Mechanical and Tribological Properties of Thin Remote Microwave Plasma CVD a-Si:N:C Films from a Single-Source Precursor

Silicon carbonitride (a-Si:N:C) films produced by remote plasma chemical vapor deposition (RP-CVD) were investigated. Tetramethyldisilazane as a single-source precursor and (H₂+N₂) upstream gas mixture for plasma generation were used. The influence of the upstream gas composition on the structure, density, mechanical and tribological properties of the films deposited on p-type Si (001) wafers (both heated—T _s =300°C and unheated—T _s =30°C) are reported. The H₂ RP-CVD process was found to result in the formation of outstanding low friction (0.04) and high hardness (H=27-31 GPa) a-Si:N:C films exhibiting promisingly high H/E values.     

Influence of chemical modification on tribological properties of elastomers

Physical properties of surface modified synthetic elastomers were studied to understand the factors that reduce friction and provide advantages in practical use. Bromination, iodination, sulfonation, and chlorination were investigated. The coefficient of friction μ was measured using a modified version of the pin-on-disc apparatus. The surface energy, morphology, mechanical properties, and extent of chemical modification were also measured. An increased stiffness and microroughness were found to correlate with changes in the coefficient of friction. Sulfonation (100% H₂SO₄) was found to be the most effective and universally acceptable method of chemical treatment from a tribological point of view. © 1995 John Wiley & Sons, Inc.     

Properties of Composite Borided Layers on Steel Produced by Combined Surface Treatments

With the increasing progress in engineering a growing need has been felt for materials that show improved surface properties, such as an increased resistance to wear and corrosion. A new method combining the known techniques of chemical and electrochemical nickel plating and plasma bonding is discussed. The paper presents properties of such produced composite and multicomponent borided layers.     

Influence of iodination on tribological properties of acrylonitrile—butadiene rubber

Surface modification of acrylonitrile-butadiene copolymer (NBR) vulcanizates by treatment with an iodine solution results in a significant decrease in the coefficient of friction. The effect of modification is attributed to formation of a thin surface layer, incorporating iodine species, which has a higher modulus than the bulk material. The surface layer also has an increased roughness which, combined with the increased local stiffness, causes the reduction in friction. These factors overcome an observed increase in the surface energy after modification, which would act to increase the friction. NBR subjected to iodination kept its bulk elasticity, which plays an important part in the mechanism of deformation of the elastomer under conditions of friction, and ensures that the modified NBR retains its properties in engineering applications. The durability of the surface modification is attributed to interactions between iodine and nitrile groups from the acrylonitrile monomer units. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1927–1936, 1997     

Gymnastic world championship in Lausanne: medical staffing

A 64-year-old man who presented with sudden, unilateral loss of vision was found to have endophthalmitis associated with a pyogenic liver abscess. The patient was successfully managed with subtotal vitrectomy and percutaneous drainage of the liver abscess. Eikenella corrodens was cultured from the blood and the pus drained from the liver abscess. This is the first reported case of Eikenella corrodens liver abscess complicated by endophthalmitis.     

Surface migration of carboxylic acid in styrene–butadiene rubber and its tribological consequences

Surface migration of the carboxylic acids (C₁₀H₂₁COOH, C₁₁H₂₃COOH, C₁₂H₂₅COOH, C₁₅H₃₁COOH, C₁₆H₃₃COOH, and C₁₇H₃₅COOH) in styrene–butadiene rubber (SBR) matrix was investigated together with its influence on tribological properties of the vulcanisates. Macro‐ and microtribological properties were correlated with properties that come from carboxylic acid addition to the samples. A plastifying effect was characterized by a decrease of the rubber glass transition temperature measured by the DSC method. Thickness of an acid bloom was directly determined from an indentation experiment and estimated from the DSC curve as well as from FTIR reflection spectra. Morphology of the bloom was studied using an AFM technique to characterize topography as well as microroughness of the bloom surface. Macrofriction was studied using block‐on‐ring tribometer. Microfriction was examined with a Nano Test apparatus, applying ball‐on‐plate contact. Despite correlation found between plastification, morphology, and bloom thickness on the one hand, and tribologic properties of the rubber on the other hand, influence of the chain length of carboxylic acids on properties of the samples still needs further qualitative investigation. Tribological properties of SBR modified with carboxylic acids are the result of balance of two opposite effects: plastification of rubber—leading to an increase of friction and lubrication—which causes a decrease of friction of the rubber. Apart from plastifying and lubrication effects microroughness also plays an important role in friction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3368–3376, 2002     

The corrosion characteristics and solderability of immersion tin coatings on copper

Immersion tin is widely used as a lead free surface finish in the printed circuit board technology. Tin prevents the underlying copper from corrosion and preserves its solderability during a long storage and lead‐free assembly processes. Investigated immersion tin coatings were deposited on copper foil from thiourea‐type baths with hydrochloric acid addition (SnHCl coatings) or methanesulfonic acid addition (SnMSA coatings). Obtained coatings were investigated in the as deposited state and after aging (4 h at 155 °C, in air). The scanning electron microscopy studies revealed differences in structure of tin samples deposited from different baths. Results of polarization and impedance investigations indicated that as deposited SnHCl coatings had better corrosion resistance in 0.5 M NaCl solution than SnMSA coatings. The aging resulted in the improvement of the corrosion resistance of thinner coatings (0.2 and 0.5 µm thick SnHCl and 0.3 µm thick SnMSA), which were thoroughly converted into Sn–Cu intermetallic (IMC) phases. In contrary, thicker coatings exhibited some worsening of the corrosion resistance upon aging. The solderability of all as‐deposited tin coatings was acceptable, but decreased after aging, especially for thinner coatings, showing the through conversion into Sn–Cu IMC phases.     

Electrochemical and Spectrophotometric Control of Pd/Sn Catalyst for Electroless and Electrochemical Metallisation

The characterisation of the palladium-tin mixed catalyst on the different stages of preparation, ageing and practical use can be done successfully using cyclic voltammetry and UV-VIS spectroscopy. In this paper, particular examples of the catalyst characteristics with qualitative or quantitative treatment have been presented and explained in terms of the catalyst formation processes and catalyst properties. The presented procedures have been proved in practice in the printed circuit board industry.