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See detailTransport properties of an intermetallic with pseudo-hollandite structure as potential thermoelectric materials: the example of TlxCr5Se8.
Hidefumi, Takahashi; Nunna, Raghavendra ULg; Franck, Gascoin et al

in Chemistry of Materials (2013), 25(9), 18091815

The transport properties of TlxCr5Se8 pseudo-hollandite have been investigated, from 2 up to 800 K. A semiconducting behavior is observed from 200 down to 2 K, with a transition observed at T ∼ 43 K, at ... [more ▼]

The transport properties of TlxCr5Se8 pseudo-hollandite have been investigated, from 2 up to 800 K. A semiconducting behavior is observed from 200 down to 2 K, with a transition observed at T ∼ 43 K, at the antiferromagnetic transition. Above 200 K, small values of ρ are obtained, close to 10 mΩ·cm at 800 K. The Seebeck coefficient continuously increases in this range of temperature, reaching 300 μV/K at 800 K. Moreover, the thermal conductivity of this low dimensional structure is small, leading to a figure of merit ZT = S2T/(ρκ) = 0.5 at 800 K. All the electronic transport properties can be fitted by a standard Boltzmann equation, with a large scattering parameter (r = 3/2, characteristic of diffusion by ionized impurities). The combination of small thermal conductivity, large scattering parameter, and low concentration of carriers (4.5 × 1019 cm−3) is at the origin of this large ZT. [less ▲]

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See detailNbVO5 Mesoporous Thin Films by Evaporation Induced Micelles Packing: Pore Size Dependence of the Mechanical Stability upon Thermal Treatment and Li Insertion/Extraction
Krins, Natacha ULg; Bass, John D; Grosso, David et al

in Chemistry Of Materials (2011), 23(18), 4124-4131

Mesoporous thin films (MTFs) appear as an interesting architecture for positive electrodes in Li-ion energy storage systems because they offer high specific area and interconnected porosity presenting ... [more ▼]

Mesoporous thin films (MTFs) appear as an interesting architecture for positive electrodes in Li-ion energy storage systems because they offer high specific area and interconnected porosity presenting homogeneous pore size and wall thickness. However, it must be ascertained that the mesostructure survives template removal or/and crystallization and is retained on electrochemical cycling. In order to investigate the potentialities and limits of the soft-templating approach in the case of complex transition metal oxide networks, we deliberately selected a "difficult" compound: NbVO5 was chosen because it combines a challenging synthesis with reported severe structural distortions during the first lithium insertion in the bulk material. In this work, NbVO5 MTFs with different pore sizes were synthesized using the evaporation induced micelles packing (EIMP) method. PS-b-PEO diblock copolymers of different molar weights were used as structure directing agent in order to obtain wormlike porous networks with pore size and wall thickness ranging from 15 to 100 nm. Thermal ellipsometry analysis, used to track surfactant removal and crystallization of the layer, reveals that partial crystallization is possible while retaining the mesoporous architecture. Electron tomography complements result from environmental ellipsometric porosimetry, atomic force microscopy, and transmission electron microscopy to provide a comprehensive description of the structure. A multilayer process is also proposed to build crack-free thick mesoporous films. The mechanical stability of MTFs presenting three different pore sizes is tested by inserting Li(+) in amorphous NbVO5 MTFs using cyclic voltammetry. Capacity retention data show that the mechanical stresses associated with Li+ insertion are better accommodated by MTFs compared to nonporous films, and this ability is enhanced as the pore size decreases. [less ▲]

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See detailThick and crack-free nanocrystalline mesoporous TiO2 films obtained by capillary coating from aqueous solutions
Krins, Natacha ULg; Faustini, M.; Louis, B. et al

in Chemistry of Materials (2010), 22

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See detailQuantitative Characterization of Pore Corrugation in Ordered Mesoporous Materials Using Image Analysis of Electron Tomograms
Gommes, Cédric ULg; Friedrich, Heiner; Wolters, Mariska et al

in Chemistry of Materials (2009), 21

Electron tomography and image analysis are combined to characterize ordered mesoporous silica SBA-15. The morphology of the mesopores with average diameter 6 nm is analyzed in terms of cylinders having ... [more ▼]

