Linear and nonlinear optical properties of hollow core photonic crystal fiber

We review the optical guidance properties of hollow-core photonic crystal fibers. We follow a historical perspective to introduce the two major optical guidance mechanisms that were identified as operating in these fibers: photonic bandgap guidance and inhibited coupling guidance. We then review the modal properties of these fibers and assess the transmission loss mechanisms in photonic bandgap guiding hollow-core photonic crystal fiber. We dedicate a section to a review of the technical basics of hollow-core photonic crystal fiber fabrication and photonic microcell assembly. We review some of the early results on the use of hollow-core photonic crystal fiber for laser guiding micro-sized particles, as well as the generation of stimulated Raman scattering, electromagnetically induced transparency and laser frequency stabilization when the fiber core is filled with a gas-phase material. We conclude this review with a non-exhaustive list of prospects where hollow-core photonic crystal fiber could play a central role.     

Single crystalline oxide fibres for heat-resistant composites

A brief review of the methods of fabrication of single crystalline oxide fibres is presented. It is shown that the internal crystallisation method (ICM), that is crystallisation of the fibres in continuous channels in an auxiliary matrix (molybdenum carcass), yields high-productivity rate, which provides a base for the development of fabrication technology of oxide fibres as reinforcement for composites for high and very high use temperatures. The method has been used to produce a family of fibres including sapphire, aluminium–yttrium garnet, mullite as well as some oxide eutectics. Microstructure, strength and high-temperature creep of the fibres are discussed with the emphasis on creep properties. Results of creep tests of composites with matrices based on TiAl, nickel superalloys and oxides are also presented. It is shown that special microstructure of composites with brittle matrices, intermetallic and oxides, yields quasi-ductile behaviour of the composites.     

Crystallization of fibres inside a matrix: a new way of fabrication of composites

Fibrous composites are normally fabricated by inserting premade fibres into a matrix and trying to tailor mechanical or physical properties of the material by a proper choice of fibre arrangement, fibre volume fraction, structure and properties of interface, etc. As a rule, this method satisfies all the needs fairly well. But in many cases, particularly when heat-resistant composites are involved, it leads to complications which cause composite experts to refrain from being involved in technically very attractive projects. So the need for alternative methods of composite fabrication obviously exists. The process described here is an example of such an alternative. It is based on the fibres growing from the melt within the volume of the matrix. The matrix should have prefabricated continuous cylindrical channels to be filled with the melt of the fibre material. The process is described using as a model a composite with a molybdenum matrix and single crystalline sapphire fibres. It is shown that the productivity of oxide fibre fabrication based on the process described can be some orders of magnitude higher than that based on the well known Czochralsky's and Stepanov's methods. The strength of the single-crystalline sapphire fibres obtained has been studied, as well as the high-temperature creep strength of composites containing such fibres. Some of the results of these experiments are reported here.     

Effect of thermochemical treatments on the strength and microstructure of SiC fibres

The room-temperature strength of commercially available polymer-derived SiC fibres degrades during the typical high-temperature thermal cycle used in ceramic matrix composite fabrication. Substantial improvements in retained room-temperature strength for two different commercially available fibres were observed after annealing in carbon powder at temperatures up to 1600 °C. Further improvements in strength were observed for both fibres when heat treated in CO atmospheres. X-ray diffraction, TEM, SEM, auger electron spectroscopy, and optical microscopy were used to characterize the microstructure and chemistry of these heattreated fibres in order to understand better the degradation mechanisms of the fibres as well as their improved strength retention.     

The relevance of the surface structure and surface chemistry of carbon fibres in their adhesion to high temperature thermoplastics

This paper has three principle thrusts: (i) the fabrication of unidirectionally reinforced composites made from carbon fibres subjected to different surface treatments in combination with various (polycarbonate, polyethersulphone and epoxy) matrices, (ii) a study of some of the mechanical properties (that is, the interlaminar-shear strength (ILSS) and the failure behaviour) of these composites; and (iii) determination of the correlations between the adhesion of the matrix polymers as measured by the ILSS and the surface structure as well as the surface chemistry of the various fibres. It will be shown that the surface structure of the fibres has a minor effect, while the surface chemistry appears to have an extraordinarily great influence on the adhesion of the fibres to high-temperature thermoplastics. The data clearly show that, depending on the processing temperature during the fabrication of the composites, chemical bonds can be formed at the fibre-polymer interface. This bond formation is initiated by the decomposition of carboxylic groups and, as a consequence, dangling carbon atoms are free to react with the functional groups of the polymer.     

Interfacial Interaction in Coated Carbon Fibre Reinforced Aluminous Mg-based Composites

Four kinds of Mg alloys reinforced with carbon fibres were fabricated by a gas pressure infiltration technique. The fibres were pre-coated a SiO2 layer prior to fabrication. DifFerent microstructures and interactions in the fibre-matrix interface of these composites were observed by transmission electron microscopy （TEM）. The results showed that the interracial interaction strongly depended on the content of Al in the Mg-based matrices. The microstructure of the interface could then be controlled by adjusting the Al content of the Mgbased matrix. In addition, fibres extracted from different Mg-based matrix all had some degradation owing to the interracial reaction and the fibre-matrix interdiffusion.     

