Carne-Sanchez A.,Catalan Institute of Nanoscience and Nanotechnology |
Stylianou K.C.,Catalan Institute of Nanoscience and Nanotechnology |
Carbonell C.,Catalan Institute of Nanoscience and Nanotechnology |
Naderi M.,Surface Measurement Systems Ltd. |
And 3 more authors.
Advanced Materials | Year: 2015
A one-step, alternative, rapid, and scalable spray-drying (SD) synthesis of metal-organic frameworks (MOF)@polymer composites with enhanced hydrolytic stabilities was reported. SD was used to encapsulate preformed MOF crystals in a polymeric matrix to generate microscale MOF@polymer spheres. For proof-of-concept Hong-Kong University of Science and Technology-1 (HKUST-1) was chosen as the water-sensitive MOF, and polystyrene (PS) as the organic polymer. The synthesis of HKUST-1@PS began with preparation of a stable colloidal suspension of HKUST-1 crystals and a solution of PS in dichloromethane (DCM). This mixture was atomized using a two-fluid nozzle. After 40 min of continuous spraying, 1.7 g of a blue powder was recovered. The sample was then washed with ethanol and dried at 120°C under vacuum. This product was analyzed through field-emission scanning electron microscopy (FESEM), which indicated that it comprised smooth microspheres of HKUST-1@PS composites and did not contain any free HKUST-1. X-ray powder diffraction (XRPD) analysis of these spheres revealed a perfect match with the HKUST-1 pattern. The exclusive presence of microspheres and the match in XRPD patterns evidenced that HKUST-1 crystals were indeed entrapped within the polymeric matrix of PS.
Moghaddam S.,University of Illinois at Urbana - Champaign |
Pengwang E.,University of Illinois at Urbana - Champaign |
Jiang Y.-B.,Sandia National Laboratories |
Garcia A.R.,Surface Measurement Systems Ltd |
And 5 more authors.
Nature Nanotechnology | Year: 2010
Proton exchange membrane fuel cells have the potential for applications in energy conversion and energy storage, but their development has been impeded by problems with the membrane electrode assembly. Here, we demonstrate that a silicon-based inorganic-organic membrane offers a number of advantages over Nafionthe membrane widely used as a proton exchange membrane in hydrogen fuel cellsincluding higher proton conductivity, a lack of volumetric size change, and membrane electrode assembly construction capabilities. Key to achieving these advantages is fabricating a silicon membrane with pores with diameters of ∼ 5-7nm, adding a self-assembled molecular monolayer on the pore surface, and then capping the pores with a layer of porous silica. The silica layer reduces the diameter of the pores and ensures their hydration, resulting in a proton conductivity that is two to three orders of magnitude higher than that of Nafion at low humidity. A membrane electrode assembly constructed with this proton exchange membrane delivered an order of magnitude higher power density than that achieved previously with a dry hydrogen feed and an air-breathing cathode. © 2010 Macmillan Publishers Limited. All rights reserved.
Lyn M.E.,U.S. Department of Agriculture |
Burnett D.,Surface Measurement Systems Ltd. |
Garcia A.R.,Surface Measurement Systems Ltd. |
Gray R.,Surface Measurement Systems Ltd.
Journal of Agricultural and Food Chemistry | Year: 2010
Two obstacles for biopesticide commercialization, long shelf life and reliable efficacy, are both affected by moisture availability. Three biopesticide delivery systems, TRE-G, PEC-G, and PESTA, were analyzed by dynamic vapor sorption analysis. The objective was to investigate the moisture sorption profile of each system in air at 25 °C and a relative humidity (RH) ranging from 0 to 90%. The formulations sorbed up to 12.7% moisture. In rehydrating from 0.00 to 90% RH, TRE-G and PEC-G were ≥63% and ≥58% faster than Pesta, respectively. In losing moisture from 90 to 0.00% RH, Pesta was 3.4 and 2.3 times slower than TRE-G and PEC-G, respectively. The GAB model was inadequate for describing moisture sorption, but the Young and Nelson model showed good correlation (r> 0.990) for all three formulations. Moisture distribution for all formulations was obtained. The implications of the findings as they relate to shelf life and dew period requirements of biopesticides are discussed. © 2010 American Chemical Society.
