Changes In Film Thickness Research Articles

Magnetohydrodynamic effects on liquid metal film flowing along an inclined plate relating to plasma facing components

The liquid metal film plasma facing component (PFC) is considered to be one of the most promising ways to realize a PFC capbable of operating for long periods. However, in the presence of a magnetic field, magnetohydrodynamic effects appearing in the liquid metal film flow directly influence the reliability of the flowing liquid metal limiter or divertor. In the present study, we consider the influence of flow rate, transverse magnetic field, and inclination angle, and conduct experiments on a liquid metal film flowing along an inclined conducting stainless steel plate. A laser profilometer (LP) and a high-speed camera are respectively adopted to obtain the local film thickness quantitatively, and its free surface structures qualitatively. We observe the magnetohydrodynamic effects of liquid metal film flow, such as the nonmonotonic change of film thickness, the reduction of film flow velocity, and the weakening of free surface waves in the direction of magnetic lines. Moreover, the film thickness increases with an increasing flow rate, whereas it decreases with an increasing inclination angle at a constant value of the magnetic field. When plotting the relative film thickening δen, and the reduction of flow velocity against the Stuart number N, we find that there is a critical N, Ncr ≈ 0.1, at which δen begins to increase dramatically. The δensinβ with , based on all of the experimental data, collapses into one line, which can be scaled as δensinβ ∼ N. The present experimental data and its scaling law may prove useful for estimating magnetohydrodynamic effects on liquid metal film flows when considering the design of liquid metal film PFCs.

Evolution of electrical and magnetotransport properties with lattice strain in La0.7Sr0.3MnO3 film**Project supported by the National Natural Science Foundation of China (Grant No. 10974105), the Double-Hundred Talent Plan, Shandong Province, China (Grant No. WST2018006), the Recruitment Program of High-end Foreign Experts, China (Grant Nos. GDW20163500110 and GDW20173500154), and the Top-notch Innovative Talent Program of Qingdao City, China (Grant No. 13-CX-8).

In this paper, we investigate the effects of lattice strain on the electrical and magnetotransport properties of La0.7Sr0.3MnO3 (LSMO) films by changing film thickness and substrate. For electrical properties, a resistivity upturn emerges in LSMO films, i.e., LSMO/STO and LSMO/LSAT with small lattice strain at a low temperature, which originates from the weak localization effect. Increasing film thickness weakens the weak localization effect, resulting in the disappearance of resistivity upturn. While in LSMO films with a large lattice strain (i.e., LSMO/LAO), an unexpected semiconductor behavior is observed due to the linear defects. For magnetotransport properties, an anomalous in-plane magnetoresistance peak (pMR) occurs at low temperatures in LSMO films with small lattice strain, which is caused by two-dimensional electron gas (2DEG). Increasing film thickness suppresses the 2DEG, which weakens the pMR. Besides, it is found that the film orientation has no influence on the formation of 2DEG. While in LSMO/LAO films, the 2DEG cannot form due to the existence of linear defects. This work can provide an efficient way to regulate the film transport properties.

Ternary blending with metakaolin and silica fume to improve packing density and performance of binder paste

Abstract In theory, ternary blending of cement with metakaolin (MK), which is of finer size, and silica fume (SF), which is even finer, would improve the packing density (PD) by successively filling the voids between cement grains. This should release more excess water (water in excess of that filled into voids) for fresh properties improvement and densify the microstructure for hardened properties improvement. To verify this postulation and reveal how and why (cement + MK + SF) ternary blending improves the fresh and hardened properties, 21 binder pastes with various MK and SF contents and a constant water/binder ratio were produced for flowability, adhesiveness, strength, sorptivity and porosity testing and microstructure observation, and the corresponding binder mixes were produced for PD measurement. The results showed that such ternary blending could improve the PD and both the fresh and hardened properties. In-depth analysis proved that the additions of MK and/or SF exerted influence through the eventual changes in PD and water film thickness (WFT). Lastly, plots depicting the concurrent flowability-strength and flowability-durability performances are produced to help find the optimum MK and SF contents for best overall performance.

