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

Thin high-strength zirconia tapes with extreme flexibility

The yttria stabilized zirconia ceramics (Y-TZP) are known for their high fracture toughness and high strength. Due to their excellent mechanical properties, the thin zirconia tapes can possess extraordinary behavior - extreme flexibility. In the present work, we introduce an adaptation of gel-tape casting method for the preparation of thin, high-strength zirconia tapes from water-based suspensions. Fine ceramic powder with a particle size of around 100 nm was used. The negative effect of sodium ions on the strength and toughness of sintered ceramic samples was revealed and explained. Ceramic tapes with a thickness of 190 mu m with as-sintered surfaces reached a characteristic biaxial strength of 1805 MPa. The huge elastic deformation of ceramic tapes was demonstrated in a 3- point bend test, and a bending radius of 25 mm for a 75 mu m thick tape was reached

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)

Influence of processing techniques on microstructure and mechanical properties of a biodegradable Mg-3Zn-2Ca alloy

New Mg-3Zn-2Ca magnesium alloy was prepared using different processing techniques: gravity casting as well as squeeze casting in liquid and semisolid states. Materials were further thermally treated; thermal treatment of the gravity cast alloy was additionally combined with the equal channel angular pressing (ECAP). Alloy processed by the squeeze casting in liquid as well as in semisolid state exhibit improved plasticity; the ECAP processing positively influenced both the tensile and compressive characteristics of the alloy. Applied heat treatment influenced the distribution and chemical composition of present intermetallic phases. Influence of particular processing techniques, heat treatment, and intermetallic phase distribution is thoroughly discussed in relation to mechanical behavior of presented alloys.Web of Science911art. no. 88

Nanočástice Fe a Fe3O4 v matrici ZrO2

Changes in the phase composition and the mean particles size of nanocrystalline Zr-Fe powdered prepared by mixing of pure ZrO2 and iron oxides were investigated in dependence of the heat treatment in vacuum and hydrogen atmosphere

Preparation and properties of nanocomposites based on Zr-Fe

The spark erosion of the pure Zr and Fe electrodes in hydrogen yielded nanocrystalline powder consisting of the mixture of Zr-rich (Zr3FeH7, ZrO2, and Zr(Fe)) and Fe-rich phases with the mean chemical composition Zr-3.2wt.%Fe. Heat treatment in hydrogen atmosphere at 973K induced phase decomposition and transitions with the final composition of bcc Fe, Zr3Fe, ZrH2 and dominating ZrO2 phases. The result indicates that formation of Fe-rich phase (bcc Fe) embedded in ZrO2 could be possible using an appropriate heat treatment of the as-prepared powder

Properties of nanocrystalline powder based on Fe-Zr

The phase composition of nanocrystalline Zr–Fe powder prepared by spark synthesis was investigated by means of Mossbauer spectroscopy, X-ray diffraction and magnetic measurements. The ability of hydrogen absorption is decreasing with the annealing steps and is connected with the increase in Fe2Zr phase content

PREPARATION OF FE-TI COMPOSITES BY BALL MILLING

The similar Ti-Fe powders were prepered from pure precursors as well as from splinters. The difference of structural and phase composition was determined by XRD and Mössbauer spectroscopy

Příprava Fe-Ti kompozitů mletím v kulovém mlýnku

The materials were prepared by mechanical alloying in the ball mill. The first type of sample consists of pure commercial precursors (TiH2 and ferrihydride). The slightly changes of phase composition of the powder were under the detection limit of X-ray powder diffraction. The MS determined the changes from the first step of milling. The second type of sample was prepared from turnings. The reduction of the splinters volume and the mechanical alloying was running simultaneously. The huge crystalline size differences decreased the credibility of computation of phase composition by XRD. MS was able determined phase composition more exactly and in additional to differentiate crystalline and amorphous FeTi phase

Fázové přechody v nanokrystalické slitině Zr-Fe indukované vodíkem

Nanocrystalline composite based on Zr-Fe alloy is investigated. In the as-prepared powder composite ZrO2, Zr3FeH7, alpha-Fe, Fe2Zr and amorphous phases were recognized. During an annealing in vacuum crystalline and a few manner of amorphous phases transforms to ZrO2. The attempts to hydrogenate the same sample by annealing in hydrogen of the ambient pressure were successful at temperatures above - 673 K