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› Find signed collectible books: 'The Adjustable Table E 1027 by Eileen Gray (Design Classics)'
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British filmmaker Peter Adam grew up in Hitler's Germany. In this important book, now available in paperback for the first time, he presents hundreds of examples of artwork that was officially sanctioned by the Third Reich, and which has not been seen by the public since the 1940s. Many of the illustrations are taken from German publications of the era, and reveal how all of the nation's arts--including painting, film, and architecture--were methodically manipulated by the regime into tools of Nazi propaganda. Adam's film documentary of the same name, on which this book is based, received a British Academy of Film and Television Arts award for Best Arts Program.
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The official art of Hitler's National Socialist regime remains largely unknown. Since 1945, few have seen the works; many were destroyed during World War II and most of what survived is hidden away, accesible only to scholars. Peter Adams offers a comprehensive examination, in English, of the art of Nazism. He explores the development of a traditionalist German style linked to nature and the family, and the suppression of modern art. Painting, sculpture, architecture, film, and all other art disciplines were compelled to serve the state ideology, in order to forge the people's collective mind in the National Socialist mould. Hitler's belief that architecture, above all, was the most forceful manifestation of absolute political power lay behind his grandiose schemes for redesigning German cities. The author's research took him to concealed repositories in the United States and Germany. From contemporary publications, as well as the visual arts, he has selected a range of illustrations to cover the gamut of Nazi aesthetics and propaganda.
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Based on a candid conversation with the artist, Peter Adam's "Outline" leads us through David Hockney's endlessly inventive artistic development. From the perspective of his enduring fascination with the male nude, it also charts his relationships with the friends and lovers who fired his imagination and whom he portrayed, both intimately and formally, in his work - including those in London, such as W.H. Auden, Ossie Clark and Patrick Procktor, and later those in the United States, notably Christopher Isherwood, Don Bachardy, Peter Schlesinger and Gregory Evans. It tells the story of a wonderfully engaging artistic personality, from his swinging sixties' peroxided hair and gold lame jacket, through his impatience with English prudery and censoriousness, to the present day when so many of those he has painted or drawn are no longer alive.
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› Find signed collectible books: 'Eileen Gray: Architect / Designer - A Biography'
Eileen Gray (1878-1976) was one of the most innovative architect/designers of the 20th century. Her pioneering tables, mirrors, lamps, and lacquer screens have become modern classics, coveted by museums and collectors, and some of the designs are still reproduced today. First published in 1987 and hailed as a "splendid book, gripping and unpretentious" (Arts Review), this "informative and affectionate" portrait (New York Times) by documentary filmmaker and author Peter Adam, a longstanding friend, is the first full-scale biography of this remarkable woman.
Adam draws upon his exclusive access to Gray's personal archives as he re-creates her life and architectural projects. Two houses she designed in the South of France are now considered architectural landmarks of the 20th century. In addition to more than 300 photographs, designs, and architectural plans, the new edition of the book provides a revised catalogue raisonn of Gray's furniture, architecture, and drawings-an indispensable reference source for collectors and students of one of the leaders of 20th-century design.
PETER ADAM is a prize-winning documentary filmmaker and writer. He is the author of Abrams' Art of the Third Reich and has written books on David Hockney, Alfred Eisenstaedt, and Andr Kertesz. He lives in London and the South of France.
335 illustrations, 35 in full color, plans and diagrams, 71/2 x 103/8"
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Eileen Gray (18781976) is regarded as one of the most important furniture designers and architects of the early 20th century and the most influential woman in those fields. Her work inspired both modernism and Art Deco. Her design style was as distinctive as her way of working, and Gray developed an opulent, luxuriant take on the geometric forms and industrially produced materials used by the International Style designers, such as Le Corbusier, Charlotte Perriand and Mies Van Der Rohe, who shared many of her ideals. Her voluptuous leather and tubular steel Bibendum Chair, and clinically chic E-1027 glass and tubular steel table are now as familiar as icons of the International Style as Le Corbusier and Perriands classic Grand Confort club chairs, yet for most of her career she was relegated to obscurity by the same proud singularity that makes her work so prized today. This stunningly illustrated volume is set to be the definitive biography and survey of her eventful life and groundbreaking career.
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Many discussions of Christian spirituality draw on a range of traditions and "disciplines." Little attention, however, appears to have been given to the Bible itself for its teaching on this theme or as a source of spirituality. Similarly, it is commonly assumed that, when it comes to spirituality, the evangelical tradition has little to offer. In response, Peter Adam urges us to renew our confidence in a biblical model of spirituality and to test our spirituality by the Bible. Drawing on a selection of Old and New Testament texts, along with significant insights from the Christian tradition (including John Calvin and the Puritans), this New Studies in Biblical Theology volume expounds the shape and structure of a gospel-centered "spirituality of the Word" through which we know God himself and receive the life he gives. Addressing key issues in biblical theology, the works comprising New Studies in Biblical Theology are creative attempts to help Christians better understand their Bibles. The NSBT series is edited by D. A. Carson, aiming to simultaneously instruct and to edify, to interact with current scholarship and to point the way ahead.
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The book of Malachi fittingly sits in Christian Bibles as the last book of the Old Testament, which it assumes, summarizes and applies. Yet it also looks forward to the New Testament with its promises of the coming reign of God. A striking feature of the book is the way in which every word of God is contradicted or questioned by his people. God's persistence in speaking to them is a clear picture of sin and grace in close proximity. Furthermore, God's people neither served him wholeheartedly nor turned entirely away in blatant disobedience. This was not neutral territory but a dangerous whirlpool of self-deception. Peter Adam's thorough exposition shows how Malachi is God's effective remedy for such a situation. The greatest sin of God's people is the sin against Godthe source of all sin against ourselves and others. At the heart of God's people, the church, must lie a deep, overwhelming conviction that God loves themjust as he reminds Israel in his first words to them in this book.
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The autobiography of this BBC producer, from his childhood as a Jewish survivor of Nazi Germany through to his success in establishing BBC2 and his direction of around 100 programmes celebrating some of the most influential artists of our time.
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Peter Adam's emphasis on the biblical basis of all truly christian preaching will make Speaking God's Words valuable for expository preachers. His book is a model of the theologically deep but accessible communication he recommends for all pastors.
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There are many books on preaching, but few, if any, on the theology of preaching. Yet, whether it is recognized or not, theology underlies any preaching that claims to be biblical. In Speaking God's Words Peter Adam builds confidence in preaching by laying a firm theological foundation for it. Preaching rests upon three great pillars: God has spoken, his words are now recorded in Scripture and he commissions people "to explain, preach and teach his written words to their contemporaries." Throughout the book, using well-chosen illustrations, Dr Adam encourages preachers to give themselves to the demanding yet thrilling task of "preaching God's words" today.
