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Effect of tungsten carbide particles on microstructure and mechanical properties of cu alloy composite bit matrix

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Journal of Iron and Steel Research International 2024年第2期31卷 519-530页

作者： Ding-qian Dong Feng-yuan He Xin-hui chen hui Li Kai-hua Shi hui-wen Xiong Xin Xiang Li Zhang college of mechanical Engineering Sichuan University of Science and EngineeringZigong643000SichuanChina State Key Laboratory of Powder metallurgy Central South UniversityChangsha410083HunanChina Zigong cemented carbide co. Ltd.Zigong643011SichuanChina material corrosion and Protection Key Laboratory of Sichuan Province Sichuan University of Science and EngineeringZigong643000SichuanChina

copper alloy composite bit matrix was prepared by pressureless vacuum infiltration,using at least one of the three kinds of tungsten carbide particles,for example,irregular cast tungsten carbide,monocrystalline tungsten carbide and sintered reduced tungsten carbide *** effects of powder particle morphology,particle size and mass fraction of tungsten carbide on the microstructure and mechanical properties of copper alloy composite were investigated by means of scanning electron microscopy,X-ray diffraction and abrasive wear test in *** results show that tungsten carbide morphology and particle size have obvious effects on the mechanical properties of copper alloy *** tungsten carbide partially dissolved in the copper alloy binding phase,and layers of cu_(0.3)W_(0.5)Ni_(0.1)mn_(0.1)c phase with a thickness of around 8–15μm were formed on the edge of the cast tungsten *** 45%irregular crushed fine cast tungsten carbide and 15%monocrystalline cast tungsten carbide were used as the skeleton,satisfactory comprehensive performance of the reinforced copper alloy composite bit matrix was obtained,with the bending strength,impact toughness and hardness reaching 1048 mPa,4.95 J/cm^(2) and 43.6 HRc,*** main wear mechanism was that the tungsten carbide particles firstly protruded from the friction surface after the copper alloy matrix was worn,and then peeled off from the matrix when further wear occurred.

关键词： Polycrystalline diamond compact Pressureless vacuum infiltration copper alloy composite bit matrix microstructure characterization Abrasive wear behavior

Generic Existence of Infinitely many Non-contractible closed Geodesics on compact Space Forms

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Acta mathematica Sinica,English Series 2024年第7期40卷 1674-1684页

作者： hui Liu Yu chen Wang School of mathematics and Statistics Wuhan UniversityWuhan430072P.R.China School of mathematics Tianjin Normal UniversityTianjin300384P.R.China

Let m=S^(n)/Γand h be a nontrivial element of finite order p inπ_(1)(Μ),where the integers n,p≥2,Γis a finite abelian group which acts freely and isometrically on the n-sphere and therefore m is diffeomorphic to a compact space *** this paper,we prove that there are infinitely many non-contractible closed geodesics of class[h]on the compact space form with c^(r)-generic Finsler metrics,where 4≤r≤∞.The conclusion also holds for cr-generic Riemannian metrics for 2≤r≤∞.The proof is based on the resonance identity of non-contractible closed geodesics on compact space forms.

关键词： compact space forms non-contractible closed geodesics generic Finsler metrics resonance identity

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On hypersurfaces of H2×H2

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Science china mathematics 2024年第2期67卷 339-366页

作者： Dong Gao hui ma Zeke Yao School of Science Beijing University of Civil Engineering and Architecture Department of mathematical Sciences Tsinghua University

In this paper, we study hypersurfaces of H2× H2. We first classify the hypersurfaces with constant principal curvatures and constant product angle functions. Then we classify homogeneous hypersurfaces and isoparametric hypersurfaces, respectively. Finally, we classify the hypersurfaces with at most two distinct constant principal curvatures, as well as those with three distinct constant principal curvatures under some additional conditions.

