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Direct oxidation of organosilanes is one of the most straightforward ways to access silanols. Herein, we describe a novel photo-induced strategy for oxidation of organosilanes to access silanols, promoted by a photoactive charge-transfer complex (CTC) between sodium benzenesulfinate and molecular O2. A streamlined sequence transformation of organosilanes to silyl ethers was also readily achieved. This developed protocol represents the first example of CTC-based oxidation of organosilanes, offering a facile approach to access a series of silanol and silyl ether products. [ABSTRACT FROM AUTHOR]

A slurry-based laser cladding technique was used to repair the SiC coated carbon/carbon composites. The oxidation resistance of repaired samples at 1773 K for 10 h was investigated. Samples were characterized by X-ray diffraction pattern, scanning electron microscopy and confocal microscope; its interface characteristics were studied with scratch, thermal shock and internal friction tests. The results show that there is no obvious interface between the newly-formed coating and the original coating, and the newly-formed coating has a much smoother surface. With optimizing parameters, the new coating of 180 μm thickness possesses refined grains, flat surface, dense microstructure and good thermal stability. The number of internal defects in the samples repaired by laser cladding drops, compared with the damaged/undamaged samples. The weight loss of repaired samples decreases by 64.8% in comparison with the damaged ones, and it is almost the same with the undamaged samples according to a test of anti-oxidation behaviors. This is attributed to the enhanced oxidation resistance of dense newly-formed coating, which makes carbon/carbon composites well protected. [ABSTRACT FROM AUTHOR]

A porous carbon was synthesized from cotton black liquor. The carbon produced at the optimal condition was used for H 2 S oxidation at 423K at different experimental conditions. The H 2 S oxidation was modeled by a novel CFD approach by coupling the stoichiometric reaction with variation of porosity as the user-defined scalars (UDS). The established model can be a useful tool for studying the fluid dynamics of H 2 S oxidation by AC catalyst at experimental conditions in this work. • A porous carbon (AC) was synthesized from cotton black liquor. • The AC prepared under the optimal condition was applied to the direct H 2 S catalytic oxidation. • Complete parametrical computational fluid-dynamic (CFD) model was constructed. A porous activated carbon (AC) was synthesized from cotton black liquor, and the synthesis process was optimized using response surface method (RSM). The AC prepared under the optimal condition was applied to the direct H 2 S catalytic oxidation. Complete parametrical computational fluid-dynamic (CFD) model, coupling stoichiometric reaction with variation of porosity as the user-defined scalars (UDS), was developed to simulate the removal process. Various experiments, including breakthrough, pressure drops, and H 2 S conversion at different experimental conditions, were carried out. The CFD model was validated by results from the experiments, as the experiment results were found to adequately match model predictions. Hence, the model developed in this study can be a useful tool for studying the fluid dynamics of H 2 S oxidation by AC catalyst at investigated experimental conditions. [ABSTRACT FROM AUTHOR]

• Heat stress induces mitochondrial dysfunction and oxidative changes in duck meat. • Heat stress-responding proteins in duck chest muscle are comprehensively evaluated. • Some proteins are reported for the first time as potential indicators of heat stress in duck. Heat stress causes oxidative damage and quality reduction in poultry. Here, a tandem mass tag proteomic approach was applied to investigate the proteomic differences in duck meat from birds exposed to heat stress. Altogether 212 differential proteins were identified, including 178 down-regulated and 34 up-regulated proteins, compared to the control. Malondialdehyde and carbonyl content and cooking loss of the chest muscle significantly increased under heat stress. The proteomic analysis indicated that heat stress suppressed mitochondrial functions and respiratory chains, which might be responsible for the higher oxidation level. The results also revealed potential protective proteins involved in the defensive mechanisms against heat stress in duck muscles, such as sarcoplasmic/endoplasmic reticulum calcium ATPases, Mn-superoxide dismutase, heat shock protein family B member 7, methyltransferase like 21C, myosin-binding protein C, and carbonic anhydrase 3. These results provide potential targets for the research and identification of oxidative meat products due to heat stress. [ABSTRACT FROM AUTHOR]

