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高圧・高温下における液体金属の密度はその圧縮特性や弾性特性を理解するうえで基本的で重要な情報を与える。本研究では外熱式ダイヤモンドアンビルセルを用いたX線吸収測定によって液体ガリウムの密度測定を10GPa、533Kまでの圧力・温度範囲で行った。液体ガリウムの弾性特性は3種の状態方程式で密度のデータをフィッティングすることで得られた。得られた体積弾性率は用いた状態方程式に因らずほとんど同じであった。以前の結果に比べ、本研究で得られた液体ガリウムの圧縮曲線からは、より高い圧力でわずかに硬くなる傾向が示された。

The dissolution of molecular nitrogen in Ga and Fe was investigated by ab initio calculations and some complementary experiments. It was found that the N bonding inside these solvents is fundamentally different. For Ga, it is between Ga4s and Ga4p and N2p states whereas for Fe this is by N2p to Fe4s, Fe4p and Fe3d states. Accordingly, the energy of dissolution of N2 for arbitrarily chosen starting atomic configurations was 0.535 eV/mol and −0.299 eV/mol for Ga and Fe, respectively. For configurations optimized with molecular dynamics, the difference between the corresponding energy values, 1.107 eV/mol and 0.003 eV/mol, was similarly large. Full thermodynamic analysis of chemical potential was made employing entropy-derived terms in a Debye picture. The entropy-dependent terms were obtained via a normal conditions path to avoid singularity of ideal gas entropy at zero K. Nitrogen solubility as a function of temperature and N2 pressure was evaluated, being much higher for Fe than for Ga. For T=1800 K and p=104 bar, the N concentration in Ga was 3×10−3 at. fr. whereas for Fe, it was 9×10−2 at. fr. in very good agreement with experimental data. It indicates that liquid Fe could be a prospective solvent for GaN crystallization from metallic solutions.

The structure of liquid gallium in a wide temperature range has been studied. Analysis of data obtained by diffraction method allowed us to make some conclusions about the structural features of the liquid gallium. In particular there is a clear asymmetry of the first maximum of the structure factor (SF) and existence of shoulder on its right hand side. Also the temperature dependence of structural factors for liquid gallium in terms of its heterogeneous structure was analyzed. Interpretation was carried out under the assumption that the structure of liquid gallium consists of clusters with different distribution of atoms, as well as different types of chemical bonds between atoms. The structural units are sensitive to temperature. Splitting of the structure factor main maximum on the Gaussian partial curves, which corresponded to certain structural units of the melt, was also performed. Each structural component of the melt reveals a different nature of the temperature dependence. It is also assumed that the partial peaks for each cluster are described by Gaussian functions.

Molecular dynamics (MD) simulation has been employed to study the wetting transitions of liquid gallium droplet on the graphene surfaces, which are decorated with three types of carbon nanopillars, and to explore the effect of the surface roughness and morphology on the wettability of liquid Ga. The simulation results showed that, at the beginning, the Ga film looks like an upside-down dish on the rough surface, different from that on the smooth graphene surface, and its size is crucial to the final state of liquid. Ga droplets exhibit a Cassie&ndash, Baxter (CB) state, a Wenzel state, a Mixed Wetting state, and a dewetting state on the patterned surfaces by changing distribution and the morphology of nanopillars. Top morphology of nanopillars has a direct impact on the wetting transition of liquid Ga. There are three transition states for the two types of carbon nanotube (CNT) substrates and two for the carbon nanocone (CNC) one. Furthermore, we have found that the substrates show high or low adhesion to the Ga droplet with the variation of their roughness and top morphology. With the roughness decreasing, the adhesion energy of the substrate decreases. With the same roughness, the CNC/graphene surface has the lowest adhesion energy, followed by CNT/graphene and capped CNT/graphene surfaces. Our findings provide not only valid support to previous works but also reveal new theories on the wetting model of the metal droplet on the rough substrates.

