Micro-scale wear characteristics of electroless Ni-P/SiC composite coating under two different sliding conditions

The electroless nickel composite (ENC) with various silicon carbide contents was deposited onto aluminium alloy (LM24) substrate. The wear behaviour and the microhardness of the composite coating samples were investigated and compared with particles free and aluminium substrate samples using micro-scale abrasion tester and microhardness tester respectively. The wear scar marks and wear volume were analysed by optical microscope. The wear tracks were further studied using scanning electron microscopy (SEM). The embedded particles were found to get pressed into the matrix which helps resisting further wearing process for composite samples. However, random orientation of microcuts and microfallow were seen for ENC sample but more uniform wearing was observed for EN sample. The composite coating with low content of SiC was worn minimum. Early penetration into the substrate was seen for samples with higher SiC content. Microhardness was improved after heat treatment for all the samples containing various SiC content. Under dry sliding condition, inclusion of particles in the matrix did not improve the wearing resistance performance in as-deposited state. The wearing worsened as the content of the particles increased generally. However, on heat treatment, the composite coatings exhibited improved wear resistance and the best result was obtained from the one with low particle contents.

Elaboration and optimization of (Y,Er)Al(3)(BO(3))(4) glassy planar waveguides through the sol-gel process

In this work, a sol-gel route was used to prepare Y(0.9)Er(0.1)Al(3)(BO(3))(4) glassy thin films by spin-coating technique looking for the preparation and optimization of planar waveguides for integrated optics. The films were deposited on silica and silicon substrates using stable sols synthesized by the sol-gel process. Deposits with thicknesses ranging between 520 and 720 nm were prepared by a multi-layer process involving heat treatments at different temperatures from glass transition to the film crystallization and using heating rates of 2 degrees C/min. The structural characterization of the layers was performed by using grazing incidence X-ray diffraction and Raman spectroscopy as a function of the heat treatment. Microstructural evolution in terms of annealing temperatures was followed by high resolution scanning electron microscopy and atomic force microscopy. Optical transmission spectra were used to determine the refractive index and the film thicknesses through the envelope method. The optical and guiding properties of the films were studied by m-line spectroscopy. The best films were monomode with 620 nm thickness and a refractive index around 1.664 at 980 nm wavelength. They showed good waveguiding properties with high light-coupling efficiency and low propagation loss at 632.8 and 1550 nm of about 0.88 dB/cm. (C) 2009 Elsevier B.V. All rights reserved.

Influence from the sulfonate group (RSO(3)(-)) on the conversion process and emission efficiency of poly(p-phenylene vinylene)

The discovery of an alternative route to convert poly(xylyliden tetrahydrothiophenium chloride) (PTHT) into poly(p-phenylene vinylene) (PPV) using dodecylbenzenesulfonate (DBS) has allowed the formation of ultrathin films with unprecedented control of architecture and emission properties. In this work, we show that this route may be performed with several sufonated compounds where RSO(3)(-) replaces the counter-ion (Cl(-)) of PTHT, some of which are even more efficient than DBS. Spin-coating films were produced from PTHT and azo-dye molecules, an azo-polymer and organic salts as counter-ions of PTHT. The effects of the thermal annealing step of PTHT/RSO(3)(-) films at 110 and 230 degrees C were monitored by measuring the absorption and emission spectra. The results indicate that the exchange of the counterion Cl(-) of PTHT by a linear long chain with RSO(3)(-) group is a general procedure to obtain PPV polymer at lower conversion temperature (ca. 110 degrees C) with significant increase in the emission efficiency, regardless of the chemical position and the number of sulfonate groups. With the enhanced emission caused by Congo Red and Tinopal as counter-ions, it is demonstrated that the new synthetic route is entirely generic, which may allow accurate control of conversion and emission properties. (C) 2010 Elsevier B.V. All rights reserved.

Coating of Cotton Yarn with Poly(vinyl alcohol) and Poly(N-vinyl-2-pyrrolidone) Crosslinked via Ultraviolet Radiation

The coating of cotton fiber is used in the textile industry to increase the mechanical resistance of the yarn and their resistance to vibration, friction, impact, and elongation, which are some of the forces to which the yarn is subjected during the weaving process. The main objective of this study was to investigate the use of synthetic hydrophilic polymers, poly(vinyl alcohol) (PVA), and poly(N-vinyl-2-pyrrolidone) (PVP) to coat 100% cotton textile fiber, with the aim of giving the fiber temporary mechanical resistance. For the fixation of the polymer on the fiber, UV-C radiation was used as the crosslinking process. The influence of the crosslinking process was determined through tensile testing of the coated fibers. The results indicated that UV-C radiation increased the mechanical resistance of the yarn coated with PVP by up to 44% and the yarn coated with PVA by up to 67% compared with the pure cotton yarn, that is, without polymeric coating and crosslinking. This study is of great relevance, and it is important to consider that UV-C radiation dispenses with the use of chemical substances and prevents the generation of toxic waste at the end of the process. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2560-2567, 2011

