Edge Of Film Research Articles

The Development of Manufacturing Technology of CVD Diamond Thick Film Tools

The key manufacturing technology of CVD diamond thick film tools is introduced, including thick film preparation, cutting, welding and edge polishing. The problems existing in manufacturing of CVD diamond thick film tools are analysed. The development trends of manufacturing technology of CVD diamond thick film tools are discussed.

Marangoni Flow in Freely Suspended Liquid Films.

We demonstrate controlled material transport driven by temperature differences in thin freely suspended smectic films. Films with submicrometer thicknesses and lateral extensions of several millimeters were studied in microgravity during suborbital rocket flights. In-plane temperature differences cause two specific Marangoni effects, directed flow and convection patterns. At low gradients, practically thresholdless, flow transports material with a normal (negative) temperature coefficient of the surface tension dσ/dT<0 from the hot to the cold film edge, it accumulates at the cold film edge. In materials with dσ/dT>0, the reverse transport from the cold to the hot edge is observed. We present a model that describes the effect quantitatively. It predicts that not the temperature gradient in the film plane but the temperature difference between the thermopads is relevant for the effect.

Freely suspended smectic films with in-plane temperature gradients

Freely suspended smectic films with in-plane temperature inhomogeneities can exhibit remarkable thermocapillary (Marangoni) effects. The temperature dependence of the surface tension promotes flow in the film plane, convection roll patterns, and climbing of smectic layers against gravitational forces. We discuss several experimental geometries where macroscopic material transport is driven by temperature gradients, including experiments under normal gravity and observations in microgravitation during suborbital rocket flights and on the International Space Station. In all these experiments, the temperature dependence of the surface tension drives unidirectional material flow. The divergence of this flow near the hot and cold film edges, and at the boundaries of film islands in the film, is associated with the creation, motion and removal of dislocations. These dissipative processes limit the flow velocity.

Numerical study on dynamic characteristics of double droplets impacting a super-hydrophobic tube with different impact velocities

ABSTRACTThe coupled level set and volume of fluid method is applied to the numerical study on the successive impact of double droplets on a super-hydrophobic tube. The impact velocity varies from 0.25 to 2 m/s. These impact processes present spread, retract, rebound, breakup and splash. The out-of-phase impact takes place with the impact velocity from 0.25 to 1.25 m/s, while the in-phase impact takes place with the impact velocity from 1.44 to 2 m/s. With the impact velocity larger than 1.25 m/s, the liquid crown presents and deforms after the trailing droplet impact, then it would gather at the film edge, rebound or break up. When impact velocities range from 1.44 to 1.5 m/s, the finger liquid film presents before the liquid crown appearing. The finger head breaks with the impact velocity of 1.5 m/s during the leading droplet spreading. The zigzag liquid film becomes more obvious for larger velocities.

Enhanced photocurrent and photocatalytic degradation of methyl orange in cobalt hydroxide loaded titanium dioxide film

We report experimental investigation of the effect of the cobalt hydroxide (Co(OH)2) decoration on the photocatalytic activity of the titanium dioxide (TiO2) films. We demonstrate that the decoration of Co(OH)2 is able to red-shift the absorption edge of the TiO2 film from UV to the visible light region, enhance the optical absorption, and facilitate the charge separation and transfer. As a result, the Co(OH)2-TiO2 composite film is found to exhibit much larger photocurrent and higher performance in photocatalytic degradation of methyl orange than the pure TiO2 film.

XANES analysis and structural properties of CdS-doped TiO2

The present paper reports on fabrication of the undoped and cadmium sulphide (CdS) doped titanium dioxide (TiO2) samples (1 wt% CdS-TiO2 and 2 wt% CdS-TiO2) and their characterization. Effect of the dopant on microstructural, optical and electronic properties of the fabricated samples are presented by X-ray diffraction (XRD), atomic force microscope (AFM), Raman spectra, UV–visible absorption spectra and X-ray absorption near edge spectroscopy (XANES). XANES spectra of the Ti L edges and O K edges of the CdS-TiO2 films revealed that with 2 wt% CdS doping in theTiO2, crystal structure changes from the anatase type to the rutile type. Ti L edges as well as O K edges both exhibits that 2 wt% CdS doping in TiO2 has modified the electronic structure of TiO2. Results of XRD and AFM show that crystallite size and roughness of the TiO2 significantly reduces with the CdS doping. It is observed from Raman spectra that the peaks shift towards higher wave number with increasing CdS contents indicating decrease in bond lengths. Optical band-gap for the undoped TiO2 is 3.33 eV and 2.71eV with 2 wt% CdS doped and it is found that absorption band-gap of TiO2 is red shifted to visible region.

