Low ZrO2 Research Articles

Enhancement of CO2 adsorption and oxygen transfer properties on γ-Al2O3 support through surface modification with MgO-ZrO2 for coke suppression over Ni catalyst in CO2 reforming of methane

This work focuses on employing commercial γ-Al2O3 for surface modification with MgO-ZrO2 mixed oxide to enhance the potential of CO2 adsorption and oxygen mobility. This enhancement facilitates its application as a support in catalysts for CO2 utilization such as CO2 reforming of methane (CRM). To achieve this perspective, γ-Al2O3 was modified with 10 wt.% of various MgO and ZrO2 contents (MgO:ZrO2= 10:0, 9:1,7:3, 5:5, 3:7, 1:9 and 0:10) using the impregnation method. All samples including unmodified γ-Al2O3 (Al) were characterized. Due to the increase in basicity and oxygen transfer around the surface, the improvement of the CO2 adsorption was observed on γ-Al2O3 modified with 9 wt.% MgO-1 wt.% ZrO2 (9Mg1ZrAl) and 10 wt.% MgO (10MgAl), respectively. An application of these two superior samples as a support of 10 wt.% Ni (10Ni) catalysts for CRM was investigated and compared with an unmodified γ-Al2O3. Characterization results suggest the formation of NiO-MgO solid solution at the surface due to the decrease in metal-support interaction and the increase in metal dispersion. The Ni catalysts with the surface-modified support show higher CO2 activity that raises carbon deposition resistance. The greatest coke prevention was observed on 10Ni/9Mg1ZrAl that lowers the coke deposition by 42 % compared to 10Ni/Al. It indicates that the composition of this modification allowed very low ZrO2 portion to merge with MgO and MgO to form solid solution with NiO. This enables the 10Ni/9Mg1ZrAl catalyst to generate labile oxygens which can be conveyed to the Ni metal sites on the catalyst.

Thermal shock resistance of industrial foam filters-a comparative study

For ceramic foams, there is no thermal shock resistance testing standard available at the moment. This work aims to investigate the influence of the different test conditions. Among the descending thermal shock test conditions, heating mode, thermal shock temperature, and quench medium, the latter has the highest impact on the residual mechanical properties. Reference alumina (Al2O3) foams and commercially-available ceramic foam filters (ZrO2, Al2O3–ZrO2, Al2O3–P, and SiC) were subjected to thermal shock with water and air as quenching medium. Due to the low thermal expansion coefficients, SiC and ZrO2 possess the highest calculated thermal shock resistance Rfoam. SiC and ZrO2 foams also had the highest experimentally evaluated residual strength after being quenched in water. An immersion thermal shock procedure with molten metal was tested on Al2O3 reference test pieces. The residual elastic moduli and strengths decrease with increasing temperature which is a function of immersion duration and depends on the usage of an interlayer between the foams and the melt. In order to evaluate the temperature gradient and its development over time, temperature measurements were conducted using a thermocouple inserted and fixed in the midplane of the foams and bulk test pieces.

The role of zircon in hydrothermal heavy REE mineralisation: The case for unconformity-related ore deposits of north-west Australia

Zircon is hailed for its chemical and physical durability, but can undergo extensive chemical and structural modification due to radiation damage via the emission of alpha (α) particles, and subsequent low-temperature hydrothermal alteration. Here, we investigate Archean zircons from arkosic metasediments of the Browns Range Metamorphics (BRM) to evaluate their role in the formation of local unconformity-related heavy rare earth element (REE) ore deposits, within the Browns Range Dome, Western Australia. We determine that the heavy REE inventory of the BRM are primarily hosted in zircon, and that these zircons have a wide range of major element totals (77 to ~100 wt%, including low SiO2 and ZrO2 contents), and high and variable ‘non-formula’ components (U, Th, Y, REE, Nb, P, Al, Ca, Fe, Ti, F and OH− or H2O). Concentrations of Y + REE in some cases exceed 8 wt%. Extensive radiation damage (metamictisation) is confirmed by structural features including porous and amorphous domains, cavities, and voids. The lack of regional thermal events over an extended period likely prevented thermal annealing of these radiation-damaged zircons. Uptake of non-formula elements in metamict zircon, most likely during sedimentation in the late Archean, promoted further radiation damage, such that these grains remained highly susceptible to alteration by subsequent hydrothermal fluid circulation. We propose that the unconformity-related REE mineralisation was formed by saline fluids leaching Y + REE (and possibly P) from metamict zircon in the BRM, followed by ore mineral precipitation in fault zones near, and along the regional unconformity. More broadly, this model of ore formation may be relevant to other basin-hosted mineral systems, and could be used to guide exploration for unconformity-related REE deposits in Australia, and globally.

