Electrical Transport Properties of Single-Crystalline β-Zn<Subscript>4</Subscript>Sb<Subscript>3</Subscript> Prepared Through the Zn-Sn Mixed-Flux Method

β-Zn₄Sb₃ is a promising p-type thermoelectric material for utilization in moderate temperatures. This study prepares a group of single-crystalline β-Zn₄Sb₃ samples using the Zn-Sn mixed-flux method based on the stoichiometric ratios of Zn_4+x Sb₃Sn _y . The effect of Zn-to-Sn proportion in the flux on the structure and electrical transport properties is investigated. All samples are strip-shaped single crystals of different sizes. The actual Zn content of the present samples is improved (>3.9) compared with that of the samples prepared through the Sn flux method. Larger lattice parameters are also obtained. The carrier concentration of all the samples is in the order of over 10¹⁹ cm^?3. With increasing Sn rate in the flux, this carrier concentration decreases, whereas mobility is significantly enhanced. The electrical conductivity and Seebeck coefficients of all the samples exhibit a behavior that of a degenerate semiconductor transport. Electrical conductivity initially increases and then decreases as the Sn ratio in the flux increases. The electrical conductivity of the x:y = 5:1 sample reaches 6.45 × 10⁴ S m^?1 at 300 K. Benefitting from the electrical conductivity and Seebeck coefficient, the flux proportion of the x:y = 7:1 sample finally achieves the highest power factor value of 1.4 × 10^?3 W m^?1 K^?2 at 598 K.     

Preparation and high-frequency soft magnetic property of FeCo-based thin films

A series of FeCo-based thin films were prepared by magnetron sputtering without applying an induced magnetic field.The microstructure,electrical properties,magnetic properties and thermal stability of FeCo,FeCoSiN monolayer thin film and[FeCoSiN/SiN_x]_n multilayer thin film were investigated systematically.When FeCo thin film was doped with Si and N,the resistivity and soft magnetic properties of the obtained FeCoSiN thin film can be improved effectively.The coercivity(H_c),resistivity(ρ) and ferromagnetic resonance frequency(f_r) can be further optimized for the[FeCoSiN/SiN_x]_n multilayer thin film.When the thickness of FeCoSiN layer and SiN_x layer is maintained at 7 and 2 nm,the H_c,p and f_r for[FeCoSiN/SiN_x]_n multilayer thin film are 225 A·m~(-1)392 μΩ·cm~(-1) and 4.29 GHz,respectively.In addition,the low coercivity of easy axis(H_(ce) ≈ 506 A·m~(-1)) of[FeCoSiN/SiN_x]_n multilayer thin film can be maintained after annealing at 300 ℃ in air for 2 h.     

Temperature-Dependent Flow Behavior and Microstructural Evolution During Compression of As-Cast Mg-7.7Al-0.4Zn

The microstructure and mechanical properties improve substantially by hot working. This aspect in as-cast Mg-7.7Al-0.4Zn (AZ80) alloy is investigated by compression tests over temperature range of 30-439°C and at strain rates of 5 × 10^?2, 10^?2, 5 × 10^?4 and 10^?4 s^?1. The stress exponent (n) and activation energy (Q) were evaluated and analyzed for high-temperature deformation along with the microstructures. Upon deformation to a true strain of 0.80, which corresponds to the pseudo-steady-state condition, n and Q were found to be 5 and 151 kJ/mol, respectively. This suggests the dislocation climb-controlled mechanism for deformation. Prior to attaining the pseudo-steady-state condition, the stress-strain curves of AZ80 Mg alloy exhibit flow hardening followed by flow softening depending on the test temperature and strain rate. The microstructures obtained upon deformation revealed dissolution of Mg₁₇Al₁₂ particles with concurrent grain growth of α-matrix. The parameters like strain rate sensitivity and activation energy were analyzed for describing the microstructure evolution also as a function of strain rate and temperature. This exhibited similar trend as seen for deformation per se. Thus, the mechanisms for deformation and microstructure evolution are suggested to be interdependent.     

