Alloying behavior of zinc with rare earth metals: The Dy–Gd–Zn system

The isothermal section at 400 °C of the Dy–Gd–Zn system was studied, and the vertical sections at the Dy/Gd ratio=1 was investigated. The experimental techniques used were Differential Thermal Analysis (DTA), X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) coupled with electron probe microanalysis (EPMA-EDX).No ternary compounds were found in the system. As regard to the intermetallic phases, the (Dy,Gd)Zn, (Dy,Gd)Zn₂, (Dy,Gd)Zn₃, (Dy,Gd)₃Zn₁₁, (Dy,Gd)₁₃Zn₅₈, (Dy,Gd)₂Zn₁₇ and (Dy,Gd)Zn₁₂ solid solutions form in the full field of composition, while the Gd₃Zn₂₂ compound did not show dysprosium dissolution.     

Thermodynamic assessment of the V–Zn system supported by key experiments and first-principles calculations

The V–Zn system was investigated by a combination of CALPHAD modeling with key experiments and first-principles calculations. Based on a critical literature review, one diffusion couple and nine alloys were designed to reinvestigate the stabilities of the phases reported in the literature. The samples were annealed and cooled under different conditions, followed by examination with X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectrometry. Four phases ((V), (Zn), V Zn₃ and V ₄Zn₅) were confirmed to exist in the phase diagram, while V Zn₁₆ and V ₃Zn were not observed. By means of first-principles calculations, the enthalpies of formation for V Zn₃ and V ₄Zn₅ were computed to be −4.55 kJ mol-atoms⁻¹ and −4.58 kJ mol-atoms⁻¹, respectively. A set of self-consistent thermodynamic parameters for this system was obtained by considering the reliable experimental phase diagram data and the enthalpies of formation acquired from first-principles calculations. The calculated V–Zn phase diagram agrees well with the experimental data.     

Isothermal section of Mg-Zn-Zr ternary system at 345 ° C

Isothermal section of Mg-Zn-Zr ternary system at 345 ^°C has been determined by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy assisted with energy dispersive X-ray spectroscopy using a series of Mg-Zn-Zr alloys. The results show that there exist three intermetallic compounds ZnZr, Zn₂Zr₃, (Mg,Zn)₂Zr, and a liquid phase in equilibrium with the α-Mg phase. The presence of two other three-phase regions in equilibrium, Liquid+MgZn+(Mg,Zn)₂Zr and MgZn+Mg₂Zn₃+(Mg,Zr)Zn₂, has also been confirmed. The addition of Zn can significantly increase the solubility of Zr and vice-versa in the α-Mg matrix.     

Digitally-controlled array of solid-state microcoolers for use in surgery

This paper presents an approach for generating a well-defined cooling pattern over an area of tissue. An array of solid-state microcoolers is used, which could be included in a probe that provides local cooling. This medical instrument can be used for removal of scar tissue in the eye or for the rapid stopping of bleeding due to micro-cuts, which makes it a useful tool to medical doctors and could make surgery more secure to the patient. The array of microcoolers is composed of 64 independent thermo-electric elements, each controlled using an integrated circuit designed in CMOS. The independent control allows the flexible programming of the surface temperature profile. This type of control is very suitable in case abrupt temperature steps should be avoided. Cooling by lateral heat flow was selected in order to minimize the influence of heat by dissipation from the electronic circuits. Moreover, a thermo-electric component with lateral heat allows fabrication of the cooling elements using planar thin-film technology, lithography and wet etching on top of the silicon wafer. This approach is potentially CMOS compatible, which would allow for the fabrication of the thermo-electric elements on top of a pre-fabricated CMOS wafer as a post-process step. Each pixel is composed of thin-films of n-type bismuth telluride, Bi₂Te₃ and p-type antimony telluride, Sb₂Te₃, which are electrically interconnected as thermocouple. These materials have excellent thermoelectric characteristics, such as thermoelectric figures-of-merit, ZT, at room temperatures of 0.84 and 0.5, respectively, which is equivalent to power-factors, PF, of 3.62 × 10⁻³ W K⁻¹ m⁻² and 2.81 × 10⁻³ W K⁻¹ m⁻², respectively. The theoretical study presented here demonstrates a cooling capability of 15°C at room temperature (300 K ≈ 27°C). This cooling performance is sufficient to maintain a local tissue temperature at 25°C, which makes it suitable for the intended application. A first prototype was successfully fabricated to demonstrate the concept.     