Electron tomography and image analysis are combined to characterize ordered mesoporous silica SBA-15. The morphology of the mesopores with average diameter 6 nm is analyzed in terms of cylinders having variable radii and centers that are statistically centered on the points of a distorted hexagonal lattice. The variations in the mesopore centers and radii add up and result in pore wall corrugation with amplitude of 1.6 nm. The correlation length of the corrugation along the pore axis was found to be 4-5 nm. The amplitude of the corrugation compared well with the 1.9 nm thick microporous corona obtained from X-ray diffraction (XRD). In general, the present approach provides a detailed microscopic 3D model of nanostructured materials that complements macroscopic measurements such as physisorption and XRD. [less ▲]

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See detailControlled RAFT synthesis of polyacrylonitrile-b-poly(acrylic acid) diblocks as precursors of carbon nanocapsules with assistance of gold nanoparticles
Aqil, Abdelhafid ULg; Detrembleur, Christophe ULg; Gilbert, Bernard ULg et al

in Chemistry of Materials (2007), 19(9), 2150-2154

A new strategy for the synthesis of carbon nanocapsules has been developed, based on the preparation of well-defined polyacrylonitrile-b-poly(acrylic acid) (PAN-b-PAA) block copolymers followed by their ... [more ▼]

A new strategy for the synthesis of carbon nanocapsules has been developed, based on the preparation of well-defined polyacrylonitrile-b-poly(acrylic acid) (PAN-b-PAA) block copolymers followed by their micellization in basic water to form spherical micelles with a PAN core and PAA shell. The PAN is then cross-linked by the use of gold nanoparticles. After pyrolysis, carbon nanocapsules are produced by graphitization of the PAN core and diffusion of the molten gold nanoparticles out of the nano-objects. [less ▲]

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See detailSynthesis of adherent hydrophilic polypyrrole coatings onto (semi)conducting surfaces
Gabriel, Sabine ULg; Cecius, Michaël ULg; Fleury-Frenette, Karl ULg et al

in Chemistry of Materials (2007), 19(9), 2364-2371

Hydrophilic and adherent polypyrrole coatings were prepared by a two-step electrochemical method. First, alpha-pyrrole, omega-acrylate polyethylene oxide (Py-PEO-A) dual macromonomer was synthesized by ... [more ▼]

Hydrophilic and adherent polypyrrole coatings were prepared by a two-step electrochemical method. First, alpha-pyrrole, omega-acrylate polyethylene oxide (Py-PEO-A) dual macromonomer was synthesized by anionic polymerization and electrografted onto (semi)conducting substrates by cathodic polymerization of the acrylic end-group. The obtained adherent coating is hydrophilic and thus swells in water and bears a pyrrole ring, a precursor of the conducting polymer. In a second step, the coating is anodically polarized in a mixture of Py and Py-PEO to give the hydrophilic and adherent polypyrrole. Properties such as morphology, adherence, electroactivity, and hydrophilicity of these coatings were investigated by conventional methods and compared to those of pure polypyrrole coatings. These novel coatings exhibit efficient protein adsorption repellency and are thus good candidates for applications in biomaterials and biosensors. [less ▲]

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See detailHierarchical multimodal mesoporous carbon materials with parallel macrochannels
Su, Bao-Lian; Vantomme, Aurelien; Surahy, Lidwine et al

in Chemistry of Materials (2007), 19(13), 3325-3333

Hierarchically structured multimodal meso-macroporous carbon materials have been prepared by using the nanoreplication of the mesoporous walls of a meso-macroporous zirconia exotemplate. Like the zirconia ... [more ▼]

