Search

Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required. In this work, we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo2C on carbon fiber paper (Ni-Mo2CCB/CFP) for hydrogen evolution reaction (HER). The effects of nickel nitrate concentration on the phase composition, morphology, and electrocatalytic HER performance of Ni-doped Mo2C@CFP electrocatalysts was investigated. With the continuous increase of Ni(NO3)2 concentration, the morphology of Mo2C gradually changes from granular to flower-like, providing larger specific surface area and more active sites. Doping nickel (Ni) into the crystal lattice of Mo2C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity. The as-developed Mo2C-3 M Ni(NO3)2/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm−2. This catalyst has a fast HER kinetics, as demonstrated by a very small Tafel slope of 27.4 mV·dec−1, and persistent long-term stability. A further higher Ni concentration had an adverse effect on the electrocatalytic performance. Density functional theory (DFT) calculations further verified the experimental results. Ni doping could reduce the binding energy of Mo-H, facilitating the desorption of the adsorbed hydrogen (Hads) on the surface, thereby improving the intrinsic catalytic activity of Ni-doped Mo2C-based catalysts. Nevertheless, excessive Ni doping would inhibit the catalytic activity of the electrocatalysts. This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity, but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.

Background: As a major public health problem in the world, malignant tumor seriously threatens human life and health. The pathogenesis of cancer has been widely discussed. It is usually caused by the dysfunction of genes that regulate the basic process of cells. Studies have confirmed that Bcl-2-associated antiapoptotic gene 2 (BAG2) is widely expressed in a variety of malignant tumors. Through interaction with relevant signal molecules in the tumor microenvironment, BAG2 is involved in regulating tumor cell apoptosis, proliferation, and migration. BAG2 is expected to become a new target for tumor therapy in the future. Although emerging a large number of evidence supports the relationship between BAG2 and cancers, no pan-cancer analysis is available. Methods and Results: We thus explored the potential oncogenic roles of BAG2 based on the datasets of TCGA (The cancer genome atlas) and GEO (Gene expression omnibus). The comprehensive analyses for BAG2 in various tumors, including gene expression, diagnosis, prognosis, immune-related features, genetic alteration, and function enrichment, were conducted based on multiple databases and analysis tools. Immunofluorescence to detect the locations of BAG2 in three cancer cell lines. To verify the results further, immunoblotting was used to measure the expression of BAG2 in KIRC patients’ tissue samples. The drug of BAG2 were analyzed by using the Drugbank database. Take together, from our comprehensive pan cancer analysis of BAG2, we found a statistical association between BAG2 expression and clinical prognosis, immune cell infiltration, tumor mutation burden or microsatellite instability of a variety of human cancers. Conclusions: These results suggest that BAG2 might be served as prognostic biomarkers for cancer.

Monotonic tensile and fatigue tests of a SiC/SiC composites were conducted at 1300 °C in the full stress range. The macroscopic behaviors were studied based on the strain data. The mesoscopic morphology was observed by X-ray computed tomography, and the microanalysis was conducted using SEM, EDS and XRD. Besides, the interfacial debonding strength (IDS) were measured by nano-indenter. The results reveal that the fatigue behaviors can be divided into three zones. The inelastic strains accumulation and stiffness reduction can be observed in all three zones due to matrix cracking, interface damage, and failure of fibers. The fatigue life is long in the run-out zone because the maximum stress is lower than the proportional limit stress (PLS). In the stress-insensitive zone, the fracture depends on high-temperature and oxidation effects. The failure in the stress-sensitive zone is dominated by the fiber strength. The interface behaviors greatly affect the fatigue life above the PLS.

ZrSiO4 demonstrates applicability as the SiC/SiC interphase. Via a non-hydrolyzed sol-gel method, the pyrolysis product, synthesis condition, and the formation effectiveness of the ZrSiO4 coating on SiC fibers were investigated. Mini-SiC/SiC composites with two layers of ZrSiO4 interface coatings were oxidized to preliminarily verify their oxidation resistance effect.