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› Find signed collectible books: 'The Very Pure Word of God: The Book of Common Prayer as a Model of Biblical Liturgy'
The recent celebration of the 350th anniversary of the 1662 Book of Common Prayer has helped to stimulate a renewed interest in its teaching and fundamental contribution to Anglican identity. Archbishop Cranmer and others involved in the English Reformation knew well that the content and shape of the services set out in the Prayer Book were vital ways of teaching congregations biblical truth and the principles of the Christian gospel. Thus the aim of this series of booklets which focus on the Formularies of the Church of England and the elements of the different services within the Prayer Book is to highlight what those services teach about the Christian faith and to demonstrate how they are also designed to shape the practice of that faith. As well as providing an account of the origins of the Prayer Book services, these booklets are designed to offer practical guidance on how such services may be used in Christian ministry nowadays. In this overview of the Book of Common Prayer, Peter Adam brings us back again and again to its emphasis on the 'very pure word of God', setting the gold standard and hallmark of all our liturgy. Peter Adam served as Vicar of St Jude's Carlton, and as Principal of Ridley College in Melbourne Australia. He is currently Vicar Emeritus of St Jude's, and Canon of St Paul's Cathedral Melbourne.
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Viele Dinge sind schön. Viele Dinge sind nützlich. Aber nur wenige schreiben schon kurz nach ihrem Erscheinen Geschichte. Die Bücher der Reihe "Design-Klassiker" widmen sich ausgewählten Produkten, die in Form, Funktion und Markenkommunikation neue Maßstäbe setzten. Jeder Band informiert mit zahlreichen Fotos und kurzen, aufschlussreichen Texten über die Geschichte des jeweiligen Kult-Objekts sowie über die Personen, die sie entworfen haben.
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› Find signed collectible books: 'Eileen Gray, Une Biographie.'
Paris: Adam Biro, 1989. Tall softcover in photo-illustrated wraps. 400 pages, with 335 illustrations (35 in color). A French translation of the now out of print English biography, 'Eileen Gray, Architect/Designer.'
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by: TechnoGuff | 364
# Added Quiz Review Feature
Nepali Quiz is very useful app for students and users of almost all age groups. This app not only checks your knowledge about Nepal but also helps you to know more about Nepal.
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from 364 reviews

subset: commoncrawl


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Riverside Resort & Conference Center
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... had a list of questions and further hints from Helen Craig on how to find some of the details I asked her about this morning at another visit / research session. I have a lot of computer work ahead of me now, but that is what the winter months are good ...
Historic Marysville and the Upper Nashwaak.
... She did not die until 1935 so Harriett had a sister-in-law for comfort. I travelled further north on Highway 8 and turned west along Provincial Road 107 through Stanley and on to the Williamsburg cemetery. Harriet's father Aaron Hay is listed in the County Directory for 1884 as a farmer in the Williamsburg Settlement with postal service in Stanley. The road was not friendly but the farmer I asked directions from was. ...
Pre-trip Planning
... up with the tour group in the evening, so if I am not sleeping off the jet lag (probable) then I will be taking a stroll around to see some sites on my own. I do know someone else on my tour already - my friend Lynn from England, who I met on my Sri Lanka trip last year. The first thing I'll need to do when I arrive at the airport is to get some local currency ... the Moroccan Dirham is not available outside ...
The Trafalgar Adventure Begins
... street, but when you've got cast iron bats adorning your gate posts, a fancy turret one end, and a tower on the other, you've got to expect some gawkers! There were a few lurking just outside the gate, but they wouldn't oblige by moving out of the way, so you'll have to put up with people in that shot! After lunch at Portland, in a Ruby Tuesdays restaurant, we continued on our long road trip. On the way up we followed the main highway through Massachusetts, New Hampshire and ...
A Day in Saint John
... as fit as ever, although she said she's not been getting around as well as she used to.
It was very nice to be back in Nanny's apartment. In good tradition, one of the first things I did was help myself to the dish of M & Ms she keeps on her coffee table. We had a lovely evening catching up and we all snuggled into bed and looked forward to a day of exploring Fredericton tomorrow. ...


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Hi all,
After finishing my first scratch build, I wasn't completely satisfied with it, because it had been before I knew all the itty-gritty details about the Boba Fett helmet.
Anyhow, I have begun it!
I will allow the pictures to tell the rest (up to now)
(pic heavy!)
I began with the inside support:
And proceeded to cover it up:
I cut out the area for the cheeks:
I decided to use some 1mm sintra for the outside because it sands unlike cardboard...but we'll see how that goes
Advice and criticism is very much appreciated.


text:
3 more days to go! Be there the big day! Hope to get a few Heroic bosses down if not more!
25 Man Dragon Soul GDKP Run Saturday Nights
Love this run, great group that moves along well. I'm glad it's going well and filling quickly now, I saw you've bumped minimum item level to increase success in heroics, looking forward to it!
If you guys need a tank/Rdps hit me up b4 you start your run so I can save him. I do about 3 10mans but would love to save a toon for 25.
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Prices vary based on delivery destination (it's a tax thing), so please change it if you're not shipping within United States as it might affect the price! (Why?)
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Really nice summer drink. Has more depth than Pimms. Gordon's Sloe gin tastes artifically sweet; Plymouth has a natural, berry flavour
5th January 2015
What an excellent product, and tastes just like my friends home-made, very morish and absolutely delicious! Ordering and delivery was a sinch too.
3rd March 2013


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"You take one of those routes, it was probably a challenging route to begin with and we just look at the restructuring and the loss of the other flights as the straw that's going to break that camel's back."
Related quotes
"We're going to diversify the route system into a lot of new routes. We feel really good about what we're doing going forward."
"He still works hard and runs good routes. If anything, he's had one or two drops at critical situations that if he had made those plays, we would say that his training camp continued to the regular season. He made those drops, and that shows a sign of inconsistency."
"I remember a game against Denver in 2001, he had an in route, but he gave me one of these ... and he was gone."
"The Santa Fe Route, or the Atchison, Topeka and Santa Fe Railroad, which has in modern times developed into one of the largest and most profitable railroad systems in this country, was projected long before the idea of a transcontinental line to the Pacific coast had taken full possession of men's minds."
"That was fascinating because you can follow the escape route that the robbers took (unsuccessfully), find the place where one of them dropped dead and track down the prison where some of them ended up. It was one of the most modern jails in Europe at the time - the cells were in a circle with the governor's house in the middle. It's a housing estate now with a green in the middle."


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Distinguished Professor of Philosophy Lectures at Nyack
Posted by Deborah.Walker on Saturday October 27, 2007
Dr. Merold Westphal, Distinguished Professor of Philosophy at Fordham University will be the guest lecturer hosted by the Philosophy Senior Seminar on Tuesday, October 30 at 9:30 a.m. in Hilltop Classroom 4 on Nyack's Rockland County campus. His subject will be "Faith in the Midst of Secular Thought."
Dr. Westphal's expertise is in the field of Continental Philosophy, which includes the work of Kant, Hegel, Kierkegaard, Husserl, and Heidegger. An author of eight books and some 200 published articles, he is a scholarly consultant for the university press of several universities and academic journals.
