SiO2 Powder Research Articles

Potential Utilization of Iron Oxidation Reaction Heat for the Generation of SiO2–FeO System Melts

Silicon-containing steel forms an oxide layer within the scale during hot rolling. This layer comprising oxides such as Fe2SiO4 and FeO adversely affect the surface quality of steel owing to strong adhesion between Fe2SiO4 and the steel substrate. A method to melt this silicon-containing oxide layer through the oxidation reaction of iron plates by applying SiO2 powder to the surface is proposed. The aim of this study is to understand the reaction mechanism and identify the optimal conditions for this process. Application of SiO2 coating to the surface of an iron plate at 6.67 × 10–4 g·mm−2 and maintaining the plate at 1423 K, just below the eutectic temperature of Fe2SiO4–FeO system (1450 K), cause the surface oxide scale to melt when exposed to oxidation in an atmospheric environment. Notably, reducing the electric furnace temperature hinders the melting process, whereas excessive application of SiO2 hampers the formation of sufficient liquid phase. On the surface of the iron plate, primarily FeO and Fe2SiO4 are formed. Heat generation is mainly due to the formation of FeO, which leads to the rapid generation of Fe2SiO4. Eutectic reactions within SiO2–Fe2SiO4 or FeO–Fe2SiO4 systems drive the formation of the liquid phase. Once the liquid phase was established, rapid diffusion of iron ions within it resulted in rapid iron oxidation and additional heat generation. Ultimately, a liquid phase in equilibrium with FeO is formed across the entire surface of the iron plate.

The spectrally resolved photoluminescence decay in YAG:Er, ZnO and SiO2 crystals

We present an optical setup for measuring spectrally resolved photoluminescence (PL) mean decay time using conventional UV LED with sinusoidal excitation and a phase shift method. The phase sensitive detection was applied on the Er-doped yttrium aluminium garnet single crystal (YAG:Er, grown by the micro-pulling-down method) and hydrothermally grown zinc oxide micro-crystallites (ZnO). Commercial ZnO and silicon oxide (SiO2) microcrystalline powders were measured for comparison. SiO2 powder was annealed in O2 plasma at 500 °C for cleaning. While YAG:Er shows well resolved greenish PL peaks with mean decay time about 15 μs related to the Stark splitting of Er3+ (4f11) states and ZnO micro-powder broad reddish PL with similar PL decay time, the plasma treated SiO2 powder shows weak bluish defect-related PL with significantly faster mean decay times below 100 ns.

Evolution of different third bodies and their influences on the tribological properties of C/C-SiC composites

Friction film has an important influence on the tribological properties of C/C-SiC composites, which is closely related to its composition. In this study, exogenous third bodies in the form of powders of graphite, SiC, SiO2 and a mix of graphite, SiC, and SiO2 powders were added to the friction surface of the C/C-SiC composites under a constant speed. By comparing the change in the coefficient of friction (COF) and the wear rate of the C/C-SiC composites before and after addition of exogenous third bodies, the influence of each component on the tribological properties of the C/C-SiC composites and its mechanism were proposed. The graphite third body had a solid lubrication effect, with the average COF bellowing 0.344 and a 24% reduction in wear rate after addition. With the addition of SiC and SiO2 third body, the average COF was greater than 0.550 and 0.441, and the wear rate increased by 128.4% and 25.1%, respectively. SiO2 with a stronger pinning effect, promoted the formation of friction film and ultimately resulted in a smaller increase in average COF and wear rate. With the addition of the multi-component third bodies, the first platform containing SiO2 and SiC was formed, which resulted in a reduction in sharpness and being prone to refinement. Meanwhile, the large first platform accelerates the formation of friction film. Furthermore, while the first platform exceeded to the bearing capacity, SiC and SiO2 started to decompose, and redistributed in the friction film, which cause the instantaneous COF tended to stable with a low wear rate.

