Zr Solid Solution Research Articles

Mineralogy of Zirconium in Iron-Oxides: A Micron- to Nanoscale Study of Hematite Ore from Peculiar Knob, South Australia

Zirconium is an element of considerable petrogenetic significance but is rarely found in hematite at concentrations higher than a few parts-per-million (ppm). Coarse-grained hematite ore from the metamorphosed Peculiar Knob iron deposit, South Australia, contains anomalous concentrations of Zr and has been investigated using microanalytical techniques that can bridge the micron- to nanoscales to understand the distribution of Zr in the ore. Hematite displays textures attributable to annealing under conditions of high-grade metamorphism, deformation twins (r~85˚ to hematite elongation), relict magnetite and fields of sub-micron-wide inclusions of baddeleyite as conjugate needles with orientation at ~110˚/70˚. Skeletal and granoblastic zircon, containing only a few ppm U, are both present interstitial to hematite. Using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) spot analysis and mapping, the concentration of Zr in hematite is determined to be ~260 ppm on average (up to 680 ppm). The Zr content is, however, directly attributable to nm-scale inclusions of baddeleyite pervasively distributed throughout the hematite rather than Zr in solid solution. Distinction between nm-scale inclusions and lattice-bound trace element substitutions cannot be made from LA-ICP-MS data alone and requires nanoscale characterization. Scandium-rich (up to 0.18 wt. % Sc2O3) cores in zircon are documented by microprobe analysis and mapping. Using high-angle annular dark field scanning transmission electron microscopy imaging (HAADF-STEM) and energy-dispersive spectrometry STEM mapping of foils prepared in-situ by focused ion beam methods, we identify [011]baddeleyite epitaxially intergrown with [22.1]hematite. Lattice vectors at 84–86˚ underpinning the epitaxial intergrowth orientation correspond to directions of r-twins but not to the orientation of the needles, which display a ~15˚ misfit. This is attributable to directions of trellis exsolutions in a precursor titanomagnetite. U–Pb dating of zircon gives a 206Pb/238U weighted mean age of 1741 ± 49 Ma (sensitive high-resolution ion microprobe U–Pb method). Based on the findings presented here, detrital titanomagnetite from erosion of mafic rocks is considered the most likely source for Zr, Ti, Cr and Sc. Whether such detrital horizons accumulated in a basin with chemical precipitation of Fe-minerals (banded iron formation) is debatable, but such Fe-rich sediments clearly included detrital horizons. Martitization during the diagenesis-supergene enrichment cycle was followed by high-grade metamorphism during the ~1.73–1.69 Ga Kimban Orogeny during which martite recrystallized as granoblastic hematite. Later interaction with hydrothermal fluids associated with ~1.6 Ga Hiltaba-granitoids led to W, Sn and Sb enrichment in the hematite. By reconstructing the evolution of the massive orebody at Peculiar Knob, we show how application of complimentary advanced microanalytical techniques, in-situ and on the same material but at different scales, provides critical constraints on ore-forming processes.

Fatigue behavior of Ti50Zr alloy for dental implant application

The microstructure, tensile and fatigue behavior of a hot-rolled Ti50Zr alloy applied for dental implant were investigated. The commercial Ti16Zr alloy was taken as a reference material. The load vs. number of cycling curves of the one-piece type Ti16Zr and Ti50Zr dental implants were tested according to ISO 14801 standard testing methods. The results show that the yield strength and fatigue limit of Ti50Zr alloy are up to 1001±8 MPa and 500 ± 10 MPa, respectively, 23% and 32% higher than Ti16Zr alloy. The enhanced strength of Ti50Zr alloy is attributed to multiple mechanisms, including acicular martensite strengthening, Zr solid solution strengthening, nano-twins and dislocations strengthening. The maximum cycling loads of Ti50Zr implants in air, artificial saliva solution and with sand blasting plus acid etching (SLA) treated surface reach 400 N, 400 N and 350 N (5 × 106 cycles without failure), respectively, 33%∼75% higher than Ti16Zr implants. High surface roughness harms the fatigue performance of the Ti-Zr implants owing to the promotion role of notch-type defects to fatigue crack initiation. A corrosion-assisted fatigue process in artificial saliva solution under large load reduces the fatigue life of the Ti-Zr implants. Ti50Zr alloy is an ideal candidate material applied for dental implant with regards to its good biocompatibility, excellent mechanical properties and economic processing route.

