Amorphous Silica Powder Research Articles

Silica extraction from sodium silicate for wollastonite synthesis at low temperatures

In this study, ceramic wollastonite was prepared at low temperatures by using amorphous silica and calcium oxide powders. The amorphous silica was extracted from sodium silicate, while calcium oxide (CaO) was obtained through the calcination of calcium carbonate (CaCO3) particles. The effect of reaction temperature on the formation of wollastonite was systematically investigated. The synthesized powders were analyzed using various characterization techniques, including X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results indicate that the synthesized silica nanopowders exhibit a notable surface area, with specific surface area (SSA) values reaching 148 m²/g for samples subjected to calcination at 600°C. Furthermore, based on XRD and differential scanning calorimetry (DSC) analyses, it is evident that β-CaSiO3 forms at approximately 780°C and subsequently undergoes complete transformation into α-CaSiO3 at 1200°C. Notably, this study underscores that the utilization of amorphous silica expedites wollastonite formation at lower temperatures compared to those reported in existing literature.

SYNTHESIS AND CHARACTERIZATION OF NANOSILICA (SiO2) VOLCANIC ROCK OF MOUNT BATUR IN BALI

This research was conducted to synthesize and characterize silica minerals (SiO2) from volcanic rocks in the active volcano in Bali, namely Mount Batur. The synthesis carried out on five different color variants of this rock sample is by the coprecipitation method which begins with the process of taking rock samples on Mount Batur, crushing the rock until it becomes powder with a size of 100 mesh, washing with distilled water and drying, immersing the rock powder in the solution. 2 M HCl for 12 hours, then the results of the soaking were reacted again with 7 M NaOH solution as a hydrolysis process to obtain pure SiO2 in the sample. In the form of sodium silicate precursor (Na2SiO3), the sample was titrated with a 2 M HCl solution to obtain silica gel which was then washed and dried until amorphous silica powder was produced. The results of the XRF analysis showed that the SiO2 mineral content in the sample after going through the synthesis process was 94.9% and the Si element was 89.9%. The XRD characterization results show that the phase formed from the sample has a quartz structure with the highest peak at an angle of 2θ = 23.07o, then decreases and levels out at an angle of 2θ = 32.94o which is characteristic of an amorphous structure and with a silica grain size of 8.47 nm – 8.65 nm.

Insecticidal activity of two amorphous silica powders applied to concrete surfaces against the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

The increased demand for residue-free food grains has led to exploring diatomaceous earth formulations as potential alternatives to synthetic insecticides. In the present study, we evaluated the efficacy of two amorphous silica powders 1 and 2 with different elemental composition, particle diameter, and shape characteristics against the confused flour beetle, Tribolium confusum Jacquelin du Val. The insecticidal activity of the two silica powders was determined by exposing T. confusum adults to silica powder treated concrete arenas at different application rates (0, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 g/m2) for 12, 24, 36, and 48 h. Mortality assessments were made after 14 d, and adult progeny counts were made at 42 d. Silica powder 2 demonstrated greater efficacy and produced 100% adult mortality and completely inhibited adult progeny production when adults were exposed for 24 h to an application rate of 4.0 g/m2. Complete mortality and complete suppression of adult progeny production was noticed after 36 h exposure to 3.5 g/m2 of silica powder 1. Exposure of T. confusum adults to 6 g/m2 of silica powder 1 and 4 g/m2 of silica powder 2 gave complete mortality after 24 and 20 h, respectively. No adult progeny production was observed when adults were exposed for 24 h to 6 g/m2 and 4 g/m2 of silica powder 1 and silica powder 2, respectively. These findings suggest that the two silica powders hold promise for managing T. confusum, particularly in treating empty bin floors before storing new grains.

