Experimental Investigation and Thermodynamic Assessment of Phase Equilibria in the Ag-Au-Sn System

The phase equilibria of the Ag-Au-Sn ternary system at 300°C, 400°C, and 500°C were experimentally investigated. The equilibrium compositions of the equilibrated alloys and diffusion couples between Ag _x Au_1−x (x = 0.25, 0.75) alloys and liquid Sn were determined by electron probe microanalysis (EPMA). The phase transformations were investigated by means of differential scanning calorimetry (DSC). Based on the experimental data of phase equilibria and thermodynamic properties, the thermodynamic assessment of the Ag-Au-Sn system was carried out based on the calculation of phase diagrams (CALPHAD) method. The thermodynamic parameters for describing the Gibbs free energies of the phases were optimized, and reasonable agreement between the calculations and experimental data was obtained.     

The Effect of Sb Addition on Sn-Based Alloys for High-Temperature Lead-Free Solders: an Investigation of the Ag-Sb-Sn System

Today there is renewed interest in alloys belonging to the Sb-Sn-X (X = Cu, Ag, Bi) ternary systems and their phase equilibria, phase transformations, and thermodynamic properties because of their possible use as high-temperature lead-free solders in the electronics industry. The integral mixing enthalpy of Ag-Sb-Sn liquid alloys has been measured along five different sections (Ag_0.25Sn_0.75, Ag_0.50Sn_0.50, Sb_0.30Sn_0.70, Sb_0.50Sn_0.50, and Sb_0.70Sn_0.30) at 530°C, 600°C, and 630°C, using a high-temperature Calvet calorimeter by dropping pure elements (Ag or Sb) in the binary alloy liquid bath. The ternary extrapolation models of Muggianu and Toop were used to calculate the integral enthalpy of mixing and to compare measured and extrapolated values. Selected ternary alloys have been prepared for thermal investigation by using a differential scanning calorimeter at different heating/cooling rates in order to clarify the temperature of the invariant reactions and the crystallization path.     

Theoretical evaluation of InTIP,InTIAs, and InTISb As longwave infrared detectors

We have evaluated three III-V semiconductor alloys—In_1−xTl_xP (ITP), In_1−xTl_xAs (ITA), and In_1−xTl_xSb (ITS)—as possible candidates for future long-wave infrared (LWIR) detector materials. The cohesive energies, elastic constants, band structures, electron mobilities, and phase diagrams are calculated and are compared to those of Hg_1−xCd_xTe (MCT) alloys. The band gaps of all three III-V alloys change from negative to positive values as the alloy composition x decreases from 1 to 0. The x values for the 0.1-eV gap are estimated to be 0.67, 0.15, and 0.08, respectively, for ITP, ITA, and ITS. While both ITP and ITA form stable zincblende solid solutions for all alloy compositions, zincblende ITS is stable only for a range of x less than 0.15. The complication of the phase diagram in ITS is caused by the existence of a stable CsCl phase for pure TISb. The alloy mixing enthalpies for ITP and ITA are comparable to those in MCT, and their phase diagrams should be qualitatively similar, characterized by simple lensshape liquidus and solidus curves. Both ITP and ITA have considerably larger cohesive energies and elastic constants than those of MCT, indicating that they are structurally robust. At a 0.1-eV gap, the band structures near the gap and the electron mobilities in ITP, ITA, and ITS are also found to be comparable to those of MCT. Since the lattice constants of TIP and TIAs are less than 2% larger than the respective values in InP and InAs, the latter should provide natural substrates for the growth of active LWIR alloys and offer a potential to integrate the detector array and read-out circuit.     

The temperature-composition phase diagram and the miscibility gap of Hg1-xCdxTe solid solutions by dynamic mass-loss measurements

The dynamic mass-loss technique has been employed to measure Hg partial pressures over Te-saturated Hg_1-xCd_xTe solid solutions with x = 0.40, 0.54, and 0.70 in the 10^-1 to 10^-4 atm range. The relative chemical potentials of HgTe in Hg_1-xCd_xTe solid solutions have been calculated using the measured Hg partial pressures at temperatures below 413°C, and fitted into an analytical expression. A Gibbs-Duhem integration yielded the relative chemical potentials of CdTe. By combining the relative chemical potentials of the binary components HgTe and CdTe, an expression for the Gibbs free energy of mixing was derived. The binodal (miscibility gap) and spinodal curves of the Hg_1-xCd_xTe solid solutions have been established with the critical temperature and composition of 221°C and Hg_0.40Cd_0.60Te.     

