Dilatometric Softening Point Research Articles

Glass formation and properties of glasses in the system SrO–B2O3–SiO2–xAl2O3 (x=0; 10 mol.%)

The paper shows the prospects of the system SrO–Al2O3–B2O3–SiO2 as a basis for the synthesis of new vitreous and glass-ceramic materials, which are widely used as electrical insulated and high-temperature coatings, for sealing of solid oxide fuel cells, and in the production of heat resistant materials. We experimentally established the conditions of glass formation, regions of glass-forming melts and properties of glasses, the chemical composition of which is limited by the following content of components (mol.%): SrO 30–80, B2O3 10–60, SiO2 10–60, and Al2O3 0–10. It is shown that during the synthesis of glasses in the corundum crucible at the temperature of 13500С the region of glass formation in the system SrO–B2O3–SiO2 is limited by the following content of components (mol.%): SrO 30–60, B2O3 10–60, and SiO2 10–50. It is found that the introduction of Al2O3 to the composition of these glasses expands the region of glass formation towards increase of the SiO2 content in the glass up to 60 mol.%. Experimentally determined values of glass properties are within the following limits: coefficient of linear thermal expansion (67–118)10–7 К–1; glass transition temperature 570–6600С; dilatometric softening point 580–7000С; and density 2.62–3.71 g cm–3. The established patterns of influence of the components and conditions of glass formation on the physical and chemical characteristics of glasses may serve as an experimental basis for designing of new materials with a complex of specified properties, which allows solving the problems of their practical use.

Properties of glasses in the system BaO–B2O3–SiO2–xAl2O3 (x=0; 5; 10 mol.%)

This article shows the prospect of the system BaO–Al2O3–B2O3–SiO2 as the basis of vitreous and glass ceramic materials, which are widely used in rocket production for high-temperature protection of heat resistant alloys, in the power industry for sealing solid oxide fuel cells, and in the production of heat resistant glass ceramic materials. We examined the conditions of glass formation and properties of glasses with the following content of components (mol.%): BaO 30–70, B2O3 10–50, SiO2 20–60, and Al2O3 0–10. We established experimentally that the physical and chemical properties of glass, depending on its chemical composition, vary within the following limits: coefficient of linear thermal expansion of (71–122)10–7 К–1; glass transition temperature of 500–6500С; dilatometric softening point of 540–6700С; and density of 3.20–4.21 g cm–3. The volume resistivity of the studied glasses is within 1011–1013 Ohmcm at the temperature of 1500С. Generalization of the dependences of glass properties on their chemical composition was carried out with the use of the additive equations, for which the partial contributions of oxides to the values of the corresponding properties were determined by experimental and statistical methods. The established patterns of influence of components and conditions of glass formation on the physical and chemical characteristics of glasses allows implementing the process of designing of a wide range of glass compositions with the complex of specified properties in order to solve the tasks of their practical use.

Enhanced thermal stability of high-bismuth borate glasses by addition of iron

Glasses with nominal molar composition 20B2O3 – (80−x)Bi2O3 – xFe2O3 (where x = 0–40) were successfully prepared by melt-quenching. These glasses were characterised by multiple techniques including density, X-ray diffraction (XRD), X-Ray fluorescence (XRF), Raman, FT-IR and Mössbauer spectroscopies, dilatometry and differential thermal analysis (DTA). Partial replacement of Bi2O3 by Fe2O3 leads to decreasing density and molar volume and a substantial increase in thermal stability, as measured by several parameters, with maximum improvements achieved when x = 10–20. These improvements are accompanied by modest increases in dilatometric softening point. FT-IR and Raman spectra confirm the presence of BO3 and BiO6 structural units in all glasses, with glass structure apparently little affected by Fe2O3. Mössbauer spectroscopy confirms that iron is present partly as 4-fold coordinated Fe3+ in all glasses, with some 5- and/or 6- coordinated Fe3+ sites also present.

Compositional effects on the crosslink density of Ca–(Mg)–(Y)–Si–Al–oxyfluoronitride glasses

