Materials Literature
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A highly tetrahedrally bonded form on nonhydrogenated amorphous carbon (a-C) is produced by deposition from filtered medium-energy ion beams. A range of such films was grown and the ${\mathit{sp}}^{3}$-bonded fractions, plasmon energies, compressive stresses, and resistivities were measured as a function of ion energy…
The nonlinear optical behaviour of the organic crystal MBA-NP has been investigated at 1064 and 532 nm, with both nanosecond and picosecond pulses. The second-order effective susceptibility for second harmonic generation, and the damage thresholds compare favourably with those of most inorganic crystals. Two-photon ab…
A summary is given of theories founded on concepts such as roughening transitions, kinetic roughening, and connected nets which in principle allow the prediction of the conditions under which a crystal face (hkl) will grow as a flat face, by a layer mechanism, or as a rough face. Starting with Jackson's theory based o…
The growth kinetics of m-chloronitrobenzene crystals from acetone solutions were measured and analysed to see the effects of the presence of microcrystals in the solution. The microcrystals generated by the added fine crystals were found to cause significant enhancement of the growth rate by a factor of 2-5. Possible…
Vogel-Fulcher-Tammann temperature dependence of sigma ( sigma varies as exp(-E a /k(T-T 0 ))) was found in a KTiOPO 4 single crystal for the (001) direction. The values of T 0 and E a were 150 K and 0.16 eV respectively. Below 150 K fast ion transport can therefore be expected to be frozen.
The information required from optical assessment of nonlinear organic materials differs widely depending on the application envisaged for the material in question. Accordingly, a suitable assessment scheme must be devised which will give a reliable indication of the promise of these materials in a wide variety of appl…
The quest for more efficient nonlinear optical materials of increased optical quality is being spurred by the development of optical communication systems that require ultrafast broad band optical signal processing functions. Conversely, nonlinear optical phenomena enlarge traditional spectroscopic approaches to encom…
Atomic force microscopy was used to obtain images of lysozyme crystals growing in their native solution environment. The authors growth by both two-dimensional nucleation and screw dislocation mechanisms. Nucleation centres appeared to occur randomly over the surface, and were uncorrelated from layer to layer. Surface…
Phenytoin crystal growth kinetics have been measured in phosphate buffer as a function of pH, supersaturation, and temperature. Incorporation of growth units into the crystal lattice is controlled by surface integration and follows a screw-dislocation mechanism. This mechanism explains the observed dependence of growt…
The underlying crystal-growth theory and structural molecular chemistry important in the understanding of the methodology behind the theoretical prediction of crystal morphology is presented together with its application to the molecular solid benzophenone. Benzophenone crystallizes in the orthorhombic space group P2…
Tailor-made molecular auxiliaries for the control of nucleation and growth of molecular crystals may be classified into two broad categories: inhibitors and promoters. Tailor-made inhibitors of crystal growth can be used for a variety of purposes which include morphological engineering, reduction of crystal symmetry,…
Polymorphism has critical implications in material design of organic crystals for elucidating specific functions in optics, pharmaceuticals, foods, biology etc. This is because diversified properties are revealed in polymorphic modifications. Depending on the selection of the specific polymorphs, one has to deal with…
Protein and virus crystals commonly grown in the laboratory on earth have also been grown in a microgravity environment on the US Space Shuttle. Two techniques for growth of the crystals were investigated: vapour diffusion and direct liquid-liquid diffusion. Crystals produced in microgravity, although generally isomor…
The production of uniform fine crystalline particles is highly desirable for pharmaceutical products in order to enhance stability and dissolution rates and, thereby, to favour high bioavailability. Precipitation under high-supersaturation conditions favours nucleation over growth processes and will result in smaller…
The effect of solvent in crystallization of polymorphs has been studied using the drug sulphathiazole as a model compound. The solubilities of the four polymorphic forms of sulphathiazole were determined as a function of temperature in various solvents. Within the temperature ranges studied, the rank order of solubili…
The light scattering properties of polymer-dispersed liquid crystal (PDLC) films depend on several aspects of the film structure and nematic alignment. In this study we gauge the relative importance of some of these factors by varying the structure and properties of PDLC films in a systematic way, and measuring the va…
Abstract The emulsification and electrodeposition properties of mixtures of polyoxypropylene‐(POP) modified cationic epoxy resin (III) and nonionic trimethylolpropane–toluene diisocyanate–2‐ethylhexanol (TMP–TDI–2EH, V) were investigated and the compositions of their electrodeposited films were obtained by Fourier Tra…
Abstract The development of early colour and the dehydrochlorination rate were compared for poly(vinyl chloride) samples obtained by suspension polymerization using two different initiators, dicetylperoxydicarbonate and butylperoxyneodecanoate. The degree of discolouration was measured on pressed plates and expressed…
The structures of the three phases of DBr and DI were determined using neutron powder profile techniques. The highest temperature phases are cubic, Fm3m, with the deuteriums in twelvefold disordered positions about the halogens. The intermediate temperature phases are orthorhombic, Cmca, with the deuteriums in twofold…
We report on complete wave-front control with amplitude- and phase-modulation liquid-crystal devices (LCD's). A twisted nematic device is used for amplitude modulation, and an electrically controlled birefringent device is used for phase modulation. Because the LCD's are optically coupled with afocal optics and are dr…