Abiotic reduction of 2-line ferrihydrite: effects on adsorbed arsenate, molybdate, and nickel

Chinese hamster ovary (CHO) cells were given short heat pulses (5 to 20 min) at 45.0 degrees C and incubated at 37 degrees C for up to 20 h under either pH 7.3 or 6.6 conditions. Thermotolerance developed under both pH conditions, but at a slower rate in the pH 6.6 medium. Intracellular pH (pHi) was measured with the dye, 1,4-diacetoxy-2,3-dicyanobenzene, combined with flow cytometry. Time-dependent changes in the intracellular pH occurred under either pH condition. CHO cells incubated under normal pH conditions had a transient increase in the pHi. This pHi elevation was followed by a rapid intracellular acidification of approximately 0.15 to 0.25 pH units. The timing of both the increases and decreases in the pHi was dependent on the magnitude of the initial heat dose. With heat doses less than or equal to 10 min, the pHi returned to normal unheated levels after the acidification phase. Although cells incubated under low pH (6.6) conditions showed similar pHi alterations, differences in the kinetics were measured. The intracellular pH increased immediately after heating. In addition, when intracellular acidification occurred, the rate of acidification was significantly reduced. With heat doses longer than 5 min under the low pH conditions, the pHi did not return to normal unheated levels.

This study is concerned with the theoretical description of a quasi-stationary process of directional crystallization of binary melts and solutions in the presence of a quasi-equilibrium two-phase region. The quasi-equilibrium process is ensured by the fact that the system supercooling is almost completely compensated by heat released during the phase transformation. Quasi-stationarity of the process determining constancy of the crystallization rate is ensured by given temperature gradients in the solid and liquid phases. The system of heat and mass transfer equations and boundary conditions to them under these assumptions is dependent on a single spatial variable in the reference frame moving with the crystallization rate relative to a laboratory coordinate system. Exact analytical solutions to the formulated problem in parametric form are obtained. The parameter of the solution is the solid phase fraction in a two-phase region. The distributions of temperature and impurity concentration in the solid, liquid and two-phase regions of the crystallizing system, the rate of solidification, and the spatial coordinate in the two-phase region depending on the solid phase fraction in it are found. An algebraic equation for the solid phase fraction at the interface between the solid material and the two-phase region is derived. Exact analytical solutions show that the impurity concentration in the two-phase layer increases as the solid phase fraction increases. Moreover, the solid phase fraction at the interface solid phase — two phase region and its thickness increase as the temperature gradient in the solid phase and the solidification rate increase. The developed theory allows us to determine analytically the permeability of the two-phase region and a characteristic interdendritic spacing in it. Analytical solutions show that the relative permeability in the two-phase region increases from a certain value at the interface with the solid phase to unity at the interface with the liquid phase. The selection theory of stable dendritic growth allows us to determine analytically a characteristic interdendritic distance in the two-phase layer that decreases as the temperature gradient in the solid phase increases. An increase of impurity in the molten phase gives a decrease in the interdendritic spacing within a two-phase region.

Mechanics of porous media with phase transformations and periodical structures 2. Solutions of local and global problems

Iron (oxyhydr-)oxide reduction has been extensively studied because of its importance in pollutant redox dynamics and biogeochemical processes. Yet, experimental studies linking oxide reduction kinetics to thermodynamics remain scarce. Here, we used mediated electrochemical reduction (MER) to directly quantify the extents and rates of ferrihydrite, goethite, and hematite reduction over a range of negative reaction free energies, ΔrG, that were obtained by systematically varying pH (5.0 to 8.0), applied reduction potentials (-0.53 to -0.17 V vs SHE), and Fe2+ concentrations (up to 40 μM). Ferrihydrite reduction was complete and fast at all tested ΔrG values, consistent with its comparatively low thermodynamic stability. Reduction of the thermodynamically more stable goethite and hematite changed from complete and fast to incomplete and slow as ΔrG values became less negative. Reductions at intermediate ΔrG values showed negative linear correlations between the natural logarithm of the reduction rate constants and ΔrG. These correlations imply that thermodynamics controlled goethite and hematite reduction rates. Beyond allowing to study iron oxide reduction under defined thermodynamic conditions, MER can also be used to capture changes in iron oxide reducibility during phase transformations, as shown for Fe2+-facilitated transformation of ferrihydrite to goethite.