Influence of Zinc on Coarsening of δ-Ni<Subscript>2</Subscript>Si Particles,Aging Behavior and Hardness in a Cu-Ni-Si Alloy

In the present paper, the aging precipitation and coarsening of disk-like δ-Ni₂Si particles in Cu and Cu-10Zn alloys aged at 450 °C have been investigated by hardness, electric resistivity measurement and transmission electron microscopy observation. The coarsening dynamics of the average diameter of the δ-Ni₂Si particles coincides with the t ^1/3 time law for both alloys. The coarsening of the diminution of supersaturation related to aging time t coincides with the t ^?1/3 time rule. Adding Zn to the Cu-Ni-Si alloy increases the growth and coarsening rate of the particles mainly because of the increased diffusivity D of the δ-Ni₂Si particles in the matrix. The value of D of the δ-Ni₂Si particles in the Cu-xZn (x = 0, 10 wt.%) matrix and the Cu/δ-Ni₂Si interfacial energy γ are independently calculated by using the Lifshitz–Slyozov–Wagner theory which was extended to include disk-like particles by Boyd and Nicholson. The values of D and γ increase from 0.77 × 10^?19 to 2.21 × 10^?19 m²/s and 0.19 to 0.63 J/m², respectively, when Zn is added to the Cu-Ni-Si alloy. These calculations and the analysis show that the properties of Cu-Ni-Si-Zn alloy can significantly be enhanced by reducing the aging temperature.     

Isothermal Oxidation Comparison of Three Ni-Based Superalloys

Ni-based superalloys are used for high-temperature components of gas turbines in both industrial and aerospace applications due to their ability to maintain dimensional stability under conditions of high stress and strain. The oxidation resistance of these alloys often dictates their service lifetime. This study focuses on the isothermal oxidation behavior of three Ni-based superalloys, namely, polycrystalline cast IN738LC, single-crystal N5, and a ternary Ni-Fe-Cr (TAS) powder metallurgy alloy. The isothermal oxidation tests were conducted at 900 °C in the static air up to 1000 h, and the specific aspects studied were the oxidation behavior of these chromia-forming and alumina-forming alloys that are used extensively in industry. In particular, the behavior of oxide scale growth and subsurface changes were analyzed in detail using various techniques such as SEM, EDS, and AFM. From the isothermal oxidation kinetics, the oxidation rate constant, k _p, was calculated for each alloy and found to be; k _p = 2.79 × 10^?6 mg² cm^?4 s^?1 for IN738LC, k _p = 1.42 × 10^?7 mg² cm^?4 s^?1 for N5 and k _p = 1.62 × 10^?7 mg² cm^?4 s^?1 for TAS. Based on a microstructural analysis, IN738LC exhibited a continuous dense outer scale of Cr₂O₃ and discontinuous inner scale of Al₂O₃, whereas N5 and TAS showed a dense outer scale of Al₂O₃ alone. The results suggested that the N5 and PM-TAS alloys are more oxidation resistant than the IN738LC under these conditions.     

Deformation mechanisms in Cr20Ni80 alloy at elevated temperatures

The mechanisms of plastic deformation of Cr20Ni80 nichrome with an initial grain size of 80 μm were studied in the temperature range 600–950°C and the strain-rate range 1.5 × 10^?6?5 × 10^?2s^?1. Nichrome is shown to exhibit anomalously high values of stress exponent n and a high deformation activation energy Q. These unusual properties were found to be caused by “threshold” stresses below which deformation does not occur. An analysis of the deformation behavior with allowance for threshold stresses reveals the regions of hot, warm, and cold deformation in nichrome. At normalized strain rates \(\dot \varepsilon \) kT/D _{1 Gb} < 10^?8, the true values of n and Q are ～4 and 285 ± 30 kJ/mol, respectively. In the normalized-strain range 10^?8?10^?4 n ～ 6 and the deformation activation energy decreases to 175 ± 30 kJ/mol. This change in the deformation-behavior characteristics is explained by the transition from high-temperature dislocation climb, which is controlled by lattice self-diffusion, to low-temperature dislocation climb, which is controlled by pipe diffusion, as the temperature decreases. At \(\dot \varepsilon \) kT/D _{1 Gb} = 10^?4, a power law break-down takes place and an exponential law (which describes the deformation behavior in the range of cold deformation) becomes operative.     

