SiO2 In Wt Research Articles

Study of the Scattering Effect by SiO2 Nanoparticles, in a Luminescent Solar Concentrator Sensitized with Carbon Dots.

Luminescent solar concentrators (LSCs) have become an attractive way to produce green energy via their integration into buildings as photovoltaic windows. Recently, carbon quantum dots (C-QDs) have become the most studied luminescent material for the manufacture of luminescent solar concentrators due to their advantages, such as low toxicity, sustainability, and low cost. Despite the advantages of carbon quantum dots, they remain a low-efficiency material, and it is difficult to fabricate LSCs with a good performance. To address this problem, some of the research has used SiO2 nanoparticles (Nps) to produce a light-scattering effect that helps to improve the system performance. However, these studies are limited and have not been discussed in detail. In this regard, this research work was designed to evaluate the contribution of the scattering effect in different systems of carbon quantum dots used in a possible luminescent solar concentrator. To carry out this study, C-QDs and SiO2 Nps were synthesized by hydrothermal methods and the Stober method, respectively. We used different concentrations of both materials to fabricate film LSCs (10 × 10 cm2). The results show that the light scattered by the SiO2 Nps has a double contribution, in terms of light redirected towards the edges of the window and as a secondary source of excitation for the C-QDs; thus, an improvement in the performance of the LSC is achieved. The best improvement in photoluminescence is achieved when the films are composed of 20% wt carbon quantum dots and 10% wt SiO2 Nps, reaching a gain of 16% of the intensity of the light incident on the edges of the window with respect to the LSCs where only C-QDs were used.

Investigation Of Mode II Interlaminar Fracture Toughness Of Silicon-Di-Oxide Filled Glass Fiber Reinforced Epoxy Composites

Fracture is a new failure mode due to unstable propagation of a delamination crack growth in composite structures caused by applied load. The efficient characterization of the crack growth in composite structures enhances to estimate the duration of life. This paper mainly focusses on characterization of the fracture toughness of GFRP/epoxy matrix with SiO<sub>2</sub> filler form of composites and studying the crack behaviour in the (Mode II) ENF specimen which leads to interlaminar fracture in structural applications. The laminates are arranged to specify the Mode II interlaminar fracture toughness and interlaminar shear strength of GFRP/ epoxy matrix, GFRP/5% wt SiO2, GFRP/10% wt SiO<sub>2</sub>, using ASTM D7905 M-14 and JIS test methods. The results show that unfilled SiO<sub>2</sub> GFRP/epoxy matrix composites are of more facture toughness; the result reveals that the JIS methods in plane shear Mode II test were lower value of fracture toughness than that of ASTM D7905 M-14 Mode II test. As recommend in ASTM standard, ENF (shear pre-cracked) specimen is applicable to measure Mode II fracture toughness.

Evaluation of Corrosion Resistance of Bi-layered Plasma-sprayed Coating on Titanium Implants

There are several attempts to improve surface characteristics of biomaterials with thick film coatings. In this research, a class of protective coating layers of bi-layered Hydroxyapatite (HA)/Al2O3-SiO2 (with 10, 20, 30 %wt SiO2) were deposited on titanium (Ti) surfaces by plasma spray technique. The surface features of the applied coating layers were evaluated in detail to confirm the effectiveness of the technique for further biomedical applications. The results demonstrated that uniform and bi-layered plasma sprayed coatings can be successfully prepared through the optimization of engineering parameters. Also, it was found that the roughness of the bi-layered coatings increases with increasing the number of coating layers. The corrosion behavior of the coated and uncoated samples was comparatively investigated using electrochemical tests. The measured current densities (icorr) for HA, (HA)/Al2O3-SiO2 (with 10, 20, 30 %wt SiO2) were 0.27μA/cm2, 0.28 μA/cm2, 0.23 μA/cm2, 0.79 μA/cm2, respectively. According to the results, corrosion resistance of samples with 20% SiO2 is significantly improved compared to the single-layer HA and bare Ti. The outcomes of FESEM results revealed that porosity and cavities related to evaporation of adhesive PVA and it is confirmed by increasing the percentage of silica to more than 20%, porosity has increased. In conclusion, the proposed coating system showed promising abilities for future biomedical applications. It could be optimized and improved by changing the structural characteristics of the substrate, chemical composition and porosity of the coating layers.

