Amount Of Zirconia Research Articles

Synthesis of sol–gel Na2Zr x Ti6−x O13 (0≤x≤1) materials and their performance in photocatalytic degradation of organic dyes

In this work we present the synthesis and characterization of four compositions of the solid solution with the general formula Na2Zr x Ti6−x O13 (0≤x≤1) which was prepared by a sol-gel method. The main goal of this work is to evaluate the influence of the incorporation of different amounts of zirconium into the binary phase Na2Ti6O13 on two properties: the textural surface and E g values. This titanate phase crystallizes in a monoclinic unit cell and is built into an octahedral TiO6 framework forming a rectangular tunnel structure. Additionally, we have compared their photocatalytic performances in degradation of organic dyes under visible light. The heat-treated sol-gel samples were characterized by X-ray powder diffraction, N2 physisorption, thermal analysis, UV and FT-IR spectroscopy. According to the X-ray powder diffraction results, the new ternary tunnel compound Na2ZrTi5O13 was obtained as a single phase at 800°C. The cell parameters for the two end-member phases of that solid solution were refined to confirm that Zr ion was incorporated into the structural framework. This ternary compound had an E g value of about 2.9 eV. The activity of all heat-treated Na2ZrTi5O13 samples was tested in the photocatalytic degradation of methylene blue and Rhodamine B under visible light. The Na2ZrTi5O13 calcined at 400°C showed the best performance with 95% of photodegradation of methylene blue and a half time t 1/2 of 15 min.

Adsorption voltammetry of the zirconium-alizarin red S complex at a multi-walled carbon nanotubes modified carbon paste electrode

We used a carbon paste electrode modified with multi-walled carbon nanotubes as a working electrode and studied the electrochemical behavior of zirconium-alizarin red S complex on it. It was found that the modified electrode exhibited a significant catalytic effect toward the reduction of free alizarin red S and the complex. The second derivative linear scan voltammograms of the complex were recorded by a polarographic analyser from 0 to −1000 mV (vs. SCE), and it was found that the complex can be adsorbed on the surface of the modified electrode, yielding a peak at about −470 mV, corresponding to the reduction of alizarin red S in the complex. The linear range was found to be 2.0 × 10−11–8.0 × 10−7 mol L−1, and the detection limit was 1.0 × 10−11 mol L−1 (S/N = 3) for 3 min accumulation. The procedure was successfully applied to the determination of trace amounts of zirconium in the ore samples.

Microstructure formation in thermally-sprayed duplex and functionally graded NiCrAlY/Yttria-Stabilized Zirconia coatings

NiCrAlY bond coats were deposited on a number of Inconel-738LC specimens using HVOF spray technique. For duplex coating, a group of these specimens were coated with Yttria Stabilized Zirconia (YSZ) using plasma spray technique. Functionally graded NiCrAlY/YSZ coatings were fabricated by plasma spray using co-injection of the two different powders in a single plasma torch. The amount of Zirconia in functionally graded coatings were gradually increased from 30 to 100 vol.%. Duplex and functionally graded coatings were then characterized using optical microscope, Scanning Electron Microscopy (SEM), Energy Dispersive x-ray Spectrometry (EDS), map analysis and X-ray Diffraction (XRD). The strength of the Adhesive coatings of the substrate was also measured. The results show that microstructure, porosity and compositions are gradually varied in the functionally graded coatings. EDS analyses revealed that oxidation of aluminum, chromium and yttrium in the NiCrAlY alloy are occur in the high-temperature plasma-spray stream during deposition. The oxidized products, mixed with zirconia at high temperature in a wide composition range, produce ceramic composites and increase the cohesion strength between the layers. The results also show a better performance in as-sprayed functionally graded coatings comparing with duplex coatings, especially regard to the adhesion strength of the coatings.

Effect of ZrO2 Addition on Vickers Hardness of Modified Basalt Glass-Ceramics

Improvement of mechanical properties of cordierite glass-ceramics using modified Egyptian basalt rocks by addition of different amounts of zirconia (ZrO2) was investigated. Crystallization behavior of modified basalt glass was studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The Vickers hardness of glass-ceramics containing different amounts of ZrO2 and formed at 1050°C for various heat-treatment time was compared. Toughness of the glass-ceramics increased with increasing the amount of transformable ZrO2, which process is probably caused by crack deflection due to the high stress field around transformed ZrO2.

