Composition Dependence Of Properties Research Articles

Correlation between the composition-dependent properties and phase stability of Co2YGa(Y=Cr,V) shape-memory alloys from first-principles study

The composition-dependent properties and phase stability of ${\mathrm{Co}}_{2}\phantom{\rule{4pt}{0ex}}Y\text{Ga}\phantom{\rule{4pt}{0ex}}(Y=\text{Cr},\text{V})$-based shape-memory alloys are investigated by using the first-principles exact muffin-tin-orbital method in combination with the coherent potential approximation. It is shown that both ${\mathrm{Co}}_{2}\mathrm{CrGa}$ and ${\mathrm{Co}}_{2}\mathrm{VGa}$ alloys possess $L{2}_{1}$ structures at the ferromagnetic (FM) state but tetragonal structures at the paramagnetic (PM) state. In off-stoichiometric ${\mathrm{Co}}_{2}Y\mathrm{Ga}$ alloys, the excess Ga atom has a strong tendency to take the $Y$ sublattice, whereas the excess Co atom tends to take the $Y$ site in the FM $L{2}_{1}$ phase when $Y=\phantom{\rule{0.16em}{0ex}}\text{Cr}$ but the Ga site in the other phases when $Y=\phantom{\rule{0.16em}{0ex}}\text{V}$. The off-stoichiometric Cr78 and Cr79 alloys can occur in the normal martensitic transformation (MT) at the PM state but the reentrant martensitic transformation (RMT) at the FM state, whereas only the normal MT is obtained in the V50 and V15 alloys, where the small difference of the magnetization between the austenite and martensite is supposed to suppress the RMT. In all four groups of off-stoichiometric alloys, the correlation between the composition-dependent properties with the experimental ${T}_{M}$ values for the normal MT has been established. In the Cr78 and Cr79 alloys, ${T}_{M}$ for the RMT is also predicted to decrease with increasing $e/a$. The PM ordering tends to soften the elastic constants of all these $L{2}_{1}$ alloys. In the four groups of FM $L{2}_{1}$ alloys, ${C}^{\ensuremath{'}},G,E,\mathrm{\ensuremath{\Theta}}$, and G/B decrease whereas $A$ increases with increasing $e/a$, which favors ${T}_{M}$ for their RMT decreasing but that for their normal MT increasing with $e/a$. The composition dependence of the MT of these alloys could be explained from their minority density of states around the Fermi level of the $L{2}_{1}$ phase by means of the Jahn-Teller effect.

Efficient Control of Atom Arrangement in Ternary Metal Chalcogenide Nanoparticles Using Precursor Oxidation State

Controlling both the concentration and the distribution of elements in a given material is often crucial to extracting and optimizing synergistic properties of the various constituents. An interesting class of such multielement materials is metal chalcogenide nanoparticles, which exhibit a wide range of composition-dependent optoelectronic properties including both bandgap-mediated processes and localized surface plasmon resonance properties, each of which is useful in applications ranging from energy conversion to sensing. Because metal chalcogenide nanoparticles can support several different metal elements in a variety of chalcogen lattices, this material class has particularly benefited from the ability to control both atom concentration and atom arrangement to tailor final particle properties. The primary method to access complex, multimetallic chalcogenide particles is via a postsynthetic cation exchange strategy. One-pot syntheses have been less explored to access these complex particles, although t...

Influence of liquid composition on diffusive mass transfer in the lubricating film of Taylor flow—A study related to the hydrogenation of nitrobenzene

Micro-structured reactors operated in Taylor flow are promising for intensifying heterogeneously catalyzed gas-liquid reactions. By reaction progress or dilution, physical properties may change with liquid composition. Here, the effect of composition on physical mass transfer in the liquid film of Taylor flow is studied with regard to the hydrogenation of nitrobenzene to aniline. For the liquid mixtures nitrobenzene-aniline and nitrobenzene-ethanol, composition-dependent physical properties are determined using information from literature. By numerical solution of the unsteady one-dimensional diffusion equation with composition-dependent physical properties, the instantaneous hydrogen concentration across the liquid film is obtained for different nitrobenzene mole fractions. The results indicate that in a wide composition range of reactant (nitrobenzene) and product (aniline), hydrogen diffuses slower in the mixture than in pure liquids. On the other hand, dilution of nitrobenzene by ethanol increases hydrogen mass transfer in the liquid film. A theoretical relation is provided which allows estimating for given capillary number the necessary bubble length to achieve a certain hydrogen saturation in the liquid film during the passage of one Taylor bubble. This non-dimensional relation can be applied to other physical systems and may be useful to guide optimal hydrodynamic operation conditions for applications with Taylor flow in chemical engineering.

