Effect Of Ga Addition Research Articles

Effects of Ga addition on the corrosion behaviours of high strain rate rolled Mg–Ga alloy sheets

ABSTRACT The effects of Ga addition (1, 2, 3 and 5 wt-%) on the corrosion behaviour of high strain rate rolled Mg–Ga alloys are firstly investigated by weight loss measurement and electrochemical testing. Solute Ga atoms can reduce the corrosion potential but improve the corrosion resistance of the alloy with the Ga content lower than 3 wt-%. The Mg–3Ga alloy sheet is the most corrosion-resistant with the weight loss rate of 0.52 mg cm−2 day−1 for 7 days immersion in 3.5% NaCl solution. The corrosion resistance improvement can be ascribed to the enhanced compactness of the corrosion film associated with Ga addition. The Ga addition affects the DRX degree, but the DRX degree is not the crucial factor in the corrosion of the alloys. The Mg5Ga2 dynamic precipitates are detrimental to the corrosion resistance of the Mg–Ga alloys and play a relatively important role in the corrosion of the Mg–5Ga alloy.

Effect of Ga addition on the microstructure and magnetic properties of melt-spun (Nd0.8Ce0.2)13.8Fe68.96−xGaxCo11.49B5.74 alloys

The effects of Ga addition on the magnetic properties and microstructure of (Nd0.8Ce0.2)13.8Fe68.96−xGaxCo11.49B5.74 ribbons are investigated in this paper. The results indicate that the Ga doping is significantly effective in increasing the coercivity Hcj of the samples being improved from 15.93 kOe to 19.19 kOe. The XRD patterns show that the Ga addition reduces the amount of soft magnetic α-Fe phase. The highest positive peak in Henkel plot is obtained by 0.5 at% Ga doping, which indicates strongest intergranular exchange interaction. The best remanence Jr = 7.6 kG, and maximum energy product (BH)max = 12.51 MGOe are obtained in (Nd0.8Ce0.2)13.8Fe68.46Ga0.5Co11.49B5.74 alloy ribbon. The Curie temperature (Tc) monotonically decreases from 674 K for the Ga free alloy to 667 K for 1.0 at% Ga doping. The improvement in magnetic properties can be attributed to the increase in volume fraction of the 2:14:1 main phase and grain refinement as a result of Ga doping.

Effects of Ga Additives on the Thermal and Wetting Performance of Sn-0.7Cu Solder

The effects of Ga additions on thermal behavior, wettability, microstructure and properties of Sn-0.7Cu solder were investigated. The addition of Ga influences the surface tension of the solder and improves the wetting performance. The best wetting was achieved when the Ga content approached 0.5% (by weight), but further increases of Ga did not improve the wettability of the Sn-0.7Cu solder. The most uniform and refined grain structure was obtained with ∼ 0.5% Ga. The interfacial intermetallic (IMC) layer was also refined and reduced in thickness with the addition of Ga. Also, the hardness increases with increases in Ga content compared to SnCu solder without Ga. This is likely due to the refinement of grain structure and the uniform distribution of IMC phases in the solder.

Synthesis, characterization, resistivity and magnetoresistance of Ba2Fe1−xGaxMoO6 double perovskite

Effect of Ga addition on structure, resistivity and magnetoresistance of Ba2Fe1−xGaxMoO6 (x = 0.0, 0.1, 0.25 and 0.3) double perovskite. The sol–gel procedure was used to synthesize Ba2Fe1−xGaxMoO6 double perovskite and consolidated at 1150 °C under Ar/H2 atmosphere. Single phase with cubic crystal structure confirmed for all the samples through X-ray diffraction studies. Variation of grain size behavior on the samples surface has been studied by scanning electron microscopy (SEM). The spectra from energy dispersive X-ray spectroscopy (EDS) showed that all the elements Ba, Fe, Ga, Mo and O are present in the samples and there are no impurities in the materials. Fourier transform infrared spectroscopy (FTIR) spectral analysis of samples produced three characteristic absorption bands of Mo–O and Fe–O vibrations in the wave number range 400–1000 cm−1 which confirmed the present materials are double perovskite phase. Magneto-resistance (MR %) of these samples reduce with the addition of Ga content at room temperature (RT). Whereas, MR% at 5 K exhibits opposite trend to the MR% at RT with the Ga-content. It is found that all samples show semiconductor behavior at 5 K and changes into metallic nature as temperature increases showing a semiconductor-metallic transition. This value is larger for composition x = 0.3 and smaller for parent compound.