To protect carbon/carbon composites against oxidation and ablation, a Fe 2 O 3 modified ZrB 2 –SiC–Si coating was prepared by a two-step pack cementation. The microstructure, oxidation and ablation resistance of the Fe 2 O 3 modified ZrB 2 –SiC–Si coating were studied. The results showed that the Fe 2 O 3 modified ZrB 2 –SiC–Si coating had good oxidation and ablation resistance, and could effectively protect the carbon/carbon composites from oxidation at 1773 K for 150 h and ablation at 2573 K for 60 s. The excellent oxidation and ablation resistance of the coating were mainly attributed to its dense and large amount of ZrB 2 in the coating. [ABSTRACT FROM AUTHOR]

Abstract: A self-sealing Si–Mo–B oxidation resistance coating was prepared on C/SiC coated carbon/carbon (C/C) composites by slurry and high temperature treatment method. The oxidation resistance of the coating increases at 1173K and first increases then decreases at 1873K with the increase of B content from 0 to 20wt.%. The C/SiC/gradient Si–Mo–B multilayer coating can protect C/C composite from oxidation for 100h at 1173K and 125h at 1873K. The good oxidation resistance of the coating in broad temperature range could be attributed to its good self-sealing property. [Copyright &y& Elsevier]

To protect carbon/carbon (C/C) composites against oxidation, ZrSiO oxidation protective coating was prepared on SiC-coated C/C composites by supersonic plasma spraying. X-ray diffraction and scanning electron microscopy were used to analyze the phase and microstructure of the coating. The results show that the as-prepared ZrSiO coating is continuous and well bonded with the SiC inner layer without penetrating crack, which exhibits good oxidation-resistant properties. After oxidation at 1773 K in air for 97 h and nine thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 0.08%. The excellent oxidation-resistant properties of the coating were attributed to its dense structure and the formation of the stable ZrO-SiO glassy mixture on the surface of ZrSiO coating. [ABSTRACT FROM AUTHOR]

Abstract: ZrB2–SiC–Si/B-modified SiC coating was prepared on the surface of carbon/carbon (C/C) composites by two-step pack cementation. The coating could efficiently provide protection for C/C composites from oxidation and ablation. The improvement of oxidation resistance was attributed to the self-sealing property of the multilayer coating. A dense glassy oxide layer could afford the high temperature up to 2573K and efficiently protect C/C composites from ablation. [Copyright &y& Elsevier]

A multicomposition resistant coating for SiC coated carbon/carbon (C/C) composites was produced by pack cementation technique in an argon atmosphere. This multicomposition coating was characterized by X-ray diffraction and scanning electron microscopy technique, and the oxidation behaviors of C/C with this multicomposition coating were also investigated in air using thermogravimetry. The results indicate that a dense coating with an average thickness of 200 μm can be got using pack cementation technique. The coating is composed of Al2O3, CrAl0.42Si1.58, SiC, and AI4SiC4, This multicomposition costing could effectively protect the composites from exposure to atmosphere at 1873 K for 49 h with the weight loss of the coated C/C composites being only 1.84%. [ABSTRACT FROM AUTHOR]

Abstract: A MoSi2–CrSi2–Si/B-modified SiC coating was prepared by two-step pack cementation. The coating could protect C/C composites from oxidation at 1173K for 600min and at 1873K for 300h and from erosion at 1873K for 50h, respectively. B2O3 oxidised from B-modified SiC layer could seal cracks at intermediate temperatures, resulting in improving the oxidation resistance of the coating. Large cracks caused by the bending of the coated specimens and excessive local stress resulted in the fracture of the tested specimens. [Copyright &y& Elsevier]

Abstract: The high-temperature erosion resistance of multi-layer MoSi2–CrSi2–Si/SiC coated carbon/carbon (C/C) composites was investigated in a wind tunnel. To study the aerodynamic oxidation mechanism and analyze the failure of the coated C/C composites, the shear force and bending moment distribution of the tested specimens in a wind tunnel were calculated. Flexural strengths and thermogravimetric analysis of the coated specimens were measured. These results show that the multi-layer MoSi2–CrSi2–Si/SiC antioxidation coating can protect the C/C composites from high-temperature erosion in a wind tunnel at 1873K for more than 86h. Due to the high viscosity of SiO2, the multi-layer coating lacked effective oxidation resistance from 900 to 1500K, resulting in extensive mechanical damage and the fracture of the tested specimens. [Copyright &y& Elsevier]

