Photonics-to-electronics integration for optical interconnects in the early 21st century

It is useful to examinethe history of penetration opti-cal datalinksinto communication over thelast 30 years .Fig.1 shows an approxi mate perspective of the rate ofpenetration of optics versus the link distance and thebandwidth.Thelower horizontal axis re…     

Lead-strontium titanate glass ceramics: I – crystallization and microstructure

The crystallization behaviour of glasses in the system [(Pb Sr ) O·TiO₂]-[2SiO₂· B₂O₃]-[K₂O]-[BaO] (0.2 ≤ x ≤ 0.9) have been studied. Perovskite titanate was found to be the major phase in all the glass ceramic samples investigated. The actual composition of crystalline phases could not be confirmed on the basis of shift in the X-ray diffraction (XRD) peak positions because of similar effects due to solid solution formation and strain due to crystal clamping. Comparison of the observed intensities of various XRD peaks of the perovskite titanate phase with the calculated intensities for (Pb Sr )TiO₃ with same lead/strontium ratio confirmed the formation of lead strontium titanate solid solution. Microstructural characteristics of various glass ceramics are also discussed. The advantages of using K₂O and BaO as additives instead of only K₂O are also discussed.     

Structural and optical properties of tin oxide branched nanostructures

Branched nanostructures of tin oxide (SnO2) have been synthesized by Vapor-Liquid-Solid (VLS) mechanism using a gold catalyst in the temperature range of 800-850 degrees C under an ambient gas flow of 200 sccm. The microstructural and the optical properties of the as prepared products have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-Raman, and photoluminescence (PL) studies. SnO2 branches with a rutile phase are found to have a preferential orientation along (101). Typical lengths of these branches are found to be approximately 3-5 microm and diameters in the range of 50-100 nm. Selected area electron diffraction (SAED) pattern shows that the SnO2 branches have a tetragonal cross section with [101] crystal direction. A Raman line at 631 cm(-1) (Sn-O bond) is obtained in the micro Raman spectra. Low temperature PL spectrum shows a strong green emission band near 506 nm.     

In Situ Synthesis, Microstructure, and Properties of TiC and (Ti,W)C-Reinforced Fe-Mn-Al Austenitic Steel Matrix Composites

In situ synthesis, microstructures, and properties of 10 vol.% TiC and (Ti,W)C-reinforced Fe-Mn-Al austenitic steel matrix composites have been reported in this paper. The microstructure of the prepared samples has been characterized by using scanning electron microscopy and X-ray diffraction technique. The abrasion wear resistance and mechanical properties such as hardness and impact energy of both the composites as well as the unreinforced Fe-Mn-Al austenitic steel have been evaluated. The (Ti,W)C-reinforced composite has higher impact energy and slightly lower hardness values compared to that of TiC-reinforced composite. The TiC-reinforced composite exhibits the best abrasive wear resistance of all the materials tested.     

Zinc oxide-based thin film functional layers for chemiresistive sensors

Sol-gel wet-chemical techniques were used to prepare ZnO, Al-ZnO (Al:Zn = 1:10 mol/mol) and Cu-ZnO (Cu:Zn = 1:10 mol/mol) thin films for characterization as functional layers for chemiresistive oxygen sensors. Cu and Al minor components influence the ZnO films' topography and their thermally induced chemical and structural evolution. As prepared (room temperature) films have the structure of layered basic zinc acetate, a lamellar ZnO precursor. Upon annealing at temperatures through 973 K, the films display similar chemical evolution patterns—temperatures above 773 K are needed to completely desorb solvents and decompose precursors. Cu facilitates c-axis orientation of the film as its structure matures, while Al slows its crystallization. Chemiresistive sensors, fabricated by coating thin film functional layers onto interdigitated electrode (IDE) transducers, were evaluated for their responses to oxygen at operating temperatures through 873 K. A ZnO/IDE sensor displays high sensitivity for O₂ at an intermediate temperature, 673 K, reflecting an optimal balance between surface O₂ coverage and carrier availability. At 1:10 mol/mol Cu:Zn and Al:Zn, the developing ZnO structure cannot accommodate all minor component atoms. Surplus atoms accumulate in independent phases at grain boundaries, contributing to both high base resistances (in N₂) and low sensitivity to oxygen.     

