Enhanced photocatalytic activity of electrospun TiO2/polyacrylonitrile membranes in a crossflow reactor using dual lights

Photocatalytic membranes reactors have become one of the most efficient technologies to treat polluted waters. However, a major drawback is the unilateral irradiation of the membrane, where only one side of the membrane is exploited. To overcome this issue, we developed a reactor where the membrane can be irradiated on both sides. Polyacrylonitrile membranes containing different amounts of TiO2 nanoparticles up to 60% were first prepared by electrospinning. These membranes were used in a 3D-printed crossflow photocatalytic membrane reactor for the degradation of methylene blue under different combinations of lights. The use of both sides of the photocatalytic membrane significantly enhanced the photocatalytic activity for the decolorization of methylene blue in water. The prepared membranes showed the best decolorization rate for a loading of 60% of TiO2 and the use of dual ultraviolet lights, where the methylene blue solution was completely discolored after 90 min. This is the first report of a such system configuration, and this new irradiation concept is promising for photocatalytic membrane reactions and water cleaning.publishedVersio

3D-printed polyamide structures coated with TiO2 nanoparticles, towards a 360-degree rotating photocatalytic reactor

3D-printed polyamide structures coated with TiO2 nanoparticles were obtained by a simple impregnation method. This novel type of 3D reactor was evaluated for its photocatalytic activity towards the degradation of methylene blue under UV light using a 360-degree rotating stage. Rotation improved the photocatalytic activity under UV light for all the 3D structures. The best photocatalytic structure showed a 94.1 % methylene blue degradation, after 180 min under UV irradiation with 360-degree rotation.publishedVersio

Conductive epoxy/carbon nanofiber coatings for scale control

Calcium carbonate (CaCO3) is one of the most widespread scaling minerals and has been a long-standing problem within many industrial sectors. Scaling of calcium carbonate on conductive surfaces can be prevented electrochemically by anodic polarization. Anodic polarization, however, cannot be applied directly to metal surfaces like e.g., steel that will suffer from corrosion when polarized anodically in an aqueous environment. Thus, in this paper it is proposed to apply a conductive coating to a metal surface to allow anodic polarization and inhibit surface scaling, without corrosion of the underlying metal surface taking place. To this end an epoxy/carbon nanofiber conductive coating was developed and deposited at steel surfaces. The coating showed good adhesion to the surface and the bulk and surface resistivities were in the order of 52.80 kΩcm and 31.87 kΩ/cm2, respectively. The anti-scaling performance of the coating without- and under anodic polarization was tested upon exposure to 1.5 wt % CaCl2 solution being in contact with CO2. The coating has been tested at several different potentials to find optimal conditions for scale inhibition. Potentials above +3 VOCP caused a degradation of the coating due to oxygen evolution at the anode, as well as evolution of chlorine gas. At +1.5 and +2 VOCP the coating remained intact and the precipitation of CaCO3 was limited. On the other hand, cathodic polarization of the coating surface enhanced scaling and no coating degradation was observed at cathodic polarization even at potentials as high as -5 VOCP. The coating has thus proven a good solution to control surface scale deposition. Both anodic scale inhibition and cathodic scale acceleration have been achieved at the coating surfaces.publishedVersio

Study of materials and textile based on titanium dioxide for the photocatalytic degradation of chemical warfare agents