Heterogeneous AgxCdyS-AgCd Nanoparticles with Chiral Bias for Enhanced Photocatalytic Efficiency

Stereoselective catalysis is common in living systems mediated by natural nanoenzymes. However, few artificial nanomaterials are developed for enantioselective and stereoselective catalysis. In this study, Ag_xCd_yS-AgCd nanoparticles (NPs) with specific heterojunctions, strong chiral optical activities, and excellent enantioselective catalytic ability are constructed. Similar to photosensitive enzymes, Ag_xCd_yS-AgCd NPs stabilized with l -/d -penicillamine (l -/d -Ag_xCd_yS-AgCd NPs) can serve as photocatalysts, which show the highest catalytic efficiency toward the photodegradation of methyl blue compared with that of Ag₂S and CdS NPs and lead to 50% enhancement of photoconversion efficiency of Cr⁶⁺ to Cr³⁺ as well. Moreover, attributed to the higher chiral preference between l -Ag_xCd_yS-AgCd NPs and l -Tartaric acid (l -TA), d -Ag_xCd_yS-AgCd NPs and d -Tartaric acid (d -TA), the photoreduction efficiency of Cr⁶⁺ to Cr³⁺ mediated by l -Ag_xCd_yS-AgCd NPs with l -TA, and d -Ag_xCd_yS-AgCd NPs with d -TA samples is enhanced as high as 30% compared with the samples of l -Ag_xCd_yS-AgCd NPs with d -TA, and d -Ag_xCd_yS-AgCd NPs with L-TA. This study establishes a versatile way to construct enantioselective inorganic catalysts for biocatalysis, biomedicine, and other applications.     

Electrophysical properties of solid solutions of silver in PbTe

The thermopower coefficient α₀ and the electrical conductivity σ of Pb_{1 − x} Ag _x Te solid solutions, where x = (0–0.007), are measured at T = 300 K. The hole concentration p is calculated. All samples are of the p type. With increasing silver content, α₀ decreases, while p and σ increase. For undoped crystals, α₀ = 251.0 μV/K, p = 1.1 × 10¹⁸ cm⁻³, and σ = 165 Ω⁻¹ cm⁻¹. At the silver-solubility limit for x = 0.007, α₀ = 193.8 μV/K, p = 2.3 × 10¹⁸ cm⁻³, and σ = 216 Ω⁻¹ cm⁻¹. The hole concentration in all samples is much lower than the concentration of introduced silver atoms. The hole gas in Pb_{1 − x} Ag _x Te solid solutions is weakly degenerate in the entire silver-concentration range.     

Theory of molecular optoelectronics. X: Calculations for MBANP and NMBA

Components of the crystal quadratic susceptibility tensor x⁽²⁾ for second-harmonic generation are calculated for the title compounds 2-(α-methyl benzylamino)-5-nitropyridine (MBANP) and 4-nitro-4'-methyl(benzylidene aniline) (NMBA). Input data are the crystal structure and refractive indices and CNDO hyperpolarizabilities. The calculations also yield effective polarisabilities and local electric fields. Susceptibility components reach 66 pm V^?1 in MBANP and 27 pm V^?1 in NMBA in the crystal axes; agreement with experiment is poor for MBANP but satisfactory for NMBA. These features seem to reflect the better defined charge transfer axis in NMBA. Screened dipole–dipole interactions calculated from CNDO dipole moments stabilise MBANP by 70 kJ mol^?1 and NMBA by 20 kJ mol^?1 and imply permanent electric fields of a few GV m^?1.     

