Film Thickness Measurements Research Articles

Observation of Grease Film Behavior in Sliding-Rolling Concentrated Contacts

Abstract In sliding-rolling concentrated contacts, the grease film is subjected to shear action. In this study, grease film behaviors have been observed under different sliding-rolling ratios (SRRs) by measuring film thickness and friction coefficient simultaneously. The evolution patterns of the grease films with disc revolutions are affected by SRR, entrainment speed, and grease consistency. The severe starvation due to film decay at low shear and the film recovery at high shear has been recognized. The grease with low consistency is in a fully flooded state due to improvement in lubricant replenishment. In addition, the corresponding friction coefficient tends to increase or be constant in terms of contact states. The mechanisms of the grease behavior related to shear actions and grease properties are analyzed.

Cross-Linked Polymer Brushes Containing N-Halamine Groups for Antibacterial Surface Applications.

Microbial contamination is a significant issue in various areas, especially in the food industry. In this study, to overcome microbial contamination, cross-linked polymer brushes containing N-halamine were synthesized, characterized, and investigated for antibacterial properties. The cross-linked polymer brushes with different N-halamine ratios were synthesized by in-situ cross-linking methods with reversible addition−fragmentation chain transfer (RAFT) polymerization using a bifunctional cross-linker. The RAFT agent was immobilized on an amine-terminated silicon wafer surface and utilized in the surface-initiated RAFT polymerization of [N-(2-methyl-1-(4-methyl-2,5-dioxoimidazolidin-4-yl)propane-2-yl)acrylamide] (hydantoin acrylamide, HA), and N-(2-hydroxypropyl)methacrylamide) (HPMA) monomers. Measurement of film thickness, contact angle, and surface morphology of the resulting surfaces were used to confirm the structural characteristics of cross-linked polymer brushes. The chlorine content of the three different surfaces was determined to be approximately 8–31 × 1013 atoms/cm2. At the same time, it was also observed that the activation–deactivation efficiency decreased during the recharge–discharge cycles. However, it was determined that the prepared N-halamine-containing cross-linked polymer brushes inactivated approximately 96% of Escherichia coli and 91% of Staphylococcus aureus. In conclusion, in the framework of this study, high-performance brush gels were produced that can be used on antibacterial surfaces.

Simultaneous measurement of liquid film thickness and temperature on metal surface

The flow and evaporation of liquid films widely exist in various industrial fields. The investigation into liquid films is essential to design and optimize the relevant industrial processes. In this work, a simultaneous measurement method of liquid film thickness and temperature on metal surface based on diode laser absorption spectroscopy (DLAS) was proposed, and a corresponding measurement system was developed. First, static liquid films of 200–800 μm on the horizontal metal plate were studied, ultrasonic pulse-echo method (UPEM) and thermocouple were employed to compare with DLAS data. It revealed that the relative deviations of film thicknesses and temperatures measured by different methods were 3.3% and 2.0%, respectively. Furthermore, the evaporation processes of static liquid films were investigated. For the liquid films with different initial thicknesses (490.0/624.6/744.5 μm), the average relative deviations of the film thicknesses and temperatures measured by different methods were 0.1%/0.8%/4.1% and 0.1%/2.6%/3.0%, respectively. Finally, the flow processes of liquid films at different initial temperatures (40.0/60.0/80.0 °C) on the inclined metal plate were researched. It was found that the variation trends of the liquid film thicknesses and temperatures measured by different methods were in good agreement. In the stable stages of flow processes, the average relative deviations of liquid film thicknesses and temperatures measured by different methods were 9.0%/8.4%/5.1% and 3.6%/1.2%/2.5%, respectively. This work is helpful to understand the heat and mass transfer mechanisms in the evaporation and flow processes of liquid films.

Design and performance evaluation of edible film printing machine based on automatic casting knife

The development of edible films has been widely applied in recent years as an environmentally friendly food packaging, increasing shelf life and improving food quality. The most commonly used technique for producing starch-based films was classical casting, leading to film thickness measurement difficult. Therefore, this study aimed to design an edible film printing machine based on an automatic casting knife. The method used in this research was the engineering method. The edible printing machine was designed for a laboratory scale with a 1200 mm length, 500 mm width and 300 mm height. There were three main parts, namely an automatic casting knife, automatic pouring and control box. The performance evaluation showed that the automatic casting knife could be printing an edible film thickness between 0-20 mm with an accuracy level of 99.3%. An edible film with a length of 200 mm and 130 mm width can be printed in a shorter time (10 seconds). The edible film also has a smoother appearance on microscopic observation and was preferred by panellists to its appearance, texture and transparency parameters compared with edible film from manual casting. Based on the performance evaluation results that promise to be more efficient in printing edible film, this machine was expected to be scaled up and become a solution for the realization of Indonesian green packaging in the industrial revolution 4.0.

