This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 within the LDRD program.

1. Préparation de Polisseuse et lisier Première préparer le système de polissage Convergent (spécifiquement appelé C onvergent, je préside d&#39;abord surface indépendant, S Ingle itération, R ogue Polisseuse de particules libres ou CISR (prononcé &#39;ciseaux&#39;)) 7,17 en installant le pad &amp; septum, conditionné le pad, dilution et de stabilisation chimique de la suspension, la suspension et l&#39;incorporation dans le système de filtration. <ol><li> Sur le polisseur de CISR, respecter un tampon de polyuréthane sur la base de granit tour. Adhérer pad une première arête et appliquer une pression dans la direction du bord opposé à réduire les écarts de l&#39;air. Coupez le pad en surplomb, puis utiliser une lame de rasoir et le rouleau à la perforation et éliminer les bulles d&#39;air si nécessaire. </li><li> Pour la première utilisation et après chaque ~ 100 hr de polissage, l&#39;état de diamant le pad en utilisant un diamant conditionneur CMP (de 50 mm de diamètre; 0,6 psi pression appliquée; 5 min séjour à chaque emplacement de tour radiale avec des incréments d&#39;espacement de 25 mm; genoux rotation 25 tours) avec de l&#39;eau DI fluide. </li><li> Entre itérations de polissage, enlever les boues et produits en verre résiduels du tampon en utilisant un nettoyeur à ultrasons in situ (~ 2 min arrêt sur ​​chaque emplacement radial; genoux rotation 5 rpm) avec de l&#39;eau qui coule de DI. </li><li> Sur le poids de la cloison de forme unique, respecter ruban adhésif double face de mousse puis le matériau du septum (par exemple, le verre pré-coupés ou autre matériau non-port). Coupez tout ruban de mousse en surplomb pour épouser la forme de la matière du septum et le poids. Remarque la conception du septum (à la fois de forme et de poids) change pour différentes tailles de la pièce et genoux 7,17. </li><li> Préparer suspension de polissage à Baume 4 concentration (spécifiquement mélanger en volume ~ 1 partie d&#39;oxyde de cérium suspension de polissage et ~ 9 parties déminéralisée (DI) de l&#39;eau dans un 11 L buprise située). Vérifiez Baume utilisant un flotteur Baume. Ajouter ~ 5 ml de KOH (10 M) pour ajuster le pH à 9,5 et ajouter 120 ml (~ 1 vol%) de tensioactif exclusive 19. Réajuster le pH et Baume toutes les 24 h de polissage. </li><li> Installation de godet avec la suspension préparée dans un système de filtration. Puis installer les filtres de particules souhaitées CMP dans le système de filtration. Soit suspension recirculation dans le système de filtration pendant plusieurs heures. </li><li> Distribution de la taille des particules mesure de la suspension (par exemple, en utilisant une seule particule de techniques de détection optique) afin d&#39;assurer la fin de la queue de la distribution est adéquatement 9,20 voyous sans particules. </li></ol> 2. Préparation de la pièce (Eau-forte et blocage) Avant le polissage, gravure chimique de la pièce finement broyée telle que reçue de réduire la quantité d&#39;enlèvement de matière nécessaire pour éliminer le sous-surface de meulage dommages 21. Ensuite, bloquer la pièce à usiner (si le rapport d&#39;aspect (ce est à dire, le rapport longueur / épaisseur) est&gt; 10) en utilisant une nouvelle technique de tangage bouton de blocage (PBB) pour empêcher la pièce de blocage au cours de la flexion et de polissage 22. <ol><li> Graver la pièce de terre fine (spécifiquement un 265 x 265 x 8 mm 3 verre de silice fondue plat) dans un réservoir rempli avec HF: NH 4 F (6: 1 gravure d&#39;oxyde tamponnée (BOE) 3x dilué avec de l&#39;eau déminéralisée) pendant 6 heures enlever 10 um de verre de la surface de la pièce. ATTENTION! BOE est extrêmement dangereux; porter