Abstract Zirconium Research Articles

Trapping Capability of Small Vacancy Clusters in the α-Zr Doped with Alloying Elements: A First-Principles Study

Zirconium alloys are subjected to a fast neutron flux in nuclear reactors, inducing the creation of a large number of point defects, both vacancy and self-interstitial. These point defects then diffuse and can be trapped by their different sinks or can cluster to form larger defects, such as vacancy and interstitial clusters. In this work, the trapping capability of small-vacancy clusters (two/three vacancies, V2/V3) in the α-Zr doped with alloying elements (Sn, Fe, Cr, and Nb) has been investigated by first-principle calculations. Calculation results show that for the supercells of α-Zr containing 142-zirconium atoms with the two-vacancy cluster, alloying elements of Sn and Nb in the second vacant site (V2) and Cr in the first vacant site (V1) are more easily trapped by two vacancies, respectively. However, the two sites are both captured more easily by two vacancies for Fe in the supercells of α-Zr containing 142-zirconium atoms inside due to the similar value of the Fermi level. For the supercells of α-Zr containing 141-zirconium atoms with the three-vacancy cluster, the alloying element of Sn in the third vacant site (V’3), Fe in the first vacant site (V’1), and Cr and Nb in the second vacant site (V’2) are more easily trapped by three vacancies, respectively.

Enhanced biomedical applicability of ZrO2\u2013SiO2 ceramic composites in 3D printed bone scaffolds

Zirconia (ZrO2) has been widely used in clinical applications, such as bone and dental implantation, because of its favorable mechanical properties and resistance to fracture. However, the poor cell affinity of ZrO2 for bone regeneration and tissue binding, as well as its shrinkage due to crystal phase transformation during heat treatment, limits its clinical use and processing plasticity. This study aims to investigate an appropriate ZrO2–SiO2 composite recipe for ceramic 3D printing processes that can strike a balance between the mechanical properties and cell affinity needed in clinical applications. Specimens with different ZrO2–SiO2 composite recipes were fabricated by a selective laser gelling method and sintered at temperatures ranging from 900 to 1500 °C. The S5Z5 composite, which consists of 50 wt% ZrO2, 35 wt% SiO2 and 15 wt% SiO2 sol, showed an appropriate compressive strength and bending strength of 82.56 MPa and 55.98 MPa, respectively, at a sintering temperature of 1300 °C. The shrinkage rate of the S5Z5 composite was approximately 5% when the sintering temperature was increased from 900 to 1500 °C. All composites exhibited no cytotoxicity after 144 h of MG63 cell incubation, and the S5Z5 composite exhibited the most obvious cell affinity among the composite recipes. From these results, compared with other composites, the S5Z5 composite was shown to possess mechanical properties and a cell affinity more comparable to those of natural human bone.

Application of Zirconia Ceramic Biomaterial Implants in the Restoration of Tooth Loss Caused by Periodontal Disease

Zirconia ceramics (ZiC) has become a biomaterial with good clinical application prospects due to its good biocompatibility, stability, and excellent mechanical properties. In this study, bioactive glass (BioS) was undertaken as the modifier, and the ZiC precursor solution was penetrated on the surface of the ZiC body or the ZiC particles were coated with the BioS precursor solution, so as to obtain the ZiC with biological activity by introducing the BioS phase. While the material was characterized, its mechanical properties and biological activity were analyzed by simulating the mineralization of the body fluid, including the cell adhesion, proliferation, and differentiation of the material. The ZiC was applied as an implant for restoration of patients with teeth loss caused by periodontal disease. In the test, after surface infiltration of BioS sol or coating of ZiC particles, a very thin BioS phase can be formed on the surface of ZiC after high temperature sintering. The in vitro mineralization test showed that the activation of the grain boundary promoted the deposition of calcium and phosphorus layers on the surface of the sample. The mechanical test revealed that the relative density, flexural strength, and fracture toughness of the material decreased with the infiltration and coating of BioS. However, under proper preparation conditions, the modified ZiC still showed good mechanical properties and can promote the spreading, adhesion, and differentiation of mouse bone marrow mesenchymal stem cells (mBMSCs). Clinical trials proved that after the modified ZiC implant material was implanted in patients with teeth loss, the structure was not loose or broken, and the intraoral prosthesis could function normally. After treatment, the level of IL-1β in the gingival crevicular fluid of the patient decreased obviously (P <0.05). In addition, the probing depth (PD), clinical attachment loss (CAL), and other indicators decreased greatly (P <0.05).

