Effect Of Surface Preparation Research Articles

The effect of surface preparation on the nucleation of diamond on silicon

A series of investigations into the surface preparation and modification techniques has been undertaken to study the influence of surface pre-treatment on nucleation enhancement of diamond film growth on silicon by microwave plasma-enhanced chemical vapour deposition. This paper deals with different scratching, cleaning and etching techniques. Polishing with dry diamond powder resulted in a high and uniform uncleation density and in good quality dense films, 2 μm thick, after deposition for 2 h, and the nucleation density increased with increasing polishing time. Polishing with fine-grained sprays is less effective than polishing with powders, and the nucleation density is reduced with increasing grain size with no growth for a 6 μm spray. By ultrasonic treatment in a diamond dispersion, neither a high density nor uniformity of nucleation has been obtained. The nucleation density decreased as a function of the length of the ultrasonic cleaning after the pre-treatment. The results support the theory that the residue left on the surface after pre-treatment is important to the nucleation.

X-ray photoelectron spectroscopic studies with a bias-potential method for studying silane-aluminium interfaces

Deposited organosilanes with the structural formula X3Si(CHz)nY (where X is a hyrolysable group, Y is an organofunctional group, and n = 0-3) are commonly employed as adhesion promoters [1], and there is considerable interest in developing an understanding of their surface bonding [1-6] and of the effects of surface preparation for improved coating adhesion, for example in corrosion protection. Matienzo et al. [7] investigated several silane treated samples of 7075-T6 A1 alloy with regard to corrosion protection. They found that 7aminopropyltrimethoxysilane (7-APS) gave poor resistance, whereas 7-mercaptopropyltrimethoxysilane (7-MGPS) performed well and 7-glycidoxytrimethoxysilane (7-GPS) was intermediate. Although a range of spectroscopic and analytical methods have been applied to study organosilane adhesion to metals (M), the evidence regarding the formation of direct M O S i bonding has been conflicting [2, 5]. Generally it has not been possible to relate the behavioural differences observed for different polymers to information at the atomic level. A recent paper from this laboratory [8] hypothesized that angle-dependent X-ray photoelectron spectroscopy (ADXPS) [9, 10], in combination with a bias-potential technique [11], may provide a way of probing the existence of direct AI -O-S i bonding at aluminium-silane interfaces, and assessing the relationships between the interfacial structure and corrosion stability. That idea was probed further here by investigating interfaces formed between 7075-T6 A1 panels and 7-MGPS [HS(CH2)3Si(OCH3)3] and 7-APS [NH2(CH2)3Si(OCH3)3]. Following our recent report, the A1 panels were degreased with acetone and acid-etched [8] before coating with silane solutions formed in 50 vol % distilled water and 50 vol% methanol. The surface pretreatment used is believed to provide carbon-free A1Ox regions on the surface [8]. Investigations were made on three interfaces formed by immersing the pretreated A1 panel in lvo1% 7-MGPS for 5min, lvo1% 7-APS (pH 3.0) for 15 min and 1 vol % 7-APS (pH 10.4) for 15 min. XPS measurements were made using a Leybold MAX200 spectrometer following procedures detailed previously [8]. Table I gives atomic composition information for the 7-MGPS interface obtained from measured XPS

Effects of surface preparation on the friction and wear behaviour of silicon nitride/silicon carbide sliding pairs

Silicon carbide and silicon nitride specimens were fabricated to provide three different surface finishes. They were subjected to sphere-on-flat (pin-on-disc) testing in order to determine the interaction of load, velocity, disc surface finish, and material effects on unlubricated friction and wear. Tests were conducted in air using applied loads of 1 and 10N, velocities of 0.1 and 0.5 ms−1, and surface preparations of 150-grit grinding, 220-grit grinding and fine polishing. The test duration was kept constant at 1000m of sliding distance for the pin specimen. In half the tests silicon nitride was the pin material and silicon carbide was the disc material. For the other half, the pin and slider materials were reversed. There was a much greater effect of normal force on steady-state friction coefficient than of either surface finish or material pairing. Increasing the sliding velocity raised the friction coefficient for both material pairings and for all surface roughnesses. Higher wear resulted when the velocity increased, but the effect of surface finish on wear ranged from none in some cases to about a factor of 10 in other cases. A trend of increasing run-in period duration with increasing smoothness was observed. The results are interpreted in terms of material properties, the Lim and Ashby model, and the friction force-velocity product.

Effect of surface preparation on performance of acrylic adhesive joints: Part II

The adhesion performance of four second-generation acrylic adhesives bonded to 4130 steel, 2024 T-351 aluminium and glassfibre epoxy with four surface treatments was studied. Best results were obtained with chromic acid anodized 2024 aluminium, sand-blasted 4130 steel and glassfibre epoxy at ambient conditions and after exposure to elevated temperature and humidity. The morphology of failure surfaces using SEM analysis revealed rubber spheres dispersed in the acrylic matrix, specific to each of the toughened adhesives.