Microscale Thermal Energy Transfer Over a Combined System of Thin Films: Analytical Approach

An analytical approach for the solution of the equation for phonon transport is presented for the combination thin films system. The transient phonon radiative transport model is considered and the combination of the silicon–diamond–silicon films is accommodated in the analysis. The multi-film system is thermally disturbed from the edges through introducing temperature difference across the combined films. Equivalent equilibrium temperature is considered quantifying the distribution of the phonon intensity in the films. Equivalent equilibrium temperature obtained from the analytical approach is compared with that predicted from the numerical solution. It is found that numerical predictions of equivalent equilibrium temperature agree well with those obtained from the analytical approach. The boundary scattering of phonons at the film edges causes equivalent equilibrium temperature jump at film edges, which becomes apparent in the early heating periods. Phonon scattering in the combined films causes sharp decay of temperature in the films, which is more pronounced in the silicon film than that of the diamond.

Spatio-temporal imaging of terahertz electric-field vectors: observation of polarization-dependent knife-edge diffraction

We develop a terahertz electric-field vector imaging system that uses the rotating polarizer technique. The imaging system is used to investigate the polarization-dependent optical response of a patterned indium tin oxide (ITO) film deposited on a glass substrate. While ITO is transparent for near-infrared probe light, it acts as a metal for terahertz light. Therefore, polarization-dependent diffraction can be observed at the edge of the ITO thin film, and only electric field components perpendicular to the edge boundary can propagate behind the ITO layer. By comparison with a numerical simulation, we reveal the polarization dependence of this so-called knife-edge diffraction.

Optical Second-harmonic Observation of Stimulated Sacran Aggregates

Second-order nonlinear optical images of aggregates of the ampholytic megamolecular polysaccharide sacran under various stimuli were observed by optical second-harmonic generation (SHG) microscopy. SHG intensity microspots of several tens of micrometers in size are seen for sacran cotton-like lumps and fibers and they have very clear incident polarization dependence. In these microspots, the sacran molecules are oriented in concentric multilayers. We also observed SHG images of sacran prepared in a needle-ring electrode with applied voltage, where SHG was enhanced near the negatively biased needle electrode. We also observed SHG signals near the cast film edges of sacran. The appearance of the SHG image suggested a phase-separation structure in sacran aggregates. These results show that sacran molecules aggregate in several different ways.

Relationship between the thermal stress and structures of thermal-cycling-induced cracks in electroless nickel plating on metalized substrates

The cracking of nickel-plating films, which are typically utilized to prevent the oxidation of underlying metal conductor layers, is an important issue that affects the reliability of metalized ceramic substrates at high temperatures. In this study, we examined the structures of cracks formed in electroless nickel-phosphorous plating films deposited on copper-metalized silicon–nitride substrates, in response to thermal cycling over a temperature range of − 40 to 250 °C. Further, we calculated the stress induced by the thermal cycling and evaluated the relationship between the crack structure and thermal stress. The results revealed that the structures of the cracks could be categorized into three areas of the films. Essentially no cracks are formed in the film corners. In addition, the cracks formed near the film edges were oriented perpendicular to the edges themselves. Finally, the cracks formed in the center of the films exhibited a cobweb-like structure. The reason for the difference in the structures and quantity of the cracks depending on areas was explained by the thermal stress induced in the films. We estimated that the tensile stress induced at lower temperatures, instead of higher temperatures, during thermal cycling could cause brittle fractures in the films, leading to the generation and propagation of cracks. In other words, cracks could be formed at lower temperatures during thermal cycling. Further, we believed that cracking in the nickel-phosphorous plating films could be predicted by estimating the thermal stress induced in the films in numerical calculations.

