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. Preparazione di lucidatrice e Slurry Prima di preparare la lucidatura sistema Convergent (specificamente chiamato C onvergent, ho nitial superficie Independent, S Ingle Iterazione, ogue lucidatore R Particle-Free o CISR (si pronuncia &#39;forbice&#39;)) 7,17 installando il pad e setto, condizionata al pad, diluendo e stabilizzare chimicamente slurry, e incorporando la sospensione all&#39;interno del sistema di filtrazione. <ol><li> Sul lucidatrice CISR, aderire un tampone in poliuretano sulla base di granito giro. Aderire pad un bordo prima e applicare una pressione in direzione verso il bordo opposto di minimizzare traferri. Tagliare il pad sovrastante e quindi utilizzare una lama di rasoio e rullo per puntura e rimuovere le bolle d&#39;aria, se necessario. </li><li> La prima volta e dopo ogni ~ 100 hr di lucidatura, condizioni di diamante il pad con un condizionatore di diamante CMP (50 mm di diametro; 0,6 psi pressione applicata; 5 minuti di sosta in ogni sede giro radiale con incrementi di spaziatura 25 millimetri; rotazione giro 25 giri) con acqua DI scorre. </li><li> Tra iterazioni lucidatura, rimuovere eventuali fanghi e prodotti in vetro residui dal pad con un detergente in-situ ad ultrasuoni (~ 2 min di sosta in ogni posizione radiale; rotazione lap 5 giri) con acqua DI scorre. </li><li> Il peso setto forma unica, aderire doppio nastro biadesivo e quindi il materiale setto (esempio vetro pre-tagliati o altro materiale resistente all&#39;usura). Tagliare il nastro in schiuma a sbalzo per abbinare la forma del materiale setto e il peso. Si noti il disegno setto (sia la forma e peso) cambia per le diverse dimensioni del pezzo e giro 7,17. </li><li> Preparare lucidatura liquami di Baume 4 concentrazione (in particolare mescolare in volume ~ 1 parte di ossido di cerio lucidatura liquami e ~ 9 parti di acqua deionizzata (DI) di acqua in un 11 L bucket). Controllare Baume utilizzando un galleggiante Baume. Aggiungere ~ 5 ml di KOH (10 M) per aggiustare il pH a 9,5 e aggiungere ~ 120 ml (1 vol%) di tensioattivo proprietario 19. Regolare il pH e Baume ogni 24 ore di lucidatura. </li><li> Installare secchio con l&#39;impasto preparato nel sistema di filtraggio. Quindi installare i filtri antiparticolato CMP desiderati nel sistema di filtraggio. Lasciare ricircolo slurry all&#39;interno del sistema di filtrazione per diverse ore. </li><li> Particella Misura distribuzione delle dimensioni di liquami (ad esempio, con singola particella tecniche di rilevamento ottico) per garantire la coda della distribuzione è adeguatamente canaglia 9,20 priva di particelle. </li></ol> 2. Preparazione del pezzo (Acquaforte e Blocking) Prima di lucidatura, incidere chimicamente come-ha ricevuto il pezzo di terra fine per ridurre la quantità di rimozione del materiale necessario per eliminare il sub-superficiale di macinazione danno 21. Quindi, bloccare il pezzo (se il rapporto di aspetto (ad esempio, la lunghezza / spessore) è&gt; 10) con una tecnica innovativa pulsante di passo di blocco (PBB) per evitare che il pezzo si pieghi durante il blocco e la lucidatura 22. <ol><li> Etch il pezzo di terra fine (in particolare un 265 x 265 x 8 mm 3 vetro silice fusa piano) in una vasca piena di HF: NH 4 F (6: 1 tamponata etch ossido (BOE) 3x diluito con acqua deionizzata) per 6 ore la rimozione 10 micron di vetro dalla superficie del pezzo. ATTENZIONE! BOE è molto pericoloso; indossare adeguati dispositivi di protezione individuale (DPI). Rimuovere pezzo dal serbatoio di decapaggio e aggressivamente risciacquare