Amount Of Zirconia Research Articles

Fabrication of Multi-Layered Ti-Ta-Zr Coatings by Non-Vacuum Electron Beam Cladding

In this study Ti-Ta-Zr coatings fabricated on VT1-0 titanium substrates by non-vacuum electron beam cladding in one, two and three passes were investigated. Coatings were characterized by a high quality; such defects as cracks and voids were not observed. The structure of coating was commonly dendritic. The acicular structure in the one-layered coating and in the first layer of multilayered coatings was revealed by using scanning electron microscopy (SEM). The results of the energy dispersive X-ray (EDX) analysis indicated the presence of tantalum and zirconium segregations in dendrite arms and in the space between them. It was found that dendritic branches contained the maximum of tantalum while an increased amount of zirconium was concentrated in the interdendritic space. The maximum concentration of alloying elements (56.87 wt. % Ta and 22.22 wt. % Zr) was obtained in the layer cladded in the third pass of an electron beam. The microhardness of Ti-Ta-Zr layers rose from 4.5 GPa to 6 GPa with an increase in .the percentage of alloying elements

Influence of Zirconium Addition in Platinum–Hexagonal Mesoporous Silica (Pt-HMS) Catalysts for Reforming of n-Heptane

A series of platinum/zirconium–hexagonal mesoporous silica (Pt/Zr-HMS) catalysts with different molar ratios of Si/Zr have been prepared and used for reforming reaction. The prepared catalysts were characterized by XRD, XRF, NH3-TPD, FTIR, Py-IR, nitrogen sorption, SEM, and TGA (for studying the coke deposition) techniques. The effects of various amounts of zirconium on the activity, selectivity, and coke deposition in the temperature range of 200–500 °C were compared. By increasing the incorporation of Zr into the Pt-HMS structure, the acidity of catalysts increased. The results show that the catalytic activity and selectivity for desired products (especially isomerization products) increased with decreasing Si/Zr amount (or increasing zirconium content). The best i-C7 selectivity (64.1%) was observed for Zr(5)-HMS at T = 200 °C.

Inhibition of order–disorder phase transition and improvements in the BICUVOX.1 properties by using yttria-stabilized zirconia particles

Composite solid electrolytes were prepared varying the addition of yttria-stabilized zirconia (3Y-TZP) from 3 to 26wt% using a matrix of copper-substituted bismuth vanadate (BICUVOX.1). The effects of stabilized zirconia concentration were added and their relation with the tensile strength, thermal expansion, phase transition and electrical conductivity were evaluated. When compared to pristine BICUVOX.1, the addition of 26wt% of 3Y-TZP led to an increase of 144% in tensile strength and a reduction of the thermal expansion coefficient from 12.3×10−6°C−1 to 9.6×10−6°C−1. Such improvements stems from grain growth inhibition due to the Zener pinning effect. Impedance measurements and thermal analyses showed that the addition of high zirconia concentrations is an effective way to prevent the γ′↔γ phase transition in the BICUVOX.1 matrix. Nevertheless, the total electrical conductivity has been continuously reduced with a progressive increase in the amount of zirconia.

Development of a Zirconia-Graphite Refractory for a SEN Application

Zirconia-graphite refractories are generally used in the slag-like zone of the subentry nozzle in continuous casting. A zirconia-graphite refractory has superior thermal shock resistance and corrosion resistance compared to MgO-C and Al2O3-C refractories. The effect of graphite on the zirconia-graphite refractory is not well documented. Therefore, in the present work an attempt has been made to evaluate the effect of graphite on the properties of the zirconia refractory. Graphite can be classified in terms of fixed carbon content and in this work three different types of graphite with varying fixed carbon content were used (99, 94, and 80%). The amount of zirconia was maintained at 82% and that of the graphite at 18%. Other processing parameters and ingredient concentrations were constant throughout the work. Refractory samples were fabricated using the cold isostatic method and refractory samples were coked at 1000°C in a reducing atmosphere. The effect of fixed carbon percentage on apparent porosity, bulk density, spalling resistance, and oxidation resistance were evaluated.

