scholarly journals Absorption and Photoluminescence Study of Cds Quantum Dots: The Role of Host Matrix and Nanocrystal Size and Density

1999 ◽  
Vol 571 ◽  
Author(s):  
Yu.P. Rakovich ◽  
A.G. Rolo ◽  
M.V. Stepikhova ◽  
M.I. Vasilevskiy ◽  
M.J.M. Gomes ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Optical Transition ◽  
Spectral Position ◽  
Host Matrix ◽  
The Matrix ◽  
Mean Size ◽  
Free Films ◽  
Matrix Free ◽  
Cds Crystallites

ABSTRACTIn this paper we present results of the absorption and photoluminescence (PL) of CdSdoped Si02 films fabricated by RF co-sputtering (semiconductor volume fraction f=1–15%, nano-crystallite's mean size 5–7nm) and matrix-free films of close-packed CdS nanocrystallites (f∼30%, size 2–5nm) produced by an original chemical method. The absorption spectra have been modelled using the modified Maxwell-Garnett model. This gives the e-h pair state energies and evidence of a strong absorption in the glass matrix containing CdS. The temperature dependence of the spectral position and broadening of the PL peak is analysed. It is concluded that a photo-generated hole is captured on an acceptor-type trap before the radiative recombination with a confined electron. The excitation of this ‘band-edge’ PL occurs through some states in the matrix and directly in the CdS crystallites for the two kinds of samples, respectively. The temperature coefficients of the optical transition energies for the nearly matrix-free films are similar to those of bulk CdS, while for the CdS/glass films they are smaller. This may be because of the different boundary conditions for the thermal expansion of CdS crystallites.

scholarly journals Effect of the matrix subsystem on hydrostatic parameters of a novel 1–3-type piezo-composite

2015 ◽  
Vol 08 (05) ◽  
pp. 1550049 ◽  
Author(s):  
Vitaly Yu. Topolov ◽  
Christopher R. Bowen ◽  
Paolo Bisegna ◽  
Anatoly E. Panich
Keyword(s):  
Elastic Properties ◽  
Electromechanical Coupling ◽  
Volume Fraction ◽  
Electromechanical Coupling Factor ◽  
Ferroelectric Ceramic ◽  
Coupling Factor ◽  
Polyurethane Composite ◽  
The Matrix ◽  
Type Composite

The influence of the aspect ratio and volume fraction of ferroelectric ceramic inclusions in a 0–3 matrix on the hydrostatic parameters of a three-component 1–3-type composite is studied to demonstrate the important role of the elastic properties of the two-component matrix on the composite performance. Differences in the elastic properties of the 0–3 matrix and single-crystal rods lead to a considerable dependence of the hydrostatic response of the composite on the anisotropy of the matrix elastic properties. The performance of a 1–0–3 0.92 Pb ( Zn 1/3 Nb 2/3) O 3–0.08 PbTiO 3 SC/modified PbTiO 3 ceramic/polyurethane composite suggests that this composite system is of interest for hydroacoustic applications due to its high hydrostatic piezoelectric coefficients [Formula: see text] and [Formula: see text], squared figure of merit [Formula: see text], and electromechanical coupling factor [Formula: see text].

scholarly journals Role of titanium carbide and alumina on the friction increment for Cu-based metallic brake pads under different initial braking speeds

Friction ◽  
2020 ◽  
Author(s):  
Tao Peng ◽  
Qingzhi Yan ◽  
Xiaolu Zhang ◽  
Yan Zhuang
Keyword(s):  
Wear Resistance ◽  
Titanium Carbide ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Interface Bonding ◽  
Brake Pads ◽  
Reinforced Composite ◽  
The Poor ◽  
The Matrix

AbstractTo understand the effect of abrasives on increasing friction in Cu-based metallic pads under different braking speeds, pad materials with two typical abrasives, titanium carbide (TiC) and alumina (Al2O3), were produced and tested using a scale dynamometer under various initial braking speeds (IBS). The results showed that at IBS lower than 250 km/h, both TiC and Al2O3 particles acted as hard points and exhibited similar friction-increasing behavior, where the increase in friction was not only enhanced as IBS increased, but also enhanced by increasing the volume fraction of the abrasives. However, at higher IBS, the friction increase was limited by the bonding behavior between the matrix and abrasives. Under these conditions, the composite containing TiC showed a better friction-increasing effect and wear resistance than the composite containing Al2O3 because of its superior particle-matrix bonding and coefficient of thermal expansion (CTE) compatibility. Because of the poor interface bonding between the matrix and Al2O3, a transition phenomenon exists in the Al2O3-reinforced composite, in which the friction-increasing effect diminished when IBS exceeded a certain value.