Zr-Catalyzed Microwave Assisted Functionalization of Alkyne and Nitroalkene

Water and zirconium(IV) as catalyst were found to be effective in the transformation of terminal aromatic alkyne to aromatic methyl ketone in the microwave. This terminal alkyne hydration reaction proceeded in excellent yield with Zr(cp)2Cl2. The reaction was moved efficiently in presence of electron donating or electron withdrawing substituent on aromatic ring. An eco-friendly synthesis of aldehyde by oxidative cleavage of nitroalkene was developed with Zr(cp)2Cl2 catalyst and water in microwave.

Impedance spectroscopic studies of zirconium substituted 0.8BaTiO3-0.2Bi0.5K0.5TiO3 lead free ceramics

Zirconium substituted 0.8BaTiO3-0.2Bi0.5K0.5TiO3 lead free ceramic materials were prepared by solid state reaction followed by high energy ball milling process. To understand its frequency dependent electrical properties, impedance spectroscopic studies were carried out. From the impedance studies it is observed that relaxation taken place from 375 °C. Single depressed semicircle was observed from the Cole-Cole plots. This indicates non-Debye kind of relaxation process. Grain resistance value was calculated from the Cole-Cole plots and it is found to be increasing with increase of Zr substitution. Modulus spectroscopic studies also confirm the non-Debye kind of relaxation process in the material. Variations in normalized values of / max & / max as a function of logarithm of frequency indicates short range conductivity in the present material.

Effect of neodymium and zirconium substitution on electrical properties of SrBi4Ti4O15

Neodymium and zirconium modified strontium bismuth titanate ceramics with content changing from 2.5 to 10 at% Nd and a 2.5 at% Zr of SrBi4Ti4O15 (SrNdxBi4-xZryTi4-yO15, (x = 0.00, 0.025, 0.05, 0.075, and 0.1, y = 0.00 and 0.025) have been prepared by solid state reaction method and analyzed by X-ray diffraction (XRD), dielectric response, ferroelectric hysteresis, electromechanical coupling coefficient, and piezoelectric charge coefficient. From hysteresis loop, the remnant polarization and coercive field were calculated and explained. Dielectric analysis explained the sample behavior. Piezoelectric charge and electromechanical coupling coefficients were found to be increased with the addition of Zr and Nd.

An experimental investigation on milling features of fully-sintered zirconia ceramics using PCD tools

ABSTRACT Zirconia ceramics have emerged as a promising restorative material owing to their superior physical properties and excellent biocompatibility. Among the zirconia family, fully-sintered samples show the highest mechanical properties but the poorest machinability compared with those fabricated at pre-sintering temperatures. The current work aims to study the milling characteristics of fully-sintered zirconia ceramics when using polycrystalline diamond (PCD) tools under varying cutting conditions. The machining responses of fully-sintered zirconia ceramics, such as cutting forces, specific cutting energy, milling temperatures, and surface topographies, were carefully addressed. The obtained results were correlated with the applied milling parameters. The tool wear morphologies were eventually characterized to figure out the underlying wear mechanisms governing the performance of PCD tools. The results indicate that increasing the feed per tooth definitely raises the milling forces and temperatures, while increasing the cutting speed elevates the milling temperatures but decreases the cutting forces. The feed per tooth significantly affects the surface topographies of cut zirconia surfaces due to its effects on the ductile-brittle transition of the workpiece. The PCD tool shows the feasibility of carrying out hard milling of fully-sintered zirconia ceramics, which undergoes a minor degree of wear along its cutting edge.

Development of Alternative Method for Manufacturing Structural Zirconium Elements for Nuclear Engineering.

