Additional Solid Solution Research Articles

Effect of tantalum solid solution additions on the mechanical behavior of ZrB2

Mechanical properties and microstructure were compared for zirconium diboride and two zirconium diboride solid solutions containing 3 and 6 at% tantalum diboride. X-ray diffraction indicated that the ceramics were nearly phase-pure and that tantalum dissolved into the ZrB2 lattice to form (Zr,Ta)B2 solid solutions. Microstructural analysis indicated that samples achieved nearly full relative density with average grain sizes that ranged from 3−5 μm. The three compositions had similar values of Young’s modulus (510−531 GPa), shear modulus (225−228 GPa), Vickers hardness (15.2–16.4 GPa), and flexural strength (391−452 MPa). Fracture toughness ranged from 2.6 to 3.7 MPa m1/2 and with increasing tantalum content, the fracture mode changed from predominantly intergranular to predominantly transgranular. Diboride solid solution materials had comparable properties to the single metal diboride, but differences in microstructure, secondary phases, and strain state among the three ceramics partially obscured the actual effects of the solid solution on fracture behavior.

Effect of solid solution addition on the dislocation emission in aluminum alloys

Solid solution strengthening plays a key role in the strength increasing of alloying metals, due to that a solid solution of alloying element causes lattice distortion to a certain extent. In the paper, the effect of solid solution magnesium additions on the edge dislocation emission from a blunted crack tip in aluminum alloys is investigated. The critical stress intensity factor for the dislocation emission considering different magnesium solute concentrations is analyzed under the mode I and mode II loading conditions. The results show that within a certain concentration range the magnesium solute concentration does affect dislocation emission, although the influence appears not very strong. The critical stress intensity factor for the dislocation emission decreases with the increment of solute concentration. This means that relatively increasing the solute concentration can promote the dislocation emission, cause effective blunting of cracks and thus improve the fracture toughness of materials.

A novel wormhole-like mesoporous hybrid MnCoOx catalyst for improved ethanol catalytic oxidation

A series of wormhole-like mesoporous hybrid MnCoOx catalysts have been successfully prepared using a soft template combining the sol-gel method. The physical and chemical properties of these mesostructured materials are systematically characterized using XRD, BET, Raman, XPS, HRTEM, H2-TPR and O2-TPD and compared with pure MnOx and Co3O4. Their catalytic performances for ethanol oxidation are investigated and carried out on a fixed-bed reactor. It is found that the molar ratio of transition metal precursors has a remarkable influence on the nanoparticle morphology, open-framework structure dispersion, surface element distribution, and redox property. Among the MnCoOx catalysts, Mn1Co1 catalyst composed by uniform worm-like nanoparticles shows the highest BET surface area (208 m2/g), most surface proportion of Co3+ and Mn4+ (18.7%), lowest reducibility potential and best catalytic activity (T50 = 80 °C) as well as an excellent CO2 selectivity (S170 = 100%) with a GHSV of 60,000 mL·(g·h)−1. Based on the structure-function analysis of catalysts, it is deduced that the synergistic effect between Mn and Co in MnxCo1−xOy solid solution and proton scavenger addition in preparation can improve the mesostructured, active sites distribution and catalytic performance. Consequently, it can be expected that the mesoporous hybrid MnCoOx catalysts are promising materials for catalytic removal of VOCs, and the related results in this research would also provide some new insights into the porous composite material design and application exploration for ethanol catalytic oxidation.

Microstructure and mechanical properties of reaction‐hot‐pressed zirconium diboride based ceramics

AbstractZrB2 ceramics were prepared by in‐situ reaction hot pressing of ZrH2 and B. Additions of carbon and excess boron were used to react with and remove the residual oxygen present in the starting powders. Additions of tungsten were utilized to make a ZrB2‐4 mol%W ceramic, while a change in the B/C ratio was used to produce a ZrB2‐10 vol% ZrC ceramic. All three compositions reached near full density. The baseline ZrB2 and ZrB2–ZrC composition contained a residual oxide phase and ZrC inclusions, while the W‐doped composition contained residual carbon and a phase that contained tungsten and boron. All three compositions exhibited similar values for flexure strength (~520 MPa), Vickers hardness (~15 GPa), and elastic modulus (~500 to 540 GPa). Fracture toughness was about 2.6 MPa m1/2 for the W‐doped ZrB2 compared to about 3.8 MPa m½ for the ZrB2 and ZrB2–ZrC ceramics. This decrease in fracture toughness was accompanied by an observed absence of crack deflection in the W‐doped ZrB2 compared with the other compositions. The study demonstrated that reaction‐hot‐pressing can be used to fabricate ZrB2 based ceramics containing solid solution additives or second phases with comparable mechanical properties.

