Amount Of Ga Research Articles

(Invited) Hydrogen Evolution from Water Using Modified Chalcogenide Photocathodes

Copper chalcopyrite semiconductors of Cu(In,Ga)(S,Se)2 include a wide range of compounds that are of interest for photoelectrochemical (PEC) water splitting due to their band gaps in the range of 1.0 eV to 2.5 eV by varying the alloy ratio. The conduction band of the compounds is also well positioned above the reduction potential of water, enabling them to be used as photocathodes for H2 generation. Two of important factors required for photocathodes of PEC water splitting are photocurrent (photocurrent density) and onset potential (photovoltage), i.e., photocathodes having positive onset potentials coupled with high photocurrents are promised in order to induce water splitting by using a tandem system without applied bias energy. For chalcopyrite materials applied to the photocathode part, this can be achieved through band engineering by altering the composition of the alloy. In this study, wide-gap Cu(In,Ga)S2 (CIGS) films with various amounts of Ga were fabricated using spray pyrolysis followed by sulfurization. Photoelectrochemical water splitting properties of photocathodes based on these films were evaluated after modification with a CdS layer and Pt nanoparticles. Both photocurrent densities and onset potentials of the photocathodes were gradually improved by increase in the amount of Ga in the CIGS films up to a Ga/(In+Ga) ratio of 0.25 using 0.1 M Na2SO4 (pH 9) as an electrolyte under illumination of simulated sunlight (AM 1.5G). Further inclusion of Ga in the CIGS film was detrimental for both photocurrent density and onset potential. The maximum photocurrent density of 6.8 mA cm-2 (at 0 V vs. RHE) and the highest photocurrent onset potential of 0.84 V vs. RHE were obtained by using such photocathode. Achievements of a relatively wide interface band gap of the CIGS/CdS heterointerface and formation of relatively large grains in the CIGS with Ga/(In+Ga) ratio of 0.25 were likely to be responsible for such superior water reduction properties. The preliminary result of band engineering via replacement of Cu with Ag in the Cu(In,Ga)(S,Se)2 system in relation with its application as photocathode also will be presented.

The influence of growth conditions on the surface morphology and development of mechanical stresses in Al(Ga)N layers during metalorganic vapor phase epitaxy

We have studied the influence of technological parameters on the surface morphology and development of mechanical stresses in Al(Ga)N layers during their growth by metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates. Minimization of tensile stresses under conditions of a retained atomically smooth surface can be achieved by using a combination of factors including (i) nitridation of substrate in ammonia flow, (ii) formation of two-layer AlN–Al(Ga)N structures by introducing a small amount (several percent) of Ga after growth of a thin AlN layer, and (iii) reduction of ammonia flow during growth of an Al(Ga)N layer.

About electrochemical stability and biocompatibility of two types of CoCr commercial dental alloys

The present paper is an investigation of two commercial Co‐Cr dental alloys, named Wirobond 280 and Wirobond C. The two alloys have similar composition; the difference is made by the small amount of Ga and Mn existing in Wirobond 280. The electrochemical behavior of the alloys was tested in the artificial Erikson saliva at different temperatures between 25 and 55 °C. The electrochemical methods used have been the potentiodynamic polarization and the electrochemical impedance spectroscopy. The investigation have been performed in the presence of two different fluoride ions concentrations and permitted to compute corrosion rate and the energy activation. In order to complete the tests the cell response has been studied in vitro. The stability of Wirobond 280 alloy is correlated with the greater cell viability and with a smaller level of ROS in comparison with the Wirobond C alloy. Regarding fluoride doping effect, based on the experimental data, we can conclude that NaF increases the corrosion rate of the Wirobond 280 and decrease the corrosion rate in the case of the Wirobond C. The study established that the Wirobond 280 alloy is the one with best properties.

Type-II GaSb/GaAs Nanostructures Grown by Droplet Epitaxy with Various Ga Amounts

We study the GaSb/GaAs nanostructures (NSs) grown by droplet epitaxy technique with various Ga amounts. Ga amount deposited on the GaAs (001) substrate was varied between 3-5 ML to form the different size and density of liquid Ga droplets. The Sb flux was subsequently irradiated to crystallize the droplets. Morphology of GaSb NSs was investigated by atomic force microscopy (AFM). Quantum rings were obtained after crystallizing 3-ML Ga droplets, whereas some kind of quantum dots were formed after crystallizing 4-and 5-ML Ga droplets. The formation mechanisms leading to the different structure are discussed. The photoluminescence (PL) measurement was performed to examine the optical properties of GaSb/GaAs NSs.

