Increasing ZrO2 Content Research Articles

Effect of Zr4+ on the microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 NTC ceramics

In this study, 0.6Y2O3-0.4YCr0.5Mn0.5O3 negative temperature coefficient (NTC) ceramics doped with different ZrO2 contents were prepared using a two-step sintering method. The effects of Zr4+ content on the microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 were mainly investigated. For the microstructure, X-ray diffraction (XRD) reveals the presence of two main crystalline phases in the samples: Y2O3 and YCr0.5Mn0.5O3. Scanning electron microscopy (SEM) reveals a clear two-phase appearance, and the porosity tends to decrease with the addition of ZrO2. Combined with energy dispersive spectrometer (EDS) to derive the distribution of the elements, Zr4+ is mainly present in the Y2O3 phase, with a small amount in the YCr0.5Mn0.5O3 phase. In addition, the grain sizes of different groups were counted, and the grain size of Y2O3 decreased from 2.73 ± 1.80 μm to 1.65 ± 0.93 μm with the increase of ZrO2 content. For the electrical properties, the resistance-temperature curves were measured from 298.15 K to 1073.15 K, and all the samples exhibited NTC characteristics. And with the increase of ZrO2 content, the resistivity increased from 1.91 × 107 Ω cm to 1.96 × 108 Ω cm, and the B25/100 value decreased from 3315 K to 1310 K. In addition, the chemical state forms of the elements on the surface of the samples were analysed by X-ray photoelectron spectroscopy (XPS), and the valence states as well as the occupancy of the transition elements Cr and Mn were analysed in detail according to the principle of multiple splitting. Finally, the mechanism of influence on microstructure and electrical properties is explained by combining the theory of grain boundary migration and thermal ceramic conductivity.

Controlled synthesis of CeNbZrO solid solution with high thermal stability and application in catalytic degradation of C6H5CH3 and C6H5Cl

A series of CeNbZrO composite oxides with different (CeNb)/Zr molar ratios were prepared by urea homogeneous precipitation method and systematically characterized. The thermal stability, degradation performance and structure-activity relationship of these catalysts for eliminating C6H5CH3 and C6H5Cl mixed pollutants were evaluated. The results indicated that with the increase of ZrO2 content, the catalytic activity of CeNbxZrO increased first and then decreased. Among them, the CeNb3.3ZrO catalyst (Ce/Nb/Zr=2/1/3.3, molar ratio) exhibited the highest catalytic activity (C6H5CH3: T90%=310oC, C6H5Cl: T90%=344oC) and thermal stability. Compared with the traditional CeO2-MnO2 catalyst, the T90% of the CeNb3.3ZrO catalyst in the degradation of C6H5Cl was reduced by 100oC. CeNb3.3ZrO exhibited high specific surface area and strong oxidation ability, which enhanced the redox cycles and promoted the interactions between metal ions. In addition, the formation of Ce2Zr3O10 solid solution made its structure stable even at high temperature. Overall, the optimized CeNb3.3ZrO has broad prospects in the catalytic treatment of volatile organic compounds and some other related fields in thermal catalysis. Environmental implicationC6H5CH3 and C6H5Cl are typical VOCs with certain toxicity, which pollute air environment and cause harm to human health. In this paper, CeNbZrO composite oxides with different (CeNb)/Zr molar ratios were prepared by urea homogeneous precipitation method. It was found that the CeNb3.3ZrO catalyst had higher specific surface area and stronger oxidation ability, and promoted the complete degradation of C6H5CH3 and C6H5Cl at lower temperatures by destroying the C-C, C-H and C-Cl bonds of the reactants.