Adherence of HDPE powder coating on Co‐Cr surfaces: Effect of substrate preparation and gas sterilization

As part of the development of a hemiarthroplasty implant with a compliant surface layer, the effect of surface preparation of a cast Co-Cr alloy substrate on the adhesion of a polymeric coating was studied. High-density polyethylene (HDPE) coatings were deposited on Co-Cr alloys without adhesive by spraying powder onto the surface of specimens maintained at a controlled temperature. Prior to deposition, two different types of surface preparation were carried out: chemical etching and grit-blasting. Adherence tests were performed in order to study the effect of the surface preparation of a Co-Cr alloy on the adherence of the HDPE film. The etching process enhanced the adherence by a factor of 10 compared to the grit-blasting process. For coatings deposited on grit-blasted Co-Cr surfaces, rupture occurred at the interface (adhesive mode) as well as in the coating (cohesive mode). A full cohesive mode was observed for films deposited on etched surfaces. Gas sterilization with an ethylene oxide and Freon 12 solution did not change significantly the adherence of the film deposited on etched surfaces. Examination of the surfaces indicated that the etching process created a specific type of porosity consisting of dendritic cavities whereas grit-blasting produced surface irregularities. Cavities produced by etching were larger that the polymer powder particles and could be easily filled. The coating of an etched Co-Cr alloy substrate with a layer of HDPE provided an interface that could probably sustain the physiological loading in a normal synovial joint.

Effect of Surface Preparations on Electrical and Chemical Surface Properties of P‐Type Silicon

The effects of chemical etching and mechanochemical polishing on p‐type silicon have been studied using capacitance measurements. The flatband potential , as determined from Mott‐Schottky plots, was found to be unrealistically large and very sensitive to the surface preparations used. The positive shifts of are explained in terms of a compensating effect from the silicon bulk. This compensating effect is partially suppressed by annealing. Elemental analysis of the surface using secondary ion mass spectroscopy and x‐ray photoelectron spectroscopy indicates that the most likely cause of the compensating effect is hydrogen. The source of hydrogen is the aqueous media used in the surface treatment processes.

The effect of surface preparation on properties of cadmium telluride thin film heterojunctions

The effects of surface preparation on CdTe-based thin film heterojunctions have been investigated through characterisation of ITO//p-CdTe and CdS/p-CdTe solar cells. The surface treatment methods include air exposure at laboratory temperature for several months, heat treatment, bromine-in-methanol etching, and bromine-in-methanol etching with subsequent hydrogen heat treatment. The authors have found that the behaviour of CdTe heterojunctions was significantly improved by the surface treatment of CdTe films exposed to air for several months at laboratory temperature prior to window material deposition. The stability of as-prepared cells has been considerably enhanced. Other methods of surface treatment seem to have insignificant effects on the improvement of subsequent heterojunctions. The explanations given for the improved performance of the solar cells are discussed.

The effect of surface preparation by TIG remelting on fatigue life: Gregor, V.Zvaracske Spravy (Weld. News) 1989 39, (3), 60–65 (in English and Slovak)

Non-lubricated, laboratory wear tests were done on two partially spheroidized eutectoid rail steels to determine the effects of increasing fragmentation of both thick and thin lamellae on dry-wear properties. The tests simulated heavy-duty stress conditions on the outer (high) rail of sharply curved railway track. The first steel, of Standard carbon composition, was heat treated in both the hot-rolled (thick cementite lamellae) and oil-quenched (fine cementite lamellae) conditions, and significantly lower rates were obtained for partially spheroidized hot-rolled oil-quenched specimens of similar hardness. The wear rates of the partially spheroidized second steel, a Cr-Mo alloy, corresponded very closely to those indicated by the wear rate vs. hardness curve of the oil-quenched specimens. Thus, wear rates of partially spheroidized microstructures are not uniquely defined by initial hardness, and are indeed better defined by the hardness of the worn surface. Image analysis observations suggest that the mean ferrite path is also an influential parameter in controlling the wear rate, irrespective of initial lamellar thickness. This could also explain why pearlite of hardness 38 HRC has a superior dry-wear resistance to harder upper bainites and tempered martensites.

Effects of surface preparation on ion implantation in GaAs

The influence of different polishing methods on the atomic profiles obtained by direct ion implantation in semi-insulating GaAs has been investigated, along with the effects of preimplantation etching. The results indicate that chem-mechanical polishing technologies, contrary to chemical only polishes, produce residual damage that results in shallower and more sharply peaked profiles. Polishing related damage, however, may not be the factor preventing a good electrical activation of implanted species. The acidity of the polishing fluid seems more important in determining the activation. Also, the dose implanted in uncapped, damaged wafers seems to be different, and generally lower, than the dose measured by the implanter.

