Corrosion of SiC fibres with HNO3

The corrosion of SiC fibres with HNO₃ has been studied. Characterization has been carried out by means of infrared spectroscopy, scanning electron microscopy and adsorption of nitrogen and benzene. Corrosion attack changes the specific surface area of the fibres and increases the surface roughness along the fibres. The microstructure of the fibres is not modified by the attack. The surface heterogeneity of the original fibres shows a different feature when the fibres have been corroded; the distribution of active sites on the surface of the fibres is changed by acid attack.     

Toughness of glass fibres reinforced glass-ionomer cements

Two fracture toughness parameters, the critical stress intensity factor, K _c and the work of fracture, W _f have been used to characterise the toughness of conventional and resin-modified glass-ionomer cements reinforced with glass fibres. The critical stress intensity factor was determined from the peak load, and the work of fracture was determined as the energy required to extend an introduced crack through the respective glass ionomers. For both materials, crack propagation became more stable as the weight fraction of glass fibres was increased. Additionally, when the weight percent of glass fibres was increased the work of fracture increased. Fibre bridging at the crack tip resulted in the increase in the work of fracture. As the percentage weight of fibres was increased, the critical stress intensity factor decreased proportionally to the increase in porosity.     

Properties of glass fibres in cement environment

Fibres produced from a soda-silica-zirconia glass were reacted with Portland cement extracts at 20 and 65° C for various lengths of time and their strength and stiffness determined. The results indicate that these glass fibres resist the attack of cement extracts reasonably well at ambient temperatures. Fibre strengths of the order of 1200 to 1300 N mm^–2 are obtainable after 2 years at 20° C, sufficient to reinforce cement, and there is no change in the Young's modulus of the fibre during this period. At higher temperatures both strength and stiffness are reduced but these temperatures are unlikely to be encountered in practice over extended periods of time. When fibres removed from cement composites containing commercially made alkali-resistant glass fibres are examined, it is found that fibre strengths depend very strongly on the environment in which the composites were kept. For air storage, fibre properties remain relatively unaffected but for composites kept under water continuously, an initial loss in fibre strength is observed. This difference in fibre strength is reflected in the relative strength of the cement composites.     

Crystallization behaviour of calcium aluminate glass fibres

Crystallization behaviour of as-spun and fully-nucleated calcium aluminate (CA) glass fibres produced via inviscid melt spinning (IMS), was studied. Differential thermal analysis (DTA) scans on the as-spun and fully-nucleated CA fibres were performed at different heating rates. By applying the Kissinger method to the DTA scan data the activation energy values for crystallization were determined to be 569 and 546 kJ mol–1, respectively for the as-spun and fully-nucleated CA fibres. The Ozawa analysis on the DTA scan data gave the Avrami parameters at 2.7 and 2.4, respectively, for the as-spun and fully-nucleated CA fibres, which indicates high tendency of bulk crystallization mode. The formation of equilibrium phases of Ca12Al14O33 and CaAl2O4 in the crystallized CA fibres was identified by using X-ray diffraction (XRD).     

Oxide impurity absorptions in Ge-Se-Te glass fibres

Oxide impurity absorptions in Ge-Se-Te glass fibres and the cause of the absorption loss around 943 cm^–1, the frequency of the CO² laser, have been investigated. The oxygen in the glass bounds preferentially to germanium and causes the absorptions due to Ge-O bond vibrations at 765 cm^–1 (band I) and 1230cm^–1 (band II). The excess absorptions due to these bands were determined as 0.228cm^–1/P.p.m. wt O₂ for band-I and 0.006cm^–1 /p.p.m. wt O₂ for band II. The loss of the fibre at 943cm^–1 increased with the oxygen content. It was, however, revealed from the deconvolution of the IR spectra into the independent absorption components that the absorption tails of band I and band II did not affect the loss at 943 cm^–1. The content of the impurities except oxygen analysed by a mass spectroscopy was too low to affect the loss at 943 cm^–1.     

Analysis of fatigue failure of optical glass fibres

Journal of Materials Science Letters -     

Denture base materials reinforced with glass fibres

Glass fibres for industrial use were laid on denture base materials such as self-curing and heat-curing resins to reinforce them. The use of heat-curing rather than self-curing resin as a base resin indicated a superior effect on bending properties.     