Effect of Zirconia Substitution on Structural and Mechanical Properties of ZTA Composites

Zirconia Toughened Alumina (ZTA) composites are attractive structural materials, which combine the high hardness and elastics modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In the present study, ZTA composites containing different amounts of zirconia (in the range 0-16 wt %) were prepared by slurry method and sintered at 1450oC and 1550oC for two hour. Microstructure of the composites was observed using scanning electron microscopy and phase content was detected by means of X- ray diffraction. Mechanical properties such as hardness, elastic modulus and flexural strength were measured. Density was increased with the increase of zirconia content for both sintering temperature, while grain size and elastic modulus was decreased with the same change of zirconia content. Hardness and flexural strength were carried out using the Vickers indentation and were discussed as a function of the ZrO2 content and sintering temperature. The toughening effect is attributed mainly to the zirconia t→m phase transformation. About 61% more flexural strength was found for 16 wt % ZTA composites when compared to the pure alumina.

Crystal-structure refinement of zirconium-rich eudialyte and its place among calcium-poor eudialyte-group minerals

The repeated refinement of the crystal structure of zirconium-rich eudialyte based on the X-ray diffraction data set collected earlier revealed new structural features. The trigonal unit-cell parameters are a = 14.222(3) A, c = 30.165(5) A, V = 5283.9 A3. The refinement resulted in the reduction of the R factor from 0.045 (2347F > 4σ(F)) to 0.035 (3124F > 3σ(F)). It was found that the ordering of Ca and Fe in six-membered rings leads to the lowering of the symmetry to R3. An excess amount of zirconium (more than three atoms per symmetrically independent unit) is located in the M2 microregion in square and five-vertex polyhedral positions. However, this amount is insufficient to be dominant, and the deficiency of zirconium is compensated for by sodium atoms. Based on the new data, zirconium-rich eudialyte can be assigned to the oneillite subtype, being a zirconium-rich and aluminum variety of raslakite.

Elaboration of Alumina-Zirconia Composites: Role of the Zirconia Content on the Microstructure and Mechanical Properties.

Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young’s modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5–20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h. Green bodies were then prepared by two methods: uniaxial pressing of spray-dried granules and slip casting of slurries, obtained by re-dispersing the spray dried granulates. After pressureless sintering at 1500 °C for 1 h, the slip cast samples gave rise to fully dense materials, characterized by a quite homogeneous distribution of ZrO2 grains in the alumina matrix. The microstructure, phase composition, tetragonal to monoclinic transformation behavior and mechanical properties were investigated and are here discussed as a function of the ZrO2 content. The material containing 10 vol % ZrO2 presented a relevant hardness and exhibited the maximum value of KI0, mainly imputable to the t → m transformation at the crack tip.

Synergistic Effect between TiO2, Zirconium and Carbon in the Photodegradation of Methyl Orange and Methylene Blue

The photocatalytic behaviour of TiO2 prepared from titanium (IV) ethoxide was determined with regard to the decomposition of methyl orange (MO) and methylene blue (MB) dyes, respectively. In addition, we compared the behaviour of TiO2 photocatalysts prepared in a similar fashion but which were (1) doped with different amounts of zirconium, (2) mixed with active carbon and (3) doped with different amounts of zirconium and mixed with active carbon. All of the TiO2 samples were found to be mesoporous with some microporosity having an average particle size between 200 and 500 nm and with anatase crystallographic modification. The kinetics of the MO and MB dyes' photocatalytic degradation fitted well with the Langmuir-Hinshelwood model and were found to follow pseudo-first-order kinetics. The rates were highest for the TiO2 samples doped with both Zr and mixed with the activated carbon. Characterization of these TiO2 photocatalysts was carried out by X-ray diffraction, scanning electron microscopy and adsorpti...

Production and Characterization of Hydroxyapatite-Zirconia Composites

AbstractHydroxyapatite (HA) ceramics are used extensively in different medical applications, such as biomaterial for repair or replacement of bone tissues since it resembles mineral component of bone and teeth. However, HA exhibits low fracture toughness due to its lack of strength and brittleness, thereby providing an obstacle to its application in implants that must withstand to high loads. In this study, HA was synthesized from human teeth by using a single calcinations method. Hydroxyapatite powders were mixed with different amounts of zirconia. The composites were sintered at different temperatures and characterized in terms of mechanical properties and the optimum sintering temperature was determined for good mechanical properties.

