Effect Of ZrO2 Research Articles

Effect of Hot Pressing Technology on the Microstructure and Mechanical Properties of ZrO<sub>2</sub> Nano-Composite Ceramic Tool and Die Material

A new nano-composite ceramic tool and die material was prepared by vacuum hot pressing technique. The effect of hot pressing technology on the microstructure and mechanical properties of ZrO2 nano-composite ceramic tool and die material was investigated systemically, and the ceramic tool and die material with good mechanical properties was fabricated successfully. Results show that, the highest flexural strength, fracture toughness and hardness of ZrO2 nano-composite ceramic tool and die material reaches 1055 MPa, 10.57 MPa∙m1/2 and 13.59 GPa, respectively by means of the vacuum hot pressing technique at 1430 °C for 60min at 35MPa. The flexural strength and fracture toughness has been improved greatly by the optimization of hot pressing technology. In the materials, the optimum sinter process could ensure the t-ZrO2 stabilized till room temperature that can enhance the toughening effect of ZrO2. The microstructure of ZrO2 nano-composite ceramic tool and die materials were improved by the optimization of hot pressing technology, and the fracture mode is the typical mixed trans/inter-granular fracture mode.

Effect of ZrO 2 Crystalline Phase on the Performance of Ni-B/ZrO 2 Catalyst for the CO Selective Methanation

Amorphous Ni-B/ZrO 2 catalysts were prepared by coprecipitation-chemical reduction with KBH 4 aqueous solution, and various crystalline phase ZrO 2 (amorphous-ZrO 2, tetragonal-ZrO 2 and monoclinic-ZrO 2) supported Ni-B catalysts were obtained by thermal treatment in 5%H 2-N 2 stream at different temperature. The effect of ZrO 2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated, and the catalysts were characterized by N 2 physisorption, Powder X-ray diffraction (XRD), Temperature-Programmed Desorption (CO-TPD and H 2-TPD), and Differential Scanning Calorimeter (DSC). The treatment temperature affected strongly the crystalline structure of ZrO 2, and the CO methanation activity and selectivity of the Ni-B/ZrO 2 catalysts were significantly influenced by the crystalline phase of ZrO 2. Of the three forms of ZrO 2 polymorphs (amorphou-ZrO 2, tetragonal-ZrO 2 and monoclinic-ZrO 2), the amorphous-ZrO 2 supported nickle catalyst showed highest CO methanation activity, attributing in large part to the largest specific surface area and the optimum CO/H 2 absorption intensity of the Ni-B/amorphous-ZrO 2 catalyst.

Methanation of carbon dioxide on Ni/ZrO 2-Al 2O 3 catalysts: Effects of ZrO 2 promoter and preparation method of novel ZrO 2-Al 2O 3 carrier

Abstract The novel nickel-based catalysts with a nickel content of 12 wt% were prepared with the zirconia-alumina composite as the supports. The new carriers, ZrO 2 improved alumina, were synthesized by three methods, i.e., impregnation-precipitation, co-precipitation, and impregnation method. The catalytic properties of these catalysts were investigated in the methanation of carbon dioxide, and the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. The new catalysts showed higher catalytic activity and better stability than Ni/γ-Al 2O 3. Furthermore, as a support for new nickel catalyst, the ZrO 2-Al 2O 3 composite prepared by the impregnation-precipitation method was more efficient than the other supports in the methanation of carbon dioxide. The highly dispersed zirconium oxide on the surface of γ-Al 2O 3 inhibited the formation of nickel aluminate-like phase, which was responsible for the better dispersion of Ni species and easier reduction of NiO species, leading to the enhanced catalytic performance of corresponding catalyst.

Effect of ZrO 2 addition on crystallization and properties of the glass-ceramics contained NaNbO 3 crystals

Ferroelectric glass-ceramics containing NaNbO 3 crystals are prepared from the Na 2O–Nb 2O 5–SiO 2 system employing heat treatment process. ZrO 2 is systematically added to the glass compositions to study its effect on crystallization behavior of the glass and dielectric properties of the associated glass-ceramics. DTA trace measured from the as-quenched samples reveals shifting of the glass transition and the crystallization ranges to the higher temperature with increasing of ZrO 2 content. Then, the glass samples are subjected to heat treatment process at appropriate temperatures and times. Phase identifications through XRD analysis have shown that only the NaNbO 3 phase is devitrified in the glass-ceramics treated at 750 °C for 1 h. At 800 °C, precipitation of the secondary phase NaNb 3O 8 is additionally found but it present in only a small proportion. Crystallite size of the NaNbO 3 crystals determined from the X-ray diffracted peaks are in range 20–50 nm. The dielectric constants of the glass-ceramics measured at room temperature depend on the volume fraction of NaNbO 3 which varied with the ZrO 2 content.

