Evaluation of Constants of Electron–Phonon Coupling between Gas Molecules and Graphene

The adsorption of CO, NO, NO₂, Н₂О, and NH₃ molecules on ideal graphene and graphene doped with aluminum is analyzed using simple models. The constants of electron–phonon coupling are evaluated with the Lennard-Jones 6–12 potential for ideal graphene and the 2–4 potential for doped graphene. It is demonstrated that the dimensionless electron–phonon-coupling constant for ideal graphene is ζ ? 1, while ζ ~ 1 corresponds to graphene doped with aluminum. Ways to use both types of graphene as a resistive gas sensor are discussed.     

Study of the relationship between nanofluid＇s stability and conductivity

基于Maxwell电磁理论中电解质悬浮液中粒子质量分数和电导率之间的关系,提出了一种判定纳米流体悬浮稳定性的方法,并进行了实验验证。实验中,采用＂两步法＂经超声振荡制备了CuO/去离子水纳米流体。利用电导率仪测量了不同质量分数时纳米流体的电导率,建立了质量分数与电导率的关系,同时研究了温度对电导率的影响。结果表明电导率随着颗粒质量分数的增加而增加,随着质量分数的减小而减小;随着温度的增长,电导率只有微小变化,可以忽略温度对电导率的影响。     

The thermal conductivity of α-plutonium between 3 and 100 K

The thermal conductivity of -plutonium has been measured over the range 3–100 K. For the highest purity material (50 ppm metallic impurities) a small peak in the conductivity is seen at 10 K, followed by a shallow minimum at 40 K. The maximum measured conductivity is 34.3 mW/K cm at 100 K. A decrease in conductivity occurs at low temperatures as a result of radioactive self-damage, which saturates with an exponential dependence. It is shown that most of the heat conduction is by phonons, electronic thermal conduction being small but rising with temperature.     

The Ultrasonic NDT of Adherent Area between Metal and Nonmetal Surfaces and the Prediction of Its Destruction Strength

A new approach so-called multi-reflection scanning method by transvers ultrason-ic wave is described for the NDT of adherend between metal and.nonmetal surfaces.Accord-ing to the adherent state,the destruction strength can be predicted by Bayesian inference. A skew probe scanning on the metal side is used to transform the longitudinal wave,dis-patched by a PZT transducer,after entering the metal layer into transversal.Then the lat-ter propagates in a zigzag path along the adhesive layer.The reflected wave strength are de-tected and integrated with respect to time.The relation between the adherent area along thescanned path and the time integral of reflected wave magnitude is founded. The prediction model by Bayesian inference has been studied.As the adhesive process isfixed,the relation batween the destruction strength of a part versus the measured adherentarea proportion and their distribution can be established.Practice shows that,even the rateof spoilage as high as 60%,the software can strictly judge     

Adhesion between bitumen and aggregate: implementation of spectroscopic ellipsometry characterisation and estimation of Hamaker’s constant

Refractive indices of seven bitumen samples and three aggregates (typical components in flexible asphalt pavement) were determined by ellipsometry in order to predict dispersive bitumen–aggregate adhesion and dispersive bitumen–bitumen cohesion using Hamaker’s constant. Hamaker’s constant according to Lifshitz was introduced to the asphalt field by two of the authors to describe and estimate van der Waal’s interaction and bitumen–aggregate adhesion. Lifshitz used the refractive index to estimate the dispersive non-polar van der Waal’s interaction component of adhesion, the predominant component in adhesion between minerals and bituminous binder. The impact of an intervening thin medium such as air or water on the adhesion can be estimated using Hamaker’s coefficient, which in turn can be related to stripping potential. The bitumen binders studied were delivered as a paving grade 70/100 according to EN 12591:2009 and came from different bitumen suppliers. The three aggregates studied were two types of granite and one diabase. It is concluded from the measurement of refractive indices and calculations of the dispersive component of Hamaker’s constant that there was a larger spread in refractive index among the three aggregate samples studied than among the seven bitumen samples.     

Electrolytic Domain Boundary between Ionic and Electronic Conduction of Doped Ceria

The electrolytic domain boundary (EDB) of doped ceria between ionic and electronic conduction is theoretically investigated with the consideration of defect association. Data from the early reports on EDB of singly, double and triply doped ceria are summarized and interpreted based on the theoretical investigation. It is proposed that samarium and gadolinium among the rare earth elements are mostly suitable for the main dopants of ceria, while further minor additions of other elements can benefit the improvement of the EDB.     

