Ultra-high Temperature Research Articles

Quantification of pesticide residues in milk by HPLC-UV analysis in Gilan province, Iran

ABSTRACT Eighty milk samples, comprising raw cow’s milk, pasteurised milk, ultra-high temperature milk, and camel milk, were collected randomly from supply centres from December 2022 to March 2023 in Gilan province, Iran. Aldrin, diazinon, and dichlorodiphenyltrichloroethane (DDT) were determined using high-performance liquid chromatography. Aldrin and diazinon were observed in all samples. Furthermore, 87.5% of the milk samples were contaminated with DDT. The raw milk sample showed the greatest concentration of aldrin, measuring 9.31 ± 0.80 µg L−1, and there was no significant difference with the camel milk. The samples of camel milk, raw milk, and ultra-high temperature milk demonstrated the greatest levels of DDT, whereas the lowest concentration was detected in pasteurised milk. In all samples, the maximum residue level (MRL) of Codex Alimentarius and the national Iran standard (20 µg L−1 for DDT) was only exceeded by 25.1% of the milk samples.

Children's Iodine Intake from Dairy Products and Related Factors: A Cross-Sectional Study in Two Provinces of China.

Dairy products are a significant source of iodine, and their contribution to iodine intake must be evaluated regularly. However, there is a lack of data on iodine intake from dairy products in China. Through a cross-sectional study, we determined the iodine content of dairy products in the Chinese diet and estimated iodine intake among Chinese children. Intake records for 30 consecutive days were used to investigate the consumption of dairy products by 2009 children from Yunnan and Liaoning Provinces. The iodine contents of 266 dairy products with high intake frequency were determined using inductively coupled plasma-mass spectrometry (ICP-MS). We then calculated the iodine intake and contribution of dairy products and explored the related factors of dairy iodine intake through a generalized linear mixed model. Ultra-high-temperature (UHT) sterilized milk accounted for 78.7% of the total dairy products, with an iodine content of 23.0 μg/100 g. The dairy product intake rate of children in China was 83.6%, with an average daily intake of 143.1 g. The median iodine intake from milk and dairy was 26.8 μg/d, 41.5% of the estimated average recommendation (EAR) for younger children and 31.8% of the EAR for older children. The daily milk iodine intake of children in Yunnan Province was 9.448 μg/day lower than that of children in Liaoning Province (p < 0.001), and the daily iodine intake of children in rural areas was 17.958 μg/day lower than that of children in urban areas (p < 0.001). Chinese dairy products were rich in iodine, and the content of iodine was intermediate to that reported in Europe and the USA. However, children's daily intake of milk iodine was lower than that of children in other developed countries due to the lower daily intake of dairy products, especially those in rural areas.

Exploration of laser ablation protection for HfC coatings on C/C composites above 2900K

Enhancing the laser ablation resistance of C/C composites is of paramount importance for their prospective application as thermal protection materials, given the rapid advancements in high-energy continuous laser technology. Herein, HfC coating was prepared by chemical vapor deposition (CVD) on the surface of C/C composites to resist the irradiation of high-energy continuous laser. The melting occurred with the formation of oxide products, and these molten phases accumulated at the edge of the ablation pit after laser ablation with two different powers. Furthermore, many cracks were formed around the ablation pit due to the formation of phase transformation stress during ablation. With the increase of laser power, the surface temperature and damage area of the coating increased, and the melting of oxide scale caused by ultra-high temperature was the main reason for the failure of coating. This work could be helpful to provide a theoretical basis for the design and application of laser protective coatings.

