Gallium Alloy Research Articles

Replacing −CH2CH2– with −CONH– Does Not Significantly Change Rates of Charge Transport through AgTS-SAM//Ga2O3/EGaIn Junctions

This paper describes physical-organic studies of charge transport by tunneling through self-assembled monolayers (SAMs), based on systematic variations of the structure of the molecules constituting the SAM. Replacing a -CH(2)CH(2)- group with a -CONH- group changes the dipole moment and polarizability of a portion of the molecule and has, in principle, the potential to change the rate of charge transport through the SAM. In practice, this substitution produces no significant change in the rate of charge transport across junctions of the structure Ag(TS)-S(CH(2))(m)X(CH(2))(n)H//Ga(2)O(3)/EGaIn (TS = template stripped, X = -CH(2)CH(2)- or -CONH-, and EGaIn = eutectic alloy of gallium and indium). Incorporation of the amide group does, however, increase the yields of working (non-shorting) junctions (when compared to n-alkanethiolates of the same length). These results suggest that synthetic schemes that combine a thiol group on one end of a molecule with a group, R, to be tested, on the other (e.g., HS~CONH~R) using an amide-based coupling provide practical routes to molecules useful in studies of molecular electronics.

Recovery of gallium from Bayer liquor: A review

Bayer liquor is the biggest raw material resource for gallium production. Four kinds of methods have been developed to recover gallium from Bayer solutions, including fractional precipitation, electrochemical deposition, solvent extraction, and ion exchange. The fractional precipitation method is based on Al–Ga precipitation with CO2 and subsequent separation of Al and Ga with lime milk or sodium aluminate solutions. This approach is more environmentally friendly and with low cost, but the process is complicated. The electrochemical method includes both mercury cathode electrolysis and cementation. The electrolysis with mercury cathode has been prohibited in most countries because of high toxicity of mercury. Cementation is an electrochemical process realized by a displacement reaction between gallium and reductants, such as sodium amalgam, aluminum and aluminum–gallium alloy. Solvent extraction is an efficient method and by using Kelex 100 system about 80% of the gallium in Bayer liquor can be extracted. However, the kinetics of the extraction process has been proved to be very slow, which generally requires several hours. Ion exchange is the main method applied in industry for gallium recovery from Bayer liquor. Duolite ES-346 and DHG586 exhibit good extracting properties for gallium, and are used as industrial resins. Unfortunately, the co-extraction of vanadium and the degradation of the amidoxime groups still remain as the main problems during industrial application. In order to recover gallium from Bayer liquor efficiently, further research and development are necessary.

Hydrogen generation from water by means of activated aluminum

Abstract An important part of the hydrogen energy problems is the search of hydrogen sources for feeding hydrogen–air fuel cells. One of the most convenient methods for hydrogen generation is based on oxidation of aluminum by water. In this paper the method of aluminum activation based on the application of gallium alloys (gallams) is suggested. In this work the activated aluminum powders made of commercially available aluminum wires are investigated. The kinetic parameters of the reaction of activated aluminum with water (hydrogen generation rate and hydrogen yield) depending on the gallam’s amount and composition, powder particle sizes and reaction temperature are studied.

Mixing enthalpies of liquid nickel–gallium alloys

The partial mixing enthalpies of melt components in the Ni–Ga system are measured using hightemperature isoperibolic calorimetry at 1770 ± 5 K in a wide composition range. The partial mixing enthalpy of gallium in liquid nickel is –96 kJ/mol. for infinite dilution, while the same function of nickel in liquid gallium is –75 kJ/mol. The integral mixing enthalpy of liquid alloys in this system is calculated from partial enthalpies for the entire composition range (∆m H min = –32 kJ/mol. at xNi = = 0.5). The mixing enthalpies ∆m H of Ni–B (Al, Ga, In) binary alloys are compared. It is shown that the indicated systems are arranged in the Ni–In → Ni–Ga → Ni–B → Ni–Al series according to the increase in interaction energy of dissimilar components. The ∆m H min values of liquid Ni–B(Al, Ga, In) alloys are compared with the values of electrochemical and size factors.