Efficacy of two amorphous silica powders applied to soft red winter wheat against the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The increased demand for residue-free grains and development of insect resistance to insecticides has led to a surge in the utilization of diatomaceous earths as grain protectants. Diatomaceous earth formulations, effective at lower application rates, are crucial for managing stored product insects without compromising grain quality. In this study, the efficacy of two different amorphous silica powders applied to soft red winter wheat was tested against the lesser grain borer, Rhyzopertha dominica (F.). Twenty adults of R. dominica were exposed to 100 g of organic soft red winter wheat admixed with varying application rates (0 for the untreated control, 0.05, 0.1, 0.15, and 0.20 g/kg) of silica powders 1 and 2. Mortality assessments were made after 14 d of exposure, and data on adult progeny production, insect-damaged kernels, and grain weight loss were determined at 42 d. Exposing R. dominica adults to wheat treated with 0.20 g/kg of silica powder 1 resulted in a mean ± SE of 94.5 ± 5.5% mortality and 1.3 ± 1.3 adult progeny production. Insect-damaged kernels and grain weight loss caused by R. dominica exposed to 0.20 g/kg of silica powder 1 were 0.19 ± 0.19 and 0.1 ± 0.1%, respectively. Exposure of R. dominica adults exposed to wheat mixed with 0.20 g/kg of silica powder 2 resulted in complete mortality, with no observed adult progeny production, insect-damaged kernels, or grain weight loss. Overall, silica powder 2 exhibited greater efficacy than silica powder 1, and this superior performance can be attributed to its higher oil adsorption capability and low pH (<8.5) value.

Insecticidal efficacy of two candidate diatomaceous earth powders against the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The insecticidal efficacy of amorphous silica powders 1 and 2 with different physical and elemental compositions were evaluated against the lesser grain borer, Rhyzopertha dominica (F.) using concrete arenas. The particle diameter and shape characterization (circularity, elongation, aspect ratio, and convexity) of the two silica powders were performed using Morphology G3 instrument. The particle diameter and shape characteristics (circularity and elongation) of silica powder 1 were significantly higher compared to silica powder 2. However, these factors did not influence the efficacy of silica powders against R. dominica. Silica powder 2 showed higher mortality at lower application rates and shorter exposure times compared to silica powder 1. The efficacy of silica powder 2 was due to its higher oil adsorption capability, low pH, and high silicon dioxide content compared to silica powder 1. Adult progeny production was inversely related to the powder application rate. Silica powder 2 was more effective on R. dominica in inhibiting adult progeny production at 0.25 g/m2. Lower percentages of insect-damaged kernels and grain weight loss were observed at lower application rates (0.10–0.20 g/m2) following exposure to silica powder 2 compared to silica powder 1, which required higher application rates (2.0–3.5 g/m2). Overall, silica powder 2 demonstrated superior efficacy against R. dominica in terms of mortality, progeny production, insect-damaged kernels, and grain weight loss.

Contact Efficacy of Two Amorphous Silica Powders against the Red Flour Beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae).

The contact efficacy of two amorphous silica powders 1 and 2 procured from Imery's chemicals, Lompoc, CA, USA, were evaluated against the red flour beetle, Tribolium castaneum (Herbst). The efficacy of the silica two powders was evaluated by exposing 10 adults of T. castaneum to twelve different concentrations of silica powder 1 and 2 for 12, 24, 36, and 48 h. Mortality assessments were made after 14 d, and data on adult progeny production were recorded at 42 d. Complete mortality of T. castaneum was observed when adults were exposed for 36 h to concentrations of 1.5 to 5 g/m2 of silica powder 1. Conversely, in tests with silica powder 2, complete mortality was only achieved when adults were exposed for 48 h to concentrations ranging from 0.75 to 5 g/m2. Silica powder 1 exhibited greater efficacy in inhibiting adult progeny production in T. castaneum, particularly at a concentration of 2.0 g/m2 after 24 h exposure. Overall, silica powder 1 displayed superior performance in terms of adult mortality and the suppression of T. castaneum adult progeny production. This advantage can be attributed to the smaller particle size of silica powder 1 when compared to silica powder 2.