Ablation resistant C/C-HfC-ZrC-TaC-SiC composites prepared by reactive melt infiltration

Ultra-high temperature ceramics (UHTCs) modified C/C composites for extreme high-temperature environments are fascinating, the rapid introduction of UHTCs and structural temperature resistance are essential for the long-term service. Herein, C/C-HfC-ZrC-TaC-SiC composites with continuous ceramic-rich layers were designed and prepared to improve the ablation resistance. HZT441 (HfC:ZrC:TaC = 4:4:1) sample exhibited pseudo-plastic fracture with a flexural strength of 195.27 ± 11.11 MPa. After 80 s of oxyacetylene ablation (4.2 MW/m2), the mass and linear growth rates were 0.10 mg/s and 1.02 μm/s. This is attributed to the dense oxide layer, including (Hf,Zr)6Ta2O17, (Hf,Zr)O2 and SiO2, which effectively inhibits oxygen intrusion and carbon fiber damage. In addition, the thermal response behavior and stress distribution of ceramic-rich layers to C/C composites were investigated, which is contributed to provide a theoretical basis for the material design of thermal protection systems in extreme high-temperature environments.

The antioxidative protection mechanism of the ultra-high temperature radome composite material BNf/SiBN

In the study, a BNf/SiBN composite was fabricated through precursor infiltration and pyrolysis (PIP) method. The oxidation resistance of the composite was investigated at different oxidation temperatures, focusing on the micro-structure evolution, the phase composition and oxidation kinetics of bare fibers versus fibers protected by the matrix under various oxidation states. The result indicates that the BNf/SiBN composite remains stable at 1100 °C in air atmosphere, while the fibers protected by matrix maintain their complete structure even at 1500 °C. Furthermore, we elucidated the oxidation mechanism of SiBN matrix: SiBN matrix undergoes a prior oxidation stage and transforms into amorphous SiO2 and B2O3 at high temperatures to impede the oxygen attachment to fibers while preserving the integrity of internal structure. The emergence of ultra-high temperature resistant BNf/SiBN composite and along with the exploration of oxidation behavior has opened up new approach for advancing radome material development.

A first-principles study of the phase transitions in ultrahigh temperature shape memory alloy RuNb

Ultrahigh temperature shape memory alloys (UHT-SMAs) have transition temperatures above 600 °C. They are needed for sensing and actuating devices in aerospace applications. However, very few such UHT-SMAs have been found. Among them are Ru-based alloys such as RuNb and RuTa, whose martensite structures and phase transitions are totally different from those of NiTi-based SMAs and were poorly understood. In this work, we carried out a systematical study of RuNb using first-principles total energy calculations and molecular dynamics (MD) simulations. We revealed the transition paths and mechanisms in cubic → tetragonal → monoclinic transitions. We determined the transition sequence and martensitic transition temperatures (MTTs) by evaluating the Gibbs free energies using thermodynamic integration. The calculated MTTs are in very good agreement with the experimental data. We also found that the monoclinic phase at the second transition has the P21/m symmetry instead of experimentally identified P2/m. The insights gained by this study and the verified ab initio methods for accurate MTT calculations can be applied to fast screen and quantitatively design novel UHT-SMAs having similar properties with desirable MTTs and much reduced cost.

Characterization of the flavor profile of UHT milk during shelf-life via volatile metabolomics fingerprinting combined with chemometrics

Ultra-high temperature (UHT) milk is popular among consumers. However, its flavor and texture change in its shelf life. Flavor is highly determinative for the success of dairy products and for consumers’ willingness to buy. It is important to milk producers to ensure the optimal flavor of their products in the shelf life. In order to be able to control and predict the flavor quality of UHT milk during the shelf life, this study compared the variations in sensory quality, volatile aroma release and backbone flavor factors and developed a discriminant model to assess flavor quality based on flavouromics data of five competing milk sample during storage. Using partial least squares discriminant analysis (PLS-DA) with Electronic-nose (E-nose) data excellent classification sensitivity and specificity were achieved compared to models based on gas chromatography-mass spectrometry (GC–MS) data. The PLS-DA model using E-nose data exhibited a 100% correct classification rate for the storage period, and a 92% correct rate based on the eight variable importance in the projection (VIP) elements screened for volatile components from different groups. The discriminative model developed herein based on E-nose combined with chemometrics demonstrated advantages such as speed, efficiency, and environmental friendliness. This method shows promise as a precise tool for analyzing aroma changes in UHT milk during its shelf life, and provide support for controlling the flavor substances and milk product development.

