Degree Of Surface Contamination Research Articles

Spatial distribution of cadmium concentrations in street dust in an arid environment

Cadmium (Cd) concentration and its chemical speciation were studied in surface dust samples collected from 26 locations at Amman–Zarqa basin highways. The study area represents a heavily trafficked arid environment associated with highly calcareous soils with an average of 53 % CaCO3; such combination gives the investigation further speculations on abundant Cd bonded forms. Sequential extraction technique (SET) was used to assess the exchangeable, bound to carbonates, bound to iron oxide, bound to organic matter, and residual fractions in surface dust samples. Total and fractional Cd spatial distributions were spatially investigated and utilized to generate Cd contamination factor map. Total Cd concentrations ranged between 4.1 and 17.9 mg/kg where maximum contamination was allocated at the study area center. The exponential behavior of Cd distribution in space gave further distinction of the possible contamination sources. The main Cd speciation was in the following order: bound to iron oxide > residual > exchangeable > bound to carbonate > bound to organic matter. The degree of surface contamination was determined by individual contamination factor that delineated those areas located close to the wastewater treatment plant that had high potential risk to fauna and flora. Relationship between the total and fractional Cd concentrations with soil chemical properties showed that pH, CEC, and amorphous Fe were positively related to total extracted Cd, while carbonate content and OM are negatively correlated with Cd.

Evaluation of contamination of ceramic surfaces and its effect on epoxy bleed

A degree of surface contamination has been found to be beneficial for assembly quality of optoelectronics because it reduces the surface free energy of the ceramic substrates, therefore inhibits bleed of the epoxy adhesives used to assemble components to them. This study aimed to examine the implications for process control of current industrial practice where the control of ceramic surface free energy is not considered. This has been achieved by identifying and characterising the potential sources of the contamination found on ceramic sleds, which had passed through the optoelectronic supply chain, so that the variation in chemical composition and the degree of contamination could be determined. Two types of ceramic substrates, aluminium oxide and aluminium nitride were cleaned by plasma, then stored in commercial polymer waffle packs used for transportation and a variety of storage atmospheres for one month. XPS measurements to characterize the surface chemistry were subsequently carried out following the storage to identify the composition of contamination that had built up. Contact angle and bleed distance measurements were also made to quantify the effect of the contamination on the wetting properties of the contaminated surfaces. It was found that the composition of the contamination was not directly associated with the storage method or environment, but the quantity was. The highest degree of contamination occurred on samples stored using the industrial standard method of containment in polymer waffle packs with paper and polyethylene anti-static inserts, higher even than storage in open air. The major source of the contamination in this case was probably from the inserts, with a much smaller contribution from the waffle pack. The levels of contamination built up in such case produced apparent surface free energies only slightly lower than 30 mJ/m 2, the threshold for acceptable levels of bleed to occur during the assembly process. This has indicated that if storage were to be used as a method of controlling epoxy bleed, it is likely that episodes of epoxy bleed would occur in a random manner on the production line, due to variation in the sample storage conditions and tendency to adsorb contaminants.

Frictional Duality Observed during Nanoparticle Sliding

One of the most fundamental questions in tribology concerns the area dependence of friction at the nanoscale. Here, experiments are presented where the frictional resistance of nanoparticles is measured by pushing them with the tip of an atomic force microscope. We find two coexisting frictional states: While some particles show finite friction increasing linearly with the interface areas of up to 310 000 nm(2), other particles assume a state of frictionless sliding. The results further suggest a link between the degree of surface contamination and the occurrence of this duality.

Overblasting effects on surface properties of low-carbon steel

The influence of overblasting on surface properties of low-carbon steel was investigated. In detail, surface roughness, contact angle, Vickers-hardness, degree of surface contamination, and pull-off strength were evaluated. It was shown that overblasting had notable effects on the surface properties. Most importantly, the surface roughness was significantly reduced, and the microhardness of the substrate increased. Also, overblasting increased surface wettability. The influence on the pull-off strength of applied coating systems was only marginal.