Abstract: To extend the oxidation protective temperature range of coating for carbon/carbon (C/C) composites, a SiC/ZrB2–SiC/SiC multilayer coating was prepared by a three-step method of pack cementation, slurry and chemical vapor deposition. The prepared coating is composed of three layers with about 150μm in thickness. It can protect C/C composites from oxidation for more than 300h at 1173K which is attributed to the oxidation ability of ZrB2. The coating can also effectively protect C/C composites from oxidation at 1773K for 217h which is due to the SiO2–ZrSiO4 compound glass during oxidation test. [Copyright &y& Elsevier]

To improve ablation resistance of silicon carbide (SiC)-coated carbon/carbon (C/C) composites, in this study, zirconium carbide (ZrC) coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. The coating exhibits dense structure, and a good bonding with substrate. The oxyacetylene ablation results show that the ZrC coating greatly improved the ablation resistance of SiC-coated C/C composites. After ablation for 30 s in oxyacetylene flame, the linear ablation rate is only 0.9 × 10 mm/s, and the weight is increased by 2.0 × 10 g/s. The excellent ablation resistance is mainly attributed to the formation of a dense and continuous zirconia (ZrO) layer during the oxidation of the ZrC coating. [ABSTRACT FROM AUTHOR]

Abstract: A MoSi2–CrSi2–SiC–Si multi-component coating was prepared on the surface of carbon/carbon (C/C) composites by a two-step pack cementation method. The microstructure, oxidation behavior and mechanical properties of the coating were studied. These results show that the multi-component coating could protect the C/C composites from oxidation in air at 1873K for 300h and withstand 30 thermal cycles between 1873K and room temperature, respectively. The mass loss and mechanical property loss of the coated C/C composites are considered due to the worse fluidity of SiO2 at intermediate temperatures and the thermal mismatch between the coating and C/C composites. [Copyright &y& Elsevier]

Abstract: To improve the oxidation resistance of carbon/carbon (C/C) composites, a C/SiC/MoSi2–Si multilayer oxidation protective coating was prepared by slurry and pack cementation. The microstructure of the as-prepared coating was characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The isothermal oxidation and erosion resistance of the coating was investigated in electrical furnace and high temperature wind tunnel. The results showed that the multilayer coating could effectively protect C/C composites from oxidation in air for 300h at 1773K and 103h at 1873K, and the coated samples was fractured after erosion for 27h at 1873Kh in wind tunnel. The weight loss of the coated specimens was considered to be caused by the formation of penetration cracks in the coating. The fracture of the coated C/C composites might result from the excessive local stress in the coating. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a self-sealing multilayer oxidation resistant coating including a C/SiC gradient inner layer, a Si-Mo-B middle layer and a glass exterior layer was prepared by pack cementation and slurry method. Scanning electron microscopy and X-ray diffraction were used to analyze the microstructure and phase composition of the as-prepared coating. The isothermal and thermal shock oxidation resistance of the coating was also investigated. The results showed that the multilayer coating exhibited excellent oxidation resistance from room temperature to 1873K. It could effectively protect C/C composites for 100h at 1173K and 150h at 1873K, and endure 40 thermal cycles between 1873K and room temperature. The excellent oxidation and thermal shock resistance could be attributed to the gradient structure and the self-sealing property of the multilayer coating. [Copyright &y& Elsevier]

To improve the oxidation resistance of the SiC-MoSi2 coating prepared by two-step pack cementation, a liquid Si infiltrating method was adopted to modify it. The phase composition and microstructure of the coatings were analyzed by XRD and SEM. The results show that the size and number of the cracks in the modified coating decreased evidently after infiltrating Si. The oxidation test results in air at 1773 K show that the mass loss of the SiC-MoSi2 coating coated carbon/carbon (C/C) composites was up to 1.18% after oxidation for 206 h, while that of the modified coating coated C/C composites was only 0.77% after oxidation for 460 h. The reason is that the cracks formed in the pack cementation process were partly sealed and there were no penetrable cracks in the modified coating. Therefore, there were no direct channels for the oxygen to diffuse into the C/C substrate. [ABSTRACT FROM AUTHOR]