Ultrasensitive refractive index and temperature sensor based on D-shaped photonic crystal fiber by group birefringence response in a Sagnac interferometer

In this paper, a D-shaped photonic crystal fiber (PCF) sensor based on a Sagnac interferometer is proposed, and it can achieve ultrahigh refractive index (RI) and temperature sensitivity when operating around the turning point of group birefringence (Bg). We undertake a theoretical analysis on Bg and a simulation calculation to study the sensing characteristics and obtain the optimized structure parameters of the D-shaped PCF sensor. The simulation results show that the maximum average RI sensitivities can reach 3253.33 and 15500 nm/RIU in the RI range of 1.33 to 1.35 and 1.40 to 1.42, respectively. When the temperature changes from -50 to 0 °C and 0 to 50 °C, the maximum average temperature sensitivities are up to 10.11 and 10.67 nm/°C, respectively. The proposed D-shaped PCF sensor can achieve dual-parameter sensing and has great potential for practical applications in biochemical and environmental science.

Molten salt synthesis of MnO2/Mn2O3 composite as a high-performance cathode material for rechargeable button zinc‑manganese ultra-high temperature battery

Herein, a novel rechargeable button zinc‑manganese ultra-high temperature battery is first reported for the efficient utilization and conversion of thermal and electrical energy. The battery system uses zinc anode, Zn-K-Cl molten salt electrolyte and MnO2/Mn2O3 composite cathode to work at 300 °C. In this study, MnO2/Mn2O3 composites were synthesized by molten salt method, and the crystal structure of the materials was adjusted by adding reduced graphene oxide (rGO). The results showed that the spherical nanoparticles and nanobelts of MnO2/Mn2O3 composite cathode materials increased the active sites and ion transport channels of the electrochemical reaction, thus providing high coulombic efficiency. By modifying with rGO, the MnO2/Mn2O3 (Mn-O-2) composite cathode material exhibits excellent electrochemical performance in the button zinc‑manganese ultra-high temperature battery. The as-prepared button ultra-high temperature battery exhibits a relatively high specific capacity (300 and 175 mAh g−1 at 1 mA cm−2 and 30 mA cm−2) and competent cyclability (> 95 % coulombic efficiency after 50 cycles). This work firstly and systematically reveals the role of the Mn cathode materials and shows that the application in button molten salt batteries.

Effects of slag on mechanical and microstructural properties of iron-rich phosphoaluminate cement subjected to high temperature oil well environment

Iron-rich phosphoaluminate cement (shortened as PAC) exhibits excellent high temperature resistance characteristic, enabling it to withstand the ultrahigh temperatures required for the in situ combustion (ISC) of heavy oil. The addition of slag could influence its high temperature resistance by altering its hydration products. Hence the thickening time, physical properties, phase components and microstructure of PAC with slag that were subjected to different high temperature environment (315, 550 and 800 °C) were investigated deeply in this paper. The experimental analysis results revealed that PAC had better high temperature resistance than CAC with and without slag. The addition of slag improved effectively the high temperature resistance of PAC. The influencing mechanism of slag were as follows. C2ASH8 formed at 50 °C inhibited the conversion of C(A,P)H10 to C3AH6. C2AS3H, C3AS2H2 and C3(Fe,Al)S3 formed at 315 °C alleviated the rapid release of the compound water. The phase Ca5(PO4)3OH and C2AS was stable in the range of 550–800 °C. In addition, the capillary pore structure of PAC was optimized. Therefore, PAC with slag had the potential to be used for high temperature oil well cementing.