un équipement de protection individuelle (EPI). Retirer la pièce à partir du réservoir de gravure et rincer agressivement la pièce avec de l&#39;eau DI et laisser la pièce sécher à l&#39;air verticalement. </li><li> Inspectez la pièce pour les dommages profonde pendant le broyage à l&#39;aide d&#39;une inspection de lumière dans une pièce sombre. Si aucun dommage profonde se trouve, passez à l&#39;étape suivante, sinon envoyer pièce arrière pour re-broyage. </li><li> Chauffer bloquant pas dans un pistolet à colle pour ~ 95 ºC et placer gouttelettes (également appelés boutons) de hauteur (~ 0,06 g) sur la face de laplaque de blocage dans une matrice 9 x 9 (81 boutons avec un espacement de 26 mm). Pour différentes pièces de taille, reportez-vous à concevoir des règles pour le nombre idéal, la taille, et les espacements de touche de pas 22. Placer la plaque de blocage avec les boutons appliqués face vers le haut dans un four préchauffé à 70 ºC. </li><li> Appliquer du ruban à la face de la pièce qui ne est pas d&#39;être poli. Éviter de générer des bulles d&#39;air ou excessivement étirer la bande. </li><li> Placez la pièce avec la face latérale de la bande vers le bas sur les boutons sur la plaque de blocage dans le four. Couvrir la pièce-button-bloc pour minimiser le flux de convection. Après 1,5 h, régler le four à refroidir à 10 ° C / h à la température ambiante. Après refroidissement, l&#39;épaisseur de pas sur la pièce à usiner doit être bloqué ~ 1 mm. </li></ol> 3. Convergent Polissage <ol><li> Tournez sur le système de l&#39;humidité dans la chambre de l&#39;environnement CISR polisseuse pour éviter la suspension de sécher pendant le polissage et de minimiser les particules voyous de rayer la pièce. </li><li> Insde hauteur et monter la cloison spécialement conçu et préparé dans polisseuse. Installez PBB pièce dans CISR polisseuse et de la flèche inférieure pour maintenir la pièce. </li><li> Pièce polonaise sur CISR pendant 4 heures à un tour et la pièce taux de rotation apparié de 25 tours par minute avec une course radiale de ~ 75 mm et avec un débit de suspension à partir du système de filtration de 1 gal / min. REMARQUE: La plaque de blocage sert également de poids de charge sur la pièce à usiner correspondant à 0,6 psi pression appliquée. </li><li> Éteignez genoux et la pièce de rotation et le débit de boue. Retirer PBB pièce du CISR polisseuse et plonger dans l&#39;eau DI rempli bain. Essuyez la surface de la pièce avec un chiffon de salle blanche tout submergé. Retirer PBB pièce du bain et pulvériser rincer à l&#39;eau DI. </li><li> Deblock pièce en insérant une cale à l&#39;interface pièce-bloc. Retirer le ruban de la surface de la pièce. Rincez avec de l&#39;eau agressive pièce de DI et l&#39;air sec. </li><li> PBB la face opposée de la pièce comme décrit au paragraphe 2. Ensuite, répétez poinstituant procédure décrite à la section 3. </li></ol> 4. métrologie et d&#39;inspection <ol><li> Mesure de front d&#39;onde réfléchie (ce est-chiffre de la surface) des deux faces de la pièce ainsi que front d&#39;onde transmis à l&#39;aide d&#39;un interféromètre. </li><li> Mont pièce sur la station d&#39;inspection de la lumière vive et mesurer les propriétés de zéro / DIG utilisant des méthodes standards de fabrication optique. Une gravure de BOE courte de la pièce, comme décrit dans l&#39;étape 2.1, peut être utilisé pour exposer rayures cachés pour des pièces utilisées dans les applications laser de haute fluence. Pour la mesure de fines rayures ou la rugosité sur la pièce, la microscopie optique standard ou interférométrie en lumière blanche peuvent être utilisés. </li><li> Magasin terminé pièce dans un contact de minimisation de conteneurs avec la face de la pièce. </li></ol>

