Changes In Film Thickness Research Articles

High-performance flexible strain sensors based on silver film wrinkles modulated by liquid PDMS substrates.

Flexible strain sensors based on controllable surface microstructures in film-substrate systems can be extensively applied in high-tech fields such as human-machine interfaces, electronic skins, and soft robots. However, the rigid functional films are susceptible to structural destruction and interfacial failure under large strains or high loading speeds, limiting the stability and durability of the sensors. Here we report on a facile technique to prepare high-performance flexible strain sensors based on controllable wrinkles by depositing silver films on liquid polydimethylsiloxane (PDMS) substrates. The silver atoms can penetrate into the surface of liquid PDMS to form an interlocking layer during deposition, enhancing the interfacial adhesion greatly. After deposition, the liquid PDMS is spontaneously solidified to stabilize the film microstructures. The surface patterns are well modulated by changing film thickness, prepolymer-to-crosslinker ratio of liquid PDMS, and strain value. The flexible strain sensors based on the silver film/liquid PDMS system show high sensitivity (above 4000), wide sensing range (∼80%), quick response speed (∼80 ms), and good stability (above 6000 cycles), and have a broad application prospect in the fields of health monitoring and motion tracking.

Chemical expansion of CeO2−δ and Ce0.8Zr0.2O2−δ thin films determined by laser Doppler vibrometry at high temperatures and different oxygen partial pressures

The chemical expansion of ceria (CeO2−δ) and ceria-zirconia (Ce0.8Zr0.2O2−δ, CZO80) thin films is investigated by high-temperature laser Doppler vibrometry (LDV) at temperatures from 600 to 950 °C. The films are deposited on single-crystalline 8 mol-% yttria-stabilized zirconia substrates, which act as pumping cells to adjust oxygen non-stoichiometry in the thin films. Oxygen deficiency causes film expansion, leading to mechanical strain that bends the sample. The total displacement, i.e., the sum of bending and film-thickness change, is determined contact-less by LDV. A differential laser Doppler vibrometer (D-LDV) is realized to enable measurements on a very long time scale, which is necessary due to the long equilibrium times of the ceramic films. These displacements are compared to those acquired with a commercial single-point laser Doppler vibrometer (SP-LDV) for motions above 1 Hz. Here, both devices yield similar results. CZO80 films are found to bend a substrate much more than ceria films under similar experimental conditions. A model describing the displacement of the sample is derived from the Stoney model and applied to calculate deflections using literature data. The displacements at the center of the CZO80 sample measured with the SP-LDV increase from 0.18 nm at 10 Hz and 600 °C to 32.7 nm at 0.1 Hz and 800 °C. For ceria, the displacements range from 1.6 nm (10 Hz, 800 °C) to 79.4 nm (0.1 Hz, 900 °C). The D-LDV enables the detection of quasi-static displacements at very low frequencies. The ceria sample exhibits 218 nm at 0.001 Hz and 800 °C.

Changes in Thickness and Gloss of Dry Films According to Spray Methods of Water-Soluble Metallic Base Coat

Changes in Thickness and Gloss of Dry Films According to Spray Methods of Water-Soluble Metallic Base Coat

