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1
Xiao, Quanlan, Wei Lin, Gengxu Chen, Chengjie Ding, Guoping Dong, Chensheng Lin, Botao Wu, E. Wu, Heping Zeng et Jianrong Qiu. « Morphology and polarization-dependent second harmonic generation in single hexagonal sodium niobate micro/nano-crystals ». Journal of Materials Chemistry C 3, no 16 (2015) : 4070–76. http://dx.doi.org/10.1039/c5tc00226e.
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The SHG responses from single hexagonal NaNbO3 micro/nano-crystals with different morphologies and sizes were studied in detail. It was demonstrated that the same crystal structure displays a similar SHG response.
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Zhang, Haobin, Jinjiang Xu, Shichun Li, Jie Sun et Xiaolin Wang. « Characterization of Nano-Scale Parallel Lamellar Defects in RDX and HMX Single Crystals by Two-Dimension Small Angle X-ray Scattering ». Molecules 27, no 12 (16 juin 2022) : 3871. http://dx.doi.org/10.3390/molecules27123871.
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Nano-scale crystal defects extremely affect the security and reliability of explosive charges of weapons. In this work, the nano-scale crystal defects of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) single crystals were characterized by two-dimension SAXS. Deducing from the changes of SAXS pattern with sample stage rotating, we firstly found the parallel lamellar nano-scale defects in both RDX and HMX single crystals. Further analysis shows that the average diameter and thickness of nano-scale lamellar defects for RDX single crystal are 66.4 nm and 19.3 nm, respectively. The results of X-ray diffraction (XRD) indicate that the lamellar nano-scale defects distribute along the (001) in RDX and the (011) in HMX, which are verified to be the crystal planes with the lowest binding energy by the theoretical calculation.
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Lee, Chang Kyu, Jong Sung Kwon, In Chul Na, Byung Il Han, Young Min Kim et Jea Gun Park. « Dependency of Electrical Characteristics on Au Nano-Crystal Size for Non-Volatile Memory Fabricated with Au Nano-Crystal Embedded in PVK(Poly(N-Vinylcarbazole)) Layer ». Solid State Phenomena 124-126 (juin 2007) : 33–36. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.33.
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We demonstrated a nonvolatile memory fabricated with the sandwich device structure of Al/Au nano-crystals embedded in the PVK/Al. The bi-stable conduction switching characteristic (Ion/Ioff ratio) was >1x102, depending on Au nano-crystal size. The size and distribution of Au nano-crystals were determined by the inserted Au-layer thickness between PVK layers. The size of Au nano-crystals increased with the inserted Au-layer thickness. The uniform distribution of isolated Au nano-crystals was obtained with 5 nm of the inserted Au-layer thickness.
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SUMMERS, CHRISTOPHER J., CURTIS W. NEFF et WOUNJHANG PARK. « ACTIVE PHOTONIC CRYSTAL NANO-ARCHITECTURES ». Journal of Nonlinear Optical Physics & ; Materials 12, no 04 (décembre 2003) : 587–97. http://dx.doi.org/10.1142/s0218863503001663.
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The development of nano-scaled photonic crystal structures has resulted in many new devices exhibiting non-classical optical behavior. Typically, in these structures a photonic band gap and associated defect mode are used to create waveguides, resonators, couplers and filters. In this paper we propose that the functionality of these structures can be significantly enhanced by the infiltration of the photonic crystal with other classes of materials, particularly highly nonlinear liquid crystals and electro-optical materials. The properties of conventional 2D PC slab waveguides were simulated by the finite difference time domain method and shown to exhibit very large refraction and dispersion, and significant tunable effects under bias when infiltrated with liquid crystal. In particular, a new superlattice photonic crystal concept is proposed and shown to exhibit up to ~50° tunability in the angle of refraction when alternate liquid crystal infiltrated pixel rows were modulated from their aligned to unaligned state. This modulation corresponds to index changes from 1.5 to 2.1; it is assumed that a refractive index change of up to approximately Δn=0.6 can be achieved. The superlattice effect was also demonstrated to induce new switching and out-coupling effects that were strongly dependent on the direction of propagation and index modulation. These simulations demonstrate the potential of a new class of optically-active photonic crystal architectures to tune giant refraction and dispersion characteristics and to enable new switching phenomena.
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Abdalameer, N. Kh, S. N. Mazhir, H. M. Salim, J. Kh Hammood et Z. H. Abdul Raheem. « Design of micro-jet plasma system : a novel nanoparticles manufacturing method in atmospheric pressure ». Journal of Optoelectronic and Biomedical Materials 14, no 4 (20 décembre 2022) : 203–10. http://dx.doi.org/10.15251/jobm.2022.144.203.
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Micro jet atmospheric (MPJ) plasma was first utilized to create nano-sized crystals. Nanosized particles may have advantageous characteristics such as better internal quality and dissolving rates of the product compared to traditional crystalline goods. A nebulizer system sprays an aerosol solution into plasma by use of a carrier gas in a cold plasma crystal (argon). The plasma warms and loads the droplets causing solvent and columbic fission evaporation, and then the nucleation and crystal formation start within the limited volume given by the tiny drops. This produces nano-sized crystals. MPJ was used to establish the operating parameters for producing nano-sized ZnSe material crystals using electron microscope transmitting and X-ray powder diffraction tests as well as sensitivity testing have been carried out. Sensitivity tests showed lower friction sensitivity for the nano-scale product, suggesting a better internal quality of the crystal product.
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Zhang, Yunjie, Xu Wang, Guodong Zhang, Razvan Stoian et Guanghua Cheng. « Nano-Crystal and Microstructure Formation in Fluoride Photo-Thermo-Refractive Glass Using Chirp-Controlled Ultrafast Laser Bessel Beams ». Nanomaterials 11, no 6 (28 mai 2021) : 1432. http://dx.doi.org/10.3390/nano11061432.
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Nano-crystals were formed in the exposed regions of photo-thermo-refractive glass undergoing irradiation with zeroth order chirp-controlled ultrafast laser Bessel beams and subsequent heat treatment. Effects of various writing powers, pulse durations and heat treatment time on the distribution and the size of the nano-crystals were investigated. The results show that nano-crystals’ distribution depended on the laser power density spatial shape, while the size of the nano-crystals is quasi-independent. However, the average diameter of the nano-crystals was affected by the heat treatment time, decreasing from 175 to 105 nm with the time halved. In addition, using crystallographic characterization by X-ray diffraction, the nano-crystal composition in the laser-exposed regions was detected to be sodium fluoride.
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Dufresne, Alain. « Polysaccharide nano crystal reinforced nanocomposites ». Canadian Journal of Chemistry 86, no 6 (1 juin 2008) : 484–94. http://dx.doi.org/10.1139/v07-152.
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There are numerous examples of animals or plants that synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by nano sized crystalline domains. Cellulose and chitin are classical examples of these reinforcing elements, which occur as whisker-like microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, and whose axial physical properties therefore approach those of perfect crystals. During the last decade we have attempted to mimic biocomposites by blending cellulose or chitin whiskers from different sources with polymer matrices. Aqueous suspensions of such nano crystals can be prepared by acid hydrolysis of the substrate. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspensoid by subsequent vigorous mechanical shearing action. The resulting nano crystals occur as rod-like particles or whiskers, whose dimensions depend on the nature of the substrate. They are typically a few hundred nm long and between 5 and 20 nm in diameter. Starch can also be used as a source for the production of nano crystals. The constitutive nano crystals appear as platelet-like nano particles with a length ranging between 20 and 40 nm, a width ranging between 15 and 30 nm, and a thickness ranging between 5 and 7 nm. Since the first announcement of using cellulose whiskers as a reinforcing phase, they have been used extensively as model fillers in several kinds of polymeric matrices, including synthetic and natural ones. Casting mixtures of polysaccharide nano crystals and lattices led to the production of nano composite materials with drastically enhanced mechanical properties, especially at T > Tg of the matrix, by virtue of the formation of a whiskers network, even when the whisker volume fraction was only a few percent. The formation of this rigid network, resulting from strong interactions between whiskers, was assumed to be governed by a percolation mechanism. This hydrogen-bonded network induced a thermal stabilization of the composite up to 500 K, the temperature at which polysaccharides start to decompose. Any factors that perturb the formation of this percolating network directly affect the reinforcing effect of polysaccharide nano crystals. In addition to some practical applications, the study of these nano composite materials can help researchers understand such physical properties as the geometric and mechanical percolation effect.Key words: nano composites, polysaccharide, polymer, cellulose, nano crystal.