<ol>
	<li>Anderson, D., Burge, J., Thompson, B., Malacara, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ch+28.+Handbook+of+optical+engineering.">Ch 28. Handbook of optical engineering.</a> Optical fabrication. , (2001).</li><li>Karow, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fabrication Methods for Precision Optics. , (1993).</li><li>Brown, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+short+course+in+optical+fabrication+technology.">A short course in optical fabrication technology.</a> , (1981).</li><li>Cook, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+processes+in+glass+polishing.">Chemical processes in glass polishing.</a> J. Non-Crystal. Solids. 120, 152-171 (1990).</li><li>Preston, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Structure+of+Abraded+Glass+Surfaces.">The Structure of Abraded Glass Surfaces.</a> Trans. Opt. Soc. 23 (3), 141-14 (1922).</li><li>Suratwala, T., Feit, M., Steele, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+Deterministic+Material+Removal+and+Surface+Figure+During+Fused+Silica+Pad+Polishing.">Toward Deterministic Material Removal and Surface Figure During Fused Silica Pad Polishing.</a> J. Am. Ceram. Soc. 93 (5), 1326-1340 (2010).</li><li>Suratwala, T., Steele, R., Feit, M., Desjardin, R., Mason, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Convergent+Pad+Polishing+of+amorphous+fused+silica.">Convergent Pad Polishing of amorphous fused silica.</a> International Journal of Applied Glass Science. 3 (1), 14-28 (2012).</li><li>Suratwala, T., Feit, M., Steele, R., Wong, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+Temperature+and+Material+Deposit+on+Material+Removal+Uniformity+during+Optical+Pad+Polishing.">Influence of Temperature and Material Deposit on Material Removal Uniformity during Optical Pad Polishing.</a> J. Am. Ceram. Soc. , (2014).</li><li>Suratwala, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscopic+removal+function+and+the+relationship+between+slurry+particle+size+distribution+and+workpiece+roughness+during+pad+polishing.">Microscopic removal function and the relationship between slurry particle size distribution and workpiece roughness during pad polishing.</a> J. Am. Ceram. Soc. 91 (1), 81-91 (2014).</li><li>Terrell, E., Higgs, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrodynamics+of+Slurry+Flow+in+Chemical+Mechanical+Polishing.">Hydrodynamics of Slurry Flow in Chemical Mechanical Polishing.</a> J. Electrochem. Soc. 153 (6), 15-22 (2006).</li><li>Runnels, S., Eyman, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tribology+Analysis+of+Chemical+MechanicalPolishing.">Tribology Analysis of Chemical MechanicalPolishing.</a> J. Electrochem. Soc. 141 (6), 1698-1701 (1994).</li><li>Park, S., Cho, C., Ahn, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrodynamic+Analysis+of+Chemical+Mechanical+Polishing+Process.">Hydrodynamic Analysis of Chemical Mechanical Polishing Process.</a> J. Tribology Int. 33, 723-730 (2000).</li><li>Luo, J., Dornfeld, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Abrasive+Size+Distribution+in+Chemical+Mechanical+Planarization:+Modeling+and+Verification.">Effects of Abrasive Size Distribution in Chemical Mechanical Planarization: Modeling and Verification.</a> IEEE T. Semicond. M. 16 (3), 469-476 (2003).</li><li>Luo, J., Dornfeld, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Material+Removal+Mechanism+in+Chemical+Mechanical+Polishing:+Theory+and+Modeling.">Material Removal Mechanism in Chemical Mechanical Polishing: Theory and Modeling.</a> IEEE T. Semiconduct. M. 14, 112-133 (2001).