ELUCIDATION OF INTERNAL FLOW AND ITS EFFECT ON THE JET OF A TWIN-FLUID ATOMIZER FOR GAS TURBINE CROSSFLOW COMBUSTORS

Conventional liquid fuel jet injection into a crossflow is widely used for large-scale power generation in gas turbine combustors. The authors proposed a new twin-fluid injection technique as a potential alternative and conducted a series of studies on the internal flow of the atomizer and liquid jet/spray characteristics. In this study, experimental and numerical studies were first performed on internal flow behaviors and liquid and atomizing air interactions. The important behaviors of the internal flow of the atomizer, such as the dynamic change in the liquid film thickness, the rapidly changing velocity of the wave front, and the liquid impingement distance on the inner wall of the atomizer, were measured by both the experiment and numerical analysis. Atomizing air generates a high-speed oscillating annular liquid film flow that flows at the exit of a twin-fluid atomizer. This dynamic of the annular liquid film is considered fairly advantageous for achieving good atomization, which is investigated by analyzing only the liquid's behaviors in jet/spray and twin-fluid injection in a crossflow. High-speed photography and image processing were applied to observe the liquid jet/spray phenomena in the crossflow and reveal the atomization characteristics such as jet/spray trajectories and breakup length. Furthermore, the atomizing air can dominate the trajectory of the liquid jet/spray in the crossflow. The twin-fluid injection provides improved atomization properties compared to conventional liquid-only injection.

AlScN-Based Dual-Mode Devices With Temperature Compensated Strategy and Process Optimization

MEMS resonators with interdigital transducer (IDT) based on aluminum nitride (AlN) thin-film (a few micrometers thickness) materials gradually arouse researchers’ interest due to their ability to excite multiple modes of acoustic waves. However, the low electromechanical coupling coefficient is still one of the main reasons that limit the AlN-based resonators. In this article, we demonstrate a design journey for 10% scandium-doped AlN-based dual-mode acoustic wave resonators. Also, we investigated the influence of stack architectures with and without introduced AlN interlays, as well as the influence of stacked film thicknesses, on the performance of resonators. Simulation results show that changes in the SiO2 film thickness have different effects on the TCF of the two acoustic wave modes, providing a way for sensors to decouple two parameters that jointly affect the frequency drift. Moreover, measured results show that the introduced AlN interlayer (AlN-IL) induces a better crystalline orientation of the scandium-doped AlN (AlScN) thin film and a higher coupling coefficient of the leaky longitudinal (LL) mode ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}^{{2}}$ </tex-math></inline-formula> : from 4.19% to 4.96%), which make the resonators have great potential in surface acoustic wave (SAW)-based applications such as sensors and high-frequency applications.

Investigation of thickness effect on NO2 gas sensing properties of ZnO/Na thin films

This present communication studies the dependences of film thickness, electrical properties, and film morphology on the gas detection capability of Na/ZnO thin films. The phase formation, microstructure, surface composition, and electrical parameters of these films were analyzed by XRD, FESEM-EDAX, and Hall measurement. XRD measurements reveal that the crystal quality of Na doped ZnO films is enhanced with the increase in the sensing layer thickness. The morphology of samples shows a transition of grain shape from spherical to irregular as the films become thicker. The film thickness shows variations in the range from 132 nm to 356 nm. Hall measurement concludes that Na doping concentration induces p-type conductivity in ZnO. The Na/ZnO film of a thickness of 132 nm emerged as the suitable NO2 sensor with better sensitivity and the fastest res/rec property. The obtained discrepancy in responsivity is attributed to the difference in grain size and carrier concentration with a change in film thickness.

Influence of film thickness and substrate roughness on the formation of laser induced periodic surface structures in poly(ethylene terephthalate) films deposited over gold substrates

A study of the formation of Laser Induced Periodic Surface Structures (LIPSS) using near-infrared femtosecond pulsed laser irradiation on poly(ethylene terephthalate) (PET) films deposited over gold substrates has been carried out. We report the influence of the gold substrate roughness and the PET film thickness on LIPSS formation and analyze it in terms of the features of the electric field distribution obtained by computer simulations using COMSOLTM. We obtain LIPSS with periods close to the irradiation wavelength as long as the aforementioned substrate and film parameters remain below certain threshold values, in particular for polymer thicknesses below 200 nm and substrate roughness of few nm. However, experiments show the impossibility of LIPSS formation for rough substrates as well as thick films above these threshold values. In our numerical simulations, we notice the generation of Surface Plasmon Polariton (SPP) in the film-substrate interface that gives rise to a periodical field pattern on the surface of the thin film. This periodicity is broken for a certain level of substrate roughness or film thickness. Moreover, the evolution of the period of the SPP as the substrate roughness and film thickness change for given laser parameters is qualitatively in good agreement with the experimental LIPSS period (below but close to the irradiation laser wavelength). In conclusion, the experimental findings are explained by the formation and behavior of SPP in the thin film-substrate interface. On these grounds, we propose that, for our case of study, this SPP formation and the subsequent inhomogeneous rise in temperature induced by the periodic field on the surface of the sample is the leading mechanism contributing to LIPSS formation.