Bio-tribocorrosion behavior of a nanocrystalline TiZrN coating on biomedical titanium alloy

A nanocrystalline TiZrN graded coating was deposited on biomedical titanium alloy by DC reactive magnetron sputtering process. The microstructure and compositions of the coating were characterized by XRD, TEM and EPMA. The electrochemical corrosion and bio-tribocorrosion behavior of the coated titanium alloy under open circuit potential (OCP) and applied potentials (−0.15 V ~ +0.25 V) were investigated in Hank's solution with and without 25% calf serum. Compared with TiN coating, the hardness of TiZrN coating is greatly increased due to the Zr solid solution strengthening and nanocrystalline strengthening. Under the conditions of OCP and applied anodic potentials, the TiZrN coated Ti alloy exhibits significantly improved anti-tribocorrosion and anti-friction performances, which are attributed to that the stable Ti and Zr oxide or oxynitride passive film on coating near surface and the increased mechanical properties of the coating decrease the synergistic effect of corrosion and wear. 25% calf serum in Hank's solution enhances the chemical stability of the TiZrN coating through adsorption and bio-lubrication mechanism, and therefore further improves the tribocorrosion performance of the coated Ti alloy.

Irradiation-induced Nb redistribution of ZrNb alloy: An APT study

We have investigated proton irradiation induced Nb redistribution in Zr-xNb alloy (x = 0.4, 0.5, 1.0) by using Scanning Transmission Electron Microscopy (STEM) and Atom Probe Tomography (APT). Initially without an irradiation effect, the Zr matrix only contains βNb and native Laves phase native precipitates. However, after 2 MeV proton irradiation at 350 °C, STEM/EDS showed irradiation induced precipitation of Nb-rich needle-like particles (up to ∼100 nm in length) in the Zr matrix. APT also revealed that Fe- and Nb -enriched nano-clusters (less than 20 nm diameter) are present in the Zr matrix for Zr-0.5Nb and Zr-1.0Nb. Irradiation was found to reduce the matrix Nb concentration in the Zr solid solution, This reduction may contribute to the improved corrosion resistance of ZrNb alloys in the reactor environment at high burnup.

First principle study of occupancy, bonding characteristics and alloying effect of Zr, Nb, V in bulk <i>α</i>-Fe(C)

The volume change rate, total energy, binding characteristics, state density, charge distribution number and mechanical properties of cells formed by solid solution of Zr, Nb and V in α-Fe(C) are calculated by using the first-principles method. Thus, the effect of Zr, Nb, V on α-Fe(C) are studied in this paper. The results show that V displaces Fe atoms which is at the apex angle of α-Fe (C) cells preferentially, while Zr and Nb displace Fe atoms at the body center of α-Fe(C) cells. Zr and Nb reduce the stability of ferrite, but Zr is more difficult to solidly solubilize in α-Fe(C) than Nb. Solid solution of V increases the binding energy of crystal cells, meanwhile the toughness of crystal cell is mainly improved. After solid is solubilized in ferrite, Zr and Nb atoms only form metal bonds with Fe atoms while V and Fe atoms form the metal bonds and Fe—V ionic bonds. The ionic bonds of Fe—V are stronger than metal bonds of Zr and Nb atoms with Fe atoms, which is the main factor of the cell increasing. Zr and Nb mainly improve the mechanical properties of steel material by means of dispersion strengthening. To some extent, V solid solution can improve the toughness of ferrite, which is the main reason for improving the mechanical properties.

Facilely fabricating mesoporous nanocrystalline Ce–Zr solid solution supported CuO-based catalysts with advanced low-temperature activity toward CO oxidation

The synergistic effect between CuO and mesoporous Ce–Zr solid solution greatly enhanced the advanced low-temperature catalytic activity toward CO oxidation.

