Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied ...Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied at room temperature and 800 ℃ using SiC balls as the counterpart. The Zr-Y jointly modified silicide coating is mainly composed of a thick （Nb,X）Si2 outer layer and a thin （Ti,Nb）5Si4 inner layer. The coatings possess much higher microhardness than the base alloy. The wear rates of both the base alloy and coatings increase with increasing the sliding loads. However, the coatings have much lower wear rates than the base alloy under the same sliding conditions. The coatings have superior anti-friction property, and can provide effective protection for the base alloy at both room temperature and 800 ℃ in air.展开更多
The sugar cane bagasse was treated with chemical treatment including sodium hydroxide and silane. The characterization of the modified bagasse was achieved with Fourier transform infrared spectroscopy （FTIR）, and sc...The sugar cane bagasse was treated with chemical treatment including sodium hydroxide and silane. The characterization of the modified bagasse was achieved with Fourier transform infrared spectroscopy （FTIR）, and scaning electron microscopy （SEM）. Results showed that the presence Si-CH3 group occurred on bagasse surface after chemical modification. In addition, the roughness of the modified bagasse was higher than that of unmodified bagasse due to chemical modification from sodium hydroxide. Two polymer composite types, namely （1） natural rubber NR/sugar cane bagasse and （2） NR/plaster via two-roll mill method, were prepared. The optimum cure （t90） and torque of the NR/plaster increased with increasing plaster loading in composite. In case of NR/bagasse, the tgo of this sample decreased as a function of sugar cane bagasse while torque of this sample increased with increasing sugar cane bagasse. The modulus of the resulting composite increased with increasing both plaster and sugar cane bagasse, but the tensile strength and elongation at break of the composite decreased as a function of both piaster and sugar cane bagasse in composite.展开更多
The effects of olefins were quantified by measuring the decreased amount of thiophenes removed by modified zeolites with an increasing olefin concentration in model fuels （300 ppm） via fixed-bed adsorption technique...The effects of olefins were quantified by measuring the decreased amount of thiophenes removed by modified zeolites with an increasing olefin concentration in model fuels （300 ppm） via fixed-bed adsorption technique at room temperature and atmosphere pressure. The influence of olefins on adsorptive desulfurization of model fuel had been investigated by FT-IR techniques, which revealed that the protons in the zeolites were the sites responsible for the adsorption of olefins. On the CeY zeolite, in the presence of strong hydroxyl species in the zeolites, the adsorbed olefin compounds can attach to the protons molecularly via electrophilic interaction and undergo the opening of the C=C bonds depending on the acidity of the zeolites. The reduced desulfurization performance of CeY zeolite was attributed to the direct occupation of the absorbent＇s active sites by olefins. In contrast to the CeY zeolite, the NiY zeolites were unable to react directly with pure olefins. However the sulfur compounds and olefins adsorbed on the protons may subsequently undergo olefin alkylation reactions, which can block the zeolite pores and then prevent sulfide molecules from having access to super-cages to contact with the metal cations. This work demonstrates also that the NiY zeolites exhibit excellent performance for selective adsorption desulfurization of model fuel containing olefin compounds.展开更多
The hot corrosion behaviour of a modified Ti3Al-based alloy under thin Na2SO4deposit film was investigated at910and950°C in air.The corrosion product was identified by XRD and its morphologies on the surface and ...The hot corrosion behaviour of a modified Ti3Al-based alloy under thin Na2SO4deposit film was investigated at910and950°C in air.The corrosion product was identified by XRD and its morphologies on the surface and cross-section were observed bySEM.The alloy suffered from considerable hot corrosion attack.The mass gain versus time curves obtained by TGA exhibited tworegions of different kinetics.The whole corroded layer consisted of loose and porous mixture oxides of TiO2,Nb2O5and Al2O3.Numerous small nodules of corrosion product were observed.An illustrative schematic was established to describe the formationprocess of such nodules.It seemed that the refractory oxides played a significantly important role in determining the development ofhot corrosion attack.展开更多
Poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF-HFP） based composite polymer electrolyte （CPE） modified with CeO2, La2O3 and Y2O3 nano-rare earth oxides was prepared by phase inversion technique. Physical...Poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF-HFP） based composite polymer electrolyte （CPE） modified with CeO2, La2O3 and Y2O3 nano-rare earth oxides was prepared by phase inversion technique. Physical and chemical properties of the modified CPEs were studied by SEM, TG-DSC and electrochemical methods. The results show that the CPE modified with 10% La2O3 （mass fraction） has the best practical applicability, which indicates that the thermal and electrochemical stability can reach over 400 ℃ and 4.5 V, respectively, and temperature dependence of ionic conductivity follows Vogel-Tamman-Fulcher （VTF） relationship and ionic conductivity at room temperature is up to 3.3 mS/cm. The interfacial resistance Ri reaches a stable value about 557 Ω after 6 d storage.展开更多
Adhesive bonding technology is often the preferred solution for the joining of polymers. In many cases a wet chemical pretreatment has to he used to achieve sufficient adhesion strength and durability of the adhesive ...Adhesive bonding technology is often the preferred solution for the joining of polymers. In many cases a wet chemical pretreatment has to he used to achieve sufficient adhesion strength and durability of the adhesive joint. Since several years, plasma treatment has been a proven method to attain these goals. However, conventional treatments in oxidizing gases such as air are often not satisfying. In this work, the PP （polymers polypropylene）, PVDF （polyvinylidene fluoride）, PA6 （polyamide 6）, POM （polyoxymethylene） and PC （polycarbonate） were pretreated by means of a plasma jet running at atmospheric pressure in a virtually oxygen-free atmosphere. The goal was the grafting of reactive nitrogen-containing functional groups on the plastic surfaces in order to increase the adhesive strength.展开更多
Glycidyl azide polymer （GAP） with the advantages of non-volatility and excellent thermal stability is a candidate as a re- placement for nitroglycerine （NG） in a double base propellant. The GAP-NC double base prop...Glycidyl azide polymer （GAP） with the advantages of non-volatility and excellent thermal stability is a candidate as a re- placement for nitroglycerine （NG） in a double base propellant. The GAP-NC double base propellants were formulated with GAP and nitrocellulose （NC） fibers. Tensile test and SEM characterization indicated that GAP-NC propellants had a homoge- neous structure. Thermogravimetric analysis of GAP-NC propellants revealed that the onset decomposition temperature reached a high level ranging from 192.9 to 194.6 ℃, which indicated that the substitution of NG with GAP contributed to the safe storage and process operations for double base propellant. The result analysis of decomposition products of GAP-NC propellants showed that the main gas decomposition products of the propellants were NO, NO〉 CO, CO2, NH3, CH4, HCN, N2 CH20 and C2H40. The thermal decomposition process of the specimens was proposed.展开更多
Conductive polymer coatings can boost the power storage capacity of lithiumsulfur batteries. We report here on the design and preparation--by combining a facile and green chemical deposition method with an oxidative p...Conductive polymer coatings can boost the power storage capacity of lithiumsulfur batteries. We report here on the design and preparation--by combining a facile and green chemical deposition method with an oxidative polymerization approach--of polyaniline （PANI）-modified cetyltrimethylammonium bromide （CTAB）-graphene oxide （GO）-sulfur （S） nanocomposites with significantly enhanced performance in lithium-sulfur batteries. Such conductive polymer modified CTAB-GO-S nanocomposites as sulfur cathode materials can deliver high specific discharge capacities and long-term cycling performance, i.e., -970 mAh-g-1 at 0.2 C and -715 mAh-g-1 after 300 cycles, -820 mAh.g-1 at 0.5 C and -670 mAh.g-1 after 500 cycles, -770 mAh.K at 1 C and -570 mAh.g-~ after 500 cycles. The capacity decay was as low as 0.036% per cycle at 0.5 C, and 0.051% per cycle at 1 C. Under the same condition, batteries using PANI-modified CTAB-GO-S as cathodes exhibited higher specific capacity and higher average coulombic efficiency compared with CTAB-decorated GO-S and GO--S nano- composites. The improved performance can be attributed to the lower charge transfer resistance and the alleviated dissolution of polysulfides in the PANI- modified CTAB-GO-S cathodes.展开更多
基金Projects(51371145,51431003,U1435201,51401166)supported by the National Natural Science Foundation of ChinaProject(B080401)supported by the Programme of Introducing Talents of Discipline to Universities,China
文摘Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied at room temperature and 800 ℃ using SiC balls as the counterpart. The Zr-Y jointly modified silicide coating is mainly composed of a thick （Nb,X）Si2 outer layer and a thin （Ti,Nb）5Si4 inner layer. The coatings possess much higher microhardness than the base alloy. The wear rates of both the base alloy and coatings increase with increasing the sliding loads. However, the coatings have much lower wear rates than the base alloy under the same sliding conditions. The coatings have superior anti-friction property, and can provide effective protection for the base alloy at both room temperature and 800 ℃ in air.
