Percentage Of SiO2 Research Articles

Chemical and technological characterization and beneficiation of Jezza sand (North West of Tunisia): Potentialities of use in industrial fields

This work aims to study natural deposit sand formed at Miocene–Pliocene age from Jezza area in North West of Tunisia. This sand contained high percentage of silica, low percentages of carbonate and traces of clay minerals. The chemical analysis showed that the percentage of SiO2 was almost constant reaching a value of 98wt.%, the percentage of iron oxide was 0.17wt.% and that of Aluminum oxide was 0.32wt.%. The mineralogical analysis revealed that these sands contained more than 95wt.% of quartz. The calcite and phyllosilicates were the minor detected phases. The grain size analysis showed that sand samples varied between poorly graded and well graded sand with a 70wt.% of useful fraction. The morphological tests showed a dominance of siliceous grains with a shape varying from angular to well rounded grains. The specific gravity average was 2.63g/cm3. The sand equivalent value was 83wt.% against a specific surface area ranging from 8.37m2/g to 20.93m2/g due to the presence of impurities. The sand treatment by attrition process indicated an exponential increase of the SiO2 content, unlike to the significant decrease of iron oxide (38wt.%) and aluminum oxide (14wt.%). The sand of Jezza can be used in various industrial fields, such as glass, foundry, ceramics, and concrete according to different analysis.

Improvement, characterization and use of waste corn cob ash in cement-based materials

This work investigates the development of waste corn cob ash as supplementary cement replacement materials. The study focused on the effects of heat treatment on chemical composition, physical properties and engineering properties of corn cob ash. The results suggest corn cob ash that was heat treated at 600°C for 4 h shows percentage of SiO2 + Al2O3 + Fe2O3 around 72%, which can be classified as Class N calcined natural pozzolan, as prescribed by ASTM C618. The X-ray diffraction patterns indicated that the amorphous silica phase increased with increasing calcining temperatures. The water requirement, initial setting time and final setting time of specimens increased with increasing replacement percentage of raw or treated corn cob ash. The morta cubes which used 20% of treated corn cob ash replaced cement showed 103% of the 28 days compressive strength as compared to reference samples. The corn cob ash that was treated at 600°C for 4 h samples shows slightly higher effectiveness for improving the splitting tensile strength and compressive strength of concrete when compared to the untreated corn cob ash.

Glass ceramic sealants belonging to BAS (BaO–Al2O3–SiO2) ternary system modified with B2O3 addition: A different approach to access the SOFC seal issue

Four compositions in the BaO–Al2O3–SiO2 system modified with B2O3 were investigated with regard to their use as glassy seals in anode supported SOFC or iT-SOFC. The glassy system studied contains varying percentages of SiO2, Al2O3, B2O3, and high content of BaO as modifier (67–74%-wt). Their glass transition (Tg) and maximum densification point lies between 630 and 680°C, and 734°C to 828°C, respectively. The viscosities of the four glasses are situated between 107 to 109.5 Pa.s, in the sealing range (730–830°C). Heat treatment at 850°C, revealed crystalline phases identified as BaAl2Si2O8 (hexacelsian) and BaSiO3. The thermal expansion coefficient (TEC) of the obtained glasses (8.8–10.5ppm/K) was comparable to zirconia (YSZ) electrolyte, and shows chemical compatibility and high characteristic bond strength (up to 33±7MPa). The compositions with higher BaO content in the system studied seem to be good candidates for iT-SOFC sealant application.

Composition of individual ferrospheres of different morphological types

We have studied the composition of three types of individual spheres differing in microstructure (single-block, platelike, and skeletal–dendritic spheres) in the–40 + 32 μm size fraction of ferrospheres containing 92.72 wt % FeO. The results demonstrate that the single-block spheres have the highest Fe content (95–97% FeO), a basicity factor Mb > 48, and an Fe/O atomic ratio of 0.68–0.71. They consist of block individuals of a partially martitized (oxidized to hematite) spinel ferrite. The platelike spheres feature high calcium content (11–12% CaO); lower basicity factor, Mb ≃ 20–21; and a higher degree of oxidation of Fe, with an Fe/O atomic ratio of 0.63–0.66. They consist of spinel ferrite blocks with large percentages of FeO (up to 90%) and MgO (up to 6%), surrounded by regions with a platelike structure, reduced FeO content (down to 57%), and high CaO content (up to 34%). The skeletal–dendritic spheres feature increased percentages of SiO2 (≃ 4.7 %) and Al2O3 (3.6–4.6%) and low basicity factor: Mb ≃ 10–11. They consist of unidirectional or branched crystalline spinel ferrite individuals with partial Mg2+ substitution for Fe2+, which prevents oxidation of the spinel to hematite, as evidenced by the large Fe/O atomic ratio: 0.72–0.73.

