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Experimental Study on Molecular Arrangement of Nanoscale Lubricant Films——A Review

Chinese Journal of Mechanical Engineering 2015年第5期28卷 896-903页

作者： zhang shaohua LIU Yuhong State Key Laboratory of Tribology Tsinghua University

In order to understand lubrication mechanism at the nanoscale, researchers have used many physical experimental approaches, such as surface force apparatus, atomic force microscopy and ball-on-disk tribometer. The results show that the variation rules of the friction force, film thicknessand viscosity of the lubricant at the nanoscale are different from elastohydrodynamic lubrication （EHL）. It is speculated that these differences are attributed to the special arrangement of the molecules at the nanoscale. However, it is difficult to obtain the molecular orientation and distribution directly from the lubricant molecules in these experiments. In recent years, more and more attention has been paid to use new techniques to overcome the shortcomings of traditional experiments, including various spectral methods. The most representative achievements in the experimental research of molecular arrangement are reviewed in this paper： The change of film structure of a liquid crystal under confinement has been obtained using X-ray method. The molecular orientation change of lubricant films has been observed using absorption spectroscopy. Infrared spectroscopy has been used to measure the anisotropy of molecular orientation in the contact region when the lubricant film thickness is reduced to a few tens of nanometers. In situ Raman spectroscopy has been performed to measure the molecular orientation of the lubricant film semi-quantitatively. These results prove that confinement and shear in the contact region can change the arrangement of lubricant molecules. As a result, the lubrication characteristics are affected. The shortages of these works are also discussed based on practicable results. Further work is needed to separate the information of the solid-liquid interface from the bulk liquid film.

关键词： nano-scale lubricating film in situ measurement molecular arrangement

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Anisotropic Creep Rupture Properties of a Nickel-base Single Crystal Superalloy at High Temperature

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Journal of Materials Science & Technology 2011年第2期27卷 107-112页

作者： shaohua zhang Jian zhang Langhong Lou Superalloys Division Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The creep rupture properties of a single crystal superalloy were tested at 975℃/255 MPa as a function of the deviation degrees from [001].The misorientation of the specimens away from [001] distributed approximately along a line between [001]-[011] and [001]-[111] boundaries in the triangle of the stereographic *** rupture lifetimes of the specimens were not sensitive to the misorientation until the deviation degree exceeded ～30 *** steps of lattice rotation were found in all specimens during creep,first towards the [001]-[111] boundary,and then to [001] or [111] along the *** slip and strong asymmetric deformation were observed during the first stage of lattice rotation in specimens with large *** rotation mechanism was associated with the activated slip systems according to the calculated Schmid *** impact of lattice rotation on the rupture properties was also discussed.

关键词： Nickel-base single crystal superalloy Stress rupture property Orientation Dislocation

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Defect- and dopant-controlled carbon nanotubes fabricated by self-assembly of graphene nanoribbons

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Nano Research 2015年第9期8卷 2988-2997页

作者： Cun zhang and shaohua Chen LNM Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

Molecular dynamics simulations showed that a basal carbon nanotube can activate and guide the fabrication of single-walled carbon nanotubes （CNTs） on its internal surface by self-assembly of edge-unpassivated graphene nanoribbons with defects. Furthermore, the distribution of defects on self-assembled CNTs is controllable. The system temperature and defect fraction are two main factors that influence the success of self-assembly. Due to possible joint flaws formed at the boundaries under a relatively high constant temperature, a technique based on increasing the temperature is adopted. Self-assembly is always successful for graphene nanoribbons with relatively small defect fractions, while it will fail in cases with relatively large ones. Similar to the self-assembly of graphene nanoribbons with defects, graphene nanoribbons with different types of dopants can also be self-assembled into carbon nanotubes. The finding provides a possible fabrication technique not only for carbon nanotubes with metallic or semi-con- ductive properties but also for carbon nanotubes with electromagnetic induction characteristics.

