Synthesis of anatase TiO2 supported on porous solids by chemical vapor deposition

Coating anatase TiO2 onto three different particle supports, activated carbon (AC), gamma -alumina (Al2O3) and silica gel (SiO2), by chemical vapor deposition (CVD) was studied. The effect of the CVD synthesis conditions on the loading rate of anatase TiO2 was investigated. It was found that introducing water vapor during CVD or adsorbing water before CVD was crucial to obtain anatase TiO2 on the surface of the particle supports. The evaporation temperature of precursor, deposition temperature in the reactor, flow rate of carrier gas, and the length of coating time were also important parameters to obtain more uniform and repeatable TiO2 coating. High inflow precursor concentration, high CVD reactor temperature and long coating time tended to cause block problem. Coating TiO2 onto small particles by CVD involved both chemical vapor deposition and particle deposition. It was believed that the latter was the reason for the block problem. In addition, the mechanism of CVD process in this study included two parts, pyrolysis and hydrolysis, and one of them was dominant in the CVD process under different synthesis route. Among the three types of materials, silica gel, with higher surface hydroxyl groups and macropore surface area, was found to be the most efficient support in terms of both anatase TiO2 coating and photocatalytic reaction. (C) 2001 Elsevier Science B.V. All rights reserved.

Modifying fish gelatin electrospun membranes for biomedical applications: cross- linking and swelling behavior

Development of suitable membranes is a fundamental requisite for tissue and biomedical engineering applications. This work presents fish gelatin random and aligned electrospun membranes cross-linked with glutaraldehyde (GA). It was observed that the fiber average diameter and the morphology is not influenced by the GA exposure time and presents fibers with an average diameter around 250 nm. Moreover, when the gelatin mats are immersed in a phosphate buffered saline solution (PBS), they can retain as much as 12 times its initial weight of solution almost instantaneously, but the material microstructure of the fiber mats changes from the characteristic fibrous to an almost spherical porous structure. Cross-linked gelatin electrospun fiber mats and films showed a water vapor permeability of 1.37 ± 0.02 and 0.13 ± 0.10 (g.mm)/(m2.h.kPa), respectively. Finally, the processing technique and cross-linking process does not inhibit MC-3T3-E1 cell adhesion. Preliminary cell culture results showed good cell adhesion and proliferation in the cross-linked random and aligned gelatin fiber mats.

Solubility of Ethene in Water and in a Medium for the Cultivation of a Bacterial Strain

The solubility of ethene in water and in the fermentation medium of Xanthobacter Py(2) was determined with a Ben-Naim-Baer type apparatus. The solubility measurements were carried out in the temperature range of (293.15 to 323.15) K and at atmospheric pressure with a precision of about +/- 0.3 %. The Ostwald coefficients, the mole fractions of the dissolved ethene, at the gas partial pressure of 101.325 kPa, and the Henry coefficients, at the water vapor pressure, were calculated using accurate thermodynamic relations. A comparison between the solubility of ethene in water and in the cultivation medium has shown that this gas is about 2.4 % more soluble in pure water. On the other hand, from the solubility temperature dependence, the Gibbs energy, enthalpy, and entropy changes for the process of transferring the solute from the gaseous phase to the liquid solutions were also determined. Moreover, the perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS) model was used for the prediction of the solubility of ethene in water. New parameters, k(ij), are proposed for this system, and it was found that using a ky temperature-dependent PC-SAFT EOS describes more accurately the behavior solubilities of ethene in water at 101.325 kPa, improving the deviations to 1 %.

Effect of argon ion energy on the performance of silicon nitridemultilayer permeation barriers grown by hot-wire CVD on polymers

One of the authors (S.M.) acknowledges Direction des Relations Extérieures of Ecole Polytechnique for financial support.

