Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Nano-Order Structural Analysis of White Light-Emitting Silicon Oxide Prepared by Successive Thermal Carbonization/Oxidation of the Porous Silicon (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 561-565 (Oct. 2007), p. 1127-1130 
    Details
    ISSN: 1662-9752
    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
    Notes: Recently the present authors’ group found that porous silicon showed strong and stablewhite/white-blue light emission after successive thermal carbonization and oxidation by water vapor.This material can be considered as a price-competitive solid-state white-light source. We examinedthese layers by electron energy-loss spectroscopy (EELS), energy-filtering transmission electronmicroscopy (EFTEM). The EEL spectra indicated that the silicon skeleton in the porous layer wascompletely oxidized by the thermal treatment in wet argon ambient and multi-types of carbon phaseswere present in the 1073 K oxidized sample of stronger emission, while carbon complexes includingSi and/or O were formed in the 1223 K oxidized sample of weaker light emission. EF-TEM imagesshowed that carbon/oxygen were more uniformly distributed in the 1223 K oxidized sample. It isassumed that the strong light-emitting properties are controlled by the size and internal chemicalbonding states of carbon clusters incorporated
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/17/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.561-565.1127.pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Carbonization of Porous Silicon for 3C-SiC Growth (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 556-557 (Sept. 2007), p. 167-170 
    Details
    ISSN: 1662-9752
    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
    Notes: In the present work, the carbonization of porous silicon for the subsequent 3C-SiCgrowth has been systematically studied. The effect of temperature and acetylene flow-rate on thechemical state of the surface and structure relaxation was studied. It was found that the porousnano-crystalline morphology is unstable and tends to recrystallize in temperature range typical of3C-SiC growth on Si (10000C-13000C). The carbonization impedes recrystallization at 10000C, butat 13000C the full recrystallization takes place. Pyrolytic amorphous graphite-like carbon was foundon porous silicon carbonized at temperature and with acetylene flow-rate above critical values
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/17/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.556-557.167.pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    X-Ray Powder Diffraction Characterization of Residual Stresses and Strains in Y〈sub〉3〈/sub〉Al〈sub〉5〈/sub〉O〈sub〉12〈/sub〉:Nd〈sup〉3+〈/sup〉 Nanoceramics (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 571-572 (Mar. 2008), p. 303-308 
    Details
    ISSN: 1662-9752
    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
    Notes: Y3Al5O12:Nd3+ nanoceramics were obtained by sintering nanocrystalline Y3Al5O12:Nd3+powders at 450 oC under different pressures between 2 and 8 GPa. The structural purity, residualstress, strain, texture, and crystallite size of the products were analysed with X-ray powderdiffraction. The results indicate that the average crystallite size remains unchanged at about 30 nmin spite of the heating and the pressure applied. No texture was observed. On the other hand, themicrostrains increase with increasing pressure, while the residual stresses are at their maximum inthe green body and the sample processed at 8 GPa. Increasing strains were observed to increase thewidth of the luminescence lines and to decrease the luminescence decay times
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/18/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.571-572.303.pdf
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    A Kinetic Study on Crystallization of an Amorphous Lubricant (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 899-904 
    Details
    ISSN: 1573-904X
    Keywords: amorphous material ; crystallization ; solid state reaction kinetics ; XRPD ; DSC ; microcalorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of the work was to study the crystallization kinetics of amorphous sterotex K at different temperatures and with different methods, and to compare the obtained kinetic and thermodynamic results. Methods. Isothermal microcalorimetry was the principal technique to determine the crystallization behavior of sterotex K. X-ray powder diffraction and differential scanning calorimetry were employed to interpret the microcalorimetric heat flow curves and compare the kinetics and the calculated value for the transition enthalpy. Results. The best way to analyze the x-ray diffractograms was the statistic Wakelin's correlation method. The method gave consistent quantitative results with microcalorimetry and both methods showed crystallization to consist of two partially parallel part-processes, which attached probably to the different growing rates of the forms consisting of different lattice planes having the same spacing. The quantitative analysis of differential scanning calorimetry scans was troublesome to perform but the obtained average value of −51 J/g for the enthalpy of the crystallization was in good agreement with the values obtained with the other methods, the average being −52 J/g. Calculating heat flow versus released energy plots from the microcalorimetric data the crystallization mechanism was observed to change as a function of temperature. Conclusions. A sensitive isothermal microcalorimeter can give precise and fast knowledge about possible solid state transition mechanism, but the source of the heat flow signal must be verified with other analytical methods to avoid incorrect conclusions. Due to the sensitivity and the real-time data the microcalorimetry can show up the mechanism of the transition for varying as a function of temperature and reveal the uselessness of the conventional Arrhenius relationship for extrapolations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012151900923
