Chemical damage created by or-particles in cellulose nitrate (LR115) have been studied by infrare... more Chemical damage created by or-particles in cellulose nitrate (LR115) have been studied by infrared spectroscopy. This technique enables identifying the sensitive bonds and giving an order of magnitude of their scission cross sections for given m-particle energies. The high cross sections observed suggest a new description of the track etch velocity in this material.
When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear ... more When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear track detectors, this latent track can be specifically etched by an appropriate chemical solution. This enlargement process is due to a higher etch velocity (V T ) along the ion's path than in the non-damaged part of the detector. The etched track velocity is definitely linked to the damage created by the incoming ion in the detector material. A relationship between the physical parameters of the energy deposition and the variation in this etched track velocity with the ion energy cannot easily be explained. We present here our study on the chemical damage created by several ions in a cellulose nitrate type detector and our first attempt to simulate them by the use of the hit theory.
This paper describes a methodology to characterize the response of a detector to alpha particles ... more This paper describes a methodology to characterize the response of a detector to alpha particles of different incidences and energies using an experimental irradiation system and an etching model. Implications for radon dosimetry are discussed. For each incident energy there is a particular angle above which alpha particles no longer induce an observable etched track. This angle also depends on the etching and on the conditions of observation of the detector. It is necessary to known the variation of that critical angle with incident alpha particle energy for given etching and observation conditions in order to determine the theoritical detection efficiency of a radon detector. This variation was studied for a CR39 detector (Tastrack, G.B.) over the energy range of the alpha particles emitted by radon (5,5 MeV) and its two short-life daughters : Po218 (6 MeV) and Po214 (7,7 MeV).
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
We present a dosimeter prototype, devoted to ion beam dosimetry, tested with Helium, Carbon and N... more We present a dosimeter prototype, devoted to ion beam dosimetry, tested with Helium, Carbon and Neon ions having an equivalent range in water of 150 mm. A polyvinyltoluene based plastic scintillator is used to convert the deposited energy into scintillation, a measurement probe and a long optical fibre guide the light to a photon counting unit. Using 10-40 µm thick scintillators we show that the dosimeter gain is enough to provide useful measurements, the ion-induced scintillation can be interpreted using a model taking into account the energy deposited by secondary electrons. For a practical purpose it is shown that a linear relationship can be established between the scintillation signal and the relative dose.
The form factor of Λ 0 b baryons is estimated using 3.46 · 10 6 hadronic Z decays collected by th... more The form factor of Λ 0 b baryons is estimated using 3.46 · 10 6 hadronic Z decays collected by the DELPHI experiment between 1992 and 1995. Charmed Λ + c baryons fully reconstructed in the pK − π + , pK 0 S , and Λπ + π + π − modes, are associated to a lepton with opposite charge in order to select Λ 0 b → Λ + c l − ν l decays. From a combined likelihood and event rate fit to the distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be : ρ 2 = 2.03 ± 0.46 (stat) +0.72 −1.00 (syst). The exclusive semileptonic branching fraction Br(Λ 0 b → Λ + c l −ν l ) can be derived fromρ 2 and is found to be (5.0 +1.1 −0.8 (stat) +1.6 −1.2 (syst))%. Limits on other branching fractions are also obtained.
Chemical modification along ion tracks in PADC films has been studied by means of FT-IR spectrome... more Chemical modification along ion tracks in PADC films has been studied by means of FT-IR spectrometry, which was exposed to proton and heavy ions of He, C, Ne, Ar, Fe, Kr and Xe with energies around the Bragg peaks. This study covers a wide region of the stopping power ranging from 10 to 10,000 keV/μm. Removal cross sections for the loss
h i g h l i g h t s < Characteristics of tracks in PADC formed after vacuum irradiations are exam... more h i g h l i g h t s < Characteristics of tracks in PADC formed after vacuum irradiations are examined. < G values are not sensitive for irradiation environment for He and C ions. < G value for gamma ray in vacuum is about half of that in air. < Generated OH groups should be the damage which enhance track etch rate.
We have measured the deterioration of the scintillation yield of anthracene samples under carbon ... more We have measured the deterioration of the scintillation yield of anthracene samples under carbon beams at nine di erent energies between 25 and 100 MeV. The real-time measurement of the scintillation yield has been performed by means of an optical ÿbre connected to a compact photon counting head. Results are interpreted by the Birks model from which we deduce the uence needed to reduce the scintillation yield by a factor of two and also an estimation of the damage cross-sections of scintillation centres.