Component interaction in the Zr-Cr-Sb system at 870 K

The component interaction in the Zr - Cr - Sb ternary system was studied at 870 K over the whole concentration range using methods of X-ray diffraction and metallographic analysis. The alloys for investigation were prepared by direct arc melting the stoichiometric amounts of the constituent elements under high purity Ti-gettered argon atmosphere on a water-cooled copper hearth. The arc-melted ingots were then annealed at 870 K in evacuated quartz glass tubes for 720 hours and subsequently cold water quenched. The 3-5 wt. % excess of Sb was required to compensate the evaporative losses during arc-melting. The synthesized and annealed samples are stable in atmospheric conditions. For the characterization of the annealed samples X-ray powder diffraction on DRON-2.0m diffractometer with Fe K α radiation was performed. The chemical and phase compositions of the obtained samples were examined by Scanning Electron Microscopy (SEM) using Carl Zeiss DSM 962 and REMMA-102-02 electron microscopes. In the Cr–Sb and Zr–Sb systems a formation of the all binaries reported in the literature was confirmed. In the Zr-Cr system аt 870 K ZrCr 2 binary was realized in high-temperature hexagonal modification with MgZn 2 structure type. According to EPMA data the homogeneity range of the ZrCr 2 binary is limited by the Zr 33.05 Cr 66.95 and Zr 37.59 Cr 62.41 compositions ( а = 0.5113(2)-0.5110(1), с = 0.8289(7)-0.8292(7) nm). At the temperature of investigation phase relations in Zr-Cr-Sb system are characterized by existence of one ternary compound Zr 5 Cr 0 . 5 Sb 2 . 5 with W 5 Si 3 structure type (space group I 4/ mcm ; a = 1.1097(1), c = 0.5566(2) nm). The substitutional solid solution Zr 5 Sb 4- x Cr x up to 5 at. % Cr based on the binary antimonide Zr 5 Sb 4 with Ti 5 Ga 4 structure type ( а =0.8532(4)-0.8482(2), с =0.5858(4)-0.5820(1) nm) was observed. Solubility of Sb in ZrCr 2 compound (MgZn 2 -type) is up to 6 at. % ( а = 0.5113(2)-0.5127(1), с = 0.8289(7)-0.8354(9) nm) along isoconcentrate of 33 at. % Zr. Solubility of the third component in other binary compounds is less than 1-2 at. %. Analysis of the Zr-Cr-Sb system and studied early Zr-M-Sb (M = Mn, Fe, Co, Ni, Cu) showed that the ternary compounds with W 5 Si 3 structure type appear in all these systems. The reduced number of the ternary phases in the Zr-Cr-Sb system comparing with related Zr-M-Sb systems shows an important influence of d -metal on the formation and structure of intermediate ternary phases. Keywords : intermetallics, ternary system, phase equilibria.

Effects of Zr ion implantation on crystal structure and nanoindentation behavior of TC18 titanium alloy

In this study, TC18 titanium alloy was ion implanted with Zr ions to a fluence of 3.56 × 1016, 5.53 × 1016 and 7.12 × 1016 ions cm−2. The surface morphologies were characterized by the scanning electron microscopy (SEM) and atomic force microscope (AFM). The crystal structure of the Zr implanted TC18 titanium alloy was evaluated by the x-ray diffraction (XRD) and the corresponding calculations were used to analysis the nanoindentation behavior. Nanoindentation tests with different loads (5 mN, 10 mN and 15 mN) were used to investigate the nanoindentation behavior of samples. Zr ion implantation not only affected the surface microstructures of substrate, but also affected the crystal structure. When the implantation fluence was 3.56 × 1016 ions cm−2, the surface roughness of sample was reduced, while the residual compressive stress caused the XRD peak shift to higher angle compared with the baseline of substrate. The irradiation effect increases with increasing implantation fluence which led to generation of etch pits and cracks, and therefore increased surface roughness of TC18 titanium alloy. At the same time, the increase of lattice parameters shifted the XRD peak to low angle. The result of nanoindentation test showed that Zr solid solution strengthening improved the hardness of substrate. However, the dislocation density gradually decreased with the increasing of implantation fluence, which therefore reduced the nanohardness of samples. The highest hardness values of TC18 titanium alloy under different indentation loads were all found in samples treated with the ion fluence of 3.56 × 1016 ions cm−2, as a result of Zr solid solution strengthening and high dislocation density.