Improved charge-transfer resonance in graphene oxide/ZrO2 substrates for plasmonic-free SERS determination of methyl parathion

This work reports a sensitive SERS substrate based on graphene oxide (GO) and quantum-sized ZrO2 nanoparticles (GO/ZrO2) for label-free determination of the organophosphate pesticide methyl parathion (MP). The enhanced light-matter interactions and the consequent SERS effect in these substrates resulted from the effective charge transfer (CT) mechanism attributed to synergistic contributions of three main factors: i) the strong molecular adherence of the MP molecules and the ZrO2 surface which allows the first layer-effect, ii) the relatively abundant surface defects in low dimensional ZrO2 semiconductor NPs, which act as intermediate electronic states that reduce the large bandgap barrier, and iii) the hindered charge recombination derived from the transference of the photoinduced holes to the GO layer. This mechanism allowed an enhancement factor of 8.78 × 104 for GO/ZrO2-based substrates, which is more than 5-fold higher than the enhancement observed for platforms without GO. A detection limit of 0.12 μM was achieved with an outstanding repeatability (variation ≤4.5%) and a linear range up to 10 μM, which is sensitive enough to determine the maximal MP concentration permissible in drinking water according to international regulations. Furthermore, recovery rates between 97.4 and 102.1% were determined in irrigation water runoffs, strawberry and black tea extracts, demonstrating the reliability of the hybrid GO/ZrO2 substrate for the organophosphate pesticides quantification in samples related to agri-food sectors and environmental monitoring.

Combined effect of low ZrO2 content and carbon nanostructures on mechanical and wear properties of hot-pressed Al2O3/ZrO2 hybrid nanocomposites

Al2O3/ZrO2 systems with higher ZrO2 amounts (≥20 wt%) are known to offer improved properties such as fracture toughness, but are restricted in their hardness, wear and strength performances. The incorporation of a third phase carbon nanostructure (such as CNTs and GN) to Al2O3/ZrO2 reinforced with low ZrO2 content (≤5wt%) has emerged as a novel process to overcome this property trade-off by exploring the remarkable mechanical properties of these hybrid nanocomposite systems. Therefore, in the current work, colloidal mixing followed by hot-pressing process (@ 1600°C) were used to consolidate monolith Al2O3, Al2O3/ZrO2, Al2O3/ZrO2/CNTs and Al2O3/ZrO2/GN nanocomposite structures using low ZrO2 content (4wt%) and optimum amounts of CNTs (2wt%) and GN (0.5wt%) as the hybrid reinforcement phases. Microhardness, fracture toughness and flexural strength properties were improved from 19GPa, ∼3MPa.m1/2 and ~260MPa up to 24GPa, ∼7MPa.m1/2 and ~374MPa respectively, with hybrid additions of ZrO2/CNTs and ZrO2/GN to the monolith Al2O3. The primary source of the property enhancement in the hybrid nanocomposites was due to reduction in the matrix and ZrO2 grain sizes (decreased up to ∼78%), good interaction between reinforcement phases and combined mechanisms such as crack bridging and deflection, matrix grain wrapping and grain gluing by CNTs and GN. The wear rate of the parent Al2O3 was also improved from 9.71 × 10−5 mm3/N.m up to 0.81 × 10−5 mm3/N.m (showing ∼92% decrease) with ZrO2/CNTs and ZrO2/GN hybrid inclusions, which was attributed to the overall enhanced mechanical properties and wear resistant mechanisms during the dry sliding.

