Browsing by Subject "Morphology"

Now showing 1 - 20 of 30

Open Access
Ab initio temperature dependent studies of the homoepitaxial growth on Si(0 0 1) surface
(2001) Dağ, S.; Çıracı, Salim; Kılıç, Ç.; Fong, C. Y.
We performed ab initio zero temperature and finite temperature molecular dynamics calculations to investigate the homoepitaxial growth on the Si(0 0 1) surface. How do the deposited atoms (adatoms) form addimers and how do the addimers reach their favorable positions at the nucleation site of the growth process are presented. Once two epitaxial addimers, one over the dimer row and oriented perpendicular to the surface dimer bonds and the other over the adjacent trough, are aligned at high temperature, the nucleation site of the growth process is formed. The concerted bond exchange between these addimers and the reconstructed surface dimers is found to be the atomistic mechanism that leads to the homoepitaxial growth. © 2001 Elsevier Science B.V.
Open Access
Antibacterial electrospun nanofibers from triclosan/cyclodextrin inclusion complexes
(Elsevier, 2014) Celebioglu A.; Umu, O. C. O.; Tekinay, T.; Uyar, Tamer
The electrospinning of nanofibers (NF) from cyclodextrin inclusion complexes (CD-IC) with an antibacterial agent (triclosan) was achieved without using any carrier polymeric matrix. Polymer-free triclosan/CD-IC NF were electrospun from highly concentrated (160% CD, w/w) aqueous triclosan/CD-IC suspension by using two types of chemically modified CD; hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD). The morphological characterization of the electrospun triclosan/CD-IC NF by SEM elucidated that the triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF were bead-free having average fiber diameter of 520±250nm and 1100±660nm, respectively. The presence of triclosan and the formation of triclosan/CD-IC within the fiber structure were confirmed by 1H-NMR, FTIR, XRD, DSC, and TGA studies. The initial 1:1molar ratio of the triclosan:CD was kept for triclosan/HPβCD-IC NF after the electrospinning and whereas 0.7:1molar ratio was observed for triclosan/HPγCD-IC NF and some uncomplexed triclosan was detected suggesting that the complexation efficiency of triclosan with HPγCD was lower than that of HPβCD. The antibacterial properties of triclosan/CD-IC NF were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. It was observed that triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF showed better antibacterial activity against both bacteria compared to uncomplexed pure triclosan.
Open Access
Chalcogenide microresonators tailored to distinct morphologies by the shaping of glasses on silica tapers
(OSA - The Optical Society, 2017) Aktaş, O.
Production of chalcogenide (As2Se3) microresonators in sphere, loop, and bottle morphologies by the shaping of glasses at appropriate temperatures between cleaved silica tapers is reported. The quality factors exceed QS = 6.2×105, QB = 6.7 × 105, and QL = 1.6 × 104 for the sphere, bottle, and loop microresonators, respectively. All-optical thermally assisted tuning with a rate of 0.61 nm/mW is demonstrated for a bottle microcavity pumped via a silica taper at a wavelength of 670 nm. This technique enables practical and robust in situ production of chalcogenide microresonators thermally spliced to silica fibers in several morphologies with a wide tuning range of size.
Open Access
Design and synthesis of soluble dibenzosuberane-substituted fullerene derivatives for bulk-heterojunction polymer solar cells
(2014) Kolemen, S.; Cakmak, Y.; Ozdemir, T.; Erten Ela, S.; Buyuktemiz, M.; Dede, Y.; Akkaya, E. U.
Two new dibenzosuberane-substituted fullerene derivatives, dibenzosuberane-C60 monoadduct (DBSCMA) and bis-adduct (DBSCBA) were synthesized using a classical cyclopropanation reaction via a tosylhydrazone route for application as acceptor materials in polymer solar cells (PSCs). DBSCBA shows good solubility in common organic solvents and both derivatives were characterized by 1HNMR, 13C NMR, MALD-TOF, elemental analysis and UV-vis absorption measurements. The shift of fullerene energy levels induced by the dibenzosuberane substitution was investigated by using theoretical simulations and ultraviolet photoelectron spectroscopy. Bulk-heterojunction PSCs based on poly (3-hexylthiophene) (P3HT) and dibenzosuberane-C60 derivatives were fabricated and optimized by adjusting the donor/acceptor ratio and using thermal annealing and solvent additive. The morphologies of the active layers processed under different conditions were also examined by atomic force microscopy. When tested under an illumination of AM 1.5 G at 100 mW/ cm2, the highest power conversion efficiency of the devices using DBSCBA is 3.70% which is superior to that of conventional P3HT:PCBM devices. © 2013 Elsevier B.V.