scholarly journals Recent Advances on Nanocomposite Resists With Design Functionality for Lithographic Microfabrication

2021 ◽  
Vol 8 ◽  
Author(s):  
E. D. Martínez ◽  
A. Prado ◽  
M. Gonzalez ◽  
S. Anguiano ◽  
L. Tosi ◽  
...  
Keyword(s):  
Functional Materials ◽  
Host Matrix ◽  
Size Dependent ◽  
Current Trends ◽  
Functional Composites ◽  
The Matrix ◽  
Carbon Based Nanomaterials ◽  
Novel Devices ◽  
Near Future

Nanocomposites formed by a phase-dispersed nanomaterial and a polymeric host matrix are highly attractive for nano- and micro-fabrication. The combination of nanoscale and bulk materials aims at achieving an effective interplay between extensive and intensive physical properties. Nanofillers display size-dependent effects, paving the way for the design of tunable functional composites. The matrix, on the other hand, can facilitate or even enhance the applicability of nanomaterials by allowing their easy processing for device manufacturing. In this article, we review the field of polymer-based nanocomposites acting as resist materials, i.e. being patternable through radiation-based lithographic methods. A comprehensive explanation of the synthesis of nanofillers, their functionalization and the physicochemical concepts behind the formulation of nanocomposites resists will be given. We will consider nanocomposites containing different types of fillers, such as metallic, magnetic, ceramic, luminescent and carbon-based nanomaterials. We will outline the role of nanofillers in modifying various properties of the polymer matrix, such as the mechanical strength, the refractive index and their performance during lithography. Also, we will discuss the lithographic techniques employed for transferring 2D patterns and 3D shapes with high spatial resolution. The capabilities of nanocomposites to act as structural and functional materials in novel devices and selected applications in photonics, electronics, magnetism and bioscience will be presented. Finally, we will conclude with a discussion of the current trends in this field and perspectives for its development in the near future.

scholarly journals Dynamics of matrix-free Ca2+ in cardiac mitochondria: two components of Ca2+ uptake and role of phosphate buffering

2012 ◽  
Vol 139 (6) ◽  
pp. 465-478 ◽  
Author(s):  
An-Chi Wei ◽  
Ting Liu ◽  
Raimond L. Winslow ◽  
Brian O'Rourke
Keyword(s):  
Mitochondrial Permeability Transition ◽  
High Capacity ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Cardiac Mitochondria ◽  
The Matrix ◽  
The Relationship ◽  
Matrix Free ◽  
Trigger Cell Death

Mitochondrial Ca2+ uptake is thought to provide an important signal to increase energy production to meet demand but, in excess, can also trigger cell death. The mechanisms defining the relationship between total Ca2+ uptake, changes in mitochondrial matrix free Ca2+, and the activation of the mitochondrial permeability transition pore (PTP) are not well understood. We quantitatively measure changes in [Ca2+]out and [Ca2+]mito during Ca2+ uptake in isolated cardiac mitochondria and identify two components of Ca2+ influx. [Ca2+]mito recordings revealed that the first, MCUmode1, required at least 1 µM Ru360 to be completely inhibited, and responded to small Ca2+ additions in the range of 0.1 to 2 µM with rapid and large changes in [Ca2+]mito. The second component, MCUmode2, was blocked by 100 nM Ru360 and was responsible for the bulk of total Ca2+ uptake for large Ca2+ additions in the range of 2 to 10 µM; however, it had little effect on steady-state [Ca2+]mito. MCUmode1 mediates changes in [Ca2+]mito of 10s of μM, even in the presence of 100 nM Ru360, indicating that there is a finite degree of Ca2+ buffering in the matrix associated with this pathway. In contrast, the much higher Ca2+ loads evoked by MCUmode2 activate a secondary dynamic Ca2+ buffering system consistent with calcium-phosphate complex formation. Increasing Pi potentiated [Ca2+]mito increases via MCUmode1 but suppressed [Ca2+]mito changes via MCUmode2. The results suggest that the role of MCUmode1 might be to modulate oxidative phosphorylation in response to intracellular Ca2+ signaling, whereas MCUmode2 and the dynamic high-capacity Ca2+ buffering system constitute a Ca2+ sink function. Interestingly, the trigger for PTP activation is unlikely to be [Ca2+]mito itself but rather a downstream byproduct of total mitochondrial Ca2+ loading.

