4 research outputs found
RevĂȘtements UV-aqueux pour le bois renforcĂ©s par la Cellulose Nano-Cristalline
La prĂ©sente thĂšse vise Ă augmenter la performance de revĂȘtements UV-aqueux pour le bois, en utilisant la ressource forestiĂšre. Dans ce but, nous pensons remplacer les nanoparticules Ă©tudiĂ©es prĂ©cĂ©demment par de la cellulose nanocristalline (CNC), un produit canadien et quĂ©bĂ©cois, issu de la forĂȘt. Il existe plusieurs cas dans la littĂ©rature de composites de nanocellulose-thermoplastique, mais il y a peu d'Ă©tudes sur les revĂȘtements renforcĂ©s par des CNC. L'un des aspects clĂ©s de la technologie des nanocomposites reste la dispersion des nanoparticules dans la matrice. Pour quantifier la qualitĂ© de la dispersion, des mĂ©thodes efficaces de caractĂ©risation sont nĂ©cessaires. Dans cette thĂšse, deux nouvelles mĂ©thodes de caractĂ©risation basĂ©es sur la microscopie Ă force atomique et la rĂ©trodiffusion de la lumiĂšre laser (He-Ne 632,8 nm) sont appliquĂ©es pour caractĂ©riser ces revĂȘtements nanocomposites. Une forte corrĂ©lation entre la nano-rugositĂ© de surface du revĂȘtement et la distribution angulaire de la lumiĂšre du laser rĂ©trodiffusĂ©e a Ă©tĂ© constatĂ©e. L'objectif gĂ©nĂ©ral de cette recherche est de dĂ©velopper des revĂȘtements UV-aqueux renforcĂ©es par les nanoparticules pour les applications sur le bois, et d'Ă©tudier l'effet, principalement sur les propriĂ©tĂ©s d'usure, des revĂȘtements composites. Les CNC ont Ă©tĂ© mĂ©langĂ©es Ă la formulation de revĂȘtements dans le but d'amĂ©liorer les propriĂ©tĂ©s mĂ©caniques des revĂȘtements secs. Les formulations de revĂȘtements ont Ă©tĂ© pulvĂ©risĂ©es sur des planches d'Ă©rable Ă sucre, qui ont Ă©tĂ© ensuite placĂ©es dans un four pour Ă©vaporer l'eau et cuire le revĂȘtement par rayonnement UV. Les CNC ont Ă©tĂ© modifiĂ©es soit par les bromures d'ammonium quaternaire alkylĂ©s ou le chlorure d'acryloyle. Les propriĂ©tĂ©s mĂ©caniques (rĂ©sistances Ă lâabrasion et Ă©gratignure, la duretĂ© et lâadhĂ©rence) ont Ă©tĂ© analysĂ©es et comparĂ©es Ă celles des vernis de rĂ©fĂ©rence sans nanoparticules. L'ajout de la CNC modifiĂ©e dans les revĂȘtements UV-aqueux a entraĂźnĂ© une augmentation de 30-40% de la rĂ©sistance Ă l'usure (abrasion et Ă©gratignure), sans perte d'apparence. Ces revĂȘtements sur substrat de bois, avec et CNC ajoutĂ©e, ont Ă©tĂ© soumis Ă un vieillissement accĂ©lĂ©rĂ© pendant 1200 h. Les rĂ©sultats montrent que lâajout de CNC dans les revĂȘtements non seulement augmente les propriĂ©tĂ©s mĂ©caniques, mais augmente Ă©galement la stabilitĂ© de la couleur des bois ainsi peints.This thesis is aimed to increase the performance of UV - waterborne coatings for wood, using the forest resources. For this purpose, we believe replacing nanoparticles studied previously by the cellulose nanocrystals (CNC), a Canadian and Quebec product from the forest. There are several instances in the literature of nanocellulose-thermoplastic composites, but there are few studies on coatings reinforced by CNC. One of the key aspects in the technology of nanocomposites remains the dispersion of the nanoparticles within the matrix. To quantify the dispersion, efficient methods of characterization are needed. In this thesis two new characterization methods based on atomic force microscopy and back scattering of laser light (He-Ne 632.8 nm) are applied to characterize such nanocomposite coatings. A strong correlation between surface nano-roughness of coatings and angular distribution of backscattered laser light was found. The overall objective of the research is to develop nanoparticles reinforced UV-water-based coatings for wood applications, and to study the effect mainly on wear properties of the final composite coatings. CNC were mixed to the coating formulation in order to improve the mechanical properties of the coatings. The coating formulations were sprayed on sugar maple boards, which were then placed in an oven to evaporate the water to finally be UV-cured. CNC was modified by either alkyl quaternary ammonium bromides or acryloyl chloride. The mechanical properties (abrasion and scratch resistances, hardness and adhesion) were analyzed and compared to the reference varnish without nanoparticles. The modified CNC addition in UV-water-based coatings results in a ca 30 - 40% increase in wear resistance (abrasion and scratch), without any loss of appearance. These coatings on wood substrate, with and without added CNC, were submitted to accelerated weathering during 1200 h. The results show that the addition of CNC to coatings not only increases mechanical properties but also increases color stability of coated wood
Progress towards slice emittance measurements at PITZ
Transverse emittance is one of the most important properties for high-brightness electron beams used for X-Ray free-electron lasers. The photo injector test facility at DESY in Zeuthen (PITZ) focuses on the development of high-brightness electron sources. The two main methods to measure the emittance are the quadrupole scan and the slit scan. Combining either of these methods with a transverse deflecting cavity allows the measurement of the slice emittance. At PITZ, space-charge effects at the low beam momentum of 24 MeV/c complicate in particular the quadrupole scan. This has to be considered in the emittance measurements. First slit-scan based slice emittance results will be shown next to studies on the beam transport for quadrupole scans