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A new approach to improving the interfacial compatibility of SiCf/Ti-6Al-4V composites by using fiber coating coupled with subsequent heat treatment was presented. The SiCf/Ti-6Al-4V composites with C-coated and C/Mo-coated fibers were prepared using the foil-fiber-foil method and subsequently heat treated in vacuum at 750 °C to obtain several kinds of the SiCf/Ti-6Al-4V composites with different interfacial characteristics. Interfacial microstructures of these composites were systematically characterized by means of scanning electron microscopy and X-ray energy dispersive spectroscopy to investigate the interfacial microstructure evolution and reaction dynamics. The effects of interfacial microstructures on interfacial mechanical properties were also investigated using thin-slice fiber push-out tests. The results show that the brittle interfacial reaction layer of TiC in the C-coated SiCf/Ti-6Al-4V composites was obviously thickened and some microvoids even formed near the matrix with increasing heat treatment durations, whereas the matrix adjacent to Mo coating in the C/Mo-coated SiCf/Ti-6Al-4V composites gradually transformed into a ductile β-Ti layer. Interfacial shear strengths of the C/Mo-coated composites were slightly increased with increasing the heat treatment time, while those of the C-coated composites were remarkably improved. Critical issues on modifying interfacial compatibility of the SiCf/Ti composites for further improving the mechanical behavior of the composites were discussed.

Optical fiber measurement systems have recently gained popularity following a multitude of intensive investigations. A new technique has been developed for these measurement systems that uses Rayleigh backscatter to determine the distributed strain measurement over the total length of a fiber. These measurement systems have great potential in civil engineering and structural health monitoring. This paper addresses some preliminary comparisons between three different fiber coatings and six different adhesives on steel structures. The results are based on a bending test with specimens made of precision flat steel; optical fiber strain measurements were compared with photogrammetric strain measurements. Analysis of the test data showed a strong correlation between the optical measurement system’s results and the theoretical results up to the yielding point of the steel. Furthermore, the results indicate that fibers with the Ormocer® and polyimide coatings have almost no loss in the strain measurements. The main results of this investigation are a guideline describing how to attach optical fibers to steel surfaces for distributed fiber optical strain measurements and recommendations for coatings to obtain realistic strain values. Additionally, the advantages of distributed strain measurements were revealed, which illustrates the potential of Rayleigh backscattering applications.

Protective fiber coating decides the mechanical strength of an optical fiber as well as its resistance against the influence of environment, especially in some special areas like irradiation atmospheres. According to the experiment in this paper, it was found that the tensile force and peeling force of resistant radiation optical fiber was improved because of the special optical fiber coating.

The main limitation in the standard application of head space analysis employing solid phase microextraction (HS-SPME) for the evaluation of plants as sources of essential oils (EOs) are different quantitative relations of EO components from those obtained by direct analysis of EO which was got in the steam distillation (SD) process from the same plant (EO/SD). The results presented in the paper for thyme, mint, sage, basil, savory, and marjoram prove that the quantitative relations of EO components established by HS-SPME procedure and direct analysis of EO/SD are similar when the plant material in the HS-SPME process is replaced by its suspension in oil of the same physicochemical character as that of SPME fiber coating. The observed differences in the thyme EO composition estimated by both procedures are insignificant (F(exp)

In order to develop a practical process for the carbon coating on SiC fiber, high-speed and continuous pyrocarbon (PyC) coating process are under development by using a continuous CVD furnace with open-ends structure. The effects of process gas and winding speed have been investigated. It was revealed that the growth rate of PyC is in proportion to winding speed and the flow rate of process gas. PyC growth rate was reached up to 250 nm/min, which is several hundred higher than those of conventional CVI/CVD methods This results indicates that the mass production of PyC coated SiC fiber without unexpected residual deformation (torsion and curvature) is possible. And, the mass production and practical use of SiC/SiC using PyC coated SiC fiber will be largely promoted.