scholarly journals Prediction of the Elastic Tensor of 3D Composites by an Analytical Model

1999 ◽  
Vol 8 (5) ◽  
pp. 096369359900800
Author(s):  
C. Tallaron ◽  
S. Barre
Keyword(s):  
Volume Fraction ◽  
Unidirectional Composite ◽  
Second Step ◽  
Relative Role ◽  
Elastic Tensor ◽  
The Matrix ◽  
Three Bundles ◽  
Transversally Isotropic

The aim of this study is the determination of the overall elastic tensor of two 3D composites. These materials have a multiscale architecture. The representative volume element of the composite architecture (symbolised by a unit-cell) is composed of three bundles in three orthogonal directions and two matrix pockets. Each bundle is a unidirectional composite formed by a juxtaposition of long fibres surrounded by the matrix. Due to their symmetry, the bundles are considered transversally isotropic according to the fibres axis, whereas the pockets are macroscopically isotropic. The analytical computation is produced in two steps. The first step consists of determining the elastic tensor of the bundles. The second step is the calculation of the elastic tensor of the whole composite. The most part of the used equations comes from bibliography, excepted the determination of shear coefficients of the composite. The last part of this study devoted to the influence of material parameters presents the relative role of the fibres, the matrix and their volume fraction.

Magnetic Properties of Co Nanoparticles in an AlMCM41 Mesoporous Host

2001 ◽  
Vol 676 ◽  
Author(s):  
Jin-Seung Jung ◽  
Jun-Yong Kim ◽  
Weon-Sik Chae ◽  
Yong-Rok Kim ◽  
Jong-Ho Jun ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Volume Fraction ◽  
Magnetic Measurements ◽  
X Ray Diffraction ◽  
Host Matrix ◽  
Transmission Electron ◽  
Small Volume Fraction ◽  
Size Of Particles ◽  
Co Nanoparticles

ABSTRACTUltrafine cobalt particles in AlMCM41 silica tubes have been synthesized by ion exchange and the reduction with sodium borohydride. The role of this stable host matrix of AlMCM41 silica is to prevent agglomeration of the magnetic particles attached to the walls of AlMCM41 silica pores. The size of the host pores naturally limits the particle dimensions and thus improves their size distribution. Both magnetic susceptibility measurements and transmission electron microscopy (TEM) show a narrow distribution size of the nanoparticles. Well controlled insertion of the magnetic material to the host channel excludes formation of bulk particles outside the host material grains, which was confirmed by the TEM studies. X-ray diffraction data did not show peaks corresponding to a crystalline cobalt, but this maybe due to small size of particles and their relatively small volume fraction. The content of Co in the AlMCM41 host was measured using both magnetic measurements and elemental analysis.

scholarly journals Analysis of creep behavior of SiC/Al metal matrix composites based on a generalized shear-lag model

2004 ◽  
Vol 19 (12) ◽  
pp. 3633-3640 ◽  
Author(s):  
Ho J. Ryu ◽  
Kyung H. Chung ◽  
Seung I. Cha ◽  
Soon H. Hong
Keyword(s):  
Effective Stress ◽  
Volume Fraction ◽  
Matrix Composites ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Sic Particles ◽  
Al Composite ◽  
The Matrix ◽  
Lag Model

The creep behaviors of 20 vol% SiCw/2124Al, extruded with different ratios, and SiCp/2124Al, reinforced with 10–30 vol% SiC particles, were investigated to clarify the effects of aspect ratio, alignment, and volume fraction of reinforcement on creep deformation. The effective stresses on the matrix of SiC/Al composites are calculated based on the generalized shear-lag model. The minimum creep rates of SiCw/2124Al extruded with different ratios and SiCp/2124Al reinforced with different volume fractions of SiC particles are found to be similar under a same effective stress on matrix, which is calculated by the generalized shear-lag model. The subgrain sizes in matrices of crept SiC/Al composites are dependent on the effective stress on matrix but not on the applied stress on the composite. It is suggested that the role of SiC reinforcements is to increase the creep resistance of SiC/Al composite by reducing the effective stress on matrix.