Open Access
Doğru terim "Muhakeme" değil "Yargılama"dır
(Marmara Üniversitesi Hukuk Fakültesi, 2013) Selçuk, Sami
Türk öğretisi ve yasa koyucusu, hukuk terminolojisi açısından Merhum Kunter’in etkisiyle “yargılama” terimini dışlamış, “muhakeme” terimini benimsemiştir. Ancak bu seçim yerinde değildir. Kunter’in yargı erki yerine yargılama erki denmesi önerisi, yargılamanın yapıbilimsel (morfolojik) açıdan bir canlı gibi doğan, yaşayan ve tükenen maddi içerikli bir olgu, çok basamaklı bir etkinlik olduğunu vurgulaması yerinde ise de, yargılamayı süreç (processus) yerine oluş (devenir) olarak görmesi ve terimlere yüklediği anlamlar hukukun iç ve kavramlar dili açısından tutarlı değildir. Özellikle muhakeme ile yargılama kavramlarının eşanlamlı olduğunu gözetmemesi, mantık ile düşünme kurallarına uymayarak, çağın gerisine, yanıltmacalara (sophism, fallacy), yanıltılara (fallacy, paralogysm), çelişkiye, tarihsel evrime ters düşme pahasına bunlar arasında “kapsam” (extension)-“içlem” (compehension) ilişkisi kurması yerinde olmamıştır. Türkçede “yargılama hukuku” ya da “muhakeme hukuku” yerine “süreç hukuku” (Strafprozessrecht, diritto processuale) denmesi artık çok zor olduğu için anlambilim, etimoloji, yargılama sözcüğünün tarihsel gelişimi, “muhakeme” ve “yargılama” sözcüklerinin eşanlamlı olduğunu ortaya koyduğundan ve bilim ezbere dayanan yabancı dilde değil, düşündüren anadilde yapılabileceğinden muhakeme yerine Türkçe yargılama terimi yeğlenmelidir. Sonuç olarak bir süreç bulunan ceza yargılaması, Foscihini’nin vurguladığı üzere, çözümlemeci (analitik) yaklaşıldığında hukuki yapı açısından “duruk” (statik); hukuk düzeni açısından devinimli (hareketli, dinamik), hukuki akış açısından kinematik bir nitelik sergilemekte; birleşimci (sentetik) yaklaşıldığında ise yapıbilimsel açıdan üç evre karşımıza çıkmaktadır: 1-Soruşturma, 2-bilişme (cognition), 3-yerine getirme (infaz). Ceza Yargılama Yasası (CYY), ikinci evreye “kovuşturma”, yani geniş anlamda “duruşma” demiştir. Bu evre, aslında terimin geniş anlamında “duruşma”dır (débat) ve üç aşamayı içine almaktadır: 1-Önduruşma (duruşma hazırlığı), 2-duruşma (dar anlamda duruşma), 3-sonuç çıkarım (istidlal, duruşma sonrası görüşme ve yargı oluşturma). Tam bu noktada Batı dillerinde kavga, dövüşme gibi anlamlara da gelen ve “tartışma” (débat) denilen kovuşturmanın bu aşamasının “duruşma” terimi yerine yargılamanın temel ilkelerinden olan sözlülük, yüz yüzelik ve ortaklaşalık ilkelerini çok daha iyi yansıttığından, “tartışma” olarak adlandırılması yerinde olurdu. Ancak Ceza Yargılama Yasası ile uyum sağlamak için bu evrenin adı artık “kovuşturma”dır. Bütün bunların bileşkesini aldığımız zaman sonuç olarak ceza yargılaması kanımızca soruşturma, kovuşturma ve yerine getirme (infaz) olarak üç evreden; kovuşturma evresi de “hazırlık”, “duruşma” ve “yargı ya da sonuç çıkarım” olmak üzere üç aşamadan oluşmaktadır.
Open Access
The effect of cationic surfactant and some organic/inorganic additives on the morphology of mesostructured silica templated by pluronics
(Elsevier, 2008-11-01) Poyraz, A. S.; Albayrak, C.; Dag, Ö.
