Heat-treated Glass Research Articles

Enhanced Electrochemical Performance of the Cathode for a Lithium Ion Secondary Battery Using Lithium Ion Conductive Glass-Ceramics

Ceramics powder such as SiO2 and Al2O3 are incorporated in to the polymer electrolyte to form the composite film for the sake of improving ionic conductivity, mechanical and thermal properties. Though these filler enhanced ionic conductivity of gel electrolyte due to the disruption of polymer matrix and increasing micro pores, these are not ionic conductive material. We found that the gel electrolyte film (Pvdf based polymer) was enhanced ionic conductivity by adding LICGCTM. We have developed lithium ion conducting glass-ceramics LICGCTM with a NASICON type structure for solid lithium ion electrolyte.1- 3) The ionic conductivity of the glass ceramics with a Li1+x+yAlxTi2-yGeyPO4 composition shows over 1×10-4 Scm-1 at room temperature. Such ceramics have a very stable in ionic conduction. In addition, the ionic conductivity does not decrease, even if it was soaked in an aqueous of Li salt solution4-5), and does not lose the weight in boiling distilled-water for 1 h. The glass-ceramics with the crystalline form of Li1+x+yAlxTi2–xSiyP3–yO12 with a NASICON-type structure by heat-treated glass with a specific composition1-2). This glass-ceramics has a high lithium-ion conductivity that is equal to or more than 10–3 Scm–1at room temperature. Furthermore, because it is very stable in the atmosphere and even to exposure to moist air, it is possible to use this material to apply a solid-electrolyte for a lithium ion secondary battery using organic liquid electrolyte. In this work, the effect of LICGCTM as additive for a lithium ion secondary battery was investigated. We synthesized LiCoO2 cathode with 5wt.% LICGCTM filler and evaluated it the charge and discharge property using a half cell. We confirm the rate performance at room temperature is enhanced at 0.2-3.0C comparing pristine LiCoO2 cathode. The rate performance was indicated 20 percent increasing at 2.0C rate as compared to pristine LiCoO2 cathode. The charging performance was also enhanced at higher rate at room temperature.

Crystallization features and physico-chemical properties of alkali and alkaline aluminoborate glass–ceramics

Preparation and characterization of glass–ceramics based on CaO–Al2O3–B2O3 system, modified by replacing CaO by different alkali and alkaline earth oxides, and In2O3/Al2O3 substitustion were implemented. Different crystalline phases, including β-CaAl2B2O7, Na2Al2B2O7, LiAl5O8, Li4Al4B6O17, Li2AlBO4, SrAl2B2O7, BaAl2B2O7, α-(Ca1-x,Inx)Al2B2O7, and InBO3, were developed from the heat-treated glasses. The incorporation of In3+ in the position of Ca2+ in β-CaAl2B2O7 crystal lattice was responsible for phase transition of β-CaAl2B2O7 to α-CaAl2B2O7 phase. The coefficient of thermal expansion CTE of prepared glass–ceramics was between −65 × 10−7 and 72 × 10−7 K−1 in the temperature range from 25 to 600 °C. The glass–ceramic specimens containing XAl2B2O7 as the principal crystalline phase were characterized by negative CTE values. In contrast, the replacement of CaO in the base glass by alkali oxides like Na2O and Li2O led to a dramatic transformation of the negative CTE to postive values. The complete replacement of calcium oxide in the base glass by various alkali and alkaline earth oxides markedly decreased the chemical durability of the investigated glass–ceramic specimens, while substitution of Al2O3 by In2O3 resulted in improving the chemical stability of the crystalline samples. The density of the glass specimens were found to be within the range 2.35–3.38 g/cm3, while the density of the glass–ceramic samples was in the range of 2.37–3.13 g/cm3.