</li><li>Bastaninejad, M., Ahmadi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+the+Effects+of+Abrasive+Size+Distribution,+Adhesion,+and+Surface+Plastic+Deformation+on+Chemical+Mechanical+Polishing.">Modeling the Effects of Abrasive Size Distribution, Adhesion, and Surface Plastic Deformation on Chemical Mechanical Polishing.</a> J. Electrochem. Soc. 152 (9), 720-730 (2005).</li><li>Sampurno, Y., Sudargho, F., Zhuang, Y., Ashizawa, T., Morishima, H., Philipossian, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Cerium+Oxide+Particles+Sizes+in+Oxide+Chemical+Mechanical+Planarization.">Effect of Cerium Oxide Particles Sizes in Oxide Chemical Mechanical Planarization.</a> Electrochem. Solid State. 12 (6), 191-194 (2009).</li><li>Suratwala, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+and+system+for+Convergent+Polishing.">Method and system for Convergent Polishing.</a> US Provisional Patent Application. , (2011).</li><li>Suratwala, T., Feit, M., Steele, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apparatus+and+Method+for+Deterministic+Control+of+Surface+Figure+During+Full+Aperture+Polishing.">Apparatus and Method for Deterministic Control of Surface Figure During Full Aperture Polishing.</a> US Patent Application. US. , (2010).</li><li>Dylla-Spears, R., Feit, M., Miller, P., Steele, R., Suratwala, T., Wong, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+for+preventing+agglomeration+of+charged+colloids+without+loss+of+surface+activity.">Method for preventing agglomeration of charged colloids without loss of surface activity.</a> US Provisional Patent Application. , (2012).</li><li>Dylla-Spears, R., Wong, L., Miller, P., Feit, M., Steele, R., Suratwala, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Charged+Micelle+Halo+Mechanism+for+Agglomeration+Reduction+in+Metal+Oxide+Particle+Based+Polishing+Slurries.">Charged Micelle Halo Mechanism for Agglomeration Reduction in Metal Oxide Particle Based Polishing Slurries.</a> Colloid Surface A. 447, 32-43 (2014).</li><li>Wong, L., Suratwala, T., Feit, M., Miller, P., Steele, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Effect+of+HF/NH4F+Etching+on+the+Morphology+of+Surface+Fractures+on+Fused+Silica.">The Effect of HF/NH4F Etching on the Morphology of Surface Fractures on Fused Silica.</a> J. Non-Crystal. Solids. 355, 797 (2009).</li><li>Feit, M., DesJardin, R., Steele, R., Suratwala, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimized+pitch+button+blocking+for+polishing+high-aspect-ratio+optics.">Optimized pitch button blocking for polishing high-aspect-ratio optics.</a> Appl. Opt. 51 (35), 8350-8359 (2013).</li><li>Suratwala, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sub-surface+mechanical+damage+distributions+during+grinding+of+fused+silica.">Sub-surface mechanical damage distributions during grinding of fused silica.</a> J. Non-Crystal. Solids. 352, 5601 (2006).</li><li>Miller, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Distribution+of+Sub-surface+Damage+in+Fused+Silica.">The Distribution of Sub-surface Damage in Fused Silica.</a> SPIE. 5991, (2005).</li><li>Suratwala, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Rogue+particles+on+the+sub-surface+damage+of+fused+silica+during+grinding/polishing.">Effect of Rogue particles on the sub-surface damage of fused silica during grinding/polishing.</a> J. Non-Crystal. Solids. 354, 2003 (2008).</li><li>Suratwala, T., Miller, P., Ehrmann, P., Steele, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polishing+slurry+induced+surface+haze+on+phosphate+laser+glasses.">Polishing slurry induced surface haze on phosphate laser glasses.</a> J. Non-Crystal. Solids. 351, 2091-2101 (2004).</li></ol>

