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Thickness Loss (thickness + loss)
Selected AbstractsEffect of mating surface on the high temperature wear of 253 MA alloyMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2004M. Roy Abstract The wear behaviour of metallic material is influenced by the friction force, which in turn, is governed by the hardness and oxidation kinetics of the mating surface. In view of this, present investigation is undertaken to find the influence of mating surface on the high temperature wear of 253 MA alloy. This alloy is developed for high temperature application. In this work 253 MA alloy is made to slide against two different types of counter face material, namely 100Cr6 steel and PM 1000 alloy, at five different temperatures. 100Cr6 steel gets soften with increase of temperature whereas PM 1000 alloy retains its strength even at high temperature. The friction coefficient and the thickness loss of 253 MA alloy is measured and compared against both variety of mating surfaces as function of temperatures. The morphology of the worn surfaces and the transverse section of the worn surfaces are examined under scanning electron microscope (SEM) to identify the material removal mechanisms. The results showed that the friction coefficient of test material against PM 1000 alloy is around 40% higher than the friction coefficient against 100Cr6 steel. The transverse section of the worn surface showed presence of a transfer layer, mechanically mixed layer and composite layer, which govern the wear behaviour particularly at elevated temperature. The chemical characteristics of these layers are dependent on the test temperature and the counter face material. [source] Deposition and Characterization of Dielectric Thin Films from Allyltrimethylsilane Glow DischargesPLASMA PROCESSES AND POLYMERS, Issue 4 2007Antonella Milella Abstract Thin films with a dielectric constant in the range of 1.9,4.5 have been deposited under different experimental conditions from allyltrimethylsilane (ATMS) and oxygen fed glow discharges. The thermal stability of the coatings is evaluated from thickness loss during the annealing process at 400 and 450,°C. Extremely low values of dielectric constant can be obtained at low input power and oxygen flow rate. However, control over the annealing temperature must be gained in order to avoid excessive film matrix collapse with subsequent deterioration of dielectric properties. For the lowest dielectric constant of 1.9, thickness shrinkage of 11% has been detected. Deposition temperature is also found to strongly affect film dielectric constant and chemical composition while input power modulation does not improve the dielectric properties of the films. [source] Relationship of meniscal damage, meniscal extrusion, malalignment, and joint laxity to subsequent cartilage loss in osteoarthritic kneesARTHRITIS & RHEUMATISM, Issue 6 2008Leena Sharma Objective Progressive knee osteoarthritis (OA) is believed to result from local factors acting in a systemic environment. Previous studies have not examined these factors concomitantly or compared quantitative and qualitative cartilage loss outcomes. The aim of this study was to test whether meniscal damage, meniscal extrusion, malalignment, and laxity each predicted tibiofemoral cartilage loss after controlling for the other factors. Methods Laxity and alignment were measured at baseline in individuals with knee OA. Magnetic resonance imaging included spin-echo coronal and sagittal imaging for meniscal scoring and axial and coronal spoiled gradient echo sequences with water excitation for cartilage quantification. Tibial and weight-bearing femoral condylar subchondral bone area and cartilage surface were segmented. Cartilage volume, denuded bone area, and cartilage thickness were quantified in each plate, with progression defined as cartilage loss >2 times the coefficient of variation for each plate. Qualitative outcome was assessed as worsening of the cartilage score. Logistic regression analysis with generalized estimating equations yielded odds ratios for each factor, adjusting for age, sex, body mass index, and the other factors. Results We studied 251 knees in 153 persons. After full adjustment, medial meniscal damage predicted medial tibial cartilage volume loss and tibial and femoral denuded bone increase, while varus malalignment predicted medial tibial cartilage volume and thickness loss and tibial and femoral denuded bone increase. Lateral meniscal damage predicted every lateral outcome. Laxity and meniscal extrusion had inconsistent effects. After full adjustment, no factor except medial laxity predicted qualitative outcome. Conclusion Using quantitative cartilage loss assessment, local factors that independently predicted tibial and femoral loss included medial meniscal damage and varus malalignment (medially) and lateral meniscal damage (laterally). A measurement of quantitative outcome was more sensitive at revealing these relationships than a qualitative approach. [source] Grafting CVD of Poly(vinyl pyrrolidone) for Durable Scleral Lens Coatings,CHEMICAL VAPOR DEPOSITION, Issue 1-3 2010Kyra L. Sedransk Abstract Grafting (g)CVD from the monomer 1-vinyl-2-pyrrolidone (VP) and the Type II initiator benzophenone (BP) under 254,nm UV irradiation yields durable hydrophilic coatings on substrates of poly(methacrylic acid) (PMA) derivatives, desirable for scleral lens applications. The gCVD polymerization of the VP monomer is essentially complete, and little excess BP remains in the film. Process optimization, through single variable and two fractional factorial experiments, result in retention of >90% of the as-deposited film thickness after rinsing. Increasing the initiator dosing time beyond 10,min, or the UV exposure time beyond 5,min, has little effect on the as-deposited thickness, or percentage of film retained after rinsing. This suggests that UV irradiation rapidly transforms most of the BP absorbed on the surface to initiating radicals. Once sufficient initiator dosage and UV exposure have been achieved, the initial deposition thickness is controlled primarily by the total flux of monomer to the surface, which is consistent with previous studies. For all samples, thickness loss occurs primarily during the first 30 days of saline soak-testing with no statistically significant loss (p,>,0.25) during the next 90 days of soak testing. While the additional UV exposure time has a limited effect on initial film thickness, it does increase long term thickness retention, most likely by forming crosslinked and branched structures within the film. All samples tested retain sufficient gCVD coating thickness to impart improved hydrophilicity at the surface throughout the entire 120 day saline soak-testing period. The fractional factorial experiments correlate improved hydrophilicity with an interaction between initiator dosage time and UV exposure time. Indeed, decreasing these two process variables in tandem provides the greatest reduction in contact angle. While the uncoated PMA displayed 92.3°,±,2.1° advancing and 86.7°,±,3.0° receding contact angles with water, the most hydrophilic gCVD coating lowers the advancing and receding contact angles to 39.5°,±,2.6° and 36.2°,±,1.6°, respectively. [source] | ||||||||||