Interaction behaviors at the interface between liquid Al–Si and solid Ti–6Al–4V in ultrasonic-assisted brazing in air

Power ultrasonic vibration (20 kHz, 6 μm) was applied to assist the interaction between a liquid Al–Si alloy and solid Ti–6Al–4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti–6Al–4V surface, chemical dissolution of solid Ti–6Al–4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2–20 μm diameter-sized pits formed on the Ti–6Al–4V surface. Propagation of ultrasonic waves in the liquid Al–Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti–6Al–4V substrate, excessive chemical dissolution of solid Ti–6Al–4V into liquid Al–Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al–Si and Ti–6Al–4V can be produced by ultrasonic-assisted brazing in air.     

Surface waves at the interface between tunable LC–MTMs and nonlinear media

The surface wave propagation at the interface between tunable metamaterials (MTMs) and nonlinear media is investigated. Tunable MTMs have a refractive index which can be tuned to negative?Czero?Cpositive values. The nonlinear media are assumed to have a Kerr-like refractive index. The dispersion equation is analytically derived and solved numerically. Results display the different behaviors of the propagating waves as the refractive index is tuned.     

Ternary compounds and isothermal section in Lu–Fe–Ga ternary system at 773 K

The isothermal section of the Lu–Fe–Ga ternary system at 773?K was investigated and constructed based on X-ray powder diffraction analysis. Thirteen binary compounds, Lu₂Fe₁₇, Lu₆Fe₂₃, LuFe₂, LuGa₃, LuGa₂, Lu₃Ga₅, LuGa, Lu₃Ga₂, Lu₅Ga₃, Fe₃Ga, Fe₆Ga₅, Fe₃Ga₄, FeGa₃, nine ternary solid solutions, T₁-LuFe_2–1.43Ga_0–0.57, T₂-LuFe_1.34–0.92Ga_0.68–1.08, T₃-LuFe_0.52–0.26Ga_1.48–1.74, T₅-LuFe_2.04–1.72Ga_0.96–1.28, T₆-Lu₆Fe_23–21.4Ga_0–1.6, T₇-Lu₂Fe_17–14.5Ga_0–3.5, T₈-Lu₂Fe_12.9–8.1Ga_4.1–8.9, T₉-LuFe_6.8–5.5Ga_5.2–6.5, T₁₀-LuFe_5.2–4.5Ga_6.8–7.5, and two ternary compounds, T₄-LuFe_2.35Ga_0.65 and T₁₁-Lu₂FeGa₈ have been confirmed. The structures of the five new ternary compounds or solid solution T₂, T₃, T₄, T₅ and T₈ are determined by Rietveld refinement method.     

Semi-empirical determination of Kα1,2, Kβ1,3, and Kβ2,4 X-ray natural line widths for various elements between 29 ≤ Z ≤ 74 at 123.6 keV

Abstract

In this study, K_α1,2, K_β1,3, and K_β2,4 X-ray natural line widths for various elements were determined semi-empirically at 123.6?keV by using K shell fluorescence yields obtained from energy dispersive X-ray fluorescence measurements. The obtained results contribute to a database for the development of new theoretical models of atomic structure, radiation shielding materials, and designing new technological devices related to the structural analysis of materials. The obtained results were compared with the literature, while new fitting polynomials for the studied parameters were acquired. The results showed that the natural linewidths of K X-ray lines fit fourth-order polynomials except for K_β2,4.     

Mutual transformations between the P–Q,Q–P,and generalized Weyl ordering of operators

Based on the generalized Weyl quantization scheme, which relies on the generalized Wigner operator Ok （p, q） with a real k parameter and can unify the P-Q, Q-P, and Weyl ordering of operators in k = 1, - 1,0, respectively, we find the mutual transformations between 6 （p - P） （q - Q）, （q - Q） 3 （p - P）, and （p, q）, which are, respectively, the integration kernels of the P-Q, Q-P, and generalized Weyl quantization schemes. The mutual transformations provide us with a new approach to deriving the Wigner function of quantum states. The - and - ordered forms of （p, q） are also derived, which helps us to put the operators into their - and - ordering, respectively.     

Gauge-theoretic invariants for topological insulators: a bridge between Berry,Wess–Zumino,and Fu–Kane–Mele

We establish a connection between two recently proposed approaches to the understanding of the geometric origin of the Fu–Kane–Mele invariant \(\mathrm {FKM}\in \mathbb {Z}_2\), arising in the context of two-dimensional time-reversal symmetric topological insulators. On the one hand, the \(\mathbb {Z}_2\) invariant can be formulated in terms of the Berry connection and the Berry curvature of the Bloch bundle of occupied states over the Brillouin torus. On the other, using techniques from the theory of bundle gerbes, it is possible to provide an expression for \(\mathrm {FKM}\) containing the square root of the Wess–Zumino amplitude for a certain U(N)-valued field over the Brillouin torus. We link the two formulas by showing directly the equality between the above-mentioned Wess–Zumino amplitude and the Berry phase, as well as between their square roots. An essential tool of independent interest is an equivariant version of the adjoint Polyakov–Wiegmann formula for fields \(\mathbb {T}^2 \rightarrow U(N)\), of which we provide a proof employing only basic homotopy theory and circumventing the language of bundle gerbes.     