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Witika, Bwalya A., Vincent J. Smith et Roderick B. Walker. « Top-Down Synthesis of a Lamivudine-Zidovudine Nano Co-Crystal ». Crystals 11, no 1 (30 décembre 2020) : 33. http://dx.doi.org/10.3390/cryst11010033.
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Lamivudine (3TC) and zidovudine (AZT) are antiretroviral agents used to manage HIV/AIDS infection. A wet media milling top-down approach was used to develop and produce nano co-crystals of 3TC and AZT. Micro co-crystals were prepared by solvent evaporation and subsequently milled in the presence of two surfactants, viz., sodium lauryl sulfate (SLS) and α-tocopheryl polyethylene glycol succinate 1000 (TPGS 1000). Optimisation was undertaken using design of experiments (DoE) and response surface methodology (RSM) to establish and identify parameters that may affect the manufacturing of nano co-crystals. The impact of SLS and TPGS 1000 concentration, milling time, and number of units of milling medium on the manufacturing of nano co-crystals, was investigated. The critical quality attributes (CQA) monitored were particle size (PS), Zeta potential (ZP), and polydispersity index (PDI). Powder X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, transmission electron microscopy, energy dispersive X-ray spectroscopy scanning electron microscopy, and cytotoxicity assays were used for additional characterization of the optimised nano co-crystal. The mean PS, PDI, and ZP of the optimised top-down nanocrystal were 271.0 ± 92.0 nm, 0.467 ± 0.073, and −41.9 ± 3.94 mV, respectively. In conclusion, a simple, inexpensive, rapid, and precise method of nano co-crystal manufacturing was developed, validated, and optimised using DoE and RSM, and the final product exhibited the target CQA.
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Liu, Hailu, Dong Xie, Huayan Shen, Fayong Li et Junjia Chen. « Functional Micro–Nano Structure with Variable Colour : Applications for Anti-Counterfeiting ». Advances in Polymer Technology 2019 (8 décembre 2019) : 1–26. http://dx.doi.org/10.1155/2019/6519018.
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Colour patterns based on micro-nano structure have attracted enormous research interests due to unique optical switches and smart surface applications in photonic crystal, superhydrophobic surface modification, controlled adhesion, inkjet printing, biological detection, supramolecular self-assembly, anti-counterfeiting, optical device and other fields. In traditional methods, many patterns of micro-nano structure are derived from changes of refractive index or lattice parameters. Generally, the refractive index and lattice parameters of photonic crystals are processed by common solvents, salts or reactive monomers under specific electric, magnetic and stress conditions. This review focuses on the recent developments in the fabrication of micro-nano structures for patterns including styles, materials, methods and characteristics. It summarized the advantages and disadvantages of inkjet printing, angle-independent photonic crystal, self-assembled photonic crystals by magnetic field force, gravity, electric field, inverse opal photonic crystal, electron beam etching, ion beam etching, laser holographic lithography, imprinting technology and surface wrinkle technology, etc. This review will provide a summary on designing micro-nano patterns and details on patterns composed of photonic crystals by surface wrinkles technology and plasmonic micro-nano technology. In addition, colour patterns as switches are fabricated with good stability and reproducibility in anti-counterfeiting application. Finally, there will be a conclusion and an outlook on future perspectives.
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Lie, Guang Hua, Zhi Lie Tang, Gan Wen Lie, Ting Yang et Xiu Wen Tang. « Measure of the Optical and Electrical Properties of Semiconductor SiO2 Nano-Crystalline by Using Photo-Acoustic Technology ». Advanced Materials Research 415-417 (décembre 2011) : 2156–59. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.2156.
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By using a new type of single-beam normalized photo-acoustic spectroscopy that with weak signal detection and non-invasive testing, the photo-acoustic spectroscopy of semiconductor SiO2 nano-crystals was measured，the measured spectra of semiconductor SiO2 nano-crystals absorption coefficient was 0.20, and powders band gap is 3.4eV. The TEM image shows that the semiconductor SiO2 nano-crystals are round lump structure, while the grain size of the semiconductor SiO2 nano-crystals is about 70x200 nm, and the average particle size after the reunion is 100x300 nm. Compared with their micron crystal, the optical and electrical properties of semiconductor nano-crystals and nano-particle size are closely related. By changing the size of semiconductor nano-crystals, the mix could achieve the goal of changing the optical and electrical properties. Because of the semiconductor SiO2 nano-crystals‘ special properties of optics and electronics and photo-semiconductor nano-materials, they are widely used in many areas of modern science and technology.
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Schmahl, Wolfgang, Erika Griesshaber, Lurdes Fernandez-Diaz, Andreas Ziegler, Klemens Kelm, Bernd Maier, Fitriana Nindiyasari et Guntram Jordan. « Hierarchical structure of CaCO3biominerals – mesocrystals and functionalization ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C239. http://dx.doi.org/10.1107/s2053273314097605.
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Skeletal parts and teeth of marine organisms, avian eggshells, trilobite and isopod eyes, and many more biomineralized tissues consist of bio-calcite or bio-aragonite crystals. We explore the nano- to micro-scale architectures of these materials by electron backscatter diffraction (EBSD) and complementary techniques. In contrast to their inorganic cousins the biogenic "crystals" are hybrid composites with small amounts of organic matrix controlling morphogenesis and critically improving mechanical performance or other functions. For the biominerals meso-crystal-like structures are ubiquitous, consisting of co-oriented nano-blocks with a mosaic-spread of a few degrees, depending on the organism and on the size of the mesocrystal entity[1, 2, 3]. The nano-mosaic can be attributed to growth by nano-particle accretion from an amorphous or gel-like precursor, where relics of organic matrix cause misorientations between the crystallized nano-blocks. Recently we were able to reproduce this feature in gel-grown calcite [Nindiyasari et al., Crystal Growth and Design, in press]. The mesocrystal-co-orientation spreads on to the micro- and even millimeter-scale, frequently with a fractal nature of co-oriented hierarchical units [Maier et al., Acta Biomaterialia, accepted for publication]. The hierarchically structured morphology of the composite crystal or polycrystal is always directed by organic matrix membranes. Sea urchin teeth show a multiplex composite crystal architecture, where different subunits of engineered shapes, Mg-contents, and small misalignments are essential prerequisites for self-sharpening [1]. The figure shows an EBSD map of dendritic interdigitating calcite crystals in an avian egg shell (color coding for crystal orientation) with an misorientation profile along the grey line.
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Lie, Guang Hua, Zhi Lie Tang, Gan Wen Lie, Ting Yang, Xiu Wen Tang et Le Xi Shao. « Measure of the Optical Properties of Semiconductor Pb3O4 Nano-Crystalline of Using Photo-Acoustic Technology ». Advanced Materials Research 354-355 (octobre 2011) : 246–50. http://dx.doi.org/10.4028/www.scientific.net/amr.354-355.246.
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The application of new single-beam normalized photo-acoustic spectroscopy in semiconductor Pb3O4 nano-crystals photo-acoustic spectroscopy was carried out. The measured spectra of semiconductor Pb3O4 nano-crystals absorption coefficient of 0.95, and then measured the semiconductor Pb3O4 nano-crystals powders band gap is 2.3 . The TEM image shows the semiconductor Pb3O4 nano-crystals are round granular structure, while the XRD spectrum indicates that the semiconductor Pb3O4 nano-crystals are tetragonal. The grain size measured to be about 30nm, and the average particle size after the reunion is 100nm. Compared with the micron crystal, the optical properties of semiconductor nano-crystals and nano-particle size are closely related. By changing the size of semiconductor nano-crystals, doped to change shape and optical, electrical properties of the goal. Because the defense and photoconductive materials with very special properties, they were widely used in many areas of modern technology, especially in delay bombings and stealth coating.
