TiO2 SiO2 Research Articles

Heterogeneous Reactions of Phenol on Different Components of Mineral Dust Aerosol: Formation of Oxidized Organic and Nitro-Phenolic Compounds.

Phenol, a common semi-volatile compound associated with different emissions including from plants and biomass burning, as well as anthropogenic emissions and its derivatives, are important components of secondary organic aerosols (SOAs). Gas and aqueous phase reactions of phenol, in the presence of photochemical drivers, are fairly well understood. However, despite observations showing aromatic content within SOA size and mass increases during dust episodes, the heterogeneous reactions of phenol with mineral dusts are poorly understood. In the current study, surface reactions of phenol at the gas/solid interface with different components of mineral dust including SiO2, α-Fe2O3, and TiO2 have been investigated. Whereas reversible surface adsorption of phenol occurs on SiO2 surfaces, for both α-Fe2O3 and TiO2 surfaces, phenol reacts to form a wide range of OH substituted aromatic products. For α-Fe2O3 surfaces that have been nitrated by gas-phase reactions of nitric acid prior to exposure to phenol, unique compounds form on the surface including nitro-phenolic compounds. Moreover, additional surface chemistry was observed when adsorbed nitro-phenolic products were exposed to gas-phase SO2 as a result of the formation of adsorbed nitrite from nitrate redox chemistry with adsorbed SO2. Overall, this study reveals the extensive chemistry as well as the complexity of reactions of prevalent organic compounds leading to the formation of SOA on mineral surfaces.

Reinforced dielectric properties and energy storage performance of BaO–Na2O–Nb2O5–SiO2–TiO2–ZrO2 dielectric glass ceramics

Glass ceramic capacitors with ultra-fast discharge speed and high energy density play a key role in pulse power systems. However, the low dielectric performance of glass ceramics limits their energy storage density. To reinforce the dielectric properties and energy storage capacity of glass ceramics, the microstructures and contents of the ceramic phases composing BaO–Na2O–Nb2O5–SiO2–TiO2–ZrO2 glass ceramics can be effectively controlled by adjusting different crystallization conditions. At the optimum crystallization temperature of 950 °C, the maximal theoretical energy storage density of BaO–Na2O–Nb2O5–SiO2–TiO2–ZrO2 dielectric glass ceramics reaches 9.54 J/cm3 at 1394 kV/cm, which is 1.47 times that of dielectric glass ceramics crystallized at 750 °C. Moreover, glass ceramics exhibit a rapid discharge rate of approximately 0.237 μs and superior power density (2.39 MW/cm3) at 800 kV/cm. Significant enhancement in energy storage performance of the above ceramics is attributed to the component regulation and the reduction of interface polarization.

Nanoscale dielectric properties of TiO2 in SiO2 nanocomposite deposited by hybrid PECVD method

In this paper, nanocomposites (TiO2 in SiO2) are produced by an advanced hybrid aerosol-PECVD method based on direct liquid injection of a non-commercial colloidal solution in an O2 / hexamethyldisiloxane (HMDSO) low-pressure plasma. Dielectric properties are investigated at nanoscale using techniques derived from Atomic Force Microcopy in terms of relative dielectric permittivity, charge injection and transport. Results show that a concentration in TiO2 up to 14% by volume makes it possible to increase the relative dielectric permittivity up to 4.8 while maintaining the insulating properties of the silica matrix. For a TiO2 concentration in the range 15%–37% by volume, the relative dielectric permittivity increases (up to 11 for 37% TiO2 by volume) and only few agglomerated nanoparticles lowering the insulating properties are observed. For TiO2 concentration above 40% by volume, the relative dielectric permittivity still increases but the quantity of agglomerated nanoparticles is very high, which greatly increases the charge transport dynamic and degrades the insulating properties. Finally, 37% of TiO2 by volume in the SiO2 matrix appears to be the best compromise, between high dielectric permittivity and low leakage current for the MIM applications aimed.

