High-performance bulk Ti-Cu-Ni-Sn-Ta nanocomposites based on a dendrite-eutectic microstructure

Using a Ti–Cu–Ni–Sn–Ta alloy as an example, we demonstrate a strategy for the in situ formation of nanocomposite microstructures that can lead to simultaneous high strength and ductility. Our approach employs copper mold casting for the production of bulk alloys from the melt, and the solidification microstructure is designed to be composed of micrometer-sized ductile dendrites uniformly distributed inside a matrix of nanoscale eutectic reaction products. The nanostructured matrix is achieved at a relatively deep eutectic, which facilitates the formation of an ultrafine eutectic microstructure over a range of cooling rates. The multi-component recipe stabilizes a ductile solid solution as the toughening phase and helps to reduce the eutectic spacing down to nanoscale. The multi-phase microstructure (including phase distributions, morphologies, and interfaces) has been examined in detail using transmission electron microscopy (TEM) and high-resolution TEM. The metastable eutectic reaction and the nanoscale spacing achieved are explained using thermodynamic and solidification modeling. The benefits expected from the microstructure design are illustrated using the high strength and large plasticity observed in mechanical property tests. Our nanocomposite design strategy is expected to be applicable to many alloy systems and constitutes another example of tailoring the microstructure on nanoscale for extraordinary properties.

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Dynamic studies of silicide-mediated crystallization of amorphous silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100131395 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1352-1353

Author(s):

C. Hayzelden ◽

J. L. Batstone

Keyword(s):

Ion Implantation ◽

Solid Phase ◽

Metallic Phase ◽

Single Crystal Substrate ◽

Free Electrons ◽

Melt Temperature ◽

Transmission Electron ◽

Crystal Substrate ◽

High Resolution Tem

Epitaxial reordering of amorphous Si(a-Si) on an underlying single-crystal substrate occurs well below the melt temperature by the process of solid phase epitaxial growth (SPEG). Growth of crystalline Si(c-Si) is known to be enhanced by the presence of small amounts of a metallic phase, presumably due to an interaction of the free electrons of the metal with the covalent Si bonds near the growing interface. Ion implantation of Ni was shown to lower the crystallization temperature of an a-Si thin film by approximately 200°C. Using in situ transmission electron microscopy (TEM), precipitates of NiSi2 formed within the a-Si film during annealing, were observed to migrate, leaving a trail of epitaxial c-Si. High resolution TEM revealed an epitaxial NiSi2/Si(l11) interface which was Type A. We discuss here the enhanced nucleation of c-Si and subsequent silicide-mediated SPEG of Ni-implanted a-Si.Thin films of a-Si, 950 Å thick, were deposited onto Si(100) wafers capped with 1000Å of a-SiO2. Ion implantation produced sharply peaked Ni concentrations of 4×l020 and 2×l021 ions cm−3, in the center of the films.

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In situ observation of the martensitic transformation in (Mg,Y)-PSZ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144036 ◽

1986 ◽

Vol 44 ◽

pp. 500-501

Author(s):

R-R. Lee

Keyword(s):

Martensitic Transformation ◽

High Strength ◽

Nucleation And Growth ◽

In Situ Observation ◽

Considerable Potential ◽

Transmission Electron ◽

Structural Applications ◽

Applied Stresses ◽

Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

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Novel Carbon Dots Derived from Glycyrrhizae Radix et Rhizoma and Their Anti-Gastric Ulcer Effect

Molecules ◽

10.3390/molecules26061512 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1512

Author(s):

Yuhan Liu ◽

Meiling Zhang ◽

Jinjun Cheng ◽

Yue Zhang ◽

Hui Kong ◽

...

