Influence Of Annealing Conditions Research Articles

Preparation and subsequent degradation of poly( l-lactic acid) microspheres suitable for aerosolisation: a physico-chemical study

The encapsulation of nedocromil sodium and beclomethasone dipropionate with microspheres of poly( l-lactic acid) has been studied and preparation conditions optimised for entrapment efficiency and microsphere size suitable for inhalation. DSC was used to characterise the microspheres both in terms of drug/polymer interaction and influence of annealing conditions on the T g and degree of crystallinity. The absence of molecular interaction was confirmed by FTIR. Incubation of the microspheres in phosphate buffer at 37°C for 8 days demonstrated no chemical degradation of the polymer as evidenced by IR spectral analysis and estimates of percentage crystallinity. Surface morphology (SEM) and internal structure (TEM) were consistent with a homogeneous degradation pattern.

Giant magnetoresistance and microstructure of Co[sbnd]Cu and FeCo[sbnd]Cu granular films

CoCu and FeCoCu granular films were prepared by DC (or RF) magnetron sputtering and post-deposition annealing. The influence of annealing conditions (temperature, duration) on GMR has been investigated systematically. It is found that the cumulative isothermal annealing at an optimal temperature (moderately high) promotes the precipitation of magnetic grains but limits their excessive growth, and therefore, leads to more homogenous and smaller particles, which is in favor of the GMR improvement. By a combined study of TEM, magnetization and GMR, it is believed that the GMR in these granular films mainly originates from the spin-dependent scattering of conducting electrons in the surfaces between magnetic particles and Cu matrix; especially, the very fine particles with a diameter of a few nm may be most effective for spin-dependent scattering.

Morphology and melting behaviour of poly(ethylene terephthalate) crystallized from the glassy state

AbstractThe influence of annealing conditions on the morphology and melting behaviour of poly(ethylene terephthalate) (PET) was studied. PET annealed under isothermal conditions often shows double melting endotherms depending on the annealing temperature (Ta) and the heating rate of the calorimeter. It was found that the morphological structure and the lower melting peak depend strongly on the annealing temperature, Ta. The increase of the lower melting peak temperature with Ta is due to an increase of the lamellar thickness within the spherulitic structure and to a higher crystallite perfection.

Effect of in situ post-deposition annealing on the formation of ?-In2Se3 thin films grown by elemental evaporation

Stoichiometric polycrystalline In2Se3 thin films have been grown by elemental evaporation on both glass and quartz substrates. The compositions are examined by DAN fluorimetry and X-ray photoelectron spectroscopy (XPS). Structure of the films are characterized by X-ray diffraction. The structure of this α-form of thin films have been determined to be hexagonal. Optimization of the preparative conditions employed for elemental evaporation, helped in preparing monophasic films by the suppression of other phases to a very minor extent. Influence of annealing conditions on the stoichiometry of the films are investigated in detail.

Superconducting Bi1.5Pb0.5Sr2Ca2Cu3Ox ceramics by rapid melt quenching and glass crystallization

A glass of nominal Bi1.5Pb0.5Sr2Ca2Cu3Ox composition, prepared by rapid quenching of the melt, showed a glass transition temperature of 383 °C, crystallization temperature of 446 °C, melting temperature of 855 °C, and bulk density of 5.69 g/cm3 in air. The activation energy for crystallization of the glass has been estimated to be 292 kJ/mol from nonisothermal differential scanning calorimetry. On heating in oxygen, the glass showed a slow and continuous weight gain starting at 530 °C which reached a plateau at 820 °C. The weight gained during heating was retained on cooling to ambient conditions indicating an irreversible oxidation step. The influence of annealing conditions on the formation of various phases in the glass has been investigated. The Bi2Sr2Ca0Cu1O6 phase crystallized out first followed by formation of other phases at higher temperatures. The high-Tc phase, isostructural with Bi2Sr2Ca2Cu3O10, was not detected below 840 °C, but its fraction increased with the annealing time at 840 °C. A sample annealed at 840 °C for 243 h in air and furnace cooled showed the highest Tc(R=0) of 107.2 K and a narrow transition width, ΔTc (10%–90%), of 2 K. The high-Tc phase does not seem to crystallize out directly from the glass but is rather produced at high temperature by reaction between the phases formed at lower temperatures. The kinetics of 110-K phase formation was sluggish. It appears that the presence of lead helps in the formation and/or stabilization of the 110-K phase.

Influence of annealing conditions on structural properties of YBaCu oxide superconductors

AbstractThe chemical composition, the topography, and the defect structure of high‐temperature superconducting YBaCu oxide samples have been studied in dependence on the annealing conditions by scanning electron microscopy, energy dispersive X‐ray analysis, Rutherford backscattering, nuclear reaction analysis, and transmission electron microscopy. The topography is characterized by smooth and rough grains. The chemical composition of samples varies in dependence on the annealing time and temperature. The microstructure of the superconducting material is dominated by a lamellar twin structure.

