Applications and Notable Materials

Applications and notable materials

Applications and Notable Materials 1

An important application of mosaic crystals is in monochromators for x-ray and neutron radiation. The mosaicity enhances the reflected flux, and allows for some phase-space transformation. Pyrolitic graphite (PG) can be produced in form of mosaic crystals (HOPG: highly ordered PG) with controlled mosaicity of up to a few degrees.

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Materials

The textile potholder was nonexistent in art or writing until around the 19th century. Evidence in art points towards hooks that were used to carry hot-handled pots in ancient Greece, but it was not until the Antislavery Bazaars of the mid-19th century that equivocally the first home-made potholders were made. These crafts were illustrated with various designs and advertised the phrase 'Any holder but a Slave Holder. " By creating such a political craft, which shares similar dimensions and fabrication with the contemporary potholder, women who may have never associated with the abolitionist movement had the opportunity to do so. The popularity of potholders is concomitant with the rise in proliferation of magazines. In these magazines, patterns were given for 'teapot holders' which strongly resemble potholders. Insulation capability was limited in early models. Since their genesis as standard household items, potholders have been largely associated with home crafting, and crocheting has long been the leading method in this strain followed by knitting and patchwork. Needlework patterns in the 1950s were often impractical and over-designed with holes and elaborate spacing that would burn the user or wear out the holder quickly. In the 1970s, quilting and applique-made potholder patterns gained popularity, enduring into the present day.

Applications and Notable Materials 2

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Strengthening mechanisms in amorphous materials

PolymerPolymers fracture via breaking of inter- and intra molecular bonds; hence, the chemical structure of these materials plays a huge role in increasing strength. For polymers consisting of chains which easily slide past each other, chemical and physical cross linking can be used to increase rigidity and yield strength. In thermoset polymers (thermosetting plastic), disulfide bridges and other covalent cross links give rise to a hard structure which can withstand very high temperatures. These cross-links are particularly helpful in improving tensile strength of materials which contain lots of free volume prone to crazing, typically glassy brittle polymers. In thermoplastic elastomer, phase separation of dissimilar monomer components leads to association of hard domains within a sea of soft phase, yielding a physical structure with increased strength and rigidity. If yielding occurs by chains sliding past each other (shear bands), the strength can also be increased by introducing kinks into the polymer chains via unsaturated carbon-carbon bonds. Adding filler materials such as fibers, platelets, and particles is a commonly employed technique for strengthening polymer materials. Fillers such as clay, silica, and carbon network materials have been extensively researched and used in polymer composites in part due to their effect on mechanical properties. Stiffness-confinement effects near rigid interfaces, such as those between a polymer matrix and stiffer filler materials, enhance the stiffness of composites by restricting polymer chain motion. This is especially present where fillers are chemically treated to strongly interact with polymer chains, increasing the anchoring of polymer chains to the filler interfaces and thus further restricting the motion of chains away from the interface. Stiffness-confinement effects have been characterized in model nanocomposites, and shows that composites with length scales on