ZrO2 SiO2 Research Articles

High Performance SiO2–ZrO2 Binary Oxide for Ethanol Conversion to Ethylene

Zirconia catalysts doped with Si were prepared by co-precipitation method. The effects of zirconium precursor, precipitant and Si on the selective conversion of ethanol to ethylene over zirconia catalysts were investigated. The addition of Si afforded high surface area and enlarged amount of acidic sites. Higher ethanol conversion and ethylene yield were obtained over SiO2–ZrO2 catalysts. The highest yield of ethylene reached 95.9% over SiO2–ZrO2 synthesized by ZrO(NO3)2·2H2O and (NH2CH2)2.

Comparative Analysis of the Properties of ZrO2–SiO2 and ZrO2–Al2O3–SiO2 Composition Fiber Composite Materials

Strength, morphology, and phase composition are analyzed for a ceramic composite system based on fibers of tetragonal ZrO2 and a matrix with different content of SiO2 and Al2O3. It is shown that with an Al2O3 content from 0 to 20 wt.% there is formation of a precipitation-hardened structure and an increase in material ultimate strength in bending. The reduction in strength with a further increase in Al2O3 content is due to a deficiency in SiO2 binder and inadequate Al2O3 and mullite particle sintering with each other. Features of the structure and phase composition are demonstrated for a composite based on ZrO2 fibers with a different Al2O3:SiO2 ratio in the matrix.

Development of a Novel Hydrophobic ZrO2–SiO2 Based Acid Catalyst for Catalytic Esterification of Glycerol with Oleic Acid

The inevitably low value of glycerol has led to extensive investigations on glycerol conversion to value-added derivatives. The esterification of glycerol with oleic acid is currently a very important industrial process. In this work, a novel heterogeneous acid catalyst featuring hydrophobic surface is developed on modified ZrO2–SiO2 support as water-tolerant solid acid catalyst is vital for biphasic esterification reactions that produce water. The novel ZrO2–SiO2–Me&Et-PhSO3H catalyst was prepared through silication and surface modification with trimethoxymethylsilane and 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane. This work showed that it is possible to control the acidity and hydrophobicity of the catalyst by tailoring the amount of surface modification agents. It was found that the hydrophobicity of the catalyst decreased as its acidity increased. Furthermore, at constant catalyst acidity, the more hydrophobic catalyst showed a better yield.

Novel self-reinforcing ZrO2–SiO2 aerogels with high mechanical strength and ultralow thermal conductivity

Novel self-reinforcing ZrO2–SiO2 aerogels with high mechanical strength and ultralow thermal conductivity are fabricated by impregnating hydrolyzed ZrO2–SiO2 sol into wet gel matrix and drying. The ZrO2–SiO2 sol fills the macropores and defects of ZrO2–SiO2 aerogel matrix generating during the gelation process, which contributes to the improvement of the mechanical properties of the ZrO2–SiO2 aerogel matrix. The mechanical and thermal properties of the as-prepared ZrO2–SiO2 aerogel are investigated and discussed. The results show that the mechanical strength of the self-reinforcing aerogels obviously increases from 0.51 to 3.11 MPa with the increase of impregnation times, while the thermal conductivity of the aerogels slightly increases from 0.0235 to 0.0306 W m−1 K−1. The novel self-reinforcing ZrO2–SiO2 aerogel could have interesting applications in aerospace and energy because of its outstanding mechanical and thermal properties.

Dual-phase-lag analysis of CNT–MoS2–ZrO2–SiO2–Si nano-transistor and arteriole in multi-layered skin

• Two new finite-volume solvers have been developed for DPL non-Fourier model. • The solvers can capture curved boundaries in 3D arbitrary shapes. • The solvers have been checked using 4 benchmarks. • Temperature distribution in human’s skin with a circular arteriole was obtained. • A newly invented 1 nm nano-device of MoS 2 –ZrO 2 –CNT–Si–SiO 2 has been thermally analyzed. The numerical simulation of non-Fourier dual-phase-lag heat conduction in three-dimensional bio and nano media has been investigated with two developed solvers using the OpenFOAM C++ finite-volume libraries. Despite the rapid growth in the use of non-Fourier heat transfer model, most researchers conduct simulations over simple geometries due to numerical restrictions. The developed solvers have been verified for four benchmark cases. After that, two complex geometries have been selected to show the accuracy of the solvers for complicated geometries. The first case is the temperature distribution in the human hand skin in the presence of a circular arteriole, while the second case is the thermal analysis of a newly constructed CNT–MoS 2 transistor with 1 nm gate length. Both cases are multilayered structures with curved boundaries. The computed temperature rises in the blood vessel and in the transistor are 63°C after 15 s and 16 °C after 10 ps, respectively. It is found that considering the temperature-dependent electrical properties of ZrO 2 and CNT is essential to present an accurate mathematical model.

