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ON QUADRATURE OF HIGHLY OSCILLATORY FUNCTIONS

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Journal of Computational Mathematics 2006年第5期24卷 579-590页

作者： Shu-huang xiang Yong-xiong Zhou Department of Applied Mathematics and Software Central South University Changsha 410083 China

Some quadrature methods for integration of ∫a^bf（x）e^iwg（x）dx for rapidly oscillatory functions are presented. These methods, based on the lower order remainders of Taylor expansion and followed the thoughts of Stetter [9], Iserles and NФrsett [5], are suitable for all w and the decay of the error can be increased arbitrarily in case that g＇（x）≠0 for x∈[a, b], and easy to be implemented and extended to the improper integration and the general case I[f]=∫a^b f（x）e^ig（w,x）dx.

关键词： Oscillatory integral quadrature Filon-type method Taylor expansion.

Pretreatment of heterocyclic pesticide wastewater using ultrasonic/ozone combined process

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Journal of Environmental Sciences 2011年第5期23卷 725-730页

作者： Zhenglong xiong xiang Cheng Dezhi Sun College of Environmental Science & Engineering Beijing Forestry University Beijing 100083 China

Ultrasonic/O3 combined process was employed to pretreat heterocyclic pesticide wastewater for increasing biodegradability and reducing biological toxicity. Influences of ultrasonic frequency, ultrasonic power, probe diameter, initial pH and 03 dosage on the COD removal were studied. The results showed that the ultrasonic/O3 process significantly improved the biodegradability and reduced the biological toxicity of the wastewater. The ratio of BODs/COD was increased from 0.03 to 0.55 and the EC50 increased from 11% to 52% under ultrasonic/O3 treatment. Low ultrasonic frequency brought better COD removal. Initial pH was found to have a high influence on the COD removal and alkaline conditions were more favorable. The influences of ultrasonic power and probe diameter were small. With an increase in O3 dosage, COD removal was effectively improved. The optimal operational parameters for the combined process on COD removal were ultrasonic frequency 20 kHz, initial pH 9.00, ultrasonic power 300 W and dosage of O3 454.8 mg/（***）, under which the efficiency of COD removal reached 67.2%.

关键词： heterocyclic pesticide wastewater ultrasonic O3 BOD5/COD biological toxicity

Preparation and properties of C/C-SiC brake composites fabricated by warm compacted-in situ reaction

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International Journal of Minerals,Metallurgy and Materials 2010年第4期17卷 500-505页

作者： Zhuan Li Peng Xiao xiang xiong State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

Carbon fibre reinforced carbon and silicon carbide dual matrix composites（C/C-SiC） were fabricated by the warm compacted-in situ *** microstructure,mechanical properties,tribological properties,and wear mechanism of C/C-SiC composites at different brake speeds were *** results indicate that the composites are composed of 58wt%C,37wt%SiC,and 5wt%*** density and open porosity are 2.0 ***^（-3） and 10%,*** C/C-SiC brake composites exhibit good mechanical *** flexural strength can reach up to 160 MPa,and the impact strength can reach 2.5 kJ.m^（-2）.The C/C-SiC brake composites show excellent tribological *** friction coefficient is between 0.57 and 0.67 at the brake speeds from 8 to 24 m·s^（-1）.The brake is stable,and the wear rate is less than 2.02×10^（-6） cm^3·J^（-1）.These results show that the C/C-SiC brake composites are the promising candidates for advanced brake and clutch systems.

关键词： C/C-SiC ceramic matrix composites tribological properties microstructure

Oxidation behavior of boron-containing(Zr,Ti)C_(x)B_(y)solid solution ceramics at 1600℃in air

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Journal of Advanced Ceramics 2023年第10期12卷 1989-2002页

作者： Huilin Lun Yi Zeng xiang xiong Houbu Li State Key Laboratory of Performance and Structural Safety for Petroleum Tubular Goods and Equipment Materials CNPC Tubular Goods Research InstituteXi’an 710077China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Key Laboratory of Petroleum Tubular Goods and Equipment Ouality Safety for State Market Regulation CNPC Tubular Goods Research InstituteXi’an 710077China

Multicomponent boron-containing carbide coatings(i.e.,(Zr,Ti)C_(x)B_(y))on a C/C composite show good ablation ***,the high-temperature oxidation behavior of this new type of boron-containing(Zr,Ti)C_(x)B_(y)solid solution ceramics has not been clarified *** present work fabricated(Zr,Ti)C_(x)B_(y)solid solution block ceramics by spark plasma sintering,and their oxidation behavior at 1600℃in air(N2–20-vol%O2)was investigated for the first *** effects of boron on the oxidation resistance of(Zr,Ti)C_(x)B_(y)ceramics were *** results indicate that the(Zr,Ti)C_(x)B_(y)ceramics display good oxidation resistance with the parabolic rate law describing the oxidation *** the trace solution of boron(0.5 wt%)into(Zr,Ti)Cx,the oxidation resistance of carbide ceramics is significantly enhanced,leading to a decrease of 30%in the oxidation rate *** formed oxide scale in the(Zr,Ti)C_(x)B_(y)ceramics is dense,and the interlayer shows stronger ability to inhibit inward diffusion of *** addition,the introduction of boron leads to more negative binding energy of(Zr,Ti)C_(x)B_(y)and improves the oxidation resistance of carbides.

