sintering
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- MeSH
- dýchací soustava patologie MeSH
- hygiena práce MeSH
- krysa rodu rattus MeSH
- zemědělská chemie MeSH
- Check Tag
- krysa rodu rattus MeSH
- Publikační typ
- srovnávací studie MeSH
Due to unique osteogenic properties, tricalcium phosphate (TCP) has gained relevance in the field of bone repair. The development of novel and rapid sintering routes is of particular interest since TCP undergoes to high-temperature phase transitions and is widely employed in osteoconductive coatings on thermally-sensitive metal substrates. In the present work, TCP bioceramics was innovatively obtained by Ultrafast High-temperature Sintering (UHS). Ca-deficient hydroxyapatite nano-powder produced by mechanochemical synthesis of mussel shell-derived calcium carbonate was used to prepare the green samples by uniaxial pressing. These were introduced within a graphite felt which was rapidly heated by an electrical current flow, reaching heating rates exceeding 1200 °C min-1. Dense (> 93%) ceramics were manufactured in less than 3 min using currents between 25 and 30 A. Both β and α-TCP were detected in the sintered components with proportions depending on the applied current. Preliminary tests confirmed that the artifacts do not possess cytotoxic effects and possess mechanical properties similar to conventionally sintered materials. The overall results prove the applicability of UHS to bioceramics paving the way to new rapid processing routes for biomedical components.
There has recently been an increased demand for porous magnesium materials in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such materials. Many works have dealt with the preparation of porous magnesium; however, the effect of sintering conditions on material properties has rarely been investigated. In this work, we investigated porous magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of porous magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of porous magnesium.
- MeSH
- biokompatibilní materiály chemie MeSH
- difuze MeSH
- hořčík chemie MeSH
- hutnictví metody MeSH
- kovové nanočástice chemie ultrastruktura MeSH
- pevnost v tlaku MeSH
- plazmové plyny chemie MeSH
- poréznost MeSH
- povrchové vlastnosti MeSH
- prášky, zásypy, pudry MeSH
- testování materiálů MeSH
- tvrdost MeSH
- vysoká teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The present work studies the microstructure and mechanical performance of tricalcium phosphate (TCP) based cermet toughened by iron particles. A novelty arises by the employment of spark plasma sintering for fabrication of the cermet. Results showed partial transformation of initial alpha TCP matrix to beta phase and the absence of oxidation of iron particles, as well as a lack of chemical reaction between TCP and iron components during sintering. The values of compressive and tensile strength of TCP/Fe cermet were 3.2 and 2.5 times, respectively, greater than those of monolithic TCP. Fracture analysis revealed the simultaneous action of crack-bridging and crack-deflection microstructural toughening mechanisms under compression. In contrast, under tension the reinforcing mechanism was only crack-bridging, being the reason for smaller increment of strength. Elastic properties of the cermet better matched values reported for human cortical bone. Thereby the new TCP/Fe cermet has potential for eventual use as a material for bone fractures fixation under load-bearing conditions.
The structure degradation and strength changes of calcium phosphate scaffolds after long-term exposure to an acidic environment simulating the osteoclastic activity were determined and compared. Sintered calcium phosphate scaffolds with different phase structures were prepared with a similar cellular pore structure and an open porosity of over 80%. Due to microstructural features the biphasic calcium phosphate (BCP) scaffolds had a higher compressive strength of 1.7 MPa compared with the hydroxyapatite (HA) and β-tricalcium phosphate (TCP) scaffolds, which exhibited a similar strength of 1.2 MPa. After exposure to an acidic buffer solution of pH = 5.5, the strength of the HA scaffolds did not change over 14 days. On the other hand, the strength of the TCP scaffolds decreased steeply in the first 2 days and reached a negligible value of 0.09 MPa after 14 days. The strength of the BCP scaffolds showed a steady decrease with a reasonable value of 0.5 MPa after 14 days. The mass loss, phase composition and microstructural changes of the scaffolds during degradation in the acidic environment were investigated and a mechanism of scaffold degradation was proposed. The BCP scaffold showed the best cell response in the in vitro tests. The BCP scaffold structure with the highly soluble phase (α-TCP) embedded in a less soluble matrix (β-TCP/HA) exhibited a controllable degradation with a suitable strength stability and with beneficial biological behavior it represented the preferred calcium phosphate structure for a resorbable bone scaffold.
