Ion Beam Analysis of He-implanted fusion solid breedes

Introduction Lithium-based ceramics (silicates, titanates, ?) possess a series of advantages as alternative over liquid lithium and lithium-lead alloys for fusion breeders. They have a sufficient lithium atomic density (up to 540 kg*m-3), high temperature stability (up to 1300 K), and good chemical compatibility with structural materials. Nevertheless, few research is made on the diffusion behavior of He and H isotopes through polycrystalline structures of porous ceramics which is crucial in order to understand the mobility of gas coolants as well as, the release of tritium. Moreover, in the operating conditions of actual breeder blanket concepts, the extraction rate of the helium produced during lithium transmutation can be affected by the composition and the structure of the near surface region modifying the performance of BB materials

Fabrication of luminescent nanostructures by electron-beam direct writing of PMMA resist

We report on the conversion of non-luminescent conventional poly(methylmethacrylate) (PMMA)-based electron-beam resists into luminescent materials when used as negative-tone resists, that is, when exposed to high electron irradiation doses. Raman spectroscopy reveals the chemical transformation induced by electron irradiation which is responsible for the observed luminescence in the visible (blue) region. The emission intensity from exposed PMMA-based patterns can be controlled by the electron irradiation dose employed to create them.

Focused beam reflectance technique for in situ particle sizing in wastewater treatment settling tanks

Due to the complexities involved with measuring activated sludge floc size distributions, this parameter has largely been ignored by wastewater researchers and practitioners. One of the major reasons has been that instruments able to measure particle size distributions were complex, expensive and only provided off-line measurements. The Focused Beam Reflectance Method (FBRM) is one of the rare techniques able to measure the particle size distribution in situ. This paper introduces the technique for monitoring wastewater treatment systems and compares its performance with other sizing techniques. The issue of the optimal focal point is discussed, and similar conclusions as found in the literature for other particulate systems are drawn. The study also demonstrates the capabilities of the FBRM in evaluating the performance of settling tanks. Interestingly, the floc size distributions did not vary with position inside the settling tank flocculator. This was an unexpected finding, and seriously questioned the need for a flocculator in the settling tank. It is conjectured that the invariable size distributions were caused by the unique combination of high solids concentration, low shear and zeolite dosing. (C) 2004 Society of Chemical Industry.

Focused ion beam manufacturing of magnetic nanostructures

A number of patterning methods including conventional photo-lithography and E-beam lithography have been employed to pattern devices with critical dimensions of submicrometer levels. The methods of device fabrication by lithography and multilevel processing are usually specific to the chemical and physical properties of the etchants and materials used, and require a number of processing steps. As an alternative, focused ion beam (FIB) lithography is a unique and straightforward tool to rapidly develop nanomagnetic prototyping devices. This feature of FIB is critical to conduct the basic study necessary to advance the state-of-the-art in magnetic recording. ^ The dissertation develops a specific design of nanodevices and demonstrates FIB-fabricated stable and reproducible magnetic nanostructures with a critical dimension of about 10 nm. The project included the fabrication of a patterned single and multilayer magnetic media with areal densities beyond 10 Terabit/in 2. Each block had perpendicular or longitudinal magnetic anisotropy and a single domain structure. The purpose was to demonstrate how the ability of FIB to directly etch nanoscale patterns allowed exploring (even in the academic environment) the true physics of various types of nanostructures. ^ Another goal of this study was the investigation of FIB patterned magnetic media with a set of characterization tools: e.g. Spinstand Guzik V2002, magnetic force microscopy, scanning electron microscopy with energy dispersive system and wavelength dispersive system. ^ In the course of this work, a unique prototype of a record high density patterned magnetic media device capable of 10 terabit/in 2 was built. The read/write testing was performed by a Guzik spinstand. The readback signals were recorded and analyzed by a digital oscilloscope. A number of different configurations for writing and reading information from a magnetic medium were explored. The prototype transducers for this work were fabricated via FIB trimming of different magnetic recording heads. ^

Resist-substrate interface tailoring for generating high density arrays of Ge and Bi2Se3 nanowires by electron beam lithography

The authors report a chemical process to remove the native oxide on Ge and Bi2Se3 crystals, thus facilitating high-resolution electron beam lithography (EBL) on their surfaces using a hydrogen silsesquioxane (HSQ) resist. HSQ offers the highest resolution of all the commercially available EBL resists. However, aqueous HSQ developers such as NaOH and tetramethylammonium hydroxide have thus far prevented the fabrication of high-resolution structures via the direct application of HSQ to Ge and Bi2Se3, due to the solubility of components of their respective native oxides in these strong aqueous bases. Here we provide a route to the generation of ordered, high-resolution, high-density Ge and Bi2Se3 nanostructures with potential applications in microelectronics, thermoelectric, and photonics devices.                         

