Solid Ag Research Articles

Improving p-type thermoelectric performance of Mg2(Ge,Sn) compounds via solid solution and Ag doping

Mg2X (X = Si, Ge, and Sn) compounds have attracted increasing attention owing to their promising thermoelectric properties and “green” constituent elements. While most studies to date have been on n-type Mg2(Si,Sn) solid solutions, we herein report Ag-doping study in Mg2(Ge,Sn) solid solutions to pursue higher p-type performance. Two series of samples, Mg2Ge1−xSnx and Mg2−yAgyGe0.4Sn0.6, were prepared by melting in evacuated Ta tubes, followed by hot pressing, and the thermoelectric properties of the solid solutions were investigated from room temperature to 723 K. An n- to p-type crossover in the Seebeck coefficient was observed for Mg2Ge0.4Sn0.6 and Mg2Ge0.2Sn0.8 at elevated temperatures. To enhance p-type performance, we doped Ag in Mg2Ge0.4Sn0.6 that exhibited lowest thermal conductivity among the Mg2(Ge,Sn) solid solutions. It was found that (1) p-type behavior has been established in Mg2−yAgyGe0.4Sn0.6 (y = 0.005, 0.01, 0.02, 0.04) samples in the entire temperature range studied; and (2) the electrical conductivity increased with increasing Ag content until reaching the solution limit ∼0.02. As a result, a dimensionless figure of merit ZT ∼0.38 is attained for Mg1.98Ge0.4Sn0.6Ag0.02 at 675 K, which is one of the highest reported values in p-type Mg2X compounds.

Differential SERS Activity of Gold and Silver Nanostructures Enabled by Adsorbed Poly(vinylpyrrolidone)

We report that poly(vinylpyrrolidone) (PVP), a common stabilizer of colloidal dispersions of noble metal nanostructures, has a dramatic effect on their surface-enhanced Raman scattering (SERS) activity and enables highly selective SERS detection of analytes of various type and charge. Nanostructures studied include PVP-stabilized Au-Ag nanoshells synthesized by galvanic exchange reaction of citrate-reduced Ag nanoparticles (NPs), as well as solid citrate-reduced Ag and Au NPs, both before and after stabilization with PVP. All nanostructures were characterized in terms of their size, surface plasmon resonance wavelength, surface charge, and chemical composition. While the SERS activities of the parent citrate-reduced Ag and Au NPs are similar for rhodamine 6G (R6G) and 1,2-bis(4-pyridyl)ethylene (BPE) at various pH values, PVP-stabilized nanostructures demonstrate large differences in SERS enhancement factors (EFs) between these analytes depending on their chemical nature and protonation state. At pH values higher than BPE's pK(a2) of 5.65, where the analyte is largely unprotonated, the PVP-coated Au-Ag nanoshells showed a high SERS EF of >10(8). In contrast, SERS EFs were 10(3)- to 10(5)-fold lower for the protonated form of BPE at lower pH values, or for the usually highly SERS-active cationic R6G. The differential SERS activity of PVP-stabilized nanostructures is a result of discriminatory binding of analytes within-adsorbed PVP monolayer and a subsequent increase of analyte concentration at the nanostructure surface. Our experimental and theoretical quantum chemical calculations show that BPE binding with PVP-stabilized Au-Ag nanoshells is stronger when the analyte is in its unprotonated form as compared to its cationic, protonated form at a lower pH.

Development of heat resistant Pb-free joints by TLPS process of Ag and Sn-Bi-Ag alloy powders

TLPS (Transient Liquid Phase Sintering) process is a candidate method of heat-resistant bonding, which makes use of the reaction between low-melting temperature powder of Sn-Bi base alloys and reactive powder of Ag. During heat treatment above the melting temperature of a Sn-Bi base alloy, the molten Sn-Bi reacts rapidly with solid Ag particles, which results in the formation of heat-resistant intermetallic compound (IMC). In this study, the TLPS properties between Sn-17Bi-1Ag (at.%) powder with its liquidus temperature of 200?C and pure Ag powder were investigated. During differential scanning calorimetry (DSC) measurement, an exothermic reaction and an endothermic reaction occurred, which correspond to the formation of the e-Ag3Sn IMC phase and the melting of the Sn-17Bi-1Ag alloy, respectively. After the overall measurement, the obtained reactant consists of the Ag3Sn-IMC and Bi-rich phases, both of which start melting above 250?C, with a small amount of the residual Sn-Bi eutectic phase. These results suggest that the TLPS process can be applied for Pb-free heatresistant bonding.