关键词： ultra-high-temperature ceramics(UHTCs) (Zr,Ti)CxBy solid solution oxidation behavior oxidation resistance

Preparation,Properties and Application of C/C-SiC Composites Fabricated by Warm Compacted-in situ Reaction

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Journal of Materials Science & Technology 2010年第3期26卷 283-288页

作者： Peng Xiao Zhuan Li Zibing Zhu xiang xiong State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China China Aviation Power Plant Research Institute Zhuzhou 412002 China

Carbon fibre reinforced carbon and SiC dual matrices composites （C/C-SiC） show superior tribological properties,high thermal shock resistance and good abrasive resistance,and they are promising candidates for advanced brake and clutch *** microstructure,mechanical properties,friction and wear properties,and application of the C/C-SiC composites fabricated by warm compacted-in situ reaction were *** results indicated that the composites were composed of 50-60 wt pct carbon,2-10 wt pct residual silicon and 30-40 wt pct silicon *** C/C-SiC brake composites exhibited good mechanical *** value of flexural strength and compressive strength could reach 160 and 112 MPa,*** impact strength was about 2.5 kJ·*** C/C-SiC brake composites showed excellent tribological performance,including high coefficient of friction （0.38）,good abrasive resistance （1.10 μm/cycle） and brake steadily on dry *** tribological properties on wet condition could be mostly *** silicon carbide matrix in C/C-SiC brake composites improved the wear resistance,and the graphite played the lubrication function,and right volume content of graphite was helpful to forming friction film to reduce the wear *** results showed that C/C-SiC composites fabricated by warm compacted-in situ reaction had excellent properties for use as brake materials.

关键词： C/C-SiC Ceramic-matrix composites Tribology Warm compacted-in situ reaction

Ultra-lightweight Ti3C2Tx MXene modified separator for Li–S batteries:Thickness regulation enabled polysulfide inhibition and lithium ion transportation

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Journal of Energy Chemistry 2020年第3期29卷 116-125页

作者： Nuo Li Ying Xie Shuting Peng xiang xiong Kai Han Hunan Provincial Key Laboratory of Chemical Power Sources College of Chemistry and Chemical EngineeringCentral South UniversityChangsha 410083HunanChina State Key Laboratory for Powder Metallurgy Powder Metallurgy Research InstituteCentral South UniversityChangsha 410083HunanChina

The practical application of lithium–sulfur(Li–S)batteries is limited by the easy dissolution of polysulfides in the electrolyte,resulting in the lithium polysulfide(LPS)shuttle *** two-dimensional(2D)materials with abundant active binding sites and high surface-to-volume ratios have been developed to prepare functional separators that suppress the diffusion of ***,the influence of modified layer thickness on Li+transport has not been ***,we synthesized individual and multilayered 2D Ti3C2Tx MXene nanosheets and used them to fabricate a series of Ti3C2Tx-PP modified *** separators had mass loadings ranging from 0.16 to 0.016 mg cm-2,which is the lowest value reported for 2D materials to the best of our *** corresponding reductions in thickness ranged from 1.2μm to 100 *** shuttling was effectively suppressed,even at the lowest mass loading of 0.016 mg *** was due to the strong interaction between LPS intermediates and Ti atoms and hydroxyl functional groups on the separator *** lithium-ion diffusion coefficient increased with the reduction of Ti3C2Tx layers on the *** cycling stability and rate performance were attained when the separator with a Ti3C2Tx-PP mass loading of 0.016 mg cm-2 was incorporated into a Li–S *** nanotubes(CNTs)were introduced into the separators to further improve the electrical and Li+ionic conductivity in the cross-plane direction of the 2D *** the ultralightweight Ti3C2Tx/CNTs modified PP separator,the cell maintained a capacity of 640 m Ah g-1after 200cycles at 1C with a capacity decay of only 0.079%per cycle.