il pezzo con acqua deionizzata e lasciare il pezzo all&#39;aria verticale asciugare. </li><li> Controllare il pezzo per danni profondo durante il processo di rettifica con un&#39;ispezione luce brillante in una stanza buia. Se non si trova nessun danno profondo, passare alla fase successiva, altrimenti inviare pezzo indietro per ri-macinare. </li><li> Riscaldare il blocco campo in una pistola per colla a ~ 95 ºC e luogo gocce (detti anche bottoni) di passo (~ 0,06 g) sulla faccia dellablocco piatto in un array di 9 x 9 (81 tasti con 26 millimetri spaziatura). Per pezzi di dimensioni diverse, fare riferimento a progettare le regole per il numero ideale, dimensioni e distanze di pulsante passo 22. Posizionare la piastra di blocco con i pulsanti applicati a faccia in su in forno pre-riscaldato a 70 ºC. </li><li> Applicare il nastro alla faccia del pezzo che non deve essere lucido. Evitare la generazione di bolle d&#39;aria o eccessivamente estendendo il nastro. </li><li> Posizionare il pezzo con la faccia laterale del nastro verso il basso sui pulsanti sulla piastra di bloccaggio in forno. Coprire il pezzo-button-block per ridurre al minimo il flusso convettivo. Dopo 1,5 ore, impostare il forno a raffreddare 10 ºC / hr a temperatura ambiente. Dopo il raffreddamento, lo spessore passo sul pezzo bloccato dovrebbe essere ~ 1 mm. </li></ol> 3. Convergent lucidatura <ol><li> Accendere il sistema di umidità in camera climatica di CISR lucidatrice per impedire liquami si secchi durante la lucidatura e per ridurre al minimo le particelle canaglia graffiare il pezzo. </li><li> Insalto e montare il setto specificamente progettato e preparato in lucidatrice. Installare PBB pezzo in CISR lucidatrice e boma in basso per tenere il pezzo. </li><li> Pezzo Polish sulla CISR per 4 ore in un giro e velocità di rotazione del pezzo abbinato di 25 rpm con una corsa radiale di ~ 75 mm e con un flusso slurry dal sistema di filtrazione di 1 gal / min. NOTA: La piastra di bloccaggio serve anche come il peso di carico sul pezzo corrispondente a 0,6 psi di pressione applicata. </li><li> Spegnere giro e pezzo di rotazione e il flusso di liquami. Rimuovere PBB pezzo dal CISR lucidatrice e immergere in acqua deionizzata bagno riempita. Pulire la superficie del pezzo con un panno camere bianche in immersione. Rimuovere PBB pezzo da bagno e spruzzare risciacquare con acqua deionizzata. </li><li> Deblock pezzo inserendo uno spessore all&#39;interfaccia pezzo-block. Rimuovere il nastro dalla superficie del pezzo. Aggressivamente risciacquare pezzo con acqua deionizzata e asciugare all&#39;aria. </li><li> PBB il volto opponendosi del pezzo, come descritto nella sezione 2. Quindi ripetere poistituisce procedure come descritto nella Sezione 3. </li></ol> 4. metrologia e ispezione <ol><li> Misura riflessa fronte d&#39;onda (cioè, forma della superficie) di entrambi i lati del pezzo così come fronte d&#39;onda trasmessa utilizzando un interferometro. </li><li> Mount pezzo su luminosa stazione di controllo della luce e misurare le proprietà antigraffio / dig usando metodi standard di fabbricazione ottica. Breve etch BOE del pezzo, come descritto nel passaggio 2.1, può essere utilizzato per esporre graffi nascosti per pezzi utilizzati in applicazioni laser ad alta fluenza. Per la misurazione di graffi fini o rugosità sul pezzo, possono essere utilizzati microscopia ottica standard o luce bianca interferometria. </li><li> Conservare completato pezzo in contatto minimizzazione contenitore con la faccia del pezzo. </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.

