The generalized Cauchy relation as an universal property of the amorphous state

2005 ◽  
Vol 129 ◽  
pp. 45-49 ◽  
Author(s):  
J. K. Krüger ◽  
U. Müller ◽  
R. Bactavatchalou ◽  
J. Mainka ◽  
Ch. Gilow ◽  
...  
Keyword(s):  
Amorphous State ◽  
Universal Property ◽  
Cauchy Relation

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

Structures and crystallization of vacuum-deposited amorphous Se and Sb films

1990 ◽  
Vol 48 (4) ◽  
pp. 140-141
Author(s):  
Makoto Shiojiri ◽  
Toshiyuki Isshiki ◽  
Tetsuya Fudaba ◽  
Yoshihiro Hirota
Keyword(s):  
Monte Carlo ◽  
Electron Microscope ◽  
Monte Carlo Method ◽  
Computer Program ◽  
Radial Distribution ◽  
Film Formation ◽  
Amorphous State ◽  
Two Dimensional ◽  
Amorphous Films ◽  
Binding Condition

In hexagonal Se crystal each atom is covalently bound to two others to form an endless spiral chain, and in Sb crystal each atom to three others to form an extended puckered sheet. Such chains and sheets may be regarded as one- and two- dimensional molecules, respectively. In this paper we investigate the structures in amorphous state of these elements and the crystallization.HRTEM and ED images of vacuum-deposited amorphous Se and Sb films were taken with a JEM-200CX electron microscope (Cs=1.2 mm). The structure models of amorphous films were constructed on a computer by Monte Carlo method. Generated atoms were subsequently deposited on a space of 2 nm×2 nm as they fulfiled the binding condition, to form a film 5 nm thick (Fig. 1a-1c). An improvement on a previous computer program has been made as to realize the actual film formation. Radial distribution fuction (RDF) curves, ED intensities and HRTEM images for the constructed structure models were calculated, and compared with the observed ones.

Microstructure of YBa2Cu3O7-x thin films deposited by dc sputtering

1989 ◽  
Vol 47 ◽  
pp. 172-173
Author(s):  
O. Eibl ◽  
G. Gieres ◽  
H. Behner
Keyword(s):  
Thin Films ◽  
Cross Sections ◽  
Intermediate Layer ◽  
Amorphous State ◽  
Critical Currents ◽  
Dc Sputtering ◽  
State Process ◽  
Diffraction Patterns ◽  
Film Substrate ◽  
Substrate Temperatures

The microstructure of high-Tc YBa2Cu3O7-X thin films deposited by DC-sputtering on SrTiO3 substrates was analysed by TEM. Films were either (i) deposited in the amorphous state at substrate temperatures < 450°C and crystallised by a heat treatment at 900°C (process 1) or (ii) deposited at around 740°C in the crystalline state (process 2). Cross sections were prepared for TEM analyses and are especially useful for studying film substrate interdiffusion (fig.1). Films deposited in process 1 were polycristalline and the grain size was approximately 200 nm. Films were porous and the size of voids was approximately 100 nm. Between the SrTiO3 substrate and the YBa2Cu3Ox film a densly grown crystalline intermediate layer approximately 150 nm thick covered the SrTiO3 substrate. EDX microanalyses showed that the layer consisted of Sr, Ba and Ti, however, did not contain Y and Cu. Crystallites of the layer were carefully tilted in the microscope and diffraction patterns were obtained in five different poles for every crystallite. These patterns were consistent with the phase (Ba1-XSrx)2TiO4. The intermediate layer was most likely formed during the annealing at 900°C. Its formation can be understood as a diffusion of Ba from the amorphously deposited film into the substrate and diffusion of Sr from the substrate into the film. Between the intermediate layer and the surface of the film the film consisted of YBa2Cu3O7-x grains. Films prepared in process 1 had Tc(R=0) close to 90 K, however, critical currents were as low as jc = 104A/cm2 at 77 K.

Formation, Physicochemical Characterization, and Thermodynamic Stability of the Amorphous State of Drugs and Excipients

2016 ◽  
Vol 22 (32) ◽  
pp. 4959-4974 ◽  
Author(s):  
Piera Di Martino ◽  
Federico Magnoni ◽  
Dolores Vargas Peregrina ◽  
Maria Rosa Gigliobianco ◽  
Roberta Censi ◽  
...  
Keyword(s):  
Thermodynamic Stability ◽  
Physicochemical Characterization ◽  
Amorphous State

Enhanced oral bioavailability of Etodolac by liquisolid compact technique: optimisation, in-vitro and in-vivo evaluation

2020 ◽  
Vol 17 ◽  
Author(s):  
Bhumin K. Pathak ◽  
Meenakshi Raghav ◽  
Arti R. Thakkar ◽  
Bhavin A. Vyas ◽  
Pranav J. Shah
Keyword(s):  
Dissolution Rate ◽  
Amorphous State ◽  
Immediate Release ◽  
Angle Of Repose ◽  
Oral Suspension ◽  
Load Factor ◽  
In Vivo Evaluation ◽  
Rate Of Dissolution ◽  
Q 30