Nanoscale ductile grinding of glass by diamond fibres

Chemical vapour-deposited diamond fibres have been used to grind soda glass. The surface topography was studied using scanning electron microscopy and atomic force microscopy techniques. The diamond surface facets and edges led to grinding without surface cracking and to surface roughness, Ra, values in the range 3–50 nm. The grinding mechanism involved the formation by ductile flow of glass ribbons adjacent to the grinding grooves. This grinding mechanism was similar to that reported for single-point diamond machining. The potential for ductile grinding with diamond fibres is discussed.     

Surface thermodynamic analysis of cleaned silicoaluminate glass fibres

Inverse gas chromatography has been used to measure the surface adsorption of alkane probes on cleaned silicoaluminate glass fibres. The thermodynamic variables (enthalpy, H _A ; entropy, S _A ; free energy, G _A ) and the dispersive component of the surface free energy ( _S ^D ) have been evaluated by the measurement of specific retention volumes of the alkanes on the silicoaluminate glass fibres. The effectiveness of the acetone extraction procedure and the thermal treatment for the cleaning of the samples was also evaluated. The London (dispersive) component of the surface free energy has been used as a measurement of surface contamination by comparing the results for the washed samples and thermal treated samples.     

Mechanical properties of glass fibres containing aluminium dispersoids

Glass fibres containing metallic aluminium dispersoids up to 7.5 at% AI have been made using ceramic bushings. The metallic granules have diameters ranging from 5 to 40 nm. A new technique based on strength-strain regression analysis has been used to determine the Young's moduli of the glass fibres. The Weibull parameters have been evaluated by both the graphical regression (GRE) and maximum likelihood (MLE) techniques. Fracture studies have also been carried out. The presence of aluminium particles increases the Young's modulus of the fibres but reduces the strength. The latter arises due to the metallic particles acting as stress concentrators within the glass matrix.     

Liquid nitrogen strengths of coated optical glass fibres

The strengths of plastic-coated glass fibres have been measured at liquid nitrogen temperatures using a bending technique. The method yields data on the strengths of coated optical fibres in the absence of stress corrosion. Pristine strengths corresponding to a breaking strain of 21% have been measured for silica fibre and 12% for sodium borosilicate compound glass fibre, corrected to 50 cm gauge length. The low temperature strength was found to be directly related to the tensile strength measured at room temperature, and the relationship was valid for a variety of glass compositions with differing amounts of surface damage.     

Impact properties of polyurethane and glass fibres reinforced composites

Impact resistance of the polyurethane matrix and composites with glass fibres of various volume fractions was investigated. The theory of linear elastic fracture mechanics (LEFM) was successfully applied to obtain a quantitative assessment of a parameter of toughness, the critical strain energy release rate (G _c), which was determined from the energy (W ^*) required to fracture sharply-notched specimens by taking into account specimen dimensions and notch depth. It is found that the G ^* is not a linear function of reinforcement concentration. The impact resistance with low volume fraction _f=0.045 of glass fibres decreases as compared to that of the matrix. However, with further incorporation of glass fibres, the impact resistance gradually increases, reaching its maximum for the volume fraction _f=0.158. An explanation of this non-linear behaviour is provided in this paper.     

Soluble phosphate glass fibres for repair of bone-ligament interface

Phosphate-based fibres of the generic composition (CaO)0.46-(Na2O)n-(Fe2O3)y-(P2O5)0.50 have been evaluated, in vitro, as three dimensional scaffolds for tissue engineering of the hard-soft tissue interface by assessing the fibre solubility and growth and functional gene expression of human cells. Primary human osteoblasts and fibroblasts were seeded onto scaffolds and maintained in culture for up to 21 days. Fluorescent immunolabeling revealed the spread cell morphology and significant proliferation pattern on these fibres, particularly on the 3 mol% Fe2O3-containing formulation. Real-time quantitative Polymerase Chain Reaction (rtQ-PCR) analysis of gene expression using TaqMan Probes was preformed and it has been established that committed cell differentiation was maintained by both cell types, and was strongly related to the 3 mol% Fe2O3 glass composition. These novel, readily manufactured, soluble glass fibres offer a biocompatible and biochemically favourable alternative in the search for suitable degradable materials used in Tissue Engineering.