Preparation of carbon/carbon‐ultra high temperature ceramics composites with ultra high temperature ceramics coating

AbstractIn order to increase the oxidation resistance of carbon/carbon (C/C) composites at long‐term high temperature, C/C‐Ultra High Temperature Ceramics composites (UHTCs) with a dual‐layer UHTCs oxidation coating was successfully designed and fabricated. The microstructure and ablation resistance were investigated and discussed. After ablation in arc‐heated wind tunnel with temperature being 2200°C for 1000s, the mass ablation rate and linear ablation rate were −1.9 × 10−2 mg/cm2s and 2.9 × 10−5 mm/s, respectively. The formation of thermodynamically compatible oxide scale including ZrO2 skeleton and SiO2 or Zr–Si–O glass on the surface were mainly contributed to the excellent ablation resistance of the composite.

New chiral proline-based catalysts for silicon and zirconium oxides-promoted asymmetric Biginelli reaction

4-Hydroxy-(2S)-prolines bearing 3,4-dihydro-2H-1,4-benzoxazine or 1,2,3,4-tetrahydroquinoline fragments were synthesized and studied as chiral catalysts in the Biginelli reaction. The target product ethyl 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate was obtained with 54% enantiomeric excess (ee). An increase in ee values of the reaction product up to 76% was observed in the presence of nanosized oxides SiO2–ZrO2 as heterogeneous promoters.

The usage of newly developed glass fibre in cement structure and their characterization

In this work, recently developed Zrn1 glass fibres belonging to the SrO–Mn2O3–Fe2O3–MgO–ZrO2–SiO2 (SMFMZS) system have been used as reinforcing materials in cement. The highest (2.610 N/mm2) compressive strength value was obtained with the addition of 3 wt% of Zrn1 fibres into Portland cement. The microstructural behaviour of these fibres along with commercially available ones in the cement structure were investigated using a scanning electron microscope (SEM). Microstructures were fully compatible with mechanical results obtained. Eventually, it was determined that Zrn1 fibre can be a good candidate for cement reinforcement leading to high strength values.

Preparation of SiO2–ZrO2 xerogel and its application for the removal of organic dye

SiO2–ZrO2 xerogel was prepared via a sol–gel method followed by ambient pressure drying. The xerogel was characterized by X-ray diffraction, thermal analysis, fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption/desorption analysis. The results showed that the SiO2–ZrO2 xerogel was amorphous and possessed a three-dimensional network structure with a narrow distribution of pore size. Its specific surface area reached up to 525.6 m2/g after 600 °C heat treatment, with a pore volume of 1.16 cm3/g and an average pore size of 8.5 nm. In order to explore the potential application of the SiO2–ZrO2 xerogel for the removal of organic dyes, its adsorption capacity was studied by removal of Rhodamine B (RhB) from aqueous solution through batch experiments. The results showed that the adsorption process of RhB onto SiO2–ZrO2 xerogel was slightly promoted under acidic conditions and significantly inhibited under strong alkaline conditions. And adsorption equilibrium can be achieved in 30 min. The kinetic data of the adsorption were analyzed using pseudo-first-order and pseudo-second-order models. The results indicated that the pseudo-second-order model described the adsorption mechanism better. The sorption behavior was evaluated by Langmuir and Freundlich isotherm models. The results suggested that the Langmuir model could accurately describe the experimental data and the adsorption capacity qmax was 177.7 mg/g. Thermodynamic analysis revealed that the adsorption of RhB onto the SiO2–ZrO2 xerogel was both spontaneous and exothermic in nature. Thus, the as-prepared SiO2–ZrO2 xerogel might be used as an adsorbent for wastewater treatment, especially for the removal of dyes.