Nucleation-growth processes and isothermal kinetics of phase transformations in the methylhydrazine monohydrate

Effect of non-equilibrium solid state phase transformation on welding temperature field during keyhole mode laser welding of Ti6Al4V alloy

Membrane fouling, which is mainly caused by adsorption of non-polar solutes and hydrophobic particles, is directly related to hydrophobicity of the membrane, and thus membranes are often modified to improve their hydrophilicity. Membranes are modified via various techniques to improve their performance of which the incorporation of inorganic nanoparticles in polymeric membranes has shown great potential. The effort to improve the membrane performance is still an ongoing progress and current trend in the field of membrane research is to develop new membrane materials and structures specifically to reduce fouling effects and to improve their function. A new two-dimensional zeolitic imidazolate framework (ZIF) with leaf-shaped morphology (ZIF-L) was incorporated into polyethersulfone (PES) ultrafiltration membranes to investigate how the ZIF nanoflakes affect membrane properties. The modified UF membrane with 0.5% ZIF-L loading showed around 75% increase in water flux while retaining its solute rejection. Also, the same membrane showed almost twice the fouling resistance with more than 80% water flux recovery. The improvement was due to the combined effect of the more negative zeta potential of the modified membrane, increased hydrophilicity and reduced surface roughness. While studying the stability of ZIF-L in organic solvent for the preparation of PES membrane, a new phase transformation of a zinc-2-methylimidazole-based ZIF was discovered, from ZIF-L to ZIF-8. The potential of the ZIF phase transformation in various solvents and also in solid phase were studied. Results indicated that the phase transformation occurs in the solid phase via the geometric contraction model (R2), a kinetic model new to ZIF. This work demonstrates the first topotactic phase transformation in porous ZIFs, from a 2D layered structure to a 3D structure, and provides a new insight into metal–organic framework crystallization mechanisms. Additionally, nanoporous titania nanoparticles synthesized via hydrothermal reaction was doped into polyethersulfone (PES) ultrafiltration membranes at a low concentration to improve nanoparticles dispersion in dope solution. All modified membranes showed narrower pore size distribution as TiO2 loading was increased. The composite membrane with 0.5% TiO2 nanoparticles loading showed ~20% increase in water flux and improvement in solute rejection (rejection of 100 kDa PEG from ~90% to ~92%). In addition, the same membrane showed improved fouling resistance (fouling rate of 0.58 kPa/ min compared to 0.70 kPa/ min of control membrane) with about 79% water flux recovery due to increased hydrophilicity, reduced surface free energy and reduced pore size. Beyond optimum loading of TiO2, the improvement was less significant due to the effect of agglomeration. Modification of the substrates’ properties is one of the most effective methods to improve the performance in forward osmosis (FO) process. A new Zn2GeO4 nanowire-modified PES ultrafiltration substrate with increased surface porosity and high water flux was used as a substrate for the fabrication of thin film composite (TFC) FO membrane, by coating a thin layer of polyamide on top of the substrate. The composite TFC membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was improved.

