Borosilicate Fibers Research Articles

InP/ZnS Quantum Dots for High-Sensitivity Temperature Sensors.

In this work, we report the synthesis of high-quality, nontoxic InP/ZnS core-shell quantum dots (QDs). The temperature-dependent optical properties such as photoluminescence (PL), absorption, and PL decay with time have been investigated. Based on the temperature dependence of optical properties of QDs, three different configurations of temperature sensors using PMMA as the QD host material were fabricated. The temperature sensor configurations are planar thin-film (InP/ZnS QD)/PMMA deposited on a Si wafer (sensor 1), (InP/ZnS QD)/PMMA-filled borosilicate fibers (sensor 2), and InP/ZnS QD-doped electrospun PMMA nanofibers deposited on a Si wafer (sensor 3). After fabrication, the performance of the temperature sensors have been thoroughly investigated through photoluminescence reversibility tests in consecutive heating-cooling cycles, and the sensitivity of the sensors has been calculated. The three sensors have shown different critical reversible temperatures above which they go through irreversible structural damage and lose their reversibility. The highest critical reversible temperature of 95 °C and the highest sensitivity of 2.1% °C-1 have been achieved, which are comparable to Cd- and dye-based temperature sensors reported to date. The sensors were found to be highly stable, which demonstrated negligible degradation even after 30 days of exposure to ambient conditions. The InP/ZnS QD-based optical temperature sensors can be considered to be a potential replacement for toxic heavy-metal QD-based optical temperature sensors.

Characterization of biodegradable core–clad borosilicate glass fibers with round and rectangular cross‐section

AbstractHere, we report on core–clad bioactive borosilicate fibers, that we have prepared both with round and rectangular cross‐section profile. The exposed approach, which relies on the stacking and drawing of glass slabs, demonstrates our ability to develop bioactive‐based glass fibers with tailored cross‐section profiles. Tens‐of‐meters‐long fibers were successfully drawn, although suffering from elevated losses in the case of the rectangular ones. The response of the fibers in simulated body fluid was studied for both geometries. We found that a round cladding can act as protective layer, tempering effects of the corrosion. We also noticed that rectangular fibers are more prone to degradation, the enhanced corrosion beginning from their sharp corners as they accumulated residual tensile stress during drawing. To the best of our knowledge, this is the first report on the effect of residual tensile stresses from surface tension deformations applied to the corrosion of rectangular fibers. As geometry plays a critical role on the biodegradation behavior of the fiberglass, we believe the enclosed results could lead to the design of fiber devices with tailored cross‐section profile in order to tune their rate of degradation on solely based geometrical effects.

Influence of H3O+ on the structure formation of oligomers in aluminium sols prepared from basic aluminium acetate: Experiments and computations

In-depth insight into the structure of oligomers in sols plays an important role in determining the structure and properties of the final materials, such as aluminium borosilicate fibers, flakes, microspheres and composites. In this study, the influence of H3O+ on the structure formation of oligomers in sols prepared from basic aluminium acetate (BAA) was studied by Fourier-transform infrared spectroscopy (FT-IR), 27Al NMR spectroscopy and density functional theory (DFT) calculation. The results indicated that BAA consisting of tetrahedral Al species existed in dimeric form (BAA2-2). The polymerization of BAA2-2 was more thermodynamically favourable than its hydrolysis both in neutral and acidic solutions. The oligomers formed in neutral aqueous solution were beneficial to prepare different polymers with dendritic or three-dimensional structures. The oligomers formed in acidic solution (H+/BAA = 0.5) were mostly linear tetramers composed of three octahedral and one tetrahedral Al species, which were beneficial to the spinnability of sols during the preparation of ceramic fibers. The addition of H+ changed the electronic properties of Al(III) and significantly promoted the coordination ability of water and Al3+, leading to an increase in the octahedral Al species and a great change in the structure of the sol. The DFT results were consistent with the experimental results, which provided a necessary theoretical guidance to improve the properties of aluminium sols and meet the needs of the final materials.