Effect of Treated Zirconium Oxide (ZrO2) Nanoparticles on the Color and Surface Properties of Interim Fixed Prostheses.

ABSTRACTObjective:Zirconium oxide (ZrO2) nanoparticles addition to interim fixed prostheses (IFPs) was suggested to improve the mechanical properties. However, the effect of ZrO2 on the color and surface properties of IFP was neglected. Therefore, this study aimed to investigate the effect of ZrO2 on the color, hardness, and surface roughness of IFP.Materials and Methods:Customized split-press metal molds were used for the fabrication of forty disk-shaped acrylics (10 mm × 1.5 mm). The salinized ZrO2 particles were weighed using an electronic balance and added in concentrations of 1wt %, 2.5wt %, and 5wt % of auto-polymerized acrylic polymer powder. Based on ZrO2 concentrations, specimens were divided into one control group without ZrO2 and three ZrO2 study groups 1 ZrO2, 2.5 ZrO2, and 5 ZrO2, respectively. A double beam ultraviolet-visible reflection spectrophotometer was the instrument used for recording the color measurements (CIEDE2000). The Microhardness and surface roughness (Ra, μm) of all samples were tested. ANOVA test was used for data analysis (α = 0.05)Results:Notable changes were seen between the group containing 1% and the other two groups in Δa*, ΔΕab, and ΔΕ00 parameters. Statistically significant differences were observed among the three groups for the ΔL* parameter. No notable changes were seen between the group containing 1% and the group containing 5% for the Δb* parameter. The 1% group showed a statistically significant difference in hardness in comparison to the 5% group. For surface roughness, the 2.5% group presented statistically significant higher surface roughness as opposed to the 0% control group.Conclusions:The addition of ZrO2 in high concentrations resulted in a noticeable color change in IFP. However, the surface properties did not change hardness and roughness with ZrO2 addition except roughness increased with 2.5% ZrO2. Low ZrO2 addition did not result in a change in color and surface properties of IFP.

The Effect of ZrO2 as Different Components of Ni-Based Catalysts for CO2 Reforming of Methane and Combined Steam and CO2 Reforming of Methane on Catalytic Performance with Coke Formation

The role of ZrO2 as different components in Ni-based catalysts for CO2 reforming of methane (CRM) has been investigated. The 10 wt.% Ni supported catalysts were prepared with ZrO2 as a support using a co-impregnation method. As a promoter (1 wt.% ZrO2) and a coactive component (10 wt.% ZrO2), the catalysts with ZrO2 were synthesized using a co-impregnation method. To evaluate the effect of the interaction, the Ni catalyst with ZrO2 as a coactive component was prepared by a sequential impregnation method. The results revealed that the activity, the selectivity, and the anti-coking ability of the catalyst depend upon the ZrO2 content, the Ni-ZrO2 interaction, basicity, and oxygen mobility of each catalyst resulting in different Ni dispersion and oxygen transfer pathway from ZrO2 to Ni. According to the characterization and catalytic activation results, the Ni catalyst with low ZrO2 content (as a promoter) presented highest selectivity toward CO owning to the high number of weak and moderate basic sites that enhance the CO2 activation-dissociation. The lowest activity (CH4 conversion ≈ 40% and CO2 conversion ≈ 39%) with the relatively high quantity of total coke formation (the weight loss of the spent catalyst in TGA curve ≈ 22%) of the Ni catalyst with ZrO2 as a support is ascribed to the lowest Ni dispersion due to the poor Ni-ZrO2 interaction and less oxygen transfer from ZrO2 to the deposited carbon on the Ni surface. The effect of a poor Ni-ZrO2 interaction on the catalytic activity was deducted by decreasing ZrO2 content to 10 wt.% (as a coactive component) and 1 wt.% (as a promoter). Although Ni catalysts with 1 wt.% and 10 wt.% ZrO2 provided similar oxygen mobility, the lack of oxygen transfer to coke during CRM process on the Ni surface was still indicated by the growth of carbon filament when the catalyst was prepared by co-impregnation method. When the catalyst was prepared by a sequential impregnation, the intimate interaction of Ni and ZrO2 for oxygen transfer was successfully developed through a ZrO2-Al2O3 composite. The interaction in this catalyst enhanced the catalytic activity (CH4 conversion ≈ 54% and CO2 conversion ≈ 50%) and the oxygen transport for carbon oxidation (the weight loss of the spent catalyst in TGA curve ≈ 7%) for CRM process. The Ni supported catalysts with ZrO2 as a promoter prepared by co-impregnation and with ZrO2 as a coactive component prepared by a sequential impregnation were tested in combined steam and CO2 reforming of methane (CSCRM). The results revealed that the ZrO2 promoter provided a greater carbon resistance (coke = 1.213 mmol·g−1) with the subtraction of CH4 and CO2 activities (CH4 conversion ≈ 28% and CO2 conversion ≈ %) due to the loss of active sites to the H2O activation-dissociation. Thus, the H2O activation-dissociation was promoted more efficiently on the basic sites than on the vacancy sites in CSCRM.

