Effective Domain Size Research Articles

Characterizing Phase Separation of Amorphous Solid Dispersions Containing Imidacloprid.

Amorphous-Amorphous phase separation (AAPS) is an important phenomenon that can impede the performance of amorphous solid dispersions (ASDs). The purpose of this study was to develop a sensitive approach relying on dielectric spectroscopy (DS) to characterize AAPS in ASDs. This includes detecting AAPS, determining the size of the active ingredient (AI) discrete domains in the phase-separated systems, and accessing the molecular mobility in each phase. Using a model system consisting of the insecticide imidacloprid (IMI) and the polymer polystyrene (PS), the dielectric results were further confirmed by confocal fluorescence microscopy (CFM). The detection of AAPS by DS was accomplished by identifying the decoupled structural (α-)dynamics of the AI and the polymer phase. The α-relaxation times corresponding to each phase correlated reasonably well with those of the pure components, implying nearly complete macroscopic phase separation. Congruent with the DS results, the occurrence of the AAPS was detected by means of CFM, making use of the autofluorescent property of IMI. Oscillatory shear rheology and differential scanning calorimetry (DSC) detected the glass transition of the polymer phase but not that of the AI phase. Furthermore, the otherwise undesired effects of interfacial and electrode polarization, which can appear in DS, were exploited to determine the effective domain size of the discrete AI phase in this work. Here, stereological analysis of CFM images probing the mean diameter of the phase-separated IMI domains directly stayed in reasonably good agreement with the DS-based estimates. The size of phase-separated microclusters showed little variation with AI loading, implying that the ASDs have presumably undergone AAPS upon manufacturing. DSC provided further support to the immiscibility of IMI and PS, as no discernible melting point depression of the corresponding physical mixtures was detected. Moreover, no signatures of strong attractive AI-polymer interactions could be detected by mid-infrared spectroscopy within this ASD system. Finally, dielectric cold crystallization experiments of the pure AI and the 60 wt % dispersion revealed comparable crystallization onset times, hinting at a poor inhibition of the AI crystallization within the ASD. These observations are in harmony with the occurrence of AAPS. In conclusion, our multifaceted experimental approach opens new venues for rationalizing the mechanisms and kinetics of phase separation in amorphous solid dispersions.

라그랑지안 입자확산모델을 이용한 광양만 권역에서의 공기괴 재순환현상 수치모의

Air mass recirculation is a common characteristic in the coastal area as a result of the land-sea breeze circulation. This study simulates the recirculation of air mass over the Gwangyang Bay using WRF-FLEXPART and offers a basic information about the effective domain size that can reflect recirculation. For this purpose, WRF is set up four nested domains and three cases are selected. Subsequently FLEXPART is operated on the basis of WRF output. During the clear summer days with weak wind speed, particles that emitted from Yeosu national industrial complex and Gwangyang iron works flow into emission sources because of the land-sea breeze. When land-sea breeze is strengthen, the recirculation phenomena appears clearly. However particles aren't recirculated under weak synoptic condition. Also plume trajectory is analyzed and as a consequence, the smallest domain area have to be multiplied by 1.3 to understand recirculated dispersion pattern of particles.

Anomalous circular ac susceptibility and magnetoimpedance for nearly nonmagnetostrictive amorphous wire

The frequency dependent low-field circular ac susceptibility χ=χ′−jχ″ of a nearly nonmagnetostrictive Co68.2Fe4.3Si12.5B15 amorphous wire annealed at 470 °C is determined by impedance Z measurements under stepwise decreased longitudinal dc field Hdc from 216 to −216 A/m after premagnetization at 16 kA/m. It is found that compared with the results of the classical eddy-current model, the measured low-frequency loss factor is larger by an anomaly factor η between 1.5 and 3, depending on the value of Hdc. However, the χ(f) curve at each value of Hdc may be well fitted by an eddy-current model of bamboo-domain wall displacements if the material conductivity is replaced by a greater effective one and a proper value of effective domain size is chosen. The physical mechanism of such a fitting is discussed based on previous studies on anomalous dc circular susceptibility. This anomalous χ(f,Hdc) leads to an anomalous magnetoimpedance Z(Hdc) with a two-peak feature when frequency is high.