Skovbjerg L.L.,Copenhagen University |
Skovbjerg L.L.,Haldor Topsøe |
Okhrimenko D.V.,Copenhagen University |
Khoo J.,Surface Measurement Systems Ltd. |
And 4 more authors.
Energy and Fuels | Year: 2013
The demand for oil is increasing, but many reservoirs are reaching the end of their productive lifetime. A clearer understanding of the fundamental chemical and physical controls on the wetting behavior of reservoir pore surfaces would provide clues for developing methods to improve, or enhance, recovery of the currently inaccessible oil (improved/enhanced oil recovery, IOR/EOR). In this work, the surfaces of chalk were investigated to understand hydrophobicity at nanometer scale spatial resolution. Chalk samples from the gas and water zones of the Danish sector in the North Sea Basin were used. With inverse gas chromatography (IGC), the surface characteristics were compared. Chalk from the gas zone has a lower surface energy, dispersive as well as specific, than chalk from the water zone, clearly indicating that the gas zone pore surfaces are more hydrophobic. X-ray photoelectron spectroscopy shows that the concentration of hydrocarbons is higher in gas zone chalk than in water zone chalk, which is consistent with IGC measurements. With combined atomic force microscopy and chemical force mapping, we demonstrated that the hydrophobicity of chalk is not correlated spatially with the calcite of the coccolith elements, but rather with nanometer-sized authigenic clay crystals that decorate the surfaces of the coccoliths. Our results suggest that clay and adsorbed organic material, not calcite, are responsible for wettability alterations in chalk during the introduction of hydrocarbons. Furthermore, we show that surface hydrophobicity is heterogeneous, even within single-clay laths. © 2013 American Chemical Society.
Sacui I.A.,U.S. National Institute of Standards and Technology |
Sacui I.A.,Georgetown University |
Nieuwendaal R.C.,U.S. National Institute of Standards and Technology |
Burnett D.J.,Surface Measurement Systems LTD. |
And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2014
This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphology, aspect ratio, and surface chemistry. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymatic, mechanical, and 2,2,6,6-tetramethylpiperidinyl-1- oxyl (TEMPO)-mediated oxidation), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and 13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148 ± 147 for tunicate-CNCs to 23 ± 12 for wood-CNCs. Hydrophobic interactions, measured using inverse gas chromatography (IGC), were found to be an important contribution to the total surface energy of both types of cellulose. In all cases, a trace amount of naturally occurring fluorescent compounds was observed after hydrolysis. Confocal and Raman microscopy were used to confirm that the fluorescent species were unique for each cellulose source, and demonstrated that such methods can be useful for monitoring purity during CNC/CNF processing. This study reveals the broad, tunable, multidimensional material space in which CNCs and CNFs exist. © 2014 American Chemical Society.
Smith R.R.,Imperial College London |
Williams D.R.,Imperial College London |
Burnett D.J.,Surface Measurement Systems Ltd. |
Heng J.Y.Y.,Imperial College London
Langmuir | Year: 2014
A computational model to predict the relative energy site contributions of a heterogeneous material from data collected by finite dilution-inverse gas chromatography (FD-IGC) is presented in this work. The methodology employed a multisolvent system site filling model utilizing Boltzmann statistics, expanding on previous efforts to calculate "experienced energies" at varying coverage, yielding a retention volume distribution allowing calculation of a surface free energy distribution. Surface free energy distributions were experimentally measured for racemic ibuprofen and β-mannitol powders, the energies of each were found in the ranges 43-52 and 40-55 mJ/m2, respectively, over a surface coverage range of 0-8%. The computed contributions to surface energy values were found to match closely with data collected on macroscopic crystals by alternative techniques (±<1.5 mJ/m 2). © 2014 American Chemical Society.