Effect of ZrO2 Particles on the Microstructure and Ultrasonic Cavitation Properties of CoCrFeMnNi High-Entropy Alloy Composite Coatings

CoCrFeMnNi-XZrO2 (X is a mass percentage, X = 1, 3, 5, and 10) high-entropy alloy composite coatings were successfully prepared on 0Cr13Ni5Mo martensitic stainless steel substrates using laser cladding technology. The phase composition, microstructure, mechanical properties, and cavitation erosion behavior of the composite coatings under different contents of ZrO2 were studied. The mechanism of ZrO2 particle-reinforced cavitation corrosion resistance was studied using ABAQUS2023 finite element software. The results show that the phase structure of the composite coating organization is composed of FCC phase reinforced by ZrO2 phase. The addition of ZrO2 causes lattice distortion. The coatings have typical branch crystals and an equiaxed crystal microstructure. With the increase in ZrO2 content, the microhardness of the composite coatings gradually increases. When X = 10%, the coating’s microhardness reached 348 HV, which was 95.53% higher than the high-entropy alloys without ZrO2 added. Adding ZrO2 can prolong the incubation period of high-entropy alloys; the high-entropy alloy composite coating with 5 wt.% ZrO2 exhibited the best cavitation resistance, with a cumulative volume loss rate of only 15.74% of the substrate after 10 h of ultrasonic cavitation erosion. The simulation results indicate that ZrO2 can withstand higher stress and deformation in cavitation erosion, reduce the degree of substrate damage, and generate higher compressive stress on the coating surface to cope with cavitation erosion.

ZrO2 reinforced porous Si3N4-based ceramics with improved mechanical properties fabricated via vat photopolymerization (VPP)

Porous Si3N4 ceramics are widely applied in many fields owing to their excellent properties such as high electromagnetic wave permeability, oxidation resistance, and wear resistance. Besides, the vat photopolymerization (VPP) technique can fabricate porous Si3N4-based ceramics with complex shapes and high precision. Nevertheless, The high absorptivity and refractive index of Si3N4 to ultraviolet light make it difficult to form porous Si3N4-based ceramics with the VPP technique. In this work, the addition of ZrO2 simultaneously improved the printability of Si3N4 slurries and the performance of Si3N4 ceramics via VPP technology. Rheological behavior and curing properties of the slurries were investigated, and the influence of ZrO2 content on the mechanical properties of printed Si3N4-based ceramics was investigated systematically. The addition of ZrO2 decreased the UV absorptivity of composite powder, thus improving the curing depth from 25.2 ± 2.6 μm to 64.8 ± 3.7 μm. XRD analysis revealed that ZrO2 in the composite ceramics mainly exists as the phase of yttria-stabilized tetragonal zirconia (Zr0.92Y0.08O1.96), which could ensure the effect of phase transformation toughening. With the increase of ZrO2 content, flexural strength and fracture toughness of porous Si3N4-based ceramics exhibited a trend of increase first and then decrease. As ZrO2 content increased to 10 wt%, the flexural strength and fracture toughness of porous Si3N4-based ceramics were improved from 214.7 MPa and 4.23 MPa·m1/2 to 345.0 MPa and 5.69 MPa·m1/2, respectively. Therefore, this work provided an important reference for the fabrication of high-performance porous Si3N4-based ceramic components with complex structures.

Influence of ZrO2 on non-isothermal crystallization kinetics, structure and optical properties of calcium borosilicate glasses

The objective of the present work is to study the effect of ZrO2 on the structure, crystallization behavior and optical properties of 30SiO2-30B2O3-10Y2O3-(30-x)CaO-xZrO2 glasses using Raman, DSC and UV–visible spectroscopy, respectively prepared by melt and quench method. The optical gap is decreased with ZrO2 content except BSZ-7.5. The refractive index, optical basicity, and oxide ion polarizability are exhibited increasing trend with increasing ZrO2 content due to the conversion of bridging oxygens into non-bridging oxygens. The FTIR spectra revealed that Q1 unit of glasses increases instead of Q2 with increasing ZrO2 content. Lasocka, Kissinger and Augis-Bennette approaches are employed to study the crystallization behavior of the glasses. Various thermal parameters such as Avrami’s constant, thermal stability and fragility index are also studied to find out their possible application. In the present study, ZrO2 acts as a modifier up to 5.0 mol% and enhance bulk crystallization whereas at higher concentration (beyond 5.0 mol%), it behaves as a former and enhance surface crystallization.