Efficacy of Olive Stones and Corncobs Crystalline Silica Nanoparticles (SiO2, NPs) Treatments on Potato Tuber Moths (Phthorimaea Operculella)

Morphological and microstructural properties of silica (SiO2) are essential factors that need to be considered during the experimental applications. In this report, SiO2 nanoparticles (NPs) have been prepared at different concentrations from SiO2 powder derived from olive stones and corncobs by an alkali leaching extraction method. Thermal treatment has been used to modify the morphological and microstructural properties of the extracted SiO2. X-ray diffraction (XRD) shows that the extracted amorphous SiO2 has been transformed into a crystalline phase after the thermal treatment. Nitrogen adsorption–desorption measurements revealed significant reduction in both the specific surface area (SABET) and the total pores volume (Vtotal) of the derived SiO2 samples after the thermal treatment. The acquired thermal treatment properties of SiO2 found to have high impacts on the influence of the SiO2 NPs on the survival and development of larvae and pupae of P. opercullela. SiO2 NPs prepared from the crystalline silica samples exhibited less efficiency on suppressing potato tuber moth comparing to SiO2 NPs of the amorphous silica powders. Varied effects on biological parameters including larvae mortality, pupae weight, larval and pupal development time, fecundity and fertility are also linked to the SiO2 NPs source type and showed concentration depending manner effects. SiO2 NPs are conditionally effective as an alternative pesticide against P. opercullela, based on their sources, mesoporous structures and concentrations.

Development of a preparation method of transparent soil-rock mixture for geotechnical laboratory modeling

This paper introduces a preparation method of a transparent soil-rock mixture (T-SRM) for geotechnical laboratory modeling. The T-SRM uses n-dodecane and white oil as the fluid phase, amorphous silica powder as the soil phase, and quartz glass particle as the rock block phase. The T-SRM sample prepared using the proposed method is of good transparency: the glass particles are “disappeared” under visible light, whereas their outlines are clearly evident when using a laser light sheet slicing the sample. A series of direct shear tests were carried out to investigate the mechanical behaviors of the T-SRM. It is found that the pre-consolidation pressure during preparation is of significant influence on the mechanical strength of T-SRMs, and by adjusting the value of pre-consolidation pressure, we can obtain T-SRM samples with different mechanical strengths. A trial test shows that, by controlling the rock content and block size close to that of natural SRM and adjusting the pre-consolidation pressure during the preparing process, the T-SRM sample with similar mechanical strength to that of natural SRM can then be obtained, which demonstrates the practicability of using the proposed material in the visualization of SRM in modeling tests.

Synthesis of synthetic amorphous silica powder from palm oil mill fly ash extract by carbon dioxide impregnation

Palm oil mill fly ash (POMFA) is rich in amorphous silica and can be extracted by sodium hydroxide solvent. This work aims to synthesize synthetic amorphous (SAS) powder silica that has mesoporous pores and a high specific surface area. The sol–gel precipitation process was applied by CO 2 impregnation and polyethylene glycol (PEG) 400 was used as the surfactant to obtain the synthetic silica powder from the extract. A temperature-controlled 1000 cm 3 glass precipitator equipped with a stirrer was used for the precipitation process. The extracted silica was mixed with PEG at pre-determine concentration, and 500 cm 3 of the mixed liquid was put in the precipitator and stirred at 1000 RPM. The carbon dioxide impregnated at a flow rate of 100 cm 3 min −1 to destabilize the silica extract. The study was done by using PEG-400 as a dispersant to improve the specific surface area of the obtained precipitated silica. The temperature, precipitation time, and the PEG concentration were varied to study their effect on SAS yield. The optimum SAS yield of 80.01% was obtained at a temperature of 70 °C, time of 90 min, and a PEG concentration of 5%. The characteristics of the SAS obtained are SSA of 198.55 m 2 g −1 , volume pore of 0.289 cm 3 g −1 , and pore diameter of 5.32 nm.