Low‐temperature curable adhesive for joining SiC/SiC components: Their application in wide range of temperatures

AbstractHerein we report the formulation of phenolic resin–based adhesive to join SiC substrates for a wide range of application temperatures. The formulation consists of phenolic resin as a binder and a mixture of B4C, Al2O3, Y2O3, Si, and SiO2 powders as active filler. The X‐ray diffraction, thermogravimetric analysis, porosity, and scanning electron microscopy analysis were carried out to understand the reactions occurring within this adhesive during its exposure to application temperatures. These results were also used to understand thermal stability and morphological changes that are involved in the formulated adhesive during its application. The shear strength values of lap joints of SiC substrates made with this phenolic adhesive after exposure to temperatures between 200 and 1500°C were studied to evaluate its adhesive capacity. Obtained SiC joints with this adhesive have shown an excellent lap shear strength value of 24 MPa after its cure. These joints were also found to be intact with good shear strength values of more than 5 MPa even after exposure to temperatures ranging from 200 to 1500°C. The results further confirm that the adhesive is potentially viable for joining SiC segments for their application at a wide range of temperatures in oxidative environments.

Dissolution-induced oxide synthesis using SiO2 microparticles for oxide dispersion strengthening of Fe-based alloys

This study reports on a single-track laser surface alloying process that utilizes SiO2 powder to disperse both SiO2 particles and oxide inclusions in 316L stainless steel for oxide dispersion strengthening (ODS) purposes. In this process, the SiO2 powders partially dissolve in the melt pool, and the released silicon and oxygen atoms nucleate to form oxide inclusions in-situ within the metal matrix. This dissolution-induced oxide synthesis route demonstrated a high potential for ODS, achieving a high particle number density (6.6 × 104 mm−2) and area fraction (3.3%) comparable to that of bulk 316L samples produced via directed energy deposition. The hardness of the SiO2/316L composites reached a maximum of 232.4 HV compared to that of the 316L substrate (average 170.8 HV). The improvement in hardness was theoretically explained and quantified, significantly originating from the enhanced dislocation density strengthening mechanism resulting from the large difference in the coefficient of thermal expansion between SiO2 and 316L.

Effects of SiO2 on the microstructure and electrical properties of ZnO-based varistors (ZBSCCM) prepared by two-step sintering routework

In this work, ZBSCCM varistors were fabricated by precalcining of raw materials, including nanosized ZnO, Bi2O3, Sb2O3, Cr2O3, Co2O3, MnO2 and different amount of SiO2 powders at 800 °C and then sintering at 950 °C, and the effects of the SiO2 content on the microstructure and electrical properties of the varistors were explored. SiO2 doping formed two additional phases that played opposite roles; that is, Zn2SiO4 spinel, which was pinned at ZnO grain boundaries and restrained ZnO grain growth, and a Bi12SiO20 glass phase could promote ZnO grain growth. Nevertheless, all the samples were highly densified above 99%. The SiO2 dopant reacted with ZnO and diffused faster in or reacted with liquid Bi2O3. SiO2 doping, conversely, slowed the diffusion of MnO2, Co2O3, and Cr2O3 in the liquid and facilitated their reaction with ZnO, which increased the interfacial state density and barrier height. Therefore, the nonlinear coefficient and leakage current density increased and decreased, respectively. At 1.0 mol% SiO2, the ZBSCCM varistor exhibited the optimal comprehensive electrical properties, including a breakdown field, nonlinear coefficient, and leakage current density of 982.7 V/mm, 74.0, and 0.4 μA/cm2, respectively.

Spatially Resolved Characterisation of Low Mass Fraction Uranium Glass Working Reference Materials

We present the results of a study to generate reference glasses that reflect an environment analogous to historic nuclear fallout samples of interest for post‐detonation nuclear forensics. The glasses were generated by melting and then quenching SiO2, Al2O3 and CaCO3 powders. Two suites of glasses with three distinct U isotopic ratios were successfully made with enrichments in the 235U isotope (~ natural [0.72%], ~ 53% and 94%), but the bulk elemental data showed heterogeneity (~ 10% RSD) with U mass fractions ranging from 331.47 to 373.63 μg g‐1. Spatially resolved U isotopic measurements were performed using three mass spectrometry techniques (secondary ion mass spectrometry‐single stage accelerator mass spectrometry [SIMS‐SSAMS], large geometry [LG] ‐ SIMS, and laser ablation‐inductively coupled plasma‐mass spectrometry [LA‐ICP‐MS]) across five National Laboratories. The results showed good agreement with the bulk U isotopic data for the low, medium, and high U mass fractions. We conclude that despite elemental heterogeneity, these samples can serve as useful working reference materials for spatially resolved nuclear fallout analyses, as well as for other related spatially resolved analyses.