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics.

The formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O_{3}. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

Effects of (Ti,Ta,Nb,W)(C,N) on the microstructure, mechanical properties and corrosion behaviors of WC-Co cemented carbides

Homogeneous solid-solution (Ti, Ta, Nb,W)(C,N) powders were synthesized through carbothermal reduction-nitridation method. The effects of (Ti, Ta, Nb,W)(C,N) powders on the microstructure, mechanical properties and corrosion resistance of WC-10Co cemented carbides were investigated using XRD, SEM, electrochemical test and mechanical properties tests. The results showed that cemented carbides with pre-alloyed powder addition had a similar microstructure appearance: weak core/rim structure consisting of solid-solution phase embedded in the WC-Co system. The black core and gray rim, both of which contained similar elements, were identified as (Ti, Ta, Nb,W)(C,N), but the latter contained higher amount of heavy elements.With the addition of (Ti, Ta, Nb,W)(C,N) powders, the density, transverse rupture strength and fracture toughness of samples decreased monotonously. However, the hardness rose sharply at first, reached a peak at 15wt% solid-solution addition, then slightly decreased, and finally increased again. Results also revealed that increasing (Ti, Ta, Nb,W)(C,N) made the open circuit potential (OCP) in 1M sulphuric acid solution more negative than that of WC-Co, and all specimens exhibited pseudo-passivation phenomenon in the test solution. In addition, increasing pre-alloyed powders led to decreasing corrosion current density, which implies that (Ti, Ta, Nb,W)(C,N) could remarkably improve the corrosion resistance of WC-Co cemented carbides.

A study on the solid state characteristics of spray-congealed glyceryl dibehenate solid lipid microparticles containing ibuprofen

Objective: To study the solid state modifications of ibuprofen (IBU)-loaded spray-congealed glyceryl dibehenate (GB) solid lipid microparticles (SLMs) and the influence of polymeric additives using a combination of calorimetric and spectroscopic techniques.Materials and methods: IBU-loaded SLMs were produced by spray congealing with GB as the matrix material. Polyvinyl-2-pyrrolidone-vinyl-acetate (PVP/VA) and ethylcellulose (EC) were employed as additives. Of particular interest in this study were the solid state modifications of the drug and GB matrix induced by spray congealing and the effects of aging, as well as drug–matrix interactions. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, hot stage microscopy and powder X-ray diffraction provided complementary analyses in understanding drug and lipid matrix polymorphism and interaction. The yield, morphology, drug content and encapsulation efficiencies of SLMs were also investigated.Results and discussion: Drug encapsulation efficiencies and yields of spray congealed SLMs were consistently high for all formulations. GB congealed as an unstable α-polymorph which reverted to the stable β′-polymorph within a few weeks. PVP/VA accelerated the polymorphic conversion in less than a week, while EC took about a year. IBU formed a solid solution with GB regardless of the GB polymorphic form.Conclusions: Spray congealing is efficient for producing drug-loaded SLMs. It induces polymorphic changes in GB. The latter incorporated 20%, w/w IBU as a solid solution and polymeric additives exerted contrasting effects on the GB polymorphic conversion.

Thermal Properties of (Zr, TM)B2 Solid Solutions with TM = Ta, Mo, Re, V, and Cr

The thermal properties were investigated for hot‐pressed zirconium diboride containing solid solution additions of tantalum, molybdenum, rhenium, vanadium, and chromium. The nominal additions were equivalent to 3 at.% of each metal with respect to zirconium. Using 0.5 wt% carbon as a sintering aid, powders were hot‐pressed to near full density at 2150°C. Rietveld refinement of X‐ray diffraction data was used to measure lattice parameters and to ensure that the additives formed solid solutions. Thermal conductivities were calculated from measured thermal diffusivities and temperature‐dependent values for density and heat capacity. Thermal conductivities at 25°C ranged from 88 W·(m·K)−1 for nominally pure ZrB2 down to 28 W·(m·K)−1 for (Zr,Cr)B2. Electron contributions to thermal conductivity were calculated from electrical resistivity measurements using the Wiedemann–Franz law. Decreases in phonon and electron conduction correlated with the size of the metallic additive, indicating that changes in atom size in the Zr lattice positions reduced thermal transport.