Microstructural studies on lattice imperfections in irradiated titanium and Ti-5 Pct Ta-2 Pct Nb by X-ray diffraction line-profile analysis

Microstructural parameters such as the average domain size, effective domain size at a particular crystallographic direction, and microstrain within the domains of titanium and Ti-5 pct Ta-2 pct Nb, irradiated with 116 MeV O5+ ion, have been characterized as a function of dose by X-ray diffraction line-profile analysis (XRDLPA) using different model-based approaches. The dislocation density and stacking-fault probabilities have also been estimated from the analysis. The analysis revealed that there was a significant decrease of the average domain size with dose as compared to the unirradiated sample. The estimated values of dislocation density increased significantly for the irradiated samples and were found to be an order of magnitude more as compared to the unirradiated one. However, the dislocation density became saturated with an increase in dose. The deformation (stacking-fault) probabilities were found to be negligible even with the increase in dose of irradiation.

A linearized kinetic formulation including a second-order slip model for an impulsive start problem at arbitrary Knudsen numbers

We investigate the time evolution of an impulsive start problem for arbitrary Knudsen numbers ( $\hbox{\it Kn}$ ) using a linearized kinetic formulation. The early-time behaviour is described by a solution of the collisionless Boltzmann equation. The same solution can be used to describe the late-time behaviour for $\hbox{\it Kn}\,{\gg}\,1$ . The late-time behaviour for $\hbox{\it Kn}\,{ is captured by a newly proposed second-order slip model with no adjustable parameters. All theoretical results are verified by direct Monte Carlo solutions of the nonlinear Boltzmann equation. A measure of the timescale to steady state, normalized by the momentum diffusion timescale, shows that the timescale to steady state is significantly extended by ballistic transport, even at low Knudsen numbers where the latter is only important close to the system walls. This effect is captured for $\hbox{\it Kn}\,{ by the slip model which predicts the equivalent effective domain size increase (slip length).

Charge carrier dynamics in bulk poly(3-hexylthiophene) as a function of temperature

The charge carrier mobility in bulk samples of regioregular poly-3-hexylthiophene is determined from -100 to +140°C with the pulse-radiolysis time-resolved microwave conductivity technique. The lower limit to the mobility obtained increases only slightly with temperature in this range from 0.003 cm 2 /Vs to 0.01 cm 2 /Vs. However, the decay kinetics of the charge carriers is strongly dependent on temperature. This is attributed to changes in the effective domain size in which the charge carriers are able to move.

Mechanism for the magnetoresistance of Pure Bulk Ferromagnets and Composite Thin Film Structures

ABSTRACTA unified explanation is given of the long-standing question of the origin of the low-field magnetoresistance, MR, behavior in pure ferromagnetics and the large magnetoresistance effects seen in magnetic layered and granular structures. It is shown that the main contributions to these effects are due to the scattering that occurs at the magnetic boundaries between non-aligned magnetic regions. This scattering occurs because the predominant conduction electrons in 3d ferromagnetics are the highly polarized itinerant d electrons. As a result of this polarization the Majority-band d electrons are strongly reflected at an antiparallel magnetic boundary due to a lack of available states for occupancy. The traversing electrons are further scattered as they cross the boundary due to a discontinuity in the potential caused by the interchange of their kinetic and exchange energies at the boundary. Expressions for the magnetoresistance due to these scattering mechanisms are derived and shown to describe very well the wide variety of magnetoresistance values and other features found in the literature for both pure Fe and nano-structures of Fe or Co with non-Magnetic Materials. The MR Magnitude is seen to vary inversely with the domain size. Thus the domain size and sample purity are seen to be the main factors that determine the magnitude of the MR effect in pure ferromagnets. The large MR values seen in layered and granular magnetic structures arise from the small effective domain size attainable in these structures. This is achieved by introducing a non-Magnetic Material into these structures which allows the effective domain size to be decreased from the micron range of the pure ferromagnetic elements into the nanometer range.

A study of stacking faults in deformed austenitic stainless steel by X-ray diffraction

Making use of the data obtained already in our laboratory on elongated, quenched samples of austenitic steel lCrl8Ni9, such as the effective domain size Deff, the average dislocation density-ρ, the average dislocation configuration parameter, -M, the range of strain field -Re, the elastic energy density 〈E/V〉,etc., some exact and clear expressions for the relation of intrinsic stack-ing fault (SF) density α′, extrinsic SF density α″, twin fault density β, SF energy γ, true particle size D0, minimum value of the fault width Tmin, and maximum particle size Dmax are given.