Chemical approaches for doping nanodevice architectures

Advanced doping technologies are key for the continued scaling of semiconductor devices and the maintenance of device performance beyond the 14 nm technology node. Due to limitations of conventional ion-beam implantation with thin body and 3D device geometries, techniques which allow precise control over dopant diffusion and concentration, in addition to excellent conformality on 3D device surfaces, are required. Spin-on doping has shown promise as a conventional technique for doping new materials, particularly through application with other dopant methods, but may not be suitable for conformal doping of nanostructures. Additionally, residues remain after most spin-on-doping processes which are often difficult to remove. In-situ doping of nanostructures is especially common for bottom-up grown nanostructures but problems associated with concentration gradients and morphology changes are commonly experienced. Monolayer doping (MLD) has been shown to satisfy the requirements for extended defect-free, conformal and controllable doping on many materials ranging from traditional silicon and germanium devices to emerging replacement materials such as III-V compounds but challenges still remain, especially with regard to metrology and surface chemistry at such small feature sizes. This article summarises and critically assesses developments over the last number of years regarding the application of gas and solution phase techniques to dope silicon-, germanium- and III-V-based materials and nanostructures to obtain shallow diffusion depths coupled with high carrier concentrations and abrupt junctions.

RELATIONSHIP BETWEEN PHYSICAL AND CHEMICAL PROPERTIES OF STRAIGHT AND RECOVERED ASPHALT BINDERS FROM ONTARIO

Thermal and fatigue cracking are the major pavement distresses that contribute to a drastic reduction of the pavement’s service life and performance in Ontario. Chemical oxidation and hardening of asphalt binders deteriorates its physical properties since physical properties of asphalts depend on its chemical composition. This thesis is aimed to establish a relationship between physical and chemical properties of asphalt binders. A secondary objective is to show the strong correlation between CTOD and temperature. All recovered and straight Ministry of Transportation of Ontario (MTO) samples were investigated using conventional Superpave® test method dynamic shear rheometer (DSR) as well as improved MTO test methods such as extended bending beam rheometer (eBBR) and double-edge-notched tension (DENT) test. DENT test was conducted for all Ontario contract samples at three different temperatures based on their performance grade after three hours of thermal conditioning and compared the results in terms of essential work of fracture, plastic work of fracture and CTOD at different temperatures. Good correlation exists between CTOD and temperature according to the DENT data. X-ray fluorescence (XRF) analysis was conducted to detect the presence of heavy metals such as zinc and molybdenum believed to have originated from waste engine oil. Fourier transform infra-red spectroscopy (FTIR) was performed to determine the abundance of functional groups such as carbonyl, sulfoxides, polyisobutylene, etc. XRF and FTIR analysis confirmed that most of the samples contain waste engine oil and/or oxidized residues, which is believed to be a root cause of premature pavement failures.

Physical and Chemical Performance Testing of Ontario Asphalt Pavements

Thermal and fatigue cracking are the two of the major pavement distress phenomena that contribute significantly towards increased premature pavement failures in Ontario. This in turn puts a massive burden on the provincial budgets as the government spends huge sums of money on the repair and rehabilitation of roads every year. Governments therefore need to rethink and re-evaluate their current measures in order to prevent it in future. The main objectives of this study include: the investigation of fatigue distress of 11 contract samples at 10oC, 15oC, 20oC and 25oC and the use of crack-tip-opening-displacement (CTOD) requirements at temperatures other than 15oC; investigation of thermal and fatigue distress of the comparative analysis of 8 Ministry of Transportation (MTO) recovered and straight asphalt samples through double-edge-notched-tension test (DENT) and extended bending beam rheometry (EBBR); chemical testing of all samples though X-ray Fluorescence (XRF) and Fourier transform infrared analysis (FTIR); Dynamic Shear Rheometer (DSR) higher and intermediate temperature grading; and the case study of a local Kingston road. Majority of 11 contract samples showed satisfactory performance at all temperatures except one sample. Study of CTOD at various temperatures found a strong correlation between the two variables. All recovered samples showed poor performance in terms of their ability to resist thermal and fatigue distress relative to their corresponding straight asphalt as evident in DENT test and EBBR results. XRF and FTIR testing of all samples showed the addition of waste engine oil (WEO) to be the root cause of pavement failures. DSR high temperature grading showed superior performance of recovered binders relative to straight asphalt. The local Kingston road showed extensive signs of damage due to thermal and fatigue distress as evident from DENT test, EBBR results and pictures taken in the field. In the light of these facts, the use of waste engine oil and recycled asphalt in pavements should be avoided as these have been shown to cause premature failure in pavements. The DENT test existing CTOD requirements should be implemented at other temperatures in order to prevent the occurrences of premature pavement failures in future.