Zirconia nucleating agent on microstructural and electrical properties of a CaMgSi2O6 diopside glass–ceramic for microwave dielectrics

Addition of different amount of zirconia (ZrO2) nucleating agent into MgO–CaO–SiO2 system to enhance the quality factor (Q×f) of CaMgSi2O6 diopside glass–ceramic for low sintering temperature process (from 850 to 950°C) was carried out in this work. The microstructures, microwave dielectric properties and nucleating/growth mechanism of m-ZrO2 added CaMgSi2O6 system were analyzed using transmission electron microscopy (TEM) and electrical property measurements. Experimental results demonstrate that a solid solution of an amorphous phase MgO–CaO–SiO2 and ZrO2 forms after melted at 1500°C. The t-ZrO2 appears in the amorphous matrix first and then crystalline CaMgSi2O6 particle grows up at around the boundary of t-ZrO2 after thermal treatment at 850°C due to heterogeneous nucleating. Formation of t-ZrO2 is attributed to diffusion of Ca2+ to stabilize the m-ZrO2. The quality factor of CaMgSi2O6 was significantly enhanced by adding 3wt.% m-ZrO2, indicating that the ZrO2 nucleating agent could enhance crystallization and therefore increase the quality factor.

Porous Hydroxyapatite–Zirconia Composites Prepared by Powder Deposition and Pressureless Sintering

In the present study, hydroxyapatite was synthesized from local gypsum by microwave-hydrothermal method. Different percentage amounts of zirconia (0, 20, 30 and 40 wt.%) and poly-methyl methacrylate (40, 50 and 60 wt.%) mixed with hydroxyapatite (HA) for six hours. These powder mixture were deposited using deposition machine to produce specimens. These specimens were sintered at a temperature of 140°C with holding time for 1 hour into the green parts. These green parts were sintered at temperature of 1450°C with holding time for 2 hours. This process produces porous hydroxyapatite-zirconia composites with porosity between 62.76-73.92 percent. These composites were examined by XRD, XRF, SEM-EDX, BET analysis and compressive strength testing. Compressive strength of porous hidroxyapatite-zirconia composite decreased from 3.706 to 0.039 MPa when percentage amounts of zirconia increased up to 40 wt.%. This caused by several factors i.e. increased porosity, grain zirconia cracked, zirconia reacted with HA to produce CaZrO3, β-TCP and α-TCP, HA matrix cracks because of the phase change of tetragonal-zirconia into monoclinic-zirconia.

Effect of Zirconia, Zirconite and Zircon Mullite Additives on the Properties of Alumina Castable

The effect of the zirconia, zirconite, and zircon mullite additives on the properties of alumina-spinel castable has been investigated in present work. Results showed that the density of castables calcined at 110oC with the addition of zirconia and zirconite was higher than that of zircon mullite. With the increasing amount of additives, the densities of castables added with zirconia and zirconite were increased and that added with zircon mullite had not obviously difference. The apparent porosities of castables heated at 1600oC for 1h were about twice of those calcined at 110oC. The bulk densities of castables heated at 1600oC were lower than those calcined at 110oC. All the samples were expanded and the increasing amount of additives led to higher expansion rate. Though the densities of castables heated at 1600oC were lower than those calcined at 110oC, the cold crushing strength were much higher. When the amount of zirconia was less than 4maa%, the addition of zirconia was beneficial to improve the bending strength, and the addition of 4mass% zirconia led to the 18.2% improvemnt at the strength.

Influence of Zirconia Content and Grain Size on Physical and Mechanical Properties of Zirconia Toughened Alumina Ceramics

Physical and mechanical properties as well as microstructure of zirconia toughened alumina ceramics with different zirconia content were tested. The results show that the best physical and mechanical properties are obtained in sub-micron composite ceramic when zirconia content is 25%; while the physical and mechanical properties of nano-zirconia toughened alumina ceramics are far better than those of sub-micron zirconia toughened alumina ceramics. Therefore physical and mechanical properties of ceramics can be improved significantly by adding proper amount of zirconia into alumina matrix and refining zirconia particles.