Physical Properties of Sn<Subscript>96.5</Subscript>Ag<Subscript>3.5</Subscript>-Based Solders with Additions of Bi,Ge, and In

The melting temperature, electrical resistivity, surface tension, and density of the (Sn_0.965Ag_0.035)_95.17Bi_4.83, (Sn_0.965Ag_0.035)_95.17Bi_4.73Ge_0.1, and (Sn_0.965Ag_0.035)₉₄-Bi₂In₄ alloys have been studied in comparison with the Sn₆₀Pb₄₀ and Sn_96.5Ag_3.5 binary alloys (all wt.%). The electrical conductivity of the solid alloys based on Sn_96.5Ag_3.5 is comparable to that of the Sn₆₀Pb₄₀ alloy. The wetting behavior on Cu and Ni surfaces has been investigated in a wide temperature interval. It is established that the addition of Bi to Sn_96.5Ag_3.5 decreases the surface tension and improves the wetting properties of the alloy. The addition of a small quantity of Ge to the Sn-Ag-Bi alloy did not improve the wetting behavior on either Cu or Ni surfaces. The wetting ability of the (Sn_0.965Ag_0.035)₉₄Bi₂In₄ alloy was slightly worse as compared with (Sn_0.965Ag_0.035)_95.17Bi_4.83.     

Lowering of Sn−Sb alloy melting points caused by substrate dissolution

Sn−5wt.%Sb alloy is used for the soldering of ceramic devices. Reaction couples, dissolution, and differential scanning calorimetry experiments are conducted to examine the interfacial reactions and dissolution of Ag substrates with the molten Sn−5wt.%Sb solder. One intermetallic compound, Ag₃Sn, is formed at 260°C at the Sn−5wt.%Sb/Ag contact. With the intake of Ag from the substrate, the binary Sn−5wt.%Sb alloy becomes a ternary (Sn−5wt.%Sb)_100−xAg_x melt. It is found that a small amount of Ag addition significantly lowers the melting point of the Sn−5wt.%Sb alloy. This phenomenon is illustrated with the (Sn−5wt.%Sb)_100−xAg_x isoplethal section.     

Power factor improvement of delafossite CuAlO2 by liquid-phase sintering with Ag2O addition

Thermoelectric delafossite (CuAlO₂)_1−x(Ag₂O)_x with 0<x<0.06 is prepared at three different sintering temperatures, 1323 K, 1373 K, and 1473 K. The samples are obtained from a mixture of CuO, Al₂O₃, and additive Ag₂O powders. The mixture is ground and then pressed with uniaxial pressure into pellets. Differential scanning calorimetry and X-ray diffraction spectroscopy show that the sintering temperature to synthesize delafossite CuAlO₂ with Ag₂O addition is below 1473 K. X-ray diffraction patterns show the major phase of delafossite 3R-CuAlO₂ along with a trace amount of 2H-CuAlO₂. A small amount of the Ag phase is present in the samples depending on the amount of Ag₂O addition and sintering temperature. Energy dispersive spectroscopy and backscattered electron image analyses show that the Ag phase is segregated around the grain boundary. Liquid-phase sintering is used to explain the growth mechanism. The CuAlO₂ samples with Ag₂O addition obviously exhibit enhanced bulk density, grain size, and electrical conductivity. The highest power factor (PF), obtained by CuAlO₂ with 2 at% of Ag₂O sintered at 1373 K, is 8.23×10⁻⁵ W/(m K²) at 873 K. Hence, our findings show an improvement for delafossite CuAlO₂ by Ag₂O addition.     

Highly Stable Nanoporous Sulfur‐Bridged Covalent Organic Polymers for Carbon Dioxide Removal

Carbon dioxide capture and separation requires robust solids that can stand harsh environments where a hot mixture of gases is often found. Herein, the first and comprehensive syntheses of porous sulfur‐bridged covalent organic polymers (COPs) and their application for carbon dioxide capture in warm conditions and a wide range of pressures (0–200 bar) are reported. These COPs can store up to 3294 mg g^?1 of carbon dioxide at 318 K and 200 bar while being highly stable against heating up to 400 °C. The carbon dioxide capacity of the COPs is also not hindered upon boiling in water for at least one week. Physisorptive binding is prevalent with isosteric heat of adsorptions around 24 kJ mol^?1. M06–2X and RIMP2 calculations yield the same relative trend of binding energies, where, interestingly, the dimer of triazine and benzene play a cooperative role for a stronger binding of CO₂ (19.2 kJ mol^?1) as compared to a separate binding with triazine (13.3 kJ mol^?1) or benzene (11.8 kJ mol^?1).     