Zirconium is used as a structural material for use in aggressive environments, including the core of nuclear reactors. The traditional technology of manufacturing the structural elements of zirconium nuclear reactors is characterized by a long technological process and a significant amount of waste in the form of metal shavings. The paper presents the results of an alternative technology, spark plasma sintering, for manufacturing zirconium products. A complex of microstructural and mechanical studies of the obtained samples was carried out according to the ASTMB-351 standard. The sintering of zirconium powder and options for subsequent processing by various methods, including non-standard ones such as radial shear rolling, are justified.

Nondestructive Structural Investigation of Yttria-Stabilized Zirconia Fiber Insulation Tile by Synchrotron X-ray In-Line Phase-Contrast Microtomography

Zirconia (ZrO2) aerogels show excellent insulating performance and have been widely applied as a thermal protector in furnaces, nuclear reactors, and spacecraft. The nondestructive determination of their interior microstructure is significant for evaluating their mechanical and insulating performance. In this study, we performed nondestructive structural investigation of an yttria-stabilized ZrO2 fiber insulation tile using synchrotron X-ray in-line phase-contrast microtomography at a pixel resolution of 6.5 µm. Taking advantage of the edge enhancement of phase-contrast imaging, single yttria-stabilized ZrO2 fibers were clearly distinguished; furthermore, interior aggregates were nondestructively observed at this spatial resolution. This work demonstrates the advantages and potential of synchrotron X-ray microtomography for the structural analysis of porous ceramic materials. By combining higher-brilliance synchrotron radiation sources and CCD detectors with higher spatial and temporal resolutions, we anticipate that we can further understand the relationship between aerogel microstructure and function, especially under in-service conditions at high temperatures.

Slurry Coating of Hydroxyapatite on Zirconia Substrate.

Zirconia dental implants require excellent biocompatibility and high bonding strength. In this study, we attempted to fabricate biocompatible zirconia ceramics through surface modification by hydroxyapatite (HA) slurry coating. A hydroxyapatite slurry for spin coating was prepared using two sizes of hydroxyapatite particles. The hydroxyapatite slurry was obtained by adjusting the solid loading, pH range, and dispersant content. The surface roughness of the HA-coated layers on the zirconia substrate depended on the change in microstructural evolution and coating thickness. With repeated coating, the coating thickness gradually increased for both small and large particles. The specimen with two coatings had the maximum surface roughness but displayed different values depending on the size of the HA particles. High surface roughness (Ra; 0.49 μm) could be obtained from the slurry of small particles compared with that of the large particles (Ra; 0.35 μm). During a 14 days in vitro experiment in SBF solution at pH 7.4, no changes were observed in the surface microstructure of the HA coating layer on the zirconia substrate.

Effect of Raw Material Purity on Structure and Properties of Metallic Glasses

Zirconium base metallic glasses [Zr0.73(Cu0.59Ni0.41)0.27]87Al13 was fabricated by industrial zirconium with low purity and high purity zirconium according to different quality ratios in order to study the effect of raw material purity on the structure and properties of metallic glasses. The results showed that the complete metallic glasses was failed to be fabricate with low purity zirconium. And the compression process was typical brittle fracture with low compressive strength and without plastic strain. The glasses forming ability of low purity zirconium metallic glass with different purity was significantly improved after the addition of yttrium element. The compression experiments showed that the compressive strength and plasticity of metallic glasses were improved, and the microhardness was also increased. It indicates that yttrium element can eliminate the adverse effect of impurity in low purity zirconium on the glasses forming ability of the alloy and improve the structural properties of the metallic glasses.

Influence of the sintering method on densification, microstructure and electrical conductivity of 12Ce-TZP

ABSTRACT Zirconia containing 12 mol-% cerium oxide ceramics were prepared by solid state reaction utilising the conventional, fast firing and two-step sintering methods. The sintering temperature and time were varied aiming to determine ideal sintering profile for these methods. The monoclinic and tetragonal phase contents, microstructure and electrical conductivity of dense specimens were investigated. The linear shrinkage was found negligible up to 1100°C and the maximum rate of shrinkage was achieved at 1150°C. Densification increased up to 2 h for conventional sintered specimens. Stabilisation of tetragonal phase in non-isothermally sintered specimens occurred at a high temperature (1500°C). Specimens sintered by the two-step method attained high density along with small grain sizes. Optimised sintering profiles were determined for all the sintering methods used.

