Emmanuel Véron

Relationships Between Carbonation Rate of Carbapatite and Morphologic Characteristics of Calcium Phosphate Stones and Etiology

OBJECTIVES To examine the significance of the carbonation rate (CR) in carbonated apatite (carbapatite [CA]) stones and its relationships with the morphologic characteristics of CA and etiology. CA stones without struvite can result from metabolic disorders or urinary tract infection, but the latter etiology is still debated. Infection stones caused by urea-splitting bacteria are made of CA admixed with struvite and exhibit a high CO(3)(2-)/PO(4)(3-) ratio (CR). However, little is known as to the significance of the CR of CA in the absence of struvite in idiopathic calcium phosphate stones. METHODS We studied 39 urinary calculi mainly composed of CA without struvite. Of the 39 patients, 13 had a past or present history of urinary tract infection, 24 had hypercalciuria, and 2 had medullary sponge kidney. The stones were examined by Fourier transform infrared spectroscopy and scanning electron microscopy. The presence of amorphous carbonated calcium phosphate or whitlockite was also considered. RESULTS The CR of CA was 14% +/- 9%. On scanning electron microscopy, the CA particles appeared as spherules of 4.5 +/- 3.0 mum in diameter and were significantly larger in females than in males. In 16 cases, scanning electron microscopy showed bacterial imprints. In these calculi, the CR was significantly greater (22% +/- 7%) than in those without a visible bacterial imprint (8% +/- 5%, P < .0001). Amorphous carbonated calcium phosphate was found in 15 of 16 stones (93.8%) with imprints and in none of the 23 stones without imprints (P < .0001). CONCLUSIONS A close relationship was observed between the presence of bacterial imprints, indicative of past or current urinary tract infection, and both the presence of amorphous carbonated calcium phosphate (or whitlockite) and a high CR of CA.

Recycled Material for Sensible Heat Based Thermal Energy Storage to be Used in Concentrated Solar Thermal Power Plants

Current technologies of concentrated solar power plants (CSP) are under extensive industrial development but still suffer from lack of adapted thermal energy storage (TES) materials and systems. In the case of extended storage (some hours), thousands of tonnes of materials are concerned leading to high investment cost, high energy and GHG contents and major conflicts of use. In this paper, recycled industrial ceramics made by vitrification of asbestos containing wastes (ACW) are studied as candidates to be used as sensible TES material. The material presents no hazard, no environmental impact, good thermophysical properties (λ= 1.4 W m -1 K -1 ; Cp = 1025 J kg -1 K -1 ; p= 3100 kg m -3 ) and at very low investment cost. Thanks to the vitrification process of the wastes, the obtained ceramics is very stable up to 1200 °C and can be directly manufactured with the desired shape. The vitrified ACW can be used as TES material for all kinds of the CSP processes (from medium up to high concentration levels) with properties in the same range than other available materials but with lower cost and without conflict of use. The proposed approach leads also to sustainable TES allowing a pay back of the energy needed for the initial waste treatment. Furthermore, this new use of the matter can enhance the waste treatment industry instead of land fill disposal.

Examination of whewellite kidney stones by scanning electron microscopy and powder neutron diffraction techniques

# 2009 International Union of Crystallography Printed in Singapore – all rights reserved Kidney stones made of whewellite, i.e. calcium oxalate monohydrate, exhibit various morphological aspects. The crystalline structure of whewellite at the atomic scale was revisited through a single-crystal neutron study at room temperature using a four-circle automated diffractometer. The possible relationships between the various morphological types of whewellite stones and their structural characteristics were examined at the mesoscopic scale by the use of scanning electron microscopy and at the nanometric scale by powder neutron diffraction. All types of whewellite stones displayed a similar structure at the nanometric scale. However, significant differences were found at the mesoscopic scale. In particular, the crystallites in kidney stones resulting from a genetic hyperoxaluria exhibited a peculiar structure. There was a close relationship between stone morphology and crystallite organization at the mesoscopic level and the effectiveness of extracorporeal shockwave lithotripsy.