the order of nanometers increase the effect of the fillers on polymer stiffness dramatically. Increasing the bulkiness of the monomer unit via incorporation of aryl rings is another strengthening mechanism. The anisotropy of the molecular structure means that these mechanisms are heavily dependent on the direction of applied stress. While aryl rings drastically increase rigidity along the direction of the chain, these materials may still be brittle in perpendicular directions. Macroscopic structure can be adjusted to compensate for this anisotropy. For example, the high strength of Kevlar arises from a stacked multilayer macrostructure where aromatic polymer layers are rotated with respect to their neighbors. When loaded oblique to the chain direction, ductile polymers with flexible linkages, such as oriented polyethylene, are highly prone to shear band formation, so macroscopic structures which place the load parallel to the draw direction would increase strength. Mixing polymers is another method of increasing strength, particularly with materials that show crazing preceding brittle fracture such as atactic polystyrene (APS). For example, by forming a 50/50 mixture of APS with polyphenylene oxide (PPO), this embrittling tendency can be almost completely suppressed, substantially increasing the fracture strength. Interpenetrating polymer networks (IPNs), consisting of interlacing crosslinked polymer networks that are not covalently bonded to one another, can lead to enhanced strength in polymer materials. The use of an IPN approach imposes compatibility (and thus macroscale homogeneity) on otherwise immiscible blends, allowing for a blending of mechanical properties. For example, silicone-polyurethane IPNs show increased tear and flexural strength over base silicone networks, while preserving the high elastic recovery of the silicone network at high strains. Increased stiffness can also be achieved by pre-straining polymer networks and then sequentially forming a secondary network within the strained material. This takes advantage of the anisotropic strain hardening of the original network (chain alignment from stretching of the polymer chains) and provides a mechanism whereby the two networks transfer stress to one another due to the imposed strain on the pre-strained network. GlassMany silicate glasses are strong in compression but weak in tension. By introducing compression stress into the structure, the tensile strength of the material can be increased. This is typically done via two mechanisms: thermal treatment (tempering) or chemical bath (via ion exchange). In tempered glasses, air jets are used to rapidly cool the top and bottom surfaces of a softened (hot) slab of glass. Since the surface cools quicker, there is more free volume at the surface than in the bulk melt. The core of the slab then pulls the surface inward, resulting in an internal compressive stress at the surface. This substantially increases the tensile strength of the material as tensile stresses exerted on the glass must now resolve the compressive stresses before yielding. σ y = m o d i f i e d = σ y , 0 σ c o m p r e s s i v e displaystyle sigma _y=modified=sigma _y,0sigma _compressive Alternately, in chemical treatment, a glass slab treated containing network formers and modifiers is submerged into a molten salt bath containing ions larger than those present in the modifier. Due to a concentration gradient of the ions, mass transport must take place. As the larger cation diffuses from the molten salt into the surface, it replaces the smaller ion from the modifier. The larger ion squeezing into surface introduces compressive stress in the glass's surface. A common example is treatment of sodium oxide modified silicate glass in molten potassium chloride. Examples of chemically strengthened glass are Gorilla Glass developed and manufactured by Corning, AGC Inc.'s Dragontrail and Schott AG's Xensation.

