The adsorbed film controversy

Adsorption force fields that (i) decay with distance and (ii) act preferentially on liquid water relative to ice should cause “ordinary” water and ice to behave in a manner often perceived as incompatible with expected behavior, especially when viewed from outside the force field. This illusion, its relationship to freezing temperature and to the mechanism of frost heave, is demonstrated using a simple example in which earth and its gravitational field interact with water and ice.     

The energy of fracture of a film of carbon monoxide adsorbed on a tungsten single crystal surface

The adsorption and desorption of carbon monoxide were studied on a tungsten single crystal in a field electron microscope. The most interesting effects were observed for the CO desorption from the crystal surface regions containing the {100} W cubic faces. In the course of desorption from these regions, the adsorbed electropositive film, retaining sharp boundaries, shrank toward the <100> poles. The desorption energy value (3.4±0.1 eV), determined using the Arrhenius plots for the boundary velocity, is indicative of a considerable strength of the adsorbed CO film. Behavior of the CO phase desorbing from the {100} W regions can be consistently explained by assuming that this phase comprises a network of adsorbed CO dipoles oriented perpendicularly to the crystal surface, with the carbon atoms facing vacuum.     

The torque on a rotating disk in the surface of a liquid with an adsorbed film

Summary In this paper we consider the problem of calculating the resistive torque on a disk rotating slowly with constant angular speed in the surface of a liquid with an adsorbed surface film. Using the method of complementary representations for generalised axially symmetric potential functions, the boundary-value problem for the azimuthal velocity component is reduced to the solution of a Fredholm integral equation of the second kind. This equation is solved numerically and asymptotically for all values of the ratio of the surface shear viscosity of the film to the viscosity of the substrate fluid, and values calculated for the substrate and film torques on the disk. The results are compared with previous work of Goodrich and his co-workers.     

Resonant gravitational antennas: Zero-point fluctuations of an evacuated optomechanical converter containing an absorbing mirror

A fine structure is considered for the zero-fluctuations of the vacuum in an optomechanical converter containing an absorbing mirror as sensing element for resonant gravitational antennas. A formula is given for the threshold sensitivity of such an antenna in relation to the absorption coefficient in optimal data processing. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 3–5, January, 2008.     

Nuclear magnetic relaxation of helium-3 adsorbed on Mylar film

Pulsed NMR measurements on helium-3 adsorbed on Mylar film have been made at a Larmor frequency of 5 MHz for fractional monolayer coverages between 0.3 and 1. Relaxation times were measured at temperatures between 1.2 and 4 K for different orientations of the substrate plane with respect to the static magnetic field. Our results are consistent with a patchy solid model where approximately 0.1 of a monolayer remains relatively immobile, providing the relaxation mechanism, while the rest of the adsorbate remains fluid. We have no evidence for an abrupt transition of this fluid to a solid phase.     

Magnetization measurement of 3He film adsorbed on sintered silver powder

The static magnetization of ³He film adsorbed on sintered silver powder has been measured for coverages from 0.10 to 0.54 atoms/»² in steps of 0.02 atoms/»² and at a coverage of 4.5 atoms/»². Below 0.20 atoms/»² the magnetization well obeys the Curie law, while above that coverage a ferromagnetic tendency appears. The coverage dependence of the magnetization greatly differs from that for graphite. At 0.23 atoms/»² the magnetization has apeak like that for graphite; however, the magnitude of the peak is not so large. Furthermore, a multipeak structure is found in the isotherm of the magnetization at 0.2 mK. It has two prominent peaks at 0.23 and 0.29 atoms/»², and two other peaks are found at 0.35 and 0.41 atoms/»². These appear periodically with an interval of 0.06 atoms/»², which is nearly equal to the coverage of one liquid layer.     