微量のジルコニウムまたは炭素を添加した Co-Cr-Mo 合金の細胞適合性

微量のジルコニウムまたは炭素を添加した Co-Cr-Mo 合金の細胞適合性

Influence of ball milling on quasicrystal formation in melt-spun Zr-based glassy ribbons

The effect of mechanical deformation on the formation of quasicrystals in Zr57Ti8Nb2.5Cu13.9Ni11.1Al7.5 glassy ribbons has been investigated. The mechanical treatment drastically affects the crystallization behavior and, in particular, suppresses primary quasicrystal formation. However, quasicrystals can be formed by the addition of the appropriate amount of zirconium. This indicates that if a particular short-range order (e.g., icosahedral) is required for quasicrystal formation and if this short-range order is altered during milling, it can be restored by appropriately adjusting the chemical composition.

The effect of zirconium on corrosion behavior of NiAl intermetallic compound in molten carbonate salt

Abstract The corrosion of NiAl alloys containing zirconium in molten carbonate salt at 650 °C was studied as a potential coating material on a stainless steel separator. A mixed layer of NiO, ZrO2, and Al2O3 was formed on the surface of the NiAl alloy during preoxidation at 1000 °C in air. The Ni2AlZr phase, precipitated along the grain boundaries of NiAl alloys containing zirconium, was the source of the formation of the outermost layer of Al2O3 only on the mixed oxide layer during the oxidation. The Al2O3 layer inhibited the dissolution of NiO on the NiAl-Zr alloy in molten carbonate salt. Therefore, the oxide layer formed on the NiAl-Zr alloy was more corrosion-resistant than the oxide layer on the NiAl alloy. As the amount of zirconium in NiAl-Zr alloy was increased, the corrosion rate greatly decreased due to an increasing amount of Al2O3 at the outermost surface layer oxide. The mixed oxide layer on the NiAl alloy was spalled off the alloy by air cooling after high temperature isothermal oxidation, ...

On the mechanism of fast oxygen storage and release in ceria-zirconia model catalysts

CO oxidation over fresh and aged CexZr1−xO2 (0.15≤x≤1) mixed oxides was carried out under oscillating feed-stream composition by feeding the reactor with CO, He and O2 at a frequency of 0.2Hz. The activity of fresh, high surface area (HSA) catalysts of different compositions is similar and depends mainly on exposed surface redox centers; on the contrary, aged, low surface area (LSA) samples of ceria-zirconia show larger differences of activity with the composition. The sequence and the shape of the product peaks suggest that the kinetics of oxygen storage/release is influenced by surface phenomena that are not taken into account when the reaction is carried out under stationary condition. In particular, in HSA samples the CO2 peak splits into two components. The first component is observed when CO is pulsed over the catalyst, while the second component appears when O2 is pulsed. Temperature and composition of the catalyst determine the intensity ratio of the two peaks. The first peak increases with the amount of zirconia and is the result of direct reaction of CO with the oxygen from the oxide. The second contribution to CO2 production is highly influenced by surface-area and temperature and may be related to a more complex surface dynamic. In situ diffuse reflectance infrared (DRIFT) spectra show that chemisorbed carbonate-like species are involved as intermediates. On the basis of these results, a mechanism and a model for CO oxidation is proposed.

微小径ビーズを用いた湿式ビーズミル処理によるナノシリカ粒子の分散性検討

Wet dispersion mechanism of manometer-sized silica powder was investigated in a verticaltype beads mill using fine zirconium oxide (zirconia) beads. Zirconia beads of various sizes were used to disperse coagulated silica powders in nanometer size. The dispersed particles were measured by TEM and a dynamic light scattering technique and the contamination during the dispersion was also evaluated. Fine beads with the average diameters of 20μm and 50μm were found to be very effective for suppressing contamination from the beads as well as for achieving its homodispersity. 300μm-zirconia beads used in the present work had a very rough surface, which resulted in the silica powder contamination with zirconia in the level of 3250ppm. On the contrary, the surface of 20μm-beads was smooth and zirconia-contamination in the silica powder was decreased to 240ppm. The observation of bead surface and the amount of zirconia (impurity) suggested that the surface of large bead is easily worn away due to the collisions between the beads compared to smaller beads. The coagulated silica powder can be dispersed homogeneously using the beads with size smaller than 50μm, whereas coagulated silica particles were observed using the beads with size larger than 100μm. For coagulates of nanoparticles, main dispersion mechanism with large beads is pulverization while that with small beads is deflocculation. It is important not to give excessive energy to the coagulated particles for preventing the recoagulation and the contamination from the beads. Smaller beads (below 100μm) is suitable in this case.