Legras A.,University of Queensland |
Kondor A.,Surface Measurement Systems LTD |
Heitzmann M.T.,University of Queensland |
Truss R.W.,University of Queensland
Journal of chromatography. A | Year: 2015
Inverse gas chromatography (IGC) is an alternative technique to determine the specific surface area of natural fibres. Natural fibres have a complex surface chemistry and unique microstructure that challenge the current capabilities to perform surface characterisation. This study investigated the influence of multiple parameters on the measured Brunauer-Emmett-Teller (BET) specific surface area for samples of flax, kenaf and BioMid(®) cellulose fibres using IGC. The BET surface area of kenaf and flax differed with 0.51m(2)g(-1) and 1.35m(2)g(-1) respectively, the former being similar to the cellulose fibres (0.54m(2)g(-1)). The data was calculated under conditions where the BET equation showed good linearity (R(2)⩾0.995). Repeatability was excellent so that two runs sufficed to obtain representative BET surface area values. The findings showed the choice of solvent was important for all specimens to avoid any misleading data comparison due to molecular orientation effects that impact the adsorbent-adsorbate interactions. The higher surface area of the flax sample, and its higher variability, was correlated with a higher surface roughness observed under optical microscopy. Packing the chromatography column with long or chopped fibres produced results that were statistically insignificant. Copyright © 2015 Elsevier B.V. All rights reserved.
Burnett D.J.,Surface Measurement Systems Ltd. |
Khoo J.,Surface Measurement Systems Ltd.
International SAMPE Technical Conference | Year: 2012
Carbon fiber composite quality depends strongly on the interfacial interaction between the fiber and epoxy or polymer matrix. This interfacial adhesion is highly dependent on the materials' surface energies. In this study, surface energies were measured by Inverse Gas Chromatography (IGC). In particular, the energetic heterogeneity of a series of carbon fibers with different surface modifications have been investigated using new finite concentration IGC methods. This allows accurate determination of dispersive and acid-base surface energy heterogeneity distributions. The measured surface energy values are compared to composite performance properties.
Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Development of Prototype | Award Amount: 125.40K | Year: 2016
In our modern world, many classes of important materials such as pharmaceuticals, foods, polymers, catalysts and nanomaterials will absorb molecules such as water in the air, otherwise known as humidity. Indeed the manufacture, performance and stability of these materials is often dependent on this sorption behavior. Surface Measurement Systems has pioneered the development of scientific instruments for use in academic and industrial laboratories throughout the world for measuring the sorption behavior of materials based on sample mass changes: the so called gravimetric sorption method. This project will lead to the development of a new class of gravimetric sorption analysers which will allow experiments to be performed using either gas or vapour phase molecules for the first time, as well as allowing for multiple gas phase species to be analysed simultaneously. Combined with a new generation of microbalances for measuring the mass changes, these new sorption analysers will meet the more challenging and diverse needs of academic and industrial researchers, and will represent the new gold standard in gravimetric materials characterisation and are certain to be sought by leading researchers in laboratories throughout the world. Key applications for the use of these instruments will include the development of new materials for carbon capture, materials for separating methane from biogas as well as the development of the new catalysts and pharmaceuticals.
Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Proof of Concept | Award Amount: 100.00K | Year: 2015
One of the most important methods currently available for characterising the surface properties of powders and porous materials is their ‘Brunauer–Emmett–Teller’ (BET) surface area which is determined using a gas adsorption isotherms, normally using nitrogen . Such isotherms also provide key information on the pore structure, surface chemistry and morphology of powders. So utilitarian has become this laboratory technique that there are probably worldwide over 50,000 of these BET instruments in daily laboratory operation. However, these systems cannot be used to study monolithic thin film samples. The characterisation of such thin films is an area of increasing importance for semi-conductor, nano-porous films, graphene, catalysts and photo-voltaic materials to name but a few important industrial applications. The ability to study the surface properties and structures of these classes of materials is key to both their development and their future commercialisation. This project will evaluate the technical feasibility of determining gas and vapour adsorption isotherms on thin film substrates with surface areas of only a few square millimetres using a novel ellipsometric adsorption instrument. This instrument would allow a range of surface properties of monolithic thin films to be determined for the first time routinely including surface area, surface energy, surface heterogeneity, surface diffusion, surface reactivity and surface porosity. Such property measurements are key to the development of many classes of new nano-structured thin film materials. Such a successful development would offer the scope of commercialising Adsorption Ellipsometer as a major new research tool for the development of thin film materials.