Structure,growth and morphology of polyphenylene sulphide

The crystallinity, particle size and morphology of polyphenylene sulphide synthesized from 1, 4-dibromobenzene and sodium sulphide have been investigated by X-ray diffraction and scanning electron microscopy. It was found that the crystallinity increased from 62 to 68% with an increase in reaction time. A reordering of crystalline structure with increase of reaction time was also noted. The particle size growth was slower as compared to the reaction rate and the distribution was very sharp. The results are compared with those for polyphenylene sulphide obtained from 1, 4-dichlorobenzene and sodium sulphide.NCL Communication No. 4504.     

Structure,nucleation, growth and morphology of secondary carbides in high chromium and Cr-Ni white cast irons

Heat-treated high chromium and Cr-Ni white cast irons are widely used by the mining and mineral industries for impact and abrasion resistance. With certain heat treatments, Fe-Cr carbides are precipitated within the chromium- and carbon-rich austenitic matrix, thereby destabilizing the austenite which transforms substantially to martensite on subsequent cooling. The crystal structures of these carbides were determined indirectly by referring electron microprobe analyses of the austenitic matrix to the appropriate isothermal solid-state sections of the Fe-Cr-C phase diagram and directly by microprobe analyses of exposed secondary carbides. The nucleation, growth and morphology of these carbides were studied by a combination of selective removal of the austenitic matrix and subsequent scanning electron microscopy of the exposed carbides.     

Cobalt sulphide thin films: Chemical bath deposition,growth and properties

In the present report synthesis of CoS thin films was carried out by a modified liquid phase chemical growth process. Dark green coloured CoS thin films with hexagonal wurtzite polycrystalline structure and average grain size of ≈ 15 nm were deposited. Surface morphology reveals a randomly oriented network of elongated thread like grains. The absorption coefficient of the CoS thin film is high (α ≈ 10⁴–10⁵ cm^? 1) and a direct band gap of 1.13 eV has been observed. n-type conduction is found in the deposited films which can be attributed to the lack of stoichiometry.     

An unusual morphology and crystallization behavior in in situ formed polyphenylene oxide/polyamide 6 blends

Novel polyphenylene oxide/polyamide 6 (PPO/PA6) blends were synthesized via in situ polymerization of ε-caprolactam with PPO dissolved in it. The introduction of 10 wt% PPO into PPO/PA6 led to phase inversion of the blends, which was nearly completed by incorporating 15 wt% PPO into the blends. A single crystallization temperature (T _c) of PA6 was detected for PPO/PA6 with 1–4 wt% PPO, while double T _c existed in the blends with 6–15 wt% PPO. After eliminating previous thermal history, PPO/PA6 containing no more than 6 wt% PPO gave a single melting point (T _m), but the blends with 10–15 wt% PPO exhibited double T _m. Increasing PPO content in PA6 resulted in the transformation of its crystal form from α-crystal to γ-crystal, which might be attributed to hindrance of crystallization of PA6 particles in PPO-rich phase.     

The effects of temperature and liquid crystalline polymer (LCP) on mechanical properties of a blend of polyphenylene sulphide and LCP

The mechanical properties of polyphenylene sulphide (PPS) and liquid crystalline polymer (LCP) blends were investigated over a range of temperatures. The effect of blend composition on the brittle-ductile transition temperature (B-D) was also studied by differential scanning calorimetry and scanning electron microscopy. Blends of various compositions (PPS/LCP; 90/10, 75/25, 50/50 and 25/75) were prepared and injection moulded. The bending test temperature was varied between –40 and 150 °C. The results showed a rapid load drop at the B-D transition region. The B-D transition temperature occurred in unannealed pure PPS, 90/10, 25/75 and 50/50 blends around 75 °C whilst in the annealed sample it was observed around 100 °C. In pure LCP and 25/75, no transition occurred. Partial miscibility of PPS and LCP was confirmed by SEM observations, bending modulus and thermal properties. The use of LCP, as a good reinforcing agent which can improve processability and modulus, is discussed.     

Humidity sensing performance of in-situ fabricated Cu/Cu2O/Cu2S-polymer nanocomposite via polyphenylene sulphide cyclisation route

We herein report the feasibility of novel polymer-inorganic solid state reaction route for simultaneous in situ generation of Cu2S and Cu nanostructures in polymer network. Polyphenylene Sulphide (PPS) which is engineering thermoplastic acts as chalcogen source as well as stabilizing matrix for the resultant nano products. Typical solid state reaction was accomplished by simply heating the physical admixtures of the two reactants i.e., copper acetate and PPS by varying molar ratios mainly 1:1, 1:5, 1:10, 1:15, 1:20 at the crystalline melting temperature (285 degrees C) of PPS. The synthesized products were characterized using various physicochemical characterization techniques like X-ray Diffractometry, Field emission Scanning Electron Microscopy, Transmission Electron Microscopy, UV-Visible spectroscopy and X-ray photoelectron spectroscopy. The prima facie observations suggest occurrence of nanocrystalline Cu2S in case of product obtained with equimolar ratio, whereas remaining samples show mixture of Cu and Cu2O. The TEM analysis reveals nanoscale polydispersity (5-60 nm) and prevalence of mainly spherical morphological features in all the cases with occasional indications of plate like and cubical morphological features depending upon the molar ratio of the reactants. The humidity sensing characterization of these nanocomposites was also performed. The resistivity response with the level of humidity (20 to 70% RH) was compared for these nanocomposites. The linear response is obtained for all the samples. The sensitivity of 1:1 molar ratio sample was found to be maximum among all the samples.     