Effect of Ga addition on the valence state of Ce and magnetic properties of melt-spun Ce17Fe78-xB6Gax (x = 0-1.0) ribbons

The Ce17Fe78-xB6Gax (x=0-1.0) ribbons were fabricated by a melt-spinning technique in order to study the mechanism of the valence variation of Ce and their magnetic properties as well as improve the thermal stability of Ce-based rare earth permanent magnets. The systematic investigations of the Ce17Fe78-xB6Gax (x=0-1.0) alloys show that the room-temperature coercivity increases significantly from 352 kA/m at x = 0 to 492 kA/m at x = 1.0. The Curie temperature (Tc) increases monotonically from 424.5 K to 433.6 K, and the temperature coefficients of remanence (α) and coercivity (β) of the ribbons are better off from -0.56 %/K, -0.75 %/K for x = 0 to -0.45 %/K, -0.65 %/K for x = 0.75 in the temperature range of 300–400 K, respectively. The Ce L3-edge X-ray absorption near edge structure (XANES) spectrums reveal that there is more Ce4+ in ribbons under total electron yield than fluorescence yield as Ce has a high affinity with oxygen. The weight of Ce3+ increases while the weight of Ce4+ decreases in Ga-added alloys. The refined grain size and a more uniform microstructure are mainly attributed to the improved magnetic properties and thermal stability with Ga doping. This paper may serve as a reference for further developing the so-called gap magnets and the effective utilization of the rare earth resources.

Effects of Ga Addition on the Formability of Main Phase and Microstructure of Hot-Deformed Ce–Fe–B Magnets

The powders of Ce29.82Fe69.18B1.0 (CeFeB) and Ce29.82Fe68.65Ga0.53B1.0 (CeFeGaB) (wt%) were prepared by melt spinning. Microstructure and phase composition of the prepared powders were characterized by X-ray diffraction (XRD) and Mossbauer spectrometry. The results indicated that the as-spun ribbons comprised multi-phases, including CeFe17, Ce-rich phase, $\alpha $ -Fe phase, and continuous phase. The proportion of the main phase (Ce2Fe14B) in the CeFeGaB ribbons increased as a result of Ga addition. Then, the bulk samples were produced by hot pressing at 700 °C followed by hot deformation (HD) at 800 °C with a height reduction of 75%, and then investigated by field emission scanning electron microscope, high resolution transmission electron microscope, XRD, and vibrating sample magnetometer. The investigation showed a strong crystallographic texture in the HD CeFeGaB magnet and a weak magnetic anisotropy in the HD CeFeB magnet, which could be attributed to the Ga addition that modified the microstructure of grain boundary and the distribution of the Ce–Ga-rich phase.

Effects of Ga Addition on Interfacial Reactions Between Sn-Based Solders and Ni

The use of Ga as a micro-alloying element in Sn-based solders can change the microstructure of solder joints to improve the mechanical properties, and even suppress the interfacial intermetallic compound (IMC) growth. This research investigated the effects of Ga addition (0.2–1 wt.%Ga) on the IMC formation and morphological evolution in the Sn-based solder joints with Ni substrate. In the soldering reaction at 250°C and with less than 0.2 wt.%Ga addition, the formed phase was Ni3Sn4. When the Ga addition increased to 0.5 wt.%, it changed to a thin Ni2Ga3 layer of ∼1 μm thick, which stably existed at the interface in the initial 1-h reaction. Subsequently, the whole Ni2Ga3 layer detached from the Ni substrate and drifted into the molten solder. The Ni3Sn4 phase became dominant in the later stage. Notably, the Ga addition significantly reduced the grain size of Ni3Sn4, resulting in the massive spalling of Ni3Sn4 grains. With 1 wt.%Ga addition, the Ni2Ga3 layer remained very thin with no significant growth, and it stably existed at the interface for more than 10 h. In addition, the solid-state reactions were examined at temperatures of 160°C to 200°C. With addition of 0.5 wt.%Ga, the Ni3Sn4 phase dominated the whole reaction. By contrast, with increasing to 1 wt.%Ga, only a thin Ni2Ga3 layer was found even after aging at 160°C for more than 1200 h. The 1 wt.%Ga addition in solder can effectively inhibit the Ni3Sn4 formation in soldering and the long-term aging process.

