Gallium Application Research Articles

Gallium's Application in Medicine and Hygiene: Examples of Antineoplastic and Anti-Microbial

Gallium's Application in Medicine and Hygiene: Examples of Antineoplastic and Anti-Microbial

Literature Review of Gallium: Conductive Ink Alternative?

Although there are currently different applications for gallium in microelectronics, literature is sparse about its applications in the area of conductive inks. The important characteristics to consider from the ink are viscosity, corrosion and surface tension. The importance of viscosity is a critical parameter in the printing ink mixture, which requires a metal to fulfill the function of conductor, such as gold, copper, and silver. Gallium as a conductor replacement is proposed due to the high cost of such metals currently used. The valence electrons are discussed in this paper due to the direct relation that has with metal conductivity, to provide a justified analysis about gallium application in conductive ink. The application of gallium could mean a significant change in conductive ink elaboration process. Thus, the aim of this research is to analyze the application of gallium as conductive ink, which is done by a literature review on gallium as a semi-conductor because of his valence electrons. Results about gallium as a potential conductive ink show that there is evidence that gallium shares similar properties as the current of materials conductive inks being adopted. This first literature review has some implications on the potential use of gallium as a conductive ink, requiring further experimental research to better test for conducting efficiency.

On the Growth of High-Temperature Epitaxial AlN (AlGaN) Layers on Sapphire Substrates by Ammonia Molecular Beam Epitaxy

The growth of high-temperature AlN and AlGaN layers on (0001) sapphire substrates by ammonia based molecular-beam epitaxy is studied. Factors affecting the formation of inverted domains in high-temperature AlN films are examined. The density of inverted domains is found to correlate with the density of nucleation islands during the initial stages of growth. The denser coverage of a surface by nucleation islands suppresses the formation of inverted domains. It is possible to increase the density of surface coating at the nucleation growth stage by increasing the degree of substrate nitriding, reducing the deposition temperature, and using intense ammonia fluxes during deposition of the initial layers. The kinetic model in the mean field approximation is developed to explain the observed effects of growth parameters on the density of nucleation islands. The growth features of AlN and its structure are taken into account. The obtained results are used to grow AlN/AlGaN layers with improved structural quality. The grown films have a root-mean-square surface roughness of 2 A and 120 arc s FWHM of X-ray diffraction peaks for the AlN 0002 reflection. The density of inverted domains is decreased to below 105 cm-2. Improvement in the quality of the AlN films is achieved by using two-step growth and by the application of gallium as a surfactant.

Growth of AlGaN under the conditions of significant gallium evaporation: Phase separation and enhanced lateral growth

The growth kinetics of AlGaN in NH3 MBE under significant Ga desorption was studied. It was found that the addition of gallium stimulates 2D growth and provides better morphology of films compared to pure AlN. The effect was experimentally observed at up to 98% desorption of the impinging gallium. We found that under the conditions of significant thermal desorption, larger amounts of gallium were retained at lateral boundaries of 3D surface features than at flat terraces because of the higher binding energy of Ga atoms at specific surface defects. The selective accumulation of gallium resulted in an increase in the lateral growth component through the formation of the Ga-enriched AlGaN phase at boundaries of 3D surface features. We studied the temperature dependence of AlGaN growth rate and developed a kinetic model analytically describing this dependence. As the model was in good agreement with the experimental data, we used it to estimate the increase in the binding energy of Ga atoms at surface defects compared to terrace surface sites using data on the Ga content in different AlGaN phases. We also applied first-principles calculations to the thermodynamic analysis of stable configurations on the AlN surface and then used these surface configurations to compare the binding energy of Ga atoms at terraces and steps. Both first-principles calculations and analytical estimations of the experimental results gave similar values of difference in binding energies; this value is 0.3 eV. Finally, it was studied experimentally whether gallium can act as a surfactant in AlN growth by NH3 MBE at elevated temperatures. Gallium application has allowed us to grow a 300 nm thick AlN film with a RMS surface roughness of 2.2 Å over an area of 10 × 10 μm and a reduced density of screw dislocations.