- MeSH
- buněčná adheze MeSH
- DNA metabolismus MeSH
- fosforečnany vápenaté chemie MeSH
- keramika chemie MeSH
- koncentrace vodíkových iontů MeSH
- kosti a kostní tkáň fyziologie MeSH
- lidé MeSH
- mezenchymální kmenové buňky cytologie MeSH
- pevnost v tlaku MeSH
- poréznost MeSH
- tkáňové podpůrné struktury chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Shrinkage of ceramic objects produced by Fused Depositon Ceramics 3D printing technology was studied as model procedure for production of biocompatible scaffolds. The formulation of ceramic composite filament tested was based on components such as aluminium and silicium oxides and thermoplastic polymer. The resulting ceramic material after sintering is approaching the chemical composition of the mullite ceramics, which has several interesting material properties. The shrinkage of the produced testing objects was studied as function of the particle content in starting composite and sintering temperature. Observed shrinkage of the ceramic bodies produced was on the level of 17% for 65 weight % and the 23% for 40 weight % of inorganic filler content at temperature 1200 °C, respectively, with well maintained shape. The tested ceramic scaffolds were produced using slice thickness of 0.50 mm and fill gap of 0.58 mm, with regular rectilinear infill pores generated by Slic3r.
Like all production areas the production of dental replacements, either prosthetic or aesthetic, has recently undergone great advancement due to computer-aided design of dental parts and their computer aided manufacturing. CNC milling, which belongs to the group of subtractive production methods, is very well established in dental production. For the last several years, methods of additive manufacturing, such as Selective Laser Melting (SLM), Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS), have gone mainstream. In general, both additive and subtractive methods have their technological pros and cons; therefore, the aim of this paper is to determine how accurate in terms of tolerance of production of ± 50 μm both technologies are and afterwards to determine which of the technologies is more accurate. Given that nowadays the most commonly used material in the dental area is cobaltchromium (Co-Cr) alloy, this alloy was chosen for the experiment. Thirty Co-Cr dental crowns were manufactured for analysis according to the referential CAD model, 15 by CNC milling and 15 by SLM. The crowns were subsequently scanned using a dental 3D scanner, and their inner areas were extracted and compared to the nominal CAD model. The percentage agreement of production is on the level of approximately 94% with both devices, and the average value of agreement as well as the standard deviation and range variation are better with additive production.
A hybrid organo-silica sol was used as a binder for reinforcing of commercial titanium dioxide nanoparticles (Evonic P25) deposited on glass substrates. The organo-silica binder was prepared by the sol-gel process and mixtures of titania nanoparticles with the binder in various ratios were deposited by materials printing technique. Patterns with both positive and negative features down to 100 µm size and variable thickness were reliably printed by Fujifilm Dimatix inkjet printer. All prepared films well adhered onto substrates, however further post-printing treatment proved to be necessary in order to improve their reactivity. The influence of UV radiation as well as of thermal sintering on the final electrochemical and photocatalytic properties was investigated. A mixture containing 63 wt % of titania delivered a balanced compromise of mechanical stability, generated photocurrent density and photocatalytic activity. Although the heat treated samples yielded generally higher photocurrent, higher photocatalytic activity towards model aqueous pollutant was observed in the case of UV cured samples because of their superhydrophilic properties. While heat sintering remains the superior processing method for inorganic substrates, UV-curing provides a sound treatment option for heat sensitive ones.
- MeSH
- nanočástice chemie MeSH
- oxid křemičitý chemie MeSH
- titan chemie MeSH
- ultrafialové záření MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