Interfacial Reactions of Low-Melting Sn-Bi-Ga Solder Alloy on Cu Substrate

A new ternary solder alloy Sn62Bi32Ga6 (in wt.%) with melting point of 128°C, which is 10°C lower than that of eutectic Sn-Bi, has been developed. The composition was obtained by adding the maximum possible amount of Ga without causing Ga segregation and the formation of a liquid phase inside the solder. Solders were reflowed on Cu substrates to investigate their interfacial morphologies during liquid reactions. The only intermetallic compound detected at the interfaces was CuGa2, which initially formed with a discrete basin type at the interfaces. As the reflow time was increased, the basin-type compound formed a continuous layer that inhibited Cu dissolution. Solid-state aging tests were also performed on the system, and the activation energy for the formation of CuGa2 was found to be 2.82 kJ/mol, which is much lower than that of the Cu-Sn compound.

Enhancement of thermoelectric properties of CoSb3 skutterudite by addition of Ga and In

Filled skutterudites are known as excellent thermoelectric (TE) materials. The voids in the structure of skutterudites such as cobalt antimonide (CoSb3) can be filled or partially filled with a variety of different atoms. In the present study, we tried to fill both gallium (Ga) and indium (In) into the voids of CoSb3. The polycrystalline samples with nominal compositions of Ga0.2InxCo4Sb12 (x = 0.15, 0.20, 0.25, and 0.30) were prepared and their TE properties were examined from room temperature to 773 K. Ga and In added to CoSb3 partly filled the voids and most of the residual precipitated as nanoparticles at the grain boundaries. A tiny amount of Ga substituted for Sb at the Sb site of CoSb3, while it was more likely for In to fill the voids than Ga. All the samples exhibited negative values for the Seebeck coefficient. The lattice thermal conductivity was reduced effectively by the co-addition of Ga and In without degrading the power factor. The maximum dimensionless figure of merit (ZT) value of 0.95 at 725 K was obtained for the sample with the nominal composition Ga0.2In0.3Co4Sb12.

Development of a gas-cylinder-free plasma desorption/ionization system for on-site detection of chemical warfare agents.

A gas-cylinder-free plasma desorption/ionization system was developed to realize a mobile on-site analytical device for detection of chemical warfare agents (CWAs). In this system, the plasma source was directly connected to the inlet of a mass spectrometer. The plasma can be generated with ambient air, which is drawn into the discharge region by negative pressure in the mass spectrometer. High-power density pulsed plasma of 100 kW could be generated by using a microhollow cathode and a laboratory-built high-intensity pulsed power supply (pulse width: 10-20 μs; repetition frequency: 50 Hz). CWAs were desorbed and protonated in the enclosed space adjacent to the plasma source. Protonated sample molecules were introduced to the mass spectrometer by airflow through the discharge region. To evaluate the analytical performance of this device, helium and air plasma were directly irradiated to CWAs in the gas-cylinder-free plasma desorption/ionization system and the protonated molecules were analyzed by using an ion-trap mass spectrometer. A blister agent (nitrogen mustard 3) and nerve gases [cyclohexylsarin (GF), tabun (GA), and O-ethyl S-2-N,N-diisopropylaminoethyl methylphosphonothiolate (VX)] in solution in n-hexane were applied to the Teflon rod and used as test samples, after solvent evaporation. As a result, protonated molecules of CWAs were successfully observed as the characteristic ion peaks at m/z 204, 181, 163, and 268, respectively. In air plasma, the limits of detection were estimated to be 22, 20, 4.8, and 1.0 pmol, respectively, which were lower than those obtained with helium plasma. To achieve quantitative analysis, calibration curves were made by using CWA stimulant dipinacolyl methylphosphonate as an internal standard; straight correlation lines (R(2) = 0.9998) of the peak intensity ratios (target per internal standard) were obtained. Remarkably, GA and GF gave protonated dimer ions, and the ratios of the protonated dimer ions to the protonated monomers increased with the amount of GA and GF applied.