High-resolution measurements of sulphur isotope variations in sediment pore-waters by laser ablation multicollector inductively coupled plasma mass spectrometry

A novel combination of the technique of diffusive gradients in thin films (DGT) and laser ablation high-resolution multicollector inductively coupled plasma mass spectrometry was developed to study sulphur isotope variations of dissolved pore-water sulphide in freshwater and marine sediments. The technique enables two-dimensional mapping of isotopic variations (δ 34S) in dissolved sulphide captured as solid Ag 2S in DGT polyacrylamide gels. Measurements can be performed at a spatial resolution (~ 100 μm) relevant to microbiological processes and formation of individual iron sulphide grains in surface sediments. Values of δ 34S measured in BaSO 4–DGT gel isotope standards (δ 34S = 9.28 ± 0.36‰ to 9.33 ± 0.57‰) are within 1‰ of the accepted value determined with conventional analytical techniques (δ 34S = 10.13 ± 0.29‰). Sulphur isotope measurements were performed in sediments from a eutrophic lake (Esthwaite Water, UK) contained in laboratory mesocosms. Bacterial sulphate reduction and sulphide formation in this sediment are predominantly localized to discrete, mm-sized microniches, where oxidation of labile organic matter such as fresh algae and faecal pellets drives the reduction of sulphate. The results emphasize the importance of microniches as localized, highly dynamic reaction sites in sediments, where significant shifts in δ 34S of up to + 20‰ relative to the local background were measured across microniches. The improved spatial resolution for pore-water sulphur isotope measurements, compared to that of conventional sampling and analytical techniques, is essential for improving our understanding of the global biogeochemical cycling of sulphur as well as trace metal–sulphide interactions in modern sediments.

Fast Growth Synthesis of Silver Dendrite Crystals Assisted by Sulfate Ion and Its Application for Surface-Enhanced Raman Scattering

This paper reports the fast growth synthesis of silver (Ag) dendrite crystals on a copper (Cu) substrate assisted by sulfate (SO42–) ions based on a electroless galvanic displacement reaction between solid Cu and Ag(I) ion. The growth of Ag dendrites is succeeded by using an aqueous solution of Ag+ ion and a Cu foil. Interestingly, the morphology, apparent color, and growth rate of Ag dendrites on Cu foil using 2.5 mM Ag2SO4 aqueous solution are different from that of 5.0 mM AgNO3 aqueous solution even though they contain the same concentration of Ag+ ion. The growth rate of Ag dendrites is proved to be much accelerated for a solution of Ag+ ions with SO42–. The growth process can be readily observed under a microscope. The resultant Ag dendrites are characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The effect of SO42– ion on the growth of Ag dendrites on Cu foil has been investigated in detail. The diffusion-limited growth and oriented attachment explain the formation of the Ag dendrites under the nonequilibrium growth conditions. The synthesized Ag dendrites have been successfully employed as a Raman probe for surface-enhanced Raman spectroscopic (SERS) analysis of melamine. The SERS results demonstrate that Ag dendrites can be a useful solid substrate for SERS analysis. Our work provides a very simple, convenient, cost-effective, and fast route to synthesize Ag dendrites which is potentially useful in SERS.

Formation of gold and silver sulfides in the system Ag–Au–S

Gold and silver sulfides were synthesized from melts Ag 2- χ Au χ S ( χ = 0.1, 0.4, 0.8, 1.6) in the system Ag–Au–S with Au/Ag = 0.1–7.4. Optical microscopy, X-raying, electron probe microanalysis, and scanning electron microscopy were used to identify and analyze the solid products. It has been established that acanthite, solid solutions Ag 2- χ Au χ S ( χ < 0.5), and electrum are produced in the Ag-rich binary system Ag 2S–Au 2S. Petrovskaite, high-fineness gold, and sulfur are produced in the systems with low Ag contents ( χ > 1). The systems with an intermediate composition produce petrovskaite, uytenbogaardtite, and solid solutions Ag 2- χ Au χ S (0.5 < χ < 1). The results of experimental studies together with data on the compositions of natural gold and silver sulfides suggest that the wide variations in Au and Ag contents in uytenbogaardtite and petrovskaite from different deposits are, most likely, due to the inhomogeneous structure of mineral grains and the presence of solid solutions Ag 2- χ Au χ S. It is assumed that gold and silver sulfides crystallizing from Au-Ag-containing sulfide melts might be of magmatic genesis. Poorly extractable gold in sulfide ores might be present as microinclusions of Au-Ag sulfides.