文摘The sugar cane bagasse was treated with chemical treatment including sodium hydroxide and silane. The characterization of the modified bagasse was achieved with Fourier transform infrared spectroscopy （FTIR）, and scaning electron microscopy （SEM）. Results showed that the presence Si-CH3 group occurred on bagasse surface after chemical modification. In addition, the roughness of the modified bagasse was higher than that of unmodified bagasse due to chemical modification from sodium hydroxide. Two polymer composite types, namely （1） natural rubber NR/sugar cane bagasse and （2） NR/plaster via two-roll mill method, were prepared. The optimum cure （t90） and torque of the NR/plaster increased with increasing plaster loading in composite. In case of NR/bagasse, the tgo of this sample decreased as a function of sugar cane bagasse while torque of this sample increased with increasing sugar cane bagasse. The modulus of the resulting composite increased with increasing both plaster and sugar cane bagasse, but the tensile strength and elongation at break of the composite decreased as a function of both piaster and sugar cane bagasse in composite.
基金supported by the National Natural Science Foundation of China(No. 20476042 and No.20776064)the Ministry of Science and Technology of the People's Republic of China under the National Basic Research Program of China(973 Program) (2007CB216403)
文摘The effects of olefins were quantified by measuring the decreased amount of thiophenes removed by modified zeolites with an increasing olefin concentration in model fuels （300 ppm） via fixed-bed adsorption technique at room temperature and atmosphere pressure. The influence of olefins on adsorptive desulfurization of model fuel had been investigated by FT-IR techniques, which revealed that the protons in the zeolites were the sites responsible for the adsorption of olefins. On the CeY zeolite, in the presence of strong hydroxyl species in the zeolites, the adsorbed olefin compounds can attach to the protons molecularly via electrophilic interaction and undergo the opening of the C=C bonds depending on the acidity of the zeolites. The reduced desulfurization performance of CeY zeolite was attributed to the direct occupation of the absorbent＇s active sites by olefins. In contrast to the CeY zeolite, the NiY zeolites were unable to react directly with pure olefins. However the sulfur compounds and olefins adsorbed on the protons may subsequently undergo olefin alkylation reactions, which can block the zeolite pores and then prevent sulfide molecules from having access to super-cages to contact with the metal cations. This work demonstrates also that the NiY zeolites exhibit excellent performance for selective adsorption desulfurization of model fuel containing olefin compounds.
基金Projects(51271191,51571205)supported by the National Natural Science Foundation of China
文摘The hot corrosion behaviour of a modified Ti3Al-based alloy under thin Na2SO4deposit film was investigated at910and950°C in air.The corrosion product was identified by XRD and its morphologies on the surface and cross-section were observed bySEM.The alloy suffered from considerable hot corrosion attack.The mass gain versus time curves obtained by TGA exhibited tworegions of different kinetics.The whole corroded layer consisted of loose and porous mixture oxides of TiO2,Nb2O5and Al2O3.Numerous small nodules of corrosion product were observed.An illustrative schematic was established to describe the formationprocess of such nodules.It seemed that the refractory oxides played a significantly important role in determining the development ofhot corrosion attack.