Integral analysis plays an important role in study and quality control of substances with complex matrices in our daily life. As the preliminary construction of integral analysis of substances with complex matrices, developing a relatively comprehensive and sensitive methodology might offer more informative and reliable characteristic components. Flavoring mixtures belonging to the representatives of substances with complex matrices have now been widely used in various fields. To better study and control the quality of flavoring mixtures as additives in food industry, an in-house fabricated solid-phase microextraction (SPME) fiber was prepared based on sol-gel technology in this work. The active organic component of the fiber coating was multi-walled carbon nanotubes (MWCNTs) functionalized with hydroxyl-terminated polydimethyldiphenylsiloxane, which integrate the non-polar and polar chains of both materials. In this way, more sensitive extraction capability for a wider range of compounds can be obtained in comparison with commercial SPME fibers. Preliminarily integral analysis of three similar types of samples were realized by the optimized SPME-GC-MS method. With the obtained GC-MS data, a valid and well-fit model was established by partial least square discriminant analysis (PLS-DA) for classification of these samples (R2X=0.661, R2Y=0.996, Q2=0.986). The validity of the model (R2=0.266, Q2=-0.465) has also approved the potential to predict the "belongingness" of new samples. With the PLS-DA and SPSS method, further screening out the markers among three similar batches of samples may be helpful for monitoring and controlling the quality of the flavoring mixtures as additives in food industry. Conversely, the reliability and effectiveness of the GC-MS data has verified the comprehensive and efficient extraction performance of the in-house fabricated fiber.

To measure the various diameters of laser fibers from various manufacturers and compare them with the advertised diameter.Fourteen different unused laser fibers from 6 leading manufacturers with advertised diameters of 200, 270, 272, 273, 365, and 400 μm were measured by light microscopy. The outer diameter (including the fiber coating, cladding, and core), cladding diameter (including the cladding and the fiber core), and core diameter were measured. Industry representatives of the manufacturers were interviewed about the diameter of their fibers.For all fibers, the outer and cladding diameters differed significantly from the advertised diameter (P.00001). The outer diameter, which is of most practical relevance for urologists, exhibited a median increase of 87.3% (range, 50.7%-116.7%). The outer, cladding, and core diameters of fibers with equivalent advertised diameters differed by up to 180, 100, and 78 μm, respectively. Some 200-μm fibers had larger outer diameters than the 270- to 273-μm fibers. All packaging material and all laser fibers lacked clear and precise fiber diameter information labels. Of 12 representatives interviewed, 8, 3, and 1 considered the advertised diameter to be the outer, the cladding, and the core diameter, respectively. Representatives within the same company frequently gave different answers.This study suggests that, at present, there is a lack of uniformity between laser fiber manufacturers, and most of the information conveyed to urologists regarding laser fiber diameter may be incorrect. Because fibers larger than the advertised laser fibers are known to influence key interventional parameters, this misinformation can have surgical repercussions.

Several approaches for fiber-optic evanescent-wave detection of small amounts of liquid hydrocarbons are investigated in the paper. These approaches use polydimethylsiloxane-coated silica (PCS) fibres and detect changes of the fiber attenuation induced by the penetration of hydrocarbons into the fiber coating. The detection ability of bent PCS fibres both in the spectral region from 400 to 600 nm and near-infrared region from 900 to 1700 nm is studied by using available commercial or laboratory spectroscopic techniques. Straight sensing fibres coated with a thin high-refractive index layer and selective excitation of the fibres at 670 nm are investigated as well. A novel approach employing straight fibres coated with a thin siloxane coating and an output mode filter is described as a promising technique for increasing the detection sensitivity of fiber-optic evanescent-wave sensors to petrol fuels.

The applicability of the retention index system to hcadspacc solid phase microextraxtion (HS–SPME) was investigated. In headspace SPME, the two equilibria gas phase/matrix and fiber coating/gas phase have to he considered. In this paper the equilibrium fiber coating/gas phase is discussed separately to characterize it more detailed and to investigate several methodical aspects. Therefore, the different distribution constants Kfiber/gas of n-alkanes, which were used for reference compounds, were related to their Kovats retention indices. The validity of the derived linear relationship log Kfiber/gas versus retention index I is demonstrated for various examples. This relation is helpful for the assessment of distribution constants of substances not available and for the choice of a suitable fiber coating. Furthermore, quantification of analytes in the gas phase can be done without authentic substances.

Measurement of the coating geometry of optical fibers is important in maintaining the optical and mechanical integrity of fibers and in the control of splice loss in multiple-fiber ribbons. A method of measuring coating geometry using a side-view system with a novel dark-field illumination technique is presented. A high contrast image is produced with this system from which the coating diameter noncircularity and concentricity error of a fiber can be determined. The measurement repeatabilities of coating diameter and concentricity error are typically 0.20 /spl mu/m and 0.25 /spl mu/m respectively. A means of calibrating the side-view system using a glass rod has been developed and comparison with an interferometric method has shown that a total uncertainty on outer coating diameter of 0.5 /spl mu/m has been achieved. >

Over the past decades, discrete or distributed Fiber Optic Sensing (FOS) applications have seen an increased acceptance in many areas. High level optical and mechanical reliability of optical fiber is necessary to guarantee reliable performance of FOS. In this paper, we review recent research and development activities on new specialty fibers. The main approaches to enhancing fiber attributes include new refractive index profile design and fiber coating modification.

