Synthesis of molybdenum (IV) sulphide: Part II. Reaction of molybdenum (VI) oxide with (a) zinc sulphide and (b) cadmium sulphide in the presence of ammonium chloride

Reactions of molybdenum (VI) oxide with (a) zinc sulphide and (b) cadmium sulphide were studied in the temperature range 723–973 K. Small amounts of mixtures of molybdenum (IV) sulphide and molybdenum (IV) oxide, which are difficult to separate, were produced. When ammonium chloride was added to the reactants, 89.1% pure MoS₂ at 773 K and 96.17% pure MoS₂ at 798 K were produced in the case of zinc sulphide and cadmium sulphide respectively.     

Tensile modulus of carbon nanotube/polypropylene composites – A computational study based on experimental characterization

Micromechanical and computational models significantly over-predict the tensile modulus of composites, as they ignore many experimentally observed factors. Computational models that capture the effect of polymer-filler contact, the presence of carbon nanotube (CNT) agglomerates and the alignment of CNTs with respect to the applied load on the tensile modulus of CNT-reinforced polypropylene (PP) are proposed and discussed in detail in this study. The CNT/PP composites are made by melt mixing and injection molding. The CNT/PP contact area is characterized in terms of width and modulus using Atomic Force Microscope (AFM). The presence, including the size and distribution of CNT agglomerates, is characterized using Scanning Electron Microscope (SEM). The tensile modulus of CNT/PP composites, measured as a function of CNT content according to ASTM D638, is compared to predictions made using numerical methods based on Finite Element Analysis (FEA) within the composite’s elastic regime. The model over-predicts the modulus of the CNT/PP composites by 85% for 5 wt.% CNT/PP composites assuming perfect filler–polymer interfacial contact. When imperfect CNT/PP contact, CNT agglomerates and alignment are accounted for in the model the effective composite modulus predicted is in good agreement with the experimental data. The computational design tools proposed in this study by systematically incorporating experimentally observed characteristics, in combination with the manufacturing method used to make the CNT/PP composites, can lead to composites with engineered properties made by a scalable and cost effective method.     

Thickness dependence of ac electrical conductivity and dielectric behavior of plasma polymerized 1, 1, 3, 3–tetramethoxypropane thin films

AC electrical conductivity (σ_ac), dielectric constant (?′), and dielectric loss tangent (tan δ) of plasma polymerized 1, 1, 3, 3‐tetramethoxy‐propane (PPTMP) thin films of thicknesses 100, 150, and 200 nm prepared by plasma polymerization technique using a capacitively coupled glow discharge reactor have been investigated in the frequency range of 30–10⁶ Hz. It is observed that σ_ac increases as frequency increases with a higher slope in the medium frequency (<10⁵Hz) region in the PPTMP thin films of three thicknesses. These observations suggest that the conduction may be dominated by hopping of carriers between the localized states. The general trend of ?′ is to increase with increasing thickness, ?′ remains independent of frequency upto about 10⁴Hz and then falls rapidly. The dependence of tanδ with frequency for PPTMP thin films of different thicknesses showed small relaxation peak at the very low frequencies (<10²Hz) and then it decreases slightly with a broad minimum at 10³ Hz and again increases. Cole–Cole plot reveals that Debye type of mechanism is operative in the experimental frequency range. POLYM. ENG. SCI., 58:1342–1345, 2018. © 2017 Society of Plastics Engineers     

A transgressive brown rice mediates favourable glycaemic and insulin responses

BACKGROUND: We evaluated glycaemic response of a brown rice variant (BR) developed by cross‐breeding. Subjects (n = 9) consumed 50 g carbohydrate equivalents of BR, white rice (WR) and the polished brown rice (PR) in comparison to 50 g glucose reference (GLU) in a cross‐over design. Plasma glucose and insulin at 0, 15, 45, 60, 90, 120 and 180 min were measured and incremental area under the curve (IAUC) and indices for glucose (GI) and insulin (II) calculated. RESULTS: BR compared to PR or WR produced the lowest postprandial glycaemia (GI: 51 vs 79 vs 86) and insulinaemia (II: 39 vs 63 vs 68) irrespective of amylose content (19 vs 23 vs 26.5%). Only BR was significantly different from GLU for both plasma glucose (P = 0.012) and insulin (P = 0.013) as well as IAUC_glu (P = 0.045) and IAUC_ins (P = 0.031). Glycaemic and insulinaemic responses correlated positively (r = 0.550, P < 0.001). Linear trends for IAUC_glu and IAUC_ins indicated a greater secretion of insulin tied in with a greater glycaemic response for WR (r² = 0.848), moderate for PR (r² = 0.302) and weakest for BR (r² = 0.122). CONCLUSION: The brown rice variant had the lowest GI and II values but these advantages were lost with polishing. Copyright © 2011 Society of Chemical Industry     

Epitaxial growth of Dy2O3 thin films on epitaxial Dy-germanide films on Ge(0 0 1) substrates

Ultra-thin films of Dy are grown on Ge(0 0 1) substrates by molecular beam deposition near room temperature and immediately annealed for solid phase epitaxy at higher temperatures, leading to the formation of DyGe_x films. Thin films of Dy₂O₃ are grown on the DyGe_x film on Ge(0 0 1) substrates by molecular beam epitaxy. Streaky reflection high energy electron diffraction (RHEED) patterns reveal that epitaxial DyGe_x films grow on Ge(0 0 1) substrates with flat surfaces. X-ray diffraction (XRD) spectrum suggests the growth of an orthorhombic phase of DyGe_x films with (0 0 1) orientations. After the growth of Dy₂O₃ films, there is a change in RHEED patterns to spotty features, revealing the growth of 3D crystalline islands. XRD spectrum shows the presence of a cubic phase with (1 0 0) and (1 1 1) orientations. Atomic force microscopy image shows that the surface morphology of Dy₂O₃ films is smooth with a root mean square roughness of 10 Å.     

