Effects of nano silica on synthesis and properties of glass ceramics in SiO2–Al2O3–CaO–CaF2 glass system: A comparison
TL;DR: In this paper, the authors compared the properties of normal and nano-SiO2-containing glass ceramics and found that the nano-siO2 particles gave higher Vickers hardness, shrinkage, lower water absorption, and higher acid resistance than the normal silica containing glass, thus making it more useful for industrial building, internal and external wall facing and tiles applications.
Abstract: Glass ceramics of composition 34SiO2–29Al2O3–25CaO–12CaF2 (wt.%) was made by conventional melting and quenching process using either normal or nano-SiO2 respectively. The glasses were characterized by differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The crystallization, microstructure, mechanical and chemical properties were compared for the two systems. With nano-SiO2 addition, the crystallization peak temperature (Tp) decreases, activation energy (E) and Avrami parameter (n) have very little change, and the mechanism of crystallization of the glass ceramics changed from surface crystallization to two-dimensional crystallization. The crystallite size of nano-SiO2 containing glass is lower than the normal SiO2 containing glass. Introduction of nano-SiO2 particles in glass ceramics gives higher Vickers hardness, shrinkage, lower water absorption, and higher acid resistance than the normal silica containing glass ceramics, thus making it more useful for industrial building, internal and external wall facing and tiles applications.
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TL;DR: The use of graphene is reported to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration and suggests a great potential of graphene/nano- 58S composite scaffold for bone tissue engineering applications.
Abstract: Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications.
139 citations
TL;DR: In this article, the most promising doping combinations for white light luminophores within the research are europium-dysprosium and europarbium-terbium, which allow obtaining white light both in glasses and glass-ceramics under 355 and 450 nm excitation.
48 citations
TL;DR: Oxyfluoride glass-ceramics containing CaF 2 nanocrystals were prepared by one-step crystallization of SiO 2 -Al 2 O 3 -CaO-CaF 2 glasses at different temperatures X-ray diffraction (XRD) results have revealed that CaF2 was the only precipitated crystalline phase in glassceramic samples as discussed by the authors.
43 citations
TL;DR: Nanosilica powders were synthesized from sodium silicate solution (SSS) and their effects on ceramics engobes were investigated in this paper, where the best results were found when the NS powder content increases, whiteness as well as linear shrinkage increased whereas thermal expansion coefficient, water absorption and bulk density decreased.
Abstract: Nanosilica (NS) powders were synthesized from sodium silicate solution (SSS) and their effects on ceramics engobes were investigated. Synthesized NS powder was subjected to various characterization studies by transmission electron microscopy (TEM), X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF), Brunauer–Emmett–Teller (BET) method, Fourier transform infrared measurements and gravimetric/differential thermal analysis (TGA and DTA) techniques. The results indicate that the synthesized NS consisted of pure silica particles (96.8%) with the particle size in the range 8.64–18.31 nm, amorphous structure having surface area 160.29 m2/g and the thermal analysis show that the weight losses of 6.23. The study showed that NS powder significantly improved physico-chemical properties of prepared ceramics engobes such as whiteness, thermal expansion coefficient (TEC), the crystallinity, water absorption (WA), linear shrinkage (LSH), breaking strength and bulk density (BD). The study can serve as theoretical basis for further traditional ceramics applications of NS powder. The best results were found when the NS powder content increases, whiteness as well as linear shrinkage increased whereas thermal expansion coefficient, water absorption and bulk density decreased.
42 citations
Cites background from "Effects of nano silica on synthesis..."
...NS has high surface area making it attractive for a wide range of application such as, reinforcing filler in rubber industry [7], enhance plant development, growth and yield of many crop species [8], improve the properties of concrete [9,10], food industry [11], medicine [12,13], insecticide industry [14], painting field [15,16], as adsorption materials in recyclable ceramic membrane [17], preparation of glass ceramic system (SiO2–Al2O3–CaO–CaF2) [18]....