Hierarchically structured multimodal meso-macroporous carbon materials have been prepared by using the nanoreplication of the mesoporous walls of a meso-macroporous zirconia exotemplate. Like the zirconia exotemplate, the pure carbon material possesses funnel shaped straight macrochannels, parallel to each other and perpendicular to the tangent of the particles' dense mesoporous shell. As a result of the funnel-like shape, each macrochannel has a pore size gradient with a large opening centered at 300-700 nm. The walls of the macrochannels and the dense mesoporous shells are formed by a hierarchical mesostructured porous system with uniform mesopore sizes centered at 3, 15-17, and 25-50 nm. Macrochannels are interconnected with hierarchically mesostructured walls and shells. A high surface area of 950 m(2)/g with a mesopore volume of 0.44 cm(3)/g is obtained. The possibility of the nanoreplication of other meso-macroporous oxides such as aluminosilicates, titania, and niobium oxide with different macrochannel size, shape, and organization has also been studied to generate meso-macroporous carbon materials with different organizations of the macrochannels. [less ▲]

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See detailNew nanostructured materials based on fullerene and biodegradable polyesters
Stoilova, Olya; Jérôme, Christine ULg; Detrembleur, Christophe ULg et al

in Chemistry of Materials (2006), 18(20), 4917-4923

Star-shaped poly(epsilon-caprolactone) (PCL) with a fullerene (C-60) core, C-60[N(CH2)(12)OPCLOH](x), was successfully synthesized by reaction of azide-terminated PCL with C-60. Both the experimental ... [more ▼]

Star-shaped poly(epsilon-caprolactone) (PCL) with a fullerene (C-60) core, C-60[N(CH2)(12)OPCLOH](x), was successfully synthesized by reaction of azide-terminated PCL with C-60. Both the experimental conditions and the stoichiometry were optimized, such that an average of six PCL chains was grafted per fullerene core. The molecular weight of the polyester chains directly controlled the length of the arms of the star-shaped polymers. Singlet oxygen was generated on irradiation of the C-60[N(CH2)(12)OPCLOH] x nanohybrids. These C-60[N(CH2)(12)OPCLOH](x) nanohybrids were then processed in two kinds of nanomaterials. First, they were encapsulated within the core of micelles formed by biocompatible amphiphilic block copolymers. In water, the particle size distribution of these nanoparticles was narrow, and their diameter was in the range of 100 to 200 nm. Second, C-60-containing micro-/nanosized polymer fibers were prepared, for the first time, by electrospinning. The average diameter of the fibers was varied by tuning the PCL/C-60[N(CH2)(12)OPCLOH](x) weight ratio. Grafting of polyester chains onto C-60 is thus a suitable strategy for producing easily processable C-60 and attractive building blocks for incorporation of C-60 in nanomaterials. [less ▲]

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See detailRietveld texture analysis of alumina ceramics by neutron diffraction
Guilmeau, E.; Chateigner, D.; Suzuki, T. S. et al

in Chemistry of Materials (2005), 17(1), 102-106

The orientation distributions of alpha-Al2O3 textured ceramics are determined from neutron diffraction spectra. A curved position-sensitive detector coupled to a tilt angle (chi) scan allowed the whole ... [more ▼]

The orientation distributions of alpha-Al2O3 textured ceramics are determined from neutron diffraction spectra. A curved position-sensitive detector coupled to a tilt angle (chi) scan allowed the whole diffraction pattern treatment in the combined Rietveld-WIMV-Popa algorithm. Four textured alumina ceramics were prepared by slip-casting under a high magnetic field and sintered at 800, 1300, 1400, and 1600 degreesC. The calculation of the distribution density, correlated to the representation of the normal and inverse pole figures, highlights the influence of the magnetic field and sintering temperature on the texture development. The principal pole figures show a pronounced (00l) texture: (001) pole parallel to the direction of slip-casting, and (110) pole with higher distribution density for the directions perpendicular to the expected fiber axis. The inverse pole figures calculated for the fiber direction show a major (001) component for all the samples. With the increasing sintering temperature, the texture strength is enhanced and the c-axis distribution is sharper. The effectiveness of the approach for determining the crystallite size is also evident. As a global trend, the calculated crystallite size and observed grain size are similar and increase with the increasing sintering temperature. The mechanism of the texture development in the sintered specimens is certainly initiated from the preferred orientation of the green body after slip-casting under a high magnetic field. The basal texture is enhanced during sintering by selective anisotropic grain growth. We evidenced here the powerfulness of the Rietveld texture analysis to provide a basis for the correlation of texture, microstructural parameters, and anisotropic properties. [less ▲]