At Wheaton College, he completed undergraduate studies summa cum laude and earned both his M.A.and Ph.D. from Yale University. Dr. Westphal has taught philosophy at Fordham for twenty years and at a number of other colleges and seminaries, among them Wheaton College, Yale University, Harvard Divinity School and Fuller Theological Seminary.
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Pie Bear Model
Suzanne WintersModel Female Scottsdale, Arizona, US
Mayhem # 143707
About Me
Just moved to Scottsdale, AZ !!!
Looking for commercial modeling assignments, especially well suited for Magazine, Print, Calendar and Poster work. I am willing to travel, but not for free.
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|Publication number
|Publication type
|Application number
|Publication date
|Jul 8, 2004
|Filing date
|Aug 18, 2003
|Priority date
|Aug 16, 2002
|Also published as
|Publication number
|Nicholas Leventis, Chariklia Leventis
|Original Assignee
|Nicholas Leventis, Chariklia Leventis
|Export Citation
|BiBTeX, EndNote, RefMan
|Patent Citations (6), Referenced by (46), Classifications (10), Legal Events (6)
|External Links: USPTO, USPTO Assignment, Espacenet
[0001] This application claims priority from U.S. provisional applications having Ser. No. 60/404,032, filed on Aug. 16, 2002; and Ser. No. 60/405,693, filed Aug. 22, 2002, both of which are incorporated herein in their entirety.
[0002] The present invention relates generally to the field of aerogels. More specifically, it relates to cross-linked aerogels.
[0003] Aerogels are chemically inert, highly porous ceramic materials. Generally, these materials are produced by forming a gel containing a solvent and a porous solid component, and then removing the solvent to leave behind the porous solid. Removal of the solvent while preserving the porous solid structure is difficult because the gel often shrinks upon removal of the solvent and causes the porous solid structure to crack and break. This obstacle has been overcome by transforming the solvent within the gel into a vapor above its supercritical point, and allowing the vapor to escape and leave the intact porous solid structure. The first true aerogels were producted by exchanging water in the gel with alcohol that was then converted to a supercritical fluid and allowed to escape. This produced an aerogel that was transparent, low density, and highly porous. A major advance took place when this technique was combined with the application of sol-gel chemistry to prepare silica aerogels. This process replaced the sodium silicate that was typically used with an alkoxysilane, (for example, tetramethyorthosilicate, TMOS). Hydrolyzing TMOS in a solution of methanol produced a gel in one step that was called an "alcogel". This eliminated two of the drawbacks of the previously used procedure, namely, the water-to-alcohol exchange step and the presence of inorganic salts in the gel. Drying these alcogels under supercritical alcohol conditions produced high-quality silica aerogels. In subsequent years, this approach was extended to prepare aerogels from a wide variety of metal oxide aerogels.
[0004] Recent advances have produced aerogels that are the product of a sol-gel process, whose final stage involves extracting the pore-filling solvent with liquid CO2. The latter is gasified supercritically and is vented off, leaving behind a very low density solid (0.002-0.8 gram/cm−3), with the same volume as the original hydrogel and a chemical composition identical to glass.
[0005] Aerogels have been considered for thermal insulation, catalyst supports, or as hosts for a variety of functional materials for chemical, electronic, and optical applications. However, practical application of aerogels has been slow because aerogels are brittle and hygroscopic. These properties cause several known aerogels to absorb moisture from the environment which causes them to collapse due to the capillary forces developing in the pores. Therefore, aerogels having superior strength characteristics that would overcome the deficiencies of the past would be useful in a large variety of applications.
[0006] The invention provides methods to prepare a cross-linked sol-gel like material comprising contacting a sol-gel like material with a cross-linking agent.
[0007] The invention also provides methods to prepare a cross-linked aerogel comprising drying a cross-linked sol-gel like material.
[0008] The invention also provides cross-linked aerogels.
[0009] Definitions
[0010] Aerogel: What remains when the liquid part of a sol-gel like material is removed without damaging the solid part (most often achieved by supercritical extraction). If made correctly, the aerogel retains the original shape of the sol-gel like material and at least 50% (typically >85%) of the sol-gel like material's volume.
[0011] The terms alkyl, alkenyl, alkynyl, denote both straight and branched groups; but reference to an individual radical such as "propyl" embraces only the straight chain radical, a branched chain isomer such as "isopropyl" being specifically referred to.
[0012] Aryl: denotes a phenyl radical or an ortho-fused bicyclic carbocyclic radical having about nine to ten ring atoms in which at least one ring is aromatic (e.g. phenyl, indenyl, or naphthyl).
[0013] Attached group: An attached group is an organic or inorganic molecule or molecules that are part of a cross-linking agent such that the attached group becomes bonded to a sol-gel like material. Examples of attached groups include, but are not limited to, absorbants, catalysts, flurophores, biomolecules, redox active labels, reactive groups such as amines, epoxides, hydroxyls, anhydrides, acylhalides, and carboxyl groups.
[0014] Condensation: A condensation reaction occurs when two metal hydroxides (M—OH+HO—M) combine to give a metal oxide species (M—O—M). The reaction forms one water molecule.
[0015] Cross-linking agent: A cross-linking agent can be an organic or an inorganic compound that forms a bond with a reactive side group accessible on a sol-gel like material to form a cross-linked sol-gel like material that can be dried to form a cross-linked aerogel.
[0016] Cross-linked aerogel: an aerogel having at least two side groups that are linked by a cross-linking agent that forms a bond with the side groups.
[0017] Gel Point: The point in time at which the network of linked oxide particles spans the container holding the Sol. At the gel point the Sol becomes a sol-gel like material.
[0018] Hydrolysis: The reaction of a metal alkoxide (M—OR) with water, forming a metal hydroxide (M—OH).
[0019] Sol: A solution of various reactants that are undergoing hydrolysis and condensation reactions. The molecular weight of the oxide species produced continuously increases. As these species grow, they may begin to link together in a three-dimensional network.
[0020] Sol-gel like material: A sol-gel material is a material that results from a sol-gel process as is known in the art and described herein. For example, a sol-gel forms a rigid substance called a sol-gel like material. The sol-gel like material can be removed from its original container and can stand on its own. A sol-gel like material consists of two parts, a solid part and a solvent part. The solid part is formed by the three-dimensional network of linked oxide particles. The solvent part fills the free space surrounding the solid part. The solvent and solid parts of a sol-gel like material occupy the same apparent volume.
[0021] Substantially: A sol-gel like material that is substantially filled with a solvent refers to a sol-gel material that is filled with at least about 75%, 80%, 90%, 95%, or 98% solvent by volume.
[0022] Supercritical fluid: A substance that is above its critical pressure and critical temperature. A supercritical fluid possesses some properties in common with liquids (density, thermal conductivity) and some in common with gases (fills its container, does not have surface tension).
[0023]FIG. 1 illustrates the process conditions for both the carbon dioxide substitution/drying process, and the alcohol drying process.