Hybrid Composite Nano-Sized WC-Co Cemented Carbide

2007 ◽  
Vol 534-536 ◽  
pp. 1197-1200 ◽  
Author(s):  
Sun Yong Park ◽  
Wan Jae Lee
Keyword(s):  
Wear Resistance ◽  
Volume Fraction ◽  
Rupture Strength ◽  
Granule Size ◽  
Drying Method ◽  
Transverse Rupture Strength ◽  
Matrix Volume ◽  
The Matrix ◽  
Mean Size ◽  
The Mean

To improve the mechanical properties of WC-Co cemented carbides, a dual composite was studied. The compositions of granule and matrix were nano-sized WC-6 wt% Co(granule) and normal sized WC-20 wt% Co(matrix), respectively. The granules were made by spray-drying method and sintered at 1380°C for 10 minutes in vacuum. After sieving, the granules were grouped to 50, 100 and 150 ㎛ and mixed with WC and Co powders as the volume fractions of granule to matrix were 50 to 50, 40 to 60 and 30 to 70. These compacts were sintered at 1380°C for 10 minutes in vacuum. The microstructure, transverse rupture strength and wear resistance were investigated. The relative densities of the dual composites were about 98% after sintering. The mean size of the WC grains in the dual composite was about 300~400 nm. As the volume fraction of the matrix in the dual composite increased, the transverse rupture strength increased and hardness decreased. The wear resistance of the dual composite increased with decreasing matrix volume fraction and increasing granule size.

Heterogeneity of mitochondrial matrix free Ca2+: resolution of Ca2+ dynamics in individual mitochondria in situ

1999 ◽  
Vol 276 (5) ◽  
pp. C1193-C1204 ◽  
Author(s):  
Gregory R. Monteith ◽  
Mordecai P. Blaustein
Keyword(s):  
Short Term ◽  
Long Duration ◽  
The Matrix ◽  
Resolution Imaging ◽  
Temporal And Spatial ◽  
Rapid Signaling ◽  
Matrix Free ◽  
Mitotracker Green

The role of mitochondria in Ca2+ homeostasis is controversial. We employed the Ca2+-sensitive dye rhod 2 with novel, high temporal and spatial resolution imaging to evaluate changes in the matrix free Ca2+ concentration of individual mitochondria ([Ca2+]m) in agonist-stimulated, primary cultured aortic myocytes. Stimulation with 10 μM serotonin (5-HT) evoked modest cytosolic Ca2+ transients [cytosolic free Ca2+ concentration ([Ca2+]cyt) <500 nM; measured with fura 2] and triggered contractions in short-term cultured myocytes. However, 5-HT triggered a large mitochondrial rhod 2 signal (indicating pronounced elevation of [Ca2+]m) in only 4% of cells. This revealed heterogeneity in the responses of individual mitochondria, all of which stained with MitoTracker Green FM. In contrast, stimulation with 100 μM ATP evoked large cytosolic Ca2+ transients (>1,000 nM) and induced pronounced, reversible elevation of [Ca2+]m(measured as rhod 2 fluorescence) in 60% of cells. This mitochondrial Ca2+ uptake usually lagged behind the cytosolic Ca2+ transient peak by 3–5 s, and [Ca2+]mdeclined more slowly than did bulk [Ca2+]cyt. The uptake delay may prevent mitochondria from interfering with rapid signaling events while enhancing the mitochondrial response to large, long-duration elevations of [Ca2+]cyt. The responses of arterial myocytes to modest physiological stimulation do not, however, depend on such marked changes in [Ca2+]m.

Computational micromechanical modelling of the material removal process in a carbon fibre composite under single-erodent particle impact

2020 ◽  
Vol 234 (10) ◽  
pp. 1605-1617
Author(s):  
Ajaz A Deliwala ◽  
Chandra S Yerramalli
Keyword(s):  
Carbon Fibre ◽  
Volume Fraction ◽  
Matrix Material ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Erosion Behaviour ◽  
The Matrix ◽  
Material Erosion ◽  
Erodent Particle

A multiscale model is developed to understand the material removal process in a unidirectional carbon fibre epoxy composite impacted by a single-erodent particle. The embedded cell approach is used to model the carbon fibre and epoxy at a microscale. The micromodel is embedded centrally in the macroscale lamina of the composite plate. The carbon fibre is considered to be elastic with orthotropic strain limits as the failure criteria. The epoxy matrix is modelled as an elastic--plastic material with multilinear isotropic hardening. The maximum equivalent plastic strain limit is used as the matrix material failure limit. Using this embedded micromechanics model, the role of matrix and the fibre in developing the composite material erosion behaviour has been clearly elucidated. The results from the simulation indicate the change in the matrix erosion behaviour as a function of the fibre volume fraction. For the current thermoset matrix, material erosion response changes from brittle behaviour to ductile behaviour with an increase in fibre volume fraction. The current study has been able to highlight the individual role of matrix and the fibre in developing the semi-ductile erosion response peculiar to a fibre-reinforced composite material.

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