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Real Time Detection of Photoreactivity in Pharmaceutical Solids and Solutions with Isothermal Microcalorimetry (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 368-373 
    Details
    ISSN: 1573-904X
    Keywords: photoreactivity ; photochemistry ; isothermal microcalorimetry ; nifedipine ; ascorbic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In this study an irradiation cell made as an accessory for an isothermal microcalorimeter is introduced, and its suitability for detection photoreactivity in pharmaceutical solutions and solids is demonstrated. The pharmaceuticals employed are chosen as sample materials to evaluate the usefulness and stability of the irradiation cell. Methods. An irradiation cell has been constructed and tested in an isothermal microcalorimeter with pharmaceutical solutions and solids known to be sensitive to daylight or UV light. Light is produced with an Xe-arc lamp, split into two parts and introduced into calorimetric vessels with optical light cables. One of the vessels containing the reference sample gives the response to the heat absorbed by the material (radiant power), and the other vessel containing the sample material gives the response also to the photoreaction. The two irradiation cells are positioned in the sample sides of two separate twin microcalorimetric units. Results. Nifedipine and L-ascorbic acid were found to be photosensitive in solutions and solid states, the extent of the degradation depending on the irradiation intensity and wavelength. The threshold values of the wavelength for the photoreactions, as well as the wavelengths for the maximum reaction rates, were estimated via the scanning irradiation measurements. The ability of photons with different energies to produce heat in the photosensitive reaction of nifedipine was calculated using constant λ measurements. Conclusions. The technique introduced offers a rapid and versatile method to study the photosensitivity of materials in any state. In the measurements, various conditions can be simulated and thus provide information on the real behavior of materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018865400593
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Simultaneous Determination of the Heat and the Quantity of Vapor Sorption Using a Novel Microcalorimetric Method (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 701-706 
    Details
    ISSN: 1573-904X
    Keywords: vapor sorption ; molar heat of adsorption ; kinetics ; isothermal microcalorimetry ; recrystallization ; hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In this study, instrumentation for measuring vapor sorptionenthalpies and sorption uptakes simultaneously with an isothermalmicrocalorimeter is introduced. Various pharmaceutical modelsubstances undergoing phase transitions when exposed to humid conditions(25°C), were employed to evaluate the usefulness and sensitivity ofthe constructed experimental method. Methods. The sample is placed in the sample vessel of a RH cell andthe moisture content of the air flow is controlled. From the RH cellthe air flow is conducted into a subsequent perfusion cell in which asaturated salt solution has been loaded. The RH cell and perfusioncells are positioned in the sample sides of two twin calorimetric units.Depending on the moisture content in the outlet flow leaving thepreceding RH cell, the heat flow signal from the subsequent perfusioncell will vary. By means of blank measurement with identical settings,the rate of water sorption can be calculated and, by integration, theamount of sorbed water is obtained. Results. Amorphous lactose and cefadroxil undergo recrystallizationwhen the moisture level in the surroundings exceeds the thresholdvalues specific to each compound. During the sorption phase, heat isevolved fairly linearly as a function of consumed moisture, and alsoafter the recrystallization, the heats indicate linear behavior. The heatvalues for the desorption phase of amorphous lactose and the adsorptionof crystalline lactose coincide. With the different anhydrous forms oftheophylline, the hydration takes place more rapidly in the metastableform I, and generally, the process is more energetic in form I. In allcases, the gravimetric results agree with the water sorption uptakescalculated from the calorimetric data. Conclusions. The technique introduced offers a rapid and sensitivemethod to gain new insights into the transitions in which vapors areinvolved. In addition, different kinds of surfaces with various energeticscan now be studied more closely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007530315652
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...