English

Induced mutation in plant improvement has been proven to be one of the alternative ways to generate new sources of genetic variation in blackgram. In this study, dry seeds of VBN 4 blackgram were treated with combination treatment of both gamma rays (400, 500 and 600 Gy) and ethyl methane sulphonate (EMS) (50, 60 and 70 mM) to study the polygenic characters in M2 generation. The mean values for plant height, number of primary branches, number of clusters per plant, number of pods per plant, number of seeds per pod and single plant yield decreased below the control in most of the treatments. The mean single plant yield was more than for the control at 400 Gy+60 mM and 600 Gy+50 mM. Moderate and high phenotypic coefficients of variation (PCV) and genotypic coefficients of variation (GCV) were recorded in yield component characters such as plant height, number of primary branches, number of clusters per plant and number of pods per plant. A high amount of heritability and GA as per cent of mean was noted for plant height, number of clusters per plant, number of primary branches per plant, number of pods per plant, pod length, number of seeds, 100 seed weight and single plant yield. This denoted that these characters are governed largely by additive gene effect, which may be favorably exploited for improvement through simple selection in M2 generation.   Key words: Gamma rays, ethyl methane sulphonate (EMS), blackgram, polygenic variability, M2 generation.&nbsp

Photosplitting of Water from Wide-Gap Cu(In,Ga)S2Thin Films Modified with a CdS Layer and Pt Nanoparticles for a High-Onset-Potential Photocathode

Photoelectrochemical water splitting from photocathodes based on wide-gap Cu(In,Ga)S2 (CIGS) thin films modified with a CdS layer and Pt nanoparticles was investigated. CIGS films with various amounts of Ga were fabricated using spray pyrolysis followed by sulfurization. As analyzed using 0.1 M Na2SO4 (pH 9) as an electrolyte under illumination of simulated sunlight (AM 1.5G), both photocurrent densities and onset potentials of the photocathodes were gradually improved by an increase in the amount of Ga in the CIGS films up to a Ga/(In + Ga) ratio of 0.25 (Pt-CdS/CIGS(25)). Further inclusion of Ga in the CIGS film was detrimental for both photocurrent density and onset potential. The maximum photocurrent density of 6.8 mA cm–2 (at 0 V vs RHE) and the highest photocurrent onset potential of 0.89 V vs RHE were obtained by using the Pt-CdS/CIGS(25) photocathode. Achievements of a relatively wide interface band gap of the CIGS/CdS heterointerface and formation of relatively large grains in the Pt-CdS/CIGS(25)...

The role of U-Pb ages of detrital zircons in sedimentology—An alarming case study for the impact of sampling for provenance interpretation

U-Pb ages on detrital zircons are often utilised for stratigraphic and paleogeographic interpretations and correlation. Sampling is carried out in such a way that the samples are representative for a formation, and then used for provenance identification and/or defining a maximum time limit for deposition. Is it possible that sedimentological factors and sampling would influence the results? This is perhaps an obvious consideration for sedimentologists, but is in many studies treated as asecondary concern or even not mentioned.U-Pb LA-ICP-MS analysis on detrital zircons from two samples of Cambrian age (Herrería Formation, Cantabrian Mountains, Spain) revealed very different provenance signatures at the base and top of the formation. Both successions have been deposited in a shallow marine environment, are lithologically comparable (arenites, feldspathic arenites, siltstone, shales intercalated with marls and dolomite) and differ only slightly in age. Nearly 80% of all detrital zircons (n=152; discordance≤10) at the base of the formation are younger than 650Ma. Detrital zircons older than 1.0Ga amount to only 10% (n=16) of the entire population. In contrast, only around 32% of all detrital zircons from the top of the formation (n=123; discordance ≤10) are younger than 650Ma while more than 16% are Archean and nearly 50% Paleoproterozoic. This implies a fundamental change in provenance, with a shift from Neoproterozoic to Paleoproterozoic (1.9–2.2Ga) aged sediment sources. Consequently, changes of sediment transport systems have had an extremely profound impact on the provenance of the formation. Therefore, when correlating sedimentary rocks, interpreting source rocks and modelling paleogeography from U-Pb ages of detrital zircons, sedimentological parameters are possibly paramount and these need to be at least discussed before any interpretation is made.

Carrier concentration dependent optical and electrical properties of Ga doped ZnO hexagonal nanocrystals.

Colloidal trivalent gallium (Ga) doped zinc oxide (ZnO) hexagonal nanocrystals have been prepared to introduce more carrier concentration into the wide band gap of ZnO. The dopant (Ga) modifies the morphology and size of ZnO nanocrystals. Low content of Ga enhances the optical band gap of ZnO due to excess carrier concentration in the conduction band of ZnO. The interaction among free carriers arising from higher concentration of Ga gives rise to narrowing of the band gap. Surface plasmon resonance absorption appears in the infrared region due to excessive carrier concentration. A broad emission band consists of blue, yellow and green colors associated with different native defects of ZnO. Intrinsic defects and extrinsic dopant Ga control the defect related emission spectrum in the visible region. Replacement of Zn by Ga induces a room temperature metallic state in a degenerate semiconductor. Cationic disorder leads to metal-semiconductor transition at low temperature strongly dependent on the concentration of Ga. Pure semiconducting behavior up to about 80 K is observed for the highest amount of Ga. Temperature dependent metal-semiconductor transition has been interpreted by localization of charge carriers due to disorder arising from random Ga substitution.