Keyword(s):

Gastric Ulcer ◽

Photoelectron Spectroscopy ◽

Carbon Dots ◽

High Performance ◽

Raw264.7 Cells ◽

Mice Model ◽

X Ray ◽

Glycyrrhizae Radix ◽

Transmission Electron ◽

High Resolution Tem

Glycyrrhizae Radix et Rhizoma (GRR) is one of the commonly used traditional Chinese medicines in clinical practice, which has been applied to treat digestive system diseases for hundreds of years. GRR is preferred for anti-gastric ulcer, however, the main active compounds are still unknown. In this study, GRR was used as precursor to synthesize carbon dots (CDs) by a environment-friendly one-step pyrolysis process. GRR-CDs were characterized by using transmission electron microscopy, high-resolution TEM, fourier transform infrared, ultraviolet-visible and fluorescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and high-performance liquid chromatography. In addition, cellular toxicity of GRR-CDs was studied by using CCK-8 in RAW264.7 cells, and the anti-gastric ulcer activity was evaluated and confirmed using mice model of acute alcoholic gastric ulcer. The experiment confirmed that GRR-CDs were the spherical structure with a large number of active groups on the surface and their particle size ranged from 2 to 10 nm. GRR-CDs had no toxicity to RAW264.7 cells at concentration of 19.5 to 5000 μg/mL and could reduce the oxidative damage of gastric mucosa and tissues caused by alcohol, as demonstrated by restoring expression of malondialdehyde, superoxide dismutase and nitric oxide in serum and tissue of mice. The results indicated the explicit anti-ulcer activity of GRR-CDs, which provided a new insights for the research on effective material basis of GRR.

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Crystallization of Amorphous Silicon-Aluminum thin Films: IN-SITU Observation and Thermal Analysis.

MRS Proceedings ◽

10.1557/proc-237-609 ◽

1991 ◽

Vol 237 ◽

Cited By ~ 3

Author(s):

Toyohiko J. Konno ◽

Robert Sinclair

Keyword(s):

Activation Energy ◽

Amorphous Alloys ◽

Amorphous Matrix ◽

In Situ Observation ◽

Scanning Calorimetry ◽

Transmission Electron ◽

High Resolution Tem ◽

Higher Temperature ◽

Sputter Deposited

ABSTRACTThe crystallization of sputter-deposited Si/Al amorphous alloys was examined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). In-situ high-resolution TEM reveals the existence of an Al layer between the amorphous matrix and the growing crystalline phase. The activation energy for the growth is about 1.2eV, roughly corresponding to the activation energy of Si diffusion in Al. These two observations support the view that a crystallization mechanism, in which an Al buffer layer provides the shortest reaction path, is responsible for the reaction. The product microstructure exhibits secondary crystallization at a higher temperature.

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Reaction Synthesized Boron Nitride-Containing Composites (BNCC)

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.280-283.1385 ◽

2007 ◽

Vol 280-283 ◽

pp. 1385-1390

Author(s):

Guo Jun Zhang ◽

Tatsuki Ohji ◽

Shuzo Kanzaki

Keyword(s):

Boron Nitride ◽

Hot Pressing ◽

High Performance ◽

Hexagonal Boron Nitride ◽

High Strength ◽

Reactive Sintering ◽

Boron Source ◽

Inorganic Reactions ◽

Reactive Hot Pressing

Based on the proposed inorganic reactions a series of high performance hexagonal boron nitride-containing composites (BNCC), include SiC-BN, Si3N4-SiC-BN, SiAlON-BN, AlN-BN, Al2O3-BN, AlON-BN and mullite-BN, have been prepared via reactive hot pressing or pressureless reactive sintering. Various boron-bearing components such as B, B4C, AlB2, SiB4, SiB6, B2O3 or H3BO3, 9Al2O3×2B2O3 (9A2B) and 2Al2O3×B2O3 (2AB) are used as the boron source. On the other hand, nitrogen gas or solid state nitirgen-bearing metal nitrides such as Si3N4 and AlN can be used as the nitrogen source. The in situ synthesized composites demonstrated homogeneous and isotropical microstructures with very fine (nano-sized) BN platelets or their agglomerates distributed in the matrixes. These composites showed high strength, low elasticity and improved strain tolerance. In this article the reaction design, thermodynamics, reaction mechanisms, reactive hot pressing or pressureless reactive sintering, microstructures and mechanical properties will be discussed.