Synthesis and Thermoelectric Properties of LAST System Bulk Materials: Substitution of Sulfur for Tellurium

Nonstoichiometric lead-antimony-silver-tellurium (LAST) system thermoelectric bulk materials Ag_0.8Pb_22.5SbTe_20?x S _x (x?=?0 to 8.0) were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS). The electrical and thermal transport properties were investigated in the temperature range of 300?K to 700?K. The x-ray diffraction (XRD) results indicated that sulfur entered the PbTe during MA process, but gradually precipitated in the sintering process in the form of PbS from the PbTe matrix when the sulfur content was changed from x?=?2.0 to x?=?8.0. It was confirmed that the addition of sulfur effectively reduced the lattice thermal conductivity. A low thermal conductivity of 0.83?W?m^?1?K^?1 at 673?K was obtained for the Ag_0.8Pb_22.5SbTe₁₂S₈ sample. Benefiting from the high electrical conductivity, the Ag_0.8Pb_22.5SbTe₁₈S₂ sample reached a maximum ZT value of ??0.97 at 673?K, which is 32% higher than its counterpart without sulfur substitution.     

Electrochemical Properties of Joints Formed Between Sn-9Zn-1.5Ag-1Bi Alloys and Cu Substrates in a 3.5 wt.% NaCl Solution

The electrochemical properties of the joints formed between Sn-9Zn-1.5Ag-1Bi alloys and Cu substrates in a 3.5 wt.% NaCl solution have been investigated by potentiodynamic polarization, X-ray diffraction, and scanning electron microscopy. For the Sn-9Zn-1.5Ag-1Bi/Cu joints in a 3.5 wt.% NaCl solution, corrosion current (I _corr), corrosion potential (E _corr) and corrosion resistance (R _p) are 2.46 × 10⁻⁶ A/cm², −1.18 V, and 7.54 × 10³ Ωcm², respectively. Cu₆Sn₅, Cu₅Zn₈, and Ag₃Sn are formed at the interface between the Sn-9Zn-1.5Ag-xBi solder alloy and Cu substrate. The corrosion products of ZnCl₂, SnCl₂ and ZnO are formed at the Sn-9Zn-1.5Ag-xBi/Cu joints after polarization in a 3.5 wt.% NaCl solution. Pits are also formed on the surface of the solder alloys.     

Magnetic properties of Pb1−x GexTe alloys doped with ytterbium

Temperature dependences of magnetic susceptibility and magnetic-field dependences of magnetization in the Pb_1?x?y Ge_xYb_yTe (0≤x≤0.02, y≤0.065) solid solutions were studied. It was found that diamagnetic response was replaced by the Curie-Weiss paramagnetic response as temperature decreased. This indicates that Yb³⁺(4f ¹³) magnetic ions are present in the alloys. The magnetic ion concentration and the occupancy of the Yb-induced impurity band were determined from the experimental data.     

H2xMnxSn3‐xS6 (x = 0.11–0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH Conditions

The H_2xMn_xSn_3‐xS₆ (x = 0.11–0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K_2xMn_xSn_3–xS₆ (x = 0.5–0.95) (KMS‐1) upon treating it with highly acidic solutions. We demonstrate that LHMS‐1 has enormous affinity for the very soft metal ions such as Hg²⁺ and Ag⁺ which occurs via a rapid ion exchange process. The tremendous affinity of LHMS‐1 for Hg²⁺ is reflected in very high distribution coefficient K_d^Hg values (>10⁶ mL g^?1). The large affinity and selectivity of LHMS‐1 for Hg²⁺ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO₃ acids. LHMS‐1 is significantly more selective for Hg²⁺ and Ag⁺ than for the less soft cations Pb²⁺ and Cd²⁺. The Hg²⁺ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg–S bonds as suggested by pair distribution function (PDF) analysis. LHMS‐1 could decrease trace concentrations of Hg²⁺ (e.g. <100 ppb) to well below the acceptable limits for the drinking water in less than two min. Hg‐laden LHMS‐1 shows a remarkable hydrothermal stability and resistance in 6 M HCl solutions. LHMS‐1 could be regenerated by treating Hg‐loaded samples with 12 M HCl and re‐used without loss of its initial exchange capacity.     

Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol . dm^-3 FeSO₄ at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol . dm^-3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional to both [Fe²⁺]² and po₂, exhibiting an activation energy of 51.6 . kJ mol^-1. In another path the reaction rate was proportional to [Fe²⁺]², [SO_4-], and po₂ with an activation energy of 144.6 kJ . mol^-1. A reaction mechanism in which the SO_4- ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol . dm^-3, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]² and Po₂, and was also affected by [H⁺] and [SO_2- ⁴]. The decrease in [H⁺] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation reaction of Fe (II).     