Investigation on various types of silica fibre as thermoluminescent sensors for ultra-high dose radiation dosimetry

With high-dose applications lacking the benefit of an economic yet versatile dosimeter that provides for a wide dynamic dose range, ongoing research is seeking to introduce suitable thermoluminescent (TL) material for such needs. Acknowledging the high potential of silica fibres, as developed by members of this group over the past few years, in present work evaluation has been made of 13 types of fibre, differing in dopant, dopant concentration and diameter including P−, Al−, Er−, Ge− and Al-Tm-doped fibres, ultra-high numerical aperture and borosilicate fibre, and two non-doped fibres, quartz and suprasil F300. Evaluation is made in terms of TL response to photon and electron irradiations with the objective of determining a TL material that can offer sensitive yet extended dose capability, saturating only above the few tens of kGy range. The various silica fibres that have been investigated were found to show saturation levels from 5 kGy for Ge-doped fibre (4 mol %) to 80 kGy for 2 mol % Al−doped silica fibre. Borosilicate fibres demonstrated the greatest potential for high dose dosimetry, maintaining a highly-linear response, any tendency towards saturation only being indicated to beyond receipt of doses of 100 kGy. For this fibre type detailed TL characterizations were conducted, including glow curve analysis, reproducibility and fading tests. The results suggest borosilicate fibre to be suitable for high dose TL dosimetry, providing sufficient sensitivity and appropriate dosimetric characteristics.

Thermal and structural characterization of erbium-doped borosilicate fibers with low silica content containing various amounts of P2O5 and Al2O3

We report results on the processing and characterization of different glass preforms and single core fibers within the SiO2–Na2O–B2O3–Er2O3–P2O5–Al2O3 system. Micro-Raman spectroscopy was used to identify post-draw structural modification. The differences in the micro-Raman spectra recorded on the preform and on the fiber glass were attributed to a change in the structure induced by the drawing process. Changes in the silicate network organization and small scale molecular orientation within the glass matrix are suspected to occur during the fiber drawing process. We found that the extent in the changes between the preform and fiber properties depend on the glass composition. The glass network of the Al-containing fiber is expected to be less sensitive to the drawing process than that of the fiber matrix as the network of this Al-containing fiber is formed by a larger number of Si-BO units in the network and neutral three-coordinated boron compared to the network of the fiber matrix. From the micro-Raman spectra, formation of small crystals is suspected to occur in the P-containing glasses during the fiber drawing process. The resulting fibers were found to have propagation losses at 1330nm and Er3+ absorption between (7±1) and (25±1)dB/m and (36±1) and (47±1)dB/m, respectively, depending on the glass composition.

Polycyclic aromatic hydrocarbons (PAHs) in exhaust emissions from diesel engines powered by rapeseed oil methylester and heated non-esterified rapeseed oil

Polycyclic aromatic hydrocarbons (PAHs) of exhaust emissions were studied in four direct-injection turbocharged four-cylinder diesel engines, with power ratings of 90–136 kW. The engines were operated on biodiesel (B-100), a blend of 30% biodiesel in diesel fuel (B-30), and heated rapeseed oil (RO) in two independent laboratories. Diesel particle filters (DPF) and selective catalytic reduction (SCR) systems were used with B-30 and B-100. Concentrations of individual PAHs sampled in different substrates (quartz, borosilicate fiber and fluorocarbon membrane filters, polyurethane foam) were analyzed using different methods. Benzo[a]pyrene toxic equivalents (BaP TEQ) were calculated using different sets of toxic equivalency factors (TEF). Operation on B-100 without aftertreatment devices, compared to diesel fuel, yielded a mean reduction in PAHs of 73%, consistent across engines and among TEF used. A lower PAH reduction was obtained using B-30. The BaP TEQ reductions on DPF were 91–99% using B-100, for one non-catalyzed DPF, and over 99% in all other cases. The BaP TEQ for heated RO were higher than those for B-100 and one half lower to over twice as high as that of diesel fuel. B-100 and RO samples featured, compared to diesel fuel, a relatively high share of higher molecular weight PAH and a relatively low share of lighter PAHs. Using different sets of TEF or different detection methods did not consistently affect the observed effect of fuels on BaP TEQ. The compilation of multiple tests was helpful for discerning emerging patterns. The collection of milligrams of particulate matter per sample was generally needed for quantification of all individual PAHs.

