Effect Of Surface Coatings Research Articles

Study on the Effect of Surface Coating on Thermal Manikin's Repeatability

Thermal manikin is a system of simulating figures and heat states of human body. Present thermal manikin is always enclosed by hard materials, and not covered with surface coating. So the surface condition of thermal manikin is very different with real body, which reduces thermal manikin's repeatability. Therefore the research on thermal manikin's surface coating and its effect on thermal manikin's repeatability are necessary. In this paper, an appropriate material was selected to be thermal manikin's surface coating and the satisfying result in improving the repeatability of thermal manikin was achieved. Firstly, five kinds of candidate surface coating materials were selected, which were HTV, EVA, TPU, natural rubber latex and cotton fabric. To evaluate the synthetic performance of these materials, parameters characterizing material's mechanical and thermodynamic properties were achieved by series of experiments. Meanwhile, fuzzy mathematic theory was employed to do data analysis, which showed that HTV had satisfying optimization performance and can be used as thermal manikin's surface coating. Finally, to verify the function of HTV surface coating in improving thermal manikin's repeatability, comparative repeated experiments were performed in climate chamber when thermal manikin covered with HTV surface coating and did not cover with HTV surface coating. Results show that HTV surface coating can improve the repeatability of thermal manikin obviously.

Surfactant Effects on Efficiency Enhancement of Infrared-to-Visible Upconversion Emissions of NaYF4:Yb-Er

Infrared-to-visible rare earth doped upconversion phosphors that convert multiple photons of lower energy to higher energy photons offer a wide range of technological applications. The brightness (i.e., emission intensities) and energy efficiency of phosphors are important performance characteristics that determine which applications are appropriate. Optical efficiency can be used as a measure of the upconversion emission performance of these rare earth doped phosphors. In this work, hexagonal-phase NaYF(4):Yb-Er was synthesized using the hydrothermal method in the presence of surfactants like trioctylphosphine, polyethylene glycol monooleate, and polyvinylpyrrolidone. The upconversion emission optical efficiencies of NaYF(4):Yb-Er were measured to quantify and evaluate the effects of surface coatings and accurately reflect the brightness and energy efficiency of these phosphors. Polyvinylpyrrolidone-modified NaYF(4):Yb-Er particles were found to be ~5 times more efficient and brighter than the unmodified particles. The difference in efficiency was attributed to reduced reflectance losses at the particle-air interface via refractive index mismatch reduction between the core NaYF(4):Yb-Er particles and air using polyvinylpyrrolidone as a surfactant.

The Effects of Surface Coatings on the Onset of Rail Gouging

In solid-armature railguns, hypervelocity gouging damage can significantly limit the useful life of rails. Most solutions to this problem have involved the use of hard rail materials, which tend to be poor electrical conductors. However, it has also been observed that precoating the conductors of a railgun can significantly delay the onset of gouging. This is usually accomplished by launching several aluminum-alloy armatures on a set of rails below the gouging threshold. When an aluminum-alloy armature is launched at high speeds on copper-alloy rails, a thin (tens of microns) layer of aluminum is deposited on the surface of the rail. Subsequent tests at higher speeds often result in the delay or absence of gouging at speeds where it is normally expected to occur. However, this effect is not particularly robust, since gouging can still occur with sufficient lateral loads. In the experiments reported here, tests were conducted on UNS C15725 (Glidcop Al-25) copper rails to examine the effect of a controlled precoating applied with an electroplating process. Aluminum thicknesses of 2, 5, 25, and 50 μm were tested, providing a well-characterized aluminum layer as opposed to the rough variable-thickness layer typically deposited with an aluminum armature. Results of the experiments and analysis are reported in this paper.

Simulations of the effect of surface coatings on plasticity at small scales

Three-dimensional dislocation dynamics simulations were employed to examine how hard coatings affect plastic deformation in micron- and submicron-sized, single-crystal pillars (“micropillars”) of nickel. Cross-slip of dislocations in the coated samples was found to be necessary for the formation of banded structures and subcells. Our simulations thus offer an explanation for both the significant increases in compressive strength and the higher strain-hardening rate as well as formation of banded structures in coated micropillars.