Light guidance in new chalcogenide holey fibres from GeGaSbS glass

Holey fibres have a broad range of optical properties thanks to their microstructuration and offer a wide range of applications. The combination of intrinsic properties of compound glass, such as chalcogenide glass, and a microstructured fibre geometry allows to consider exacerbated optical properties such as dispersion and nonlinearity for these fibres. In this study, high-index sulphide glass holey fibres (n = 2.251 at 1.55 μm) have been accomplished using the capillary-stacking technique. Sulphide glasses from the GeGaSbS system are used. The drawing step is crucial for microstructuration and for determination of optical properties. Sulphide holey fibres, which were optically characterised with near-field spectroscopy at 1.55 μm, show a single-mode guidance with an effective mode area of 108 μm².     

The relevance of the surface structure and surface chemistry of carbon fibres in their adhesion to high temperature thermoplastics

The paper is concerned with the surface chemistry of several different carbon fibres subjected to various surface treatments. The microstructure and nanostructures of these fibres were investigated in the Part I of this series of papers. For analysis of the surface chemistry of the fibres, X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) were employed; the first method was used for identification and semi-quantitative determination of functional surface groups, while the second method was used for a quantitative determination of these groups. The possible interactions of the various carbon-fibre surfaces due to different surface treatments (and therefore to different functional groups) were analysed by wetting studies using the Wilhelmy technique and aqueous solutions of different pH values as test liquids. By variation of the pH value of the test liquids, the distinct acid-base complexes that formed with the functional groups were identified. The same test liquids were used for characterization of the surface chemistry of the high-temperature thermoplastics (polycarbonate and polyethersulphone) used as matrix materials in the fabrication of the composites in this study. Acid-base interactions at the carbon-fibre surfaces are mainly determined by carboxylic groups of different acidity. The concentration of these groups as determined by desorption of carbon dioxide up to 500 °C is shown to be directly proportional to the measured work of adhesion of each group.     

The effect of polypropylene,polyvinyl-alcohol,carbon and glass fibres on geopolymers properties

Recently, the inclusion of different types of fibres into geopolymers, as reinforcement, has amplified due to the rapid increase in geopolymers developments. In spite of geopolymers have prospective properties such as low carbon footprint, low consumption of energy, good compressive strength, resistance to fire, resistance to flame, resistance to corrosion and good durability, they undergo from low tensile strength and flexural strength. To avoid these shortages, different types of fibres could be incorporated into geopolymers to enhance their toughness, tensile strength and ductility. The current survey aims to review the effect of different types of fibres named polypropylene (PP), polyvinyl alcohol (PVA), carbon and glass fibres on the fresh and hardened properties of geopolymers.     

Thermal expansion characteristics of cast Cu based metal matrix composites

Like any other metal/alloy, copper and its alloys also soften at elevated temperatures. Reinforcing with ceramic or carbon fibres is one of the suggested solutions to overcome this. Very limited literature is available on Cu based metal matrix composites (MMCs); none of these pertain to liquid phase fabrication. Hence, a systematic investigation was carried out on MMCs based on copper, with alumino-silicate fibres and carbon fibres as reinforcements. The MMCs thus produced exhibit a uniform distribution of reinforcement in the matrix. Coefficient of thermal expansion (CTE) values are lower than that of pure copper.     

Bibliography Resource structure properties of natural cellulosic fibres — an annotated bibliography

We present a review of the work on the structure and properties of some natural lignocellulosic fibres with a classified list of references on resource, structure, physico-mechanical properties and on the uses of these fibres. This list of references includes papers published in scientific journals and in the proceedings of conferences.     

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.     

Photoelastic study of the elastic stress distribution around discontinuous fibres

The mechanism by which load is transferred from a discontinuous fibre to surrounding unbroken fibres has been examined in some detail using two dimensional photoelastic models in which the applied load is aligned with the fibre axes. The gap in the broken fibre is assumed to have occurred during fabrication and is thus filled with the matrix material. Three different end gap configurations have been analysed and it is concluded that, for all practical purposes, the disturbance due to the broken fibre does not extend beyond the immediately adjacent fibres. Substantial shear stresses are developed in the matrix for some distance along the fibre from the discontinuity with a consequent early transfer of load. Paradoxically, this effect is not accompanied by the development of reduced maximum stresses at the broken fibre tip for any of the configurations included in these tests.     