The authors have nothing to disclose.

Comme indiqué dans l&#39;introduction, la mise en œuvre réussie de Convergent polissage par rapport à la surface la figure consiste à éliminer ou réduire tous les phénomènes qui influencent spatiale non-uniformité du matériel, sauf que de la pièce tours disparité due à la forme de la pièce. Si l&#39;un de ces phénomènes ne est pas atténués de façon appropriée, soit par contrôle de processus ou par technique appropriée de la polisseuse, alors le point de convergence souhaitée ne peut être obtenu ...

Les principales étapes d&#39;un processus de fabrication optique typique comprennent façonnage, broyage, polissage pleine ouverture, et parfois petit outil de polissage 1-3. Avec la demande croissante pour des composants optiques de haute qualité pour les systèmes d&#39;imagerie et de laser, il ya eu des progrès importants dans la fabrication optique au cours des dernières décennies. Par exemple, la précision, l&#39;enlèvement de matière déterministe est maintenant possible au cours de la mise en forme et les processus de broyage des progrès dans la Computer Numerical machines de formage (CNC) de verre contrôlés. De même, les technologies de polissage petits outils (par exemple, commandé par ordinateur revêtement optique (CCOS), ions figurer, et la finition magnéto-rhéologique (MRF)) ont conduit à l&#39;enlèvement de matière déterministe et le contrôle de la figure de surface, donc un impact fortement l&#39;industrie de la fabrication optique. Cependant, l&#39;étape intermédiaire du processus de finition, complète le polissage d&#39;ouverture, manque encore élevé déterminisme, nécessitant généralement opticia qualifiéens pour effectuer multiple, souvent longues, cycles itératifs avec plusieurs changements de processus pour atteindre le chiffre de surface souhaitée 1-3. Le grand nombre de méthodes de polissage, les variables de processus et le produit chimique complexe et les interactions mécaniques entre la pièce, genoux et suspension 3-4 ont fait qu&#39;il est difficile de transformer polissage optique d&#39;un «art» à une science. Pour atteindre déterministe polissage pleine ouverture, le taux d&#39;enlèvement de matière doit être bien comprise. Historiquement, le taux d&#39;enlèvement de matière a été décrit par l&#39;équation Preston largement utilisé 5 <img alt="Equation 1" fo:content-width="1in" fo:src="/files/ftp_upload/51965/51965eqn1.jpg" src="/files/ftp_upload/51965/51965eqn1.jpg" width="100px" /> (1) où dh / dt est le taux moyen d&#39;élimination d&#39;épaisseur, p k est la constante Preston, σ o est-la pression appliquée, et V r est la vitesse relative moyenne entre la pièce et les genoux. La figure 1 illustre schématiquement les concepts physiques qui influent sur ​​le taux d&#39;enlèvement de matière tel que décrit l&#39;équation Preston, y compris les variations spatiales et temporelles de la vitesse et de la pression, les différences entre le la pression appliquée et la répartition de la pression que les des expériences de la pièce, et les effets de friction 6-8. En particulier, la distribution réelle de la pression subie par la pièce à usiner est régi par un certain nombre de phénomènes (décrits en détail ailleurs 6-8) qui affectent fortement résultant chiffre de surface de la pièce à usiner. En outre, dans l&#39;équation Preston, les effets au niveau microscopique et moléculaire sont essentiellement repliés l&#39;un dans l&#39;macroscopique Preston constante (k p), qui influe sur le taux global de matériau de suppression, la micro-rugosité, et même rayer sur la pièce. Diverses études ont élargi le modèle de Preston pour tenir compte<html> pour les interactions particules-pad-pièce lisier microscopique pour expliquer le taux d&#39;enlèvement de matière et microrugosité 9-16. Pour obtenir un contrôle déterministe de courbure de face complète pendant le polissage de l&#39;ouverture, chacune des phénomènes décrits ci-dessus doit être entendu, puis quantifiés et contrôlée. La stratégie derrière Convergent polissage est d&#39;éliminer ou atténuer les causes indésirables de enlèvement de matière non-uniforme, soit par la conception de polissage ingénierie ou en contrôle de processus, tels que l&#39;enlèvement est entraîné que par l&#39;inadéquation pièce-tour en raison de la forme de la pièce 7,17- 18. La figure 2 illustre la façon dont la forme de la pièce peut conduire à une convergence basé sur le concept d&#39;incompatibilité pièce-tour. Envisager un tour plat et d&#39;une pièce de forme complexe hypothétique montré en haut à gauche. Le décalage de la hauteur d&#39;interface (dénommé l&#39;écart, oL Dh) influence la répartition de pression d&#39;interface (σ) en tant que: contenu &quot;fo: keep-together.within-page =&quot; always &quot;&gt; <img alt="Equation 2" fo:content-width="1in" fo:src="/files/ftp_upload/51965/51965eqn2.jpg" src="/files/ftp_upload/51965/51965eqn2.jpg" width="100px" /> (2) où H est une constante décrivant la vitesse à laquelle la pression diminue avec une augmentation de l&#39;écart Dh oL 6. Dans cet exemple, la pièce a la plus haute pression locale dans le centre (voir en bas à gauche de la figure 2), et donc cet endroit observera le taux initial plus élevé d&#39;enlèvement de matière pendant le polissage. Comme la matière est enlevée, le différentiel de pression à travers la pièce à usiner diminue en raison d&#39;une diminution de la non-concordance pièce-tour, et la pièce convergera à la forme de la nappe. A la convergence, la répartition de la pression de la pièce à usiner, et l&#39;enlèvement d&#39;où la matière, sera uniforme à travers la pièce à usiner (voir partie droite de la figure 2). Cet exemple est illustré pour un tour plat, however, le même concept se applique pour un tour sphérique (concave ou convexe). Encore une fois, ce processus de convergence ne fonctionne que si tous les autres phénomènes affectant spatiale non-uniformité du matériel ont été éliminés. Les mesures d&#39;atténuation de procédure et d&#39;ingénierie spécifiques mises en œuvre dans le protocole de polissage Convergent sont décrits dans la discussion. Le protocole décrit dans l&#39;étude suivante est le processus Convergent polissage spécifiquement pour un 26,5 cm carré verre de silice fondue pièce à partir d&#39;une surface de terrain très bien. En huit heures de polissage (4 heures / surface), cette pièce peut atteindre une planéité polie / 2 de ~ avec une très haute qualité de surface (ce est à dire, la densité de zéro faible).

