Their pH values ranged between 6.98 and 7.15. The produced artificial saliva had a wetting time ranging from 7.53 to 9.70 min, which is similar to the typical human saliva. Artificial saliva could form a film in the mouth after certain periods. It was found that artificial saliva exhibited many adsorption bands corresponding to various biomolecules, such as protein, carbohydrate, and lipid, and had a unique peak at 275 nm. The results of this investigation suggest that a formulation including mucilage from P. dactylifera may be utilized to treat xerostomia patients by temporarily lubricating and hydrating their mouths when they experience persistent dry mouth. [ABSTRACT FROM AUTHOR]

Purpose: The current study investigated whether sustained mild dehydration affects thermoregulatory function and cognitive performance during prolonged exercise. Methods: Twelve young adults performed a test consisting of three sets of 20-min exercise with 2-min intervals under euhydrated (control, CON) and mildly dehydrated conditions (MDEH) at an ambient temperature of 30 °C and 60% relative humidity. MDEH was established by restricting water intake for 24 h, resulting in urine specific gravity of ≥ 1.020. Heart rate (HR), mean arterial blood pressure (MAP), skin blood flow (SkBF), sweat rate (SR) on the chest and forearm, and ear canal and mean skin surface temperatures (Tear and mean Tskin, respectively) were continuously recorded. For each exercise set, thermal and humid sensations and thermal discomfort were assessed using visual analog scales (VAS), and the rating of perceived exertion (RPE) was estimated. Cognitive performance on the Go/No-Go (easy) and incongruent Stroop (difficult) tasks was assessed before and after the test. Results: No differences were observed in HR, MAP, SkBF, SR, Tear, and mean Tskin between the CON and MDEH. Thermal and humidity sensations, thermal discomfort, and RPE were higher in MDEH than in CON. Moreover, response time to the Stroop task was prolonged in MDEH. Conclusion: These findings suggest that sustained mild dehydration does not affect autonomic thermoregulation during exercise. Augmented thermal perception and perceived exertion, which are necessary for behavioral thermoregulation, were noted; however, cognitive function may be attenuated under MDEH. [ABSTRACT FROM AUTHOR]

Projects related to Geotechnical Engineering require thorough ground study to know the soil behaviour thus making it necessary to determine the strength and stability parameters of soil. The soils of Assam are primarily of four types viz., Alluvial (old and new), Piedmont, Hill and Lateritic soils with the alluvium abundantly available in the state. The most important soil parameters are the shear strength parameters, namely, cohesion (c) and angle of internal friction (Φ) which can be obtained using triaxial tests with different drainage conditions. But one triaxial test may take weeks to complete and are very expensive. Moreover, for large projects it is practically preposterous to conduct large number of triaxial tests. Hence, an alternate way is to develop a relation between different parameters which enable us to determine others. The main objective of this study is establishing prediction models that allow the shear parameters to be predicted from soil index properties. For this, three prediction models are developed by combining various soil parameters viz., Liquid Limit (LL), Plastic Limit (PL), Specific Gravity (G) and Optimum Moisture Content (OMC) using Multivariate Regression Analysis (MRA) and Artificial Neural Network (ANN). The results show better performance for ANN than MRA. [ABSTRACT FROM AUTHOR]

A large part of ocean surface is covered by calcareous deposits. The Low stiffness and weak particles of calcareous soils deposited by marine organisms showed significant particle breakage under applied loads, which resulted in different behavior compared to terrigenous soils. A series of compression drained triaxial tests were carried out to evaluate the monotonic shear behavior of crushable and non-crushable soils. Three different soils, including Firoozkuh siliceous sand (as a non-crushable soil) and Hormuz and Bushehr calcareous sands (as crushable soils) which were different in mineralogy compositions were obtained from northern and southern Iran. The specimens were prepared in different relative densities (i.e., loose, medium and dense conditions) and consolidated under confining pressures ranging from 100 to 600 kPa. The monotonic shear and dilatancy behaviors of the soils have been presented in detail and the effect of particle breakage has been discussed. The results showed that particle breakage has a significant effect on the mobilized friction and dilatancy angles of marine crushable soils. There is a linear relationship between the amount of particle breakage occurring during a triaxial test and breakage angle. In addition, the mineralogical difference influences the breakage properties of calcareous deposits. [ABSTRACT FROM AUTHOR]