Superhydrophobic and Photocatalytic Self-Cleaning Cotton Fabrics Coated with SiO2–TiO2 Janus Particles and PDMS

Superhydrophobic and Photocatalytic Self-Cleaning Cotton Fabrics Coated with SiO2–TiO2 Janus Particles and PDMS

The Preparation and Properties of Ti(Nb)-Si-C Coating on the Pre-Oxidized Ferritic Stainless Steel for Solid Oxide Fuel Cell Interconnect.

Cr2O3 scale growth and volatilization are the main cause of the performance degradation of solid oxide fuel cells (SOFCs) with an Fe-based ferritic stainless steel (FSS) interconnect. In this work, an amorphous Ti(Nb)-Si-C coating is prepared on the pre-oxidized SUS430 with D.C. magnetron sputtering as the protective coating. The amorphous Ti(Nb)-Si-C coated alloy exhibits significantly enhanced oxidation resistance, and the oxidation kinetics obey the parabolic law with a low parabolic rate of 9.36 × 10-15 g2·cm-4·s-1. A dual-layer oxide scale is formed composed of an inner layer rich in Cr2O3 and an outer layer rich in rutile TiO2 and amorphous SiO2. MnCr2O4 appears at the interface between the inner and outer oxide layers. Meanwhile, the amorphous Ti(Nb)-Si-C coating also effectively blocks the outward diffusion of Cr. In addition, the coated steel presents good electrical properties with an area-specific resistance (ASR) of 13.57 mΩ·cm2 at 800 °C after oxidation at 800 °C in air for 500 h.

SiO2-TiO2 Nanoparticle Aqueous Foam for Volatile Organic Compounds' Suppression.

Volatile organic compounds (VOCs) are prevalent soil contaminants. During the ex situ soil remediation process, VOCs may overflow from the soil and cause gas to diffuse into the atmosphere. Moreover, some VOCs, such as trichloromethane, are categorized by the EPA as emerging contaminants, imparting toxicity to organs, and the endocrine and immune systems, and posing a huge threat to human health and the environment. To reduce VOCs' emissions from contaminated soil, aqueous foam suppression is a prospective method that provides a durable mass transfer barrier for VOCs, and it has been widely used in odor control. Based on an aqueous foam substrate, in order to enhance the foam's stability and efficiency of suppression, SiO2-TiO2-modified nanoparticles have been used as stabilizing agents to improve the mechanical strength of liquid film. The nanoparticles are endowed with the ability to photocatalyze after the introduction of titanium dioxide. From SEM imaging, IR, and a series of morphological characterization experiments, the dispersibility of the SiO2-TiO2-modified nanoparticles was significantly improved under the polar solvent, which, in turn, increased the foam duration. The foam dynamic analysis experiments showed that the foam liquid half-life was increased by 4.08 h, and the volume half-life was increased by 4.44 h after adding the novel synthesized nanoparticles to the bulk foam substrate. From the foam VOC suppression test, foam with modified nanoparticles was more efficient in terms of VOCs' suppression, in contrast with its nanoparticle-free counterparts, due to the longer retention time. Moreover, in a bench-scale experiment, the SiO2-TiO2 nanoparticles foam worked against dichloroethane, n-hexane, and toluene for almost 12 h, with a 90% suppression rate, under UV irradiation, which was 2~6 h longer than that of UV-free SiO2-TiO2 nanoparticles, the KH-570-modified nanosilica foam, and the nanoparticle-free bulk foam. XPS and XRD results indicate that in SiO2-TiO2 nanoparticles, the proportion of titanium valence was changed, providing more oxygen vacancies compared to raw titanium dioxides.