In this study, SiC nanowires (SiCNWS) were grown in situ on the surface of PyC interface through chemical vapor infiltration (CVI) to improve the mechanical characteristics and thermal conductivity of three-dimensional SiCf/SiC composites fabricated via precursor infiltration pyrolysis (PIP). The effect of SiCNWS on the properties of the obtained composites was investigated by comparing them with conventional SiCf/PyC/SiC composites. After the deposition of SiCNWS, the flexural strength of the SiCf/SiC composites was found to increase by 46 %, and the thermal conductivity showed an obvious increase at 25−1000 °C. The energy release of the composites in the damage evolution process was analysed by acoustic emission. The results indicated that the damage evolution process was delayed owing to the decrease in porosity, the crack deflection and bridging of the SiCNWS. Furthermore, the excellent thermal conductivity was attributed to the thermally conductive pathways formed by the SiCNWS in the dense structure.

Precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI) were used to fabricate SiC/SiC composites on a four-step 3D SiC fibre preform deposited with a pyrolytic carbon interface. The effects of fabrication processes on the microstructure and mechanical properties of the SiC/SiC composites were studied. Results showed the presence of irregular cracks in the matrix of the SiC/SiC composites prepared through PIP, and the crystal structure was amorphous. The room temperature flexural strength and modulus were 873.62 MPa and 98.16 GPa, respectively. The matrix of the SiC/SiC composites prepared through CVI was tightly bonded without cracks, the crystal structure had high crystallinity, and the room temperature bending strength and modulus were 790.79 MPa and 150.32 GPa, respectively. After heat treatment at 1300 °C for 50 h, the flexural strength and modulus retention rate of the SiC/SiC composites prepared through PIP were 50.01% and 61.87%, and those of the composites prepared through CVI were 99.24% and 96.18%, respectively. The mechanism of the evolution of the mechanical properties after heat treatment was examined, and the analysis revealed that it was caused by the different fabrication processes of the SiC matrix. After heat treatment, the SiC crystallites prepared through PIP greatly increased, and the SiOxCy in the matrix decomposed to produce volatile gases SiO and/or CO, ultimately leading to an increase in the number of cracks and porosity in the material and a decrease in the material load-bearing capacity. However, the size of the SiC crystallites prepared through CVI hardly changed, the SiC matrix was tightly bonded without cracks, and the load-bearing capacity only slightly changed.

Emerging evidence suggests that microRNAs (miRNAs) participate in hepatocellular carcinoma (HCC) progression. Nevertheless, the mechanism of miR-7-5p in HCC cells has not been researched. In the research, the underlying biological function of miR-7-5p and SPC24 in HCC was explored. qRT-PCR was performed to measure the miR-7-5p and SPC24 level in HCC tissues and cells. The effect of miR-7-5p on HCC progression was detected by performing CCK-8, BrdU, and transwell assay. The relationship between miR-7-5p and SPC24 was determined using luciferase and RNA pull-down assays. Our findings showed that miR-7-5p was downregulated in HCC whereas SPC24 was upregulated in HCC. It was also showed that miR-7-5p upregulation restricted malignant behaviors of HCC cells, but this inhibitory effect of miR-7-5p could be relieved by its target gene SPC24. In conclusion, this research suggested that by inhibiting SPC24, miR-7-5p could act as a tumor inhibitory factor in HCC.

The present research intends to explore the progressive failure in the case of five-harness SiCf/SiC satin-woven sheet composites consisting of twelve layers using a combination of numerical and experimental methods. For derivation and characterization of the bending behavior, a three-point bending procedure was used under conditions of atmospheric temperature. A charge-coupled device (CCD) camera was used to monitor the initiation and evolution of the failures. Variations in the strain fields were quantified following the digital image correlation (DIC) approach, whereas the resultant failure markings were elucidated by conducting microscopic assessments. The 3D finite element modeling (FEM) of the experiment was accomplished via ABAQUS/Explicit, thereby reproducing the material performance. A 3D-modified theory of the Tsai-Wu failure initiation was executed by exploiting the VUMAT subroutine. The evolutionary rule was used to study the complementary failure. A cohesive zone element of the composite interlayer was utilized to mimic the intra-deformation interfacial damage. The DIC-based experimental values of the strain fields agreed favorably with the numerical computations and the strength value error was less than 10%. An in-depth investigation was performed concerning the advantage of the 3D modeling approach to study the applicability of the method for the foreseeable distribution of the complex field parameters (e.g., progressive failure deposition and free edge effect) inside the critical specimen section.