Catalysts by pyrolysis: Direct observation of chemical and morphological transformations leading to transition metal-nitrogen-carbon materials

Transition metal-nitrogen-carbon materials (M-N-C catalysts) are promising electrocatalysts in polymer electrolyte fuel cells (PEFCs) and electrolyzer applications. High temperature treatment in inert atmosphere (pyrolysis) is the essential, most common method for the synthesis of M-N-C catalysts and critical to achieve high electrocatalytic activity and electronic conductivity. To this day, despite many uses and successful implementations in materials manufacturing, pyrolysis has been an entirely empirical technology, with process control and optimization relying exclusively on “Edisonian” approach. The knowledge gap in the mechanism about how the precursor is being transformed into catalysts hinders further development of the M-N-C catalysts regardless of the precursor class and processing protocols. Herein, we probed the morphological evolution and chemical transformation of a nitrogen-containing charge transfer organic salt, mixed with transition metal (iron) salt and amorphous silica powder (precursor) during the pyrolysis process via a combination of in situ synchrotron and laboratory-based diagnostic techniques. The pyrolysis process is found to be divided into three stages. During a controlled temperature ramp, the selected organic N-C precursor (nicarbazin) began melting and decomposing just below 400 °C, forming a certain number of micrometer-scale pores and pathways. With increase in temperature from 400 °C to 900 °C, amorphous carbon domains started forming, and reduced (metallic) iron nanoclusters appeared, being dispersed uniformly throughout the carbonaceous matrix. When temperature advanced above 900 °C, graphitization of carbon commenced, associated with appearance and evolution of atomically dispersed metal-nitrogen moieties in the carbonaceous matrix. As the graphitization advanced further, a secondary process of agglomeration of metal nanoparticles occurred. Multi-analytical technique observations conducted here provide a base for rational design and optimization of M-N-C electrocatalysts via pyrolysis.

Toolbox for atomic layer deposition process development on high surface area powders.

Atomic layer deposition (ALD) is an industrially applied technique for thin film deposition. The vast majority of processes target flat substrates rather than powders. For ALD on powders, new processes are needed, as different reaction conditions are required. Here, two setups are described in detail, which enhance the ALD process development for powders. The first setup described is capable of directly measuring the vapor pressure of a given precursor by a capacitance diaphragm gauge. Promising precursors can be pre-selected, and suitable precursor saturation temperatures can be determined. The second setup consists of four parallel reactors with individual temperature zones to screen the optimal ALD temperature window in a time efficient way. Identifying the precursor saturation temperature beforehand and subsequently performing the first ALD half cycle in the parallel setup at four different reactor temperatures simultaneously will drastically reduce process development times. Validation of both setups is shown for the well-known ALD precursors, trimethylaluminum to deposit aluminum oxide and diethyl zinc to deposit zinc oxide, both on amorphous silica powder.

Infrared transparent mullite ceramics fabricated by solid-state reactive sintering

Infrared transparent mullite ceramics were fabricated by solid-state reactive sintering under vacuum without pressure. High purity α-alumina and amorphous silica (molar ratio, 63: 37) powders were used as raw materials. The densification process and mullitization process of the mixed powders were investigated and compared with the sintering of mullite powder. As the sintering temperature increased to 1400 °C, mullite formed and silica transformed into cristobalite. Cristobalite disappeared at 1600 °C and α-alumina did at 1650 °C. However, α-alumina precipitated when the temperature increased to 1750 °C. For the sintering of mullite powder, shrinkage happened at 1400 °C. While, shrinkage almost finished for the reactive sintering of alumina and silica. When reactive sintered at 1780 °C, the transmittance of the mullite ceramics was the highest, which was 65% at 4.1 μm. The method used in this work is promising for the preparation of large and complex shaped transparent mullite ceramics.