We report results concerning the degradation of the scintillation yield of the plastic scintillat... more We report results concerning the degradation of the scintillation yield of the plastic scintillator BC-418 under ion beam irradiation. Lithium, carbon and iodine ions have been used at different energies. For each ion the decrease of the scintillation yield, as a function of fluence, can be described by summation of several exponential functions. The scintillation yield at low fluence can be described by a model taking into account the energy deposited by secondary electrons, which leads to an evaluation of the quenching density for this scintillator between 0.2 and 0.7 erg/cm 3 .
Chemical and optical modiÿcations induced by 22:5 MeV protons slowed down into a 4:4 mm polyallyl... more Chemical and optical modiÿcations induced by 22:5 MeV protons slowed down into a 4:4 mm polyallyl diglycol carbonate (CR-39) stack, which was composed of 16 detectors of di erent thicknesses, are studied. Irradiation was performed perpendicular to the stack surface, in a vacuum chamber, with proton uences ranging from 10 11 to 10 14 particles=cm 2 . These transformations are analyzed using fourier transform infrared (FTIR) absorption spectroscopy in the total attenuation re ection mode and UV-visible spectroscopy by following CKO, CKC and O-H bands evolution and by following the shift in the absorption edge towards the higher wavelengths. The chemical changes occurring in the CR-39 absorption spectra (both FTIR and UV) are analyzed versus the ion beam uence, the beam penetration depth into the stack and the average deposited energy density. The results show that degradation of CR-39 presents a maximum in the depths ranging between 3500 and 4000 m.
Geoscience is one of the application fields of nuclear tracks. In the Laboratory of Nuclear Micro... more Geoscience is one of the application fields of nuclear tracks. In the Laboratory of Nuclear Micro-Analysis, applications in geochronology, micromapping and radon dosimetry are studied. For these purposes, theoretical models are developed and applied to mineral and polymeric detectors. First, uranium fission tracks (FT) are analysed in order to trace the thermal history of a rock. The apatite/fission track system is particularly well suited to such studies due to its low closing temperature. Then, several different models are developed to understand, and to use, the partial annealing phenomena. With this aim in mind, we propose a model allowing simulation of the projected track length distributions. According to this model, track distributions are transferred onto a time scale graph (the "age function"). This highlights the type of thermal history of the mineral and corrects the apparent FT age. Using the traditional law for the production of tracks, and experimental results for annealing kinetics, an analytical model based on a reaction situation associated with one or several activation energies has been developed. The aim of this approach is to obtain a single solution for both direct and inverse problems linking thermal history and track length data. The fission track etching process in apatite is also studied in order to model the evolution of track characteristics. A computer program has been developed, taking into account track segmentation during annealing and crystallographic parameters of apatite. Secondly, the track etching process is studied in polymeric detectors. A geometrical approach based on two distinct etching velocities is used. For light ions such as alpha particles with nonrelativistic energies, etching times are short, so the bulk velocity can be considered constant. The track velocity, however, is variable. The critical angle of registration can then be determined as a function of incident energy and etching conditions. Such a model can be applied in alpha microcartography, for example, in order to determine the uranium and thorium content of geological materials. Finally, in the context of this work, a mathematical model to determine the solid state nuclear track detector (SSNTD) detection efficiency for an alpha particle emitter has been developed. This work is specially intended to measure radon using a cylindrical cell. This theoretical work makes it possible to choose the size of the cell for which the SSNTD response does not depend on the radon daughters (218po and 214po) behaviour. This size guarantees the reproducibility of the results. Such a device can be used to study radon emanation over wide areas in radioprotection and earth science applications (thermal prospecting, volcanology, etc....).