Nous cherchons ici, dans un premier temps, à optimiser les propriétés photocatalytiques de TiO2 pour la dégradation d'agents chimiques de guerre ou leurs simulants pour des longueurs d'onde appartenant au spectre du visible, permettant ainsi d'utiliser une grande partie du spectre solaire. Deux principales approches ont ainsi été développées: (i) une méthode de synthèse sol-gel de TiO2 de phases cristallographiques mixtes anatase/rutile (ii) L'utilisation de nanotubes de titanates couplés à un autre semi-conducteur, le WO3. L'activité photocatalytique de ces nanomatériaux unidimensionnels sous illumination solaire artificielle vis-à-vis de la dégradation sous flux du sulfure de diéthyle (simulant de l'ypérite) a montré une meilleure activité. Ces résultats sont le fruit d'une corrélation intime entre une grande surface spécifique, une absorption dans la partie visible du spectre solaire, une acidité de surface favorable et une limitation de la recombinaison des charges photogénérées. Par la suite, une dernière partie de cette étude visait le dépôt homogène des nanomatériaux sur des fibres textiles. Différentes techniques "classiques" ont été utilisés tel que le trempage dans une solution colloïdale ou encore le dépôt par spray à l'aide d'un pulvérisateur haute pression. Une étude plus innovante a été menée en utilisant une technique dite de multicouches utilisant l'alternance d'absorption d'un électrolyte cationique (polyéthylèneimine, PEI+) et de nanotubes de titanate / 4% WO3. Ces textiles ont ensuite été testés pour la dégradation de microgouttellettes de diméthyle méthylphosphonate (simulant des organophosphonates) sous illumination solaire. L'ajout de ce photocatalyseur a permis d'augmenter d'un facteur trois à quatre l'activité de dégradation totale de l'agent chimique en contact avec le textile fonctionnalisé. Nous avons ainsi pu obtenir une dégradation complète de l'agent toxique en quelques minutes (entre 7 et 10min), éliminant ainsi toute la toxicité présente sur le textile.We report on the photocatalytic degradation of chemical warfare (CW) agents and simulants using different types of template-assisted TiO2 rutile-based nanomaterials and nanoscale tubular titanate-based structures. Decontamination of paints, fabrics or textiles contaminated by chemical warfare agents is of great importance for application in the civil, military as well as counterterrorism fields, and therefore the search for self-decontaminating paints and textiles if of high interest. DMMP (dimethylmethylphosphonate), DES (diethylsulfur), and yperite were used as chemical simulants and real chemical agents, respectively. Different methods for covering and anchoring photocatalytic nanomaterials on textiles or paints substrates were discussed and compared, such as spraying, dip-coating and the Layer-by-Layer method, from a material aspect with bulk and surface characterization techniques as well as from a kinetic and reactivity point of view. Efficient UVA- and solar light-activated chemical warfare degradation have been obtained on paints and textiles covered by photocatalytic nanoparticles. Results on chemical simulants and real chemical warfare agents are compared, and some kinetics of chemical degradation detailed, allowing paints and textiles to exhibit global self-decontaminating properties

Study of materials and textile based on titanium dioxide for the photocatalytic degradation of chemical warfare agents

Nous cherchons ici, dans un premier temps, à optimiser les propriétés photocatalytiques de TiO2 pour la dégradation d'agents chimiques de guerre ou leurs simulants pour des longueurs d'onde appartenant au spectre du visible, permettant ainsi d'utiliser unWe report on the photocatalytic degradation of chemical warfare (CW) agents and simulants using different types of template-assisted TiO2 rutile-based nanomaterials and nanoscale tubular titanate-based structures. Decontamination of paints, fabrics or te

3D-printed polyamide structures coated with TiO2 nanoparticles, towards a 360-degree rotating photocatalytic reactor

3D-printed polyamide structures coated with TiO2 nanoparticles were obtained by a simple impregnation method. This novel type of 3D reactor was evaluated for its photocatalytic activity towards the degradation of methylene blue under UV light using a 360-degree rotating stage. Rotation improved the photocatalytic activity under UV light for all the 3D structures. The best photocatalytic structure showed a 94.1 % methylene blue degradation, after 180 min under UV irradiation with 360-degree rotation

Cool coatings with high near infrared transmittance for coil coated aluminium

The temperature of a surface that is exposed to sunlight is influenced by the solar reflectance and the infrared emittance of the surface. A coating that reduces the surface temperature is often referred to as a cool coating. Cool coatings on building surfaces have several potential benefits, such as reduction of energy needed for cooling, improved thermal comfort, and mitigation of the urban heat island effect. In addition to low weight, aluminium is a metal that is known for its excellent reflectance properties. Recycled aluminium is now increasingly requested by the building market, both due to reduced cost as well as for environmental considerations. For building applications, surface treatments and coatings that completely hide the aluminium substrate are needed in order to obtain an attractive appearance, good corrosion properties and overall protection against outdoor environments. We see a need for a low-cost approach that can be used to obtain a cool coating on aluminium sheet. For this we have developed several different one-layer coating systems that can be applied in a coil-coating process. A total of 8 different coloured pigments with low absorption in the near infrared have been investigated with the goal to make cool coatings with various desirable colours. The coated surfaces achieved high solar reflectance by utilizing the excellent reflectance properties of the aluminium substrate. Good hiding of the substrate in the visible range and high infrared emittance has also been obtained. The colours include black and different shades of red, orange and yellow. Solar reflectance spectra and infrared reflectance spectra have been measured. From these spectra, optical properties of the coated surface such as total solar reflectance (TSR), infrared emittance and solar reflectance index (SRI) have been calculated. In addition, we also present results from weathering testing of the coated materials. The results show that the one-layer approach can be used to obtain cool coatings with high near infrared transmittance that are feasible to apply in a coil coating process.publishedVersio