Crosslinking of Poly(N-vinyl-2-pyrrolidone) in the Coating of Cotton Yarn

Coating of cotton yarn is employed in the textile industry to increase the mechanical resistance of the yarns and resistance to vibration, friction, impact, and elongation, which are some of the forces to which the yarn is subjected during the weaving process. The main objective of this study is to investigate the usage of a synthetic hydrophilic polymer, poly(N-vinyl-2-pyrrolidone) (PVP), to coat 100% cotton textile yarn, aiming to give the yarn a temporary mechanical resistance. For the improvement of the mechanical resistance of the yarn, the following crosslinking processes of PVP were investigated: UV-C (ultraviolet) radiation, the Fenton and photo-Fenton reactions, and sensitized UV-C radiation. The influence of each crosslinking process was determined through tensile testing of the coated yarns. The results indicated that the best crosslinking process employed was UV-C radiation; increasing the mechanical resistance of the yarn up to 44% if compared with the pure cotton yarn, that is, without polymeric coating and crosslinking. POLYM. ENG. SCI., 51:445-453, 2011. (C) 2010 Society of Plastics Engineers

Photovoltaic Process Development and innovative Techniques

Photovoltaic processing is one of the processes that have significance in semiconductor process line. It is complicated due to the no. of elements involved that directly or indirectly affect the processing and final yield. So mathematically or empirically we can’t say assertively about the results specially related with diffusion, antireflective coating and impurity poisoning. Here I have experimented and collected data on the mono-crystal silicon wafers with varying properties and outputs. Then by using neural network with available experimental data output required can be estimated which is further tested by the test data for authenticity. One can say that it’s a kind of process simulation with varying input of raw wafers to get desired yield of photovoltaic mono-crystal cells.

Frictional behaviour and wear performance of a nitrocarburised coating sliding against AISI 1019 steel

This work employed a commercial nitrocaburising process to diffuse a coating onto M2 grade high speed tool steel. Properties of the nitrocaburised coating (CN) such as thickness, roughness and hardness were characterised using a variety of techniques including Glow-Discharge Optical Emission Spectrometry (GD-OES) and Scanning Electron Microscopy (SEM). A tribological test has been developed in which two nominally identical crossed cylinders slide over each other under selected test conditions. The test has been employed to investigate the wear performance of both CN coated and uncoated M2 specimens and frictional behaviour of the sliding interface between the tool and a AISI 1019 steel workpiece under unlubricated (dry) and lubricated conditions. Fourier Transform Infrared Spectroscopy (FTIR) was used to monitor the formation of chemical species from the oxidation of lubricant during tribological testing.

Fault detection in a cold forging process through feature extraction with a neural network

This paper investigates the application of neural networks to the recognition of lubrication defects typical to an industrial cold forging process employed by fastener manufacturers. The accurate recognition of lubrication errors, such as coating not being applied properly or damaged during material handling, is very important to the quality of the final product in fastener manufacture. Lubrication errors lead to increased forging loads and premature tool failure, as well as to increased defect sorting and the re-processing of the coated rod. The lubrication coating provides a barrier between the work material and the die during the drawing operation; moreover it needs be sufficiently robust to remain on the wire during the transfer to the cold forging operation. In the cold forging operation the wire undergoes multi-stage deformation without the application of any additional lubrication. Four types of lubrication errors, typical to production of fasteners, were introduced to a set of sample rods, which were subsequently drawn under laboratory conditions. The drawing force was measured, from which a limited set of features was extracted. The neural network based model learned from these features is able to recognize all types of lubrication errors to a high accuracy. The overall accuracy of the neural network model is around 98% with almost uniform distribution of errors between all four errors and the normal condition.

Biomimetic processing of nanocrystallite bioactive apatite coating on titanium-zirconium alloy

In this paper nanocrystallite apatite coating on TiZr substrate was prepared by a biomimetic process. Surface morphology, thickness, crystalline phases a~nd bond strength of the coating were investigated by SEM, XRD and tensIle test, respectively. Results show that the apatite coating exhibIts a nanocrystalIite structure with similar stoichiometry to that of natural bone. The apatite layer becomes thicker with the increasing of the SBF immersion time and is firmly adhered to the substrate with the highest average bond strength of 15.5 MPa. This nanocrystallite apatite coating is expected to bond to surrounding bone tissue directly in vivo after implantation.

Fibre coating composition

An abrasion-resistant, electrically conductive material comprising a natural fibre-containing substrate and an electrically conductive conjugated polymer coating thereon is disclosed. A process for preparing an abrasion-resistant, electrically conductive material is also disclosed. The process comprises providing at least one monomer capable of forming an electrically conductive conjugated polymer, and a suitable substrate having a substrate surface, subjecting the substrate surface to a surface treatment step to improve abrasion resistance, and exposing the substrate surface to a vapour of the monomer to form an electrically conductive conjugated polymer coating thereon.