Microscale Thermal Energy Transfer Between Thin Films with Vacuum Gap at Interface

Abstract Transfer of phonons through a silicon–diamond thin film pair with a nano-size gap at the interface is examined. The thin film pair is thermally disturbed by introducing 301 K at the silicon film left edge while keeping the other edges of the thin films at a low temperature (300 K). The radiative phonon transport equation is solved numerically to quantify the phonon intensity distribution in the combined films. The frequency dependent formulation of phonon transport is incorporated in the transient analysis. The thermal boundary resistance is adopted at the interface in the formulations. The near-field radiative heat transfer is also adopted at the gap interface, as the vacuum gap size falls within the Casimir limit. The predictions of thermal conductivity are validated through the thermocouple data. It is observed that predictions of thermal conductivity are in agreement with the experimental data. The ballistic phonons play a major role in energy transfer through the gap; their contribution is more significant than that of the near-field radiative heat transfer. Enlarging the size of the gap reduces the influence of the ballistic phonons on the energy transfer in the films. Increasing the silicon film thickness alters the energy transfer through the gap; in this case, the equivalent equilibrium temperature difference is increased at the interface.

The Thermal, Electrical and ThermoelectricProperties of Graphene Nanomaterials.

Graphene, as a typical two-dimensional nanometer material, has shown its unique application potential in electrical characteristics, thermal properties, and thermoelectric properties by virtue of its novel electronic structure. The field of traditional material modification mainly changes or enhances certain properties of materials by mixing a variety of materials (to form a heterostructure) and doping. For graphene as well, this paper specifically discusses the use of traditional modification methods to improve graphene’s electrical and thermoelectrical properties. More deeply, since graphene is an atomic-level thin film material, its shape and edge conformation (zigzag boundary and armchair boundary) have a great impact on performance. Therefore, this paper reviews the graphene modification field in recent years. Through the change in the shape of graphene, the change in the boundary structure configuration, the doping of other atoms, and the formation of a heterostructure, the electrical, thermal, and thermoelectric properties of graphene change, resulting in broader applications in more fields. Through studies of graphene’s electrical, thermal, and thermoelectric properties in recent years, progress has been made not only in experimental testing, but also in theoretical calculation. These aspects of graphene are reviewed in this paper.

Flow Statistics and Visualization of Multirow Film Cooling Boundary Layers Emanating From Cylindrical and Diffuser Shaped Holes

The research presented in this paper strives to exploit the benefits of near-wall measurement capabilities using hotwire anemometry and flowfield measurement capabilities using particle image velocimetry (PIV) for analysis of the injection of a staggered array of film cooling jets into a turbulent cross-flow. It also serves to give insight into the turbulence generation, jet structure, and flow physics pertaining to film cooling for various flow conditions. Such information and analysis will be applied to both cylindrical and diffuser shaped holes, to further understand the impacts manifesting from hole geometry. Spatially resolved PIV measurements were taken at the array centerline of the holes and detailed temporally resolved hotwire velocity and turbulence measurements were taken at the trailing edge of each row of jets in the array centerline corresponding to the PIV measurement plane. Flowfields of jets emanating from eight staggered rows, of both cylindrical and diffuser shaped holes inclined at 20 deg to the main-flow, are studied over blowing ratios in the range of 0.3–1.5. To allow for deeper interpretation, companion local adiabatic film cooling effectiveness results will also be presented for the geometric test specimen from related in-house work. Results show “rising” shear layers for lower blowing ratios, inferring boundary layer growth for low blowing ratio cases. Detachment of film cooling jets is seen from a concavity shift in the u′rms line plots at the trailing edge of film cooling holes. Former rows of jets are observed to disrupt the approaching boundary layer and enhance the spreading and propagation of subsequent downstream jets. Behavior of the film boundary layer in the near-field region directly following the first row of injection, as compared to the near-field behavior after the final row of injection (recovery region), is also measured and discussed. The impact of the hole geometry on the resulting film boundary layer, as in this case of cylindrical verses diffuser shaped holes, is ascertained in the form of mean axial velocity, turbulence level (u′rms), and length scales profiles.