Assessment of Air Particulate Pollution in New Badoosh Cement Factory/ Iraq

In this research, measurements of total (TSP) and fine suspended particulate PM1, PM2.5, PM7 and PM10atBadoosh cement factory were carried out. Seventeen locations inside the factory are selected. The effect on soil around the cement factory was also studied by collecting samples in the four directions North, South, East and West to a distance of five kilometers from the factory with one kilometer spacing. The result of the study revealed that;the concentration of very fine suspended particulate PM2.5 was over the international standard limits at different locations of the factory and the overall average concentration for the factory was (47 g/m3). For PM10 suspended particulates, the results at all locations were over the international limits and the overall average concentration reached 869 g/m3, which was much more than the standards of 150 g/m3. On the other hand, the total suspended particulate concentration exceed the standard at several locations in the factory. Significant correlations were found among the suspended particulate concentrations according to their size.The results of soil test around the cement factory showed significant differences of oxides percentages among the directions. Higher percentages were recorded in the South and East directionsthan North-West direction. The results also revealed that the percentages of SiO2 and Al2O3 were 40.94% and 10.53% in the east direction whereas higher percentage for Fe2O3 (4.86%), CaO (36.81%), MgO (4.49%),and SO3(0.76%) were recorded in the south direction of factory.

Preparation of Zeolite MCM-22 Using the Rice Husk Ash as Silica Source

Brazil is a great producer of rice generating large amounts of husks after rice processing. These hulls contain high percentage of SiO2, and a great potential as raw material for the development of silica based materials, as zeolites. Thus, this work aims to use the silica of rice hulls as an alternative raw material for the production of zeolite MCM-22. This material was characterized through X-ray diffraction, X-ray spectrophotometry and physical adsorption of N2 (BET). The diffraction pattern of precursor MCM-22 presented typical peaks of topology MWW. Calcined sample did not presented peaks related with the organic material used in of the zeolite MCM-22, indicating that the thermal treatment was efficient for organic removal. It was confirmed, through the EDX, that the synthesized materials present high amount of SiO2 and low quantity of Al2O3. The BET isotherms indicated that the materials presented structures with microporous, concluding that the alternative silica was promisingly for the development of zeolites.

A Phase Change Storage Material that May be Used in the Fire Resistance of Building Structure

This study prepared polyethylene glycol/silicon dioxide composite, a kind of form-stable phase change material. The composites can be made into mortar which is able to adhere to the surface of building structure and absorb the fire heat. This paper aims to study the effect of the composites on the fire resistance of building structure. Scanning electronic microscope and differential scanning calorimeter were adopted to investigate the structural and thermal properties of the composites. It was found that the polyethylene glycol was well dispersed into the network of solid SiO2. And the latent heat of PEG/SiO2 increased with the decrease of SiO2 content. The required weight percentage of SiO2 was found to be 15% at least if the composites remain solid without leakage. It was also found that a phase change of pure PEG6000 happened with an enthalpy of 158J/g while the 80 wt% PEG composite is 133J/g. In conclusion, the phase change storage material may be used for fire resistance of building structure.

Study of an intermediate temperature solid oxide fuel cell sealing glass system

This study investigates the effect of composition on the atomic level structure and thermal characteristics of sealing glass for solid oxide fuel cells (SOFCs). The glass systems studied contain varying percentages of SiO2, Al2O3, SrO, La2O3, and B2O3; and the composition variables examined are SrO and B2O3. Atomic level parameters, including boron coordination number with silicon, the probability of boron coordination with silicon, and glass network connectivity are calculated. Thermal expansion coefficients, glass softening temperatures, and glass transition temperatures are measured by dilatometry. The glasses are then thermally treated at 700 °C for up to 1500 h in order to study their long term thermal stability at SOFC operating conditions. The resulting data show that the most desired glass composition is stable for at least 1500 h without devitrification and is a very promising sealant for solid oxide fuel cells.