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See detailSpinel-structured gallium oxynitride (Ga3O3N) synthesis and characterization: An experimental and theoretical study
Soignard, E.; Machon, D.; McMillan, P. F. et al

in Chemistry Of Materials (2005), 17(22), 5465-5472

Recently the new family of spinel-structured nitrides and oxynitrides of group 14 elements (Si, Ge, Sn) has been explored using high-pressure synthesis techniques. The solid-state compounds have high ... [more ▼]

Recently the new family of spinel-structured nitrides and oxynitrides of group 14 elements (Si, Ge, Sn) has been explored using high-pressure synthesis techniques. The solid-state compounds have high hardness, and they are semiconducting materials that are predicted to have a wide direct band gap. Here we have prepared the corresponding gallium oxynitride spinel with ideal formula Ga3O3N. The synthesis conditions and stability of the new phase were predicted using first-principles calculations, and the experimental study was realized using a combination of laser-heated diamond anvil cell and multianvil high-pressure, high-temperature synthesis techniques. Chemical analysis and X-ray structure refinement indicate that the new phase contains vacancies on the octahedrally coordinated Ga sites, to give an experimental stoichiometry of Ga2.8N0.64O3.24. The Raman spectrum consists of broad bands and resembles the phonon density of states, due to N/O disorder on the anion sites. Optical excitation of the sample with 325 nm laser light at room temperature results in strong photoluminescence between 400 and 750 nm. [less ▲]

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See detailSynthesis of pyrene-containing polymers and noncovalent sidewall functionalization of multiwalled carbon nanotubes
Lou, Xudong; Daussin, Raphaël; Cuenot, Stéphane et al

in Chemistry of Materials (2004), 16(21), 4005-4011

Pyrene-containing polymers have been prepared for noncovalent sidewall functionalization of multiwalled carbon nanotubes (MWNTs). (1-Pyrene)methyl 2-methyl-2-propenoate (PyM-MP) has been synthesized and ... [more ▼]

Pyrene-containing polymers have been prepared for noncovalent sidewall functionalization of multiwalled carbon nanotubes (MWNTs). (1-Pyrene)methyl 2-methyl-2-propenoate (PyM-MP) has been synthesized and copolymerized with methyl methacrylate (MMA). Poly(ethylene-co-butylene)-b-poly(MMA-co-PyMMP) diblocks have also been synthesized. The surface of MWNTs, produced by both the CCVD and arc discharge methods, has been modified by these copolymers for making them dispersible in a variety of organic solvents. The modified MWNTs have been characterized by thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. [less ▲]

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See detailPLA-coated gold nanoparticles for the labeling of PLA biocarriers
Qiu, Hongjin; Rieger, Jutta ULg; Gilbert, Bernard ULg et al

in Chemistry of Materials (2004), 16(5), 850-856

POly-DL-lactide end-capped by a protected thiol was synthesized by bulk ring-opening polymerization (ROP) of DL-lactide initiated by the reaction product of aluminum isopropoxide [Al (iOPr) (3)] with ... [more ▼]