Anomalous short-to-medium-range structural characteristics of P in Pd43Ni43P14 and Pd40Ni40P20 glass-forming liquids

ab initio molecular dynamics simulations were performed to systematically investigate the short-to-medium-range structural characteristics of P atoms in Pd43Ni43P14 and Pd40Ni40P20 glass-forming liquids for understanding the correlation between structure and the composition-dependent properties. It is found that P atoms in Pd43Ni43P14 liquid prefer the local configurations with larger coordination number (CN), such as <0,2,8,0>. However, P atoms in Pd40Ni40P20 liquid tend to form clusters with smaller CN, such as <0,3,6,0>. More importantly, the major P-centered clusters in two liquids are found to resemble those in different crystal phases, which is key to understanding the physical origin of glass forming ability in these glass-forming alloys. Surprisingly, P atoms in Pd43Ni43P14 liquid show more significant medium-range structural ordering than those in Pd40Ni40P20 liquid. To understand the effect of P content on the short-to-medium-range structural characteristics in the glass-forming liquids, a saturation degree model was proposed for the maximum fraction of P atoms without direct P–P bonds populated. This finding provides new insights into the composition-sensitive properties in (Pd0.5Ni0.5)100-xPx glass-forming alloys.

Composition dependent structural, morphological, optical and electrical properties of CdS:Co window layer grown by chemical bath deposition

CdS as an n–type layer plays an important role in the fabrication of solar cells. Cd1-xCoxS thin-films with variable Co doping levels (x = 0 to 0.06) were deposited on glass and indium tin oxide-coated (ITO) glass substrates by simple and inexpensive chemical bath deposition. The effects of Co doping on the structural, optical, morphological, elemental, and vibrational properties of CdS films were systematically examined. XRD results revealed that Co concentrations increase and the crystallite size of the film decreases from 20.4 to 13.6 nm due to the incorporation Co in Cd sites. The optical bandgap was reduced from 2.44 to 2.32 eV due to the incorporation of Co, which was found with a UV–Vis spectrophotometer. Urbach energy, refractive index and extinction coefficient of all deposited films was estimated, and the results were discussed. The intensity of PL peaks was reduced by increasing the Co concentration in the red region. The resistivity and carrier concentration were measured from Hall measurement system and the film current density was increased from 7 to 26 mA/cm2 by cobalt doping.

Electrospray deposition tool: Creating compositionally gradient libraries of nanomaterials.

Electrospray deposition (ESD) enables the growth of solution deposited thin films in a precise and continuous manner by the delivery of submicron droplets of dilute solutions to a heated substrate. By combining ESD with programmable motor control and gradient solution pumping in a first-of-its-kind user tool at the Center for Functional Nanomaterials at Brookhaven National Laboratory, we show the ability to create one or two dimensional compositional gradient nanoscale films via ESD. These capabilities make it possible to construct thin film multicomponent "libraries" on a single substrate to rapidly and systematically characterize composition-dependent properties in a variety of material systems such as thin films involving homopolymer and block copolymer blends. We report the design, construction, and validation of a gradient ESD tool that allows users to carefully control the jet stability, flow composition, spray position, and substrate temperature. Calibrated thin films range in thickness from tens to hundreds of nanometers. We demonstrate gradient thin films using a ternary dye triangle as well as a gradual blending of polystyrene homopolymer with poly(styrene-block-methyl methacrylate) on a single substrate. Paired with the rapid measurement capabilities of synchrotron small angle X-ray scattering, this tool forms an integral part of a new platform for high-throughput, autonomous characterization and design of nanomaterial thin films and soft materials more generally.

