Relations between cold drawing behaviour and optomechanical properties of vestan (polyester) fibres

A modified stress-strain device is used to investigate the dynamical behaviour of optomechanical properties. The optical properties and strain produced in vestan fibres by different stresses have been measured at room temperature interferometrically. It has been found that the relation between strain and birefringence is linear up to strain of 12%. For greater strain the rate of change of birefringence with strain is cut off due to breaking. An empirical formula is suggested to represent the variation of the cross-sectional area of vestan fibres with draw ratio and the constants of this formula are determined. An expression has also been suggested for the birefringence related to the strain. The strain optical coefficient is determined. Poisson's ratio, Young's modulus, elastic shear modulus and the compressibility are calculated over different strain values. Microinterferograms are given for illustration.     

Structural and optical properties of wurtzite InN grown on Si(111)

We report the structural and optical properties of InN films on Si(111) prepared by ion-beam-assisted filtered cathodic vacuum arc technique. X-ray diffraction and Raman spectroscopy measurements indicated that all the InN films were hexagonal crystalline InN. The InN films deposited at substrate temperature of 475 °C exhibited highly (0001) preferred orientation and texturing (cratered) surface morphology. The oxygen incorporated in the InN films was segregated in the form of amorphous indium oxide or oxynitride phases at the grain boundaries. Photoluminescence emission of ∼ 1.15 eV was observed at room temperature from the InN films.     

Structural integrity analysis of embedded optical fibres in composite structures

The virtues of having sensors in manufactured goods for increased functionality purposes have been well documented. Benefits include sophisticated structures requiring less maintenance and repair, increased safety and reliability, and avoidance of ‘over design’. Though many schemes of sensing are available, these so-called ‘smart’ products in the near future, will increasingly rely on the optical fibres (OF) principles because of numerous inherent advantages. Optical fibres are small, lightweight, possess geometrical flexibility, Electromagnetic interference (EMI) immunity, operate over a wide range of environmental conditions, and can be configured to respond to many physical parameters.

This paper will report on the suitability of embedding OF in commonly used carbon-fibre composites. These panels will be designed, manufactured and tested for the effects of typical fibre-optic geometrical and physical parameters such as types of fibre coating polymers, fibre diameter and fibre distribution. Corroboration of these test results with finite element (FE) results will be shown. Based on tensile and compression tests on OF-embedded composites, it is shown that significant deterioration on strength is observed beyond a certain OF density level. This paper will focus on the macroscopic effect of having optical fibres in composites from a structural integrity point of view. To this end, an exposition on the theoretical considerations using continuum mechanics and energy principles is provided.     

The fabrication and optical properties of Nd3+ in silica-based optical fibres

We discuss the fabrication and optical properties of Nd³⁺-doped silica-based optical fibres as a function of core glass composition. The absorption and fluorescence spectra are shown to be very dependent on P₂O₅ concentration. This has resulted in multi-component host glass type optical behaviour from silica-based fibres.     

Structural, electronic and optical properties of (Sc,Y)N solid solutions

The refractory nitrides ScN and YN are candidate semiconductors for optoelectronic and DMS applications. Studies have included alloying ScN with other III-V semiconductors such as GaN to engineer the electronic, optical and structural properties. We suggest that ScN-YN and higher order alloys will lead to further control of these properties. We demonstrate complete solid solubility in the ScN-YN system through analysis of sputter deposited composition-spread thin films. Characterization of electrical, optical and structural properties is presented as a function of composition, demonstrating excellent epitaxy, high mobility, high absorptivity and high energy optical gap across the entire composition range.     

Effects of structure on the tensile,creep and fatigue properties of polyester fibres

The behaviour of two types of polyester fibres have been compared and the differences observed explained in terms of the differences in molecular structure. One fibre which had a higher crystallinity than the other showed improved creep behaviour however shorter fatigue lifetime. Crack propagation during fatigue suggests a macrofibrillar structure superimposed on the microfibrillar molecular arrangement. Fatigue lifetime is suggested as being greatly influenced by the time necessary for crack initiation which involves modification of the molecular structure. The influence of the minimum cyclic load on fatigue lifetime has been studied for both fibres.     