A bending-mode galfenol electric power harvester

Iron–gallium alloys (galfenol) are promising transducer materials that combine high magnetostriction, desirable mechanical properties, high permeability, and a wide operational temperature range. In this study, we present results from a proof-of-concept prototype energy harvester that produces an output voltage proportional to the load-induced bending of the galfenol element caused by a base acceleration of the device. The device consists of a polycrystalline galfenol strip bonded to an aluminum cantilever beam, which has an effective length of 35.81 mm. Two brass pieces, each containing a permanent magnet, are used to mass load each end of the beam and to provide a magnetic bias field through the galfenol strip. The voltage induced in an induction coil closely wound around the cantilever beam captures the time rate of change of magnetic flux within the galfenol strip as the beam vibrates. The first bending-mode resonant frequency of the device was 223 Hz. The power generated from the prototype when subjected to a 1g acceleration at 222 Hz was 2.2 mW (root mean square), which corresponded to an efficiency of more than 60% for the electrical power output per unit mechanical power input to the harvester.

Role of Ga-doping in iron—gallium alloy clusters

The structural and magnetic properties of Fen−mGam (n = 3 ∼ 6, m = 0 ∼ 2; n = 13, m = 0 ∼ 3) alloy clusters have been studied using density functional theory. The substitutional doping is favourable for small clusters with up to six atoms at low Ga concentration and substitutional Ga atoms in 13-atom clusters prefer surface sites. The Ga-doping generally could reduce the energetic stability but enhance the electronic stability of Fe clusters, along with a decrease of the local magnetic moments of Fe atoms around Ga dopants. These findings provide a microscopic insight into Fe—Ga alloys which are well-known magnetostriction materials.

S102015 磁歪式振動発電の高次共振モードにおける発電特性

We propose energy- harvesting device using an iron- gallium alloy (Fe-Ga), which is capable of generating electrical energy from ambient vibrations. The device consists of parallel beams structure of yoke and Fe-Ga plate wound with coils, and a bias magnet. A bending force applied at the tip of the device yields a flux change of Fe-Ga plate, which the time variations generates a voltage on the wound coils. In this paper, power generation characteristic of high frequency mode is investigated. The experimental results and modal analysis clarified that high power generation is possible if the uniform bending deformation is occurred in the parallel beam structure in high frequency resonance.

A study on corrosion behavior of austenitic stainless steel in liquid metals at high temperature

The purpose of this study is to investigate the interaction between austenitic stainless steel, AISI 316L, and gallium liquid metal at a high temperature, for the potential application to advanced fast reactor coolants. Test specimens of AISI 316L were exposed to static gallium at 500°C for up to 700h in two different cover-gas conditions, including air and vacuum. Similar experimental tests were conducted in gallium alloy liquid metal environments, including Ga–14Sn–6Zn and Ga–8Sn–6Zn, in order to study the effect of addition of alloying elements. The results have shown that the weight change and metal loss of specimens were generally reduced in Ga–14Sn–6Zn and Ga–8Sn–6Zn compared to those in pure gallium at a high temperature.

Gallium poisoning: A rare case report

The authors present a case of a college student who suffered acute gallium poisoning as a result of accidental exposure to gallium halide complexes. This is extremely rare and has never been reported in the literature. Acute symptoms after the incident, which initially presented as dermatitis and appeared relatively not life-threatening, rapidly progressed to dangerous episodes of tachycardia, tremors, dyspnea, vertigo, and unexpected black-outs. Had there been effective emergency medical care protocols, diagnostic testing, treatment and antidotes, the latent manifestations of irreversible cardiomyopathy may have been prevented. Given how quickly exposure led to morbidity, this article aims to raise an awareness of the toxic potential of gallium. This has particular relevance for workers involved in the production of semiconductors where there is a potential for accidental exposure to gallium by-products during device processing. It may also have implications for dentists who use gallium alloys to replace mercury containing amalgam. In the absence of threshold limit values and exposure limits for humans, as well as emergency medical guidelines for treatment of poisoning, the case calls on the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration to establish guidelines and medical management protocols specific for gallium.

Microfluidic circuits harvest mechanical energy

Embedded in a pair of shoes, circuits composed of a train of conductive droplets could generate a few watts of power—enough to charge a cell phone from a casual stroll.