지르코니아를 첨가한 치과용 폴리카복실레이트 시멘트의 생체적합성 및 기계적 성질 개선

Objectives: In this study, zirconia-incorporated polycarboxylate cement (PCC) (ZrO2/PCC) was developed to reduce the cytotoxicity and improve the mechanical properties of PCC. Methods: The ZrO2 was incorporated into a commercial PCC powder 0∼20 wt%. Its mechanical properties and dimensional stability were evaluated, and its cell biocompatibility was assessed using an MTS analysis with human dental pulp stem cells (hDPSCs). analysis with human dental pulp stem cells (hDPSCs). Results: As the ZrO2 content increases, the mechanical properties strength values increase; there was a statistically significant difference in the cell survival rate (p<0.05). Conclusions: The research results have demonstrated improvements in the mechanical properties and biocompatibility stability of ZrO2 in dental porcelain ceramics.

Network structure, crystallization behavior, and microwave dielectric properties of ZnO-B2O3 glass-ceramics with ZrO2 additions

The effects of ZrO2 addition on the glass network structure, crystallization behavior and microwave dielectric properties of ZnO-B2O3 glass-ceramics were investigated. The introduction of ZrO2 decreases the connectivity of the superstructure in the borate glass network and thus affects the crystallization behavior of glass, leading to the transformation of the main crystalline phase from Zn4B6O13 to ZnB4O7 and Zn3B2O6. With the increase of ZrO2 content, the microstructure changed from the branch-like structure into the net-like structure. For the sintered glass-ceramics, the relative permittivity increased with the ZrO2 content, which relates to the decrease in the vibrational energy of the B-O bond. In addition, the glass-ceramic with 0.25 mol% ZrO2 exhibits the maximum Q×f value due to the low disorder of B3+ cations. The ZnO-B2O3 glass-ceramic with 0.25 mol% ZrO2 sintered at 660 °C for 5 h exhibits the optimum microwave dielectric properties with εr = 6.18, Q×f = 23,670 GHz, τf = −65 ppm/°C. The high Vickers hardness of 662 kgf/mm2 and excellent chemical compatibility with Ag electrode demonstrated that the glass-ceramic is a good candidate for ULTCC application.

Machine learning in Al2TiO5 flexible ceramics with microcrcaks strengthened for damage mode automatic identification

AbstractThe damage modes of Al2TiO5 flexible ceramics (AT) with microcracks strengthened were studied by machine leaning for damage mode identification. Results show that the optimal number of clusters increases from 3 to 4 with the increase of ZrO2 content. Meanwhile, the concentrated region of cluster with the same label gradually shifts to the direction of low amplitude with increase of ZrO2. In addition, the quantity of cluster is easy saturated since the AT grain boundary microcracks are strengthened by the formation of ZrTiO4. For achieving the automatic identification of different damage modes, support vector machine based on Kennard‐stone training set selection was used to distinguish the damage modes of other samples in the same sample set. Almost the same evolution trend of corresponding clusters in new samples and training samples proves high efficiencies of this method.

In Situ ZrB2 Formation in B4C Ceramics and Its Strengthening Mechanism on Mechanical Properties.

In order to reduce the sintering temperature and improve the mechanical properties of B4C ceramics, ZrB2 was formed in situ using the SPS sintering method with ZrO2 and B4C as raw materials. Thermodynamic calculations revealed that CO pressure affected the formation of ZrB2 at temperatures from 814 °C to 1100 °C. The experimental results showed that the ZrB2 grain size was <5 µm and that the grains were uniformly distributed within the B4C ceramics. With an increase in ZrO2 content, the Vickers hardness and flexural strength of the B4C ceramics first increased and then decreased, while the fracture toughness continuously increased. When the content of ZrO2 was 15 wt%, the Vickers hardness, fracture toughness and flexural strength of B4C ceramics were 35.5 ± 0.63 GPa, 3.6 ± 0.24 MPa·m1/2 and 403 ± 10 MPa, respectively. These results suggest that ZrB2 inhibits B4C grain growth, eliminates crack tip stress, and provides fine grain to strengthen and toughen B4C ceramics.