关键词： graphene nanoribbon,carbon nanotube,defect,dopant,self-assembly molecular dynamics

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Study of seismic behavior of PHC piles with partial normal-strength deformed bars

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Earthquake Engineering and Engineering Vibration 2020年第2期19卷 307-320页

作者： zhang Xizhi zhang shaohua Xu Shengbo Niu Sixin Architectural Design&Research Institute of Tianjin University Tianjin 300072China Key Laboratory of Coast Civil Structure Safety Ministry of EducationTianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China Shandong Tong Yuan Design Group Co. Ltd.Jinan 250101China

Nine PHC piles with partial normal-strength deformed bars were prepared in present study,and cyclic loading tests were implemented to evaluate these piles’seismic *** influence of the axial compression ratio and the amount of normal-strength deformed bars on failure modes,crack patterns,strength,stiffness,and ductility were *** test findings indicate that the change of axial compression ratio has a noticeable influence on the failure mode of PHC piles.A larger axial compression ratio results in a higher cracking bending resistance,ultimate bending resistance,and initial stiffness,but the propagation heights of flexural cracks decrease as the axial compression ratio ***,increasing the amount of normal-strength deformed bars causes a slight decrease in ***,a calculation formula was proposed to predict the flexural capacity of PHC piles with partial normal-strength deformed bars.

关键词： PHC pile prestressed tendons deformed bars seismic behavior cyclic loading test flexural capacity

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Strong Goldbach Conjecture and Generalized Moser-Type Inequalities

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Wuhan University Journal of Natural Sciences 2021年第1期26卷 15-18页

作者： zhang shaohua School of Mathematics and Statistics Yangtze Normal UniversityChongqing 408102China

In this paper,we consider the generalized Moser-type inequalities,sayφ(n)≥kπ(n),where k is an integer greater than 1,φ(n)is Euler function andπ(n)is the prime counting *** computer,Pierre Dusart’s inequality onπ(n)and Rosser-Schoenfeld’s inequality involvingφ(n),we give all solutions ofφ(n)=2π(n)andφ(n)=3π(n),***,we obtain the best lower bound that Moser-type inequalitiesφ(n)>kπ(n)hold for k=2,*** consequences,we show that every even integer greater than 210 is the sum of two coprime composite,every odd integer greater than 175 is the sum of three pairwise coprime odd composite numbers,and every odd integer greater than 53 can be represented as p+x+y,where p is prime,x and y are composite numbers satisfying that p,and x and y are pairwise ***,we give a new equivalent form of Strong Goldbach Conjecture.

关键词： Strong Goldbach Conjecture pairwise coprime Euler totient function prime-counting function

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Orientation Dependence of Stress Rupture Properties of a Ni-based Single Crystal Superalloy at 760℃

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Journal of Materials Science & Technology 2012年第3期28卷 229-233页

作者： shaohua zhang Dong Wang Jian zhang Langhong Lou Superalloys Division Shenyang National Laboratory for Materials ScienceInstitute of Metal ResearchChinese Academyof Sciences72 Wenhua RoadShenyang 110016China

The orientation dependence of creep rupture lives of a single crystal superalloy at 760℃/760 MPa was *** orientations of the specimens tested were about 30°away from [001].The results showed that specimens with orientations on the [001]-[011] boundary had the longest rupture *** deformation of these specimen were controlled by a/2〈110〉 slip and a few stacking faults with two orientations were *** the other hand,specimens with orientations near the [001]-[011] boundary or on the [001]-[111] boundary showed short rupture lives,and stacking faults with single orientation were observed in these *** rupture properties and the deformation mechanisms were discussed based on the dislocation pattern and the calculated Schmid factors for different specimens.

关键词： Single crystal superalloy Stress rupture Orientation

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An Equivalent Form of Strong Lemoine Conjecture and Several Relevant Results

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Wuhan University Journal of Natural Sciences 2019年第3期24卷 229-232页

作者： zhang shaohua School of Mathematics and Statistics Yangtze Normal University

In this paper, we consider some problems involving Strong Lemoine Conjecture in additive number theory. Based on Dusart's inequality and Rosser-Schoenfeld's inequality, we obtain several new results and give an equiva... 详细信息

关键词： Lemoine Conjecture Dusart’s inequality Rosser-Schoenfeld’s inequality Euler totient function primecounting function

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Advances in theoretical calculations of organic thermoelectric materials

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Chinese Chemical Letters 2024年第8期35卷 112-127页

作者： shaohua zhang Liyao Liu Yingqiao Ma Chong-an Di Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Organic SolidsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049China

Organic thermoelectric(OTE)materials and devices have garnered significant attention in the past decade for flexible and wearable *** to the numerous combinations of different backbones,side chains,and functional groups for polymer molecules,further efficient developments of high perfor-mance OTEs rely on reverse and rational molecular design as well as fundamental understanding to the structure-property relationship,which both require precise theoretical ***,many theo-retical efforts and progresses have been made to predict TE properties and develop high performance OTE ***,we present first the general methods and principles for OTE theoretical ***,the latest theoretical advances regarding the effects of molecular design,chemical dop-ing,ambipolar charge transport etc.,to TE conversion are carefully *** theoretical advances not only significantly deepen the fundamental understanding of OTEs,but also provide precise guidance to the molecular design of OTE ***,we propose several perspectives for future theoretical investigations of OTEs.