Tri-block copolymers (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), represented as EOxPOyEOx), pluronics (F127=EO106PO70EO106, P65=EO20PO30EO20, P85=EO27PO39EO27, P103= EO17PO55EO17, and P123 = EO20PO70EO20) and cationic surfactants (cethyltrimethylammonium bromide (CTAB)), two surfactant systems, form complex micelles that self-assemble into mesostructured particles with distinct morphology depending on the pluronic type, the concentration of the cationic surfactant and the organic-inorganic ingredients in a siliceous reaction media under acidic conditions. The CTAB-P65 and CTAB-P85 systems form spheres, CTAB-P103 and CTAB-P123 systems form wormlike particles, and CTAB-F127 system form single crystals of mesostructured silica particles under very similar conditions. However addition of various salts (such as KCI and NaNO3) into a CTAB-P103 or CTAB-P123 solution system and cyclohexane and KCI into a CTAB-P85 solution system produces the mesostructured silica spheres and wormlike particles, respectively. By controlling the hydrophilic-hydrophobic character of the pluronics, core-corona interface, by means of additives, such as small organic molecules or salts, one could obtain the desired morphology that is dictated by the shape of the micelles of the pluronic-cationic surfactant complex. The effects of the additives and the formation mechanism of those morphologies have been discussed using spectroscopy (FT-IR and Raman), diffraction (XRD) and microscopy (POM and SEM) data. (c) 2008 Elsevier Inc. All rights reserved.
Open Access
The effect of cucurbit[n]uril on the solubility, morphology, and the photophysical properties of nonionic conjugated polymers in an aqueous medium
(2010) Tuncel, D.; Artar, M.; Hanay, S. B.
The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine-based polymer, namely, poly[9,9-bis{6(N,N-dimethylamino) hexyl}fluorene-co-2,5-thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UV-vis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including 1H and selective 1D-NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water-soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8-assisted self-assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy.
Open Access
Effects of milling and annealing on formation and structural characterization of nanocrystalline intermetallic compounds from Ni-Ti elemental powders
(2012) Ghadimi, M.; Shokuhfar, A.; Rostami H.R.; Ghaffari, M.
Nickel and Titanium elemental powders with a nominal composition Ni-50 at.%Ti were mechanical alloyed in a planetary high-energy ball mill in different milling conditions (5, 10, 20, 40 and 60 h). The investigation revealed that increasing milling time leads to a reduction in crystallite size, and after 60 h of milling, the Ti dissolved in Ni lattice and NiTi (B2) phase was obtained. With milling time, morphology of pre-alloyed powders changed from lamella to globular. Annealing of as-milled powders at 1173 K for 900 s led to formation of nanocrystalline NiTi (B19′), grain growth and release of internal strain. The results indicated that this technique is a powerful and high productive process for preparing NiTi intermetallic compound with nanocrystalline structure and appropriate morphology. © 2012 Elsevier B.V. All rights reserved.
Open Access
Electrospinning of gelatin with tunable fiber morphology from round to flat/ribbon
(Elsevier, 2017) Topuz, F.; Uyar, T.
The electrospinning of gelatin with tunable fiber morphology from round to flat/ribbon was shown, and the detailed studies were conducted to correlate the fiber morphology with electrospinning process parameters and gelatin concentration in electrospinning solution. Particularly, variations in the applied voltage and the concentration of gelatin led to the transition of fiber shape from round to flat/ribbon. The formation of flat-shaped fibers was attributed to rapid evaporation of the solvent (formic acid) from the fiber matrix with increasing the applied voltage and gelatin concentration. On the other hand, round fibers were due to the steady evaporation of formic acid throughout the cross-section of fibers. WAXS analysis revealed that the loss of triple-helical crystalline structure in gelatin after the electrospinning process. The gelatin fibers were cross-linked through treatment with toluene 2,4-diisocyanate (TDI) in a mixed solution of acetone and pyridine, and XPS confirmed the cross-linking of the fibers over an increased carbon content on the elemental composition of the fiber surface due to the incorporated TDI moieties. Overall, this study focuses on morphological tuning of gelatin electrospun fibers towards a flat/ribbon-like structure by variation of electrospinning parameters and polymer concentration, and thus, the proposed concept can be adapted towards flattened/ribbon-like fibers of other protein-based systems by electrospinning.
Open Access
Electrospun BiOI nano/microtectonic plate-like structure synthesis and UV-light assisted photodegradation of ARS dye
(Royal Society of Chemistry, 2014) Babu, V. J.; Bhavatharini, R. S. R.; Ramakrishna, S.