Influence of Varying SiO2 % on the Mechanical Properties of Al Based MMC

The current investigation is focused on effective utilization of rice husk ash (RHA) SiO2—an industrial waste available in abundance, by systematically dispersing into an Al–Mg (0.5, 1.0, 2.5, and 5.0 % by weight) matrix resulting in synthesis of composites via Liquid Metallurgy route. The effect of increasing Mg % to improve the wettability with the increase in SiO2 % as reinforcement was studied comparatively. The increase in the percentage of SiO2 beyond 5 % as reinforcement into Al–Mg alloy increases the agglomeration of SiO2 particles which creates more sites for crack initiation and hence lowers down the load bearing capacity of the composite while microhardenss and wear testing analysis. For the composite, Al–Mg (2.5 %)–SiO2 (5.0 %) the hardness was observed to be maximum corresponding to minimum wear loss. The uniform distribution of maximum amount of hard spinel structure of extremely small size within the matrix confirms maximum wetting characteristic of 2.5 wt% Mg.

Determination of Silica Activity Index and XRD, SEM and EDS Studies of Amorphous SiO2 Extracted from Rice Husk Ash

Rice husk ash (RHA) contains 20% SiO2 in hydrated amorphous form (Si–OH). On thermal treatment, the SiO2 converts to cristobalite, the crystalline form which is not reactive. However under controlled conditions, amorphous SiO2 with high reactivity is produced. Therefore rice husk has been one of the useful bio-mass. The silica activity index was determined to be equal to 97.73 which was used to determine the percentage of amorphous SiO2 in RHA. The values of the soluble fraction and silica activity index were also stated. Comparative study of amorphous and crystalline SiO2 done by X-ray diffraction revealed the total amorphous nature of SiO2. The scanning electron microscopy (SEM) images displayed the comparative morphological features of the rice husk and RHA. The energy dispersive spectroscopy analysis of rice husk was done to determine the presence of SiO2 on the upper portion of rice husk and to determine the percentage of SiO2 in RHA. The SiO2 particles in an agglomerated form was found to be of micron size when observed under SEM.

Geology, mineralogy, and chemistry of the M’zila bentonitic clay deposit (Mostaganem, NW Algeria)

Bentonitic clay deposit of M’zila locates in the North border of the upstream portion of the Chelif basin “Bas Chelif” down to 35 km NE of Mostaganem. It consists of 14 layers (most recent) 1 to 14 (oldest) forming the North and South flanks of an E–W Syncline. These layers are enclosed in the median blue marls formation of the Upper Miocene of the “Bas Chelif” basin lying unconformably on the ante thrust sheet sandstone formation. This median member contains metric cinerites thick continuous levels and could beings originally bentonitic clay region of M’zila. The cinerites are the product of explosive type in the volcanic eruption, usually deposited in the marine environment. They are formed by a more or less rich feldspar and biotite volcanic glass dust. Bentonitic clay layers have average thicknesses vary between 2 and 6 m. They are distributed by centimeter to decimeter levels of soft sandstone, sandy, and rich black mica. Sandstone is greywacke clay and carbonated cemented, matrix consisting of quartz, feldspars, biotite as major minerals, zircon, and glauconite as accessory minerals. They deposited in a marine, reduced, and confined environment. Mineralogical composition of bentonitic clay region of M’zila is as follows: (1) Clay minerals are represented by the montmorillonite with a small amount of kaolinite. (2) Non-clay minerals are composed mainly of quartz, albite, biotite, calcite, heulandite, chlorite, dolomite, and gypsum. Infrared spectroscopy shows that bentonitic clay has highlighted the presence of the disorderly a high temperature silica tridymite. Geochemistry of the major elements of M’zila bentonitic clay shows high a percentage of SiO2 and Al2O3. Chemical analysis shows that the 10, 12, 14 B 7, 4 A, and 4 clay layers are ferric clay; 11 and 3 layers are magnesian clay. Particle size analysis by sedimentation shows bentonitic clays are accrued mainly clay fractions to silt. Bentonitic clay deposit of M’zila has probably volcanic origin and deposited in a marine, reduced, and confined environment.