Background: Poor dissolution of Etodolac is one of the major challenges in achieving the desired therapeutic effect in oral therapy. Objective: This study aimed to assess the potential of liquisolid compact technique in increasing the rate of dissolution of Etodolac and thus its bioavailability. Methods: Liquisolid compacts were prepared using PEG 400, Avicel PH-200 and Aerosil 200 as non-volatile liquid, carrier and coating material respectively. Optimisation was carried out by applying a 32 full factorial design using Design expert software 11.0.3.0 to examine the effects of independent variables (load factor and carrier: coating ratio) on dependent variables (angle of repose and % cumulative drug release at 30 min [Q 30 min]).Assessment of bioavailability was based on pharmacokinetic study in rabbits and pharmacodynamics evaluation in rats respectively. Results: The formulation M3 was identified as the optimised formulation based on the better flow (lower angle of repose) and a higher rate of dissolution (Q 30 min >95%). The higher dissolution rate could be due to conversion of Etodolac into an amorphous molecularly dispersed state, availability of larger surface area, enhancement of aqueous solubility and enhanced wetting of drug particles. Studies with DSC, XRD, and SEM verified the transformation of Etodolac from crystalline to amorphous state, a key factor responsible for improving the dissolution rate. Pharmacokinetic profile of M3 was prominent, demonstrating higher absorption of Etodolac in comparison of oral suspension and immediate-release conventional tablets in rabbits. Liquisolid formulation exhibited 27% increment in paw thickness as compared to 57% and 46% increments for oral suspension and immediate-release conventional tablets respectively, after 7 hrs in carrageenan-induced paw model in rats. Conclusion: The results indicated liquisolid compact technique to be a promising strategy to enhance the bioavailability of Etodolac.

Exploiting Kinetic Solubility Differences for Low Level Detection of Crystallinity in Amorphous Drug Formulations

2020 ◽  
Vol 16 (5) ◽  
pp. 529-538
Author(s):  
Gregory K. Webster ◽  
Cynthia A. Pommerening ◽  
Whitney W. Harman ◽  
Mathew A. Gragg ◽  
Jian-Hwa Han ◽  
...  
Keyword(s):  
Dosage Form ◽  
Amorphous State ◽  
Analytical Techniques ◽  
Drug Level ◽  
Drug Substance ◽  
Phase Iii ◽  
Drug Formulations ◽  
Total Recovery ◽  
Amorphous Drug ◽  
Kinetic Solubility

Background: Enabling formulations have been implemented by the pharmaceutical industry as an effective tool for keeping Active Pharmaceutical Ingredient (API) in an amorphous state. Upon dosing in the amorphous state, many drugs which fail to demonstrate bioactivity due to the limited solubility and bioavailability of their crystalline form become bioavailable. Purpose: The analytical techniques use today for crystallinity detection are challenged by the sensitivity and robustness needed to achieve a 5% quantitation limit in low dose drug products. Our laboratory has developed a novel procedure capable of meeting this sensitivity and selectivity requirement. This is achieved by exploiting the differences in kinetic solubility of the formulated amorphous and free crystalline forms of API currently being used in dosage form platforms. Methods: Representative amorphous drug formulations were prepared and spiked with varying levels of crystalline drug substances to evaluate the selectivity and recovery of the crystalline drug substance from the product formulation. Kinetic solubility testing using a (i) Particle wetting phase, (ii) Particle suspending/erosion phase, (iii) Sampling time point and (iv) A total recovery determination for the drug substance. Results: The method selectively and quantitatively distinguishes crystalline drug substance from amorphous drug substance for samples spiked from 2.5% to 10% of the nominal label concentration of the API in the dosage form matrix. Conclusion: The kinetic solubility approach reported here achieves sensitive crystallinity quantitation for low drug level amorphous drug formulations at levels not yet achieved by complimentary analytical techniques.

scholarly journals Comparative Physical Study of Three Pharmaceutically Active Benzodiazepine Derivatives: Crystalline versus Amorphous State and Crystallization Tendency

2021 ◽  
Vol 18 (4) ◽  
pp. 1819-1832
Author(s):  
Sofia Valenti ◽  
Maria Barrio ◽  
Philippe Negrier ◽  
Michela Romanini ◽  
Roberto Macovez ◽  
...  
Keyword(s):  
Amorphous State ◽  
Physical Study ◽  
Benzodiazepine Derivatives ◽  
Crystallization Tendency

scholarly journals Electrospun Janus Beads-On-A-String Structures for Different Types of Controlled Release Profiles of Double Drugs

Biomolecules ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 635
Author(s):  
Ding Li ◽  
Menglong Wang ◽  
Wen-Liang Song ◽  
Deng-Guang Yu ◽  
Sim Wan Annie Bligh
Keyword(s):  
Controlled Release ◽  
Combined Therapy ◽  
Diffusion Mechanism ◽  
Amorphous State ◽  
Electrospinning Process ◽  
Fickian Diffusion ◽  
In Vitro Dissolution ◽  
Sem Images ◽  
Release Profiles

A side-by-side electrospinning process characterized by a home-made eccentric spinneret was established to produce the Janus beads-on-a-string products. In this study, ketoprofen (KET) and methylene blue (MB) were used as model drugs, which loaded in Janus beads-on-a-string products, in which polyvinylpyrrolidone K90 (PVP K90) and ethyl cellulose (EC) were exploited as the polymer matrices. From SEM images, distinct nanofibers and microparticles in the Janus beads-on-a-string structures could be observed clearly. X-ray diffraction demonstrated that all crystalline drugs loaded in Janus beads-on-a-string products were transferred into the amorphous state. ATR-FTIR revealed that the components of prepared Janus nanostructures were compatibility. In vitro dissolution tests showed that Janus beads-on-a-string products could provide typical double drugs controlled-release profiles, which provided a faster immediate release of MB and a slower sustained release of KET than the electrospun Janus nanofibers. Drug releases from the Janus beads-on-a-string products were controlled through a combination of erosion mechanism (linear MB-PVP sides) and a typical Fickian diffusion mechanism (bead KET-EC sides). This work developed a brand-new approach for the preparation of the Janus beads-on-a-string nanostructures using side-by-side electrospinning, and also provided a fresh idea for double drugs controlled release and the potential combined therapy.

Sign in / Sign up

Export Citation Format

Share Document