Formation Of Zr Research Articles

Model development for oxidation and degradation behavior of accident tolerant Cr coating on Zr alloy cladding under high temperature steam atmosphere

The oxidation and degradation mechanisms of Cr coating on Zr alloy cladding under high temperature steam atmosphere are summarized. Six basic phenomena are considered for model development, including: oxidation of Cr, growth of ZrCr2, formation of Zr(Cr) solid solution, outward diffusion of Zr, reduction of Cr2O3, and volatilization of Cr2O3. The mathematical analysis model is established and validated, demonstrating its good capacity to predict the increase and subsequent decrease in the thickness of Cr2O3 scale, as well as the thickness changes in other individual layers. The developed model is applied in the analysis of the structure evolution of Cr coating under steady state, transient heating conditions and postulated accident scenarios.

Novel three-dimensional Ti3C2-MXene embedded zirconium alginate aerogel adsorbent for efficient phosphate removal in water

Excessive phosphorus in water causes environmental security problems like eutrophication. Advanced two-dimensional material MXene has attracted raising attention in aquatic adsorption, while lack of selectivity and difficult recovery limit its application in phosphate removal. In this study, Ti3C2-MXene embedded zirconium-crosslinked SA (MX-ZrSA) beads were synthesized and their phosphate adsorption performance under different conditions was assessed. Investigations using SEM/EDS, XRD, BET, TGA and contact angle meter reveal that the addition of Ti3C2-MXene enhanced the thermal stability, mechanical strength, hydrophilicity, and formed loose network-like mesoporous inner structure with large surface area. The theoretical maximum adsorption capacity was 492.55 mg P/g and was well fitted by Freundlich and optimized Langmuir models. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis showed that chemisorption was involved, and the formation of Zr–O–P and Ti–O–P complexes accounted for high selectivity and affinity to phosphate. The adsorption experiments in real waters and lab-scale continuous flow Anaerobic-Anoxic-Oxic reactor further indicated the application potential of MX-ZrSA beads. Our study will provide insight into MXene and SA aerogel synergistic adsorption of aquatic contaminants and help with the removal and recovery of finite phosphorus resource.

Amorphous zirconium oxide activates peroxymonosulfate for selective degradation of organic compounds: Performance, mechanisms and structure-activity relationship

Application of heterogeneous advanced oxidation processes (AOPs) for wastewater treatment suffers from the low oxidant utilization efficiency, slow catalytic cycling and severe matrix interference. Herein, we report that amorphous zirconium dioxide (aZrO2), a redox-inert metal oxide, can efficiently activate peroxymonosulfate (PMS) to degrade organic micropollutants under very low oxidant doses and complex coexisting matrices. Distinct from conventional AOPs where radicals are formed, the surface Zr(IV)-PMS* complex was identified as the principal reactive species, and primarily conducted oxygen-atom-transfer route with selected molecules. Quantitative structure-activity relationship analysis indicated that the formation of Zr(IV)-PMS* complex was governed by the density of the surface hydroxyl groups. The strong interaction between the Zr atom and PMS caused the deviation of the negative charge from Zr(IV) metal sites to the oxidant. As a result, the O-O bond of the adsorbed PMS was prolonged and its oxidation potential elevated, which enabled it to directly react with contaminants. This study indicates the potential of aZrO2 as a novel and eco-friendly catalyst that activates PMS to selectively tackle organic contaminants, and sheds light on the designing of Fenton-like catalysts using redox-inert metals.

Rapid and efficient removal of toxic ions from water using Zr-based MOFs@PIM hierarchical porous nanofibre membranes

The development of new adsorbent materials to improve adsorption capacity and selectivity constitutes a significant research direction for removing toxic ions from water. In this study, a series of Zr-based metal–organic framework hierarchical porous nanofibre membranes (MOFs@PIM-W) was designed and successfully synthesised, and their adsorption properties and mechanism for fluoride ions in water were investigated. The formation of Zr–F bonds in Zr-based MOFs is a primary reason for the rapid, effective, and stable removal of fluoride ions from water. Moreover, in contrast to common powder adsorbents and the conventional static adsorption process, the obtained hierarchical porous nanofibre membranes improve the removal rate of fluoride ions, which may be attributed to the formation of hierarchical porous structures. Specifically, by modifying the types of MOFs, the obtained nanofibre membranes can effectively remove Hg(II) ions from water under a wide range of pH environments (pH = 2–10) with a removal rate of up to 99 %. This indicates that the hierarchical porous design of nanofibre membranes incorporated with their specific adsorption provides a viable option for rapidly and efficiently removing toxic ions from water.