Greener processing of SrFe12O19 ceramic permanent magnets by two-step sintering

With an annual production amounting to 800 kilotons, ferrite magnets constitute the largest family of permanent magnets in volume, a demand that will only increase as a consequence of the rare-earth crisis. With the global goal of building a climate-resilient future, strategies towards a greener manufacturing of ferrite magnets are of great interest. A new ceramic processing route for obtaining dense Sr-ferrite sintered magnets is presented here. Instead of the usual sintering process employed nowadays in ferrite magnet manufacturing that demands long dwell times, a shorter two-step sintering is designed to densify the ferrite ceramics. As a result of these processes, dense SrFe12O19 ceramic magnets with properties comparable to state-of-the-art ferrite magnets are obtained. In particular, the SrFe12O19 magnet containing 0.2% PVA and 0.6% wt SiO2 reaches a coercivity of 164 kA/m along with a 93% relative density. A reduction of 31% in energy consumption is achieved in the thermal treatment with respect to conventional sintering, which could lead to energy savings for the industry of the order of 7.109 kWh per year.

Optimization of the Electrochemical Performance of a Composite Polymer Electrolyte Based on PVA-K2CO3-SiO2 Composite.

Composite polymer electrolyte (CPE) based on polyvinyl alcohol (PVA) polymer, potassium carbonate (K2CO3) salt, and silica (SiO2) filler was investigated and optimized in this study for improved ionic conductivity and potential window for use in electrochemical devices. Various quantities of SiO2 in wt.% were incorporated into PVA-K2CO3 complex to prepare the CPEs. To study the effect of SiO2 on PVA-K2CO3 composites, the developed electrolytes were characterized for their chemical structure (FTIR), morphology (FESEM), thermal stabilities (TGA), glass transition temperature (differential scanning calorimetry (DSC)), ionic conductivity using electrochemical impedance spectroscopy (EIS), and potential window using linear sweep voltammetry (LSV). Physicochemical characterization results based on thermal and structural analysis indicated that the addition of SiO2 enhanced the amorphous region of the PVA-K2CO3 composites which enhanced the dissociation of the K2CO3 salt into K+ and CO32− and thus resulting in an increase of the ionic conduction of the electrolyte. An optimum ionic conductivity of 3.25 × 10−4 and 7.86 × 10−3 mScm−1 at ambient temperature and at 373.15 K, respectively, at a potential window of 3.35 V was observed at a composition of 15 wt.% SiO2. From FESEM micrographs, the white granules and aggregate seen on the surface of the samples confirm that SiO2 particles have been successfully dispersed into the PVA-K2CO3 matrix. The observed ionic conductivity increased linearly with increase in temperature confirming the electrolyte as temperature-dependent. Based on the observed performance, it can be concluded that the CPEs based on PVA-K2CO3-SiO2 composites could serve as promising candidate for portable and flexible next generation energy storage devices.

Controlling the setting times of one-part alkali-activated slag by using honeycomb ceramics as carrier of sodium silicate activator