Seeded Stage III glass dissolution behavior of a statistically designed glass matrix

AbstractThe dissolution rate of some glasses accelerates after prolonged time spent at a slow, residual dissolution rate. This phenomenon is referred to as Stage III behavior. The acceleration in glass dissolution rate linked to Stage III behavior is significant and may be the most impactful behavior to long‐term performance of glass in a repository. This work is aimed at understanding the effect of glass composition on Stage III behavior to add a level of technical defensibility to glass disposal. To this end, a set of 24 glass compositions were statistically designed, where eight glass components (SiO2, B2O3, Al2O3, CaO, Na2O, SnO2, ZrO2, and Others) have been independently varied in order to study the individual effects of each glass component. These glasses have been subjected to static dissolution tests at 90°C in deionized water and then seeded with zeolite Na‐P2 28 days into the testing to induce Stage III behavior. The response of the glasses to the zeolite seeds fell into four primary types: (1) no response to seeds; (2) an immediate linear sustained acceleration in the rate; (3) an immediate linear acceleration in the rate followed by a decrease; and (4) a progressive acceleration in the rate that is concurrent with the addition of the seeds. The main glass components observed to influence these behaviors were CaO, Al2O3, B2O3, and ZrO2, where (1) CaO influenced which glasses showed a Stage III response to seeds (high CaO: types 2, 3, and 4) or did not respond to seeds (low CaO: type 1), (2) Al2O3 and B2O3 influenced which glasses showed a sustainable Stage III response (high Al2O3: types 2 and 4) versus transitory response (low Al2O3 and high B2O3: type 3), and (3) ZrO2 concentration influenced whether glasses showed a linear (high ZrO2: type 2) versus progressive (low ZrO2: type 4) response to seeds.

Improving Mechanical Properties of Polymeric Materials Using Oxide Nanoparticles

This paper investigated the effect of zirconium oxide (ZrO2) and titanium oxide (TiO2) on the morphology and mechanical properties of poly (methyl methacrylate) (PMMA) blends. Composites of PMMA (5/95 wt%) with ZrO2 and TiO2 were prepared by modified sol-gel reaction and then the composites were integrated by compression. The dispersion of ZrO2 and TiO2 nanoparticles in the polymer matrix was investigated after deposition as thin films, using optical microscope. It was studied also the transparency and the band gap of thin films of the individual compounds and of the mixed zirconia composites. It was observed that the dispersion of ZrO2 nanoparticles was relatively good with low ZrO2 content, but the aggregates of ZrO2 particles in a polymer matrix increased with increasing the ZrO2 content. The Vickers hardness test on PMMA and ZrO2-PMMA showed that the value of hardness increases as the percentage of ZrO2 increases. The adding of zirconia nanoparticles showed that the composites can be used in fabrication of different application as metal protection, dental materials, abrasion resistant materials, transparent protection due to the hardness tests.