Pseudo-flexible resistive switching characteristics of nano-bowl-like NiO arrays on mica substrates

Nano-bowl-like NiO (nb-NiO) arrays on flexible Pt-coated mica substrates have been fabricated by electro-deposition and magnetron sputtering with the assistance of the monolayer colloidal sphere template. The nano-bowl array makes the polycrystalline NiO film thickness change periodically in the range of 150–450 nm, and the HfO2 buffer layer effectively depresses the local leakage current. A voltage which is lower than ±0.4 V can make the Ag/HfO2/nb-NiO/Pt cell reversibly switch between the high and the low resistance states within 11 μs. This cell exhibits a ratio of the high to the low resistance (RH/RL) of 103 ∼ 104, a data retention time over 104 s and an endurance of >1200 cycles. Driven by the non-uniform electric field, oxygen ions accumulated at the HfO2/NiO interface prefer to occur the Fowler-Nordheim tunneling at the thinnest bowl bottom, which decreases switching voltages. The bent cell almost keeps initial resistive switching properties before the bending radius (r) is below 2.5 cm. Though its properties greatly degrade when the r further reduces below 1.5 cm, it can recover most of initial memory window after returning to the flat state again, showing potential applications in new types of pseudo-flexible memory devices.

Air entrainment dynamics of aqueous polymeric droplets from dilute to semidilute unentangled regimes

Recent studies have revealed the air-cushioning effect of droplet impact upon various surfaces and although pure water droplets have extensively been studied, the air entrainment dynamics for aqueous polymeric droplets was the focus of this study. Herein, droplets of low to moderate Weber numbers, We ∼ O(1−10), displayed air film thickness gradients which was strongly influenced by the viscoelastic properties of the aqueous polymeric droplets in the dilute to the semidilute unentangled regimes. Aqueous polyethylene oxide droplets impacting a smooth thin oil film surface formed a submicrometer air layer, moments prior to impact, which was tracked by a high-speed total internal reflection microscopy technique. The radial changes in the air film thickness were related to the polymer concentration, thus providing an alternative tool for comparing the rheometer-derived overlap concentrations with a contactless optical technique.

Effect of thermal oxidation on structural and tribological properties of MoS2 films

AbstractThe aim of this study is to investigate the structural, mechanical and tribological behaviours of thermally oxidized MoS2 films. MoS2 coatings were deposited on D2 tool steel substrates using the closed field unbalanced magnetron sputtering method (CFUBMS). The thermal oxidation process was carried out at four different temperatures. Tribological properties were determined by pin‐on‐disc wear tests in the atmospheric environment. It was determined that thermal oxidation temperatures affected the chemical composition of MoS2 films, but did not cause any change in film thickness. The wear rates of the samples differed depending on the oxidation temperature and the applied load. The lowest wear rate was determined as 1.97 × 10−8 mm3/Nm in the oxidized film at 350°C. In addition, the highest hardness value was obtained as 655 HV in the film oxidized at 400°C, and the lowest coefficient of friction was obtained as 0.01 in the film oxidized at 350°C.

Measurements of Temperature and Humidity Responsive Swelling of Thin Hydrogel Films by Interferometry in an Environmental Chamber.