Bragg gratings written in multimode borosilicate fibres using ultrafast infrared radiation and phase mask

Inscription of Bragg grating structures is reported for the first time in multimode borosilicate fibres using femtosecond pulse duration 800 nm infrared radiation and a phase mask. Thermal annealing of the gratings up to 700°C reveals a behaviour similar to type I-IR gratings made in silica fibre with ultrafast infrared radiation.

Influence of time and temperature of hydrothermal treatment on glass fibers surface

Leaching appears to be a suitable method of obtaining a high hydroxyl population at the surface of borosilicate fibers. Several procedures were investigated and the treated fibers have been characterized by Fourier transform infrared spectroscopy (silanol band), and elemental analysis (carbon content) after trimethylsilylation. The texture of leached fibers was examined by scanning electron microscopy and the result was compared to that of original fibers. The modified fibers which exhibited the highest hydroxyl population with minimum alteration of the texture, as could be seen by scanning electron microscopy, were characterized by using nitrogen, krypton and water adsorption techniques in order to get information on surface area and porosity. The procedure revealed textural modifications: the surface area was increased and a micropore volume was formed.

Neutron focusing lens using polycapillary fibers

Multiple mirror reflection at small grazing angles from the smooth surfaces of the narrow channels of polycapillary fibers can be used to transport, bend, and focus thermal neutron beams. We report the results of the focusing of a polychromatic cold neutron beam using a compact lens of borosilicate fibers and with a focal distance of 57 mm. The intensity profile of the beam at the focus is approximately conical in shape with a full width at half-maximum of 0.49 mm, and with an average gain in intensity of about 20. These experimental results agree well with those obtained by computer simulation.

Coalescing filters — reduced operating costs and greatly extended service life

Constructed from borosilicate fibres rather than HEPA paper, today's compressed air coalescing filters are robust, they minimise pressure drop and possess a greatly extended service life.

Preparation of Polyborosiloxane as a Precursor for Borosilicate Fibers

A precursor for borosilicate fibers was prepared by a new method via polyborosiloxane (PBS) prepared by condensation polymerization of silicon tetraacetate (STA) with boron trialkoxide (BTA). A spinnable polymer was obtained from PBS by partial alkoxylation, subsequent hydrolysis, and aging for various time periods.

Optical transmission loss of germanium borosilicate fibres as a function of drawing conditions

Previous work showed that the transmission loss of step-index phosphosilicate fibre is dependent upon the draw tension. Similar experiments with graded-index germanium-borosilicate fibres do not show the same dependence over a range of tension from 5 g to 100 g and a range of draw speeds from 0.25 m/s to 5 m/s.

Single polarization optical fibers: Exposed cladding technique

A simple method is described for fabricating fibers with large strain birefringence starting with standard MCVD preforms. The method is illustrated using borosilicate fibers. The birefringence and polarization properties are measured in a long fiber and the birefringence is also measured using a fiber slice and polarizing microscope.

Polarization characteristics of noncircular core single-mode fibers

It is well known that geometrical or dielectric imperfections in conventional graded-index single-mode fibers depolarize light after a few centimeters. A slight improvement in the polarization performance of these fibers is achieved by introducing noncircularity in the core shape. This is evident from the measurements on borosilicate fibers with dumbbell shaped cores. This result is correlated with Marcatili's analysis, which shows that changing the core geometry, from square to rectangular, does not appreciably alter the difference in the propagation constants of the two fundamental modes with orthogonal polarizations. Thus, the noncircular geometry and the associated increase in stress-induced birefringence introduced during the manufacturing process alone are not sufficient to improve the polarization performance, and the enhancement of the anisotropic birefringence is necessary to achieve single-polarization fibers.