[0024]FIG. 2 shows SEM images from randomly selected spots in the interior of fractured monoliths of a native silica aerogel with ?b=0.169 g/cm−3 (A) and a di-ISO cross-linked silica aerogel composite with ?b=0.380 g cm−3 (B).
[0025]FIG. 3 illustrates photographs of four pairs of aerogel monoliths (diameter: 0.9-1.0 cm; length: 3-4 cm; densities in g cm−3 are reported directly on the vials and include 0.169; 0.141; 0.297 and 0.390). The left-most sample (?b=0.169 g cm−3) is native silica. The right vial of each pair contains a similar-density aerogel that has been submerged in liquid N2 in a drybox.
[0026]FIG. 4 is a graph illustrating load-strain curves for the four composites of FIG. 3. The arrow correlates the particular data point with the image in FIG. 5.
[0027]FIG. 5 illustrates bending under a 14.4 kg load of the monolith with ?b=0.447 g cm−3; span=1.738 cm).
[0028]FIG. 6 illustrates photographs of two aerogel monoliths. The left-most sample was supercritical fluid extraction (SCF) dried, and the right-most sample was pentane dried at ambient pressure.
[0029] In one example, the invention provides silica aerogel monoliths wherein the strength has been improved by a factor of over 100 through cross-linking the nanoparticle building blocks of preformed silica hydrogels with a cross-linking agent, such as poly(hexamethylene diisocyanate). The composite monoliths of the invention offer the advantage that they are much less hygroscopic than native silica, and they do not collapse when contacted with liquids.
[0030] Base-catalyzed silica aerogels typically consist of large voids (mesopores, ˜50 nm in diameter) in a "pearl-necklace" network of microporous, so-called secondary particles (Brinker and Scherer, Sol-Gel Science; The Physics and Chemistry of Sol-Gel Processing, Academic Press: New York, (1990)) which are the smallest entities visible in FIG. 2A (5-10 nm in diameter). Those particles are connected by "necks" formed by dissolution and reprecipitation of silica during aging (Brinker and Scherer, Sol-Gel Science; The Physics and Chemistry of Sol-Gel Processing, Academic Press: New York, (1990); Woignier and Phalippou, J. Non-Cryst. Solids, (1998) 100, 404-408). Reasonably, the strength of monolithic aerogels could be improved by making the necks wider. To accomplish this with minimum addition of new material, the contour surface of silica can be used as a template for the deposition and growth of the interparticle cross-linker.
[0031] Silica is surface-terminated with silanols (—SiOH). A polyurethane, (—CONH—R—NHCOOR′O—)n, is formed by the reaction of a diisocyanate (OCN—R—NCO) and a diol (HO—R′—OH) (Smith and March, March's Advanced Organic Chemistry Reactions, Mechanism and Structure; John Wiley and Sons: New York, 2001). A similar reaction of an isocyanate cross-linking agent with the free hydroxyl groups of a sol-gel like material provides cross-linked aerogels having superior properties that allow them to be used in a large variety of applications.
[0032] I. General Preparation of Aerogels from Silicon Alkoxide Precursors
[0033] The formation of aerogels, in general, involves two major steps, the formation of a sol-gel like material, and the drying of the sol-gel like material to form an aerogel. Originally, sol-gel like materials were made by the aqueous condensation of sodium silicate, or a similar material. While this process worked well, the reaction formed salts within the gel that needed to be removed by many repetitive washings (a long, laborious procedure). With the rapid development of sol-gel chemistry over the last few decades, the vast majority of silica aerogels prepared today utilize silicon alkoxide precursors. The most common of these are tetramethyl orthosilicate (tetramethoxysilane, TMOS, Si(OCH3)4), and tetraethyl orthosilicate (tetraethoxysilane, TEOS, Si(OCH2CH3)4). However, many other alkoxides, containing various organic functional groups, can be used to impart different properties to the gel. Alkoxide-based sol-gel chemistry avoids the formation of undesirable salt by-products, and allows a much greater degree of control over the final product. The balanced chemical equation for the formation of a silica gel from TEOS is:
Si(OCH2CH3)4 (liq.)+2H2O(liq.)=SiO2 (solid)+4HOCH2CH3 (liq.)
[0034] The above reaction is typically performed in ethanol, with the final density of the aerogel dependent on the concentration of silicon alkoxide monomers in the solution. Note that the stoichiometry of the reaction requires two moles of water per mole of TEOS. In practice, this amount of water leads to incomplete reaction, and weak, cloudy aerogels. Most aerogel recipes, therefore, use a higher water ratio than is required by the balanced equation (anywhere from 4-30 equivalents).
[0035] Catalysts
[0036] The kinetics of the above reaction are impractically slow at room temperature, often requiring several days to reach completion. For this reason, acid or base catalysts are added to the formulation. The amount and type of catalyst used play key roles in the microstructural, physical and optical properties of the final aerogel product.
[0037] Acid catalysts can be any protic acid, such as HCI. Basic catalysis usually uses ammonia, or ammonia buffered with ammonium fluoride. Aerogels prepared with acid catalysts often show more shrinkage during supercritical drying and may be less transparent than base catalyzed aerogels. The microstructural effects of various catalysts are harder to describe accurately, as the substructure of the primary particles of aerogels can be difficult to image with electron microscopy. All generally show small (2-5 nm diameter) particles that are generally spherical or egg-shaped. With acid catalysis, however, these particles may appear "less solid" (looking something like a ball of string) than those in base-catalyzed gels. As condensation reactions progress, the sol will set into a rigid gel. At this point, the gel is usually removed from its mold. However, the gel should typically be kept covered by alcohol to prevent evaporation of the liquid contained in the pores of the gel. Evaporation causes severe damage to the gel and will lead to poor quality aerogels
[0038] Single-Step vs. Two-Step Aerogels
[0039] Typical acid or base catalyzed TEOS gels are often classified as "single-step" gels, referring to the "one-pot" nature of this reaction. A more recently developed approach uses pre-polymerized TEOS as the silica source. Pre-polymerized TEOS is prepared by heating an ethanol solution of TEOS with a sub-stoichiometric amount of water and an acid catalyst. The solvent is removed by distillation, leaving a viscous fluid containing higher molecular weight silicon alkoxides. This material is redissolved in ethanol and reacted with additional water under basic conditions until gelation occurs. Gels prepared in this way are known as "two-step" acid-base catalyzed gels. Pre-polymerized TEOS is available commercially in the United States from Silbond Corp. (i.e., Silbond� H-5).
[0040] These slightly different processing conditions impart subtle, but important changes to the final aerogel product. Single-step base catalyzed aerogels are typically mechanically stronger, but more brittle, than two-step aerogels. While two-step aerogels have a smaller and narrower pore size distribution and are often optically clearer than single-step aerogels.