The role of silica on the superiority of corrosion barrier performance and biological properties of sintered titania-silica composite coating electrophoretically deposited on 316L stainless steel

TiO2 and TiO2–SiO2 composite coatings were electrophoretically deposited on anodized 316L stainless steel substrates and then sintered at 1100 °C. TiO2 coating showed a rutile phase composition involving a cracked surface with a wide diffusion region rich in chromium element near the substrate. While TiO2–SiO2 composite coating showed a crack-free surface with an anatase phase comprising a continuous interlayer. Formation of the dense interlayer prevented the diffusion of substrate elements toward the coating during the sintering and thus inhibited the formation of diffusion region. According to the EIS study after 1 day of immersion in PBS solution, the highest barrier performance belonged to TiO2–SiO2 composite coating where its total faradic resistance (84 MΩ cm2) was 1500 times higher than TiO2 coating and 5.6 times higher than the anodized substrate. This was related to the crack-free surface and the interlayer formed in the composite coating owing to the improving effects of silica. After 28 days of immersion, the total faradic resistance of the TiO2–SiO2 composite coating remained significantly higher (order of 106–107 Ω cm2) than TiO2 coating (∼104 Ω cm2). Furthermore, TiO2–SiO2 composite coating enhanced the apatite formation compared to TiO2 coating or anodized substrate during immersion in SBF solution.

Apatite Geochemical and Nd Isotopic Insights into Trachyte Petrogenesis in the Tianchi Volcanic Area of Changbai Mountain, NE China

AbstractWe report the oxide, element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium‐ and fine‐grained trachyte in the Tianchi volcanic area (TVA) of Changbai Mountain, discussing the relationship between apatite and the composition of the whole rock. The purpose is to use the apatite geochemical data to constrain the evolutionary process of trachytic magma and the petrogenesis of trachyte in the cone‐forming period of the Tianchi volcano. Apatite (Ca5(PO4)3(OH, F, Cl)) is a common accessory mineral that occurs widely in volcanic rocks in the TVA. The apatites in the trachyte are mainly subhedral–anhedral, having the characteristics of magmatic apatite. In terms of oxide and element geochemistry, they have homogeneous Al2O3, SiO2, MgO, P2O5, K2O, CaO and heterogeneous TiO2, with high F content. They are generally enriched in Th, U and LREEs, depleted in Nb, Ta, Zr, Hf and HFSEs, showing negative Ba, Sr and Ti anomalies, similar to those of the whole‐rock host trachytes. The ratios of high (La/Yb)N, low δEu (Eu/Eu*), Sr/Y value and ΣREE content in apatite, and the F, Sr, Y, Th/U, La/Sm, and Nd/Tb with ΣREE and δEu anomalies showed a linear correlation, all of those indicating that the host magma has the characteristic of high differentiation. The apatite grains generally having 147Sm/144Nd, 143Nd/144Nd ratios and εNd(t) values of 0.1072–0.1195, 0.5123–0.5126 and –3.49 to –0.10, respectively, are similiar to those of the host rock. The Nd model ages TDM1 are 949–803 Ma in apatite. Combined with the εNd(t) value of the apatite core (–7.06 to –3.49), we conclude that the initial magma of the host trachyte was derived from the partial melting of Proterozoic crustal material and there was an assimilation of wall rocks during its evolution.

Insight into (Electro)magnetic Interactions within Facet-Engineered BaFe12O19/TiO2 Magnetic Photocatalysts.