Effects of Surface Coating on Cylinder Rods Prepared Using Sputtering Deposition Method with Modulated Magnetic Field

Tungsten (W), carbon (C), and titanium (Ti) thin films were prepared on carbide steel cylinder rods using a new magnetron sputtering deposition method to prevent their corrosion or increase their friction resistance. In this method, plasma was generated between the cylinder rod anode substrate and the cylinder pipe targets, and it moved toward the axial direction with the generation of a modulated magnetic field by a low-frequency alternating coil current. Experimental results showed that the surface morphology of the film became smooth, and the surface roughness of the film decreased. Deposition rate and film uniformity increased with the use of a modulated magnetic field, and friction coefficient increased as a result of the film preparation used.

Investigating the effect of surface coatings on the wear behaviour of the friction contact in ultrasonic motors

Nowadays, ultrasonic motors (USMs) are used widely in a large variety of applications such as camera auto-focus mechanisms, devices in automobiles, industrial servo control in precision positioning, intelligent robotics, ultra-precision measuring, and medical equipment. USM is driven by traction force at high-frequency oscillations (>40 kHz) and the characteristics and life of the motor are strongly related to the friction material used in the tribological contact. In this study, two purposely built test rigs, including a USM and a high-frequency (up to 4000 r/min) reciprocating machine (HFRM), were developed. The reciprocating machine ran with a small amplitude and a high-frequency motion was used to examine the wear behaviour of the friction pairs. Different materials such as advanced surface coating (chromium titanium aluminium nitride, and diamond-like coating) on stainless steel substrates were used to investigate their combined tribological performance with the aim to be used in the USM context. A matrix screening test for material selection purpose were also carried out using the HFRM and the tribological performance of the chosen material pairs were subsequently investigated using the USM. The ranking results of the material pairs from the USM tests agreed with those from the HFRM tests. HFRM results could correlate well with the USM results by considering energy input into the wear system. Thus, HFRM can be used as a screening tool for selecting materials using in USMs.

Effects of Surface Coating on the Electrochemical Properties of Amorphous CeMg12 Composite

Amorphous CeMg 12 was prepared by ball milled CeMg 12 alloy with Ni powder. The effects of mechanical grinding and electroless deposition of nickel (EDN) on the electrochemical properties of CeMg 12 composites have been studied systematically. Amorphous CeMg 12 composites have a maximum discharge capacity of 1209.6 mAh/g, but their cycling stability is poor. The cycling retention rate of the electrode is 37.26% after 10 cycles. After EDN treatment, the cycling stability of CeMg 12 composite is improved markedly, and the cycling retention rate increases to 63.67% after 10 cycles. The improvement of cycling retention rate can be attributed to compact nickel coating that prevents the inner Mg from further corrosion by alkali. The nickel coating also enhances the high rate discharge ( HRD ) property of the composite owning to the good electrochemical catalytic properties of Ni. As oxidation and corrosion is unavoidable during EDN treatment, the maximum discharge capacity decreases slightly for CeMg 12 composite with EDN treatment.

Testing the effect of surface coatings on alkali atom polarization lifetimes

The evaluation of different surface coatings used in alkali metal atomic magnetometers is necessary for the improvement of sensitivity of these devices. A method to measure the polarization lifetime of alkali atoms in the region between substrates with different coatings was developed to determine the effectiveness of the coating at preserving alkali spin polarization as well as chemical compatibility and high-temperature stability. Multiple coatings can be compared under identical experimental conditions, using an experimental geometry that allows surface characterization before and after evaluation of the polarization lifetime. Multilayered, cross-linked octadecyltrichlorosilane films, alkyltrichlorosilane monolayers, and octadecylphosphonic acid monolayers were evaluated using this approach.