Cyclopropane-d6: The C–D Stretching Bands ν6and ν8at High Resolution

The two infrared active C–D stretching bands ν₆and ν₈of C₃D₆were recorded on a large Fourier transform spectrometer with a linewidth close to the Doppler–Fizeau limit. The perpendicular band of theE′ vibration ν₈near 2209.6 cm⁻¹is found to be highly perturbed by anharmonic resonances with the states ν₇+ 3ν₁₄, ν₇+ ν₉+ ν₁₄, and ν₄+ ν₁₀+ ν₁₄, and by aJ_x,yCoriolis-type interaction with an unidentified[formula]state. In contrast, the structure of the parallel band of the[formula]vibration ν₆near 2336.7 cm⁻¹appears to be relatively unperturbed. Spectroscopic constants are reported for the two fundamentals and for some of the perturbers of the ν₈state.     

Reflection–refraction of attenuated waves at the interface between a thermo-poroelastic medium and a thermoelastic medium

Phenomenon of reflection and refraction is considered at the plane interface between a thermoelastic medium and thermo-poroelastic medium. Both the media are isotropic and behave dissipative to wave propagation. Incident wave in thermo-poroelastic medium is considered inhomogeneous with deviation allowed between the directions of propagation and maximum attenuation. For this incidence, four attenuated waves reflect back in thermo-poroelastic medium and three waves refract to the continuing thermoelastic medium. Each of these reflected/refracted waves is inhomogeneous and propagates with a phase shift. The propagation characteristics (velocity, attenuation, inhomogeneity, phase shift, amplitude, energy) of reflected and refracted waves are calculated as functions of propagation direction and inhomogeneity of the incident wave. Variations in these propagation characteristics with the incident direction are illustrated through a numerical example.     

Identity period and thermal expansion coefficient for rare-earth hexaborides at temperatures of 5–320 K

The temperature dependences of the lattice spacing and thermal expansion coefficient for five hexaborides MB₆ (M=Ce, Pr, Nd, Gd, and Tb) are experimentally investigated.     

On the pyroelectricity of DKDP single crystals and PZT-40 ceramics at 1.5–30 K

By analyzing experimental data, the lowest modes that are responsible for pyroelectricity in DKDP single crystals (87.3 and 201.6 cm^?1) and in PZT-40 ferroelectric ceramics (20.7, 54.75, and 171.3 cm^?1) are determined. A set of physical mechanisms that occur in real polar dielectrics that are piroelectrically active in the temperature range 0–30 K is discussed; and methods of their identification, separation, and determination of quantitative characteristics for each component of spontaneous polarization are shown.     

Correlation between mechanical,thermal and electronic properties in Zr–Ni,Cu amorphous alloys

We show that mechanical properties (stiffness and hardness) of Zr–Ni, Cu amorphous alloys increase linearly with Ni, Cu content over a wide composition range (22?≤?x _Ni,Cu?≤?65 at%). This correlates with the observed increase in the Debye temperatures and densities with x and shows that the strength of interatomic bonding increases with x in these alloys. Accordingly, the thermal stability (e.g. the crystallization and glass transition temperatures) of these alloys also increases with x. Since the electronic density of states at the Fermi level decreases linearly with x within the same x-range, a very simple relationship exists between the electronic structure and mechanical and thermal properties. We also deduce the mechanical properties of hypothetic amorphous Zr and briefly discuss the possibility of its preparation.     

Phase diagram of the Al–Er–Mo ternary system at 873 K

The phase relationship in the Al–Er–Mo ternary system at 873 K has been investigated based on the equilibrated method mainly by means of X-ray powder diffraction and scanning electron microscopy. The existence of 10 binary compounds and two ternary compounds has been confirmed. The results present that the isothermal section at 873 K is governed by 15 single-phase regions, 29 two-phase regions and 15 three-phase regions. By using the phase-disappearing method, Al₈Mo₃ has a narrow homogeneity range (from 72 to 73 at% Al), while the homogeneity range of AlMo₃ is from 21% to 28.5% at% Al. Also, the maximum solubility of Al in Mo is about 16 at%.     

UV–Vis and NMR spectroscopic investigations on effective and selective non-covalent interactions between fullerenes and calix[6]arene

Ground state non-covalent interactions between a macro cyclic calixarene receptor, namely, 4-tert-butylcalix[6]arene (1), and fullerenes (C₆₀ and C₇₀) were studied in toluene medium by absorption spectrophotometric method. Absorption band due to the charge transfer (CT) transition have been observed in the visible region between fullerenes and 1. Utilizing the CT absorption bands, various important physicochemical parameters like oscillator strength, resonance energy, transition dipole strength of the fullerene-1 complexes and ionization potential of 1 is determined in present investigations. From Jobs method of continuous variation, it is observed that both C₆₀ and C₇₀ form stable 1:1 complexes with 1. The most fascinating feature of the present study is that 1 binds selectively C₇₀ compared to C₆₀ as obtained from binding constant (K) data of C₆₀–1 (K_C60–1) and C₇₀–1 (K_C70–1) complexes, i.e., K_C60–1 = 32,400 dm³·mol^? 1 and K_C70–1 = 110,000 dm³.mol^? 1 and selectivity (K_C70–1/K_C60–1) = 3.4. ¹H NMR analysis provides very good support in favor of strong binding between C₇₀ and 1.     

