Chemical Wet Synthesis and Characterization of Copper-Silver Nanoparticles

AgCu nanoparticles (NPs) of near-eutectic composition were prepared by various route of wet synthesis. Nanoparticles suspended in nonpolar solvents were prepared by solvothermal synthesis from metallo-organic precursors. AgCu colloids in aqueous solution were obtained by hydride reduction of Ag and Cu nitrates under action of different stabilization substances. The different surface stabilizing agents were used. Chemical characterisations of as-synthesized AgCu NPs were done using inductively-coupled plasma-optical emission spectrometry (ICP-OES). The optical properties of nanoparticles were monitored using UV-Vis spectrophotometer. The size of colloid nanoparticles was measured by both dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) method in some extra cases. Zeta potential of AgCu colloids was measured by electrophoretic method. Size and shape of metal core of nanoparticles and morphology of aggregates were investigated by electron microscopy (SEM, TEM and HRTEM), the thermal properties of AgCu nanoparticles were evaluated by differential scanning calorimetry (DSC) and temperature controlled X-ray diffraction method (t-XRD). Mass loss under heating inside inert and air was monitored by thermo gravimetric analysis (TGA). The fraction of organic matter was deduced from ICP-OES analysis and compared to TGA mass loss. The adsorption maxima in UV-Vis region were occurred. Hydrodynamic size of AgCu NPs measured by DLS was compared with the metallic core size obtained by electron microscopy. The morphologies of aggregates were observed as well as the phase transformation (t-XRD) that undergoes at heating to liquid temperature (DSC). The obtained results were compared with respect to perspective use.Nanočástice AgCu (NPS)s téměř eutektickým složením byly připraveny různými způsoby mokré syntézy. Nanočástice suspendované v nepolárních rozpouštědlech byly připraveny solvothermal syntézou z prekurzorů organokovovů. AgCu koloidy ve vodném roztoku byly získány hydridovou redukcí dusičnanů Ag a Cu za přítomnosti různých stabilizačních látek. Chemická složení bylo stanoveno pomocí indukčně vázané emisní spektrometrie (ICP-OES). Optické vlastnosti nanočástic byly sledovány pomocí UV-VIS spektrofotometru. Velikost koloidních nanočástic byla měřena jak dynamickým rozptylem světla (DLS) tak i metodou sledování XDR malých úhlů (SAXS). Zeta potenciál AgCu NPs byl měřen elektroforetickou metodou.Velikost a tvar kovového jádra nanočástic a morfologie agregátů byly zkoumány elektronovým mikroskopem (SEM, TEM a HRTEM), tepelné vlastnosti AgCu nanočástic byly hodnoceny pomocí diferenční skenovací kalorimetrie (DSC), a rentgenové difrakční metody s řízenou změnou teploty (t -XRD). Úbytek hmotnosti při zahřívání v inertu a na vzduchu byl sledován pomocí termogravimetrické analýzy (TGA). Frakce organické hmoty byla odvozena z ICP-OES analýzy a srovnání s TGA. Hydrodynamická velikost AgCu NP měřená DLS byla porovnána s velikostí kovového jádra

On thermal stability of nanocrystalline Ag–Cu-S powders

The nanocrystalline semiconducting compounds based on the AgCuS system are considered as low-cost candidates of thermoelectric materials with improved thermal stability. The nanocrystalline Ag–Cu—S powders were prepared from metal nitrates and sulphur powder in tetraethylene glycol (TEG) solvent by reductive agent NaBH4. The crystallite sizes of the observed phases were in the range between 60 and 80 nm. The chemical compositions of the as-received samples were analysed by the ICP-AES method and their phase compositions were evaluated by XRPD. The investigation was supplemented by DSC and in situ HTXRD thermal analysis. A more detailed in situ experiment was performed for a sample containing ternary phases. The nucleation and growth of silver micro-wires were first observed on the substrate involving ternary phases at isothermal heat treatment. The formation of silver wires and semi-conductive ternary thermoelectric phase (stromayerite τ3) is explained by observed phase transformation. The obtained results are complemented by microscopy (LM, SEM, TEM)