Flexible organic–inorganic hybrid layer encapsulation for organic opto-electronic devices

In this work we produce and study the flexible organic–inorganic hybrid moisture barrier layers for the protection of air sensitive organic opto-electronic devices. The inorganic amorphous silicon nitride layer (SiNx:H) and the organic PMMA [poly (methyl methacrylate)] layer are deposited alternatingly by using hot wire chemical vapor deposition (HW-CVD) and spin-coating techniques, respectively. The effect of organic–inorganic hybrid interfaces is analyzed for increasing number of interfaces. We produce highly transparent (∼80% in the visible region) hybrid structures. The morphological properties are analysed providing a good basis for understanding the variation of the water vapor transmission rate (WVTR) values. A minimum WVTR of 4.5 × 10−5g/m2day is reported at the ambient atmospheric conditions for 7 organic/inorganic interfaces. The hybrid barriers show superb mechanical flexibility which confirms their high potential for flexible applications.

A double layer model of the gas bubble/water interface

Zeta potential is a physico-chemical parameter of particular importance to describe sorption of contaminants at the surface of gas bubbles. Nevertheless, the interpretation of electrophoretic mobilities of gas bubbles is complex. This is due to the specific behavior of the gas at interface and to the excess of electrical charge at interface, which is responsible for surface conductivity. We developed a surface complexation model based on the presence of negative surface sites because the balance of accepting and donating hydrogen bonds is broken at interface. By considering protons adsorbed on these sites followed by a diffuse layer, the electrical potential at the head-end of the diffuse layer is computed and considered to be equal to the zeta potential. The predicted zeta potential values are in very good agreement with the experimental data of H-2 bubbles for a broad range of pH and NaCl concentrations. This implies that the shear plane is located at the head-end of the diffuse layer, contradicting the assumption of the presence of a stagnant diffuse layer at the gas/water interface. Our model also successfully predicts the surface tension of air bubbles in a KCl solution. (c) 2012 Elsevier Inc. All rights reserved.

The stable hydrogen and oxygen isotope variation of water stored in polyethylene terephthalate (PET) bottles

A set of bottled waters from a single natural spring distributed worldwide in polyethylene terephthalate (PET) bottles has been used to examine the effects of storage in plastic polymer material on the isotopic composition (delta(18)O and delta(2)H values) of the water. All samples analyzed were subjected to the same packaging procedure but experienced different conditions of temperature and humidity during storage. Water sorption and the diffusive transfer of water and water vapor through the wall of the PET bottle may cause isotopic exchange between water within the bottle and water vapor in air near the PET-water interface. Changes of about +4 parts per thousand for delta(2)H and +0.7 parts per thousand for delta(18)O have been measured for water after 253 days of storage within the PET bottle. The results of this study clearly indicate the need to use glass bottles for storing water samples for isotopic studies. It is imperative to transfer PET-bottled natural waters to glass bottles for their use as calibration material or potential international working standards. Copyright (C) 2008 John Wiley & Sons, Ltd.

Stable O and H isotopic composition of hydrous minerals as proxies for paleoclimate and -topography : application to the European Alps