W-doped concentration improved the hardness, elastic modulus, elastic anisotropy and thermodynamic properties of ZrC ultrahigh temperature ceramics

Although ZrC is a promising ultrahigh temperature ceramics due to the high melting point, high strength, high hardness and low density, the improvement of mechanical properties and thermal stability is very significance for it's ultrahigh temperature application. To improve the mechanical and thermodynamic properties of ZrC ultrahigh temperature ceramics, we apply the first-principles calculations to study the influence of W-doped concentration on the structural stability, hardness, elastic modulus, elastic anisotropy and thermodynamic properties of the cubic ZrC ceramics. The calculated results show that three W-doped ZrC are thermodynamic stability. In particular, the calculated impurity formation energy of the W-doped ZrC increases with increasing W concentration. Importantly, the calculated elastic modulus of the W-doped ZrC increases with increasing W concentration. Although the hardness of W-doped ZrC is bigger than the parent ZrC, the hardness of W-3.125 at.% is higher than the W-doped ZrC with the high concentration of W. Naturally, the high hardness and elastic modulus of the W-doped ZrC is that the metal W enhances the localized hybridization between Zr and C, which is demonstrated by the change of ZrC bond. In addition, the parent ZrC and the W-doped ZrC show excellent elastic anisotropy. Furthermore, the calculated Debye temperature of W-3.125 at.% ZrC is higher than the parent ZrC and the other W-doped ZrC. Therefore, we predict that the W-3.125 at.% ZrC shows excellent mechanical properties and better thermodynamic properties in comparison to the other W-doped ZrC ceramics.

Preparation of Ultra-High Temperature Resistant Cyclodextrin-Based Filtration Loss Reducer for Water-Based Drilling Fluids.

In the development of ultra-deep wells, extremely high temperatures can lead to inefficiency of additives in drilling fluids. Hence, there is a need to prepare additives with a simple preparation process and good effects at ultra-high temperatures to ensure stable drilling fluid performance. In this study, a high temperature resistant filtration loss polymer (LY-2) was prepared using γ-methacryloyloxypropyltrimethoxysilane (KH570), N,N-dimethylallyl ammonium chloride (DMDAAC), sodium p-styrenesulfonate (SSS), and β-cyclodextrin (β-CD). The impact of the different monomer ratios on particle size, rheology, and filtration performance was systematically investigated. Infrared spectroscopy afforded the structural features. Thermogravimetric Analysis detected the temperature stability, and scanning electron microscopy characterized the polymer micromorphology. LY-2 was completely decomposed at a temperature above 600 °C. Experiments showed FLAPI of the drilling fluid containing 3% LY-2 aged at 260 °C/16 h was only 5.1 mL, which is 85.4% lower compared to the base fluid. This is attributed to the synergistic effect of the polymer adsorption through chemical action at high temperatures and the blocking effect of carbon nanoparticles on the filter cake released by cyclodextrin carbonization at high temperatures. Comparing LY-2 with commercial filter loss reducers shows that LY-2 has excellent temperature resistance, which exhibited five times higher filtration performance and relatively low cost, making it possible to be applied to ultra-high temperature drilling operations in an industrial scale-up.

Thermal insulating performance of thermal protection system with sandwich structure based on Al2O3/SiC composites aerogels

The thermal protection system (TPS) are an indispensable component of aerospace vehicles that can withstand harsh aerothermal conditions during the reentry process. Recently, the sandwich structures of TPS have been widely used to meet the development trend of structure-performance integrated design. In this study, a TPS with a sandwich structure based on Al2O3 aerogels reinforced by SiC nanowire are proposed. The Al2O3/SiC composites aerogels are synthesized via the low-cost method, including sol-gel, freeze-casting and high-temperature treatments processes. The microstructure, phase composition, thermal insulation and compressive resistance of composite aerogels at different SiC nanowires content are investigated in detail. The resulting Al2O3/SiC composites aerogels, exhibiting better compressive strength and thermal stability with the increase of SiC nanowires content, achieve the purpose of being an excellent thermal insulation material of TPS at high temperature. The characterization of thermal insulating performances of the TPS are also evaluated by the oxyacetylene torch testing. The TPS shows extraordinary high-temperature resistance, and the average linear ablation rate and mass ablation rate are 0.0032 mm/s and 0.005 g/s, respectively, which can satisfy the requirement of TPS for aerospace vehicles under ultra-high temperature conditions.