R-curve behavior of alumina toughened with molybdenum and zirconia particles

Alumina matrix was added with metal molybdenum and different amounts of zirconia's particles. R-curves were measured during stable crack propagation and a piezo-spectroscopic technique has been used to assess the bridging stresses developed along the crack wake at the critical condition for crack propagation. The theoretical R-curves calculated from the average (microscopic) bridging stress distribution obtained by in situ Raman spectroscopy were in good agreement with the experimental data. If the molybdenum content is kept constant but the ZrO 2 amount is increased, the toughening due to t- m transformation increases, but at the same time the metal/ceramic interface is weakened by the presence of zirconia and the toughening due to metal particles bridging decreases. As a result of that, the presence of zirconia has only a limited beneficial influence on the overall toughness. The overall composite toughness is due to transformation and bridging toughening mechanisms, however, the two mechanisms do not have synergistic effects and crack bridging by molybdenum particles appears to be the dominant toughening mechanism.

A mechanism for the formation of equiaxed grains in welds of aluminum–lithium alloy 2090

In this technical note, the formation and presence of a zone of equiaxed grains (EQZ) along the fusion boundary of welded aluminum–lithium alloy 2090 using filler metals containing zirconium and lithium is presented and discussed. However, no EQZ was evident in welded joints of alloy 2090 using the commercial filler metals: aluminum alloy 2319 and 4145. Under identical conditions, aluminum–lithium alloy 2090 was fusion welded using several new filler metals containing various amounts of zirconium and lithium. Results reveal an increase in the width of the zone of equiaxed grains with an increase in zirconium and lithium content in the filler metal. A viable mechanism for the formation of equiaxed grains and its relationship to filler metal composition is highlighted.

酸性溶媒を用いたボールミルによるPZTセラミックスからの鉛の回収

The possibility of preferential recovery of lead from lead zirconate titanate (PZT) ceramics by wet ball milling with aqueous H2SO4 solution was investigated. The wet ball milling was performed using a pot mill apparatus in air for 0-96h at room temperature with the rotational speed fixed at 300rpm. Untreated PZT was dipped in aqueous H2SO4 solution for comparison with the wet-ball-milled specimen. The diffraction lines of the PZT crystallites disappeared completely from the XRD results, and only the diffraction lines of PbSO4 were confirmed by the wet ball milling for more than 48h. For all the dipped specimens, the diffraction lines of PZT were identified even when the specimens were treated in 4.5mol/dm3 H2SO4 solution for 96h. According to ICP analysis of the dissolved components into the H2SO4 filtrate, the amounts of zirconium and titanium dissolved in the solution were found to increase with increasing treatment time, and the leaching behavior of both ions conformed closely to the collapsing behavior of the PZT crystal structure. As for lead ion in the solution, the dissolution amount was below 0.1% compared with the initial lead content in PZT ceramics under all the ball milling conditions. These results indicated that more than 99.9mass% of lead in PZT can be recovered as PbSO4 by wet ball milling for more than 48h. The purity of the recovered PbSO4 calculated from the ICP results was approximately 98mass%.

Microfabrication of Al2O3/ZrO2 bi-phase ceramics with continuous fibrillar microstructure by co-extrusion