Nanopatterned monolayers of an adsorbed chromophore

A simple lift-off process was developed to rapidly fabricate nanopatterned photofunctional surfaces. Dye molecules of a perylene derivative (PDID) were adsorbed irreversibly on clean silicon through the holes of an electron-beam lithographied polymer mask. The subsequent removal of the mask in a proper solvent results in PDID nanosized regions of width as small as 30?nm for stripes and of diameter as small as 120?nm for dots. Numerical analyses of atomic force microscopy and laser-scanning confocal microscopy images show that the dye molecules are confined to the regions defined by the lithographic process, with the integrated fluorescence intensity being essentially proportional to the size of the nanofeatures. This demonstrates that a simple organic lift-off process compatible with clean-room technology, and not involving any chemical step, is able to produce photofunctional nanopatterned surfaces, even though the dye is not chemically bonded to the silicon surface.     

Free-standing flexible graphene-based aerogel film with high energy density as an electrode for supercapacitors

Two-dimensional graphene film exhibits sluggish ion diffusivity while three-dimensional(3D)graphene aerogel has low packing density and poor mechanical flexibility.Consequently,there is an urgent need for graphenebased film with both mechanical robustness and high specific capacitance.Here,we present an easy and scalable strategy for fabricating a free-standing flexible graphene-based aerogel film electrode with a two-layered structure,in which the top layer is an interconnected macroporous reduced graphene oxide/carbon nanotube(RGO/CNT)aerogel,and the bottom layer is a flexible electrospun polyacrylonitrile(PAN)nanofiber membrane.The porous 3D structure of the aerogel provides fast transport of electrolyte ions and electrons,while the nanofiber membrane provides both strong support for the aerogel and mechanical flexibility.Polypyrrole(PPy)can be uniformly loaded on RGO/CNT/PAN(RCP)composite aerogel film to provide pseudocapacitance,and nitrogen-doped RGO/CNT/carbon nanofiber(NRCC)aerogel film can be obtained by further pyrolysis.The resultant RCP@PPy-0.05//NRCC based asymmetric supercapacitor can have a maximum voltage of 1.7 V and a maximum energy density of 60.6 W h kg^-1at 850.2 W kg^-1.This indicates that free-standing graphene-based aerogel film can be used in flexible supercapacitors.     

Surface energy and adhesion energy of solution-based patterning in organic thin film transistors

This study elucidates the patterning of pentacene by adjusting its surface energy. The surface energy was modified by self-assembled monolayer treatment and exposure to ultra-violet (UV) light through a quartz-glass mask. Then, following pentacene deposition, dipping in water was used to remove pentacene from the UV-exposed area. The adhesion energy and the intrusion energy were analyzed to determine the mechanism of this patterning process. The variation of the intrusion energy with the surface energy was found to be the main issue in pentacene patterning. The characteristics of pentacene-organic thin film transistors were also measured to confirm the proposed method.     

Optical solitons through an anharmonic vibrational mode

An optic field interacting with an infrared active vibrational mode with a cubic nonlinearity is considered. The slowly varying envelope of the electric field is shown to satisfy the nonlinear Schrödinger equation. Various aspects of the model are discussed.     

A micromachined carbon nanotube film cantilever-based energy cell

This paper reports a new type of energy cell based on micromachined carbon nanotube film (CNF)-lead zirconate titanate cantilevers that is fabricated on silicon substrates. Measurements found that this type of micro-energy cell generates both AC voltages due to the self-reciprocation of the microcantilevers and DC voltages due to the thermoelectric effect upon exposure to light and thermal radiation, resulting from the unique optical and thermal properties of the CNF. Typically the measured power density of the micro-energy cell can be from 4 to 300?μW?cm(-2) when it is exposed to sunlight under different operational conditions. It is anticipated that hundreds of integrated micro-energy cells can generate power in the range of milliwatts, paving the way for the construction of self-powered micro-?or nanosystems.     

Photoluminescence and energy transfer of terbium doped titania film

Strong visible luminescence of Tb³⁺ions due to intra-4f shell transitions are obtained from Tb³⁺-doped titania (TiO₂) films fabricated by sol-gel method. Based on the overlap of excitation band of Tb³⁺-doped TiO₂ and absorption band of undoped TiO₂, we propose an energy transfer mechanism from TiO₂ host to Tb³⁺ions. Photoluminescence (PL) intensity is found to have a well matching relation with the doping concentration of Tb³⁺ ions. Concentration quenching of PL occurs when Tb³⁺ concentration exceeds a certain value (9.5 mol%). Luminescence intensity is improved obviously after co-doped with Ce³⁺ ions because of the sensitization effect of Ce³⁺ ions and the dispersion of Tb³⁺ ions in TiO₂ system.     