Archean UHT metamorphism with counterclockwise P–T path: Insights from pelitic granulites from East Hebei, North China Craton

Archean supracrustal rocks that occur as rafts within tonalite–trondhjemite–granodiorite (TTG) gneisses can reach ultra-high temperature (UHT) conditions. Their metamorphic P–T paths and geodynamic regimes are debated. Herein, we present detailed analyses of UHT pelitic migmatites (JD1730 and JD1733) from the East Hebei, North China Craton, using petrology, phase equilibria modelling, and zircon dating, to recover the metamorphic history. Sample JD1730 is a sillimanite–orthopyroxene–cordierite migmatite that contains the sillimanite + orthopyroxene (+cordierite) symplectites, which are interpreted to be the pseudomorphs after sapphirine. JD1733 is a corundum-bearing garnet–cordierite–sillimanite migmatite that contains the corundum + spinel ± ilmenite/rutile aggregates, representing a stable mineral association of low pressures in local Si-unsaturated domains. The two rocks record consistent counterclockwise P–T paths involving pre-peak up-P processes to the UHT peak conditions followed by cooling. The pre-peak up-P processes occurred at 5–7 kbar and > 970 °C constrained from the textural relations involving (i) spinel enveloped by sillimanite and cordierite and mantled by the Sil + Opx symplectites in JD1730, and (ii) the inclusion variation in garnet of JD1733 with the Spl + Crn (±Ilm) aggregates embayed by sillimanite in the core and mantle, and worm-like quartz in the rim. The UHT peak conditions can be constrained to be 7–8 kbar, 980–1060 °C based on the stability of the inferred peak mineral assemblages in P–T pseudosections added with the plots of the re-integrated anorthite contents from perthite. The post-peak cooling processes to 5–8 kbar / 820–850 °C are marked by the growth of biotite in leucosomes of both samples. Zircon dating and geothermometry results suggest that the UHT metamorphism might have persisted for more than 20 Myr from ∼ 2.52 Ga to ∼ 2.50 Ga and the post-UHT cooling continued another 20 Myr or even 40 Myr. Considering the geological features in the terrane, a vertical sagduction regime was preferred for the Neoarchean tectonic evolution of the East Hebei terrane.

Nanoengineering-Enhanced Capillary Cooling Achieves Sustained Thermal Protection for Ultra-High Heat Flux and Temperature.

Extreme thermal conditions with heat flux densities exceeding 1 MW·m-2 or temperatures reaching up to 1000 °C are prevalent in various situations. However, the ability of thermal protection either depends on specialized materials or is currently limited with existing cooling schemes. Herein, we propose an innovative cooling scheme that relies on evaporation-driven capillary flow enhanced by nanoengineering-designed porous structures with common materials. Experimentally-obtained capillary flow cooling curve identifies critical heat flux corresponding to evaporation-driven flow stage, where coolants cool the surface and subsequent vapor impedes heat transfer from thermal boundaries. Nanoengineering provides opportunities for enhanced capillary flow, which proves to endow bronze, TC4, and Al2O3 with thermal protection ability 50%-180% higher than that without nanoengineering-designed. Our scheme achieves critical heat flux up to 2.0-3.1 MW·m-2, and performs thermal dissipation capacity almost twice higher than inherent latent heat of coolant. Furthermore, in a supersonic wind tunnel with total temperature reaching up to 1792 K, our scheme effectively protects surfaces by cooling them to surface temperatures below 500 K. Nanoengineering-enhanced capillary cooling gives access to the application of common materials for high-temperature and high-heat-flux environments and paves the way for the development of lightweight, long-lasting, and large-scale solutions for thermal protection. This article is protected by copyright. All rights reserved.

