Patrick Baillif

Experimental seawater-basaltic glass interaction at 50°C: Study of early developed phases by electron microscopy and X-ray photoelectron spectrometry

Experiments on seawater-basaltic glass interaction were made using a particulary high seawater-basaltic glass ratio (14.5 g/cm2; weight ratio: 50). A layered alteration skin is observed at the glass surface, while the variations in the composition of the seawater are imperceptible. Three zones of different composition and structure are distinguished: 1. 1) An external zone, the composition of which evolved to saponite. 2. 2) A median zone of hydrotalcite-like hydroxycarbonate (Mg6Al2CO3(OH)164H2O). 3. 3) An internal zone, between glass and hydroxycarbonates, richer in Fe and in Mg and in which a 10 A interval is observed (by dark field examination) compatible with a TOT type clay mineral. The composition of this zone indicates a mixing of poorly crystalline products. The principal chemical exchanges between glass and solution are the release of Ca in solution and the contribution of Mg and CO2 from seawater to form hydroxycarbonates, which are considered precursors of phyllosilicates. Comparison with natural phenomena (palagonitization) is made.

Characterization of boron nitride films deposited from BCl3-NH3-H2 mixtures in chemical vapour infiltration conditions

Boron nitride (BN) thin films deposited by isopressure and isothermal chemical vapour infiltration (ICVI) from BCl3-NH3-N2 mixtures have been characterized from a physicochemical point of view as functions of both the deposition conditions and the destabilizing action of moisture. As-deposited (deposited at 773 K and post-treated at 1273 K), the BN films are turbostractic (d0 0 2=0.36 nm, Lc=1.5 nm), have a low density (1.4 g cm−3) and contain oxygen (about 20 at%). A first oxygen content (191.5 eV by XPS) is inserted in the films during the CVI step in relation to the hygroscopy of intermediate solid products and the quasi-equilibrium between the formation of BN and B2O3. A second oxygen content (192.5 eV) is due to the hydrolysis of BN by moisture which induces a very drastic transformation of BN. This destabilization affects both boron and nitrogen atoms and leads to the formation of ammonium borate hydrates. Different post-treatments have been investigated to stabilize the BN films and it appears that nitriding under ammonia is the most efficient.

Fixation of Zn2+ and Pb2+ by a Ca-montmorillonite in brines and dilute solutions: Preliminary results

Abstract This paper presents preliminary results on the fixation of Zn 2+ and Pb 2+ by a purified Wyoming Ca-montmorillonite, in different experimental conditions: variable (3 · 10 −5 I −2 M or constant ( I = 3.10 −2 M) low ionic strength solution, and high ( I = 3 M) ionic strength solutions at 20°C and 50°C. In low ionic strength solutions, the fixation of Zn 2+ and Pb 2+ appears to be controlled by ionic exchange mechanism; Zn 2+ and Pb 2+ adsorption are strongly favoured over Ca 2+ adsorption, Pb 2+ being more strongly fixed than Zn 2+ . In high ionic strength solutions, for both metals, amounts of exchanged heavy metals are very small. The fixation is higher in 1 M CaCl 2 than in 3 M NaCl solutions. Temperature has different effects on zinc and lead fixation. At 50°C, all the adsorption isotherms are shifted to higher values, except for lead in 1 M Cacl 2 solutions. XRD characterizations of samples exchanged in dilute solutions show a decrease of hydration states with increasing Zn 2+ and Pb 2+ contents in the interlamellar space. Systematic determinations of CEC were performed on these samples, using Cu(EDA) 2 Cl 2 . The CEC decreases with increasing Pb 2+ in clay, indicating that a part of exchanged Pb 2+ ecomes unexchangeable with (Cu(EDA) 2) 2+ . On Zn-exchanged samples, the CEC remains constant.

An XPS study of the dissolution kinetics of chrysotile in 0.1 N oxalic acid at different temperatures

The dissolution of chrysotile is studied in regard to the surfaces analysis by photoelectron spectrometry. After leaching of chrysotile (Provenance: Thetford; about 200 mg of fibers of 1 cm length) in nonstirred 0.1 N oxalic conditions, the composition of the mineral surfaces is determined by XPS; kinetic curves of dissolution are given in the range 22–80°C.Two conditions for the rate-limiting step are involved for the explanation of the dissolution: diffusion of Mg2+ through the fibrous gel or dissociation of chrysotile. By the former, some values of the diffusion coefficient are proposed: D varies from 5·10−19 cm2s−1 to 5·10−16 cm2s−1, in the range 22–80°C. By the second model, the leaching rate is estimated from 3 Å (22°C) per h to 250 Å (80°C) per h. For the 2 models, the activation heat energy is in the range 15–20 Kcal.

