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Science china(Technological Sciences) 2010年第8期53卷 2232-2238页

作者： li wei,zhang shouyang ,yan xiafeng,li hejun&li kezhi state key laboratory of solidification processing,northwestern polytechnical university,xi’an 710072,china 1. state key laboratory of solidification processing Northwestern Polytechnical University Xi’an 710072 China

Chemical vapor infiltration of carbon fiber felts with uniform initial bulk density of 0.47 g·cm-3 was investigated at the ethanol partial pressures of 5-20 kPa,as well as the temperatures of 1050,1100,1150 and 1200°***,diluted by nitrogen,was employed as the precursor of pyrolytic *** light microscopy(PLM),scanning electron microscopy and X-ray diffraction were adopted to study the texture of pyrolytic carbon deposited at various temperatures.A change from medium-to high-textured pyrolytic carbon was observed in the sample infiltrated at 1050°***,homogeneous high-textured pyrolytic carbons were deposited at the temperatures of 1100,1150 and 1200°*** angles of 19°-21° were determined for different regions in the samples densified at the temperatures ranging from 1100 to 1200°*** electron microscopy of the fracture surface after bending test indicated that the prepared carbon/carbon composite samples exhibited a pseudo-plastic fracture *** addition,fracture behavior of the carbon/carbon samples was obviously effected by their infiltration *** fracture mode of C/C composites was transformed from shearing failure to tensile breakage with increasing infiltration temperature. Results of this study show that ethanol is a promising carbon source to synthesize carbon/carbon composites with homogeneously high-textured pyrolytic carbon over a wide range of temperatures(from 1100 to 1200°C).

关键词： C/C composites ethanol ICVI high-textured pyrolytic carbon

A judicious approach to induce large size growth of hydroxyapatite via applying graphene modified silicon nitride nanowires

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Journal of Materiomics 2024年第2期10卷 490-498页

作者： lina Sun Leilei zhang Ruonan zhang hejun li state key laboratory of solidification processing Shanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an710072China

Mimicking the structure of natural bone collagen fibers/hydroxyapatite(HA)to synthesize large size of HA for accelerated bone repair remains a ***,silicon nitride nanowires(SN)-graphene(GE)was designed by the chemical vapor deposition,forming SN-GE(SG)similar to collagen ***,the large size HA was assembled onto SG by pulsed electrochemical deposition,the SG/HA(SGH)mimics the collagen fibers/HA structure of *** introduction of SG induces HA to large size grow in the form of *** can be grown on a large size inextricably with the existence of GE modified *** the one hand,the upright GE sheets effectively increases the surface roughness which enhances the nucleation site of *** the other hand,the C■O provides chemical bonding and induces HA *** with SN/HA(SH),the porosity of SGH decreased by 71%.The average diameter of the SGH is(9.76±0.25)*** with SH,the diameter of SGH is 22 times larger than the diameter of *** that SG induces large size growth of *** work can provide a general strategy for the efficient preparation of biological scaffolds with large size HA that can be used in bone tissue engineering.

关键词： Hydroxyapatite Graphene Large size Silicon nitride nanowires Bone tissue engineering

Micro-and Nano-structure Characterization of Isotropic Pyrocarbon Obtained via Chemical Vapor Deposition in Hot Wall Reactor

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Journal of Materials Science & Technology 2010年第12期26卷 1133-1138页

作者： kezhi li,Dongsheng zhang,lingjun Guo and hejun li state key laboratory of solidification processing,northwestern polytechnical university,xi an 710072,china [a] state key laboratory of solidification processing northwestern polytechnical university xi'an 710072 china

The hot wall reactor was used to deposit isotropic pyrocarbon. The density of the product was measured by Archimedes method. The fracture morphology and texture of the product were investigated by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Raman spectroscopy was also applied to characterizing the structure of the product. The results show that the density of the product is about 1.31 g/cm^3. The pyrocarbon consists of granular particles with the size of about 1.5 μm under SEM images. Under TEM images, the pyrocarbon is composed of irregular grains and onion-like particles are also detected. The orientation angle （180 deg.） of pyrocarbon reveals its isotropic character. The ID/IG ratio in Raman spectrum is about 1.2, indicating the isotropic feature of the product qualitatively.