Thermodynamic properties and phase transformations in methylhydrazine monohydrate

The aim of this study is to report from the analyses of a corroded iron dagger from the Iron Age city at Tall Abu al-Kharaz, Jordan Valley, and to present the conservation procedures. Preliminary condition assessment was carried out by visual examination and stereomicroscope. X-ray radiography was used to reveal surface details under the external deposits and corrosion layers. X-ray diffraction (XRD) analysis was used to identify the mineralogical composition of the corrosion products. Polarized light microscopy (PLM) was used to examine a cross-section taken from the dagger to determine its corrosion profile and internal metallographic microstructure. The dagger’s radiograph showed that the edges and tip of the dagger were its weakest and most corroded parts. XRD results showed that goethite (α-FeOOH), lepidocrocite (γ-FeOOH) and magnetite (Fe3O4) were the main corrosion products. PLM examination showed that the dagger had greatly converted into magnetite. It also showed signs of hammering, carburization and heat treatment during the manufacturing process of the artifact. The dagger was treated by immersion in an alkaline solution to extract any chloride ions present in the artifact. It was then treated with tannic acid to produce a coherent film of black ferric tannate. Finally, it was coated with Paraloid B72 to consolidate it and protect it from atmospheric humidity and corrosive ions in the environmentally uncontrolled storage area.

The oxidation of Mn(II) by oxygen in the presence of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), silica and alumina was studied. All the solids, except perhaps alumina,enhanced the rate of Mn(II) oxidation. The degree of enhancement was as follows: lepidocrocite > goethite > silica > alumina. At constant pO2 Mn(II) oxidation on goethite, lepidocrocite and silica can be described by the following equation [Equation; see abstract in scanned thesis for details.] where is the concentration of the surface hydroxyl group and a is the solids concentration. Mn(II) oxidation in the presence of goethite or lepidocrocite is first order in pO2. Both these reactions are strongly temperature dependent (apparent activation energy ~100 kJ/mol). Normal laboratory lighting has no effect on the rate of these reactions. The rate of Mn(II) oxidation in the presence of lepidocrocite is about 4 times slower in 0.7M NaClO4, than in 0.1M NaClO4. This reaction is inhibited by the following ions; Mg2+, Ca2+, silicate, salicylate, phosphate, chloride, and sulfate. Phthalate has little or no effect on the rate of this reaction. The adsorptive behaviour of Mn(II) on the metal oxides studied could be described using a surface complexation model. Using this model it was shown that the rate of Mn(II) oxidation on the metal oxides studied is described by the equation [Equation; see abstract in scanned thesis for details.] where (≡SOH)2Mn is a bidentate surface complex. It is possible that a hydrolyzed surface complex (≡SOMnOH) rather than the bidentate complex is involved in the reaction. The results of the laboratory studies indicate that in natural waters the important factors which influence Mn(II) on metal oxides are pH, iron oxide concentration, temperature, [Mg2+], [Cl-], and ionic strength. These studies predict that at pH

The exposure to environmental variations in pH and temperature has proven impacts on benthic ectotherms calcifiers, as evidenced by tradeoffs between physiological processes. However, how these stressors affect structure and functionality of mollusk shells has received less attention. Episodic events of upwelling of deep cold and low pH waters are well documented in eastern boundary systems and may be stressful to mollusks, impairing both physiological and biomechanical performance. These events are projected to become more intense, and extensive in time with ongoing global warming. In this study, we evaluate the independent and interactive effects of temperature and pH on the biomineral and biomechanical properties of Argopecten purpuratus scallop shells. Total organic matter in the shell mineral increased under reduced pH (~ 7.7) and control conditions (pH ~ 8.0). The periostracum layer coating the outer shell surface showed increased protein content under low pH conditions but decreasing sulfate and polysaccharides content. Reduced pH negatively impacts shell density and increases the disorder in the orientation of calcite crystals. At elevated temperatures (18 °C), shell microhardness increased. Other biomechanical properties were not affected by pH/temperature treatments. Thus, under a reduction of 0.3 pH units and low temperature, the response of A. purpuratus was a tradeoff among organic compounds (biopolymer plasticity), density, and crystal organization (mineral plasticity) to maintain shell biomechanical performance, while increased temperature ameliorated the impacts on shell hardness. Biopolymer plasticity was associated with ecophysiological performance, indicating that, under the influence of natural fluctuations in pH and temperature, energetic constraints might be critical in modulating the long-term sustainability of this compensatory mechanism.