关键词： Lithium sulfur batteries Separator MXene Thicknesses 2D materials

Microstructural evolution and electromagnetic wave absorbing performance of single-source-precursor-synthesized SiCuCN-based ceramic nanocomposites

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Journal of Advanced Ceramics 2023年第7期12卷 1299-1316页

作者： Jincan Yang Qingbo Wen Bo Feng Yalei Wang xiang xiong State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Fundamentals Department Air Force Engineering UniversityXi'an 710051China

Copper(Cu)-containing single-source precursors(SSPs)for the preparation of SiCuCN-based ceramic nanocomposites were successfully synthesized for the first time using polysilazane(PSZ),copper(II)acetate monohydrate(CuAc),and 2-aminoethanol via nucleophilic substitution reactions at silicon(Si)centers of *** synthesis process,polymer-to-ceramic transformation,and high-temperature microstructural evolution of the prepared ceramics were *** properties and electromagnetic wave(EMW)absorbing performance of the ceramics were investigated as *** results show that the polymer-to-ceramic transformation finishes at ca.900 ℃,and Cu nanoparticles are homogeneously distributed in a SiCN matrix,forming a SiCN/Cu *** annealing at 1200 ℃,the Cu nanoparticles completely transform into copper silicide(CusSi).Interestingly,the thermal stability of the Cu nanoparticles can be strongly improved by increasing the free carbon content,so that a part of metallic Cu nanoparticles can be detected in the ceramics annealed even at 1300 ℃,forming a SiCN/Cu/Cu_(3)Si/C *** with SiCN,the SiCuCN-based nanocomposites exhibit strongly enhanced dielectric properties,which results in outstanding EMW absorbing *** minimum reflection coefficient(RC_(min))of the SiCN/Cu/Cu_(3)Si/C nanocomposites annealed at 1300 ℃ achieves-59.85 dB with a sample thickness of 1.55 mm,and the effective absorption bandwidth(EAB)broadens to 5.55 GHz at 1.45 *** enhanced EMW absorbing performance can be attributed to an in situ formed unique network,which was constructed with Cu and Cu_(3)Si nanoparticles connected by ring-like carbon ribbons within the SiCN matrix.

关键词： polymer-derived ceramics(PDCs) dielectric property electromagnetic wave(EMW)absorbing copper(Cu) microstructure

Elucidating the role of preferential oxidation during ablation:Insights on the design and optimization of multicomponent ultra-high temperature ceramics

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Journal of Advanced Ceramics 2022年第12期11卷 1956-1975页

作者： Ziming YE Yi ZENG xiang xiong Qingbo WEN Huilin LUN State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Multicomponent ultra-high temperature ceramics(UHTCs)are promising candidates for thermal protection materials(TPMs)used in aerospace ***,finding out desirable compositions from an enormous number of possible compositions remains ***,through elucidating the role of preferential oxidation in ablation behavior of multicomponent UHTCs via the thermodynamic analysis and experimental verification,the correlation between the composition and ablation performance of multicomponent UHTCs was revealed from the aspect of *** found that the metal components in UHTCs can be thermodynamically divided into preferentially oxidized component(denoted as MP),which builds up a skeleton in oxide layer,and laggingly oxidized component(denoted as ML),which fills the oxide ***,a thermodynamically driven gradient in the concentration of MP and ML forms in the oxide *** on these findings,a strategy for pre-evaluating the ablation performance of multicomponent UHTCs was developed,which provides a preliminary basis for the composition design of multicomponent UHTCs.

关键词： multicomponent ceramics ultra-high temperature ceramics(UHTCs) preferential oxidation oxidation behavior ablation resistance

Ablation characteristics of mosaic structure ZrC-SiC coatings on low-density, porous C/C composites

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Journal of Materials Science & Technology 2019年第12期35卷 2785-2798页

作者： Yonglong Xu Wei Sun xiang xiong Fuqun Liu Xingang Luan State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China China Academy of Launch Vehicle Technology Beijing 100076China Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi'an 710072China

Mosaic structure ZrC-SiC coatings were fabricated on low-density, porous C/C composites via thermal evaporation and an in-situ method. ZrC was packed in a typical lamellar mode, and the mosaic structure was formed by the deposition of Zr and Si atoms on the shallow surface of the porous C/C *** analysis showed that the defects in the coatings originate from the boundary between the ZrC and holes created by the consumption of SiC at 2500℃. After ablation for 200 s at 3000℃, a dense ZrO2 layer formed on the coating surface, and the defects were sealed owing to the continuous supply of ablative components. The mass and line ablation rates of the Zr C-SiC coatings were-0.46 ± 0.15 mg cm^-2·s^-1 and-1.00± 0.04 μm s^-1, respectively.

关键词： ZrC SiC Coating Mosaic structure Porous C/C composites Ablation