Abstract: To protect carbon/carbon (C/C) composites against oxidation, a Si–Mo coating was prepared on C/SiC-coated C/C composites by a simple slurry method. The microstructure of the coating was characterized by X-ray diffraction, scanning electron microscopy and Raman spectra. Results showed that the coating was mainly composed of SiC, MoSi2 and Si. It could protect C/C composites from oxidation at 1873K in air for 300h and withstand 13 thermal cycles between room temperature and 1873K. The excellent oxidation and thermal shock resistance of the coating was attributed to the formation of dense SiO2 glass at high temperature. The volatilization of MoO3 and SiO2 at 1873K was the main reason of the weight loss of the coated C/C composites. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites from oxidation at elevated temperature, an effective WSi2–CrSi2–Si ceramic coating was deposited on the surface of SiC coated C/C composites by a simple and low-cost slurry method. The microstructures of the double-layer coatings were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analyses. The coating exhibited excellent oxidation resistance and thermal shock resistance. It could protect C/C composites from oxidation in air at 1773K for 300h with only 0.1wt.% mass gain and endure the thermal shock for 30 cycles between 1773K and room temperature. The excellent anti-oxidation ability of the double-layer WSi2–CrSi2–Si/SiC coating is mainly attributed to the dense structure of the coating and the formation of stable vitreous composition including SiO2 and Cr2O3 produced during oxidation. [ABSTRACT FROM AUTHOR]

Abstract: To protect carbon/carbon (C/C) composites against oxidation, MoSi2-based oxidation protective coatings for SiC-coated carbon/carbon composites were prepared on them by supersonic plasma spraying. The MoSi2-based coatings primarily consist of MoSi2, Mo5Si3 and glassy SiO2. Only a few pinholes and some microcracks are observed on the surface and no through-thickness cracks penetrate the cross-section. Weight loss of the MoSi2-based coated specimens is only 1.14% after 400h oxidation in air at 1773K and the coated C/C composites remain intact after 11 thermal cycles between 1773K and room temperature. The outstanding anti-oxidation ability is mainly attributable to the formation of SiO2-based layer on the surface of MoSi2-based coatings. [ABSTRACT FROM AUTHOR]

Abstract: Multi-layer MoSi2–CrSi2–Si anti-oxidation coatings with different compositional ratios were prepared on the surface of SiC coated carbon/carbon (C/C) composites by a two-step pack cementation method. The microstructure and anti-oxidation performance of the coating were studied. The results show that the multi-layered coatings could protect the C/C composites from oxidation in air at 1773K for 1000h or 1873K for 750h, respectively. The anti-oxidation performance of the multi-layer MoSi2–CrSi2–Si coating is mainly attributed to their dense and microcrack-free structure, appropriate thermal expansion coefficient and the well dispersed MoSi2 and CrSi2 in the coating. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites against oxidation, a SiC nanowire-toughened MoSi2–SiC coating was prepared on them using a two-step technique of chemical vapor deposition and pack cementation. SiC nanowires obtained by chemical vapor deposition were distributed random-orientedly on C/C substrates and MoSi2–SiC was filled in the holes of SiC nanowire layer to form a dense coating. After introduction of SiC nanowires, the size of the cracks in MoSi2–SiC coating decreased from 18±2.3 to 6±1.7μm, and the weight loss of the coated C/C samples decreased from 4.53% to 1.78% after oxidation in air at 1500°C for 110h. [Copyright &y& Elsevier]