A series of facet-engineered TiO2/BaFe12O19 composites were synthesized through hydrothermal growth of both phases and subsequent deposition of the different, faceted TiO2 nanoparticles onto BaFe12O19 microplates. The well-defined geometry of the composite and uniaxial magnetic anisotropy of the ferrite allowed alternate interfaces between both phases and fixed the orientation between the TiO2 crystal structure and the remanent magnetic field within BaFe12O19. The morphology and crystal structure of the composites were confirmed by a combination of scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses together with the detailed study of BaFe12O19 electronic and magnetic properties. The photocatalytic activity and magnetic field effect were studied in the reaction of phenol degradation for TiO2/BaFe12O19 and composites of BaFe12O19 covered with a SiO2 protective layer and TiO2. The observed differences in phenol degradation are associated with electron transfer and the contribution of the magnetic field. All obtained magnetic composite materials can be easily separated in an external magnetic field, with efficiencies exceeding 95%, and recycled without significant loss of photocatalytic activity. The highest activity was observed for the composite of BaFe12O19 with TiO2 exposing {1 0 1} facets. However, to prevent electron transfer within the composite structure, this photocatalyst material was additionally coated with a protective SiO2 layer. Furthermore, TiO2 exposing {1 0 0} facets exhibited significant synergy with the BaFe12O19 magnetic field, leading to 2 times higher photocatalytic activity when ferrite was magnetized before the process. The photoluminescence emission study suggests that for this particular combination, the built-in magnetic field of the ferrite suppressed the recombination of the photogenerated charge carriers. Ultimately, possible effects of complex electro/magnetic interactions within the magnetic photocatalyst are shown and discussed for the first time, including the anisotropic properties of both phases.

Influence of TiC contents on the microstructure, mechanical properties, and oxidation behavior of Mo–10Si–8B alloys

The microstructure, mechanical properties, and oxidation behavior of Mo–10Si–8B-xTiC (at.%, x = 0,5,10,15) alloys fabricated via oscillatory pressure sintering are studied. The phase constitution of three TiC-added alloys is α-Mo + Mo3Si + Mo5SiB2 + Mo2C + TiC; in 15TiC alloy α-Mo phase no longer maintains its contiguity as in the other three alloys. With further TiC addition, the microhardness improves by 60–90 % (up to 1500 HV), Young's elastic modulus increases from 328 to 368 GPa, and the fracture toughness decreases from 14.23 to 10.8 MPa m1/2, accounting for the less-ductile phase and newly introduced brittle phases. Thermogravimetric analysis indicates that the addition of TiC reduces the oxidation resistance. For isothermal oxidation at 800, 1000, and 1200 °C, the serious oxidation occurs for all TiC-added alloys except for 15TiC alloy at 1200 °C because the oxidation sequence changes to TiC → Mo5SiB2 → Mo3Si → α-Mo. The anomalous phenomenon for 15TiC alloy at 1200 °C could be attributed to the rapid formation and cover of protective SiO2–TiO2 layer on alloy surface after the transient MoO3 volatilization.

IR Spectra and Component Ratios in SiO2–TiO2*Organic Acid Composites―New Catalysts for the Asymmetric Biginelli Reaction

IR Spectra and Component Ratios in SiO2–TiO2*Organic Acid Composites―New Catalysts for the Asymmetric Biginelli Reaction

Highly photocatalytic efficiency and scour-durable of CO2 capture photocatalytic materials

Cement-based photocatalytic materials have attracted considerable attention for their potential in the degradation of air pollutants. However, there is a pressing need to enhance the environmental stability of surface photocatalyst loads and improve the low-carbon preparation of the loaded matrix. In this study, a novel TiO2-SiO2 (TS) based CO2 capture photocatalytic material (TSC) was prepared by compressing molding method. TSC exhibits excellent photocatalytic efficiency, as demonstrated by its performance in NOx degradation tests and rhodamine B degradation. Notably, the photocatalytic efficiency of TSC in removing NO and its nitrate selectivity did not decrease significantly after the 7200-minute scouring test, primarily due to the increased specific surface area and low Ti element leaching. These results suggest that the carbonation binding materials used in TSC shows great promise for photocatalytic building applications. Meanwhile, the carbonation process during curing enables the absorption of CO2, making it beneficial for achieving a “Carbon Neutral” approach.