Effect of nano silica, silica fume and steel slag on concrete properties

Concrete is a common material utilized in the structure sector in huge amounts. This man-made construction material is utilized for the construction of bridges, buildings, roads, dams, etc. It has waste usage from structure to roads, drains pipes, etc.Engineers are continuously trying to improve the performance properties of concretes by incorporating supplementary material like blast furnace slag, fly ash, steel slag, silica fume, etc. This review paper is based on the findings of three such supplementary materials – nano-silica (NS), silica fume (SF), and steel slag (SS) which have been reinforced in concrete. However a thorough study of the use, to better understand its mechanism, of NS, SF and SS in concrete is missing. This paper, therefore, seeks to provide a study of the usage of concrete NS, SF, and SS. The Nano silica is comprised of a high purity amorphous silica powder which generally exists in a powdered form. Other materials that are discussed herein are SF and SG. SF is a by-product obtained while producing silicon metal and ferrosilicon alloys whereas SS is obtained when impurities are separated from molten metal in the steelmaking furnace. The main motivation behind this review paper is to gather the relevant papers in a single place so that a concrete mixture can be developed by reinforcing NS, SF, and SS in different percentages. From the results of previous studies, it can be inferred that the combined use of NS, SF, and SS increases certain properties of concrete, particularly mechanical, which may help to produce superior concrete properties in the further studies of NS, SF, and SS. Also, the results from the pilot experiment to affirm that the combined effects of NS, SF, and SS enhance the mechanical properties of concrete are presented herein.

Optical properties and photostability of silicon dioxide powders modified with SiO2 hollow particles and nanoparticles of various oxides

The change in the diffuse reflection spectra in the UV, visible, and near-IR regions of amorphous SiO2 powders modified with SiO2, ZrO2, Al2O3 nanoparticles and hollow SiO2 particles after irradiation by the quanta of the solar spectrum. Heating at 800 °C and modification with nano and hollow particles of SiO2 leads to an increase in the photostability of amorphous SiO2 powders, while the modification with ZrO2 and Al2O3 nanoparticles reduces the photostability of amorphous silica powders. The analysis of changes in the intensity of the formed absorption bands was carried out, the processes of powder degradation during irradiation were considered.

Transparent Synthetic Soil and Its Application in Modeling of Soil-Structure Interaction Using Optical System

This article introduces the uses of transparent synthetic soil for geotechnical problems using optical system, including transparent materials, sample preparation, geotechnical properties, experimental methods, and applications in physical modeling. Four typical kinds of transparent synthetic soil are shown and compared. For amorphous silica powder, normally the consolidated amorphous silica has a higher normalized strength but a lower modulus than the natural clays. For amorphous silica gels, the stress-strain behaviors are consistent with the typical stress-strain behaviors of sand for both dense and loose conditions. For fused silica, it has a higher shearing strength and higher modulus than the natural sand does; the deviatoric stress increases with the confining pressure, but the stress-strain curves of fused silica and the natural sand are particularly similar. For glass sand, with increasing of the relative density, the strain-stress relationship varies from strain hardening to stress softening, while its failure form is essentially the same as that of standard sand. According to the geotechnical properties of four typical materials of transparent synthetic soil grain, they are used to simulate different conditions and analyze practical engineering problems in different physical model tests. The process included the generation of a speckle pattern created by the interaction of laser light with transparent particles. Using digital image processing technology, speckle patterns can be obtained and used to calculate the displacement field. By utilizing this optical system, transparent synthetic soil can be used to non-intrusively investigate internal soil deformation, flow problems, and ground movement in physical model tests. Finally, both the advantages and disadvantages of the transparent soil experimental technique are analyzed.

Коретрон для терапии крупного рогатого скота при бовиколезе

Коретрон для терапии крупного рогатого скота при бовиколезе

Deconstruction of microfibrillated cellulose into nanocrystalline cellulose rods and mesogenic phase formation in concentrated low-modulus sodium silicate solutions