Abstract: A MoSi2–CrSi2–Si multi-composition coating was prepared on the surface of SiC coated carbon/carbon (C/C) composites by pack cementation in argon. The crystalline structure of the multi-composition coating was measured by X-ray diffraction. The morphology and element distribution were analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively. The isothermal oxidation and erosion resistance of the multi-layer coating were investigated in electrical furnace and high temperature wind tunnel, respectively. These results indicated that the weight loss of the coated C/C composites was only 0.8% after oxidation in air at 1873K for 500h, and the sample was fractured after erosion at 1873K for 32h in wind tunnel. The weight loss of the coated C/C composites was considered due to the excessive depletion of the outer coating and the appearance of defects in the coating. The mismatch of thermal expansion coefficient between the multi-layer coating and C/C composites caused excessive local stress and resulted in the fracture of the coated C/C composites. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a multilayer oxidation resistant coating was prepared. The inner SiC coating was prepared by pack cementation, and the outer SiC–MoSi2 three-layer coating was obtained by slurry coating using silicon–sol as the caking agent. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to analyze the phase, microstructure and element distribution of the as-prepared coating. The results show that, the as-received multilayer coating has a crack-free structure with the thickness of about 300μm. It is provided with excellent oxidation resistance from room temperature to 1500°C in air and can protect C/C composites from oxidation for more than 120h at 900°C and more than 110h at 1500°C in air. The weight loss of the coated samples during oxidation tests mainly resulted from the oxidation of Mo5Si3 and the volatilization of SiO2 in the coating. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites against oxidation, a B2O3 modified SiC–MoSi2 coating was prepared by a two-step pack cementation. The microstructure and the oxidation resistant property of the coating were studied. The results show that, the as-received coating is a dense structure, and is composed of α-SiC, β-SiC and MoSi2. The B2O3 modified SiC–MoSi2 coating has excellent oxidation resistant property, and can protect C/C composites from oxidation at 1773K in air for more than 242h. The failure of the coating was considered to arise from the existence of the penetration cracks in the coating during the slow cooling from 1873 to 673K. [Copyright &y& Elsevier]

In order to protect carbon/carbon (C/C) composites against oxidation, a Si–Mo–W coating was prepared on the surface of SiC-coated C/C composites by a simple reaction method. The microstructures of the as-received coating were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy analyses. The results show that the SiC/Si–Mo–W coating can protect C/C composites from oxidation in air at 1673 K for 220 h with a mass loss of 0.003%, and at 1773 K for 252 h with a mass gain of 1.56%. The excellent oxidation-resistant property of the SiC/Si–Mo–W coating at 1673–1773 K is attributed to the formation of SiO2 film on the coating surface. The mass loss of the coated C/C composites during the oxidation test at 1873 K in air primarily resulted from the reaction of C/C substrate and oxygen diffusing through the penetration cracks in the coating. [ABSTRACT FROM AUTHOR]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a Si–SiC coating has been prepared by a two-step pack cementation technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis show that the coating obtained by the first step pack cementation is a porous β-SiC structure, and a dense structure consisting α-SiC, β-SiC and Si is obtained after heat-treatment by the second step pack cementation. By energy dispersive spectroscopy (EDS) analysis, a gradient C–SiC transition layer can be formed at the C/C-coating interface. The as-received coating has excellent oxidation protection ability and can protect C/C composites from oxidation for 166h at 1773K in air. The weigh loss of the coated C/C is due to the formation of bubble holes on the coating surface and through-coating cracks in the coating. [Copyright &y& Elsevier]

In order to protect carbon/carbon (C/C) composites from oxidation at 1700°C, a MoSi2–SiC–Si/MoSi2 coating was prepared on the surface of these composites by a simple and effective method. The MoSi2–SiC–Si inner layer was obtained by pack cementation, and the MoSi2 outer layer was prepared by slurry coating using silicon-sol as the caking agent. The microstructures of the as-prepared coating were examined by X-ray diffraction and scanning electron microscope. Oxidation test shows that, the as-received coating can protect C/C composites from oxidation for more than 107 h at 1700°C in air. The excellent anti-oxidation ability of this coating is attributed to its dense structure and the formation of the SiO2 film on the coating surface during oxidation. [ABSTRACT FROM AUTHOR]

A novel Mo–Si–B double-layer coating was prepared for the carbon/carbon (C/C) composites by pack cementation in an argon atmosphere. The structures of the double-layer coatings were characterized by XRD and SEM. The as-received coating shows an excellent oxidation resistance at high and intermediate temperature. It could effectively protect C/C composites from oxidation for 30 h with a weight loss of 0.9% in air at 1873 K, and for 25 h with a weight loss of l.7% at 1173 K. The oxidation protective coating was principally due to producing eutectic glass film for decreasing oxygen diffusing through the penetrable cracks in the coating. [ABSTRACT FROM AUTHOR]