Solid state intermetallic compound growth between copper and high temperature,tin-rich solders—part I: Experimental analysis

An experimental study was performed which examined the solid state growth kinetics of the interfacial intermetallic compound layers formed between copper and the high temperature, tin-rich solders 96.5Sn-3.5Ag (wt.%) and 95Sn-5Sb. These results were compared with baseline data from the 100Sn/copper system. Both the 96.5Sn-3.5Ag and 95Sn-5Sb solders exhibited the individual Cu₃Sn and Cu₆Sn₅ layers at the interface; the thickness of the Cu₃Sn layer being a function of the aging time and temperature. The total thickness of the intermetallic compound layer formed in the 96.5Sn-3.5Ag solder/copper couple showed a mixture of linear and √t dependencies at the lower temperatures of 70,100, and 135°C, and a t^0.42 dependence at 170 and 205°C. The combined apparent activation energy was 59 kJ/mol, the Arrhenius plot showed a knee between the low and high temperature data. The total layer thickness of the 95Sn-5Sb/copper system exhibited √t dependence at the three lower temperatures and t^0.42 growth kinetics at 170 and 205°C. The combined apparent activation energy was 61 kJ/mol.     

Structure–Thermodynamic‐Property Relationships in Cyanovinyl‐Based Microporous Polymer Networks for the Future Design of Advanced Carbon Capture Materials

Nitrogen‐rich solid absorbents, which have been immensely tested for carbon dioxide capture, seem until this date to be without decisive molecular engineering or design rules. Here, a family of cyanovinylene‐based microporous polymers synthesized under metal‐catalyzed conditions is reported as a promising candidate for advanced carbon capture materials. These networks reveal that isosteric heats of CO₂ adsorption are directly proportional to the amount of their functional group. Motivated by this finding, polymers produced under base‐catalyzed conditions with tailored quantities of cyanovinyl content confirm the systematical tuning of their sorption enthalpies to reach 40 kJ mol^?1. This value is among the highest reported to date in carbonaceous networks undergoing physisorption. A six‐point‐plot reveals that the structure–thermodynamic‐property relationship is linearly proportional and can thus be perfectly fitted to tailor‐made values prior to experimental measurements. Dynamic simulations show a bowl‐shaped region within which CO₂ is able to sit and interact with its conjugated surrounding, while theoretical calculations confirm the increase of binding sites with the increase of Ph? C?C(CN)? Ph functionality in a network. This concept presents a distinct method for the future design of carbon dioxide capturing materials.     

Analysis of nitride storage non-volatile memories with HfSiOx blocking dielectric and TiN metal gate for low power embedded applications

Nitride storage non-volatile memories with hafnium silicate (HfSiO_x) blocking dielectric and titanium nitride (TiN) metal gate aimed at low power embedded applications beyond the 45 nm node, have been fabricated and investigated. In addition to presenting the typical figures of merit of flash memories, the scalability of the devices has been assessed. We have also investigated the physical origin of the observed memory features.     

Effect of Homogenization on the Indentation Creep of Cast Lead-Free Sn-5%Sb Solder Alloy

Creep behavior of cast lead-free Sn-5%Sb solder in unhomogenized and homogenized conditions was investigated by long time Vickers indentation testing under a constant load of 15 N and at temperatures in the range 321–405 K. Based on the steady-state power law creep relationship, the stress exponents were found for both conditions of the material. The creep behavior in the unhomogenized condition can be divided into two stress regimes, with a change from the low-stress regime to the high-stress regime occurring around 11.7 × 10⁻⁴ < (H _V /E) < 18 × 10⁻⁴. The low stress regime activation energy of 54.2 kJ mol⁻¹, which is close to 61.2 kJ mol⁻¹ for dislocation pipe diffusion in the Sn, and stress exponents in the range 5.0–3.5 suggest that the operative creep mechanism is dislocation viscous glide. This behavior is in contrast to the high stress regime in which the average values of n = 11.5 and Q = 112.1 kJ mol⁻¹ imply that dislocation creep is the dominant deformation mechanism. Homogenization of the cast material resulted in a rather coarse recrystallized microstructure with stress exponents in the range 12.5–5.7 and activation energy of 64.0 kJ mol⁻¹ over the whole ranges of temperature and stress studied, which are indicative of a dislocation creep mechanism.