First‐principles study of the thermal properties of Zr2C and Zr2CO

AbstractFirst‐principles calculations of lattice thermal conductivities and thermodynamic properties of Zr2C and Zr2CO were performed using the quasi‐harmonic approximation. Oxygen in the lattice gives Zr2CO higher bonding strength than Zr2C. Thus, the mechanical properties of Zr2C are enhanced when the vacancies in its crystal structure are filled with oxygen. Among the critical parameters that determine the lattice thermal conductivity, Zr2C has significantly higher Grüneisen parameters, thus Zr2C has lower lattice thermal conductivity than Zr2CO. In addition, Zr2CO has a higher heat capacity and thermal expansion coefficient than Zr2C at most temperatures. These results indicate that the addition of oxygen has increased the stiffness and thermal conductivity of zirconium carbide that contains a large fraction of carbon vacancies due to the filling of vacancies in the Zr2C lattice and the formation of Zr–O bonds.

The oxidation mechanisms of the Xe20+ ion-irradiated Cr coatings on Zr alloy coupons: Accelerated diffusion and internal oxidation

Protective coatings of fuel claddings inevitably suffer from irradiation damage under actual nuclear operating condition. Here, effect of ion irradiation on the high-temperature oxidation behavior was studied for the Cr coatings on Zr alloy coupons that had already experienced the irradiation of 5 MeV Xe20+ ions at room temperature with the fluences of 1 × 1013 - 1 × 1015 ions/cm2. Although the irradiation damage concentrated in the ~1 µm thick surface layer, the oxidation resistance of the coatings was drastically degraded after the irradiation. It was observed that the irradiation-induced structural defects migrated and aggregated into cavities in large columns, which greatly accelerated the inward-diffusion of O and the outward-diffusion of Cr and Zr. The oxides rapidly nucleated within the irradiated area in the low-oxygen-partial-pressure conditions. During the 1200 °C steam oxidation, the oxides scales could not remain structural integrity, because the formation of Zr(O) phases along the oxide-metal interfaces resulted into bubbles and cracks. Therefore, the oxidation process was very sensitive to the irradiation-induced structural defects, and the irradiated coatings mainly proceeded the internal oxidation mechanism.

Corrosion characteristics of Mo and TZM alloy for plasma facing components in molten lithium at 623 K

In this study, the corrosion behaviours of molybdenum (Mo) and a Mo-based alloy (TZM) were investigated using a static immersion corrosion technique. Weight loss, surface microstructure, and corrosion depth of Mo and the TZM alloy were correlated with elements. The compatibility of Mo and the TZM alloy in static liquid Li was suitable. Mo demonstrated uniform corrosion with a homogenous dissolution of free C and Mo, and TZM alloy exhibited a nonuniform corrosion behaviour with a preferential grain boundary attack caused by the selective dissolution of free C, Ti, and Zr. When the surface oxidation layer of the samples was consumed, free C from Mo and TZM diffused into molten Li to form Li2C2 and then was captured by Zr, Ti, and Mo to form thermodynamically stable carbides, which resulted in the enrichment of the C layer near the sample surfaces. In addition, Ti and Zr acted as N-trappers in liquid Li; the formation of Zr and Ti nitrides resulted in the enrichment of N, Ti, and Zr elements on the surface and led to TZM corrosion increase. Thus, Zr and Ti depletion, pitting, and grain boundary corrosion were problematic for TZM under long-term exposure to liquid Li. Reducing the content of free C and nonmetallic N and increasing the amount of Ti and Zr carbides on the surface of and inside the raw TZM alloy helped improve the corrosion resistance of TZM in liquid Li.