关键词： Isotropic pyrocarbon Chemical vapor deposition Structure characterization Onion-like pyrocarbon

Constructing orthogonally structured graphene nanointerface on SiC nanowires reinforced carbon/carbon composites to boost mechanical strength and strength retention rate

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Journal of Materiomics 2024年第3期10卷 615-623页

作者： Yao Guo shouyang zhang Qiang Song Fei Zhao Longkang Cong wei li Ruimei Yuan state key laboratory of solidification processing Shaanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an 710072China Advanced Interdisciplinary Research Center for Flexible Electronics Academy of Advanced Interdisciplinary ResearchXidian UniversityXi'an 710072China

Carbon/carbon composites with higher mechanical strength and better reliability at elevated tempera-tures are urgently needed to satisfy the practical applications *** nanowires(SiCNWs)modified C/C(SC-CC)composites have attracted an abundance of attention for their excellent mechanical *** further boost the mechanical strengths of composites and maximize the reinforcing efficiency of SiCNWs,we introduce orthogonally structured graphene nanosheets(OGNs)into SC-CC composites,in which OGNs are grafted on the SiCNWs via chemical vapor deposition(CVD)method,forming SC-G-CC *** from the nano-interface effects,uniform stress distribution,strong SiCNWs/PyC interfacial bonding and elevated stress propagation efficiency in the PyC matrix are achieved,thus SC-G-CC composites accomplish brilliant mechanical properties before and after 1,600℃ heat *** temperature rises to 2,100℃,SiCNWs lose efficacy,whereas OGNs with excellent thermal stability continue to play the nano-interface role in the PyC ***,SC-G-CC com-posites show better mechanical performance after 2,100℃ heat treatment,and the mechanical strength retention rate(MSR)of interlaminar shear strength,out-of-plane and in-plane compressive strength of SC-G-CC composites reach 61.0%,55.7%and 55.3%,*** work proposes an alternative thought for maximizing the potentiality of nanomaterials and edifies the mechanical modification of composites.

关键词： SiC nanowires Orthogonally structured graphene nanosheets Carbon/carbon composites Mechanical properties Heat treatment

Elevating mechanical and biotribological properties of carbon fiber composites by constructing graphene-silicon nitride nanowires interlocking interfacial enhancement

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Journal of Materiomics 2024年第5期10卷 1080-1090页

作者： xinyi Wan Leilei zhang Bihan zhang Qian Gao Tiantian Wang Haiyang li Hongchao Sheng hejun li Shaanxi key laboratory of Fiber Reinforced light Composite Materials Northwestern Polytechnical UniversityXi'an710072China Department of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang212003JiangsuChina

Carbon fiber reinforced dual-matrix composites(CHM)including carbon fiber reinforced hydroxyapatite-polymer matrix composites(CHMP)and carbon fiber reinforced hydroxyapatite-pyrolytic carbon matrix composites(CHMC)have great potential application in the field of artificial hip joints,where a combination of high mechanical strength and excellent biotribological property are *** this work,the graphene-silicon nitride nanowires(Graphene-Si_(3)N_(4)nws)interlocking interfacial enhancement were designed and constructed into CHM for boosting the mechanical and biotribological *** graphene and Si_(3)N_(4)nws interact with each other and construct interlocking interfacial *** from the Graphene-Si_(3)N_(4)nws synergistic effect and interlocking enhancement mechanism,the mechanical and biotribological properties of CHM were *** with CHMP,the shear and compressive strengths of Graphene-Si_(3)N_(4)nws reinforced CHMP were increased by 80.0% and 61.5%,*** friction coefficient and wear rate were reduced by 52.8% and 52.9%,*** with CHMC,the shear and compressive strengths of Graphene-Si_(3)N_(4)nws reinforced CHMC were increased by 145.4% and 64.2%.The friction coefficient and wear rate were decreased by 52.3% and 73.6%.Our work provides a promising methodology for preparing Graphene-Si_(3)N_(4)nws reinforced CHM with more reliable mechanical and biotribological properties for use in artificial hip joints.

