Silver Grain Size Research Articles

Fe-Ag pseudo-alloys obtained by wire electric explosion, ball milling and spark plasma sintering

• Fe-Ag pseudo-alloys formed by wire electric explosion and spark plasma sintering. • WEE powder was ball-milled to improve its structural uniformity. • In pseudo-alloy formed from milled powder, silver grains were 300-500 nm in size. • Material sintered from ball-milled powder showed a higher microhardness. • Porous silver with a uniform structure was obtained from sintered material. Structural features of Fe-25 wt.% Ag pseudo-alloys obtained by spark plasma sintering of the product of wire electric explosion (WEE) and the product of WEE processed by ball milling were comparatively investigated for the first time. In the sintered pseudo-alloy produced from the WEE powder, inclusions of iron 5-10 μm were found in the Fe-Ag composite matrix. The size of silver grains was of the order of 1 μm and 300-500 nm in the sintered materials produced from the WEE powder and ball-milled powder, respectively. The pseudo-alloys sintered from the ball-milled powder showed a higher microhardness than the material sintered from the WEE powder. Porous silver obtained from the pseudo-alloy sintered from the WEE powder by selectively dissolving iron showed micrometer-sized pores in the former places of iron particles of those sizes. In contrast, porous silver obtained from the pseudo-alloy sintered from the ball-milled powder had a uniform structure free from large pores.

Enhanced thermopower in (013)-oriented silver selenide films produced by thermal annealing

Nanocrystalline thin films of thermoelectric compound Ag2Se (AS) were deposited on the glass substrate kept at room temperature by thermal evaporation technique. Deposited films were annealed in vacuum of 2 × 10–5 mbar at 90 °C, 120 °C, 150 °C, 180 °C and 210 °C for 1 h. A sudden change in crystal orientation from (121) to (013) was observed as annealing temperature was increased to 210 °C. Seebeck coefficient for (013) oriented film was also found to be − 114.6 μV/K at room temperature compared to − 62.3 μV/K for as-deposited film. Formation of silver segregates in the film was observed where variation of size of silver grains on annealing played a crucial role in optimising Seebeck coefficient. Energy filtering effect by silver grains in combination to (013) orientation of silver selenide crystals was inferred as a reason for enhancement of Seebeck coefficient. Room temperature value of power factor was optimised at annealing temperature of 120 °C (AS-120) which was calculated to be 755.0 μW/mK2 and was also found to be comparable to that of film annealed at 210 °C (AS-210) i.e., 705.6 μW/mK2. Unlike AS-120, power factor value of AS-210 was due to considerable value Seebeck coefficient.

Localized surface plasmon resonance in SnS:Ag nano-composite films

Nano-composite films of Tin Sulfide (SnS) and silver fabricated by thermal evaporation showed two prominent peaks in the visible region of their extinction spectra. Theoretical modeling of the extinction spectra suggests that these two peaks (≈500 nm and ≈580 nm) correspond to the longitudinal mode and transverse mode surface plasmon resonance peaks arising from oblate silver nano-particles. Using grain size of silver and SnS obtained from structural and morphological characterizations of the samples and dielectric constants as per actuals, we have compared the experimental results with those from theory. The study shows that silver nano-particles efficiently scatters light and can be used for developing plasmonic based SnS solar cells with improved efficiencies.

Fabrication and characterization of nano silver powder prepared by spray pyrolysis

Silver powder was fabricated by spray pyrolysis, using 2%–20% AgNO3 solution, 336–500 mL/h flux of AgNO3 solution, 0.28–0.32 MPa flux of carrier gas and in the 620–820 °C temperature range. The effects of furnace set temperature, concentration of AgNO3 aqueous solution, flux of AgNO3 aqueous solution as well as carrier gas on the morphology and particle size distribution of silver powder, were investigated. The experimental results showed that with the high concentration of AgNO3 aqueous solution, the average grain size of silver decreased with the increasing of furnace set temperature. But the gain size distribution was not homogenous, the discontinuous grain growth occurred. With the low concentration of AgNO3 aqueous solution, the higher furnace set temperature made the nano sliver grains sintered together to grow. Nano silver powder about 100 nm was fabricated by spray pyrolysis, using 2wt% AgNO3 solutions, 336 mL/h flux of AgNO3 aqueous solution, 0.32 MPa flux of carrier gas at 720 °C furnace set temperature.

Oxidation of silver electrodes induces transition from conventional to inverted photovoltaic characteristics in polymer solar cells

Oxidation of silver top electrodes in polymer solar cells induces the devices to exhibit a transition from conventional to inverted photovoltaic characteristics. As silver oxidizes, its work function increases from 4.3 to 5.0 eV. The silver top electrode thus reverts from collecting electrons to collecting holes during device operation. We have quantified the extent of this transformation and find it to be correlated with the rate of silver oxidation, which we can influence by altering the annealing sequence of the polymer photoactive layer, ultimately varying the grain size of silver in the top electrode.

Influence of the current applied to the silver target on the structure and the properties of Ag–Cu–O films deposited by reactive cosputtering

Ag–Cu–O films were deposited on glass substrates by reactive magnetron cosputtering of silver and copper targets. In this manuscript, the current applied to the copper target and the oxygen flow rate introduced into the deposition chamber were kept constant, whereas the current applied to the silver target ( I Ag) was varied. Films deposited without silver crystallised into the paramelaconite structure (Cu 4O 3). At low silver target current, incorporation of Ag into Cu 4O 3-based did not modify the film structure. Silver atoms substituted some Cu(+I) atoms leading to the formula: Ag 2− x Cu 2+ x O 3. On the other hand, when I Ag exceeded a critical value, X-ray diffraction analyses revealed a biphased structure: Ag 2− x Cu 2+ x O 3 and Ag. Contrary to the diffraction peak intensity of the Ag 2− x Cu 2+ x O 3 phase, that of silver was increased with I Ag. For the highest value of I Ag, no silver–copper oxide was detected and the mean crystal size of silver grains was close to 2 nm. Due to the occurrence of the nanocrystallised silver phase, the film electrical resistivity strongly decreased. Optical reflectance measurements confirmed the structural changes versus the silver target current.

Novel Fabrication of Ag Thin Film on Glass for Efficient Surface-Enhanced Raman Scattering

This paper describes a very simple electroless-plating method used to prepare optically tunable nanostructured Ag films. Very stable Ag films can be reproducibly fabricated simply by soaking glass substrates in ethanolic solutions of AgNO3 and butylamine. The grain size of silver can be readily controlled to range from 20 to 150 nm, and these nanostructural features correlated well with their UV/vis absorption characteristics, as well as with their surface-enhanced Raman scattering (SERS) activities. It is also very advantageous that the Ag films prepared exhibit very even SERS activity over an area up to hundreds thousand square-micrometers, and the enhancement factor estimated using benzenethiol as a prototype adsorbate reaches approximately 2 x 10(5). Since the proposed method is cost-effective and is suitable for the mass production of diverse Ag films irrespective of the shapes of the underlying substrates, it is expected to play a significant role in the development of surface plasmon-based analytical devices.

Electrodeposition of Nanocrystalline Silver: Study of Grain Growth by Measurement of Reversible Electromotive Force

Electrodeposition of pure nanocrystalline silver from a highly concentrated potassium iodide solution containing silver nitrate was described and discussed. The reversible electrode potential of the nanocrystalline material was measured versus polycrystalline silver. Grain growth of the deposit could be quantitatively determined from the decrease of the electrode potential with time. A parabolic law of growth is fulfilled, which gives the initial grain size of silver by extrapolation.