Effect of ZrO 2 addition on the microstructure and electromagnetic properties of YIG

In this work, we reported the microstructure and electromagnetic properties of a series of zirconium substituted yttrium iron garnet ferrites (YCaZrIG) with iron deficiency composition of Y 3− x Ca x Zr x Fe 4.93− x O 12 ( x = 0.1, 0.2, 0.3, and 0.4, with electrostatic balance by Ca 2+ substituted for Y 3+ ions) prepared by a solid-reaction method. The addition of ZrO 2 shows no obvious influence on the phase, density and dielectric constant of YIG ferrites. When Zr addition x ≤ 0.3, the substitution of Zr 4+ for Fe 3+ decreases the amount of Fe ions, increases the lattice parameter and enhances the grain growth of garnet phase. The solubility of zirconium in YCaZrIG ferrite was found to be approximately 0.3, above which excess ZrO 2 would lead to the precipitation of a second phase inside the YCaZrIG ferrite. This would inhibit the grain growth of garnet phase and cause an increase in the dielectric loss and coercivity. The observed reduce for saturation magnetization when x = 0.4 is possibly due to antiparallel alignment of magnetic moment of Fe 3+ in the d site caused by the decrease of a–d exchange interaction. Additionally, we got the optimum electromagnetic properties in the samples with x = 0.3: ɛ r = 14.1, tan δ e = 2.5 × 10 −4, H c = 47 A/m, 4 πM s = 1936 × 10 −4 T, Δ H = 7.1 KA/m.

Research on effect of ZrO2 on thermal stability and structure of Ga/In based fluoride glasses

A systematic investigation on glass formation in the 20GaF3-15InF3-20CdF2-15ZnF2-(20-x)PbF2-10SnF2-xZrO2 (xZ-GICZPS) system (x = 0, 2, 4, 6, 8 in mol.%) was carried out. These glasses were characterized by differential scanning calorimetry (DSC), infrared (IR) spectra and Raman spectra. The DSC results show that the thermal stability is affected by PbF2 and ZrO2 contents. With increasing ZrO2 content, the thermal stability is improved at first and then reduced, which is proved by thermal stability factors ΔT and S determined by DSC. As a result, the 20GaF3-15InF3-20CdF2-15ZnF2-14PbF2-10SnF2-6ZrO2 glass shows the largest parameters ΔT and S, processing the most excellent thermal stability. Analyses of IR spectra reveal that glasses have broad transparency range in IR region. According to Raman spectra, the glass network structures are basically composed of mixed [(In, Ga)F6] and In[O, F]6 units and ZrO2 mainly acts as network modifier in this system.

Increasing the resistance of electrode glasses to fluorine-containing media

The effect of ZrO2, P2O5, and F– ions on the resistance of electrode glass to fluorine-containing media is investigated. It is established that the most stable glasses have the minimum content of P2O5 (no more than 2.5%) and molar content of ZrO2 to 3%. It is shown that for glass electrodes whose active part consists of experimental glass the electrode should be soaked for 3 – 7 days in a HF solution with concentration to 1000 mg/liter.

Controlling of Grain Size with Different Additives in Tm3+:Y2O3 Transparent Ceramics

(Tm0.01Y0.99)2O3 transparent ceramics have been fabricated in a vacuum condition using high-purity Y2O3 and Tm2O3 powders as raw materials, and ZrO2 and tetraethyl orthosilicate (TEOS) as additives. Effects of ZrO2 and TEOS on controlling the growth of grain size were investigated to obtain high-optical-quality transparent ceramics. Self-compensation of ZrO2 at high temperature offers vacancies, which promote the diffusion and densification rate. Meanwhile, the solid solution formed by substitution and interstice mechanism improves the optical quality of transparent ceramics significantly. The growth of grain size under different criteria was observed by field-emission scanning electron microscopy. The spectroscopic properties were also investigated. The result indicates that ZrO2 is necessary for the sintering of yttrium-transparent ceramics, but TEOS fails to contribute in the yttrium system.