Tests of Heat-Treated Glass with Full-Coverage Ceramic Frit

Tests of Heat-Treated Glass with Full-Coverage Ceramic Frit

Effect of ZnF2 addition on the crystallization behaviour of a zinc borosilicate glass

A series of zinc borosilicate glasses with a molar composition (65-x) ZnO–x ZnF2-15B2O3-20SiO2, where x ranged from 0 to 5mol%, were prepared by a melt quenching technique. The effect of zinc fluoride (ZnF2) substitution for ZnO on the structural, thermal and crystallization features of the glasses was investigated. Structural information via vibration modes was provided by FTIR analysis that revealed an increased band definition and intensity for the highest content of ZnF2. The incorporation of F− ions caused the SiOSi bond breakage and appearance of non-bridging oxygens in the network. DTA results indicated that ZnF2 addition decreased slightly the onset and peak crystallization temperatures, lowering the thermal stability of the glasses. XRD analysis of glasses heat-treated at 615°C revealed the formation of willemite (Zn2SiO4) crystals, which was enhanced in glasses containing the highest ZnF2 addition. Microstructural observations by SEM of heat-treated glasses confirmed that the amount and the mean size of willemite crystals precipitated within the glass matrix increased with the addition of ZnF2, which acted as a crystallization promoting agent.

TEM studies on thermally nanocrystallized vanadium-containing glassy analogs of LiFePO4 olivine

Three series of glasses of the Li2O-FeO-V2O5-P2O5 system were thermally nanocrystallized and their microstructure was studied, at a nanometer resolution by transmission electron microscopy (TEM). Those observations were complemented by DTA and XRD studies on the same materials. It was shown that appropriate heating of the as-received glasses leads to formation of crystalline nanosize grains embedded in the glassy matrix. Average size of those grains reached even a few nm, was much smaller than that reported for LiFePO4-based nanostructured materials obtained by other methods. The crystal structure of most nanograins was identified as that of the LiFePO4 olivine, but some grains of the Nasicon-like Li3V2(PO4)3 phase were also present. The presence of both phases was confirmed independently by XRD patterns. Due to small size of crystalline grains (down to ca 5nm) the interfacial regions around them occupy an important fraction of the total volume of the material and their properties can strongly influence the effective properties of the whole material. We have postulated that the defective nature of interfacial regions leads to an increased concentration of Fe2+/Fe3+, V4+/V5+ or V3+/V4+ aliovalent pairs, crucial for a small polaron hopping mechanism of the electronic transport, and to an enhanced electrical conductivity. The presence of highly conducting interfacial regions in the system where either the glass matrix and both crystalline phases (LiFePO4 and Li3V2(PO4)3) are very poor conductors is the main cause of the observed strong enhancement of the electrical conductivity of the heat-treated glasses of the Li2O-FeO-V2O5-P2O5 system.

Lithium ion conductivity and dielectric relaxation in dendritic nanostructured LiTaO3 glass–nanocrystal composites

Lithium tantalate in single-crystalline and coarse-grained configurations is a poor ionic conductor and does not qualify as a solid electrolyte for lithium-based batteries. In this work, ionic conductivity was sought to be enhanced by the use of nanocrystals of LiTaO3 embedded in a borate-based glass matrix. Glasses of composition 3Li2O–4B2O3–Ta2O5 were formed by melt-quenching. The crystallization process was described by using isothermal crystallization kinetics, invoking the Johnson–Mehl–Avrami–Kolmogorov equation, which indicated a three-dimensional growth with an Avrami exponent of 3.5 and an effective activation energy for crystallization of 735 ± 65 kJ mol–1. Heat treatment of the as-quenched glasses was performed between 530 and 560 °C, and the evolution of LiTaO3 phase was studied by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The heat treatment yielded coalesced LiTaO3 nanocrystals of 18–32 nm size, forming dendritic structures in the glass matrix. Impedance analyses of the as-quenched and heat-treated glasses showed a dramatic improvement in dc conductivity (σdc), with a maximum around 3 × 10–3 S m−1 at 200 °C (σdcT = 1.5 S m−1 K) and activation energy of 0.54 eV for 530 °C/3 h heat-treated glasses. The values of σdc of the as-quenched glasses and of the 530 °C/3 h and 540 °C/3 h heat-treated glasses were about seven orders of magnitude higher than those of the single crystalline LiTaO3. Furthermore, the effect of heat treatment on lithium ion dynamics in the 40–200 °C temperature range was investigated by modulus formalism invoking the stretched exponential Kohlrausch–Williams–Watts function. The 7Li magic angle spinning NMR was used to investigate lithium self-diffusion in the nanostructured glass nanocrystal composites as a function of temperature between −10 °C and 60 °C.