Dielectric properties of Erbium doped CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> prepared by sol–gel self combustion method

The dielectric properties of Erbium doped CaCu₃Ti_(4–x)Er_xO_(12–δ) with x = 0, 0.05, 0.1 were synthesized by the sol–gel self combustion method. XRD (X-ray powder diffraction) analysis confirmed the formation of single-phase material in the samples calcined at 800 °C. Crystal structure does not change on doping with Erbium and it remains cubic in all the three compositions studied. It is found that lattice parameter increases slightly with Erbium doping. The surface morphology of CaCu₃Ti_(4–x)Er_xO_(12–δ) powders sintered at 950 °C in air for 3 h was observed using high resolution—scanning electron microscope and it shows that the grain size is in the range of 1–8 μm for these samples. Energy dispersive X-ray spectroscopy pattern confirmed the presence of Erbium with 1.9 and 4.86 atomic percentages with doping concentration. The dielectric characteristics of CaCu₃Ti_(4–x)Er_xO_(12–δ) were studied by LCR meter in the frequency range (100 Hz–1 MHz) at various temperatures (RT to 500 °C). Interestingly, the dielectric constant increases and dielectric loss had lower values than those of undoped CCTO.     

Phyto-inspired silica nanowires: characterization and application in lipase immobilization

Silica nanostructures were phyto-fabricated on different surfaces by using pomegranate (Punica granatum) leaf extracts. On zinc films, nanowires were obtained. On other surfaces such as silica, alumina, zinc oxide, and glass, spherical aggregates, cubic assemblies, microflakes, and acicular structures, respectively, were observed. The nanowires developed on Zn surfaces were characterized by scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), photoluminescence, and Fourier transform infrared (FTIR) spectroscopic analysis. XRD profiles displayed peaks at 2.4, 4.9, and 12.1° indicating the presence of silica nanostructures. When excited at 340 nm, the reaction mixtures displayed a characteristic blue luminescence at 404 nm. FTIR spectra showed the existence of Si-OH and Si-O-Si bonds. The nanowires were functionalized with amine groups and used for the covalent immobilization of Candida rugosa lipase. The immobilized enzyme displayed better pH and temperature stability and retained 80% activity after 20 cycles. This paper highlights a novel route for the phyto-mediated growth of silica nanowires on Zn surfaces, their characterization and effective use as a matrix for enzyme immobilization.     

Studies on the photochemical deposition (PCD) of II–VI compound semiconductor thin films of ZnS from aqueous solution

Zinc sulphide (ZnS) thin films were depositedon Indium oxide coaled glass substrates by Photo Chemical Deposition (PCD) with starting precursor of Zinc sulphate and sodium thiosulphate as a source material for Zn and S respectively. In addition the pH was varied (3 to 8) using sulphuric acid by adding up in the precursor. Later the ZnS thin films were annealed at 500°C and it was found that crystalline structure was improved. Zinc blende crystalline structure was observed on the thin films using X-ray diffractometer (XRD). The morphological behavior was observed using Scanning electron microscope (SEM) and it reveals that the size of the grain increases after annealing at 500°C. UV-spectrometer was used to analyze the aqueous solution optical behavior before and after deposition. The average thickness of thin film was estimated as ～1.02 micron measured by stylus profilometer method.     

Modeling electrification of suspended particulate matter (SPM) in a two phase laminar boundary layer flow and heat transfer over a semi-infinite flat plate

The present paper envisages the effects of electrification of particles, volume fraction and diffusion of SPM on the boundary layer flow and heat transfer over a semi-infinite flat plate. Irrespective of the particle material density, it has been observed that the range of validity of the solution remains fixed and at x = 2.12 the nature of the profiles of the flow variables changes. Electrification of particles causes the particles to move faster for x < 1.0 and slows down for x > 1.0 but particle temperature increases with increase of M. It has been observed that heat transfer always occurs from the fluid to plate.