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Induction and Transcription Studies of the Dextransucrase Gene in Leuconostoc mesenteroides NRRL B-512F

Applied and Environmental Microbiology ◽

10.1128/aem.65.12.5504-5509.1999 ◽

1999 ◽

Vol 65 (12) ◽

pp. 5504-5509 ◽

Cited By ~ 31

Author(s):

M. Quirasco ◽

A. López-Munguía ◽

M. Remaud-Simeon ◽

P. Monsan ◽

A. Farrés

Keyword(s):

High Performance ◽

Leuconostoc Mesenteroides ◽

Carbon Sources ◽

Promoter Sequence ◽

Culture Conditions ◽

Start Codon ◽

Reaction Products ◽

Product Specificity ◽

First Time

ABSTRACT Dextransucrase production by Leuconostoc mesenteroidesNRRL B-512F in media containing carbon sources other than sucrose is reported for the first time. Dextransucrases were analyzed by gel electrophoresis and by an in situ activity assay. Their polymers and acceptor reaction products were also compared by 13C nuclear magnetic resonance and high-performance liquid chromatography techniques, respectively. From these analyses, it was found that, independently of the carbon source, L. mesenteroides NRRL B-512F produced dextransucrases of the same size and product specificity. The 5′ ends of dextransucrase mRNAs isolated from cells grown under different culture conditions were identical. Based on this evidence, we conclude that dextransucrases obtained from cells grown on the various carbon sources result from the transcription of the same gene. The control of expression occurs at this level. The low dextransucrase yields from cultures in d-glucose ord-fructose and the enhancement of dextransucrase gene transcription in the presence of sucrose suggest that an activating phenomenon may be involved in the expression mechanism. Dextransucrase mRNA has a size of approximately 4.8 kb, indicating that the gene is located in a monocistronic operon. The transcription start point was localized 34 bp upstream from the ATG start codon. The −10 and −35 sequences found, TATAAT and TTTACA, were highly homologous to the only glycosyltransferase promoter sequence reported for lactic acid bacteria.

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Large plasticity in magnesium mediated by pyramidal dislocations

Science ◽

10.1126/science.aaw2843 ◽

2019 ◽

Vol 365 (6448) ◽

pp. 73-75 ◽

Cited By ~ 45

Author(s):

Bo-Yu Liu ◽

Fei Liu ◽

Nan Yang ◽

Xiao-Bo Zhai ◽

Lei Zhang ◽

...

Keyword(s):

Energy Efficiency ◽

Electron Microscope ◽

Plastic Strain ◽

Crystal Size ◽

High Stress ◽

High Strength ◽

High Plasticity ◽

Transmission Electron ◽

Small Crystal Size

Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for widespread applications is the limited ductility of magnesium, which has been attributed to 〈c+a〉 dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that 〈c+a〉 dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more 〈c+a〉 dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.

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Growth and Characterization of Cobalt-filled Carbon Nanotubes Prepared by a Simple Catalytic Method

MRS Proceedings ◽

10.1557/proc-776-q8.17 ◽

2003 ◽

Vol 776 ◽

Author(s):

Xicheng Ma ◽

Yuanhua Cai ◽

Xia Li ◽

Ning Lun ◽

Shulin Wen

Keyword(s):

Carbon Nanotubes ◽

Metallic Nanoparticles ◽

Low Cost ◽

Catalytic Method ◽

Selected Area Electron Diffraction ◽

Transmission Electron ◽

High Resolution Tem ◽

One Step

AbstractHigh-quality cobalt-filled carbon nanotubes (CNTs) were prepared in situ in the decomposition of benzene over Co/silica-gel nano-scale catalysts. Unlike the previous reports, the catalysts needn't be pre-reduced prior to the forming of Co-filled CNTs, thus the advantage of this method is that Co-filled CNTs can be produced in one step, at a relatively low cost. Transmission electron microscopy (TEM) investigation showed that the products contained abundance of CNTs and most of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified always as high temperature alpha-Co phase with fcc structure, which frequently consists of twinned boundaries and stacking faults. Based on the experimental results, a possible growth mechanism of the Co-filled CNTs was proposed.

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