Ca Zr Research Articles

Elucidating the dependence of corrosion behavior and mechanical property on the grain structure of low-temperature as-extruded Mg–Zn–Ca–Zr alloy

Elucidating the dependence of corrosion behavior and mechanical property on the grain structure of low-temperature as-extruded Mg–Zn–Ca–Zr alloy

Microstructural evolution, high temperature tensile deformation behavior, and deformation mechanism in an Mg–Zn–Y–Ca–Zr alloy processed by multidirectional forging and hot rolling

To explore high temperature ductility, a new Mg-2.70Zn-1.34Y-0.37Ca-0.02Zr (wt.%) alloy has been fabricated by novel multidirectional forging (MDF) and hot rolling. The microstructure and mechanical properties were investigated. The average grain size of MDF + hot rolled alloy is 10.89 ± 0.90 μm refined from the as-cast average grain size of 60.03 ± 0.72 μm. The ultimate tensile strength of 260.51 ± 1.03 MPa, yield strength of 192.29 ± 1.21 MPa, and elongation of 17.83 ± 0.72 % were obtained at room temperature. For high temperature tensile behavior, microstructural examination revealed that continuous dynamic recrystallization and discontinuous dynamic recrystallization are the main softening mechanism in the temperature range of 573–673 K, while dynamic grain growth with bimodal grains and twins is discovered at 723 K in this alloy. X-ray diffraction and scanning electron microscopy –energy dispersive spectroscopy examinations revealed that the constituent phases are composed of α-Mg solid solution and intermetallic compounds of Ca2Mg6Zn3, Mg3YZn6 (I-phase), and Mg3Zn3Y2 (W-phase). The microstructural evolution, such as dynamic recrystallization and dynamic grain growth at desired tensile temperatures, is related to the thermal stability of constituent phases. The elongation to failure of 215.4 % was demonstrated at 673 K and 1.67 × 10−2 s−1, exhibiting high strain rate quasi-superplasticity. A power-law constitutive equation was established. The deformation activation energy of 177.948 kJ/mol and stress exponent of 4.494 revealed that the dominant deformation mechanism of this alloy at elevated temperatures of 573–723 K is dislocation climb controlled by lattice diffusion.

Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

The structural and chemical properties of zirconolite (ideally CaZrTi2O7) as a host phase for separated REE–actinide-rich wastes are considered. Detailed analysis of both natural and synthetic zirconolite-structured phases confirms that a selection of zirconolite polytype structures may be obtained, determined by the provenance, crystal chemistry, and/or synthesis route. The production of zirconolite ceramic and glass–ceramic composites at an industrial scale appears most feasible by cold pressing and sintering (CPS), pressure-assisted sintering techniques such as hot isostatic pressing (HIP), or a melt crystallization route. Moreover, we discuss the synthesis of zirconolite glass ceramics by the crystallization of B–Si–Ca–Zr–Ti glasses containing actinides in conditions of increased temperatures relevant to deep borehole disposal (DBD).

Research of Dynamic Corrosion Behavior, Microstructure, and Biocompatibility of Mg–Zn–Ca–Zr Alloys in Simulated Body Fluid Solution Induced by Zn Element Addition