Composition dependent magnetic and microwave properties of exchange-coupled hard/soft nanocomposite ferrite

In the present work, exchange-coupled BaFe12O19 (BaM)/Ni0.5Zn0.5Fe2O4 (NZFO) nanocomposites with different weight ratio were prepared by sol-gel autocombustion method. The effect of relative weight fraction on structural, morphological, magnetic and microwave properties were investigated. X-ray diffraction patterns of composites confirmed the co-existence of BaM and NZFO phases without any secondary phase. Smooth hysteresis loops without kink confirmed that BaM/NZFO phases were well exchange-coupled. Non linear change in magnetization (Ms) and coercivity (Hc) with NZFO content were observed. The drastic increase in Ms with corresponding sharp decrease in Hc for 70/30 wt ratio was observed. The change in Ms and Hc was explained with the schematic model of interfacial spin interactions. Complex permeability and permittivity in Ku-band showed oscillatory behaviour for higher weight fraction of NZFO. Reflection loss frequency found to depends on NZFO content and maximum loss (−41 dB) was observed for 70/30 wt ratio at 13.8 GHz frequency.

Experimental study on mass transfer during scrap melting in the steelmaking process

ABSTRACT The effects of natural and forced convection on mass transfer were investigated, especially the composition-dependent material properties were used. Under natural convection, the stationary specimen became a cone. The mass transfer coefficient increased from 3.14 × 10−5 to 5.31 × 10−5 m s−1 at the temperatures of 1300–1450°C. The empirical formulas Sh = 0.144(GrSc)0.325 and k = M(Δρ)0.325(L)−0.025 were found within the ranges of 1 × 108 < GrSc < 5 × 108. Under forced convection, the rotating scrap cylinder became an irregular spiral. When the rotational speed changed from 141 to 423 r min−1, the mass transfer coefficients were 7.50 × 10−5–1.72 × 10−4 m s−1 at the temperatures of 1300-1400°C. The empirical formulas JD = 0.133(Re)−0.356 and k = M(n)0.644(L)0.288 were obtained within the ranges of 1000 < Re < 4000.

Bi(Zn0.5Ti0.5)O3 induced domain evolution and its effect on electrical property and thermal stability of 0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 ceramics

0.8Na0.5Bi0.5TiO3-(0.2-x)K0.5Bi0.5TiO3-xBi(Zn0.5Ti0.5)O3 (NBT-KBT-BZT, x = 0–0.05 with interval of 0.01) lead-free piezoceramics were prepared and investigated. The addition of BZT has not led to deviation of rhombohedral-tetragonal morphotropic phase boundary, but apparently composition-dependent electrical property and monotonously improved thermal stability. The x = 0.02 has the optimal electrical property with remnant polarization, bipolar total strain, piezoelectric constant of 26.5 μC/cm2, 0.30%, 121 pC/N respectively, while the depolarization temperature is increased from 93 °C for x = 0–135 °C for x = 0.05 based on dielectric measurement. Detailed investigation reveals that the domain structure transforms from labyrinthian domain for x = 0 to coexistence of nanodomain and labyrinthian domain for x = 0.02, end up with large amount of nanodomain (x = 0.04). Such domain evolution should be responsible for the composition dependent electrical property and improved thermal stability. Our work confirms that domain engineering is an alternative method to develop high performance piezoelectric materials.

Impact of PVDF/PEO blend composition on the β-phase crystallization and dielectric properties of silica nanoparticles incorporated polymer nanocomposites