Performance of Energy Harvester Using Iron–Gallium Alloy in Free Vibration

We propose a micro energy-harvesting device, using an iron-gallium alloy (Galfenol), capable of generating electrical energy from ambient vibrations. Galfenol is a ductile magnetostrictive material with a high piezomagnetic constant, good machinability, and a large inverse magnetostrictive effect by which magnetization can be varied by mechanical stress. The device consists of two beams of Galfenol combined with iron yokes, coils, and a bias magnet. A bending force applied at the tip of the cantilever yields a flux increase by tensile stress in one beam, and a flux decreases in the other by compression. The time variation of the flux generates a voltage on the wound coils. This energy harvester has advantages over conventional types of device, such as those using piezoelectric materials, with respect to size, and efficiency, and it has high robustness and low electrical impedance. In addition, the structure needs only a low mechanical force to generate electricity. In this paper, the free vibration characteristic to accrue electric energy effectively is examined. From the experimental results, the energy conversion efficiency in the vibration is inverse proportional to the resonant frequency.

Experimental evidence of Alfvén wave propagation in a Gallium alloy

Experiments with a liquid metal alloy, Galinstan, are reported and show clear evidence of Alfvén wave propagation as well as resonance of Alfvén modes. Galinstan is liquid at room temperature and, although its electrical conductivity is not as large as that of liquid sodium or NaK, it has still been possible to study Alfvén waves, thanks to the use of intense magnetic fields up to 13 T. The maximal values of Lundquist number, around 60, are similar to that of the reference experimental study by Jameson [J. Fluid Mech. 19, 513 (1964)]. The generation mechanism for Alfvén waves and their reflection is studied carefully. Numerical simulations have been performed and have been able to reproduce the experimental results, despite the fact that the simulated magnetic Prandtl number was much larger than that of Galinstan. An originality of the present study is that a poloidal disturbance (magnetic and velocity fields) is generated, allowing us to track its propagation from outside the conducting domain, hence without interfering.

Ga 及び Ga 合金の過冷却挙動に及ぼす溶湯加熱温度の影響

Ga 及び Ga 合金の過冷却挙動に及ぼす溶湯加熱温度の影響

Electrochemical study of one-step electrodeposition of copper–indium–gallium alloys in acidic conditions as precursor layers for Cu(In,Ga)Se 2 thin film solar cells

This paper investigates one step electrodeposition of copper indium gallium metallic precursor layers for preparing CuIn 1− x Ga x Se 2 (CIGS) absorber layers in thin film solar cells (0 ≤ x ≤ 1). Electrodeposition was carried out in acidic aqueous solutions at about pH 2. At first partial single or binary electrodeposition systems Cu, In, Ga, Cu–Ga, Cu–In were investigated by cyclic voltammetry. Then ternary Cu–In–Ga electrodeposition system was studied. The nature of the supporting electrolyte (sodium sulfate vs. sodium chloride) and the influence of sodium citrate were more specifically investigated. The applied potential, the pH and the nature of the electrolyte were optimized to obtain x values around 0.3 needed for high efficiency devices. Depositions were carried out under potentiostatic conditions in a paddle cell configuration. The electrodeposited Cu–In–Ga alloys were annealed under Se atmosphere at temperatures between 400 and 600 °C to produce CIGS absorbers. Films were characterized by XRF, SEM and XRD analysis. Device efficiencies up to 9.3% are achieved for optimal gallium content.

Investigation on a low-melting-point gallium alloy MHD power generator

A magnetic hydrodynamic (MHD) power generator using an electro-conductive low-melting-point gallium alloy is introduced. An experimental setup is designed and established to investigate its performance with aids of numerical simulations. Theoretical derivations based on Faraday Law are also presented as a theoretical foundation of the present study. It is found that the electric output increases with flow velocity, magnetic strength and electric conductivity, and the theoretical predictions and numerical results are in good agreement with the experimentally measured data. It is understood that in order to obtain a practical power generation, priority should be put on increasing fluid flow velocity and magnetic field strength. The present MHD power generation system has shown to be operated reliably in a long time at room temperature and could be used as a micro-distributed energy supply system for domestic use in the future. Copyright © 2010 John Wiley & Sons, Ltd.