Three kinds of four-step three-dimensional braided silicon carbide fiber-reinforced silicon carbide matrix composites with pyrocarbon interface were prepared through precursor infiltration and pyrolysis under 1100 °C, 1300 °C, or 1500 °C, and they were oxidized at 1300 °C with simulated air. The effects of pyrolysis temperature on the microstructure and oxidation behavior of the composites were investigated. Results indicated that the SiC crystallite size and crystallinity of the as-fabricated composites increased with increasing pyrolysis temperature. During oxidation, the three composites initially underwent similar near-linear mass-loss stages associated with the consumption of carbon component. Subsequently, they exhibited different mass-gain stages associated with the oxidation of SiC component. The composites prepared at 1100 °C followed a linear mass-gain rule, whereas the composites prepared at 1300 °C and 1500 °C followed a two-step parabolic mass-gain rule. The mechanism of mass-gain behavior change was proposed, which might be associated with the pyrolysis-temperature-dependent precursor-derived ceramic SiC microstructure and its evolution during oxidation.

Three types of SiCf/SiC composites with a four-step three-dimensional SiC fibre preform and pyrocarbon interface fabricated via precursor infiltration and pyrolysis at 1100 °C, 1300 °C, and 1500 °C were heat-treated at 1300 °C under argon atmosphere for 50 h. The effects of the pyrolysis temperature on the microstructural and mechanical properties of the SiCf/SiC composites were studied. With an increase in the pyrolysis temperature, the SiC crystallite size of the as-fabricated composites increased from 3.4 to 6.4 nm, and the flexural strength decreased from 742 ± 45 to 467 ± 38 MPa. After heat treatment, all the samples exhibited lower mechanical properties, accompanied by grain growth, mass loss, and the formation of open pores. The degree of mechanical degradation decreased with an increase in the pyrolysis temperature. The composites fabricated at 1500 °C exhibited the highest property retention rates with 90% flexural strength and 98% flexural modulus retained. The mechanism of the mechanical evolution after heat treatment was revealed, which suggested that the thermal stability of the mechanical properties is enhanced by the high crystallinity of the SiC matrix after pyrolysis at higher temperatures.

In this paper, the three-dimensional needled carbon fiber reinforced C-SiC-TiC ceramic composites (Cf/C-SiC-TiC) were successfully fabricated by chemical vapor infiltration (CVI) and Ti, Si mixed powders (Si content is the eutectic point of the Ti-Si alloy, 9.2 w.t.%) reactive melt infiltration (RMI) process. The open porosity and bulk density were about 4.71% and 2.14 g/cm3. The formation and distribution of the composites were investigated by XRD and EDS maps, and no residual Ti or Si phases were found. TiC and a layered SiC ceramics were formed in carbon fiber reinforced pyrolytic carbon (Cf/C) preforms due to the in situ reaction between pyrolytic carbon and Ti, Si powders. Their mechanical properties were improved compared with Cf/C-SiC composites. The flexural strength, flexural modulus and failure strains of the prepared composites were 218.44 ± 16.23 MPa, 68.17 ± 8.69 GPa and 2.22 ± 0.12%, respectively. In addition, the Cf/C-SiC-TiC composites showed a pseudoplastic fracture behavior because of debonding and pullout of fibers as well as propagation and deflection of cracks. Furthermore, the enhanced mechanism of the composites was proposed.

In this paper, porous SiCf/SiC composites are prepared by chemical vapor infiltration of SiC matrix on stitched fibrous preforms with different fabrics laminate structure. The microstructure of the fibrous preforms before and after infiltration of SiC matrix and the permeability and the regeneration efficiency of the porous SiCf/SiC composites with different laminate structure have been determined. Experimental results show that the porous SiCf/SiC composites with twill fabrics laminate structure exhibits a higher permeability with a higher volume porosity and mean pore diameter. In comparing the regeneration ability of two types laminate structure filter medium, as expected, the twill fabrics laminate structure exhibits a better regeneration efficiency than the plain fabrics laminate structure due to its higher air permeability.