Biomimetic Polyimide-Supported Cuprous Oxide Photocatalytic Film with Tunable Hydrophobicity, Improved Thermal Stability, and Photocatalytic Activity toward CO2 Reduction

Flexible and thermally stable polyimide (PI) films containing a hierarchical surface structure were synthesized as substrates to support visible-light active cuprous oxide for photocatalytic reduction of carbon dioxide for the first time. With the nanocasting technique, the surface structure on the leaves of Xanthosoma sagittifolium was successfully duplicated on PI films. Followed by the ion-exchange process and adequate thermal treatment, cuprous oxide nanoparticles were successfully immobilized on the artificial PI leaves and exhibited the capability to photoreduce carbon dioxide into carbon monoxide under visible-light illumination. With the selection of biomimetic structures and adjustment of fabrication parameters, the hydrophobicity and optical absorption edge of the photocatalytic film were tunable. An increase in hydrophobicity improved the yield of carbon monoxide. The introduction of a hierarchical structure on the surface and cuprous oxide within the matrix dramatically enhanced the thermal st...

Interpretation of linear dichroism at S L2,3 x-ray absorption edges of small organic molecules at surfaces

Resonant soft x-ray absorption was applied at the S L2,3 (2p) edges of thin films of 1,4-benzenedimethanethiol (BDMT) on gold and of sexithiophene (6 T) on flat and patterned CaF2 surfaces. Linear dichroism effects were clearly observed depending on the orientation of the electric field vector of the incoming radiation. They were related to the organization of the molecules. For the interpretation of the angular dependencies of the spectral features, density functional theory (DFT) simulations of the absorption cross sections were calculated. It was possible to confirm the generally accepted chemisorption geometry of BDMT on Au(111), composed of molecules nearly vertical at the surface with one of the S atoms participating in the bonding with Au and the other left pending at the outermost surface and contributing mostly to the measured x-ray absorption. For 6 T on CaF2 a new chemisorption phase was identified on ridge-patterned CaF2(110), coexisting with a previously known phase given by 6 T crystallites highly oriented along the ridges. The new phase being composed of molecules oriented perpendicular to the ridges and lying on their edges.

Tuning the point-defect evolution, optical transitions, and absorption edge of zinc oxide film by thermal exposure during molecular beam epitaxy growth

We study the optical properties of ZnO films grown using plasma-assisted molecular beam epitaxy. We employ three different growth temperatures (Tgrowth) of 298, 373, and 423 K. The XRD patterns and field-emission SEM images indicate that Tgrowth increment linearly increases the c-axis strain and average growth rate. The photoluminescence spectra show that Tgrowth increment from 298 to 373 K induces the blue-violet emission promoted by Zn interstitials (Zni). We also observe the blue emission promoted by the few O interstitials (Oi). However, this Tgrowth increment significantly reduces oxygen antisites (OZn) and eliminates oxygen and zinc vacancies (VO, VZn). We find that Tgrowth increment to 423 K enhances Oi and eliminates Zni inducing the excellent blue emission the O-rich condition. Notably, the point defects suppress the exciton-exciton scattering emission for Tgrowth = 373 and 423 K. Furthermore, the Kubelka-Munk spectra show that the strain provokes the free-excitonic absorption edge redshift. Our result emphasizes the significant thermal dependences of point-defect evolution, blue emission, and excitonic absorption in ZnO film. This study opens a possible application of ZnO in tunable-emission blue LEDs.

Entropy analysis for thermally disturbed thin films

Entropy generation rate during phonon transport across consecutively placed two thin films is examined. The films are thermal disturbed via setting the temperature differential at the edges. The Boltzmann transport equation is introduced to model the micro/nano scale heat transfer across the films. Thermal resistance is incorporated at the edges and at the interface of the films to model the boundary scattering. Thermodynamic irreversibility in association with the entropy generation rate is formulated in the films while adopting the phonon intensity distribution. The thermal conductivity predictions are validated adopting the previous data. It is demonstrated that the thermal conductivity data predicted and obtained from the experiments are in good agreement. The phonon scattering at the film edges and at the interface results in temperature jump in these regions. As the film thickness reduces, the entropy generation rate becomes large, which is related to the thermodynamic irreversibility caused by temperature jump. The entropy generation rate predicted through the Fourier heating model remains significantly larger than that obtained from the phonon radiative transport model, which is more pronounced for the small film thicknesses.