Development of a Thickness Meter for Conductive Thin Films Using Four-Point Probe Method

A thin film thickness meter was developed that is essential for thin film thickness management in the manufacturing process of flat panel displays such as touch panels and touch screens. The thickness measurement method of the meter is based on four-point probe method (Arther Uhlir in The Potentials of Infinite Systems of Sources and Numerical Solutions of Problems in Semiconductor Engineering 34:105-128, 1955; Valdes in Resistivity Measurements on Germaniumfor Transistors 42:420-427, 1954) and in the method, a thickness is determined by dividing the known electrical resistivity of a thin film material by the sheet resistance, and the thin film thickness measurement range is practically 1 nm–1 mm although the performance of the meter was confirmed in the range of 2.2 nm–22 μm. In order to conveniently measure the thickness of a thin film sample at a desired (to be measured) position, a probe station and a four-point probe were made. Place the four-point probe and the thin film sample at the probe station. When the four-point probe is brought into contact with the surface of the thin film sample using the upper and lower control knobs, the thickness measurement value is displayed on the meter, so the thickness of the thin film can be measured quickly and accurately. In addition, 5 types of samples such as Pd, Al, Au, Nb, and Cu were used to confirm the performance of the measuring device for the thin film thickness measurement function. For sample preparation, 5 types of samples were deposited on a silicon wafer with 75 mm in diameter, and the thickness was measured within 10 mm of the center of the sample, and the thickness of the cross-section was observed by SEM and TEM. As the result, the agreement for the thickness values between by the measurement results and SEM or TEM was confirmed in the range of 14 nm–1.6 μm.

Liquid film thickness and heat transfer measurements during downflow condensation inside a small diameter tube

The determination of the liquid film thickness during annular flow condensation in a small diameter channel is complex and very rare in the literature, although important to understand the heat transfer mechanisms involved during the phase change process. In the present paper, the liquid film thickness and heat transfer coefficients have been measured during vertical downflow condensation inside a 3.38 mm inner diameter channel. Condensation tests have been run with R245fa at 40 °C saturation temperature and mass velocity ranging from 30 kg m−2 s−1 to 150 kg m−2 s−1. The test section is composed of two heat transfer sectors connected with a glass tube. The glass tube has been realized with a special external shape that produces a magnification of the liquid film thickness and allows the use of a chromatic confocal sensor. The liquid film thickness is determined by coupling a shadowgraph technique with the measurements performed by the chromatic confocal sensor. An ad-hoc algorithm has been developed for the statistical characterization of the wave structures in terms of amplitude, frequency and velocity, with the aim to better understand how the interfacial waviness affects the heat transfer.

Axisymmetric bare freestanding films of highly viscous liquids: Preparation and real-time investigation of capillary leveling

Hypothesis: Thin liquid films are important in many scientific fields. In particular, films with both the surface layers exposed to a different fluid phase, known as freestanding films, are relevant in the ambit of foams and emulsions. Hence, there is a great interest in developing novel techniques allowing to form large and stable freestanding liquid films and to follow their dynamics.Experiments: We develop a novel opto-mechanical tool allowing to perform and study the preparation and the capillary leveling flow of axisymmetric bare freestanding liquid films. The tool is composed by a customized motorized iris diaphragm and by an innovative joint imaging setup combining digital holography and white light color interferometry that enables real-time measurement of film thickness over a large field of view. The dynamics of films made of a model Newtonian fluid, i.e., high-viscosity silicone oil, is studied. Direct numerical simulations and a hydrodynamic model based on the lubrication theory are used to support the experimental results.Findings: Iris opening induces the formation of large circular freestanding films with a stepped profile. Once iris opening is stopped, the films undergo a capillary leveling flow tending to flatten their profile. The leveling flow follows the theoretical scaling given by Ilton et al. [1]. We prove through numerical simulations that an equi-biaxial extensional flow occurs at the film center. Furthermore, we observe the formation and dynamics of dimples in bare freestanding films for the first time.