Background Non-small cell lung cancer (NSCLC) is a common malignancy around the globe. Increasing long non-coding RNAs (lncRNAs) have been confirmed to be associated with the progression of cancers, including NSCLC. Long intergenic non-protein coding RNA 1783 (LINC01783) is a novel lncRNA and its regulatory function as competing endogenous RNA (ceRNA) has not been studied in NSCLC. Methods RT-qPCR measured the expression level of LINC01783 in NSCLC cells. CCK-8, EdU, transwell and wound healing assays were conducted to detect cell proliferation, migration and invasion in NSCLC. The relationship between miR-432-5p and LINC01783 along with delta like 1 (DLL-1) was illustrated by RNA pull down, RIP and luciferase reporter assays. Results LINC01783 was found remarkably increased in NSCLC cell lines, and down-regulation of LINC01783 suppressed cell proliferation, migration and invasion. Then, we discovered Notch pathway was related to the progression of NSCLC, and DLL-1 expression was reduced by LINC01783 knockdown. Furthermore, DLL-1 overexpression could counteract the suppressive effects of LINC01783 down-regulation on the growth of NSCLC cells. MiR-432-5p was observed to be the mutual miRNA that could bind with both LINC01783 and DLL-1. Overexpression of miR-432-5p inhibited DLL-1 expression. In the rescue assays, miR-432-5p depletion offset the impacts of LINC01783 knockdown, and then DLL-1 silence recovered the influence of miR-432-5p down-regulation on NSCLC cell growth. Conclusion LINC01783 aggravates NSCLC cell growth by regulating Notch pathway and sponging miR-432-5p, being a potential target in the treatment for NSCLC.

Objective: To investigate the mRNA levels of peroxisome proliferator-activated receptor α (PPARα), hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial growth factor (VEGF) in the liver tissues of rats with alcoholic liver disease. Methods: A total of 50 Wistar rats were randomly divided into a 4-week model group (n = 10), an 8-week model group (n = 10), a 12-week model group (n = 10), a 16-week model group (n = 10), and a control group (n = 10). The control group got the same volume of distilled water, and the rats in the model groups were given ethanol to establish alcoholic liver disease model. The mRNA levels of PPARα, HIF-1α, and VEGF in the rats’ liver tissues, the fatty liver degree, and the inflammation degree in each group were examined and compared. Results: The liver tissues in 4 model groups showed a more worsened fatty liver degree and inflammation degree than those in control group (P < 0.05). With the extension of the modeling time, the fatty liver degree and inflammation levels were significantly increased (P < 0.05). All the model groups showed lower mRNA level of PPARα, and higher levels of HIF-1α and VEGF than the control group (P < 0.05). With the extension of the modeling time, the relative mRNA level of PPARα was decreased, while the mRNA levels of HIF-1α and VEGF increased (all P < 0.05). The fatty liver degree and inflammation level were negatively correlated with the PPARα mRNA level (r = -0.899, -0.893, P < 0.05) and positively correlated with the HIF-1α and VEGF mRNA levels (r = 0.791, 0.679, 0.744, 0.597, P < 0.05). The PPARα mRNA level was negatively correlated with HIF-1α and VEGF mRNA levels (r = -0.732, -0.681, P < 0.05). Conclusion: High PPARα mRNA levels and low HIF-1α and VEGF mRNA levels in the liver tissues of rats with alcoholic liver disease may be closely related to fatty liver and inflammation reactions.

Sonar image registration plays a key role in intelligent perception of underwater target. Corner is an important feature of the image. Image registration algorithms based on corner detection have been widely used. Common corner detection algorithms include Harris algorithm, small univalue segment assimilating nucleus (SUSAN) algorithm, features from accelerated segment test (FAST) algorithm, scale-invariant feature transform (SIFT) algorithm, etc. This paper examines the application of these four corner detection algorithms in sonar image registration and gives the experimental results. At the same time, this paper compares these four corner detection algorithms from five aspects: the number of detected corners, corners logarithm participating in registration, corners logarithm of correct matching, matching rate, and matching time.

The active oxidation of C/C composites at high temperature is a great obstacle for its application. In this study, a method of preparing SiC/Si–ZrB2–CrSi2/SiC multilayer oxidation-resistant coating for C/C composites by combining preoxidation and chemical vapor deposition (CVD) was proposed, and the results show that the coating has excellent oxidation resistance at 1473 K, 1573 K and 1673 K. Moreover, based on the uniform deformation model, the track of phases transition, lattice strain and internal stress for the protection/failure mechanisms at different temperatures/time were investigated by the agents of strain compatibility and stress distribution soured from XRD and Raman spectra.