Effect of ZrO<SUB>2</SUB> Addition on the Properties of CuMn<SUB>2</SUB>/Al-Ti Monolithic Catalysts for Benzene Catalytic Combustion

Effect of ZrO<SUB>2</SUB> Addition on the Properties of CuMn<SUB>2</SUB>/Al-Ti Monolithic Catalysts for Benzene Catalytic Combustion

Effect of ZrO 2 promoter on structure and catalytic activity of the Ni/SiO 2 catalyst for CO methanation in hydrogen-rich gases

Ni-based catalysts supported on SiO 2 aerogel that is unpromoted (Ni/SiO 2) or promoted (Ni/ZrO 2–SiO 2) with ZrO 2 are prepared by the incipient-wetness impregnation method. Their catalytic activities for CO methanation in hydrogen-rich gases with 1 vol.% CO are studied with a continuous flowing microreactor. It is found that the Ni/ZrO 2–SiO 2 catalyst shows higher catalytic activity, over which CO can be completely converted into CH 4 at 240 °C. However, CO cannot be completely converted until the temperature was raised to 320 °C over the Ni/SiO 2 catalyst under the same reaction conditions. Characterizations using FT-IR, XRD, TEM, NH 3-TPD, H 2-TPR and H 2-TPD suggest that the formation of Si–O–Zr bond results in stronger acid strength and larger amounts of acid of the ZrO 2–SiO 2 support. The changes of acidity lead to the increase of the interaction between NiO species and the ZrO 2–SiO 2 support and then enhance the dispersion degree and the reduction degree of NiO species. Thus, the Ni/ZrO 2–SiO 2 catalyst possesses smaller Ni crystallite size, higher Ni dispersion, more active Ni species and stronger adsorption ability for H 2, which may contribute to its higher catalytic activity for CO methanation.

Atomic oxygen erosion resistance of polyimide/ZrO 2 hybrid films

A series of polyimide/zirconia (PI/ZrO 2) hybrid films were synthesized based on zirconium n-butoxide, pyromellitic acid dianhydride (PMDA) and 4,4′-oxydianiline (ODA) by a sol–gel process. The atomic oxygen (AO) exposure tests were carried out using a ground-based atomic oxygen effects simulation facility. The effects of ZrO 2 content on the morphology and structure evolvement of PI/ZrO 2 hybrid films were investigated using field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectrometer (XPS), respectively. The results indicated that a zirconia-rich layer was formed on the polyimide film sourcing from the zirconium n-butoxide after AO exposure, which decreased the erosion rate and obviously improved the AO resistance of polyimide films.

ZrO 2-doped Y 2O 3 transparent ceramics via slip casting and vacuum sintering

Commercial Y 2O 3 powder was used to fabricate highly transparent Y 2O 3 ceramics with the addition of ZrO 2 via slip casting and vacuum sintering. The effects of ZrO 2 addition on the transparency, grain size and lattice parameter of Y 2O 3 ceramics were studied. With addition of ZrO 2 the transparency of Y 2O 3 ceramics increased markedly and the grain size of Y 2O 3 ceramics decreased markedly by cation diffusivity mechanism and the lattice parameter of Y 2O 3 ceramics slightly decreased. The highest transmittance (at wavelength 1100 nm) of the 5.0 mol% ZrO 2–Y 2O 3 ceramic (1.0 mm thick) sintered at 1860 °C for 8 h reached 81.7%, very close to the theoretical value of Y 2O 3.

Effect of ZrO 2 on the sinterability and spectral properties of (Yb 0.05Y 0.95) 2O 3 transparent ceramic

(Yb 0.05Y 0.95) 2O 3 transparent ceramics were fabricated by vacuum sintering technique using high purity Y 2O 3 powder as starting material and ZrO 2 as additive. The results indicated that the introduce of ZrO 2 can improve the transmittance of yttria ceramics greatly and the mechanism was also analyzed. 3.0 at.% ZrO 2 doped (Yb 0.05Y 0.95) 2O 3 transparent ceramics sintered at 1800 °C for 20 h had the optimum transmittance. The microstructure is uniform and no secondary phase is observed in the ceramics with the average grain size of 15 μm. The relative density is 99.68% and the transmittance in near-infrared band is as high as 83.7% (up to 98.5% of theoretical value). The spectroscopic properties of 3.0 at.% ZrO 2 doped (Yb 0.05Y 0.95) 2O 3 ceramics were also investigated. The absorption, emission cross-section and fluorescence lifetime have been estimated as 1.175 × 10 −20, 1.767 × 10 −20 cm 2 and 0.93 ms, respectively. All the results indicate that Yb 3+ doped Y 2O 3 transparent ceramic is promising laser material.