Improvement of Thermal and Environmental Stabilities of Short Channel Coplanar Amorphous InGaZnO Thin‐Film Transistors by Introducing Amorphous ZrAlOx Interlayer

The short channel coplanar amorphous indium gallium zinc oxide (a‐IGZO) thin‐film transistor (TFT) is reported by introducing a ZrAlO x (ZAO) interlayer deposited by spray pyrolysis at the substrate temperature of 350 °C. The atomic ratio (at. %) of In:Ga:Zn:O is 1:2.5:1.2:5.2 in the a‐IGZO film deposited by sputtering. The a‐IGZO TFT with ZAO layer with 0.87 μm channel length exhibits the field‐effect mobility of 6.44 cm2 V−1 s−1, the threshold voltage of −2.16 V, and on/off current ratio of 7.6 × 107. It is found from the X‐ray photoelectron spectroscopy depth profile and high‐resolution transmission electron microscope analysis that some Zr atoms diffuse into the a‐IGZO underlayer. The formation of ZrO bonds on a‐IGZO surface region reduces the carrier concentration in the a‐IGZO TFT offset region, between source/drain contact and the channel, and blocks the carrier diffusion into the channel. This reduces the field‐effect mobility of 10 μm channel length TFT from 21.86 to 14.01 cm2 V−1 s−1, but the ZAO layer protects the a‐IGZO from the diffusion of H2O and O2. As a result, 0.87 μm TFT shows high on/off current ratio and stable under 85 °C and 85% relative humidity test for 2 days.

Preparation of composite powders containing TiB2 and ZrB2 particles through combustion synthesis of TiO2–ZrO2–B2O3–Mg system

Composite powders containing TiB2 and ZrB2 particles were successfully prepared through combustion synthesis of (2-x)TiO2–xZrO2–2B2O3–(10 + y)Mg system. Results showed increase in the x-value from 0 to 2 mol and y-value from 0 to 2.5 mol didn't have any considerable impact on reaction front velocity. In the case of TiO2–B2O3–Mg system with stoichiometric composition, agglomerates containing large TiB2 particles with hexagonal plate-like morphology embedded in a MgO matrix were remained after leaching. The addition of 25 wt% excess Mg (y = 2.5) to this mixture resulted in the dissolution of unwanted phases and the formation of pure submicron TiB2 particles. On the contrary, for the ZrO2–B2O3–Mg mixture (x = 2) unreacted ZrO2 remained and a ZrB2/ZrO2 composite powder was acquired. Both TiB2 and ZrB2 particles were only attained at x = 1.5 mol. The addition of 25 wt% excess Mg to this sample had an inverse effect and removed ZrB2 instead of ZrO2. Lastly, a TiB2/ZrO2 composite powder having submicron titanium boride particles was prepared after leaching process. Simultaneous thermal analyses results showed the combustion reaction sequence in the TiO2–ZrO2–B2O3–Mg system involves; dehydration of powders, melting of B2O3, reaction of molten B2O3 with solid Mg, solid-state reaction of TiO2 and Mg and the formation of Ti, partial reaction of ZrO2 with Mg and the formation of Zr and finally, development of TiB2 and ZrB2 through reaction of Ti and Zr with B element.

Sol-gel synthesis and characterization of ZrO2-25wt.%CeO2-2.5wt.%Y2O3 (CYSZ) nanoparticles

This study is intended to improve the high-temperature properties of micro-CYSZ: ZrO2-25 wt%CeO2-2.5 wt%Y2O3 in order to apply it in new generation of thermal barrier coatings (TBCs) through substituting micro-CYSZ with nano-CYSZ. Nano-CYSZ was synthesized by sol-gel method followed by calcination for 3 h at 1000 °C, and subsequently underwent a heat treatment at 1300 °C for 50 h. Results obtained from Fourier-transform infrared spectroscopy (FTIR) and thermogravimetry/differential scanning calorimetry (TGA/DSC) indicated the formation of Zr–Y–Ce bonds, and proper calcination at 1000 °C, respectively. The microstructure and morphology of the product was studied by field emission scanning electron microscopy (FESEM), revealing the formation of CYSZ nanoparticles with the mean size of 40 nm. X-ray diffraction (XRD) and Raman analysis also confirmed the formation of non-transformable (t') ZrO2 phase (ca2<1.01) as well as the stability of this phase after heat treatment. Results suggest nano-CYSZ as a promising choice for advanced TBCs in the new aero-engine and power generation applications.