Studies of Correlations between Surface Composition Changes and Ion Bombardment Fluences of Multicomponent Materials

Correlations between surface composition changes and ion bombardment fluences were studied formulticomponent materials by using a dynamic Monte Carlo program,including the preferentialsputtering and bombardment-induced Gibbsian segregation (BIGS) processes.For the case of1 keV KR-~(10)B_(0.02)~(11)B_(0.08) (the most simple multicomponent material system),it is found that the ~(10)Bcomposition enriches at the surface at low fluences but depletes at the surface at high fluences.Forthe case of 1 keV Ar-Pt_(0.5)Cu_(0.5).it is found that the Cu composition at the topmost surface is alwaysunder the bulk composition between zero and high fluences,but the evident composition gradient ofCu(the segregation species) exists in the surface at low fluences.The effects of the preferentialsputtering and BIGS processes on above two surface composition profiles are also discussed.     

Compressive deformation of an Mg-Al-Si-RE alloy between 120 and 180 °C

The deformation behaviour of an Mg-Al-Si-RE (ASE210) alloy between 120 and 180 °C was investigated by means of uniaxial compression tests to identify possible differences in the deformation response compared with uniaxial tensile data. Early fracture was observed in the low-temperature/high strain rate regime, fracture occurring by crack propagation at 45° with respect to the compression axis. In the high-temperature/low strain rate regime, the flow curves exhibited the typical shape that is usually observed in materials where deformation is controlled by recovery of substructure. The peak flow stresses obtained in this regime of temperature and strain rate were compared with other data obtained by testing the same alloy in tension. The strength of the alloy was found to be slightly greater in compression than in tension, this difference gradually disappearing as strain rate decreased.     

Relationship between Grain Size and Fatigue-Creep Interaction Behaviour of Superalloy GH698

The deformation and fracture behaviourof nickel-base superalloy GH698 with differentgrain size have been studied at 700℃ underfatigue-creep interaction conditions. Comparedwith coarse-grained specimens, the grain refiningprocess shows obvious effect on the mechanicalbehaviour of the alloy, i. e. in F and C zones,the fraction of pure fatigue and creep fractureon fracture surfaces is greatly reduced, whichdecreases and increases the fracture life inzones F and C respectively, in FC and C zones,creep deformation is greatly restrained by thealternating stress component, which increasesthe fracture life remarkably. It is also provedthat in spite of the difference in microstru-tures such as grain size, for a constant tem-perature, a unique life equation t_r=A~n canbe used to predict rupture life within the stressregion controlled by the same fracture mode.     

Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current vs bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)--bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT‘s electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.     

Further Investigation on the Correlation between Ionization Potential and Superconductivity of Oxides

The relations of oxygen content, critical temperature TC and mean ionization potential < U0> of superconducting oxides are reported. We found that in oxides oxygen is the major element which governs their < U0> te values and thus oxygen content plays an jmportant role in their superconducting properties. As for Y(123)- and T1-systems oxygenation may improve their TC values, but for Biand Hg-systems oxygenation process is not so important. In Y(123), as the oxygen content increase results in the increase of TC upon < U0>to, while the substitution of Ba2+ by Sr2+ causes the decrease of TC upon < U0 >. These results may provide some clues about the superconductivity of oxides and support further that < Uo > is really a good criterion for oxide superconductivity. Two kinds of possible superconducting oxides are predicted in this paper according to the mean ionization potential criterion.     

Nature and Growth of Interaction Layers Formed during the Reaction between Solid Ni and Liquid Al

The nature and growth of the interaction layers between solid Nb and liquid Al has been studied by carrying out the tests on Nb(s)-Al(l)and Nb(s)-Al(l)-Ni(s) reaction couples isothermally reacted between 700℃and 900℃for different time intervals.It has been found that the interaction layer between Nb and Al contains two parts:a thin continuous layer of NbAl3 adjacent to the Nb surface and a two-phase zone constituted of NbAl3 particles dispersed in an Al matrix.Although the nature and growth of interaction layers follows the sour-stage mechanism,a typical cruciform pattern does not occur in Nb(s)-Al(l) reaction couples.However,a cruciform pattern was observed in Nb(s)-Al(l)-Ni(s)reaction couples.The movement of NbAl3 particles is important to the production of cruciform pattern in the reaction couples.     

The relationship between the electrical and mechanical properties of polymer–nanotube nanocomposites and their microstructure

A range of polymer–nanotube nanocomposites were produced using different processing routes. Both polymer-grafted and as-grown nanotubes were used and latex and polystyrene matrices investigated. The microstructures of the nanocomposites were studied, mainly by electron microscopy, in terms of the dispersion state of the nanotubes and the polymer–nanotube interface. The mechanical and electrical properties of the composites were also measured. The relationship between the microstructures observed and the resulting physical properties are discussed. It is found that composites with apparently similar microstructures can exhibit similar mechanical properties but very different electrical behaviours. Moreover, the nanocomposites produced using polymer-grafted nanotubes exhibit a clear improvement of the stress at large deformation. Thus, from our results, it appears that the mechanical and electrical properties do not necessarily depend on the same microstructural parameters. However it is still a challenge to simultaneously improve both physical properties.     