Topological, Geometric, and Chemical Order in Materials: Insights from Solid-State NMR

Unlike the long-range order of ideal crystalline structures, local order is an intrinsic characteristic of real materials and often serves as the key to the tuning of their properties and their final applications. Although researchers can easily assess local ordering using two-dimensional imaging techniques with resolution that approaches the atomic level, the diagnosis, description, and qualification of local order in three dimensions is much more challenging. Solid-state nuclear magnetic resonance (NMR) and its panel of continually developing instruments and methods enable the local, atom-selective characterization of structures and assemblies ranging from the atomic to the nanometer length scales. By making use of the indirect J-coupling that distinguishes chemical bonds, researchers can use solid-state NMR to characterize a variety of materials, ranging from crystalline compounds to amorphous or glassy materials. In crystalline compounds showing some disorder, we describe and distinguish the contributions of topology, geometry, and local chemistry in ways that are consistent with X-ray diffraction and computational approaches. We give examples of materials featuring either chemical disorder in a topological order or topological disorder with local chemical order. For glasses, we show that we can separate geometric and chemical contributions to the local order by identifying structural motifs with a viewpoint that extends from the atomic scale up to the nanoscale. As identified by solid state NMR, the local structure of amorphous materials or glasses consists of well-identified structural entities up to at least the nanometer scale. Instead of speaking of disorder, we propose a new description for these structures as a continuous assembly of locally defined structures, an idea that draws on the concept of locally favored structures (LFS) introduced by Tanaka and coworkers. This idea provides a comprehensive picture of amorphous structures based on fluctuations of chemical composition and structure over different length scales. We hope that these local or molecular insights will allow researchers to consider key questions related to nucleation and crystallization, as well as chemically (spinodal decomposition) or density-driven (polyamorphism) phase separation, which could lead to future applications in a variety of materials.

Spray-dried mesoporous silica microspheres with adjustable textures and pore surfaces homogenously covered by accessible thiol functions

Micrometric mesoporous spheres with textures possessing a relative high degree of ordering and incorporating up to 0.1 thiol function per siloxane unit have been synthesised through sol–gel, self-assembly and—for the first time—spray-drying processes. The sol preparation was optimised as a function of the final properties: morphology, texture, and proportion of thiol functions. A two step synthesis allows the positioning of these functions at the pore surface as proven in particular by 1H solid state NMR. From Ag+ sorption experiments, we have shown that the thiol functions are also homogenously distributed in the spheres volume and fully accessible to external chemical species. So these materials could be used for environmental remediation or metallic nano-particle syntheses. In order to increase the stability and applicability of the materials, different post-synthesis treatments have been studied. A thermal treatment under mild conditions is enough to preserve most of the properties. From the hydrothermal treatments tested, the use of ammonia is shown to be quite interesting for the modulation of the properties. In particular, hierarchical porosities and high specific surface areas have been created. The high degree of ordering observed for the smaller pores is accompanied by a re-ordering of the surfactant polar head groups as deduced from 14N NMR. Lastly, the synthesis can be extended under some conditions to other functions or to higher proportions of thiol functions (up to 0.2).

Long-lasting luminescent ZnGa2O4:Cr3+ transparent glass-ceramics

Highly transparent ZnGa2O4 glass-ceramic materials are elaborated via a simple heat treatment of a 55SiO2–5Na2O–17ZnO–23Ga2O3 parent glass composition, which presents nanoscale spinodal phase separation. This optimized glass-ceramic exhibits 50 wt% of ZnGa2O4 nanocrystals showing a homogeneous and tuneable size. To describe the crystallization process, the glass and glass-ceramic nanostructures are studied by high resolution scanning transmission electron microscopy analysis coupled with in situ high temperature X-ray diffraction and optical measurements. From these results, an original mechanism is proposed to explain the crystallization process occurring in a spinodal phase separated glass. Remarkably, red long-lasting luminescence arising from the entire sample volume is observed in the Cr3+ doped transparent glass-ceramics, opening the route to a wider range of performing applications for this famous zinc gallate persistent phosphor.