Self-sustained combustion of carbon monoxide over CuCe0.75Zr0.25Oδ catalyst: Stability operation and reaction mechanism

The self-sustained combustion of carbon monoxide (CO) has been studied over the CuCe0.75Zr0.25Oδ catalyst by sol–gel method, and compared with the CuCe0.75Zr0.25Oδ(H) and Ce0.75Zr0.25Oδ to investigate sensitivity of different active sites, such as dispersed CuO, Cu–Ce and Ce–Zr solid solution. The CuCe0.75Zr0.25Oδ(H) is obtained via CuCe0.75Zr0.25Oδ sonicated in nitric acid to remove surficial CuO species, and the Ce0.75Zr0.25Oδ is prepared as the reference catalyst. Using the temperature programmed oxidation of CO together with an infrared camera (CO-TPO + FLIR), the catalytic activity for CO self-sustained combustion is determined not only by the ignition temperatures, following the decreasing order CuCe0.75Zr0.25Oδ (81 °C) > CuCe0.75Zr0.25Oδ(H) (131 °C) > Ce0.75Zr0.25Oδ (167 °C) at the flow rate of 200 mL/min, but also by corresponding limits of lean combustion (equivalence ratio Φ) of 0.06–0.09, 0.10–0.13, 0.24–0.37, respectively, under the flow rate of 100–1000 mL/min. The M-K mechanism, in which adsorbed CO reacts with lattice oxygen, is crucial for all the catalysts via temperature programmed surficial reaction and in situ infrared analysis (TPSR + DRIFT). The sensitivity of active sites as follows: well-dispersed CuO > Cu–Ce solid solution > Ce–Zr solid solution. As rate-determining step for CO self-sustained combustion, CO is preferentially adsorbed on surficial dispersed CuO to yield carbonyls, and then the carbonyls interact with lattice oxygen to form CO2 release. CO is secondly adsorbed on the surficial oxygen of copper and cerium sites in solid solution to yield carbonates. The carbonates formed are more stable and thus CO2 is produced at the lower rate than carbonyls, indicating that the solid solution is less active than dispersed CuO. Exposed Ce3+ favors to form vacancies on the Cu–Ce solid solution surface, which is beneficial to adsorbing both CO and O2, thus presenting the higher activity than Ce–Zr solid solution.

Preparation of Zr(Mo,W)2O8 with a larger negative thermal expansion by controlling the thermal decomposition of Zr(Mo,W)2(OH,Cl)2\u22192H2O

Solid solutions of Zr(Mo,W)2O7(OH,Cl)2∙2H2O with a preset ratio of components were prepared by a hydrothermal method. The chemical composition of the solutions was determined by energy dispersive X-ray spectroscopy (EDX). For all the samples of ZrMoxW2−xO7(OH,Cl)2∙2H2O (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0), TGA and in situ powder X-ray diffraction (PXRD) studies (300–1100 K) were conducted. For each case, the boundaries of the transformations were determined: Zr(Mo,W)2O7(OH,Cl)2∙2H2O → orthorhombic-ZrMoxW2−xO8 (425–525 K), orthorhombic-ZrMoxW2−xO8 → cubic-ZrMoxW2−xO8 (700–850 K), cubic-ZrMoxW2−xO8 → trigonal-ZrMoxW2−xO8 (800–1050 K for x > 1) and cubic-ZrMoxW2−xO8 → oxides (1000–1075 K for x ≤ 1). The cell parameters of the disordered cubic-ZrMoxW2−xO8 (space group Pa-3) were measured within 300–900 K, and the thermal expansion coefficients were calculated: −3.5∙10−6 – −4.5∙10−6 K−1. For the ordered ZrMo1.8W0.2O8 (space group P213), a negative thermal expansion (NTE) coefficient −9.6∙10−6 K−1 (300-400 K) was calculated. Orthorhombic-ZrW2O8 is formed upon the decomposition of ZrW2O7(OH,Cl)2∙2H2O within 500–800 K.