<table border="0" cellpadding="0" cellspacing="0" width="634">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:251px;">Name of Material/Equipment</td>
			<td style="width:245px;">Company</td>
			<td style="width:139px;">Catalog Number</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MHN 50 mil Polyurethane Pad&#160;</td>
			<td>Eminess Technologies</td>
			<td>PF-MHN15A050L-56</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cerium oxide polishing slurry</td>
			<td>Universal Photonics</td>
			<td>HASTILITE PO</td>
		</tr>
		<tr height="21">
			<td dir="LTR" height="21" style="height:21px;width:251px;">Septum Glass (waterjet cut)</td>
			<td dir="LTR" style="width:245px;">Borofloat ; Schott&#160;</td>
			<td dir="LTR" style="width:139px;">NA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Diamond conditioner</td>
			<td>Morgan Advanced Ceramics&#160;</td>
			<td>CMP-25035-SFT</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic Cleaner</td>
			<td>Advanced Sonics Processing System</td>
			<td>URC4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Purification Optima Filter cartridge</td>
			<td>3M</td>
			<td>CMP560P10FC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Blocking Pitch</td>
			<td>Universal Photonics</td>
			<td>BP1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Blocking Tape</td>
			<td>3M</td>
			<td>#4712</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cleanroom Cloth</td>
			<td>ITW Texwipe</td>
			<td>AlphaWipe TX1013</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Single Particle Optical Sensing</td>
			<td>Paritcle Sizing Systems</td>
			<td>Accusizer 780 AD</td>
		</tr>
	</tbody>
</table>

convergent polishing: a simple, rapid, full aperture polishing process of high quality optical flats &amp; spheres

Convergent polissage est un nouveau système de polissage et la méthode pour la finition optique de verre plat et sphériques dans lequel une pièce, indépendamment de sa forme initiale (ce est à dire, la figure de surface), converge vers chiffre final de surface avec une excellente qualité de surface sous, un ensemble immuable fixe de polissage paramètres en une seule itération de polissage. En revanche, les méthodes classiques de polissage complète d&#39;ouverture nécessitent plusieurs souvent de longues, les cycles itératifs, impliquant de polissage, de métrologie et de processus de changements pour atteindre le chiffre de surface souhaitée. Le processus de polissage Convergent est basé sur le concept de la pièce tours hauteur décalage résultant de la pression différentielle qui diminue avec l&#39;enlèvement et les résultats dans la pièce convergeant vers la forme de la tour. La mise en œuvre réussie du processus Convergent polissage est le résultat de la combinaison d&#39;un certain nombre de technologies pour éliminer toutes les sources d&#39;enlèvement de matière spatiale non uniforme (sauf pour pièce-tourdécalage) pour la convergence de la figure de surface et de réduire le nombre de particules voyous dans le système pour des densités de gratter bas et une faible rugosité. Le processus Convergent polissage a été démontrée pour la fabrication de deux appartements et des sphères de différentes formes, tailles et formats d&#39;image sur divers matériaux de verre. L&#39;impact pratique est que les composants optiques de haute qualité peuvent être fabriqués plus rapidement, plus plusieurs reprises, avec moins de métrologie, et avec moins de travail, entraînant des coûts unitaires plus faibles. Dans cette étude, le protocole Convergent polissage est spécifiquement décrite pour la fabrication de 26,5 cm de côté fusionnés appartements de silice à partir d&#39;une surface du sol à une amende ~ λ / 2 chiffre de surface polie après le polissage 4 h par surface sur un diamètre de 81 cm polisseuse.

Le protocole Convergent polissage décrite ci-dessus permet un terrain silice fondue pièce (dans ce cas un carré de 26,5 cm) à polir, en une seule itération de 4 h par la surface, d&#39;une planéité de crête à creux ~ λ / 2 (~ 330 nm) pour les basses pièces de rapport d&#39;aspect et ~ 1λ (~ 633 nm) pour le ratio d&#39;aspect élevé pièces (voir Figure 3). Encore une fois, ce processus converge plusieurs reprises pièces à la même figure de surface final sans avoir à modifier les paramè...

Watch this Scientific Journal Video about Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats & Spheres at JoVE.com

Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats &amp; Spheres

A novel optical polishing process, called &#8220;Convergent Polishing&#8221;, which enables faster, lower cost polishing, is described. Unlike conventional polishing processes, Convergent Polishing allows a glass workpiece to be polished in a single iteration and with high surface quality to its final surface figure without requiring changes to polishing parameters.