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Wang, Li Hsiang, et Su Hua Yang. « Nano Photoelectric Material Structures – Photonic Crystals ». Advanced Materials Research 677 (mars 2013) : 9–15. http://dx.doi.org/10.4028/www.scientific.net/amr.677.9.
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Photonic crystals are periodic dielectric structural materials that have photonic band gaps, and are divided into on-dimensional, two-dimensional, and three-dimensional structures based on their spatial distributions. One-dimensional photonic crystals have already found real-world applications. Three-dimensional photonic crystals are still in the experimental phase in laboratories. Due to their superior characteristics, photonic crystal materials are sure to be widely developed and applied in the future. This paper briefly introduces the principle of photonic crystals, facts about their theoretical research, production and preparation of materials, as well as their related applications. Photonic crystal materials have a lot of potential, and could be one of the most significant materials of this century. Since the concept was proposed in the late 80’s of the previous century, the research and application of photonic crystals has advanced significantly. Currently, photonic crystals are already used in fiber optics as well as semiconductor lasers. This paper introduces the structures of various types of photonic crystals, including photonic crystals with semiconductor and fiber optic material bases, and describes some of the special optoelectronic characteristics and possible applications of photonic crystals. Photonic crystals can be used in the production of many new types of optoelectronic devices. Most significantly, they can dramatically reduce the size of components and result in dense integration. Photonic crystals are expected to have a revolutionary impact on the development of optoelectronic technologies.
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Larsen, Brecken, Christopher Ausbeck, Timothy F. Bennet, Gilberto DeSalvo, Riccardo DeSalvo, Tugdual LeBohec, Seth Linker, Marina Mondin et Joshua Neilson. « Crystallization in Zirconia Film Nano-Layered with Silica ». Nanomaterials 11, no 12 (19 décembre 2021) : 3444. http://dx.doi.org/10.3390/nano11123444.
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Gravitational waves are detected using resonant optical cavity interferometers. The mirror coatings’ inherent thermal noise and photon scattering limit sensitivity. Crystals within the reflective coating may be responsible for either or both noise sources. In this study, we explored crystallization reduction in zirconia through nano-layering with silica. We used X-ray diffraction (XRD) to monitor crystal growth between successive annealing cycles. We observed crystal formation at higher temperatures in thinner zirconia layers, indicating that silica is a successful inhibitor of crystal growth. However, the thinnest barriers break down at high temperatures, thus allowing crystal growth beyond each nano-layer. In addition, in samples with thicker zirconia layers, we observe that crystallization saturates with a significant portion of amorphous material remaining.
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DIWAN, BHOOPENDRA DHAR, et N. KUMAR SWAMY. « DEPENDENCY OF THERMO-PHYSICAL PROPERTIES ON SURFACE BONDING OF BN NANO-CRYSTAL ». International Journal of Modern Physics : Conference Series 22 (janvier 2013) : 525–29. http://dx.doi.org/10.1142/s2010194513010611.
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In this paper we have studied the variation of normalized per-atom pair cohesive (binding) energy and melting temperature with size and number of atom-pairs in the BN nano-crystal by simple model approach. In small nano-particles, large proportions of their atoms reside either at or near the surface, and those in clusters are basically all on the surface. So, we have to study the surface configuration in detail that leads the constancy of the crystals. Even for bulk materials, parameters that ensure this constancy involving normalized cohesive energy, surface reconstruction, iconicity, bulk structure, hybridization and charge balance, melting point. It is worthwhile to say that many of these factors are quite interdependent. These all factors influence the whole cohesive energy of crystals and give important information about the deflections from inverse size dependence. The per-atom-pair binding energy and melting temperature of BN nano-crystal is a quadratic function of the inverse of the crystal size. The binding energy and melting temperature comes near their bulk value with increasing the crystal size and same as the bulk material when the crystal size is above than 100 nm.
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Bai, Yun Shan, Rong Shao, Lu De Lu et Jian Chun Bao. « Synthesis and Characterization of Neodymium Zirconate Nanocrystals Doped with Aluminium Ions by a Salt-Assistant Combustion Method ». Applied Mechanics and Materials 275-277 (janvier 2013) : 1775–80. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.1775.
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Neodymium zirconate nanocrystals doped aluminium ion NdxAl2-xZr2O7 with pyrochlore structure were prepared by a salt-assistant glycine combustion method. Zirconium nitrate, aluminium nitrate and neodymium nitrate were used as chemicals, and glycine was used as burning agent. The as-prepared NdxAl2-xZr2O7 nano-crystals were characterized by XRD, FT-IR, TEM and HRTEM. The results showed the Nd ions can be partially replaced by Al ions. For crystalline Nd1.9Al0.1Zr2O7, there are four strong diffraction peaks at 2θ = 29.02°, 33.70°, 48.37° and 57.37° corresponding crystal faces are 0.308nm, 0.266nm, 0.188nm and 0.161 nm, respectively, which indicates that the interstices of corresponding crystal faces are smaller than that of Nd2Zr2O7. Furthermore, the fluorescent properties of Nd1.9Al0.1Zr2O7 nano-crystals evaluated by the fluorescence spectra indicate that the prepared nano-crystals are a kind of potential fluorescent-emitted material.
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Wang, Likun, Zhaoran Chu, Xuanjun Ning, Ziwei Huang, Wenwei Tang, Weizhong Jiang, Jiayi Ye et Cheng Chen. « Inverse Colloidal Crystal Polymer Coating with Monolayer Ordered Pore Structure ». Crystals 12, no 3 (11 mars 2022) : 378. http://dx.doi.org/10.3390/cryst12030378.
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A functional lens coating, based on the structure of inversed colloidal photonic crystals, is proposed. The color-reflecting colloidal crystal was first prepared by self-assembly of nano-colloids and was infiltrated by adhesive polymer solution. As the polymer was crosslinked and the crystal array was removed, a robust mesh-like coating was achieved. Such a functional coating has good transmittance and has a shielding efficiency of ~9% for UV–blue light according to different particle sizes of the nano-colloids, making it an ideal functional material.
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Zheng, Kui, Tao Chen, Jian Zhang, Xiuquan Tian, Huilin Ge, Tiantao Qiao, Jia Lei, Xianyan Li, Tao Duan et Wenkun Zhu. « Nano-Montmorillonite Regulated Crystallization of Hierarchical Strontium Carbonate in a Microbial Mineralization System ». Materials 12, no 9 (29 avril 2019) : 1392. http://dx.doi.org/10.3390/ma12091392.
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In this paper, nano-montmorillonite (nano-MMT) was introduced into the microbial mineralization system of strontium carbonate (SrCO3). By changing the nano-MMT concentration and the mineralization time, the mechanism of mineralization was studied. SrCO3 superstructures with complex forms were acquired in the presence of nano-MMT as a crystal growth regulator. At low concentrations of nano-MMT, a cross-shaped SrCO3 superstructure was obtained. As the concentration increased, flower-like SrCO3 crystals formed via the dissolution and recrystallization processes. An emerging self-assembly process and crystal polymerization mechanism have been proposed by forming complex flower-like SrCO3 superstructures in high concentrations of nano-MMT. The above research indicated that unique bionic synthesis strategies in microbial systems could not only provide a useful route for the production of inorganic or inorganic/organic composites with a novel morphology and unique structure but also provide new ideas for the treatment of radionuclides.
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Li, Ge, Qing Long Zhang, Ming Chen et Lin Yong Zhou. « Analysis on Crack Propagation Mechanism of Nano-Single Crystal Copper about Temperature Influence ». Advanced Materials Research 581-582 (octobre 2012) : 341–44. http://dx.doi.org/10.4028/www.scientific.net/amr.581-582.341.