We have investigated the effect of solution parameters on the adsorption of phosphate ions and on... more We have investigated the effect of solution parameters on the adsorption of phosphate ions and on charges and structures, i.e., on the nature of species, at the a-Al 2 O 3 colloid/solution interface by using the batch method, f potential measurements, and in situ ATR-FTIR spectroscopy. The uptake of phosphate decreases with the extent of surface deprotonation (i.e., pH), imparts negative charges to the colloid surface, and induces IEP shifts showing chemical sorption. Use of complementary techniques provides evidence that phosphate is sorbed at low pH (3.3) by a combination of surface reactions of complexation and precipitation, whose relative contributions depend on phosphate loading. Surface complexation includes fast reactions of ligand exchange with single coordinated hydroxyls, and electrostatic attraction of H 2 PO À 4 ions at positively charged surface sites. This is supported by experiments at low coverage showing sharp and linear decrease of f potential (i.e., surface charge) with amount of phosphate sorbed. At high coverage, f potential values are low and independent of phosphate loading. Formation of surface precipitates of Al-phosphate is inferred from the assignment of the ATR-FTIR absorption band at 1137 cm À1 , whose intensity increases with phosphate solution content and reaction time, to the P-O-stretching vibration mode for phosphate sorbed at high concentrations on a-Al 2 O 3 . In situ ATR-FTIR spectroscopy reveals also structural reorganizations of surface hydroxyls with time, due to surface hydration and to surface precipitation continuing over extended periods along alumina dissolution.
This study presents new in situ electrophoretic and ATR-FTIR data on the surface species controll... more This study presents new in situ electrophoretic and ATR-FTIR data on the surface species controlling the cosorption of uranyl and phosphate ions in a-Al 2 O 3 suspensions at acidic pH (3.3). It was shown that the uranyl sorption (i) was promoted in the presence of phosphate, (ii) induced significant changes in zeta potential of P-loaded alumina, and (iii) was governed by two mechanisms, surface complexation and surface precipitation, with the predominant species being mainly dependent on phosphate surface coverage. Formation of surface precipitates of uranyl phosphate at high phosphate surface coverage was inferred from the high negative charges imparted to the surface by uranyl and phosphate (co)sorption, and from assignments of IR bands at 1107, 1024, and 971 cm À1 to P-O-stretching vibrations for phosphate coordinated to uranyl, at the alumina surface. The ATR-FTIR study showed that the precipitates of uranyl phosphate formed at the surface of a-Al 2 O 3 for aqueous concentrations of uranyl at trace levels. It also evidenced that formation of surface precipitates of U(VI)-phosphate was occurring along with the transformation of alumina into secondary surface precipitates of Al-phosphate, at very high phosphate concentrations. These findings are relevant to the mechanisms of adsorption of trace uranyl on naturally occurring oxide surfaces, in soils with low pH where cosorption of phosphate and uranyl ions is known to play a crucial role in the long-term retention of U.
ABSTRACT The damage structure of latent tracks in poly(ethylene terephthalate) (PET) has been exa... more ABSTRACT The damage structure of latent tracks in poly(ethylene terephthalate) (PET) has been examined by Fourier transform infrared (FT-IR) measurements. Results are compared with those from previous studies on bisphenol A polycarbonate (PC) and poly(allyl diglycol carbonate) (PADC). These polymers are exposed to protons and heavy ions (He, C, Ne, Si, Ar, Fe, Kr, and Xe) in air with energies less than 6 MeV/n, as well as gamma rays from an intense Co-60 source. Chemical damage parameters, namely, damage density, which is the number of losses of considered functional groups per unit length of tracks, radial size of the track core, in which the considered chemical groups are lost, and radiation chemical yields (G values) for each group are evaluated as a function of the stopping power. It has been confirmed that latent tracks will be etchable when the radial track core size is larger than the distance between two adjacent breaking points of polymer chains. The predominant breaking points are the C–O bonds in ether, ester, and carbonate ester bonds. # 2012 The Japan Society of Applied Physics
This paper is devoted to the study of the radon emanation coefficient vs. water mass fraction for... more This paper is devoted to the study of the radon emanation coefficient vs. water mass fraction for mineral samples. Modeling is performed considering only the direct recoil phenomena and assuming planar pores with high lengths-to-width aspect ratios. Water is assumed either to fill the pore alternatively with air or to form a continuous film on the pore surface. This modeling is applied to uranium mine tailings for which the pore size distribution was experimentally measured. It enables a good description of the change of the experimental radon emanation coefficients with the moisture content of the studied samples. Copyright
Detailed understanding of the respective roles of solution and surface parameters on the reaction... more Detailed understanding of the respective roles of solution and surface parameters on the reactions at uranyl solution / Al-(hydr)oxide interfaces is crucial to model accurately the behaviour of U in nature. We report studies on the effects of the initial aqueous uranyl speciation in moderately acidic solutions, e.g. of mononuclear, polynuclear uranyl species and / or (potential) U(VI) colloids, on the sorption of U by large surface areas of amorphous Alhydroxide. Investigations by Extended X-ray Absorption Fine Structure (EXAFS) and Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS) reveal similar U coordination environments on Al-hydroxide for low to moderate U loadings of sorption samples obtained at pH 4-5, independently of the presence of mononuclear or polynuclear aqueous species, or of the potential instability of initial solutions favoring true U-colloids formation. EXAFS data can be interpreted in terms of a dimeric, bidentate, inner-sphere uranyl surface complex as an average of the U surface structures. TRLFS data, however, provide valuable insights into the complex U surface speciation. They indicate multiple uranyl surface species under moderately acidic conditions, as predominant mononuclear and / or dinuclear, inner-sphere surface complexes and as additional minor species having U atoms in a uranyl (hydr)oxide -like coordination environment. The additional species probably occur as surface polymers and / or as adsorbed true U colloids, depending on the aqueous U concentration level (1 to 100 µM).