关键词： Carbon fiber composites Graphene-Si_(3)N_(4)nws reinforcement Interlocking enhancement Mechanical property Biotribological property

Oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient friction and wear reduction

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Friction 2024年第7期12卷 1499-1511页

作者： Jianxi liU Yong QIAN Dongsheng li wei WU Mengchen zhang Jie yan Bin li Feng ZHOU state key laboratory of solidification processing Center of Advanced Lubrication and Seal MaterialsSchool of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Shaanxi Engineering Research Center of Special Sealing Technology Xi'an Aerospace Propulsion InstituteXi'an 710100China state key laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

Nanomaterials as lubricating oil additives have attracted significant attention because of their designable composition and structure,suitable mechanical property,and tunable surface ***,the poor compatibility between nanomaterials and base oil limits their further *** this work,we demonstrated oil-soluble poly(lauryl methacrylate)(PLMA)brushes-grafted metal-organic frameworks nanoparticles(nanoMOFs)as lubricating oil additives that can achieve efficient friction reduction and anti-wear *** were synthesized by free-radical polymerization,which was coordinatively grafted onto the surface of the UiO-67 ***,PLMA brushes were grown on the macroinitiator-modified UiO-67 by surface-initiated atom transfer radical polymerization,which greatly improved the lipophilic property of the UiO-67 nanoparticles and significantly enhanced the colloidal stability and long-term dispersity in both non-polar solvent and base *** adding UiO-67@PLMA nanoparticles into the 500 SN base oil,coefficient of friction and wear volume reductions of 45.3%and 75.5%were achieved due to their excellent mechanical properties and oil ***,the load-carrying capacity of 500 SN was greatly increased from 100 to 500 N by the UiO-67@PLMA additives,and their excellent tribological performance was demonstrated even at a high friction frequency of 65 Hz and high temperature of 120℃.Our work highlights oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient lubricating additives.

关键词： MOFs polymer brushes surface modification tribological properties friction reduction anti-wear

Oxidation Protective C/SiC/Si-SiC Multilayer Coating for Carbon/Carbon Composites Applying at 1873 K

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Journal of Materials Science & Technology 2010年第12期26卷 1139-1142页

作者： Yulei zhang,hejun li,xinfa Qiang and kezhi li C/C Composites Research Center,state key laboratory of solidification processing,northwestern polytechnical university,xi an 710072,china [a] C/C Composites Research Center state key laboratory of solidification processing northwestern polytechnical university xi(an 710072 china

A C/SiC/Si-SiC multilayer coating for protecting carbon/carbon （C/C） composites against oxidation was prepared by slurry and pack cementation. X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） analysis showed that the inner coating obtained from the slurry and pack cementation was a C/SiC gradient layer acting as bonding layer, and the exterior coating formed in the second pack cementation was a Si-SiC double phase coating. Oxidation tests at 1873 K in air showed that the coating exhibited excellent oxidation protective ability and thermal shock resistance. The coating could effectively protect C/C composites from oxidation at 1873 K in air for 170 h and undergo the thermal cycling between 1873 K and room temperature for 8 cycles. The weight loss of the coated C/C composites is due to the formation of cracks and holes in the coating and the volatilization of SiO2 glass at high temperature.

关键词： Carbon/carbon composites Oxidation Coating

Pyrolysis of Copper Phthalocyanine as Non-noble Metal Electrocatalysts for Oxygen Reduction Reaction

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Journal of Wuhan university of Technology(Materials Science) 2024年第5期39卷 1087-1092页

作者： zhang lijuan LU Jinhua WANG yan li xiang School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an 710021China state key laboratory of solidification processing Carbon/Carbon Composites Research CenterNorthwestern Polytechnical UniversityXi’an710072China

We investigated the relationship between oxygen reduction reaction(ORR)activity and the pyrolysis temperature(650-850℃)of CuPc in alkaline *** highly active sites were formed through the decomposition of CuPc or Cu-N_(4) structure after releasing ***-Nx incorporated with carbon were the main active *** XPS measurement results show that,at lower temperature,the contents of pyridinic-N and pyrrolic-N account for the most of the total *** the temperature is higher than 750℃,the content of graphitic N(26.11%)increases and pyridinic-N(58.81%)becomes the dominant *** the temperature is higher than 850℃,the content of graphitic N increases remarkably and becomes the dominant ***,the specific surface areas decrease with increased pyrolysis *** from the synergistic effect,the pyrolysis temperature at 750℃of CuPc displays superior electrocatalytic *** obtained results reveal that the fabricated non-noble metal catalysts can be used as low-cost,efficient catalyst for water splitting ORR in metal-air batteries and fuel cells.