Herein, the effect of Zn (2,3,4 and 5 wt%) addition on the microstructure, corrosion behavior, and biocompatibility of Mg‐xZn‐0.5Ca‐0.4Zr alloys is discussed by micromorphology, immersion/electrochemical, and cytotoxicity experiments. The results reveal that all as‐cast samples with a duplex morphology consist of Mg7Zn3 phase and α‐Mg matrix. With the addition of Zn element, the quantities of Mg7Zn3 phase increase gradually; while its micromorphology obviously changes from dot‐like to network shape, the average grain size decreases gradually. In addition, corrosion mechanism demonstrates that all as‐cast alloys suffer from microgalvanic corrosion between eutectic Mg7Zn3 and α‐Mg substrate due to potential difference of |ΔE| = 180 mV. However, the strip‐shape Mg7Zn3 contained in the Mg–4Zn–0.5Ca–0.4Zr alloy and compared with dot‐like\network shape phase can effectively hinder the spreading of corrosion from one grain to another, which causes Mg–4Zn–0.5Ca–0.4Zr to exhibit superior corrosion resistance. In addition, the biocompatibility conducted by methyl‐thiazolyl‐tetrazolium method via L929 cells reveals that as‐cast Mg–4Zn–0.5Ca–0.4Zr alloy is confirmed with low hemolysis rate (H% = 2.5%) and excellent proliferation capability (P% > 100%), which suggest that Mg–4Zn–0.5Ca–0.4Zr may be a good candidate for implant application.

Effect of Different Ca2+ and Zr4+ Contents on Microstructure and Electrical Properties of (Ba,Ca)(Zr,Ti)O3 Lead-Free Piezoelectric Ceramics

In the preparation of (Ba,Ca)(Zr,Ti)O3 lead-free piezoelectric ceramics, different Ca2+ and Zr4+ contents will greatly affect the phase structure, microstructure, and electrical properties of the ceramics. XRD shows that all samples have pure perovskite phase structure, and the (Ba0.85Ca0.15)(ZryTi1−y)O3 ceramics morphotropic phase boundary region from tetragonal phase to rhombohedral phase near 0.08 ≤ y ≤ 0.1. From the dielectric temperature curve, the phase transition temperature (TO-T) was found near room temperature at 0.12 ≤ x ≤ 0.18 for the (Ba1−xCax)(Zr0.1Ti0.9)O3 ceramics. Both Ca2+ and Zr4+ increase have a significant decrease on the Curie temperature Tc. All samples were revealed as relaxers with diffusivities in the range 1.29 ≤ γ ≤ 1.82. Different from the undoped ceramics, ceramics doped with Ca and Zr ions exhibit saturated P–E hysteresis loops, and their ferroelectric properties are significantly optimized. In particular, the (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramic demonstrated optimal properties, namely d33 = 330 pC/N, kp = 0.41, εr = 4069, Pr = 4.8 μC/cm2, and Ec = 3.1 kV/cm, indicating that it is a viable lead-free piezoelectric contender. Variations in Ca and Zr content have a significant effect on the crystal grain sizes and densities of ceramics, which is strongly associated with their piezoelectricity.

1,4-Butanediol Selective Dehydration to 3-Butene-1-ol over Ca–Zr–Sn Composite Oxide Catalysts

Ca–Zr–Sn composite oxides catalysts for 1,4-butanediol (BDO) selective dehydration to 3-butene-1-ol (BTO) are synthesized by impregnation and co-precipitation in the present work. The results show that Ca–Zr–Sn catalysts prepared from co-precipitation by using NaOH-Na2CO3 mixing alkali solution as precipitant exhibit an excellent catalytic property for BDO dehydration to BTO. For instance, Ca–Zr–Sn oxide with Ca/Zr and Sn/Zr molar ratio of 0.68 and 0.28 calcined at 650 °C gives a BDO conversion and BTO selectivity of about 97% and 82%, respectively, and exhibits no deactivation during 1000 h scale-up experimental testing. X-ray diffraction results indicate that catalytic active centers for BDO dehydration to BTO are from Ca0.15Zr0.85O crystal phase. NH3- and CO2-temperature programmed desorption prove that the surface of obtained catalysts can provide a large amount of acid and base sites simultaneously. FT-IR spectra of pyridine-adsorbed samples show that acid sites on the surface of Ca–Zr–Sn oxide catalyst mainly exist in a state of Lewis acid, which activates terminal -OH groups of BDO molecule through complexing. The activated -OH interacts with β-H activated on base sites O2− anions relative to Ca species, thereby the CH2=CH- bonds are produced through dehydration to form BTO.