Effect of CeO$lt;inf$gt;2$lt;/inf$gt;-based Solid Solutions on Hydrogen Storage Kinetic Properties of Mg$lt;inf$gt;2$lt;/inf$gt;Ni Alloy

Nanosized Ce1-x(Eu0.5La0.5)xO2 and Ce1-x(Fe0.5La0.5)xO2 solid solutions were synthesized via hydrothermal method, and the doping effect was characterized by analyzing the structure and spectrum features of the solid solu- tions. The results showed that the cell parameters of the solid solutions increased, the absorption edge of the UV diffuse reflectance spectroscopy was drifted, and the characteristic Raman F2g vibration peak shifted to lower wave numbers. Then the mixtures of Mg2Ni alloy powders and the solid solution additives were ball-milled to obtain composites. XRD results showed that the fraction of amorphous and nanocrystalline in the as-prepared composites was increased. The hydrogen storage kinetic measurements demonstrated that surface activity and degree of re- versibility of the composites was optimized, and the diffusion rate and diffusion coefficient of hydrogen atoms in the bulk of Mg2Ni were increased.

Using polycrystal plasticity modeling to determine the effects of grain size and solid solution additions on individual deformation mechanisms in cast Mg alloys

The tensile and compressive yielding of cast Mg–Zn alloys, with varying grain sizes and compositions ranging from 0 to 2.3 at.% Zn, are simulated using a polycrystal plasticity model. The results are used to determine the grain size and composition dependences of the critical resolved shear stresses (CRSS) of basal slip and tensile twinning.

Mechanical and hardness evaluations of Fe–18Cr–18Mn alloys

A series of Fe–18Cr–18Mn–N–C alloys was produced and evaluated to determine their mechanical and hardness properties. In one group, different levels of nitrogen and carbon were added to a base composition of Fe–18Cr–18Mn. The base Fe–18Cr–18Mn alloy had a fcc–bcc duplex microstructure. The addition of nitrogen and carbon stabilised the fcc phase. These alloys had increasing room temperature hardness, strength, and failure energy with increasing interstitial concentrations. At cryogenic and elevated temperatures, these alloys had increasing hardness (and by implication, increased strength) with increasing interstitial concentrations. In a second group, different levels of nitrogen and carbon were added to the base Fe–18Cr–18Mn composition to which minor solid solution additions of silicon, molybdenum, and nickel had been added. Minor alloy additions made only nominal improvement to mechanical and hardness properties. Nitrogen remained interstitial. However, these minor solid solution additions reduced carbon solubility resulting in the formation of M23C6 precipitates that, while increasing alloy hardness and strength, greatly reduced fracture toughness. The present study suggests that replacing nickel with manganese in stainless steels results not only in more economical alloys but also in alloys with higher strength and hardness.

Wear Performance of Mo3Si Alloys with Nb

Samples alloyed from zero up to 20 Nb at.% were produced by arc casting. Wear resistance is evaluated under dry sliding wear test conditions at different loads. Samples with a higher Nb at.% worn on an AISI 9840 steel disk had better resistance in comparison with samples without Nb reaching values up to 30%. This effect is explained considering the differences in oxidation between the substrate and the sample surfaces obtained by SEM analysis which explains the resistance improvement for the alloys with the Nb solid solution additions.