Distribution laws and characteristics of mud films at casing–cement interfaces in horizontal wells

The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing–cement interfaces. So far, however, the distribution laws of mud film thickness on the outer surface of casing at different inclinations and its effect on the interfacial cementing strength have never been reported in literatures. In this paper, the mud film thickness at different parts on the outer surface of simulated casing (steel pipe) was measured at the inclination of 0°, 30°, 60° and 86°, respectively, using the independently designed experimental device. Then, the distribution law of mud film thickness on the outer surface of casing and its effect on the interfacial cementing strength were summarized. And the following research results were obtained. First, when the inclination increases from 0° to 86°, the mud film thickness changes from uniform distribution to thin-and-thick distribution, and the area proportions of thinner and thicker mud films both increase. And especially at the inclination of 86°, the mud film thickness on the upper surface is very large, and there are large exposed areas on the left and right surfaces of the steel pipe. Second, the cementing strength at the casing–cement interface of the exposed casing is much higher than that at the interface with mud film. And with the increase of inclination, the interfacial cementing strength with mud film tends to increase. Third, with the increase of inclination, the interfacial cementing strength increases successively, which is closely related to the area proportion of the exposed steel pipe to the solid mud film on the outer surface. In conclusion, the exposed area of the simulated casing on the outer surface is a key factor affecting its interfacial cementing strength.

A novel zinc oxide eugenol modified by polyhexamethylene biguanide: Physical and antimicrobial properties.

This study was to prepare and screen a novel root canal sealing agent modified by polyhexamethylene biguanide (PHMB) that was in accordance with the ISO 6876:2001 standard and to study its physical and antimicrobial properties. The modified sealers were produced by mixing a certain amount of zinc oxide with eugenol containing different concentrations of PHMB (0.05, 0.1, 0.2, 0.4, 0.6 and 0.8%) at a ratio of 1:1 (w/v). The setting time, flow, film thickness, solubility and dimensional change after solidifying were assessed to screen out the modified sealing agents that the physical properties met the mentioned standards. The modified direct contact test (DCT) was used to evaluate the antimicrobial activity against Enterococcus faecalis. The results suggested that when the concentrations of PHMB were 0.05, 0.1 and 0.2%, the modified root canal sealers showed the best performance in physical and antimicrobial properties.

Thermal Transport at Interface Between Single-Layer Graphene and Water Film

Through a series of molecular dynamics (MD) simulations, the interfacial thermal transport between liquid water and single-layer graphene film on the silicon substrate was studied. Three factors were justified for the interfacial thermal transport including interfacial interaction strength, water film thickness and water density. The results show that the interfacial heat transport capacity exhibits a significant dependence on the interaction strength, and this change in interfacial thermal conductance (ITC) was verified by calculating the vibrational density of states (VDOS). Meanwhile, dramatic oscillation was observed in the density of the liquid water near the wall, indicating that the motion law of water molecules was affected by the interaction force at the interface. Further study on the effect of water film thickness and density on the interfacial thermal transport, it is found that there is a critical value for the ITC with the change of water film thickness. When the water film thickness is greater than 4 nm, the effect on the interfacial thermal transport is not obvious, and the ITC gradually tends to a stable value. However, for the liquid water density, the ITC basically shows an increasing trend with the increase of density. In addition, the solid–liquid interface spacing was found to be variability and the distance is determined by the thickness and density of the water film.