金属ガリウムの融点及び沸点は，それぞれ29.76℃，2205℃ であり，液体として存在する温度範囲が最も広い元素である．室温近傍で液体状態をとることから，水に代わる有望な高効率冷却材料としても期待されている．また，液体状態での構造，ダイナミクス及び電子状態に加え，融点近傍での液体から固体への相転移（凝固），あるいはその逆の融解の初期過程や非平衡状態等にも学術的関心が持たれる．X線回折・散乱法やその他の多くの分析技術は，試料全体を均質と見なし，場所による違いが生じないという仮定のもとで用いられており，凝固の初期組織内の結晶粒の大きさ，形状，方位やそれらの試料内で分布等を知ることはできない．投影型X線回折イメージング法は，従来のX線回折法を拡張し，試料上の個々の場所からの回折X線をきわめて迅速に画像化する新技術である．本論文では，この方法を用い，液体金属ガリウムの凝固，融解過程で生じる不均一結晶組織のin situ観察を初めて行った結果を報告する．

Experiments were performed for visual observation and investigation of liquid Gallium flow at a temperature of 40oC in a rotating magnetic field. Two different measuring methods were developed to determine the revolution number of rotating melt. In both cases the frequency of magnetic induction was 50, 100 and 150 Hz and the values of magnetic induction could be changed between 0 and 70 mT. The magnetic Taylor number changed between 0 and 3.54x107 during the experiments.

International audience; Due to discrepancies in the literature data the thermodynamic properties of liquid gallium arestill in debate. Accurate measurements of adiabatic sound velocities as a function of pressureand temperature have been obtained by the combination of laser picosecond acoustics andsurface imaging on sample loaded in diamond anvil cell. From these results thethermodynamic parameters of gallium have been extracted by a numerical procedure up to10 GPa and 570 K. It is demonstrated that a Murnaghan equation of state accounts well for thewhole data set since the isothermal bulk modulus BT has been shown to vary linearly withpressure in the whole temperature range. No evidence for a previously reported liquid–liquidtransition has been found in the whole pressure and temperature range explored

The kinetics of liquid Ga penetration along grain boundaries in pure Al, Al-Mn (50 ppm Mn) and Al-Ga alloys (with concentration 0.7, 1 and 3% mass. Ga) was studied. It was shown that crack-like channels filled by liquid Ga were formed along all grain boundaries. Their width was about 1-3 µm. Investigation of quenched state showed that in all samples, channels had grown with linear kinetics, and that the propagation rate depended on impurity concentration in alloys: 35µm/s for Al-Mn alloy, 14 µm/s for pure Al and 9±1 µm/s for Al with (0.7-3) % Ga alloys. The difference in penetration rates of pure Al and Al based alloys are discussed in terms of internal stress and mechanical properties.

Thermal conductivity of liquid gallium as a function of temperature has been determined by the transient hot-wire method with an alumina-coated probe. Theoretical analysis of the temperature increase of the hot wire with coating indicates that the coating layer affects absolute measurements by this method and its presence is prone to yield smaller values of thermal conductivity. Relative measurements were carried out over the temperature range 310-471 K on liquid mercury and gallium at 310K as standard samples to establish the correction line. The thermal conductivities obtained for liquid gallium are as follows: 29.3 W m - 1 K - 1 at 338 K, 30.5 W m - 1 K - 1 at 379 K, and 31.8 W m - 1 K - 1 at 471 K. These values are greater than those derived from absolute measurements but smaller than the values predicted from the Wiedemann-Franz law and smaller than several reported values.

The influence of liquid gallium on the decomposition process of thin GaN films have been studied in situ in an optical microscope up to 800°C in Ar/H 2 and N 2 /H 2 gas mixtures at atmospheric pressure. A pure GaN film showed no apparent decomposition even after a 30 min anneal at 800°C. With liquid gallium deposited on the surface, dissociation occurs at temperatures around 720°C starting from the Ga/GaN interface and independent of the composition of the gas phase. The GaN decomposition, GaN→Ga (liq)+gas, is kinetically blocked due to the high nucleation barrier for the formation of liquid gallium droplets.

The overpotential of hydrogen on a liquid gallium electrode has been studied in the equilibrium phases of isobutanol-water-hydrochloric acid systems. According to our investigations, the η-lg j curves measured in equilibrium aqueous (W) and organic (O) phases practically coincide. This can probably be explained by the fact that the rate of hydrogen evolution in the equilibrium phases studied is determined by the quasi-independence of the structure of W|Ga or O|Ga boundary layers, as well as of the correlation between the Ψ o potential and the acid concentration of the composition of phases.

The EXAFS technique has been applied for obtaining information on the local atomic arrangements in the near neighbor region of liquid gallium. The EXAFS data of liquid gallium at temperatures of 323 and 473 K can be well explained by considering four immediate neighbors and another four slightly more distant neighbors located so as to form a local structure around each atom. The present results can account for the first peak asymetry of the radial distribution function obtained from X-ray diffraction studies.