Colloidal layers play an important role in environmental studies, for example in the movement of ... more Colloidal layers play an important role in environmental studies, for example in the movement of radionuclides in nuclear waste management. New characterization techniques are required for studying such complex, porous layers. The purpose of this work is to adapt coherence probe microscopy (CPM), which is typically used for measuring the surface roughness of single surfaces, to the analysis of thick inhomogeneous colloidal layers. Two types of layers, either composed of 80 nm or 400 nm alumina colloidal particles deposited on glass slides by decantation have been studied. One of the problems in performing routine roughness measurements of colloidal layers using CPM is the appearance of apparent pits below the level of the substrate surface. We demonstrate that this is due to partial detection of the buried colloid/substrate interface. Further, we have developed the "Z-scan" technique, which consists of building up an XYZ image stack by scanning the full depth of the sample. Any point in an XY image can then be investigated to study the local buried internal structure, layer thickness, and effective refractive index. Comparison of results with AFM and SEM confirm the structure found with CPM and the new "Z-scan" technique, which opens up new and useful applications.
Chemical damage created by or-particles in cellulose nitrate (LR115) have been studied by infrare... more Chemical damage created by or-particles in cellulose nitrate (LR115) have been studied by infrared spectroscopy. This technique enables identifying the sensitive bonds and giving an order of magnitude of their scission cross sections for given m-particle energies. The high cross sections observed suggest a new description of the track etch velocity in this material.
When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear ... more When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear track detectors, this latent track can be specifically etched by an appropriate chemical solution. This enlargement process is due to a higher etch velocity (V T ) along the ion's path than in the non-damaged part of the detector. The etched track velocity is definitely linked to the damage created by the incoming ion in the detector material. A relationship between the physical parameters of the energy deposition and the variation in this etched track velocity with the ion energy cannot easily be explained. We present here our study on the chemical damage created by several ions in a cellulose nitrate type detector and our first attempt to simulate them by the use of the hit theory.
This paper describes a methodology to characterize the response of a detector to alpha particles ... more This paper describes a methodology to characterize the response of a detector to alpha particles of different incidences and energies using an experimental irradiation system and an etching model. Implications for radon dosimetry are discussed. For each incident energy there is a particular angle above which alpha particles no longer induce an observable etched track. This angle also depends on the etching and on the conditions of observation of the detector. It is necessary to known the variation of that critical angle with incident alpha particle energy for given etching and observation conditions in order to determine the theoritical detection efficiency of a radon detector. This variation was studied for a CR39 detector (Tastrack, G.B.) over the energy range of the alpha particles emitted by radon (5,5 MeV) and its two short-life daughters : Po218 (6 MeV) and Po214 (7,7 MeV).
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
We present a dosimeter prototype, devoted to ion beam dosimetry, tested with Helium, Carbon and N... more We present a dosimeter prototype, devoted to ion beam dosimetry, tested with Helium, Carbon and Neon ions having an equivalent range in water of 150 mm. A polyvinyltoluene based plastic scintillator is used to convert the deposited energy into scintillation, a measurement probe and a long optical fibre guide the light to a photon counting unit. Using 10-40 µm thick scintillators we show that the dosimeter gain is enough to provide useful measurements, the ion-induced scintillation can be interpreted using a model taking into account the energy deposited by secondary electrons. For a practical purpose it is shown that a linear relationship can be established between the scintillation signal and the relative dose.