This work demonstrates for the first time the deconstruction of microfibrillated cellulose (MFC) into rod-like cellulose nanocrystals (CNCs) in concentrated low modulus sodium silicate solutions. To this aim, MFC suspensions at different concentrations were first treated in sodium hydroxide solutions and then amorphous silica powder was added. Optical microscopy and transmission electron microscopy observation showed how MFC was efficiently deconstructed into CNCs, evidencing the occurrence of a phase separation into an isotropic and mesogenic phase. The extracted CNCs were characterized by a remarkably higher length (600–1200 nm) in comparison with the plant-derived ones commonly reported in literature. FT-IR spectroscopy and 29Si MAS NMR confirmed that the Qn equilibrium of the suspended silicate species was affected, proportionally to the amount of MFC. It was also shown, that due to the excluded volume effect exerted by silicate anions, nematic or smectic ordering could be achieved for CNC concentrations far below the critical rod concentration predicted by the Doi-Edwards model.

Non-firing ceramics: Effect of adsorbed water on surface activation of silica powder via ball milling treatment

“Non-firing” ceramics have recently attracted much attention because many functional ceramics can be achieved by this method without the sintering process. The underlying idea of this method is to activate the surface of the particles by ball milling. In this study, the effect of adsorbed water on the surface of raw silica powder was investigated. Amorphous silica powder was mechanically treated by a rotating ball mill system and the surface activity of the raw and treated silica powders was measured based on the water adsorbed volume on the powder surface. The results showed that the surface activity of the silica powder increased with the increasing adsorbed water volume on the surface of the silica powder. In addition, better mechanical properties evaluated by the Vickers hardness test were achieved for the silica with more water adsorbed on its surface. The effect of milling energy and ball to powder ratio on activation of the silica was also investigated.

Screen-Printed Sensors for Colorimetric Detection of Hydrogen Sulfide in Ambient Air.

A fast and sensitive method to monitor hydrogen sulfide (H2S) in ambient air based on a visible color change of a printed disposable sensor has been developed. As gas-sensitive material, an immobilized copper(II) complex of the azo dye 1-(2-pyridylazo)-2-naphtol (H-PAN) was synthesized and prepared in an ethyl cellulose matrix for screen printing. If H2S is present in ambient air, the gas sensitive layer changes its color from purple to yellow. A pre-primed polyethylene (PE) foil and a coated offset paper served as the printing substrate. The colorimetric response to the target gas was measured by UV/Vis spectroscopy in reflection at H2S concentrations between 1 to 20 ppm. Possible cross-sensitivities of the printed sensors towards methane (CH4), formaldehyde (CH2O), carbon monoxide (CO), ammonia (NH3), and nitrogen dioxide (NO2), as well as the long-term stability was investigated. Furthermore, reflection measurements of the Cu-PAN complex on an amorphous silica powder under gas admission served as preliminary test for the subsequent paste development.

Synthesis of nano-crystalline forsterite based on amorphous silica powder from natural sand by mechanical activation method

The synthesis of nano-forsterite powders has been succeeded using an amorphous SiO2 powder base material from the purification of natural silica sands from Tanah Laut and MgO Merck with a combination of duration of mechanical activation and calcination temperature. The silica and magnesia powders are mixed and mechanically activated using ball mill for 1, 2, 3 hours. The mixture was then calcined at a temperature of 950, 1050, and 1150°C for 4 hours to form a forsterite powder. Phase characterization was performed using XRay Diffraction (XRD), while the crystalline size using Transmission Electron Microscopy (TEM). The analysis of diffraction data was done using the Rietica software method. Overall the phases formed after calcination are forsterite, periclase, cristobalite, and protoenstatite. The highest percentage of forsterite weight was obtained in the sample with a 3-hour mechanical activation treatment with a calcination temperature of 950 °C, i.e. 87.9 wt. At all temperatures, the forsterite content increases with increasing time of mechanical activation. An important invention in this study, when compared with earlier literature, is that high concentrations of forsterite can be formed at lower calcination temperatures. Observations with TEM show that the size of forsterite crystals is reduced along with the increase in the time of mechanical activation. The size of the forsterite crystals in the calcined samples of 950° C after mechanical activation for 3 hours was about 81 nm, whereas in the calcined samples 1050 °C without mechanical activation about 94 nm.