Comparative studies on microstructure and mechanical properties of CrN, Cr–C–N and Cr–Mo–N coatings

Abstract Two different CrN-based ternary coatings were synthesized by hybrid coating system of arc ion plating (AIP) and DC magnetron sputtering technique. In this work, the effects of C addition for anion solid solution (Cr–C–N) and Mo addition for cation solid solution (Cr–Mo–N) on microstructures and mechanical properties of CrN coating were investigated. The microhardness values of Cr–C–N and Cr–Mo–N coatings were largely depended on C and Mo contents, respectively. The maximum hardness values of Cr–C–N and Cr–Mo–N coatings were 23 and 34 GPa, respectively. These values were much enhanced ones compared with 18 GPa of CrN coating. The enhanced hardness values of Cr–C–N and Cr–Mo–N coatings were explained with the solid solution hardening as well as defect hardening. The residual stresses in both coatings were compressive and less than 5 GPa. The average friction coefficient of Cr–C–N and Cr–Mo–N coatings was measured 0.5 and 0.4, respectively. The decreased friction coefficients of Cr–C–N and Cr–Mo–N coatings was explained by the formation of carbon rich transfer layer (or amorphous carbon layer) and the formation of MoO3 layer known as self-lubricant materials.

Dynamic recrystallisation and superplasticity in pure aluminium with zirconium addition

When commercial superplastic aluminium alloys were first under development it was concluded that to be successful the alloy should contain both a solid solution addition and a dispersion of fine, thermally stable dispersoids. In contrast to early beliefs, the present work demonstrates that a simple Al–1 wt.%Zr alloy can exhibit good superplastic performance despite the absence of a solid solution element. The starting material was in the form of ∼1 mm diameter particles produce via impulse atomisation that conferred a solidification rate ∼10 3 K s −1. After extrusion consolidation, heat treatment to produce a fine distribution of metastable Al 3Zr precipitates, and rolling, the resulting sheet exhibited superplastic ductilities in excess of 500% at a strain rate of 10 −1 s −1. An EBSD study of the deformation behaviour demonstrated substantial grain refinement resulting from dynamic recrystallisation.

Preparation and properties of a γ-Al 2O 3 washcoat deposited on a ceramic honeycomb

Washcoat deposited on ceramic honeycomb was prepared using pseudoboehmite, the CeO 2–ZrO 2–La 2O 3 solid solution, pore enlarger and other additives. The microstructures and surface performances of washcoat/honeycomb were investigated by SEM, BET surface area, XRD, ultrasonic vibration and hot shock simulation. The results show that the performance and loading of washcoat are affected obviously by the properties of slurry gel, such as the apparent viscosity, solid content, particle size and its distribution. When the apparent viscosity of slurry is lower, the gel with a narrow particle size distribution and finer particles can be obtained, with which the coating having an excellent performance can be prepared. Adding a small quantity of the CeO 2–ZrO 2–La 2O 3 solid solution can promote the thermal stability of washcoat, such as, after calcined at 1000 °C for 5 h the sample exhibits mainly the γ-Al 2O 3 phases and the θ-Al 2O 3 α-Al 2O 3 and κ-Al 2O 3 phases have not been detected in the XRD spectra. It is found also that the washcoat prepared has excellent properties of the vibration-resistant, heat-resistant and its BET surface area reaches 50 m 2/g.

Characterizing alloy additions to carbon high-nitrogen steel

Alloy compositions are designed for specific industrial needs and applications. In this study, alloying elements that are known to enhance specific material properties of commercial Fe-Cr-Ni stainless steels were found to be similarly successful when added to Fe-15Cr-15Mn stainless steels. Unique to this study is the alloy addition of both carbon and nitrogen in excess of approximately 0.4 wt%. The nitrogen and carbon remained as interstitials without the formation of nitride or carbide precipitates even in carbon and nitrogen concentrations as high as 2wt%. Nitrogen and carbon alloying increased hardness, strength (σYIELD 850 MPa and σTMAX 2 GPa), toughness and wear resistance. Precipitate formers such as niobium and solid solution additives such as silicon and molybdenum enhanced σYIELD but to a much smaller extent than interstitial alloying. Additions of silicon and molybdenum significantly improved oxidation protection at all temperatures and are necessary to prevent spallation at temperatures above 800 K. In corrosion tests, alloys form a passive region, but small concentrations of nickel are necessary to ensure repassivation.

High temperature solid solution strengthening by Nb additions on Mo3Si matrix

Abstract Ternary element Nb addition on a Mo3Si matrix resulted in improved mechanical properties. Solid solution additions on the alloys at different Nb concentrations were evaluated. High temperature compression test at 1300 and 1400 °C at 10−5 s−1 shown a strong temperature and composition dependence. The calculated stress exponent from compressive analysis resulted to be n=6. Diffusion analysis were performed by using a couple of samples with and without Nb in two different conditions (t, at.%). The results from the strengthening obtained, are interpreted by calculating the diffusion coefficient. This increment in the creep strength is rationalized in terms of substitutional considering the atomic sizes for Mo and Nb.