Morphology and magnetic properties of electroplated Co-rich Co-Zn thin films

This work explores the microstructure and magnetic properties of electrodeposited Co-Zn thin films. Using pulse-reverse electroplating technique, Co-rich Co-Zn films are deposited 0.4–1.9 μm thick from aqueous sulfate-based baths at low temperature (55°C). The influence of current density (25–100 mA/cm²) and electrolyte Zn concentration (0–0.28 M) on the microstructure and magnetic properties are investigated. All of the Co-Zn films exhibit higher out-of-plane coercivity, as compared to in-plane. With increasing current density, the out-of-plane coercivity decreases from 50 to 40 kA/m (628–500 Oe). The influence of the Zn concentration in the electrolyte is more pronounced, affecting the grain size, film composition, and magnetic properties. The best magnetic properties were obtained from a bath with 0.21 M Zn and an average current density of 25 mA/cm², resulting in a Co₉₇Zn₃ composition and an out-of-plane coercivity of 92 kA/m (1,160 Oe).     

Calphad-type assessment of the Sb–Sn–Zn ternary system

The ternary Sb–Sn–Zn phase diagram was investigated experimentally by scanning electron microscopy (SEM) and differential thermal analysis (DTA) of long-term annealed samples. The overall composition of each sample was measured by energy-dispersive X-ray spectroscopy (EDX). The experimental results, together with additional available literature data, were used to perform a CALPHAD-type thermodynamic assessment of this ternary system. Two calculated isothermal sections (250 and 350 °C), an isopleth (x(Sn)=17.57%) and the Zn activity in liquid ternary Sb–Sn–Zn alloys at 550 °C for the composition ratio Sn/Sb=1/3 and at 650 °C for the ratio Sn/Sb=9 are presented with experimental points superimposed. The liquidus projection for the ternary Sb–Sn–Zn system is also presented. The agreement between calculated and experimental results is reasonable.     

Experimental investigation of phase equilibria in the Co–Fe–La system at 600 and 500 °C

Phase equilibria in the Co–Fe–La ternary system have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Isothermal sections at 600 (in the whole concentration region) and 500 °C (in the La-rich region) for this system have been constructed. It was shown that the ternary compound La₂(Co,Fe)₁₇ (τ) (Th₂Zn₁₇-type structure) is stable at 600 °C and has homogeneity range from 67 to 72 at.% Co. It co-exists with the majority of solid phases (αFe,Co), LaCo₁₃, LaCo₅, La₂Co₇ and La₂Co₃ at 600 °C. The LaCo₁₃ phase has the widest homogeneity region and dissolves up to 32.5 at.% Fe at 600 °C. The character of phase equilibria at 500 °C in the studied region is similar to those at solidus temperature. The character of phase equilibria at 600 °C is different from those at the solidus temperature. The main difference involves the fact that the equilibrium τ + LaCo₅ which is present in the Co–Fe–La system at solidus temperature, is absent at 600 °C. Instead, the alternative equilibrium (αFe,Co) + La₂Co₇ is present at 600 °C.     