Structure,thermal properties,dissolution behaviour and biomedical applications of phosphate glasses and fibres: a review

For the last few decades, there has been a growing interest in using glasses for biomedical applications. Bioactive glasses are a group of surface reactive glasses which can initiate a range of biological responses by releasing ions into the local environment. Silicate, borate and phosphate glasses are known to show good bioactive characteristics and could be potentially used as favourable templates for bone-tissue formation. Phosphate glasses are unique group of materials that offer great potential for hard and soft tissue engineering over other types of bioactive glasses due to their fully resorbable characteristics, with some formulations possessing chemical composition similar to the mineral phase of natural bone. Moreover, these phosphate glasses can be prepared as fibres which could be used for soft tissue engineering and as fibrous reinforcement for resorbable polymers such as poly-(lactic acid) for fracture fixation applications. This review details some of the properties of phosphate glasses, such as thermal, viscosity/temperature, dissolution and biocompatibility of and how different factors can effectively alter these properties. The effect of the addition of different modifier oxides on the structure in terms of chain length is included. This review also reports on the manufacturing process, mechanical properties and biomedical application of phosphate glass fibres. A brief comparison between three different types of bioactive glasses has also been presented in this review. The main aim of this review is to present the factors affecting the properties of phosphate glasses and glass fibres and how these may be exploited in the design of a biomaterial.     

Extraction and preparation of bamboo fibre-reinforced composites

Natural plant fibre composites have been developed for the production of a variety of industrial products, with benefits including biodegradability and environmental protection. Bamboo fibre materials have attracted broad attention as reinforcement polymer composites due to their environmental sustainability, mechanical properties, and recyclability, and they can be compared with glass fibres. This review classifies and describes the various procedures that have been developed to extract fibres from raw bamboo culm. There are three main types of procedures: mechanical, chemical and combined mechanical and chemical extraction. Composite preparation from extracted bamboo fibres and various thermal analysis methods are also classified and analysed. Many parameters affect the mechanical properties and composite characteristics of bamboo fibres and bamboo composites, including fibre extraction methods, fibre length, fibre size, resin application, temperature, moisture content and composite preparation techniques. Mechanical extraction methods are more eco-friendly than chemical methods, and steam explosion and chemical methods significantly affect the microstructure of bamboo fibres. The development of bamboo fibre-reinforced composites and interfacial adhesion fabrication techniques must consider the type of matrix, the microstructure of bamboo and fibre extraction methods.     

Silver coating on carbon and SiC fibres

Electroless silver coating on carbon fibres using silver nitrate solutions has been studied. It was observed that the rate of silver coating depends on the degree of graphitization of carbon fibres. Fibres with a higher degree of graphitization were coated faster than those with a lower degree of graphitization. A physical model considering the number of nucleation sites on the carbon fibre surface as a function of the degree of graphitization is proposed for the silver coating process. The strength and modulus of coated and uncoated fibres have been determined using a high-sensitivity load cell with an Instron tensile testing machine. It was observed that silver coating did not alter the strength or modulus of the fibre. Aluminium matrix composites have been successfully fabricated with these fibres. The same coating technique was also used to coat silicon carbide fibres. Improvement in the infiltration during composite fabrication was observed when the fibres were silver-coated.     

短纤维定向增强金属基复合材料的制备及性能研究

研究了短纤维定向增强金属基复合材料（ＳＦＭＭＣ） 的制备工艺，获得了硅酸铝短纤维定向增强的Ａｌ２Ｏ３ ＳｉＯ２（ｓｆ）／ＺＬ１０９ 复合材料。力学性能测试结果表明，短纤维在金属基体中呈平行状态分布，能够有效地发挥对基体的增强作用，从而使该类复合材料的力学性能得到显著提高。另外，利用ＳＥＭ 对Ａｌ２Ｏ３ ＳｉＯ２（ｓｆ）／ＺＬ１０９ 复合材料的拉伸断口以及纤维的损伤机理进行了分析。     

Processing and microstructure of non-oxide ceramic fibres

Research and development efforts on high-temperature, oxidation-resistant fibres have increased over the past decade due to the demand for light-weight, stiff and strong composite materials in aerospace applications. Varieties of ‘high-performance’, continuous, non-oxide fibres with low-density, high tensile strength and tensile modulus have been developed either from organic precursors or via chemical vapour deposition for fabrication of ceramic matrix composites. Fibres derived from polymer precursors (e.g. Nicalon, Tyranno, HPZ) are small in diameter (compared to CVD monofilaments) and are ideally suited for ceramic composites. Processing, microstructural stability and mechanical properties of these newly developed SiC and Si₃N₄ base fibres are briefly reviewed in this paper.     

Conventional and novel processing methods for cellular ceramics

Cellular ceramics are a class of highly porous materials that covers a wide range of structures, such as foams, honeycombs, interconnected rods, interconnected fibres, interconnected hollow spheres. Recently, there has been a surge of activity in this field, because these innovative materials have started to be used as components in special and advanced engineering applications. These include filtering liquids and particles in gas streams, porous burners, biomedical devices, lightweight load-bearing structures, etc. Improvements in conventional processing methods and the development of innovative fabrication approaches are required because of the increasing specific demands on properties and morphology (cell size, size distribution and interconnection) for these materials, which strictly depend on the application considered. This paper will cover the main fabrication methods for cellular ceramics, focusing primarily on foams, offering some insight into novel fabrication processes and recent developments.