Copper In Germanium Research Articles

Phase Change Material of Copper–Germanium Alloy as Solar Latent Heat Storage at High Temperatures

A copper–germanium alloy (Cu–Ge alloy) was examined as a phase change material, at temperatures exceeding 600°C, for latent heat storage in solar thermal applications. First, the thermo-physical properties of the Cu–Ge alloy were examined using differential scanning calorimetry, thermomechanical analysis, and laser flash analysis. Second, to evaluate the thermal response and reliability of the Cu–Ge alloy, the cyclic properties of thermal charge/discharge were examined under various thermal conditions. The alloys obtained after the tests were examined for their chemical compatibility with the stainless steel container using an electron probe micro analyzer. The elemental distribution of each Cu–Ge alloy was evaluated using cyclic performance tests. Finally, the chemical compatibility of the Cu–Ge alloy was evaluated using a high-temperature test with candidate materials of a phase change material container vessel [stainless steel (SUS310S), Inconel625, silicon carbide (SiC), and alumina (Al2O3)]. The Cu–Ge alloy exhibited significant potential as a latent heat storage material in next-generation solar thermal power plants because it demonstrates various advantages, including a superior storage capacity at a temperature of 644°C, temperature coherence to the phase diagram, a quick thermal response, satisfactory cyclic behavior of charge/discharge modes, a thermodynamically stable metallographic structure, and non-reactivity with container ceramic materials (SiC and Al2O3).

Structural, electronic properties and reflectivity of ScTGe (Ag, Cu) Compounds

We have investigated structural, electronic and optical properties of half-Heusler materials Scandium Silver Germanium (ScAgGe) and Scandium Copper Germanium (ScCuGe) compounds by using state of the art FPLAPW based on the DFT. Optimization procedure is used to obtain the structural properties of the compounds. The bands of these compounds ScTGe(T= Ag, Cu) cross the Fermi level so these compounds show semi-metallic nature. The density of states shows mixed s and d states in the bands. From the optical spectrum of compounds, it is observed that reflectivity of these compounds is very high.

The equilibrium of germanium(IV) and copper(II) ions sorption from chloride solutions on the anion-exchange resin AN-31

Isotherms of Ge(IV) and Cu(II) ions sorption on to the weakly basic anion-exchange resin AN-31 from chloride solutions have been constructed and described. The dependence of equilibrium parameters of Ge(IV) and Cu(II) ions sorption from chloride ions concentration was shown. Based on the electron spectra of diffuse reflectance of copper-containing sorbent, isotherms of sorption and isomolar copper–germanium ions distribution diagram in solutions with different chloride concentrations the nature of extracted particles has been established, and the effect of the mineral background on the sorbent capacity has been determined. The synergistic effect of Cu(II) ions sorption in the presence of Ge(IV) ions has been established. It was found that the ionic and uncharged associates formed by hydroxy-chloride polynuclear cuprate(II) cations and methagermanate anions extract from the chloride solutions onto AN-31. The possibility of selective Cu(II) ions sorption from germanium containing 1 M chloride solutions in wide range of Ge(IV):Cu(II) molar ratios from 1:3 to 1:1 has been established.

Design, optimization and critical analysis of graphene based surface plasmon resonance sensor for DNA hybridization

In this paper, the design, optimization and critical analysis of Surface Plasmon Resonance sensor is presented, which works on angular interrogation method. It comprises of five layers which are “Prism–Copper–Germanium–Graphene–Sensing medium”. The influence of the chemical potential (µc) of graphene on the sensor performance has been studied in detail. Thickness of all the layers has been optimized. Remarkable results are achieved for the optimal thickness of copper and germanium layers as 50 nm and 6 nm respectively, while two layers of graphene having µc of 0.5 eV are introduced to boost-up the performance. Best results in terms of detection accuracy, sensitivity and quality factor have been achieved that fulfill the necessary requirements for good sensing applications.

