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- Petfordlong, Amanda K., et al.
(författare)
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On the growth of small crystals of Cd, Zn, Pt and Rh during electron microscope observations
- 1987
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 80:2, s. 218-224
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Tidskriftsartikel (refereegranskat)abstract
- The growth of small supported metal crystals under the influence of an electron beam has been studied in real-time using a 400 keV ultra-high-resolution electron microscope. Samples of Pt, Rh, Cd and Zn supported on amorphous C or Si films were prepared ex situ and crystal growth in situ was recorded directly using a TV imaging/video system attached to the microscope. The different types of observed crystal growth are reported: the fcc metals (Pt and Rh) grow by coalescence, or by the addition of atoms along the particle surface followed by structural rearrangements which result in approximately spherical particles. The hcp metals (Cd and Zn) grow in the form of long rafts along the surface of the substrate film.
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| 2. |
- Cerreta, M.K., et al.
(författare)
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The structure of aqueous solutions of some dihydrogen orthophosphates by laser Raman spectroscopy
- 1987
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 84:4, s. 577-588
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Tidskriftsartikel (refereegranskat)abstract
- Powdered crystals and pure, aqueous solutions of ammonium, sodium, and potassium dihydrogen orthophosphates in concentrations ranging from 0.01M to supersaturated were investigated at 30°C using laser Raman spectroscopy between 700 and 1350 cm-1. With increasing solute concentration, the peak position of the 875 cm-1 P-(OH)2 symmetric strech band increased. Extreme asymmetry in the 1075 cm-1 P=O2 symmetric stretch band developed to lower energy. The integrated intensity ratio of the 875 cm-1 band to the 1075 cm-1 band envelope remained constant. These observations are consistent with anion-anion association via hydrogen bonds. Deconvolution of the spectral bands showed only 40% and 20% of the phosphates exist as monomers in saturated potassium and ammonium solutions, respectively, and that anion association does not cease at the dimer. The spectra provided no evidence of quasi-crystalline entities in solution. The necessary breaking and reforming of hydrogen bonds during the growth process can explain rapid z-direction growth, growth activation energy, and the rate-limiting surface growth mechanism.
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