Raymond Houriet

Surface modification of polyester films by RF plasma

Plasma treatment of PET films was carried out under argon, followed by exposure to an oxygen atmosphere. The films underwent considerable changes in surface composition and morphology, as demonstrated by contact angle measurements, FTIR-ATR, AFM, and XPS. It was found that the surface acquired oxygen containing polar functional groups such as -C=O, -OH, and -OOH, which increased in number as the plasma treatment time increased. During storage, the treated films underwent significant surface reorganization, and both the time and temperature contributed to the increase in the contact angle. As revealed by AFM measurements, these changes were accompanied by an increase in roughness in the form of ridges. The ridges were observed to grow in height with increasing treatment time, although their spacing showed little evolution. A correlation among the observations obtained from various techniques was established, giving a comprehensive picture of the structure and dynamics of plasma-treated PET surfaces

Two-dimensional Fourier transform ion cyclotron resonance mass spectrometry

Abstract Two-dimensional Fourier transform (2D FT) spectroscopy is applied to ion cyclotron resonance (ICR) to obtain direct evidence for mass transfer due to ion-molecule collisions. The 2D FT ICR experiment, which is closely analogous to 2D exchange NMR spectroscopy (NOESY), yields similar information to tandem mass spectroscopy (MS/MS), but could in principle be extended to study a manifold of mass-transfer processes simultaneously.

Indium-tin oxide thin films by metal-organic decomposition

In 2 O 3 –SnO 2 films were produced by thermal decomposition of a deposit which was dip coated on borosilicate glass substrates from an acetylacetone solution of indium and tin acetoacetonate. Thermal analysis showed complete pyrolysis of the organics by 400 °C. The thermal decomposition reaction generated acetylacetone gas and was found to be first order with an activation energy of 13.6 Kcal/mole. Differences in thermal decomposition between the film and bulk materials were noted. As measured by differential scanning calorimetry using a 40 °C/min temperature ramp, the glass transition temperature of the deposited oxide film was found to be ∼462 °C, and the film crystallization temperature was found to be ∼518 °C. For film fabrication, thermal decomposition of the films was performed at 500 °C in air for 1 h followed by reduction for various times at 500 °C in a reducing atmosphere. Crystalline films resulted for these conditions. A resistivity of ∼1.01 × 10 −3 Ω · cm, at 8 wt. % tin oxide with a transparency of ∼95% at 400 nm, has been achieved for a 273 nm thick film.

Processing of nano-scaled silicon powders to prepare slip cast structural ceramics

For slip casting of ceramic powders it is necessary to have a well-defined and thus disagglomerated colloidal suspension. Proper selection of the solvent is required in order to achieve separation of the particles to obtain a homogenous mixture of the powders which is necessary for shaping complex geometrical structures, often used in structural ceramics. Here we report a preliminary investigation of the deagglomeration phenomena of nano-scaled silicon powders obtained by plasma induced dissociation of silane and compare it with silicon nitride powders prepared by laser induced condensation reactions and a commercial product (UBE SE E-10). The size dispersion of aggregates in colloidal suspensions, determined by photon correlation spectroscopy and sedimentation particle size analysis techniques, varies from 20 to 500 nm. Variation in the deagglomeration properties of the particles in different solvents depends on the surface property of the powders, and on the inter-particle interactions. These are studied with respect to the variations in the surface property of the powders in different solvents. Ethanol was found to be a suitable solvent for the colloidal suspension as the average aggregate radii of the silicon powders could be reduced to 80 nm.

The kinetic energy dependence of ion/molecule collisions studied by FT-ICR spectrometry

Abstract The effect of translational excitation of reactant ions is studied in a Fourier transform ion cyclotron resonance (FT-ICR) spectrometer. It is shown that useful binding energies in ions can be deduced from the experimentally determined threshold energy values for endothermic ion/molecule reactions and for collision-induced dissociation processes.