A solid alkali source is a great choice to make one-part alkali activated materials (AAM). Conventional slag-based AAM always suffer from short setting time and unsafe operation with liquid alkaline activators, thus restricting their usage in industry. This study aims to synthesize a new kind of one-part alkali-activated slag cement by using a porous honeycomb ceramic (HCC) as the carrier of sodium silicate activator. The solid activator was produced by making the honeycomb ceramic absorb water glass (Ms = 3.24, 8.21 wt% Na2O, 25.8%wt SiO2), drying for 5 h at 125 °C and then grinding it to powder with particle sizes between 10 and 50 μm. In this study, the result indicates that setting time of alkali activated slag cement (AASC) was successfully extended to at least 5 h by using the solid activator. The maximum compressive strength of the specimens made with 5% NaOH + 40% HCC and 6% NaOH + 40% HCC was ~40 MPa after 28 d of curing time. XRD (X-ray diffraction), FTIR (Fourier Transform infrared spectroscopy), SEM (Scanning Electron Microscope) and linear shrinkage analysis were applied in order to study the hydration product and the effect of the addition of HCC to the AASC. In terms of the strength properties and setting time, this one-part AASC could be classified as a Type 32.5 N and CEM IIIC class cement according to the European standard EN-197.

Effects and mechanism of SiO2 on photocatalysis and super hydrophilicity of TiO2 films prepared by sol-gel method

TiO2/SiO2 films were deposited on glass substrates by sol-gel method, and the effects of SiO2 on the photocatalysis and hydrophilicity of TiO2 films were studied. Zeta potential measurements show that SiO2 can effectively inhibit the growth of TiO2 colloidal particles, and improve the stability of sols. XRD and AFM observations discover that, with the increase of SiO2, the size and crystallinity of TiO2 particles, and the porosity and roughness of films all gradually decrease. XPS and FTIR analyses indicate that SiO2 also affect the composition of the films. In addition, the blue shift of the absorption boundary gradually increases with SiO2. The fitting results show that the photocatalytic reaction of films basically follows the first-order kinetics law. The films with 15% SiO2 exhibit the best photocatalytic activity, whose degradation efficiency is about twice that of the pure TiO2 films. The films with 20%wt SiO2 have the best super hydrophilicity, whose water contact angle (WCA) drops to 2° in 3s. More significantly, its super hydrophilicity can last for more than 6 days under dark, that is, the films obtain an enhanced durable super hydrophilicity. In summary, the films with 15%wt–20%wt SiO2 own the best overall performance.

A new double-layer hydroxyapatite/alumina-silica coated titanium implants using plasma spray technique

There have been several attempts to modify the surface characteristics of tissue engineering implants in order to stimulate specific characteristics. In this research, a single layer of hydroxyapatite (HA) and a new double-layer of HA/Al2O3-SiO2 nanocomposites (SiO2, 10, 20, 30 wt%) were deposited, respectively, on the surface of titanium implants by a plasma spray technique. The results indicated that the applied coating systems featured some specific characteristics on the surface such as higher surface roughness and hydrophilicity resulting in a better cellular response and apatite forming ability in vitro, compared to the bare titanium sample. In addition, among different applied coating, the double layer plasma-sprayed HA/Al2O3-20%wt SiO2 coating has shown an enhanced cellular behavior and biocompatibility compared to the single-layer HA. In conclusion, the new bi-layer coatings could significantly affect the surface characteristics of the implants for better biological response without deteriorating the basic characteristics of the implants.

Preparation of transparent and robust superhydrophobic surfaces for self-cleaning applications

Superhydrophobic surfaces have recently attracted a lot of attention due to their high water repellency along with a wide range of applications in many fields. The application of such surfaces for self-cleaning purposes, such as in solar cell modules, has been limited due to the lack of mechanical robustness, thermal stability and ultraviolet radiation resistance. The fabrication of superhydrophobic water-repellent surfaces with mechanical robustness and high transmittance remains a major challenge. This paper presents a method for fabrication of transparent, robust and stable superhydrophobic surfaces by simple spray coating process. The developed coating solution can be sprayed on all kinds of materials to create a superhydrophobic self-cleaning surface. Proper molar ratios of Methyltrimethoxysilane (MTMS) and (3-Glycidyloxypropyl)trimethoxysilane (GLYMO) are used to bond the functionalized silica nanoparticles to various substrates and promote robustness. Optimum spraying cycles (layers) of 1.0%wt SiO2 nanoparticles after adhesive layer has resulted in contact angles of the order of 170˚ with a hysteresis of 6° and sliding angle of 1°. Developed surfaces also exhibited excellent stability under pressurized jet water, abrasion and ultraviolet radiations. Improvement of surface transmittance was achieved by annealing the surface under temperatures up to 300 °C without losing superhydrophobicity. The optical transmittance of the optimum annealed surface varied between 75% of that of virgin glass, at the visible light wavelength of 400 nm and 90% at 800 nm. The unique combination of the above-mentioned desired properties of the fabricated surface, makes them a promising candidate for outdoor self-cleaning applications even under harsh environmental conditions.