Molecular and atomic adsorption states of oxygen on Cu(111) at 100–300 K

Adsorption states of oxygen on Cu(111) at 100–300 K were investigated by means of HREELS. Two molecular species were characterized by different OO stretching frequencies (v(OO)) at 610 cm⁻¹ and 820–870 cm⁻¹, which are assigned to the peroxo-like species (O²⁻₂) adsorbed in a bridged form and the one in a bidentate form bound on an atop site, respectively. The bridged peroxo species is preferred at the low coverage and the atop peroxo species becomes dominant at the higher coverage. In addition to the peaks due to the molecular oxygen, a peak assigned to v(CuO) of atomic oxygen was observed at 370 cm⁻¹ at the high coverage. The frequency of this mode was higher than the frequency reported for Cu(111) exposed to oxygen above 300 K, indicating that the adsorption state of atomic oxygen formed at 100 K is different from that above 300 K. The v(OO) modes became faint after annealing to 170 K because of O₂ dissociation. The v(CuO) mode of the atomic oxygen formed at 100 K remained up to 230 K and disappeared after annealing to 300 K. No desorption of O₂ was detected on annealing to 300 K. It was also found that vibrational spectra for adsorbed NH₃ are influenced by the adsorption states of atomic oxygen on Cu(111).     

Effect of the surface oxidization and nitridation on the normal spectral emissivity of titanium alloys Ti–6Al–4V at 800–1100 K at a wavelength of 1.5 μm

This work strived to model the effect of surface oxidization and nitridation on the normal spectral emissivity of Ti–6Al–4V alloys at a temperature range of 800–1100 K and a wavelength of 1.5 μm. In experiments, the detector was as close to perpendicular to the surface of the specimens as possible so that only the normal spectral emissivity was measured. Two thermocouples were symmetrically welded near the measuring area for accurate measuring and monitoring of the temperature at the surface of the specimen. The specimens were heated for 6 h at a certain temperature. During this period, the normal spectral emissivity values were measured once every 1 min during the initial 180 min, and once every 2 min thereafter. The measurements were made at certain temperatures from 800 to 1100 K in intervals of 20 K. One strong oscillation in the normal spectral emissivity was observed at each temperature. The oscillations were formed by the interference between the radiation stemming from the oxidization and nitridation layer on the specimen surface and radiation from the substrate. The uncertainty in the normal spectral emissivity caused only by the surface oxidization and nitridation was found to be approximately 9.5–22.8%, and the corresponding uncertainty in the temperature generated only by the surface oxidization and nitridation was approximately 6.9–15.5 K. The model can reproduce well the normal spectral emissivity, including the strong oscillation that occurred during the initial heating period.     

Densities and mixing volumes of mixtures of fluorobenzene, α,α,α-trifluorotoluene, tert-butylmethyl ether, and ethanol at temperature 298.15 K and pressure 0.1 MPa

The volumetric properties were evaluated from density data for the binary mixtures of (fluorobenzene + tert-butylmethyl ether), (α,α,α-trifluorotoluene + tert-butylmethyl ether), (tert-butylmethyl ether + ethanol), and the ternary mixtures of (fluorobenzene + tert-butylmethyl ether + ethanol) and (α,α,α-trifluorotoluene + tert-butylmethyl ether + ethanol). The observed densities were obtained by means of a vibrating-tube densimeter at the temperature 298.15 K and the pressure 101 kPa.The excess molar volumes of the ternary mixtures were estimated from binary solution data using several empirical equations with mean standard deviation less than 0.03 cm³·mol^-1. Stable chemical cross-associations among the molecules forming the mixtures were revealed.     

The isothermal section of the Tb–Co–Cr ternary system at 873 K

The isothermal section of the phase diagram of the Tb–Co–Cr ternary system at 873?K was investigated by means of X-ray diffraction, metallography, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. Ternary phases and their lattice parameters as a function of composition of solid solution were systematically studied. The existence of one ternary phase reported previously was confirmed. The ternary compound Tb(Co,?Cr)₁₂ crystallizes with ThMn₁₂-type structure, space group I4/mmm. The linear homogeneity range along the line of 7.69 at.% Tb in TbCo_{12? x} Cr _x was found to be about x?=?3.6–5.7, i.e., 27.7–43.8 at.% Cr. The lattice parameters are a?=?0.8326–0.8352?nm and c?=?0.4709–0.4740?nm. The maximum solid solubilities of Cr in Tb₂Co₁₇, TbCo₃, and TbCo₂ are about 20.0, 8.2, and 7.9 at.%, respectively.