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By molecular dynamics method, the tensile processes of nano-single crystal copper with the type I crack under different temperature were simulated, and the effect of different temperature to crack propagation mechanism was analyzed. The results indicate that the temperature has significant effect on crack propagation mechanism of nano-single crystal copper. While the crack is the intrinsic brittle cleavage extension under low temperature and room temperature, the twin crystal is not easily to generate; whereas, dislocation climb caused twin crystal belt appears near the crack tip under high temperature. With load increasing, the length and the width of twin crystals belt increase gradually, and the existence of the twin crystal belt causes the crack branch change to the extending direction.
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Kamanina, N. V., S. V. Likhomanova, Yu A. Zubtcova, A. A. Kamanin et A. Pawlicka. « Functional Smart Dispersed Liquid Crystals for Nano- and Biophotonic Applications : Nanoparticles-Assisted Optical Bioimaging ». Journal of Nanomaterials 2016 (2016) : 1–9. http://dx.doi.org/10.1155/2016/8989250.
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Functional nematic liquid crystal structures doped with nano- and bioobjects have been investigated. The self-assembling features and the photorefractive parameters of the structured liquid crystals have been comparatively studied via microscopy and laser techniques. Fullerene, quantum dots, carbon nanotubes, DNA, and erythrocytes have been considered as the effective nano- and biosensitizers of the LC mesophase. The holographic recording technique based on four-wave mixing of the laser beams has been used to investigate the laser-induced change of the refractive index in the nano- and bioobjects-doped liquid crystal cells. The special accent has been given to novel nanostructured relief with vertically aligned carbon nanotubes at the interface: solid substrate-liquid crystal mesophase. It has been shown that this nanostructured relief influences the orienting ability of the liquid crystal molecules with good advantage. As a result, it provokes the orientation of the DNA. The modified functional liquid crystal materials have been proposed as the perspective systems for both the photonics and biology as well as the medical applications.
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Bommineni, Praveen K., et Sudeep N. Punnathanam. « Enhancement of nucleation of protein crystals on nano-wrinkled surfaces ». Faraday Discussions 186 (2016) : 187–97. http://dx.doi.org/10.1039/c5fd00119f.
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The synthesis of high quality protein crystals is essential for determining their structure. Hence the development of strategies to facilitate the nucleation of protein crystals is of prime importance. Recently, Ghatak and Ghatak [Langmuir 2013, 29, 4373] reported heterogeneous nucleation of protein crystals on nano-wrinkled surfaces. Through a series of experiments on different proteins, they were able to obtain high quality protein crystals even at low protein concentrations and sometimes without the addition of a precipitant. In this study, the mechanism of protein crystal nucleation on nano-wrinkled surfaces is studied through Monte Carlo simulations. The wrinkled surface is modeled by a sinusoidal surface. Free-energy barriers for heterogeneous crystal nucleation on flat and wrinkled surfaces are computed and compared. The study reveals that the enhancement of nucleation is closely related to the two step nucleation process seen during protein crystallization. There is an enhancement of protein concentration near the trough of the sinusoidal surface which aids in nucleation. However, the high curvature at the trough acts as a deterrent to crystal nucleus formation. Hence, significant lowering of the free-energy barrier is seen only if the increase in the protein concentration at the trough is very high.
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SONG, KAI, RENAUD VALLEE, MARK VAN DER AUWERAER et KOEN CLAYS. « SPONTANEOUS EMISSION OF NANO-ENGINEERED FLUOROPHORES IN PHOTONIC CRYSTALS ». Journal of Nonlinear Optical Physics & ; Materials 15, no 01 (mars 2006) : 1–8. http://dx.doi.org/10.1142/s0218863506003128.
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The spontaneous emission of fluorophores embedded in a photonic crystal has been studied. By nano-engineering a sandwich-like photonic structure, such that fluorophore-coated photonic atoms constitute a middle layer between the photonic crystals, we have been able to precisely control the location of fluorophores in photonic crystals and exclude the presence of fluorophores at the surface of the crystal. It has been found that the stopband in the transmission spectrum is deeper than the stopband in the emission spectrum. We conjecture that the omnidirectional propagation of the emission from a point source in an incomplete photonic bandgap is the cause of the shallower stopband in emission.
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Olyaee, Saeed. « Ultra-fast and compact all-optical encoder based on photonic crystal nano-resonator without using nonlinear materials ». Photonics Letters of Poland 11, no 1 (3 avril 2019) : 10. http://dx.doi.org/10.4302/plp.v11i1.890.
Texte intégralRésumé :
In this paper an ultra-compact all-optical encoder is presented by using a two-dimensional photonic crystal. The designed logic gate is based on the interference effect. The proposed structure consists of several photonic crystal waveguides connected by 2 nano-resonators. The nano-resonators are designed to reduce the size of the radius of the dielectric rods. The contrast ratios and delay time for the proposed all-optical encoder are respectively 6 dB and 125 fs. The size of the structure is equal to 132 µm2. Equality of the output power in the logic states “one”, the small dimensions, the low delay time, compact and simple structure have shown that the logic gate is suitable for the using in optical integrated circuits. Full Text: PDF ReferencesA. Salmanpour, Sh. Mohammadnejad, A. Bahrami, "Photonic crystal logic gates: an overview", Optical and Quantum Electronics. 47, 2249 (2015). CrossRef S. C. Xavier, B. E. Carolin, A. p. Kabilan, W. Johnson, "Compact photonic crystal integrated circuit for all-optical logic operation", IET Optoelectronics. 10, 142 (2016). CrossRef Y. Miyoshi, K. Ikeda, H. Tobioka, T. Inoue, S. Namiki, K. Kitayama, "Ultrafast all-optical logic gate using a nonlinear optical loop mirror based multi-periodic transfer function", Optics Express. 16, 2570 (2008). CrossRef D. K. Gayen, A. Bhattachryya, T. Chattopadhyay, J. N. Roy, "Ultrafast All-Optical Half Adder Using Quantum-Dot Semiconductor Optical Amplifier-Based Mach-Zehnder Interferometer", Journal of Lightwave Technology. 30, 3387 (2012). CrossRef A. Mohebzadeh-Bahabady, S. Olyaee, "All-optical NOT and XOR logic gates using photonic crystal nano-resonator and based on an interference effect", IET Optoelectronics. 12, 191 (2018). CrossRef Z. Mohebbi, N. Nozhat, F. Emami, "High contrast all-optical logic gates based on 2D nonlinear photonic crystal", Optics Communications. 355, 130 (2015). CrossRef M. Mansouri-Birjandi, M. Ghadrdan, "Full-optical tunable add/drop filter based on nonlinear photonic crystal ring resonators", Photonics and Nanostructures-Fundamentals and Applications. 21, 44 (2016). CrossRef H. Alipour-Banaei, S. Serajmohammadi, F. Mehdizadeh, "Effect of scattering rods in the frequency response of photonic crystal demultiplexers", Journal of Optoelectronics and Advanced Materials. 17, 259 (2015). DirectLink A. Mohebzadeh-Bahabady, S. Olyaee, H. Arman, "Optical Biochemical Sensor Using Photonic Crystal Nano-ring Resonators for the Detection of Protein Concentration", Current Nanoscience. 13, 421 (2017). CrossRef S. Olyaee, A. Mohebzadeh-Bahabady, "Designing a novel photonic crystal nano-ring resonator for biosensor application", Optical and Quantum Electronics. 47, 1881 (2015). CrossRef F. Parandin, R. Malmir, M. Naseri, A. Zahedi, "Reconfigurable all-optical NOT, XOR, and NOR logic gates based on two dimensional photonic crystals", Superlattices and Microstructures. 113, 737 (2018). CrossRef F. Mehdizadeh, M. Soroosh, H. Alipour-Banaei, "Proposal for 4-to-2 optical encoder based on photonic crystals", IET Optoelectronics. 11, 29 (2017). CrossRef M. Hassangholizadeh-Kashtiban, R. Sabbaghi-Nadooshan, H. Alipour-Banaei, "A novel all optical reversible 4 × 2 encoder based on photonic crystals", Optik. 126, 2368 (2015). CrossRef T. A. Moniem, "All-optical digital 4 × 2 encoder based on 2D photonic crystal ring resonators", Journal of Modern Optics. 63, 735 (2016). CrossRef S. Gholamnejad, M. Zavvari, "Design and analysis of all-optical 4–2 binary encoder based on photonic crystal", Optical and Quantum Electronics. 49, 302 (2017). CrossRef H. Seif-Dargahi, "Ultra-fast all-optical encoder using photonic crystal-based ring resonators", Photonic Network Communications. 36, 272 (2018). CrossRef S. Olyaee, M. Seifouri, A. Mohebzadeh-Bahabady, and M. Sardari, "Realization of all-optical NOT and XOR logic gates based on interference effect with high contrast ratio and ultra-compacted size", Optical and Quantum Electronics. 50, 12 (2018). CrossRef C. J. Wu, C. P. Liu, Z. Ouyang, "Compact and low-power optical logic NOT gate based on photonic crystal waveguides without optical amplifiers and nonlinear materials", Applied Optics.51, 680 (2012). CrossRef Y. C. Jiang, S. B. Liu, H. F. Zhang, X. K. Kong. "Realization of all optical half-adder based on self-collimated beams by two-dimensional photonic crystals", Optics Communications. 348, 90 (2015). CrossRef A. Salmanpour, S. Mohammadnejad, P. T. Omran, "All-optical photonic crystal NOT and OR logic gates using nonlinear Kerr effect and ring resonators", Optical and Quantum Electronics. 47, 3689 (2015). CrossRef E. H. Shaik, N. Rangaswamy, "Single photonic crystal structure for realization of NAND and NOR logic functions by cascading basic gates", Journal of Computational Electronics. 17, 337 (2018). CrossRef
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Armstrong, Ronald W., et Wayne L. Elban. « Crystal Strengths at Micro- and Nano-Scale Dimensions ». Crystals 10, no 2 (5 février 2020) : 88. http://dx.doi.org/10.3390/cryst10020088.