The isotopie composition of clay minerals can be used to gain information on paleoaltitude, -topography and -climate during the time of their formation, as they form in isotopie equilibrium with ambient water, which has an isotopie composition that is determined by previous rain-out. In this thesis, the usability of this approach is evaluated for sample material from both the North Alpine Foreland Basin and internal parts of the European Alps. The isotopie composition of precipitation is determined by the air temperature and the extent of previous rain-out, which in turn is affected by the distance to the point of origin of the water vapor and the condensation conditions. An orographic barrier leads to uplift and adiabatic cooling of air masses and thereby enhances rainfall with a characteristic depletion in heavy 0 and H isotopes. Processes such as evaporation and mixing of water with different origin affect the isotopie composition further on the surface. Clay minerals are hydrous phyllosilicates that can form during weathering or pedogenesis in isotopie equilibrium with the present water and inherit its isotopie composition with a characteristic fractionation. If their isotopie composition was preserved after formation and the necessary parameters are known, it is possible to calculate the isotopie composition of the ambient water and thereby reconstruct climatic and topographic conditions during their formation. Due to the hygroscopic behavior of the sample material, analytical procedures needed to be modified to allow an analysis of the oxygen and hydrogen isotopie composition of the hydroxyl water built into their crystal structure and not the one of recently adsorbed water. In order to determine typical 5lsO and 8D values of meteoric water and minerals in the weathering environment in high Alpine regions, samples of surface water and soils from the valley of Visp in the Swiss Alps were studied that were collected along a transect with varying altitudes and host rock lithologies. The actual aim to attempt the reconstruction of Alpine paleoelevations was addressed by the analysis of sediments deposited under marine and terrestrial conditions during the Miocene and Oligocene, which were sampled from different locations in Switzerland, Germany and Austria. Further bentonite and fault gouge clay samples were used as reference material from low and high elevations. Results show that the isotopie composition of clay minerals can be influenced by several factors, such as the mode and site of their formation, possible isotope exchange (which is evident for 8D values), the samples' mineral composition (such as the presence of detrital material) and the deposition environment. With a consideration of these parameters and limitation to certain sample material, conclusions are drawn on the isotopie composition of the water from which the clay minerals formed. Most of the obtained values lie in the same range as has been reported in literature for foreland precipitation. The reconstruction of paleoelevation might be possible for selected sites with a geographical setting close to the Alpine chain or for intramontane basins. - La composition isotopique des argiles, qui se forment typiquement en contact avec des eaux superficielles, peut être utilisée pour obtenir des informations sur la paléoaltitude, la paléotopographie et le paléoclimat pendant leur création. La composition en isotopes stable (oxygène et hydrogène) des eaux de pluie est déterminée par l'altitude, la température, la distance depuis le lieu d'évaporation et par le taux de précipitation. Certains processus comme l'évaporation, l'interaction avec des minéraux et le mélange d'eaux d'origines variées peuvent aussi changer la composition des eaux de surface. Les argiles sont des pliyllosilicates hydratés qui sont crées par l'altération des roches au contact de ces eaux de surface et ils acquièrent une composition isotopique qui est soumise à un certain fractionnement. L'objectif de cette thèse est d'évaluer si l'effet de l'altitude des Alpes, est détectable dans la composition isotopique des sédiments du bassin d'avant-pavs pendant le Miocène. Après avoir établi la procédure analytique, des compositions isotopiques typiques de régions de hautes altitudes ont été determine sur les eaux de surfaces (rivières) et sur des échantillons de sols, le long d'une coupe dans la valée de Visp, dans les Alpes Suisses. Une reconstruction des paléoaltitudes Miocènes Alpines a ensuite été mené par l'analyse de sédiments marins et terrestres en utilisant des échantillons d'âges variés et provenant de Suisse, d'Allemagne et d'Autriche. Les résultats montrent que la composition isotopique des échantillons est impactée par de multiples facteurs, tels que le mode de et le lieu de formation. un possible échange isotopique tardif (surtout pour 5D). leur composition minéralogique et l'environnement de leur sédimentation. Après un examen prudent de ces paramètres, et en se limitant à un certain assortiment d'échatillons, on peut tirer des conclusions sur la composition isotopique des eaux originelles pour en déduire l'effet du climat et de la topographie.

Transepidermal water loss and resting energy expenditure in preterm infants.

Skin water loss of preterm infants, nursed naked in incubators under thermoneutral conditions, was assessed by a method based on the measurement of water vapor pressure gradient close to the skin surface. The corresponding skin evaporative heat loss was calculated using an energy equivalent of 0.58 kcal/g water vaporised. During the first 5 weeks of life, 128 sets of measurements were made on 56 infants whose gestational age ranged from 28 to 37 weeks. In the first week of life, infants of less than 30 weeks of gestation had substantially higher transepidermal water loss (TEWL) and skin evaporative heat loss (skin EHL) (41.5 +/- 11.5 g/kg X day TEWL; 24.1 +/- 6.5 kcal/kg X day skin EHL) than infants of 34 weeks and greater (11.1 +/- 4.1 g/kg X day; 6.4 +/- 2.4 kcal/kg X day). Infants of 30-33 weeks of gestation had intermediate values (22.4 +/- 7.6 g/kg X day; 13 +/- 4.4 kcal/kg X day). From the third week of life on, TEWL was similar for all preterm infants, i.e. 14.2 +/- 2.6 to 12.7 +/- 1.9 g/kg X day and corresponds to skin EHL of 8.2 +/- 1.5 to 7.4 +/- 1.1 kcal/kg X day. There was a significant inverse relationship between gestational age and TEWL and also between postnatal age and TEWL. In an additional group of 7 preterm infants (30-34 weeks of gestation, mean postnatal age of 21 +/- 9 days) transepidermal water loss and energy expenditure were measured simultaneously. The skin evaporative heat loss (8.8 +/- 2.5 kcal/kg X day) accounted for 17 +/- 5% of energy expenditure (53.3 +/- 4.1 kcal/kg X day). This study emphasizes that in infants of less than 30 weeks of gestation, the transepidermal water loss is of great importance and makes a major contribution to water and heat balances.