The Effects of Surface Coating on the Structural and Magnetic Properties of CoAg Core-Shell Nanoparticles

We have investigated the impact of Ag surface coating on the microstructure of CoAg core-shell nanoparticles, and the consequences for the magnetic properties. Atomic structures were simulated using a molecular dynamics approach utilizing the embedded atom method. The magnetic properties were then simulated using an atomistic approach using a classical spin Hamiltonian, taking into account the long-range nature, atomic separation and directional and phase dependence of the exchange interactions in Co. For pure cobalt nanoparticles with a diameter less than approximately 3 nm the internal crystal structure showed multiple twinned regions and the morphology of an icosahedron. The addition of a monolayer silver coating alters the internal cobalt crystal structure to a regular planar form along the cubic [111] direction with a mixture of face centred cubic (fcc) and hexagonal close packed (hcp) atomic arrangements. The local atomic environment was used to assign anisotropies to the atoms on a site by site basis. Moreover, the capping layer influences the shape of the particle and yielded a morphology similar to that of a truncated octahedron. Taking into account the effects of surface anisotropy in addition gives an overall picture of anisotropy for CoAg nanoparticles. We present the results of calculations estimating the energy barrier to magnetization reversal and the intrinsic coercivity for these particles

Uptake of microparticles into the epithelium of human nasopharyngeal lymphoid tissue

The M cells of nasopharyngeal lymphoid tissue (NALT) have been considered to play an important role for vaccine delivery systems in humans. A number of investigations have reported particle uptake data in NALT of rodents. However, there have been no reports indicating any involvement of the nasopharyngeal lymphoid tissue in human vaccination. In the present study, we investigated whether the epithelium of human adenoid tissues might incorporate fluorescent microparticles using electron and fluorescent microscopy. The dissected adenoid tissues were incubated with various sizes and concentrations of fluorescent microparticles for 120 min at 37 degrees C. Furthermore, the effect of surface coatings of microparticles with cations on the uptake into the epithelium of adenoid tissues was investigated. Transmission electron microscopy revealed that microparticles were taken up by the M cells of human nasopharyngeal lymphoid tissues. The NALT-M cells showed greater uptake of the smallest particles, 0.2 microm in diameter, than those of 0.5, 1.0, or 2.0 microm diameter. It was also revealed that surface coatings with poly-L: -lysin or chitosan resulted in efficient uptake into the NALT. These results indicate that nasal administration of antigenic microparticles, which were coated with cationic materials, probably leads to a useful method of transnasal vaccination against respiratory and intestinal infections in humans.

The Effect of Surface Coating on the Stability of Leafcast Paper

Le colmatage (« leafcasting) » est non seulement une technique de conservation qui se pratique rapidement, mais il est d'une qualite esthetique superieure et donne une homogeneite plus forte entre l'ancienne couche de papier et le nouveau revetement Dans le cadre d'un travail de recherche intitule « Optimisation de la technique de conservation du leafcasting » on a etudie l'influence d'un traitement de surface fait avec des polymeres comme l'amidon ou des ethers de cellulose sur les proprietes du papier fabrique. L'objet de cette etude etait d'analyser l'effet des differentes sortes d'amidon et de cellulose de methyle utilisees par la technique du « Leafcasting ». 15 echantillons differents ont fait l'objet de mesures relatives a leurs proprietes chimiques, mecaniques et optiques. Les resultats confirment l'hypothese selon laquelle chaque type de polymere provoque des son application sur la surface du papier differents effets sur ses proprietes qu'il convient de considerer avant de les utiliser pour la conservation. L'amidon d'avoine et la cellulose de methyle a degre faible de polymerisation ont fait preuve d'un comportement favorable au cours du vieillissement. D'autres substances etudiees se sont revelees etre moins stables et donc moins appropriees pour la restauration du papier.

Effect of surface coating of particulate on the overall damping of particulate-reinforced metal matrix composites

A novel model for calculating the damping capacity of particulate-reinforced metal matrix composites (PMMCs) is proposed from the viewpoint of energy loss, in which particulates of equal volume but with different shape morphologies have been employed. Effect of surface coatings of particulate on the overall damping of composite has been investigated by varying the thickness and the material properties of the coating. The calculated results reveal that the large aspect ratio of particulate is beneficial for the improvement of damping. In the case of elastic coating, the damping increases with the elastic modulus of coating. While for the plastic coating, the weak coating or the hard coating may help in improving the overall damping of composites.