The growth and properties of epitaxial layers of zinc sulphide on germanium

Vacuum deposition of epitaxial films of zinc sulphide onto (111) 0.1 cm p type germanium substrates is described. The films contain stacking faults similar to those observed in epitaxial thin films of other substances and possess similar electrical characteristics to bulk crystals. Activation studies show that a.c. electroluminescence may be obtained by an embedding process. The zinc sulphide/germanium heterojunctions fabricated by the methods described are not efficient radiation detectors.     

Structure and morphology of iron-modified titania powders

We have studied the phase transitions, particle size, and morphology of titania powders modified with Fe(III) in a wide composition range.     

Structure,mechanical properties and surface morphology of the snapping shrimp claw

The snapping shrimp preys by rapidly closing its snapping claw to generate a fast water jet, creating a shockwave that bombards the nearby prey and other shrimp. This behaviour has led to considerable interest and research. However, the structure, surface morphology and mechanical properties of the snapping claw are unreported. We used a combination of techniques including scanning electron microscopy and nanoindentation to characterise the claw. These measurements were coupled with computational fluid dynamics (CFD) to understand how the microstructure contributes to drag reduction. We found that cone-shaped micropapillae, rhombic dents and short straight stripes were hierarchically distributed on the surface of the claw. CFD simulation showed that the micropapillae units changed the interaction between the turbulent and the wall from sliding friction to rolling friction, resulting in tire-shaped vortices. This also reduced the turbulent kinetic energy in the near-wall region, thereby contributing to drag reduction. The cross section of the claw revealed four layers comprising an epicuticle, exocuticle, endocuticle and a membranous layer. The exocuticle is composed of chitin fibres arranged vertically in a lamellar fashion and the endocuticle has a Bouligand-type structure. This special structure provides the snapping shrimp with good mechanical resistance during rapid closure. Both modulus and hardness decreased from the outermost epicuticle to the innermost membranous layer. The gradient modulus and hardness may help to suppress microcracks at the interfaces between different layers. The findings improve our understanding of the unique mechanism of the snapping claw and may lead to the development of novel biomimetic materials with enhanced drag reduction, impact and crack resistance properties.     

Structure, morphology and fibroblasts adhesion of surface-porous titanium via anodic oxidation

Surface-porous titanium samples were prepared by anodic oxidation in H₂SO₄, H₃PO₄ and CH₃COOH electrolytes under various electrochemical conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were employed to characterize the structure, morphology and chemical composition of the surface layer, respectively. Closer analysis on the effect of the electrochemical conditions on pore configuration was involved. It can be indicated that porous titania was formed on the surface layer, and the pore configuration was influenced by electrolyte composition and crystal structure of the titania. The fibroblast cells experiment showed that anodic oxidation of titanium surface could promote fibroblast adhesion on Ti substrate. The results suggested that anodic oxidation of Ti in CH₃COOH was suitable to obtain surface-porous titanium oxides layers, which might be beneficial for better soft tissue ingrowths.     

Structure, surface morphology, composition and optical properties of dip coated CdS films

Cadmium sulphide is a promising semiconductor material. In the photovoltaic solar cells it can be used as a window material. In this paper the preparation of CdS film by chemical bath deposition and its solid state properties by taking XRD, SEM, XPS and optical properties has been reported. The XRD and SEM analyses of as deposited and annealed at 400°C clearly indicate the polycrystalline hexagonal phase of the film with (002) orientation. The surfaces are uniform. The XPS measurements indicate the ratio of Cd/S in both the films to be equal to 1·1 at the surface and bulk. It is observed that the thickness of the film depends upon the deposition duration and 5 min deposited films are good for device applications.     

Flexural fatigue of short glass fiber reinforced a blend of polyphenylene ether ketone and polyphenylene sulfide

Flexural fatigue tests were conducted on injection molded glass fiber reinforced a blend of polyphenylene ether ketone and polyphenylene sulfide composite using four-point bending with different stress ratios and different frequencies. The fatigue behavior of this material was described. The constructed S-N curves shift their trends obviously at the maximum cyclic stress being about 80% of the ultimate flexural strength. Examinations of failure surfaces for various loading conditions show that the fatigue failure mechanisms appear to be matrix yielding at high stresses and crack growth at low stresses. Analyses of the fatigue data at various stress ratios reveal that the data at low stress superimpose to form a single curve which is nearly linear when they are plotted as stress range versus number of cycles to failure in bilogarithmic axes, while the data at high stresses also converge to yield a single curve when they are plotted as (S _max S _range)^1/2 against specimen lifetimes (S _max is the maximum stress andS _range is the stress range). These results show that for the studied material the main factor influencing the lifetime is the stress range at low stresses and the parameter (S _max S _range)^1/2 at high stresses. Comparison of fatigue data in the frequency range of 0.89–7.0 Hz was made, no significant effect of frequency on the fatigue behavior is found.     

Nucleation,growth and morphology of poly(hydroxybutyrate) and its copolymers

Measurements of the melting temperatures, growth rates and nucleation rates of meltcrystallized polyhydroxybutyrate (PHB) and two poly(hydroxybutyrate-co-hydroxyvalerate) (PHB/HV) copolymers are reported for crystallization over a wide range of temperature. Examples are shown of the spherulitic morphologies obtained. From the variation in melting point with crystallization temperature values for the equilibrium melting points of PHB and PHB/HV are obtained. Growth and nucleation rate measurements are analysed using secondary nucleation theory to obtain approximations to surface energies within the crystals. PHB and PHB/7% HV are described well by secondary nucleation theory. PHB/23% HV exhibits more complex crystallization and melting behaviour, which suggests temperature-dependent exclusion of HV units from the crystals.