Ag nanoparticles induced luminescence enhancement of Eu3+ doped phosphate glasses

Abstract Sodium phosphate glasses co-doped with Eu3+/Ag NPs were prepared by the melt quenching method. A thermal annealing process is proposed to control the aggregation and growth of Ag NPs. The amorphous nature is confirmed by the x-ray diffraction patterns for all the glasses. TEM picture analyses revealed the presence of silver nanoparticles of almost spherical shape and various sizes inside the glass matrix depending on the annealing time. The absorption spectra revealed seven absorption peaks of Eu3+ions in addition to the surface Plasmon resonance (SPR) band of Ag NPs centered at 400 nm. The luminescence properties of Eu3+ doped phosphate glass containing silver nanoparticles (NPs) are investigated. The observed enhancement of the photoluminescence and the PL lifetime relative to 5D0 → 7F2 transitions are explained not only by the energy transfer ions, but NPs to Eu3+ ions but also by the enhancement of local field effect LFE induced by SPR of silver NPs. Based on the emission spectra, Judd Offelt (JO) parameters (Ω2 and Ω4), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors, the quantum yield of luminescence and the stimulated cross-section emissions for 5D0→7F2 transition are calculated. The fluorescence quantum efficiencies are found to be enhanced with the increase of heat treatment until it attains 85% for the sample PAZE20. The results indicated that the heat-treated glass for 20 h has a good prospect as a gain medium applied for 615 nm broadband and high-gain europium-doped fiber amplifiers.

Leaching of phase-separated glasses in Na2O-B2O3-SiO2-Fe2O3 system

The leaching behavior of heat-treated phase-separated iron-containing sodium borosilicate glasses within the range of compositions of 8Na 2 O·(22 – х )B 2 O 3 ·70SiO 2 · х Fe 2 O 3 , where х varies from 0.3 to 10 mol.%, and (8 – x )Na 2 O∙22B 2 O 3 ∙70SiO 2 · x Fe 2 O 3 , where х varies from 2 to 6 mol.%, in the 3M aqueous HCl solution at boiling, was studied. It has been shown that the introduction of Fe 2 O 3 in these phase-separated glasses increases their chemical durability, the values of porosity and the average pore diameter, but reduces the specific surface area in the porous glasses based on them, compared with glass without Fe 2 O 3 . The compositions suitable for producing porous glasses were determined. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.14800

Highly conductive cathode materials for Li-ion batteries prepared by thermal nanocrystallization of selected oxide glasses

Glassy analogs of two important cathode materials for Li-ion cells: V2O5 and phosphoolivine LiFePO4 were heat-treated in order to prepare nanocrystallized materials with high electronic conductivity of up to 7×10−2Scm−1 and ca 7×10−3Scm−1 at 25°C, respectively. There is a clear correlation between the crystallization phenomena and the increase in the electrical conductivity for both groups of glasses. Electrochemical tests of heat-treated glasses of the V2O5–P2O5 system, used as cathodes in lithium cells confirm their good gravimetric capacity and reversibility. Heat-treatment of glasses of the Li2O–FeO–V2O5–P2O5 system also leads to a high increase in the conductivity and to formation of nanocrystalline grains in the glassy matrix, evidenced by HR-TEM images. The temperature dependence of the conductivity of these materials follows the Arrhenius formula. The presented results indicate that the overall increase in conductivity in nanocrystallized materials is due to good charge transport properties of their interfacial regions.

Low Cost Double Curvature – Exploratory Computational Modelling, FE-analysis and Prototyping of Cold-Bent Glass

The fabrication of projects with complex geometries often implies a significant waste of material, since custom molds need to be created and irregular shapes need to be cut out of larger sized elements. For low curvatures, cold elastic bending processes can be applied. However, elastic bending techniques have mainly been utilized to create simple curvature panels for architectural projects. This paper explores computational simulation in relation to a digitally controlled fabrication method of bending rectangular glass sheets elastically into irregular double curvature. This is done through exploratory prototyping within the framework of a Master of Science course on digital production, and additional computational modeling and FE-analysis. We used algorithmic real-time simulation to approximate the bending process of cold-bent glass and elaborated on details of the simulation process and possible surface types and curvatures. Our empirical tests on simply curved, ruled and doubly curved surface types used float glass as well as heat-treated glass. A detailing system was developed to clamp the glass panels into position. We evaluated the results of the computational simulation (Rhino with plug-ins) as well as FE-Analysis (Strand 7) and compared the resulting geometries to the measurements of the physical prototypes. In order to demonstrate the system’s capacities on a larger multi-panel geometry, we constructed a 5m x 4m prototype of a doubly-curved glass surface.