Phase transformations and phase equilibria in the La-Ni and La-Ni-Fe systems. Part 2: Isothermal sections at 750, 600 and 500 °C

The ternary phase diagram La-Ni-Fe was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Three isothermal sections, at 750, 600 and 500 °C were constructed covering the whole concentration range. In addition, vertical sections at 15 and 35 at.% La were evaluated based on the abovementioned methods and DTA analysis. Among binary compounds, LaNi₅, La₅Ni₁₉ and La₂Ni₇ have the widest homogeneity regions. The LaNi₅ phase dissolves 19.9, 19.6 and 19.4 at.% Fe at 750, 600 and 500 °C, respectively. The solubility of Fe in La₅Ni₁₉ is 14.5, 12.1 and 8.9 at.% at 750, 600 and 500 °C, respectively. For the La₂Ni₇ phase, the Fe-solubility was found to be 13.9, 11.3 and 10.1 at.% at 750, 600 and 500 °C, respectively. The homogeneity regions of the remaining phases are much smaller. The character of phase equilibria at 750 °C in the Ni-rich region is similar to those at solidus temperature. The character of the phase equilibria at 600 and 500 °C, however, differs from those at higher temperatures. In particular, the equilibrium (γFe,Ni) + La₅Ni₁₉ which is present in the La-Ni-Fe system at solidus temperature and 750 °C, is absent at 600 and 500 °C. Instead, the alternative equilibrium LaNi₅ + La₂Ni₇ is present at 600 °C. Furthermore, the equilibrium La₂Ni₇ + La₂Ni₃ which is present at solidus temperature, is replaced by the alternative equilibrium (αFe) + La₇Ni₁₆ at lower temperatures.     

The B-rich side of the B–C phase diagram

The melting behavior of ß-boron at the boron-rich side of the B–C binary phase diagram is a long standing question whether eutectic or peritectic. Floating zone experiments have been employed to determine the melting type on a series of C-containing feed-rods prepared by powder metallurgy and sinter techniques. Melting point data as a function of carbon-content clearly yielded a peritectic reaction isotherm: L+B_4+δC=(ßB). The partition coefficient of carbon is ~2.6. The experimental melting point data were used to improve the existing thermodynamic modeling of the system B–C. Relative to the thermodynamically accepted melting point of pure ßB (T_M=2075 °C), the calculated reaction isotherm is determined at 2100.6 °C, a peritectic point at 0.75 at% C and a maximum solid solubility of 1.43 at% C in (ßB) at reaction temperature. With the new melting data the refractory system Hf–B–C has been recalculated and the liquidus surface is presented. The influence of the melting behavior of (ßB) on the phase reactions in the B-rich corner of M–B–C diagrams will be discussed and demonstrated in case of the Ti–B–C system.     

Phase equilibria investigation of the Al–Ni–Er ternary system at 600 °C and 700 °C

Phase equilibria of the Al–Ni–Er ternary system at 600 °C and 700 °C were experimentally investigated through X-ray diffraction, scanning electron microscopy and electron probe micro-analysis. New ternary compounds τ11-AlNiEr₄, τ12-AlNi₆Er₁₃ and τ13-AlNi₂Er were discovered in the equilibrated alloy samples. Compounds τ5, τ10, τ13, AlNi₃, AlNi, Al₃Ni₂, Al₂Er, ErNi₂ and ErNi₅ have a certain range of solid solubility. The solid solubility of Ni in Al₂Er is 10.3 at.% and 11.25 at.% at 600 °C and 700 °C, respectively. The solid solubility of Al in ErNi₂ is 3.6 at.% and 5.09 at.% at 600 °C and 700 °C, respectively. Experiments have verified that CaCu₅–ErNi₅ is a continuous solid solution and the maximum solubility of Al is up to 33.33 at.%.     