[0041] Aging and Soaking
[0042] When a sol reaches the gel point, it is often assumed that the hydrolysis and condensation reactions of the silicon alkoxide reactant are complete. This is far from the case. The gel point simply represents the time when the polymerizing silica species span the container containing the sol. At this point the silica backbone of the gel contains a significant number of unreacted alkoxide groups. In fact, hydrolysis and condensation can continue for several times the time needed for gelation. Failure to realize, and to accommodate this fact is one of the most common mistakes made in preparing silica aerogels. Sufficient time must be given for the strengthening of the silica network. This can be enhanced by controlling the pH and water content of the covering solution. Common aging procedures for base catalyzed gels typically involve soaking the gel in an alcohol/water mixture of equal proportions to the original sol at a pH of 8-9 (ammonia). The gels are best left undisturbed in this solution for up to 48 hours.
[0043] This step, and all subsequent processing steps, are typically diffusion controlled. That is, transport of material into, and out of, the gel is unaffected by convection or mixing (due to the solid silica network). Diffusion, in turn, is affected by the thickness of the gel. In short, the time required for each processing step increases dramatically as the thickness of the gel increases.
[0044] After aging the sol-gel like material, all water still contained within its pores should be removed prior to drying. This is simply accomplished by soaking the sol-gel like material in a solvent, such as alcohol, several times until the water is removed. Again, the length of time required for this process is dependent on the thickness of the sol-gel like material. Any water left in the gel will not be removed by supercritical drying, and will lead to an opaque, white, and very dense aerogel.
[0045] Supercritical Drying
[0046] The final process in making silica aerogels is typically supercritical drying. This is where the liquid within the sol-gel like material is removed, leaving only the linked silica network. The process can be performed by venting the ethanol above its critical point (high temperature-very dangerous) or by prior solvent exchange with CO2 followed by supercritical venting. This process should be performed in an autoclave specially designed for this purpose (small autoclaves used by electron microscopists to prepare biological samples are acceptable for CO2 drying). The process is as follows. The sol-gel like materials are placed in the autoclave (which has been filled with ethanol). The system is pressurized to at least 750-850 psi with CO2 and cooled to 5-10 degrees Celsius (C). Liquid CO2 is then flushed through the vessel until all the ethanol has been removed from the vessel and from within the sol-gel like materials. When the sol-gel like materials are ethanol-free the vessel is heated to a temperature above the critical temperature and pressure of CO2 (31� C. and 1050 psi respectively). As the vessel is heated the pressure of the system rises. The system is held at these conditions for a short time followed by the slow, controlled release of CO2 to ambient pressure. As with previous steps, the length of time required for this process is dependent on the thickness of the gels. The process may last anywhere from a few hours to several days.
[0047]FIG. 1 shows the process conditions for both the carbon dioxide substitution/drying process and the alcohol drying process.
[0048] A Procedure to Produce a Single-Step Base Catalyzed Silica Aerogel
[0049] The following procedure will produce an aerogel with a density of approx. 0.08 g/cm3. The gel time is approximately 60-120 minutes, depending on temperature.
[0050] A catalyst solution containing 35 mL of ethanol, 70 mL of water, 0.275 mL of 30% aqueous ammonia, and 1.21 mL of 0.5 M ammonium fluoride is slowly added to a silica solution containing 50 mL of TEOS and 40 mL of ethanol with stirring. The mixture of the catalyst solution and the silica solution is then poured into a mold until gelation. The gel can be processed as described above.
[0051] A Procedure to Produce a Two-Step Acid-Base Catalyzed Silica Aerogel
[0052] The following procedure will produce an aerogel with a density of approx. 0.08 g/cm3. The gel time is approximately 30-90 minutes, depending on temperature.
[0053] A catalyst solution containing 35 mL of ethanol, 75 mL of water, and 0.35 mL of 30% aqueous ammonia is slowly added to a silica solution containing 50 mL of precondensed silica (Silbond H-5, or equivalent) and 5OmL of ethanol with stirring. The mixture of the catalyst solution and the silica solution is then poured into an appropriate mold until gelation. The gel can be processed as described above.
[0054] II. Cross-Linking Aerogels
[0055] General Procedure
[0056] A cross-linked aerogel can be produced by contacting a sol-gel like material with a cross-linking agent, and then drying the cross-linked sol-gel like material to produce a cross-linked aerogel. A sol-gel like material may be produced according to methods known in the art and disclosed herein. The sol-gel like material can be cross-linked by contacting the sol-gel like material with a solvent containing a cross-linking agent during the wash steps used during the production of an aerogel from the sol-gel like material.
[0057] In one example, a diisocyanate cross-linker is introduced into an aerogel structure as follows. Hydrogels (1 cm diameter, 3-4 cm long) are prepared from tetramethoxysilane via a base-catalyzed route and are aged for 2 days at room temperature (Leventis et al., Chem. Mater., 1999, 11, 2837-2845; Leventis et al., Nano. Lett., 2002, 2, 63-67). Subsequently, according to a post-gelation doping protocol, pores are filled with a diisocyanate (di-ISO) solution by washing successively with methanol, propylene carbonate (PC), and PC/di-ISO (4�8 h in each bath) (Leventis et al., Nano. Lett., 2002, 2, 63-67; Morris et al., Non-Cryst. Solids, 2001, 285, 29-36). The di-ISO employed was poly(hexamethylene diisocyanate) (Aldrich) or Desmodur 3200 (Bayer). The product specifications for the Aldrich di-ISO are monomer <0.5% w/w; isocyanate (NCO) group content was 23.1%. The theoretical NCO content for the dimer, OCNCH2(CH2)4CH2NH(CO)O(CO)NH—CH2(CH2)4CH2NCO, is 23.7%. The vials containing the gels in the last bath were heated at 100� C. for 3 days, then are cooled to room temperature. The solution was decanted, and the gels were washed with PC (1�8 h), PC/acetone (1:1, 1:3, v/v; 1�8 h each), and acetone (4�8 h) and were dried supercritically.
[0058] Cross-Linkers
[0059] Cross-linking agents within the scope of the invention include those compounds that are able to form a chemical bond with at least two reactive groups on a sol-gel material that can be made into an aerogel. For example, silica is surface-terminated with silanols (—SiOH). Thus, a cross-linking agent of the invention (A) includes those compounds having at least two reactive groups that can bond to at least two silanols on a gel-sol material (i.e., SiO—A−OSi). Examples of such reactive groups include, but are not limited to, activated bis acids such as bis(acid chlorides) and bis(acid anhydrides), where the acid can be a carboxylic acid, a phosphoric acid, a sulfonic acid, a sulfinic acid, or a phosphonic acid; diisocyanates, acid anhydrides, bis(acid anhydrides), acylchlorides, and bis(acylchlorides). Non-exclusive examples of diisocyanates are provided herein at Table III. Cross-linkers of the invention can have two reactive groups that are the same, or can have two reactive groups that are different from each other.
[0060] Cross-linkers of the invention also include compounds that react with each other to form a chemical linkage between two silanols on a sol-gel material. For example, a cross-linker (B) can bond to a single silanol group on a sol-gel material and to another cross-linker (C) that bonds to a single silanol group on the sol-gel material to form a chemical linkage between the two silanol groups (i.e., SiO—B—C—OSi).
