Wyniki wyszukiwania - BazTech

1

Crystallization kinetics of polyamide 2200 in the modelling of additive manufacturing processes by FE analyses

Bajerski Paweł, Pęcherski Ryszard Bolesław, Chudy Damian, Jarecki Leszek

Engineering Transactions

|

2019

|

Vol. 67, iss. 3

301--309

EN

The thermoplastic polymers present amorphous or semi-crystalline structures which are very important factors in describing volumetric shrinkage. The thermoplastic materials are commonly used for production of daily life products, industrial or as the prototypes. Different techniques of manufacturing polymer structures are considered like: injection molding, extrusion, milling, additive manufacturing (AM). AM is a very fast developing field in the manufacturing and research. Unfortunately, components or prototypes made using the thermoplastic semi-crystalline materials in 3D techniques have quite low mechanical strength compared to the parts made by injection molding processes. It is caused by porosity obtained during the processing, as well as by fraction of crystallinity in the volume of the components. Additionally, the volumetric shrinkage is hard to predict without knowledge of its origin. Therefore, it is necessary to consider crystallization kinetics and the melting of the analysed materials. The investigations presented in this work concern the crystallization and melting model to be implemented in the finite element (FE) analyses. With use of the model, one can predict development of the structure during the real processes and, in the future, to control the warpage of the manufactured components.

2

Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

Ahmadi R., Sadrnezhad S. K., Zangeneh R. N., Oghabian M. A.

Materials Science Poland

|

2016

|

Vol. 34, No. 2

260--265

EN

ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD), ultraviolet (UV) visible absorption and photoluminescence (PL) spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate oxygen adsorption capacity was suggested as a means of PL emission intensity control.

3

The kinetics of nucleation in inhomogeneous media based on the classical Avrami model

Rogowski R. Z.

Materials Science Poland

|

2005

|

Vol. 23, No. 4

961--969

EN

n this paper, the kinetics of nucleation is studied in inhomogeneous media such as a mixture of the nematic liquid crystals p-methoxybenzylidene-p-butylaniline (MBBA) and p-ethoxybenzylidene-p-n-butylaniline (EBBA). Experimental data are analysed in terms of the classical Avrami model for nucleation. The observed non-uniform nucleation is explained within the framework of the Landau model for phase transitions. A modification to the Avrami model is proposed in order to describe the kinetics of nucleation in highly inhomogeneous media.