Effect of Zr ions on the structure and optical properties of lithium borosilicate molybdate glass system

The glass system with the composition [(20-x) MoO3– x ZrO2–15 SiO2– 65 Li2B4O7, x = 0, 1, 2, 3, 4, and 5 mol %] was successfully synthesized using the melt quenching method. The XRD results of this glassy system confirmed the glassy nature of the prepared glasses. The density of this glassy system presented higher values while the molar volume provided lower values with increasing ZrO2 content. The FTIR result showed that the spectrum of each sample consisted of broad bands that de-convoluted into several peaks. These peaks were characterized and the structure of each sample was recognized. Additionally, the optical measurements showed that sample x = 0 mol% provided a sharp ultra-violet cut-off at 380 nm, while the other samples showed a transition peak in the (210–230) nm range. The energy of optical band gaps of these glass samples decreased and the Urbach energy increased by increasing ZrO2 content. Moreover, the different optical parameters of these glass samples were calculated and showed that the studied glasses could be considered promising materials to be used in different optical applications such as nonlinearity and optoelectronics.

Contribution to the Understanding of the Dielectric Breakdown Mechanism of ZTA Ceramics

Herein, the breakdown mechanism of alumina‐based ceramics (Al2O3–ZrO2) is studied. The specimens are characterized for their density, phase structure, micromorphology, breakdown process, and breakdown channel by micro computed tomography, high‐speed cameras, etc. The study reveals that the dielectric breakdown stability of the samples shows a decreasing trend and the dielectric loss shows an upward trend with the increase of ZrO2 content. The tetragonal phase zirconia is beneficial to enhance the dielectric breakdown strength of the sample, which is related to the martensitic transformation to prevent crack propagation. Before the ceramic breakdown, the insulating oil first breaks down, causing electric sparks. Once the ceramic breakdown occurs, the charges are rearranged, and a large amount of heat energy is generated instantly to melt the substance around the breakdown channel and erupt to the surface to form pits under the action of high internal stress.

Spark plasma sintering of ZrO2 reinforced Ni-Cr alloy: Microstructure and mechanical behavior

Ni-Cr-ZrO2 composites with varying amounts of ZrO2 additive (5 wt%, 7.5 wt%, 10 wt% and 12.5 wt%) were fabricated using spark plasma sintering method at a sintering temperature of 1000°C, heating rate of 100°C/min, holding time of 5 min, and a pressure of 50 MPa. The effect of ZrO2 addition on the microstructure, tribological and mechanical properties of the developed composites were studied. The results showed that maximum densification was attained at 10 wt% ZrO2. Further increase in the fractions of ZrO2 within the composites results in a decrease in the relative density of the sintered composite. A significant increase in hardness from 433.24 HV to 510.11 HV and elastic modulus from 252.67 GPa to 294.6 GPa was observed in the fabricated samples as the ZrO2 content increase from 5 to 12.5 wt%. An appreciable improvement in the wear performance of the sintered samples was obtained with increasing ZrO2 content. The observed improvement in the properties of the sintered composites was attributed to the presence of the hard dispersoids of ZrO2 and formation of solid solution strengthening and hard Cr3Ni2 phases within the matrix of the sintered composites.

Borotellurite glass system doped with ZrO2, potential use for radiation shielding

Boro-tellurite former based glasses have recently sparked the interest of a number of researchers as a powerful optical device and shielding material. In this study, novel glasses of composition (60B2O3 –(10-x) CaO–10Na2O – 20TeO2 - xZrO2) where x is varied from 0.0 to 3.0% mol have been integrated using the melt-quenching method. Even at high concentrations of ZrO2, the obtained X-ray diffraction (XRD) patterns revealed the absence of crystalline peaks, confirming the glassy nature of all glass samples. The physio-chemical and radiation shielding characteristic were evaluated for specimens. The thermal transition temperatures as well as the glass thermal stability were determined using a Differential Scanning Calorimeter (DSC) test. Glass stability was found to deteriorate with increasing ZrO2 content. Radiation shielding characteristics were calculated theoretically using the Phy-X/PSD and WinXCom databases, and the findings reveal that the glass sample with the greatest ZrO2 concentration has the best gamma ray shielding in the energy range of (0.015 MeV−15 MeV). Furthermore, when compared to ordinary concrete, the computed fast neutron removal cross-section (FNRC) revealed a 36.84 percent improvement. The shielding results show that light-weight transparent ZrO2-doped boro-tellurite glasses compositions might be a promising candidate for a variety of shielding applications. The optimum proportion of ZrO2 additive is determined by the balance between greater shielding and glass stability qualities, which varies depending on the application.