Static Performance of a Hydrostatic Thrust Foil Bearing for Large Scale Oil-Free Turbomachines

Abstract This work presents a novel design of a hydrostatic thrust foil bearing (HSTFB), with an outer diameter of 154 mm, along with simulation and test results up to a specific load capacity of 223 kPa (32.3 psi). This bearing has high load capacity, low power loss, and no friction/wear during startup and shutdown. In addition, the HSTFB allows for bidirectional operation. The paper also presents an advanced simulation model that adopts the exact locations of tangentially arranged bumps to a cylindrical two-dimensional plate model of the top foil. This method predicts top foil deflection with better accuracy than the traditional independent elastic foundation model, which distributes the bump locations over the nodal points in the cylindrical coordinates, and with less computational resources than the finite element method applied to the entire bumps/top foils. The presented HSTFB was designed for organic Rankine cycle (ORC) generators, but its performance was predicted and measured using air in this paper. The bearing static performance is compared analytically against the rigid counterpart and presented at different supply pressures, speeds, and minimum film thicknesses. Experimental verification is conducted at 10, 15, and 20 krpm. The measured load capacity and frictional loss agree well with the prediction. The measured film thickness also agrees with the prediction after the structural deflection of the thrust runner disk is compensated. Overall, the novel HSTFB demonstrates excellent static performance and good potential for the intended ORC generators and other large oil-free turbomachines.

Measurement of Film Thickness by Double-slit Experiment

We show that a simple double-slit experimental setup can be used to measure the thickness of a transparent thin film. The phase difference between the light passing through one slit covered with photoresist film and that passing through the other slit without film was estimated using the simple Fraunhofer diffraction formula for a double slit. Our method gave error of a few percent or less for film thicknesses ranging from 0.7 to 1.7 μm, demonstrating that a laboratory double-slit experimental setup can be utilized in practical film-thickness measurements.

Formation of Various Polymeric Films via Surface‐Initiated ARGET ATRP on Silicon Substrates

The growth of various polymeric films such as neutral, zwitterionic, and anionic ones was investigated over time from the initiator‐immobilized silicon substrates. The polymerization reactions were carried out under ambient conditions via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) without any predeoxygenating process. Each of the examined polymeric films showed linear/exponential growth over reaction times according to the measurement of ellipsometric film thickness. The successful formation of various polymeric films was further proved by X‐ray photoelectron spectroscopy, contact angle goniometry, and measurement of surface free energies. We think that this study can provide a basis for other researches that require to graft polymers with the adjustable film thickness for modulating chemical/physical properties at interfaces.

High-accuracy incident signal reconstruction for in-situ ultrasonic measurement of oil film thickness

The oil film thickness in an oil-lubricated tribo-pair can be measured using reflected ultrasonic waves and various transformation models. Conventionally, this approach requires the incident signal to be calibrated using off-line methods prior to testing, and this limits the on-line measurement of oil film thickness in sliding components such as journal bearings. To enable on-line calibration, we propose a method of reconstructing the incident signal from the easily obtained reflected signal. This involves analyzing the amplitude and phase spectrum of the reflection coefficient to reconstruct the incident signal. More specifically, the following main findings of the amplitude and phase of reflection coefficient at the resonance frequency are reported. 1) There is a zero-crossing at the resonance frequency, and therefore the phases of the incident and reflected signal are the same. 2) If part of the reflected signal is included for calculation, the frequency of the extreme point in the amplitude spectrum of the reflected signal is equal to the resonance frequency only when the extreme point phenomenon occurs at the center frequency of the transducer. At other positions, the frequency of the minimum amplitude in the amplitude spectrum of the reflected signal is not equal to the resonance frequency. Utilizing these relationships, the phase and amplitude of the incident signal can be accurately reconstructed by following the proposed method, provided the thickness of the oil film between the tribo-pairs can be widely ranged to cover both the blind and the resonance zones. Correspondingly, a practical schedule for the on-line reconstruction of the incident signal is proposed, which includes an operation to adjust the oil film thickness within the blind and the resonance zone. This method is validated on a test rig by comparing it with the traditional off-line methods.

Thickness measurement of circular metallic film using single-frequency eddy current sensor

In many advanced industrial applications, the thickness is a critical index, especially for metallic coatings. However, the variance of lift-off spacing between sensors and test pieces affects the measured voltage or impedance, which leads to unreliable results from the sensor. Massive research works have been proposed to address the lift-off issue, but few of them applies to the thickness measurement of planar metallic films with finite-size circular (disk) geometry. Previously, a peak-frequency feature from the swept-frequency inductance was used to compensate the measurement error caused by lift-offs, which was based on the slow-changing rate of impedance phase term in the Dodd-Deeds formulas. However, the phase of measured impedance is nearly invariant merely on a limited range of sample thicknesses and working frequencies. Besides, the frequency sweeping is time-consuming, where a recalibration is needed for different sensor setups applied to the online real-time measurement. In this paper, a single-frequency algorithm has been proposed, which is embedded in the measurement instrument for the online real-time retrieval of thickness. Owing to the single-frequency measurement strategy, the proposed method does not need to recalibrate for different sensor setups. The thickness retrieval is based on a triple-coil sensor (with one transmitter and two receivers). The thickness of metallic disk foils is retrieved from the measured electrical resistance of two transmitter-receiver sensing pairs. Experiments on materials of different electrical conductivities (from direct current), thicknesses and planar sizes (radii) have been carried out to verify the proposed method. The error for the thickness retrieval of conductive disk foils is controlled within 5% for lift-offs up to 5 mm.