Cu2GeS3 derived ultrafine nanoparticles as high-performance anode for sodium ion battery

Germanium based sulfides are potentially attractive as anode material for sodium ion batteries but rarely investigated. Herein, we firstly investigated Na+ storage properties of pristine Cu2GeS3 (PCGS) and found an effective strategy to improve its performance by a single lithiation/delithiation cycle obtaining ultrafine nanoparticle copper germanium sulfide (NCGS). The lithiation/delithiation process leads to the formation of a stable Li-containing solid electrolyte interphase film and a significant improvement of sodiation kinetics. Therefore, the NCGS anode delivers favorable capacity retention and better rate capability compared with that of a PCGS whether in the half cell or in the full cell, showing great promise for energy storage application.

High open-circuit voltage of ternary Cu2GeS3 thin film solar cells from combustion synthesized Cu-Ge alloy

Ternary chalcogenide semiconductor copper germanium sulfide (Cu2GeS3) composed of earth-abundant and non-toxic elements is considered to be a suitable light harvesting material for photovoltaics. In this study, Cu2GeS3 thin film solar cells are creatively fabricated based on combustion method. XRD and Raman analyses reveal that the combustion synthesized product is composed of Cu-Ge alloy rather than metal oxides. The structural, morphological, optical and electrical properties of CGS films are analyzed in detail. The best power conversion efficiency of Cu2GeS3 thin film solar cell achieve 2.67% with a high open-circuit voltage of 592mV. The experiment results reveal that the p-type semiconductor Cu2GeS3 is an extremely promising light harvesting material for photovoltaics due to its suitable band gap and carrier concentration.

Palladium diffusion in germanium

Palladium diffusion in germanium is fundamentally and technologically important as it has an extremely low activation energy and this can impact metal induced lateral crystallisation to produce large grain crystals. Recent theoretical studies calculated that the activation energy of migration of palladium in germanium is 0.03 eV. This constitute the experimental determination of the palladium diffusion properties very difficult. In the present study we calculate palladium diffusivity in germanium by employing theoretical results and comparing to the diffusion of copper in germanium. Finally, by employing a thermodynamic model we derive a relation describing palladium diffusivity to bulk materials properties.

Effects of Ni addition on the microstructure and properties of nanostructured copper–germanium alloys

The effects of Ni addition on the structure and various phase transitions of nanocrystalline Cu–Ge alloys were investigated for the first time. Cu84Ge16−xNix (x = 0,1,3 and 5 wt.%) alloys were mechanically alloyed at room temperature and evaluated by means of X-ray diffraction, differential thermal analysis, thermal gravimetry, and scanning and transmission electron microscopy observations. Nanocrystalline α−Cu(Ge) solid solution was observed to form during the early stages of mechanical alloying. After prolonged milling times, it was partially transformed into the ζ−Cu5Ge intermetallic compound with an hcp structure. Increased quantities of Ni in the alloys not only delayed the formation of the intermetallic phase upon mechanical alloying and the nanocrystallization transition during annealing but also decreased the crystallite and particle size, which gave rise to nanocrystalline alloys with a high thermal stability at temperatures near their melting points. The mechanism leading to the high stability achieved was also investigated and described.

Grain-boundary diffusion of germanium in copper and Cu-Ge and Cu-Fe alloys

The grain-boundary diffusion (GBD) of germanium in copper and its alloys Cu-2% Ge and Cu-0.5% Fe is investigated in the temperature range of 500–590°C by means of electron-probe microanalysis. The GBD parameters (triple product P = sδDGB and effective activation energy E) are found. The temperature dependence of the triple product for germanium GBD in pure copper can be described by equation P = 3 × 1015exp[−80 kJ mol−1/(RT)] m3 s−1. It is shown that the addition of Ge has almost no effect on the GBD parameters in copper, while doping with iron leads to a considerable reduction in the triple product.