In order to protect carbon/carbon (C/C) composites against oxidation, a (Mo,W)Si2 coating was prepared on the surface of SiC-coated C/C composites by a simple in situ information method using Si, Mo and W as starting materials. The microstructures and oxidation protective ability of the as-received coating were investigated. The results show that the (Mo,W)Si2 outer layer coating containing free Si has a good bonding with SiC inner layer. The as-prepared SiC/(Mo,W)Si2 coating can protect C/C composites from oxidation in air at 1773 K for 252 h with a weight gain of 1.56 wt.%. The excellent oxidation resistant property of the double-layer coating is attributed to its dense microstructure and the formation of the stable glassy SiO2 film on the (Mo,W)Si2 coating surface during its exposure to air at high temperatures. [ABSTRACT FROM AUTHOR]

Abstract: A microwave-assisted persulfate oxidation method followed by ion chromatographic determination of nitrate was developed for total nitrogen determination in atmospheric wet and dry deposition samples. Various operating parameters such as oxidation reagent concentrations, microwave power, and extraction time were optimized to maximize the conversion of total nitrogen to nitrate for subsequent chemical analysis. Under optimized conditions, 0.012M K2S2O8 and 0.024M NaOH were found to be necessary for complete digestion of wet and dry deposition samples at 400W for 7min using microwave. The optimized extraction method was then validated by testing different forms of organic nitrogen loaded to pre-baked filter substrates and NIST SRM 1648 (urban particulate matter), and satisfactory results were obtained. In the case of wet deposition samples, standard addition experiments were performed. The suitability of the method for real-world application was assessed by analyzing a number of wet and dry deposition samples collected in Singapore during the period of March–April 2007. The organic nitrogen content was 15% (wet) and 30% (dry) of the total nitrogen. During the study period, the estimated wet fluxes for nitrate (NO3 −), ammonium (NH4 +), organic nitrogen (ON), and total nitrogen (TN) were 16.1±6.5kgha−1 year−1, 11.5±5.7kgha−1 year−1, 3.8±1.5kgha−1 year−1and 31.5±13.2kgha−1 year−1, respectively, while the dry fluxes were 2.5±0.8kgha−1 year−1, 1.4±0.9kgha−1 year−1, 2.3±1.4kgha−1 year−1 and 7.5±2.6kgha−1 year−1, respectively. [Copyright &y& Elsevier]

Abstract: This work proposes a multi-composition oxidation resistant coating for SiC-coated carbon/carbon (C/C) composites by slurry method using the mixture of Y2O3, ZrO2, Al2O3, Si and C. XRD analysis shows that the phases of the composite coating are composed of SiC, Al2O3, Y2O3, ZrO2, Al4SiC4 and Y3Al2(AlO4)3. SEM analysis of the cross section of the coating displays the microstructure with 500μm thickness which filled the porous SiC. Oxidation test shows that, after 19h oxidation in air at 1873K, the weight loss of the coated SiC-C/C is only 1.76%. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks and bubble holes in the coating. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a multilayer coating based on molybdenum disilicide and titanium disilicide was formed using a two-step pack cementation technique in argon atmosphere. XRD and SEM analysis showed that the internal coating was a bond SiC layer that acts as a buffer layer, and that the external multilayer coating formed in the two-step pack cementation was composed of two MoSi2–TiSi2–SiC layers. This coating, which is characterized by excellent thermal shock resistance, could effectively protect the composites from exposure to an oxidizing atmosphere at 1773K for 79h. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating. [Copyright &y& Elsevier]

Abstract: A series of CrO x –Y2O3 catalysts were prepared by a deposition–precipitation method and tested for the fluorination of 2-chloro-1,1,1-trifluoroethane (CF3CH2Cl) to synthesize 1,1,1,2-tetrafluoroethane (CF3CH2F). The highest activity was obtained on a pre-fluorinated catalyst calcined at 400 °C, with 19% of CF3CH2Cl conversion at 320 °C. The effect of the calcination temperature on the CrO x species was investigated. X-ray diffraction and Raman results indicated that the CrO x species (Cr(VI)) were well dispersed on the catalyst surface when the catalyst was calcined at 400 °C. With increasing calcination temperature, most of the CrO x species changed from high oxidation state Cr(VI) to low oxidation state Cr(V) or Cr(III) species, which resulted in difficulty in pre-fluorination of the catalyst. It was also found that the CrF x , CrO x F y or Cr(OH) x F y phases originated from high oxidation state Cr(VI) species were the active sites for the fluorination reaction. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites from oxidation, a dense coating has been produced by a two-step pack cementation technique. XRD and SEM analysis shows that the as-obtained coating was composed of MoSi2, SiC and Si with a thickness of 80–100 μm. The MoSi2–SiC–Si coating has excellent anti-oxidation property, which can protect C/C composites from oxidation at 1773 K in air for 200 h and the corresponding weight loss is only 1.04%. The weight loss of the coated C/C composites is primarily due to the reaction of C/C substrate and oxygen diffusing through the penetration cracks in the coating. [Copyright &y& Elsevier]

