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  • 11
    Electronic Resource
    Electronic Resource
    Mechanical Properties of Silicon Oxycarbide Ceramic Foams (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical properties of ceramic foams obtained through a novel process that uses the direct foaming and pyrolysis of preceramic polymer/polyurethane solutions were investigated. The elastic modulus, flexural strength, and compressive strengths were obtained for foams in the as-pyrolyzed condition; values up to 7.1 GPa, 13 MPa, and 11 MPa, respectively, were obtained. The strength of the foam was virtually unchanged at temperatures up to 1200°C in air; however, long-term exposure at 1200°C led to a moderate degradation in strength, which was attributed to the evolution of intrastrut porosity during the oxidation of residual free carbon, as well as devitrification of the foams struts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00996.x
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  • 12
    Electronic Resource
    Electronic Resource
    Conductive Ceramic Foams from Preceramic Polymers (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ceramic foams in the system Si-O-C, possessing different bulk densities and morphologies, were obtained from preceramic polymers using two different direct foaming approaches. The electric properties of the foams were varied by adding suitable fillers to the precursor mixtures in amounts up to 80 wt%. The electrical conductivity of the foams was varied by several orders of magnitude. The effects of the type of filler and preceramic polymer (methylsiloxane or methylphenylsiloxane resins), as well as the used filler precursor, on the properties of the ceramic foams were investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01000.x
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  • 13
    Electronic Resource
    Electronic Resource
    Comparison of Microwave Hybrid and Conventional Heating of Preceramic Polymers to Form Silicon Carbide and Silicon Oxycarbide Ceramics (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Six different preceramic polymers were pyrolyzed via conventional and microwave hybrid heating; these polymers provide a range of carbon content and local atomic coordination. The products were compared with each other using X-ray diffractometry and transmission electron microscopy. Nanocrystalline β-SiC was the principal crystal phase detected, and the amount and size of the nanocrystals increased as the processing temperature increased. Differences were observed in the amount and size of the β-SiC nanocrystals and the graphitization of residual carbon between the microwave hybrid heating and the conventional oven heating of polycarbosilanes. Conventional heating of a high-carbon polysiloxane in an oven (in flowing argon) produced a greater amount of β-SiC from carbothermal reduction at high temperature. Microwave hybrid heating led to better β-SiC nanocrystal development for polyureasilazane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01440.x
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  • 14
    Electronic Resource
    Electronic Resource
    Ceramic Foams: Fabrication, Properties and Applications (2001)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 206-213 (Dec. 2001), p. 1913-1918 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/46/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.206-213.1913.pdf
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  • 15
    Electronic Resource
    Electronic Resource
    Ceramic Foams from a Preceramic Polymer and Polyurethanes: Preparation and Morphological Investigations (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 195-199 
    Details
    ISSN: 1573-4846
    Keywords: preceramic polymers ; foams ; silicon oxycarbide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Open-cell ceramic foams were obtained from a preceramic polymer (silicone resin) and blown polyurethanes. The preceramic polymer, which is crosslinked by condensation of silanol groups, was dissolved in CH2Cl2 and added to a liquid polyol containing the surfactant and the amine catalyst. Isocyanate was then added to the mixture and the foam was obtained through a twofold blowing mechanism (physical and chemical blowing). The morphology of the expanded polyurethane, which can be flexible or semirigid, characterized the final structure of the ceramic foam. The materials obtained were pyrolyzed in a nitrogen flux at temperatures of 1000–1200°C, thus allowing for the polymer-to-ceramic transformation to occur in the preceramic polymer. The ceramic foams produced in this way consisted of an amorphous silicon oxycarbide ceramic (SiOC). They presented a density ranging from 0.1 to 0.3 g/cm3. The average pore diameter ranged from 200 to 400 μm and they possessed 80 to 90% open porosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008604800737
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  • 16
    Electronic Resource
    Electronic Resource
    Silicon Oxycarbide Foams from a Silicone Preceramic Polymer and Polyurethane (1999)
    Springer
    Journal of sol gel science and technology 14 (1999), S. 103-111 
    Details
    ISSN: 1573-4846
    Keywords: foams ; preceramic polymers ; silicon oxycarbide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ceramic open-cell foams were obtained from a preceramic polymer (a silicone resin) and blown polyurethanes, by pyrolysis at 1200°C in nitrogen. Silicon carbide submicron powders were also added to the silicone resin to give SiOC + SiC composite foams. The morphology of the foams was dependent on the architecture of the blown polyurethanes. The crushing strength as well as the elastic modulus increased with increasing relative density, reaching values as high as 14 and 450 MPa, respectively. Some of the foams displayed an excellent thermal stability (resistance to oxidation in air and decomposition in inert atmosphere) up to elevated temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008736100788
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  • 17
    Electronic Resource
    Electronic Resource
    Iontophoresis Enhances the Transport of Acyclovir Through Nude Mouse Skin by Electrorepulsion and Electroosmosis (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1623-1627 