Micro abrasion-corrosion of ferritic stainless steels

The synergistic effect between abrasion and corrosion has been widely investigated and debated, where according to some works this synergy accentuates wear, and for others attenuates it. Despite the considerable effort to understand the synergy between abrasion and corrosion, little progress has been made to understand this phenomenon for ferritic stainless steels. This paper analyses the micro abrasion-corrosion performance of ferritic stainless steel with different chemical compositions (11%wt Cr with and without Ti stabilization; 16%wt Cr with and without Nb stabilization) and, for comparative purposes, austenitic stainless steel (18%wt Cr − 8%wt Ni) and carbon steel (0.2%wt C). The specimens were tested for corrosion (turbulent and aerated environment), micro abrasion and micro abrasion-corrosion. For the corrosion tests, a 1N H2SO4 solution was used, a 10%wt mixture of SiO2 in distilled water for the micro abrasion tests, and an abrasive-corrosive environment of 10%wt SiO2 in 1N H2SO4 for the micro abrasion-corrosion tests. In the micro abrasive wear tests there was not a clear trend between the different materials tested, despite differences in their chemical composition, mechanical properties and microstructure. On the other hand, their performance was ruled by their chemical composition, in particular the Chromium content, under abrasion-corrosion conditions. This indicated the predominant role played by corrosion in abrasive-corrosive environments in this particular tribo-system. For all materials tested, micro abrasion wear coefficients were higher (4×) than those measured under abrasion-corrosion conditions. Friction coefficients could also be measured by a 3D load cell strategically positioned in the specially developed micro abrasion-corrosion device, showing a strong reduction (2×) in friction coefficient under abrasion-corrosion conditions when compared with solely abrasion conditions. This was attributed to the formation of a corrosion product, mainly constituted of iron sulphate (identified via FTIR), which has lubricant properties.

TiO<sub>2</sub>-SiO<sub>2</sub> Gel Photocatalytic Degradation of Methylene Blue and Composite Energy Gap Calculation

The objectives of this study were to mix TiO2 and SiO2 gel for photo catalyzing in methylene blue and calculated energy gap of TiO2- SiO2 gel composite. Nanoparticles of TiO2-doped SiO2 gels have been synthesized for use as composites in photodegradation of methylene blue. SiO2 gel was synthesized by a sol-gel method from rice husk ash. TiO2 was synthesized by microwave method from TiOSO4. The composite of TiO2-SiO2 was prepared by mixing of 25% wt TiO2 and 75% wt SiO2 gel and SiO2 gel bead. This work can be dived into two kinds of TiO­2 sources were TiO2 from microwave synthesis (MW) and TiO2 from P25. The UV absorption values of methylene blue after used TiO2-SiO2 composite were measured. Wavelengths of composites were measured by Uv-vis reflectometer and energy gap were calculated.