EXAFS (Extended X-ray Absorption Fine Structure) spectra of liquid gallium near the Ga K-edge have been collected in wide pressure and temperature ranges. Reliable short-range pair distribution functions have been determined using advanced ab initio calculations (GNXAS) taking into account the medium and long-range structure obtained by previous neutron and X-ray-scattering studies.

An overview of experimental work recently performed in the Lisbon laboratories is provided. Several physical properties of liquids as well as those of the coexistence between two liquid phases and between liquid and solid have been determined at absolute negative pressures. Examples for this include thermal pressure coefficients, loci of temperature of maximum density, negatively sloped melting lines, speed of propagation of low-intensity ultrasound waves, and (p, T, x) conditions of occurrence of liquid-liquid phase separation. The major achievements that emerged within the scope of this research program were: (i) the first experimental evidence for the existence of a TMD in supercooled and stretched gallium, and (ii) the first experimental detection of phase separation phenomena in molecular liquid mixtures under tension.

Energy-dispersive x-ray diffraction measurements have been carried out on liquid gallium at pressures up to 6. 1 GPa and on liquid tellurium at pressures up to 5. 1 GPa using synchrotron radiation and a cubic-type high-pressure apparatus. The structure of liquid gallium changes with pressure from an fct-like structure to one with higher symmetry. The first peak of the structure factor S(Q) of liquid tellurium grows with pressure below 2. 6 GPa, and the structure of liquid tellurium at 5. 1 GPa is totally different from that below 2. 6 GPa. Des mesures de diffraction de rayon X en energie dispersif ont ete effectuees sur du gallium liquide sous pressions jusqu' a 6. 1 GPa et sur du tellure liquide jusqu' a 5. 1 GPa, utilisant une radiation synchrotron et un appareil de haute pression de type cubique. La structure du Ga liquide change avec pression du comme tetragonal a faces centres a une plus haute symetrie. Le premier pic de facteur de structure S(Q) du Te liquide augmente avec p

The first report of an X-ray absorption spectroscopy (XAS) study of liquid gallium, carried out at several temperatures in liquid and crystalline phases and in the supercooled state, is presented. Data analysis has shown the presence of two resolved first-neighbour distances and a detectable signal due to three-body configurations.

The oxygen content in the compound Bi 2 Sr 2 CaCu 2 O 8+δ (2212) may be varied from δ=0.1 to δ =0.4. This variation influences the physical properties as observed in other high-T c systems (Y 1 Ba 2 Cu 3 O 7−δ , Y 2 Ba 4 Cu 7 O 15+δ , Tl 2 Ba 2 Cu 2 O 6+δ ). It determines the hole doping p ( Cu 2 + p ) which can be related to the critical temperature T c , the Meissner fraction and the normal-state susceptibility. In this work on the Pb-free Bi-2212 system, we present the diagram of the critical temperature T c in the (p,T) plane for 10 -5 ⩽ p ⩽ 10 2 bar (O 2 ) and 300 ⩽ T ⩽ 840 °C. The equilibrium oxygen content is frozen by quenching the samples into liquid gallium. The sharp Meissner diamagnetic transitions vary between 50 and 94 K and the Meissner fraction increases with T c . The highest T c (optimum hole concentration) is obtained at T Quench = T 0 + a log 10 P( O 2 ) with T 0 =870 ° C , a=60 °C and P(O 2 ) in bar. The slope of the normal-state susceptibility d χ /dT, which is strongly negative for the oxidized samples, increases with progressing reduction and vanishes for the optimum doping.

The surface tension of high-purity liquid gallium has been measured by the pendant-drop method. The experiments were conducted in a nitrogen atmosphere over a temperature range of 4–40°C. The average value of the surface tension was 723.2, 724.6, 723.9, 723.7 and 725.0 dynes/cm at 40, 30, 29.6, 25 and 17°C, respectively. Other values obtained from single measurements within the temperature range are also reported. The temperature coefficient of the surface tension was −0.068 dynes/cm°C−1.

A brief description of the experimental arrangement to get the structure factor of liquid gallium at 50°C, 200°C, 300°C and 500°C is given. The evaluated structure factors and pair correlation functions are presented. A comparison of the nearest neighbour values and the radii of the first coordination shell of various authors is made. Some structure models are compared with the experimental data. Eine kurze Beschreibung der Versuchsanordnung zur Bestimmung des Strukturfaktors von flussigem Gallium bei 50°C; 200°C; 300°C und 500°C wird gegeben. Die berechneten Strukturfaktoren und die Paarkorrelationsfunktionen werden mitgeteilt. Ein Vergleich der Werte nachster Nachbarn und der Radien der ersten Koordinationspharen verschiedener Autoren sowie Strukturmodelle im Vergleich zu experimentellen Daten werden diskutiert.