Texte intégralRésumé :
Higher strength levels, achieved for dimensionally-smaller micro- and nano-scale materials or material components, such as MEMS devices, are an important enabler of a broad range of present-day engineering devices and structures. Beyond such applications, there is an important effort to understand the dislocation mechanics basis for obtaining such improved strength properties. Four particular examples related to these issues are described in the present report: (1) a compilation of nano-indentation hardness measurements made on silicon crystals spanning nano- to micro-scale testing; (2) stress–strain measurements made on iron and steel materials at micro- to nano-crystal (grain size) dimensions; (3) assessment of small dislocation pile-ups relating to Griffith-type fracture stress vs. crack-size calculations for cleavage fracturing of α-iron; and (4) description of thermally-dependent strain rate sensitivities for grain size strengthening and weakening for macro- to micro- to nano-polycrystalline copper and nickel materials.
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Kar, Soumitra, Swadeshmukul Santra et Subhadra Chaudhuri. « Direct Synthesis of ZnS Nanoribbons, Micro-Sheets and Tetrapods ». Journal of Nanoscience and Nanotechnology 8, no 6 (1 juin 2008) : 3222–27. http://dx.doi.org/10.1166/jnn.2008.150.
Texte intégralRésumé :
ZnS nano and micro structures such as nanoribbons, large sheets and tetrapod shaped crystals were fabricated by direct thermal evaporation of ZnS powder without using any catalyst. Formation of the one dimensional structures such as nanoribbons and micron order sheets was attributed to the vapor-solid growth mechanism. The formation of octahedron nucleus with cubic crystal structures was proposed as the growth unit of the wurtzite crystal structured tetrapods. Appearance of the periodic stacking faults or twining planes in between alternate cubic and hexagonal crystal structured zones along the growth direction of the ribbons provided secondary growth sites for the octahedron nucleus and subsequent crystal growth resulted in to the formation of the tetrapod arrays. These nano/micro structures of ZnS exhibited a green emission band at room temperature.
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Sun, H. P., H. Li, H. D. Li, G. T. Zou, Z. Zhang et X. Q. Pan. « Electron Beam Irradiation Induced Structural Modulation and Damage in GaN Nano Crystals ». Microscopy and Microanalysis 7, S2 (août 2001) : 492–93. http://dx.doi.org/10.1017/s1431927600028531.
Texte intégralRésumé :
GaN is a semiconductor material with promising applications in display and laser devices. GaNbased thin films have been grown by various methods and intensively investigated. Additionally, GaN nano particles have been prepared by various different methods. in this paper, we report our new finding of the structural modulation of GaN nano crystals induced by electron beam irradiation within a transmission electron microscope (TEM). The origin of the modulation structure is due to the ordering of N vacancies in the GaN nano crystals.The GaN nano crystals were prepared by d.c arc plasma method. A Philips CM200 TEM with a field emission gun (FEG) operating at 200KV was used in this study. The GaN nano crystals normally show hexagonal shape (see Fig.la). Corresponding electron diffraction pattern along [0001] axis indicates the Wurtzite structure (see Fig. lb). It was unexpected that satellite reflections gradually appeared in the diffraction pattern after the GaN nano crystal had been exposed to the electron beam (see Fig.lc-d).
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Intatha, Uraiwan, Krit Sujarittangtham et Sukum Eitssayeam. « Effect of SrTiO3 Nano-Crystals on the Dielectric Properties of Na0.47K0.47Li0.06NbO3 Ceramics by Seed-Induced Method ». Key Engineering Materials 690 (mai 2016) : 162–66. http://dx.doi.org/10.4028/www.scientific.net/kem.690.162.
Texte intégralRésumé :
A solid-state reaction method is generally used to fabricate ceramics. This work studies the influence of heterogenous nano-crystallites on electrical properties of lead free Na0.47K0.47Li0.06NbO3 (NKLN) ceramics by adding SrTiO3 nano-crystals as the initial phase of reaction. The lead-free piezoelectric ceramics were synthesized by the seed-induced method. The SrTiO3 nano-crystals used as seeds were prepared by molten salt technique. The seed content was varied from 0 to 10.0 mol%. The investigation reports microstructure and electrical properties of ceramics. The XRD showed a mixed tetragonal and orthorhombic phase structure. Tc decreasing with increased SrTiO3nano-crystal concentration.
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Ando, Shinji, Katsuhiro Oyabu, Kousei Hirayama, Masayuki Tsushida et Hideki Tonda. « Crack Propagation Behavior in Nano Size HCP Crystals by Molecular Dynamic Simulation ». Key Engineering Materials 297-300 (novembre 2005) : 280–85. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.280.
Texte intégralRésumé :
A crack propagation behavior of hcp crystal has been simulated by molecular dynamics method using Lennard-Jones type potential. A notch was introduced to model crystals with free surfaces. The size of the model was 13nm×24nm×4.6nm and about 80000 atoms were included in the model. A crack propagated by applying tensile strain on top and bottom layer of the model crystal. A definite dependence of crystallographic orientation on crack propagation behavior was obtained. In a model crystal with initial notch plane and direction were (101 0), [1 210], the crack propagated parallel to notch plane and two sets of prismatic slips were occurred at the crack. Therefore, the crack in this crystal is deduced to extend by alternating shear on two intersecting {101 0}, <1 210> prismatic slip systems. In a model crystal with (0001), [101 0] initial crack, {101 1} first order pyramidal slip occurred at crack tip and following {101 2} twin was also observed. In a model crystal with (10 1 0), [0001] initial crack, the crack propagates parallel to initial crack plane. Crack propagation rate of the crack near surface is faster than the crack in interior of the model. In this case, two prismatic slips were occurred in front of the crack. This result explains a mechanism of forming ‘Herring-born pattern’ which was observed in the titanium single crystal. Results obtained by these three models are well described the fatigue crack propagation behavior in hcp titanium crystals.
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Degawa, M., F. Szalma et E. D. Williams. « Nano-scale equilibrium crystal shapes ». Surface Science 583, no 2-3 (juin 2005) : 126–38. http://dx.doi.org/10.1016/j.susc.2005.03.032.
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Ha, Taewan, et Seunggu Kang. « Crystallization Mechanism and Photoluminescence Properties of CaF2–Al2O3–SiO2 : Eu Glass-Ceramics Based on Nano-Scale Phase Separation Phenomenon ». Journal of Nanoscience and Nanotechnology 20, no 11 (1 novembre 2020) : 6609–15. http://dx.doi.org/10.1166/jnn.2020.18773.