关键词： Organic thermoelectricity Theoretical study Organic semiconductor Structure-property relation Single-molecular device

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Molecular behaviors in thin film lubrication——Part one: Film formation for different polarities of molecules

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Friction 2019年第4期7卷 372-387页

作者： shaohua zhang Yijun QIAO Yuhong LIU Liran MA Jianbin LUO State Key Laboratory of Tribology Tsinghua UniversityBeijing100084China Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms Beijing Institute of ControlEngineeringBeijing100094China

There are three unsolved problems in thin film lubrication(TFL) since it was proposed 20 years ago, i.e., the determination of the type of molecules that can enter the contact region efficiently during sliding, the orientation of molecules in the contact region, and the effect of solid surfaces on the liquid molecular orientation in TFL. In order to answer the first two questions, an in situ measurement system comprising a self-designed Raman microscopy and relative optical interference intensity(ROⅡ) system was set up to study the molecular behaviors. A variety of binary mixtures were used as lubricants in the test, and the concentration distribution profile and orientation of the additive molecules in TFL were characterized. The molecular behavior was determined via a combination of shearing, confinement, and surface adsorption. Furthermore, the difference in molecular polarity resulted in different competing effect of surface adsorption and intermolecular interaction, the influence of which on molecular behavior was discussed. Polar additive molecules interacted with the steel surface and exhibited an enrichment effect in the Hertz contact region when added into a nonpolar base oil. No enrichment effect was observed for nonpolar molecules that were added into the nonpolar base oil and polar molecules added into polar base oil. The enrichment of additive molecules enhanced the film-forming ability of the lubricant and resulted in a reduction in the friction coefficient of up to 61%. The orderly arrangement of the additive molecules was another reason for the friction-reducing. A binary multilayer model was proposed to illuminate the molecular behavior in the TFL, and the model was supported by contrary experiment results in elastohydrodynamic lubrication. This research may aid in understanding the nanoscale lubrication mechanism in TFL and the development of novel liquid lubricants.

关键词： thin film lubrication in situ Raman spectroscopy molecular distribution molecular orientation

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Microstructures,corrosion behavior and mechanical properties of as-cast Mg-6Zn-2X(Fe/Cu/Ni)alloys for plugging tool applications

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 697-711页

作者： Baosheng Liu Jiali Wei shaohua zhang Yuezhong zhang Pengpeng Wu Daqing Fang Guorui Ma School of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China Intelligent Equipment Research and Development Center Zhuhai Institute of Advanced Technology Chinese Academy of SciencesZhuhai 519080China Advanced Materials Research Institute Zhuhai Dingmei Medical Technology Co.Ltd.Zhuhai 519000China

Mg-6Zn-2X(Fe/Cu/Ni)alloys were prepared through semi-continuous casting,with the aim of identifying a degradable magnesium(Mg)alloy suitable for use in fracturing balls.A comparative analysis was conducted to assess the impacts of adding Cu and Ni,which result in finer grains and the formation of galvanic corrosion *** electronic microscopy examination revealed that precipitated phases concentrated at grain boundaries,forming a semi-continuous network structure that facilitated corrosion penetration in Mg-6Zn-2Cu and Mg-6Zn-2Ni *** corrosion was observed in Mg-6Zn-2Fe,while galvanic corrosion was identified as the primary mechanism in Mg-6Zn-2Cu and Mg-6Zn-2Ni *** the tests,the Mg-6Zn-2Ni alloy exhibited the highest corrosion rate(approximately 932.9 mm/a)due to its significant potential *** testing showed that Mg-6Zn-2Ni alloy possessed suitable ultimate compressive strength,making it a potential candidate material for degradable fracturing balls,effectively addressing the challenges of balancing strength and degradation rate in fracturing applications.

关键词： magnesium alloys microstructure micro-galvanic corrosion mechanical properties

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