Research on the combined effect of silencers and dyes on the coloring of enamel coatings

We investigated the combined effect of paired compositions of TiO2, МоО3 silencers, and CoO, NiO, K2Cr2O7+CuO, Fe2О3 dyes on the quality and optical-color characteristics of enamel coatings based on the matrix glass of the R2O–ВаО–ZnO–Al2O3–В2О3–TiO2–SiO2 system. It was established that in the presence of CoO, NiO, K2Cr2O7+CuO dyes, the addition of МоО3 in the amount of up to 3 wt.% improved the quality of coatings, but did not lead to significant changes in the color tone, and only affected its shade. Introduction of Fe2О3 in the amount of up to 0.75 wt.% into the composition of the matrix glass, simultaneously combined with CoO, K2Cr2O7+CuO dyes, showed a similar pattern. The combination of Fe2О3 with NiO resulted in obtaining brown coatings of various shades characterized by =594–613 nm (orange region of the spectrum). The inexpediency of adding 15 wt.% TiO2 as a silencer for colored coatings based on the experimental matrix glass was established and the reasons for the absence of a silencing process at a firing temperature of 8000С were revealed.

Multi-functional monodispersed SiO2–TiO2 core-shell nanostructure and TEOS in the consolidation of archaeological lime mortars surfaces

Archaeological traditional lime mortars are susceptible to many environmental conditions such as the impact of water (rain, humidity, groundwater, etc.), variation of temperatures' degrees, wind and/or pollution. Accordingly, this research aims to provide newly assessed multifunctional Nano-coating for the purpose of archaeological lime mortar protection. For this, the study combined physicochemical and mechanical characterizations in performance assessment of 3%, 5%, and 7% of the synthesized SiO2–TiO2 core-shell nanostructure and TEOS as consolidants on the surfaces of the experimental lime mortars. A series of techniques and tests were fulfilled for the evaluation. For analysis, X-ray diffraction and UV–Vis along with scanning electron microscopy were used to identify microstructure. Furthermore, wettability, colorimetric, self-cleaning, petrophysical, Nano-indentation, and uniaxial compressive strength tests were performed to select the most durable consolidant between 3%, 5%, and 7% SiO2–TiO2/TEOS. Durability assessments were carried out through salt weathering, thermal and UV aging tests. The results showed that 3% and 5% of SiO2–TiO2/TEOS enhanced the physical and mechanical properties of the lime mortars. On the other hand, 7% SiO2–TiO2/TEOS proved their insufficient efficacy in improving the surfaces of lime mortars for the high amount of TiO2 and its behavior for aggregation.

Effect of TiO2 Additions on the Properties of Bioactive Granulated Materials of the TiO2–SiO2–P2O5/СаO(ZnO) System

Effect of TiO2 Additions on the Properties of Bioactive Granulated Materials of the TiO2–SiO2–P2O5/СаO(ZnO) System

Study on the structure and optical properties of the Tb3+-doped SrO–MgO–SiO2–TiO2–B2O3 glasses

In this investigation, Tb3+-doped SrO–MgO–SiO2–TiO2–B2O3 glasses were prepared using the melting-cooling technique. The amorphous nature of the glass was confirmed through XRD analysis. The thermodynamic parameters of the glass were determined by DSC testing, and the crystallization activation energy was calculated. Using infrared spectroscopy, the network structure of the glass was investigated. At 376 nm excitation, the emission spectrum was obtained, which contained six emission bands: 415 nm (5D3→7F5), 437 nm (5D3→7F4), 489 nm (5D4→7F6), 545 nm (5D4→7F5), 586 nm (5D4→7F4) and 623 nm (5D4→7F3). With the increase of Tb2O3 ion-doping concentration, the emission intensity of the 5D3 excited state decreases gradually, while that of the 5D4 excited state increases gradually. Also measured were the lifetimes of Tb3+: 5D3 and 5D4 fluorescence decay. The luminescence of the glass falls within the green region of the CIE chromaticity coordinates, and the correlated color temperature index indicates that the luminescence is pale green. The results show that the Tb3+ doped SrO–MgO–SiO2–TiO2–B2O3 glasses system has a potential application prospect in the field of green light display.