Texte intégralRésumé :
In this paper, CaF2–Al2O3–SiO2 glass containing nano-sized CaF2 crystals were fabricated using phase separation phenomenon and the effects of rare earth ion (Eu) addition on the optical properties were investigated. The formation conditions for nano-sized CaF2 crystal phase were confirmed using non-isothermal analysis and X-ray diffraction (XRD) measurement, while inhibiting anorthite or wollastonite crystal formation. The phase separation phenomenon in the mother glass and the nano-sized crystals generated by heat treatment were observed through the microstructure analysis using scanning electron microscopy (SEM). In addition, photoluminescence (PL) spectra and decay time analysis were performed to confirm the emission characteristics of Eu-doped glass-ceramics. The Eu-doped glass-ceramics produced in this study showed strong red light. The overall luminescence properties according to the heat treatment temperatures were found to shift from red to blue as indicated in the Commission International de l’Eclairage (CIE) color coordinate system.
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WANG, DINGDI, WENHAO GUO, SHENGWANG DU et Z. K. TANG. « FROZEN IODINE MOLECULES IN NANO-PORES OF ZEOLITE SINGLE CRYSTALS ». Modern Physics Letters B 27, no 18 (11 juillet 2013) : 1330014. http://dx.doi.org/10.1142/s0217984913300147.
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We review the recent study of novel optical properties of iodine molecules trapped inside the nano-channels of single zeolite crystals. It has been verified by Raman spectroscopy and molecular dynamics simulation that there are two favorite orientations of iodine molecules inside the AlPO 4-11 (AEL) and AlPO 4-5 (AFI) crystal channels: "lying" along the channel direction or "standing" inside the channel. Switching between the "lying" and "standing" configurations of iodine molecules inside the AEL crystals can be controlled by varying the density of water molecules inside the crystal channels. For extremely low iodine-loaded samples, the frozen "standing" iodine molecules in AEL crystals were observed whose Raman linewidth is independent of temperature. We also show that the radius of iodine atom can be determined from the fading nature and the broadening characteristics of overtones in Raman spectra of confined iodine molecules.
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Kotrechko, Sergiy, Igor Mikhailovskij, Tatiana Mazilova et Oleksandr Ovsjannikov. « Strength Hierarchy for Nano-Sized Crystals ». Key Engineering Materials 592-593 (novembre 2013) : 301–6. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.301.
Texte intégralRésumé :
A concept of atomic mechanisms governing strength of nanosized defect-free crystals is presented. It is exhibited that these mechanisms consist in local instability of the lattice. Two main reasons for localization of instability in three-dimension (3D) crystals are analyzed, namely, (i) fluctuation of local stresses induced by thermal vibrations of atoms, and (ii) non-uniform distribution of local stresses caused by a surface tension. Based on this conception, explanations of both the temperature dependence of strength of 3D nanocrystals and scale effect are given. Ideas on the reasons for and regularities of change in strength at transition from 3D to 2D (graphene) and 1D (monatomic chain) crystals are represented. It is shown that dimensionality of crystal is one of the main factors governing strength of defect-free crystals. Experimental values of the strength of carbon monatomic chains are given, which times exceeds the strength of graphene and is the highest attainable level of strength in the world.
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Bai, Yun Shan, Song Chen, Lu De Lu et Jian Chun Bao. « Study of Degradation of Photocatalytic Methyl Orange on Nano NdxCo2-xZr2O7 ». Advanced Materials Research 602-604 (décembre 2012) : 169–73. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.169.
Texte intégralRésumé :
Cubic pyrochlore type NdxCo2-xZr2O7 nano-crystals were prepared by salt-assistant glycine solution combustion method (SGCM), with neodymium nitrate, cobalt nitrate and zirconium nitrate as raw materials, glycine as the incendiary agent, and KCl as a reaction inert salt. The NdxCo2-xZr2O7 nano-crystals were characterized by means of XRD (X-ray powder diffraction), FT-IR (Fourier trans-form-infrared spectroscopy), Raman spectroscopy, TEM (Transmission electron microscope) and HRTEM (High resolution transmission electron microscopy). The results showed that neodymium ions were partially substituted by cobalt ions, while maintaining the original pyrochlore structure. The nano particles obtained had a perfect crystal structure, good dispersion, and the size was about 31nm. For Nd1.9Co0.1Zr2O7 nanocrystals, the four strong diffraction peaks were at 2θ=29.18°, 33.80°, 48.49° and 57.53°. The corresponding crystal plane distances calculated by Bragg equation λ = 2dSinθ were 0.306, 0.265, 0.188 and 0.160 nm. With the study of the photocatalytic activity of the product, it is found that compared with the undoped crystals, photocatalytic activity of dopped products had been significantly improved and different doping amount led to different levels of catalytic activity. When nNd:nCo = 9:1, the 2 hours net degradation amount was as high as 83%.
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Ishizuka, Kazuo, Paul H. C. Eilers et Toshihiro Kogure. « Optimal Noise Filters in High-Resolution Electron Microscopy ». Microscopy Today 15, no 5 (septembre 2007) : 16–21. http://dx.doi.org/10.1017/s1551929500061186.
Texte intégralRésumé :
Most of the specimens for high-resolution electron microscopy have amorphous surface layers due to contamination during observation and/or damaged surface layers during specimen preparation. Moreover, many specimens are radiation sensitive, and a part of the specimen easily becomes amorphous during the observation. These amorphous materials make clear observation of crystal structure difficult. A periodic structure may be extracted by simply using a periodic mask in Fourier space. However, this kind of mask often introduces a periodic feature in addition to the crystal structure. To reduce such artifacts a Wiener filter or an average background subtraction filter has been discussed. However, these filters do not work for non-ideal crystals, such as cylindrical crystals and nano-crystals, where a translational periodicity is limited to the order of nano-meter. In this report we improve these filters by introducing new ways to estimate a contribution from the amorphous materials.
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Bai, Li Mei, Yue Xin Han, Li Xia Li, Ri Xiao et Shu Juan Dai. « Effect of Crystal Contolling Agents on Shapes of Nanometer Calcium Carbonate ». Advanced Materials Research 92 (janvier 2010) : 79–85. http://dx.doi.org/10.4028/www.scientific.net/amr.92.79.
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In laboratory, there polymorphs’ nano-calcium carbonates were synthesized through adding on different crystal controlling agents by the bath-type carburizing reagent in the given conditions. When selecting addition J as the crystal controlling agent, lamellar nano-calcium carbonate products with average size about 150×110×15 nm were synthesized. When selecting annexing agent I as the crystal controlling agent, rod nano-calcium carbonates were synthesized, which average grain diameter was 90 nm, average length was 944 nm, and aspect ratio was 10.5. When selecting annexing agent G as the crystal controlling agent, chain nano-calcium carbonate with average grain size 20~30nm, aspect ratio 10~15nm were synthesized.
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Gorthy, Rukmini, Susan Krumdieck et Catherine Bishop. « Process-Induced Nanostructures on Anatase Single Crystals via Pulsed-Pressure MOCVD ». Materials 13, no 7 (3 avril 2020) : 1668. http://dx.doi.org/10.3390/ma13071668.
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The recent global pandemic of COVID-19 highlights the urgent need for practical applications of anti-microbial coatings on touch-surfaces. Nanostructured TiO2 is a promising candidate for the passive reduction of transmission when applied to handles, push-plates and switches in hospitals. Here we report control of the nanostructure dimension of the mille-feuille crystal plates in anatase columnar crystals as a function of the coating thickness. This nanoplate thickness is key to achieving the large aspect ratio of surface area to migration path length. TiO2 solid coatings were prepared by pulsed-pressure metalorganic chemical vapor deposition (pp-MOCVD) under the same deposition temperature and mass flux, with thickness ranging from 1.3–16 μm, by varying the number of precursor pulses. SEM and STEM were used to measure the mille-feuille plate width which is believed to be a key functional nano-dimension for photocatalytic activity. Competitive growth produces a larger columnar crystal diameter with thickness. The question is if the nano-dimension also increases with columnar crystal size. We report that the nano-dimension increases with the film thickness, ranging from 17–42 nm. The results of this study can be used to design a coating which has co-optimized thickness for durability and nano-dimension for enhanced photocatalytic properties.