The permeability is a key property of SiCf/SiC porous composites using as filter in high temperature. In this study, an analytical model based on Hagen–Poiseuille flow was used to investigate the relationship between the structural properties and the filtration performance of the fiber architecture, including fabric and stitched preform. The air flow through the fabric was considered in two different regions: inter-yarn and inter-fiber, as well as the pore properties of the fabrics. The key feature of the model was that the parameter of flow channel based on the pore shape was taken account into the calculation of the equivalent pore size. After determining the pore characteristics, the flow rates of the pore unit cell were obtained; subsequently, permeability of the fabrics and stitched preforms were predicted to compare with the experimental ones. This turns out that the analytical model shows a good correlation between the experimental and predicted permeability values, and the difference between different woven-type fabrics was well presented.

To improve the oxidation resistance and alleviate the thermal stress of the HfB2-SiC-Si/SiC coatings for C/C composites, in-situ formed SiC whiskers (SiCw) were introduced into the HfB2-SiC-Si/SiC coatings via chemical vapor deposition (CVD). Effects of SiCw on isothermal oxidation and thermal shock resistance for the HfB2-SiC-Si/SiC coatings were investigated. Results showed that the SiCw-HfB2-SiC-Si/SiC coatings exhibited excellent oxidation resistance for C/C composites with only 0.88% weight loss after oxidation for 468 h at 1500 °C, which was markedly superior to 4.86% weight loss for coatings without SiCw. Meanwhile, after 50 times thermal cycling, the weight loss of the SiCw-HfB2-SiC-Si/SiC coated samples was 4.48%, which showed an obvious decrease compared with that of the HfB2-SiC-Si/SiC coated samples. The SiCw-HfB2-SiC-Si/SiC coatings exhibited excellent adhesion to the C/C substrate and had no penetrating cracks after oxidation. The improved performance of the SiCw-HfB2-SiC-Si/SiC coatings could be ascribed to the SiCw, which effectively relieved CTE mismatch and remarkably suppressed the cracks through toughening mechanisms including whiskers pull-out and bridging strengthening. The above results were confirmed by thermal analysis based on the finite element method, which demonstrated that SiCw could effectively alleviate thermal stress generated by temperature variation. Furthermore, the SiCw-HfB2-SiC-Si/SiC coating can provide a promising fail-safe mechanism during the high temperature oxidation by the formation of HfSiO4 and SiO2, which can deflect cracks and heal imperfections.

Carbon nanotube (CNT)-reinforced SiCf/SiC composites were prepared through in-situ growth of CNTs on SiC fiber via catalytic chemical vapor deposition (CCVD) and subsequent densification by precursor infiltration and pyrolysis (PIP) to optimize electromagnetic interference (EMI) shielding performance in the frequency range of 8.2–12.4 GHz. The influence of CNTs on the dielectric properties and EMI shielding properties of the SiCf/SiC composite were studied. The SEM/TEM morphology showed that the CNT network was formed on the surface of SiC fibers. The electrical conductivity of composites increased owing to the introduction of CNTs, leading to markedly increased conductive loss. Elevated CNT concentration was found to enhance complex permittivity and tan δ. Experimental results exhibited that absorption shielding effectiveness was the dominant EMI shielding mechanism. With the increase in CNT amount, the EMI total shielding effectiveness of the composite increased and reached a maximum of 39 dB with Co loading of 8%, an increase of 60% over that of plain SiCf/SiC composites. The achieved EMI shielding properties suggested the potential of CNT-reinforced SiCf/SiC composites as new-generation EMI shielding materials.

Pre-oxidized fibers as reinforcement are candidates for reducing the overall cost of C/C composites with superior properties. This study investigated the dynamic oxidation and protection of the pre-oxidized fiber C/C composites (Pr-Ox-C-C). According to the Arrhenius equation, the oxidation kinetics of the Pr-Ox-C-C consisted of two different oxidation mechanism with the transition point was at about 700 °C. Scanning electron microscopy investigation showed that oxidation initiated from the fiber/matrix interface of composites, whereas the matrix carbon was easily oxidized. To improve the anti-oxidant properties of Pr-Ox-C-C, a ceramic powder-modified organic silicone resin/ZrB2-SiC coating was prepared by the slurry method. The coated samples were subjected to isothermal oxidation for 320 h at 700 °C, 800 °C, 900 °C, 1000 °C and 1100 °C with incurred weight losses of − 1.6%, 0.77%, − 1.28%, 0.68% and 1.19%, respectively. After 110 cycles of thermal shock between 1100 °C and room temperature, a weight loss of 1.30% was obtained. The Arrhenius curve presented four different phases and mechanisms for coating oxidation kinetics. The excellent oxidation resistance properties of the prepared coating could be attributed to the inner layer which was able to form B2O3-Cr2O3-SiO2 glass to cure cracks, and the ZrB2-SiC outer layer that could provide protective oxides to reduce oxygen infiltration and to seal bubbles.