Abstract: Yttrium silicates interlayer coatings of the SiC/yttrium silicates/borosilicate glass multi-layer coating system were prepared by a novel in-situ formation method using Si and Y2O3 as starting materials in an oxidation atmosphere. The surface and cross-section microstructures of the coatings were characterized by XRD and SEM analyses. Oxidation resistance of the coated samples was tested. Results showed that dense yttrium silicate interlayer coatings with good bond to SiC and borosilicate glass were prepared and the as-prepared multi-layer coating could protect C/C composites from oxidation at 1873K in air for 202h with a weight loss of 2.87×10−3g/cm2. [Copyright &y& Elsevier]

Abstract: A SiC whisker-toughened SiC–CrSi2 oxidation protective coating was prepared on the surface of C/C composites by a two-step technique of slurry and pack cementation. The oxidation protective ability and thermal stress resistance of the coating exhibit the trend of increase first and decrease afterwards as the SiCw content increases from 0 to 20wt.%. The compound effect of SiCw and CrSi2 on the oxidation protective ability of SiC coating is better than their individual ones. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a SiC–CrSi2 protective coating toughened with SiC whiskers (SiCw) has been prepared by a two-step technique of slurry and pack cementation. SEM and XRD analysis show that with the SiCw content increasing from 0 to 20wt.%, the coating thickness is reduced from 420 to 100μm, and the CrSi2 proportion in the coating first increases and then decreases. Oxidation tests in the range 1473–1773K shows that the coating toughened with 15wt.% SiCw possesses a better oxidation protective ability because of its more suitable thickness and microstructure. As the oxidation temperature increases from 1473 to 1773K, the oxidation protective ability of the coating improves gradually. The weight loss of the coated samples is primarily due to the reaction of C/C matrix and oxygen diffusing through the cracks in the coating. [Copyright &y& Elsevier]

Abstract: In order to eliminate the mismatch of the thermal expansion coefficient between SiC coating and C/C composites, a C/SiC gradient oxidation protective coating has been produced by a two-step technique. The first step is to prepare a slurry coated carbon layer, and the second one is to obtain a dense C/SiC concentration gradient coating by a pack cementation technique. The structures of the coatings were characterized by XRD, SEM and EDS analyses. Oxidation behaviour of the C/SiC coated C/C composites was also investigated. It was found that the as-prepared C/SiC gradient coating could effectively improve the oxidation resistance of SiC coating and could protect C/C composites from oxidation at 1773 K in air for 35 h with a weight loss of 2.46%. The gradient distributions of Si and C elements in the coating, which can suppress the generation of the thermal stresses, induce the excellent anti-oxidation ability of the C/SiC gradient coating. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites from oxidation, a new type of oxidation protective coating has been produced by a pack cementation technique in an argon atmosphere. XRD and SEM analysis showed that the phases of the composite coating were composed of SiC, MoSi2, and (Ti0.8Mo0.2)Si2. Oxidation test discovered that the weight loss of the SiC coated C/C was up to 11.26% after 5 h oxidation in air at 1773 K and the weight loss of the SiC–MoSi2–(Ti0.8Mo0.2)Si2 coated C/C composites characterized by excellent thermal shock resistance was only 2.18% in the same condition for 49 h. The oxidation of the coated C/C composites was primarily due to the reaction of the C/C matrix and oxygen diffusing through the penetrable cracks in the coating. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation at 1873 K, a dense SiC–Si–MoSi2 coating toughened with SiC whiskers (SiCw) was prepared by a two-step technique. The first step technique is to prepare a porous SiC coating toughened with SiCw by slurry, and the second one is to fill Si and MoSi2 in the holes of SiC coating by pack cementation. Oxidation test shows that the oxidation protective ability of SiC–Si–MoSi2 coating can be improved largely by adding 5–15 wt.% SiCw. After 38 h oxidation in air at 1873 K, the weight loss of the coated C/C sample without SiCw was up to 3.52%, while the weight loss of the coated sample with 10 wt.% SiCw was only 1.43%. [Copyright &y& Elsevier]

