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Effect of sintering parameters using the central composite design method, electronic structure and physical properties of yttria-partially stabilized ZrO2 commercial ceramics

Abstract

In this work, the effect of sintering parameters on electronic structure and physical properties of yttria-partially stabilized ZrO2 (YPSZ) commercial ceramics has been studied using the central composite design (CCD) method. The CCD method allows using empirical modelling with better fitting, by considering the interaction between both factors. Different temperature ranges and sintering times for processing of YPSZ ceramics have been used in order to evaluate the grain growth, hardness and volumetric shrinkage by the CCD method. X-ray diffraction patterns and Rietveld refinement data indicate that non-sintered YPSZ ceramics exhibits two phases related to tetragonal and monoclinic structures, while the sintered YPSZ ceramics exhibits a single phase related to a tetragonal structure. Moreover, the monoclinic structure presents zirconium (Zr) atoms coordinated to seven oxygen (O) atoms, while in the tetragonal structure Zr atoms are coordinated to eight O atoms. Field emission scanning electron microscopy images were employed to monitor the sintering and growth process. In addition, the response surfaces obtained from calculations presented the effect of thermal and kinetic variables on the physical properties such as average grain size, volumetric shrinkage and hardness of YPSZ ceramics.

Open access
Wing and Engine Sizing by Using the Matching Plot Technique

Abstract

The research focuses on the development of an Unmanned Aircraft System. For design purposes, a rather new design method called Systems Engineering Approach is used. Development of the whole system takes much time and effort. This paper contains a concise description of the research on the preliminary development phase of Unmanned Aircraft System air vehicle. The method was first introduced by NASA and later developed by authors of books on aircraft design used for information purposes for design and are mentioned in references. The obtained results are rather realistic and promising for further design process. The method is simple and understandable, and it should be used more often to make it more steady and reliable.

Open access
Parametric optimization of NiFe2O4 nanoparticles synthesized by mechanical alloying

Abstract

In this study, the Taguchi robust design method is used for optimizing ball milling parameters including milling time, rotation speed and ball to powder weight ratio in the planetary ball milling of nanostructured nickel ferrite powder. In fact, the current work deals with NiFe2O4 nanoparticles mechanochemically synthesized from NiO and Fe2O3 powders. The Taguchi robust design technique of system optimization with the L9 orthogonal array is performed to verify the best experimental levels and contribution percentages (% ρ) of each parameter. Particle size measurement using SEM gives the average particle size value in the range of 59–67 nm. X-ray diffraction using Cu Kα radiation is also carried out to identify the formation of NiFe2O4 single phase. The XRD results suggest that NiFe2O4 with a crystallite size of about 12 nm is present in 30 h activated specimens. Furthermore, based on the results of the Taguchi approach the greatest effect on particle size (42.10 %) is found to be due to rotation speed followed by milling time (37.08 %) while ball to powder weight ratio exhibits the least influence.

Open access