Temperature- and pressure-dependent elastic properties, thermal expansion ratios, and minimum thermal conductivities of ZrC, ZrN, and Zr(C0.5N0.5)

Abstract We investigated the temperature- and pressure-dependent properties of ZrC, ZrN, and Zr(C0.5N0.5) solid solution using first-principles calculations with Debye–Gruneisen theory. The properties investigated included elastic moduli, thermal expansion coefficients, and thermal conductivities. Equilibrium volumes were determined by obtaining the energy–volume (E–V) curves of ZrC, ZrN, and Zr(C0.5N0.5) at different temperatures and external pressures. We adopted quasi-harmonic and quasi-static approximations to examine the influence of temperature and pressure on the elastic properties. Throughout the temperature and pressure ranges studied, the bulk modulus of the ZrN phase was higher than that of the other two phases, whereas its shear and Young's moduli were lower. An increase in nitrogen content resulted in an increase in the thermal expansion coefficient. The hardness, anisotropic properties, and minimum thermal conductivities of Zr(C0.5N0.5) and ZrC were similar, whereas those of the Zr(C0.5N0.5) phase were somewhat larger. Given its elastic properties, anisotropy, hardness, and minimum thermal conductivity, Zr(C0.5N0.5) is the best of the three phases for extreme environmental applications. Our results provide fundamental and useful information on the ZrC, ZrN, and Zr(C0.5N0.5) phases.

The NO oxidation performance over Cu/Ce0.8Zr0.2O2 catalyst

The Cu-doped Ce0.8Zr0.2O2 (CZ) catalyst was investigated in terms of its NO oxidation activity, structure and surface characteristics. The Cu/CZ catalyst with 6 wt% Cu loading and 550°C calcination temperature of CZ support showed the best catalytic performance, and over 50% NO conversion was obtained in a wide temperature range (250–370°C). Moreover, this catalyst showed good resistance to H2O and SO2. The dispersion of CuO species on the smaller crystallite size CZ support was favorable for NO adsorption. The Cu–Ce–Zr solid solution provided the sites of oxygen vacancies, prompted the formation of active oxygen, which in sum improved the oxidation activity of NO.

Temperature-dependent stable phase domains of Zr–C–N (Zr–ZrC–ZrC0.96–Zr(C1−xNx)−ZrN, x = 0.1–0.9) systems from ab initio calculations and experimental results

Despite the importance of ZrC, ZrN, and their intermediate solid solutions, the temperature-dependent phase stability of the Zr–C–N system has not previously been determined precisely. This work reports these phase stabilities determined experimentally and using ab initio calculations within the quasi-harmonic approximation. Special quasi-random structure models and supercell models with random substitution were used to mimic the random atomic distribution of C and N in the sublattice of Zr(C1−xNx) solid solutions. The results indicated that volume and high-temperature entropy changes are important to determine the free energy of the solid solutions and that moderate temperatures (∼1500–2000 K) were needed to synthesize Zr(C1−xNx) solid solutions. The calculated stable phase domains were then successfully produced. Our results clarify the synthesis and stable phase prediction of the Zr–C–N system under certain external conditions, and they will help broaden the applicability of ZrC, ZrN, and their solid solution phases.

Effect of zirconium on thermal stability of nanocrystalline aluminium alloy prepared by mechanical alloying

In the present study, a series of Al-x% Zr (x = 1–10 at.%) compositions were prepared by mechanical alloying (MA) to investigate the solid solubility extension of Zr in Al and its thermal stability. The elemental powder blends were mechanically alloyed under high purity argon atmosphere in stainless steel grinding media using SPEX 8000 M high energy ball mill. The milling was carried out for 8 h at room temperature and the ball to powder ratio was maintained at 10:1. Formation of disordered solid solutions is validated using Miedema’s semi-empirical model. X-ray diffraction (XRD) analysis confirms the formation of disordered solid solution up to 1at.% Zr; whereas, Al3Zr and Al9.83Zr0.17 intermetallic phases were found to form as per the XRD pattern of 2–10% Zr alloys. Variation of lattice parameter confirmed the formation of Al-1% Zr solid solution. Crystallite size was estimated to be 41 and 30 nm, respectively, for the as-milled 1 and 10% Zr alloys. The matrix grains were found to be stabilized after annealing at 550 °C, and the XRD crystallite size of Al-10% Zr retained at ∼58 nm. TEM and AFM analysis confirmed that the grain size of the as-milled as well as annealed samples was retained in the nanometre range (<100 nm), which corroborates well with the XRD crystallite size. Vickers microhardness of the as-milled 10% Zr alloy was found to be 2.4 GPa, which decreased to 1.7 GPa after annealing at 550 °C. This demonstrated that the dissolution of Zr in Al has a larger strengthening effect and Zr plausibly played a pivotal role in retaining the matrix grains size in the nanoscale range at high temperature.