[0061] Cross-linkers of the invention also include compounds that polymerize and form a chemical bond with reactive groups on a sol-gel material. For example, polyurethane is formed by the reaction of a diisocyanate with a diol. Thus, a diisocyanate may be used as a cross-linker in the presence of a diol such that polyurethane formation occurs until the chain is terminated upon bonding to a silanol on the sol-gel like material. Such a cross-linker will form urethane bonds in association with the cross-linked sol-gel like material. Urethane bonds of this type are thought to be useful for increasing the strength and resistance to breakage of cross-linked aerogels.
[0062] A cross-linker of the invention may also include an attached group that is bonded to a reactive group that bonds to a sol-gel material. An example of such a cross-linker is a diisocyanate (OCN—R—NCO) where R is an attached group that becomes chemically bonded to a sol-gel material through reaction of the isocyanates with the silanols on the sol-gel like material. Thus, the invention includes cross-linking agents having the same or different reactive groups linked to an attached group and that form a chemical bond with a reactive group on a sol-gel like material. An example of an attached group includes a phosphate group that would be useful as a fire retardant if chemically bonded to an aerogel. Additional examples of attached groups include, but are not limited to, absorbants, catalysts, flurophores, biomolecules, redox active labels, reactive groups such as amines, epoxides, hydroxyls, anhydrides, acylhalides, and carboxyl groups.
[0063] The methods and materials of the invention do not include those described or prepared according to the disclosure of Yim et al., Korean J. Chem. Eng., 19:159-166 (2002) or Mizushima and Hori, J. Non-Cryst. Solids, 170:215-222 (1994).
[0064] III. Preparation of Cross-Linked Aerogel Films
[0065] Cross-linked aerogel films can be prepared from the cross-linked aerogels described herein. Such films may be prepared by forming a sol-gel like material on a surface where the sol-gel like material forms a film. Examples of such surfaces include, but are not limited to, plastic, metal, metal foil, or surfaces that have been coated, for example, through use of a sputtering process. A surface can be made of a material that dissolves in a solvent to which a cross-linked aerogel is resistant. Such a surface may be used as a support to form a cross-linked aerogel film and then dissolved to free the film from the support.
[0066] The sol-gel material can be processed into a cross-linked aerogel while contained on a surface. For example, the sol-gel material can be washed with a desired solvent, treated with a cross-linking agent, and dried to produce a cross-linked aerogel while contained on a surface. Such a process should allow rapid production of cross-linked aerogel films due to the large surface area of the film relative to the thickness of the film. This feature allows solvents to be rapidly vaporized.
[0067] Cross-linked aerogel films offer many benefits because they will have a large surface area. For example, a cross-linking agent that contains an attached group that is a catalyst may be used to produce an aerogel film having a catalyst cross-linked to the surface. Such a film may be useful in the production of catalytic converters in the automotive industry or in the production of catalyst supports in the chemical industry. In another example, a cross-linking agent that contains an absorbant as an attached group may by linked to the film to produce a film having a very large absorbant surface area.
[0068] IV. Properties of Cross-Linked Aerogels
[0069] Diisocyanate (di-ISO) modified aerogels are often translucent (FIG. 3), with properties (Table II) that depend on their density, which in turn depends on the concentration of di-ISO in the PC/di-ISO bath. Relative to native silica, composite aerogels may shrink by up to 10-12% and they often become up to ˜3 times more dense as the di-ISO concentration in the bath increases. Both size and density level off for bathing solutions more concentrated than ˜40% w/w, but even the most dense monoliths fall in the density range of aerogels. Shrinking is probably associated with cross-linking. IR analysis shows that as the density increases, the urethane C═O stretch (at ˜1690 cm−1) becomes comparable to, and eventually even stronger than, the Si—O stretch at 1078 cm−1. Note also that while the urethane C═O stretch is present in di-ISO, the dominant stretch at ˜2272 cm−1 comes from the isocyanate (N═C═O) (Husing et al., Chem. Mater., 1998, 10, 3024-3032). However, the latter absorption is consistently extremely weak or absent. Therefore, it was concluded that both ends of practically all di-ISO have reacted. A typical SEM image of one of the most dense composites (FIG. 2B) shows that (a) a new material has been introduced conformally to the secondary particles, as not only the necklace-like structure but also individual particles remain clearly visible; and (b) the mesoporocity has been somewhat reduced, as several secondary particles appear fused (clustered) together, forming the larger domains that promote light scattering and haziness (Novak et al., Chem. Mater., 1994, 6, 282-286). These observations are all consistent with reaction and binding of di-ISO to the surface of silica. Considering the total surface area of native silica (˜1000 g cm−3, Table II) and the density change between native silica and the most dense composite (ρb=0.447 g cm−3), it is calculated that the amount of di-ISO corresponds to 4.7 monolayers. Hence, terminal NCOs appear to undergo not only condensation with surface-silanols but also further reaction with themselves causing extensive cross-linking. It should be emphasized further that the estimated 4.7 monolayer coverage is actually a lower limit, because the first monolayer blocks the channels and cuts off access to the micropores of the secondary particles. This is concluded from the fact that the Brunauer-Emmett-Teller (BET) surface area decreases, and the average pore diameter jumps from ˜13 to ˜20 nm as the monolith density increases (Table II).
[0070] Composite monoliths are less hygroscopic and more robust than pure silica (Table II). Native silica aerogels submerged in liquid N2 (in a glovebox) absorb ˜6.5 times their weight in liquified gas (which they subsequently lose over a period of ˜10 min). At the same time, however, those monoliths undergo extensive cracking, losing their structural integrity completely (FIG. 3). Cracking was also observed consistently with all samples of the lighter composite (ρb=0.241 g cm−3), but the mode of fracture was different from that of native silica, yielding few large pieces with structural integrity rather than the loose foamy material obtained from the disintegration of the latter. Composites with μb>0.3 g cm−3 uptake, <1.7 times their weight in liquid N2, but no structural change were observed, even after repetitive dip-freeze/thaw cycling. The structural collapse of pure silica aerogels in contact with liquids is a known phenomenon and is due to the capillary tension at the liquid-gas interface in the pores (Fricke, Sci. Am., 1998 (March) 92-97). An upper bound for the volume relaxation energy, VRE (in J cm−3), upon collapse is calculated from the work done per unit volume by the capillary tension via the relationship
VRE=γ LV cos(θ)[Aρ a/(1−ρ]
[0071] by assuming that the contact angle θ=0� and that the pore liquid is water (whose surface tension −γLV=0.072 J m−2 is higher than that of many other liquids), A is the specific (BET) surface area of the aerogel, and the relative density ρ≈0.3 (Brinker and Scherer; Sol-Gel Science; The Physics and Chemistry of Sol-Gel Processing, Academic Press: New York, 1990). Thus, it is calculated that upon collapse our native aerogel monoliths are stabilized by ≦17 J cm−3. Meanwhile, considering the mass-gain over silica of our most dense composite (0.447 g cm−3) and the heats of formation of dicarbamate and isocyanurate, it is calculated that the composite is more stable than native silica by ˜55 J cm−3. This was calculated based on a 4.7 monolayer coverage (7.85�10-4 mol of di-ISO per cm3), where half of the NCOs of the first monolayer from urethane with the surface silanols, releasing (based on bond heats of formation) 61 kJ per mol of di-ISO reacting, while all other NCO groups in the remaining 3.7 monolayers form isocyanurate, releasing 32 kJ per mol of NCO. Therefore, there should be no particular tendency for collapse upon wetting, because the energy that would be expended to destroy cross-linking is more than the energy that would be gained by the subsequent structural collapse. Even in water, denser composites have been stable for at least two months.