Experimental determination of phase equilibria in the Y–Co–Ti system through diffusion couples and equilibrium alloys

Two isothermal sections of the Y–Co–Ti system at 600 °C and 800 °C were constructed for the first time using the diffusion couple technique and the equilibrium alloy method in combination with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron probe microanalysis (EPMA), and X-ray diffraction (XRD). The stable ternary intermetallic compound YCo_12-xTi_x was detected and was confirmed to have a ThMn₁₂-type structure. The composition range in this ternary compound was measured to be 8.3–18.2 at.% at 600 °C and 8.9–19.1 at.% at 800 °C, resulting in the stable formation of YCo_12-xTi_x with x = 1.1–2.4 at 600 °C and x = 1.2–2.5 at 800 °C. The experimental results measured by EDS and EPMA demonstrate that the maximum solubilities of Ti in YCo₂, YCo₃, Y₂Co₇ and Y₂Co₁₇ compounds at 600 °C are 3.3, 5.6, 5.7 and 6.6 at.%, respectively, while the maximum solubilities of Y in Co₃Ti, Co₂Ti(h), Co₂Ti(c) and CoTi compounds are 2.7, 2.1, 2.6, 3.8 and 1.1 at.%. Meanwhile, the maximum solubilities of Ti in YCo₃, Y₂Co₇, YCo₅ and Y₂Co₁₇ compounds at 800 °C were determined to be 5.4, 3.2, 2.5 and 5.4 at.%, respectively, while the maximum solubilities of Y in Co₂Ti(c), Co₂Ti(h) and Co₃Ti compounds were measured to be 2.5, 2.1 and 3.8 at.%. The phase equilibria of the Y–Co–Ti system obtained in this work would provide the experimental information for phase stability of YCo_12-xTi_x compound and then explore the design of Y–Co–Ti based magnetic alloys with good magnetic properties.     

Gas sensing properties of ZnO thin films prepared by microcontact printing

In situ patterned zinc oxide (ZnO) thin films were prepared by precipitation of Zn(NO₃)₂/urea aqueous solution and by microcontact printing of self-assembled monolayers (SAMs) on Al/SiO₂/Si substrates. The visible precipitation of Zn(OH)₂ from the urea containing Zn(NO₃)₂ solution was enhanced by increasing the reaction temperature and the amount of urea. The optimized condition for the ZnO thin films was found to be the Zn(NO₃)₂/urea ratio of 1/8, the precipitation temperature of 80 °C, the precipitation time of 1 h and the annealing temperature of 600 °C, respectively. SAMs are formed by exposing Al/SiO₂/Si to solutions comprising of hydrophobic octadecylphosphonic acid (OPA) in tetrahydrofuran and hydrophilic 2-carboxylethylphosphonic acid (CPA) in ethanol. The ZnO thin film was then patterned with the heat treatment of Zn(OH)₂ precipitated on the surface of hydrophilic CPA. The ZnO gas sensor was exposed to different concentrations of C₃H₈ (5000 ppm), CO (250 ppm) and NO (1000 ppm) at elevated temperatures to evaluate the gas sensitivity of ZnO sensors. The optimum operating temperatures of C₃H₈, CO and NO gases showing the highest gas sensitivity were determined to be 350, 400 and 200 °C, respectively.     

Experimental investigation and thermodynamic assessment of the Mn–Zr system

The Mn–Zr binary system has been investigated via experimental measurements and thermodynamic calculations. In order to investigate phase equilibria in the Mn–Zr system, five alloys were prepared by arc melting under vacuum. All alloys were examined by means of X-ray diffraction, scanning electron microscopy and electron probe microanalysis after annealing at 650 °C for 70 days or 950 °C for 30 days. The homogeneity range of ZrMn₂ was determined to be from 25.0 to 33.2 at.% Zr at 950 °C and from 26.7 to 34.3 at.% Zr at 650 °C. The solubility of Mn in (αZr) was 1.6 at.% Mn, while that of Zr in (αMn) was 0.2 at.% Zr at 650 °C. The invariant reaction temperatures of liquid → ZrMn₂ + (βZr) and (βZr) → ZrMn₂ + (αZr) were determined to be 1131 and 785 °C, respectively. A thermodynamic assessment of the Mn–Zr system was conducted by taking into account the present experimental results and reliable literature data. The calculated results using the presently obtained parameters can well reproduce the experimental data.     