Influência do sulfato de condroitina na formação de filmes isolados de polimetacrilato: avaliação do índice de intumescimento e permeabilidade ao vapor d'água

Natural or modified chondroitin sulfate was incorporated in to polymethacrylate to obtain isolated films. The addition of polysaccharide to synthetic polymers occurred at different rates. Isolated films were micro and macroscopically characterized and swelling index and water vapor transmission were determined. Results indicated changed transparency and flexibility, coupled to their dependence on increase in polysaccharide concentration. A similar occurrence was reported in the permeability to water vapor and swelling degree. Films composed of modified chondroitin sulfate, 90:10 concentration, showed hydration levels, permeability and morphological properties which allow them to be applied as excipients in the development of new drug delivery systems.

Alteração do caráter hidrofílico de filmes de quitosana por tratamento de plasma de HMDS

Alteration in hydrophilicity feature of chitosan films by hexamethyldisilazane (HMDS) cold-plasma treatment is evaluated. All treated films were colorless and transparent with no apparent textural changes. The effect on surfaces was characterized through contact angle measurements, degree of swelling and water vapor permeation. A significant reduction in all of the hydrophilicity parameters was observed. It is assumed that the HMDS treatment forms nonpolar silicone type structures. The goal is to investigate the formation of a stable hydrophobic barrier in order to increase the chitosan films usefulness in packaging applications.

Estudo comparativo da caracterização de filmes biodegradáveis de amido de mandioca contendo polpas de manga e de acerola

Most compounds reinforcements have been used to improve thermals, mechanical and barrier properties of biopolymers films, whose performance is usually poor when compared to those of synthetic polymers. Biodegradables films have been developed by adding mango and acerola pulps in different concentrations (0-17,1% w/w) as antioxidants active compounds to cassava starch based biodegradable films. The effect of pulps was studied in terms of tensile properties, water vapor permeability, DSC, among other analysis of the films. The study demonstrated that the properties of cassava starch biodegradable films can be significantly altered through of incorporation mango and acerola pulps.

Propriedades físicas de filmes biodegradáveis à base de amido de mandioca, álcool polivinílico e montmorilonita

The objective of this work was to manufacture biodegradable films based on cassava starch, polyvinyl alcohol (PVA) and sodium montmorillonite (Na-MMT), using glycerol as a plasticizer. These films were characterized according to their microstructure, optical, mechanical, and barrier properties. The combination of starch-PVA-MMT resulted in films with a more homogeneous surface than starch films. The introduction of PVA into the starch matrix led to the formation of films with lower water vapor permeability (WVP), higher tensile strength and greater elongation. MMT was exfoliated in the films, resulting in greater stability for different relative humidities, lower WVP, higher resistance and lower flexibility.

BIOFILMS BASED ON CANIHUA FLOUR (Chenopodium Pallidicaule): DESIGN AND CHARACTERIZATION

This work aims to (1) produce and characterize the flour obtained from two varieties of canihua, cupi and illpa-inia, and (2) evaluate the ability of these flours to form biofilms. The flours produced contain proteins, starches, lipids, organic substances containing phenol groups, and high percentages of unsaturated fatty acids. Films produced from the illpa variety presented lower water vapor permeability and larger Young’s modulus values than the films formed from the cupi variety. Both films were yellowish and displayed a high light blocking ability (as compared with polyethylene films), which can be attributed to the presence of phenolic compounds. Furthermore, they showed lesser solubility and water permeability than other polysaccharide films, which may be the result of the higher protein (12%–13.8%) and lipid (11%) contents in canihua flours, as well as the formation of a larger number of S–S bonds. On the other hand, these films presented a single vitreous transition temperature at low temperatures (< 0 °C), crystallization of the A and Vh types, and an additional diffraction peak at 2 = 7.5º, ascribed to the presence of essential fatty acids in canihua flour. Canihua flour can form films with adequate properties and shows promise for potential applications in food packaging, because it acts as a good barrier to incident ultraviolet light.