    Details
    ISSN: 1573-904X
    Keywords: iontophoresis ; acyclovir ; electroosmosis ; electrorepulsion ; transdermal delivery ; nude mouse skin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Iontophoresis was employed for enhancing the transdermal delivery of acyclovir through nude mouse skin in vitro, with the aim of understanding the mechanisms responsible for drug transport, in order to properly set the conditions of therapeutical application. Methods. Experiments were done in horizontal diffusion cells, using as donor a saturated solution of acyclovir at two different pH values (3.0 and 7.4). Different electrical conditions (current density and polarity) were employed. Results. At pH 3.0, acyclovir anodal transport was due to electrorepulsion, since acyclovir was 20% in the protonated form. In acyclovir anodal iontophoresis at pH 7.4 the main mechanism involved was electroosmosis, since the drug was substantially unionized and the negative charge of the skin at this pH caused the electroosmotic flow to be from anode to cathode. In the case of cathodal iontophoresis at pH 3.0, acyclovir transport was enhanced approx. seven times, due to the presence of an electroosmotic contribution caused by the reversal of the charge of the skin. At pH 7.4 during cathodal iontophoresis acyclovir transport was not enhanced because the electroosmotic flow was in the opposite direction, compared to drug electric transport, i.e. anode to cathode. The increased skin permeability caused by current application was demonstrated to be less important than electrorepulsion and electroosmosis. Conclusions. Anodal iontophoresis shows potential applicability for enhancing acyclovir transport to the skin, considering that both electric transport and electroosmosis can be used by appropriately setting the pH of the donor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016284815501
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  • 18
    Electronic Resource
    Electronic Resource
    Delivery of Nasal Powders of β-Cyclodextrin by Insufflation (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 734-738 
    Details
    ISSN: 1573-904X
    Keywords: nasal powder ; powder properties ; nasal powder delivery ; insufflation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Delivery of nasal powders of granulated β-cyclodextrin by insufflation was studied in order to find the relationship between powder properties and delivery behavior. Methods. Three nasal powder formulations, prepared by granulating β-cyclodextrin with different binders, were delivered from a powder insufflation device, in which the dose to be emitted was loaded in a gelatin capsule. The delivery sequence of powder was recorded and characterized using an image analysis program. Results. Particle size was the main parameter affecting nasal powder delivery, both as to the amount of dose sprayed and the aspect of cloud produced. Between 50–150 µm of particle size a substantial change in delivery behavior of powders was observed. Powder of around 100 µm in size showed useful insufflation characteristics for nasal delivery. Bioavailability of nasal formulations of progesterone/β-cyclodextrin powders was discussed in term of delivery behavior. Conclusions. The formulation approaches for improving nasal delivery of powders require the use of size optimized carriers. Insufflation of powders over 50 µm can favour the particle deposition by impaction, whereas for powders below 50 µm, deposition by sedimentation is moved. β-cyclodextrin is a suitable carrier for achieving high systemic availability following nasal administration of powder formulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016099516757
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  • 19
    Electronic Resource
    Electronic Resource
    Drug Reservoir Composition and Transport of Salmon Calcitonin in Transdermal Iontophoresis (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 63-66 
    Details
    ISSN: 1573-904X
    Keywords: iontophoresis ; transdermal delivery ; calcitonin ; reservoir ; peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of the work was to study iontophoretic transdermal administration of salmon calcitonin (sCt) in rabbits, with particular attention to drug reservoir composition. A dry sCt disc, to be dissolved on the application site, was used for preparing the reservoir for transdermal iontophoresis. As a reference drug reservoir, a pad wetted with drug solution was used. Methods. Experiments were done in rabbits depositing 100 IU of salmon calcitonin on skin and applying anodal iontophoresis. Serum calcium concentration was measured during iontophoresis, passive diffusion and after i.v. administration. Parameters such as pH value and reservoir type were examined. Results. Transdermal iontophoresis of sCt elicited a decrease in the serum calcium level, whereas, in the absence of electric current, no significant fall was measured. Using the reservoir prepared from drug solution, anodal iontophoresis at pH 4.2 was more effective than at pH 7.4, probably due to higher sCt net positive charge. Using the reservoir prepared from dry disc, similar kinetics and extent of drug effect were observed at both pH values. The reservoir prepared from solid drug deposit concentrated sCt next to the skin. Conclusions. Anodal iontophoresis for transdermal calcitonin administration shows therapeutical applicability. The type of reservoir is an important parameter affecting sCt transdermal iontophoresis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012055401038
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  • 20
    Electronic Resource
    Electronic Resource
    The mechanisms of disintegration of compressed particulate systems (1987)
    Springer
    Polymer bulletin 18 (1987), S. 541-544 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Disintegration of compacts in the presence of a solvent is followed by measurement of the disintegration force development as a function of time. The process is described by the delamination of the compact and the rate of expansion of the detached layers using a new equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255339
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