Synthetic layered and tube-like silica nanoparticles as novel supports for metallocene catalysts in ethylene polymerization

Synthetic hybrid layered (HLNP) and tube-like (SNTP) silica nanoparticles were used to support the (nBuCp) 2ZrCl 2 metallocene catalyst for ethylene polymerization. Different amounts of zirconium were directly supported on the nanoparticles either with or without methylaluminoxane (MAO) treatment, allowing the effect of catalyst loading and particle surface on catalytic behaviour and polymer properties to be studied. Our results show that outstanding catalytic activities, comparable to a homogeneous polymerization, can be obtained when the metallocene catalyst is directly supported on the silica nanoparticles. The catalytic activity of the metallocene catalyst supported on MAO-treated nanoparticles increases with the amount of zirconium in the support. The molecular weights of the polyethylenes synthesized using both supported systems were higher than those from homogeneous polymerization. TEM images show that both nanoparticles were well dispersed in the polymer matrix and the HLNPs were exfoliated into the polymer. The presence of these nanoparticles in the resulting polymer improves the thermal stability of the matrix.

Crystallization Behavior of Lithium–Iron-Phosphate Glasses with Additions of ZrO2

Lithium–iron-phosphate (LIP) glasses with different amounts of zirconia were prepared by conventional melting and annealing process. The influence of the nucleation agent, zirconia, on the crystallization behavior of LIP glasses has been studied using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electronic microscopy (SEM) techniques. The results show that addition of 2 wt% of zirconia results in increases in the glass transition and crystallization temperatures and a decrease in the activation energy of crystallization. However, both temperatures decrease with increased addition of zirconia while the activation energy increases. The zirconia-free LIP glass only shows surface crystallization with crystals of LiFeP2O7. The glass containing 2 wt% of zirconia also has surface crystallization; however, mixed ZrP2O7 and LiFeP2O7 are crystallized. The addition of 5 and 8 wt% of zirconia leads to bulk crystallization and increasing formation of ZrP2O7 crystals besides the LiFeP2O7 phase.

Development of Computational Models for the Mark-IV Electrorefiner—Effect of Uranium, Plutonium, and Zirconium Dissolution at the Fuel Basket-Salt Interface

The electrochemical processing of spent metallic nuclear fuel has been demonstrated by and is currently in operation at the Idaho National Laboratory (INL). At the heart of this process is the Mark-IV electrorefiner (ER). This process involves the anodic dissolution of spent nuclear fuel into a molten salt electrolyte along with a simultaneous deposition of pure uranium on a solid cathode. This allows the fission products to be separated from the fuel and processed into an engineered waste form. A one-dimensional model of the Mark-IV ER has begun to be developed. The computations thus far have modeled the dissolution of the spent nuclear fuel at the anode taking into account uranium (U3+), plutonium (Pu3+), and zirconium (Zr4+). Uranium and plutonium are the two most important elements in the system, whereas zirconium is the most active of the noble metals. The model shows that plutonium is quickly exhausted from the anode, followed by dissolution of primarily uranium, along with small amounts of zirconium. The total anode potential as calculated by the model has been compared to experimental data sets provided by INL. The anode potential has been shown to match the experimental values quite well with root-mean-square (rms) values of 2.27 and 3.83% for two different data sets, where rms values closer to zero denote better fit.

Analysis of Component Depth Profiles at the Interface of Ti6242 Alloy and SiC, SiN Coatings after High Temperature Oxidation in Air

We have analyzed the interfacial elemental depth profile evolution after high temperature isothermal oxidation of SixCy and SixNy protective coatings deposited by dynamic ion mixing on a Ti6242 alloy (Ti-6Al-2Sn-4Zr-2Mo). Isothermal oxidation tests have been carried out at 600°C during 100 hours in air. We have observed a non-monotonic depth distribution of zirconium in GDOES and SIMS depth profiles after oxidation of SiC/Ti6242 and SiN/Ti6242 and we propose a kinetic model based on rate equations for analyzing the results. It is shown by modeling that a non-monotonic depth profile of zirconium occurs because zirconium from the Ti6242 alloy forms a zirconium oxide compound. As a result, the atomic concentration of zirconium decreases at the interface which induces a diffusion flux of zirconium from the bulk to the interface. This process leads to the increase of the total amount of zirconium at the film interface and thus formation of a non-monotonic depth profile.