Determination of Johnson–Cook Plasticity Model Parameters for Inconel718

In order to simulate foreign object damage (FOD) phenomenon in aircraft high-pressure compressor blades made of a nickel-based super-alloy, Johnson–Cook (J–C) plasticity model was used. For prediction of material’s plastic behavior at temperature of 400 °C (working temperature of the blades) in the range of strain rates associated with the FOD phenomenon (in order of 10⁶ s^?1), material parameters of A, B, C, n and m for the J–C plasticity model had to be determined experimentally. Parameters of A, B and n with values of 1108, 699 MPa and 0.5189, respectively, were obtained from quasi-static tensile tests. Moreover, m was determined to be 1.2861, also through quasi-static tensile tests with a strain rate of 1 s^?1 at three temperatures of 475, 550 and 625 °C. However, in order to determine C, firstly a steel ball was impacted on the surface of a flat specimen made of a precipitation-hardening alloy, and then, the impact site was 3D scanned to obtain the induced crater profile. Finally, the impact test (ballistic) was simulated using Abaqus, and a C value of 0.0085 was determined by comparing the actual crater profile with the one obtained from the simulation through a trial-and-error approach.     

Experimental Investigation of the Isothermal Section at 800 °C of the Nd-Fe-Co Ternary System

The phase equilibrium of the ternary Nd-Fe-Co system at 800 °C was investigated by means of powder x-ray diffraction and scanning electron microscopy–energy dispersive x-ray spectroscopy. Seven binary compounds, i.e., Nd₂Co₁₇, NdCo₅, Nd₅Co₁₉, Nd₂Co₇, NdCo₃, NdCo₂, Nd₂Fe₁₇ were identified to exist at this isothermal section. This isothermal section consists of ten single-phase, ten two-phase and six three-phase regions. All measured compositions and unit-cell refinements were performed at room temperature from quenched samples annealed at 800 °C for one week. The maximum solubility at 800 °C of Fe in NdCo_2?x Fe _x (MgCu₂-type structure, Fd-3 m), NdCo_3?x Fe _x (PuNi₃-type structure, R-3 m space group), Nd₂Co_7?x Fe _x (Ce₂Ni₇-type structure, R-3 m), Nd₅Co_19?x Fe _x (CeCo₁₉-type structure, R-3 m space group), NdCo_5?x Fe _x (CaCu₅-type structure, P6/mmm), Nd₂Co_17?x Fe _x (Th₂Zn₁₇ type structure, R-3 m) and Nd₂Fe_17?x Co _x (Th₂Zn₁₇ type structure, R-3 m) are about 31.6 at.% Fe, 47.9 at.% Fe, 13.3 at.% Fe, 8.6 at.% Fe, 10.37 at.%, 36.35 at.% Fe, and 58.23 at.% Fe respectively. The solid solubility range of Co in Nd₂Fe₁₇ form discontinuous series of 2 ranges is about 0-30.14 at.% Co, and 51.9-100 at.% Co and the solid solubility range of Fe in Nd₂Co₁₇ is about 0-48.1 at.% Fe, and 69.86-100 at.% Fe.     

The Effect of Thermo-Mechanical Treatment on Structure of Ultrahigh Carbon PM Steel

The effects of thermo-mechanical treatment on selected properties related to the structure of Fe-0.85Mo-0.65i-1.4C powder metallurgy (PM) steel are reported. Three kinds of initial microstructure of specimens, i.e., pearlite + ferrite + cementite, martensite + retained austenite and α + spheroidized cementite were examined. Processing was carried out on a plastometer-dilatometer Bähr machine by compression cylindrical specimens at 775 °C at a strain rate of 0.001 s^?1. X-ray diffraction was carried out with symmetrical Bragg-Brentano and grazing incident angle methods on a D8-Advance diffractometer with filtered radiation of cobalt CoK _α . The following features were determined: texture, density of dislocations, density of vacancies, lattice parameter of Fe _α and mean size of crystallites. Significant differences in structure were observed, especially in quenched specimen, as a result of the thermo-mechanical treatment. Regardless of initial state of the specimens, the determined properties were on a similar level. Crystallite size was in the range 97-106 nm, crystallite texture (I{200}/I{110}) × 10 = 1.15-1.62 and density of vacancies I{110}/I{220} = 7.06-7.52.     