Rapid heating (

Ultrahigh-temperature (UHT) metamorphism is the most thermally extreme form of regional crustal metamorphism, with temperatures exceeding 900°C. The duration and heat source of UHT metamorphism are critical constraints on the tectonic evolution of orogenic systems. Here, we report the discovery of a sapphirine-bearing granulite from the east-central Himalaya which preserves UHT evidence. The reconstructed pressure-temperature-time path indicates that the temperature increased by almost 200°C within ~2 Ma which is consistent with rapid asthenospheric heat input. Numerical simulations illustrate potential mechanisms for such heating: juxtaposition of the deep crustal accretionary system with the upwelling asthenospheric mantle through newly developed apertures generated by slab break-off and/or associated vertical tearing of down-going Indian lithosphere. Spatial-temporal consistencies among the UHT metamorphic phases, postcollisional magmatism, geophysical constraints, and crustal deformation indicate that slab break-off or tearing controls broad swaths of Himalayan tectonics. The consequent upwelling asthenosphere may have been a significant heat source for the Miocene Himalaya and for similar ancient collisional orogenic systems.

Response of 11B enriched ZrB2 ultra-high temperature ceramic to neutron irradiation at elevated temperatures

ZrB2, an ultra-high temperature ceramic (UHTC) is being considered for use in fusion reactor first-wall structures, yet its response to irradiation remains poorly understood. This study employed scanning/transmission electron microscopy (S/TEM), synchrotron X-ray diffraction (XRD), finite element calculations, and thermal property measurements to thoroughly investigate the neutron-irradiation effects on 11B-enriched ZrB2. Neutron irradiations were conducted at 220 °C and 620 °C, with a neutron fluence of 2.2 × 1025 neutron/m2 (energy > 0.1 MeV), resulting in 3.9 dpa and 4200 appm He. The study revealed the unusual prevalence of prism loops and a > c anisotropic lattice swelling, likely linked to the low c/a ratio of ZrB2, leading to grain boundary microcracking. Reducing the grain sizes was effective in reducing intergranular cracking and macroscopic swelling. The observation of cavities in ZrB2 irradiated at 620 °C, as opposed to 220 °C, prompts questions about the temperature at which vacancies in ZrB2 become mobile, and the role of neutron absorption by 10B in elevating irradiation temperatures. Isotopic enrichment in 11B proves to be a viable strategy for mitigating helium production in transition-metal diborides, which is a critical consideration for nuclear applications. Irradiation-induced defects reduce the thermal diffusivity and conductivity of ZrB2 by a factor of 4–9, which has important implications for its role as a plasma-facing material in fusion reactors that drive high heat fluxes through first-wall materials. This comprehensive study lays the foundation for understanding ZrB2 behavior under neutron irradiation and highlights important phenomena to consider for various material applications.

Ultrahigh temperature ablation resistant HfB2-SiC composites: From liquid SiHfCB precursor synthesis to light weight bulk preparation and characterization