关键词： copper phthalocyanine pyrolysis electrocatalytic oxygen reduction reaction

Bending behaviors of large diameter thin-walled CP-Ti tube in rotary draw bending

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Progress in Natural Science:Materials International 2011年第5期21卷 401-412页

作者： Zhi-yong zhang,He yanG,Heng li,Ning REN,Yu-li TIAN state key laboratory of solidification processing,School of Materials Science and Engineering, northwestern polytechnical university,xi’an 710072,china state key laboratory of solidification processing School of Materials Science and Engineering Northwestern Polytechnical University Xi'an 710072 China

The rotary draw bending(RDB) of large diameter thin-walled(LDTW) tube needs the strict cooperation of multiple processing parameters to avoid possible multiple *** to the specific properties,the bending behaviors of LDTW commercial pure titanium(CP-Ti) tube are much more complex to achieve precise *** the CP-Ti tube of 50.8 mm(out diameter, D)×0.508 mm(wall thickness,t)×101.6 mm(bending radius,R) as a representative component,the bending behaviors of LDTW CP-Ti tube under different processing conditions were *** experiments and analytical analysis,the bending characteristics of the CP-Ti tube were ***,based on the orthogonal experimental design,a series of three-dimensional FE models of RDB for LDTW CP-Ti tube were established,and the effects of processing parameters on the bending behaviors were numerically *** results show that:1) Wrinkling is the primary behavior for the LDTW CP-Ti tube in RDB,and the larger the difference between the maximum wall thickening and the maximum wall thinning degrees of the bent tube,the larger the wrinkling tendency;2) The bending behaviors of the LDTW CP-Ti tube are very sensitive to the some processing parameters,and the wrinkling is significantly affected by the mandrel shank diameter,while the wall thinning is remarkably affected by the clearance between wiper die and tube,mandrel shank *** qualified bent tube with the wall thinning of 11.43%,the cross-section distortion of 2.69%and the wrinkling height less than 2%is then obtained.

关键词： CP-Ti tube large diameter rotary draw bending bending behaviors processing parameters

Superior synergistic oxidation resistance of medium-entropy carbide ceramic powders rather than multi-phase carbide ceramic powders

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Journal of Advanced Ceramics 2024年第8期13卷 1223-1233页

作者： Jiachen li Fanyu Lu Tao li yanqin Fu Junhao Zhao Junshuai Lv Yulei zhang Shaanxi key laboratory of Fiber Reinforced light Composite Materials State Key Laboratory of Solidification ProcessingNorthwestern Polytechnical UniversityXi'an 710072China

To date,some questions about medium-entropy carbide ceramics and the corresponding multi-phase carbide ceramics with the same cations and proportions remain *** oxidation behavior,do both have synergistic oxidation abilities and what role does entropy stabilization play in medium-entropy carbides?In this work,the oxidation behaviors of HfC-ZrC-TiC multi-phase carbide(HZT-MPC)and(Hf_(1/3)Zr_(1/3)Ti_(1/3))C medium-entropy carbide(HZT-MEC)powders were *** thermogravimetry(TG)oxidation,the TG curve of HZT-MPC had a bimodal ***"preferential oxidation"of HfC/ZrC occurred within HZT-MPC,followed by the formation of multi-phase oxides(HfO_(2),ZrO_(2),and TiO_(2)).The uneven compositional distribution slowed their solid solution reactions to form Ti-doped(Hf,Zr)O_(2) and(Hf,Zr)TiO_(4).The TG curve of HZT-MEC had a single peak.A uniform compositional distribution at the atomic scale promoted the rapid interdiffusion of oxides,forming Ti-doped(Hf,Zr)O_(2) and(Hf,Zr)TiO_(4) without ZrO_(2),HfO_(2),and TiO_(2) after TG ***,HZT-MEC had a higher onset oxidation temperature(To;470℃)than did HZT-MPC(430℃),and the TG single peak of HZT-MEC was between the TG bimodal peaks of ***,HZT-MEC showed superior oxidation resistance compared to HZT-MPC,which was attributed to the entropy stabilization effect of HZT-MEC suppressing the"preferential oxidation"of HfC/ZrC and the"delayed oxidation"of TiC,promoting the synergistic oxidation ability of multiple principal elements.

关键词： medium-entropy carbide multi-phase carbide synergistic oxidation ability oxidation resistance