Phosphorus recovery from acidic wastewater by hydroxyapatite precipitation

Effects of high pressure (6 GPa) on the solid state phase transformation kinetic parameters of aluminum bronze during the cooling process are investigated, based on the measurement and calculation of its solid state phase transformation temperature, duration and activation energy and the observation of its microstructures. The results show that high pressure treatment can reduce the solid phase transformation temperature and activation energy in the cooling process and can shorten the phase transformation duration, which is favorable when forming fine-grained aluminum bronze.

During an earthquake, the physical and chemical transformations along a slip zone lead to alteration and formation of minerals within the gouge layer of a mature fault zone. The gouge contains ferromagnetic minerals, which could be formed under the combined action of friction heat and fluid. Thus, gouge has the capacity to behave as a magnetic recorder during an earthquake. This may constitute an efficient way to identify earthquakes slip zones. Besides, altered and neoformed magnetic minerals can be used as tracers of some earthquake processes. In this study, we investigate the rock magnetism and paleomagnetism of the Chelungpu Fault gouge that hosts the principal slip zone of the Chi-Chi earthquake (Mw 7.6, 1999, Taiwan) using Taiwan Chelungpu-Fault Drilling Project (TCDP) hole-B core samples. We also took a Chelungpu fault outcrop sample for identification of nanoparticle, which associated with fracture energy estimation in fault gouge. In the first part of this thesis, we studied the rock magnetism and paleomagnetism of the 0.16 m thick gouge at 1,136 m depth (labeled FZB1136). The rock magnetic investigation pinpoints precisely the location of the Chi-Chi mm-thick principal slip zone. A modern magnetic dipole of Earth magnetic field is recovered throughout this gouge but not in the wall rocks nor in the two other adjacent fault zones. This magnetic record resides essentially in two magnetic minerals; magnetite in the principal slip zone, and neoformed goethite elsewhere in the gouge. We propose a model where the magnetic record: 1) is preserved during inter-seismic time, 2) is erased during co-seismic time and 3) is imprinted during post-seismic time when fluids cooled down. We suggest that the identification of a stable magnetic record carried by neoformed goethite may be a signature of friction-heating processes in the seismic slip zone. In the second part of the thesis, we investigate pyrite and magnetic minerals within the host Chinshui siltstone and the FZB1136 gouge. In the Chinshui siltstone, pyrite framboids of various sizes and euhedral pyrite are observed. The magnetic mineral assemblage comprises stoichiometric magnetite, greigite, and fine-grained pyrrhotite. The pyrite content is generally lower in the gouge compared to the wall rock. The magnetic mineral assemblage in the gouge consists of goethite, pyrrhotite, and partially oxidized magnetite. The pyrrhotite, goethite and some magnetite are neoformed. Pyrrhotite likely formed from high temperature decomposition of pyrite (>500°C) generated during co-seismic slip of repeated earthquakes. Goethite is inferred to have formed from hot aqueous co-seismic fluid (>350°C) in association with the 1999 Chi-Chi seismic event. Elevated fluid temperatures can also explain the partial alteration of magnetite and the retrograde alteration of some pyrrhotite to pyrite. We suggest that characterization of neoformed magnetic minerals can provide important information for studying earthquake slip zones in sediment-derived fault gouge. In the third part of the thesis, we aimed to model the observed 40 mm shift between the maximum of magnetic susceptibility and the maximum of magnetic remanence. The result of the model suggests that the maximum of the concentration of magnetite and goethite correspond to the maximum of magnetic susceptibility and magnetic remanence, respectively. By modeling the concentrations of these two magnetic minerals, we explain satisfactorily the profiles of magnetic susceptibility and remanence. This modeling indicates that ~300 ppmv of magnetite formed in the principal slip zone and its main contact area. Similarly, ~1% of goethite is formed in the center of the gouge, where the fluids are more enriched in iron. We propose that the magnetite and goethite are formed and altered during successive seismic cycles. In the fourth part of the thesis, we determined the ultrafine nano-scale grains of the Chelungpu fault gouge. The particle size range was analyzed using the synchrotron X-ray diffraction and observed through transmission electron microscopy. The minerals of gouge are predominantly composed of quartz, plagioclase, smectite, illite, chlorite, and kaolinite. The mineral association of <100 nm particles are quartz, smectite, and illite. However, there are only smectite and illite without quartz in the 1 to 25 nm fractions. We propose that quartz is the index mineral associated with co-seismic fracture and the minimum grain size is 25 nm. The smectite and illite nano-particles may be associated with weathering process of gouge at shallow or surface conditions. In the fifth part of this thesis, we show the preliminary results of magnetic analysis of FZB1194 and FZB1243. These two fault zones have a very dark centimeter black material disk (BMD) that is not present in the FZB1136. In both fault zone, the paleomagnetic record indicates the presence of stable components with normal and reverse polarities. However, these components appear to result from an overlap of several contributions, which the analysis did not separate properly. The identification of opposite polarity, could have serveral origins: 1) an age of Chelungpu fault greater than 780 ka, 2) earthquake occuring during paleomagnetic excursion, 3) self-reversal processes of magnetic mineral. There are similarities between these two fault zones and FZB1136. A shift between the peak of remanence and susceptibility is observed, which may reflect varying concentrations of magnetic minerals in the gouge. Magnetite and goethite are found ubiquitously in both fault zones. However, three observations mark a fundamental difference with FZB1136: 1) the absence of a homogeneous single component paleomagnetic throughout the gouge, 2) the preservation of magnetic nano-grains in FZB1194 and FZB1243, 3) the absence of pyrrhotite, which could be an indicator of high temperature transformation. We suggest that seismic events recorded in these two fault zones had a magnitude lower than that recorded in the FZB1136 (Chi-Chi, Mw 7.6).