Influence of chromium, titanium and tantalum carbides on corrosion resistance of cemented carbides: A. Lackner et al. (Plansee Tizit GmbH, Reutte, Austria.)

Homogeneous solid-solution (Ti, Ta, Nb,W)(C,N) powders were synthesized through carbothermal reduction-nitridation method. The effects of (Ti, Ta, Nb,W)(C,N) powders on the microstructure, mechanical properties and corrosion resistance of WC-10Co cemented carbides were investigated using XRD, SEM, electrochemical test and mechanical properties tests. The results showed that cemented carbides with pre-alloyed powder addition had a similar microstructure appearance: weak core/rim structure consisting of solid-solution phase embedded in the WC-Co system. The black core and gray rim, both of which contained similar elements, were identified as (Ti, Ta, Nb,W)(C,N), but the latter contained higher amount of heavy elements.With the addition of (Ti, Ta, Nb,W)(C,N) powders, the density, transverse rupture strength and fracture toughness of samples decreased monotonously. However, the hardness rose sharply at first, reached a peak at 15 wt% solid-solution addition, then slightly decreased, and finally increased again. Results also revealed that increasing (Ti, Ta, Nb,W)(C,N) made the open circuit potential (OCP) in 1 M sulphuric acid solution more negative than that of WC-Co, and all specimens exhibited pseudo-passivation phenomenon in the test solution. In addition, increasing pre-alloyed powders led to decreasing corrosion current density, which implies that (Ti, Ta, Nb,W)(C,N) could remarkably improve the corrosion resistance of WC-Co cemented carbides.

The effect of solid solution W additions on the mechanical properties of nanocrystalline Ni

Although pure metals with grain sizes below about 10 nm are very difficult to prepare, alloying enables the realization of finer grain sizes, often down to the amorphous limit. In this work, the role of solid solution additions of ~13 at% W are considered with respect to the structure and mechanical properties of electrodeposited Ni alloys with grain sizes below 10 nm. Structure of the nanocrystalline alloys is analyzed by high-resolution transmission electron microscopy, and related to the mechanical properties assessed by instrumented nanoindentation and nano-scratch experiments. The Ni-W alloys exhibit higher hardness and scratch resistance as compared to the finest pure nanocrystalline Ni alloys, although the contribution of solid solution strengthening from W is expected to be essentially negligible. The improved properties are therefore most likely due to the finer length scale available in multicomponent nanocrystalline alloys, and suggest that alloying may suppress the breakdown of Hall-Petch strengthening to finer grain sizes. Finally, the present data are shown to smoothly bridge the hardness-grain size trend between nanocrystalline Ni (grain size>10 nm) and amorphous Ni-based alloys.

Effects of additives on the phase formation and microstructural evolution of Ba 2Ti 9O 20 microwave ceramic

Preparation of dense and phase-pure Ba 2Ti 9O 20 is generally difficult using solid state reaction, since there are several thermodynamically stable compounds in the vicinity of the desired composition and a curvature of Ba 2Ti 9O 20 equilibrium phase boundary in the BaO–TiO 2 system at high temperatures. It was reported that a small amount of solid solution additives is essential for the formation of a pure Ba 2Ti 9O 20 phase, however, contradictory results were also addressed in the literature. In this study, TiO 2, MnO, and ZrO 2, were used to investigate the effects of additives on the densification, microstructural evolution and phase stability of Ba 2Ti 9O 20. With the addition of 2.8 wt.% TiO 2 and sintering at 1200 °C, ceramic yielded a pure Ba 2Ti 9O 20 phase. It indicates that Ba 2Ti 9O 20 is a nonstoichiometric compound, which can accommodate an excess amount of TiO 2. With the addition of 4 wt.% ZrO 2, phase pure Ba 2Ti 9O 20 was obtained in the sintering temperatures of 1200 °C and 1300 °C. Results also indicated that MnO addition could promote the formation of Ba 2Ti 9O 20, compared with that of pure host material, though pure Ba 2Ti 9O 20 was not obtained. SEM microstructures are consistent with the observations in XRD patterns.