Non chemical natural organic matter removal with a contact TiO2 process

Dissertação de Mestrado, Tecnologia dos Alimentos, Instituto Superior de Engenharia, Universidade do Algarve, 2014

Energy Loss Function of Solids Assessed by Ion Beam Energy-Loss Measurements: Practical Application to Ta2O5

We present a study where the energy loss function of Ta2O5, initially derived in the optical limit for a limited region of excitation energies from reflection electron energy loss spectroscopy (REELS) measurements, was improved and extended to the whole momentum and energy excitation region through a suitable theoretical analysis using the Mermin dielectric function and requiring the fulfillment of physically motivated restrictions, such as the f- and KK-sum rules. The material stopping cross section (SCS) and energy-loss straggling measured for 300–2000 keV proton and 200–6000 keV helium ion beams by means of Rutherford backscattering spectrometry (RBS) were compared to the same quantities calculated in the dielectric framework, showing an excellent agreement, which is used to judge the reliability of the Ta2O5 energy loss function. Based on this assessment, we have also predicted the inelastic mean free path and the SCS of energetic electrons in Ta2O5.

OC-OT-LIBS: A novel approach to the chemical characterization of single particles

Spectral identification of individual micro- and nano-sized particles by the sequential intervention of optical catapulting, optical trapping and laser-induced breakdown spectroscopy is presented [1]. The three techniques are used for different purposes. Optical catapulting (OC) serves to put the particulate material under inspection in aerosol form [2-4]. Optical trapping (OT) permits the isolation and manipulation of individual particles from the aerosol, which are subsequently analyzed by laser-induced breakdown spectroscopy (LIBS). Once catapulted, the dynamics of particle trapping depends on the laser beam characteristics (power and intensity gradient) and on the particle properties (size, mass and shape). Particles are stably trapped in air at atmospheric pressure and can be conveniently manipulated for a precise positioning for LIBS analysis. The spectra acquired from the individually trapped particles permit a straightforward identification of the inspected material. The current work focuses on the development of a procedure for simultaneously acquiring dual information about the particle under study via LIBS and time-resolved plasma images by taking advantage of the aforementioned features of the OC-OT-LIBS instrument to align the multiple lines in a simple yet highly accurate way. The plasma imaging does not only further reinforce the spectral data, but also allows a better comprehension of the chemical and physical processes involved during laser-particle interaction. Also, a thorough determination of the optimal excitation conditions generating the most information out of each laser event was run along the determination of parameters such as the width of the optical trap, its stability as a function of the laser power and the laser wavelength. The extreme sensibility of the presented OC-OT-LIBS technology allows a detection power of attograms for single/individual particle analysis.

INVESTIGATIVE COMPARISON OF TANK AND RECOVERED ASPHALT SAMPLES THROUGH PHYSICAL PERFORMANCE TESTING AND CHEMICAL ANALYSIS

Despite the development of improved performance test protocols by renowned researchers, there are still road networks which experience premature cracking and failure. One area of major concern in asphalt science and technology, especially in cold regions in Canada is thermal (low temperature) cracking. Usually right after winter periods, severe cracks are seen on poorly designed road networks. Quality assurance tests based on improved asphalt performance protocols have been implemented by government agencies to ensure that roads being constructed are at the required standard but asphalt binders that pass these quality assurance tests still crack prematurely. While it would be easy to question the competence of the quality assurance test protocols, it should be noted that performance tests which are being used and were repeated in this study, namely the extended bending beam rheometer (EBBR) test, double edge-notched tension test (DENT), dynamic shear rheometer (DSR) test and X-ray fluorescence (XRF) analysis have all been verified and proven to successfully predict asphalt pavement behaviour in the field. Hence this study looked to probe and test the quality and authenticity of the asphalt binders being used for road paving. This study covered thermal cracking and physical hardening phenomenon by comparing results from testing asphalt binder samples obtained from the storage ‘tank’ prior to paving (tank samples) and recovered samples for the same contracts with aim of explaining why asphalt binders that have passed quality assurance tests are still prone to fail prematurely. The study also attempted to find out if the short testing time and automated procedure of torsion bar experiments can replace the established but tedious procedure of the EBBR. In the end, it was discovered that significant differences in performance and composition exist between tank and recovered samples for the same contracts. Torsion bar experimental data also indicated some promise in predicting physical hardening.