Characterization of carbonated tricalcium silicate and its sorption capacity for heavy metals: A micron-scale composite adsorbent of active silicate gel and calcite

Adsorption-based processes are widely used in the treatment of dilute metal-bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of continuing interest. This paper examines the preparation, characterization and performance of a micro-scale composite adsorbent composed of silica gel (15.9 w/w%), calcium silicate hydrate gel (8.2 w/w%) and calcite (75.9 w/w%), produced by the accelerated carbonation of tricalcium silicate (C(3)S, Ca(3)SiO(5)). The Ca/Si ratio of calcium silicate hydrate gel (C-S-H) was determined at 0.12 (DTA/TG), 0.17 ((29)Si solid-state MAS/NMR) and 0.18 (SEM/EDS). The metals-retention capacity for selected Cu(II), Pb(II), Zn(II) and Cr(III) was determined by batch and column sorption experiments utilizing nitrate solutions. The effects of metal ion concentration, pH and contact time on binding ability was investigated by kinetic and equilibrium adsorption isotherm studies. The adsorption capacity for Pb(II), Cr(III), Zn(II) and Cu(II) was found to be 94.4 mg/g, 83.0 mg/g, 52.1 mg/g and 31.4 mg/g, respectively. It is concluded that the composite adsorbent has considerable potential for the treatment of industrial wastewater containing heavy metals.

Fabrication of Sub-micron Active Layer SSOI Substrates using Ion Splitting and Wafer Bonding Technologies

This paper reports the fabrication of SSOI (Silicon on Silicide On Insulator) substrates with active silicon regions only 0.5mum thick, incorporating LPCVD low resistivity tungsten silicide (WSix) as the buried layer. The substrates were produced using ion splitting and two stages of wafer bonding. Scanning acoustic microscope imaging confirmed that the bond interfaces are essentially void-free. These SSOI wafers are designed to be employed as substrates for mm-wave reflect-array diodes, and the required selective etch technology is described together with details of a suitable device.

Micron-scale fast electron filaments and recirculation determined from rear-side optical emission in high-intensity laser-solid interactions

The transport of relativistic electrons generated in the interaction of petawatt class lasers with solid targets has been studied through measurements of the second harmonic optical emission from their rear surface. The high degree of polarization of the emission indicates that it is predominantly optical transition radiation (TR). A halo that surrounds the main region of emission is also polarized and is attributed to the effect of electron recirculation. The variation of the polarization state and intensity of radiation with the angle of observation indicates that the emission of TR is highly directional and provides evidence for the presence of mu m-size filaments. A brief discussion on the possible causes of such a fine electron beam structure is given.

Ethanol (C2H5OH) spray of sub-micron droplets for laser driven negative ion source

Liquid ethanol (C₂H₅OH) was used to generate a spray of sub-micron droplets. Sprays with different nozzle geometries have been tested and characterised using Mie scattering to find scaling properties and to generate droplets with different diameters within the spray. Nozzles having throat diameters of 470 µm and 560 µm showed generation of ethanol spray with droplet diameters of (180 ± 10) nm and (140 ± 10) nm, respectively. These investigations were motivated by the observation of copious negative ions from these target systems, e.g., negative oxygen and carbon ions measured from water and ethanol sprays irradiated with ultra-intense (5 × 1019 W/cm2), ultra short (40 fs) laser pulses. It is shown that the droplet diameter and the average atomic density of the spray have a significant effect on the numbers and energies of accelerated ions, both positive and negative. These targets open new possibilities for the creation of efficient and compact sources of different negative ion species.

Generation of a quasi-monoergetic proton beam from laser-irradiated sub-micron droplets

Proton bursts with a narrow spectrum at an energy of (2.8 +/- 0.3 MeV) are accelerated from sub-micron water spray droplets irradiated by high-intensity (similar to 5 x 10(19)W/cm(2)), high-contrast (similar to 10(10)), ultra-short (40 fs) laser pulses. The acceleration is preferentially in the laser propagation direction. The explosion dynamics is governed by a residual ps-scale laser pulse pedestal which "mildly" preheats the droplet and changes its density profile before the arrival of the high intensity laser pulse peak. As a result, the energetic electrons extracted from the modified target by the high-intensity part of the laser pulse establish an anisotropic electrostatic field which results in anisotropic Coulomb explosion and proton acceleration predominantly in the forward direction. Hydrodynamic simulations of the target pre-expansion and 3D particle-in-cell simulations of the measured energy and anisotropy of the proton emission have confirmed the proposed acceleration scenario. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731712]

MFM imaging of micron-sized permalloy ellipses

The magnetic domain structure of micron-sized elliptic permalloy elements has been studied by magnetic force microscope (MFM) measurements, and has been compared to results from micromagnetic simulations. The elements all have the same aspect ratio, whereas the inter-elemental distance has been varied. Both the zero-field states and in field domain configurations have been studied. In zero-applied field, two different stable flux-closure states were found in both the MFM measurements and in the simulations. The different stable domain states occur as a result of minute differences in the local magnetic environment occurring during the demagnetization process. (C) 2004 Elsevier B.V. All rights reserved.

