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Limited bone bank capacity and risk of infection are some of the main drawbacks of autologous and allogenic grafts, giving rise to synthetic materials for bone tissue implants. The aim of this study was to process and evaluate the mechanical properties and bioactivity of magnesium and strontium doped hydroxyapatite (HAp) scaffolds and investigate the effect of adding zirconium oxide and gelatine coating the scaffolds. Doped nanosized hydroxyapatite powder was synthesized by the hydrothermal method and the scaffolds were made by the foam replica technique and sintered at different temperatures. Yttria-stabilized zirconium oxide (YSZ), synthesized by plasma technology, was used as reinforcement of calcium phosphate scaffolds. Element analysis, phase composition, morphology of the powders and microstructure of the scaffolds were investigated, as well as the compressive strength of the coated and uncoated scaffolds and bioactivity in simulated body fluid (SBF). A microporous structure was achieved with interconnected pores and bioactivity in SBF was confirmed in all cases. The best mechanical properties were given by the coated composite HAp/YSZ scaffolds, withstanding average stresses of over 1019 kPa. These results encourage the idea of use of these scaffolds in bone regenerative therapy and bone tissue engineering.

Limited bone bank capacity and risk of infection are some of the main drawbacks of autologous and allogenic grafts, giving rise to synthetic materials for bone tissue implants. The aim of this study was to process and evaluate the mechanical properties and bioactivity of magnesium and strontium doped hydroxyapatite (HAp) scaffolds and investigate the effect of adding zirconium oxide and gelatine coating the scaffolds. Doped nanosized hydroxyapatite powder was synthesized by the hydrothermal method and the scaffolds were made by the foam replica technique and sintered at different temperatures. Yttria-stabilized zirconium oxide (YSZ), synthesized by plasma technology, was used as reinforcement of calcium phosphate scaffolds. Element analysis, phase composition, morphology of the powders and microstructure of the scaffolds were investigated, as well as the compressive strength of the coated and uncoated scaffolds and bioactivity in simulated body fluid (SBF). A microporous structure was achieved with interconnected pores and bioactivity in SBF was confirmed in all cases. The best mechanical properties were given by the coated composite HAp/YSZ scaffolds, withstanding average stresses of over 1019 kPa. These results encourage the idea of use of these scaffolds in bone regenerative therapy and bone tissue engineering.

Two-step synthesis of Fe2O3 particles, performed by precipitation from iron(III) chloride (FeCl3 center dot 6H(2)O) using ammonium hydroxide in first step and calcination at 400 and 700 degrees C during 4 h, provided Fe2O3 400 degrees C and Fe2O3 700 degrees C photocatalysts, respectively. The electrospinning process was used to prepare iron oxide fibers, named Fe2O3 fiber. Morphological and structural properties of samples were determined by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infra-Red (FT-IR) and BET/BJH analysis. It was found that the alpha-Fe2O3 phase (hematite) has shown the compaction of the structure at 700 degrees C, i.e. lower textural properties. Hematite particles and fibers are used for bisphenol A (BPA) removal by photocatalytic decomposition and the enhanced catalytic performance was found with the use of Fe2O3 400 degrees C particles.

Composites based on HAP and oxidized multi-walled carbon nanotubes (o-MWCNT) and monophase HAP materials were processed by spark plasma sintering. Starting from stoichiometric nano-sized HAP powder, monophase bioceramics were obtained with a density close to the theoretical one and with an average grain size of several hundred nanometers to micron dimensions. It was shown that decreasing the sintering temperature resulted in a decrease of the grain size, which affected an increase in the fracture toughness and hardness. The fracture toughness of an HAP/ o-MWCNT bioceramic processed at 900°C for only 5 min was 30 % higher than that of monophase HAP materials obtained under the same conditions. The addition of MWCNT during SPS processing of HAP materials caused a decrease in the grain size to the nano-dimension, which was one of the reasons for the improved mechanical properties., Kompoziti na bazi hidroksiapatita i oksidovanih višeslojnih karbonskih nanotuba i monofazni hidroksiapatitni materijali dobijeni su spark plazma sinterovanjem. Polazeći od stehiometrijskog nanočestičnog praha hidroksiapatita, dobijeni su monofazni hidroksiapatitni biokeramički materijali sa gustinama bliskim teorijskim vrednostima i prosečnom veličinom zrna od nekoliko stotina nanometara do mikronskih dimenzija. Pokazano je da se sa smanjenjem temperature sinterovanja smanjuje prosečna veličina zrna, što utiče na povećanje žilavosti i tvrdoće materijala. Žilavost kompozitnog biokeramičkog materijala dobijenog na 900°C za svega 5 minuta bila je 30 % veća od žilavosti monofazne hidroksiapatitne biokeramike dobijene pri identičnim parametrima procesiranja. Dodatak oksidovanih karbonskih nanotuba tokom procesiranja spark plazma sinterovanjem, prouzrokovao je smanjenje veličine zrna na nono dimenzije, što je jedan od razloga za poboljšanje mehaničkih svojstava dobijenih materijala.

Alumina based refractories are usually used in metallurgical furnaces and their thermal shock resistance is of great importance. In order to improve thermal shock resistance and mechanical properties of alumina based refractories short ceramic fibers were added to the material. SEM technique was used to compare the microstructure of specimens and the observed images gave the porosity and morphological characteristics of pores in the specimens. Standard compression test was used to determine the modulus of elasticity and compression strength. Results obtained from thermal shock testing and mechanical properties measurements were used to establish regression models that correlated specimen properties to process parameters., Aluminozni vatrostalni materijali najčešće se koriste u pećima u metalurškom inženjerstvu gde je od izuzetne važnosti njihova termostabilnost (otpornost na termošok). U cilju poboljšavanja termostabilnosti i mehaničkih svojstava ove grupe materijala dodavana su kratka keramička vlakna. Karakterizacija mikrostrukture uzoraka određena je skening elektronskom mikroskopijom (SEM), a rezultati su korišćeni radi poređenja poroznosti i morfoloških karakteristika posmatranih uzoraka. Korišćena je standardna laboratorijska metoda određivanja čvrstoće i Jungovog modula elastičnosti. Dobijeni rezultati vezani za termostabilnost i mehanička svojstva poslužila su za formiranje modela koji povezuje svojstva uzorka sa procesnim parametrima.

Alumina based refractories are usually used in metallurgical furnaces and their thermal shock resistance is of great importance. In order to improve thermal shock resistance and mechanical properties of alumina based refractories short ceramic fibers were added to the material. SEM technique was used to compare the microstructure of specimens and the observed images gave the porosity and morphological characteristics of pores in the specimens. Standard compression test was used to determine the modulus of elasticity and compression strength. Results obtained from thermal shock testing and mechanical properties measurements were used to establish regression models that correlated specimen properties to process parameters.