Experimental and theoretical investigations of the copper–lead–germanate glasses

Glasses in the system xCuO·(100 − x)[7GeO 2·3PbO 2] with 0 ⩽ x ⩽ 60 mol% have been prepared from melt quenching method. In this paper, we investigated changes in coordination number of the germanium in copper–lead–germanate glasses through investigations of FTIR, UV–VIS and EPR spectroscopy and calculations of density functional theory (DFT). The observations presented in these mechanisms show that by increasing of CuO content up to 20 mol%, the [GeO 4] tetrahedral structural units were converted in [GeO 6] octahedral structural units up to the maximum. In this manner the excess oxygen added to the glass upon the addition of the CuO is taken up by forming [GeO 6] octahedrons and the excess negative charge is compensated by nearby copper ions. In addition, non-bridging oxygens do not frame. The conversion of Ge(IV) to Ge(VI) does not continue further to the formation of the isolated octahedrons because begins to reconvert Ge(VI) back to Ge(IV) and Ge(V) with the simultaneous formation of non-bridging oxygens. The excess of oxygen can be accommodated in the host network by the formation of the [CuO n ] structural units.

Electrochemical Behavior of (100) Germanium in Copper (II) Containing Solutions

The electrochemical behavior of n and p-type germanium in aqueous copper sulphate solutions was studied by means of cyclic voltammetry an chronoamperometry. It appeared that reduction at p-type occurs by charge transfer from the valence band, whereas the electron transfer mechanism at n-type electrodes is not clear. At both type of electrodes, anodic dissolution of the electrodeposited copper layer was possible, which may point to the formation of an ohmic contact. Current time experiments revealed a different nucleation mechanism at n-type specimens as compared to p-type electrodes. Possible explanations to explain the differences are suggested

Electrochemical Behavior of (100) Germanium in Copper (II) Containing Solutions

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Crystal structure and specific heat of GdCuGe

A single crystal study of GdCuGe revealed full copper–germanium ordering: NdPtSb type, space group P6 3 mc, a = 423.2 ( 1 ) , c = 753.7 ( 2 ) pm , w R 2 = 0.0443 , 414 F 2 values and 10 variables. The copper and germanium atoms build up two-dimensional networks of ordered [Cu 3Ge 3] hexagons with Cu–Ge distances of 244 pm. Consecutive [Cu 3Ge 3] layers are rotated by 60° around the perpendicular c-axis with respect to each other. The [Cu 3Ge 3] hexagons show a weak puckering. Heat capacity measurements on the polycrystalline sample of GdCuGe establishes antiferromagnetic ordering around 14 K in agreement with reports in the literature. The curves of heat capacity measured in different applied fields crosses each other at two well-defined points exhibiting a behavior usually associated with heavy fermion compounds. The results of the structural analysis and heat capacity measurements are discussed in the light of these interesting observations for a gadolinium intermetallic.

High-energy resolution alpha spectrometry using cryogenic detectors

Applications such as environment monitoring implying alpha emitters activity measurement associated with isotope identification, require high-energy resolution detectors. Conventional silicon detectors are inexpensive therefore widely used, although intrinsically limited in energy resolution. Thermal detection principle of cryogenic detectors introduces a breakthrough in alpha particle measurement. For the first time, spectra with 5.5 keV FWHM energy resolution have been obtained for several external alpha emitting sources using a copper–germanium bolometer specially developed for alpha spectrometry.

Superconducting behaviors of copper–germanium alloys

We have observed superconducting properties in three dimensional Cu x Ge 100− x samples with 38⩽ x⩽67. Transition temperature T c is about 0.4 K . Upper critical magnetic field H c2 has been measured in these samples confirming that they are indeed superconductors. Near the zero field T c o , H c2 depends linearly on temperature. Our results show robust superconducting properties present in CuGe samples with weakly disorder.

Structure of molten copper–germanium alloys

Copper–germanium alloys in liquid state at 1373 K have been investigated. Non-linear behaviour of the structure-sensitive parameters and electrical resistivity of the alloys versus concentration have been observed. Close relation between the crystal structure and the local ordering in molten Cu–Ge alloys has been found. The inhomogeneous structure of the liquid Cu–Ge alloys at a microscopic level was established. Melts are shown to contain clusters from pure components and clusters with composition corresponding to that of the intermetallic compound Cu 3Ge existing in the solid phase.