The MgO–TiO2–SiO2 system: Experiments and thermodynamic assessment

AbstractPhase relations in the MgO–TiO2–SiO2 system have been investigated in air over a wide temperature range using the equilibration method. X‐ray powder diffraction, scanning electron microscopy combined with wave length X‐ray spectroscopy (SEM/EPMA), and differential thermal analysis (DTA) have been used for sample characterization. Based on the obtained experimental results, isothermal sections of the system at 1523, 1673, and 1773 K have been established. The solid‐state invariant reaction MgTi2O5 + T‐SiO2⇋P‐MgSiO3 + TiO2 has been detected at 1625 ± 8 K by step‐wise heat treatment. A partial liquidus projection has been suggested, and the temperatures and compositions of three eutectic invariant reactions have been experimentally measured by DTA and ex‐situ analysis of the sample microstructures after melting using SEM/EPMA. Considering the newly obtained experimental data, thermodynamic parameters describing the system have been thermodynamically evaluated within the CALPHAD approach.

The Addition of TiO2 Ratios in SiO2–TiO2 Nanocomposite by Sonochemical Process for the Enhancement in Self-cleaning Property

This research aims to study self-cleaning property for removing atmosphere pollutants on the substrate surface. Thus, the modification of nanocomposite material for self-cleaning property is an important challenge to solving the organic pollutants on various surfaces. Nanocomposite material in this work is focused on SiO2-TiO2 based metal oxide materials that synthesized by sonochemical process with the precursors of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TTIP). The crucial parameter of different amount of titanium ratios in SiO2 matrix is related to the improvement on structural and self-cleaning properties. The ratios of Si:Ti precursor were varied at 1:0.1, 1:0.5, 1:1 and 0:1 (pure TiO2). The structural phase of SiO2-TiO2 nanocomposite powder was detected by X-ray diffraction technique (XRD). Chemical bonding structure in SiO2-TiO2 nanocomposite was analysed by Fourier transform infrared spectrophotometer (FTIR). Surface morphology of SiO2-TiO2 nanocomposite was monitored by field emission scanning electron microscope (FE-SEM). SiO2-TiO2 nanocomposites synthesized by sonochemical process were in form of composite powder with the spherical SiO2 particles and decorated TiO2 on its surface. After that, the products of SiO2-TiO2 nanocomposite with different TiO2 ratios were mixed with TES 40 WN solution and deposited on glass slides substrate by spray coating to study its hydrophilic property by contact angle method. The contact angle of SiO2-TiO2 nanocomposite film was reduced with the increase of Ti ratio in SiO2 matrix resulting to the development of hydrophilic surface on substrate. The influence of TiO2 in SiO2 matrix on self-cleaning and property would be improved by hydroxyl groups on the composite surface corresponding to Ti–O–Si linkages. For self-cleaning property, Si:Ti ratio at 1:1 in SiO2-TiO2 nanocomposite showed the optimized condition with decreasing contact angle at 28.97 degree in 60 min after UVA irradiation.

Effect of TiO2–SiO2 hybrid nanofluids on enhanced oil recovery process under different wettability conditions

Effect of TiO2–SiO2 hybrid nanofluids on enhanced oil recovery process under different wettability conditions

Silicate glass-ceramic fibers with nonlinear optical crystals: Evaluation of propagation loss and comparison to optical materials

Optical glass fibers can propagate light signals, while their control depends on nonlinear optical crystals. In this study, we fabricated nonlinear optical glass-ceramic (GC) fibers in which the polar fresnoite phase was crystallized based on perfect surface crystallization (PSC) in the SrO–TiO2–SiO2 system. GC fibers free from voids were obtained from precursor glass fibers with a diameter of ∼100 μm by controlling PSC. The propagation loss of a GC fiber was evaluated to be ∼0.37 dB/cm, which is comparable to that of the LiNbO3 single-crystal optical waveguide.