BiOI electrospun nanofibers were prepared by using PAN as a supporting polymer. Subsequent annealing at 500 °C for 5 h, with a ramp rate of about 5 °C min-1 in air, breaks the nanofibers down to tectonic plate-like nano/microstructures. The surface physical and chemical structural changes were then further characterized by FE-SEM, TEM, XRD and XPS. The results reveal that the morphology and crystallite size of BiOI vary strongly depending on the precursor concentration used in the synthesis method. These nanostructures were later employed for photocatalytic degradation of a synthetic textile dye, Alizarin Red S (ARS). The photocatalytic efficiencies were found to be about 93.34% after 100 min of UV-light (340 nm) illumination. Photocatalytic activity (PCA) performance depends on morphology and band alignment. All the compositions follow first order pseudo-kinetics, which was found to be 0.1197 min-1 for a doping concentration of 3%. The enhancement in photodegradation could be possibly by photocatalysis and a photosensitization phenomenon. This has been explained based on the band edge position. © the Partner Organisations 2014.
Open Access
Evaluation of fiber diameter and morphology differences for electrospun fibers on bacterial immobilization and bioremediation performance
(Elsevier, 2017-05) Sarioglu O.F.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this report, morphology and fiber diameter differences of electrospun polysulfone (PSU) fibers on bacterial immobilization and bioremediation performance were evaluated. PSU fibers were produced with aligned or randomly oriented morphologies, and PSU fibers with thinner and thicker diameters were also produced. PSU fibers were utilized as carrier matrices for bacterial integration and the sample showing highest bacterial immobilization was tested for bioremediation of ammonium and methylene blue dye in water. It was found that randomly oriented and thinner PSU fibers are the optimal system for bacterial immobilization, hence bioremediation studies were performed with this sample. The results demonstrated that bacteria immobilized PSU fibers are promising candidates for simultaneous removal of ammonium and methylene blue dye, and they have a potential to be used in remediation of water systems.
Open Access
Fe promoted NOx storage materials: structural properties and NOx uptake
(American Chemical Society, 2010) Kayhan, E.; Andonova, S. M.; Şentürk, G. S.; Chusuei, C. C.; Ozensoy, E.
Fe promoted NOx storage materials were synthesized in the form of FeOx/BaO/Al2O3 ternary oxides with varying BaO (8 and 20 wt %) and Fe (5 and 10 wt %) contents. Synthesized NOx storage materials were investigated via TEM, EELS, BET, FTIR, TPD, XRD, XPS, and Raman spectroscopy, and the results were compared with the conventional BaO/Al2O3 NOx storage system. Our results suggest that the introduction of Fe in the BaO/Al2O3 system leads to the formation of additional NOx storage sites which store NOx mostly in the form of bidentate nitrates. NO2 adsorption experiments at 323 K via FTIR indicate that, particularly in the early stages of the NOx uptake, the NOx storage mechanism is significantly altered in the presence of Fe sites where a set of new surface nitrosyl and nitrite groups were detected on the Fe sites and the surface oxidation of nitrites to nitrates is significantly hindered with respect to the BaO/Al2O3 system. Evidence for the existence of both Fe3+ as well as reduced Fe2+/(3-x)+ sites on the freshly pretreated materials was detected via EELS, FTIR, Raman, and XRD experiments. The influence of the Fe sites on the structural properties of the synthesized materials was also studied by performing ex situ annealing protocols within 323-1273 K followed by XRD and Raman experiments where the temperature dependent changes in the morphology and the composition of the surface domains were analyzed in detail. On the basis of the TPD data, it was found that the relative stability of the stored NOx species is influenced by the morphology of the Ba and Fe containing NOx-storage domains. The relative stabilities of the investigated NOx species were found to increase in the following order: N2O3/NO+ < nitrates on γ-Al2O3 < surface nitrates on BaO < bidentate nitrates on FeOx sites < bulk nitrates on BaO.
Open Access
Fine-tuning the dispersion and the mobility of BaO domains on NO x storage materials via TiO2 anchoring sites
(American Chemical Society, 2010) Andonova, S. M.; Şentürk, G. S.; Ozensoy, E.
