Materials

Single and Mixed Phase TiO2 Powders by Excess Hydrolysis of Titanium Alkoxide

by Material Science

To investigate excess-hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium-tetra-isopropoxide... more To investigate excess-hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium-tetra-isopropoxide using 6:1 and 100:1 H2O:Ti (r) ratios. Powders were dried and fired at a range of temperatures (≤800ºC). Hydroxylation and organic content in powders were characterised using ATR-FTIR, laser Raman microspectroscopy, and elemental microanalysis; surface area and pore size distribution were evaluated using N2 gas adsorption; phase composition was analysed using XRD and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near-complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500°C. Powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an amorphous structure, with crystallisation of anatase occurring at ~300°C and transformation to rutile beginning at 500°-600°C.

Analytical Bond-Order Potential for the Cadmium Telluride Binary System

by Bryan Wong

Physical Review B, 85, 115206 (2012)

Effect of immersion in water partially alkali-activated materials obtained of tungsten mine waste mud

by Antonio Albuquerque

Silva I., Castro-Gomes J. & Albuquerque A.
Construction and Building Materials, V. 35, 117-124.

Alkali-activated binders can be obtained using several sources of alumino-silicate materials, from calcinatedmore Alkali-activated binders can be obtained using several sources of alumino-silicate materials, from calcinated
clays, like kaolin, to industrial by-products, such as fly ash and, more recently, to calcinated waste mud from mining activities. The technology to obtain alkali-activated binders, also designated as geopolymers, is gaining increasing interest, since, in some cases, the properties of geopolymeric materials
are superior to other existing cementitious systems. The research presented in this paper intends to deepen
the knowledge regarding the properties of geopolymeric materials obtained using tungsten mining waste mud, particularly to study its behaviour after being immersed in water. However, in the current work, focus is given to follow compressive strength results in partially alkali-activated samples immersed in water, during different curing periods of time. Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy analysis (FTIR) were also utilised to investigate changes in the microstructure at different conditions of water immersion. A significant decrease in compressive strength occurring after 24 h of immersion in water was found out, of specific partially alkali-activated materials, despite of its initial high compressive strength after 35 days curing, at different temperatures.

Evaluation of the stability of waste-based geopolymeric artificial aggregates for wastewater treatment processes under different curing conditions

by Antonio Albuquerque

I. Silva, J. Castro-Gomes, A. Albuquerque
Advances in Science and Technology, 2010, V. 69, 86-91.

Waste geopolymeric artificial aggregates (WGA) with different atomic ratios of mining waste mud/Na2SiO (4 to 5) and... more Waste geopolymeric artificial aggregates (WGA) with different atomic ratios of mining waste mud/Na2SiO (4 to 5) and Na2SiO/NaOH (1.25 to 5) were produced using curing temperatures of 20ºC and 130ºC and its structural stability and pH variation after immersion in water was observed during 3 months. Results showed that WGA with mud/Na2SiO and Na2SiO/NaOH of 5 and 4, respectively, cured at 20ºC presented good stability in water and pH decreased from 10 to 7
in 24 days. Compressive strength was determined in additional samples cured at 20ºC and 80ºC in dry conditions, for 13 curing ages and 15 water immersion periods (up to 14 weeks). Results of this second stage showed that increasing temperature to 80ºC accelerated compressive strength gain but
only during the first 3 weeks (up to 15.4 MPa). After 24 h in water compressive strength decreased to half of the initial values determined in dry conditions in all samples and, therefore, the increase of temperature did not bring benefits to WGA strength in water. Regardless the curing temperature and the dry curing age comprehensive strength stabilizes between 1 MPa and 2 MPa after 4 weeks immersion in water, which are values that makes WGA suitable to be used as bed material for wastewater treatment processes.