Effect of ZrO2 on crystallization behavior and mechanical property of Dy2O3–Al2O3–SiO2 glasses

Effects of ZrO2 content on the crystallization kinetics, formation mechanism of voids and mechanical property of Dy2O3–Al2O3–SiO2 glass were studied. The crystallization method of DAS glasses transforms from surface crystallization into bulk crystallization with an increase in ZrO2 content from 0-3% to 6–9%. When ZrO2 content is 0–3%, the crystalline phases of DAS glass ceramics are Dy2Si2O7 and Al2O3, accompanied by formation of voids. When ZrO2 content is 6–9%, the DAS glass ceramics consist of Dy2Si2O7, Al2O3 and ZrO2. At the same time, no voids are found in the glass ceramics. Therefore, formation of voids during crystallization can be attributed to combined effect of the crystallization method and the density difference before and after crystallization. In addition, for glassy samples, the flexural strength increases from 80.4 MPa to 219.3 MPa with an increase in ZrO2 content from 0% to 9%. Moreover, crystallization further improves the mechanical properties of the DAS glass ceramics with bulk crystallization method.

Microstructure and Piezoelectric Properties of Lead Zirconate Titanate Nanocomposites Reinforced with In-Situ Formed ZrO2 Nanoparticles.

Lead zirconate titanate (PZT)-based ceramics are used in numerous advanced applications, including sensors, displays, actuators, resonators, chips; however, the poor mechanical characteristics of these materials severely limits their utility in composite materials. To address this issue, we herein fabricate transgranular type PZT ceramic nanocomposites by a novel method. Thermodynamically metastable single perovskite-type Pb0.99(Zr0.52+xTi0.48)0.98Nb0.02O3+1.96x powders are prepared from a citrate precursor before both monoclinic and tetragonal ZrO2 nanoparticles ranging from 20 to 80 nm are precipitated in situ at a sintering temperature of 1260 °C. The effects of ZrO2 content on the microstructure, dielectric, and piezoelectric properties are investigated and the mechanism, by which ZrO2 toughened PZT is analyzed in detail. The ZrO2 nanoparticles underwent a tetragonal to monoclinic phase transition upon cooling. The fracture mode changed from intergranular to transgranular with increasing ZrO2 content. The incorporation of ZrO2 nanoparticles improved the mechanical and piezoelectric properties. The optimized piezoelectric properties (εT33/ε0 = 1398, tan δ = 0.024 d33 = 354 pC N−1, kp = 0.66 Qm = 78) are obtained when x = 0.02. Tc initially increased and subsequently decreased with increasing ZrO2 content. The highest Tc = (387 °C) and lowest εT33/ε0 was obtained at x = 0.01.

Microstructure and crystallization properties of Na2O-CaO-SiO2 glass system with different ZrO2 content

Glass-ceramics based on Na2O-CaO-SiO2 system show attractive properties due to the high transparency even with large crystals size. In this work, effects of ZrO2 on glass structure and crystallization behaviors of Na2O-CaO-SiO2 glasses were investigated. The introduction of ZrO2 has significant influence on glass network and resultant thermal and crystallization properties. Glass transition temperature and first crystallization temperature increase monotonically with the increase of ZrO2 content. In addition to Na4Ca4(Si6O18) crystalline phase, Na4Zr2(SiO4)3 and Na2ZrSi2O7 crystalline phases are precipitated when the content of ZrO2 is high. Vickers hardness of the as-prepared and heat-treated glass increases significantly with the increase of ZrO2 content and heat-treatment temperature.

A study of zircon crystallization, structure, and chemical resistance relationships in ZrO2 containing ceramic glazes

This study aims to investigate zircon (ZrSiO4) formation during thermal treatment and its influence on the structure and properties of the ceramic glazes. Four raw ceramic glazes with the addition of 5, 9, 13, and 17wt% of ZrO2 (<5μm) at the expense of SiO2 were prepared by the ceramic traditional route. To obtain homogeneous melting and consequently a high-quality surface, 5wt% of colemanite (2CaO·3B2O3·5H2O) was added to the ceramic glazes formulation. XRD, NMR, Raman spectroscopy and FTIR measurements revealed the formation of ZrSiO4. An increase of ZrSiO4 from 35 to 86wt% with an increase of ZrO2 content in the composition of ceramic glazes was observed. 29Si solid-state MAS NMR measurements also showed that with successive increases of ZrO2 concentration the relative intensity of zircon resonance increases. The evaluation of the chemical resistance revealed the beneficial effect of ZrSiO4 on this property.