Cr-pyrope xenocrysts with oxide mineral inclusions from the Chompolo lamprophyres (Aldan shield): Insights into mantle processes beneath the southeastern Siberian craton

AbstractPyrope xenocrysts (N = 52) with associated inclusions of Ti- and/or Cr-rich oxide minerals from the Aldanskaya dyke and Ogonek diatreme (Chompolo field, southeastern Siberian craton) have been investigated. The majority of xenocrysts are of lherzolitic paragenesis and have concave-upwards (normal) rare earth element (REEN) patterns that increase in concentration from light REE to medium–heavy REE (Group 1). Four Ca-rich (5.7–7.4 wt.% CaO) pyropes are extremely low in Ti, Na and Y and have sinusoidal REEN spectra, thus exhibiting distinct geochemical signatures (Group 2). A peculiar xenocryst, s165, is the only sample to show harzburgitic derivation, whilst demonstrating a normal-to-weakly sinusoidal REEN pattern and the highest Zr (93 ppm) and Sc (471 ppm). Chromite–magnesiochromite, rutile, Mg-ilmenite and crichtonite-group minerals comprise a suite of oxide mineral inclusions in the pyrope xenocrysts. These minerals are characteristically enriched in Cr with 0.6–7.2 wt.% Cr2O3 in rutile, 0.7–3.6 wt.% in Mg-ilmenite and 7.1–18.0 wt.% in the crichtonite-group minerals. Complex titanates of the crichtonite group enriched in large ion lithophile elements (LILE) are high in Al2O3 (0.9–2.2 wt.%), ZrO2 (1.5–5.4 wt.%) and display a trend of compositions from the Ca–Sr-specific varieties to the Ba-dominant species (e.g. lindsleyite). In the pyrope xenocrysts the oxides coexist with silicates (clino- and orthopyroxene and olivine), hydrous silicates (talc, phlogopite and amphibole), carbonate (magnesite), sulfides (pentlandite, chalcopyrite, breakdown products of monosulfide and bornite solid solutions), apatite and graphite. P–T estimates imply the inclusion-bearing pyrope xenocrysts have been derived from low-temperature peridotite assemblages that resided at temperatures of ~600–800°C and a pressure range of ~25–35 kbar in the graphite stability field. Pyrope genesis is linked to the metasomatic enrichment of peridotite protoliths by Ca–Zr–LILE-bearing percolating fluid–melt phases containing significant volatile components. These metasomatic agents are probably volatile-rich melts or supercritical C–O–H–S fluids that were released from a Palaeo-subduction slab.

Synthesis, Temperature Behavior, and Hydrolytic Stability of Na–Zr and Ca–Zr Phosphate Molybdates and Phosphate Tungstates

Synthesis, Temperature Behavior, and Hydrolytic Stability of Na–Zr and Ca–Zr Phosphate Molybdates and Phosphate Tungstates

Resistance-temperature characteristics of a new high-temperature thermistor ceramics of Mn-doping Ba–Ca–Zr–Ti–O system

Resistance-temperature characteristics of a new high-temperature thermistor ceramics of Mn-doping Ba–Ca–Zr–Ti–O system

Investigation of temperature-induced phase transitions in (Ba,Ca)(Zr,Ti)O3 ceramics

Investigation of temperature-induced phase transitions in (Ba,Ca)(Zr,Ti)O3 ceramics