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Related materialsPublished in Ulmann's lifetimeUlmann, D. (1919). The faculty of the College of Physicians & Surgeons, Columbia University in the City of New York. New York, Hoeber. Ulmann, D. (1920). The faculty of the College of Physicians & Surgeons, Columbia University in the City of New York: twenty-four portraits. New York, Hoeber. Ulmann, D. et al. (1922). A book of portraits of the faculty of the Medical Department of the Johns Hopkins University, Baltimore. Baltimore, Johns Hopkins Press. Ulmann, D. (1925). A portrait gallery of American editors. New York, W.E. Rudge. Ulmann, D. (1928). "Among the Southern mountaineers: camera portraits of types of character reproduced from photographs recently made in the highlands of the South," The Mentor, v.16 pp. 23-32. New York, N.Y., Crowell Pub. Co. Peterkin, J. M., D. Ulmann, et al. (1933). Roll, Jordan, roll. Indianapolis, Bobbs-Merrill. [unattributed] (1930). "The stuff of American drama in photographs by Doris Ulmann," Theatre Arts Monthly, v. 14 pp. 132-146. New York, NY: Theatre Arts, Inc.Later worksEaton, A. H., D. Ulmann, et al. (1937). Handicrafts of the Southern highlands; with an account of the rural handicraft movement in the United States and suggestions for the wider use of handicrafts in adult education and in recreation. New York, Russell Sage Foundation. Ulmann, D. (1971). The Appalachian photographs of Doris Ulmann. Penland, N.C. Jargon Society. Ulmann, D., R. Coles, et al. (1974). The darkness and the light. [New York] Aperture. Ulmann, D., J. J. Niles, et al. (1976). The Appalachian photographs. Highlands, N.C., Jargon Society. Ulmann, D. (1976). Photographs of Appalachian craftsmen: a retrospective exhibition, April 6-May 1, 1976. Cullowhee, N.C., Western Carolina University. Ulmann, D., et al. (1978). An exhibition for the dedication of the Traylor Art Building, Berea College, Berea, Kentucky: Doris Ulmann's photographs; ritual clay: Walter Hyleck; the Berea College collection. Berea, Ky., Berea College. Ulmann, D. and D. Willis-Thomas (1981). Photographs by Doris Ulmann: the Gullah people [exhibition] June 1-July 31, 1981, Schomburg Center for Research in Black Culture, The New York Public Library Astor Lenox and Tilden Foundations. New York, The Library. Banes, R. A. (1985). Doris Ulmann and her mountain folk. Bowling Green, Ohio, Bowling Green State University. Featherstone, D. (1985). Doris Ulmann: American portraits. Albuquerque, University of New Mexico Press. Curtis, E. S., D. Ulmann, et al. (1986). The last photographs. Haverford, Pa., Comfort Gallery Haverford College. Keller, J. (1988). After the manner of women: photographs by Ksebier, Cunningham, and Ulmann. Malibu, Calif., J. Paul Getty Museum. McEuen, M. A. (1991). Changing eyes: American culture and the photographic image, 1918-1941. Oeltman, M. T. (1992). Doris Ulmann, American photographer, and the Southern Agrarian movement. Lovejoy, B. (1993). The oil pigment photography of Doris Ulmann. Lexington, Ky., [s.n.]. Lamuniere, M. C., J. M. Peterkin, et al. (1994). Roll, Jordan, roll: the Gullah photographs of Doris Ulmann. University of Oregon. Sperath, A. (1995). Ceramics Kentucky 1995. Murray, Ky., The Gallery. Ulmann, D. (1996). Doris Ulmann: photographs from the J. Paul Getty Museum. Malibu, Calif., The Museum. Ulmann, D. and J. Keller (1996). Doris Ulmann: photography and folklore. Los Angeles, J. Paul Getty Museum. Ulmann, D. et al. (1997). Picture gallery photography by Doris Ulmann. University of Oregon. Rosenblum, N., S. Fillin-Yeh, et al. (1998). Documenting a myth: the South as seen by three women photographers, Chansonetta Stanley Emmons, Doris Ulmann, Bayard Wootten, 1910-1940. Portland, Or., Douglas F. Cooley Memorial Art Gallery Reed College. Ulmann, D. et al. (1999). Myth, memory and imagination: universal themes in the life and culture of the South: selections from the collection of Julia J. Norrell. McKissick Museum. Columbia, S.C., McKissick Museum University of South Carolina. Kowalski, S. (2000). Fading light: the case of Doris Ulmann. University of Oregon. Jacobs, P. W. (2001). The life and photography of Doris Ulmann. Lexington, University Press of Kentucky. Gillespie, Sarah Kate (2018). Vernacular modernism: The photography of Doris Ulmann. Athens, Georgia Museum of Art.— — — — — —MaterialsThe modern Wiener Oboe is most commonly made from grenadilla, though some manufacturers also make oboes out of the traditional European material boxwood— — — — — —Design and materialsNormally they come in two or three tiers, although more elaborate versions can have four. The bottom tier, sometimes larger than the others, is the one usually used for rice. Tiffin carriers are opened by unlocking a small catch on either side of the handle. Tiffin carriers are generally made out of steel and sometimes of aluminium, but enamel and plastic versions have been made by European companies. Two dabbawalas in Mumbai delivering meals packed in tiffin carriers Thai Tiffin box in Bangladesh. Tiffin carrier, Burmese Lacquerware Malaysia, Peranakan Tiffin Carrier
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