With a high-temperature microcalorimeter the molar excess enthalpies H E of liquid gallium + antimony alloys have been measured at 995 K over the entire mole fraction range. Using an indirect drop method, which is more accurate than the classical drop method, we could determine small excess enthalpies and particularly the limiting partial molar excess enthalpies. We find H E ( x = 0.5) = −(260 ± 10) cal th mol −1 , H Ga E.∞ = −(900 ± 30) cal th mol −1 , and H Sb E.∞ = −(85 ± 5) cal th mol −1 . At 978 K we measured the enthalpy of formation of gallium antimonide: ΔH t = −(7300 ± 300) cal th mol −1 . By three different methods we obtained the enthalpy of melting of GaSb; the value (7200 ± 300) cal th mol −1 seems to us most reliable. With all these thermodynamic values and the phase diagram already known we can propose the activities of gallium and antimony at 1000 K. The values already published of these functions are numerous and often divergent. Our calculated results seems to confirm those measured by Chu-Hsi-Hsiung et al .

The results on the As- and P-diffusion in gallium melt are discussed. The definition method of P- and As-diffusion coefficients in liquid gallium was stated. This method was based on the analysis of concentration profile formed during the diffusion annealing with following tempering. The diffusion coefficients were measured on temperature region 1113 to 1383 K. The expression for temperature dependence of diffusion coefficients was obtained. Russian text ignored

We report an evaluation of the surface tension σ of liquid gallium and indium in a palladium-diffused hydrogen atmosphere at temperatures up to 1150 K. Small and large sessile drops of gallium have σ(TMP) = 680 mJ m−2 at the melting point and a temperature dependence d σ d T = −0.091 mJ m −2 K −1 . Large sessile drops of indium have σ(TMP) = 560 mJ m−2 at the melting point and a temperature dependence d σ d T = −0.10 mJ m −2 K −1 .

A modified streaming method has been elaborated to determine the potential of zero charge of liquid gallium in aqueous solution. This method takes into consideration the disturbing effect of faradaic processes and provides reliable values for the potential of zero charge. Experimental verification of the applicability of this method is furnished by comparison of literature data and data of the present paper. Results, obtained at various pHs in KCl + HCl solutions, and the effect of thiourea or N -substituted thioureas on the pzc, are presented.

The viscosity of cesium at 1620 K and 40 bar has been determined to 41· 10−6 (Pa· s) by the oscillating cup method. The saturated vapor density at 1580 K could be derived from the viscosity measurements. The viscosity of liquid gallium has been determined from 370 K to 1800 K. The experimental results have been compared with calculations based on the Enskog hard-sphere transport theory for dense fluids. Die Viskositat von Casium wurde mit der Methode des schwingenden Gefases gemessen und betragt bei 1620 K und 40 bar 41 · 10−6 (Pa · s). Die Sattigungsdichte des Dampfes bei 1580 K konnte aus den Viskositatsmessungen abgeleitet werden. Die Viskositat von flussigem Gallium wurde zwischen 370 K und 1800 K gemessen. Die experimentellen Daten wurden mit der nach einer erweiterten Enskog-Transporttheorie dichter Gase berechneten Kurve verglichen.

The gallium-rich side of some rare earth-gallium binary systems was studied using a diffusion couple technique. Diffusion couples were formed by annealing rare earth metals immersed in liquid gallium at various temperatures. The nature and composition of the compound layers formed at the rare earth metal-gallium interface were determined by metallographic and electron microprobe analysis. The results indicate that in the light rare earth metals (R ≡ La-Gd) the ϵ phase extends from the stoichiometric composition RGa 2 to the gallium-rich compositions R 1− x Ga 2+ x . In these systems the RGa 6 layer is dominant in the diffusion region. No RGa 3 layer is present in these systems, in contrast with the two heavy rare earth-gallium couples (Tb-Ga and Dy-Ga) in which the ϵ phase appears at the stoichiometric composition only and the RGa 3 layer is dominant.

The rate of silicon contamination of a gallium melt in contact with silica is controlled by the water content and flow rate of the hydrogen atmosphere. Calculated contamination rates are in good agreement with the work of Weiner.