Quantum chemical modeling of the adsorption of chloride ion and water molecule on group 1B metals

Quantum chemical modeling (at DFT-B3LYP level) of the adsorption of Cl^? and H₂O particles on top and into hollow sites of defect-free low index faces of copper, silver, and gold simulated by n-atomic clusters with n = 9 to 17 is carried out. The validity of simulations is confirmed by the comparison to the available literature data on the work function of the metals and the calculated gas-phase adsorption of chlorine. Relative effects of the chemical (metal nature), macrostructural (crystal face), and coordination (adsorption site) factors on the parameters of the chemisorption bond and molecular characteristics of the adsorbate and adsorbent, namely, the E _ads ads adsorption energy at % = 0K, R (Me^? Cl^?) and R(Me-O) adsorption bond lengths, Q effective charges of chlorine atom and water molecule, O-H distance and ∠HOH angle in H₂O molecule, deviation of the H₂O dipole moment vector from normal orientation to the cluster surface, and E _HOMO energies of the highest occupied molecular orbital of Me _n , [Me _n Cl]^?, Me _n H₂O, and [Me _n ClH₂O]^? clusters, are considered. The inner hydration shell of Cl^? is shown to involve six water molecules, the most stable configuration of (H₂O)₆ cluster being prism-like. An electron density shift from chlorine and water molecule to the metal cluster is found to accompany the adsorption and be more pronounced in the case of anion. The character of differences in the hydrophilicity of the group 1B metals and their diverse crystal faces is discussed. The role of hydration effects in the chemisorption of chloride ion on copper, silver, and gold is analyzed in terms of the continuum, molecular, and combined molecular-continuum models.     

Study on the Hot Workability of SiCp/Al Composites Based on a Critical Strain Map

We used the isothermal compression test (conducted in a Gleeble-3500 system) to study the hot deformation behaviors of SiCp/Al composites over a wide range of temperatures (623-773 K) and strain rates (0.001-10 s^?1). A 3D hot-processing map was constructed based on the Malas stability criteria and experimental data. An artificial neural network model of four hot work quality characteristic parameters (strain rate sensitivity m, its derivative m′, temperature sensitivity s, and its derivative s′) were established. A new hot-processing map, known as a hot-processing critical strain map, has been proposed based on the smallest strain prior to instability. Two optimized processing regions at 623-660 K, 0.05-0.075 s^?1 and 720-773 K, 0.04-0.18 s^?1 were determined based on this map.     

Volatilization and Transport Mechanisms During Cr Oxidation at 300 °C Studied In Situ by ToF-SIMS

The oxidation of chromium at 300 °C was investigated in situ by ToF-SIMS for three different oxygen pressures (\(P_{{{\text{O}}_{2} }} = 2.0 \times 10^{ - 7}\), 6.0 × 10^?7 and 2.0 × 10^?6 mbar). Sequential exposure to the ¹⁸O isotopic tracer was performed to reveal the governing transport mechanism in the oxide film. The evolution of the oxide thickness was monitored. Volatilization of Cr₂O₃ was evidenced. A model was used to describe the kinetics resulting from the measurements. Both the parabolic and volatilization constants showed a dependence on oxygen partial pressure like \(P_{{{\text{O}}_{2} }}^{ - 1/n}\), with n = 1.9 ± 0.1, indicating a defect structure mainly consisting of oxygen vacancies. The re-oxidation in ¹⁸O₂ shows a growth of the oxide layer at the metal/oxide interface, demonstrating an oxidation process governed by anionic transport via oxygen vacancies. The diffusion coefficient of oxygen in the oxide was determined by fitting the ToF-SIMS depth profiles. It is 2.0 × 10^?18 cm² s^?1.     