基金Project(2011FJ1005)supported by the Major Provincial Science and Technology Program of Hunan Province,ChinaProject(2010qzzd0101)supported by the Central College on the 2010 Operational Costs of Basic Research Program,China
文摘Poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF-HFP） based composite polymer electrolyte （CPE） modified with CeO2, La2O3 and Y2O3 nano-rare earth oxides was prepared by phase inversion technique. Physical and chemical properties of the modified CPEs were studied by SEM, TG-DSC and electrochemical methods. The results show that the CPE modified with 10% La2O3 （mass fraction） has the best practical applicability, which indicates that the thermal and electrochemical stability can reach over 400 ℃ and 4.5 V, respectively, and temperature dependence of ionic conductivity follows Vogel-Tamman-Fulcher （VTF） relationship and ionic conductivity at room temperature is up to 3.3 mS/cm. The interfacial resistance Ri reaches a stable value about 557 Ω after 6 d storage.
文摘Adhesive bonding technology is often the preferred solution for the joining of polymers. In many cases a wet chemical pretreatment has to he used to achieve sufficient adhesion strength and durability of the adhesive joint. Since several years, plasma treatment has been a proven method to attain these goals. However, conventional treatments in oxidizing gases such as air are often not satisfying. In this work, the PP （polymers polypropylene）, PVDF （polyvinylidene fluoride）, PA6 （polyamide 6）, POM （polyoxymethylene） and PC （polycarbonate） were pretreated by means of a plasma jet running at atmospheric pressure in a virtually oxygen-free atmosphere. The goal was the grafting of reactive nitrogen-containing functional groups on the plastic surfaces in order to increase the adhesive strength.
文摘Glycidyl azide polymer （GAP） with the advantages of non-volatility and excellent thermal stability is a candidate as a re- placement for nitroglycerine （NG） in a double base propellant. The GAP-NC double base propellants were formulated with GAP and nitrocellulose （NC） fibers. Tensile test and SEM characterization indicated that GAP-NC propellants had a homoge- neous structure. Thermogravimetric analysis of GAP-NC propellants revealed that the onset decomposition temperature reached a high level ranging from 192.9 to 194.6 ℃, which indicated that the substitution of NG with GAP contributed to the safe storage and process operations for double base propellant. The result analysis of decomposition products of GAP-NC propellants showed that the main gas decomposition products of the propellants were NO, NO〉 CO, CO2, NH3, CH4, HCN, N2 CH20 and C2H40. The thermal decomposition process of the specimens was proposed.
文摘Conductive polymer coatings can boost the power storage capacity of lithiumsulfur batteries. We report here on the design and preparation--by combining a facile and green chemical deposition method with an oxidative polymerization approach--of polyaniline （PANI）-modified cetyltrimethylammonium bromide （CTAB）-graphene oxide （GO）-sulfur （S） nanocomposites with significantly enhanced performance in lithium-sulfur batteries. Such conductive polymer modified CTAB-GO-S nanocomposites as sulfur cathode materials can deliver high specific discharge capacities and long-term cycling performance, i.e., -970 mAh-g-1 at 0.2 C and -715 mAh-g-1 after 300 cycles, -820 mAh.g-1 at 0.5 C and -670 mAh.g-1 after 500 cycles, -770 mAh.K at 1 C and -570 mAh.g-~ after 500 cycles. The capacity decay was as low as 0.036% per cycle at 0.5 C, and 0.051% per cycle at 1 C. Under the same condition, batteries using PANI-modified CTAB-GO-S as cathodes exhibited higher specific capacity and higher average coulombic efficiency compared with CTAB-decorated GO-S and GO--S nano- composites. The improved performance can be attributed to the lower charge transfer resistance and the alleviated dissolution of polysulfides in the PANI- modified CTAB-GO-S cathodes.