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TL;DR: In this article, a series of oxyfluoride glasses with the composition SiO2-CaF2-Al2O3-CaO, doped with Dy 2O3 (0.5 −1 −1 ) and Eu2O 3 (0 −4 −4 ) were prepared using melt quenching method.
35 citations
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10,842 citations
TL;DR: In this paper, the theory of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment.
Abstract: The theory of the kinetics of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment. The density of germ nuclei diminishes through activation of some of them to become growth nuclei for grains of the new phase, and ingestion of others by these growing grains. The quantitative relations between the density of germ nuclei, growth nuclei, and transformed volume are derived and expressed in terms of a characteristic time scale for any given substance and process. The geometry and kinetics of a crystal aggregate are studied from this point of view, and it is shown that there is strong evidence of the existence, for any given substance, of an isokinetic range of temperatures and concentrations in which the characteristic kinetics of phase change remains the same. The determination of phase reaction kinetics is shown to depend upon the solution of a functional equation of a certain type. Some of the general properties of temperature‐time and transformation‐time curves, respectively, are described and explained.
9,458 citations
TL;DR: In this article, the temperature at which the maximum deflection is observed varies with heating rate for certain types of reactions, and an expression can be derived relating this variation with the kinetics of the reaction.
Abstract: In differential thermal analysis, the temperature at which the maximum deflection is observed varies with heating rate for certain types of reactions. An expression can be derived relating this variation with the kinetics of the reaction. By making a number of differential thermal patterns at different heating rates, the kinetic constants can be obtained directly from the differential thermal data. Measurements of the variation of peak temperature with heating rate have been made for several minerals of the kaolin group, the values of the kinetic constants determined, and these values compared with corresponding values obtained for both the same samples and similar material by conventional isothermal techniques. Some factors affecting the results are discussed. The method of differential thermal analysis (DTA) has been universally accepted by mineralogical laboratories as a rapid and convenient means for recording the thermal effects that occur as a sample is heated. Changes in heat content of the active sample are indicated by deflections shown by a line representing the differential temperature. It is conventional to represent an endothermic effect by a negative deflection and an exothermic effect by a positive deflection. The deflections, whether positive or negative, are called peaks.
3,138 citations
TL;DR: In this article, an extension of the Kissinger method was proposed for the analysis of the transformation kinetics of the metastable equiatomic tin-nickel alloy with differential thermal analysis (DTA).
Abstract: Several isothermal experiments are generally needed to determine the parameters of the Avrami equation which describe most of the heterogeneous solid state reactions. Differential scanning calorimeters are suitable for such experiments. While most differential thermal analysis (DTA) apparatus cover a wider temperature range than DSC apparatus they cannot be used to perform isothermal determinations. However, Kissinger has already shown how activation energy and frequency factor can be calculated from DTA experiments for the case of homogeneous reactions following first order kinetics. We derive in this paper an extension of the Kissinger method and show its applicability to heterogeneous reactions described by an Avrami expression. The new method will allow the study of the kinetics of metallic reactions at the higher temperature range obtainable with DTA. The transformation kinetics of the metastable equiatomic tin-nickel alloy are given as an example.
1,067 citations
TL;DR: In this paper, the mechanical properties of nano-Fe2O3 and nano-SiO2 cement mortars were experimentally studied and the experimental results showed that the compressive and flexural strengths measured at the 7th day and 28th day of the cement mortar mixed with the nano-particles were higher than that of a plain cement mortar.
Abstract: The mechanical properties of nano-Fe2O3 and nano-SiO2 cement mortars were experimentally studied. The experimental results showed that the compressive and flexural strengths measured at the 7th day and 28th day of the cement mortars mixed with the nano-particles were higher than that of a plain cement mortar. Therefore, it is feasible to add nano-particles to improve the mechanical properties of concrete. The SEM study of the microstructures between the cement mortar mixed with the nano-particles and the plain cement mortar showed that the nano-Fe2O3 and nano-SiO2 filled up the pores and reduced CaOH2 compound among the hydrates. These mechanisms explained the supreme mechanical performance of the cement mortars with nano-particles.
1,052 citations