Grain boundary tracking: A four-dimensional visualization technique for determining grain boundary geometry via local strain mapping

A procedure for determining three-dimensional grain boundary geometry and its change under external loading is proposed for evaluating crystallographic deformation behaviours in polycrystalline materials, and the feasibility of this approach is confirmed for an aluminium alloy. X-ray microtomography has been combined with gallium-enhanced microscopy, in which grains are visualized in three dimensions by decorating grain boundaries with liquid gallium. Grain boundary particles are then extracted by comparing tomographic images with and without the gallium application. Three-dimensional reconstruction of grains is achieved using a connection scheme based on triplets of non-aligned points on grain boundaries. The deformation of the closed polygonal grains is visualized by combining the above technique with a microstructural tracking technique, in which the paths of particles are reconstructed by matching each pair of particles in consecutive images. This process also enables high-density four-dimensional strain mapping by tracking particles located in grains, providing direct interpretation of localized deformation caused by interaction between neighbouring grains.

Electrochemistry of Gallium

Gallium is an important element in the production of a variety of compound semiconductors for optoelectronic devices. Gallium has a low melting point and is easily oxidized to give oxides of different compositions that depend on the conditions of solutions containing Ga. Gallium electrode reaction is highly irreversible in acidic media at the dropping mercury electrode. The passive film on a gallium surface is formed during anodic oxidation of gallium metal in alkaline media. Besides, some results in published reports have not been consistent and reproducible. An increase in the demand of intermetallic compounds and semiconductors containing gallium gives rise to studies on electrosynthesis of them and an increase of gallium concentration in the environment with various application of gallium causes the development of electroanalysis tools of Ga. It is required to understand the electrochemistry of Ga and to predict the electrochemical behavior of Ga to meet these needs. Any review papers related to the electrochemistry of gallium have not been published since 1978, when the review on the subject was published by Popova et al. In this study, the redox behavior, anodic oxidation, and electrodeposition of gallium, and trace determination of gallium by stripping voltammetries will be reviewed.

Three-Dimensional Visualization and Analysis of Grain Deformation by Means of Synchrotron Radiation

The new method to investigate and visualize a strain distribution at individual grains in three-dimensional has been developed based on synchrotron radiation X-ray tomography. The tensile specimen made of a heat-treated 2024 aluminum alloy to coarse precipitate particles has repeatedly scanned by the high-resolution X-ray tomography with applying a loading just before fracture would occur. Grain boundaries in the specimen were visualized by the tomographic scan after gallium application in order to detect grain regions in three-dimensional. Total 17 grains were found by 2D and 3D image processing and were provided with strain analysis by means of the microstructural features tracking. The actual strain development on a grain was visually demonstrated during tensile deformation. The strain map on a cross section of the grain shows inhomogeneous distribution. In the vicinity of grain boundary, the partly large strain is observed. The strain distribution within a grain seems to be affected by neighbor grains. The different evolution of strain distribution was also confirmed in the two grains while the grains were deformed almost equivalently on an average. The difference of deformation microstructure depending on grain orientation is suggested.

The application of gallium as a liquid metal lubricant

Abstract The application of Ga as a base for a solid metal lubricator has been considered. Different methods were applied to investigate properties of liquid Ga in the temperature range 30–300°C. Some peculiarities of liquid Ga can be explained with structural transformations. It has been shown that Ga is characterized with combination of a high plasticity and strength of a melt. Due to the good adhesion, Ga forms stiff films on the surface of contact bodies. A mixed mode of friction usually exists when Ga is applied as a solid lubricator. Moreover, the friction process is characterized with low friction coefficients, which practically do not depend on load and velocity. Investigations have revealed that Ga is a promising metal for solid lubricators. Properties of these lubricators can be easily controlled by the preparation of suspensions on the base of Ga.

Gallium(III) Trifluormethanesulfonate: A Water-Tolerant, Reusable Lewis Acid Catalyst for Friedel-Crafts Reactions

The application of gallium(III) trifluoromethanesulfonate (triflate, OTf) in Friedel-Crafts alkylation and acylation reactions is described. Gallium triflate was found to be an excellent catalyst for the adamantylation of toluene with 1-bromoadamantane, where its activity was compared to that of well-known rare earth metal triflates. As Ga(OTf)3 does not decompose in the presence of water the isopropylation of aromatics can be carried out with isopropyl alcohol in moderate to excellent yields. While acetylation provides moderate yields in selective reactions, benzoylation of aromatics takes place in good yields in a catalytic and non-stoichiometric reaction. The catalyst can easily be recovered from the reaction mixture and can be reused without loss of activity, demonstrating its effective and environmentally friendly recyclable character.

Spreading of gallium on tin surfaces

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.