The form factor of Λ 0 b baryons is estimated using 3.46 · 10 6 hadronic Z decays collected by th... more The form factor of Λ 0 b baryons is estimated using 3.46 · 10 6 hadronic Z decays collected by the DELPHI experiment between 1992 and 1995. Charmed Λ + c baryons fully reconstructed in the pK − π + , pK 0 S , and Λπ + π + π − modes, are associated to a lepton with opposite charge in order to select Λ 0 b → Λ + c l − ν l decays. From a combined likelihood and event rate fit to the distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be : ρ 2 = 2.03 ± 0.46 (stat) +0.72 −1.00 (syst). The exclusive semileptonic branching fraction Br(Λ 0 b → Λ + c l −ν l ) can be derived fromρ 2 and is found to be (5.0 +1.1 −0.8 (stat) +1.6 −1.2 (syst))%. Limits on other branching fractions are also obtained.
Chemical modification along ion tracks in PADC films has been studied by means of FT-IR spectrome... more Chemical modification along ion tracks in PADC films has been studied by means of FT-IR spectrometry, which was exposed to proton and heavy ions of He, C, Ne, Ar, Fe, Kr and Xe with energies around the Bragg peaks. This study covers a wide region of the stopping power ranging from 10 to 10,000 keV/μm. Removal cross sections for the loss
h i g h l i g h t s < Characteristics of tracks in PADC formed after vacuum irradiations are exam... more h i g h l i g h t s < Characteristics of tracks in PADC formed after vacuum irradiations are examined. < G values are not sensitive for irradiation environment for He and C ions. < G value for gamma ray in vacuum is about half of that in air. < Generated OH groups should be the damage which enhance track etch rate.
We have measured the deterioration of the scintillation yield of anthracene samples under carbon ... more We have measured the deterioration of the scintillation yield of anthracene samples under carbon beams at nine di erent energies between 25 and 100 MeV. The real-time measurement of the scintillation yield has been performed by means of an optical ÿbre connected to a compact photon counting head. Results are interpreted by the Birks model from which we deduce the uence needed to reduce the scintillation yield by a factor of two and also an estimation of the damage cross-sections of scintillation centres.
We report results concerning the degradation of the scintillation yield of the plastic scintillat... more We report results concerning the degradation of the scintillation yield of the plastic scintillator BC-418 under ion beam irradiation. Lithium, carbon and iodine ions have been used at different energies. For each ion the decrease of the scintillation yield, as a function of fluence, can be described by summation of several exponential functions. The scintillation yield at low fluence can be described by a model taking into account the energy deposited by secondary electrons, which leads to an evaluation of the quenching density for this scintillator between 0.2 and 0.7 erg/cm 3 .
Chemical and optical modiÿcations induced by 22:5 MeV protons slowed down into a 4:4 mm polyallyl... more Chemical and optical modiÿcations induced by 22:5 MeV protons slowed down into a 4:4 mm polyallyl diglycol carbonate (CR-39) stack, which was composed of 16 detectors of di erent thicknesses, are studied. Irradiation was performed perpendicular to the stack surface, in a vacuum chamber, with proton uences ranging from 10 11 to 10 14 particles=cm 2 . These transformations are analyzed using fourier transform infrared (FTIR) absorption spectroscopy in the total attenuation re ection mode and UV-visible spectroscopy by following CKO, CKC and O-H bands evolution and by following the shift in the absorption edge towards the higher wavelengths. The chemical changes occurring in the CR-39 absorption spectra (both FTIR and UV) are analyzed versus the ion beam uence, the beam penetration depth into the stack and the average deposited energy density. The results show that degradation of CR-39 presents a maximum in the depths ranging between 3500 and 4000 m.