Defect Transfer from Nanoparticles to Nanowires

Metal-seeded growth of one-dimensional (1D) semiconductor nanostructures is still a very active field of research, despite the huge progress which has been made in understanding this fundamental phenomenon. Liquid growth promoters allow control of the aspect ratio, diameter, and structure of 1D crystals via external parameters, such as precursor feedstock, temperature, and operating pressure. However the transfer of crystallographic information from a catalytic nanoparticle seed to a growing nanowire has not been described in the literature. Here we define the theoretical requirements for transferring defects from nanoparticle seeds to growing semiconductor nanowires and describe why Ag nanoparticles are ideal candidates for this purpose. We detail in this paper the influence of solid Ag growth seeds on the crystal quality of Ge nanowires, synthesized using a supercritical fluid growth process. Significantly, under certain reaction conditions {111} stacking faults in the Ag seeds can be directly transferred to a high percentage of <112>-oriented Ge nanowires, in the form of radial twins in the semiconductor crystals. Defect transfer from nanoparticles to nanowires could open up the possibility of engineering 1D nanostructures with new and tunable physical properties and morphologies.

Formation of gold and silver sulfides from melts in the Ag-Au-S system: Experimental data

as well as solid solutions Ag 2- xS (x → 0)-Au0.1Ag1.9S, Au0.1Ag1.9S-Au0.4Ag1.6S, and Au0.4Ag1.6S-Au1.8Ag0.2S (with facecentered, volumecentered, and primitive cubic cells) are stable in the threecomponent Ag- Au-S system (Fig. 1) (1, 2). Polymorphic transforma� tions of gold and silver sulfides have been studied insufficiently (3). Uytenbogaardtite (α�Ag 3AuS2) and petrovskaite (α�AgAuS ) discovered in the 1980s (4, 5) and already established in ores of more than 30 depos� its are related to the Ag-Au-S system. A review of ore objects, mineral associations with Au-Agsulfides, and compositions of uytenbogaardtite and petrovs� kaite is given in (6). Wide variations of Au and Ag con� centrations in these minerals allowed us to assume the possible existence of solid solutions of gold- silver sulfides in natural processes. Since the transition α�Ag 2S β�Ag 2S is enantiotropic and acanthite par� amorphs after argentite are considered as geother� mometers, one of the aims of this investigation was to understand the type of polymorphic transformations for more complex gold and silver sulfides, namely uytenbogaardtite and petrovskaite. The genesis of Au- Agsulfides is not completely clear as well. The physi� cochemical models of the formation of Au-Agsul� fides in the oxidation zone and lowtemperature hydrothermal processes (6-8) supporting the "hyper� gene" and "hypogene" hypotheses were worked out on the example of the Ulakhan, Krutoe, and Yunoe deposits (Northeastern Russia) (2, 4, 5, 9, 10). In this study we consider the possibility of the "magmato� gene" hypothesis of the formation of these minerals 1 Not found in nature. from melts in the twocomponent 2 Ag2S-Au2S sys� tem. This work is aimed at investigation of Au and Ag behavior during crystallization from melts without excess of sulfur, with an initial ratio of (Au + Ag)/S = 2 and revealing of the conditions of the formation of uyten� bogaardtite, petrovskaite, and solid solutions Ag 2- хAuхS.

Thermodynamics of Si and Ti in Solid Fe at 1273 K

Equilibrium experiments were carried out with solid Fe and liquid Ag to investigate the interactions between Si and Ti in solid Fe. The thermodynamic properties of Si in γ-Fe and α-Fe phases were studied by determining the distribution equilibrium of Si in the Fe and the Ag phases. Using the activity coefficient and the self-interaction parameter of Si in solid Fe, the interaction parameter of Si and Ti in both the solid Fe phases— γ-Fe and α-Fe—was determined as follows:εSiTi = 460 ± 78 in γ-Fe, εSiTi = 350 ± 7 in α-FeThe analysis results for Si and Ti in the solid Fe phase showed reasonable agreement with previous research in α-Fe region. Furthermore, the influence of the interaction between Si and Ti in the solid Fe phases on the formation of secondary inclusions such as Ti-based inclusions was discussed. It was concluded that, during solidification, the interactions among solutes such as Si and Ti should be properly considered because the formation of not only the secondary inclusions but also ferrites may depend on the thermodynamic properties of the solutes.