Come discusso nell&#39;Introduzione, successo di Convergent lucidatura rispetto alla superficie figura coinvolge eliminando o riducendo al minimo tutti i fenomeni che influenzano spaziale materiale non uniformità diversa da quella del pezzo-lap mancata corrispondenza grazie alla forma del pezzo. Se uno qualsiasi di questi fenomeni non è opportunamente attenuato, tramite controllo di processo o mediante tecniche di ingegneria appropriata della lucidatrice, allora il punto di convergenza desiderato non può essere otten...

Le principali fasi di un tipico processo di fabbricazione ottica includono shaping, molatura, lucidatura completa apertura, e, talvolta, piccolo strumento di lucidatura 1-3. Con l&#39;aumento della domanda di componenti ottici di alta qualità per sistemi di imaging e laser, ci sono stati avanzamenti significativi nella fabbricazione ottica negli ultimi decenni. Ad esempio, la precisione, la rimozione del materiale deterministico è ora possibile durante la formatura e processi di rettifica con i progressi in computer a controllo numerico macchine per la formatura (CNC) di vetro. Allo stesso modo, le tecnologie di lucidatura piccolo strumento (ad esempio, computer controllato affioramento ottica (CCOS), ioni capire, e finitura magneto-reologico (MRF)) hanno portato alla rimozione del materiale e controllo deterministico forma della superficie, quindi forte impatto dell&#39;industria di fabbricazione ottica. Tuttavia, la fase intermedia del processo di finitura, lucidatura completa apertura, manca ancora alto determinismo, tipicamente richiedono opticia qualificatins di effettuare molteplici, spesso lunghe, cicli iterativi con più cambiamenti di processo per ottenere la forma della superficie desiderata 1-3. Il gran numero di metodi di lucidatura, variabili di processo, e il complesso chimico e interazioni meccaniche tra il pezzo, giro e liquami 3-4 hanno reso difficile trasformare lucidatura ottica da un &#39;arte&#39; di una scienza. Per ottenere deterministico lucidatura tutta apertura, il tasso di rimozione materiale deve essere ben compreso. Storicamente, il tasso di rimozione del materiale è stato descritto dalla Preston equazione ampiamente utilizzato 5 <img alt="Equazione 1" fo:content-width="1in" fo:src="/files/ftp_upload/51965/51965eqn1.jpg" src="/files/ftp_upload/51965/51965eqn1.jpg" width="100px" /> (1) dove dh / dt è il tasso medio dello spessore di rimozione, k p è la costante Preston, σ O èla pressione applicata, e V r è la velocità relativa media tra il pezzo e il giro. La figura 1 illustra schematicamente i concetti fisici che influenzano di asportazione come descritto Preston equazione, comprese variazioni spaziali e temporali nella velocità e pressione, le differenze tra la la pressione applicata e la distribuzione della pressione che le esperienze pezzo, e gli effetti di attrito 6-8. In particolare, la distribuzione della pressione effettiva sperimentato dal pezzo viene regolato da una serie di fenomeni (descritti in dettaglio altrove 6-8) che incidono fortemente risultante forma della superficie del pezzo. Inoltre, nel Preston equazione, gli effetti di livello microscopici e molecolari vengono ripiegati sostanzialmente costante macroscopica Preston (k p), che influenza il tasso complessivo materiale di rimozione, micro-rugosità, e anche graffi sul pezzo. Diversi studi hanno ampliato il modello di Preston a rendere conto<html> per liquami microscopiche interazioni particelle-pad-pezzo per spiegare di asportazione e microrugosità 9-16. Per ottenere il controllo deterministico della forma della superficie durante la lucidatura completa apertura, ognuno dei fenomeni sopra descritti deve essere compreso, quantificati e quindi controllata. La strategia dietro Convergent lucidatura è di eliminare o ridurre le cause indesiderabili di rimozione del materiale non uniforme, sia attraverso la progettazione lucidatore progettato o controllo di processo, tale che la rimozione è pilotato solo dal disallineamento pezzo giri grazie alla forma del pezzo 7,17- 18. La figura 2 illustra come la forma del pezzo può portare a una convergenza basata sul concetto di mancata corrispondenza pezzo-lap. Si consideri un giro piatta e un pezzo ipotetica di forma complessa mostrato in alto a sinistra. La mancata corrispondenza altezza interfaccia (indicato come il divario, Dh OL) influenza la distribuzione della pressione di interfaccia (σ) come: contenuto &quot;fo: keep-together.within-page =&quot; always &quot;&gt; <img alt="Equazione 2" fo:content-width="1in" fo:src="/files/ftp_upload/51965/51965eqn2.jpg" src="/files/ftp_upload/51965/51965eqn2.jpg" width="100px" /> (2) dove H è una costante che descrive la velocità con cui la pressione diminuisce con un aumento gap Dh oL 6. In questo esempio, il pezzo ha la più alta pressione locale in centro (vedi in basso a sinistra della Figura 2), e quindi questa posizione osserverà il più alto tasso di rimozione del materiale iniziale durante la lucidatura. Come materiale viene rimosso, il differenziale di pressione attraverso il pezzo diminuirà a causa di una diminuzione della mancata corrispondenza pezzo giri, e il pezzo convergerà alla forma della teletta. Alla convergenza, la distribuzione della pressione del pezzo, e quindi la rimozione di materiale, sarà uniforme attraverso il pezzo (vedi parte destra della figura 2). Questo esempio è illustrato per un giro piatta, Carner, lo stesso concetto vale per un giro sferica (sia concava o convessa). Di nuovo, questo processo di convergenza funziona solo se sono stati eliminati tutti gli altri fenomeni che influenzano spaziale materiale non-uniformità. Le specifiche attenuanti procedurali e di ingegneria realizzate nel protocollo di lucidatura Convergent sono descritti nella discussione. Il protocollo descritto nel seguente studio è il processo Convergent lucidatura specificamente per 26,5 cm quadrati vetro di silice fusa pezzo a partire da una superficie terra fine. In 8 ore di lucidatura (4 ore / di superficie), questo pezzo può raggiungere una planarità lucido di ~ λ / 2 con elevata qualità superficiale (cioè a bassa densità zero).