Geoscience is one of the application fields of nuclear tracks. In the Laboratory of Nuclear Micro... more Geoscience is one of the application fields of nuclear tracks. In the Laboratory of Nuclear Micro-Analysis, applications in geochronology, micromapping and radon dosimetry are studied. For these purposes, theoretical models are developed and applied to mineral and polymeric detectors. First, uranium fission tracks (FT) are analysed in order to trace the thermal history of a rock. The apatite/fission track system is particularly well suited to such studies due to its low closing temperature. Then, several different models are developed to understand, and to use, the partial annealing phenomena. With this aim in mind, we propose a model allowing simulation of the projected track length distributions. According to this model, track distributions are transferred onto a time scale graph (the "age function"). This highlights the type of thermal history of the mineral and corrects the apparent FT age. Using the traditional law for the production of tracks, and experimental results for annealing kinetics, an analytical model based on a reaction situation associated with one or several activation energies has been developed. The aim of this approach is to obtain a single solution for both direct and inverse problems linking thermal history and track length data. The fission track etching process in apatite is also studied in order to model the evolution of track characteristics. A computer program has been developed, taking into account track segmentation during annealing and crystallographic parameters of apatite. Secondly, the track etching process is studied in polymeric detectors. A geometrical approach based on two distinct etching velocities is used. For light ions such as alpha particles with nonrelativistic energies, etching times are short, so the bulk velocity can be considered constant. The track velocity, however, is variable. The critical angle of registration can then be determined as a function of incident energy and etching conditions. Such a model can be applied in alpha microcartography, for example, in order to determine the uranium and thorium content of geological materials. Finally, in the context of this work, a mathematical model to determine the solid state nuclear track detector (SSNTD) detection efficiency for an alpha particle emitter has been developed. This work is specially intended to measure radon using a cylindrical cell. This theoretical work makes it possible to choose the size of the cell for which the SSNTD response does not depend on the radon daughters (218po and 214po) behaviour. This size guarantees the reproducibility of the results. Such a device can be used to study radon emanation over wide areas in radioprotection and earth science applications (thermal prospecting, volcanology, etc....).
We have investigated the effect of solution parameters on the adsorption of phosphate ions and on... more We have investigated the effect of solution parameters on the adsorption of phosphate ions and on charges and structures, i.e., on the nature of species, at the a-Al 2 O 3 colloid/solution interface by using the batch method, f potential measurements, and in situ ATR-FTIR spectroscopy. The uptake of phosphate decreases with the extent of surface deprotonation (i.e., pH), imparts negative charges to the colloid surface, and induces IEP shifts showing chemical sorption. Use of complementary techniques provides evidence that phosphate is sorbed at low pH (3.3) by a combination of surface reactions of complexation and precipitation, whose relative contributions depend on phosphate loading. Surface complexation includes fast reactions of ligand exchange with single coordinated hydroxyls, and electrostatic attraction of H 2 PO À 4 ions at positively charged surface sites. This is supported by experiments at low coverage showing sharp and linear decrease of f potential (i.e., surface charge) with amount of phosphate sorbed. At high coverage, f potential values are low and independent of phosphate loading. Formation of surface precipitates of Al-phosphate is inferred from the assignment of the ATR-FTIR absorption band at 1137 cm À1 , whose intensity increases with phosphate solution content and reaction time, to the P-O-stretching vibration mode for phosphate sorbed at high concentrations on a-Al 2 O 3 . In situ ATR-FTIR spectroscopy reveals also structural reorganizations of surface hydroxyls with time, due to surface hydration and to surface precipitation continuing over extended periods along alumina dissolution.
This study presents new in situ electrophoretic and ATR-FTIR data on the surface species controll... more This study presents new in situ electrophoretic and ATR-FTIR data on the surface species controlling the cosorption of uranyl and phosphate ions in a-Al 2 O 3 suspensions at acidic pH (3.3). It was shown that the uranyl sorption (i) was promoted in the presence of phosphate, (ii) induced significant changes in zeta potential of P-loaded alumina, and (iii) was governed by two mechanisms, surface complexation and surface precipitation, with the predominant species being mainly dependent on phosphate surface coverage. Formation of surface precipitates of uranyl phosphate at high phosphate surface coverage was inferred from the high negative charges imparted to the surface by uranyl and phosphate (co)sorption, and from assignments of IR bands at 1107, 1024, and 971 cm À1 to P-O-stretching vibrations for phosphate coordinated to uranyl, at the alumina surface. The ATR-FTIR study showed that the precipitates of uranyl phosphate formed at the surface of a-Al 2 O 3 for aqueous concentrations of uranyl at trace levels. It also evidenced that formation of surface precipitates of U(VI)-phosphate was occurring along with the transformation of alumina into secondary surface precipitates of Al-phosphate, at very high phosphate concentrations. These findings are relevant to the mechanisms of adsorption of trace uranyl on naturally occurring oxide surfaces, in soils with low pH where cosorption of phosphate and uranyl ions is known to play a crucial role in the long-term retention of U.