Simple Synthesis and Characterization of Ball Milled SiOx for Use as a Negative Electrode Material

SiOxis an attractive anode material given its high specific capacity and its increased lifetime due to its supporting matrix of lithium silicates irreversibly formed during its first lithiation. While SiOxis normally created by simultaneous evaporation and vapor deposition of Si and SiO2powders, this can be very difficult and energy consuming method. It is shown here that SiOxwith controlled oxygen content can be made by ball milling crystalline silicon powder in an oxidizing medium using two different milling techniques. To characterize the SiOxpowders, oxygen content is quantified using a KOH-based method and BET surface area is measured. Electrochemical testing using coin cells is completed and the results are compared to commercially available SiO samples. The results show that SiOxwith competitive properties can be made by ball milling. Further work is required to reduce the specific surface area of the material made by ball milling.

Fabrication and characterization of glassy carbon foams with controllable porosity and high compressive strength

Glassy carbon (GC) foams for a long time have two mainly problems. First, GC foams cannot withstand heavy load application due to its relatively low strength. Second, the matrix is easy to crack during pyrolysis precursor process, leading to a long carbonization time. In this study, high-strength GC foams were fabricated by sacrificial templates method using SiO2 powder and phenolic resin as raw materials. SiO2 powder is uniformly dispersed into phenolic resin, and the interface of SiO2/phenolic resin provides fast diffusing channels for the pyrolysis gases, that reduce the risk of cracks formed in GC matrix during fast carbonization. The compressive strength of as-prepared GC foams with density ranging of 0.324–0.781 g/cm3 is 21.6–106.4 MPa. The stretch-dominated mechanical response of the porous structure accounts for the high strength of the prepared GC foams.

Preparation and Characterization of Ag Nanoparticle/SiO2 Composite for Optical Application

A facile method to fabricate volumetric light-guide plate (LGP) by micro-nanostructure of Ag/SiO2 composite was presented in this study. The Ag NPs/SiO2 composite were first prepared from a mixture of yellowish-brown Ag NPs colloids and SiO2 powder by electrostatic self-assembly method. Its chemical and physical properties were investigated by scanning transmission microscopy (TEM), scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX). The small particles (Ag/SiO2 composite) in the LGP could produce multiple scattering effect with different size of micro-nanoparticles, which could improve the light-scattering performance of the LGP. The effective light scattering of the material into LGP was obtained from the increased amount of the particles. Meanwhile, surface plasmon resonance effect of Ag NPs also improves the performance of LGP, which could be further applied to design device in optical application. In additional, optical properties and light scattering mechanism of the Ag NPs/SiO2 composite in the LGP are discussed and presented.

Full-field hard X-ray nano-tomography at SSRF.

An in-house designed transmission X-ray microscopy (TXM) instrument has been developed and commissioned at beamline BL18B of the Shanghai Synchrotron Radiation Facility (SSRF). BL18B is a hard (5-14 keV) X-ray bending-magnet beamline recently built with sub-20 nm spatial resolution in TXM. There are two kinds of resolution mode: one based on using a high-resolution-based scintillator-lens-coupled camera, and the other on using a medium-resolution-based X-ray sCMOS camera. Here, a demonstration of full-field hard X-ray nano-tomography for high-Z material samples (e.g. Au particles, battery particles) and low-Z material samples (e.g. SiO2 powders) is presented for both resolution modes. Sub-50 nm to 100 nm resolution in three dimensions (3D) has been achieved. These results represent the ability of 3D non-destructive characterization with nano-scale spatial resolution for scientific applications in many research fields.

Charged colloidal SiO2 dispersions in water and chloroform: Synthesis, properties and perspectives in dyes adsorption