AbstractThe effects of fluorine and nitrogen substitution for oxygen in aluminosilicate glasses, effectively oxyfluoronitride (OFN) glasses, modified by calcium, calcium–yttrium or calcium–magnesium on thermal and physical/mechanical properties have been compared. Thus, 42 glasses in the Ca–(Mg)–(Y)–Si–Al–O–(N)–(F) system have been prepared and characterized with respect to density (ρ), molar volume (MV), compactness (C), free volume (FV), glass transition temperatures measured by DTA (Tg,DTA) and dilatometry (Tg,dil), dilatometric softening point (TDS), microhardness (μHv) and Young's modulus (E). Gradients of property variation with nitrogen or fluorine substitutions for oxygen are similar for all three different oxyfluoronitride glass systems and are comparable with those reported for other OFN glasses, again indicating independent and additive effects of nitrogen and fluorine. In attempting to further understand how fluorine affects the cross‐link density (CLD) in OFN glasses, it becomes apparent that it is necessary to allow for a greater contribution by aluminum in a modifier role as fluorine content is increased. This modified calculation of CLD values results in good linear fits between Tg and CLD values. This analysis clearly demonstrates and endorses the concepts that thermal properties are related to CLD while physical/mechanical properties are dependent on glass compactness.

Effect of fluorine and nitrogen content on the properties of Ca-Mg-Si-Al-O-(N)-(F) glasses

X-ray amorphous glasses of composition (in equivalent percent) 15Ca:15Mg: 55Si:15Al:(100-x-y)O:xN:yF with x=0, 10, 15 and y=0, 1, 3, 5, were prepared by melting and casting. The effects of oxygen substitution by fluorine and/or nitrogen on the physical, mechanical, thermal and optical properties of the glasses have been investigated. Molar volume, fractional glass compactness, microhardness, Young's Modulus, glass-transition temperature, dilatometric-softening point and refractive index increased linearly with nitrogen substitution for oxygen, whereas molar volume and thermal expansion coefficient decreased linearly with nitrogen increase. In contrast, all properties except glass-transition temperature and dilatometric-softening point, are virtually unaffected by fluorine substitution for oxygen. Significant and linear, decreases in thermal properties occurred with increasing fluorine substitution level. All the data collected and its analysis clearly showed that the substitution effects of fluorine for oxygen on the studied properties of the glasses of the system with general formula Ca-Mg-Si-Al-O-(N)-(F) are totally independent and additive with respect to the substitution effects of nitrogen for oxygen on glass properties.

Preparation of monolithic oxynitride glasses by sol–gel method

Monolithic aerogels and xerogels were obtained by drying gels at super critical condition and ambient pressure after aging at room temperature for various lengths of time. Heat treatment of porous xerogels at low temperature (≤1000°C) in air and flowing ammonia resulted dense, homogeneous oxide and oxynitride glasses, respectively. The chemical bonding state and properties of gels and glasses were investigated employing Fourier transform infrared spectroscopy (FTIR), dilatometry, and Brunauer–Emmitt–Teller (BET) methods. Nitrogen content of oxynitride glasses were determined by oxygen nitrogen analyzer. Based on the compressive strength measurement, the strength of gels was increased from 0.73 to 1.5 (Mpa) with aging time. The pore size distribution was also changed significantly during aging process via hydrolysis and condensation reactions; the latter is confirmed by the FTIR spectra. The dilatometric softening point temperature of glasses and their micro-hardness were increased after nitridation process. Spectroscopic evidence indicated that nitrogen was chemically dissolved in the network of glass and its content was increased from 0.67 to 2.08 (wt.%) after nitridation for 5 and 15h, respectively .

Investigation of the Properties of Soda-Lime Silicate Glass Doped with TiO<sub>2</sub>

In this study, the properties of re-melted soda-lime silicate glass cullet doped with TiO2 were investigated in order to study the potentials to use as parent glass for glass-ceramics. TiO2 of 0.5, 1 and 3 mol% was doped into the 71SiO2-10Na2O-6K2O-5CaO-4MgO-2SrO-TiO2-Al2O3 glass cullet and melted at 1500°C for 3 hours, and then annealed at 550 °C. The optical and physical properties were examined. It was found that the refractive index and density of glasses were raised with increasing of TiO2 concentration. The optical properties measured by UV-Vis spectrophotometer showed that the UV edge in the absorption spectra was shifted to a higher wavelength, and the transmission at 583 nm was decreased. The CIE L*a*b* color measurement showed that the glasses were slightly colorless but the appearance of yellow increased with higher TiO2 concentration. Lower thermal expansion coefficient and higher glass transition temperature as well as the dilatometric softening point were observed as the concentration of TiO2 was increasing. Finally, the calculated activation energy was 476, 493, 506 and 637 kJ/mol with 0, 0.5, 1 and 3 mol% doped TiO2, respectively. At doped TiO2 of 3 mol%, the properties of glass were changed rapidly due to the substitution of [Ti4+] in local [Si4+] resulting in increasing the bond strength in glass structure.