A carbon/carbon (C/C)–Cu composite reinforced by novel carbon fiber 2.5D-braided preforms was fabricated through pressureless infiltration technique (PLI). The microstructure of the developed composite was characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The mechanical, tribological, and electrical properties of the C/C–Cu composite were compared with those of a C/C composite and a carbon/copper (C/Cu) contact strip material. Results showed that the proposed composite formed an excellent network conduction structure. Moreover, the composite exhibited a high flexural strength of 215 MPa, excellent compression strength of 324 MPa, and a particularly low electrical resistivity of 0.63 μΩm, validating its advantages over the C/Cu composite strip in terms of mechanical and electrical properties. The component phases (TiC) of the C/C–Cu composite formed an excellent interconnected structure, which stiffened the interface between the Cu alloy and the pyrocarbon matrix and resulted in excellent mechanical and electrical properties. The friction coefficients of the C/C, C/C–Cu, and C/Cu composites were 0.152, 0.169, and 0.062, respectively. The C/Cu composite exhibited the worst mechanical and electrical performance despite achieving the lowest friction coefficient. Thus, the C/C–Cu composite is a promising new type of sliding electrical contact material.

In this study, the mechanical properties of SiCf/SiC composites with a BN/SiC multilayer interface was evaluated after oxidized at 800 °C, 1100 °C and 1400 °C for 200 h. The damage evolution of the fabricated and oxidized composites were analyzed by acoustic emission techniques. The chemical composition and structural evolution of the SiCf/SiC composites after oxidation were observed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. Significant temperature-dependent strength degradation of the SiCf/SiC composites was observed. The results indicated that the interfacial microstructure change caused by oxidation had a significant impact on the damage process of the composites, and two different degradation mechanisms for oxidized composites are discussed. The toughening mechanism of crack deflection and fiber pull out failed after oxidation at 800 °C. The degradation of the mechanical properties after oxidation at 1100 and 1400 °C was attributed to the hysteresis of fiber breakage caused by weak interface bonding. This work could predict the service life of SiCf/SiC composites and contribute to their early application in aerospace.

SiCw-SiC foams with hollow skeleton were synthesized by a simple procedure that consisted of the chemical vapor infiltration (CVI) and oxidation process. Flexible carbon foam was employed as CVI template. A typical structure of SiCw-SiC foams consisting of SiC supporter with hollow skeleton structure accompanying numerous crooked SiC whiskers was obtained after burning out carbon skeleton of the carbon foam during oxidation process. SiCw-SiC foams have a density of 0.11 ≤ ρ ≤ 0.12 g/cm3, porosity ≥ 96% and a thermal conductivity at room temperature between 0.040 and 0.075 W/m·K. Thermal conductivity of the SiCw-SiC foams moderately increased with elevation of temperature, indicating that these foams with larger amount of whiskers exhibit excellent thermal insulation property at elevated temperature.

In this work, a strategy of preparing multilayer SiC/ZrB2-CrSi2-Si/SiC coating at low-temperature by combining chemical vapor deposition (CVD), brush-sintering and preoxidation was proposed for C/C composites. The coated C/C composites could maintain stable and long-term oxidation resistance at 1473–1673 K, and the specific mass loss was only 8.05 mg∙cm−2 after 1673 K/340 h oxidation. The coupling mechanism of the preparation process on the microstructure and performance, the kinetics process of oxidation behavior and the protection/failure mechanism of the coating were analyzed. Furthermore, the importance of organosilicon (SiCxOy) in the process of self-healing and oxidation resistance was enlightened.