Study of Ga incorporation in glassy arsenic selenides by high-resolution XPS and EXAFS

Effect of Ga addition on the structure of vitreous As2Se3 is studied using high-resolution X-ray photoelectron spectroscopy and extended X-ray absorption fine structure techniques. The "8-N" rule is shown to be violated for Ga atoms and, possibly, for certain number of As atoms. On the contrary, Se keeps its 2-fold coordination according to "8-N" rule in the amorphous phase throughout all the compositions. Crystalline inclusions appear in the amorphous structure of the investigated glasses at Ga concentrations greater than 3 at. %. These inclusions are presumably associated with Ga2Se3 crystallites and transition phases/defects formed at the boundaries of these crystallites and host amorphous matrix. The existence of Ga-As and Se-Se bonds in the samples with higher Ga content is supported by present studies.

Ga-modified As2Se3–Te glasses for active applications in IR photonics

Effect of Ga addition on physical properties of glassy As2Se3 alloys within Gax(As0.4Se0.6)100−x system (x=0–5) is studied for further improvement as rare earth ions matrix hosts. Following conventional synthesis conditions, it has been shown it is possible to introduce up to 3at.% of Ga into As2Se3 matrix without any crystallization and up to 2at.% of Ga without any changes in the properties of these alloys. The synthesized Gax(As0.4Se0.6)100−x alloys with 4 and 5at.% of Ga are partly crystallized by cubic Ga2Se3 crystallites. Tellurium has been introduced in the selected Ga2(As0.4Se0.6)98 glass following the Ga2(As0.4Se0.6)98−yTey cut-section to lower phonon energy and enhance quantum efficiency of the incorporated rare earth ions. The Ga2(As0.4Se0.6)88Te10 glass composition is the richest in Ga and Te, keeping its vitreous state without any crystallization. It has been successfully doped with 500 and 1000ppmw Pr3+ and drawn into optical fiber possessing low attenuation in mid-IR region. Emission in mid-IR was efficiently recorded by pumping Pr3+: Ga2(As0.4Se0.6)88Te10 glasses at 2μm.

Effects of Ga addition on microstructure and properties of Sn–Ag–Cu/Cu solder joints

The effects of Ga alloying on melting behaviors of the SnAgCu solder, the interfacial reaction behaviors and mechanical properties of the SnAgCu/Cu solder joints were investigated in this study. The melting behaviors of the Sn3.5Ag0.7Cu1.5Ga solder alloy was analyzed firstly and compared with the Sn3.5Ag0.7Cu solder, then the interfacial microstructure, shear and fatigue properties of the SnAgCu/Cu and SnAgCuGa/Cu solder joints were studied. It was found that addition of Ga element can obviously decrease the melting point of the SnAgCu solder. During the soldering process, the Ga element forms the Cu2Ga phase around the joint interface, which decreases the growth rate of the interfacial intermetallic compounds layer. Shear strength of the SnAgCuGa/Cu solder joints are slightly higher than the SnAgCu/Cu solder joints, and their fatigue properties are about the same. Under different mechanical loadings, there is no fracture occurs at the Cu2Ga/solder interface or the Cu2Ga/Cu6Sn5 interface, neither in the Cu2Ga phase, indicating that the Ga addition has little negative effect on interfacial mechanical property of the SnAgCu/Cu solder joint.

Effect of Ga addition on optical properties of crystalline Ga20Se80 system

GaxSe100−x (20≤x≤50) in polycrystalline form was prepared by direct fusion of stoichiometric proportions of pure elements. The spectral behavior of transmittance (T) and the reflectance (R) in the wavelength range 400–2500nm for all films of different thicknesses were measured to obtain different optical parameters (refractive index, n, and absorption index, k). The study of inter-band transitions indicates that the existence of direct forbidden transitions and indirect forbidden transitions with energy gaps decrease with increasing Ga percentage.

Effects of Ga addition on microstructure and properties of Sn–0.5Ag–0.7Cu solder

The effects of rare element Ga on solderability, microstructure, and mechanical properties of Sn–0.5Ag–0.7Cu lead-free solder were investigated. The experimental results show that Ga plays a positive role in improving the wettability and the microstructure of the solder. When the content of Ga is at 0.5 wt%, the grain size of the solder is smaller and the shear force is enhanced greatly. It is also found that the thickness of the IMCs at the solder/Cu interface is reduced with proper addition of Ga. The increase of mechanical properties may be related to the refining of IMCs of the solder due to Ga addition.

