Effect Of Composition Distribution Research Articles

Effect of composition distribution in the HgCdTe film on spectral response of device

The effect of LPE HgCdTe longitudinal composition distribution on device's spectral response was studied.A new model was proposed to calculate the spectral response of HgCdTe IR detector.This model considered the real composition distribution in HgCdTe film.The coherent and incoherent light transmission among the device were also included.The calculated result indicates that the composition gradient of LPE HgCdTe film and the built-in electric field can evidently improve the response of the device.The calculated result agreed with the measured data,and proved the accuracy of the model.

Effects of composition distribution on electronic structures of self-assembled InGaN/GaN quantum dots

In this study, we investigate the influences of different composition distributions on the electronic structures of truncated cone-shaped InGaN quantum dots (QDs). A varying parameter, , is defined as , in which w1 and w2 are the top and base diameter of QD, respectively. This factor is set to study the role of similar truncated cones with the same base diameter and height on electronic structures of QD. Three indium composition distributions are considered: ellipsoid, uniform, and linear. The single-band effective-mass equation and six-band k·p theory are used to calculate the transition energies of electrons and holes, respectively. The numerical results reveal that the parameter plays an important role in changing the piezoelectric potential. In addition, an InGaN quantum dot with a linear distribution of indium has the maximum transition energy, whereas one with an ellipsoidal distribution has the minimum value. It is noteworthy that the binding energy greatly decreases as increases for different indium distributions.

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles

Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry measurements of individual particles indicate a broad compositional distribution in both the 4.5 and 6 nm FePt nanoparticles. The effects of compositional distribution on the phase-transition and magnetic properties of the FePt nanoparticles were investigated.

Chain Localization and Interfacial Thickness in Microphase-Separated Structures of Block Copolymers with Variable Composition Distributions

The effect of composition distribution on microphase-separated structures of AB diblock and BAB triblock copolymers was investigated at the molecular level by measurements of neutron reflectivity. Monodispersed three poly(styrene)-d8-block-poly(2-vinylpyridine) (DP) and three labeled triblock copolymers (PDP) and unlabeled counterparts were synthesized by a living anionic polymerization process designed to yield constant molecular weight with different volume fractions. The selective labeling method employs the blending of copolymers for a segmental distribution study while the labeled polymers are mixed for an interfacial study. Scattering length density profiles were observed by neutron reflectivity measurements for blended thin films produced by spin-coating and successive thermal annealing. It was confirmed that the blended thin films exhibit simple alternating lamellar structures, an observation consistent with the observed structures of bulk specimens. The localization phenomenon of longer and short...

Effect of Composition Distribution on Microphase-Separated Structure from BAB Triblock Copolymers

The effects of composition distribution on microphase-separated structures formed by monodisperse BAB triblock copolymers were investigated. Monodisperse nine parent BAB triblock copolymers consisting of polystyrene for A and poly(2-vinylpyridine) for B were prepared by anionic living polymerization. These nine copolymers were designed such that polystyrene volume fraction, φs, ranged from 0.1 to 0.9, and they were blended to produce samples with various composition distributions but with constant average composition at φs of 0.5. Periodic simple alternating lamellar structures were observed for solvent cast and well-annealed blend films as long as composition distribution is relatively low. It has been found that microdomain spacing increases with increasing composition distribution of copolymer samples up to 1.25 in terms of Mw(S)/Mn(S), where Mw(S) and Mn(S) are weight-average and number-average molecular weights of polystyrene blocks, respectively, as was the case of the AB diblock copolymer system, t...

Effect of Composition Distribution on Microphase-Separated Structure from Diblock Copolymers

Microphase-separated structures of diblock copolymers with narrow molecular weight distributions but with various composition distributions were investigated. Monodisperse nine parent block copolymers composed of polystyrene and poly(2-vinylpyridine) having almost the same molecular weight but with different polystyrene volume fraction, φs, covering 0.1−0.9, were prepared. Successively they were blended variously to produce samples with various composition distributions but with constant average composition; that is, φs was kept constant at approximately 0.5. Structures from solvent-cast and well-annealed films were observed through transmission electron microscopy and small-angle X-ray scattering. It has been found that the blends with wide composition distributions show periodic alternating lamellar structure up to 1.7 in terms of Mw(S)/Mn(S), where Mw(S) and Mn(S) denote weight-average and number-average molecular weights of polystyrene block, respectively, and that the microdomain spacing increases with increase of polydispersity of each block. Further, it was clarified that the blend shows macrophase separation in between two kinds of regular microphase-separated structures if Mw(S)/ Mn(S) reaches approximately 1.8.