Improved nonlinear optical properties of chalcogenide glasses in Ge-Sn-Se ternary system by thermal treatment

In this work, a series of chalcogenide glass ceramics were prepared by thermal treating a precursor glass in molar composition of Ge20Sn5Se75 with different duration. X-ray powder diffraction (XRD) measurements showed the precipitation of nano-crystals belonging to GeSe2 and SnSe2 phases in the heat-treated glasses, which was confirmed by Raman spectra as well. The crystallization in glass matrix caused the variation of optical properties (i.e. Optical band gap, Urbach energy) due to localized field effect of the nano-crystals, while the infrared transmittance was kept unchanged. Third-order optical nonlinear properties of the precursor glass and glass ceramic samples were investigated by femtosecond Z-scan technique at telecom wavelength of 1550 nm. The maximum nonlinear refraction (γ) of the Ge-Sn-Se glass ceramics reached 5.319 × 10−16 m2/W, which is almost one order higher than that of the precursor glass, demonstrating the significant influence of nano-crystals on optical nonlinear property of the chalcogenide glasses.

Mössbauer and electrical conduction investigations of LiFe(BaTi)(PO4) NASICON nano composite

NASICON glass sample with a composition of Li 1.3Fe 0.3(BaTi) 1.7(PO 4) 3 was prepared using the conventional melt-quenching technique at 1300 ∘C for one hour after two stages of calcination process at 300 ∘C and 600 ∘C respectively. DTA was used to determine (T g) and (T c) of the as-quenched glass sample. XRD was used to confirm the glassy state of the prepared sample. The as-quenched glass sample was heat treated near its onset crystallization temperature for different times 1, 2, 3, 4, and 5 hours. The gradual precipitation of the crystalline nano-particles with NASICON type structure was also confirmed using XRD. The as-prepared sample and the five heat treated (HT) samples were investigated using Mossbauer spectroscopy, DC and AC conductivities and dielectric permittivity. FTIR, density, and TEM measurements were also performed. After HT, XRD and FTIR measurements conformed the formation of NASICON phase. The results of the dielectric permittivity showed no maximum peak in the studied temperature and frequency ranges, which indicates the absence of ferroelectric behavior of the HT glass sample. Mossbauer data showed that the iron in the glass and its HT samples include two ionic states, Fe 3+ (O h) and Fe 2+ (O h) ions. It is observed that the DC conductivity of the HT glass for 5 h was almost two orders of magnitude higher than that of the parent glass.

Structural evolution and second harmonic properties of lithium niobate–tantalate nanocrystals embedded in a borate glass

Nano-crystals of LiNbxTa1−xO3 were evolved by subjecting melt-quenched 1.5Li2O–2B2O3–xNb2O5–(1−x)Ta2O5 glasses (where x=0, 0.25, 0.5, 0.75 and 1.00) to a controlled 3-h isothermal heat treatment between 530 and 560°C. Detailed X-ray diffraction and Raman spectral studies confirmed the formation of nano-crystalline LiNbxTa1−xO3 along with a minor phase of ferroelectric and non-linear optic Li2B4O7. The sizes of the nanocrystals evolved in the glass were in the range of 19–37nm for x=0–0.75 and 23–45nm for x=1.00. Electron microscopic studies confirmed a transformation of the morphology of the nano-crystallites from dendritic star-shaped spherulites for x=0 to rod-shaped structures for x=1.00 brought about by a coalescence of crystallites. Broad Maker-fringe patterns (recorded at 532nm) were obtained by subjecting the heat-treated glass plates to 1064nm fundamental radiation. However, an effective second order non-linear optic coefficient, deff, of 0.45pm/V, which is nearly 1.2 times the d36 of KDP single crystal, was obtained for a 560°C/3h heat-treated glass of the representative composition x=0.50 comprising 37nm sized crystallites.