Polymer nanocomposite (PNC) films consisted of varying weight composition polymer blends of poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO) as host organic matrices incorporated with 5 wt% amorphous silica (SiO2) nanoparticles as inorganic nanofiller have been prepared by solution casting method. The alterations in morphology, PVDF polymorphism and relative fraction of β-phase crystals, degree of crystallinity, and the polymer-polymer and polymer-nanoparticle interactions with change of polymer blend compositional weight ratio (i.e., PVDF/PEO = 100/0, 75/25, 50/50, 25/75, and 0/100) have been investigated by the SEM, EDX, XRD, and FTIR measurements. The frequency dependent complex dielectric permittivity, ac electrical conductivity, and electric modulus of the PNC films are studied at room temperature by employing the DRS technique. The SEM images reveal that the spherulite morphology of PVDF/PEO blend structures incorporated with SiO2 nanoparticles is altered enormously with the change of polymers blend compositions in the PNC films. The XRD results of these PNC films confirm that the β-phase crystallization is considerably enhanced in the PVDF-rich PNC film but it decreases almost linearly with the increase of PEO amount in the host matrices of these films, and remains higher for the PNC films in comparison to that of the pristine polymer blend films. The degree of crystallinity of these PNC films enhances non-linearly with the increase of PEO concentration but it is found low as compared to that of the PVDF/PEO blend films without nanofiller. Dielectric dispersion in the frequency range from 20 Hz to1 MHz reveals that the interfacial polarization significantly contributed to the enhancement of dielectric permittivity in the audio frequency range of dielectric spectra of these PNC films. The addition of 5 wt% amount of SiO2 nanoparticles in the pristine PVDF and PEO matrices reduces the dielectric permittivity over the entire frequency range, whereas the presence of these nanofiller particles in the PVDF/PEO blend matrices based PNC films increases at radio frequencies which is predominantly due to enhancement of the β-phase crystals. The relaxation time values determined from the relaxation peaks exhibited in the loss part of electric modulus spectra confirm that there is an increase in hindrance to the PEO chain segmental dynamics with the increase of PVDF amount in the polymer blend compositions of these PNC films, whereas the dc electrical conductivity is found independent of the blend composition. The polymer blend compositional ratio dependent promising structural, dielectric, and electrical properties of these PNC films offer their suitability as tunable novel nanodielectric materials of multifunctionality for the flexible electronic devices.

Emissive Bi-Doped Double Perovskite Cs2Ag1–xNaxInCl6 Nanocrystals

We report the composition-dependent optical properties of Bi-doped Cs2Ag1–xNaxInCl6 nanocrystals (NCs) having a double perovskite crystal structure. Their photoluminescence (PL) was characterized b...

The Composition-Dependent Photoluminescence Properties of Non-Stoichiometric ZnxAgyInS1.5+x+0.5y Nanocrystals

A facile hot injection approach to synthesize high-quality non-stoichiometric ZnxAgyInS1.5+x+0.5y nanocrystals (NCs) in the size range of 2.8–3.1 nm was presented. The fluorescence spectra had single band gap features, and indicated the formation of alloy states rather than simple composite structures. The chemical compositions, photoluminescence (PL) emission wavelengths, and quantum yields of ZnxAgyInS1.5+x+0.5y nanocrystals were significantly influenced by the concentration of an organic capping agent. The appropriate proportion of 1-dodecanthiol in the precursor prevented the precipitation, increased the fluorescence quantum yield, and improved their optical properties. The proper ratio of capping agent allowed Zn, Ag, and In to form a better crystallinity and compositional homogeneity of ZnxAgyInS1.5+x+0.5y nanocrystals. The photoluminescence was tunable from blue to red in the range of 450–700 nm as the Ag content changed independently. The PL and absorption spectra of ZnxAgyInS1.5+x+0.5y nanocrystals showed a significant blue shift with the decrease of Ag content in the precursor. As there were no obvious differences on the average particle sizes of ZnxAgyInS1.5+x+0.5y samples, these results fully revealed the composition-dependent photoluminescence properties of ZnxAgyInS1.5+x+0.5y nanocrystals. The relative quantum yield reached 35%. The fluorescence lifetimes (τ1=115–148 ns and τ2=455–483 ns) were analogous to those of AgInS2 and (AgIn)xZn2(1−x)S2.