Effect of Ga incorporation in the As30Se50Te20 glass

The effect of Ga addition on the physical properties and structure of As30−xGaxSe50Te20 alloys is studied using atomic density measurements, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, optical spectroscopy in visible and IR regions, as well as extended X-ray absorption fine structure techniques. The process of As30Se50Te20 glass crystallization owing to Ga additives (1–10at.%) is shown to be related to extraction of droplet-like nanoinclusions in As28Ga2Se50Te20 glassy-like alloy and larger microcrystallites basically with a structure of cubic Ga2Se3 polymorphs as observed for As25Ga5Se50Te20 and As20Ga10Se50Te20. It was possible to introduce only 1at.% of Ga (substituting As) without essential crystallization within the studied system. This glass was successfully drawn into fiber and can be used for rare earth doping. The microcrystalline seeds present in As28Ga2Se50Te20 alloy can serve as a basis for further development of crystallization-controlled ceramization to produce high-reliable far-IR transmitting media.

Structure and magnetic properties of SmCo7−xGax (0⩽x⩽1.2) alloys

• Effects of Ga addition on structure and magnetic properties of SmCo 7 alloy were studied. • A stable TbCu 7 -type single phase can be obtained in as-cast SmCo 6.1 Ga 0.9 alloys. • Ga addition affects the stability, order degree and nucleation of 1:7H phase. • TbCu 7 -type phase in the ribbons is basically stable below 500 °C. • The phase transition of ribbons during the heating process was discussed. In this article, the effects of Ga addition on the structure and magnetic properties of SmCo 7 alloy were studied. The results show that a stable TbCu 7 -type single phase can be obtained in as-cast SmCo 7− x Ga x alloys when a proper amount of Ga is introduced ( x = 0.9). Meanwhile, all SmCo 7− x Ga x ribbons melt-spun at 40 m/s are composed of single TbCu 7 -type phase. So both the appropriate doping of Ga, and more especially the rapid cooling rate, can effectively stabilize the TbCu 7 -type structure. Moreover, Ga addition affects not only the stability and the order degree of 1:7H phase but also the uniformity of nucleation. Magnetic tests reveal that the coercivity, remanence and remanence ratio of the ribbons increase with the Ga addition, and reach their maximum values (7117.0 ± 2081.5 Oe, 36.7 ± 4.2 emu/g and 0.771 ± 0.037, respectively) when x = 0.9. At the same time, the maximum magnetization of ribbons and Curie temperature ( T c ) of Sm–Co phases tend to decrease with the amount of Ga. In particular, the TbCu 7 -type phase in SmCo 7− x Ga x ribbons is basically stable below 500 °C, and the phase transition during the heating process is also discussed.

Effects of Ga addition on structural and magnetic properties of nanocomposite Nd-Fe-B-Ti-C thick ribbons

Rapidly solidified Nd9Fe73B12.6C1.4Ti4-xGax (x = 0, 0.5, 1) thick ribbons were prepared by melt spinning technique at a surface speed (vs) of 5 m/s. The influences of Gallium doping on the glass-forming ability (GFA), microstructure and magnetic properties of alloys were investigated. The coercivity of Nd-Fe-B-Ti-C nanocomposite alloy thick ribbons can be dramatically enhanced by 0.5 at. % Ga addition in a low cooling-rate regime, attributing to the weakened exchange coupling interaction and grain refinement. The results of XRD showed that the GFA of Nd-Fe-B-Ti-C alloy was enhanced by the Ga addition. Therefore, Gallium addition is effective to refine grain and improve the glass-forming ability, which provides the possibility to obtain the high performance of magnetic properties by using strip casting (SC) method.

Effect of Ga addition on the magnetic properties and microstructure of nanocrystalline Nd12.3Fe81.7B6.0 ribbons

Nd12.3Fe(subscript 81.7-x)Ga(subscript x)B6.0 (x=0-1.8) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing treatment. The influences of Ga addition and annealing conditions on the magnetic properties and microstructure of the nanocrystalline alloys were systematically investigated. After being annealed at 620℃ for 20 min, the J(subscript r) and H(subscript ci) increased from 0.85 T and 582.6 kA/m for Ga-free sample to 0.97 T and 734.6 kA/m for the x=0.9 sample, respectively. The (BH)(subscript max) for the x=0.9 sample increased by about 40% from 96.3 to 135.5 kJ/m^3 compared with that of the Ga-free one. The significant improvement of magnetic properties originated from the refinement of grains in the samples by introducing Ga, which led to a stronger exchange coupling between the neighboring grains in comparison with that in Ga-free samples. The microstructure and magnetic properties of the samples depended strongly on annealing parameters, while the sensitivity of microstructure to annealing conditions could be significantly suppressed by the addition of Ga element.