Grain size effects on the transport properties of Li3V2(PO4)3 glass–ceramic nanocomposites for lithium cathode batteries

The effect of grain size on the structural and transport properties of glass–ceramic nanocomposites consisting of Li3V2(PO4)3 crystals were investigated by differential scanning calorimeter, X-ray diffraction (XRD), transmission electron micrograph (TEM), density (d) and dc conductivity. XRD patterns exhibit the formation of Li3V2(PO4)3 with monoclinic structure. It was shown by XRD and TEM studies that by appropriate heat-treatment glasses can be turned into glass–ceramic nanocomposites consisting of crystallites smaller than 56 nm embedded in the glassy matrix. Density was found to increase with increasing grain size while the molar volume decreases. The dc conductivity measured in high temperature range increased with decreasing of the grain size while the activation energy decreased. The calculated dc conductivity at 400 K for the present glass was 5.77 × 10−7 S/cm, while in its glass–ceramic nanocomposites was in the range of 1.712 × 10−5–2.10 × 10−6 S/cm. On the other hand, the calculated activation energy for the present glass was 0.542 eV, while in its glass–ceramic nanocomposites was in the range of 0.165–0.468 eV. The increase in electrical conductivity in the glass–ceramic nanocomposite annealed at 450 °C for 4 h compared to that annealed at 450 °C for 2, 8, 24 h can be attributed to the decrease in grain boundary scattering due to the reduction in grain size. The conduction was confirmed to obey non-adiabatic small polaron hopping. The electron–phonon interaction coefficient (γ p) was calculated and found to be in the range of 5.09–16.64.

Effect of Al2O3 Nano-Filler on Properties of Alkali/Alkaline-Earth Borosilicate Glass Composite Sealants.

The effect of adding Al2O3 nano-filler (5 and 10 vol%) to two different alkali/alkaline-earth borosilicate glass sealants, particularly on the viscosity and electrical characteristics of the glass composite sealants, was investigated to improve the cyclic sealing performance. The effects of the filler and base glass composition on the viscosities, electrical conductivities, and phase transformations of the sealants were investigated. The glass viscosity was decreased by replacing 20 mol% SrO with alkali and zirconium oxide in a base alkaline-earth glass. Alumina filler increased the high-temperature electrical conductivities, as well as the viscosities, of the heat-treated glass composite sealants. The replacement of 20 mol% SrO with alkali and zirconium oxide in the base alkaline-earth glass decreased the electrical conductivity of the heat-treated glass containing Al2O3 nano-filler.

Structural analysis and visible light-activated photocatalytic activity of iron-containing soda lime aluminosilicate glass

A relationship between structure and visible light-activated photocatalytic activity of iron-containing soda lime aluminosilicate (15Na2O⋅15CaO⋅40Fe2O3⋅xAl2O3⋅(30−x)SiO2) glass (xNCFAS) was investigated by means of 57Fe-Mössbauer spectroscopy, X-ray diffractometry (XRD) and UV–visible light absorption spectroscopy (UV–VIS). The 57Fe-Mössbauer spectrum of 11NCFAS glass measured after heat-treatment at 1000°C for 100min was composed of a paramagnetic doublet due to FeIII(Td) and two magnetic sextets due to regular hematite (α-Fe2O3) and hematite with larger internal magnetic field. X-ray diffraction patterns of heat-treated xNCFAS samples resulted in decrease of α-Fe2O3 and increase of Ca2Fe22O33 or CaFe2O4 with alumina content. A quick decrease in methylene blue (MB) concentration from 15.6 to 4.7μmolL−1 was observed in the photocatalytic reaction test with 40mg of heat-treated 11NCFAS glass under visible light-exposure. The largest first-order rate constant of MB decomposition (k) was estimated to be 9.26×10−3min−1. Tauc’s plot yielded a band gap energy (Eg) of 1.88eV for heat-treated 11NCFAS glass, which is smaller than previously reported Eg of 2.2eV for α-Fe2O3. These results prove that addition of Al2O3 into iron-containing soda lime silicate glass is favorable for the preparation of improved visible light-photocatalyst with ‘ubiquitous’ elements.

Effect of Heat Treatment on Properties of Glass Nanocomposite Sealants.

The objective of this study was to investigate the effect of heat treatments on the viscosities and electrical conductivities of glass sealants to be used in solid oxide fuel cells. Glass-based sealants, both with and without an alumina nanopowder added as a nanofiller, were heat treated at temperatures ranging from 750 degrees C to 770 degrees C for periods of up to 240 h. The effects of heat treatments on the viscosities, electrical conductivities and phase transformations of the sealants were investigated. The results showed that alumina nanopowder added to the glass increased both high-temperature electrical conductivities and the viscosities of the sintered glass nanocomposite sealants. However, lengthy heat treatments decreased the electrical conductivities of the glass nanocomposite sealants. This decrease in the conductivities of the heat-treated glass nanocomposites was attributed to the crystallization of glass phase, owing to the dissolution of the alumina nanofiller in the sealing glass.