SHS in the Zr–Al–C system: A time-resolved XRD study

Combustion of 2Zr–Al–C powders in a mode of frontal combustion (mode I) or thermal explosion (mode II) was studied by time-resolved XRD. Reaction route in the above SHS reactions was found to be different. No formation of ternary MAX phases was observed. In mode I, leading is the reaction yielding ZrC and the final product contains zirconium intermetallics. The SHS reaction in mode II involves the interaction of Al melt with Zr particles via consecutive formation of solid solution Zr[Al], ZrAlC1.77, and intermetallics ZrAl3, ZrAl2, Zr2Al3. The Zr–C reaction does not occur because of its low caloricity.

Some observations on the synthesis and electrolytic properties of (Ba1-xCax) (M0.9Y0.1)O3, M = Ce, Zr-based samples modified with calcium

Abstract In this paper, the impact of partial substitution of calcium for barium in (Ba1-xCax) (M0.9Y0.1) O3, M = Ce, Zr on physicochemical properties of the powders and sintered samples was investigated. The powders, with various contents of calcium (x = 0, 0.02, 0.05, 0.1), were prepared by means of thermal decomposition of organometallic precursors containing EDTA. All of the BaCeO3-based powders synthesised at 1100 °C were monophasic with a rhombohedral structure, however, completely cubic BaZrO3-based solid solutions were obtained at 1200 °C. A study of the sinterability of BaZr0.9Y0.1O3 and BaCe0.9Y0.1O3-based pellets was performed under non-isothermal conditions within a temperature range of 25 to 1200 °C. The partial substitution of barium for calcium in the (Ba1-xCax) (M0.9Y0.1) O3, M = Ce, Zr solid solution improved the sinterability of the samples in comparison to the initial BaCe0.9Y0.1O3 or BaZr0.9Y0.1O3. The relative density of calcium-modified BaCe0.9Y0.1O3-based samples reached approximately 95 to 97 % after sintering at 1500 °C for 2 h in air. The same level of relative density was achieved after sintering calcium-modified BaZr0.9Y0.1O3 at 1600 °C for 2 h. Analysis of the electrical conductivity from both series of investigated materials showed that the highest ionic conductivity, in air and wet 5 % H2 in Ar, was attained for the compositions of x = 0.02 to 0.05 (Ba1-xCax)(M0.9Y0.1)O3, M = Zr, Ce. The oxygen reduction reaction on the interface Pt│BaM0.9Y0.1O3, M = Ce, Zr was investigated using Pt microelectrodes. Selected samples of (Ba1-xCax) (M0.9Y0.1)O3, M = Zr, Ce were tested as ceramic electrolytes in hydrogen-oxygen solid oxide fuel cells operating at temperatures of 700 to 850 °C.

Novel effect of SO2 on selective catalytic oxidation of slip ammonia from coal-fired flue gas over IrO2 modified Ce–Zr solid solution and the mechanism investigation