Re-assessment of the Mg–Zn–Ce system focusing on the phase equilibria in Mg-rich corner

The Mg–Zn–Ce alloys exhibit good creep resistance and strength at elevated temperature due to the formation of intermetallic compounds. However, the ternary compounds and phase equilibria in the Mg-rich corner are still controversial which restrains the development of Mg–Zn–Ce alloys. The present work experimentally investigated the phase equilibria in Mg-rich corner of the Mg–Zn–Ce system at 350 and 465 °C and thermodynamically assessed the Mg–Zn–Ce system. The existence of ternary compounds τ₁ and τ₃ were confirmed by a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystal structure of τ₁ was resolved as space group of Cmc21 with a = 0.9852(2)–1.0137(2) nm, b = 1.1361(3)–1.1635(3) nm and c = 0.9651(2)–0.9989(2) nm by Rietveld refinement of the XRD pattern. Three invariant reactions, L→τ₃+CeMg₃+CeMg₁₂, L+CeMg₁₂→α-Mg+τ₁ and L+τ₁→τ₂+α-Mg, were revealed by differential scanning calorimeter (DSC) measurement and microstructure characterization. Then, a set of self-consistent thermodynamic parameters was thereafter constructed by assessing the phase equilibria, solid solubilities of CeMg₁₂, τ₁, CeMg₃ and τ₃, as well as the formation enthalpies of binary and ternary compounds calculated by density functional theory. The comparison of calculated phase diagram with experimental results and the literature were discussed. The calculated isothermal section of Mg–Zn–Ce system at 465 °C agreed with our experimental data. The two three-phase equilibria, τ₁+α-Mg+CeMg₁₂ and CeMg₃+τ₃+CeMg₁₂, were confirmed in the Mg-rich corner. This thermodynamic database can be used for the further alloys design of Mg–Zn–Ce system.     

Fabrication and characterization of Pb-free transparent dielectric layer for plasma display panel

Glasses within the Bi₂O₃–B₂O₃–BaO–ZnO system were examined as potential replacements for PbO-based glass frits with low firing temperatures. These frits are used in the transparent dielectric layer of plasma display panels (PDP). The glass transition temperature (T_g) of the prepared glasses varied between 450 and 460 °C. These glasses display dynamic dielectric properties, high transparency and thermal expansion as well as matching well with substrate glass. The thermal coefficient of expansion (TCE) was with the desired range of 81–86×10⁻⁷/K. Moreover, when the screen printed film was heat-treated at 570 °C for 30 min, optical transmittance (83%), root-mean square (rms) roughness (177.6 Å), dielectric constant (10.25) and withstand voltage (4.15 kV) satisfied the requirements necessary for transparent dielectric layers to be used in PDP applications.     

Application of thermoregulatory modeling to predict core and skin temperatures in firefighters

The purpose of the study was to compare body temperature responses from subjects who exercised while wearing firefighter clothing to predictive data from a real-time thermoregulatory model that had been initially developed and validated for use in the military. Data from two firefighter studies, firefighter study 1 (FFS1: 7 males and 3 females, continuous treadmill exercise at 50% VO_2max, 25 °C, 50% RH) and firefighter study 2 (FFS2: 6 males, intermittent treadmill exercise at 75% VO_2max, 35 °C, 50% RH), were utilized for the thermoregulatory modeling and comparison. The results showed that prediction error (RMSD) of the model for core and skin temperatures was 0.33 and 0.65 °C in FFS1 and 0.39 and 0.86 °C in FFS2, respectively. While the real-time thermoregulatory model tested in the present study showed the potential for providing a means for reasonably accurate prediction of body temperature responses in firefighters, further development on the model's metabolism algorithms to include adjustments for protective clothing, options to facilitate external work, inclusions of cooling effects are suggested.Relevance to industryFirefighters exposed to thermal extremes experience physiological strain, but direct monitoring of physiological variables is not always practical. Thermoregulatory models can simulate the thermal responses reasonably accurately by applying known thermo-physiological mechanisms together with heat loss mechanisms related to clothing and environment in an effort to improve firefighter safety.     