Effect of residual stress in Pb (Zr0.52Ti0.48) O3 – BiFeO3 multilayer cantilever structure

This paper discussed about the integration issues of Pb (Zr0.52Ti0.48) O3 – BiFeO3 (PZT - BFO) multilayer thin film deposited on silicon substrate for possible application in future micro-electro-mechanical system (MEMS) devices. The PZT - BFO multilayer thin film is deposited on silicon wafer by sol-gel technique. The multilayer film is annealed at 650 °C in air for 60 min. The deposited multilayer film is found to be polycrystalline in nature. The PZT-BFO multilayer exhibited room temperature multiferroic properties (remnant polarization of 37 mC/ cm 2 and remnant magnetization of 3.1 emu / cm 3 ). To fabricate the PZT - BFO multiferroic cantilever structures, a two-mask process flow is developed. Etch rates of the PZT - BFO multilayer (180 nm/ min), ZrO2 buffer layer (35 nm/ min) and SiO2 layer (350 nm/ min) are optimized in CHF3 plasma. The multiferroic cantilever structures are released by isotropic etching of silicon using SF6 plasma. Bending and cracks are observed in the released cantilever structures due to the generation of residual stress in the multilayer thin film. Effect of residual stress on the PZT - BFO cantilever structure is also verified by simulation.

Microstructure and ablation performance of SiC–ZrC coated C/C composites prepared by reactive melt infiltration

To improve the ablation resistance of carbon/carbon (C/C) composites, SiC–ZrC coating was prepared by reactive melt infiltration (RMI) on C/C composites. The microstructure and morphology of the coating were characterized by scanning electron microscopy coupled with energy dispersive spectrometry (SEM–EDS), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscope (TEM). The TEM specimen was fabricated by focused ions beam (FIB). The results show that the SiC–ZrC coating prepared on the condition of optimum parameter exhibits outstanding anti-ablation performance. After ablation for 60 s in oxyacetylene torch environment at heat flux of 4186 kW/m2, the mass ablation rate (MAR) and linear ablation rate (LAR) of the coated composites were 1.18 × 10−3g/s and 2.47 × 10−3 mm/s, which were 83.6% and 54.5% reduction compared with uncoated composites. During the ablation, the formed molten eutectics SiO2–ZrO2 can fill the pores and act as a diffusion barrier for oxygen and heat.

The deactivation of a ZnO doped ZrO2-SiO2 catalyst in the conversion of ethanol/acetaldehyde to 1,3-butadiene.

A deactivation study on the ethanol/acetaldehyde conversion to 1,3-butadiene over a ZnO promoted ZrO2–SiO2 catalyst prepared by a sol–gel method was performed. The samples were characterized by N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), NH3 temperature programmed desorption (NH3-TPD), X-ray powder diffraction characterization (XRD), thermogravimetric analyses (TGA), Fourier transform infrared resonance (FT-IR), 13C magic-angle spinning nuclear magnetic resonance (13C NMR) and X-ray photoelectron spectroscopy (XPS). The pore structure characteristics and surface acidity of Zn0.5–Zr–Si catalysts were largely decreased with time-on-stream and no crystal structure was formed in the used catalyst, indicating that the deactivation was caused by carbon deposition. Two main types of carbon deposition were formed, namely low-temperature carbon deposition with the oxidation temperature of around 400 °C and high-temperature carbon deposition with the oxidation temperature of 526 °C. The carbon species were mainly composed of graphitized carbon, amorphous carbon, carbon in C–O bonds and carbonyls. The deactivated catalyst could be regenerated by a simple oxidation process in air. Adding a certain amount of water into the feed had a positive effect on reducing the carbon deposition.