In Situ Formation of Micron-Scale Li-Metal Anodes with High Cyclability

Scanning probe microscopy methods have been used to electrodeposit and cycle micron-scale Li anodes deposited electrochemically under nanofabricated Au current collectors. An average Li volume of 5 x 10(8) nm(3) was deposited and cycled with 100% coulombic efficiency for similar to 160 cycles. Integrated charge/discharge values agree with before/after topography, as well as in situ dilatometry, suggesting this is a reliable method to study solid-state electrochemical processes. In this work we illustrate the possibility to deposit highly cyclable nanometer thick Li electrodes by mature SPM and nanofab techniques which can pave the way for inexpensive nanoscale battery arrays. 

Multiferroic PbZrxTi1-xO3/Fe3O4 epitaxial sub-micron sized structures

Large range well ordered epitaxial ferrimagnetic nominally Fe3O4 structures were fabricated by pulsed-laser deposition and embedded in ferroelectric PbZrxTi1-xO3 (x = 0.2, 0.52) epitaxial films. Magnetite dots were investigated by magnetic force microscopy and exhibited magnetic domain contrast at room temperature (RT). Embedding ferroelectric PbZrxTi1-xO3 layers exhibit remnant polarization values close to the values of single epitaxial layers. Transmission electron microscopy demonstrated the epitaxial growth of the composites and the formation of the ferrimagnetic and ferroelectric phases. Physical and structural properties of these composites recommend them for investigations of stress mediated magneto-electric coupling at room temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3692583]

Micro-abrasion-corrosion of cast CoCrMo-Effects of micron and sub-micron sized abrasives

The abrasion damage on retrieved CoCrMo based hip joints is reported to be influenced by the entrainment of micron and sub-micron sized debris/hard particles. This paper represents the first attempt to look into the effects of relatively soft abrasives with micron and sub-micron dimensions on the abrasion mechanisms and the abrasion-corrosion performance of the cast CoCrMo in simulated hip joint environments. A modified micro-abrasion tester incorporating a liquid tank and a three-electrode electrochemical cell was used. Al O (300 nm and 1 μm) and sub-micron sized BaSO abrasives were chosen as being comparable in the size and hardness to the wear particles found in vivo. Results show that the specific wear rates of cast CoCrMo are dependent on the abrasive particle size, hardness and volume concentration. Larger particle size, higher hardness and greater abrasive volume fractions gave greater wear rates. The wear-induced corrosion current generally increases with increasing wear rates, and the presence of proteins seems to suppress the wear-induced corrosion current especially when abrasive volume fractions were high. This study shows that the nature of abrasives and the test solutions are both important in determining the wear mechanisms and the abrasion-corrosion response of cast CoCrMo. These findings provide new and important insights into the in vivo wear mechanisms of CoCrMo. © 2009 Elsevier B.V. All rights reserved.

Transport of Sub-micron Aerosols in Bifurcations

The convective-diffusive transport of sub-micron aerosols in an oscillatory laminar flow within a 2-D single bifurcation is studied, using order-of-magnitude analysis and numerical simulation using a commercial software (FEMLAB®). Based on the similarity between momentum and mass transfer equations, various transient mass transport regimes are classified and scaled according to Strouhal and beta numbers. Results show that the mass transfer rate is highest at the carinal ridge and there is a phase-shift in diffusive transport time if the beta number is greater than one. It is also shown that diffusive mass transfer becomes independent of the oscillating outer flow if the Strouhal number is greater than one.

Hydrolysis of N2O5 on sub-micron mineral salt aerosols

The kinetics of reactive uptake of gaseous N2O5 on sub-micron aerosol particles composed of aqueous ammonium sulfate, ammonium hydrogensulfate and sodium nitrate has been investigated. Uptake was measured in a laminar flow reactor, coupled with a differential mobility analyser (DMA) to obtain the aerosol size distribution, with N2O5 detection using NO chemiluminescence. FTIR spectroscopy was used to obtain information about the composition and water content of the aerosol particles under the conditions used in the kinetic measurements. The aerosols were generated by the nebulisation of aqueous salt solutions. The uptake coefficient on the sulfate salts was in the range [gamma]=0.0015 to 0.033 depending on temperature, humidity and phase of the aerosol. On sodium nitrate aerosols the values were much lower, [gamma]<0.001, confirming the inhibition of N2O5 hydrolysis by nitrate ions. At high humidity (>50% r.h.) the uptake coefficient on liquid sulfate aerosols is independent of water content, but at lower humidity, especially below the efflorescence point, the reactivity of the aerosol declines, correlating with the lower water content. The lower uptake rate on solid aerosols may be due to limitations imposed by the liquid volume in the particles. Uptake on sulfate aerosols showed a negative temperature dependence at T>290 K but no significant temperature dependence at lower temperatures. The results are generally consistent with previous models of N2O5 hydrolysis where the reactive intermediate is NO2+ produced by autoionisation of nitrogen pentoxide in the condensed phase.