Epitaxial Phase Transformation between Cylindrical and Double Gyroid Mesophases

2004 ◽  
Vol 856 ◽  
Author(s):  
Lei Zhu ◽  
Lu Sun ◽  
Jianjun Miao ◽  
Li Cui ◽  
Qing Ge ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Small Population ◽  
Significant Loss ◽  
Cubic Phase ◽  
Cubic Phases ◽  
Transmission Electron ◽  
Bicontinuous Cubic ◽  
Double Gyroid ◽  
Poly Ethylene ◽  
Unit Cell Dimensions

ABSTRACTComplex phase transformation between the hexagonal cylinder (Hex) and double gyroid (G) phases in a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer was investigated using two-dimensional (2D) synchrotron small-angle X-ray scattering (SAXS), and transmission electron microscope (TEM). The PS-b-PEO sample contained a small population of another bicontinuous cubic phase having an Im3m symmetry. These two bicontinuous cubic phases (G and Im3m) had the same unit cell dimensions. Under a large-amplitude reciprocating shear, the bicontinuous cubic phases transformed into a “single-crystal”-like Hex phase. When annealed at 150 °C for 40 min, the Hex phase partially transformed into well-oriented twinned structures of the G and Im3m phases without significant loss of orientation in 2D SAXS measurements. Epitaxial phase transformation relationships between the Hex/G and Hex/ Im3m phases were identified. The mechanism of the Hex → G transformation was examined by TEM.

Crystalline phase transformation of colloidal cadmium sulfide nanocrystals

2017 ◽  
Vol 31 (06) ◽  
pp. 1750037
Author(s):  
M. Ghali ◽  
A. M. Eissa ◽  
M. M. Mosaad
Keyword(s):  
Phase Transformation ◽  
Optical Absorption ◽  
Crystalline Phase ◽  
Growth Conditions ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Solution Ph ◽  
X Ray ◽  
Ph Values ◽  
Transmission Electron

In this paper, we give a microscopic view concerning influence of the growth conditions on the physical properties of nanocrystals (NCs) thin films made of CdS, prepared using chemical bath deposition CBD technique. We show a crystalline phase transformation of CdS NCs from hexagonal wurtzite (W) structure to cubic zincblende (ZB) when the growth conditions change, particularly the solution pH values. This effect was confirmed using X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) measurements. The optical absorption spectra allow calculation of the bandgap value, [Formula: see text], where significant increase [Formula: see text]200 meV in the CdS bandgap when transforming from Hexagonal to Cubic phase was found.

Bicontinuous Cubic Phase as a Matrix for the Synthesis of Semiconductor Nanocrystallites

1996 ◽  
Vol 431 ◽  
Author(s):  
Jianping Yang ◽  
Syed Qadri ◽  
Banahalli Ratna
Keyword(s):  
Size Distribution ◽  
Cubic Phase ◽  
Lipid Matrix ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Bicontinuous Cubic ◽  
First Time

AbstractBicontinuous cubic phase of lipid has been utilized for the first time as a matrix to synthesize II–VI (CdS) and IV–VI (PbS) semiconductor nanocrystallites. The nanoparticles were isolated from the lipid matrix and stabilized by capping with a thiol compound before purification. Two different sizes (2.3 nm and 3.0 nm) of CdS particles were prepared by varying the conditions of preparation. The size was determined by a combination of UV-vis absorption spectra and X-ray diffraction (XRD). The steep absorption edges of the two CdS samples indicate very narrow size distribution. XRD and transmission electron microscopic imaging of PbS nanocrystallites revealed that the size was 4.9 nm with nearly monodispersed size distribution.