The paper proposes a new method for the synthesis of ultradispersed amorphous SiO2 powders in the reverse emulsions stabilized by sodium bis-(2-ethylhexyl) sulfosuccinate (AOT). Colloidal dispersions of the powders were obtained by ultrasonication in water and chloroform. The number average effective hydrodynamic diameter of particles in the sols was 90 and 200 nm, and ζ-potential was − 68 ± 3 and 52 ± 7 mV for water and chloroform, respectively. Accountable for charge formation and transformation are the AOT molecules that were adsorbed on the SiO2 surface during the synthesis in АОТ emulsions. In water, АОТ– ions serve as the potential-determining ones, while Na+ ions act as the counterions that form the diffusion part of the electrical double layer. With a decrease in the solvent polarity, Na+ ions become the potential-determining ones, and АОТ– ions – the counterions. Thus, the АОТ molecules embedded into the hybrid SiO2 @ АОТ particle during the synthesis are a certain switch key of the particle surface potential. The transformation of the surface charge in dependence on polarity of the organic solvent makes it possible to apply the synthesized powders both as the cation- and anion-exchange sorbents for the recovery of dyes from aqueous and non-aqueous media. In terms of fundamental advances, the novelty of our work consists in extending the ion-exchange sorption mechanism of ionic dyes to the media with a low dielectric constant.

Morphology control and blue luminescent performance of one dimensional Si3N4 via Nano-SiO2 assisted pyrolysis of polyvinylsilazane

One-dimensional Si3N4 wires and belts have been successfully synthesized via pyrolysis of polyvinylsilazane (PVSZ) with nano-SiO2 powders as the additive. The morphology of white Si3N4 was tailored from wire-like morphology to belt-like morphology by controlling pyrolysis temperature. The maxlength of Si3N4 wires and belts is up to 550 μm. The diameter of Si3N4 wires is 200–300 nm and the width and thickness of belts are 1–2.5 μm and 130–250 nm respectively. Nano SiO2 powders induced the formation of SiO2 phase in the substrate and promoted the growth of α-Si3N4 belts. Vapor-solid is the growth mechanism for Si3N4 microwires and micorbelts. Si3N4 wires and belts have broad blue emission ranging from 410 nm to 550 nm.

Controllable growth of high-density tapered N-doped SiC nanowires arrays

Tapered nitrogen-doped SiC nanowires (N-doped SiCNWs) arrays were vertically grown on the carbon cloth utilizing Si, SiO2, C, and dicyandiamide powders as raw materials via a simple Fe(NO3)3 assisted chemical vapor deposition process. High-density tapered N-doped SiCNWs possessed homogeneous morphology. The diameter of the synthesized nanowire increased from ∼120 nm at the tail to ∼1.30 μm at the tip, while the length could be up to tens of micrometers. Moreover, the as-prepared N-doped SiCNWs were examined to be 2H/3C–SiC mixed crystals. The appearance of 2H crystal might be responsible for the high density defects in 3C–SiC. And since the interesting tapered shape was significantly affected by the catalyst droplet, the growth of N-doped SiCNWs may be governed by Fe-assisted VLS mechanism. In addition, the main emission peak of PL spectrum of N-doped SiCNWs was located at 474 nm, exhibiting a certain blue shift, which was mainly attributed to the special tapered shape, defects, 2H/3C–SiC heterostructure and the quantum confinement effect of the N-doped SiCNWs.

Experimental Investigation of Jute Fabric / Nano-SiO2 Reinforced Epoxy Composite

ABSTRACT The effect of Nano-SiO2 powder on the mechanical behavior of a jute fabric/epoxy composite has been investigated experimentally. Due to qualities like biodegradability, strength, light weight, and affordability, composites are preferred for static and dynamic applications. Nano – SiO2 powder size of 15 nm was used as a filler material. Hand lay-up techniques were used to develop the composites, which had filler contents of 2%, 3%, and 5% Nano – SiO2 by weight of the epoxy resin. Tensile, Impact, Wear, Moisture Absorption, and Thermo – Gravimetric Analysis were used to characterize the mechanical properties of the composites. The results reveal that the jute/epoxy composite is significantly improved by the hybridization process using fillers. The maximum improvement in the composite’s tensile (44.09 MPa), impact (4 joules), wear, moisture absorption (0.5–4%), and thermos-gravimetric (2.96%) properties is achieved when 2 wt.% of nano-SiO2 is added.

Composite phosphor of a self-organized silica mixed YAG:Ce

Composite powders mixed with yttrium aluminum garnet (YAG:Ce) and SiO2 powders were prepared in a tetraethyl orthosilicate solution of an alkali hydrolysis bath. The state of the composite powders varies depending on the reaction conditions: the amount of ammonium water and the reaction time. The photoluminescence property of the composite powder was the same as that of pure YAG powder, while the quantum efficiency varied depending on the morphologies of the composite powders. The quantum efficiency improved for the composite powder with nano-sized silica particles covering the YAG surface.