Surface state electrons on a hydrogen film. 2. Influence of adsorbed helium films

We have investigated the conductivity of surface state electrons on liquid⁴He films supported by a quench-condensed thin solid hydrogen substrate. A pronounced dip in the ac-conductivity was observed as the He film thickness reached about 10 layers. This phenomenon was studied at different temperatures (range between 1.6 and 2 K), electron densities from 0.9 to 19×10⁸ cm^–2, frequencies between 1 and 100 kHz, and for various amplitudes of the ac driving voltage. Ripplon scattering and a ripplonic polaron are discussed as sources for the conductivity dip.     

基于神经网络的传感器零点飘移补偿方法

随着压力传感器的应用范围不断扩大,对测量准确度的要求不断提高,而由于力敏电阻器的不匹配及其漏电流的影响会产生零点漂移现象。这种现象在一定程度上影响了压力传感器的精度。本文利用RBF神经网络方法构建了双输入单输出网络模型,采用带遗忘因子的梯度下降算法实现了压力传感器零点飘移的补偿。结果表明,RBF神经网络方法收敛速度快、拟合出的数据精度高。     

Thick film adherence fracture energy: influence of alumina substrates

The adherence of a glass bonded Pt-Au thick film conductor to various alumina substrates is degraded by changes in the surface composition of and by the presence of (0001) crystallographic texture in the substrate. Using the critical fracture energy (γ_IC) required to separate the thick film from the substrate, it was found that γ_IC was reduced from a maximum of 3.7 J m⁻² using an as-received 96+ wt% alumina substrate to ∼2J m⁻² using an as-received 99+ wt% alumina. In addition, the thick film adherence γ_IC using (0001) sapphire substrates was less than that using (11ˉ23) sapphire. The 96 wt% substate exhibited essentially a random crystallographic surface texture and a considerable amount of surface silicates. The as-received 99+ wt% Al₂O₃ substrate was charactarized by a high (0001) surface texture and, while exhibiting a similar composition silicate layer as that of the as-received 96 wt% alumina, the total amount of the glass layer is greatly diminished. Fractographic analysis of the separated thick films and substrates showed that changes in the substrate crystallographic texture and the glass layer diminish the interpenetrating nature of the glass—metal interface and weaken the glass—substrate interface. Such changes in thick film microstructure lead to poorer thick film adherence.     

Behaviour of impurity atoms and adsorbed oxygen atoms on (001) face of iron epitaxial film

The behaviour of impurity atoms and adsorbed oxygen atoms on a (001) iron face were studied by a four-grid type LEED-AES system. The (001) iron face was prepared by deposition; that is, the iron atoms were evaporated from an iron wire (99.9 per cent) which was heated directly by electric current, and the iron film was grown epitaxially on the (001) face of an MgO substrate under wide ranges of experimental conditions. The orientations, (001)_Fe//(001)_MgO, [100]_Fe//[110]_MgO, were identified. No impurity atoms were detected during the film formation by AES. When the film was heated at temperatures higher than 500°C, extra spots appeared in the LEED pattern and a distinct sulphur peak appeared in the AES curve. They indicate that a super structure, Fe(001)C(2×2)S, was formed. This structure was stable but when it was treated in an oxygen atmosphere (1×10^?6torr) at 500°C, the sulphur peak vanished and another super structure, Fe(001)P(2×2)0, was formed. When the substrate was kept at a high temperature during the film formation, it seems that a super-structure, Fe(001)C(2×2)C was formed.     

Integrative square-grid triboelectric nanogenerator as a vibrational energy harvester and impulsive force sensor

Nano Research - A square-grid triboelectric nanogenerator (SG-TENG) is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional (3D)-printed...