Analytical Investigations of Disintegrated Granite Surface from the Un-finished Obelisk in Aswan

The deterioration of natural stone monuments is subject to different external reasons that take place through different weathering factors, in addition to other several factors concerning the stone itself “internal reasons” mainly pore structure and permeability index. All of these factors lead to the formation of altered surface layers, then damaging the original stone components. Here, red weathering, one of the most aggressive deterioration forms affecting one of the most famous archaeological sites in the world (Un-finished Obelisk in Aswan) was investigated and evaluated through different analytical techniques. Binuclear Microscop and SEM were used to evaluate the optical and morphological features of the highly deteriorated samples. Moreover EDX and XRD techniques were used for defining the chemical and mineralogical compositions of collected samples. Lastly, ArcGIS program was used as a tool for simulation description of red weathering symptom to evaluate their aggressive roles in the deterioration processes affecting the object. Our results proved that there are some changes in the granite regarding essential elements with high percentages of SiO2, Al2O3 and Fe2O3 especially in affected zones. In addition, increasing the weathering products, such as, microcrystalline matrix and salty products (tosudite, kaolinite, illite and gypsum) defined and calculated both in affected and none affected areas. Finally, calculation of the etching volume of sample and corroded percentages were conducted.

Wetting and in vitro bioactivity of laser processed CaP coating with presence and variation of SiO2 on Ti–6Al–4V

Calcium phosphate bioceramic and SiO2–CaP bioceramic composite coatings were prepared on Ti–6Al–4V substrates by laser cladding method. Surface energy components were calculated and the wettability of the coatings in simulated body fluid (SBF) was investigated. In vitro bioactivity of the coatings were performed by immersing in SBF and analysed for the precipitation of hydroxyapatite (HA). The effects of SiO2 content on the wettability and in vitro bioactivity of the bioceramic composite coatings were investigated. The surface energy values increased as the percentage of SiO2 in the coating precursor increased, resulting in decrease in contact angle with SBF for improved wettability. X-ray diffraction results indicated that after immersion in SBF for more than three days, 17 wt-%SiO2–CaP and 25 wt-%SiO2–CaP samples possessed highly intense peaks of HA than 100 wt-%CaP sample. Furthermore, in vitro bioactivity assays show that the SiO2–CaP bioceramic composite coatings possess a higher HA precipitation rate than CaP coating and Ti–6Al–4V control.

Melting Characteristics and Wettability of Binding Phase in Sinter

The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing n CaO: n Fe 2O 3 (molar ratio of CaO to Fe 2O 3) as well as the percentage of MgO, SiO 2, and A1 2O 3, the melting characteristics and wettability of the binding phase were discussed. The results indicated that the characteristic melting temperature was the lowest and wettability was the best at n CaO: n Fe 2O 3 = 1:1 (without addition); the addition of MgO increased the characteristic melting temperature and contact angles; when the percentage of SiO 2 or AI 2O 3 was 3%, the characteristic melting temperature was the lowest, whereas the contact angles increased with an increase in SiO 2 and A1 2O 3 contents.

CMP Friction as a Function of Slurry Silica Nanoparticle Concentration and Diameter

Chemical mechanical polishing (CMP) is vital in the manufacturing of integrated circuits (IC). CMP removes unwanted material from an IC surface by rubbing it with numerous nanoscale abrasives that are brought into contact by polishing pad asperities. Friction is a consequence of this rubbing, and this friction may damage the next generation of porous IC dielectric materials with lower dielectric constants (low k). Fundamental experiments were done to understand the source of the friction to enable less damaging CMP. The coefficient of friction of an SiO 2 substrate on a polyurethane CMP pad was measured as a function of the slurry's SiO 2 abrasive particle concentration and size with a commercial pin on disk tribometer. Very low speeds (∼10− 3 m/s) were used to remove confounding hydrodynamic effects. The coefficient of friction increased by 10% with higher weight percentages of SiO 2 particles in the slurry, suggesting that a constant real area of contact is distributed between bare pad asperity contacts and higher friction SiO 2 particle contacts. The coefficient of friction also increased for the smallest slurry SiO 2 particle size. These results suggested possible routes for controlling CMP friction by controlling slurry particle size and concentration as well as the pad material.