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Akhtar, S., D. Shukla et V. Kumar. « Studies on Effect of Nano-Talc Filler on Nucleation, Crystal Morphology and Crystallization Behaviour of Semi-Crystalline Plastics ». Solid State Phenomena 136 (février 2008) : 161–74. http://dx.doi.org/10.4028/www.scientific.net/ssp.136.161.
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The crystallization behavior of semi-crystalline plastics plays a vital role in the development of properties of plastics. The present study examines the effect of addition of 1-5% nano talc filler particles on the nucleation behavior and crystal morphology. Differential Scanning Calorimetry was used to study the dynamic crystallization kinetics of PEEK with different loadings of nano talc filler. The crystalline morphology and non-isothermal kinetics were investigated. Crystallization behaviour was studied using Avrami equation. It is found that the addition of nano-talc enhances the rate of nucleation; however, the growth rate of the crystals reduces.
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Zhao, Bo, Guo Fu Gao, Yan Wu et Feng Jiao. « Research on Micro Characteristics of Surface and Subsurface Layer in Two-Dimensional Ultrasonic Grinding Nano-Composite Ceramics ». Key Engineering Materials 375-376 (mars 2008) : 395–400. http://dx.doi.org/10.4028/www.scientific.net/kem.375-376.395.
Texte intégralRésumé :
This work mainly studied the deterioration layer structure, crystal grain size, crystal lattice distortion of ground surface in two-dimensional ultrasonic vibration grinding nano-composite ceramics. The research indicated that under a certain grinding condition the ductile deformation layer on the ground surface of nano-composite ceramics in two-dimensional ultrasonic vibration grinding is formed by the ways of material powdering, crystal grain fragmentation, materials extrusion, the crystal grain pull-off and so on. The transition layer between the surface layer and the base body is plastic deformation layer by the primarily ways of crystal lattice distortion and the crystal boundary slipping. The removed material in brittleness fracture mode is extremely few. In this work, the structural model of deterioration layer on ground surface in two-dimensional ultrasonic grinding nano-composite ceramics is put forward. The microscopic deformation mechanism of nano materials is inner grain dislocation of inner-grain-structure strengthened phase. Its deformation coordination mechanism is the the grain-boundary sliding of matrix grain and the coordinated deformation of intercrystalline second-phase. The TEM and SEM observation discovers that the nano particles dispersed in grain boundary stops crack from expanding in nano materials, which causes the materials to appear in transcrystalline fracture behavior. And this fracture behavior gives materials favorable finished surface. The plastic deformation is the dominant removal mechanism of the nano materials in two-dimensional ultrasonic vibration grinding.
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Masenelli, B., G. Ledoux, D. Amans, C. Dujardin et P. Mélinon. « Shells of crystal field symmetries evidenced in oxide nano-crystals ». Nanotechnology 23, no 30 (10 juillet 2012) : 305706. http://dx.doi.org/10.1088/0957-4484/23/30/305706.
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Zou, Xiaodong. « Single Crystal 3D Rotation Electron Diffraction from Nano-sized Crystals ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C366. http://dx.doi.org/10.1107/s2053273314096338.
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Electron crystallography is an important technique for structure analysis of nano-sized materials. Crystals too small or too complicated to be studied by X-ray diffraction can be investigated by electron crystallography. However, conventional TEM methods requires high TEM skills and strong crystallographic knowledge, which many synthetic materials scientists and chemists do not have. We recently developed the software-based Rotation Electron Diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Complete single crystal 3D electron diffraction data can be collected from nano- and micron-sized crystals in less than one hour by combining electron beam tilt and goniometer tilt, which are controlled by the RED – data collection software.3 The unit cell, possible space groups and electron diffraction intensities can be obtained from the RED data using the RED data processing software. The figure below illustrates the data collection and data processing of a zeolite silicalite-1 by RED. 1427 ED frames were collected in less than 1 hour from a crystal of 800 x 400 x 200 nm in size. A 3D reciprocal lattice of silicalite-1 was reconstructed from the ED frames, from which the unit cell parameters and space group were determined (P21/n, a=20.02Å, b=20.25Å, c=13.35Å, alfa=90.130, beta=90.740, gamma=90.030. It was possible to cut the 3D reciprocal lattice perpendicular to any directions and study the reflection conditions. The reflection intensities could be extracted. The structure of the calcined silicalite-1 could be solved from the RED data by routine direct methods using SHELX-97. All 78 unique Si and O atoms could be located and refined to an accuracy better than 0.08 Å. The RED method has been applied for structure solution of a wide range of crystals and shown to be very powerful and efficient. Now a structure determination can be achieved within a few hours, from the data collection to structure solution. We will present several examples including unknown inorganic compounds, metal-organic frameworks and organic structures solved from the RED data. Different parameters that affect the RED data quality and thus the structure determination will be discussed. The methods are general and can be applied to any crystalline materials.
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Giacobbe, Carlotta, Jonathan Wright, Catherine Dejoie, Paul Tafforeau, Camille Berruyer, Ruggero Vigliaturo, Reto Gieré et Alessandro F. Gualtieri. « Depicting the crystal structure of fibrous ferrierite from British Columbia using a combined synchrotron techniques approach ». Journal of Applied Crystallography 52, no 6 (14 novembre 2019) : 1397–408. http://dx.doi.org/10.1107/s1600576719013980.
Texte intégralRésumé :
The ferrierite crystal structure has often been subject to discussion because of the possible lowering of symmetry from the space group Immm. It mainly occurs in nature with a fibrous crystal habit, and because of the existence of line/planar defects in the framework, texture and preferred orientation effects it has been difficult to obtain an exact crystallographic model based only on the results from powder diffraction data. Therefore, nano-single-crystal diffraction and tomography data have been combined in order to improve the refinement with a meaningful model. High-quality single-crystal data, providing reliable structural information, and tomography images have been used as input for a Rietveld refinement which took into account a phenomenological description of stacking disorder and the analytical description of the preferred orientation, by means of spherical harmonics for strong texture effects. This is one of the first examples of application of synchrotron nano-diffraction for the structure solution of fibrous minerals of micrometre to nanometre size. The high quality of the crystals allowed collection of single-crystal X-ray diffraction data of up to 0.6 Å resolution, leading to an unambiguous solution and precise anisotropic refinement. Nano-single-crystal diffraction and phase contrast tomography data were collected at ID11 and the high-resolution powder diffraction patterns at ID22 of the European Synchrotron Radiation Facility. This detailed crystallographic characterization provides a basis for understanding the potential of ferrierite for toxicity and carcinogenicity.
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Zhang, Xiwen, et Sajeev John. « Photonic crystal based photoelectrochemical cell for solar fuels ». Nano Select 2, no 6 (18 janvier 2021) : 1218–24. http://dx.doi.org/10.1002/nano.202000143.
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Yang, Dao Yuan, Juan Wu, Guang Hui Wei, Kai Zhu, Hui Yu Yuan, Jing Wei Liu et Bo Chong. « Sintering Process of Mullite- Corundum Insulation Material with Nano Crystals ». Advanced Materials Research 295-297 (juillet 2011) : 311–14. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.311.
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Mullite- corundum insulation material with nano crystals in matrix was fabricated by gel-casting process. The results showed that the volatilization temperature of organisms is 285°C- 600°C, there is no glass phase appeared in specimens; The mullitization begin at 1000°C, along with the raise of temperature, the quantity of mullite phase increases, especially during 1200°C- 1400°C; when the temperature is up to 1550°C, mullite becomes the main crystal phase and there are also some corundum crystals in the specimens; The specimen matrix sintered at 1550°C is consisted of nano crystals 80nm in length and 10-20nm in diameter.