Structural and optical properties of GaGeTe thin films

Smooth and pinhole-free thin films of Ga₅Ge₁₉Te₇₆ have been obtained by vacuum evaporation. The as-deposited films are amorphous. Thermal annealing at 222°C leads to an amorphous-to-crystalline transition. A maximum contrast of 30% in reflectivity (measured at 1 µm) has been obtained on phase transition from amorphous to crystalline state. The optical constants and the bandgap are reported.     

Structural and optical properties of chlorinated plasma polymers

Amorphous hydrogenated chlorinated carbon (a-C:H:Cl) films were produced by the plasma polymerization of chloroform–acetylene–argon mixtures in a radiofrequency plasma enhanced chemical vapor deposition system. The main parameter of interest was the proportion of chloroform in the feed, R_C, which was varied from 0 to 80%. Deposition rates of 80 nm min^? 1 were typical for the chlorinated films. Infrared reflection–absorption spectroscopy revealed the presence of C–Cl groups in all the films produced with chloroform in the feed. X-ray photoelectron spectroscopy confirmed this finding, and revealed a saturation of the chlorine content at ~ 47 at.% for R_C ≥ 40%. The refractive index and optical gap, E₀₄, of the films were roughly in the 1.6 to 1.7, and the 2.8 to 3.7 eV range. These values were calculated from transmission ultraviolet–visible-near infrared spectra. Chlorination leads to an increase in the water surface contact angle from ~ 40° to ~ 77°.     

The flex fatigue of polyamide and polyester fibres

Polyamide and polyester fibres have been subjected to flex fatigue by pulling to and fro over a pin, in order to investigate the alternative damage modes, namely cracks along kink-bands due to compression, and axial splitting due to shear stresses. Initial studies determined the conditions that were sufficiently severe to give a short enough test time but not so severe that abrasion on the pin was dominant. Fibres were then cycled for varying periods, the damage viewed in a scanning electron microscope, and the change in tensile properties, including residual strength, determined.     

The flex fatigue of polyamide and polyester fibres

The flex fatigue of nylon and polyester fibres is measured by pulling them backwards and forwards over a pin in an environmental chamber. The fatigue lives vary over a 20-fold range as temperature and humidity changes. For nylon 6, the plots show a consistent increase to a maximum value and then a decrease as the temperature is increased from 20–120 °C. The peak lifetimes occur at higher temperatures at lower humidities. The results for nylon 6.6 show peaks at intermediate humidities, but little change at low and high humidities. The peak life temperature increases as humidity decreases for nylon 6.6, but is unchanged for polyester. The nylon 6 results follow the same trend as the loss modulus in variation with temperature and humidity, with a high loss correlating with a long life. A possible reason for this and the influence of other complicating factors, are discussed.     

Structural characteristics and mechanical properties of Ti(Cr) films produced on Si substrate

A series of nanogranular Ti₉₀Cr₁₀ thin films have been fabricated by pulsed-laser deposition on Si substrates at different temperatures. The crystal structure and mechanical properties of these films were investigated. The X-ray diffraction and transmission electron microscope images with selected area diffraction showed that the structure of as-prepared films is dependent on film thickness and deposition temperature. It was found that the Ti₉₀Cr₁₀ films consisted of fine hexagonal close packed microstructure with columnar grains, while body close-packed cubic structure of Cr films are composed of irregular grains, meanwhile, a chromium disilicide (CrSi₂) layer formed in the interface between the substrate and Cr films which deposited at temperature of greater than 600 °C. The crystalline and columnar grains improved with an increase of the thickness of the films and an optimum microstructure is obtained under the present experimental condition of about 50 nm thickness and deposited temperature of 500 °C for Ti₉₀Cr₁₀ films. Deposited at 300 °C, the Ti₉₀Cr₁₀ films have hardness of 12.7 GPa and elastic modulus of 174.6 GPa. Improved to 600 °C the sample shows higher hardness of 13.1 GPa and higher elastic modulus of 183.2 GPa. Using Benjamin-Weaver model, adhesion shearing force can be calculated as 34.9 MPa for 300 °C Ti₉₀Cr₁₀ film while higher value of 44.4 MPa for higher temperature of 600 °C.     