POly-DL-lactide end-capped by a protected thiol was synthesized by bulk ring-opening polymerization (ROP) of DL-lactide initiated by the reaction product of aluminum isopropoxide [Al (iOPr) (3)] with alpha- (2,4-dinitrophenylsulfenyl) ethanol. After the thiol deprotection, PLA-SH was used to stabilize gold nanoparticles. Either these nanoparticles were prepared in the presence of PLA-SH, or PLA-SH was substituted for part of the undecanethiol (C11SH) that stabilized preformed gold nanoparticles. In contrast to C11SH-coated nanoparticles, those stabilized by PLA-SH were successfully entrapped into 100-nm PLA nanocarriers prepared by nanoprecipitation. This is an easy technique to label PLA biocarriers and therefore trace their fate in vivo. [less ▲]

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See detailControlled free radical polymerization of styrene initiated from alkoxyamine attached to polyacrylate chemisorbed onto conducting surfaces
Voccia, Samuël; Jérôme, Christine ULg; Detrembleur, Christophe ULg et al

in Chemistry of Materials (2003), 15(4), 923-927

A new inimer that associates an alkoxyamine, which is an initiator/mediator in nitroxide mediated radical polymerization (NMP), and a polymerizable acrylate has been synthesized and used in a two-step ... [more ▼]

A new inimer that associates an alkoxyamine, which is an initiator/mediator in nitroxide mediated radical polymerization (NMP), and a polymerizable acrylate has been synthesized and used in a two-step "grafting-from" method. The acrylate has been first electropolymerized under a cathodic potential, such that the polymer is chemisorbed on the cathode. NMP of styrene has then been initiated from the electrografted polyacrylate chains with formation of polystyrene with controlled molecular weight and narrow polydispersity. [less ▲]

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See detailFull-electrochemical preparation of conducting/insulating binary polymer films
Jérôme, Christine ULg; Geskin, V.; Lazzaroni, Roberto et al

in Chemistry of Materials (2001), 13(5), 1656-1664

Binary polymer films consisting of an insulating polymer and a conducting polymer have been successfully prepared by sequential electropolymerization of the parent monomers. The insulating polymer ... [more ▼]

Binary polymer films consisting of an insulating polymer and a conducting polymer have been successfully prepared by sequential electropolymerization of the parent monomers. The insulating polymer (polyacrylonitrile or polyethylacrylate) is formed under cathodic polarization in a potential range where the growing chains are chemically grafted onto the nickel or carbon electrode. The conducting polymer (polybithiophene or polypyrrole) is formed by electrooxidation of the parent monomer. The electrochemical reactions and the electrochemical properties of the films have been analyzed by cyclic voltammetry and chronoamperometry. The influence of the main experimental parameters on the composition and morphology of the films has been investigated by X-ray photoelectron spectroscopy and atomic force microscopy. This approach strongly improves the adhesion of the conducting polymer as a result of its combination with the grafted polyacrylonitrile. This combination of insulating and conducting polymers is a way to tune the electroactivity of the conjugated chains. [less ▲]

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See detailPolymerization-filling technique: an efficient way to improve the mechanical properties of polyethylene composites
Alexandre, Michaël ULg; Martin, Eric; Dubois, Philippe ULg et al

in Chemistry of Materials (2001), 13(2), 236-237

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See detailWell-ordered spherical mesoporous materials CMI-1 synthesized via an assembly of decaoxyethylene cetyl ether and TMOS
Blin, Jean-Luc; Léonard, Alexandre ULg; Su, Bao-Lian

in Chemistry of Materials (2001), 13(10), 3542-3553

Well-ordered spherical CMI-1 mesoporous materials with a hexagonal arrangement of channels, analogous to MCM-41, have been directly synthesized by variation of the weight percentage of decaoxyethylene ... [more ▼]