Microstructure and Thermophysical Properties of SrZrO<Subscript>3</Subscript> Thermal Barrier Coating Prepared by Solution Precursor Plasma Spray

Strontium zirconate (SrZrO₃) thermal barrier coatings were deposited by solution precursor plasma spray (SPPS) using an aqueous precursor solution. The phase transition of the SrZrO₃ coating and the influence of the aging time at 1400 °C on the microstructure, phase stability, thermal expansion coefficient, and thermal conductivity of the coating were investigated. The unique features of SPPS coatings, such as interpass boundary (IPB) structures, nano- and micrometer porosity, and through-thickness vertical cracks, were clearly observed evidently in the coatings. The vertical cracks of the coatings remained substantially unchanged while the IPB structures gradually diminished with prolonged heat treatment time. t-ZrO₂ developed in the coatings transformed completely to m-ZrO₂ phase after heat treatment for 100 h. Meanwhile, the SrZrO₃ phase in the coatings exhibited good phase stability upon heat treatment. Three phase transitions in the SrZrO₃ coatings were revealed by thermal expansion measurements. The thermal conductivity of the as-sprayed SrZrO₃ coating was ~1.25 W m^?1 K^?1 at 1000 °C and remained stable after heat treatment at 1400 °C for 360 h, revealing good sintering resistance.     

1:13 phase formation mechanism and first-order magnetic transition strengthening characteristics in (La,Ce)Fe<Subscript>13–<Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys

The effects of the introduction of Ce to La_1?x Ce _x Fe_11.5Si_1.5 alloys on 1:13 phase formation mechanism, the first-order magnetic phase transition strengthening characteristics, and magnetocaloric property were studied, respectively. The results show that the formation mechanisms of 1:13 and LaFeSi phases in La_1?x Ce _x Fe_11.5Si_1.5 alloys are the same as those of Ce₂Fe₁₇ and CeFe₂ phases in Ce–Fe binary system, respectively. The substitution of Ce in 1:13 phase which is limited can make the first-order magnetic phase transition characteristics strengthen, which can make thermal and magnetic hysteresis increase, the temperature interval of temperature-induced phase transition decrease, and the critical magnetic field of field-induced magnetic phase transition (H _C) increase, respectively. Owing to the lattice shrink of 1:13 phase with the increase in Ce content, the Curie temperatures (T _C) show a linear decrease. The maximum change in magnetic entropy gradually increases due to the decrease in temperature interval of temperature-induced phase transition, but the relative cooling capacities are all about 80 J·kg^?1 at magnetic field of 2 T.     

Phase Equilibria in the Sb<Subscript>2</Subscript>Te<Subscript>3</Subscript>–InSb System

The phase diagram of the (Sb₂Te₃)_100?x –InSb _x system was determined based on x-ray diffraction (XRD) analysis, differential thermal analysis (DTA), and microhardness and density measurements. An intermediate compound with composition Sb₂Te₃·2InSb was formed as a result of syntectic reaction, melting incongruently at 553 °C. This compound has tetragonal lattice with unit cell parameters of a = 4.3937 Å, b = 4.2035 Å, c = 3.5433 Å, α = 93.354°, and β = γ = 90°. Sb₂Te₃·(2 + δ)InSb (?1 ≤ δ ≤ +1) and (Sb₂Te₃)_100?x (InSb) _x (90 ≤ x ≤ 100) solid solutions exist in the investigated system, based on the intermediate compound Sb₂Te₃·2InSb and on InSb, respectively. Also, two invariant equilibria exist in the system, with eutectic point coordinates at compositions of x = 60 and x ≈ 85 mol% InSb and eutectic temperatures of T _E = 541 and T _E ≈ 501 °C, respectively.     