Potential for reuse of tungsten mining waste-rock in technical-artistic value added products

by Antonio Albuquerque

J. Castro-Gomes, A. Silva, R. Cano, J. Suarez, A. Albuquerque
Journal of Cleaner Production, 2012, V. 25, 34-41

Mining and quarrying activities in Europe generate approximately 55% of total industrial wastes, according to a recent... more Mining and quarrying activities in Europe generate approximately 55% of total industrial wastes, according to a recent Eurostat report. Most of these wastes are directly dumped on land or deposited in landfill sites. The first solution may lead to negative environmental impacts on land (removal of vegetation, deforestation, land slope changes and increased risk of erosion), water (pollutant transport through surface runoff, soil infiltration and contamination of water resources), may lead to the contamination of agricultural goods and may impose risks on human health. In Portugal, about 20% of industrial waste produced originates from mines and quarries, particularly from Panasqueira mining, one of the largest tungsten mines in the world. Currently, Panasqueira mining generates almost 100 tonnes of waste-rock, per day. Such waste-rock have accumulated over a number of years into very large heaps and it is desirable to seek new economic solutions that can contribute towards their reuse. In this context, this work discusses the potential for reuse of waste-rock piles of Panasqueira tungsten mine, which may be a case statement to be followed. The proposed solution described in this paper consists in developing innovative polymer-based composite materials, obtained from non-contaminated waste-rock tailings. Such materials must have suitable properties for technical-artistic value added applications, such as conservation, restoration and/or rehabilitation of historic monuments, sculptures, decorative and architectural intervention, or simply as materials for building revetments.

Mineral wastes geopolymeric artificial aggregates as alternative materials for wastewater-treatment processes - Study of structural stability and pH variation in water

by Antonio Albuquerque

Silva I., Castro-Gomes J. & Albuquerque A.
Journal of Materials in Civil Engineering, V. 24, Nº 6, 1-6.

Artificial aggregates produced from mine waste geopolymeric binders were studied as a potential substrate for... more Artificial aggregates produced from mine waste geopolymeric binders were studied as a potential substrate for fixed-film
wastewater-treatment processes (biofilm reactors). Waste geopolymeric artificial aggregates (WGA) of 2–3 cm in size were produced using geopolymeric mine waste mud as a precursor and both sodium silicate and sodium hydroxide as alkaline activators. Seven mixtures were produced with different atomic ratios of sodium silicate to sodium hydroxide (S/H) and of precursor (waste mud) to sodium silicate (P/S), using curing temperatures of 20°C and 130°C, for a total of 112 samples. Structural stability and pH variation after immersion in water were observed over an 18-week period. The results showed that the initial water pH decreased with the increase of the curing time, taking between 17 and 42 days to reach pH 8. The mixture cured at 20°C for 28 days appears to be suitable for use as a substrate for biofilm reactors because the initial water pH was one of the lowest (approximately pH 10), and the time necessary to stabilize it to approximately pH 8 was only 17 days.

An Embedded-Atom Method Interatomic Potential for Pd-H Alloys

by Bryan Wong

Journal of Materials Research, 23, 704 (2008)

Enhanced Photocurrent Efficiency of a Carbon Nanotube p-n Junction Electromagnetically Coupled to a Photonic Structure

by Bryan Wong

Journal of Physics D: Applied Physics, 42, 055111 (2009)

Color Detection Using Chromophore-Nanotube Hybrid Devices

by Bryan Wong

Nano Letters, 9, 1028 (2009)

- Featured as "Headline News" in "physicsworld.com"
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- Featured in "MIT Technology Review"
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- Featured as "Nanotechnology News" in "PhysOrg.com"
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- Featured in "Ceramic Tech Today"
http://ceramics.org/ceramictechtoday/2009/05/26/carbon-nanotubes-used-to-detect-color/

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- Featured as "Technology" in "Photonics Spectra"
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- Featured as "Issues and Events" in "Physics Today"
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Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Comparison

by Bryan Wong

Journal of Physical Chemistry C, 115, 7778 (2011)

Accuracy of Existing Atomic Potentials for the CdTe Semiconductor Compound

by Bryan Wong

Journal of Chemical Physics, 134, 244703 (2011)

Self-Assembled Cyclic Oligothiophene Nanotubes: Electronic Properties from a Dispersion-Corrected Hybrid Functional

by Bryan Wong

Physical Review B, 84, 075115 (2011)

- Selected by the editor to appear in the August 22, 2011 issue of the "Virtual Journal of Nanoscale Science & Technology" (Volume 24, Issue 8)
http://link.aip.org/link/VIRT01/v24/i8/p92