Enhanced mechanical properties in ceramic multilayer composites through integrating crystallographic texture and second-phase toughening

Inherent brittleness and low mechanical reliability usually inhibit the application of ceramic materials in many structural applications. In this work, we demonstrate that integrating crystallographic texture and second-phase toughening strategies can effectively improve fracture resistance and mechanical reliability in alumina multilayer composites. Composites consisted of equiaxed (1-x)Al2O3-xZrO2 and highly [0001]-textured Al2O3 layers were fabricated, and effects of ZrO2 amount on fracture behavior and mechanical properties of the composites were studied. Increasing ZrO2 amount x results in larger thermal expansion difference between equiaxed and textured layers. The composites with equiaxed layers containing 30 vol% ZrO2 exhibit high apparent fracture toughness Kapt, c ~11.7 MPa·m1/2 and work of fracture γWOF ~1540 J/m2, which correspond respectively to about 260% and 410% enhancements relative to those without ZrO2 addition. Moreover, adding ZrO2 remarkably reduces sensitivity of failure stress to flaw size in the multilayer composites, and the failure stress substantially increases with increasing ZrO2 content. The greatly enhanced mechanical performance achieved here can be mainly attributed to higher magnitude of compressive stresses, more crack bifurcations and longer crack deflection paths within the textured layers. This work can provide important guidelines for developing novel “bio-inspired” materials with improved fracture resistance and flaw tolerance behavior.

Fabrication and thermal shock behavior of ZrO2 toughened magnesia aggregates

MgO-based refractories have been regarded as ideal linings for various furnaces owing to high refractoriness and excellent corrosion resistance to basic slag. However, thermal shock damage resulting from poor thermal shock resistance (TSR) of magnesia is the common failing. The present work aimed at improving TSR of magnesia aggregates by introducing microscale monoclinic ZrO2. The results showed that the ZrO2 added could increase cation vacancy concentration and inhibit abnormal growth of MgO grains, which therefore enhanced densification of the specimens. However, when the ZrO2 amount exceeded 15 wt%, densification decreased slightly due to agglomeration of ZrO2 and formation of more microcracks at the MgO grain boundaries. With increasing ZrO2 content, although the flexural strength degraded, the fracture toughness increased constantly because of the toughening effects of crack deflection and crack branching. Besides, although the addition of ZrO2 decreased the thermal conductivity, TSR of the specimens was significantly improved with increasing ZrO2 content due to the increase in toughness and decrease in strength, thermal expansion coefficient as well as Young's modulus. After thermal shock tests, 15 wt% ZrO2 containing specimen exhibited the highest TSR, whose residual strength ratio was about triple of that of the pure magnesia specimen. However, further increasing ZrO2 content to 20 wt% reduced the TSR attributing to the spalling of intergranular ZrO2 agglomerations.

Investigation of thermophysical properties of ZrO2-Sm3TaO7 ceramics

ABSTRACT This study investigates rare earth RE3TaO7 ceramics and shows that these materials may be optimal for thermal barrier coatings. ZrO2-Sm3TaO7 ceramics were prepared through a solid-state reaction. X-ray diffusion and structural refinement revealed a phase structure with an ordered orthorhombic phase for the Ccmm space group. The degree of structural disorder increased with increasing ZrO2 content. Gaussian function fitting of the oxygen 1s X-ray photoelectron spectra showed that the Sm3+ and Ta5+ ions were replaced by Zr4+ ions. At high temperatures, 8 mol% ZrO2-Sm3TaO7 has a high thermal expansion coefficient (10.9 × 10−6 K−1). The thermal conductivities of ZrO2-Sm3TaO7 (1.17 − 1.75 W·m−1 K−1) are lower than those of 7–8 wt.% yttria-stabilized zirconia, while those of 2% ZrO2-Sm3TaO7 are the lowest. The oxygen vacancies maintain the charge in equilibrium and enhance phonon scattering while decreasing the thermal conductivity. These results indicate that Sm3TaO7 can be used as a TBC.