In the last two decades, new materials have been required for lightweight rigid structures with potential for high temperature operations [1, 2]. The evolution of intermetallic alloys and monolithic ceramics has been encouraged by the needs of the aerospace industries and the realization that the more conventional alloy systems have reached a development limit in relation to high temperature stability and deformation resistance. The technical limitations of these monolithic ceramics were due either to their low fracture toughness or a high temperature ceiling dictated by oxidation and creep-cavitation initiated by sintering liquid residues. Continuous fiber-reinforced ceramic matrix composites (CMCs) are the best solution for high-risk engineering components in which high specific stiffness and high temperature tolerance are required (rocket nozzles, engine flaps, hot structures in aircraft and engines ext.) [3–5]. However, the current limitations for CMCs are the lack of a commercial fiber of reasonable cost and a thermal stability above 1200 ◦C and the lack of a flexible fabrication route in which the matrix achieves neartheoretical density within a woven fiber preform. Therefore, this work presents an innovative processing route while is designed to overcome these limitations while retaining a high proportion of the beneficial properties of both monolithic ceramics and CMCs. Co-extrusion can be defined as the passing of two or more pastes through the same die to manufacture a green body of constant cross sectional area. It has been widely used recently to produce multilayer ceramics [6], multilayer tubes [7], alumina and PbO-containing ferroic ceramics [8], zirconia and stainless steel metalceramic pipes [9] and fine-scale alumina, mullite and ZTA components [10–14]. One of the main advantages of using a co-extrusion technique is the significant reductions in the number of processing steps. It has also been proven that deliberately introduced weak interfaces in a laminar structure suppress the catastrophic failure and increase the fracture toughness and work of fracture by the operation of debonding and crack deflecting mechanisms [15]. The main objective of the present work is to demonstrate the feasibility of forming multiphase aligned fibrillar microstructures from nano-size sol particle precursors using an innovative multiple co-extrusion process. To achieve this, two sol-derived high solidsloading pastes of alumina and zirconia were coextruded in parallel (with the presence of a weak zirconia interface), and layed-up in a closed-packed linear array to form a heterogeneous macro-plug for subsequent extrusion assuming that the flow properties of the chemically different pastes are similar. Boehmite (γ -AlOOH) sol (Remal A20, Remet corp., USA) was used as the alumina source. The sol had average particle size and solids-loading of 40 nm and 20 wt%, respectively. The received sol was stable at a pH value of 4. The received boehmite sol was seeded with 2 wt% of the total mass using ultrafine (α-Al2O3 (30 nm, BDH Chemical, UK, high purity polishing powder) powders. The flow chart for the seeding process, followed by paste preparation is given in Fig. 1. To seed the boehmite sol, the seeding powder was first dispersed in distilled water and then added into boehmite sol. 1 wt% glycerol and celacol were also added in order to minimize the surface roughness of the extrudate and increase the green strength, respectively. 1 wt% celacol was first dissolved in water at 85 ◦C and then added to the seeded sol in order keep it plastically deformable during the multiple extrusion stage. The seeded sol was first stirred magnetically for 10 h and then ultrasonic agitation was employed at 15 kHz for 3 h for further dispersion of any particle agglomerates which might be present [16]. The final sol composition i.e., boehmite + 2 wt% seeding powder + 1 wt% glycerol + 1 wt% celacol was ball-mixed for 2 days using high purity zirconia balls. The mixed seeded sol was then vacuum filtered in order to obtain a gel structure. The resulting soft white gel was further compacted using pressure filtration apparatus to squeeze out the excess water, and obtain an extrudable paste. For the preparation of zirconia paste, zirconia sol was prepared using ultrafine and high purity zirconia powders (average grain size 30 nm, VP zirconia, Degussa Ltd., Germany) with the addition of 3 mol% yttria. Kinetically stable and well dispersed zirconia sol having 20 wt% solids-loading was prepared by the addition of a small amount of zirconia to the water, while the suspension was magnetically stirred. The best pH value in order to obtain the maximum stability was found to be 8.5 and this pH value was maintained using ammonia. 1 wt% glycerol and celacol were added to the prepared zirconia sol. 1 wt% cyclohexanone (C6H10O)

Structural, optical and electrical studies on sol–gel deposited Zr doped ZnO films

Transparent and conducting films of mixed oxides of zinc and zirconium have been prepared by sol–gel method. The amount of zirconium have been varied in between 0 to 3 at.%. XRD patterns showed that the nature of films are polycrystalline but the preferred orientation changes from (1 0 0) to (1 0 1) and finally (0 0 2) with increasing amount of Zr doping. The morphology and crystallite size of the films are strongly dependent on the doping concentration. The resistivity decreases with doping concentration up to 1.5 at.% but increases with concentration more than that. The maximum carrier concentration is (∼10 19 cm −3) and the mobility is minimized at this doping concentration. The optical bandgap was estimated from the reflectance and transmittance spectra. The obtained optical bandgap is about 3.3 eV, for unstrained ZnO but slight shrinkage in bandgap is noticed up to 2 at.% doping. There is corresponding rise in width of band tail which is a measure of the disorder in the system.

In Situ Preparation of ZrO2-Al2O3-SiCw Ceramic Composite Powder Mixtures by Carbothermal Reduction of Silicate Minerals

ZrO2-Al2O3-SiCw composite powder mixtures were prepared by carbothermal reduction of natural silicates (e.g., zircon, sillimanite and kaolin). Activated charcoal was used as the reducing agent. The reactions were carried out in a graphite furnace at 1650°C in argon atmosphere at a positive pressure of 0.15 MPa. XRD investigation of the product phases confirms the completion of the reaction and the phases were identified as monoclinic zirconia, tetragonal zirconia, α-alumina and β-silicon carbide. SEM investigation of the powders reveals the whisker morphology of β-silicon carbide. It was observed that a small amount of zirconia was present in tetragonal form in addition to monoclinic form which could be due to fine particle size of the starting powder.