Effect of alumina nanofiller on properties of heat-treated glass composite sealants.

Alkali/alkaline-earth borosilicate glass-alumina composites containing 10 vol% Al2O3 were prepared for use as solid oxide fuel cell sealants. The effect of heat treatment and Al2O3, addition on the viscosities and electrical conductivities was investigated to improve cyclic sealing performance. Upon a 48-h heat treatment, the viscosity of the glass-alumina composites at 750 degrees C was approximately four orders of magnitude higher than that of the base glass owing to the crystallization of the glass in the presence of Al2O3. Heat treatment increased the electrical conductivities of both the base glass and the glass-alumina composites. The electrical conductivities of glass-alumina composites in the range from 400 degrees C to 550 degrees C were three times higher than those of the base glass regardless of heat treatment. This increase in the conductivities and viscosities by heat treatment was attributed to the devitrification and structural densification of the sealing glass and the partial dissolution of the Al2O3 filler in alkali/alkaline-earth borosilicate sealing glass.

Synthesis and properties of ZnTe and Eu3+ ion co-doped glass nanocomposites

In this study, ZnTe (II-VI) semiconductor and Eu+3-ion co-doped borosilicate glass has been prepared in the SiO2-K2O-CaO-BaO-B2O3 glass system followed by controlled heat-treatment to produce glass nanocomposites. Glass transition temperature and crystallization peak temperature have been evaluated using DSC analysis. Dilatometric studies were carried out to evaluate thermal expansion co-efficient, glass transition temperature, and dilatometric softening temperature and found to be 10.7 × 10−6/K, 580° C and 628° C, respectively. TEM micrographs demonstrate formation of nano sized crystallites of less than 50 nm. The ZnTe crystal formation also established through selected area electron diffraction (SAED) analysis and high resolution images obtained through TEM studies. With increasing heat treatment time, optical transmission cut-off wavelength (λcut-off) shifted towards higher wavelength. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the 5D0 → 7F2 transition. An intense 394 nm excitation band corresponding to the 7F0 → 5L6 transition was observed. Emission spectra were then recorded by exciting the glass samples at 394 nm. When the glass is heat-treated for 30 min at 610° C, a 6-fold increase in the intensity of the red emission at 612 nm has been observed, which is attributed to the segregation of Eu3+ ions into the low phonon energy ZnTe crystallites and as the size of the nanocrystals is smaller than the size of the exciton, quantum confinement effect is visible. Further increase in heat-treatment duration led to decrease in luminescence intensity due to the growth of larger size crystals. 5D1 → 7F0 transition is visible only in the samples heat-treated for 30 min and 1 h, which is a characteristic of presence of Eu3+ ions in the low phonon energy ZnTe crystal sites. The micro hardness of the precursor glass and glass nanocomposites was evaluated; base glass shows hardness of 6.7 GPa and hardness of heat-treated glass nanocomposites has been found to decrease with increase in heat-treatment duration (5.5-5.3 GPa). However, mechanical properties are found to be suitable for device applications.

Investigation of the strength loss of glass fibre after thermal conditioning

Single fibre tensile testing of thermally conditioned water sized and γ-aminopropyltriethoxysilane (APS) sized boron-free E-glass has been carried out. The fibres were produced from identical melts following which bare fibre had only water applied to it before winding whereas the sized fibre had a solution containing only APS applied to its surface. Both fibre types experience a loss of room temperature tensile strength after exposure to elevated temperature. By application of a novel method of single fibre thermal conditioning, it was demonstrated that the tensile strength of heat-treated glass fibre can be significantly underestimated. Strength loss was found, in most cases, to be caused by a combination of thermal effect and mechanical handling damage. The latter is found to be influenced by thermal loading of the fibre. The onset of mechanical handling damage in APS-sized fibre was found to be controlled by the thermal degradation of the silane sizing. This suggests that silane-based coatings, even when they are present as only a relatively thin surface layer, can protect fibres from the development or growth of critical surface flaws. The relative contribution to overall fibre strength loss from mechanical handling damage highlights the need to minimise processes which may cause fibre mechanical damage during glass fibre recycling procedures.