The slip ammonia from selective catalytic reduction (SCR) of NOx in coal-fired flue gas can cause degeneration of the utilities and environmental issues like aerosol. To achieve selective catalytic oxidation (SCO) of slip ammonia to N2, novel IrO2 modified Ce–Zr solid solution catalysts were synthesized and tested under various conditions. It was found that IrO2/Ce0.6Zr0.4O2 (PVP) catalyst displayed outstanding catalytic activity for slip ammonia and the removal efficiency was higher than 98%. Interestingly, the effect of SO2 on NH3 oxidation was bifacial, which the presence of SO2 could result in slight deactivation of catalyst but also improve the N2 selectivity of oxidized products to as high as 100% with coexistence of SO2 and NH3. The mechanism of NH3-SCO process over IrO2/Ce0.6Zr0.4O2 (PVP) was evaluated through various techniques, and the results demonstrated that NH3 oxidation could follow both NH mechanism and internal SCR (iSCR) mechanism at different temperature regions. And the dominant pathway is the iSCR mechanism, in which adsorbed ammonia is firstly activated and reacts with oxygen atoms to form the HNO intermediate. Then, the HNO could be oxidized with atomic oxygen from O2 to form NO species. Meanwhile, the formed/adsorbed NO could interact with NH2 to N2 with N2O as by-product, and the presence of SO2 can effectively inhibit the production of N2O and NO. Also, the mechanism of SO2 effects was also evaluated and determined reasonably.

Synthesis, characterization and thermal stability of solid solutions Zr (Y, Fe, Mo)O2

The synthesis of Fe3+, Mo4+ and Y3+ fully stabilized zirconia by the nitrate/urea combustion route and thermal stability in air was investigated. The solid solution obtained was characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and used the BET method for determining specific surface. The ceramic powders obtained were calcined at 1473K in air atmosphere in order to determine their thermal stability. The scanning electron microscopy (SEM) results showed a homogeneous grain surface, measuring several tens of micrometers across. The crystallographic study revealed that by this method it was successfully achieved zirconia doped with Fe3+, Mo4+ and Y3+ ions in the zirconia tetragonal monophase, even after calcinations.

Annealing strengthening of pre-deformed Mg–10Gd–3Y–0.3Zr alloy

In the present work, pre-deformed Mg–10Gd–3Y–0.3Zr solid solution alloy was annealed, followed by subsequent compression, and the interaction between solutes and twin boundaries was analyzed. It is found that the segregation of solute atoms to deformation twin boundaries during annealing leads to the increase in strength of Mg–10Gd–3Y–0.3Zr alloy, and Gd solute atom has a larger strengthening effect than that of Y. The strengthening effect increases with increase of twin density, annealing time and annealing temperature. However, too long annealing time at low temperature decreases the strength slightly due to the recovery. It is verified that the ordered segregation of solute atoms at the deformation twin boundary becomes unstable at high temperatures, which gives rise to the rapid decrease in the strength.

Size-dependent He-irradiated tolerance and plastic deformation of crystalline/amorphous Cu/Cu–Zr nanolaminates

Nanoindentation methodology was used to measure the hardness, strain rate sensitivity (SRS) and activation volume of Cu/Cu–Zr crystalline/amorphous nanolaminates (C/ANLs) with layer thickness (h) spanning from 2.5 to 150nm before and after He ion-implantation at room temperature. It is interestingly to uncover that the ion radiation-induced devitrification (RID) occurs in the glassy Cu–Zr nanolayers, in which the nanocrystallites transit from the Cu10Zr7 intermetallics at large h to the fcc Cu–Zr solid solution at small h. Compared with the as-deposited Cu/Cu–Zr C/ANLs associated with monotonic increase in hardness and SRS (or a monotonic decrease in activation volume) with reducing h, the irradiated Cu/Cu–Zr manifested enhanced hardness in the form of two hardness plateau and an unexpected non-monotonic variation in SRS (similarly in activation volume). It was clearly unveiled that the SRS of irradiated Cu/Cu–Zr firstly decreased with reducing h down to a critical size of ∼50nm and subsequently increased with further reducing h to ∼10nm, below which a SRS m plateau emerges (The activation volume of irradiated Cu/Cu–Zr had exactly an opposite variation). These phenomena are rationalized by considering a competition between dislocation-interface and dislocation-bubble interactions. A thermally activated model based on the depinning process of bowed-out dislocations pinned by obstacles was employed to quantitatively account for the variation of SRS with h in Cu/Cu–Zr C/ANLs before and after radiation. Our findings not only provide fundamental understanding of the effects of radiation-induced defects on plastic characteristics of C/ANLs, but also offer guidance for their microstructure sensitive design for performance optimization at extremes.