Analysis of Plastic Flow Instability During Superplastic Deformation of the Zn-Al Eutectoid Alloy Modified with 2 wt.% Cu

The aim of this work is to analyze the plastic flow instability in Zn-21Al-2Cu alloy deformed under 10^?3 s^?1 and 513 K, which are optimum conditions for inducing superplastic behavior in this alloy. An evaluation using the Hart and Wilkinson–Caceres criteria showed that the limited stability of plastic flow observed in this alloy is related to low values of the strain-rate sensitivity index (m) and the strain-hardening coefficient (γ), combined with the tendency of these parameters to decrease depending on true strain (ε). The reduction in m and γ values could be associated with the early onset of plastic instability and with microstructural changes observed as function of the strain. Grain growth induced by deformation seems to be important during the first stage of deformation of this alloy. However, when ε > 0.4 this growth is accompanied by other microstructural rearrangements. These results suggest that in this alloy, a grain boundary sliding mechanism acts to allow a steady superplastic flow only for ε < 0.4. For ε values between 0.4 and 0.7, observed occurrences of microstructural changes and severe neck formation lead to the supposition that there is a transition in the deformation mechanism. These changes are more evident when ε > 0.7 as another mechanism is thought to take over.     

The formation of hysteretic magnetic properties in amorphous alloys of various classes upon thermomagmetic treatment in a transverse magnetic field

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT_⊥) on the permeability of the amorphous alloy Co₆₉Fe_3.7Cr_3.8Si_12.5B₁₁ with such a low saturation magnetostriction (λ_s 10^–7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed (K_sq > 0.90). It has been revealed that the permeability μ₄ (H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop K_sq,m in the range of 0.2 ≤ K_sq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ₄ (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe₅₇Co₃₁Si_2.9B_9.1 with λ_s = 35 × 10^–6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT_⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.     

Integrated constitutive model for flow behavior of pure Titanium considering interstitial solute concentration

The aim of this work is to develop a constitutive model that can predict the flow behavior of pure Ti with different interstitial concentrations and grain sizes. To build a database required for identifying material constants, three different grades of Ti were subjected to tensile tests at temperatures of 223, 300, 473, 673 or 773 K and at a fixed strain rate of 10^?3 s^?1. In the modeling procedure, the mechanical threshold stress model was further modified to capture both the hardening effects attributed to the changes in equivalent oxygen concentration (O _eq ) and the softening effect caused by deformation heating at high strain rates. The developed model can reasonably predict the flow behavior of pure Ti having different O _eq (0.14–0.32 wt%), and grain size (14.5–90 μm) over a temperature range of 135 to 673 K, and a strain rate range of 2×10^?4 to 1400 s^?1.     

Magnetoresistive properties of Ni-doped La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> manganites

La_0.7Sr_0.3Mn_1?x Ni _x O₃ (x = 0, 0.025, 0.050 and 0.075) ceramics were prepared by the conventional solid-state reaction method. The partial substitution of Mn by Ni²⁺ leads to a decrease in cell volume as well as a structural transition from the rhombohedral to the orthorhombic structure. Ni²⁺ doping increases the electrical resistivity, decreases the semiconductor–metal transition temperature (T _ms) and relatively enhances the room temperature magnetoresistance (MR), especially in x = 0.025 and around T _ms. With respect to conduction mechanism, the small polaron hopping (SPH) and the variable range hopping (VRH) models were used to examine conduction in the semiconducting region.     

Inverse magnetocaloric effect in the uniaxial paramagnet with non-Kramers ions

It has been shown that, in a uniaxial paramagnet with non-Kramers ions with a spin of S = 1 and single-ion anisotropy of the easy-plane type (DS _Z ² ), there is a low-field (μ₀ H ≤ D) and low-temperature (k _B T < 0.68D) region in which the isothermal magnetization along the hard direction H||OZ increases the magnetic entropy by ΔS _M (T, ΔH = H _f - H _i > 0) > 0 and the adiabatic magnetization along the same direction reduces the sample temperature by ΔT _ad(T, ΔH > 0) < 0 (inverse magnetocaloric effect (MCE)). The main features of the inverse MCE in uniaxial paramagnets with large spins (S = 2, 3, …) of the non-Kramers ions have been discussed.