Pulse Dispersion Properties of Fibers with Various Material Constituents

Intermodal dispersion properties are compared for high silica fibers with borosilicate (B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> -SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) and germania borosilicate (GeO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> -SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) graded-index profiles. Pulse transmission measurements were systematically correlated with profile shapes so that new fibers could be fabricated with closer-to-optimal profile gradients at a wavelength of 907.5 nanometers. Germania borosilicate fibers with power law profile exponents (α ≈ 2.03) lowered intermodal dispersion 50 times from the result expected for comparable step-index fibers with N.A. ≈ 0.19. By contrast, borosilicate fibers with α ≈ 1.78 caused a 100-fold pulse width reduction in fibers with N.A. ≈ 0.14, corresponding to a 2σ = 0.13 ns/km pulse-broadening rate.

Influence of noncircular core on the polarisation performance of single mode fibres

Measurements on borosilicate fibres with noncircular cores indicate that the noncircular geometry and the associated stress-induced birefringence alone are not sufficient to maintain polarisation in single-mode fibres. To achieve single polarisation fibres, it is necessary to deliberately enhance the anisotropic birefringence.

Profile dispersion effects on transmission bandwidths in graded index optical fibers

Transmission bandwidths of optical fibers would be maximized if their refractive index profiles were optimally graded. However, dispersive differences between fiber material constituents make the optimal power law profile exponent α depend on wavelength. This profile dispersion effect is significant for germanium borosilicate fibers and makes their observed transmission bandwidths change by more than 300 percent within a 650-1050 nm wavelength range. Measurements are made in spectrally filtered white light from a xenon arc lamp that is sinusoidally modulated by an electrooptic crystal. Reduction of sine wave envelope intensity due to transmission in a fiber gives its baseband frequency response. The functional dependence of bandwidth on wavelength is used to diagnose whether α is larger or smaller than the optimal value which minimizes intermodal dispersion at particular wavelengths.

A tunable 1.1-μm fiber Raman oscillator

A tunable 1.1-μm fiber Raman oscillator is reported. The oscillator is pumped by a cw mode-locked Nd : YAG laser at 1.064 μm. Wavelength tuning is obtained by using group velocity dispersion in a 600-m-long single-mode borosilicate fiber and subnanosecond pulses tunable from 1.101 to 1.125 μm are generated. The slope of the experimental tuning curve gives a group dispersion of 31 ps/nm km at 1.12 μm for the Raman fiber, in good agreement with the calculated value of combined material and waveguide dispersion.

Wavelength Dependence of Frequency-Response Measurements In Multimode Optical Fibers

A newly developed technique for directly measuring fiber dispersion in the frequency domain as a function of wavelength is described. Spectrally filtered white light from a xenon arc lamp is sinusoidally modulated in the range 0 to 1 GHz by an electrooptic modulator and injected into a fiber. The procedure is to vary the modulation frequency and measure the corresponding sideband output power with a photomultiplier and spectrum analyzer. Ratio measurements between the test fiber and a short reference fiber give the baseband frequency response. A number of germanium- and boron-doped fibers have been examined. The least dispersive borosilicate graded-index fiber has a 1 dB bandwidth of 1 GHz, after 1.07 km of propagation at λ = 908 nm. The width broadens gradually with increasing wavelengths up to λ = 1100 nm.

Surface effects and reflection refractometry of optical fibres

Refractive index profiles of several types of silica-based low-loss optical fibres have been measured by the surface reflection technique. When polished samples are used inaccurate data are obtained. For germanium- and phosphorus-doped samples good results are obtained using samples prepared by fracturing the end of the fibre. For borosilicate fibres rapid changes due to atmospheric exposure result in inaccurate data.