Bioactivating the surfaces of titanium by sol-gel process

In the present study, titanium (Ti) samples were surface-modified by titania (TiO₂), silica (SiO₂) and hydroxyapatite (HA) coatings using a sol-gel process. The bioactivity of the film-coated Ti samples was investigated by cell attachment and morphology study using human osteoblast-like SaOS-2 cells. Results of the cell attachment indicated that the densities of cell attachment on the surfaces of Ti samples were significantly increased by film coatings; the density of cell attachment on HA film-coated surface was higher than those on TiO₂ and SiO₂ film-coated surfaces. Cell morphology study showed that the cells attached, spread and grew well on the three kinds of film-coated surfaces. It can be concluded that the three kinds of film coatings can bioactivate the surfaces of Ti samples effectively. Overall, Ti sample with HA film-coated surface exhibited the best bioactivity.

Electrosprayed PLGA smart containers for active anti-corrosion coating on magnesium alloy Amlite

A novel self-healing system, consisting of poly(lactic-co-glycolic) acid (PLGA) porous particles loaded with a corrosion inhibitor, i.e. benzotriazole (BTA), has been successfully achieved via direct electro-spray deposition and subsequent epoxy spraying upon magnesium (Mg) alloy AMlite. The two-step process greatly simplified the multi-step fabrication of smart coatings reported previously. The PLGA particles demonstrate rapid response to both water and pH increase incurred by corrosion of Mg, ensuring instant and ongoing release of BTA to self-heal the protective functionality and retard further corrosion. Furthermore, nanopores in the PLGA–BTA microparticles, formed by the fast evaporation of dichloromethane during the electrospray process, also contribute to the fast release of BTA. Using Mg alloy AMlite as a model substrate which requires corrosion protection, potentiodynamic polarisation characterisation and scratch testing were adopted to reveal the anti-corrosion capability of the active coating.

Effect of different carbon-coating ways on the microstructure and electrochemical performance of LiFePO4/C cathodes

Through comparative studying on LiFePO4/C preparation process of adding carbon source in precursor and pre-sintered material, marked as LFP-1 (in-situ carbon coating) and LFP-2 respectively, by means of C-S test, XRD, SEM, BET, Raman, the effects of carbon content, morphology, particle size and surface carbon structure on the electrochemical performance of LiFePO4/C cathodes were investigated. SEM images showed that particle sizes of LFP-1 and LFP-2 are about 10μm and 100nm respectively. The EIS and galvnostatic charge-discharge tests indicated that LFP-1 has lower charge transfer resistance (Rct), better rate and cycle performance than that of LFP-2, which can be attributed to the different microstructure and the higher degree of graphitized carbon of LiFePO4/C. Raman spectroscopic analysis showed that the ratio of the ID/IG and Asp3/Asp2 of LFP-1 is lower that of LFP-2, which means the degree of graphitized carbon of LFP-1 is higher than that of LEP-2. These results have important significance for improving the overall performance of olivine cathode materials for lithium ion batteries.

Self-cleaning, superhydrophobic cotton fabrics with excellent washing durability, solvent resistance and chemical stability prepared from an SU-8 derived surface coating

Superhydrophobic cotton fabrics with a very low contact angle hysteresis were prepared using a single-pot coating solution comprising SU-8 (a negative photoresist), a fluorinated alkyl silane and silica nanoparticles. The fabric was treated using a dip-coating technique and subsequently cured under UV light. The coated fabric showed excellent superhydrophobicity with a water contact angle as high as 163° and a sliding angle as low as 2°. The coating was durable enough to withstand 100 laundry cycles. It also had excellent stability against long immersion times in organic solvents, and acid and base solutions.

Polyurethane coating with thin polymer films produced by plasma polymerization of diglyme

Aqueous-based polyurethane dispersions have been widely utilized as lubricants in textile, shoes, automotive, biomaterial and many other industries because they are less aggressive to surrounding environment. In this work thin films with different thickness were deposited on biocompatible polyurethane by plasma polymerization process using diethylene glycol dimethyl ether (Diglyme) as monomer. Molecular structure of the films was analyzed by Fourier Transform Infrared spectroscopy. The spectra exhibited absorption bands of O-H (3500-3200cm(-1)), C-H (3000-2900cm(-1)), C=O (1730-1650cm(-1)), C-O and C-O-C bonds at 1200-1600cm(-1). The samples wettability was evaluated by measurements of contact angle using different liquids such as water, glycerol, poly-ethane and CMC. The polyurethane surface showed hydrophilic behavior after diglyme plasma-deposition with contact angle dropping from 85(0) to 22(0). Scanning Electron Microscopy revealed that diglyme films covered uniformly the polyurethane surfaces ensuring to it a biocompatible characteristic.