Study of the early hydration of Ca3SiO5 by X-ray photoelectron spectrometry

C3S pastes (W/S = 0.5), have been studied from 5 seconds to 4 hours by X-ray Photoelectron Spectrometry. XPS reveals surface transformations of C3S grains from very early ages of hydration. The modifications have been evidenced by a change in the environment of Si atoms and a variation of the Ca/Si ratio. A Primary Hydrate (C/S << 3), a Secondary Hydrate (C/S ⋍2) and a Tertiary Hydrate (CSH type I) have been identified. XPS is a sensitive and reproducible method for the study of the surface C3S hydration.

Experimental hydration of two synthetic glassy blast furnace slags in water and alkaline solutions (NaOH and KOH 0.1 N) at 40° C: structure, composition and origin of the hydrated layer

The hydration of blast furnace slags has been modelled using two synthetic (CaO, SiO2, Al2O3, MgO) glasses with different Al2O3/MgO values. Experiments (duration: 16 h to 150 d) were performed at 40° C in deionized water (pH 6.5) and in NaOH and KOH (0.1 N) solutions (pH=12.9). The hydrated layer was characterized from a combination of several techniques at different scales: surface analysis by XPS and SEM; TEM of ultrathin diamond-cut sections including electron microdiffraction and EDS analysis; X-ray diffraction of scratched powders. In water, the hydrated zone is only about 0.5μm thick after 150 d with a leached layer covered by a thin siliceous film on which are scattered rare amorphous lamellae. In alkali media, the hydrated zone is composed of three parts: an inner layer made of modified residual glass, calcium-depleted and richer in magnesium and aluminium than the initial glass; an intermediate lamellar of constant thickness (O.3μm) after 15 d with magnesium and aluminium as major components (“hydrotalcite type” composition) and labelling the initial solid-solution interface, an outer layer with initially abundant C-S-H more or less carbonated after reaction with atmospheric CO2. The “hydrotalcite-type” layer separates the inner domain dominated by the formation and evolution of a leached glass layer from an outer one, where the precipitation of C-S-H and other amorphous or crystalline compounds, followed by carbonation, are the major processes.

Hydro-chemio-mechanical coupling effects on permeability and swelling behaviour of a Ca smectite soaked by Cu solutions

Hydro-chemio-mechanical coupling effects in an expansive clay have been studied along soaking paths with oedometer cells equipped with two solute injection systems. Two sets of boundary conditions for soaking were applied: solute and gas–solute mixture. The clay used for the experiments was a Ca French expansive clay known as Fo–Ca. The role of solute chemistry on clay permeability, swelling strain, porosity and on the retention curve was investigated. Copper cations were chosen for taking into account strong adsorption capacity, as the migration of toxic cations normally occurs in acid solutions, exchanges being produced with alkaline content. Permeability as well as swelling strain changes along soaking paths have been investigated with copper concentration with respect to the two sets of boundary conditions. Moreover, the ability of the Fo–Ca for ions sorption was studied by means of leachate analyses. Porosity and retention curves were also given after testing with respect to copper concentrations. Significant changes resulting from the copper solute injection have been obtained for all these material parameters.

X-ray photoelectron spectroscopy and chemical study of the adsorption of biological molecules on chrysotile asbestos surface☆

Abstract The sorptive properties of chrysotile and Mg-depleted chrysotile fibers were determined. Chemical analysis and X-ray photoelectron spectroscopy (XPS) were used in order to study the adsorption of albumin and of dipalmitoyl phosphatidyl choline liposomes on the fibers. The macromolecules are adsorbed on the surface of chrysotile fibers, the albumin being in the “end-on” position. The adsorption on Mg-depleted chrysotile fibers is different, there is a bulk incorporation of the macro-molecules in the fibers. However, the chemical analysis shows that similar amounts of macromolecules were adsorbed on the undepleted or Mg-depleted fibers. These observations suggest that some biological effects of chrysotile fibers may be related to their physicochemical properties.

Blast-furnace slag hydration. Surface analysis

Abstract X-ray photoelectron spectrometry (XPS) was used to determine the variation of the characteristic ratios Ca/Si, Al/Si and Mg/Si of two different slags (one in granulated, the other in pelletized form) during hydration. The results show that the slag surface is modified as soon as it becomes in contact with water or alkaline solution. The hydrated superficial layer is depleted of calcium but contains alkali ions if instead of water, NaOH or KOH solutions are used in mixing.

Zinc and cadmium effects on growth and ion distribution in Populus tremula × Populus alba

The effects of cadmium and zinc on growth and mineral distribution in Populus tremula × P. alba genotype 717-1B4 were investigated. Exposure to 360 mg(Cd) kg−1(soil) resulted in accumulation of Cd in all organs and inhibition of primary and secondary growth as well as of the net photosynthetic rate. No growth inhibition occurred under zinc exposure. Cd was mainly stored in the woody parts of stem, whereas zinc was preferentially localized in the leaves. Cd treatment also altered distribution of Zn2+, Ca2+, Mg2+, K+, and Fe2+ in different organs.