In an attempt to control the surface dispersion and the mobility of BaO domains on NOx storage materials, TiO2/TiOx anchoring sites were introduced on/inside the conventional γ-Al 2O3 support matrix. BaO/TiO2/Al 2O3 ternary oxide materials were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies. The synthesized NOx storage materials were studied via XRD, Raman spectroscopy, BET surface area analysis, TPD, XPS, SEM, EDX-mapping, and in situ FTIR spectroscopy of adsorbed NO2. NOx uptake properties of the BaO/TiO2/Al2O3 materials were found to be strongly influenced by the morphology and the surface structure of the TiO2/TiOx domains. An improved Ba surface dispersion was observed for the BaO/TiO2/Al2O3 materials synthesized via the coprecipitation of alkoxide precursors, which was found to originate mostly from the increased fraction of accessible TiO 2/TiOx sites on the surface. These TiO2/ TiOx sites function as strong anchoring sites for surface BaO domains and can be tailored to enhance surface dispersion of BaO. TPD experiments suggested the presence of at least two different types of NOx species adsorbed on the TiO2/TiOx sites, with distinctively different thermal stabilities. The relative stability of the NOx species adsorbed on the BaO/TiO2/Al2O3 system was found to increase in the following order: NO+/N2O 3 on alumina ≪ nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO2 domains. © 2010 American Chemical Society.
Open Access
Formulaicity in an agglutinating language: the case of Turkish
(De Gruyter Mouton, 2013) Durrant, P.
This study examines the extent to which complex inflectional patterns found in Turkish, a language with a rich agglutinating morphology, can be described as formulaic. It is found that many prototypically formulaic phenomena previously attested at the multi-word level in English - frequent co-occurrence of specific elements, fixed 'bundles' of elements, and associations between lexis and grammar - also play an important role at the morphological level in Turkish. It is argued that current psycholinguistic models of agglutinative morphology need to be complexified to incorporate such patterns. Conclusions are also drawn for the practice of Turkish as a Foreign Language teaching and for the methodology of Turkish corpus linguistics.
Open Access
Growth of high crystalline quality semi-insulating GaN layers for high electron mobility transistor applications
(2006) Yu H.; Caliskan, D.; Özbay, Ekmel
Semi-insulating character (sheet resistivity of 3.26 × 10 11 Ω/sq) of thick GaN layers was developed for AlGaN/GaN high electron mobility transistor (HEMT) applications on an AlN buffer layer. Electrical and structural properties were characterized by a dark current-voltage transmission line model, x-ray diffraction, and atomic force microscope measurements. The experimental results showed that compared to semi-insulating GaN grown on low temperature GaN nucleation, the crystal quality as well as surface morphology were remarkably improved. It was ascribed to the utilization of a high quality insulating AlN buffer layer and the GaN initial coalescence growth mode. Moreover, the significant increase of electron mobility in a HEMT structure suggests that this is a very promising method to obtain high performance AlGaN/GaN HEMT structures on sapphire substrates. © 2006 American Institute of Physics.
Open Access
Influence of gold-silica nanoparticles on the performance of small-molecule bulk heterojunction solar cells
(Elsevier BV * North-Holland, 2015) Xu, X.; Kyaw, A. K. K.; Peng, B.; Xiong, Q.; Demir, Hilmi Volkan; Wang Y.; Wong, T. K. S.; Sun, X. W.
Light trapping by gold (Au)-silica nanospheres and nanorods embedded in the active layer of small-molecule (SM) organic solar cell has been systematically compared. Nanorod significantly outperforms nanosphere because of more light scattering and higher quality factor for localized surface plasmon resonance (LSPR) triggered by nanorods. The optimum concentration of nanorod was characterized by charge carrier transport and morphology of the active layers. At optimum nanorod concentration, almost no change in the morphology of the active layer reveals that LSPR and scattering effects rather than the morphology are mainly responsible for the enhanced power conversion efficiency. In addition, the preliminary lifetime studies of the SM solar cells with and without Au-silica nanorods were conducted by measuring the current density-voltage characteristics over 20 days. The results show that plasmonic device with nanorods has no adverse impact on the device stability
Open Access
Interlocking shish-kebab morphology in polybutene-1
(John Wiley & Sons, Inc., 2002) Kalay, G.; Kalay, C. R.
The aim of this research was to explore the effect of shear-controlled orientation injection molding (SCORIM) on polybutene-1 (PB-1). This article describes the methods and processing conditions used for injection molding and discusses the properties of the moldings. Both conventional and SCORIM have been used for the production of moldings. SCORIM is based on the application of specific macroscopic shears to a solidifying melt that facilitates enhanced molecular alignment. The effect of the process was investigated by performing mechanical tests, X-ray studies, differential scanning calorimetric studies, polarized light microscopy, and atomic force microscopy (AFM). Moldings exhibited an improved mechanical performance as compared with conventional moldings. Young's modulus was increased over twofold, and the impact energy was enhanced by 60%. The improvement in mechanical performance was combined with an increase in crystallinity and enhanced molecular orientation. The application of SCORIM also favored the formation of the stable Form I' in PB-1. The formation of interlocking shish-kebab morphology following the application of SCORIM was observed in the AFM studies. Relationships between the mechanical properties of PB-1 and the micromorphologies formed during processing are demonstrated.