Effect of Surface Preparation and Thermoplastic Adhesive Structure on the Adhesion Behavior of Peek®/Graphite Composites

Adhesion behavior of APC-2/AS4 PEEK/Graphite composite has been studied by varying the surface preparation techniques such as acetone washing, grit blasting and several plasma gas etching treatments. Poly(imide-siloxane) segmented copolymer prepared in our laboratory and Ultem® 1000 were utilized as adhesives. Single lap shear samples were prepared from the PEEK/Graphite composite and compression molded adhesive films. Excellent single lap shear strength values were obtained at room temperature. The morphology and elemental change by surface preparation of the adherend were monitored by scanning electron microscope(SEM) and x-ray photoelectron spectroscopy(XPS). Plasma etch treatments were effective for improving the adhesion characteristics.

The Effect of Sample Preparation Methods on Glass Performance

ABSTRACTA series of experiments was conducted using SRL 165 synthetic waste glass to investigate the effects of surface preparation and leaching solution composition on the alteration of the glass. Samples of glass with as-cast surfaces produced smooth reaction layers and some evidence for precipitation of secondary phases from solution. Secondary phases were more abundant in samples reacted in deionized water than for those reacted in a silicate solution. Samples with saw-cut surfaces showed a large reduction in surface roughness after 7 days of reaction in either solution. Reaction in silicate solution for up to 91 days produced no further change in surface morphology, while reaction in DIW produced a spongy surface that formed the substrate for further surface layer development. The differences in the surface morphology of the samples may create microclimates that control the details of development of alteration layers on the glass; however, the concentrations of elements in leaching solutions show differences of 50% or less between samples prepared with different surface conditions for tests of a few months duration.

Some considerations pertaining to the use of the Doppler-broadening positron annihilation technique for in-field non-destructive evaluation testing

Abstract Positron annihilation techniques have been used extensively in laboratory studies of defects in metals. Because of its non-destructive nature, it is natural to consider the application of positron annihilation to in-field testing. Concerns which are raised by the consideration of in-field testing include the effect of the source-sample-detector configuration and the effect of surface preparation on the sensitivity of the technique. The present study found these two variables to have very little influence on Doppler-broadening positron annihilation measurements.

Measurement of the low temperature diffusivity and solubility of tritium in an iron-base superalloy

Tritium diffusivity and solubility measurements were made in an iron-base superalloy at 273 K by analyzing the depth distribution of 3He which is the immobile product of the radioactive decay of tritium. The measurements were made by nuclear reaction analysis using the reaction 3He(d,p) 4He. The diffusivity and solubility agreed, within the precision of the measurement technique, with predicted values from higher temperature studies. Surface preparation effects were characterized by comparing subsurface 3He concentrations, allowing relative tritium concentrations to be compared.

The effect of surface preparation on the performance of acrylic adhesive joints

The effects of four surface treatments on the bonding performance of five second generation acrylic adhesives were studied. Adhesive performance was characterized using lap shear and wedge specimens exposed to elevated temperature and humidity. For all adhesives studied, results indicated that chromic acid anodized aluminium gave superior mechanical properties as well as durability. Steel bonded adherends exhibited the best properties when grit blasting was used, while fibre glass substrates showed enhanced performance using solvent wipe. Inconclusive results were obtained with poly (methyl meta acrylate) due to its low strength compared to acrylic adhesives. Detailed analysis of the fracture surface revealed the morphology of the tougher second generation acrylics to comprise 10 μm nitrile rubber spheres dispersed in the acrylic matrix.

Modulation spectroscopy as a tool for electronic material characterization

Modulation spectroscopy is an optical characterization tool that can be of great utility to the materials scientist. We present here numerous examples where a simple photo-reflectance and electroreflectance setup is used in our laboratory to determine such important material parameters as alloy composition and carrier concentration in a very short time. For determining alloy composition in semiconductors, contactless room temperature photoreflectance is nearly as sensitive as low temperature photoluminescence. Examples will be given on how to determine: the effects of surface preparation and implant damage; alloy composition and carrier homogeneity for large area wafers to better than 1%; the segregation coefficient of isoelectronic impurities in bulk semiconductors; the sub-band energies in quantum well structures; and the presence and homogeneity of built-in electric fields in MODFET structures. Particular emphasis will be placed on band edge and exciton effects on the photoreflectance and on the criteria used to distinguish between them. Materials studied included Si doped GaAs, AlxGa1-xAs for variousx grown by OMVPE and MBE, bulk InP doped with iso-electronic As and Sb, and MODFET structures.

