Structural and chemical analysis of C : H,O /Si : H,O multilayers deposited by reactive RF sputtering

Hydro-oxygenated carbon (C : H,O) and silicon (Si : H,O) layers are deposited by RF sputtering of graphite and silicon targets in a mixture of argon, hydrogen and oxygen gases. C : H,O/Si : H,O/C : H,O/Si : H,O... multilayers are obtained by sequential deposition of C : H,O and Si : H,O layers. Infrared (IR) spectroscopy, Grazing Incidence X-ray Diffraction (GIXD) and X-ray Photoelectron Spectroscopy (XPS) techniques have been used to analyse the formed multilayers. The IR spectra made on as deposited structures show the presence of Si---C, Si---O, C---O, Si---H, C---H and C=C bonds. This result indicates an interfacial reactivity between Si : H,O and C : H,O layers. The latter result is confirmed by the XPS measurements. After an annealing at 850°c for two hours under argon atmosphere (10^-3 mbar), the concentration of the Si---C bonds is increased by a factor two while the Si---H and C---H bonds disappear complet The GIXD measurements show that the multilayers are amorphous when annealed below 750°C, and they are crystallized with the formation of the α-SiC phase if the heat treatment is made at 850°C. The mean size of the microcrystallites is 50 Å about.     

Antioxidant and α-glucosidase inhibitory activities of eight neglected fruit extracts and UHPLC-MS/MS profile of the active extracts

The 70% ethanolic extracts from eight neglected fruits; Muntingia calabura, Leucaena leucocephala, Spondias dulcis, Syzygium jambos, Mangifera caesia, Ardisia elliptica, Cynometra cauliflora and Ficus auriculata were evaluated for their 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, α-glucosidase inhibitory activities as well as total phenolic content. The results of this study revealed that M. caesia fruit extract demonstrated the most potent radical scavenging activity. Among the fruits examined for α-glucosidase inhibitory activity, M. calabura and F. auriculata exhibited strong activity with no significant difference. The Pearson correlation indicated that the activities of M. caesia and F. auriculata contributed by phenolic compounds. A total of 65 metabolites were tentatively identified by using ultra-high-performance liquid chromatography tandem mass spectrometry (UHLPC-MS/MS). These findings suggested that the possible application of M. caesia and F. auriculata as a functional food with antioxidant and α-glucosidase inhibitory properties.     

Surface functionalization of multi-walled carbon nanotubes via electron reduction of benzophenone by potassium metal

The covalent sidewall functionalization of multi-walled carbon nanotubes (MWCNTs) via the electron reduction of benzophenone by potassium metal is reported. Fourier transform infrared spectroscopy (FTIR) results show that diphenylcarbinol (DPC) groups were successfully grafted to the MWCNTs sidewalls after 10 days of reaction time. Raman and UV–vis spectroscopies reveal the presence of covalent sidewall functionalization. The percentage of residues for DPC-MWCNTs was found to be lower than that for pristine MWCNTs, which indicates the existence of functional groups on the sidewalls of DPC-MWCNTs. It is shown that the sidewall of the DPC-MWCNTs was covered by non-uniform layer of DPC, as observed by transmission electron microscopy (TEM). Results from Raman spectroscopy, FTIR, TGA, UV–vis spectroscopy and TEM confirm that the functionalization of the covalent sidewalls of MWCNTs was successfully performed by this method.     

Transparent,electrically conductive,and flexible films made from multiwalled carbon nanotube/epoxy composites

Optically transparent, conductive, and mechanically flexible epoxy thin films are produced in the present study. Two types of multiwalled carbon nanotubes (MWCNTs) with different aspect ratios are dispersed in epoxy resin through an ultrasonication process. The MWCNT content is varied during the preparation of the thin films. The light transmittance and electrical conductivity of the thin films are characterized. Results show that composites containing MWCNTs with a lower aspect ratio exhibit enhanced electrical conductivity compared to those with a higher aspect ratio. A sheet resistance as low as 100 Ω/sq with nearly 60% optical transparency in 550 nm is achieved with the addition of MWCNTs in epoxy. In summary, transparent, conductive, and flexible MWCNT/epoxy thin films are successfully produced, and the properties of such films are governed by the aspect ratio and content of MWCNTs.     

Stability of PVDF hollow fibre membranes in sodium hydroxide aqueous solution

The stability of PVDF hollow fibre membranes in sodium hydroxide (NaOH) aqueous solutions were investigated in this study. PVDF hollow fibre membranes were prepared from each of the three commercial raw PVDF materials (Kynar 761, Solef 1015 and Solef 6010) from two major suppliers (Atofina Chemicals Inc., USA and Solvay, Belgium) for comparison purposes. The effect of NaOH concentration, treatment time and temperature on mechanical properties, thermal properties and crystalline structure of the PVDF hollow fibre membranes were investigated through mechanical strength measurement, surface area analysis, XRD, FTIR and DSC analyses. The obtained results indicate that the reaction between PVDF and NaOH was initiated even at low concentrations of NaOH and was aggravated with the extended treatment time, resulting in the decrease in mechanical strength and crystallinity of PVDF hollow fibre membranes. The reaction was accelerated and intensified by increasing the concentration of NaOH and/or treatment temperature. At 70 °C, the mechanical integrity of the PVDF membranes was completely destroyed in 4 wt% NaOH solution within 24 h or in 10 wt% NaOH solution within 8 h. The deterioration of stability in NaOH solutions is considered universal for all PVDF employed in this study, irrespective of the raw materials or the corresponding hollow fibre membranes.     