Effect of Moist Air and Minor Zr Addition on Oxidation Behavior of Arc-Melted Multiphase Mo–Si–B Alloys in the Temperature Range of 1000 °C–1300 °C

Arc-melted multiphase intermetallic alloys, Mo76Si14B10, Mo74Si14B10Zr2, Mo79.5Si12B8.5 and Mo77.5Si12B8.5Zr2 with microstructures containing Moss, Mo3Si and Mo5SiB2 were isothermally exposed for 1 h or 24 h at 1000 °C, 1150 °C and 1300 °C in dry or moist air. The residual area fraction was found to be the highest on exposure at 1150 °C in dry air, but the least at this temperature in moist air. Examination of dry air formed oxide scales by X-ray diffraction, and scanning electron microscopy with energy-dispersive spectroscopy showed the presence of Mo, and MoO2 with a continuous, protective glassy B2O3–SiO2 top layer. Formation of Zr(MoO4)2 in the Zr-containing alloys had lowered mass loss by arresting MoO3 vaporization, and had enhanced the B2O3–SiO2 scale formation kinetics. Further, Si(OH)4, cristobalite, H3BO3 and MoO3·(H2O)2 appeared to be constituting the oxidation products formed in moist air. Alloying with Zr enhanced the kinetics of protective scale formation by lowering the Moss content, and microstructural refinement. The deterioration of oxidation resistance in moist air was conjectured to be due to longer duration required for protective scale to form, formation of β-cristobalite permitting grain boundary diffusion of oxygen anions, as well as volatile hydrated oxidation products as mentioned above. Formation of ZrSiO4 and dissolved ZrO2 in B2O3–SiO2 scale of the Mo-Si-B-Zr alloys in both dry air and moist air is considered to have contributed to the enhanced protective character of oxide scale by stabilizing the glassy scale.

Direct production of 2,5-diformylfuran from fructose catalysed by Mo-based composite oxides in static air

A series of MxMoyOδ composite oxides (M = Ca, Mn, Fe, Co, Ni, Cu, Zn, Y, Bi, Zr, La or Ce) was synthesized and used for the one-pot direct conversion of fructose to 2,5-diformylfuran (DFF) using atmospheric air as the oxidant. Among these materials, ZrxMoyOδ exhibited the best catalytic performance. Hence, the effects of the Zr/Mo molar ratio and calcination temperature on catalytic performance were investigated in detail and the reaction conditions were also optimized. The highest performing catalyst, Zr1Mo2Oδ, produced a DFF yield of 61 % along with the complete conversion of fructose under the optimized reaction conditions. More importantly, this material also exhibited good recycling stability and could be reused five times without a noticeable loss of activity. These ZrxMoyOδ catalysts were characterized using multiple techniques. Zirconium oxide was found to interact strongly with molybdenum oxide species via the formation of Zr(MoO4)2, thus producing a large number of surface chemisorbed oxygen species. The close linear correlation between DFF yield and surface chemisorbed oxygen confirmed that these oxygen species were the primary active sites for the oxidation reaction.

Effect of Particle Geometry and Nb2O5 Addition in the Sintering of Partially Stabilized Zirconia with Y2O3