Quantitative Effect of Zr Content on the Structure and Water–Gas Shift Reaction Activities of Gold Supported on Ceria–Zirconia

Effect of Zr content on the structure and water–gas shift reaction catalytic activities of Au-CeO2-ZrO2 catalysts were quantitatively analyzed in detail. For the low ZrO2 content (0–15 wt. %), the Ce-Zr-O solid solutions were formed through the substitutional incorporation of Zr cations into CeO2 lattice, resulting in the contraction of cell parameters a and d-spacing (i.e., lattice distortion) and the increase of microstrain and oxygen vacancies. Quantitatively, the enhanced WGS activities have good linear correlation with the cell parameters a, microstrain, Raman shift and oxygen vacancies. Whereas, for the rich-zirconia (45 wt. %) sample, Au-CeZr-45 has some isolated t-ZrO2 and fluorite CeO2 instead of solid solution. The isolated t-ZrO2 crystallites block the contact between Au and CeO2, resulting in the agglomeration of gold clusters and, as a consequence, poor WGS activity of Au-CeZr-45 catalyst.

Chemical Durability of Uranium Oxide Containing Glasses

Abstract ZrO2 doped Na-Ba-borosilicate glasses suitable as matrix materials for HLW immobilization were synthesized and corrosion behaviour was investigated in different aqueous media. Hydrolytic stability is increased with the doping level until 5 mol %; above this value the glass vitrification tendency is strongly intensified. Unexpectedly, ZrO2 doping diminished the corrosion stability in 1M HCl solution, and low ZrO2 content showed a low corrosion resistance in 1M Na2CO3 solution also. Doping effect was negligible in case of synthetic seawater. The glass structure is significantly stabilized by the integration of the 30% UO3 added.

Interfacial charge-transfer process across ZrO2-TiO2 heterojunction and its impact on photocatalytic activity

Abstract In this paper, ZrO2-TiO2 composites were synthesized by sol-gel method with different ZrO2:TiO2 molar ratios (01:99, 05:95 and 10:90). The results identified two trends; at a low ZrO2 content, the incorporation of Zr4+ into the TiO2 lattice was possible provoking generation of oxygen vacancies (1 mol% of ZrO2); while at higher ZrO2 contents, ZrO2-TiO2 heterojunctions were created (5 and 10 mol% of ZrO2). The photocatalytic activity was evaluated by measuring photodegradation of phenoxyacetic acid, 2,4-dichlorophenoxyacetic acid or 4-chlorophenol solutions. The ZT-5 composite shows the best performance attributed to surface states at the interface of ZrO2-TiO2 heterojunctions. These surface states act as traps for charge carriers favoring the spatial separation of electron-hole pairs until reaching a maximum in the composite with 5 mol% of ZrO2. The ZT-5 composite showed the most negative flat band potential and the highest donor density indicating that these surface states are in optimal concentration. At higher ZrO2 contents, charge carrier separation is less effective, which decreases the photocatalytic activity. Nevertheless, the molecule structure has an impact on the direct or indirect charge transfer process as was evidenced by EIS measurements.

Ion-conductive and transparent PVdF-HFP/silane-functionalized ZrO2 nanocomposite electrolyte for electrochromic applications

Polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) composite polymer electrolyte loaded with 3-isocyanatopropyltriethoxysilane (IPTES) functionalized zirconium oxide (ZrO2) nanoparticles is successfully synthesized and evaluated for electrochromic application. Incorporation of ZrO2 into the polymeric substrate enhances the ionic conductivity of the electrolyte. Meanwhile, the functionalization of ZrO2 nanoparticles with IPTES ligand enhances the electrolyte’s optical transmissivity. The amount of ligand and its time of reaction with ZrO2 are found to affect the overall property of the electrolyte. The electrolyte exhibits a balance of low crystallinity and low ZrO2 aggregation and agglomeration resulting to a potential next generation electrolyte for energy efficient windows.