Effects of surface-functionalized multi-walled carbon nanotubes on the properties of poly(dimethyl siloxane) nanocomposites

The effects of surface-functionalized multi-walled carbon nanotubes (MWNTs) on the properties of poly(dimethyl siloxane) (PDMS) nanocomposites are investigated in the present study. The surface functionalization of MWNTs is carried out by diphenyl-carbinol functionalization followed by reaction with multifunctional silane, 3-aminopropyltriethoxisilane. Fourier transform infrared spectroscopy (FT-IR) and energy dispersion spectroscopy (EDS) analysis are used to confirm the presence of diphenyl-carbinol and silane on the surface of the MWNTs. The effects of the MWNTs’ surface treatment on the thermal and electrical properties of poly(dimethyl siloxane)-based (PDMS) nanocomposites are also studied. The results show that the grafting of silane molecules onto diphenyl-carbinol-functionalized MWNTs (SD-MWNTs) improves the dispersion of MWNTs in PDMS; this subsequently enhances the thermal conductivity and dynamic mechanical properties as compared to those containing unmodified (U-MWNTs) and diphenyl-carbinol-functionalized MWNTs (D-MWNTs). The electrical conductivity of the nanocomposites is shown to decrease due to the wrapping of MWNTs with non-electrical-conducting organic materials.     

Integrated eco-design decision-making for sustainable product development

This paper presents an integrated eco-design decision-making (IEDM) methodology that is formed using three stages: life cycle assessment, an eco-design process (Eco-Process) model and an enhanced eco-design quality function deployment process. All product sustainability considerations are conducted within a special eco-design house of quality. This brings together the analysis of factors relating to manufacturing processes, product usage and end-of-life strategy. The concentration of environmental considerations in one place insures that product sustainability is central to any design development and that the implications of change are fully identified and justified. The IEDM methodology utilises of a set of Eco-Process parameters and their associated relationships to allow users with complementary knowledge to enter and access information in a timely and controlled manner. They are then able to contribute their expertise to support decisions with the aim of providing more sustainable products. An application of the approach is presented in the context of a case study considering the redesign of a single-use medical forceps. The materials and production methods used are investigated with a view to quantifying their environmental impact. The resulting IEDM methodology can be seen to be widely and easily applicable.     

XPS study of amorphous carbon nitride (a-C:N) thin films deposited by reactive RF sputtering

Amorphous carbon nitride (a-C:N) thin films were deposited by reactive radiofrequency (RF) sputtering. The a-C:N films were deposited, at room temperature, onto silicon substrates, from a graphite target of very high purity, in an atmosphere of pure nitrogen. The chemical properties of these films were studied by X-ray photoelectron spectroscopy (XPS). The XPS spectra of the a-C:N films reveal that nitrogen is well incorporated in the amorphous carbon network. The atomic percentage of nitrogen in the a-C:N films, calculated from the XPS spectrum, is about 32%. In addition to C–C and CC bonds, the analysis of the chemical shifts of C 1 s and N 1 s core level peaks show that nitrogen is bonded to carbon in CN double bonding and CN triple bonding configurations. The content of the CN triple bonds is found to be more important than the CN double bonds.     

A structural study of RF-sputtered …Cu/Te… multi-layers

Cu/Te multi-layers with a composition of 50 at% of Te were deposited onto glass substrates by radio frequency (RF) sputtering. Their structure was investigated by the grazing-incidence X-ray diffraction technique (GIXD). The spectra of the as-deposited sample show the formation of hexagonal Cu_2−xTe and the presence of free Te. The heat treatments at 450 K during 30 min, 1 h and 2 h show the progressive disappearance of the Cu_2−xTe phase and the appearance of a new compound—the orthorhombic rickardite Cu₇Te₅, suggesting that a Cu_2−xTe→Cu₇Te₅ transformation took place.The samples annealed for a period of 3 h at 450 K show that Cu₇Te₅ completely disappeared in favour of Cu_2−xTe and, more precisely, the Cu_0.647Te_0.353 phase dominates the spectra, suggesting that a Cu₇Te₅→Cu_2−xTe inverse phase transformation took place.The results are discussed in light of the strong inter-diffusion that occurred between the Cu and Te layers during the deposition at ambient temperature and to elemental diffusion during annealing. The phase transformations are attributed to a diffusion-induced homogenization of the sample and a loss of Te by sublimation during annealing for an extended time.