SUMMARY In recent years, soldering and three dimensional integrated-circuit (3D IC) take important parts of electronic packaging technology. Sn-based Pb-free solders have been widely used for low-temperature soldering. However, voids and brittle intermetallic compounds form at interfaces through Sn-based solder/Cu interfacial reactions. Doping elements into Sn-based solders is a common approach for improving joint reliability. In our previous work, minor addition of Ga has been found to effectively mitigate the soldering reactions between Sn-58Bi solders and Cu substrates. In this study, the reactions between Sn-0.7Cu-xGa (x = 1~3) solders and Cu substrates at 200 oC for various lengths of time up were investigated using electron probe micro analysis (EPMA) and CALPHAD thermodynamic modeling. The effect of Ga addition in Sn-0.7Cu solder is reported and the phase transformation in the Sn-0.7Cu-xGa/Cu couples is elaborated based on the Cu-Ga-Sn phase equilibria in the study. It is found that the reaction phase formation is strongly influenced by Ga concentrations. Besides, TSV process and Cu-to-Cu bonding are the crucial processes of 3D IC technology. The reactions of Cu/(Cu,Ga)NPs/Cu, Cu/Ni/(Cu,Ga)NPs/Ni/Cu and synthesized nanoparticles were investigated in this study. We proposed a bonding process for Cu-to-Cu in 3D IC with nanoparticles (NPs) synthesized by sonochemistry. After bonding process, a solid solution phase formed in the interface of Cu/Ni/(Cu,Ga)NPs/Ni/Cu and this result shows (Cu,Ga) nanoparticles have the great potential to develop in Cu-to-Cu process of 3D IC technology. Key words: Sn-0.7Cu solders, minor Ga addition, Cu-Ga-Sn phase equilibria, Sonochemistry, Nanoparticles, Cu-to-Cu bonding INTRODUCTION In recent years, soldering and three dimensional integrated-circuit (3D IC) take important parts of electronic packaging technology. Soldering has been changed to the key assembly and interconnection technology for electronic products including flip chip, ball grid array (BGA) process and 3D IC packaging. Sn-based Pb-free solders have been widely used for low-temperature soldering. However, some voids and brittle intermetallic compounds usually form at interfaces through Sn-based solder/Cu interfacial reactions. These brittle layer are called Kirkendall voids and these layer reduce the reliability of Cu-Sn joint. Doping elements into Sn-based solders is a common approach for improving joint reliability. Besides, in our previous research, adding the minor Ga into the Sn-58Bi alloy make a large difference of Sn-58Bi-xGa/Cu reaction. In this study, the reactions between Sn-0.7Cu-xGa (x=1~3) solders and Cu substrates at 200 oC were investigated while the reaction phase formation was also identified. The effect of Ga addition in Sn-0.7Cu solder is reported and the phase transformation in the Sn-0.7Cu-xGa/Cu couples is elaborated based on the Cu-Ga-Sn phase equilibria and CALPHAD thermodynamic modeling in the study. 