Effect of temperature on humido-sensitive conducting polymer actuators

Temperature dependence of water vapor sorption and electro-active polymer actuating behavior of free-standing films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) was investigated by means of sorption isotherm and electromechanical analyses. The non-porous PEDOT/PSS film, having a specific surface area of 0.13 m² g^?1, sorbed water vapor of 1080 cm³(STP) g^?1, corresponding to 87 wt%, at relative water vapor pressure of 0.95. A temperature rise from 25 °C to 40 °C lowered sorption degree, indicative of an exothermic process, where isosteric heat of sorption decreased with increasing water vapor sorption and the value reached 43.9 kJ mol^?1, being consistent with the heat of water condensation (44 kJ mol^?1). Upon application of 10 V, the film underwent contraction of 2.46% at 5 °C caused by desorption of water vapor due to Joule heating, which slightly decreased to 2.10% at 45 °C. The speed of contraction was one order of magnitude faster than that of expansion and less dependent on the temperature since water vapor sorbed in the film were forced to desorb by Joule heating. In contrast, the higher the temperature the faster the film expansion because diffusion coefficient increased as the temperature became higher.     

Optimization of the mechanical properties of ultra-fine WC-Co-Cr3C2 cemented carbides via an approach based on thermodynamic calculations and characterization of the experimental results by the Weibull distribution

The influence of sintering temperature on the grain distribution, mechanical properties and fracture probability of WC-10 wt% Co-Cr₃C₂ cemented carbide was studied. Based on thermodynamic calculations, the complete liquefaction temperature of the WC-10 wt% Co-Cr₃C₂ cemented carbides shows a descend trend with the increase of Cr content. The addition of 0.5 wt% Cr decreases the complete liquefaction temperature of the WC-10 wt% Co cemented carbides from about 1360 °C to 1310 °C, the sintering temperature were defined starting from this result and adding 30, 50 and 80 °C. For comparison, an industrial production sintering temperature of 1410 °C is also used. Compared with four sintering schedules, WC-10 wt%Co-0.5 wt% Cr cemented carbides has more uniform grain size and better mechanical properties at sintering temperature for 1360 °C. In addition, the fracture probability of WC-10 wt%Co-0.5 wt% Cr cemented carbides is improved at sintering temperature for 1360 °C. An appropriate sintering temperature can be established by thermodynamic calculations, which enables effectively control of grain size and mechanical properties.     

Humidity-insensitive and low oxygen dependence tungsten oxide gas sensors

Gas sensing characteristics of WO₃ powder and its physical properties under different heat treatment conditions have been investigated. The WO₃ powder was synthesized by wet process from ammonium tungstate parapentahydrate and nitric solution. The precipitated product was then calcined at 300–800 °C for 2–12 h. The physical properties of the products were characterized by using X-ray diffractometer (XRD), scanning electron microscope (SEM), and BET method. It was found that the crystallite size, particle size and surface area of the WO₃ powders were in the range of 30–45 nm, 0.1–3.0 μm and 1.2–3.7 m²/g, respectively. Calcination at higher temperature and longer time led to the increase of particle size by more than 300%, and reduction in specific surface area by more than 60%. However, the crystallite size was found to increase only by ∼30% under identical heat treatment. These results inferred that such heat treatment had more profound effect on crystallite aggregation than on crystallite growth. Gas sensing measurement showed that the largest change of output voltage to both ethyl alcohol and ammonia was obtained from the sensor calcined at 600 °C for 2 h, which had the highest surface area. However, the highest sensitivity which is defined as the ratio of sensor's resistance in air to that in the sample gas, R_air/R_gas, was obtained from the sensor calcined at 600 °C for 6 h due to its highest background resistance in air. Moreover, it was also found that the sensors were less sensitive to the oxygen content in the carrier gas and did not sensitive at all to water vapor.