<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 lucidatura è un nuovo sistema di lucidatura e metodo per la finitura ottica di vetro piano e sferiche in cui un pezzo, indipendentemente dalla sua forma iniziale (cioè, forma della superficie), convergerà al valore finale superficie con eccellente qualità superficiale sotto, insieme immutabile fisso lucidatura parametri in un unico lucidatura iterazione. Al contrario, convenzionali piena apertura metodi di lucidatura richiedono più spesso lunghe, cicli, iterativi coinvolgono lucidatura, metrologia e di processo modifiche per ottenere la forma della superficie desiderata. Il processo Convergent lucidatura si basa sul concetto di pezzo giri disadattamento altezza conseguente pressione differenziale che diminuisce con la rimozione e risultati nel pezzo convergente alla forma della teletta. Il successo del processo Convergent lucidatura è il risultato della combinazione di un certo numero di tecnologie per rimuovere tutte le fonti di non uniforme asportazione spaziale (eccetto pezzo girinon corrispondente) per la figura di superficie convergenza e ridurre il numero di particelle canaglia nel sistema di basse densità scratch e bassa rugosità. Il processo convergente di lucidatura è stata dimostrata per la realizzazione di due appartamenti e sfere di varie forme, dimensioni e proporzioni su vari materiali in vetro. L&#39;impatto pratico è che i componenti ottici di alta qualità possono essere fabbricate più rapidamente, più volte, con meno di metrologia, e con meno lavoro, con conseguente costi unitari inferiori. In questo studio, il protocollo Convergent lucidatura è specificatamente descritta per la realizzazione di 26,5 centimetri quadrati fusi appartamenti silice da una superficie a terra fino ad un ~ λ / 2 forma della superficie lucidata dopo la lucidatura 4 ore per superficie su un diametro 81 centimetri lucidatrice.

Il protocollo Convergent Polishing sopra descritto permette una massa fusa pezzo di silice (in questo caso da 26,5 cm quadrati) da lucidare, in una singola iterazione di 4 ore per superficie, ad una planarità picco-valle del ~ λ / 2 (~ 330 nm) per le basse pezzi proporzioni e ~ 1λ (~ 633 nm) per alto rapporto di aspetto pezzi (vedi figura 3). Ancora una volta, questo processo converge ripetutamente pezzi alla stessa figura finale superficie senza richiedere modifiche ai parametri lucidatura ed è ind...

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 lucidatura: A Simple, Rapid, massima apertura lucidatura processo di alta qualità ottica Flats &amp; Spheres

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 Views.  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.

Video: 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.

Fabbricazione di Microrisonatori silice Ultra High Quality Factor

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

Ricerca

Ingegneria

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.

Processo di creazione di microstrutture tridimensionali mediante vaporizzazione di un componente sacrificale

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.

Costruzione di un microscopio ad alta risoluzione con convenzionali e Holographic Capabilities intrappolamento ottico

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 generazione di ordine superiore Laguerre-Gauss fasci ottici ad alta precisione Interferometria

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.

Fabbricazione Processo di base di silicone elastomero dielettrici Attuatori

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.

Dispositivo adsorbimento Sulla base di un Langatate cristallo Microbilancia per ALTA TEMPERATURA ALTA PRESSIONE adsorbimento di gas a 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.

Le sfide in reologico Caratterizzazione di sospensioni altamente concentrato - un caso di studio per la serigrafia paste d&#39;argento

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.

Metodo per la registrazione dei spettri ad alta risoluzione a banda larga degli arci fulmini di laboratorio

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.

Deposizione di strati atomici di diossido di vanadio e un modello ottico temperatura-dipendente

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.

Predizione catalizzatore estruso rottura basato sul modulo di rottura

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 ...