High speed thermographic diagnostics of rotating parts of power equipment

Rotační díly patří mezi kritické komponenty energetických zařízení. Termografická diagnostika může včas odhalit jejich poškození a zabránit vážným škodám. Taková diagnostika je zpravidla možná pouze při běhu zařízení. Komplikací bývá také špatná přístupnost a vysoké rychlosti rotace, které znemožňují použití standardních termografických kamer s bolometrickým detektorem. Příspěvek je zaměřen na vysokorychlostní termografickou diagnostiku rotoru generátoru elektrárny. Je ukázán způsob použití vysokorychlostní termografické kamery na bázi kvantových detektorů s rychlostí vzorkování 1 kHz. Výstupy termografického měření jsou porovnány s výstupy měření kvantových infračervených detektorů o rychlosti vzorkování až 30 kHz. Jsou prezentovány výsledky diagnostiky rotoru a ukázány možnosti odhalení indikací poškození. Výsledky jsou porovnány s použitím bolometrické kamery s HD rozlišením a je prezentován význam integrační doby pro vysokorychlostní termografická měření.Práce vznikla za podpory projektu „LABIR-PAV / Předaplikační výzkum infračervených technologií“, reg. č.: CZ.02.1.01/0.0/0.0/18_069/0010018 financovaného z EFRR.Rotating parts belong to critical components of power devices. Thermographic diagnostics can predict their faults and prevent major failures. The diagnostics can be mostly performed only during an operation of the devices. A poor accessibility of the parts and their high speed of a rotation, which limits usability of standard bolometric infrared cameras, make such a diagnostics complicated. The contribution is focused on a thermographic diagnostics of a rotor of a power plant generator. A usage of a high-speed infrared camera, which is based on quantum detectors, with a frame-rate 1 kHz is presented. The thermographic measurements outputs are compared with high-speed infrared quantum detectors measurement results made with the sampling frequency 30 kHz. Results of the rotor diagnostics and possibilities of a detection of possible faults indications are introduced. The results are compared with a bolometric infrared camera with HD resolution results and a significance of an integration time for high-speed thermographic measurements is presented

Ag-Cu Colloid Synthesis: Bimetallic Nanoparticle Characterisation and Thermal Treatment

The Ag-Cu bimetallic colloidal nanoparticles (NPs) were prepared by solvothermal synthesis from metalloorganic precursors in a mixture of organic solvents. The nanoparticles were characterized by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The properties of metallic core and organic shell of the nanoparticles were studied by direct inlet probe mass spectrometry (DIP/MS), Knudsen effusion mass spectrometry (KEMS), double-pulse laser-induced breakdown spectroscopy (DPLIBS), and differential scanning calorimetry (DSC). The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used for particle characterization before and after thermal analysis. The experiment yielded results that were for AgCu nanoparticles for the first time. The detected liquidus temperature has been compared with the prediction obtained from calculation of the phase diagram of Ag-Cu nanoalloy. The experimental results show that of near-eutectic composition AgCu nanoparticles possess the fcc crystal lattice. Surprisingly, spinodal decomposition was not observed inside the AgCu nanoparticles at temperatures up to 230C. The depression of the eutectic AgCu melting point was calculated but not observed. The eutectic AgCu microparticles are formed before melting.Ag-Cu bimetalické koloidní nanočástice (NPs) byly připraveny solvotermální syntézou z metalických prekurzorů ve směsi organických rozpouštědel. Nanočástice byly charakterizovány metodami: DLS a SAXS. Vlastnosti kovového jádra a stabilizační obálky z organických látek byly studovány metodou přímého vstupu do hmotnostního spektrometru (DIP/MS), Knutsenovou hmotnostní spektrometrií (KEMS), double -pulse laserovou spektroskopií (DPLIBS) a diferenční skenovací kalorimetrií (DSC). Transmisní elektronová mikroskopie (TEM) a řádkovací elektronová mikroskopie (SEM) byly použity pro charakterizaci částic před a po termické analýze. Teplota likvidu zjištěna experimentálně byla srovnávána s predikcí fázového diagramu Ag-Cu nanoslitiny. Experimentální výsledky ukázaly téměř eutektické složení a fcc krystalovou mřížku AgCu NPs. Překvapivě, spinodální rozklad nanočástic nebyl pozorován při teplotách do 230C

Hard carbon films: Deposition and diagnostics

We studied the growth of microcrystalline diamond films on pre-treated Si and WC-Co substrates by microwave plasma chemical vapour deposition (MPCVD). The pre-treatment was varied and its effect on diamond film was studied

Micromechanical testing of Mo‐B‐C layers prepared by magnetron sputtering

Based on attractive mechanical properties of transition metal diborides the group of X2BC ternary compounds (X = Ti, V, Zr, Nb, Mo, Hf, Ta and W) became subject of theoretical calculations [1-3] and lately proved their applicability experimentally [4]. X2BC with X = Mo, Ta and W are the most promising candidates for protection of cutting and forming tools due to their unusually stiffness and moderately ductility. These properties can be understood by considering the electronic structure and particularly the extreme anisotropy (orthorhombic crystal lattice with a=0.309nm, b=1.735nm, c=0.305nm). Please click Additional Files below to see the full abstract

Influence of preparation technology on microstructural and magnetic properties of Fe2MnSi and Fe2MnAl Heusler alloys

