Characterisation of mechanochemically synthesised alane (AlH3) nanoparticles

A mechanochemical synthesis process has been used to synthesise alane (AlH3) nanoparticles. The alane is synthesised via a chemical reaction between lithium alanate (LiAlH4) and aluminium chloride (AlCl3) at room temperature within a ball mill and at 77K within a cryogenic mill. The reaction product formed consists of alane nanoparticles embedded within a lithium chloride (LiCl) by-product phase. The LiCl is washed with a solvent resulting in alane nanoparticles which are separated from the by-product phase but are kinetically stabilised by an amorphous particle surface layer. The synthesis of a particular alane structural phase is largely dependent on the milling conditions and two major phases (α, α′) as well as two minor phases (β, γ) have been identified. Ball milling at room temperature can also provide enough energy to allow alane to release hydrogen gas and form aluminium metal nanoparticles. A comparison between XRD and hydrogen desorption results suggest a non-crystalline AlH3 phase is present in the synthesised samples

The Mechanochemical synthesis of magnesium hydride nanoparticles

A mechanochemical method was used to synthesise magnesium hydride nanoparticles with an average crystallite size of 6.7 nm. The use of a reaction buffer was employed as a means of particle size control by restricting agglomeration. Increasing the amount of reaction buffer resulted in a decrease in crystallite size, as determined via X-ray diffraction, and a decrease in particle size, evidenced by transmission electron microscopy

Hydrogen storage properties of nanoconfined LiBH4-NaBH4

In this study a eutectic melting composite of 0.62LiBH4-0.38NaBH4 has been infiltrated in two nanoporous resorcinol formaldehyde carbon aerogel scaffolds with similar pore sizes (37 and 38 nm) but different BET surface areas (690 and 2358 m2/g) and pore volumes (1.03 and 2.64 mL/g). This investigation clearly shows decreased temperature of hydrogen desorption, and improved cycling stability during hydrogen release and uptake of bulk 0.62LiBH4-0.38NaBH4 when nanoconfined into carbon nanopores. The hydrogen desorption temperature of bulk 0.62LiBH4-0.38NaBH4 is reduced by ~107 °C with the presence of carbon, although a minor kinetic variation is observed between the two carbon scaffolds. This corresponds to apparent activation energies, EA, of 139 kJ mol-1 (bulk) and 116-118 kJ mol-1 (with carbon aerogel). Bulk 0.62LiBH4-0.38NaBH4 has poor reversibility during continuous hydrogen release and uptake cycling, maintaining 22% H2 capacity after four hydrogen desorptions (1.6 wt.% H2). In contrast, nanoconfinement into the high surface area carbon aerogel scaffold significantly stabilizes the hydrogen storage capacity, maintaining ~70% of the initial capacity after four cycles (4.3 wt.% H2)

Functional materials based on metal hydrides

Storage of renewable energy remains a key obstacle for the implementation of a carbon free energy system. There is an urgent need to develop a variety of energy storage systems with varying performance, covering both long-term/large-scale and high gravimetric and volumetric densities for stationary and mobile applications. Novel materials with extraordinary properties have the potential to form the basis for technological paradigm shifts. Here, we present metal hydrides as a diverse class of materials with fascinating structures, compositions and properties. These materials can potentially form the basis for novel energy storage technologies as batteries and for hydrogen storage