Effects of Surface Coating on the Critical Heat Flux for Pool Boiling from a Downward Facing Surface

As part of a joint U.S.−Korean International Nuclear Engineering Research Initiative investigating methods to enhance external reactor vessel cooling (ERVC) under severe accident conditions, it was proposed that surface coating be used to enhance the critical heat flux (CHF) for downward facing boiling. Toward this end, metallic microporous coatings were selected, and different compositions of the coating material were evaluated, in order to obtain a mixture with desirable qualities. Durability and adhesion tests were also done to study the performance of each of the resulting coatings. Quenching of the candidate coatings was then conducted under downward facing boiling conditions, using hemispherical test vessels to obtain the local boiling curves. Compared to a plain vessel surface under identical experimental conditions, considerable enhancement was observed in the critical heat flux for vessels with surface coatings. Optical and SEM (Scanning Electron Microscope) photos showed that the candidate coating possessed the desired porous microstructure with interconnecting channels and pores, leading to appreciable increases in the local CHF limits.

Effect of Surface Coatings on Anti-Snow Adhesion 3

Effect of Surface Coatings on Anti-Snow Adhesion 3

A Numerical Study of the Contact Mechanics and Sub-Surface Stress Effects Experienced Over a Range of Machined Surface Coatings in Rough Surface Contacts

The paper employs a rough-surface numerical elastic contact method designed to analyze Hertzian elastic contact effects of surface coatings. In particular the paper explores the differences in the surface contact mechanics and the resulting sub-surface stresses experienced over a range of differing coating material-properties, thickness, and machined roughness levels in a quantitative manner. The effect of a range of surface roughness properties and in particular root mean square roughness (σ) and correlation length β*, on the magnitude and depth of maximum shear stresses in the layer under individual asperities is investigated. This is done for a hard and stiff, and also for a soft and compliant coating, and for two coating thicknesses in each case. The results suggest that the magnitude of the local shear stress increases with increasing ratio σ/β* approximately linearly. The depth of the maximum local shear stress is found to correlate best with β*, however a further clear trend is observed between this depth and the number of profile peaks. The depth also shows a relation to the ratio σ/β* but the correlation in this case is weaker with significant deviations. Neither the magnitude nor the depth of shear stresses shows any significant trend in relation to the roughness (σ) alone. The tensile stresses at the interface, and the subsequent potential for delamination, are also investigated and found to be significant. Approximate correlation between the magnitude of interface tensile stress and root mean square roughness is achieved, but no clear trend in relation to correlation length is evident.

The influence of Fe-rich coatings on the dissolution of anorthite at pH 2.6

Surface coatings are very common on mineral grains in soils but most laboratory dissolution experiments are carried out on pristine, uncoated mineral grains. An experiment designed to unambiguously isolate the effect of surface coatings on mineral dissolution from any influence of solution saturation state is reported. Two aliquots of 53 to 63 μm anorthite feldspar powder were used. One was dissolved in pH 2.6 HCl, the other in pH 2.6 FeCl 3 solution, both for ∼6000 h in flow-through reactors. An amorphous Fe-rich, Al-, Ca- and Si-free orange precipitate coated the anorthite dissolved in the FeCl 3 solution. BET surface area of the anorthite increased from 0.16 to 1.65 m 2 g −1 in the HCl experiment and to 3.89 m 2 g −1 in the FeCl 3 experiment. The increase in surface area in the HCl experiment was due to the formation of etch pits on the anorthite grain surface whilst the additional increase in the FeCl 3 experiment was due to the micro- and meso-porous nature of the orange precipitate. This precipitate did not inhibit or slow the dissolution of the anorthite. Steady state dissolution rates for the anorthite dissolved in the HCl and FeCl 3 were ∼2.5 and 3.2 × 10 −10 mol feldspar m −2 s −1 respectively. These rates are not significantly different after the cumulative uncertainty of 17% in their value due to uncertainty in the inputs parameters used in their calculation is taken into account. Results from this experiment support previous theoretical and inference-based conclusions that porous coatings should not inhibit mineral dissolution.