Synthesis of bulk glassy Fe–C–Si–B–P–Ga alloys with high glass-forming ability and good soft-magnetic properties

Effects of Ga additions on the glass-forming ability (GFA) and magnetic properties of the Fe 76C 7.0Si 3.3B 5.0P 8.7 alloy were investigated. It was found that addition of 1–2% Ga can increase the critical diameter for glass formation from 1 to 3 mm. Moreover, the as-cast alloy containing 1% Ga exhibit good soft-magnetic properties including a high saturation magnetization value of 1.55 T and a low coercive force of 4.9 A/m. The combination of high GFA and good soft-magnetic properties make the newly developed Fe-based bulk metallic glasses promising for electric applications.

Effect of Ga addition on the microstructure and magnetic properties of hydrogenation–disproportionation–desorption–recombination processed Nd–Fe–B powder

Microstructural evolution of hydrogenation–disproportionation–desorption–recombination processed Nd 12.5Fe 72.8Co 8.0B 6.5Ga 0.2 powder has been investigated in relation to coercivity development during the desorption recombination process. Coercivity increases when residual NdH 2 is completely dehydrogenated and the decomposed Nd is segregated at the grain boundaries of the Nd 2Fe 14B phase. Three-dimensional atom probe (3DAP) analysis indicates the segregation of Ga at the grain boundary. The reason for the enhancement of the coercivity by the trace addition Ga is discussed based on the 3DAP results.

Dehydrogenation of n-butane over Pd–Ga/Al 2O 3 catalysts

Dehydrogenation of n-butane over alumina-supported Pd and Pd–Ga catalysts was studied. Catalysts were prepared by incipient wetness impregnation with a Pd content of 0.66 wt% and atomic Ga/Pd ratios from 0 to ∞, using aqueous solutions of PdCl 2 and Ga(NO 3) 3. Fresh (uncalcined) and calcined catalysts were characterized by X-ray fluorescence spectroscopy (XRF), N 2 adsorption, temperature programmed reduction (TPR), CO and H 2 chemisorptions and O 2/H 2 titrations. n-Butane dehydrogenation reaction was carried out at 500 °C, atmospheric pressure and a H 2/C 4H 10 ratio of 10. An increase in the Pd dispersion with increasing Ga content was observed for the fresh catalysts, according to CO chemisorption results. H 2 chemisorption and H 2/O 2 titrations were not reliable methods to determine the Pd dispersion in the fresh catalysts. For the calcined catalysts with low Ga contents, the CO/Pd, H/Pd and O/Pd values were very similar, but different for those with the higher Ga contents. These differences were explained based on the presence of chlorine. Coke deposition produced the deactivation of the catalysts and inhibited hydrogenolysis reactions on Pd, favoring the dehydrogenation selectivity. In the fresh catalysts, the Ga addition caused an effect similar to that produced by coke, reducing the activity and increasing the dehydrogenation selectivity. In the calcined catalysts, the effect of Ga addition on activity was diminished by the calcination treatment. The combination of calcination and high Ga content led to a catalyst with enhanced activity and very high dehydrogenation selectivity.

Effect of Ga Addition on the Electrical and Structural Properties ofr (Zn,Mg)O Transparent Electrode Films

(Zn,Mg)O (ZMO) thin films doped with Ga <TEX>$(0\~0.03mol\%)$</TEX> in the target source were prepared by pulsed laser deposition on c-plane sapphire substrates at <TEX>$500^{\circ}C$</TEX>, and the effect of Ga contents on the properties of the electrical, optical and crystal properties of the deposited films was investigated. From X-ray diffraction patterns, ZMO film doped with <TEX>$0.02 mol\%$</TEX> Ga showed crystal structure with c-axis preferred orientation, showing only the (0002) and (0004) diffraction peaks. In contrast, ZMO film doped with <TEX>$Ga=0.03 mol\%$</TEX> showed a randomly oriented crystal structure. All the samples were highly transparent, showing the transmittance values of above <TEX>$85\%$</TEX> in the visible region. For all the Ga doped ZMO films, the value of energy band gap was found to be about 3.5 eV, regardless of their Ga contents. From the Hall measurements, the resistivity and the carrier density for the ZMO film doped with <TEX>$0.01 mol\%$</TEX> Ga were about <TEX>$5\times10^{-4}\Omega-cm$</TEX> and <TEX>$2\times10^{21}cm^{-3}$</TEX>, respectively.