The resistivity and thermo-power of liquid gallium and mercury have been measured as functions of temperature at constant volume up to approximately 160°c. The resistivities are in reasonable agreement with those estimated from Bridgman's pressure coefficients. For mercury the thermo-power parameter ξ at constant volume is independent of temperature in contrast to that at constant pressure. For gallium no difference could be distinguished between the two cases. It is deduced that in mercury the pseudo-potential by which the ions scatter electrons is strongly dependent on the electron momentum, whereas in gallium this is not so.

Accurate measurements of the density and coefficient of expansion of liquid gallium at temperatures from 30° to 1000° C. have been made by a dilatometric method. The temperature was measured with a platinum resistance thermometer. An equation expressing the increase in volume as a function of the temperature has been found, and from that equation values have been calculated for the coefficient of expansion.

With increasing demand for higher computational speed and emerging microsystems, efficient thermal management is need of the hour. Microchannels using liquid coolant are apt solution to this problem. Their efficiency depends greatly upon channel's cross-section and liquid media. In this study the performance of trapezoidal (with two configurations A and V-type) and rectangular microchannels are analyzed and compared for two different coolants, liquid gallium and water. Performance is compared on the basis of maximum temperature at heated surface. For water as coolant the performance of rectangular type is found to be superior in terms of both flow rate and pump power. For liquid gallium as a coolant, microchannels having A-type cross-section is found to be performing better followed by V-type then rectangular type at same flow rate. However on comparison on basis of pump power the rectangular type of geometry is found to be more suitable.

A study of the spreading of gallium on the surface of tin at 60°–70° C showed that immediately after application of liquid gallium (within 3 min), side by side with a drop of liquid phase a solid diffusion zone (with a characteristic surface relief) is formed, which-according to X-ray diffraction data [5]-is a solid solution of gallium in tin. The rate of spreading of the liquid drop is very slow, seldom exceeding 1×10−6 mm/min. The rate of spreading of the diffusion zone changes from 1.6×10−2 mm/min (in the first few minutes after application of gallium) to 0.7×10−6 mm/min (48 hr later), which evidently is caused by the gradual reduction of the quantity of gallium available. The spreading of the diffusion zone takes place in a step-like fashion, the number and length of arrests increasing as the quantity of liquid gallium diminishes.

As for most metals, the conductivity of liquid gallium is less than that of the solid phase. Those two have reported the reverse, and on this account have likened gallium to antimony and bismuth, are thought to have used values for a non-polycrystalline solid.

Neutron scattering measurements on liquid gallium have been carried out at 293, 838 and 1 303 K on the H10 spectrometer of the EL3 reactor at Saclay. The obtained structure factors and pair correlation functions are compared to various published data. A quasi-crystalline model related to the β monoclinic form of gallium is proposed in order to explain the shape of the structure factor of liquid gallium and its behaviour versus temperature.

A novel technique is described for directly measuring the Seebeck coefficient across the solid-liquid interface of gallium as a function of temperature and crystallographic orientation. The results are compared with those calculated from the absolute thermoelectric power of solid and liquid gallium. The temperature ranges for the measurements were 248 to 302K for solid gallium, and 278 to 353K for the liquid; the liquid was supercooled up to 25K. The effect of crystal orientation on the thermoelectric power of gallium single crystals grown along the a, b, and c axes was investigated. The anisotropy of the thermoelectric power is discussed based on the electronic properties of gallium.

The performance and characteristics of a capillary-type gallium liquid ion source (LMIS) are described. While the energy spread of the source is essentially the same as that of a needle-type gallium LMIS, its current-voltage characteristics are space-charge controlled. Its stability was found to be poorer than that of indium-filled capillaries of similar construction, and considerably poorer than the stability of a typical gallium needle LMIS.

Using a bulk sample of liquid gallium the temperature dependence of the NMR frequency of 71Ga has been measured. Linearity is found with dK/dT=-2.5*10-7 degrees C-1 in both the normal and the supercooled liquid.

The mass loss of the anode of a positive-Ga-ion source is determined from microbalance measurements, when the source is operated in a steady state. The anode consists of a short W point electrode covered by a film of liquid Ga kept at 6-9 kV with respect to an earthed cathode. From spectrograms of the light emitted by this ion source it is known that neutral Ga atoms are produced during operation, besides fast positive ions. The rate of the mass loss of the emitting Ga-covered needle is found to rise approximately linearly with the current, i.e. the mass of Ga emitted per unit charge is constant, provided the current does not exceed 100 mu A. At larger currents the mass loss rate rises faster than the current. The nature of the emission of neutral atoms is briefly discussed. It is concluded that thermally activated, classical atomic evaporation cannot be the primary mechanism responsible for the neutral component of the emission.