The vertical bearing capacity of the suction caissons is vital to the safety of marine jacket foundations. The sand friction angle is a key parameter for calculating the vertical bearing capacity. The sand friction angle is state-dependent, which is affected by the compact state and stress state. However, this effect is neglected in the current study, resulting in deviations in the calculation results of the vertical bearing capacity. Therefore, a novel method is preliminarily proposed to account for this impact while evaluating the vertical bearing capacity of suction foundations. First, a new friction angle is expressed as a function of relative density and soil depth, which differs significantly from the commonly used constant friction angle. The state-dependent sand friction angle is available. Then, the general and simplified vertical bearing capacity formulas are clarified. Four key parameters in the former and a new first-order coefficient in the latter are identified. The calculation procedure based on the new friction angle is also specified. Finally, combined with model tests, a comparison study is carried out. The results show that the calculation results using the new friction angle are more accurate and practical. This study can provide a reference for the foundation design. [ABSTRACT FROM AUTHOR]

Experimental studies show that initial fabric and its evolution under different stress paths greatly influences soil behaviour. Even though different sample preparation methods create different inherent anisotropies and cause different material responses, the same initial fabric structure under different stress paths also results in different material behaviours. In this paper, a simple state-dependent, bounding surface-based elastoplastic constitutive model, which can simulate the anisotropic nature of sands including the effect of principal stress rotation, is described. The model is developed based on a semi-micromechanical concept within the multilaminate framework and, to include the inherent anisotropy of sand, a deviatoric fabric tensor describing the initial microstructure is introduced. In addition, a fabric evolution rule compatible with anisotropic critical state theory is employed to describe the evolving fabric structure and induced anisotropy towards the critical state. In contrast to the classical strain-driven formulation for fabric evolution, a micro-level evolution rule is proposed. This paper presents concise theoretical aspects of the multilaminate framework and the anisotropic elastoplastic constitutive formulation. The model's capability under drained and undrained monotonic loading conditions at different stress states, relative densities and principal stress orientations is demonstrated by simulating experimental data for Toyoura sand. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is an additive manufacturing process which can produce complex 3D parts from digital models. The performance of parts fabricated by LPBF is largely dependent on the characteristics of the powder feedstock, in particular, the particle size distribution. The coarsening of powder particles may limit the potential for reusing powder in further builds, as consistency in powder quality is crucial for ensuring consistent parts performance when using reused powder, especially in aerospace applications. However, there is a lack of systematic understanding regarding the causes and nature of powder coarsening in LPBF. In this work, the characteristics of powder samples from different locations in the build chamber during LPBF were studied to understand the particle size evolution and determine the origin of coarsening, which has not been previously reported. Meanwhile, powder coarsening was found to have a detrimental effect on the relative density and surface quality of as-built parts, highlighting the importance of exploring the mechanisms of powder coarsening and finding ways to control it in LPBF. The relationship between powder in key locations in the build chamber and its effect on powder coarsening has been established. Layer thickness is identified as a critical factor in causing powder coarsening due to the fine powder size characteristic in the powder bed. Spatter, in its various forms, plays a direct or indirect role in powder coarsening. Sintered powders resulting from spatter and the laser scanning borders of as-built parts were observed to contribute to the powder coarsening. Therefore, three main mechanisms (layer thickness, spatter, sintered powder) associated with the powder coarsening are therefore proposed. This work provides insight and potential solutions to control powder coarsening and maintain consistent parts performance. [ABSTRACT FROM AUTHOR]

This study aims to modernize commonly preferred hybrid aluminum composites in the automotive and defense industries. For this purpose, Al-4Cu/B4C-SiC hybrid composites were manufactured using the hot pressing method and their microstructure, mechanical, and tribological properties were investigated. SEM/EDS analyses of the samples were conducted to examine morphological characteristics. Hardness, relative density, and three-point bending tests were performed on the produced samples. Additionally, wear tests were conducted under dry sliding conditions and different loads (5-10-15 N) to investigate tribological properties. The addition of hybrid reinforcements resulted in high hardness (88.54 HB) and relative density (98.83%) values. The highest bending stress (556.9 MPa) was observed in sample AC-4 (Al-4Cu/2B4C-2SiC). The lowest mass loss (1.1 × 10−3 g) was encountered in sample AC-6 (Al-4Cu/6B4C-6SiC), where all reinforcements were present together. Plastic deformation, oxidation, and residual wear mechanisms were identified on the worn surfaces of the samples. Consequently, the addition of hybrid reinforcements to Al-4Cu composites shows promising potential in enhancing the mechanical and tribological performance of the composites. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is an ultrafast sintering method for the preparation of ceramics and ceramic composites with simple geometrical shapes, with the combined application of uniaxial pressure. This study aims to propose an SPS densification method for Si3N4 ceramic balls without necessitating alterations to tools and equipment. The Si3N4 ceramic balls intended for sintering are positioned within a SiC powder bed inside the conventional die used in SPS. The study systematically investigates the effects of presintering temperature (1400°C, 1500°C, and 1600°C) and SPS temperature (1600°C, 1700°C, and 1800°C) on the sphericity, relative density, phase composition, microstructure, and mechanical properties of Si3N4 ceramic balls. Experimental findings reveal that Si3N4 ceramic balls exhibiting an optimal combination of sphericity (0.94 ± 0.02), relative density (98.4%), and mechanical properties (Vickers hardness: 17.5 ± 0.4 GPa, fracture toughness: 6.4 ± 0.1 MPa·m1/2) were successfully achieved at a pre‐sintering temperature and SPS temperature of 1600°C, coupled with the use of a SiC powder bed and SPS method. Consequently, the SPS method demonstrates its capability to fabricate Si3N4 ceramic balls with excellent performance. [ABSTRACT FROM AUTHOR]