The single-crystal elastic properties of the jadeite-diopside solid solution and their implications for the composition-dependent seismic properties of eclogite

Abstract The 13 single-crystal adiabatic elastic moduli (Cij) of a C2/c jadeite sample close to the ideal composition (NaAlSi2O6) and a natural P2/n diopside-rich omphacite sample have been measured at ambient condition by Brillouin spectroscopy. The obtained Cij values for the jadeite sample are: C11 = 265.4(9) GPa, C22 = 247(1) GPa, C33 = 274(1) GPa, C44 = 85.8(7) GPa, C55 = 69.3(5) GPa, C66 = 93.0(7) GPa, C12 = 84(1) GPa, C13 = 66(1) GPa, C23 = 87(2) GPa, C15 = 5.4(7) GPa, C25 = 17(1) GPa, C35 = 28.7(6) GPa, C46 = 14.6(6) GPa. Voigt-Reuss-Hill averaging of the Cij values yields aggregate bulk modulus KS = 138(3) GPa and shear modulus G = 84(2) GPa for jadeite. Systematic analysis combing previous single-crystal elasticity measurements within the diopside-jadeite solid solution indicates that the linear trends are valid for most Cij values. The νp and νs of omphacite decrease with diopside content, though the velocity changes are small as diopside component exceeds 70%. We also found that both the isotropic νp and νs, as well as the seismic anisotropy of eclogite, changed strongly with the bulk-chemical composition. The relationship between the anisotropic velocities of eclogite and the chemical composition can be a useful tool to trace the origin of the eclogitic materials in the Earth's mantle.

The impact of composition dependent and process-related properties in the laser cutting of metallic glassy tapes

Abstract A short survey is reported on the advantageous and disadvantageous properties of soft magnetic glassy tapes to build stator and rotor elements for the increase of motor efficiency. The relative high saturation magnetization and the relative permeability of these alloy groups seem to be promising in this application field. On the other hand, the sample thickness (30 µm) displays limitations in terms of a filling factor. High hardness of tapes hinders the effectivity of mechanical shaping. Laser cutting can be successful as shaping method, presuming that the extension (thickness) of heat affected zone (HAZ) can be successfully reduced below 50µm, avoiding the brittleness evolution.

Multi-Solvent Microdroplet Evaporation: Modeling and Measurement of Spray-Drying Kinetics with Inhalable Pharmaceutics.

Evaporation and particle formation from multi-solvent microdroplets containing solid excipients pertaining to spray-drying of therapeutic agents intended for lung delivery were studied. Various water and ethanol co-solvent systems containing a variety of actives and excipients (beclomethasone, budesonide, leucine, and trehalose) were considered. Numerical methods were used to predict the droplet evaporation rates and internal solute transfers, and their results verified and compared with results from two separate experimental setups. In particular, an electrodynamic balance was used to measure the evaporation rates of multicomponent droplets and a monodisperse droplet chain setup collected dried microparticles for further analytical investigations and ultramicroscopy. The numerical results are used to explain the different particle morphologies dried from solutions at different co-solvent compositions. The obtained numerical data clearly show that the two parameters controlling the general morphology of a dried particle, namely the Péclet number and the degree of saturation, can change with time in a multi-solvent droplet. This fact complicates product development for such systems. However, this additional complexity vanishes at what we define as the iso-compositional point, which occurs when the solvent ratios and other composition-dependent properties of the droplet remain constant during evaporation, similar to the azeotrope of such systems during distillation. Numerical and experimental analysis of multi-solvent systems indicate that spray-drying near the iso-compositional ratio simplifies the design and process development of such systems.

Investigation of rheological behaviors of polyolefin blend type thermoplastic elastomers for quantifying microstructure-property relationships

Polyolefin blend type thermoplastic elastomers (TPEs) were prepared via melt blending method in a twin screw extruder by using isotactic polypropylene (i-PP), three different styrene-olefin triblock copolymers (SEBS-1 and SEBS-2 having a styrene content of 30 wt.% and 60 wt.%, respectively and SEEPS having a styrene content of 30 wt.%) and paraffinic oil. Composition-dependent and time-dependent viscoelastic properties of compounds were determined by various test procedures conducted in a rotational rheometer in melt state. It was found that the content of polystyrene blocks (or hard segment) in copolymers governed the rheological behaviors of compounds. It can be concluded that the increasing amount of styrene-olefin block copolymer or content of glassy domains into blend composition reduces miscibility between polyolefin and elastomer phases and also yields higher melt elasticity and viscosity, longer relaxation times, lower creep strain and compliance values at relatively longer time scale.