Non-synthetic polymer biomodification using gold nanoparticles

Tissue engineering, the creation of replacement tissue using natural and synthetic components, requires the ability to manipulate the local chemical environment of polymeric biomaterials, which are materials designed to augment or replace natural functions. Many polymeric biomaterials display excellent mechanical characteristics and compatibility to native tissue, but they do not readily support cell adhesion. Unfortunately, modification of these materials can be difficult. For example, agarose and poly (ethylene glycol) diacrylate (PEGDA) hydrogels only weakly support cell growth, and cell adhesion molecules must be added to improve the cell-material interface. Methods to chemically modify agarose and PEGDA hydrogels have been developed, but these methods tend to be difficult and time consuming. A new technique for modification, using gold nanoparticles embedded within a hydrogel matrix, offers a solution to these problems. The particles serve as attachment points for cell adhesion peptides to facilitate bioconjugation. These methods can be applied to many types of hydrogels with different pore sizes simply by changing the nanoparticle size, as opposed to developing novel synthetic chemistry. Several sizes of gold nanoparticles have been synthesized, entrained in agarose hydrogels, and tested to show that the bulk of particles remain in the gel for a substantial length of time. Mechanical properties of the gold nanoparticle composite hydrogels are similar to the unmodified hydrogels, retaining the native material characteristics. A cell-binding peptide has successfully been conjugated to gold nanoparticles, and the effect of this binding peptide on cell growth and adhesion is being studied by culturing cells on the unmodified and composite hydrogels. Although the initial results are promising, more testing is necessary to quantify the extent of adhesion in each case. The composite gels being examined offer many advantages over the previous methods of polymeric bioconjugation. The chemistry is simple and robust, the gel’s polymeric backbone and mechanical properties are preserved, and the modification technique can be applied to a wide range of biomaterials. Because of this flexibility, this technology is not limited to a single component or tissue type, but can be applied to all areas of tissue engineering, providing novel methods of non-synthetic bioconjugation. In addition to biomodification, these materials offer the opportunity for integrated sensing, due to the well recognized optical properties of gold nanoparticles. Biosensor detection is based on the absorbance shift resulting from surface plasmon resonance (SPR) experienced by aggregated gold nanoparticles. For example, two bound gold nanoparticles experience a SPR-induced absorbance shift as a result of proximity. When the particles are separated, the absorbance returns to its original value. In a proof-of-concept device, particle aggregation is achieved using a modified cell binding peptide (CGGGRGDSGGGC), whereas cleavage is produced by an enzyme that promotes cell detachment (trypsin), returning particles to their initial unaggregated state. Particles are also modified with tri(ethylene glycol) mono-11-mercaptoundecyl ether, a stabilizing agent that protects the particles from unwanted aggregation. Although this proof-of-concept system examines cell adhesion using the RGD peptide/trypsin protease system, the biosensor could be customized to almost any enzyme-substrate combination. Any substrate with thiol ends (which can be added through cysteine termination) has the ability to bind the gold nanoparticles together, and any substrate specific enzyme can cleave the peptide bond activating the sensor. Thus, analyte sensing can be directly built into a modified hydrogel by integrating the prepared gold nanoparticles during gel synthesis. The general modification method described here has numerous advantages. Both the increased biocompatibility and sensing applications of gold nanoparticle-biomaterial composites are improvements over systems based solely on hydrogels and polymers or just nanoparticles alone. The combined system provides the hydrogel biomaterials with increased functionality without the requirement of complicated syntheses. In addition, the nanoparticles are provided with a supportive framework. Some of the most promising biosensor models employ aqueous nanoparticles, which are not inherently portable and operate only in the liquid phase. A hydrogel support permits the development of portable devices with potential for gas phase operation. The methods described here are also very flexible as a result of the ability to functionalize the gold nanoparticles with a wide array of biomolecules, providing a composite system with a variety of features. Advisor: Jessica O. WinterNo embarg

Photomosaicing and automatic topography generation from stereo aerial photography

Master of ScienceDepartment of Mechanical and Nuclear EngineeringDale E. Schinstock, Chris LewisThe Autonomous Vehicle Systems Lab specializes in using autonomous planes for remote sensing applications. By developing an inexpensive image acquisition platform and the algorithms to post process the data, remote sensing can be performed at a lower monetary cost with shorter lead times. This thesis presents one algorithm that has shown to be an effective alternative to the traditional Bundle Adjustment (BA) algorithm used for making composite images from many individual overlapping images. BA simultaneously estimates camera poses and visible feature locations from blocks of overlapping imagery, but is computationally expensive. The alternate algorithm (ABA) uses a cost function that does not explicitly include the feature locations. For photographic sets covering large areas, but having overlap only between adjacent photos, the search space and consequently the computational cost is significantly reduced when compared to typical BA. The usefulness of the algorithm is demonstrated by comparing a digital elevation model created through the ABA with LIDAR data

Hydrogen-based Energy Storage (IEA-HIA Task 32)

The International Energy Agency (IEA) in its Hydrogen Implementation Agreement (HIA) conducts the core R&D work in Tasks byMember Experts.Task 32 'Hydrogen-based Energy Storage' addresses solutions for energy storage based on hydrogen. Task 32 is the largest international collaboration in this field involving over 50 experts from 18 countries. Currently, the task consists of six working groups, porous materials, magnesium-based hydrogen and energy storage materials, complex and liquid hydrides, electrochemical storage of energy, heat storage and hydrogen storage systems for mobile applications

Modeling Infiltration Kinetics Of Liquids Into Porous Alumina Preforms

MODELING INFILTRATION KINETICS OF LIQUIDS INTO POROUS ALUMINA PREFORMS. Alpha-alumina preform was infiltrated with different infiltrant and pressure for studying the infiltration kinetic. Effects of pre-sintering temperature, type of infiltrant, pressure and multiple infiltrations on the rate of infiltration into porous alumina preforms were described. The pore radius of alumina preform is calculated based on the preform water system by using Washburn model. The pore radius from this model, r of 0.0147 μm is good agreement to the average pore radius found by using mercury porosity measurement, r of 0.0170 μm. The pore radius of 0.0147 μm is used to calculate the rate of infiltration, k. The k factors are 64.83 x 10-5 ms½ and 27.11 x 10-5 ms½ for water and TiCl3 respectively without involving pressure in the calculation. On the other hand, by using pressure, the k factors are 75.14 x 10-5 ms½ and 31.40 x 10-5 ms½ for water and TiCl3 respectively. Other formulas were also included as comparisons. The kinetic of water and titanium trichloride alumina preform system is parabolic in time or linier in square root of time

Light-Metal-Based Nanostructures for Energy and Biomedical Applications

International audienc