A novel graphene modified high-temperature resistant adhesive for bonding carbon/carbon composites was developed. The effects of graphene content on the mechanical properties, thermal conductivities and braking properties of the carbon/carbon joints were studied. When the graphene content in the adhesive was 1.5 wt%, the specimens possessed the bonding strength of 13.2 MPa and the thermal conductivity of 23.89 W/(m•k), which were 63.09% and 145.03% higher than those of 0.0 wt%, respectively, and 24.38% and 64.53% higher than those of 5.0 wt%, respectively. The excellent properties were attributed to the uniform dispersion of graphene in the adhesive matrix, which could effectively reduce the stress concentration and provide a fast heat conductivity network chain. The adhesive properties also had an obvious influence on the braking performance. Finite element analysis considered that the main reason for the difference in braking performance was that the temperature and field distribution on the friction surface were affected by the thermal conductivity of the adhesive.

An improved sandwich structured composite with low thermal conductivity used in high temperature is discussed, which have a great potential to be used in thermal protection system. This composite was composed of compound core material and C/SiC laminates. It is crucially noted that the compound core material is composed of reticulated SiC foam and SiO 2 powders. In this paper, the thermal conductivity of compound core was much lower than that of unfilled SiC foam in high temperature. It was also observed that the thermal conductivities of compound cores with the density ranged from 1.23 to 1.38 g/cm 3 increased accordingly. A mathematical relation was derived to calculate the theoretical effective thermal conductivity of sandwich structured composite, and the results agreed with the measured data with an error of 5%.

This paper describes the preparation of ultralight flexible carbon foam (FCF) by direct carbonization of commercial melamine foam (MF). The effect of carbonization temperature on microstructure characteristics and thermal properties in FCF were evaluated. The thermal conductivity of the samples at ambient temperature was measured using the heat flow tester and the thermal conductivity of the samples at various temperatures was measured using water flow plate method. The pore distribution and microstructure morphology of the MF sample and FCF samples were also measured by mercury intrusion porosimetry and SEM imaging, respectively. The results show that the 3D network architecture and the triangle fiber shape of the MF precursor were inherited by the resulting FCF samples despite of a great reduction in volume. The average pore diameter of FCF samples reaches a lowest value for carbonization temperature of 850 °C. The thermal conductivity of FCF samples is considered to be affected by the porosity characteristic of FCF samples. The higher pore diameter of FCF samples, the greater its thermal conductivity.

The static and dynamic mechanical properties of three dimensional (3D) braided SiCf/SiC composites with pycrocarbon (PyC) and SiC and without an interphase layer prepared by polymer infiltration and pyrolysis (PIP), were investigated using static and dynamic bending tests as well as microstructural characterization. Test results indicated that the interfacial shear stress, flexural strength, elastic modulus, and storage modulus of 3D braided SiCf/SiC composites with an interphase layer were superior to those the composites without an interlayer; the former also showed a lower internal friction than the latter. Results from Weibull statistical analysis also indicated that the scale parameter σ0 (337.1 MPa and 630.6 MPa, respectively) and Weibull modulus m (16.85 and 19.91, respectively) of 3D braided SiCf/SiC composites with SiC and PyC interphase were higher than those of composites without an interphase (103.2 MPa, 14.02). The composite with the PyC interphase presented the highest flexural strength and the most ductile fractures because it featured relatively ideal interfacial bonding and a layered interphase structure, leading to effective energy-dissipation mechanisms, such as fiber pull-out. The composite with the SiC interphase exhibited highest elastic and dynamic moduli because of strong interfacial bonding and a non-layered rough interphase structure, which enhanced its ability to resist strain. The ideal interface improves load transfer and did not contribute to damping. The occurrence of interfacial damping in the 3D braided SiCf/SiC caused the internal friction to become more sensitive to temperature, frequency and amplitude. The static and dynamic mechanical properties, including internal friction and storage modulus, as well as failure behavior of the 3D braided composites were remarkably affected by the interface type.

With regard to the adiabatic principle for insulation, a new-type high-temperature vacuum insulation composite (HTVIC) was put forward as structural thermal protection system. This new structure consisted of graphite felt core material and sealing layer was prepared by Chemical Vapor Infiltration (CVI) pyrolytic carbon (PyC), CVI SiC and silicasol-infiltration-sintering (SIS) process with composite density as low as 0.306 g/cm3. In this paper, a mathematical relation was also derived to calculate the theoretical effective thermal conductivity of HTVIC, whose results agreed with the measured data with the error of