Nanoscale Effects on Heterojunction Electron Gases in GaN/AlGaN Core/Shell Nanowires

by Bryan Wong

Nano Letters, 11, 3074 (2011)

Electron Beam Synthesis of Metal and Semiconductor Nanoparticles Using Metal-Organic Frameworks as Ordered Precursors

by Bryan Wong

Nanotechnology, 22, 375601 (2011)

- Featured as "Lab Talk" in "nanotechweb.org"
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Electronic Properties of Vinylene-Linked Heterocyclic Conducting Polymers: Predictive Design and Rational Guidance from DFT Calculations

by Bryan Wong

Journal of Physical Chemistry C, 115, 18333 (2011)

Spectroscopic Properties of Nanotube-Chromophore Hybrids

by Bryan Wong

ACS Nano, 5, 7767 (2011)

Reversible, Opto-Mechanically Induced Spin-Switching in a Nanoribbon-Spiropyran Hybrid Material

by Bryan Wong

Nanoscale, 4, 1321 (2012)

Theories of Matter

by henry laycock

Journal: Synthese.
Reprinted in Mass Terms: some Philosophical Problems.

DO NOT USE QUICK VIEW - DOES NOT WORK!

Theories of Matter documents the all-pervasive doctrine which I call the Ontology of Objects - a doctrine which claims... more Theories of Matter documents the all-pervasive doctrine which I call the Ontology of Objects - a doctrine which claims that there can be no other ontic category than that of objects (along with their properties and relations). Here this doctrine and its logico-semantic basis are attacked, the influential work of Helen Cartwright is criticized, and it is denied that matter must be re-identifiable.

Synthesis and characterization of neodymium doped ceria nanocrystalline ceramic structures

by Prof.Dr. İbrahim USLU

Ceramics International
First Online March 2012
İbrahim Uslu, Arda Aytimur, Mustafa Kemal Öztürk, Serhat Koçyiğit

In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the... more In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the hybrid polymers solution of their composite precursor was put forward. Calcined and sintered nanopowders were characterized by FT-IR, XRD, BET, SEM, and AFM techniques. According to the XRD analysis, the obtained powders are single phase and independent of the dopant concentration in the range investigated. The crystallite sizes were calculated using Scherrer equation. Moreover, lattice parameters, dislocation densities and microstrain values were calculated. BET results show that the increase of the neodymium doped content decrease the surface area of the composite powders, confirming the highly ordered micro and mesostructure. SEM and AFM results show that the samples have spherical grains. According to the surface roughness measurements, the increase in the amount of neodymium and the decrease in the amount of cerium decreased the surface roughness.

Synthesis and characterization of boron doped alumina stabilized zirconia fibers

by Prof.Dr. İbrahim USLU

FIBERS AND POLYMERS
2011, Volume 12, Number 3, 303-309, DOI: 10.1007/s12221-011-0303-1
ibrahim uslu, M.K. Öztürk, T. Tunç, T.C. Karabulut, S. Keskin,

Boron doped PVA/Zr-Al acetate nanofibers were prepared by electrospinning using PVA as a precursor. The effect of... more Boron doped PVA/Zr-Al acetate nanofibers were prepared by electrospinning using PVA as a precursor. The effect of calcination temperature on morphology and crystal structure was investigated at 250, 500, and 800 °C. The study also establishes the effect of boron doping on the morphology of PVA/Zr-Al acetate nanofibers at various calcination temperatures. The measurements showed that the conductivity, pH, viscosity and the surface tension of the hybrid polymer solutions have increased with boron doping. In addition, the fibers were characterized by FTIR, DSC, XPS, XRD and SEM techniques. The addition of boron did not only increase the thermal stability of the fibers, but also increased the average fiber diameters, which gave stronger fibers. The DSC results indicated that the melting temperature (Tm) of the fibers was increased from 256 to 270 °C with the addition of boron. XRD peak patterns showed that after further heat treatment at 800 °C, zirconia exists in two phases of tetragonal and monoclinic modifications. Moreover, alumina does not transform into the γ-Al2O3 and θ-Al2O3 phase at 800 °C. The SEM appearance of the fibers showed that the addition of boron resulted in the formation of crosslinked bright surfaced fibers.