A5004317274- Muon and positron interactions and applications
- Ammonia Synthesis and Nitrogen Reduction
- Graphene research and applications
- Membrane Separation and Gas Transport
- Ion-surface interactions and analysis
- Silicon and Solar Cell Technologies
- Thin-Film Transistor Technologies
- Chemical Synthesis and Characterization
- Atomic and Molecular Physics
- Advancements in Battery Materials
- Radiation Detection and Scintillator Technologies
- Semiconductor materials and devices
- Copper Interconnects and Reliability
- Particle Detector Development and Performance
- Synthesis and characterization of novel inorganic/organometallic compounds
- Nuclear materials and radiation effects
- Silicon Nanostructures and Photoluminescence
- Drug Solubulity and Delivery Systems
- Medical Imaging Techniques and Applications
- High-pressure geophysics and materials
- Metallic Glasses and Amorphous Alloys
- Electrostatic Discharge in Electronics
- Quantum and Classical Electrodynamics
- Sports Dynamics and Biomechanics
- Catalytic Processes in Materials Science
University of Coimbra
2009-2024
We present a systematic study of isolated hydrogen in diverse forms ${\mathrm{ZrO}}_{2}$ (zirconia), both undoped and stabilized the cubic phase by additions transition-metal oxides $({\mathrm{Y}}_{2}{\mathrm{O}}_{3},{\mathrm{Sc}}_{2}{\mathrm{O}}_{3}$, MgO, CaO). Hydrogen is modeled using muonium as pseudoisotope muon-spin spectroscopy experiments. The muon also supplemented with first-principles calculations states scandia-stabilized zirconia conventional density-functional theory (DFT)...
We present imaging results of needle-like and planar22Na sources obtained with a prototype high-acceptance small-animal positron emission tomograph based on resistive plate chambers (RPC-PET). The maximum-likelihood expectation-maximization (MLEM) reconstruction the acquired data yielded an excellent stable resolution 0.4 mm FWHM.
In this paper, we revisit, theoretically and experimentally, the fall of a folded U-chain pile-chain. The model calculation implies division whole system into two subsystems variable mass, allowing us to explore role tensional contact forces at boundary subsystems. This justifies, for instance, that falls faster than acceleration due gravitational force. result, which matches quite well with experimental data independently type chain, falling chain is described by energy conservation. We...
This paper is part of an extended study oxide materials with the μSR technique. As example, we present here experimental data on yttria-stabilized zirconia (ZrO2 doped 8% Y2O3). Three different muon states can be distinguished: i) Deep muonium (less than 17(1)% fraction), seen as a fast-relaxing signal or indirectly via decoupling measurements in high longitudinal fields, ii) μ+ paramagnetic environment 62(6)% characterized by very weak but clearly-visible hyperfine interaction, and iii)...
Positron annihilation techniques are used for the structural investigation of solids but interpretation results in grainy and porous media is still unclear.A unique picture can be obtained assuming that dominant process Ps trapping competing "extended free volume" sites.In samples with a large amount volumes near-saturation will rule lifetime pattern, very long lifetimes over 100 ns might arise from o-Ps trapped mesopores.It shown parameters must corrected 3γ/2γ counting efficiency ratio.The...
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up 25 wt%.Positron measurements carried out temperature range 298-324 K mirrored phase separation of various soft and hard segments present membranes.The size amount holes determined by positron appear be correlated CO 2 gas permeability through membranes.
In the present paper,
The use of scaffolds, three-dimensional porous, biodegradable and biocompatible structures, that can be produced from natural polymers, synthetics, ceramics metals is crucial in the tissue engineering field. Chitosan a polysaccharide origin, found exoskeleton marine arthropods cell wall fungi, with enormous popularity production materials for Tissue Engineering, particular bone repair. This polymer has several advantages these structures regeneration repair: biodegradability,...
Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, case of β-cyclodextrin, with inclusion S-carvone thymoquinone. The results clearly indicate presence long components related Ps-formation. data show that addition β-cyclodextrin a decrease o-Ps we ascribe reduction free volume holes from 81.8 63.7 Å3. component disappears when thymoquinone is added -cyclodextrin, indicating this substance acts as...
Abstract Positron lifetime (LT) measurements have revealed that in porous media the annihilation pattern is probably dominated by a near‐saturation level trapping both for positron and positronium as well, which masks contribution from “free annihilation”, i.e., delocalised positrons. In this work we compare spectra of crystalline zeolites with bulk ceramic materials fabricated sintering same constituents analyse common features differences between them. For dense samples long‐living...
Abstract Positron annihilation spectroscopy (PAS) established itself as a routine method for structural studies of ordered substances in general, but some media present PAS results that are still puzzling. This situation is notably true solid porous systems. work recalls reasons possible large discordances the on such focuses attention not only sample production, preparation and treatment prior during measurements also determination appropriate measuring conditions establishing optimal range...
In this work the depth of interfaces in multilayered structures was estimated. The fractions positron annihilation as function implantation energy were estimated from an S-W plot and then converted into a sample through profile multilayer system computed reduced profile. results method Ti/Al samples are comparable to those using common analysis based on diffusion equations. analyses compared with SIMS profiles for same samples.
Positron annihilation lifetime spectroscopy was used to study the effect of water uptake on free volume a commercial epoxy exposed atmospheres with relative humidity ranging from 30.5% 95.8%. The absorption process also analyzed by gravimetric measurements. When mean hole remains constant and number holes not occupied molecules decrease increasing both exposure time as indicated constancy τ3 I3.