3D IC packaging is the most important interconnection technology in the next generation electronic packaging industry including two important processes namely trough-silicon-via (TSV) process and Cu-to-Cu bonding. In our previous research, the Cu/Ga/Cu sandwich interfacial reactions were examined and the reaction phase formation was also identified. However, a brittle interface was found between Cu substrate and Ga solder. In this study, we proposed a bonding process for Cu-to-Cu in 3D IC with nanoparticles (NPs) synthesized by sonochemistry. The Cu/(Cu,Ga)NPs/Cu and Cu/Ni/(Cu,Ga)NPs/Ni/Cu reaction couples were bonded at 300 oC to set all condition the same as the real Cu-to-Cu interconnection in 3D IC technology. Furthermore, sonochemically synthesized nanoparticles was investigated and discussed in the paper. MATERIALS AND METHODS In the Sn-0.7Cu-xGa/Cu (x=1~3) interfacial reactions, the minor Ga is added into Sn-0.7Cu solders which were prepared by mixing proper amounts of pure Sn shot, pure Cu foil and pure Ga. The Cu foils were cut into pieces, and then metallographically grinded and polished with Al2O3 powders down to 1 μm. The samples were annealed at 200 oC under a 10-5 bar vacuum for predetermined lengths of times. Besides, the Cu-Ga-Sn ternary phase diagram was constructed based on calculation of phase diagram (CALPHAD) method. Furthermore, series of ternary Cu-Ga-Sn alloys were designed to do the phase equilibrium experiments at 200 °C to verify the phase relation of calculation isothermal section. This phase equilibria of the Cu-Ga-Sn ternary system were applied to investigate the mechanism of phase transformation and microstructural evolution in the interfacial reaction. In addition, the Cu/(Cu,Ga)NPs/Cu and Cu/Ni/(Cu,Ga)NPs/Ni/Cu sandwich-type reaction couples were prepared. The (Cu,Ga) nanoparticles were sonochemically synthesized by reducing copper sulfate with excessed Ga. The Ni under-bump metallization (UBM) layer was electroplated on each Cu substrate. Then the reaction couples were annealed at 300 oC for 6 hours. Finally, the compositions of IMCs were evaluated and determined by using EPMA, and the crystallography of compounds were detected by XRD to realize the mechanism of phase transformation and microstructural evolution. RESULTS AND DISCUSSIONS In the Sn-0.7Cu-1Ga/Cu annealed at 200 oC for 120 h couple, shown in Figure 1, according to EPMA analysis and Sn-Cu binary phase diagram, the compositions of the thick light gray and the scallop-type dark gray interfacial phases are determined to be η-Cu6Sn5 and e-Cu3Sn phase with 2.34 at. % Ga and 1.97 at. % Ga, respectively. The phase formation of Sn-0.7Cu-2Ga/Cu annealed at 200 oC for 120 h couple, shown in Figure 2, were presumed to be the γ-Cu9Ga4 phase with 2.24 at. % Sn, η-Cu6Sn5 phase with 1.69 at. % Ga and the e-Cu3Sn with 0.87 at. % Ga. Besides, the interfacial reaction of Sn-0.7Cu-3Ga/Cu annealed at 200 oC for 120 h couple is shown in Figure 3. With a slightly higher doping level of Ga, only one integral IMC layer on the interface was observed. This IMC phase was presumed to be γ-Cu9Ga4 phase with 2.53at. % Sn according to the analysis of EPMA and the Cu-Ga binary phase diagram. The difference between these three