Browsing by Subject "crystallinity"

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Access status: Restricted ,
Badanie właściwości termicznych kompozytów poliacetalowych zawierających funkcjonalizowany hydroksyapatyt
(Data obrony: 2018-01-22) Janus, Weronika
Wydział Elektrotechniki, Automatyki, Informatyki i Inżynierii Biomedycznej
Access status: Open Access ,
Optimizing Piezoelectric Coefficient in PVDF Fibers: Key Strategies for Energy Harvesting and Smart Textiles
(2023) Sukumaran, Sunija; Szewczyk, Piotr K.; Knapczyk-Korczak, Joanna; Stachewicz, Urszula
Wydział Inżynierii Metali i Informatyki Przemysłowej
With the advancement in smart electronic devices and self-powered devices, the demand for piezoelectric polymers found potential research interest. Among these, electrospun polyvinylidene fluoride (PVDF) fibers have gained attention for energy harvesting due to their flexibility and higher piezoelectric coefficient. We compare various methods to enhance PVDF's piezoelectric properties, including different solvents (DMAc, DMF), conductive filler (rGO), and annealing as post-treatment. Our results indicate that PVDF/rGO fibers in DMAc solvent exhibit the highest β phase fraction and crystallinity. Moreover, for the first time, we present the piezoelectric properties of PVDF/rGO electrospun single fiber using high voltage switching spectroscopy piezoelectric force microscopy (HVSS-PFM). The highest piezoelectric coefficient (d33) was measured for PVDF/DMAc-rGO composite fibers. Notably, PVDF/rGO in DMAc solvent significantly improves the piezoelectric coefficient, leading to a remarkable fourfold increase in power density compared to pure PVDF, making it a promising material for energy harvesting applications.
Access status: Open Access ,
Structural and morphological evaluations of natural hydroxyapatite from calcined animal bones for biomedical applications
(AGH University of Science and Technology Press, 2022) Ojo, Olusola Emmanuel; Sekunowo, Olatunde Israel; Gbenebor, Oluwashina Philips; Adeosun, Samson Oluropo; Ilomuanya, Margaret Okonawan
Several biomedical materials have been employed as drug delivery systems, but natural Hydroxyapatite (HAP) has been proven to be exceptionally better than other materials owing to its excellent bioactivity and biocompatibility properties. In this study, natural HAP was obtained from bovine and caprine bones and comparatively analysed for biomedical applications. The bones were hydrothermally treated, calcined in the temperature range of 700-1100°C, held for 2 hours in an electric furnace to remove the organic contents, milled, sifted with 150 μm mesh sieve and then characterized. It was revealed by Energy Dispersive X-Ray Spectroscopy (EDS) that the bovine and caprine bone samples calcined at 1000°C had calcium/phosphorus ratio (Ca/P) of 1.66 closest to the standard of 1.67. The bovine HAP showed the best crystallinity (86.23%) at 1000°C while caprine HAP had its highest (87.25%) at 1100°C. Fourier Transform Infrared Spectroscopy (FTIR) results revealed that the calcination temperature must be greater than 700°C to isolate high quality HAP. The Scanning Electron Microscopy (SEM) showed that the samples calcined at 800°C had the largest average particle size (85.34 μm) while porosity increases with calcination temperature in both samples. The HAP obtained at a calcination temperature of 1000°C proved to have the best quality for biomedical applications.
Access status: Open Access ,
The influence of silicate content on thermal stability of 2-line ferrihydrite and properties of its transformation products
(Wydawnictwa AGH, 2014) Pieczara, Gabriela; Rzepa, Grzegorz; Gaweł, Adam
Naturally occurring ferrihydrite ($Fe_{5}HO_{8} \cdot 4H_{2}O$) is a poorly ordered iron (oxyhydr)oxide mineral, with non-stoichiometric composition and not fully understood structure. Because of its unique chemical and physical properties, such as low crystallinity, high surface area and surface reactivity, ferrihydrite plays significant role in e.g. inorganic weathering processes, biochemical cycling of iron and as a sorbent in various near-surface environments.