Effects of ZrO 2 addition on phase stability and photocatalytic activity of ZrO 2/TiO 2 nanoparticles

ZrO 2/TiO 2 nanoparticles with various Zr/Ti ratios (0–0.9) were prepared by a polymer complex solution method (PCSM). The prepared samples were characterized using transmission electron microscopy (TEM), the Brunauer, Emmett & Teller (BET) method, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The ZrO 2/TiO 2 photocatalyst showed a high specific area and small crystal size. The XRD pattern for the Zr/Ti = 0.1 sample indicated that the addition of ZrO 2 stabilized the anatase phase of TiO 2 up to 800 °C. The photocatalytic activity of Zr/Ti = 0.1 sample was higher than that of the TiO 2 sample and commercially available Degussa P25. The high photocatalytic activity can be attributed to stronger adsorption in the visible light region, higher specific area, smaller crystal size and increased surface OH groups.

Structural and Crystallization Study of a Simplified Aluminoborosilicate Nuclear Glass Containing Rare-earths: Effect of ZrO2 Concentration

AbstractZirconium is an abundant element in nuclear wastes. In this paper, we present structural and crystallization results for a simplified glass composition belonging to the SiO2-Al2O3-B2O3-Na2O-CaO-ZrO2-RE2O3 system (RE = Nd or La) developed to immobilize highly concentrated waste solutions. The effect of varying ZrO2 content on the structure and the crystallization tendency of this glass was studied using a multi-spectroscopic approach. Zr was shown to be located in six-fold coordinated sites whose charge compensation seems preferentially insured by Na+ cations. Whereas a significant decrease of the proportion of BO4 units was observed with ZrO2 content, no effect was detected on the environment of AlO4 units. However, a significant structural evolution of the silicate network occurred due to the formation of Si-O-Zr bonds. Whatever ZrO2 concentration, the crystallization of only a rare earth silicate apatite phase was observed during either slow cooling from the melt or isothermal heat treatment. Whereas nucleation mainly occurred from the surface of the glass without ZrO2, the introduction of zirconium induced apatite crystallization in the bulk. It is proposed that this nucleating effect of ZrO2 is mainly due to changes induced in the neighborhood of Nd3+ cations in glass structure.

Free energy of formation of zircon based on solubility measurements at high temperature and pressure

The standard Gibbs energy of formation of zircon was constrained by measuring the solubility of silica in H 2 O in equilibrium with zircon and baddeleyite at 800 °C, 12 kbar, by a sensitive weightchange method. Dissolution occurs incongruently according to the reaction: ZrSiO 4 = ZrO 2 + SiO 2(t) zircon baddeleyite where SiO 2(t) is total dissolved silica. Blank runs demonstrated that the effects of ZrO 2 solubility and/or capsule-Pt transfer were near the weighing detection limit, so weight losses or gains could be ascribed quantitatively to SiO 2 solubility. Precise SiO 2(t) concentrations were ensured by use of three types of starting material, by approaching equilibrium from zircon-undersaturation and oversaturation, and by demonstrating time-independence of the measurements. The results yielded a SiO 2 concentration of 0.069 ± 0.002 (1 se) moles per kg H 2 O (m s ), or a mole fraction (X s ) of 1.23 × 10 -3 ± 3.3 × 10 -5 . Two runs on zircon solubility in NaCl-H 2 O solutions at 800 °C and 10 kbar showed silica solubility to decrease by nearly 1% per mol% NaCl. The standard molar Gibbs free energy of formation of zircon from the oxides at a constant P and T is given by: where ZB and Q refer, respectively, to equilibrium with zircon-baddeleyite and quartz, γ s is the activity coefficient of total silica, and the relationship between γ s and X s accounts for aqueous silica activity. Our results yield ΔG ￮ f,ox,zr = -18.5 ± 0.7 kJ/mol at 800 °C, 12 kbar (95% confidence), or a standard apparent Gibbs free energy of formation from the elements of -1918.3 ± 0.7 kJ/mol at 25 °C, 1 bar. Our value is consistent with determinations based on phase equilibrium studies, within reported error limits, but is more precise than most previous values. However, it is less negative than high-temperature determinations by calorimetry and electrochemistry. Our results indicate that solubility measurements at high T and P may be a superior method of free energy determination of other refractory silicate minerals.