关键词： constant principal curvature homogeneous hypersurface isoparametric hypersurface 53c42 53B25 53c40

Regulations of m^(6)A and other RNA modifications and their roles in cancer

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Frontiers of medicine 2024年第4期18卷 622-648页

作者： Xin-hui chen Kun-Xiong Guo Jing Li Shu-hui Xu huifang Zhu Guang-Rong Yan Biomedicine Research center Guangdong Provincial Key Laboratory of Major Obstetric DiseaseGuangdong Provincial Clinical Research Center for Obstetrics and GynecologyState Key Laboratory of Respiratory Diseasethe Third Affiliated Hospital of Guangzhou Medical UniversityGuangzhou510150China

RNA modification is an essential component of the epitranscriptome,regulating RNA metabolism and cellular *** types of RNA modifications have been identified to date;they include N^(6)-methyladenosine(m^(6)A),N^(1)-methyladenosine(m1A),5-methylcytosine(m5c),N^(7)-methylguanosine(m^(7)G),N^(6),2′-O-dimethyladenosine(m^(6)Am),N4-acetylcytidine(ac^(4)c),*** modifications,mediated by regulators including writers,erasers,and readers,are associated with carcinogenesis,tumor microenvironment,metabolic reprogramming,immunosuppression,immunotherapy,chemotherapy,etc.A novel perspective indicates that regulatory subunits and post-translational modifications(PTms)are involved in the regulation of writer,eraser,and reader functions in mediating RNA modifications,tumorigenesis,and anticancer *** this review,we summarize the advances made in the knowledge of different RNA modifications(especially m^(6)A)and focus on RNA modification regulators with functions modulated by a series of factors in cancer,including regulatory subunits(proteins,noncoding RNA or peptides encoded by long noncoding RNA)and PTms(acetylation,SUmOylation,lactylation,phosphorylation,etc.).We also delineate the relationship between RNA modification regulator functions and carcinogenesis or cancer ***,inhibitors that target RNA modification regulators for anticancer therapy and their synergistic effect combined with immunotherapy or chemotherapy are discussed.

关键词： RNA modification writers erasers readers regulatory subunits PTms cancer

crystalline-amorphous m@mN_x(m=co,Fe,Ni)encapsulated in nitrogen-doped carbon for enhanced efficient and durable hydrogen evolution reaction

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Rare metals 2024年第4期43卷 1547-1556页

作者： Yang Yang Xiao-chuan Duan Shao-hui Guo Xian-ming Zhang college of materials Science and Engineering College of ChemistryKey Laboratory of Interface Science and Engineering in Advanced MaterialsTaiyuan University of TechnologyYuci030600China

Developing earth-abundant electrocatalysts for hydrogen evolution reaction(HER)is important for the sustainable energy ***,efficient and stable heterocatalysts consisting of crystalline-amorphous m@mN_(x)(m=co,Fe,Ni)encapsulated in N-doped carbon layers supported with N-doped graphene sheets(denoted as m@mN_(x)@Nc-NG)are synthesized by facile hydrothermal reaction and nitridation *** the nitriding process,metal ions in m(tzbc)_2(H_(2)O)_4(tzbc=4-(1H-1,2,4-triazol-1-yl)benzoic acid)complexes are reduced to crystalline m cores,accompanied by the formation of amorphous mN_(x)shells;the tzbc ligands are insitu carbonized to form outermost N-doped carbon(Nc)layers that connect with inner mN_(x)via m-N-c motifs inherited from the complex precursors and inhibit the transition of mN_(x)from amorphous to crystalline *** co@coN_(x)@Nc-NG catalyst exhibits excellent HER activity with small overpotentials of 45 and 64 mV at a cathode current density of 10 mA·cm^(-2)and low Tafel slopes of 40 and 85 mV·dec^(-1)in 0.5 mol·L^(-1)H_(2)SO_4 and1.0 mol·L^(-1)KOH electrolytes,*** co@coN_(x)@Nc-NG retains 97%of the initial overpotential after 100,000 s in both acidic and alkaline *** outstanding HER performance originates from the crystalline-amorphous co@coN_(x)that redistributes electrons around the heterointerfaces,facilitating the conversion process of H^(+)/H_(2)O to hydrogen and thereby promoting HER *** outermost Nc layers serve as the armor of co@coN_(x),and graphene nanosheets act as carriers of egg-like co@coN_(x)@Nc and conduction paths for electron shuttles,ensuring stable and continuous electrocatalytic hydrogen production.