Isolation and Physiological Characterization of PGPR from Potato Plant Rhizosphere in Medium Land of Buru Island

A total of 70 bacteria were isolated from the rhizosphere of potato cv. Hartapel that grew at an altitude of 700 m above sea level on the island of Buru-Maluku. Of these isolates, 36 isolates were capable of producing IAA, GA, Siderophore and phosphate solubilization. Among the selective isolates, isolate HB8 produced the highest amount of IAA (5.816mg l-1), while isolate HB32 produced the highest amount of GA (6.879mg l-1). Isolate HB18 had the best ability in producing salicylate type siderophore (4.214mg l-1) and isolate HB3 showed the highest phosphate solubilization (14.237mg l-1). There were three isolates (HB3, HB8 and HB31) positively produced HCN. All 36 isolate showed physiological characters which revealed the potential use for biostimulant, biofertilizer and bioprotectant against soil borne pathogens.

CIS and CIGS nanomaterials prepared by solvothermal method and their spectral properties

Uniform CIS and CIGS nanomaterials were successfully synthesized by a simple amino‐based assisted solvothermal technique using PVP‐30 as the surfactant. The influence of surfactant, temperature and Ga amount on the structure, morphology, phase and spectral property was analyzed in detail. The results show that CIS and CIGS nanomaterials with 40∼70 nm in diameter can be gained at 200 °C for 24 h. PVP‐30 surfactant can greatly improve the dispersion characteristics of particles. XRD pattern shows that the “three peaks” obviously shift to bigger 2θ after gallium implantation because of lattice contraction. EDAX and Raman show that the final product is close to CuIn0.7Ga0.3Se2. The possible reaction mechanism has also been explained in detail. UV‐vis‐NIR spectra show that the absorption peak and absorption edge of CIGS with 1.278 eV bandgap obviously shift to a lower energy compared to CIS with 1.051 eV bandgap, which shows the potential application in enhanced conversion efficiency.

Low resistive gallium doped nanocrystalline zinc oxide for gas sensor application via sol–gel process

This paper reports the effect of low concentration of Ga doping on the performance of ZnO thin-film based gas sensors. The ZnO films were synthesized on the alkali-free glass substrates by employing a sol–gel process. Different concentrations of Ga were added to the sol–gel mixture for systematic comparison of doping effect. The effect of Ga doping on the microstructure, optical properties, surface morphology, electrical conductivity and gas sensing characteristics was investigated comparing undoped and Ga-doped ZnO thin films. The results revealed that the grain size decreased after the doping of Ga in ZnO. The optical transmittance and bandgap of ZnO films were not affected by the doping of Ga. The Ga doping resulted in a significant increase in electrical conductivity of ZnO thin films. The gas sensing behavior was studied under different concentrations of H2 exposure in the air at an operating temperature of 130°C. The results indicated that the sensing response for H2 was enhanced after the doping of a trace amount of Ga. It was found that 0.3at.% was the optimum Ga doping concentration for ZnO sensors in the low Ga doping concentrations, which exhibited both high response and short response time. The selectivity of 0.3at.% Ga-doped ZnO sensor was investigated for important industrial gas mixtures. It was found that the Ga-doped ZnO sensors exhibited a better detection capability of H2 than NH3 and CH4.

Effect of Surface Morphology and Microstructure on Powdering Resistance Performance of GA Coatings with Different Aluminum Contents

The surface morphology and microstructure of galvannealed steel sheet (GA) coatings prepared at different galvannealing parameters were analyzed by X-ray diffraction and SEM, and powdering amount of GA coating was investigated by the double-Olsen powdering tester. The results show that when the Al contents below 0.16 wt%, the Ra of GA coating surface was measured namely below 1.0 μm, and powdering amount of GA coating was below 30 mg/m2, it is within a reasonable value required by automotive makers. After that with the Al contents increased in zinc liquid the amount of powdering increased, this means that the powdering resistance performance of GA coating not only depended on the iron content in the coating, but depended on the roughness profiles of the surface coating. When the galvanizing coating with 0.22 wt% Al content and galvannealing at 500 °C, with the inhibition effect of Fe2Al5Znxinhibit layer, the thickness of δ1k-phase was different in the GA coating, which deteriorated the powdering resistance performance of GA coating.