Mechanical properties of poly(vinyl alcohol) fibres and composites

This paper describes the performance of poly(vinyl alcohol) (PVOH) fibres and their composites. PVOH fibres have been studied, with the emphasis on long-term properties. Results indicated that the long-term properties of PVOH fibres are superior to those of high-performance polyethylene (HP-PE) fibres. Mechanical tests on PVOH/epoxy composites showed that, in general, their structural performance is between those of plasma-treated HP-PE and aramid fibre-reinforced composites. Structural mechanical properties of PVOH composites are better than those of HP-PE based composites due to the combination of a strong interfacial bond strength and a less pronounced anisotropic fibre character. However, the strong bonding between PVOH and epoxy results in a rather brittle failure mode of the composite and consequently relatively poor impact properties.     

Structural and the optical characteristics of PbSx thin films

Journal of Materials Science: Materials in Electronics - PbSx thin films (x?=?1, 0.9, 0.8, 0.7, 0.6) were prepared onto glass substrates using spin coating method. The phases developed...     

Structural and optical properties of nitrogen doped ZnO films

Zinc oxide is getting an enormous attention due to its potential applications in a variety of fields such as optoelectronics, spintronics and sensors. The renewed interest in this wide band gap oxide semiconductor relies on its direct high energy gap (E_g ∼ 3.437 eV at low temperatures) and large exciton binding energy. However to reach the stage of device production the difficulty to produce in a reproducible way p-type doping must be overcome.In this study we discuss the structural and optical properties of ZnO films doped with nitrogen, a potential p-type dopant. The films were deposited by magnetron sputtering using different conditions and substrates. The composition and structural properties of the films were studied combining X-ray diffraction (XRD), Rutherford backscattering (RBS), and heavy ion elastic recoil detection analysis (HI-ERDA). The results show an improvement of the quality of the films deposited on sapphire with increasing radio-frequency (RF) power with a preferentially growth along the c-axis. The ERDA analysis reveals the presence of H in the films and a homogeneous composition over the entire thickness. The photoluminescence of annealed samples evidences an improvement on the optical quality as identified by the well structured near band edge recombination.     

Structural and optical properties of GaN-based nanocrystalline thin films

We study the effect of annealing on structure, morphology and optical properties of nanocrystalline films of GaN, GaN:O and GaN:Mn prepared by ion assisted deposition on silicon, quartz and glassy carbon substrates. Blisters and holes having diameters proportional with the thickness of the film were observed in GaN:O deposited on silicon and glassy carbon. The Mn excess in GaN:Mn turns through annealing into Mn_xN_y islands. The degree of short- and intermediate-range order in the films was investigated by micro-Raman spectroscopy, extending to about 3 nm for gallium oxynitride films annealed to 973 K and to more than 10 nm in GaN samples. A diminished oxygen content following the annealing procedures on GaN:O samples is noticed from the reduced intensity of the oxygen mode at 1000 cm^− 1 in the Raman spectra. This observation is supported with X-ray photoemission spectroscopy measurements. The presence of oxygen at concentrations above 15at.% in the films leads to an abrupt nanocrystalline-amorphous transition.     

Structural and optical properties of plasma-deposited boron nitride films

The plasma-enhanced chemical vapor deposition of boron nitride films in a low pressure, parallel plate reactor incorporating an electromagnet was investigated. Films were deposited from gas mixtures of diborane, hydrogen and ammonia. The ratio of boron to nitrogen was approximately 1.7 when an ammonia-to-diborane ratio of 4 was used. The films had the following optical properties: a band gap in the range 5.6–5.8 eV, an absorption coefficient (at 6.0 eV) of about 1×10⁵ cm⁻¹ and an index of refraction of 1.7. In general the optical properties were identical, with or without the application of a low intensity magnetic field.     

Structural and optical properties of tin oxide branched nanostructures

Branched nanostructures of tin oxide (SnO2) have been synthesized by Vapor-Liquid-Solid (VLS) mechanism using a gold catalyst in the temperature range of 800-850 degrees C under an ambient gas flow of 200 sccm. The microstructural and the optical properties of the as prepared products have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-Raman, and photoluminescence (PL) studies. SnO2 branches with a rutile phase are found to have a preferential orientation along (101). Typical lengths of these branches are found to be approximately 3-5 microm and diameters in the range of 50-100 nm. Selected area electron diffraction (SAED) pattern shows that the SnO2 branches have a tetragonal cross section with [101] crystal direction. A Raman line at 631 cm(-1) (Sn-O bond) is obtained in the micro Raman spectra. Low temperature PL spectrum shows a strong green emission band near 506 nm.