Quantitative Study of Strain, Domain Size and Crystallinity in Magnesia Powders by X-ray Line Profile Analysis

X-ray line profile analysis of magnesia powders derived from three parent compounds—hydroxide, carbonate and oxalate—at various calcination temperatures ranging between 400° and 1200°C was carried out using Warren and Averbach's method to evaluate strain and effective domain size. The percentage degree of crystallinity was calculated using crystallinity index method of Wakelin, Virgin and Crystal. It has been found that residual microstrains are absent in these magnesia powders and the line broadening was only due to the small crystallite size. The parent compound influences the changes occurring during calcination and ultimately the powder properties such as degree of crystallinity, the crystallite size and the particle size etc which in turn influence the sinterability of these powders.

An x‐ray diffraction profile analysis in hexagonal cadmium films vacuum‐evaporated from normal and oblique vapor incidence

Microstructural investigations on hexagonal cadmium films, considering a number of H − K=3N (namely, 00.2, 10.0, 11.0, 00.4, N1.2, and 20.0) and H − K = 3N±1 (namely, 10.1, 10.2, 10.3, 20.1, 10.4, 20.2 and 20.3) x‐ray diffraction profiles recorded in a counter diffractometer, were done by detailed Fourier analysis of lineshape and also integral breadth measurements. The films, in the thickness range of ∠200–3300 A, were vapor deposited for both normal and oblique (∠46° to the substrate normal) vapor incidences. For both the source positions Fourier lineshape analysis of the fault‐unaffected (H − K=3N) reflections indicate that the effects from the average domain size and rms strain are relatively large in the thin range ≲600 A, and these decrease at higher thickness ∠3300 A. The size and strain values along [00.2] are found to be close to the average ones depicting the near isotropy in these parameters. As regards the effective domain size values evaluated for fault‐affected (H − K=3N±1) reflections, it h...

An X-Ray Investigation of Fatigue Behavior of Cold Worked Aluminum

AbstractDouble bending fatigue tests were performed on cold worked 1100 aluminum, with a maximum bending stress varying from 100 to 50% of the yield stress. Variation of residual macrostress from the cold worked state during the fatigue tests was measured by the photographic x-ray diffraction method. A general decrease of this macrostress was observed. Line profile analysis was used to study the change in the mean effective domain size and microstrain. A rate dependence of the increase in the effective domain size with respect to the maximum bending stress was observed. Microhardness and tensile tests were also made on the specimens during the fatigue testing and the results are correlated with the x-ray Parameters.

X-ray study of annealing in plastically deformed Ag−Sn alloys

The stacking fault probability, root-mean-square strain, and effective domain size are determined for pure silver and three Ag−Sn alloys using X-ray diffraction data. Both isochronal and isothermal annealing experiments were conducted to determine the nature of the recovery of plastic deformation in the filed powder specimens. An abrupt recovery of the above quantities was observed during isochronal annealing at temperatures that increased with solute concentration. Three recovery stages were observed in Ag-9 at. pct Sn annealed at 165°C for varying times. The principal stage is probably associated with recrystallization since both the stacking fault probability and rms strain recover together. An activation energy of 25 kcal per mol is determined for this stage.

Fe-Ni合金のマルテンサイトの格子欠陥

The effect of the Ms temperature on the lattice defects in martensite was studied by X-ray diffraction. Fe-Ni alloys with 10, 15 and 20 wt%Ni were chosen as the specimens having different Ms temperatures. The profiles of the Debye-Scherrer lines of martensites in three alloys, were taken with an X-ray diffractometer. Correction was made for the instrumental broadening, and the Fourier analysis was performed.It is concluded from the results that: (1) The integral width of the martensite line decreases with increasing the Ms temperature. (2) The index-dependences of the broadening are the same for all the specimens examined. (3) The internal strain of the 110 direction in the martensite decreases with increase of the Ms temperature, whereas the effective domain size of that direction does not change so much.The above results show that, even at a Ms temperature much higher than room temperature, considerable amounts of the lattice defect, including the stacking mistakes, are introduced during the martensitic transformation.