Contamination of polyethylene cups with polymethyl methacrylate particles: An experimental study

The articulating surfaces of 6 ultra–high molecular weight polyethylene cups were exposed to curing polymethyl methacrylate (PMMA) bone–cement and examined with scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Three of the cups were exposed to blood and bone–cement, and the rest were exposed to bone–cement only. After removal of the bone–cement bulk, PMMA particles were found and identified in all 6 cups. The particles were verified by identifying zirconium with energy-dispersive x-ray fluorescence spectroscopy in 5 cups and with LA-ICPMS in 1 cup. The degree of surface contamination was estimated with LA-ICPMS. The number of zirconium-containing particles detected was on average 10 to 20/mm2. PMMA bone–cement left in polyethylene cups during polymerization can contaminate the articulating surface with adherent PMMA particles.

Silicon Surface Cleaning by Wet Etching for IC Production in a Closed Manufacturing System

Silicon wafer cleaning by wet etching in model equipment meeting requirements for a closed manufacturing system is considered. Theoretical grounds for the new production technology, including chemical treatment, rinsing in water, and drying in a single process, are discussed. It is shown that the cleaning efficiency is improved if a heated gas (such as nitrogen) passes through the etchant, causing the wafers to vibrate, rotate in the horizontal plane, or reciprocate in the vertical plane. Also, the heated gas exerts a cavitation effect on the wafer surface. The degree of surface contamination after chemical etching, rinsing, and drying is reported.

懸濁液の知的認識法について

This paper treats the intelligent inspection system for particle suspension by using a neural network. The automated inspection system for particle suspension by an image processing has almost not been reported in the past, because of the complexity of image processing of water with particles. If the features of image processing data of particle suspension are recognized by a vision system and a neural network, the degree of surface contamination before and after washing processes will be clarified in relation to the water analyses, and also the deterioration process of many kinds of fluid, such as lubricants and finishing compounds will be cleared. The objectives of the paper are to analyze the water image by using the texture analyses, to investigate the limitation of image recognition for concentration of particles in water, and to construct the neural network system which' is able to estimate the concentration of particle suspension. It is found that the features of image data of the liquid containing particles can be decided by the texture analyses. As the results, it is possible to construct the neural network system which is composed of the features of water image as input data and the degree of particles concentration as output data.

ESCA, SIMS, SEM and XRD investigations of Pt-10%RH catalyst-gauzes

The nature and origin of harmful surface contaminants of spent Pt-10%Rh catalyst gauzes was determined by HR-SEM, ESCA, SIMS and XRD. Based on the analytical results the degree of surface contamination could be greatly reduced. Together with an appropriate optimization of several process-parameters the effective life time of the Pt-Rh catalyst could be significantly improved.

Surface pretreatment of carbon fibre-reinforced composites for adhesive bonding

Carbon fibre-reinforced composite laminates ( cfrp) have been moulded against release cloths, metal plates coated with release agent and sheets of silicone rubber. The chemical compositions of the laminate surfaces have been investigated by X-ray photoelectron spectroscopy ( xps). Results are presented to show the effect of a range of abrasive treatments on the degree of surface contamination and on the strength and mode of failure of single lap joints bonded with various adhesives.

Contact Resistance on Surfaces with Nonuniform Contaminant Films

A probe has been designed for making point-by-point mapping measurements of contact resistance over large surface areas. The probe, which operates in the low force range of 5 mg to 5 g, permits simultaneous measurement of both contact resistance as a function of load and the integral of contact resistance versus force. To accomplish this a magnetically damped torsion bar mounted pendulum/sample holder is electromagnetically driven against a smooth spherical probe tip mounted directly on a force transducer which, in turn, is mounted on an x-y precision translation stage. The associated instrument package includes a variable sweep rate electromagnetic drive, high-frequency rejecting load and contact voltage amplifiers (the latter being an ultrastable differential amplifier), a voltage-to-frequency converter, a scaler, and an x-y recorder. The probe has been used to explore spatial variations in contact resistance due to a nonuniform fiuoropolymer film on a gold substrate. The data show a large statistical variability, which is simply analyzed by assuming normally distributed surface asperities and applying this assumption to the accepted model for multi-asperity electrical contact. This procedure leads to a prediction that the square of the conductance will follow a Gaussian distribution. Contact resistances that were obtained in the course of this work as a function of force are shown to be consistent with the multi-asperity model, Data are presented which agree well with the statistical model. This insight into the statistical variability of contact resistance data is useful in that it suggests a successful data smoothing technique that presents a reasonable appearing line map of the effective contact resistance due to a nonuniform film. It is demonstrated that data smoothed in this fashion can be favorably compared to the degree of surface contamination as determined with a scanning electron microscope.