The effect of surface preparation on metal/bone cement interfacial strength.

This study is concerned with finding practical ways for strengthening metal/bone cement (M/BC) interfaces via surface alterations and identifying fundamental mechanisms underlying M/BC adherence. Shear strengths have been inferred from torsion tests using shear-lag analysis. The variables examined with regard to their effects on interfacial strength are substrate material, surface roughness, interface porosity, passivation and sterilization, surface cleaning procedures, and use of bone cement precoated metals. M/BC interfaces can be substantially strengthened by applying the bone cement to the metal with high pressure. This would be a practical way to strengthen interfaces for precoated implants. The acrylic polymerized in vivo would employ the usual low pressure method. Otherwise, the main method for improving M/BC interfaces is through changing surface topography. Cleaning or chemical treatments have relatively minor effects. Roughened surfaces, as expected, produce stronger interfaces. Dramatic strength improvements occurred with a porous arc plasma sprayed layer on the substrate. Surprisingly, highly polished surfaces also improve interface strength (compared to less polished surfaces). The hypothesis is advanced that M/BC adherence depends upon superposition of mechanical interlocking and atomic interaction effects, with the latter predominating for finer finishes and vice versa. Differences exist between materials which are independent of roughness.

Hydrogen and deuterium profiling at the surface of zirconium alloys: I. The effects of surface preparation

The H( 15N, αγ) 12 C and D( 3He, p)α reactions have been used to measure hydrogen and deuterium profiles in Zr-2.5 wt% Nb alloys loaded to contain 40–150 ppm by weight H or 56–108 ppm D. Excellent agreement is found between the results obtained by these two different techniques. Large surface H(D) peaks are found after fine metallographic sample preparation techniques. The peaks may be substantially reduced by using a fine machining operation (as the last step in surface preparation) or may be totally removed by vacuum annealing. The surface peaks appear to be associated with hydride/deuteride particles embedded in the surface layers during metallographic polishing.

Effect of surface preparation on Ge overlayer growth on (HgCd)Te

The interactions between thin Ge overlayers and both cleaved and ion-sputtered Hg1−xCdxTe surfaces have been examined using synchrotron radiation. Ge forms an unreactive layer on cleaved substrates of x=0.21 and x=0.28 with only a small loss of Hg (∼20%) from the interface. In contrast, deposition of Ge onto sputtered substrates results in approximately two (x=0.21 material) or three (x=0.28 material) times the Hg loss relative to the clean surface. The difference in behavior of the sputtered and cleaved material is due to sputter-induced defects at the surface. The increased loss of Hg from the sputtered x=0.28 material is a result of a greater number of these defects caused by the weaker Hg–Te bonding and the corresponding increase in the preferential sputtering of Hg from the surface. No difference was observed between sputtered p-type and n-type material. These results are a consequence of GeTe and HgTe having very similar heats of formation; as such, deposition of Ge provides an indication of the reactivity of (HgCd)Te surfaces.

The effect of surface preparation on the production of low interfacial charge regrown interfaces

Many optical and digital device structures could be enhanced by the ability to grow highly perfect interfaces on surfaces which have been chemically processed. Growth surfaces prepared through wet chemical processing typically exhibit a large density of carrier traps at a subsequently grown buried interface. The use of a Br based in-situ vapor etch prior to growth has been developed to substantially improve the electrical behavior of these interfaces. The removal of only ~ 0.02 μm of surface through the vapor etch at 800°C is sufficient to reduce the trap density. Such an in-situ vapor does not significantly reduce the concentration of chemical contaminates at the buried interface implying a change in the electrical behavior of impurities due to the vapor etch.

Effect of surface preparation on elastic precursor decay in shocked pure lithium fluoride

To understand the mechanisms for elastic precursor decay in pure 〈100〉 lithium fluoride (LiF) crystals under shock loading we have examined the role of large dislocation densities produced near the crystal surfaces by sample preparation. After unsuccessfully trying various methods to produce flat and undamaged samples, we chose to harden the surfaces by inward diffusion of magnesium fluoride (MgF2). A combination of heat treatments and other procedures was developed to ensure hardened or doped surfaces with a maximum depth of 600 μm and an undoped interior. Sample characterization was carried out using dislocation etch pit, hardness, and electron microprobe measurements. A 0.24-mm sample, with MgF2 completely diffused through, gave a 16.7-kbar precursor amplitude. A 2.93-mm sample with a front diffusion layer of 0.14–0.39 mm and a back diffusion layer of 0.00–0.32 mm and undoped interior gave a precursor amplitude of 2.1 kbar. These experiments indicate that the surface damage layer does not control precursor decay in pure LiF crystals.