Design and field test of crosswise belt type whole plastic-film ridging-mulching corn seeder on double ridges

In order to realize seedbed mechanization of whole plastic-film mulching on double ridges and to overcome the difficulty in crosswise belt type soil covering by whole plastic-film, a kind of crosswise belt type whole plastic-film ridging-mulching corn seeder on double ridges was designed in this study. The key components of the sample machine was designed and its working parameters of seedbed soil covering device, crosswise-belt soil covering mechanism and profiling sowing depth adjustment device were determined. After numerical simulation on the film edge and crosswise soil covering by whole plastic-film on double ridges by discrete element method, the velocity and displacement of the oscillating plate, and the variation rule of amount of covered soil with time were explored. Field test results show that, when the advancing velocity of the machine was 0.50 m/s, the qualified rate of soil width covered on film edge of the seedbed reached 96.1%, qualified rate of crosswise soil belt width was 94.5%, qualified rate of soil thickness on seedbed was 95.3%, qualified rate of sowing depth was 89.3%, qualified rate of spacing between crosswise soil belts reached 93.6%, which all met related standards in China and satisfied design requirements, and could realize seedbed mechanization of whole plastic-film mulching on double ridges. Comparison tests on working performances of practical soil covering show a basic consistence with the seedbed soil covering simulation, and verified the effectiveness of the soil covering model built by using discrete element method. Keywords: whole plastic-film on double ridges, crosswise belt soil covering, combined machine, discrete element, numerical simulation, field test DOI: 10.25165/j.ijabe.20191204.4860 Citation: Dai F, Guo W J, Song X F, Shi R J, Zhao W Y, Zhang F W. Design and field test of crosswise belt type whole plastic-film ridging-mulching corn seeder on double ridges. Int J Agric & Biol Eng, 2019; 12(4): 88–96.

A Flexible Tactile Sensor with Irregular Planar Shape Based on Uniform Electric Field.

Tactility is an essential perception for intelligent equipment to acquire external information. It can improve safety and performance during human-machine interactions. Based on the uniqueness theorem of the electrostatic field, a novel flexible film tactile sensor that can detect contact position and be made into any plane shape is proposed in this paper. The tactile sensor included an indium tin oxide (ITO) film, which was uniformly coated on the polyethylene terephthalate (PET) substrate. A specially designed strong conductive line was arranged along the edge of the flexible ITO film, which has weak conductivity. A bias excitation was applied to both ends of the strong conductive line. Through the control of the shape of the strong conductive line, a uniform electric field can be constructed in the whole weak conductive plane. According to the linear relationship between position and potential in the uniform electric field, the coordinate of the contact position can be determined by obtaining the potential of the contact point in the weak conducting plane. The sensor uses a three-layer structure, including an upper conductive layer, an intermediate isolation layer, and a lower conductive layer. A tactile sensor sample was fabricated. The experiment results showed that the principle of the tactile sensor used for the contact position detection is feasible and has certain precision of position detection. The sensor has good flexibility, and can be made into any plane shape, and has only four wires. It is capable of covering large areas of robot arms, and provides safety solutions for most robots.

Phonon transfer in silicon-diamond films: Influence of thermal boundary resistance on acoustic phonon intensities

Thermal energy transfer across two-dimensional silicon and diamond thin films are considered and the influence of the thermal boundary resistance, due to mismatching of properties, on the acoustic phonon transport characteristics is studied. The transient form of the Boltzmann equation with frequency dependency of phonons is incorporated simulating the phonon transport. Thermal boundary resistance is considered incorporating mismatches of interface conditions of films, namely cut-off and diffusive models. The ratios of longitudinal and transverse acoustic phonon wave intensities because mismatch models (cut-off and diffusive mismatches) are predicted for temperature oscillating boundary condition at the silicon edge. It is found that the ratio of the longitudinal acoustic phonon intensities ratio because of mismatch models (cut-off over diffusive) does not behave exactly the oscillation of temperature at the edge of the silicon film due to scattering of phonons in the films. The same arguments are applicable for the ratio of transverse acoustic phonon intensities because of the interfacial mismatch models (cut-off over diffusive). The consideration of the phonon frequencies cut-off results in the ballistic phonon transfer in between films, which lowers the interfacial thermal resistance.