Structure refinement of Cu8GeS6 using X-ray diffraction data from a multiple-twinned crystal.

The structure of the orthorhombic room-temperature phase of Cu(8)GeS(6) (copper germanium sulfide), M(r) = 773.27, has been refined on the basis of X-ray diffraction data from a 12-fold twinned crystal applying a six-dimensional twin refinement technique. For 1804 unique reflections measured using Mo Kalpha radiation, R(F) was 0.083 with 77 structure parameters and 12 scale factors. The symmetry operations, the unit cell and other crystal data are (0, 0, 0; (1/2), (1/2), 0) + x, y, z; y, x, z; (1/4) - x, (3/4) - y, (1/2) + z; (3/4) - y, (1/4) - x, (1/2) + z; a = b = 9.9073 (3) Å, c = 9.8703 (4) Å, alpha = beta = 90 degrees, gamma = 90.642 (4) degrees; V = 968.7 (1) Å(3), Z = 4, D(x) = 5.358 Mg m(-3), µ = 21.70 mm(-1). The standard setting of the space group and the reduced unit cell are Pmn2(1); a = 7.0445 (3), b = 6.9661 (3), c = 9.8699 (5) Å; Z = 2.

Phase formations in the copper-germanium system: Reactions, structures and resistivities

The reaction of germanium with copper begins with the formation of the monoclinic Cu 3Ge at temperatures as low as 125°C. At approximately 200°C, Cu 3Ge reacts with excess copper to form a copper-rich phase, ζ, with a hexagonal close-packed structure. These results are compared with similar ones obtained with copper-silicon samples. The resistivity of ζ, measured as 47 μΩ·cm for a germanium content of 15 at%, is compared to that which is calculated from the specific resistivity of germanium in copper. If sufficient amounts of copper are present the last process to happen is the dissolution of ζ into the remaining copper to form a solid solution: to be quite precise, the formation of the solid solution can already be found simultaneously with the formation of ζ. Marker experiments reveal that Cu 3Ge forms by the motion of copper atoms, while ζ forms by the motions of both copper and germanium in nearly equal proportions. Experiments, where Cu 3Ge was prepared next to silicon, show that silicon atoms (and consequently those of germanium also) become mobile in Cu 3Ge at a temperature considerably higher than required for the mobility of copper, namely about 250°C versus 125°C. In the presence of silicon Cu 3Ge ceases to be stable at 300°C.

Room temperature section of the phase diagram of the Cu-Fe-Ge ternary system

The room temperature section of the phase diagram of the Cu-Fe-Ge ternary system was determined by means of X-ray diffraction, microscopic investigation and electron probe microanalysis. The section consists of nine single-phase regions, σ (copper), β (Cu 5Ge), η (Cu 3Ge), τ (germanium), α-Fe, δ (Fe 3Ge), γ (Fe 3Ge 2), ρ (FeGe) and μ (FeGe 2), 15 two-phase regions and seven three-phase regions. All phase boundaries of these phase regions were established. No appreciable solid solubility of iron or copper in germanium was observed. The substitution of small amounts of germanium for copper in the terminal solid solution (copper) is very advantageous to increase the solubility of iron in copper at room temperature

Electronic properties of hydrogen-related complexes in pure semiconductors

Hydrogen has been shown to activate the neutral impurities carbon, silicon and oxygen in ultra-pure germanium and form shallow level complexes. The double acceptors beryllium and zinc in silicon and germanium, as well as the triple acceptor copper in germanium, can be partially passivated, leading to single hole acceptors. The study of the electronic level spectrum of the single carrier bound to these centers at low temperatures has provided much information on symmetry and composition. Most centers reveal a symmetry axis along [1 1 1] and are static. In some cases hydrogen has been found to tunnel between equivalent real space positions. Photothermal ionization spectroscopy (PTIS) has been the most important tool for the study of the optical transitions of the hole (electron) in these hydrogen containing complexes. This photoconductivity technique combines high sensitivity with high resolution and permits the study of shallow acceptors or donors present at concentrations as low as 108 cm-3. Even lower limits may be attained under favorable circumstances.