Synergistic Effects of Zirconia-Coated Carbon Nanotube on Crystalline Structure of Polyvinylidene Fluoride Nanocomposites: Electrical Properties and Flame-Retardant Behavior

Pristine multiwalled carbon nanotubes (MWNTs) and zirconia-coated multiwalled carbon nanotubes (ZrO(2)/MWNTs) by isothermal hydrolysis and the traditional chemical precipitation method have been dispersed into polyvinylidene fluoride (PVDF) copolymer by solution mixing in N,N-dimethylformamide (DMF). The effect of ZrO(2)-coated MWNTs on morphological properties, electrical properties, and flame-retardant behavior has been studied in comparison with virgin PVDF and PVDF/MWNTs nanocomposites. Due to the improved dispersion of the coated nanotubes, the incorporation of 3 wt % of ZrO(2)-coated MWNTs leads to an increase of the thermal stability and dielectric properties and a decrease of the peak heat-release rate.

Effect of ZrO 2 promoter on the catalytic activity for CO methanation and adsorption performance of the Ni/SiO 2 catalyst

The catalytic activities for CO methanation and adsorption performances of the Ni/SiO 2 and Ni/ZrO 2-SiO 2 catalysts were investigated by a continuous flowing microreactor apparatus and in-situ diffuse reflectance Fourier transform infrared spectroscopy. The results showed that CO was completely converted at 200°C over the Ni/ZrO 2-SiO 2 catalyst under the reaction condition of 1% of CO, GHSV of 5000 h −1, and the atmospheric pressure. However, the CO conversion was only 35% over the Ni/SiO 2 catalyst under the same reaction condition, and CO was not completely converted until 270°C, which suggested that the catalytic activity of the Ni/ZrO 2-SiO 2 catalyst increased with the addition of ZrO 2 promoter. Meanwhile, the addition of ZrO 2 promoter enhanced the CO adsorption capacity of the Ni/ZrO 2-SiO 2 catalyst. In the presence of H 2, a large number of bridged carbonyl hydrides were formed over the Ni/ZrO 2-SiO 2 catalyst at lower temperatures, resulting in high catalytic activity for CO methanation. In CO methanation, the breaking of C—O bond over catalysts was by multihydrogen carbonyl hydride rather than by direct breaking.

Effect of ZrO<SUB>2</SUB> from the Oxidation of ZrC on Ablation of ZrC Modified Carbon/Carbon Composites

Effect of ZrO<SUB>2</SUB> from the Oxidation of ZrC on Ablation of ZrC Modified Carbon/Carbon Composites

Synthesis and characterization of mesoporous materials: Silica–zirconia and silica–titania

An experimental strategy was developed to obtain mesoporous SiO 2–ZrO 2 and SiO 2–TiO 2 mixed oxides by a sol–gel method, treating the gels hydrothermally. The solids were characterized by nitrogen physisorption, pyridine thermodesorption, 29Si nuclear magnetic resonance, SEM and X-ray diffraction. The effects of ZrO 2 content, the generated pressure in the synthesis vessel and further modification of this type of procedure on the solids properties were studied. It was found that SiO 2–ZrO 2 and SiO 2–TiO 2 mixed oxides dried at atmospheric pressure developed type I isotherms. On the other hand, for the SiO 2–ZrO 2 and SiO 2–TiO 2 mixed oxides that were treated under pressure in the autoclave (at high SiO 2 content) the porosity was improved and mesoporous materials exhibiting type IV adsorption isotherms. Specific surface area and pore size distribution were a function of ZrO 2 and TiO 2 content. The materials exhibited narrow pore size distributions with pore diameters in the region of mesopores at about 4 nm and high surface areas, the highest being 481 m 2/g for the 10 wt% ZrO 2 Si–Zr material. Differences in acidity as determined by pyridine thermodesorption were observed to depend on the synthesis parameters and ZrO 2 and TiO 2 concentration.