Memristors Based on Many-Layer Non-Stoichiometric Germanosilicate Glass Films

Nonstoichiometric GeSixOy glass films and many-layer structures based on them were obtained by high-vacuum electron beam vapor deposition (EBVD). Using EBVD, the GeO2, SiO, SiO2, or Ge powders were co-evaporated and deposited onto a cold (100 °C) p+-Si(001) substrate with resistivity ρ = 0.0016 ± 0.0001 Ohm·cm. The as-deposited samples were studied by Fourier-transformed infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. A transparent indium–tin–oxide (ITO) contact was deposited as the top electrode, and memristor metal–insulator–semiconductor (MIS) structures were fabricated. The current–voltage characteristics (I–V), as well as the resistive switching cycles of the MIS, have been studied. Reversible resistive switching (memristor effect) was observed for one-layer GeSi0.9O2.8, two-layer GeSi0.9O1.8/GeSi0.9O2.8 and GeSi0.9O1.8/SiO, and three-layer SiO2/a–Ge/GeSi0.9O2.8 MIS structures. For a one-layer MIS structure, the number of rewriting cycles reached several thousand, while the memory window (the ratio of currents in the ON and OFF states) remained at 1–2 orders of magnitude. Intermediate resistance states were observed in many-layer structures. These states may be promising for use in multi-bit memristors and for simulating neural networks. In the three-layer MIS structure, resistive switching took place quite smoothly, and hysteresis was observed in the I–V characteristics; such a structure can be used as an “analog” memristor.

Removal of diisopropyl methyl phosphonate (DIMP) from heated metal oxide surfaces.

Diisopropyl methyl phosphonate (DIMP) is an organophosphorus compound used as a surrogate of sarin, a chemical weapon agent. Thermal decomposition of DIMP and similar liquids may be affected by added inorganic solids. Understanding such effects is needed to guide decontamination and environmental mitigation work. Here, liquid DIMP mixed with powders of γ-Al2O3 or SiO2, was heated to 350°C in a thermogravimetric analyzer while observing effluent gas using a mass spectrometer. For both powders, evaporation of DIMP occurred between 50 and 200°C, followed by a second mass loss step up to 350°C. The amount of DIMP evaporated in the first step varied; however, the size of the second, mass loss step was consistent between experiments for each solid used. For γ-alumina, 2-propanol and propene were released below the DIMP boiling point and mostly propene at higher temperatures. Calcining alumina prior to exposure to DIMP reduced the release of 2-propanol. For silica, the second mass loss step was smaller and only propene was released. Powders exposed to DIMP and recovered at different temperatures showed FTIR peaks corresponding to the individual bond vibrations of DIMP. At higher temperatures, only the P-CH 3 stretching vibration was observed.

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.

Surface modification and adhesive-free adhesion of polytetrafluoroethylene (PTFE) and silicone gel containing oleophilic SiO2 powder by plasma treatment.

Polytetrafluoroethylene (PTFE) has high-frequency characteristics and low transmission loss, and is expected to be used as a substrate material of printed wiring board for high-frequency applications. Meanwhile, silicone gel has superior properties such as attaching/detaching, weather resistance, and human safety. If the PTFE and silicone gel can be strongly adhered to, they can be applied to internet of things (IoT) devices that can be attached and detached freely. However, adhesion between PTFE, which has poor adhesion, and silicone gel, which has low mechanical strength, is difficult and has not been reported. In this study, PTFE was modified with heat-assisted plasma treatment, and silicone gel was treated with oleophilic SiO2 powder to improve elastic modulus and modified with plasma jet treatment, and then bonded without adhesive. The adhesion strength of PTFE/silicone gel assembly was 1.13 N mm-1 when treated moderately, but only 0.01 N mm-1 when untreated and treated excessively. To investigate the factors causing the difference in the adhesion strength, the surface of silicone gel was evaluated by water contact angle measurement, Fourier transform infrared spectroscopy, and confocal laser scanning microscopy. When treated moderately, hydrophilic functional groups and cross-linking were most frequently increased. Furthermore, when treated excessively, surface degradation was observed, which was expected to lower the adhesion strength. The adhesive-free bonding between PTFE and silicone gel can open a new path for developing IoT devices that can be freely attached and detached.