V2O5및 TeO2함유 유리를 이용한 염료감응형 태양전지 패널의 레이저 봉착

Effective glass frit compositions enabled to absorb laser energy, and to seal a commercial dye-sensitized solar-cell-panel substrate were developed by using V₂O 5 -based glasses with various amounts of TeO₂ substitution. The latter was intended to increase the lifetime of the solar cells. Substitution of V₂O 5 by TeO₂ provided a strong network structure for the glasses via the formation of tetrahedral pyramids in the glass, and changed the various glass properties, such as glass transition temperature (T g ), dilatometric softening point (T d ), crystallization temperature, coefficient of thermal expansion (CTE), and glass flowage without any detrimental effect on the laser absorption property of the glasses. The thermal expansion mismatch (Δα) between the glass frit and the substrate could be controlled within less than ±5% by addition of 10 wt% of β-eucryptite. An 810 nm diode laser was used for the sealing test. The laser sealing test revealed that the VZBT20 glass frit with 10 wt% β-eucryptite was successfully sealed the substrates without interfacial cracks and pores. The optimum sealing conditions were provided by a beam size of 3 mm, laser power of 40 watt, scan speed of 300 mm/s, and 200 irradiation cycles.

Tuning the thermal properties of borosilicate glass ceramic seals for solid oxide fuel cells

Abstract In this paper, a series of Sr–Ba–borosilicate glass-ceramics (10–40 mole% B2O3) were prepared to investigate the effect of borate content on the thermal properties as well as volatilization behavior. For crystallized samples with increasing borate contents, the dilatometric softening points decrease, from 702 to 660 °C, as do the coefficients of thermal expansion, from 9.5 to 7.5 × 10−6 K−1. In addition, the weight loss from these materials, in wet forming gas at 780 °C for 28 days, decreases by a factor of two as the borate content increases from 10 to 40 mole%. The borate-containing phase, SrB2O4, forms with increasing borate content. The significant improvement in stability against volatility can be attributed to the formation of SrB2O4, which is consistent with the results of thermochemical calculations. These results therefore indicate one way to design sealing compositions to use B2O3 to tailor thermal properties without sacrificing thermal stability.

Preparation and characterisation of diopside-based glass–ceramic foams

Foaming and crystallisation behaviours of compacted glass powders based on a diopside glass–ceramic composition were investigated using the sintering route. The foaming agent was 2wt.% SiC particles. The effect of PbO on the foaming ability of glasses was investigated. The results showed that the addition of PbO not only improved the foaming ability, by improving the wettability of the glass–SiC particles but also increased the crystallisation temperature and widened the temperature interval between the dilatometric softening point and the onset of crystallisation. The glass–SiC wetting angle was decreased from 85° for the lead-free glass, to 55° for the glass that contains 15wt.% PbO.

Strontium containing bioactive glasses: Glass structure and physical properties

The influence of substituting strontium for calcium in the following glass series 49.46 SiO 2–1.07 P 2O 5–(23.08-X) CaO–X SrO–26.38 Na 2O was studied on the physical properties. Solid state nuclear magnetic resonance and vibrational spectroscopy showed that the glasses were predominantly composed of Q 2 silicate chains. Addition of strontium did not result in any structural alteration of the glass network due to the similar role of SrO compared with that of CaO. The density increased with strontium content whilst the oxygen density decreased indicating a more expanded glass network. The glass transition temperature reduced with strontium substitution in a linear fashion and there was no evidence of a mixed alkaline earth effect with a lower than expected glass transition temperature. Dilatometric softening points also reduced with increasing strontium content, whilst the thermal expansion coefficients increased. The results are consistent with a weaker network as a result of the lower charge to size ratio of Sr 2+ compared to Ca 2+.

Effect of P 2O 5 content in two series of soda lime phosphosilicate glasses on structure and properties – Part II: Physical properties

The effect of the variation in phosphate (P 2O 5) content on the properties of two series of bioactive glasses in the quaternary system SiO 2–Na 2O–CaO–P 2O 5 was studied. The first series (I) was a simple substitution of P 2O 5 for SiO 2 keeping the Na 2O:CaO ratio fixed (1:0.87). The second series (II) was designed to ensure charge neutrality in the orthophosphate ( PO 4 3 - ), therefore as P 2O 5 was added the Na 2O and CaO content was varied to provide sufficient Na + and Ca 2+ cations to charge balance the orthophosphate present. Network connectivity’s of the glasses were calculated, and densities and thermal expansion coefficients predicted using the Appen and Doweidar models, respectively. Theoretical densities were measured using the Archimedes principle. Characteristic temperatures, namely the glass transition temperature, T g, and crystallization temperatures, T x, were obtained using differential analysis (DTA). Two crystallization exotherms were observed for both glass series ( T xi and T xii). Both T g and T x decreased with P 2O 5 addition for both series. The working range of the glasses, T x– T g was shown to increase to a maximum at around 4 mol% P 2O 5 then decrease at higher P 2O 5 contents for both series. Thermal expansion coefficients were measured using dilatometry increasing with P 2O 5 addition and showed good agreement with the Appen values. Dilatometric softening points, T s, were also measured, which increased with P 2O 5 addition. X-ray diffraction (XRD) was performed on the glasses to confirm their amorphous nature. The glass containing 9.25 mol% P 2O 5 from series I exhibited well-defined peaks on the XRD trace, indicating the presence of a crystalline phase.