International audience; Optical fibers are key components in telecommunication technologies. Apart from optical specifications, optical fibers are expected to keep most of their physical properties for 10-20 years in current operating conditions. The reliability and the expected lifetime of optical links are closely related to action of the chemical environment on the silica network. However, the coating also contributes largely to the mechanical properties of the fibers. The aim of this work was to study the strength and the mechanical behavior of the silica optical fibers in an acid environment and with a permanent deformation. A container with ammonium bifluoride acid salt was plunged into hot water at different temperatures (55 and 75 °C). This emitted acid vapors which attacked the optical fibers for a period of 1-18 days. An aging study was performed on silica optical fibers with standard polyacrylate coating and with hermetic carbon coating. A dynamic two-point bending bench at different faceplate velocities (100, 200, 400 and 800 μm/s) was used. For comparison, the same dynamic measurements were also carried out on non-aged fibers. After acid vapor condensation, salt crystal deposits on the fibers were displayed using an electron scanning microscope. These crystals became visible to the naked eye from the seventh day.

Oxide CMCs are attractive materials because they are inherently resistant to oxidation. Efforts to develop the oxide CMCs were intensified in the last decade, relying onto these and similar high temperature properties. Previous to oxide CMCs, the non-oxide CMCs were successfully developed, mainly bearing in mind the structural applications. Recently, demanding requirements for the conditions in air were set bringing the need for better materials withstanding even higher temperatures and longer exposure times (i.e. ≥ 1200°C and >10.000 hours) than those initially given. In general, space applications entail higher temperatures (i.e. 1500°C) than those anticipated for gas turbine engines, however, hereby much shorter exposure times are required (< 5 hours) making it bearable for non-oxide CMCs. Thus, the non-oxide CMCs having relatively high ultimate fracture strengths (e.g. 300–600 MPa) found an appropriate use in space applications.

This report gives progress made on the following milestones: demonstrate Ti and Nb monitoring at 3M site, demonstrate Al monitoring at LLNL, complete baseline melt and vapor plume model for the metal matrix process (3M fiber coating process), prototype a laser at LLNL to monitor Cu, ZrO{sub 2} monitoring demonstration at LLNL, Se monitoring demonstration, and process scale-up study for YBCO high-temperature superconductor.

A transducer continuum is integrated to the fiber coating by means of a sequence of on-line sputtering, electro-plating, photolithography and periodical etching processes. Applications to the distributed sensing of temperature, strain and pressure are reported.

Adhesiveless mechanical fiber optic splices may provide pullout resistance by gripping onto the bare fiber or by gripping onto the fiber coating. The possibility of creep and thermal expansion mismatch in the plastic coating makes gripping onto the stripped fiber attractive. We have determined that damage to the fiber by a gripping mechanism is measurable but not severe, particularly by comparison to mechanical stripping damage and handling damage. We have also observed fiber failures within such splices when using 900 micron diameter, tight buffered fiber. Torque, generated when the fiber is arranged into loops in an organizer tray, propagates into the bare fiber inside the splice. This torque can cause a fiber to break in torsion after a period of time.

Significant degradation of the fiber coatings occurred in an optical fiber cable that was aged for five days at 85°C. Incompatibility between the coating and the surrounding buffer tube gel was the suspected cause. To investigate this problem, fiber samples were aged in several gels, the compositions of which were determined using a variety of analytical techniques. Coating degradation occurred as cracking or discoloration in all but one of the gels. These degradations were found to have a strong temperature dependence and to be closely related to the molecular weight distributions of the gel components. Compatibility screening was identified as a necessary procedure to avoid future recurrences of this problem

This paper describes the temperature dependence of chromatic dispersion in single-mode fibers for a temperature range of -60°- 250°C. Highly accurate dispersion measurements demonstrated a linear relationship (0.025 nm/°C) between the zero dispersion wavelength and temperature for tests conducted below 150°C. Further tests in the high-temperature range showed an increase in this dependence. For both temperature ranges, the results were independent of fiber coating and structure.

The pressure sensitivity of the induced phase modulation in fiber optic acoustic sensors is studied both analytically and experimentally. The elastic parameters of commonly used coatings (thermoset plastics and acrylate based U. V. curable coatings), which govern the sensitivity, have been studied in bulk samples as a function of frequency (102–104 Hz) and temperature (0°–35 °C). The analysis, which takes into account the exact composition and geometry of multilayer fibers, is utilized to identify coatings which optimize the fiber acoustic sensitivity. The analytically predicted frequency dependence of the acoustic sensitivity is found to be in agreement with that obtained experimentally using fibers with various coatings.