Electro-caloric effects in the BaTiO3-based solid solution ceramics

Electro-caloric effect (ECE) was investigated in BaTiO3 (BT)-based solid solution ceramics, Ba(Zr,Ti)O3 (BZT), Ba(Sn,Ti)O3 (BST) and (Ba,Ca)(Zr,Ti)O3 (BCZT) with the composition near an invariant critical point (ICP). The samples were fabricated by the solid-state reaction method and the ECE was obtained by an indirect measurement. The 12BZ–88BT, 9BS–91BT, and 32BCT–68BZT samples showed the best polarization–electric field (P–E) hysteresis characteristics at room temperature and displayed dielectric peaks at 46, 58, and 66 °C, which are the Curie temperatures. With increasing temperature, the P–E loops changed from typical ferroelectric square shapes to paraelectric slanted shapes in the BT-based solid solution ceramics. The adiabatic temperature change due to the ECE (ΔTECE) showed the maximum values of 0.46 °C at 80 °C, 0.5 °C at 65 °C, and 0.47 °C at 75 °C, respectively, in the 12BZ–88BT, 9BS–91BT, and 32BCT–68BZT samples. The BT-based solid solution ceramics showed smaller maximum ΔTECE, but broader ΔTECE peaks at nearer room temperature than the BT ceramic. The enhancement of the ECE due to the multi-phase coexistence was not observed in BT-based solid solutions with the compositions near an invariant critical point (ICP) at which several phases coexist.

Electromechanical properties of Ce-doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free piezoceramics

Lead-free piezoceramics based on the (Ba, Ca)(Zr, Ti)O3 (BCZT) system exhibit excellent electromechanical properties for low-temperature actuation applications, but suffer from relatively high processing temperatures. Here we demonstrate an approach for the reduction of the sintering temperature and simultaneous increase of the electromechanical strain response of (Ba, Ca)(Zr, Ti)O3 piezoceramics by aliovalent doping with Ce. The samples were prepared by solid state synthesis and their crystallographic structure, dielectric, ferroelectric, and electromechanical properties were investigated. The highest d*33 value of 1189 pm/V was obtained for the sample with 0.05 mol% Ce, substituted on the A-site of the perovskite lattice. The results indicate a large potential of these materials for off-resonance piezoelectric actuators.

Ordered mesoporous Cu–Ca–Zr: A superior catalyst for direct synthesis of methyl formate from syngas

It is still a big challenge to obtain both highly active and stable Cu-based catalysts for direct synthesis of methyl formate (MF) from syngas. To address the issue, we have designed and synthesized a series of ternary Cu–Ca–Zr catalysts, namely, the ordered mesoporous Cu–Ca–Zr catalyst prepared by one-pot evaporation-induced self-assembly (EISA) method, and the supported CuO/CaO–ZrO2 catalysts by impregnating with copper precursor or by immobilizing copper nanoparticles. In the latter two catalysts, the ordered mesoporous CaO–ZrO2 support was also prepared by the EISA method. The catalysts were characterized by techniques such as ICP, XRD, TEM, N2 isotherm adsorption-desorption, XPS and H2-TPR, and used for direct synthesis of MF. The results indicated that the catalyst prepared by one-pot EISA method, in which the CuO species are highly dispersed in frame of CaO–ZrO2, exhibits much better activity and stability as compared with the other two catalysts with most of CuO located on the outer surface of the CaO–ZrO2 support, because the former has a higher specific surface area, enhanced synergistic effect and stronger interaction between the CaO–ZrO2 support and CuO active constituent.

Effect of Al3+ modification on cobalt ferrite and its impact on the magnetoelectric effect in BCZT–CFO multiferroic composites

One of the methods to enhance the functional properties of two-phase multiferroic magnetoelectrics is to increase magnetostriction of the ferrite phase. Al3+-modified cobalt ferrite Co(Al0.5Fe1.5)O4 shows better magnetostriction than unmodified cobalt ferrite. It is used in combination with (Ba,Ca)(Zr,Ti)O3 which has very good piezoelectric properties, to form a multiferroic composite. The composite shows good magnetoelectric characteristics, both macroscopically (converse magnetoelectric coefficient of 11 ps/m) and microscopically. Al3+ proves to be the best non-magnetic dopant to enhance magnetostriction in CoFe2O4 and thus the magnetoelectric coefficient.