Mass transfer between microbubbles

HypothesisThe role of interfacial coatings in gas transport dynamics in foam coarsening is often difficult to quantify. The complexity of foam coarsening measurements or gas transport measurements between bubbles requires assumptions about the liquid thin film thickness profile in order to explore the effects of interfacial coatings on gas transport. It should be possible to independently quantify the effects from changes in film thickness and interfacial permeability by using both atomic force microscopy and optical microscopy to obtain time snapshots of this dynamic process. Further, it is expected that the surfactant and polymer interfacial coatings will affect the mass transfer differently. ExperimentsWe measure the mass transfer between the same nitrogen microbubbles pairs in an aqueous solution using two methods simultaneously. First, we quantify the bubble volume changes with time via microscopy and second, we use Atomic Force Microscopy to measure the film thickness and mass transfer resistances using a model for the gas transport. FindingsModelling of the interface deformation, surface forces and mass transfer across the thin film agrees with independent measurements of changes in bubble size. We demonstrate that an anionic surfactant does not provide a barrier to mass transfer, but does enhance mass transfer above the critical micelle concentration. In contrast, a polymer monolayer at the interface does restrict mass transfer.

Study on Lubrication Characteristics of Metal Liquid Film Based on Electromagnetic-Elastic Mechanics-Hydrodynamics Multiphysics Coupling Model.

In an electromagnetic rail launcher, a metal liquid film is created at the armature/rail (A/R) contact interface. It has a significant impact on electromagnetic launch performance. In this paper, an electromagnetic-elastic mechanics-hydrodynamics multi physics coupling model is established in consideration of the metal liquid film’s own acceleration, magnetic pressure and dynamic changes in film thickness. Based on this model, the lubricating characteristics of magnetic pressure and fluid pressure distribution, film thickness distribution and velocity distribution of the metal liquid film were studied. When the velocity of the metal liquid film is very fast, and the magnetic pressure is reduced, it may fail to maintain stability and rupture, which may be an important reason for the transition. Finally, this paper analyzes the lubrication effect of the metal liquid film, and points out that when we want strictly to control the muzzle velocity, the lubrication effect of the metal liquid film must be considered.

Effect of film thickness on dielectric properties and energy storage performance of Ba0.95Ca0.05Zr0.3Ti0.7O3 thick films prepared by tape casting

Free-standing Ba0.95Ca0.05Zr0.3Ti0.7O3 thick films with varying thicknesses (90–200 μm) were prepared by tape casting technology. The thick films exhibited dense microstructure with fine and uniform grains (~ 1 μm). The dielectric properties, dielectric breakdown strength, and energy storage performance of the thick films were examined. The dielectric properties of the thick films were essentially unaffected by changing film thickness. The thick films with varying thicknesses showed similar dielectric constant and loss values, ferroelectric phase transition behavior, and dielectric nonlinearity. In contrast, the dielectric breakdown strength and energy storage performance were substantially dependent on film thickness. The dielectric breakdown strength and recoverable energy storage density were increased with reducing film thickness, while the energy storage efficiency at an identical applied electric field was enhanced. The film with a thickness of 90 μm achieved the optimal energy storage performance among the specimens investigated, exhibiting a recoverable energy storage density of 1.1 J/cm3 and an energy storage efficiency of 81.7% at an electric field of 260 kV/cm. The thickness dependence of the dielectric breakdown strength and energy storage performance was explained with respect to presence of oxygen vacancies in the lattice.

Simple Cosolvent-Treated PEDOT:PSS Films on Hybrid Solar Cells With Improved Efficiency

Conductivity improvement of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films up to 938.22 S·cm−1 was achieved by simply introducing the ethylene glycol (EG) as cosolvent for preparation. By conducting detailed characterizations on the film thickness, carrier concentrations, crystallinity, chemical state, and structural change of PEDOT chains, we revealed that the structural conformation was promoted from benzoid to the quinoid arrangement of PEDOT chains through the optimal EG additions, leading to the formation of the connected and aligned grains that was mediated by the dipolar–dipolar interaction, and therefore facilitated the charge hopping for allowing the improved film conductivity. The employment of such EG-treated PEDOT:PSS films with both enhanced conductivity and beneficial optical transmittance was demonstrated, indicating the sound design of hybrid solar cells with efficiency of 12.89%, which was compatible to the higher performance, low cost, and reliable cell manufacturing.

