| 1. |
- Ali, Sharafat, 1976-, et al.
(author)
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Hardness, elastic modulus and refractive index of oxynitride glasses prepared from woody biofuel ashes
- 2017
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In: European Journal of Glass Science and Techology. Part B. Physics and Chemistry of Glasses. - : Society of Glass Technology. - 1753-3562 .- 1750-6689. ; 58:6, s. 231-236
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Journal article (peer-reviewed)abstract
- This paper reports the hardness, elastic modulus and refractive index values of the oxynitride glasses prepared from woody biofuel ashes. The glasses were prepared in nitrogen atmosphere at 1350-1500°C with addition of Ca metal as a precursor to the extra addition of this modifier. The glasses were homogenous, but appeared translucent grey to black. They contained up to 23 eq% of Ca and 5 eq% of N. The glass densities vary slightly between 2·76 to 2·92 g/cm3. The molar volume and compactness values vary between 8·01 cm3/mol to 8·31 cm3/mol and 0·446 to 0·462 respectively. Mechanical properties like hardness and reduced elastic modulus show values, up to 10 and 105 GPa, respectively. These properties are strongly correlated with the amount of N in the glass. The refractive index (1·54-1·75) increases with increasing N and Ca contents.
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| 2. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(author)
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Optical and mechanical properties of amorphous Mg-Si-O-N thin films deposited by reactive magnetron sputtering
- 2019
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 372:25, s. 9-15
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Journal article (peer-reviewed)abstract
- In this work, amorphous thin films in Mg-Si-O-N system typically containing >15 at.% Mg and 35 at.% N were prepared in order to investigate especially the dependence of optical and mechanical properties on Mg composition. Reactive RF magnetron co-sputtering from magnesium and silicon targets were used for the deposition of Mg-Si-O-N thin films. Films were deposited on float glass, silica wafers and sapphire substrates in an Ar, N2 and O2 gas mixture. X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, spectroscopic ellipsometry, and nanoindentation were employed to characterize the composition, surface morphology, and properties of the films. The films consist of N and Mg contents up to 40 at.% and 28 at.%, respectively and have good adhesion to substrates and are chemically inert. The thickness and roughness of the films increased with increasing content of Mg. Both hardness (16–21 GPa) and reduced elastic modulus (120–176 GPa) are strongly correlated with the amount of Mg content. The refractive index up to 2.01 and extinction coefficient up to 0.18 were found to increase with Mg content. The optical band gap (3.1–4.3) decreases with increasing the Mg content. Thin film deposited at substrate temperature of 100 °C shows a lower value of hardness (10 GPa), refractive index (1.75), and higher values of reduced elastic modulus (124 GPa) as compared to the thin film deposited at 310 °C and 510 °C respectively, under identical synthesis parameters.
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| 3. |
- Ali, Sharafat, 1976-, et al.
(author)
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Properties of nitrogen rich Mg-Ca-Si-O-N glasses
- 2017
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In: 12th Pacific Rim Conference on Cermics and Glass Technology including Glass & Optical Materials Meeting, Hawii, USA 21-27 May 2017. ; , s. 180-180
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Conference paper (peer-reviewed)abstract
- Mg-Ca-Si-O-N glasses containing high amount of nitrogen have been prepared by melting the mixture of Mg metal, Ca metal, SiO2 and Si3N4 powders in nitrogen atmosphere using a radio frequency furnace. Chemical composition, surface morphology, glass transition temperature, hardness, reduced elastic modulus and refractive index of the glasses were investigated using X-ray (EDX) point analysis, scanning electron microscopy, differential thermal analysis, nanoindentation, and spectroscopic ellipsometry. Mg was substituted for Ca in these glasses. The obtained glasses were found to be homogenous, and most of them were not transparent in the visible region. These glasses show high values of glass transition temperature (1020°C), and crystallization temperatures (1150°C). The hardness and reduced elastic modulus increases upon substitution by Mg, up to 13 GPa and 150 GPa respectively. The refractive index of the glasses was found to decrease upon increasing substitution by Mg.
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| 4. |
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| 5. |
- Ali, Sharafat, 1976-, et al.
(author)
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Synthesis and characterization of the mechanical and optical properties of Ca-Si-O-N thin films deposited by RF magnetron sputtering
- 2017
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 315, s. 88-94
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Journal article (peer-reviewed)abstract
- Ca-Si-O-N thin films were deposited on commercial soda-lime silicate float glass, silica wafers and sapphire substrates by RF magnetron co-sputtering from Ca and Si targets in an Ar/N-2/O-2 gas mixture. Chemical composition, surface morphology, hardness, reduced elastic modulus and optical properties of the films were investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, nanoindentation, and spectroscopic ellipsometry. It was found that the composition of the films can be controlled by the Ca target power, predominantly, and by the reactive gas flow. Thin films in the Ca-Si-O-N system are composed of N and Ca contents up to 31 eq. % and 60 eq. %, respectively. The films thickness ranges from 600 to 3000 nm and increases with increasing Ca target power. The films surface roughness varied between 2 and 12 nm, and approximately decreases with increasing power of Ca target. The hardness (4-12 GPa) and reduced elastic modulus (65-145 GPa) of the films increase and decrease with the N and Ca contents respectively. The refractive index (1.56-1.82) is primarily dictated by the N content. The properties are compared with findings for bulk glasses in the Ca-Si-(Al)-O-N systems, and it is concluded that Ca-Si-O-N thin films have higher values of hardness, elastic modulus and refractive index than bulk glasses of similar composition. (C) 2017 Elsevier B.V. All rights reserved.