Low leakage ZrO2 based capacitors for sub 20 nm dynamic random access memory technology nodes

During dynamic random access memory (DRAM) capacitor scaling, a lot of effort was put searching for new material stacks to overcome the scaling limitations of the current material stack, such as leakage and sufficient capacitance. In this study, very promising results for a SrTiO3 based capacitor with a record low capacitance equivalent thickness value of 0.2 nm at target leakage current are presented. Due to the material properties of SrTiO3 films (high vacancy concentration and low band gap), which are leading to an increased leakage current, a physical thickness of at least 8 nm is required at target leakage specifications. However, this physical thickness would not fit into an 18 nm DRAM structure. Therefore, two different new approaches to develop a new ZrO2 based DRAM capacitor stack by changing the inter-layer material from Al2O3 to SrO and the exchange of the top electrode material from TiN to Pt are presented. A combination of these two approaches leads to a capacitance equivalent thickness value of 0.47 nm. Most importantly, the physical thickness of <5 nm for the dielectric stack is in accordance with the target specifications. Detailed evaluation of the leakage current characteristics leads to a capacitor model which allows the prediction of the electrical behavior with thickness scaling.

Activity of transition metal sulfides supported on Al2O3, TiO2 and ZrO2 in the parallel hydrodesulfurization of 1-benzothiophene and hydrogenation of 1-methyl-cyclohex-1-ene

Sulfided conventional transition metals Co, Ni, Mo, and W and noble metals Rh, Pd, Ir, Pt, and Re deposited over conventional support γ-Al2O3 (SBET = 262 m2g−1), and unconventional supports TiO2 (anatase, SBET = 140 m2g−1) and ZrO2 (baddeleyite, SBET = 108 m2g−1) were studied in the parallel hydrodesulfurization of 1-benzothiophene (HDS) and hydrogenation of 1-methyl-cyclohex-1-ene (o-HYD) at 360 °C and 1.6 MPa. Mo, W, Co, and Ni sulfided catalysts exhibited relatively low activity in both HDS and o-HYD. For these sulfides, the TiO2 and ZrO2 support effect relative to γ-Al2O3 varied by the factor 0.4–9.3. In contrast, the supported sulfides of Rh, Re, Pd, Pt, and Ir were highly active in HDS with low TiO2 and ZrO2 support effect relative to γ-Al2O3 (Rh/ZrO2 being an exception). Rh, Re, and Pd sulfided species exhibited relatively low activities in o-HYD reaction while Ir and Pt species exhibited high activities in o-HYD. The reference industrial bimetallic CoMo and NiMo Al2O3 supported catalysts exhibited desirable high HDS but low o-HYD activities.

Monte Carlo simulations of coupled diffusion and surface reactions during the aqueous corrosion of borosilicate glasses

Borosilicate nuclear waste glasses develop complex altered layers as a result of coupled processes such as hydrolysis of network species, condensation of Si species, and diffusion. However, diffusion has often been overlooked in Monte Carlo models of the aqueous corrosion of borosilicate glasses. Therefore, three different models for dissolved Si diffusion in the altered layer were implemented in a Monte Carlo model and evaluated for glasses in the compositional range (75−x) mol% SiO2 (12.5+x/2) mol% B2O3 and (12.5+x/2) mol% Na2O, where 0≤x≤20%, and corroded in static conditions at a surface-area-to-volume ratio of 1000m−1. The three models considered instantaneous homogenization (M1), linear concentration gradients (M2), and concentration profiles determined by solving Fick's 2nd law using a finite difference method (M3). Model M3 revealed that concentration profiles in the altered layer are not linear and show changes in shape and magnitude as corrosion progresses, unlike those assumed in model M2. Furthermore, model M3 showed that, for borosilicate glasses with a high forward dissolution rate compared to the diffusion rate, the gradual polymerization and densification of the altered layer is significantly delayed compared to models M1 and M2. Models M1 and M2 were found to be appropriate models only for glasses with high release rates such as simple borosilicate glasses with low ZrO2 content.

Sonochemical synthesis of NiMo/Al2O3–ZrO2 nanocatalyst: Effect of sonication and zirconia loading on catalytic properties and performance in hydrodesulfurization reaction