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Hayashi, Koya, M. Tomohara, K. Fujino, Genta Sakane et Y. Katayama. « Crystal Growth of Calcite Nano-Plate by Alternate Soaking Method, Using CDS Crystals ». Advances in Science and Technology 63 (octobre 2010) : 425–30. http://dx.doi.org/10.4028/www.scientific.net/ast.63.425.
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Hetero-epitaxial growth of calcite crystals on calcium dodecyl sulfate (Ca(DS)2 = CDS) single crystals was studied by alternate soaking method. The calcite (006) oriented single crystals grow on the (001) surface of the CDS. The hetero-epitaxial growth mechanism is discussed by the lattice matching of the a-c planes of calcite and CDS according to the structure data of the CDS single crystal.
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Bai, Yun Shan, Jian Ping Zeng, Lu De Lu et Jian Chun Bao. « Study of Preparation of Nano NdxCo2-xZr2O7 and its Catalytic Properties on Ammonium Perchlorate Thermal Decomposition ». Advanced Materials Research 602-604 (décembre 2012) : 178–82. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.178.
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Cubic pyrochlore type NdxCo2-xZr2O7nano-crystals were prepared by salt-assistant glycine solution combustion method (SGCM), with neodymium nitrate, cobalt nitrate and zirconium nitrate as raw materials, glycine as the incendiary agent, and KCl as a reaction inert salt. The NdxCo2-xZr2O7nano-crystals were characterized by means of XRD (X-ray powder diffraction), FT-IR (Fourier trans- form-infrared spectroscopy), Raman spectroscopy, TEM (Transmission electron microscope) and HRTEM (High resolution transmission electron microscopy). The results showed that neodymium ions were partially substituted by cobalt ions, while maintaining the original pyrochlore structure. The nano particles obtained had a perfect crystal structure, good dispersion, and the size was about 31nm. For Nd1.9Co0.1Zr2O7nanocrystals, the four strong diffraction peaks were at 2θ=29.18°, 33.80°, 48.49° and 57.53°. The corresponding crystal plane distances calculated by Bragg equation λ=2dSinθ were 0.306, 0.265, 0.188 and 0.160 nm. Study the catalyst effect of NdxCo2-xZr2O7on the thermal decomposition of ammonium perchlorate (AP) using DSC (Differential scanning calorimetry). The results showed that nano NdxCo2-xZr2O7had high catalytic activity during on the thermal decomposition of ammonium perchlorate. With 2% more nano NdxCo2-xZr2O7, the peak temperature of AP thermal decomposition reaction dropped by nearly 88°C. The apparent decomposition reaction heat increased from 655J•g-1to 1073J•g-1. The results showed that the catalytic effect of thermal decomposition of AP with nano cobalt-doped zirconium acid neodymium is better than the single component of nano-metal oxides and undoped zirconate neodymium nanocrystals.
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Qiu, Peng, Guang Long Wang, Jiang Lei Lu et Hong Pei Wang. « Properties Investigation for Single-Defect Square-Lattice Photonic Crystal Slab Cavity in Crystal Material Application ». Advanced Materials Research 578 (octobre 2012) : 170–74. http://dx.doi.org/10.4028/www.scientific.net/amr.578.170.
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Compact and high-quality cavities are essential building blocks in constructing nano-photonic systems and quantum information systems. So, it is important in understanding the properties of localized modes produced by disorder in two-dimensional photonic crystals cavity. Single defect square lattice photonic crystal slab cavity is taken as the investigation object, the relationship between structure parameters (lattice constant a, radius of hole r and slab thickness) and properties parameters (quality factor Qt, effective mode volume Vmode) is discussed for a optimization design of high performance cavity. The results of this investigation are useful reference for single defect square lattice photonic crystal slab cavity in photonic crystal material application.
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Guo, Zhan, Chenxiang Huang et Yu Chen. « Experimental study on photocatalytic degradation efficiency of mixed crystal nano-TiO2 concrete ». Nanotechnology Reviews 9, no 1 (18 mars 2020) : 219–29. http://dx.doi.org/10.1515/ntrev-2020-0019.
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AbstractThe photocatalytic mixed crystal nano-TiO2 particles were incorporated with concrete by means of the internal doping method (IDM) and spraying method (SPM) in this paper. To evaluate the photocatalytic degradation efficiency of mixed crystal nano-TiO2 concrete, the methyl orange (MO) was chosen to simulate pollutants. The physicochemical characteristics and photocatalytic performance of mixed crystal nano-TiO2 concrete prepared by above two different methods were experimentally investigated under UV irradiation and solar irradiation. Furthermore, the effects of two key influential factors including pollutant concentration and irradiation condition were also analyzed and discussed. Experimental results indicate that the nano-TiO2 concrete prepared by the spraying method (SPM) exhibits maximum photocatalytic degradation efficiency of 73.82% when the sprayed nano-TiO2 slurry concentration is 10mg/L. The photocatalytic degradation efficiency of unpolished nano-TiO2 concrete is much higher than that of polished nano-TiO2 concrete under the same exposure time of UV irradiation. Moreover, the photocatalytic degradation efficiency of nano-TiO2 concrete decreases with the increase of pollutant concentration. The irradiation condition has an obvious influence on the photocatalytic degradation efficiency of nano-TiO2 concrete. In the aspect of applications, the practical recommendations for the nano-TiO2 concrete with self-cleaning capacity were presented according to the experimental results.
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Chen Chen, Chen Chen, Ting Cheng Ting Cheng, Xiao Zhang Xiao Zhang et Ruixin Wu and Qingying Wang Ruixin Wu and Qingying Wang. « Synthesis of an Efficient Pb Adsorption Nano-Crystal under Strong Alkali Hydrothermal Environment Using a Gemini Surfactant as Directing Agent ». Journal of the chemical society of pakistan 41, no 6 (2019) : 1034. http://dx.doi.org/10.52568/000821/jcsp/41.06.2019.
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Using a gemini surfactant ([C18H37(CH3)2-N+-(CH2)3-N+-(CH3)2C18H37]Cl2) as the directing agent, K2SiO3 and KAlO2 as the source of silicon and aluminum, a Nano-crystal has been successfully synthesized under a strong alkali hydrothermal condition. The material shows hexahedron morphology and its crystal size is between around 250-500 nm. Its liquid specific surface area is 1313.2 m2and#183;g-1. The adsorption process of Pb on the Nano-crystal follows quasi-second-order kinetic model and Langmuir adsorption isotherm equation. The maximum Pb adsorption capacity of Nano-crystal is around 1105 mgand#183;g-1.
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Zhan, Zhao Lin, Ye Dong He, De Ren Wang et Wei Gao. « Micro- /Nano-Crystal Aluminized ODS Coatings ». Materials Science Forum 522-523 (août 2006) : 323–30. http://dx.doi.org/10.4028/www.scientific.net/msf.522-523.323.
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A novel technique has been developed to prepare micro-/nano-crystal aluminized ODS coatings on stainless steel and nickel-base superalloy. In this technique, the pack aluminizing is combined with the repeated ball impact. Pure Al powder is mixed with 1wt% Y2O3 powder by ball milling. The ultrafine Y2O3 powder is well dispersed in Al particles. The modified Al particles are welded to the surface of metals by ball impact, causing the refinement of coarse grains and acceleration of atomic diffusion. Micro-/nano-crystal alloy layer with Y2O3 grows outward at a much low temperature (below 600°C) and in short treatment duration, compared with conventional pack aluminizing. The effects of processing temperature and duration on formation of the coatings have been analyzed. The microstructure of the coatings is studied using the methods of SEM, AMF, EDS, XRF and XRD. The results indicate that the aluminized ODS coatings appear to be dense, homogeneous, micro-/nano-crystal structure, and consist mainly of Al-rich phases, such as Fe2Al5, FeAl3 NiAl3 and7 CrAl5. High temperature oxidation tests show that the coatings enhance the oxidation resistance.
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Fang, F. Z. « Nano-turning of single crystal silicon ». Journal of Materials Processing Technology 82, no 1-3 (octobre 1998) : 95–101. http://dx.doi.org/10.1016/s0924-0136(98)00024-7.
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