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| 6. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(author)
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Synthesis, structural characterization, and thermal properties of Ca- and La-doped soda-lime glasses by laser melting
- 2020
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In: International Journal of Applied Glass Science. - : American Ceramic Society. - 2041-1286 .- 2041-1294. ; 11:4, s. 699-706
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Journal article (peer-reviewed)abstract
- Laser melting techniques have been used in the preparation of unconventional glasscompositions with high melting temperatures. Thus, we wanted to test the feasibilityof using a CO2 laser in the preparation of nitrogen-rich oxynitride glasses and nitridesilicate glasses. Melting from oxides and metallic raw materials, we wanted to studyfirst glass formation and possible evaporation losses of the glass components. Twoglass series were prepared and studied for their structure and thermal properties, onewith Ca2+- and a higher melting La3+-doped soda-lime-silicate (SLS) series. In lessthan 3 minutes of laser melting, spheres of up to 6 mm diameter were successfullyfabricated. The obtained glass samples were homogeneous and transparent in thevisible region. X-ray diffraction and Raman spectroscopic analysis confirmed theamorphous nature of the synthesized samples. Sodium losses increase as calcium isadded to the soda-lime-silicate glass. As expected, increasing Ca2+ or La3+ additionlead to increased depolymerization of the silicate network. Moreover, the increasesin Tg with the addition of Ca2+ or La3+ ions indicating strengthening of the sodalime-silicate glass by increasing strength of the M-O bonds of divalent and trivalentions over monovalent sodium ions, weak Na-O bonds also resulting in significantevaporation loss during the short laser melting times. The thermal stability decreasesupon addition of Ca2+ or La3+ ions to the soda-lime-silicate glasses.
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| 7. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(author)
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Thermal and mechanical properties of mixed modifier oxynitride glasses
- 2016
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In: Proceeding of International conference on thermal analysis and calorimetry in Russia (RTAC-2016). - St. Petersburg : Peter the Great St.Petersburg Polytechnic University. - 9785742254478 - 9785742254461 ; , s. 136-139
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Conference paper (peer-reviewed)abstract
- Nitrogen rich oxynitride glasses in Ca-Sr-Si-O-N system were prepared by the novel synthesis route in which the modifier is used as a metal instead of metal oxide. The results show high values of glass transition (912C), and crystallization temperatures (1140C) and hardness (10.50 GPa). The viscosity increases significantly with the nitrogen content and the apparent viscosity activation energies, ranging from 855 to 2170 kJ/mole. These glasses can be classified as being both very refractory and very fragile.
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| 8. |
- Ali, Sharafat, 1976-, et al.
(author)
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Thin films in M-Si-O-N thin systems
- 2017
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In: 44th International Conference on Metallurgical Coating and Thin Films (ICMCTF), San Diego, CA, USA, 24-28 Apr 2017.
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Conference paper (peer-reviewed)
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| 9. |
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| 10. |
- Grund Bäck, Lina, 1974-, et al.
(author)
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Compositional effect on fining and oxygen activity in mixed alkali silicate glasses
- 2007
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In: ICG 2007. - : ICG. ; , s. 320-
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Conference paper (peer-reviewed)abstract
- Antimony oxide has been used as fining agent for quite some time as a substitute for arsenic oxide in low temperature furnaces, not reaching temperatures high enough to activate sulphate compounds in the fining process. Due to environmentally issues, a substitution of antimony by a less toxic fining agent is becoming more urgent. However, since all the details of the mechanisms of fining/refining with antimony are not fully known, it is necessary to further study the present mechanisms and substitution possibilities.This study is done to monitor how changes in glass composition affect the fining result and the oxygen activity of the melt. Numbers of bubbles were determined in order to evaluate the fining efficiency. The oxygen activity measurement is a way to in situ monitor the fining characteristics. Na2O-K2O-CaO-SiO2 glasses were used with constant alkali oxide content but with varying ratio Na2O/K2O. The Sb2O3 content was 0,2 mol% and NaNO3 or KNO3 was added as oxidising agent.The oxygen activity has been measured electrochemically, both during the fining process and when the melt was in equilibrium with the surrounding atmosphere. To understand the nitrates contribution to the fining, the oxygen activity was measured in melts both with and without nitrate.
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