Thermal and some physical properties of glasses in the La2O3−CaO−B2O3 ternary system

Glasses in the La2O3−CaO−B2O3 ternary system were studied. The glass forming range as determined by the appearance of the annealed cast was found to match previously published findings. Clear glasses were formed in the composition range of 5.7−19.1mol% La2O3 with constant B2O3 content of 71.4mol%, and in glasses of constant La2O3:CaO ratio of 1:4 with B2O3 content in the range of 71.4–55.0mol%. The non-linear optical crystalline phase La2Ca2B10O19 was crystallized from the clear glasses after heat treatments, as determined by powder XRD. Two types of the LaBO3 crystalline phases were detected in the partially and the fully crystallized glass compositions outside the glass forming range. Data are reported for the glass transition temperature (Tg), dilatometric softening point (Td), linear coefficient of expansion (α), onset crystallization temperature (Tx), exothermal peak temperature (TP), density (ρ) and index of refraction (nD) in the clear glasses.

Thermal properties and glass formation in the SiO2–B2O3–Bi2O3–ZnO quaternary system

Lead-free glasses in the SiO2–B2O3–Bi2O3–ZnO quaternary system were studied. The glass formation region, as determined by XRD patterns of bulk samples, was limited to glasses having more than 40mol% of the glass-forming oxides SiO2 and B2O3. Crystalline phases of Zn2SiO4 (willemite) were detected in compositions of 30SiO2·10B2O3·20Bi2O3·40ZnO and 20SiO2·10B2O3·25Bi2O3·45ZnO. Glass transition temperatures (Tg), dilatometric softening points (Td) and linear coefficients of expansion in the temperatures range of 25–300°C (α25–300) were measured for subsystems along the B2O3 join of 10, 20 and 30mol%. For these subsystems, Tg ranged from 411 to 522°C, and Td ranged from 453 to 563°C, both decreasing with increasing Bi2O3 content. The measured α25–300 ranged from 53 to 95×10−7°C−1, with values increasing with increasing Bi2O3 content. The ZnO content had the opposite effect to the Bi2O3 content. It appears that Bi3+ acts as a glass-modifier in this quaternary system.

Sintering of β.q. SS and gahnite glass ceramics

The sinterability of β.quartz solid solution, β.q. ss, and ZnAl 2O 4 glass ceramics was studied. It was found that the sinterability of glass powders with mean particle sizes greater than a threshold value rapidly decreases. Quantitative measurement of the crystalline phases and the shift of the dilatometric softening point of the residual glasses as determined by DTA, indicate that in addition to the amount of crystalline phases, the composition and viscosity of the residual glass influence the maximum densification temperature. ©

Phosphorus oxynitride glasses of variable sodium content

Nitriding phosphate glasses of variable sodium content, x NaO·(1− x ) P 2 O 5 , in anhydrous ammonia gas is described. The thermal expansion coefficient and dissolution rate in water decrease with increasing P 2 O 5 and nitrogen content The dilatometric softening point and glass transition temperature decrease with increasing P 2 O 5 and increase with increasing nitrogen content. The water content of the as-melted glasses increases dramatically with increasing P 2 O 5 content. The N 1s and O 1s spectra were determined with X-ray photoelectron spectroscopy.

Cation Effects in NaPO3 Glasses Doped with Metal Nitrides and Oxides

Oxynitride glasses were prepared by doping a NaPO3 melt with either AIN, Mg3N2, or Ca3N2 NaPO3 glasses doped with AI2O3, MgO, or CaO, so as to contain the same weight percent of each cation as in the oxynitride glasses were also prepared. The dissolution rate in water and the thermal expansion coefficient both decreased while the dilatometric softening point, glass transition temperature, and refractive index increased with increasing nitride or oxide dopant concentration. The properties of the corresponding oxide‐ or nitride‐doped glasses were essentially equal, which indicated that the cation was primarily responsible for the change in each property.