Absorption and emission features of Ho3+ ion in Nb2O5 mixed Lithium zirconium silicate glasses

Li2O–ZrO2–SiO2: Ho3+ glasses mixed with Nb2O5 were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The optical absorption spectra of all glasses recorded at room temperature in the wavelength region 300-2000 nm exhibited several absorption bands all from the ground state 5I8 to 5G5, 5G6, 5F1, 5F3, (5F4+5S2), 5F5, 5I5, 5I6, 5I7. The luminescence spectra of all the glasses recorded at room temperature in the visible and NIR regions exhibited the following prominent emission bands 5F3 → 5I8, 5S2 → 5I8, 5G4 → 5I6, 5K8 → 5I7, 5F5 → 5I8 ,5G5 → 5I6, 5F4 →5I7, 5G5 → 5I5, 5F2 → 5I6, 5F3 → 5I6, 5I5 → 5I8 (Visible region) and ,5I7 → 5I8 (NIR region). The luminescence spectra of Nb2O5 mixed Li2O–ZrO2–SiO2 glasses (free of Ho3+ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Nb5+ ions in the glass network. The Judd–Ofelt theory was successfully applied to characterize Ho3+ spectra of all the glasses. From this theory, various radiative properties like transition probability A, branching ratio βr, the radiative lifetime τr, for 5S2 emission levels in the spectra of these glasses has been evaluated. The radiative life time for 5S2 level of Ho3+ ions has also been measured and quantum efficiencies were estimated.

Tuning the structural and mechanical properties in ZrO2-SiO2 binary system through Y3 + inclusions

The present investigation explores the influence of yttrium (Y3+) inclusions in ZrO2-SiO2 binary system (YSZ) on its structural and mechanical features. The powders were synthesized through sol-gel technique and an exclusive characterization were undertaken to investigate the structural and mechanical features influenced by Y3+ additions. Characterization techniques affirmed the crucial role of Y3+ on the resultant structural and thermal stability of the YZS system. Instrumented indentation inferred the enhanced mechanical properties demonstrated by YZS system in comparison with pure ZrO2–SiO2 binary system (ZS).

Determination of sulfur-containing anions in alkaline solutions using arrays of DP-sensors based on hybrid perfluorinated membranes with proton-donor dopants

The influence of proton-donor properties and concentration of dopant nanoparticles introduced into Nafion and MF-4SС perfluorosulfonic cation-exchange membranes on the characteristics of cross-sensitive DP-sensors (sensors whose analytical signal is the Donnan potential) in alkaline solutions of sulfur-containing organic compounds were studied. The dopants were acid salts of heteropoly acids (HPAs) and hydrated silica SiO2 and zirconia ZrO2 surface-modified with sulfur-containing groups and an acid HPA salt. A correlation was revealed between the DP-sensor sensitivity to anions (and zwitter-ions) in alkaline solutions, size and proton-donor ability of the added particles, and diffusion permeability of hybrid membranes. Optimum compositions of membranes for arrays of cross-sensitive DP-sensors ensuring the simultaneous determination of cations and anions (and zwitter-ions) in the test solutions with an error of less than 18% were selected.

Exploiting copper–silica–zirconia cooperative interactions for the stabilization of tetragonal zirconia catalysts and enhancement of the visible-light photodegradation of bisphenol A

Abstract Silica-doped tetragonal mesoporous zirconia nanoparticles, SiO2/ZrO2 (SZ), were successfully prepared by a simple microwave-assisted method, and the subsequent incorporation of copper (1–10 wt%) via an electrochemical method gave CuO/SiO2/ZrO2 (CSZ) catalysts. The SiO2 stabilized the ZrO2 completely in the tetragonal phase, but that the added copper occupied oxygen vacancies in the SZ lattice to perturb the catalysts and partially reintroduce the monoclinic phase. However, CuO enhanced the photoactivity of CSZ catalysts by lowering the band gap energy (from 4.35 eV to 2.70 eV) and acting as an electron trapper to suppress the recombination of electron–hole pairs. The activity of the catalysts in the photodegradation of bisphenol A was ranked in the following order: 5 CSZ (82%) > 1 CSZ (65%) > 10 CSZ (60%) > SZ (58%). The silica–copper–zirconia cooperative interactions affected the numbers of oxygen vacancies, defect sites, Zr–O–Si and Zr–O–Cu bonds, which consequently influenced the stabilization of ZrO2 as well as the photoactivity of each catalyst. A kinetic study demonstrated that the photodegradation followed the pseudo-first-order Langmuir–Hinshelwood model.