关键词： Hydrogen evolution reaction Electrocatalysts Iron group metals Heterojunction crystalline-amorphous structure

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Quantitative understanding of phase segregation behaviors by precisely building discrete oligo-ester-b-oligo-olefin block copolymers

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Science china chemistry 2024年第3期67卷 1008-1016页

作者： Yuxin Liu Rui Tan Haibing Wu Xue-hui Dong Zhengbiao Zhang college of chemistry Chemical Engineering and Materials ScienceSoochow UniversitySuzhou 215123China State Key Laboratory of Radiation medicine and Protection Soochow UniversitySuzhou 215123China South china Advanced Institute for Soft matter Science and Technology School of Molecular Science and EngineeringSouth China University of TechnologyGuangzhou 510640China

Block copolymers(BcPs) with high Flory-Huggins parameter(χ) and balanced surface energy have aroused tremendous interest for ultra-small nanopatterns ***,high χ and balanced surface energy are generally *** fine tune of chain structure might be a useful way to achieve high χ and balanced surface *** realize this,the block copolymer with exactly uniform chain structure,i.e.,defined molecular structure,is highly desirable for accurately evaluating the phase ***,two kinds of discrete oligo ester-b-oligo olefin block copolymers with different chemical structures(oligo lactic acid-boligo olefin BcP,oLA_(n)-b-c_(m);oligo phenyl lactic acid-b-oligo olefin BcP,oPL_(n)-b-c_(m)) were modularly synthesized through iterative growth *** effect of chain structure on segregation strength and surface properties was quantitatively investigated using the discrete BcPs as precise *** the one hand,introducing rigid and nonpolar phenyl groups into oligo ester block has a negligible effect on the chemical incompatibility,as confirmed by the identical high χ values of oLA_(n)-b-c_(m) and oPL_(n)-b-c_(m)(χ_(oLA/c)=0.21 and χ_(oPL/c)=0.19).On the other hand,the incorporation of nonpolar phenyl groups creates balanced surface energy,that is,the high χ and balanced surface energy were simultaneously achieved by oPL_(n)-b-c_(m).Therefore,sub-10 nm perpendicular nanopatterns can be easily produced upon brief thermal treatment,demonstrating its potential application in semiconductor manufacturing with ultra-small feature *** discrete BcP can serve as a quantitative and exquisite model to study the critical contribution of chain structures on phase separation behavior,providing insightful understanding to facilitate the potential application in the chip process.

关键词： discrete polymer iterative growth self-assembly highχ balanced surface

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Tuning heterogeneous microstructures to enhance mechanical properties of nano-TiN particle reinforced Haynes 230 composites by laser powder bed fusion

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Rare metals 2024年第9期43卷 4548-4565页

作者： Wen-Jie Liu hui Li Qian-Xing Yin He-Jun Du School of Power and mechanical Engineering Wuhan University The Institute of Technological Sciences Wuhan University School of mechanical&Aerospace Engineering Nanyang Technological University

Laser powder bed fusion(LPBF) is considered to be one of the most promising additive manufacturing technologies for producing components with geometries and high geometrical precision that are unattainable by traditional technologies. The superalloy exhibits exceptional mechanical and high-temperature performances,rendering it a prime candidate for advanced aero-engine applications. Despite the high demand for LPBF-manufactured superalloys, the superalloy is one of the materials manufactured difficultly by LPBF due to their large laser absorptivity fluctuation, poor molten pool stability and sharp temperature gradient. Hence, superalloys are characterized by severe pores, undesirable coarse columnar grains and poor mechanical properties. In this work, the effect of nano-Ti N particles on defects, molten pool characteristics and microstructure and performance of the composites were investigated. The 4.5 wt% Ti N/Haynes230 samples exhibited exceptional nanohardness and elastic modulus with maximum values reaching 5.53 GPa and 240.03 GPa, respectively. These superior mechanical properties were attributed to the combined effects of spatter and gas pore inhibition, grain refinement and duplex nanophases strengthening. moreover, the stability of molten pool was enhanced, and spatter was effectively suppressed by adding nano-Ti N particles, while grain refinement and columnar to equiaxed transitions were promoted. Furthermore, the matrix exhibited a high dislocation density due to a significant hindrance of dislocation movement caused by massive nano-phases(e.g., Ti N and m23c6), resulting in the formation of extensive dislocation tangles and *** work offers novel insights into the role of nanoparticles reinforced superalloy composites by LPBF.