High-Temperature Friction and Wear of Ag/h-BN-Containing Ni-based Composites Against Steel

In order to attain self-lubrication in a wide range of temperatures, Ni-based powder metallurgy (P/M) composites containing different amounts (8–20 wt%) of Ag were prepared, and their friction and wear characteristics were investigated against AISI 52100 steel at temperatures of 25, 400, and 600 °C. One composite containing 12 wt% Ag and 4 wt% h-BN was also prepared and tested under the same conditions to analyze the effect of addition of h-BN on the friction and wear behaviors. The composites mainly consisted of Ni-based solid solution, free tungsten, Ag, and BN as revealed by XRD and EDS analyses. The friction coefficients and wear rates were found to decrease with increasing temperature and amount of silver. The friction coefficients shown by the composites containing relatively higher amounts of silver were in the range from 0.25 to 0.16 with temperature increasing from RT to 600 °C. The wear rates of the Ag/h-BN-containing composites were approximately an order of magnitude lower than those of the Base Alloy (having no solid lubricant) at all the temperatures. The addition of 4 wt% h-BN resulted in slightly greater friction and wear in comparison to the composites containing only silver.

Silver Microstructure Control for Fluxless Bonding Success Using Ag-In System

A fluxless bonding process is successfully developed between silicon (Si) chips and copper (Cu) substrates using the silver-indium (Ag-In) binary system. This is a new design concept that utilizes thick Ag plated over the Cu substrate to deal with the large mismatch in coefficient of thermal expansion between semiconductors, such as Si (3 ppm/°C) and Cu (17 ppm/°C). The Ag layer actually becomes a part of the Ag-Cu substrate. Ag is chosen for the cladding because of its superior physical properties of ductility, high electrical conductivity, and high thermal conductivity. Following the thick Ag layer, 5 μm In and 0.1 μm Ag layers are plated. The thin outer Ag layer inhibits oxidation of inner In. After many bonding experiments, we realize that the success of producing a joint relates to the microstructure of the Ag layer. Ag with small grains results in rapid growth of solid Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In intermetallic compounds through grain boundary diffusion. Thus, a joint is not obtained because of lack of molten phase (L). To coarsen Ag grains, an annealing step is added to the Ag-plated Cu substrate. This step makes Ag grains 200 times coarser compared to the as-plated Ag. The coarsened microstructure slows down the Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In growth. Consequently, the (L) phase stays at the molten state with sufficient time to react with the Ag layer on the Si chip to produce a joint. Nearly perfect joints are produced on Ag-plated Cu substrates. The resulting joints consist of pure Ag, Ag-rich solid solution, Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In, and Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> In. The melting temperature exceeds 650 °C. Using the present process, high temperature joints of high thermal conductivity are made between Si chips and Cu substrates at low bonding temperature (200°C). We foresee the Ag-In system as an important system to explore for various fluxless bonding applications in electronic packaging. This system provides the possibilities of producing joints of wide composition choices and wide melting temperature range. This paper provides preliminary but useful information on how the microstructure of Ag affects the bonding results.

XPS and ionic conductivity studies on Li1.3Al0.15Y0.15Ti1.7(PO4)3 ceramics

Li1.3Al0.15Y0.15Ti1.7(PO4)3 compound was synthesized by solid-state reaction, and ceramics were sintered. The surfaces of the ceramics were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Li1.3Al0.15Y0.15Ti1.7(PO4)3 samples were tested in solid galvanic cells Ag|O2+CO2|Li2CO3|Li1.3Al0.15Y0.15Ti1.7(PO4)3|LiMnO2+Mn2O3|O2|Ag. The electromotive force measurements of this cell indicated that investigated samples are practically pure Li-ion conductors. Impedance spectroscopy studies have been performed in the frequency range 10−2–3·109 Hz and temperatures from −57 °C to 334 °C. Three dispersion regions related to Li+ ionic transport in bulk, grain boundaries of the ceramics and to polarization of electrodes have been found. Total conductivity changes according to Arrhenius law in the studied temperature range, but an anomalous behavior was observed for the bulk conductivity of the ceramics.