Microstructural and magnetic properties of the X(2)YZ, namely Fe2MnSi and Fe2MnAl, Heusler alloys have been studied from the viewpoint of technology for their production and for the Z element effect. First, arc melting was applied to produce button-type ingots from which samples in a form of 500 mu m thick discs were cut. Second, planar flow casting technology yielded samples in a ribbon-form 2 mm wide and 20 m thick. The checked area chemical compositions were in agreement with the nominal ones. Nevertheless, the darker square objects and smaller bright objects observed at the wheel side of the Fe2MnSi ribbon sample yielded higher Mn content at the expense of Fe. The X-ray diffraction patterns of all samples have indicated L2(1) structure with lattice parameters, 0.567 (1) nm for Fe2MnSi and 0.584 (1) nm for Fe2MnAl, being within an experimental error independent of production technology. On the other hand, the technology has markedly influenced the microstructure clearly pointing to the larger size of grains and grain boundaries in the disc samples. From the magnetic viewpoint, both alloys are paramagnetic at room temperature without visible influence of their production. On the contrary, the low-temperature behavior of the microscopic hyperfine parameters and the macroscopic magnetic parameters exhibits differences affected by both chemical composition and microstructure.Web of Science125art. no. 71

Full-scale magnetic, microstructural, and physical properties of bilayered CoSiB/FeSiB ribbons

The paper is devoted to the detailed analysis of microstructural and magnetic properties of the as-quenched bilayered Co72.5Si12.5B15/Fe77.5Si7.5B15 ribbons prepared by the planar flow casting (PFC) method with single crucible. The interface between both amorphous Co- and Fe-based layers is not uniform and its thickness ranges from 0.5 to 6 μm over the whole ribbon length. Dependences of mechanical characteristics on the ribbon thickness show increase in Young’s modulus from 140 to 170 GPa and decrease in microhardness from 18 to 13 GPa, when measured from the wheel (Co) to air (Fe) side. By fixing the coiled ribbon on the planar sample holder a uniaxial magnetic anisotropy with the out-of-plane and the in-plane easy axis is induced on the air and wheel side, respectively. Bulk magnetic properties confirm that perpendicular anisotropy observed on the air side becomes stronger as getting deeper under the surface and overlaps the in-plane anisotropy from the wheel side. This is in good agreement with Mössbauer measurements. Magnetic characteristics (surface hysteresis loops and domains, bulk hysteresis loops and thermomagnetic curves) of the bilayered samples were further compared with the single-layered CoSiB and FeSiB alloys.Web of Science58169268

Au-Ni nanoparticles: Phase diagram prediction, synthesis, characterization, and thermal stability

The Au-Ni nanoparticles (NPs) were prepared by oleylamine solvothermal synthesis from metal precursors. The Au-Ni phase diagram prediction respecting the particle size was calculated by the CALPHAD method. The hydrodynamic size of the AuNi NPs in a nonpolar organic solvent was measured by the dynamic light scattering (DLS) method. The average hydrodynamic sizes of the nanoparticle samples were between 18 and 25 nm. The metallic composition of the AuNi NP samples was obtained by inductively-coupled plasma atomic emission spectroscopy (ICP-OES). The metallic fraction inside AuNi NPs was varied Au-(30-70)wt%Ni. The steric alkylamine stabilization was observed. The individual AuNi NPs were investigated by transmission electron microscopy (TEM). The dry nanopowder was also studied. The structures of the aggregated samples were investigated by scanning electron microscopy (SEM). The AuNi NPs reveal randomly mixed face-centered cubic (FCC) crystal lattices. The phase transformations were studied under inert gas and air. The samples were studied by differential scanning calorimetry (DSC).Nanočástice Au-Ni (NPs) byly připraveny solvotermální syntézou z kovových prekurzorů. Predikce fázového diagramu Au-Ni s ohledem na velikost částic byla vypočítána metodou CALPHAD. Hydrodynamická velikost AuNi NP v nepolárním organickém rozpouštědle byla měřena metodou dynamického rozptylu světla (DLS). Průměrné hydrodynamické velikosti vzorků nanočástic byly mezi 18 a 25 nm. Chemické složení kovů vzorků AuNi NP bylo získáno indukčně vázanou plazmovou atomovou emisní spektroskopií (ICP-OES). Kovová frakce uvnitř AuNi NP byla různá v rozmězí Au-(30-70hm%)Ni. Byla pozorována sterická stabilizace alkylaminem. Jednotlivé NP AuNi byly zkoumány tramsmisní elektronovou mikroskopií (TEM). Také byl zkoumán suchý nanoprášek. Struktury agregovaných vzorků byly zkoumány pomocí skenovací elektronové mikroskopie (SEM). AuNi nanočástice vykazovaly krystalovou mřížku náhodně smíšeného tuhého roztoku (FCC). Fázové transformace byly studovány pod inertním plynem a na vzduchu. Vzorky byly také studovány diferenční skenovací kalorimetrií (DSC)

Raman bands in microwave plasma assisted chemical vapour deposited films

Raman spectroscopy is employed to characterize thin diamond films deposited by microwave plasma assisted chemical vapour deposition technique using a gas mixture of methane and hydrogen. The surface morfology of the films was analyzed by scanning electron microscopy. We have identified submicron crystals on (100) facets of diamond crystals which gave rise to bands in the Raman spectrum centred at 1170 and 1456 cm-1