Synthesis and Characterization of Hyperbranched Polyurethane Hybrids Using Tetraethoxysilane (TEOS) As Cross-Linker

Organic−inorganic hybrid coatings were derived from a hydroxyl-terminated hyperbranched polyester, 3-isocyanatopropyl triethoxysilane (ISPTES), and then cross-linked with various percentages of SiO2. This system was able to cross-link by hydrolysis of a tetraethoxysilane group in room temperature and humid conditions and then at 120 °C for 12−14 h, forming a three-dimensional hybrid structure, where the organic and inorganic phases were bonded covalently. The main focus of this work was to study the change of properties of the coating with SiO2 modification. These hybrid coatings were also characterized by using NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dynamical mechanical thermal analyzer (DMTA), thermal analysis (TGA), and tensile strength.

Depth profiles and concentration percentages of SiO2 and SiO x induced by ion bombardment of a silicon (100) target

Very thin-film of silicone oxide is of importance in many microelectronics device fabrication. A 9 keV Ar+ beam was applied to bombard a silicon (100) target ambient oxygen gas. The measurement was performed with a fixed time of bombardment but different oxygen pressure, beam intensity and temperature. An X-ray Photoelectron Spectroscopy (XPS) was employed to analyze the depth profiles and the concentration percentages of SiO2 and SiOx within the bombarded Si (100) samples. The percentage of SiO2 in different depth of the sample is found to be proportional to the oxygen pressure. The thickness of SiO2 film formed at room temperature is larger than the thickness at temperature 650 °C. The net percentages of SiOx, except at the top layer of the surface, are varied in a small difference among different ion-bombardment conditions as the depth below 2 nm.

Anomalous Hall effect and magnetoresistance of (FexSn1−x)1−y(SiO2)y films

Structural, magnetic and transport properties were investigated for heterogeneous (FexSn1−x)1−y(SiO2)y films deposited on oxidized silicon substrates at room temperature with RF magnetron sputtering. X-ray diffraction indicated that the films consist of a nanocrystalline phase of FeSn2 embedded into an amorphous background. For (FexSn1−x)92.33(SiO2)7.67, it was demonstrated that with the increase in the Fe component an evolution from negative isotropic magnetoresistance (MR) behaviour to one with a mixture of anisotropic magnetoresistance and isotropic negative MR occurs. On fixing the SiO2 percentage and decreasing the Fe–Sn ratio, the negative transverse MR first increases and then decreases. For samples having a fixed Fe–Sn ratio, the negative transverse MR increases with the increase in SiO2. Compared with the Fe–Sn system, the addition of 7.67 at.% SiO2 enhances the saturated Hall resistivity. Further increase in SiO2 introduces a complicated saturated Hall resistivity dependence on the concentration of SiO2.

Optical properties of porous silicon

We have measured the absorption spectra and the dispersion of refractive index for porous silicon samples with different porosities in the energy range 1.5–3.5 eV at room temperatures. The experimental data are compared with the dependences calculated by using Bruggeman’s theory for the dielectric constant of a multicomponent system composed of crystal silicon, SiO2, amorphous silicon, and voids (pores). The best agreement between the experimental and theoretical dependences is achieved for a significant percentage of SiO2 in the porous silicon samples.

Ash composition of the main Albanian coals

Coal ashes from 17 mines were analysed in terms of ash yield and percentages of SiO 2, Al 2O 3, Fe 2O 3, CaO, MgO, K 2O, Na 2O, TiO 2, P 2O 5, MnO, NiO. The composition has been analysed in terms of: (1) contribution to ash contents; (2) acidic, amphoteric and basic oxides; (3) co-ordination number in solid state; (4) fluxing components; (5) cement-constituting minerals; (6) periodical table. Significant correlations were observed on expressing the percentage in mol% or ion% and not in wt%. The decrease in basic oxides was associated with an increase in acidic ones.