Nano Insulation Materials Exploiting the Knudsen Effect

As the world's focus is turned even stronger toward miscellaneous energy efficiency and saving aspects, the development of new high-performance thermal insulation materials for building applications will play an important role in this regard. The aim of the presented study is to develop an understanding for the governing thermal transport mechanisms and utilize the Knudsen effect in nanoporous insulation materials through theoretical concepts and experimental laboratory explorations, thus being able to synthesize nano insulation materials (NIM) with very low thermal conductivity values as a major goal. NIMs based on hollow silica nanospheres (HSNS) have been synthesized by a sacrificial template method, where the idea is that the heat transport by gas conductance and gas/solid state interactions decreases with decreasing pore diameters in the nano range as predicted by the Knudsen effect. HSNS with reduced thermal conductivity compared to their solid counterparts have been prepared where the hollow sphere cavities and voids between the spheres are filled with air at atmospheric pressure, i.e. eliminating the need for various measures like e.g. protective metallized foils to maintain a vacuum or expensive low-conducting gases in the cavities and voids. Hence, HSNS represent a promising stepping-stone toward the future high-performance thermal insulation materials.publishedVersio

Nano Insulation Materials Exploiting the Knudsen Effect

As the world's focus is turned even stronger toward miscellaneous energy efficiency and saving aspects, the development of new high-performance thermal insulation materials for building applications will play an important role in this regard. The aim of the presented study is to develop an understanding for the governing thermal transport mechanisms and utilize the Knudsen effect in nanoporous insulation materials through theoretical concepts and experimental laboratory explorations, thus being able to synthesize nano insulation materials (NIM) with very low thermal conductivity values as a major goal. NIMs based on hollow silica nanospheres (HSNS) have been synthesized by a sacrificial template method, where the idea is that the heat transport by gas conductance and gas/solid state interactions decreases with decreasing pore diameters in the nano range as predicted by the Knudsen effect. HSNS with reduced thermal conductivity compared to their solid counterparts have been prepared where the hollow sphere cavities and voids between the spheres are filled with air at atmospheric pressure, i.e. eliminating the need for various measures like e.g. protective metallized foils to maintain a vacuum or expensive low-conducting gases in the cavities and voids. Hence, HSNS represent a promising stepping-stone toward the future high-performance thermal insulation materialspublishedVersio

Development of Al-TiC Wire Feedstock for Additive Manufacturing by Metal Screw Extrusion

The development of customised aluminium alloys for welding and additive manufacturing (AM) is proposed to solve several quality issues and to enhance the mechanical integrity of components. The introduction of ceramic grain refining agents shows great potential as alloy addition as to limit cracking susceptibility and increase the strength. Thus, a versatile solid-state manufacturing route for nanoparticle reinforced aluminium wires has been developed based on the metal screw extrusion principle. In fact, the Al-Si alloy AA4043 mixed with 1 wt.% TiC nanoparticles has been manufactured as a wire. The accumulated strain on the material during metal screw extrusion has been estimated, classifying the process as a severe plastic deformation (SPD) method. A chemical reaction between silicon and TiC particles after metal screw extrusion was found, possibly limiting the grain refining effect. Electric arc bead-on-plate deposition was performed with metal screw extruded and commercial material. The addition of TiC induced a grain morphology transition from columnar to equiaxed after electric arc deposition, and increased the hardness. A high amount of porosity was found in the AA4043-TiC material, probably arising from hydrogen contamination on TiC surfaces prior to metal screw extrusion. The results are encouraging as a new direction for aluminium alloy development for additive manufacturing.publishedVersio