Convergent Polissage: un simple, processus rapide, pleine ouverture de polissage de haute qualité optiques Flats &amp; Sphères

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial ...

convergent-polishing-simple-rapid-full-aperture-polishing-process

Research

JoVE Journal

Engineering

11.0K vues.  Lawrence Livermore National Laboratory. A novel optical polishing process, called “Convergent Polishing”, which enables faster, lower cost polishing, is described. Unlike conventional polishing processes, Convergent Polishing allows a glass workpiece to be polished in a single iteration and with high surface quality to its final surface figure without requiring changes to polishing parameters.

Vidéo: Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats & Spheres

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

Fabrication de silice Ultra High microrésonateurs facteur de qualité

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

Recherche

Ingénierie

Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

The Vaporization of a Sacrificial Component (VaSC) process is used to fabricate microvascular structures. This procedure uses sacrificial poly(lactic) acid fibers to form hollow microchannels with precise 3D geometric positioning provided by laser micromachined guide plates.

Processus de fabrication de microstructures tridimensionnelles en utilisant la vaporisation d&#39;un composant sacrificiel

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material ...

Construction of a High Resolution Microscope with Conventional and Holographic Optical Trapping Capabilities

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular organelles 2,3, as well as for high spatial and temporal resolution readout of their position relative to the center of the trap. The system described herein has one such "traditional" trap operating at 980 nm. It additionally provides a second optical trapping system that uses a commercially available holographic package to simultaneously create and manipulate complex trapping patterns in the field of view of the microscope 4,5 at a wavelength of 1,064 nm. The combination of the two systems allows for the manipulation of multiple refractive objects at the same time while simultaneously conducting high speed and high resolution measurements of motion and force production at nanometer and piconewton scale.

The system described herein employs a traditional optical trap as well as an independent holographic optical trapping line, capable of creating and manipulating multiple traps. This allows for the creation of complex geometric arrangements of refractive particles while also permitting simultaneous high-speed, high-resolution measurements of the activity of biological enzymes.

Construction d&#39;un microscope à haute résolution avec des capacités de piégeage optique classique et holographique

High resolution microscope systems with optical traps allow for precise manipulation of various refractive objects, such as dielectric beads 1 or cellular ...

The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry

Thermal noise in high-reflectivity mirrors is a major impediment for several types of high-precision interferometric experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. This is for example the case of future gravitational wave observatories, whose sensitivity to gravitational wave signals is expected to be limited in the most sensitive frequency band, by atomic vibration of their mirror masses. One promising approach being pursued to overcome this limitation is to employ higher-order Laguerre-Gauss (LG) optical beams in place of the conventionally used fundamental mode. Owing to their more homogeneous light intensity distribution these beams average more effectively over the thermally driven fluctuations of the mirror surface, which in turn reduces the uncertainty in the mirror position sensed by the laser light.
We demonstrate a promising method to generate higher-order LG beams by shaping a fundamental Gaussian beam with the help of diffractive optical elements. We show that with conventional sensing and control techniques that are known for stabilizing fundamental laser beams, higher-order LG modes can be purified and stabilized just as well at a comparably high level. A set of diagnostic tools allows us to control and tailor the properties of generated LG beams. This enabled us to produce an LG beam with the highest purity reported to date. The demonstrated compatibility of higher-order LG modes with standard interferometry techniques and with the use of standard spherical optics makes them an ideal candidate for application in a future generation of high-precision interferometry.

Large laser-interferometers are being constructed to create a new type of astronomy based on gravitational waves. Their sensitivities, as for many other high-precision experiments, are approaching fundamental noise limits such as the atomic vibration of their components. We are pioneering technologies to overcome these limits using novel laser beam shapes.

La génération de d&#39;ordre supérieur Laguerre-Gauss faisceaux optiques pour l&#39;interférométrie de haute précision

Thermal noise in high-reflectivity mirrors is a major impediment for several  types of high-precision interferometric experiments that aim to reach the  ...

Fabrication Process of Silicone-based Dielectric Elastomer Actuators

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an elastomeric dielectric membrane sandwiched between two compliant electrodes. The large actuation strains of these transducers when used as actuators (over 300% area strain) and their soft and compliant nature has been exploited for a wide range of applications, including electrically tunable optics, haptic feedback devices, wave-energy harvesting, deformable cell-culture devices, compliant grippers, and propulsion of a bio-inspired fish-like airship. In most cases, DETs are made with a commercial proprietary acrylic elastomer and with hand-applied electrodes of carbon powder or carbon grease. This combination leads to non-reproducible and slow actuators exhibiting viscoelastic creep and a short lifetime. We present here a complete process flow for the reproducible fabrication of DETs based on thin elastomeric silicone films, including casting of thin silicone membranes, membrane release and prestretching, patterning of robust compliant electrodes, assembly and testing. The membranes are cast on flexible polyethylene terephthalate (PET) substrates coated with a water-soluble sacrificial layer for ease of release. The electrodes consist of carbon black particles dispersed into a silicone matrix and patterned using a stamping technique, which leads to precisely-defined compliant electrodes that present a high adhesion to the dielectric membrane on which they are applied.