Thermal atomic layer etching of silicon nitride using an oxidation and “conversion etch” mechanism

Thermal atomic layer etching (ALE) of silicon nitride was achieved using sequential exposures of oxygen (O2) or ozone (O3), hydrofluoric acid (HF), and trimethylaluminum [TMA, Al(CH3)3]. Thermal Si3N4 ALE will be useful to etch Si3N4 in semiconductor, optoelectronic, and MEMS devices. Thermal Si3N4 ALE was performed with Si3N4 thin films deposited on silicon wafers using low pressure chemical vapor deposition. In situ spectroscopic ellipsometry (SE) was employed to monitor the changes in the Si3N4 film thickness as well as the SiO2 layer thickness. The SE results at 290 °C yielded an Si3N4 etch rate of 0.25 Å/cycle with an O2-HF-TMA reactant sequence using partial pressures of 250, 0.65, and 1.2 Torr for O2, HF, and TMA, respectively. The O2, HF, and TMA reactants were held statically at the indicated partial pressures for 10, 5, and 5 s, respectively. Larger etch rates were observed using O3 instead of O2 as the oxidant. A higher Si3N4 etch rate of 0.47 Å/cycle was measured at 290 °C using an O3-HF-TMA reactant sequence at the same partial pressures and static exposure times as the O2-HF-TMA sequence. The Si3N4 etch rate was observed to decrease at lower temperatures. An Si3N4 etch rate of 0.07 Å/cycle was measured at the lowest temperature of 210 °C using an O3-HF-TMA reactant sequence. The Si3N4 surface roughness was reduced after Si3N4 ALE. The SiO2 layer on Si3N4 could be removed using sequential HF and TMA exposures. These sequential HF and TMA exposures could also very slowly etch the Si3N4 substrate. The Si3N4 etch rate was dependent on the reaction sequence. When an O3-TMA-HF sequence was employed with reactant partial pressures of 250, 0.65, and 1.2 Torr for O3, HF, and TMA, respectively, the Si3N4 etch rate was 0.20 Å/cycle at 290 °C. Thermal Si3N4 ALE adds to the growing list of materials that can be etched with atomic layer control using thermal chemistry.

Enhanced electrical switching of magnetism in the artificial multiferroic CoFeB/Pb(Mg1/3Nb2/3)O3–PbTiO3 heterostructure

Multiferroic heterostructure CoFeB/Pb(Mg1/3Nb2/3)O3–PbTiO3 is prepared by depositing CoFeB films on Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystal through direct current magnetron sputtering. The electric field induced magnetism change of CoFeB film was studied by magneto-optical Kerr effect measurement. The magnetic hard/easy axis change was investigated under direct current electric field. Alternative current voltage magneto-optical Kerr effect test indicates the different magnetoelectric mechanism with the change of film thickness. The microwave frequency tunability was observed under the electric field and the tunable ferromagnetic resonance field reaches 190 Oe. Our study provides great opportunities for the application of electric-field tunable information storage devices.

Changes in water vapor adsorption and water film thickness in clayey materials as a function of relative humidity