Zirconia (ZrO 2 )has several applications in diverse industrial segments due to its excellent properties, especially regarding resistance to mechanical stress and high-temperature scenarios. However, due to phase transformations that this ceramic material exhibits at various temperatures, the appearance of cracks in the sintered compact during cooling is perceived. Studies have been performed in the way to stabilize zirconia during the sintering process by adding small quantities of other oxides, such as Y 2 O 3 , CeO, MgO and Nb 2 O 5 . Some studies show that the use of Nb 2 O 5 in the system ZrO 2 -Y 2 O 3 promotes an increase in its fracture toughness. Additionally, there are several controversies about the effect of the content and the polymorph of Nb 2 O 5 on zirconia stabilization. There are several commercial zirconia powders partially stabilized in the form of granules obtained by the spray dryer method which promotes better densification of the green and sintered compacts. This study aims at evaluating the effect of adding 0.8 % and 2.0 % (by weight) of monoclinic Nb 2 O 5 in 3Y-TZ-E (Tosoh) on the stabilization of this zirconia and the grinding effect of 3Y-TZ-E granules on the densification and on the sintered compact microstructure. Sintered compacts were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results indicate that the use of 2.0 % (in weight) of Nb 2 O 5 implies in the destabilization of tetragonal zirconia and in the formation of Zr 6 Nb 2 O 17 . No significant difference was observed in the densification and in the grain size of the unground TZ-3Y-E with the addition of 0.8 % (in weight) of monoclinic Nb 2 O 5 .

Bond durability when applying phosphate ester monomer–containing primers vs. self-adhesive resin cements to zirconia: Evaluation after different aging conditions

PurposeThis study aimed to evaluate bond durability when applying 2 phosphate ester monomer-containing self-adhesive resin cements alone, versus a combination of phosphate ester monomer-containing primer conditioning plus 2 conventional resin cements requiring primers, to zirconia after different artificial aging methods. MethodsWe cemented air-abraded zirconia plates to composite resin cylinders with self-adhesive resin cements (MS; RU) alone or cemented them with traditional resin cements (ZRV; ZVN) after pre-conditioning with a zirconia primer. A shear bond strength (SBS) test were performed after subjecting them to 19 different aging conditions (n = 15) comprising 30,000× thermocycles, air storage at room temperature (RT), water storage at RT, or at 37 °C for 24 h, 1 week, 1, 3, 6, and 12 months. Zirconia powders mixed with zirconia primer or 2 self-adhesive resin cements were characterized by X-ray photoelectron spectroscopy. ResultsGroups MS and ZVN obtained the highest SBS after all of aging methods. SBS after 6 months of storage was similar to SBS after 24 h of storage, while both were higher than SBS after 1 year of storage. Water storage at 37 °C provided higher SBS than RT water storage did. We detected a Zr–O–P bond in both self-adhesive resin cement/zirconia powder mixtures. ConclusionsApplication of self-adhesive resin cements alone could be an alternative to pre-conditioning with a zirconia primer followed by the application of conventional resin cements. Formation of Zr–O–P bonds contributed to the bonding improvement of self-adhesive resin cements. Different aging conditions affected SBS values.

A Novel Precursor for the Synthesis of Mixed Non-oxide Ultra High Temperature Ceramics

Polymer-derived ceramics have gained importance due to ease of processability, less processing time and flexibility in tailoring the composition of ceramics by altering the monomer ratios in the polymer. In the present work, a preceramic oligomer containing both zirconium and titanium, viz., Zirconotitanoborosiloxane was synthesized by non-aqueous sol–gel process. Oligomer was characterized by GPC, spectral and thermal techniques. Ceramics formed at 1500 °C reveal the formation of Zr and Ti based UHTCs along with some oxides. To study the feasibility of using Zirconotitanoborosiloxane oligomer as precursor for mixed non-oxide ceramics, carbothermic and borothermic reductions were carried out by blending the precursor with phenolic resin as source of carbon and elemental boron as source of boron. XRD study confirms the formation of mixed non-oxide UHTC system containing Zr, Ti, B, Si and C. SEM–EDS analysis revealed the micro-structure of the ceramics and elemental composition.

Formation of Zr–La–O Oxide Phases in the Thermochemical Transformation of Modified Zirconium Hydroxide

The particularities of the impact of the addition of lanthanum cations on the thermochemical behavior of modified zirconium hydroxide were investigated. It is shown that the composition and properties of the obtained materials are determined by the concentration of the modifier and the formation temperature of the oxide phase.