Tensile Strength and Impact Toughness of Gallium-Bearing Near-α Titanium Alloys

The present study aims to quantify the properties of Ga-bearing near-titanium alloys in order to aid the future design of new compositions with Ga addition. The effect of different amounts of Sn and Ga, with an almost constant value in the Al equivalent without the formation of 2 phase, on microstructure, tensile strength and Charpy impact toughness was investigated at room temperature and 650°C. The microstructures after forging, hot rolling and heat treatment showed a bimodal structure. Increasing Ga decreased the 0.2% proof stress at 650°C. However, these alloys showed similar impact value at room temperature which was about 40 J/cm2. Increasing the amount of Ga increased the volume fraction of the equiaxed phase. The amount of Ga had only a minor effect on grain size, misorientation angles and grain aspect ratios of the alloy. However, Ga addition had a strong influence on the evolution of texture. Formation of <10-10> and <10-11> || normal direction (ND) fibers were observed in the Ga added samples, in addition to <0001> || ND fiber with a weak <10-11> || ND fiber. The Ga-free sample contained a strong <0001> || ND fiber. Other fibers were not observed.

A CaS:Eu based red-emitting phosphor with significantly improved thermal quenching resistance for LED lighting applications

While CaS:Eu based system can be much needed low-cost red emitting phosphors for LED lighting applications, their poor thermal quenching resistance remains an issue. In this work we have investigated the effect of adding small amount of Mg and Ga on the emission intensity of CaS:Eu at room and elevated temperatures. We found that the addition of small amount of Mg and Ga at the same time to substitute Ca leads to a significant improvement in the photoluminescence efficiency of CaS:Eu at both room and elevated temperatures. We reported that a new red-emitting phosphor of Ca0.89Mg0.01Ga0.1S:Eu can reduce the drop of its emission intensity with rising temperature by as much as 37 percentage points as compared to undoped CaS:Eu at 185°C. Its emission intensity at room temperature is also 23.9% higher than that of undoped CaS:Eu.

Compound-induced changes in thermal, structural and optical properties of indium–gallium–zinc oxides prepared by sol–gel method

In this study, IZO/IGZO powders and films of different composition ratios were fabricated by sol–gel method. The influences of the composition ratio on the decomposition temperature, crystallization behavior, structural and optical properties of multi-component oxides were thoroughly examined. Thermogravimetric/differential scanning calorimetric results revealed that in contrast to zinc and indium oxides, the high crystallization temperature and low crystallinity of gallium oxide were attributed to the high dehydroxylation temperature of gallium hydroxide, which led to the high decomposition and crystallization temperatures of IGZO compound. The XRD analysis of the IGZO films confirmed that the addition of Ga amount made the films turn into amorphous easily. However, TEM analysis suggested that the IZO film (In:Zn = 1:2) and the IGZO (In:Ga:Zn = 1:1:1) film consisted of short-range-order nanostructure although the selected area diffraction of both samples indicated that they are amorphous. The transmittance measurements agreed well with the XRD results; that is, the band gaps of the IZO/IGZO films obviously depend on the composition ratio and are closely related to the change of the structural properties.

Transitory Embrittlement of Polycrystalline Silver by Liquid Gallium

The phenomenon of embrittlement of polycrystalline silver (Ag) by liquid gallium (Ga) is known as liquid metal embrittlement (LME). An investigation was performed to determine the effects of holding the solid metal in contact with liquid Ga on the embrittlement. Solid Ag specimens in contact with liquid Ga were placed in a furnace at 308­573K for different time periods before testing at 308K. The specimens undergo severe embrittlement when the holding time is short, whereas ductility is recovered when the holding time is long. The duration of brittleness decreases with increase in furnace temperature, and it is proportional to the amount of Ga on the surface. The brittle to ductile transition is considered to occur during the formation process of an intermetallic Ga and Ag compound. [doi:10.2320/matertrans.M2013394]

Transparent Conductive Oxide GZO Thin Films by Sol-Gel Process

In this work, GZO thin films were prepared by sol-gel process and spin coating technique. The XRD results showed the preferential c-axis orientation of the crystallites and the presence of the wurite phase of ZnO and it were suggested that the presence of Ga might be changed the d-spacing of ZnO to formation the Ga-doped zinc oxide. The effects of Ga amount on the conductivity and transparency were studied. The electrical resistivity for the GZO film doped 2 at% of Ga could be lowered to be 7.510-3Ω-cm with the calcination temperature was 550°C and hydrogen treatment was conducted in the Ar/H2 (97/3) atmosphere at 500°C. In addition, the optical transmittances of GZO thin films were higher than 90% in visible wavelength region.