Nanoindentation and nanoscratch behaviour of reactive sputtered deposited W–S–C film

Transition metal dichalcogenides having layered structure are promising self lubricating film and can be considered as substitute for carbon based films in several varieties of environmental conditions. The macrotribological properties of these films are studied extensively and are fairly well understood. However, mechanical and tribological behaviour of these films in millinewton load range have hardly been reported. Study of mechanical and tribological properties at applied load in the millinewton range is useful for possible application related to microelectro mechanical systems or micromechanical assemblies. In view of the above, the present work is undertaken to understand the indentation behaviour and scratch behaviour under constant and low applied load of reactive sputtered deposited W–S–C thin films. Towards that purpose, W–S films containing various amount of C are deposited on 100Cr6 steel using a radio frequency magnetron sputtering unit. The load vs. displacement curves of all these films are generated for four different loads to assess the load effect, substrate effect and size effect on the hardness and the load displacement curves of these films. Curves showing the variation of load as a function of the square of displacement are also evaluated in order to understand deformation and fracture mechanisms of these films and the interface between various microstructures of these films. The scratch behaviour of these films under constant load is determined to examine the friction and wear performance. The results show that the film containing 54 at.% carbon has the maximum hardness and the minimum scratch depth. In contrast, the minimum friction coefficient is exhibited by the film containing the maximum carbon.     

Random coil configuration of the polyformals (CH2O (CH2)yO-): 4. Dipole moments of poly(1,3-dioxocane) (y =5) and poly(1,3-dioxonane) (y = 6)

Samples of poly(1,3-dioxocane) [CH₂O(CH₂)₅O-] and poly(1,3-dioxonane) [CH₂O(CH₂)₆O-] were prepared by reacting paraformaldehyde with 1,5-pentanediol and 1,6-hexanediol, respectively. Fractions of both polymers, obtained by liquid-liquid precipitation separations, were studied in benzene solutions by means of dielectric constant measurements from 20 to 60°C. Mean-square dipole moments 〈μ²〉₀ thus obtained were compared with theoretical results based on rotational isomeric state models of the two chains. Very good agreement is obtained for the magnitudes of the dipole moments, and for their dependence on chain length and temperature. Values of the dipole moment ratio $\text{〈μ}{}^2\text{〉}{}_0\text{nm}{}^2$, where n is the number of bond dipoles of moment m, are essentially the same for the polyformals corresponding to y = 2,4,5, and 6. This indicates that even the very short CH₂CH₂ non-polar sequences strongly suppress the correlations between the polar oxymethylene CH₂OCH₂OCH₂ sequences in this type of chain. The configurational analysis also identifies the lowest energy conformations of poly(1,3-dioxocane) and poly(1,3-dioxonane), and they are found to be the conformations adopted by the chains in crystalline state.     

Eco-innovation assessment of biodigesters technology: an application in cassava processing industries in the south of Brazil,Parana state

Clean Technologies and Environmental Policy - Eco-innovations are innovations capable of helping to reduce the environmental impacts of production processes. In this sense, the adoption of models...     

Potential use of poly(lactic acid) nanofibers mats as Nano-sachets in postharvest of climacteric fruits and vegetables

This study is reported as the first demonstration of the use of solution blow spun mats in a Nano-sachet system containing a humidity absorber hydrogel and a paraffin wax tablet impregnated with potassium permanganate (KMnO₄) for exogenous ethylene (ex-C₂H₄) oxidation, in order to delay fruit ripening. The tomatoes quality during storage time was characterized by gas chromatography (GC) (ethylene concentration and CO₂ emission analysis—respiration rate), and colorimetry (green/red color parameter). Ex-C₂H₄ production over storage time was reduced for the Nano-sachet system when compared to the control system. Color changes, from 72 to 120 h, displayed fruit still predominantly green in the Nano-Sachet system (a* from −9.1 to −6.9), color transition green-red in the TNT-sachet (−7.5 to −0.3) and increased red color fruit in the control system (−6.1 to 3.7). This work suggests that nanofibrous mats can be used as a packaging system with the ability to protect, potentialize ethylene oxidation and extend climacteric fruits and vegetables quality in shelf life.     

Carbon-based coatings doped by copper: Tribological and mechanical behavior in olive oil lubrication

We deposited C-based films doped with Cu and tested their sliding properties in olive oil as environment-friendly lubricant, which can be used in many mechanical systems, particularly in agriculture engineering. The coatings were deposited in a four unbalanced magnetron sputtering device combining C and C/Cu targets; argon (hydrogen-free films) and Ar/CH₄ (hydrogenated films) atmospheres were used. Cu content of the films was in the range 5–14 at.%. The hardness of the films was almost constant whatever the Cu content was. On the other hand, hydrogen-free coatings were much harder (about 15 GPa) than hydrogenated ones (about 4 GPa). The coatings were oleophilic and their sliding properties were evaluated using ball-on-plate tests with 200,000 cycles. The non-hydrogenated coating with 6 at.% of copper showed the best tribological performance with negligible wear for all olive oil testing temperatures (i.e. up to 120 °C).     