Synthesis of powders and films using a new laser ablation technique

Abstract A novel method to produce powders and films from ceramic targets is presented. It is shown that the laser spark atomizer (LINA-SPARK™), LSA, combines the advantages of operating at atmospheric pressure and ambient temperature to produce highly uniform films with a web-like structure which can be deposited at relatively high deposition rates (ca. 1 μm·min−1). The preparation of powder particles and coating starting from commercial ceramic specimen (Al2O3) is investigated. Highly agglomerated nanopowders and homogeneous mesoporous coatings forming a web-like structure are prepared using this new technique. The formation of the nanoparticles is explained following a liquefaction process which generates an aerosol, followed by the cooling/solidification of the droplets which results in the formation of a smoke. The general dynamic of both the aerosol and the smoke favors the aggregation process and micrometer-sized fractal-like particles are formed. The laser spark atomizer can be used to produce highly mesoporous thick films. The porosity can be modified by the carrier gas flow rate thus enabling for a control of the microstructure of the coatings which make these nanoparticulate thick films suitable candidates for application in membrane technology, catalysis and lithium ion batteries. ZrO2 and SnO2 nanoparticulate thick films are also synthesized successfully using this new process with quite identical microstructure.

Formation of metal cluster ions by gas-phase ion-molecule reactions: The bond energies of Cr2+ AND Mn2+

Abstract Ion-molecule reactions occurring in Cr(CO) 6 , Fe(CO) 5 , and Mn 2 (CO) 10 systems are carried out in a Fourier transform ion cyclotron resonance (FTICR) spectrometer. Abundant intensities of bare metal cluster ions can be formed by employing a multiple pulse sequence including selective ejections and photodissociation. In subsequent collisional activation experiments, the binding energies of Cr 2 + and Mn 2 + are determined as 1.6±0.2 and 2.1±0.3 eV, respectively, the latter being in conflict with a previously reported value.

Experimental and Theoretical-Studies on the Homoconjugation in Bicyclic Carbenium and Oxonium Ions in the Gas-Phase

Abstract Gas phase basicities and ab initio MO calculations show that non-vertical stabilization by the double bond in substituted 7-norborn-2-enyl and 7-noborna-2-dienyl cations remarkably decreases compared to the unsubstituted compounds.

Growth, microstructure and sintering behavior of nanosized silicon powders

Abstract The growth and properties of nanosized silicon particles produced by gas-phase reaction in a low-pressure silane plasma has been studied. In situ ion-mass spectroscopy and Mie scattering measurements were used to monitor the formation of powders. High resolution transmission electron microscopic (HREM) studies confirmed the observations made by Raman spectroscopy that the nanoparticles grow from medium range ordered clusters. Onset of crystallization was ∼ 700°C when structures ranging from very small crystalline ordered regions of 2.5–3.5 nm in size to fast-grown multiply twinned crystallites were formed. Size and surface roughness of the as-prepared powders were widely preserved throughout all stages of heating. It was observed that the powder morphology influences the sintering behavior. Silicon clusters which are formed during the powder synthesis acted as seeds for the crystallization process which led to the formation of polycrystalline particles. Classical sintering models offer inadequate explanation of sintering behavior, but hard-core/sinterable coating or particle sliding models can explain the sintering rate of this powder satisfactorily.

Origine et structure d'ions C4H9O+ issus de la methylation de l'acetone par l'iodomethane ionise

Abstract Electron impact ionization of a mixture of acetone and iodomethane in a high-pressure ion source induces the protonation of acetone and also the methylation yielding C 4 H 9 O + ( m/z 73) ions. The analysis of the collisional activation spectra of these ions and appropriate deuterium labelled analogues indicates the formation of dimethylmethoxycarbenium ions, a . These ions are also formed by protonation of 2-methoxypropene; however, depending upon the experimental conditions, an isomeric methyl-2-propenyl-oxonium species, b , was also detected. Ion cyclotron resonance experiments show that the C 4 H 9 O + ions are formed by methyl cation transfer from the molecular ions of iodomethane; dimethyliodonium ions (CH 3 ) 2 I + were found to be unreactive. The gas-phase basicity of 2-methoxypropene has also been measured (206.2±0.2 kcal mol −1 ) and indicates preferential protonation of the double bond to give the carbenium ions a . These results are supported by ab initio molecular orbital calculations (3–21 G) which show that ion a is more stable than b by 18 kcal mol −1 . The proposed existence of hydrogen-bonded molecule pairs of the kind propyne-H + −methanol, c , is also supported by calculations.