Thin film thermo-responsive hydrogels have become a huge interest in applications such as smart drug-delivery systems or sensor/actuator technology. So far, mostly, the response of such hydrogels has been measured only by varying the temperature in a liquid environment, but studies of the response towards humidity and temperature are rare because of experimental limitations. Often the swelling measurements are performed on samples placed on a stage that can be heated/cooled, while vapors enter the permeation chamber at their own temperature. This thermal difference leads to some uncertainties on the exact relative humidity to which the sample is exposed to. In this study, we explored the possibility of performing swelling measurements under thermal equilibrium by placing the sample and an interferometer, as a detector, in an environmental chamber and therefore exposing the smart hydrogel to adjustable temperatures and relative humidity conditions while measuring the hydrogel’s thin film thickness changes. As a case study, we used thin films of the thermo-responsive hydrogel, poly N-vinylcaprolactam deposited by initiated chemical vapor deposition (iCVD). Similar thin films were previously characterized by in situ ellipsometry while the sample was heated on a stage and exposed to humid air produced at room temperature. The comparison between the two measurement methods showed that while measurements in the presence of thermal gradients are limited mostly to low humidity, measurements in thermal equilibrium are restricted only by the operation limits of the used environmental chamber.

Influence of surface grooving methods on steady and dynamic performance of spiral groove gas face seals

In this paper, a structural form called double-sided spiral groove gas face seal is considered. Steady-state performances, such as film load-carrying capacity and film stiffness, of gas face seals with single-sided groove on the stator, single-sided groove on the rotor, and double-sided groove are compared. Introducing axial and angular excitations, coupled with gas lubrication, seal rings vibration, contact mechanics, and instantaneous changes in fluid film thickness, the complete dynamic behavior history is obtained. Two dynamic performance indicators, logarithmic decrement and period valley, are defined. The effects of groove depths and equilibrium film thickness on the dynamic performance of gas face seals with three different surface grooving methods are studied. Combined with the transient sealing performance and film dynamic coefficients, the mechanisms of several typical unstable conditions are analyzed. The results show that the double-sided grooving method has both high gas film load-carrying capacity and gas film stiffness when the equilibrium film thickness is relatively large. In addition, double-sided grooving has both advantages of high gas film damping of single-sided grooving on the stator and high gas film stiffness of single-sided grooving on the rotor, which can ensure stable operation under various operation conditions.

Film casting of polycarbonate/multi-walled carbon nanotubes composites using ultrasound-assisted twin-screw extruder: experiment and simulation

Abstract A one-step ultrasonic film casting process to manufacture nanocomposite films was developed, in which polycarbonate (PC) was mixed with multi-walled carbon nanotubes (CNT) and cast into films in one process. Numerical and experimental investigations of necking phenomenon were carried out for film casting of PC/CNT composites. Experimental results revealed that the necking along film line decreased with imposition of ultrasound and increasing CNT content, indicating that incorporation of CNT and imposition of ultrasound restrained the elongational flow behavior of melt, resulting in film of a larger width. Isothermal and nonisothermal numerical simulations of the process were performed. In isothermal simulations, the polymer melt was assumed to be maintained at the die temperature. In nonisothermal simulations, the temperature change along the film line was determined from heat transfer calculations with the WLF temperature-dependent viscosity. The simulated and experimental results on normalized film width, defined as a ratio of cast film width to die width, as a function of the distance from the die at various extension ratios were compared. The comparison indicated that changes in film width and thickness along the stretching direction in the nonisothermal process were in better agreement with experimental results than that in the isothermal process. Both experimental and simulated results showed a decrease of film width with take-up speed. Due to the presence of edge effect, the film width in experiment was lower than the simulated one. With incorporation of CNT, a better agreement between experimental and simulated results was obtained, due to a reduced edge effect in the film.