Waste-Free Recycling of Secondary Bacor Resources1

Technology is developed for two-stage processing of secondary zirconium-containing mineral resource. A production scheme includes mechanical treatment of bacor waste and subsequent chemical leaching of impurities. The main processes in the first (mechanical) stage are crushing and selective grinding with separation of high-zircon concentrate (Al2O3–ZrO2 system) and aluminum-zirconia product leaner with respect to ZrO2 (R 2O–Al2O3–ZrO2–SiO2 system). In the second stage the latter are leached with a fluoric acid solution. The waste-free technology proposed for enrichment makes it possible to use valuable secondary resources entirely with preparation of two end products: enriched bacor refractory and a slag-forming mixture for steel smelting production.

An ultralight silica-modified ZrO2–SiO2 aerogel composite with ultra-low thermal conductivity and enhanced mechanical strength

A novel, ultralight, ZrO2-fiber-reinforced ZrO2–SiO2 aerogel composite with superior thermal and mechanical properties is fabricated via a rapid gelation method. Pure ZrO2-SiO2 aerogel is modified by silica to effectively strengthen its nanostructure. The results demonstrate that the fabricated fiber-reinforced aerogel composites with ZrO2-fiber contents ranging from 0 to 15wt% exhibit ultra-low densities (0.16–0.33g/cm3), low thermal conductivities (0.0235–0.0296Wm−1K−1), and high compressive strengths (0.36–0.82MPa). The present study provides an efficient method to prepare light aerogel composites with low thermal conductivity and high mechanical strength, which can be used as superior heat-insulators in aerospace applications.

Structural relaxation of lead and barium-free crystal glasses

The structural relaxation of Na2O–K2O–CaO–ZrO2–SiO2 (NKCZ), Na2O–K2O–ZnO–ZrO2–SiO2 (NKzZ), Na2O–CaO–ZnO–ZrO2–SiO2 (NCzZ), K2O–CaO–ZnO–ZrO2–SiO2 (KCzZ), and Na2O–K2O–CaO–ZnO–ZrO2–SiO2 (NKCzZ) glasses were studied by thermomechanical analysis. The structural relaxation was described by the Tool–Narayanaswamy–Mazurin model (TNMa). The relaxation function of Kohlrausch, Williams, and Watts (KWW) was used. The parameters of relaxation model were calculated by nonlinear regression analysis of thermodilatometric curves measured under cyclic time–temperature regime by thermomechanical analyzer under the constant load. The values of the exponent b of the KWW equation, modulus K, limit dynamic viscosity η 0 of the Mazurin’s expression for relaxation time, and constant B of the Vogel–Fulcher–Tammann viscosity equation were optimized. It was found that TNMa relaxation model very well describes the experimental data. A more detailed analysis of the obtained results showed that the equimolar substitution of SiO2 by ZrO2 (i.e., the increase of the ZrO2 content in the glass) decreases the parameter b, therefore the continuous distribution of the relaxation times spectrum is widening. A wider spectrum of relaxation times was obtained even in the case of substitution of ZnO for CaO and K2O for Na2O. Substitution of ZrO2 for SiO2 decreases the dynamic viscosity limit η 0 that corresponds to an activation energy increase of temperature dependence of isostructural viscosity. Increased content of ZrO2 in the glass caused the increase of the value of the modulus K.

Hydrodeoxygenation of m-cresol over nickel and nickel phosphide based catalysts. Influence of the nature of the active phase and the support

The present work studied the effect of two supports (SiO2 and tetragonal ZrO2) on the performance of metallic nickel and nickel phosphide catalysts for the hydrodeoxygenation (HDO) of m-cresol carried out at 340°C under 4MPa. All catalysts were characterized using several techniques (ICP, N2 adsorption-desorption, XRD, H2-TPR, NH3-TPD). The active phases (Ni(0) and Ni2P) were successively prepared at 450°C under 4MPa of H2, as observed by XRD. The activity and deoxygenation properties depended on the active phase (Ni vs Ni2P) and the support (SiO2 vs ZrO2). The order of HDO activity (mmolg−1h−1) followed: Ni2P/ZrO2 (47.0)>Ni2P/SiO2 (28.3)>>Ni/ZrO2 (3.0)>Ni/SiO2 (1.1). The Ni2P phase was clearly much more active than metallic Ni. In addition, the use of zirconia as support enhanced the deoxygenation properties compared to silica, which can be attributed to the presence of oxophilic sites (Zr3+/Zr4+) favoring the adsorption of m-cresol.