reaction couples can be due to the formation of the γ-Cu9Ga4 phase. The solid solubility of Sn in γ-Cu9Ga4 layer is around 2 at. %. After γ-Cu9Ga4 phase formed in the interface, Sn hardly diffused from solder to Cu substrates. The γ-Cu9Ga4 phase act as a native diffusion barrier of Sn to suppress the growth of Cu-Sn compound. Figure 1: Sn-0.7Cu-1Ga/Cu couples reacted at 200 °C for 120 hours Figure 2: Sn-0.7Cu-2Ga/Cu couples reacted at 200 °C for 120 hours Figure 3: Sn-0.7Cu-3Ga/Cu couples reacted at 200 °C for 120 hours Because the Kidkendall voids formation will cause serious reliability concern of joints, the major objective of this research is to avoid the Kirkendall voids formation. In the literature, several voids are formed due to the rapid diffusion of Cu in the e-Cu3Sn phase. We compared Ga addition effect to the IMCs thickness, shown in Figure 4. It is indicated that the Ga addition increases as the thickness of total IMC decreases, and the thickness of e-Cu3Sn decreases as well. It is suggested the Ga addition effectively reduces the thickness of e-Cu3Sn growth, and even the interfacial reaction only forms the Cu-Ga compounds in the 3 wt. % Ga addition couple. In this situation, the Kirkendall voids can be avoid. Figure 4: IMCs thickness in different Ga addition at 200 °C for 120 hours Figure 5 is XRD analysis of nanoparticles synthesized by reducing copper sulfate with excessed Ga. The results show Cu peak slightly shift toward left indicating lattice expansion. Cu peak shifting is due to a part of Ga dissolves into FCC-(Cu) solid solution and the remaining Ga still exists in the nanoparticles after the synthesis of nanoparticles. After bonding process, γ2-Cu9Ga4 is formed at the interface which had a brittle structure in Cu/(Cu,Ga)NPs/Cu couple. However, a uniform joint of FCC-(Cu,Ga,Ni) solid solution phase formed at the interface of Cu/Ni/(Cu,Ga) NPs/Ni/Cu, shown in Figure 6. It is indicated that (Cu,Ga) nanoparticles dissolved into FCC-(Cu,Ni) because Ga has high solubility of FCC-(Cu) and FCC-(Ni). Figure 5: XRD plots of (Cu,Ga) prepared using copper sulphate solution (0.175 M, 20 mL) and Ga metal (0.5 g) after 3 min sonication Figure 5: Cu/Ni/(Cu,Ga)NPs /Ni/Cu couples annealed at 300 °C for 6 hours CONCLUSIONS In this research, the phase transformation in the Sn-0.7Cu-xGa/Cu (x=1~3) interfacial reactions was presented. The solubility of Sn is very low in γ-Cu9Ga4 layer, so γ-Cu9Ga4 layer can act as a native diffusion barrier of Sn to suppress the growth of Cu-Sn compound. The Ga addition strongly reduces the thickness of e-Cu3Sn growth, and even the interfacial reaction only forms the Cu-Ga compounds in the 3 wt. % Ga addition couple. In this situation, the Kirkendall voids can be avoid. Furthermore, a part of Ga dissolves into FCC-(Cu) solid solution and the remaining Ga still exists in the nanoparticles after the synthesis of nanoparticles. In addition, the Cu/Ni/(Cu,Ga) NPs/Ni/Cu couple had a uniform joint of FCC-(Cu,Ga,Ni). The joints proved this process has great potential to be applied and developed in Cu-to-Cu process of 3D IC technology.