Temperature compensation strategy for ultrasonic-based measurement of oil film thickness

Due to non-destructive testing characteristics, ultrasonic-based measurements are regarded as potential strategies in real-time monitoring of varied lubricant film thickness for tribological systems. Different theoretical models have been recently developed to calculate the film thickness from ultrasonic echo waves. However, the temperature influence on ultrasonic systems (for example, the acoustic parameters of materials and piezoelectric elements), which is non-negligible in the continuously running equipment, especially for heavy-loaded lubricated systems, has scarcely been considered. In this paper, the sensitivity of different parameters to the temperature variation is investigated in classical ultrasonic models. With the theoretical error analysis, a comprehensive temperature compensation strategy that considering the acoustic speed, material density, and reference signal, is proposed and integrated into the ultrasonic measurement algorithms. It is worth noting that the amplitude attenuation, waveform expansion, and signal time shift are considered in the compensation of the reference signal. Experimental verification is finally carried out in a calibrated rig with swept lubricant film thickness and different ambient temperatures. Test results suggest that the ultrasonic measurements with the proposed strategy effectively compensates the temperature influence and enables accurate calculations of lubricant film thickness under varying temperatures.

Thickness Measurements of Clear Coatings on Silver Objects using Fiber Optic Reflectance Spectroscopy

ABSTRACT Polymer films have been used extensively to coat heritage metal objects to provide protection against atmospheric oxidation and tarnish. Coating performance is directly proportional to coating thickness, but current methods used to measure coating thickness for quality control during treatment are qualitative at best. This paper demonstrates how fiber optic reflectance spectroscopy (FORS) was used to accurately determine coating thicknesses on a number of nitrocellulose-coated silver objects at Winterthur Museum. FORS appears to be significantly more accurate than other common methods used to measure film thickness, such as magnetic/eddy current techniques, but is limited to transparent or semi-transparent coatings. FORS is a simple, accurate method for measuring the thickness of protective coatings on a wide range of cultural heritage metal objects.

Analysis of Thickness Dependence of Nanoscaled Thin Film and Substrate by Ultrasonic Atomic Force Microscopy

Nanoscaled thin films are typically deposited on various substrates to achieve their unique characteristics. These thin film systems can be affected by the thickness variations between the thin film and the accompanying substrate. To investigate the thickness dependence of a nanoscaled thin film system, ultrasonic atomic force microscopy (Ultrasonic-AFM) which can evaluate the localized elastic modulus using the contact resonance frequency of a vibrating cantilever is applied. Copper thin films of low elastic modulus were deposited on silicon substrates of high elastic modulus. By contrast, Si3N4 and Ti thin films of high elastic modulus were deposited on GaAs and glass substrates of low elastic modulus, respectively. Experimental results showed that the thin films with different thickness were affected significantly by the substrate and the contact resonance frequency changes as a result of the varying thickness of the thin films. This research demonstrate that Ultrasonic-AFM may be a novel technique for the nondestructive measurement of nanoscale thin film thickness by considering substrate features.

The performance of titanium composite coatings obtained through thermal spraying and microarc oxidation