Evaluation of a miniature magnetostrictive actuator using Galfenol under tensile stress

We are, at present, developing miniature actuators using an iron–gallium alloy (Galfenol). Galfenol is an iron-based magnetostrictive material with magnetostriction exceeding 200 ppm, Young's modulus of 70 GPa and a high relative permeability (>100). The advantages of an actuator using this material are capability of miniaturization, stability against external force, low voltage driving and high power. In this study, a miniature vibrator using an E core of Galfenol under tensile stress up to 20 MPa was investigated. The vibrator did not fracture and maintained the magnetostriction even under a high tensile stress. In addition, the resonance frequency, unchanged under the tensile stress, was lower than the cutoff frequency, hence the vibrator can be driven with a low voltage even in resonance driving. The temperature rise in resonance driving was low and creep was not observed in resonance driving under tensile stress. The vibrator will be applicable in flat panel or bone conductive speakers.

Fretting Behaviors of an Ag/CuGa2 Combination and Application to Electrical Contacts

A copper and gallium alloy is easily produced through contact of liquid gallium and copper metal. A combination of CuGa2 and silver was investigated as a new electrical contact. The resistivity of the alloy is 1.1×10-5 Ωcm at room temperature. Oxide film on the alloy was suppressed during heat treatment in air. Due to mutual immiscibility without oxygen, adhesive wear of the silver during abrasion against the alloy was reduced less than that against silver itself. With exclusion of oxygen using a lubricant, the combination is a prospect for electrical contacts.

Physical properties of heavy liquid-metal coolants in a wide temperature range

The pulse-phase method, the gamma-attenuation method and the method of dumping oscillation of a crucible with a melt were used for measuring the velocity of sound, the density and the kinematic viscosity of a set of liquid-metal coolants for perspective nuclear reactors. There are liquid gallium, indium, tin, lead, bismuth and lead-bismuth eutectic alloy among the melts investigated. The accuracy of the measurements was as high as 0.3%, 0.2 to 0.4% and 1.5% for the ultrasound velocity, the density and the viscosity, correspondingly.

Study on Micro-energy Harvesting Device Using Iron-Gallium Alloy

We propose a micro-energy harvesting device using an iron gallium alloy (Galfenol) that is capable of providing electrical energy through environmental vibrations. Galfenol is a ductile magnetostrictive material with high piezomagnetic constant, good machinability, and a large inverse magnetostrictive effect in which the magnetization can be varied by mechanical stress. The proposed device consists of two columns of Galfenol those ends are connected at the end with iron yokes, coils and a bias magnet. When bending force is applied on the mover with the other end fixed like a cantilever, the magnetization in one column increases because of tensile force due to the inverse magnetostrictive effect, and the other decreases due to compression. The time variation of the magnetization generates voltage on the wound coils. This energy harvesting device is advantageous over other types such as those using piezoelectric material, in size, high robustness, and low electrical impedance. In addition, the two columns structure requires low mechanical force to provide sufficient stress to change the magnetization. We fabricated a prototype using stress-annealed Galfenol with 314 coil turns and in experiments verified a maximum voltage of 0.48 V at forced vibration with a frequency of 333 Hz. The frequency response was also measured to understand the behavior at resonances of the 1st and 2nd bending modes as well as the effect of additional weight.

Electrodeposited Gallium Alloy Thin Films Synthesized by Solid State Reactions for CIGS Solar Cell

The solid-state reactions of electroplated gallium thin films with copper, gold and molybdenum were investigated using XRD, SIMS, TEM/EDS and linear strip voltammetry. Due to the low melting temperature of gallium metal, the activation energy for gallium diffusion is lower than the other metals used. Hence Ga diffuses faster and reacts to form alloy phases with the other metals investigated. In a thin film stack of Ga with another metals (Me), (Me = Cu, Au and Mo), equilibrium compounds are formed, which compounds form depends on the relative composition and diffusion time. If there is excess Ga, or excess Me, it can further react with the metastable compounds to form an equilibrium compound. In addition, TaN was found to act as an effective barrier layer to gallium diffusion.