Phase Behavior and Thermal Properties for Binary Blends of Bacterial Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)s with Narrow‐Comonomer‐Unit Compositional Distribution

AbstractThe miscibility and the effect of compositional distribution on physical properties were investigated for binary blends of biosynthesized poly(3‐hydroxybutyrate) [P(3HB)] and comonomer compositionally fractionated poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)s [P(3HB‐co‐3HH)] with narrow compositional distribution. Biosynthesized P(3HB‐co‐3HH) samples were compositionally fractionated using solvent (chloroform)/nonsolvent (n‐heptane) mixtures. The binary blends of fractionated P(3HB‐co‐3HH)s with different 3HH unit content were prepared by casting from solution in chloroform. The miscibility and the thermal properties of these blends were analyzed by differential scanning calorimetry (DSC). It was found that the two components are miscible in the amorphous phase when the difference in 3HH unit content between the two component polymers of these blends is less than 20 mol‐%, subsequently they are immiscible when the difference is larger than 30 mol‐%. By comparing the thermal properties of the binary blends of fractions, with those for the fractions themselves, and with those for the bacterially as‐produced unfractionated copolyesters, the effects of compositional distribution on the properties of copolyesters were discussed.Glass transition temperatures of blends PHB/H10, H10/H20, and PHB/H20 versus total 3HH unit content in the blends. The solid lines are the best fits of the experimental results of the P(3HB‐co‐3HH) fractions with narrow compositional distribution.magnified imageGlass transition temperatures of blends PHB/H10, H10/H20, and PHB/H20 versus total 3HH unit content in the blends. The solid lines are the best fits of the experimental results of the P(3HB‐co‐3HH) fractions with narrow compositional distribution.

Effect of composition distribution on miscibility and co-crystallization phenomena in the blends of low density polyethylene with conventional and metallocene-based ethylene–butene copolymers

Three ethylene–butene copolymers (two metallocene-based and one conventional) having different composition distributions were blended with low density polyethylene (LDPE) in a wide proportion range. The miscibility of the blend melts was studied with the rheological method. It is found that zero-shear viscosity of all the blends does not obey the logarithmic additivity rule, indicating the immiscible state of the blend melts. The blends were rapidly quenched from the melts and co-crystallization phenomena were investigated by differential scanning calorimetry (DSC). The obtained results show that composition distribution has a great influence on co-crystallization. In the blends of the conventional ethylene–butene copolymer, which has a broad composition distribution, part of the co-crystals may segregate from the crystals of both LDPE and ethylene copolymer and exist as a separated population. This suggests that there exist three phases in the melts. In contrast, the blends of the metallocene-based ethylene–butene copolymers with a narrow composition distribution are only composed of two phases together with some exchange between the two components. It is also observed that broader composition distribution leads to more ethylene–butene copolymer transferred into LDPE.

Effect of composition distribution on holographic temperature measurement of a diffuse flame

The application of phase shift holographic interferometry to non-intrusive temperature measurement of a laminar, axisymmetric, propane diffuse flame is investigated. In our previous work the effect of composition changes on the holographic temperature measurement of reacting flows was experimentally studied for cases with axisymmetric, propane, laminar premixed lean flames (PLFs) and partially premixed flames (PPFs). To further examine this effect, in this work the effect of the diffuse flame (DF) is investigated. It has been shown that for the DF, the composition distribution is the most complicated and the composition effect is more severe than that of the PLF and the PPF. In order to obtain accurate and satisfactory holographic results, it is necessary to measure the species concentration at lower flame heights, and to use linear interpolation of the molar refractivity at higher test sections.