Improvement of thermal stability of alumina by addition of zirconia

To maintain a large surface area at elevated temperatures, zirconia was added to transition alumina. The addition of a small amount of zirconia resulted in a marked suppression of phase transformation from θ- to α-alumina. After heating at 1200°C, ZrO2‐containing alumina exhibited a large surface area of 50 m2/g. UV‐VIS and XRD measurements indicated that zirconia existed in a high dispersion state after calcining at 800°C. XPS measurement also showed that zirconia existed as monolayer. Zirconia monolayers are concluded to cover the alumina surface and the interaction between them may be the cause for the suppression of phase transformation and also for the maintenance of the large surface area at elevated temperatures. The interaction remains up to 1200°C, therefore, θ phase remained at 1200°C.

Framework modification of microporous silicates via gas‐phase treatment with ZrCl4

The boron forms of the zeolite Beta (B‐Beta) and SSZ‐33 (B‐SSZ‐33) are treated with vapors of ZrCl4 in an attempt to substitute the framework boron for zirconium. The resulting materials Zr‐Beta and Zr‐SSZ‐33 are characterized by X‐ray diffraction (XRD), solid state NMR, FTIR, pyridine adsorption and Raman spectroscopies. In the case of zeolite Beta, Zr substitutes the B present in the framework nearly in a one‐to‐one basis. No evidence is found in support of the tetrahedral Zr fully incorporated into the zeolite framework; Zr is only partially grafted to the zeolite framework giving rise to silanol groups adjacent to the Zr atom. No evidence of extra‐framework zirconia is observed. For SSZ‐33, the amount of zirconium incorporated is significantly less than the amount of boron present in the parent zeolite. Due to the size of ZrCl4, a multidimensional 12‐ring pore system is required for our procedure of Zr incorporation to be effective. Zr‐Beta is an acid catalyst superior in activity to B‐Beta for the isomerization of 1‐butene.

Structure and Orientation of Zirconium Nitride in Niobium-Zirconium Alloys

Zirconium nitride precipitates, ZrN, were produced by internally nitriding single crystals of niobium containing various (small) amounts of zirconium, at 1473 K in nitrogen gas at a partial pressure of about 5 x 10 -3 Pa. The structural changes that occurred during annealing treatments after nitridation were investigated using transmission electron microscopy. Electron diffraction patterns show that ZrN particles have the Bain type orientation relationship with the matrix.

Influence of calcination temperature on the properties of spray dried alumina-zirconia composite powders

Alumina-zirconia composite powders containing 10, 12.5, 15 or 20 wt% zirconia were prepared by spray-drying the hydroxide gels. These powders were calcined at 650 and 950 °C. The spray-dried as well as the calcined powders were characterized by means of Coulter counter, Sorptometer, infrared spectroscopy (i.r.), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Initially the spray-dried powders are amorphous and spherical in shape with a diameter of 6 μm and crystallize after calcination treatment at 950 °C. Sintered density of the 950 °C calcined powder compacts was higher than 650 °C calcined powder compacts. Compacts made from 650 °C treated powders retained 100% tetragonal phase after sintering irrespective of composition. Some amount of tetragonal phase is transformed into monoclinic phase in the composites containing higher amount of zirconia in the sintered compacts made from 950 °C calcined powders.

Incipient melting of grain boundaries in Ni 3Al alloys containing zirconium

Incipient melting due to thermal treatments has been investigated in three Ni 3Al alloys containing various amounts of zirconium. The alloys were designated as continuous cast IC-50 sheet (Ni 77.82Al 21.73Zr 0.34B 0.1), investment cast IC-50 rod (Ni 75.80Al 23.47Zr 0.54B 0.19) and investment cast IC-218 billet (Ni 74.48Al 16.98Cr 8.02Zr 0.51B 0.10). Due to enrichment of Zr, which can form eutectic alloys with Ni, the inter-dendritic regions and grain boundaries in these alloys melted at temperatures lower than that at which the bulk melts. The incipient melting temperature of the grain boundary was determined by microstructural analysis after quick heating and quenching from various temperatures. The grain boundaries in as-cast IC-50 sheet, IC-50 rod and IC-218 ingot started to melt at 1250, 1150 and 1150 °C, respectively. To accommodate stresses due to quenching, the molten layer at the boundaries often opened up, producing cracks. The higher the nominal Zr content in the alloy, the lower the temperature at which the incipient melting took place. An annealing at 1100 °C for 5 h increased the incipient melting temperature of IC-50 sheet from 1250 to 1300 °C, probably due to homogenization of Zr. However, annealing IC-218 at 1100 °C for 23 h lowered it from 1150 to 1125 °C due to release of Zr from Zr-rich eutectic structures.