Giant magnetoimpedance effect in electrodeposited CoNiFe/Cu composite wire: Experimental study and analytical modelling

Study of giant magnetoimpedance effect (GMI) in electrodeposited CoNiFe/Cu composite wire is reported in the intermediate frequency region (10 kHz–10 MHz). The room temperature M–H curve of the sample reveals that the magnetic softness is independent of the film thickness(t). The changes in GMI value is attributed to the geometric effect caused by change of film thickness. To justify this claim, a hybrid model for circumferential permeability is proposed by combining the effect of domain wall motion(μdw), spin rotation (μrot) and local dispersion of anisotropy. The spectra of circumferential permeability is modelled with domain wall relaxation with continuous distribution of relaxation times. The spin rotation part of circumferential permeability is formulated using linearized Landau–Lifshitz–Gilbert (LLG) equation with Bloch–Bloembergen damping term and dispersion of anisotropy field. The proposed model is able to reproduce all the experimental results using single set of material parameters.

CFD-DEM investigation of fluid and particle motion behaviors in initial stage of spiral separation process at low solids concentration

ABSTRACT The evolution law of fluid and solid motion in the initial stage of spiral separation process is critical for mineral particle separation. The current research intends to investigate the fluid and particle motion behaviors in the initial stage of a spiral separation process using a CFD-DEM approach. The results show that the motion behaviors of fluids and particles in the initial stage of spiral separation process could be separated into three states: the development state, the transition state, and the relatively stable state. In the development state, water flows outward with a rapid change of velocity and film thickness. Meanwhile, fluid forced particles to move outward rapidly with no obvious trajectory difference. In the transition state, a collision between the slurry and the outer trough sidewall happens with changing the moving direction of fluids and particles. Following the collision, the flow field distribution tends to be relatively constant, and the light particles progressively migrate to the spiral trough’s outer edge, while heavy particles gradually move to the spiral trough’s inner edge.

Mathematical modeling in the organization of the production process of leaching metals

The following will describe the process of how you can use mathematical modeling to organize the production of metal leaching. Mathematical models and results of computational experiments are presented. The results of studying the thickness of films of sulfuric acid-chloride solutions containing the addition of surfactants surface-active substance (SAS), which are formed when they pour out onto a frosted glass surface as a model of the surface of a piece of ore, are presented. A mathematical model how the film thickness changes depending on the feed rate of the solution and its composition, as well as on the angle of inclination of the glass surface has been determined. Underground leaching of metals from ores stimulates the search for ways and means of intensifying the process. Due to the addition of a surfactant, the leaching process is accelerated, since the thickness of the films of leaching solutions flowing over the surface of ore minerals decreases. This direction is relevant in modern science, and research in this direction the growth of indicators allows the national economy to improve and helps to improve and increase knowledge for further development of the metallurgical industry in Russia The article also discusses the results of studies on the electrochemical leaching of metals from polymetallic ore by sulfuric acid-chloride solutions with the addition of a surfactant with asymmetric current pulses. Mathematical models of the dependence of leaching indicators on the density and duration of the flow of direct and reverse polarity are presented. For ease of perception and better visualization, a table was compiled, which reflects the results of comparative analysis to assess the further possibility of processing secondary raw materials.

Investigation of omnidirectional transmittance related to ITO nanorods orientation for optical applications

Indium-doped tin oxide (ITO) nanorods thin films were fabricated on silicon (100) wafer and commercial thin film coated glass (ITO-G) substrates via ion-assisted electron-beam evaporation system with inclinable and rotatable substrate setup. The thickness was controlled in the range of 100–400 nm through the QCM monitoring. With the fixed substrate's tilted angle at 85°, the film's structures were respectively observed as the slant and vertical nanorods corresponding to the substrate's rotation speed of 0 and 30 rpm by the field-emission scanning electron microscope (FE-SEM). The grazing-incident X-ray diffraction (GIXRD) and photoelectron spectroscopy (PES) were used to analyze the crystallinity and atomic composition of the ITO nanorods films. It was observed that the films were amorphous and non-significant of composition variation relative to the change of the film's-controlled thickness and structure. The optical transmittance in omnidirectional (omni-T) of p- and s-polarized light was determined through the variable-angle UV-VIS-NIR spectrophotometer. We found the different profiles of the omni-T with the change of film's structure and thickness which could be explained through the generated birefringence of the films. In addition, the different results of the p- and s-polarized were also discussed.