On the effects of surface coatings on the high-temperature oxidation of nickel

Ni and Ni coated with superficial oxide coatings including SiO 2, CeO 2 and La 2O 3 have been oxidized in the temperature range 500–1200 °C in 10 −4–1 atm oxygen. The oxidation kinetics and the surface kinetics have been determined, and the microstructure and the composition of the oxide coatings and the thermally grown NiO scales have been characterized by a range of different microscopy and spectroscopy techniques. At 800–900 °C, the coatings decrease the oxidation rate by approximately one order of magnitude. The oxide coatings increase the relative growth inside the scale compared to uncoated Ni. Still, the major growth mechanism is governed by outward Ni diffusion, which indicates that the reason for the improved oxidation resistance is due to a decrease in the overall outward flux of Ni across the scales.

Effectiveness of surface coatings in improving concrete durability

This paper reports results of a study conducted to evaluate the durability of concrete coated with concrete surface coatings representing five generic types. The durability of the uncoated and coated concrete specimens was evaluated by assessing water absorption, chloride permeability and chloride diffusion. The chemical resistance was evaluated by immersing the uncoated and coated mortar specimens in 2.5% sulfuric acid. The results indicated that epoxy and polyurethane coatings performed better than acrylic, polymer and chlorinated rubber coatings. However, noticeable variation in the performance of the same generic type procured from different manufacturers was noted. Therefore, the selection of coatings should be done after conducting trial tests rather than basing it solely on the generic type.

Effects of surface coatings on electrochemical properties and contaminant sorption of clay minerals.

Surface charges play a major role in determining the interactions of contaminants with soils. The most important sources of soil charges are clay mineral colloids, whose electrochemical properties are usually modified by metal-oxides and organic matter in natural environments. In this study, effects of coatings of organic matter and Fe- and Al-oxides on a series of electrochemical properties and heavy metal sorption of three clay minerals (kaolinite, montmorillonite and illite) predominant in natural soils were investigated using batch techniques. The results indicate that the coatings increased the specific surface area of the clay minerals, except for the Al-oxide coated montmorillonite and organic matter coated 2:1 clay minerals. The sesquioxide coatings increased amount of positive charges but decreased negative charges. This causes great reduction of the negative potential on the clay surfaces, shift of the zero point of charge to a higher pH, and promotion of fluoride sorption due to presence of more OH- and OH2 on the oxide surfaces than on the clay surfaces. In contrast, the organic coating significantly increased the negativity of surface charges, and thus the zero point of charge and zeta-potential of the clays dropped down. The organic coating also induced a reduction of fluoride sorption on the clays. With respect to the sorption of lead and cadmium, the sesquioxide coatings produced insignificant effects. The experiments of lead/cadmium competitive sorption show that on both the oxide-coated surface and the original clay surface there exist different types of sites, each of which preferentially binds with a heavy metal.

Effect of surface coatings, grain size, and ionic strength on the maximum attainable coverage of bacteria on sand surfaces

The injection of bacteria in the subsurface has been identified as a potential method for in situ cleanup of contaminated aquifers. For high bacterial loadings, the presence of previously deposited bacteria can result in decreased deposition rates—a phenomenon known as blocking. Miscible displacement experiments were performed on short sand columns (∼5 cm) to determine how bacterial deposition on positively charged metal-oxyhydroxide-coated sands is affected by the presence of previously deposited bacteria. Approximately 8 pore volumes of a radiolabeled bacterial suspension at a concentration of ∼1×10 9 cells ml −1 were introduced into the columns followed by a 2-pore-volume flush of cell-free buffer. It was found that the presence of Al- and Fe-coated sand increased both deposition rates and maximum fractional surface coverage of bacteria on the sediment surfaces. The effect of grain size on maximum bacterial retention capacity, however, was not significant. Decreasing ionic strength from 10 −1 to 10 −2 M KCl resulted in noticeable decreases in sticking efficiency ( α) and maximum surface coverage ( θ max) for clean silica sand—results consistent with DLVO theory. In columns containing positively charged Al- and Fe-coated sands, however, changes in α and θ max due to decreasing ionic strength were minimal. These findings demonstrate the importance of geochemical controls on the maximum bacterial retention capacity of sands.