Synthesis and structure determination of CaSi1/3B2/3O8/3, a new calcium borosilicate

This article reports on the identification, synthesis, and in-situ structure determination of a new crystalline calcium borosilicate compound of composition CaSi(1/3)B(2/3)O(8/3). Synthesis was carried out by complete crystallization on annealing from a corresponding glassy composition in the widely studied CaO-SiO2-B2O3 ternary system. The crystallographic structure was determined ab initio using electron diffraction information and the charge flipping algorithm performed on synchrotron and neutron powder diffraction data collected in situ at high temperature. CaSi(1/3)B(2/3)O(8/3) is found to crystallize in the Pna2(1) (no. 33) orthorhombic space group, with a = 12.1025(4) Å, b = 5.2676(1) Å, c = 3.7132(1) Å, and V = 236.71(1) Å(3) at 650 °C. Solid-state (29)Si and (11)B NMR experiments have confirmed the existence of finite chains along the c axis, formed by corner-sharing SiO4 tetrahedra and BO3 units. Silicon and boron species share a crystallographic site, and the Si/B distribution induces different possible arrangements of the chains which are discussed in light of DFT calculations. At room temperature, the existence of a superstructure, resulting from the ordering within nanoscale domains, was explored by transmission electron microscopy.

White light and multicolor emission tuning in triply doped Yb3+/Tm3+/Er3+ novel fluoro-phosphate transparent glass-ceramics

New Yb3+, Er3+ and Tm3+ doped fluoro-phosphate glasses belonging to the system NaPO3–YF3–BaF2–CaF2 and containing up to 10 wt% of rare-earth ion fluorides were prepared and characterized by differential scanning calorimetry, absorption spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and homogeneous glass-ceramics have been reproducibly obtained with a view to manage the red, green and blue emission bands and generate white light. X-ray diffraction as well as electron microscopy techniques have confirmed the formation of fluorite-type cubic nanocrystals at the beginning of the crystallization process while complex nanocrystalline phases are formed after a longer heat-treatment. The prepared glass-ceramics exhibit high optical transparency even after 170 h of thermal treatment. An improvement of up-conversion emission intensity – from 10 to 160 times larger – was measured in the glass-ceramics when compared to the parent glass, suggesting an important incorporation of the rare-earth ions into the crystalline phase(s). The involved mechanisms and lifetime were described in detail as a function of heat-treatment time. Finally, a large range of designable color rendering (from orange to turquoise through white) can be observed in these materials by controlling the laser excitation power and the crystallization rate.

Synthesis and structure resolution of RbLaF4.

The synthesis and structure resolution of RbLaF(4) are described. RbLaF(4) is synthesized by solid-state reaction between RbF and LaF(3) at 425 °C under a nonoxidizing atmosphere. Its crystal structure has been resolved by combining neutron and synchrotron powder diffraction data refinements (Pnma,a = 6.46281(2) Å, b = 3.86498(1) Å, c = 16.17629(4) Å, Z = 4). One-dimensional (87)Rb, (139)La, and (19)F MAS NMR spectra have been recorded and are in agreement with the proposed structural model. Assignment of the (19)F resonances is performed on the basis of both (19)F-(139)La J-coupling multiplet patterns observed in a heteronuclear DQ-filtered J-resolved spectrum and (19)F-(87)Rb HMQC MAS experiments. DFT calculations of both the (19)F isotropic chemical shieldings and the (87)Rb, (139)La electric field gradient tensors using the GIPAW and PAW methods implemented in the CASTEP code are in good agreement with the experimental values and support the proposed structural model. Finally, the conductivity of RbLaF(4) and luminescence properties of Eu-doped LaRbF(4) are investigated.

Therapy modifies cystine kidney stones at the macroscopic scale. Do such alterations exist at the mesoscopic and nanometre scale

With an incidence of 1:7000 births, cystinuria, the most frequent cause of stone formation among genetic diseases, represents a major medical problem. Twentyfive cystine stones randomly selected from cystinuric patients were investigated. From a crystallographic point of view, cystine stones are composed of micrometre size crystallites, which are made up of an aggregation of nanocrystals. Through scanning electron microscopy, the morphology and size of the crystallites have been described, while the size of the nanocrystals was investigated by means of powder neutron diffraction. Powder neutron diffraction analysis and/or scanning electron microscopy examination of cystine stones provide evidence that usual alkalinization by sodium bicarbonate associated with high diuresis significantly reduces the size of both nanocrystals and crystallites, while for other treatments, including alkalinizing drugs and thiol derivatives, the data suggest mainly changes in the topology of crystallites. Alkalinization with sodium bicarbonate affects cystine kidney stones at the mesoscopic and nanoscopic scales, while other medical treatments only alter their surface. Such an approach may help to assess the interaction between drugs and cystine stones in cystinuric patients.