Infrared and ultraviolet-visible spectroscopic studies of plasma polymerized 1, 1, 3, 3 - tetramethoxypropane thin films

Plasma polymerized 1, 1, 3, 3-tetramethoxy-propane (PPTMP) thin films of different thicknesses were prepared through glow discharge of 1, 1, 3, 3-tetramethoxypropane using a capacitively coupled reactor. The scanning electron micrographs show that as-deposited PPTMP thin films are smooth, uniform and pinhole free. Infrared spectroscopic investigation indicates the formation of conjugation along with C = O bonds in as deposited PPTMP thin films. Apart from aliphatic conjugation of C = C and C = O bonds there is formation of C-O-C bond owing to rearrangement of oxygen due to heat treatment of PPTMP thin films. A red shift in the maximum absorption wavelength of the ultra violet-visible spectra for all the PPTMP thin films is observed compared to the monomer maximum absorption wavelength. The absorption coefficient, allowed direct transition, E_qd, allowed indirect transition and E_qi, energy gaps were determined. The E_qd and E_qi are found to be about 2.92 to 3.16 eV and 0.80 to 1.53 eV respectively, for as deposited PPTMP samples of different thicknesses. The E_qi of two samples of different thicknesses heat treated at 673 K for 1 hour is 0.55 and 0.65 eV .     

Optical properties of polycrystalline AgxGa2−xSe2 (0.4x1.6) thin films

Polycrystalline thin films of Ag_xGa_2−xSe₂ (0.4x1.6) were prepared onto cleaned glass substrates by the stacked elemental layer (SEL) deposition technique. All the films were annealed in situ at 300 °C for 15 min. The compositions of the films were measured by energy-dispersive analysis of X-ray (EDAX) method. The structural and optical properties of the films were ascertained by X-ray diffraction (XRD) and UV–VIS–NIR spectrophotometry (photon wavelength ranging from 300 to 2500 nm), respectively. The influence of the composition on the optical properties of the material has been investigated. Microstructural perfection is quite evident from the abrupt descent around specific energy of photons in the transmittance spectra. Stoichiometric or slightly silver-deficient films show optimum electron transition energy and minimum sub-band gap absorption.     

Manufacturing and properties of ultra-low density fiberboards with an unsaturated polyester resin by a dry process

Although ultra-low density fiberboards (ULDFs) have good sound and thermal insulation performance, formaldehyde emission in the manufacturing process and in the subsequent use of the products limits their field of application. The objective of this study was to employ an unsaturated polyester resin (UPR) in the manufacturing of the boards as a substitute of formaldehyde-based adhesives in order to develop environment-friendly ULDFs. The effects of UPR dosage, fiber treatment agent, press time and fiber consumption on the properties of fiberboards were studied. Sound absorption and thermal conductivity were also measured to ensure sound and thermal insulation properties of the fiberboards. Board density, modulus of rupture and thickness swelling in 2 h were 320 kg/m³, 4.14 MPa and 3.75%, respectively, under optimal conditions such as 12% UPR dosage, 1% fiber treatment agent, 400 g fiber consumption and 210 s press time. Noise reduction coefficient and thermal conductivity of the boards were found within a range of 0.68–0.58 and 0.038–0.048 W/(m K), respectively, while the density of boards ranged from 150 to 400 kg/m³. Therefore, sound absorption property of the fiberboards developed in this study satisfies the requirement of high-efficiency sound absorption materials, which is close to the value (0.67) of ULDF having a density of 56.3 kg/m³ obtained by a wet process. Thermal insulation property of boards was close to that of commonly used insulation materials such as rock wool [0.036 W/(m K)] and glass fiber [0.045 W/(m K)]. In conclusion, fiberboards can be used for non-structural furniture materials, sound and thermal insulation materials in buildings because of their environmental friendliness, good mechanical properties, and excellent sound and thermal insulation properties.     

Quantitative image analysis of bubble cavities in iron ore green pellets

Scanning electron microscopy and image analysis was used for quantitative analysis of bubble cavities in iron ore green pellets. Two types of pellets prepared with and without addition of flotation reagent prior to balling were studied. The bubble cavity porosity amounted to 2.8% in the pellets prepared without addition of flotation reagent prior to balling. When flotation reagent was added prior to balling, the bubble cavity porosity increased by a factor of 2.4 and the median bubble diameter was decreased slightly. It was also shown that mercury intrusion porosimetry is not suitable for determination of the distribution of bubble cavities. Finally, our data suggested that the difference in total porosity determined by mercury intrusion porosimetry and pycnometry between the two types of pellets was due to the bubble cavities.     

Three-dimensional performance analysis of plain fin tube heat exchangers in transitional regime

Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a four-row plain fin-and-tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS CFX 12.0. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 400 to 2000. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-ω) with steady and incompressible fluid flow. Model validation is carried out by comparing the simulated case friction factor (f) and Colburn factor (j) with the experimental data of Wang et al. [1]. Reasonable agreement is found between the simulations and experimental data. In this study the effect of geometrical parameters such as fin pitch, longitudinal pitch and transverse pitch of tube spacing are studied. Results are presented in the form of friction factor (f) and Colburn factor (j). For both laminar and transitional flow conditions heat transfer and friction factor decrease with the increase of longitudinal and transverse pitches of tube spacing whereas they increase with fin pitches for both in-line and staggered configurations. Efficiency index increases with the increase of longitudinal and transverse pitches of tube spacing but decreases with increase of fin pitches. For a particular Reynolds number, the efficiency index is higher in in-line arrangement than the staggered case.