This paper aims to improve the density and thermal shock resistance of Y2O3 ceramics for the preparation of ultra‐pure high‐temperature alloy crucible materials. The doping effect of MgF2 content on the densification behavior, physical properties, and thermal shock resistance of Y2O3 ceramics was systematically investigated in this paper. The results suggested that the presence of MgF2 greatly promoted the growth of Y2O3 grains and the transformation of the pore structure by liquid‐phase sintering. And the mechanical properties of the MgF2‐doped Y2O3 ceramics were significantly improved. Besides, the marked improvement in the thermal shock resistance of MgF2‐doped Y2O3 ceramics was attributed to the synergistic action resulting from the growth of grain size and the enhancement of the crack deflection effect. In particular, the relative density of Y2O3 ceramics doped with 1.5 wt% MgF2 reached 96.4% and the residual flexural strength ratio after thermal shock achieved 45.0%, showing an excellent application prospect. [ABSTRACT FROM AUTHOR]

To confer light‐blocking properties upon the Al2O3 encapsulation material, this study employed a one‐step method using α‐Al2O3 as the main raw material to synthesize CaCu3Ti4O12(CCTO)–MnO2–Co2O3 series black Al2O3 ceramics. The research investigated their coloring effect, sintering behavior, dielectric, and mechanical properties. The results indicate that the CCTO–MnO2–Co2O3 series colorants successfully dyed the Al2O3 ceramics black, while their introduction resulted in the formation of various spinel‐type compounds and facilitated the sintering of Al2O3 ceramics. The sintering mechanism and performance effects of black Al2O3 ceramics were thoroughly investigated, revealing that with an increase in the colorant content, all properties of the samples improved. When the colorant content reached 15.0 wt.%, the coloring effect reached its optimum, with a relative density of 96.7%, a dielectric constant of 12.5, a dielectric loss of.0081, a flexural strength of 314.4 MPa, and a Vickers hardness of 1254.5 Hv. [ABSTRACT FROM AUTHOR]

Gadolinium-doped ceria (GDC) is a promising electrolyte material for developing solid oxide fuel cells (SOFCs) because it offers a higher ionic conductivity at the intermediate operating temperature. In this work, nanocrystalline GDC (Ce 1-x Gd x O 2-x/2 , where x = 0.1 and 0.2) powders were synthesised through a novel co-precipitation synthesis method (benzoate route) using ammonium benzoate as a low-cost precipitant. The effect of the synthesis route and processing variables (calcination temperatures and time) on the microstructural and electrical properties of the resulting GDC powder was studied systematically. Multiple GDC electrolyte pellets were fabricated by pressing the GDC powders, followed by sintering the samples at 1100 °C for 6 h. The ionic and electronic conductivity of the GDC pellets were measured in air using EIS at different temperatures (450–750 °C). Huggins' model was used to determine the ionic and electronic conductivity of the GDC pellets. The fabricated electrolyte pellets showed a high relative density of 98.31and 99.02 % for the pre-calcined non-washed and pre-calcined washed powders, respectively, with a crystal size lower than 12 nm. Among all samples, the GDC electrolyte pellet fabricated using the pre-calcined washed powder exhibited the highest ionic conductivity of 3.63E-01 S cm −1 at 750 °C and activation energy of 0.52 eV with an average crystal size of 7–8 nm. The results of this study help to understand and design more efficient ceramic fuel cells with controlled microstructure and compositions at a lower cost. [ABSTRACT FROM AUTHOR]

In this work, high-purity alumina ceramics were prepared by using two-step reverse polarity flash sintering (PR-FS). The effects of the time distribution between the first flash and the second flash on microstructure and hardness were studied. The results show that compared to the conventional DC flash sintered alumina, the RP–FS–ed samples exhibited more uniform-microstructure, finer grains, higher relative density, and higher hardness. The underlying mechanism for such more homogeneous microstructure was related to uniform distribution of point defects under effect of reverse polarity. Two-step reverse polarity flash sintering method offers a great potential in obtaining highly densified alumina ceramics with homogeneous microstructure. [ABSTRACT FROM AUTHOR]