XPS and Mössbauer studies of amorphous FeGe

Photoemission spectra of amorphous FexGe1−x thin films prepared by thermal evaporation have been studied in situ with a XPS/Auger spectrometer. The composition varied within the range of 0⩽x⩽0.76 and the degree of surface contamination was monitored by Auger spectroscopy. The binding energies of Ge 3p and 3d as well as the Fe 3p transitions were found to be essentially independent of the alloy composition. Furthermore, no significant difference between the spectra of the alloys and the pure metallic elements could be detected. The results on a crystalline β-FeGe film (∼Fe3Ge2) were close to the data obtained on amorphous films. Mössbauer spectroscopy measurements down to 4.2 K performed on Fe0.53Ge0.47 indicated a mixed magnetic state composed of a nonmagnetically ordered doublet and a magnetically ordered broad six-line contribution, whereas the spectra of Fe0.30Ge0.70 showed only a nonmagnetically ordered doublet. By combining our results with published data, we are lead to the conclusion that a charge transfer model is not applicable to these alloys.

A Vacuum Cold Bore Test Section at the CERN ISR

A 2 m helium cooled vacuum test section has been inserted into the CERN ISR to investigate problems which could be encountered in future cold bore proton machines. The UHV bore is cooled from the helium bath via a variable pressure gas filled space which enables operation at any temperature between 2.5 K and ambient. Temperature and degree of surface contamination can be remotely controlled. First observations from nominally clean and from hydrogen contaminated surfaces operating at temperatures close to 4.2 K are presented.

A study of interfacial flow due to concentration difference

Experiments were carried out to study the effect of concentration differences on the surface-velocity distribution. The surface-velocity induced by feeding the surface-tension lowering material onto the surface of the stagnant liquid was measured in a similar type of apparatus to that used by Ruckenstein et al. [1]. The system studied was ethanol-water. From the experimental results, the dependence of surface-velocity distribution on the bulk viscosity of the solution, degree of surface contamination and concentration and feed rate of alcohol, was discussed.

Study of carbon-fiber surfaces using Auger and secondary electron emission spectroscopy

Structure at 3.0, 4.0, 7.5, 8.5, 10.0, 12.0, 14.5, and 17.5 eV in the secondary electron energy distribution of low-energy electrons back-scattered from carbon-fiber surfaces is shown to be similar to that observed from single-crystal graphite, which is due to emission from the high density of conduction-band states located 5 to 20 eV above the Fermi level. The intensity of secondary emission from these states is related to the degree of graphitic order in high- and low-modulus specimens of polyacrylonitrile (PAN-) and pitch-based carbon fibers. The results are discussed in terms of the effect of thermal treatment in high vacuum on the size and orientation relative to the fiber axis of regions of graphitic order in a surface layer of the order of 100 Å and a comparison is made with known models of carbon-fiber micromorphology. Auger electron spectroscopic analysis revealed the nature and degree of surface contamination on the different fiber types.

Optical Constants of Clean Titanium and Tungsten Surfaces as Functions of Temperature

The optical constants of single-crystal Ti (0001) and W (110) and polycrystalline W and Ti have been measured as functions of temperature at two wavelengths (5461 and 6328 A). The crystals were cleaned by ion bombardment and annealed to remove surface damage and bombardment impurities. The degree of surface contamination was monitored by Auger spectroscopy.

Impurity Effects on Heterogeneous Nucleation from the Vapor: Selenium on Glass

It has long been recognized that impurities adsorbed on the substrate can have a marked influence on the kinetics of heterogeneous nucleation. However, the detailed nature of these effects has not been demonstrated heretofore. In the present work, impurity effects have been characterized for the nucleation of selenium vapor onto Pyrex glass. It is shown that the degree of surface contamination not only affects the critical supersaturation required for nucleation, but may cause a nucleated phase of other than equilibrium structure. It is also shown that the degree of material accommodation for selenium on Pyrex is affected by surface contamination. These results are discussed in terms of the changes in substrate and nucleus interfacial energies accompanying impurity adsorption, and in terms of the possible masking of ordering influences exerted by a clean substrate.