Rasvankestävät paperit ja kartongit

Rasvankestävyydellä tarkoitetaan sitä, että materiaali hylkii tai kestää rasvaa tietyn ajan läpäisemättä sen pintaa. Rasvankestäviä papereita ja kartonkeja löytyy kaikkialta. Erilaiset ruuanvalmistuspaperit, kuten esimerkiksi leivinpaperi ja voipaperi, ovat rasvankestäviä. Myös pakkauksissa käytetään paljon rasvankestäviä papereita ja kartonkeja. Rasvankestäviltä tuotteilta vaaditaan erilaisia ominaisuuksia riippuen niiden käyttötarkoituksesta. Pakkausmateriaaleilta vaaditaan esimerkiksi lujuutta ja kestävyyttä fyysistä rasitusta, valoa, hajuja ja mikrobeja vastaan. Ruuanvalmistusmateriaaleilta vaaditaan puolestaan lujuutta ja kestävyyttä lämpöä, kosteutta ja fyysistä rasitusta vastaan. Rasvankestäviltä papereilta vaaditaan rasvankestävyyden lisäksi hyvää vetolujuutta, märkälujuutta ja hyviä optisia ominaisuuksia. Neliömassan tulee asettua 20─80 g/m2 välille ja metallipitoisuudet eivät saa olla liian korkeat. Myös tuotteiden kierrätettävyys on nostanut asemaansa viimeaikoina. Tuotteen tuotannon ja itse tuotteen ympäristöystävällisyys ovat todella arvostettuja kuluttajan, tuottajan, Suomen, EU:n ja koko maailman näkökulmista. Jotta tuotteesta saadaan rasvankestävää, vaaditaan siltä erilaisia barrier-ominaisuuksia. Rasvankestävällä paperilla vaaditaan hyviä barrier-ominaisuuksia esimerkiksi rasvan, ilman, veden, vesihöyryn sekä hapen läpäisevyyksissä. Rasvankestäviä papereita ja kartonkeja voidaan valmistaa kemiallisilla ja mekaanisilla tavoilla. Happokäsittely ja fluorokemikaalien lisääminen ovat kemiallisia tapoja, kun taas sellun jauhaminen pitkään matalassa lämpötilassa on mekaaninen tapa valmistaa rasvankestävää paperia. Näiden tapojen lisäksi rasvankestäviä papereita voidaan tehdä erilaisten pinnoitusten avulla. Erilaiset muovit ovat yleisemmin käytettyjä pinnoitemateriaaleja. Esimerkiksi PE- ja PET-päällysteet ovat käytettyjä rasvankestävissä tuotteissa. Viime aikoina on kehitetty paljon erilaisia biomateriaaleja, joista voidaan tehdä rasvankestävä pinnoite. Lipideistä, hydrokolloideista ja erilaisista komposiiteista voidaan luoda uusien tekniikoiden avulla rasvankestäviä pinnoitteita. Rasvankestävyydestä voidaan saada jonkinlainen käsitys WVTR-asteen, Cobb-arvon ja kontaktikulman mittausten avulla. Rasvankestävyyttä voidaan myös mitata erilaisten standarditestien avulla. TAPPI:lla, ISO:lla ja ASTM:llä on useita erilaisia standardeja. Lähes kaikissa rasvankestävyysstandardeissa tuloksen saaminen perustuu visuaaliseen havaintoon, mikä aiheuttaa välillä hankaluuksia tulosten luotettavuuteen, koska tuloksen määrittää ihmissilmä, ja kaikilla testin tekijöillä on erilainen silmä, joka aistii eri tavalla.