Abstract: Yttrium silicate coatings with an outer glass sealant for SiC pre-coated carbon/carbon (C/C) composites were prepared by a novel in situ formation method using Si and Y2O3 as starting materials in an oxidation atmosphere. The structures of the coatings were characterized by XRD and SEM analyses. Oxidation behavior of the multi-layer-coating-coated C/C composites was investigated. It showed that the as-prepared multi-layer coating could protect C/C composites from oxidation at 1600 °C in air for 202 h with a weight loss of 2.87×10−3g/cm2. The oxidation weight losses of the coated C/C with time accorded with linear and parabolic rule in the temperature range 400–800 and 1300–1600 °C, respectively, and the corresponding oxidation activation energy of the coated C/C composites are 99.6 and 112 kJ/mol, respectively. [Copyright &y& Elsevier]

Abstract: Four kinds of yttrium silicate oxidation protective coatings SiO2·Y2O3, 1.5SiO2·Y2O3, 1.5SiO2·Y2O3/SiO2·Y2O3 and 2SiO2·Y2O3/1.5SiO2·Y2O3/SiO2·Y2O3 were prepared by plasma spray on the surface of SiC pre-coated carbon/carbon composites. The structures of the coatings were characterized by XRD, SEM and EDS analyses. It was shown that the gradied 2SiO2·Y2O3/1.5SiO2·Y2O3/SiO2·Y2O3 multi-layer coating had better high-temperature oxidation resistance. It could protect carbon/carbon composites from oxidation at 1773K in air for 73h with a weight loss of less than 2%. The oxidation activation energy of the coated carbon/carbon composites is 87.3kJ/mol, and the oxidation process in C/C substrates with a multi-layer coating was controlled by the rate of oxygen diffusion through the holes in the coating. [Copyright &y& Elsevier]

Abstract: Oxidation protective SiC–Al2O3–mullite multi-coatings for carbon/carbon (C/C) composites were prepared with a two-step pack cementation process. The influence of preparation temperature and SiO2/Al2O3 ratio of the pack powder on the phase, microstructure and oxidation resistance of the multi-coatings were investigated. It showed that the multi-coatings that contained mullite could be produced at 1700–1800°C. A denser coating surface was acquired with the decrease of SiO2/Al2O3 ratio in the pack chemistries while a little damnification to the interface of the coating and C/C substrate. The as-prepared coating could effectively protect C/C composites from oxidation at 1600°C for 81h. [Copyright &y& Elsevier]

Abstract: A double-layer oxidation protective coating was prepared on carbon/carbon composites using a simple and low cost method. The coating consists of an inner buffer layer of β-SiC and an outer layer of molybdenum disilicide particles dispersed in a magnesium boron aluminosilicate glass (SABM). Oxidation test shows that, after oxidation in air at 1573 K for 150 h and thermal cycling between 1573 K and room temperature for 20 times, the weight loss of the coated material is only 1.07%. The decreasing of the sample weight is primarily due to the debonding of some glass on the coating surface. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites from oxidation, a new type of oxidation protective coating has been produced by a two-step pack cementation technique. XRD and SEM analysis show, the coating obtained by the first step pack cementation was a porous β-SiC structure, and a new phase of CrSi2 was generated in the porous SiC coating after heat-treatment according to the second step pack cementation process. Oxidation test shows that, the weight loss of the SiC coated C/C is up to 11.26% after 5h oxidation in air at 1773K, and the weight loss of the CrSi2–SiC coated C/C composites is only 4.15% after oxidation in air at 1773K for 34h. The oxidation of C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon composites from oxidation at 1773 K, an efficient oxidation protective glass coating has been prepared on the surface of SiC coated C/C composites by a simple and low-cost method. The microstructures and phase composition of the as-prepared coating were examined by SEM and XRD. Oxidation testing shows, after oxidation in air at 1773 K for 140 h and thermal cycling between 1773 K and room temperature for 8 times, the weight loss of the coated sample is only 0.98%. The oxidation of the coated C/C composites is attributed to the formation of bubble holes on the coating surface and microcracks in the coating. [Copyright &y& Elsevier]