Influence of pH of the electrolyte on the formation and properties of electrodeposited ZrSe2 thin films

Zirconium diselenide thin films were electrodeposited on the stainless steel substrates for various pH values ranging from 2.0 to 3.5. The deposition potential range suitable for the deposition has been optimized using cyclic voltammetry (CV). The X-Ray Diffraction (XRD) results confirm that the thin films produced were polycrystalline in nature with hexagonal structure peak at 2θ = 43.8° (003) of ZrSe2. The surface morphology of the film indicate, as the pH was increased the grain size of the film become larger due to agglomeration. The direct band gap energy of the films was found to be in the range of 1.77–1.83 eV.

Fabrication and Characterization of Zirconium Silicide for Application to Gas-Cooled Fast Reactors

Zirconium silicide (Zr3Si2) is a heavy reflector material particularly effective for application to a Gas-cooled Fast Reactor (GFR) such as the General Atomics Energy Multiplier Module (EM2) and Fast Modular Reactor (FMR). In this work, the manufacturability of a high-density Zr3Si2 compound, in the Zr3Si2 phase, was investigated using hot-pressing and spark-plasma-sintering methods. The microstructure, composition, and thermal properties of the resulting hot-pressed material were measured, resulting in a 96% relative density and a 96% phase pure material. The thermal properties were consistent with those necessary for use under GFR operating conditions. The structural and dimensional stability of the material was also measured before and after neutron irradiation up to 1017 n/cm2 in the research reactor, resulting in an average linear dimensional change of <0.12%. The preliminary irradiation tests also confirmed the micromechanical stability of the Zr3Si2 phase, with no evidence of microcracking after irradiation. The results of the irradiation tests verify the fabrication method of Zr3Si2 for nuclear applications, but further irradiation tests under high-temperature and high-irradiation conditions will be required to qualify the material for GFR applications.

Effect of ZrB2 nanopellets on microstructure, dielectric, mechanical and thermal stability of polyimide

Zirconium boride (ZrB2) with high electrical, thermal conductivity, chemical stability and low coefficient of thermal expansion has been considered promising boride ceramic. In this study, the new type polyimide(PI)-based composites filled with ZrB2 nanopellets were prepared via in-situ polymerization. The results show that the ZrB2 nanopellets are dispersed uniformly in the PI matrix and the ZrB2/PI composites with 0.5 wt.% loading exhibits outstanding dielectric, mechanical properties and thermal stability. A mechanism related to the microstructure is proposed to explain the performance improvement. ZrB2 with strong electron affinity could trigger charges to accumulate on its surface, which promotes the interface polarization and consequently enhance dielectric constant. The strong interactions between ZrB2 and PI beneficial to stress effectively transfer from the PI matrix to the ZrB2. The dense structure of the composites and the intrinsically high thermal conductivity of ZrB2 are conducive to heat transfer in the matrix and reduce heat accumulation. The dielectric constant, tensile strength and elongation at break of the composites are increased by 17.5%, 63% and 59.4% compared to pure PI. Meanwhile, the ZrB2/PI composites possess superior electrical insulation property. The comprehensive performance improvement of the composites share a broader prospect for its application in engineering.

Preparation of zirconium coating on zirconium-niobium alloy substrate by pulsed current electrodeposition from fluoride molten salt

ABSTRACT Zirconium coating on Zirconium-Niobium alloy substrate was obtained by pulsed current electrodeposition from FLINAK-K2ZrF6 molten salt at 1023 K in argon atmosphere. The microstructure and morphology of the coating were investigated. The adhesion between coating and substrate, porosity of the coating surface was tested. Metallic zirconium crystal of zirconium coating is a hexagonal crystal structure with the preferential growth orientation of (002). The porosity of the coating surface is 1.7%. The adhesion between coating and substrate is good in the scratch test, and the adhesive force of the zirconium coating is 10.5 N. Furthermore, on the inner and outer walls of a 10 mm diameter tube, the same quality zirconium coating can be obtained.