A nonenzymatic cholesterol sensor constructed by using porous tubular silver nanoparticles

Porous tubular silver (Ag) nanoparticles were successfully synthesized by electrodeposition of Ag into cadmium sulfide (CdS) modified porous anodic alumina (PAA) template and removal of CdS subsequently. Only the solid nanorods were obtained without CdS. The strong affinity between S 2− and Ag (I) caused preferential deposition of Ag on the pore walls to form tubular Ag. After removal of CdS, porous tubular Ag nanoparticles were obtained. This novel nanostructure was characterized by XRD, TEM, FESEM, EDS and nitrogen adsorption–desorption isotherms. Using porous tubular Ag nanoparticles modified glassy carbon electrode (GCE) as a working electrode, a good nonenzymatic cholesterol sensor was constructed, which showed markedly improved electrocatalytic activity toward cholesterol oxidation compared to that of solid Ag nanorods. Under optimal detection conditions, the constructed sensor had a linear response range of 2.8 × 10 −4 M to 3.3 × 10 −2 M and the detection limit was 1.8 × 10 −4 M at a signal-to-noise ratio of 3. The biosensor showed an acceptable reproducibility, good stability and low interferences. To the best of our knowledge, it is the first example of a nonenzymatic cholesterol biosensor based on Ag nanoparticles. The experimental results demonstrated that porous tubular Ag nanoparticles provided a promising platform for rational design and fabrication of nonenzymatic cholesterol sensors.

Synthesis of Ag-Mn&lt;SUB&gt;3&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt; Core–Shell Nanorods and Mn&lt;SUB&gt;3&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt; Nanotubes from Sacrificial Ag Nanorod Templates

Our research focuses on the preparation of Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes which have various engineering applications. Hausmannite manganese oxide (Mn3O4) nanotubes were synthesized via a galvanic replacement reaction at mild reaction conditions. The Mn3O4 nanotubes were prepared by solidification of manganese ions on a sacrificial silver nanorod due to the standard reduction potential difference between solid silver and manganese ions. The Mn ions were reduced to solid while the solid Ag rod was oxidized to ions. Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes were simply prepared by changing the amount of manganese ions. The Mn3O4 layer in the nanorods and nanotubes had a Hausmannite crystalline structure and showed weak hysteresis of magnetism. This weak magnetism is likely due to the diamagnetic property of silver and multiple magnetic domain of Mn3O4. This simple replacement reaction could be applied to various oxide nanotube fabrications with exact shape control.

ChemInform Abstract: Structure Chemical Aspects of Silver(I) Chalcogenide Halides and Preparation of the x = 1 Member of the Solid Solution Ag5Te2Cl1‐xBrx.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Deep desulfurization of gasoline using ion-exchange zeolites: Cu(I)- and Ag(I)-beta

Solid adsorbents Cu(I) and Ag(I) metal exchanged beta zeolites were prepared by solid-state ion-exchange (SSIE) method. Crystallographic structure of the prepared adsorbents has been characterized by XRD analysis. The texture of the prepared adsorbents was investigated using N 2 sorption. Pyridine IR measurements have been carried out to investigate the nature of the acid sites of the adsorbents. The deep-desulfurization performance of such adsorbents has been evaluated through fixed-bed adsorption technique with model gasoline containing thiophene and benzothiophene at ambient temperature and pressure. The obtained results revealed that the breakthrough capacities of Cu(I)- and Ag(I)-beta zeolite with the optimized Cu + or Ag + content are 0.239 mmol S/g and 0.237 mmol S/g, respectively. The remaining sulfur in the desulfurized gasoline is less than 1 ppmw. Their desulfurization capacity for actual FCC gasoline blend is reduced about 30% due to the competitive adsorption from olefins and aromatics. However, The capacity regeneration of Cu(I)- and Ag(I)-beta zeolite sorbents was carried out for 9 times. It is more than 95% recovery of desulfurization after the first regeneration, and it keeps little reduction after subsequent 8 times of regeneration. Such studies included the effect factors on desulfurization performance, such as metal exchange content, SiO 2/Al 2O 3 ratio, acidity, and other texture properties of the zeolite etc.