Causes of compositional diversity in a lobe of the Half Dome granodiorite, Tuolumne Batholith, Central Sierra Nevada, California

ABSTRACTThe causes of compositional diversity in the Tuolumne Batholith, whether source heterogeneity, magma mixing, or fractional crystallisation, is a matter of longstanding debate. This paper presents data from detailed mapping and a microstructural and major element, trace element and isotopic study of an elongate lobe of the Half Dome granodiorite that protrudes from the southern end of the batholith. The lobe is normally zoned from quartz diorite along the outer margin to high-silica leucogranite in the core. Contacts are steep and gradational, except for the central leucogranite contact, which is locally sharp: magmatic fabrics overprint contacts. A striking feature of the lobe is the 18 wt SiO2 range comparable to that observed for the entire Tuolumne Batholith. Feldspar-compatible elements (Sr and Ba) decrease towards the centre, while Rb increases. Light and middle REEs show a smooth decrease towards the centre of the lobe. Calculated initial isotopic ratios of 87Sr/86Sr(i) and εNd(t) have identical values within error across the lobe, except in the central leucogranite, the most silica rich phase, which shows a slightly more crustal signature. Field, structural, geochemical and isotopic data suggest that fractionation was the dominant process causing compositional variation in this lobe. It is envisioned that this fractionation/crystal sorting occurred in a vertically flowing and evolving magma column with the present map pattern representing a cross-section of this column. Thus the areal extent of the lobe represents a minimum size of interconnected melt at the emplacement level of the Tuolumne Batholith and, given its marginal position, limited width and proximity to colder host rocks, implies that fractionation in larger chambers likely occurred in the main Tuolumne Batholith magma chamber(s).

Effects of basicity and FeO concentration on the retention of 137Cs and 60Co in slag made from non-metallic radioactive wastes

Summary Simulated non-metallic wastes containing 60Co, 137Cs and 152Eu were melted to examine the effects of basicity and FeO concentration on the retention of the radioactive nuclides in a resulting solidified product (Al2O3-CaO-FeO-SiO2 quaternary slag). The retention of 60Co was almost independent of chemical composition of slag. On the other hand, the retention of 137Cs decreased with an increase of the basicity of slag, defined as a ratio of CaO to SiO2 in wt. independent of FeO concentration. Energy dispersive X-ray fluorescence spectroscopic analysis and Mössbauer spectroscopic measurement were also conducted for the solidified product. Mössbauer spectra indicated that Fe2+ ions as well as Ca2+ ions existed as network modifying cations in a silicate network structure of slag. Referring to a structure model of silicate glasses, it is inferred that the retention of 137Cs reflects differences in chemical properties between Ca2+ and Fe2+ in the internetwork region formed by modifying cations and anionic non-bridging oxygen.

Properties of Y<sub>2</sub>O<sub>3</sub>-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> Glasses as a Model System of Grain Boundary Phase of Si<sub>3</sub>N<sub>4</sub> Ceramics (Part 1)

Glasses in the system Y2O3-Al2O3-SiO2 were employed as a model of grain boundary phase of Si3N4-Y2O3/Al2O3 ceramics and examined their physical properties and structure by means of IR spectroscopy. The glass compositions studied were xY2O3⋅(60-x) Al2O3⋅40 SiO2 in wt%, where x=30, 40 and 45. It was found that the substitution of Y2O3 for Al2O3 increases the density, glass transition temperature, elastic constants and Vickers hardness, but decreases fracture toughness. These results were explained from a proposed structure that Y3+ ions act as network modifiers in contrast to Al3+ ions which are supposed to be a network former. On the basis of measurements of the properties of the glasses, some properties of Si3N4-Y2O3/Al2O3 ceramics were discussed. The Vickers hardness of Si3N4-Y2O3/Al2O3 ceramics had similar dependence on Y2O3/Al2O3 molar ratio with that of the model glasses. The flexural strength of the ceramics was related to the microstruc ture, more specifically to the aspect ratio of the Si3N4 grains and phase composition, rather than that of grain boundary phase.