ABSTRACT The damage structure of latent tracks in poly(ethylene terephthalate) (PET) has been exa... more ABSTRACT The damage structure of latent tracks in poly(ethylene terephthalate) (PET) has been examined by Fourier transform infrared (FT-IR) measurements. Results are compared with those from previous studies on bisphenol A polycarbonate (PC) and poly(allyl diglycol carbonate) (PADC). These polymers are exposed to protons and heavy ions (He, C, Ne, Si, Ar, Fe, Kr, and Xe) in air with energies less than 6 MeV/n, as well as gamma rays from an intense Co-60 source. Chemical damage parameters, namely, damage density, which is the number of losses of considered functional groups per unit length of tracks, radial size of the track core, in which the considered chemical groups are lost, and radiation chemical yields (G values) for each group are evaluated as a function of the stopping power. It has been confirmed that latent tracks will be etchable when the radial track core size is larger than the distance between two adjacent breaking points of polymer chains. The predominant breaking points are the C–O bonds in ether, ester, and carbonate ester bonds. # 2012 The Japan Society of Applied Physics
This paper is devoted to the study of the radon emanation coefficient vs. water mass fraction for... more This paper is devoted to the study of the radon emanation coefficient vs. water mass fraction for mineral samples. Modeling is performed considering only the direct recoil phenomena and assuming planar pores with high lengths-to-width aspect ratios. Water is assumed either to fill the pore alternatively with air or to form a continuous film on the pore surface. This modeling is applied to uranium mine tailings for which the pore size distribution was experimentally measured. It enables a good description of the change of the experimental radon emanation coefficients with the moisture content of the studied samples. Copyright
Detailed understanding of the respective roles of solution and surface parameters on the reaction... more Detailed understanding of the respective roles of solution and surface parameters on the reactions at uranyl solution / Al-(hydr)oxide interfaces is crucial to model accurately the behaviour of U in nature. We report studies on the effects of the initial aqueous uranyl speciation in moderately acidic solutions, e.g. of mononuclear, polynuclear uranyl species and / or (potential) U(VI) colloids, on the sorption of U by large surface areas of amorphous Alhydroxide. Investigations by Extended X-ray Absorption Fine Structure (EXAFS) and Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS) reveal similar U coordination environments on Al-hydroxide for low to moderate U loadings of sorption samples obtained at pH 4-5, independently of the presence of mononuclear or polynuclear aqueous species, or of the potential instability of initial solutions favoring true U-colloids formation. EXAFS data can be interpreted in terms of a dimeric, bidentate, inner-sphere uranyl surface complex as an average of the U surface structures. TRLFS data, however, provide valuable insights into the complex U surface speciation. They indicate multiple uranyl surface species under moderately acidic conditions, as predominant mononuclear and / or dinuclear, inner-sphere surface complexes and as additional minor species having U atoms in a uranyl (hydr)oxide -like coordination environment. The additional species probably occur as surface polymers and / or as adsorbed true U colloids, depending on the aqueous U concentration level (1 to 100 µM).
Colloidal layers play an important role in environmental studies, for example in the movement of ... more Colloidal layers play an important role in environmental studies, for example in the movement of radionuclides in nuclear waste management. New characterization techniques are required for studying such complex, porous layers. The purpose of this work is to adapt coherence probe microscopy (CPM), which is typically used for measuring the surface roughness of single surfaces, to the analysis of thick inhomogeneous colloidal layers. Two types of layers, either composed of 80 nm or 400 nm alumina colloidal particles deposited on glass slides by decantation have been studied. One of the problems in performing routine roughness measurements of colloidal layers using CPM is the appearance of apparent pits below the level of the substrate surface. We demonstrate that this is due to partial detection of the buried colloid/substrate interface. Further, we have developed the "Z-scan" technique, which consists of building up an XYZ image stack by scanning the full depth of the sample. Any point in an XY image can then be investigated to study the local buried internal structure, layer thickness, and effective refractive index. Comparison of results with AFM and SEM confirm the structure found with CPM and the new "Z-scan" technique, which opens up new and useful applications.
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Papers by Rémi Barillon