Improving Formability of Mg–Ca–Zr Sheet Alloy by Microalloying of Zn

Addition of 0.1 at% Zn to the Mg–0.5Ca–0.1Zr alloy is found to significantly improve the stretch formability and ductility. The remarkable improvement in the stretch formability and ductility is attributable to the enhanced grain boundary cohesion and weakened texture. The as‐annealed Mg–0.5Ca–0.1Zr–0.1Zn alloy sheet shows a 0.2% proof strength of ≈134 MPa along the rolling direction, which is lower than that of as‐annealed AZ31 alloy sheet (≈147 MPa). However, by post‐forming ageing, the 0.2% proof strength of the Mg–0.5Ca–0.1Zr–0.1Zn alloy sheet is considerably increased to ≈201 MPa, exceeding that for the annealed AZ31 alloy sheet.

Molecular dynamics modeling of radiation stability of Ca(Zr,Ti,Sn)O3perovskites

Molecular dynamics modeling of radiation stability of Ca(Zr,Ti,Sn)O₃perovskites

Electrocaloric Effect of Lead-Free (Ba,Ca)(Zr,Ti)O3 Ferroelectric Ceramic

In this study, (Ba,Ca)(Zr,Ti)O3 ferroelectric ceramic was fabricated by a conventional solid-state reaction process. The electrocaloric effect was investigated using P–E hysteresis loop characteristics in a wide temperature range from room temperature to 135°C. The results showed that the temperature change ΔT could be calculated as a function of temperature using Maxwell’s relation, reaching a maximum value of ~0.096°C at 110°C under an applied electric field of 15.3 kV/cm.

Calcium–Zirconium–polyvinyl alcohol polymer composite film as a promising adsorbent for removal of fluoride from aqueous solution

Calcium–Zirconium–polyvinyl alcohol (Ca–Zr–PVA) cross-linked polymer composites were prepared under microwave irradiation and characterized by X-ray fluorescence (XRF), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies. These polymer composites were used as adsorbents for removal of fluoride ions from aqueous solutions. The effects of contact time, solution pH, and adsorbent dose were studied. The adsorption was found to be nearly independent of the pH of the solution and the maximum fluoride adsorption capacity of the adsorbent was 12.72 mg g−1. Langmuir adsorption isotherm fitted better with the experimental data of adsorption equilibrium studies than Freundlich isotherm. The kinetics of the adsorption process indicated second-order uptake of fluoride by the polymer composites. The polymer composites could be considered for the development of a feasible technology for fluoride removal from aqueous solutions.

Mechanical properties and corrosion behavior of Mg–Gd–Ca–Zr alloys for medical applications

Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg–Gd–Ca–Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg–10Gd–xCa–0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β′ phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility.

The impedance analysis for the aging mechanism of CaO excess type calcium zirconate electrolyte material comparing with 8.5YSZ

A CaO excess type calcium zirconate electrolyte with a composition of Ca 1.1 Zr 0.9 O 2.9 was prepared. Its aging behavior at 900 °C and 1100 °C was evaluated by AC impedance. The conductivity decreases more seriously at higher temperature. Combined with the aging effect of 8.5 YSZ, the formation of [ Ca Zr ″ − V O •• ] promoted by annealing operation should be responsible for the aging effect in Ca 1.1 Zr 0.9 O 2.9 . The declined mobility of V O •• is viewed as the increase in hopping activation energy and the decrease in effective concentration of V O •• . Consequently, the diffusion coefficient of V O •• decreases and results in the aging behavior. • Confirmed the aging behavior in CaO excess calcium zirconate perovskite ceramics • The aging behavior works more seriously as temperature rises. • The Ca 1.1 Zr 0.9 O 2.9 presents a much more stable conductivity than the 8.5 YSZ shows. • The annealing operation enforces the formation of association [ Ca Zr ″ − V O •• ] and makes oxygen vacancy trapped. • The lock of oxygen vacancy reduces its effective diffusion coefficient.