Hydroxyapatite (HAp) coatings were applied using sol-gel method. Phosphor pentoxide and calcium nitrate were used as phosphorous and calcium precursors, respectively. Zinc nitrate and silver nitrate were used as substitute of calcium in HAp structure. As a base concentration, 1.5 wt %Ag and 2.5 wt %Zn were used. The weight percent of Ag was increased at 0.3 wt% and Zn content was scaled down at 0.5 wt%. Phase analysis and chemical bonds of synthesized materials were studied by XRD and FTIR. Antibacterial activity of Ag- and Zn-doped samples against methicilin-resistant Staphylococcus aureus (MRSA) were assessed by the plate-counting method. The XRD and FTIR results proved formation of HAp compound. Colony counting showed that silver and zinc ions prevent proliferation and growth of MRSA. Interestingly, co-presence of metal ions improves the antibacterial effectiveness of the coatings and the combined effect was greater than sum of the individual effects when each was administered alone. Overall, synergism between antibacterial activities of Zn(2+) and Ag(+) ions against MRSA can be suggested. Thus, cell toxicity decreases and biocompatibility increases without any decrement in antibacterial activity.

No abstract

Preparation of nanocrystalline ZrB 2 -based powder by aluminothermic and magnesiothermic reductions in M/ZrO 2 /B 2 O 3 (M = Al or Mg) systems was investigated.In this research, high energy ball milling was employed to persuade necessary conditions for the occurrence of a mechanically induced self-sustaining reaction (MSR).The happening of MSR reactions was recorded by a noticeable pressure rise in the system during milling. Ignition times for ZrB 2 formation by aluminothermic and magnesiothermic reductions were found to be 13 and 6 minutes, respectively. Zirconium diboride formation mechanism in both systems was explained through the analysis of the relevant sub-reactions.

The aim of this work was to study the influence of the different synthesis processes on microstructural and morphological characteristics and distribution of hydroxyapatite-bioactive glass (HAp-BG) composite nanopowders obtained by sol-gel method. HAp-BG composite nanopowders with 20 wt% bioactive glass were prepared using a sol-gel method via four routes: (I) mixing the prepared HAp solution with BG solution before aging time; (II) mixing the prepared BG solution with the prepared HAp gel after gelation; (III) mixing the calcined BG nanopowders with the prepared HAp solution; and (IV) mixing the two prepared calcined nanopowders by mechanochemical activation. The prepared nanopowders were evaluated and studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), Fourier transform infrared (FTIR), transmission electron diffraction (TEM) and Brunauer-Emmet-Teller (BET) method to investigate the phase structure, microstructure and morphology, functional groups, and the size and distribution of nanopowders. Results indicated that morphology, crystallinity, crystallite size and specific surface area (SSA) of the powders are highly correspondent to the process and type of synthesis method. These findings suggest that the modified sol-gel derived HAp-BG composite nanopowders are expected to efficiently provide a possibility to produce a good candidate to use for fabrication of a bulk nanostructured HAp-BG composite for bone tissue engineering.

Aluminium and magnesium were used in the M/ZrSiO 4 /B 2 O 3 /C (M=Al, Mg) system to induce a mechanically induced self-sustaining reaction (MSR). Aluminium was not able to reduce the system to the desired products, and the system became amorphous after 10 hours milling. However, Nanocomposite powder of ZrB 2 -SiC-ZrC was in-situ synthesized by the magnesiothermic reduction with an ignition time of approximately 6 minutes. The mechanism for the formation of the product in this system was determined by studying the relevant sub-reactions.

No abstract

Nanocrystalline zirconium diboride (ZrB 2 ) powder was produced by magnesiothermic reduction in the Mg/ZrO 2 /B 2 O 3 system. In this study, high-energy ball milling was used to generate the essential conditions to induce a mechanically induced self-sustaining reaction (MSR). The ignition time for ZrB 2 formation was found to be approximately 6 minutes. The mechanism for the formation of ZrB 2 in this system was determined by studying the relevant sub-reactions, the effect of stoichiometry, and the thermal behavior of the system.

No abstract