AbstractSoil water, with adsorbed water being an important component, plays an important role in fluid flow and chemical movement in the unsaturated zone. The adsorbed water consists of water film and interlayer water, and its content is related to the relative humidity (RH). This study theoretically and experimentally focuses on the variation in adsorbed water content in clayey materials as the RH changes. Based on a slit‐pore model, three types of water (water film, interlayer water, and capillary water) could be present in the water vapor adsorption process. The variation of water film is obtained from the analysis of interfacial forces, and then the total water content can be quantitatively subdivided into these three types of water for different RH values. The slit‐pore adsorption model was used with experimental measurements (water vapor adsorption and N2 physisorption) to quantify the amounts and interrelationships of these three different types of water to six clayey materials, namely three clay minerals (kaolinite, montmorillonite, and illite–smectite mixed layer) and three clay‐rich sediments from the Jianghan Plain in China. The main results are that (a) the volumes of water vapor adsorption are much greater than those of N2 adsorption except for kaolinite; (b) interlayer water largely dominates the growth of total water content in montmorillonite and results in a concentration of 0.090 ml g−1 at 95% RH; and (c) the minimum thickness of water film is calculated to be 0.23 nm, and the maximum value is one‐third of the pore width by considering the interfacial forces.

Applicability of Vapor-Deposited Thermoresponsive Hydrogel Thin Films in Ultrafast Humidity Sensors/Actuators

Thermoresponsive polymers reversibly react to changes in temperature and water content of their environment (i.e., relative humidity, RH). In the present contribution, the thermoresponsiveness of poly(N-vinylcaprolactam) thin films cross-linked by di(ethylene glycol) divinyl ether deposited by initiated chemical vapor deposition are investigated to assess their applicability to sensor and actuator setups. A lower critical solution temperature (LCST) is observed at around 16 °C in aqueous environment, associated with a dramatic change in film thickness (e.g., 200% increase at low temperatures) and refractive index, while only thermal expansion of the polymeric system is found, when ramping the temperature in dry atmosphere. In humid environment, we observed a significant response occurring in low RH (already below 5% RH), with the moisture swelling the thin film (up to 4%), but mainly replacing air in the polymeric structure up to ∼40% RH. Non-temperature-dependent swelling is observed up to 80% RH. Above that, thermoresponsive behavior is also demonstrated to be present in humid environment for the first time, whereas toward 100% RH, film thickness and index appear to approach the values obtained in water at the respective temperatures. The response times are similar in a large range of RH and are faster than the ones of the reference humidity sensor used (i.e., seconds). A sensor/actuator hygromorphic device was built by coating a thin flower-shaped poly(dimethylsiloxane) (PDMS) substrate with the thermoresponsive polymer. The large swelling due to water uptake upon exposure to humid environment at temperatures below the LCST caused the petals to bend, mimicking the capability of plants to respond to environmental stimuli via reversible mechanical motion.

A time-dependent reliability analysis method for bearing lubrication

In bearing lubrication, the changes of load, speed, and clearance cause the oil film thickness changes over time. The oil film will rupture when the thickness is insufficient, and the bearing lubrication will fail. In this paper, a novel lubrication reliability estimation method was presented based on the first passage method. The Dowson-Higginson formula was used to calculate the minimum oil film thickness, then the time-dependent reliability was solved by the first passage method (FPM) and first-order reliability method (FORM). The effectiveness of the proposed method was verified by numerical example. This method can be used to analyze the influence of random velocity, load, and time-dependent parameters on lubrication reliability over the whole time domain.

Measurement of Liquid Film Thickness in Vertical Multiphase Slug and Churn Flows Using Distributed Ultrasonic Method

A distributed ultrasonic method for measuring the liquid film thickness of vertical multiphase slug flow and churn flow widely existed in industrial production is proposed in this paper. First, according to the proportional relationship between transit time of ultrasonic echo and liquid film thickness, we use the twin-crystal ultrasonic probe to measure the local thickness of liquid film. In view of the non-uniform circumferential distribution of the liquid film, three ultrasonic probes are installed on the same pipe section to measure the circumferential distribution of liquid film thickness. Then, a high-speed data acquisition system suitable for multi-channel and a data transmission system based on gigabit network are designed. The experiments of gas-liquid two-phase flow and oil-gas-water three-phase are carried out in a vertical pipe with a diameter of 20 mm. The fluctuation of local liquid film thickness has been measured by the distributed ultrasonic sensor, and the average thickness of liquid film of slug flow and churn flow under different flow conditions is obtained. The result indicates that the average liquid film thickness of slug flow and churn flow gradually thickens with the increase of liquid superficial velocity, and the distributed ultrasonic sensor can accurately measure the change of film thickness.