Structural and chemical stability of Ta–Si–N thin film between Si and Cu

Thermal stability and barrier performance of reactively sputter deposited Ta–Si–N thin films between Si and Cu were investigated. RF powers of Ta and Si targets were fixed and various N₂/Ar flow ratios were adopted to change the amount of nitrogen in Ta–Si–N thin films. The structure of the films are amorphous and the resistivity increases with nitrogen content. After annealing of Si/Ta–Si–N(300 Å)/Cu(1000 Å) structures in Ar–H₂ (10%) ambient, sheet resistance measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Auger electron spectroscopy (AES) were employed to characterize barrier performance. Cu₃Si and tantalum silicide phase are formed at the same temperature, and the interdiffusion of Si and Cu occurs through the local defect sites. In all characterization techniques, nitrogen in the film appears to play an important role in thermal stability and resistance against Cu diffusion. A 300 Å thick Ta₄₃Si₄N₅₃ barrier shows the excellent barrier property to suppress the formation of Cu₃Si phase up to 800°C.     

Quantification of the Interaction between Charged Guest Molecules and Chemisorbed Monothiolated β-Cyclodextrins

The quantification of small molecules in aqueous solution by surface bound supramolecular host molecules is an important goal in the research field of chemo- and biosensor development. In this paper we present an attempt to quantify the interaction of different charged guest molecules with chemisorbed monothiolated β-cyclodextrin monolayers by means of impedance spectroscopy in the presence of the redox couple [Fe(CN)(6)](3)(-)/[Fe(CN)(6)](4)(-). Self-assembled monolayers of mercaptopropane-N-mono-6-deoxy-β-cyclodextrin amide (MPA-CD) on gold surfaces were formed with coverage of 99-100%. The inclusion of charged guest molecules was detected by monitoring the changes in the charge-transfer resistance, which is sensitive to the surface charge density in terms of repulsion or attraction of the redox active ions. Adsorption of positively charged 1-adamantanamino hydrochloride (1-ADHC) led to a considerable increase in the charge-transfer resistance, whereas the inclusion of both negatively charged 1-adamantanecarboxylic acid (1-ADC) and 2-(p-toluidinyl)naphthalene-6-sulfonate (2,6-TNS) caused a decrease. Applying the Frumkin correction to obtain the surface charge density and the Gouy-Chapman-Stern theory to account for the electrochemical double layer, we were able to quantify the binding of the charged guest molecules in terms of binding isotherms. The isotherms display a distinct two step adsorption process probably owing to the presence of two energetically different binding sites on the surface. Complete reversibility of the binding process of the guest molecules could be demonstrated by the addition of β-cyclodextrin in solution, which allowed the reuse of the functionalized surfaces.     

Finite element modelling of rubber-like materials — a comparison between simulation and experiment

In this work finite element simulations are used based on the micro structure of polymers in order to transfer the information of the micro level to the macro level. The microscopic structure of polymers is characterized by a three-dimensional network consisting of randomly oriented chain-like macromolecules linked together at certain points. Different techniques are used to simulate the rubber-like material behaviour of such networks. These techniques range from molecular dynamics to the finite element method.The proposed approach is based on a so-called unit cell. This unit cell consists of one tetrahedral element and six truss elements. To each edge of the tetrahedron one truss element is attached which models the force-stretch behaviour of a bundle of polymer chains. The proposed method provides the possibility to observe how changes at the microscopic level influence the macroscopic material behaviour. Such observations were carried out in [1]. The main focus of this work is the validation of the proposed approach. Therefore the model is compared to different experimental data and other statistically-based network models describing rubber-like material behaviour.     

Correlation between Young’s modulus and impregnation quality of epoxy-impregnated SWCNT buckypaper

Carbon nanotube (CNT) sheets, also known as buckypaper, have high potential for structural applications due to their high volume fraction of CNT, the strongest and stiffest materials known. In this work, two different techniques, one based on positive pressure and another based on vacuum infiltration, are utilized to impregnate single-walled carbon nanotube (SWCNT) buckypaper sheets of 50–70 μm in thickness, resulting in a Young’s modulus of up to 15.4 GPa. Scanning electron microscopy demonstrates that the vacuum-based technique results in more effective impregnation of the buckypaper than the positive pressure technique. Thermogravimetry analysis of vacuum-impregnated specimens indicated a void content ranging from 5% to 32%. An advanced Mori–Tanaka-based micromechanics technique is also utilized to predict the effect of SWCNT volume fraction and void content on Young’s modulus of nanocomposites. These calculations suggest a higher void content of around 40% for the vacuum-impregnated composites.     

Interaction between Standardisation and Patenting: Problems and Solutions

Economic Rationales of Patents and Standards The ambivalence of patents and standards for technological development is triggered off by two different economic mechanisms: The inventors are awarded exclusive property rights, because: 1) additional incentives for the production of new