Magnetic and Magneto-Optic Properties of PtMnSb Thin Films

PtMnSb thin films were prepared by evaporation and the influence of annealing conditions on magnetic and magneto-optic characteristics was investigated. The saturation magnetization of films in which C2-phase was formed was found to be considerably lower than that of film without it. Measurement of the Kerr rotation showed that the formation of C2-phase also had a deleterious effect on the magneto-optic effect.

Helical anisotropy induced by annealing in metglas 2826

The magnetic anistropy induced by constant torsional strain annealing of an amorphous alloy with nominal composition Fe40Ni40P14B6 has been studied. The influence of annealing conditions is reported and discussed. The experimental results indicate that magnetoelastic coupling is the main source of the induced anisotropy, the anelastic and plastic creep contributions being almost negligible.

The influence of annealing conditions on the internal oxidation and magnetic properties of silicon-aluminum bearing electrical steels

Internal oxidation often occurs in electrical steels during decarburization anneals of sufficiently long time and high oxygen potential, resulting in deterioration of magnetic properties. Relationships between subscale thickness, anneal time, and effective oxygen potential of the anneal atmosphere were established for a Si-Al-bearing electrical steel. These kinetics are described by a Rhines diffusion equation modified to accommodate the oxygen potential. Electron microprobe and Auger spectroscopy confirmed the significance of solute element diffusion. Permeability at 1.5 T was found to decrease about 50 units for each micron of subscale thickness, while core loss remained essentially constant. SEM observations of the fine structure were used to estimate that the coercivity of the subscale is sufficiently high that this region is barely magnetized. Thus, the induction of the clean interior metal must be higher than the measured average value, resulting in reduced apparent permeability. Good agreement with observation was obtained.

Conditions of fabrication that control the interfacial microstructure of metal-semiconductor contacts formed from silver metal and (100)-oriented substrates of indium phosphide

An examination was made of the microstructure of silver contacts vacuum evaporated onto (100)-oriented substrates of indium phosphide. In the investigation we utilized the technique of X-ray diffractometry combined with a chemical profiling of the silver contact. The observations made with X-ray diffractometry were correlated with direct observation of the bulk silver and the metal- semiconductor interface by using scanning electron microscopy and element mapping. The influence of annealing conditions and chemical treatment of the substrate on the development of the bulk silver and the interfacial microstructure was also examined.

Fracture surface morphology of some crystalline block copolymers—propylene/ethylene and tetramethyl-p-silphenylenesiloxane dimethylsiloxane

The fracture surface morphology of block copolymers of (i) tetramethyl-p-silphenylenesiloxane/dimethylsiloxane (TMPS/DMS) and (ii) propylene/ethylene (P/E) has been studied. The TMPS/DMS samples had compositions ranging from 90/10 to 30/70 wt% ratios. The ethylene content in the P/E samples ranged from 8 to 13%. A few polyolefin blends were also examined. Materials were fractured at liquid-nitrogen temperatures and studied under ambient conditions by scanning and transmission electron microscopy. X-ray methods and differential scanning calorimetry (DSC) techniques were also used. Copolymers with higher TMPS compositions exhibited a lamellar texture, but at high DMS contents fracture appeared ``glassy''. All TMPS/DMS samples exhibited spherulitic structures. Spherulites were mainly banded and were negatively birefringent. In samples with higher TMPS content, fracture occurred predominately between lamellar bands. The DMS component rejected by the crystalline TMPS hard segments is largely responsible for the observed fracture behavior and for the tensile properties of these copolymers particularly where this phase predominates. In the P/E copolymers both large and small globular particles are observed. Ethylene and propylene form separate crystalline phases. The interfacial characteristics between the large aggregates and the polypropylene matrix are believed to be responsible for impeding fracture porpagation in these materials, as assessed by impact tests. The influence of annealing conditions on the observed morphology has been investigated.

Relationship between structure of drawn polymers and molecular motion

AbstractIn order to study the relationship between structure and molecular motion, drawn polymers are more suitable than isotropic samples since their morphology can be characterized more easily by quantitative methods such as small angle X‐ray scattering (SAXS) and electron microscopy (EM). The effects of changes in morphological structure on molecular motion are demonstrated by comparing the results of the SAXS and EM measurements with the dynamic mechanical behavior of drawn polyethylene. In addition the NMR broad line spectra of these samples were analyzed and the influence of annealing conditions and external stress was investigated.

Annealing conditions and superconducting behaviour of Nb-based A15-type compounds

The ternary system Nb 3Au x Pt 1− x shows a maximum of the transition temperature T c for an intermediate concentration. The influence of annealing conditions on T c was studied.