The development of composite coatings essential to improve the wear and corrosion resistances of the materials employed in numerous applications, such as automobile, chemical, medicine, construction, aerospace, and biomedical industries. In this study, we presented a double-layer coating technique, which consisted of a thermal-sprayed titanium (Ti) layer and a micro-arc oxidation (MAO) film on AISI 1020 steel. The effect of the composite coatings (Ti/MAO) on wear and corrosion resistance was investigated. To obtain a coating thickness from 250 µm to 450 µm, the prepared specimens were coated with Ti (99.9% pure) by arc spraying. Then, the Ti/MAO films were deposited on Ti coatings. The current density of MAO was fixed at 35 A/dm2, the voltages were 250, 300, 350, 400, and 450 V, and the duration of the MAO process was 10 min, Measurements of film thickness, microstructure, microhardness, X-ray diffractometry analysis, and scanning electron microscopic observation were performed for determining the characteristics of the composite coatings (Ti/MAO). Potentiodynamic polarization curves were used to compare the corrosion resistance of these composite coatings. A ball-on-disc wear test, using an oscillation friction wear tester, was carried out at room temperature according to the ASTM G99 standard to determine the wear resistance. Among all the specimens, Ti/MAO (400 V) had the greatest hardness, lowest friction coefficient, least weight loss, and longest sliding distance. The sliding distance of Ti/MAO (400 V) was about 1.7 times higher than those of Ti. The open-circuit potential of Ti/MAO (400 V) was about 1.7 times better than those of Ti. The corrosion currents of Ti/MAO (250 V) and Ti/MAO (400 V) were decreased by MAO about 95% and 92%, respectively. Although the corrosion current of Ti/MAO (400 V) was higher than that of Ti/MAO (250 V), Ti/MAO (400 V) had better effects in other tests. According to the results, Ti/MAO (400 V) presented the best performance among all the specimens and provided improved protection to both Ti and substrate.

Simultaneous Measurement of Viscoelasticity and Film Thickness during Shearing of Patterned Hydrated Polymer Brush Film

Simultaneous Measurement of Viscoelasticity and Film Thickness during Shearing of Patterned Hydrated Polymer Brush Film

Simultaneous Measurement of Surface Shape and Film Thickness Using Polarization Entangled Photon Source

Simultaneous Measurement of Surface Shape and Film Thickness Using Polarization Entangled Photon Source

Investigation of the optical, morphological and structural properties of molybdenum trioxide (MoO3) and zinc oxide (ZnO) thin film layers used in inverted organic solar cells

In this study, optical, morphological and structural properties of inverted organic solar cell structure such as the electron transport layer and hole transport layer was examined. Molybdenum trioxide (MoO3) was used as a hole transport layer (HTL) in an inverted structure while zinc oxide (ZnO) used as an electron transport layer (ETL) in the same structure. Firstly, the chemical cleaning of glass was done. After, 0.5 g zinc acetate dihydrate was dissolved in 6.38 ml ethanol and zinc oxide (ZnO) solution was obtained. Zinc oxide (ZnO) solution was filtered using an 0.45 ɥm PVDF filter. Then, ZnO solution was coated on glass surfaces by spin coating at 2500 rpm for 50 sec followed by annealing at 150 °C for 10 min on a hot plate in ambient. Secondly, 10 nm thick molybdenum trioxide (MoO3) was coated on the glass surfaces using thermal evaporation at a pressure of 5 × 10−7 Torr and an evaporation rate of 1 Å/sec in the glove box system. XRD, SEM, AFM, thickness and absorption measurements of these thin films coated on glass surfaces were performed. In the next stage, fabrication and characterization of ITO/ZnO/P3HT:PCBM/MoO3/Al inverted organic solar cells structures will be performed using these films.

Safe Ulvan Silver Nanoparticles Composite Films for Active Food Packaging

Protecting food from the corruption caused by different microbes is a big problem, as we need safe methods for food packaging. In this study, Ulvan (U), edible sulfated polysaccharide extracted from Ulva lactuca, was mediated for the first time non-toxic biosynthesized silver nanoparticles (Ag-NPs) to produce new and safe bio-nanocomposite films called (U/Ag-NPs) films for active food packaging. Ulvan was extracted by hot water-extraction and ethanol-precipitation method and was characterized by FT-IR spectroscopy. Biosynthesis of silver nanoparticles using U. lactuca was proven by Ultra Violet-Visible (UV-VIS), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) analyses. Investigation of films was by incorporation 1m M of Ag-NPs into different concentrations of ulvan (3, 6 and 12%, w/v). The formation of bio-nanocomposite films was confirmed by FTIR-ATR spectroscopy and TEM analysis. Bio-nanocomposite films were further characterized by physical parameters as water vapor permeability (1.18±0.07, 0.9±0.09 and 0.55±0.1 10−8 g mm cm−2 h−1 Pa−1), film thickness (0.01, 0.03 and 0.08 mm) and contact angle measurements (70.833°, 81.066° and 109.066°) respectively. The bio-nanocomposite films also showed high antimicrobial activity using Kirby-Bauer method as antibacterial and good antioxidant activity with IC50 = 1.128 µg/ml. (U/Ag-NPs) bio-nanocomposite films exhibited good chemical and physical properties, antioxidant and antimicrobial activities making them a potential substitute for active food packaging to extend shelf-life of foods during processing, transportation and storage with no harm as previous packaging methods.