導電性固体材料とガラス融液との反応に関する研究 Ｖ 金属とケイ酸塩ガラス融液との分極下における反応について Ｗ，Ｃｒ，Ｆｅ，ＳＵＳ３０４およびＩｎｃｏｎｅｌ ６００

In the previous paper, the electrochemical phenomena of Ni and Mo in a molten silicate glass of the composition 16 Na2O·12 CaO·72 SiO2 in wt% were investigated. In this paper, W, Cr, Fe, SUS 304 and Inconel 600 were chosen as the objects to be measured. Anodic dissolution, passivation and cathodic deposition for these metals were investigated by linear potential sweep voltammetry at various potential sweep rates (5-0.05V/sec) with platinum reference and auxiliary electrodes in Ar gas atmosphere or in air. Moreover, the metal-glass interface after polarization was analysed by EPMA.On cathodic potential sweep of every metal investigated here, silicate anions were easily reduced to silicon element and a kind of silicide layer covered the electrode surface. Since the silicide has high electrical resistance, its formation made the measurement of voltammogram difficult at slower sweep rates.The anodic voltammogram of W at 3V/sec showed a large current peak around 1.7V (relative to Pt reference). The peak potential shifted to more cathodic direction with decreasing sweep rate. The current peak was attributed to the formation of a passsive layer on the W electrode. The occurrence of tungsten oxide layer with 30μm thick on the W electrode was confirmed by EPMA. The oxide layer seemed to be made up by WO3. The broad current peak was observed on anodic voltammogram of Cr due to the formation of chromium oxide Cr2O3. There was no peak on the anodic current-potential curve for the Fe electrode and Fe dissolved rapidly and easily. Both SUS 304 and Inconel 600 were subject to passivation by oxide film formation of Cr2O3 and NiO on anodic polarization.

Volatilization Loss of Sodium Borosilicate Ternary Glasses

Volatilization of glass components and formation of inhomogeneity in a glass melt during heating often result in striae, devitrification or fracture of the final glass products. Borosilicate glasses were known of their relatively high volatility at the temperatures of melting.Volatilization loss at 1410°C was measured by thermo-balance method on the ternary Na2O-B2O3-SiO2 glasses in the composition range of 0-40 Na2O, 0-40 B2O3 and 60-85 SiO2 in wt%. The glass batches were prepared using purified sand and reagent grade chemicals and were melted in a platinum crucible in electric or gas-fired furnace. For the weight loss measurements, the glasses were held in small platinum crucible suspended in a vertical electric furnace. Results were as follows:1) The amont of volatilization loss in a fixed time (for example, 1 or 6hr) and with fixed Na2O/B2O3 ratio decreased with increase of the SiO2 content, and for the constant SiO2 content the loss had its maximum at Na2O/B2O3 ratio slightly lower than 1. At these maxima, the losses were far greater than those of the corresponding Na2O- or B2O3-SiO2 binary glasses.2) In almost all the glasses, the loss increased linearly with time. at the initial periods of heating. Generally, however, volatilization rates decreased with time.3) Especially in glasses containing larger than 75wt% SiO2, crystallized surface layeres were formed in the course of the measurement, and in consequence, the volatilization rates decreased distinctly.4) Under the condition of the measurements, thermal convection was observed in the crucible. Contrary to the case of glasses with relatively high SiO2 contents, in glasses with low SiO2 contents thermal convection took place distinctly that the considerable mixing phenomenon was observed in the glass melts.5) One of the possible mechanisms which explain the results described in 1) and 2) is given in the following: At the initial periods of heating, volatilization rate is controlled by the evaporation of the volatile components from the melt to the atmosphere or by the flowing away of the gas atmosphere near the surface of the melt. Then, diffusion controlled mechanism or the effect of the lowering of the concentration of the volatile components in the melt gradually predominates, and lowers the volatilization rate.6) Quatitatively, the relation between composition an volatilization loss showed a good agreement with the results of kolykov measuring at 1200°C (ref. 5). Quantitatively, however, the loss was 10-100 times larger than those by kolykov owing to the differences of the mesuring temperatures. Under the assumption that the initial volatilization rate is proportionate to the vapour pressure of glasses, it could be inferred that phase separation in the glass melts occur in the composition range with relatively low Na2O contents.