Microstructure and mechanical properties of the SiC/Zr4 joints brazed with TiZrNiCu filler for nuclear application

SiC ceramic has been successfully joined to Zr4 alloy using TiZrNiCu filler within the temperature range 1173 K–1263 K and 15 min holding time. The morphology of the SiC/Zr4 joints was investigated by SEM, and the phases in the joints were characterized by XRD and TEM. The results indicated that part of the Zr4 substrate dissolved into the molten filler during the brazing process, contributed to the increasing Zr content and the formation of Zr[Ti] solid solution in the joints. In addition, β-Ti phase was discovered in the brazing seam. This might be attributed to the existence of β-Ti stable elements, Cu and Ni. The interface characterization showed that SiC reacted with filler alloy during the brazing process, formed a (Zr, Ti)C reaction layer on SiC surface and Zr2Si compound near SiC substrate. Finally, the mechanical properties of the joints, evaluated by a shear strength test, reached a maximum of 95 MPa at the brazing temperature of 1203 K.

Formation and Corrosion Behavior of Mechanically-Alloyed Cu–Zr–Ti Bulk Metallic Glasses

Cu60Zr30Ti10 metallic glass powder was prepared by mechanically alloying a mixture of pure Cu, Zr, and Ti powders after 5 h of milling. Cu60Zr30Ti10 bulk metallic glass (BMG) was synthesized by vacuum hot pressing the as-milled Cu60Zr30Ti10 metallic glass powder at 746 K in the pressure range of 0.72–1.20 GPa, and the structure was analyzed through X-ray diffraction and transmission electron microscopy. The pressure could enhance the thermal stability, and prolong the existence, of the amorphous phase inside the Cu60Zr30Ti10 powder. Furthermore, the corrosion behavior of the Cu-based BMG in four corrosive media was studied using a potentiodynamic method. The Cu60Zr30Ti10 BMG exhibited a low corrosion rate and current density in 1 N solutions of H2SO4, NaOH, and HNO3. X-ray photoelectron spectroscopy results revealed that the formation of Zr- and Ti-rich passive oxide layers provides a high corrosion resistance against 1 N H2SO4 and HNO3 solutions, and the breakdown of the protective film by Cl− attack was responsible for pitting corrosion in a 3 wt % NaCl solution. The formation of oxide films and the nucleation and growth of pitting were analyzed through microstructural investigations.

Dipentaerythritol penta-acrylate phosphate - an alternative phosphate ester monomer for bonding of methacrylates to zirconia.

The present work examined the effects of dipentaerythritol penta-acrylate phosphate (PENTA) as an alternative phosphate ester monomer for bonding of methacrylate-based resins to yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and further investigated the potential bonding mechanism involved. Shear bond strength testing was performed to evaluate the efficacy of experimental PENTA-containing primers (5, 10, 15, 20 or 30 wt% PENTA in acetone) in improving resin-Y-TZP bond strength. Bonding without the use of a PENTA-containing served as the negative control, and a Methacryloyloxidecyl dihydrogenphosphate(MDP)-containing primer was used as the positive control. Inductively coupled plasma-mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were used to investigate the potential existence of chemical affinity between PENTA and Y-TZP. Shear bond strengths were significant higher in the 15 and 20 wt% PENTA groups. The ICP-MS, XPS and FTIR data indicated that the P content on the Y-TZP surface increased as the concentration of PENTA increased in the experimental primers, via the formation of Zr–O–P bond. Taken together, the results attest that PENTA improves resin bonding of Y-TZP through chemical reaction with Y-TZP. Increasing the concentration of PENTA augments its binding affinity but not its bonding efficacy with zirconia.

Suppression of annealing-induced embrittlement in bulk metallic glass by surface crystalline coating

Annealing-induced embrittlement in metallic glasses (MGs) due to the running off of free volume (FV) is detrimental to their practical applications. By adding crystalline W coatings, we demonstrated that the majority of free volume (FV) could be preserved and redistributed in a Zr50.7Cu28Ni9Al12.3 bulk metallic glass (BMG) upon annealing as, thermodynamically, it was unfavorable for the FV to migrate from BMG into crystalline W. Correspondingly, the strength and ductility of the BMG were both enhanced relative to as-cast ones, due likely to decomposition processes such as the formation of Zr- and Cu-rich clusters in the BMG. The results of this study may be applied to avoid annealing-induced embrittlement in BMGs and construct a simple yet effective method to elevate both the strength and ductility of BMGs.