Optimization of batch solution polymerizations: Simulation studies using an inhibitor and a chain-transfer agent

Multiobjective constrained optimizations are carried out to compute optimal operation policies for batch solution polymerizations of styrene. It is shown by simulations how specified values for conversion, average molecular weight, and polydispersity may be achieved through the proper manipulation of the temperature profile and the initial amounts of the initiator, chain-transfer agent (modifier), and inhibitor. The optimizations show that the use of inhibitors and/or modifiers is seldomly required, unless the process economics is taken into consideration or the high-molecular weight chain fraction of the final polymer resin is to be minimized. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1137–1152, 1998     

Synthesis and ionic transport of sulfonated ring-opened polynorbornene based copolymers

The N-pentafluorophenyl-exo-endo-norbornene-5,6-dicarboximide (1a) and N-phenyl-exo-endo-norbornene-5,6-dicarboximide (1b) monomers were synthesized and copolymerized via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine)benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine[1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene]ruthenium dichloride (II). Experiments, at distinct monomer molar ratios, were carried out using catalyst I in order to determine the copolymerization reactivity constants by applying the Mayo-Lewis and Fineman-Ross methods. Moreover, both catalysts were used to produce random and block high molecular weight copolymers of 1a with 1b and 1a with norbornene (NB) which were further hydrogenated using a Wilkinson’s catalyst. Then, the saturated copolymers underwent a nucleophilic aromatic substitution by reacting with sodium 4-hydroxybenzenesulfonate dihydrate to generate new polynorbornene ionomers bearing fluorinated pendant benzenesulfonate groups. A thorough study on the electrochemical characteristics involving electromotive forces of concentration cells and proton conductivity of cation-exchange membranes based on a block copolymer of norbornene dicarboximides containing structural units with phenyl and fluorinated pendant benzenesulfonate moieties is reported. The study of electromotive forces (emf) of concentration cells with the sulfonated membrane of copolymer 8 separating electrolyte solutions of different concentration indicate that the membranes exhibit high permselectivity to protons and sodium ions at moderately low concentrations. In principle, these results suggest that the membranes can be considered candidates for ionic separation applications.     

Culture and consumer responses to web download time: a four-continent study of mono and polychronism

Most e-commerce sites would like to include as much relevant and sales-inducing content on their pages as possible. Unfortunately, resulting download delays may lead to consumer frustration and a negative attitude toward the product or service displayed. But is frustration with download delay a universal problem or is it culture-specific? How should firms view this problem? These are the primary research questions investigated in the current study. An experiment conducted on four continents was selected as an appropriate research method to answer those questions. Country sites were selected for differing cultural senses of time and how this might affect individual responses to download delay. Our sample included the US and Finnish cultures representing monochronic cultures and Egyptian and Peruvian cultures representing polychronic cultures. Consistent with the proposed hypotheses, subjects from polychronic cultures were significantly less concerned with download delays than subjects in monochronic cultures. Similarly, perceived wait times varied significantly between the mono- and polychronic groups. Practical insights derived from this study enable specific suggestions on customization of web page content richness as well as infrastructure requirements based on the cultural identity of the intended e-Consumer. Moreover, results suggest theoretical implications for future research.     

Effect of silica and rice husk ash fillers on the modulus of polysiloxane networks

The preparation of polymethylvinylsiloxane rubbers with silica (SC) and black rice husk ash (BRHA) as fillers is reported. We conducted stress–strain experiments on these vulcanized rubbers to study the reinforcement properties of the fillers. Curves showing the dependence of the stress on the reciprocal of the elongation ratio displayed, in most cases, a slow upturn starting at rather low values of the elongation ratio attributed to a rather wide distribution of chain lengths between crosslinking points. Physical crosslinks between the hydroxyl groups of SC fillers and the polymer matrix seemed to enhance the modulus. BRHA–polymer interactions were rather weak in comparison with those occurring between SC and the polymer, presumably as a consequence of the carbon coating of the surface of the former fillers. These interactions were even less important for calcined BRHA. The absence of voids in the polymer–filler interfaces was proven by the analysis of gas diffusion across the rubbers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 421–429, 2003     

Evaluation of ion exchange resins for recovery of metals from electroplating sludge

In the present study, the recovery of metal ions from industrial solid residues from a galvanoplasty industry (Rio de Janeiro, Brazil) was investigated by cationic and anionic ion exchange resins. The electroplating residues were composed of the metals Cu²⁺, Fe³⁺, Al³⁺, Ni²⁺, and Cr³⁺. The studies of sorption were conducted under batch and column conditions. Based on these studies, the sorption parameters and the breakthrough curves for both resins were determined. Studies of the sorption equilibrium and kinetics were also performed. The maximum sorption capacities q _e (mg g^?1) of the cationic resin were: Cu²⁺: 1.9, Fe³⁺: 0.6 and Al³⁺: 0.4. For the anionic resin, the maxim values of q _e were Cu²⁺: 0.4 and Fe³⁺: 0.1. The Freundlich model was more adequate to describe the ion exchange equilibrium and the sorption mechanism fit the pseudo second-order kinetic model for both resins. The breakpoint of Cu²⁺ (100 ppm) occurred after passing 1,860 and 2,220 cm³ of residue solution through 20.0 g of the resins (column with h:6.0 cm and d:4.3 cm, flow rate: 60 cm³ min^?1). The column regeneration was carried out for five sorption–desorption cycles using H₂SO₄ 2.4 mol L^?1 (cationic) and HCl 2.0 mol L^?1 (anionic).