[0072] However, the most dramatic improvement yet is in the strength of the new material (Table 11), as tested with a three-point flexural bending method. It takes more than 100 times higher load to break a monolith with density 0.447 g cm−3 (˜15 kg) than to break a native silica aerogel monolith (˜120 g). FIG. 4 shows the load-strain curves of four representative composite monoliths on the way to their respective rupture points. The least dense sample is linearly elastic, while the more dense samples behave as nonlinear elastic. Removing the load at several points before samples fail does not have an adverse effect in their ability to resume their previous shape or accept back the same load, producing the same deformation and continuing along the smooth lines of FIG. 4. The modulus of elasticity, E, (a measure of stiffness) is calculated from the slope (S) of the linear part of the load-deformation curves using
E=SL 3/12πr 4
[0073] where L is the span and r the radius of the aerogel (Gere and Timoshenko, Mechanics of Materials, 4th ed.; PWS Publishing: Boston, 1997). Measuring the deformation of native silica was not possible; however, accepting that for a native silica aerogel with ρb=0.2 g cm−3 and E≦1.0 MPa, the trend in the modulus of the cross-linked monoliths is the same as the trend in the rupture load (Novak et al., Chem. Mater., 1994, 6, 282-286). Namely, more dense monoliths are not only stronger but also more difficult to bend (stiffer). This is consistent with wider interparticle necks as the amount of accumulated di-ISO increases (Iler, The Chemistry of Silica; Wiley: New York, (1979)). Eventually, even the stiffer composites bend, accommodating up to 20% diametral deflections before rupture (see FIG. 5). The more work (i.e., the area underneath the load/deformation curve) required by denser composites to break indicates that stiffer composites are also tougher. This behavior is attributed to the flexible organic nature of the wider necks.
[0074] In summary, molecular-level synergism between silica nanoparticles and molecular cross-linkers inverts the relative host-guest roles in glass-polymer composites, leading to new strong low-density materials. Attempts to load gels with variable amounts of polyurethane precursors such as di-ISO and diol end-capped polybutylene adipate followed by heat treatment, washing, and supercritical drying led to opaque materials, somewhat stronger than silica but still quite brittle and much inferior to the materials described above. Direct mixing of a diisocyanate and an alcohol-free sol has been attempted recently by Yim et al., Korean J. Chem. Eng., 19:159-166 (2002) and Mizushima and Hori, J. Non-Cryst. Solids, 170:215-222 (1994). Reportedly, these procedure lead to week-long gelation times and require an at least equally long aging period. In the attempt to add various amounts of di-ISO in a base-catalyzed sol in PC, a week-long gelation time was noticed. The resulting aerogels were translucent but no less brittle than native silica.
[0075] Further studies are underway to (a) reduce the processing time by replacing PC with less viscous solvents and oven heating with microwave heating; (b) vary the chemical identity of the diisocyanate, as well as the composition and density of silica; and (c) cross-link the few residual NCO groups by introducing appropriate diols (Javni et al., Polym. Mater. Sci. Eng., 2002, 86, 387-388).
[0076] V. Uses of Cross-Linked Aerogels
[0077] The cross-linked aerogels described herein may be used in a large number of applications that are exemplified below. These include structural applications where cross-linked aerogels may be used as light-weight building materials, or to reinforce plastics and other materials used in construction. The cross-linked aerogels may also be used to produce more durable optical sensors, such as those used to detect oxygen. Radiation detectors may also be made from the cross-linked aerogels described herein. The resistance of the cross-linked aerogels to structural collapse makes them useful in fuel storage cells. In one example, a phosphate group may be incorporated into a sol-gel like material to produce a fire retardant cross-linked aerogel. Such an aerogel may be used within a fuel cell to provide structural support as well as protection against fires. Cross-linked aerogels may also be used as supports, such as for absorbants and catalysts.
[0078] The cross-linked aerogels may also be subjected to pyrolysis to coat the aerogels with carbon. Such a carbon-coated silica aerogel would be suitable as a dimensionally stable electrode material for electrolysis, double layer capacitors for storing electrical charge, or as a low density dielectric. Thus, cross-linked aerogels can be incorporated into integrated circuits. A cross-linked carbon-coated aerogel could also be used in the field of superconductivity. For example, the cross-linked aerogels do not collapse in the presence of liquid nitrogen or other liquefied gasses. Thus, carbon-coated cross-linked aerogels may be used in conjunction with a liquefied gas under conditions of extreme cold to conduct an electric current.
[0079] The increased strength of cross-linked aerogels allows them to be used as structural materials. Examples of structural applications for cross-linked aerogels include the production of produce building materials such as ceiling tiles, floor tiles, doors, paneling, shingles, shutters, beams, and the like. The cross-linked aerogels may be used in the automotive and aerospace industry due to their strength and light weight. Examples of such uses include automotive and aircraft panels, seats, flooring, handles, levers, and the like. The cross-linked aerogels can also be used to create protective clothing such as bullet-proof vests, jackets, and helmets; and heat resistant clothing articles.
[0080] The cross-linked aerogels can also be used in numerous applications as insulating materials due to their thermal properties. For example, the cross-linked aerogels can be used in the manufacture of refrigerator doors and panels, oven doors and panels, coolers, clothing, clothing liners, shoes, boots, insulation panels, and the like.
[0081] Preparation of Diisocyanate Cross-Linked Tetramethoxysilane Sol-Gel Monoliths
[0082] The contents of two vials: Vial A:4.514 mL of tetramethoxysilane; 3.839 mL of methanol; and Vial B: 4.514 mL of methanol; 1.514 mL water and 20 μL (microliter) of concentrated ammonium hydroxide, were mixed thoroughly to form the sol, which was poured in polyethelene cylindrical vials (1 cm diameter, 5 cm long). The molds were covered with parafilm�. To facilitate removal of the gels from the polyethylene molds, the bottom cup was covered with a teflon-tape lining. The sol gels in the molds at room temperature in about 10 min, and the resulting gels are left in the molds to age (i.e., complete polymerization and cross-linking) for 2 days. Subsequently, the bottom covers of the molds were removed together with the teflon lining, and the gels were pushed gently out of their molds directly into vials filled with methanol (one gel per vial).