Composition-dependent mechanical property changes in Au-ion-irradiated borosilicate glasses

The mechanical property changes in three kinds of ternary borosilicate glasses (named NBS glasses) induced by 8.0-MeV Au3+ were studied by nanoindentation measurements. For these borosilicate glasses, the molar ratio R = [Na2O]/[B2O3] is varied (1.34, 0.75, and 0.40 for NBS1, NBS2, and NBS3, respectively), while their molar ratio K = [SiO2]/[B2O3] is fixed at 4.04. The nanoindentation results indicate that both the hardness and reduced Young modulus were decreased after irradiation. No obvious difference in both hardness and modulus variations of these three NBS glasses was observed. Based on the main structures of their pristine samples, the reedmergnerite groups containing Si-O-BIV may be the structural origin of Au-ion-irradiated mechanical property changes in the homogeneous glasses with R > 0.5. However, the modification of the silica network and phase separation may dominate the mechanical property changes for glasses with R ≤ 0.5. The ion- and electron-irradiation-induced mechanical property changes of these NBS glasses were also compared in this study. The extended incubation dose and the slower decreasing rate can be observed in electron-irradiation-induced hardness and modulus variations, which may be caused by the different mechanisms between both irradiation scenarios.

Formation and Composition-Dependent Properties of Alloys of Cubic Halide Perovskites

Distinct shortcomings of individual halide perovskites for solar applications, such as restricted range of band gaps, propensity of ABX3 to decompose into AX + BX2, or oxidation of 2ABX3 into A2BX6, have led to the need to consider alloys of individual perovskites such as [FA,Cs][Pb,Sn][Br,I]3. This proposition creates a nontrivial material selection problem associated with a six-component structure, spanning a continuum of three sets of compositions (one for each sublattice) and requiring control of phase separation or ordering in each alloyed subfield. Not surprisingly, material and structure choices were made thus far mostly via trial-and-error explorations among a large number of arrangements. Here, we use ideas from solid-state theory of semiconductor alloys to analyze the behaviors of the canonical [FA,Cs][Pb,Sn]I3 alloy system, where FA is formamidinium. Density functional calculations utilizing specially constructed supercells are used to calculate the composition dependence of band gaps, energy o...

Structure and bandgap nonlinearity in BaSn1−xTixO3 epitaxial films

BaSn1−xTixO3 (BSTO, x = 0, 0.25, 0.5, 0.75, 1.0) epitaxial films were deposited on LaAlO3(001) substrates by employing a pulsed laser deposition system. Their composition dependent structure and optical properties were systematically investigated using density functional theory (DFT) calculations. High resolution x-ray diffraction characterization showed that the film lattice parameters decrease linearly with the increase in Ti concentrations, following Vegard's law. Optical property measurements revealed that all films have the optical transmittance of more than 70% in the visible and infrared wavelength range. Interestingly, the bandgap nonlinearity of BSTO films was observed, and the film at Ti doped x = 0.25 has the largest bandgap value of 4.04 eV. The calculated electronic structure and the density of states of BSTO films determined by DFT suggested that the strong hybridization between Sn 5s and Ti 3d orbitals caused the initial expansion of the bandgap, whereas upon further increasing the doping content, Ti 3d orbitals dominated the conduction band, leading to the bandgap reduction.

Phase Structure, Microstructure and Electrical Properties of KxNa(1-x)NbO3 Piezoelectric Ceramics with Different K/Na Ratio

The KxNa(1-x)NbO3 (x = 0.45, 0.46, 0.47, 0.48, 0.49, 0.50) lead-free piezoelectric ceramics was fabricated by conventional solid-state sintering method. It was found that the ratio of alkaline metal would affect the microstructure, bulk density, and optimum sintering temperatures of ceramics. Meanwhile, the electrical properties were also influenced by modulating the K/Na ratio, exhibiting corresponding composition-dependent properties. The optimum electrical properties of KxNa(1-x)NbO3 such as piezoelectric constant d33 = 115 pC/N, mechanical quality factor Qm = 20, Curie temperature Tc = 365 °C, eT33/e0= 588.1, dielectric loss tan δ = 0.024, bulk density (ρ) = 3.08 g/cm3, remnant polarization (Pr) = 8.87 μC/cm2 and coercive field (Ec) = 13.79 kV/cm were obtained at x = 0.46.