关键词： composites Laser powder bed fusion mechanical properties microstructure molten pool characteristics

Effect of La on the corrosion Behavior and mechanism of 3Ni Weathering Steel in a Simulated marine Atmospheric Environment

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Acta metallurgica Sinica(English Letters) 2024年第2期37卷 308-324页

作者： Gang Niu Rui Yuan R.D.K.misra Na Gong Zhi-hui Zhang Hao-Xiu chen hui-Bin Wu cheng-Jia Shang Xin-Ping mao collaborative Innovation center of Steel Technology University of Science and Technology BeijingBeijing100083China Laboratory for Excellence in Advanced Steel Research Department of MetallurgicalMaterials and Biomedical EngineeringUniversity of Texas at El PasoEl PasoTX79968USA Institute of materials Research and Engineering Agency for ScienceTechnologyand ResearchSingapore138634Singapore Department of materials Science and Engineering University of TorontoTorontoONM5S 3E4Canada

The corrosion behavior and mechanism of 3Ni weathering steel in a simulated oceanic atmospheric environment are investigated in order to comprehend the impacts of La,as determined through electrochemical analysis and rust layer *** results of this study demonstrate that the addition of La enhances the corrosion resistance of 3Ni weathering steel in the marine atmospheric environment,thereby reducing the corrosion rate and improving the protection of the rust *** influence of La on corrosion resistance can be attributed to two primary ***,La functions as a grain refiner,minimizing the potential difference of the micro-regions on the substrate surface,thereby significantly reducing the corrosion of bare steel in the marine ***,La inhibits the process of Fe_(3)O_(4) oxidation back toγ-FeOOH during corrosion at the local site,thus decreasing the formation ofγ-FeOOH and enhancing the charge transfer *** research work may serve as a reference for expanding the application of rare earth elements in the field of weathering steel.

关键词： Weathering steel Rare earth Rust layer corrosion behavior corrosion resistance

Novel Hf_(x)Ta_(1−x)c solid solution nanowire toughened Hfc coating:An effective strategy for synchronous enhanced mechanical and anti-ablation performance

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Journal of Advanced ceramics 2024年第5期13卷 590-601页

作者： hui chen Yulei Zhang Yanqin Fu Wenhan Gai Junhao Zhao Haohui Zhang Shaanxi Key Laboratory of Fiber Reinforced Light composite materials Northwestern Polytechnical UniversityXi’an 710072China Henan Key Laboratory of High Performance carbon Fiber Reinforced composites Institute of Carbon Matrix CompositesHenan Academy of SciencesZhengzhou 450046China

Ultra-high-temperature ceramic nanowires have shown increasing potential for use as thermal structural ***,novel single-crystal Hf_(0.5)Ta_(0.5)c solid solution nanowires were synthesized and incorporated with a Hfc coating to construct a robust structure with Hf_(0.5)Ta_(0.5)c solid solution nanowires uniformly distributed and interconnected within the *** novel Hf_(0.5)Ta_(0.5)c solid solution nanowires could effectively hinder crack propagation through crack tip pinning and crack *** mechanism substantially enhanced the elastic modulus and fracture toughness of the Hfc coating by 53.29%and 59.67%,*** toughened Hfc coating displayed superior fracture toughness and good interfacial binding strength with the substrate to resist severe oxidation and ***,the high thermal conductivity of the toughened Hfc coating promoted heat ***,in comparison to the pure Hfc coating,the toughened Hfc coating displayed smaller mass and linear ablation rates of−0.35 mg·s^(−1)and−0.46μm·s^(−1),which decreased by 39.66%and 36.98%,*** work not only simultaneously enhances the mechanical properties and ablation resistance of Hfc-coated carbon/carbon(c/c)composites but also provides novel prospects for advanced ultrahigh-temperature ceramic nanowires under extreme conditions.

关键词： Hf_(x)Ta_(1−x)c solid solution nanowires Hfc coating carbon/carbon(c/c)composites mechanical performance ablationresistance