This manuscript shows the fabrication process for the manufacture of dielectric elastomer soft actuators based on silicone membranes. The three key stages of production are presented in detail: blade casting of thin silicone membranes; pad printing of compliant electrodes; and the assembly of all the components.

Processus de fabrication des élastomères diélectriques Actionneurs à base de silicone

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an ...

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 &#176;C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 &#176;C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 &#176;C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 &#176;C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

A protocol for high-temperature and high-pressure gas adsorption measurements on zeolite H-ZSM-5 using an adsorption measurement device based on a langatate crystal microbalance is presented. Prior to the adsorption measurements, the synthesis of zeolite H-ZSM-5 on the langatate crystal microbalance sensor by the steam-assisted crystallization (SAC) method is demonstrated.

Adsorption dispositif basé sur un cristal Microbalance langatate pour haute température à haute pression de gaz Adsorption dans Zeolite H-ZSM-5

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Challenges in Rheological Characterization of Highly Concentrated Suspensions &amp;#8212; A Case Study for Screen-printing Silver Pastes

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

Défis à rhéologique Caractérisation des concentrés - Suspensions très Une étude de cas pour la sérigraphie argent Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Méthode d'enregistrement des spectres d'émission à haute résolution à large bande des arcs de foudre de laboratoire

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with wafer-scale uniformity and angstrom level control of thickness, the method of atomic-layer deposition was chosen. This ALD process enables high-quality, low-temperature (&#8804;150 &#176;C) growth of ultrathin films (100-1000 &#197;) of VO2. For this demonstration, the VO2 films were grown on sapphire substrates. This low temperature growth technique produces mostly amorphous VO2 films. A subsequent anneal in an ultra-high vacuum chamber with a pressure of 7x10-4 Pa of ultra-high purity (99.999%) oxygen produced oriented, polycrystalline VO2 films. The crystallinity, phase, and strain of the VO2 were determined by Raman spectroscopy and X-ray diffraction, while the stoichiometry and impurity levels were determined by X-ray photoelectron spectroscopy, and finally the morphology was determined by atomic force microscopy. These data demonstrate the high-quality of the films grown by this technique. A model was created to fit to the data for VO2 in its metallic and insulating phases in the near infrared spectral region. The permittivity and refractive index of the ALD VO2 agreed well with the other fabrication methods in its insulating phase, but showed a difference in its metallic state. Finally, the analysis of the films&#39; optical properties enabled the creation of a wavelength- and temperature-dependent model of the complex optical refractive index for developing VO2 as a tunable refractive index material.

Thin films (100-1000 &#197;) of vanadium dioxide (VO2) were created by atomic-layer deposition (ALD) on sapphire substrates. Following this, the optical properties were characterized through the metal-insulator transition of VO2. From the measured optical properties, a model was created to describe the tunable refractive index of VO2.

Dépôt de couches atomiques du dioxyde de Vanadium et un modèle optique dépend de la température

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with ...

Predicting Catalyst Extrudate Breakage Based on the Modulus of Rupture

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a fixed bed are important phenomena in catalyst technology. The mechanical strength of the catalyst is measured here by its bending strength or flexural strength. This technique is relatively new from the perspective of applying it to commercial catalysts of typical sizes used in the industry. Catalyst breakage by collision against a surface is measured after a fall of the extrudates through the ambient air in a vertical pipe. Quantifying the impact force is done theoretically by applying Newton's second law. Measurement of catalyst breakage due to stress in a fixed bed is done following the standard procedure of the bulk crush strength test. Novel here is the focus on measuring the reduction in the length to diameter ratio of the extrudates as a function of the stress.

Here we present a protocol to measure the modulus of rupture of an extruded catalyst and the breakage of said catalyst extrudates by collision against a surface or by compression in a fixed bed.

Predicting catalyseur extrudat rupture basé sur le module de Rupture

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a ...