In order to elucidate the effect of support composition and preparation method on catalytic properties and hydrodesulfurization activity, a series of NiMo/Al2O3–ZrO2 nanocatalysts with various ZrO2 contents were synthesized by using impregnation and sonochemical methods. The samples were characterized by using BET, XRD, FESEM, PSD, EDX and FTIR techniques. The results indicated that in the samples with low ZrO2 contents, zirconia particles existed as amorphous phase which confirmed the existence of stronger interaction between metal oxides. The nanocatalyst synthesized by sonochemical method resulted in smaller particles with more uniform distribution compared to impregnation method. The catalytic activity of synthesized nanocatalysts was measured in a stirred slurry-tank reactor at atmospheric pressure and 160°C using thiophene as the sulfur containing model compound. The catalytic activity of the sonochemically synthesized nanocatalysts was higher than those synthesized by impregnation method. ZrO2 loading led to a catalyst with higher activity compared to the zirconia free catalyst. Maximum catalytic activity was obtained with the zirconia content of 15wt.%. Further introduction of zirconia led to a decrease in catalytic activity due to the formation of large ensembles on nanocatalyst surface. Furthermore, this work suggested a reaction path to reveal the mechanism of thiophene hydrodesulfurization over NiMo/Al2O3–ZrO2 nanocatalyst.

Effect of ZrO2 Additive on Phase Composition of CaO-ZrO2-SiO2 Glaze

The effect of ZrO2 content on phase composition of CaO-ZrO2-SiO2 glass system was investigated in the present research. CaO, ZrO2 and SiO2 were used to made frits. It was found that glass samples of high ZrO2 content contained wollastonite, pseudowollastonite and Ca2ZrSi4O12 as the major components of crystalline phase and samples of low ZrO2 content mainly included non-crystalline phase. The present results also confirmed that firing temperature and soaking time have influence on the phase transition of wollastonite. At high temperature, the wollastonite phase was changed to the pseudowollastonite phase which was verified by thermal analysis. Microstructure observations of glaze samples revealed the formation of crystals in different directions. The thermal expansion mismatch between glaze and body led to the development of microcracks.

Formation of Low-Melting-Point Inclusions in Al-Deoxidized Steel Refined by High-Basicity Calcium Aluminate Slag in ZrO2 Crucible Experiments

ZrO2 crucible experiments were carried out in the laboratory to study the formation of low-melting-point inclusions in steel, during which aluminum deoxidization and a high-basicity calcium aluminate refining slag (CaO/SiO2: 6 to 8, Al2O3 40 to 45 pct) were used. Four experiments were done with different slag/steel reaction times (30, 60, 90, and 180 minutes). It was found that inclusions were mainly composed of CaO-Al2O3-ZrO2 with very limited SiO2, in spherical morphology and with sizes mainly less than 5 μm. They can be classified into two types according to the ZrO2 content. The first type contained much lower ZrO2, whereas a much higher level of ZrO2 was detected in the other type. An evolution of inclusions with the reaction time was observed and studied. The obtained results indicated that chemical compositions of inclusions were widely scattered in the CaO-Al2O3-ZrO2 phase diagram after 30 min reaction. However, the composition of inclusions became much more uniform and concentrated in low-melting-temperature regions at 60, 90, and 180 minutes, which would be favorable to prevent nozzle clogging and fatigue problems. Compared with the authors’ previous results obtained in MgO crucible experiments, it was found that low-melting-temperature inclusions can be targeted in shorter time in ZrO2 crucible experiments, without any degradation of cleanliness.

ZrO2 influence on structure and properties of some alkali lime zinc aluminosilicate glass ceramics

Glass–ceramics raw glazes in the Na2O–K2O–CaO–Al2O3–ZnO–SiO2 system with low ZrO2 additions (0, 3 and 5wt%), used as nucleating agent, were synthesised and thermally treated at 1250°C. Willemite (Zn2SiO4), sanidine (K0.831 Na0.169Al Si3O8), gahnite (ZnAl2O4) and zircon (Zr2SiO4) were the main crystalline phases identified by X-ray investigations in the resulting glazes. An increase of the ZrO2 content from 0 to 5wt% trigged an increase of the crystallinity degree from 71.34% to 83.73% and gahnite crystallite size from 176 to 336Å. Further, morphological and structural data of these glass–ceramics were supplementary determined by SEM, MAS-NMR of 27Al and 29Si and Raman Spectroscopy. The structural modifications in terms of the glass ceramic compositions, especially small ZrO2 additions to the expense of the SiO2 and the relationship between composition and colour characteristics of the glazes are investigated and presented in this paper.