Well-ordered spherical CMI-1 mesoporous materials with a hexagonal arrangement of channels, analogous to MCM-41, have been directly synthesized by variation of the weight percentage of decaoxyethylene cetyl ether [C 16(EO) 10] in aqueous solution. XRD, TEM, SEM, and nitrogen adsorption-desorption results led us to propose two different synthesis pathways for surfactant concentrations higher and lower than 30 wt %, respectively. For samples obtained with an elevated surfactant concentration (>30 wt %), in addition to the possible perturbation induced by methanol released in low amount during the hydrolysis of TMOS, other factors such as the interactions of the silica source with hydrophilic chain heads of surfactant molecules should also disturb the preformed hexagonal micelle array, and disordered wormhole mesostructured materials (DWM), analogous to MSU, are obtained. For the synthesis with a C 16(EO) 10 concentration less than 30 wt %, a cooperative mechanism, which involves the polymerization of silica source and the interface interactions between the hydroxyl groups of silica source produced from the hydrolysis of TMOS and hydrophilic chain heads of surfactant molecules which are present in the single rod micelle form, has been evidenced, leading to well-ordered CMI-1 materials with hexagonal arrangement of their channels. [less ▲]

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See detailSynthesis and electrooptic properties of a new chromophore dispersed or grafted in a carbazolyl methacrylate matrix
Maertens, Christophe; Detrembleur, Christophe ULg; Dubois, Philippe et al

in Chemistry of Materials (1998), 10

A copolymer of [11-(N-carbazolyl)undecyl methacrylate] and ethyl (E)-2-cyano-3[5-(5-(4-methacryloyloxy)piperidino-2-thienylcarbonyl)-2-thienyl]-2-propenoate has been prepared. The photoconductivity and ... [more ▼]

A copolymer of [11-(N-carbazolyl)undecyl methacrylate] and ethyl (E)-2-cyano-3[5-(5-(4-methacryloyloxy)piperidino-2-thienylcarbonyl)-2-thienyl]-2-propenoate has been prepared. The photoconductivity and the electrooptic properties of a hot-pressed thin film of this copolymer have been measured and compared with the properties of the dispersion of ethyl (E)-2-cyano-3[5-(5-piperidino-2-thienylcarbonyl)-2-thienyl]-2-propenoate within a poly[11-(N-carbazolyl)undecyl methacrylate] matrix. The electrooptic coefficient has been measured by both interferometric and polarimetric techniques. The interferometric technique was not appropriated because the strong electric field applied to the electrodes changes the film thickness of these low Tg materials. A value of up to 5 pm/V for the figure of merit n3(r13 − r33) has been reported for the dispersed material, which is 10 times higher than the corresponding grafted material, and a linear relationship between the poling intensity and the electrooptic coefficient has been observed for the two materials. [less ▲]

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See detailPolyimide nanofoams from aliphatic polyester-based copolymers
Hedrick, James L; Carter, K. R.; Richter, R. et al

in Chemistry of Materials (1998), 10(1), 39-49

High-temperature polymeric foams were prepared using compositionally asymmetric microphase-separated block copolymers where the major component is thermally stable and the minor component is thermally ... [more ▼]

High-temperature polymeric foams were prepared using compositionally asymmetric microphase-separated block copolymers where the major component is thermally stable and the minor component is thermally labile. Upon thermal treatment, the dispersed phase undergoes thermolysis leaving pores the size and shape of which are dictated by the initial copolymer morphology. The driving force behind the survey of aliphatic polyesters as possible labile blocks stems from their quantitative degradation into low-boiling, polar degradation products. Poly(lactones), as a general class of materials, degrade by a backbiting process producing, primarily, monomer and cyclic oligomers. A ring-opening synthetic route to poly(lactones) affords oligomers of predictable molecular weight, narrow molecular weight distribution, and controlled end-group functionality. Block copolymers were prepared using monofunctional caprolactone and valerolactone oligomers and a high-Tg polyimide. Microphase separation was observed in all cases, and the lactone blocks did not crystallize. Thermal decomposition of the caprolactone block was accomplished by heating the copolymer to 370 °C for 5 h. Significant density reductions were found with pore sizes in the 60−70 Å range. [less ▲]

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See detailA novel biodegradable and biocompatible ceramer prepared by the sol-gel process
Tian, Dong; Dubois, Philippe ULg; Grandfils, Christian ULg et al

in Chemistry of Materials (1997), 9(4), 871-874

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