Growth of Ag nanometre-sized particles in solution: molecular dynamics simulations

This work focuses on the growth of nanometre-sized Ag clusters in solution. Moleculardynamics simulations have been employed to gain the necessary detail on the dynamics ofsolute species and to study the mechanistic features of the processes governing theassociation of solute atoms in aggregates. Supersaturated liquid solutions of Ag intetrachloromethane have been considered. A systematic variation of the concentration ofAg atoms in solution permitted us to show the different mechanistic scenarios responsiblefor the growth processes of solid Ag clusters. It is shown that such processes are limited bythe thermal diffusion of solute in the solution bulk at relatively low supersaturationdegrees, whereas the growth is limited by interfacial effects at relatively highsupersaturation degrees.

Geochemical cycling of silver in marine sediments along an offshore transect

Although there have been many surface water and water column silver (Ag) analyses in the ocean, the absence of high resolution pore water and solid phase Ag profiles has hampered our understanding of its oceanic geochemical cycling. This manuscript presents pore water and solid phase profiles of Ag along an offshore transect in the northeast Pacific off the coasts of Washington/Oregon states, USA. Pore water Ag concentrations are uniformly low (< 0.3 nmol kg − 1 ) in profiles from sediments that have low bottom water oxygen concentrations, have shallow oxygen penetration depths (O 2,pen < 1 cm) and underlie short water columns (< 500 m water depth). The solid phase Ag concentrations at these sites are also low (< 1 μmol kg − 1 ). This is in contrast to sediments from intermediate water depths (~ 2000 m) that have similar oxygen penetration depths (O 2,pen < 1 cm), but have elevated pore water Ag concentrations (0.7 nmol kg − 1 ) at the sediment–water interface and higher solid phase Ag concentrations (4–8 μmol kg − 1 ). At sites from ~ 3000 to 4000 m water depth, where O 2,pen > 1 cm, pore water Ag concentrations reach extremely high concentrations in the top 5 cm (8–24 nmol kg − 1 ). High concentrations in pore waters provide evidence for a flux of Ag from ocean sediments, but the more oxidizing nature of these sediments precludes appreciable solid phase Ag accumulation in the top 30 cm (< 2 μmol kg − 1 ). The accumulation of Ag in sediments is not simply dependent on redox conditions; more oxidizing sediments do not accumulate solid phase Ag, and neither do more reducing sediments from shallow water depths. Only a sufficiently long water column will result in additional delivery of Ag to sediments by scavenging onto settling particles, and result in Ag accumulation in sediments where O 2,pen < 1 cm. Although upward Ag fluxes from sediments underlying shorter water columns are small (0.02–0.07 nmol cm − 2 y − 1 ), calculated fluxes increase for sediments underlying longer water columns and are largest for the more oxidizing sediments (2–5 nmol cm − 2 y − 1 ). Calculated fluxes of pore water Ag to the solid phase at these more oxidizing stations are inconsistent with measured solid phase Ag concentrations and suggest that the pore water profiles represent non-steady state conditions. Clearly, the early diagenesis of Ag is a highly dynamic process and more research is required to fully understand Ag cycling in sediments in continental margin locations.

Transient liquid phase bonding of titanium to aluminium nitride

Titanium has been successfully joined to aluminium nitride AlN at a temperature as low as 795 °C, using Ag–Cu Cusil ® commercial braze alloy. While reactive wetting and spreading proceeds at the AlN/braze alloy interface, chemical interactions develop at the titanium side rendering possible isothermal solidification of the joint. The determining factor in the solidification process is the fast formation of TiCu 4 crystals by heterogeneous nucleation and growth in the liquid phase. As a consequence, the braze alloy is depleted in Cu and solid Ag precipitates. After annealing, the re-melting temperature of the resulting joint can be increased up to about 910 °C which is nearly 130 °C higher than the melting point of the starting braze alloy.

Oxidant‐Free Alcohol Dehydrogenation Using a Reusable Hydrotalcite‐Supported Silver Nanoparticle Catalyst

Additive free: Hydrotalcite-supported silver nanoparticles act as a highly efficient heterogeneous catalyst for the dehydrogenation of diverse alcohols (see picture) in the absence of any acceptors such as molecular oxygen, hydrogen peroxide, or unsaturated organic compounds. The solid Ag catalyst was readily reusable without any loss of activity and selectivity. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z703161_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.