Cooling of the hot steel balls by salt –water solutions and water-based suspensions: Subcooled pool boiling experiments

In this work, the subcooled pool boiling experiments are performed during the intense cooling of the heated metal balls made of carbon steel AISI 1044 and stainless steel AISI 420L by brines and water-based suspensions of graphite and clay. The heated metal balls with an initial temperature of 1000 K are cooled down with a rate up to 300–450 K/s during the initial 2–4 s. The measured results show that a change in the mass fraction of the solid admixtures in a coolant affects the cooling process insignificantly. The phenomenon of the “step” change of the vapor film thickness during the pool film boiling of the subcooled deionized water at the surface of the immersed metal ball are discussed in detail. The brines and water-based suspensions utilization as coolants enables to eliminate the film boiling of the subcooled liquid. Besides, the optical method of the planar laser-induced fluorescence is applied to measure the temperature distributions near the liquid/vapor interface emerged when the heated metal ball is cooled down in a liquid pool.

Generating Surface-Anchored Zwitterionic Networks and Studying Their Resistance to Bovine Serum Albumin Adsorption

We report a simple method to generate surface-anchored zwitterionic network coatings that exhibit low nonspecific protein adsorption. We first synthesize amphiphilic random copolymers comprising 2-(dimethylamino)ethyl methacrylate (DMAEMA) and propargyl methacrylate (PGMA) units in two different nominal molar ratios (50:50 and 75:25) by free radical copolymerization. The DMAEMA moieties in the copolymers are then betainized with 1,3-propane sultone to obtain zwitterionic macromolecules. We create substrate-anchored network coatings by casting thin copolymer films (∼100 nm) containing 2 wt % of photoactive benzophenone onto a polystyrene substrate and cross-link them by UV-light irradiation at 365 nm (UV dose = 9–10 J/cm2). We investigate the cross-linking reaction with infrared spectroscopy, monitor the change in film thickness, and study the swelling behavior of the coatings as a function of ionic strength and electrolyte using spectroscopic ellipsometry. We demonstrate the performance of such surface-at...

Morphology and optical properties of films based on CVD graphene and nanostructured gold

In the work presented, the polymer-graphene-gold composites obtained by the methods of chemical vapor deposition and pulsed laser ablation (PLA) are studied. The morphological and optical properties of the given samples are studied in detail. It is shown that with an increase in the number of laser pulses in the PLA method, the metal coating transforms from separate small gold particles to a continuous cover with the presence of large nanoparticles. It is shown that a change in the gold film thickness influences significantly the efficiency of plasmon attenuation of a signal: with an increase in the average mass thickness, the effect increases and reaches its maximal value at film thickness of 6 nm. It is shown that the most intense plasmon absorption occurs in the wavelength range from 550 to 750 nm. A further increase in the thickness of metal coating decreases sample transparency in the studied range and does not affect the intensity of plasmon absorption and scattering.

Influence of roughness on the behavior of three-dimensional journal bearing based on fluid-structure interaction approach

In present study, a fluid-structure interaction (FSI) approach is proposed for predicting the effects of roughness on the performance of hydrodynamically lubricated three-dimensional (3D) journal bearing, taking mechanical deformation effects. The multi-phase cavitation mass flow conservation model is adopted, in which the phase change boundary condition is allowable. The results show that the mechanical deformation effect on bearing performance has been confirmed to be substantial. When the deformation of the structure is considered in calculating the change of film thickness, the bearings carry less load (i.e. 30–70 % smaller depending on the surface roughness value) as compared to the case in which the deformation is neglected. It is also highlighted that the hydrodynamic pressure and load support decrease with surface roughness.