Open Access
Lyotropic liquid-crystalline phase of oligo(ethylene oxide) surfactant/transition metal salt and the synthesis of mesostructured cadmium sulfide
(American Chemical Society, 2003) Dag, Ö.; Alayoǧlu, S.; Tura, C.; Çelik, Ö.
Lyotropic liquid-crystalline (LLC), transition metal salt: oligo(ethylene oxide) nonionic surfactant (CnH2n+1(CH2CH2O)mOH, denoted as CnEOm), systems have been studied by means of diffraction, microscopy, and spectroscopy to elucidate the structural, thermal, and templating properties. In the system, the lyotropic salts of transition metal aqua complexes, such as chlorides and sulfates, are insoluble and do not form a LC phase in CnEOm-type nonionic surfactants. However, the transition metal aqua complexes of nitrates and perchlorates are soluble and form 2D and 3D hexagonal and cubic mesophases. These phases are stable in a very broad range of salt:surfactant mole ratios (1.0 and 3.6). The nitrate salts form a hexagonal mesophase. However, in high nitrate salt concentrations (above 3.2 salt:surfactant mole ratio), the salt crystals are either insoluble or the salt:surfactant mixtures are in a cubic mesophase. The structure and thermal properties of the new system are determined by the solubility of the transition metal salts, the concentration of the salt, and the surfactant type. The LC [Cd(H2O)4](NO3)2: C12EO10 mesophase has been reacted with H2S gas to produce solid mesostructured CdS (meso-CdS). The meso-CdS particles are spherical in morphology and are made up of hierarchical organization of 2-4-nm CdS particles. The salt:surfactant LLC systems and the solid meso-CdS have been investigated using polarized optical microscopy, X-ray diffraction, Fourier transform infrared, Fourier transform Raman, and UV-vis absorption spectroscopy, scanning electron microscopy, and transmission electron microscopy.
Open Access
Matrix density effect on morphology of germanium nanocrystals embedded in silicon dioxide thin films
(Materials Research Society, 2011) Alagoz, A. S.; Genisel, M. F.; Foss, Steinar; Finstad, T. G.; Turan, R.
Flash type electronic memories are the preferred format in code storage at complex programs running on fast processors and larger media files in portable electronics due to fast write/read operations, long rewrite life, high density and low cost of fabrication. Scaling limitations of top-down fabrication approaches can be overcome in next generation flash memories by replacing continuous floating gate with array of nanocrystals. Germanium (Ge) is a good candidate for nanocrystal based flash memories due its small band gap. In this work, we present effect of silicon dioxide (SiO 2) host matrix density on Ge nanocrystals morphology. Low density Ge+SiO 2 layers are deposited between high density SiO 2 layers by using off-angle magnetron sputter deposition. After high temperature post-annealing, faceted and elongated Ge nanocrystals formation is observed in low density layers. Effects of Ge concentration and annealing temperature on nanocrystal morphology and mean size were investigated by using transmission electron microscopy. Positive correlation between stress development and nanocrystal size is observed at Raman spectroscopy measurements. We concluded that non-uniform stress distribution on nanocrystals during growth is responsible from faceted and elongated nanocrystal morphology.
Open Access
Morphological segmentation of urban structures
(IEEE, 2007-04) Akçay, H. Gökhan; Aksoy, Selim
Automatic segmentation of high-resolution remote sensing imagery is an important problem in urban applications because the resulting segmentations can provide valuable spatial and structural information that are complementary to pixel-based spectral information in classification. We present a method that combines structural information extracted by morphological processing with spectral information summarized using principal components analysis to produce precise segmentations that are also robust to noise. First, principal components are computed from hyper-spectral data to obtain representative bands. Then, candidate regions are extracted by applying connected components analysis to the pixels selected according to their morphological profiles computed using opening and closing by reconstruction with increasing structuring element sizes. Next, these regions are represented using a tree, and the most meaningful ones are selected by optimizing a measure that consists of two factors: spectral homogeneity, which is calculated in terms of variances of spectral features, and neighborhood connectivity, which is calculated using sizes of connected components. The experiments show that the method is able to detect structures in the image which are more precise and more meaningful than the structures detected by another approach that does not make strong use of neighborhood and spectral information. © 2007 IEEE.