Fabrication of High-Strength Zr-Based Composites by Spark Plasma Sintering

Zirconium (Zr) partially stabilized zirconia (PSZ) composites were fabricated using the spark plasma sintering technique with the aim of producing medical implants with reduced metal-related artifacts in magnetic resonance imaging. Composites with compositions ranging from 100% Zr to 100% PSZ were fabricated, and they exhibited high mechanical performance. Optical microscopy and density measurements revealed that dense composites were successfully produced, irrespective of the PSZ content. Hardness and bending tests were performed to evaluate the influence of the addition of PSZ on the mechanical properties of the composites. The results showed that the hardness and bending strength increased with increasing PSZ content. The elastic modulus of the composites was higher than that predicted by the rule of mixtures, and this was due to the formation of Zr oxide around the Zr phase during sintering. It was concluded that the mechanical properties of the composites could be controlled within the range of those of monolithic Zr and monolithic PSZ, and that the use of PSZ was effective for improving the mechanical properties.

Amino Functionalization of Zirconium Diboride for High Dispersion Stability and Solid Loading.

Zirconium diboride (ZrB²) is an ultrahigh-temperature ceramic (UHTC) with excellent thermal and mechanical properties. To fabricate a complexly structured UHTC sintered body with high density a high-solid-loading slurry with low viscosity is required to fill the mold well. Extensive studies have been carried out to improve the dispersion properties, including those on solvents and surfactants. In this study, a surface treatment using polyethylenimine (PEI) was investigated. This reagent was used to provide ZrB² particles with desirable properties, such as electrostatic repulsive force and steric hindrance, by the functionalization of amine groups. Additionally, surface treatments with different concentrations of PEI were performed. The appropriate content for a high dispersity was determined. The surface functional groups of the PEI-treated ZrB² were observed by Fourier-transform infrared spectroscopy. The surface charge and enhancement in dispersion were evaluated by zeta potential and particle size distribution analysis, respectively. The rheological properties of the ZrB² slurries with various solid loadings were analyzed by viscosity measurements. In conclusion, ZrB² slurries with solid loadings up to 50 vol% could be prepared through the PEI treatments.

Parametric Optimization of ZrB2–SiC Composites Sintered Through Microwave Sintering Using Grey Relational Taguchi

Zirconium Diboride (ZrB2) is known as an ultra-high temperature ceramic with applications in various industries like refractory and foundry industries. In conjunction with Silicon Carbide (SiC), ZrB2ceramic finds extensive applications in the nose caps and leading edges of atmospheric re-entry vehicles and rocket propulsion. The primary objective is to optimize the output responses viz., Vickers micro hardness, relative density, compressive strength of ZrB2-30 vol.% SiC composites developed through microwave sintering. The three control factors viz., sintering temperature, heating rate and holding time are chosen as input process parameters for microwave sintering. Taguchi’s L9orthogonal array is used to obtain experimental runs. The Grey Relational Taguchi provides the optimal process parameters by binding the multiple responses (relative density, vickers micro-hardness, and compressive strength) into single comprehensive response [i.e., Grey Relational Grade (GRG)]. The results confirm that the optimal parameters attained using Grey Relational Taguchi maximize the performance characteristics of the microwave sintering process.

Structural Characteristic and Dielectric Properties of Zirconia Toughened Alumina

Zirconia toughened alumina (ZTA) has shown a great effect in the cutting tool application due to its high hardness and comparable fracture toughness. However, the capability of the materials to be applied in as the dielectric resonator antenna (DRA) is not being discussed in detail. In this study, an attempt is made to further explore the potential of ZTA to be applied in DRA. Various related characterization techniques were applied that is subjected to DRA properties. The addition of CeO2 (0 wt.% to 15 wt.%) on ZTA has been pressed into pellets shape and sintered at 1600 °C for 2 hours under pressureless conditions. Based on the XRD analysis, only corundum and yttria doped zirconia phases were present. Shift in position of the zirconia peaks was observed due to an existence of Ce2Zr3O10 phase. For the DRA measurement, ZTA with 10 wt.% CeO2 addition have resonated at 6.76 GHz which is suitable for X-band applications. Meanwhile the radiation pattern indicated the omnidirectional characteristic, which suggested that the signal could be received by this dielectric antenna in various positions. Therefore, ZTA- 10 wt.% CeO2 have high potential to be used as DRA that operates X-band frequency range applications.