Grain-Boundary Structure and Phase-Transformation Mechanism in Yttria-Stabilized Tetragonal Zirconia Polycrystal

2007 ◽  
Vol 558-559 ◽  
pp. 921-926
Author(s):  
Koji Matsui ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Grain Growth ◽  
Tetragonal Zirconia ◽  
Cubic Phase ◽  
Phase Boundaries ◽  
Transmission Electron ◽  
Tetragonal Zirconia Polycrystal

The microstructures in 3 mol% Y2O3-stabilized tetragonal zirconia polycrystal (Y-TZP) sintered at 1100°-1650°C were investigated to clarify cubic-formation and grain-growth mechanisms. The cubic phase in Y-TZP appeared at 1300°C and its mass fraction increased with increasing sintering temperature. High-resolution transmission electron microscopy (HRTEM) and nanoprobe X-ray energy dispersive spectroscopy (EDS) measurements revealed that no amorphous layer existed along the grain-boundary faces in Y-TZP, and Y3+ ions segregated not only along the tetragonal-tetragonal phase boundaries but also along tetragonal-cubic phase boundaries. Scanning transmission electron microscopy (STEM) and nanoprobe EDS measurements revealed that the Y3+ ion distribution was nearly homogeneous up to 1300°C, but cubic phase regions with high Y3+ ion concentration clearly formed inside grains at 1500°C. These results indicate that cubic phase regions are formed from the grain boundaries and/or the multiple junctions in which Y3+ ions segregated. We termed such a new diffusive transformation phenomenon “grain boundary segregation-induced phase transformation (GBSIPT)”. The grain-growth mechanism is controlled by the solute-drag effect of Y3+ ions segregating along the grain boundary.

Simultaneous Rheology and Small-Angle Scattering Experiments on Block Copolymer Gels and Melts in Cubic Phases

1998 ◽  
Vol 31 (6) ◽  
pp. 881-889 ◽  
Author(s):  
I. W. Hamley ◽  
J. A. Pople ◽  
A. J. Gleeson ◽  
B. U. Komanschek ◽  
E. Towns-Andrews
Keyword(s):  
Block Copolymer ◽  
Small Angle ◽  
Large Amplitude ◽  
Cubic Phase ◽  
Shear Direction ◽  
X Ray ◽  
X Ray Scattering ◽  
Cubic Phases ◽  
Bicontinuous Cubic ◽  
Ray Scattering

A new instrument for simultaneous small-angle X-ray scattering and rheology experiments on soft solids is described. This device is based on a commercial rheometer with a shear sandwich geometry in which the sample is subjected to a planar oscillatory deformation. This instrument has been used for time-resolved small-angle X-ray scattering/rheology experiments at the Synchrotron Radiation Source, Daresbury Laboratory, England. The focus has been in particular on the effect of large-amplitude shearing on the orientation of cubic phases in gels of block copolymers formed in concentrated solutions, and on the bicontinuous cubic phase of a block copolymer melt. Representative results are presented for face-centred cubic (f.c.c.) and body-centred cubic (b.c.c.) phases in gels of poly(oxyethylene)–poly(oxybutylene) diblock copolymers, and for the bicontinuous cubic `gyroid' structure in a poly-(ethylene-alt-propylene)–poly(dimethylsiloxane) di-block copolymer melt. The orientations of the micellar b.c.c. phases in the gels and the gyroid structure (belonging to the b.c.c. space group Ia\bar 3d) following large-amplitude shearing are shown to be the same,i.e.directionally oriented crystals are produced in both cases, in which (111) directions are oriented along the shear direction.

Molecular design of anti-spindle-like molecules by use of siloxanyl terminals for a thermotropic bicontinuous cubic phase

2020 ◽  
Vol 22 (18) ◽  
pp. 10132-10141 ◽  
Author(s):  
Akane Kawafuchi ◽  
Shoichi Kutsumizu ◽  
Yuki Kawase ◽  
Issei Tokiwa ◽  
Taro Udagawa ◽  
...  
Keyword(s):  
Molecular Design ◽  
Cubic Phase ◽  
Cubic Phases ◽  
Bicontinuous Cubic ◽  
Core Part

By modifying the three molecular moieties, siloxane terminal, alkyl spacer, and aromatic core part, the molecular requirements for the formation of bicontinuous cubic phases are presented.

Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs

1993 ◽  
Vol 51 ◽  
pp. 884-885
Author(s):  
David M. Anderson ◽  
Tomas Landh
Keyword(s):  
Liquid Crystalline ◽  
Diblock Copolymers ◽  
Cubic Phase ◽  
List Type ◽  
Interpenetrating Networks ◽  
Triply Periodic ◽  
Wide Range ◽  
Bicontinuous Cubic ◽  
Phase Liquid ◽  
Dividing Surface

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.The study of these structures has become of increasing importance in the past five years for two reasons:1)Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and2)Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.

Ferroelectric Domain Structure of Pb(Zr.52Ti.48)03

1980 ◽  
Vol 38 ◽  
pp. 214-215
Author(s):  
E.K. Goo ◽  
R.K. Mishra
Keyword(s):  
Phase Transformation ◽  
Domain Structure ◽  
Tetragonal Phase ◽  
Ferroelectric Domain ◽  
Cubic Phase ◽  
Ion Milling ◽  
Thin Foils ◽  
Ferroelectric Domain Structure ◽  
Ferroelectric Domains

Ferroelectric domains are twins that are formed when PZT undergoes a phase transformation from a non-ferroelectric cubic phase to a ferroelectric tetragonal phase upon cooling below ∼375°C.,1 The tetragonal phase is spontaneously polarized in the direction of c-axis, making each twin a ferroelectric domain. Thin foils of polycrystalline Pb (Zr.52Ti.48)03 were made by ion milling and observed in the Philips EM301 with a double tilt stage.

Reports From the Field: “Vini Ansanm” Come Together for Inclusive Community Music Development in Port-au-Prince, Haiti

2020 ◽  
pp. 273-289
Author(s):  
Donald DeVito ◽  
Gertrude Bien-Aime ◽  
Hannah Ehrli ◽  
Jamie Schumacher
Keyword(s):  
Social Media ◽  
Inclusive Education ◽  
Children With Disabilities ◽  
Small Population ◽  
Significant Loss ◽  
Community Music ◽  
Music Learning ◽  
Loss Of Life

Haiti has experienced a series of catastrophic natural disasters in recent decades, resulting in significant loss of life and long-term damage to infrastructure. One critical outcome of these disasters is that there are approximately 400,000 orphans in the small population of just over 10 million. Throughout Haiti, children with disabilities are often considered cursed, and thus are rejected by the community in which they live. Haitian children with disabilities need creative and educational activities that will help them grow, develop, enjoy their lives, and become accepted members of the community. This chapter on the Haitian Center for Inclusive Education presents a case study of social media engagement and music learning, with an emphasis on social justice that has contributed to sustainable efforts.

scholarly journals Diffusionless transformation of soft cubic superstructure from amorphous to simple cubic and body-centered cubic phases

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jie Liu ◽  
Wenzhe Liu ◽  
Bo Guan ◽  
Bo Wang ◽  
Lei Shi ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
X Ray Diffraction ◽  
Photonic Materials ◽  
Simple Cubic ◽  
Cubic Phases ◽  
Transmission Electron ◽  
Phase Liquid ◽  
Blue Phase ◽  
Blue Phases ◽  
Temperature Window

AbstractIn a narrow temperature window in going from the isotropic to highly chiral orders, cholesteric liquid crystals exhibit so-called blue phases, consisting of different morphologies of long, space-filling double twisted cylinders. Those of cubic spatial symmetry have attracted considerable attention in recent years as templates for soft photonic materials. The latter often requires the creation of monodomains of predefined orientation and size, but their engineering is complicated by a lack of comprehensive understanding of how blue phases nucleate and transform into each other at a submicrometer length scale. In this work, we accomplish this by intercepting nucleation processes at intermediate stages with fast cross-linking of a stabilizing polymer matrix. We reveal using transmission electron microscopy, synchrotron small-angle X-ray diffraction, and angle-resolved microspectroscopy that the grid of double-twisted cylinders undergoes highly coordinated, diffusionless transformations. In light of our findings, the implementation of several applications is discussed, such as temperature-switchable QR codes, micro-area lasing, and fabrication of blue phase liquid crystals with large domain sizes.

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