Dynamics of 5-DOF aerostatic spindle with time-varying coefficients of air bearing

Aerostatic bearing spindle has been widely used in precision machining processes. This paper presents a time-varying dynamic model of aerostatic spindle due to the change of air film thickness under periodic excitation forces. The effects of the magnitude and frequency of the forces on the dynamic coefficients of air bearing and cutting tool deflection are determined quantitatively. The dynamic properties in both translational and rotational directions are considered. The predicted tool vibration with and without considering the time-varying dynamics are compared. Experiments are conducted to measure the cutting tool displacements under stationary and rotational conditions. It is concluded that the variation of the dynamic coefficients plays a significant role in the spindle dynamics when the force magnitude increases beyond a critical value. The effect of unbalance mass on the spindle vibration is investigated based on the proposed model. The results provide guidance in the structure design for the aerostatic spindle and the process planning to improve the dynamic performance of the precision manufacturing process.

Effect of stoichiometry and film thickness on the structural and magnetization dynamics behavior of Co2MnAl thin films cosputtered on Si(1 0 0)

Obtaining low gilbert damping (α) and high spin polarization (P) in Heusler alloy thin films is one of the key requirements from the device application point of view in spintronics. Both α and P are correlated, closely related to the density of states (DOS) at the Fermi level and need to be controlled for engineered material. We investigated the effect of stoichiometry (different Co to Mn atomic percent ratios, viz. 2.21, 4.53, 5.43, and 9.19) and film-thickness {(t) in the range of 24–90 nm} on the structural and magnetization dynamics behavior in co-sputtered Co2MnAl thin films grown over Si(100) substrates. While the stoichiometric (∼50 at.% of Co) films with t ≥ 38 nm were found to exhibit B2 order with low α, the off-stoichiometric films (t ∼ 50 nm) were found to stabilize in partially ordered A2 phase and exhibited higher α. The change in structural ordering due to change in stoichiometry and film-thickness in polycrystalline Co2MnAl (CMA) thin films helped in tuning α in the range of (4.11 ± 0.06) × 10-3 – (11.95 ± 0.28) × 10-3. The minimum value of α ∼ (4.11 ± 0.06) × 10-3 was achieved for stoichiometric CMA (t = 70 nm) thin films which is close to the literature value of epitaxially grown L21 and B2 ordered CMA thin films. The study shows that we can tune and attain low damping in polycrystalline CMA Heusler thin films by controlling the stoichiometry.

Acquisition Method for Micro-gap Oil Film Morphology of Hydrostatic Workbench Having Double Rectangular Cavities under Working Conditions of High-Speed and Heavy-Load

When the hydrostatic workbench is running under high-speed overload conditions, the friction by-product is partially placed, causing the micro-gap oil film to be smaller, and the tribology is exposed. The oil film morphology of hydrostatic workbench directly affects its lubrication performance, and the oil film morphology is determined by deformation of bearing friction pairs and the oil film morphology is extremely difficult to obtain. This study will provide an acquisition method for the oil film morphology through the deformation of the bearing friction pair, and the deformation prediction of hydrostatic workbench having double rectangular cavities in heavy type vertical lathe has studied based on ANSYS WORKBENCH, and these are helpful to further investigate oil film shape under the working conditions of high-speed and heavy-load. The oil film clearance test rig was established, and the simulation results were verified, which verified the effectiveness of the proposed numerical simulation method. It can be concluded that the rotational speed has a greater impact on the oil film thickness than that of load, and the oil film thickness of downstream side is smaller than that of upstream side, and oil film thickness changes more quickly inside of oil sealing edge than that of outside, and the friction behavior and failure mechanism of this kind of bearing are proved.