Speciation of Mn(II), Mn(VII) and total manganese in water and food samples by coprecipitation–atomic absorption spectrometry combination

A speciation procedure based on the coprecipitation of manganese(II) with zirconium(IV) hydroxide has been developed for the investigation of levels of manganese species. The determination of manganese levels was performed by flame atomic absorption spectrometry (FAAS). Total manganese was determined after the reduction of Mn(VII) to Mn(II) by ascorbic acid. The analytical parameters including pH, amount of zirconium(IV), sample volume, etc., were investigated for the quantitative recoveries of manganese(II). The effects of matrix ions were also examined. The recoveries for manganese(II) were in the range of 95–98%. Preconcentration factor was calculated as 50. The detection limit for the analyte ions based on 3 sigma ( n = 21) was 0.75 μg L −1 for Mn(II). The relative standard deviation was found to be lower than 7%. The validation of the presented procedure was performed by analysis of certified reference material having different matrices, NIST SRM 1515 (Apple Leaves) and NIST SRM 1568a (Rice Flour). The procedure was successfully applied to natural waters and food samples.

Simultaneous coprecipitation of lead, cobalt, copper, cadmium, iron and nickel in food samples with zirconium(IV) hydroxide prior to their flame atomic absorption spectrometric determination

A simple and new coprecipitation procedure is developed for the determination of trace quantities of heavy metals (lead, cobalt, copper, cadmium, iron and nickel) in natural water and food samples. Analyte ions were coprecipitated by using zirconium(IV) hydroxide. The determination of metal levels was performed by flame atomic absorption spectrometry (FAAS). The influences of analytical parameters including pH, amount of zirconium(IV), sample volume, etc. were investigated on the recoveries of analyte ions. The effects of possible matrix ions were also examined. The recoveries of the analyte ions were in the range of 95–100%. Preconcentration factor was calculated as 25. The detection limits for the analyte ions based on 3 sigma (n=21) were in the range of 0.27–2.50μgL−1. Relative standard deviation was found to be lower than 8%. The validation of the presented coprecipitation procedure was performed by the analysis certified reference materials (GBW 07605 Tea and LGC 6010 Hard drinking water). The procedure was successfully applied to natural waters and food samples like coffee, fish, tobacco, black and green tea.

Production of opaque frits with low ZrO2 and ZnO contents and their industrial uses for fast single-fired wall tile glazes

The amounts of zirconium and zinc oxides, which raise the production costs of ceramic glazes, were decreased in fast single-fired wall tile frit compositions and an industrial frit production was conducted. Opacity of the fired frit-based glazes was accomplished by compositional modifications of frits with no other nucleating agent. It was determined that the ratios of Al2O3/ΣR2O, Al2O3/ΣRO, and Al2O3/B2O3 have significant effects on decreasing ZrO2 and ZnO levels in the frit composition. A reduction of 25% in both zirconia and zinc oxide contents of frit batches, with respect to the reference frit (R) containing 6–10% ZrO2 and 6–10% ZnO for a glossy white opaque wall tile glaze, was achieved in the ZD glaze consisting of 4.5–7.5% zirconia and 4.5–7.5% ZnO in its frit composition. It was concluded that zircon was the main crystalline phase of the glaze contributing the opacity. The ZD frit-based glaze has a thermal expansion coefficient value of 61.13 ± 0.32 × 10−7 °C−1 at 400 °C which well matches to that of the wall tile body. TS EN ISO 10545 standard tests were also applied to the final ZD glaze. It is confirmed that the production cost of a fast single-fired wall tile glaze can be decreased by 15–20% with the successful new frit developed.