[0083] The pores of the gel was then filled with a diisocyanate solution by washing the gel four times for eight hours per wash with methanol, propylene carbonate, and then a mixture containing propylene carbonate and poly(hexamethylene diisocyanate) in succession. During the last wash, the gels were heated to 100� C. for three days, and were then cooled to room temperature. The wash solution was decanted and the gels were washed with propylene carbonate one time for eight hours. The gels were then washed in a mixture of propylene carbonate and acetone (1:1, v/v) one time for eight hours, followed by washing in a mixture of propylene carbonate and acetone (1:3, v/v) one time for eight hours. The gels were then washed in acetone four times for eight hours per wash. Following the acetone wash, the gels were dried supercritically with carbon dioxide.
[0084] Alternate Preparation of Diisocyanate Tetramethoxysilane Sol-Gel Monoliths
[0085] The tetramethoxysilane sol-gel monolith was prepared as described in Example I except that the wash conditions were altered according to the following procedure. The gels were prepared and aged for two days as described above, and then washed four times in methanol for eight hours per wash. The gels were then washed four times in acetone for eight hours per wash. The gels were then washed in a mixture of acetone and poly(hexamethylene diisocyanate) (1:1, v/v) four times for eight hours per wash. The gels were then maintained in the last wash solution at 50� C. for four days in tightly capped vials. Following the heating period, the gels were washed four times with acetone for eight hours per wash, and then dried supercritically with carbon dioxide.
[0086] Preparation of Aerogels Without Supercritical Drying
[0087] The cross-linked aerogels of the invention are resistant to collapse when contacted with fluids. Therefore, the need to process a cross-linked sol-gel by supercritical drying to form a cross-linked aerogel is unnecessary. Accordingly, a cross-linked sol-gel material was prepared by following the protocol described in Example I, except that the supercritical drying step was avoided. Rather, the cross-linked aerogels were washed in pentane four times for twelve hours per wash. The cross-linked aerogels were then removed from the pentane and placed into an oven that was heated to 40� C. The gels were completely dried in one hour. The properties of the air-dried aerogels are similar to those of aerogels prepared using supercritical fluid extraction are presented below in Table I.
TABLE I Properties of Supercritical Fluid Extraction (SCF) dried and Pentane dried aerogels Supercritical Fluid Dried Pentane Dried Density (g/cm−3) 0.57 +/− 0.02 0.56 +/− 0.01 BET Surface Area (m2/g) 150 +/− 10 132 +/− 15 Average Pore Diameter (Å) 194 +/− 6 185 +/− 20 Modulus (MPa) 67 +/− 23 75 +/− 22 Load at Rupture (kg) 34 +/− 8 34 +/− 9
[0088] Preparation of a Cross-Linked Aerogel Film
[0089] Thin films can be prepared from the cross-linked aerogels described herein. Such films may be prepared by thoroughly mixing the contents of two vials: Vial A:4.514 mL of tetramethoxysilane; 3.839 mL of propylene carbonate; and Vial B: 4.514 mL of propylene carbonate; 1.514 mL water and 20 μL (microliter) of concentrated ammonium hydroxide, to form a sol. The sol is then poured onto a gold coated glass plate. The sol-gel material contained on the surface of the plate is then evenly distributed on the plate by spinning the plate. The plate containing the sol-gel material is quickly dipped in propylene carbonate to wash the sol-gel material. The plate containing the sol-gel material is then placed into a container containing a mixture of propylene carbonate and diisocyanate and heated in a microwave oven. Following heating, the plate containing the cross-linked sol-gel material is quickly washed in propylene carbonate, washed in another desired solvent, and then allowed to dry. The gold coated plate is placed into a solution of potassium cyanide to dissolve the gold film and release the cross-linked aerogel from the plate.
TABLE II Properties of Silica/Di-ISO Aerogel Monoliths BET area (m2 g−1) (Av. diametral modulus of % di-ISO w/w pore diam, load at deflection at elasticity (E)g in the bath diameterb (cm) ρb b (g cm−3) nm) hydrophilicityd rupturee (kg) rupturef (cm) (Mpa) 0.0 0.999 � 0.002 0.169 � 0.004 997 (13.4)c 66 � 16 0.12 (h) h h 4.0 0.999 � 0.002 0.241 � 0.003 324 (i) 16 � 2 1.75 (i) 0.061 5.3 (i) 8.0 0.986 � 0.010 0.297 � 0.007 308 (18.1) 8 � 2 3.95 (4.38) 0.101 12.5 (10.5) 16 0.954 � 0.011 0.388 � 0.006 309 (22.3) 4 � 1 9.65 (9.73) 0.140 i (20.4) 25 0.936 � 0.007 0.390 � 0.013 245 (21.9) 4 � 1 10.4 (9.87) 0.129 31.3 (26.1) 34 0.908 � 0.013 0.440 � 0.009 215 (23.2) 5 � 2 8.70 (9.87) 0.110 i (40.1) 42 0.907 � 0.006 0.447 � 0.020 165 (16.6) 5 � 1 14.7 (15.6) 0.199 47.5 (46.3) 51 0.897 � 0.014 0.439 � 0.016 178 (29.8) 4 � 2 12.0 (11.8) 0.109 i (53.8) #with the homemade apparatus were carried out with four different series of variable-density monoliths, and all loads at rupture at each density were within 5% of their average. Diametral deflection vs load, however, was recorded (see footnote f) for only a single series of samples (the one reported). The Instron test was also carried out with a single series of variable-density monoliths (the one reported).
TABLE III Examples of diisocyanates cross-linking agents 1. Hexamethylene diisocyanate (HDI) And polymers thereof (e.g., Desmodur � N-3200): 2. Methylene diisocyanate (MDI) And polymers thereof (e.g., Desmodur � E-22; polyMDI): (Av. n = 2) 3. Toluene diisocyanate monomer. For example Desmodur � TD 80, which is a mixture of: 4. Triphenyl methyl triisocyanate (e.g., Desmodur � RE) 5. Desmodur � W, a monomer with structure: 1. Other cross-linking agents include the structures listed in Table II where the OCN group is replaced with other reactive groups that will react with free —OH groups on a sol-gel like material. 2. Desmodurs � are commercially available from the Bayer corporation.
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[0213] Kim, N. K., K. Kim, D. A. Payne, and R. S. Upadhye 1989 Fabrication of hollow silica aerogel spheres by a droplet generation method and sol—gel processing. J. Vac. Sci. Technol., A 7:1181-1184.
[0214] Maynard, R., R. Calemczuk, A. M. Degoer, B. Salce, J. Bon, E. Bonjour, and A. Bourret 1989 Low Energy Excitations In Silica Aerogels. Journal De Physique 50: C4107-C4112.
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[0216] Mukherjee, S. P., J. F. Cordaro, and J. C. Debsikdar 1988 Pore structures and microstructures of silica gel monoliths at different stages of sintering. Advanced Ceramic Materials 3:463-467.
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[0218] All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.
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|U.S. Classification
|521/99, 521/128, 521/117, 521/113
|International Classification
|Cooperative Classification
|European Classification
|Dec 8, 2005
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