The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields (<40 wt.%) due to the challenges in integrating significant amounts of boron, which hampers their conversion into boride-based ultrahigh temperature ceramics. To tackle these challenges, a serious of pioneering liquid multi-component hafnium-containing ceramic SiHfCB precursors (with different Hf/Si ratios) have been developed. These novel precursors are featured with stable molecular structure and high ceramic yield which were successfully created through a novel one-pot polymerization process. They present in liquid form and their structure is characterized by C-C bonds forming its main chain with branched chains of O-Si-O, Si-O-Hf, Si-O-B, and B-O-Hf which have untapped advantages including uniform component dispersion, and excellent fluidity. The ceramic yield of SiHfCB precursor with Hf/Si of 0.2 is remarkably up to 68.6 wt.% at 1500 °C, and their Hf content exceeded 50 wt.%. Of particular interest, the pyrolyzed product HfB2-SiC nanopowders derived from the SiHfCB precursor with Hf/Si of 0.2, consist of nanopowders in the 40–60 nm range with a density of 5.23 g cm−3. Remarkably, this material demonstrates exceptional performance in ultrahigh temperature oxygen-containing environments at 2500 °C, showing near-zero ablation with a linear ablation rate of just 2.5 × 10−4 mm s−1. Post-ablation analysis of the microstructure reveals that the formation of a lava-like HfO2 and HfO2-SiO2 oxide layer effectively blocks oxygen penetration and provides excellent oxidation resistance. The innovative SiHfCB hafnium-containing ceramic precursor offers a groundbreaking solution for the preparation of lightweight ultrahigh-temperature ceramics. This development is poised to provide robust technical support for the use of ultrahigh temperature ceramics in non-ablative thermal protective systems, particularly in the construction of hypersonic vehicles, where ultrahigh temperature resilience is crucial.

Densification of zirconia-based ceramics by non-conventional sintering processes and chemical pathways

The present work reports an overview of the main results we have obtained from non-conventional sintering approaches towards the densification of 3mol.% yttria stabilized zirconia (3YSZ), the lessons learned from these results, and open questions that still need to be addressed. A wide range of techniques have been developed in the field of ceramic sintering, both in high temperature regime with extreme heating rates (>10 000 °C/min), as well as in very low temperatures (<400 °C) regime involving chemical reactivity to activate sintering mechanisms. In this context, we have recently explored several of these methods in order to understand and control the different sintering parameters and their impact on microstructure, crystallinity, grain boundaries and defect chemistry. Due to its complex chemistry, 3YSZ is a playground for the exploration of sintering capabilities and their influence on ceramic properties. Our recent studies in this field are presented in the present work, highlighting the effect of high heating rates through Flash Spark Plasma Sintering ( Flash-SPS) and Ultra High temperature Sintering (UHS) on sintering, but also the combination of low temperature Cold Sintering Process (CSP) and the associated precursors chemistry, with Spark Plasma Sintering (SPS). It also shows the possible densification by reactive hydrothermal sintering, using hydroxide precursors, and the effect of High Pressure SPS (HP-SPS) on 3YSZ nanopowders. All of these results touch upon current trends in the field of sintering, and highlight the possibilities in terms of chemical reactivity of precursors and physical parameter control. In particular, they show the importance of defect chemistry, related to the sintering atmospheres and their impact on both microstructures and properties.

A Novel Nano-Laminated GdB2C2 with Excellent Electromagnetic Wave Absorption Performance and Ultra-High-Temperature Thermostability.

A novel nano-laminated GdB2C2 material was successfully synthesized using GdH2, B4C, and C via an in situ solid-state reaction approach for the first time. The formation process of GdB2C2 was revealed based on the microstructure and phase evolution investigation. Purity of 96.4 wt.% GdB2C2 was obtained at a low temperature of 1500 °C, while a nearly fully pure GdB2C2 could be obtained at a temperature over 1700 °C. The as-obtained GdB2C2 presented excellent thermal stability at a high temperature of 2100 °C in Ar atmosphere due to the stable framework formed by the high-covalence four-member and eight-member B-C rings in GdB2C2. The GdB2C2 material synthesized at 1500 °C demonstrated a remarkably low minimum reflection loss (RLmin) of -47.01 dB (3.44 mm) and a broad effective absorption bandwidth (EAB) of 1.76 GHz. The possible electromagnetic wave absorption (EMWA) mechanism could be ascribed to the nano-laminated structure and appropriate electrical conductivity, which facilitated good impedance matching, remarkable conduction loss, and interfacial polarization, along with the reflection and scattering of electromagnetic waves at multiple interfaces. The GdB2C2, with excellent EMWA performance as well as remarkable ultra-high-temperature thermal stability, could be a promising candidate for the application of EMWA materials in extreme ultra-high temperatures.