Background: Hydroxyapatite is the main mineral component of bones. Due to its high biocompatibility, it is widely used in the treatment of bone lesions or production of dental or orthopedic implants. ...Biological behavior of hydroxyapatite depends on many factors such as chemical composition and phase, microstructure, size, and porosity volume. On the other hand, other hydroxyapatite nanocrystals have received increased attention due to their improved bio-efficiency including connectivity and formation of new bones on their surface. Methods: In this research, nanocrystalline hydroxyapatite powder was synthesized by thermal synthesis or mechanochemical methods. The structures of the two types were then compared. Findings: Products obtained from both processes was single-phase hydroxyapatite. No other stable phases were detected. Degrees of crystalline of the products of thermal synthesis and mechanochemical methods were 92.86% and 6.72%, respectively. Most particles had quasi-spherical morphology. In addition, particle sizes of products of heating and mechanochemical methods were 85 and 58 nm, respectively. Conclusion: Phase analysis showed that the product of both processes was single-phase hydroxyapatite. On the other hand, all characteristic peaks were present in the product and it had high purity.
The kinetics of molybdenite roasting was studied by non-isothermal TGA–DTA with heating rate 10
°C
min
−1. Mechanical activation of molybdenite was accomplished via milling in a planetary mill under ...air atmosphere. Mechanical activation decreased the ignition temperature of reaction from 470 to 180
°C after 36
h of milling. The model-fitting kinetic approach has been applied to TGA data. The reaction mechanism for non-activated molybdenite was determined to be chemically controlled with
E
=
34.25
kcal
mol
−1 and
A
=
2
×
10
8
s
−1. In the activated molybdenite the reaction mechanism changed to diffusion control with
E
=
60.55
kcal
mol
−1 and
A
=
6
×
10
19
s
−1.
Nickel-based nanocomposite coatings were prepared from a Watts-type electrolyte containing reinforcement’s particles (silicon carbide and graphite) to deposit onto the steel St-37 substrate. The ...electrochemical plating of the coatings in absence and presence of surfactants and reinforcements particles was carried out to optimize high quality coatings with appropriate mechanical and morphological features. The surfactants such as cetyltrimethylammonium bromide (CTAB), sodyumdodecyl sulfate (SDS), and saccharine affected electrodeposition plating and subsequently changed mechanical characteristics. Based on XRD results, the dominant phases in the absence of surfactants were nickel oxide (NiO), nickel, and silicon carbide (SiC), while the main phases in presence of surfactants were nickel (Ni) and SiC. The hardness of the resultant coatings was found to be from 332 to 593 (Hv) depending on the bath parameter and the reinforcements weight percentage (wt%) in the Ni matrix. Microscopic observations illustrated a cluster-like structure which consisted of some fine sphere particulates with average particle size of 65–150 nm. According to elemental mapping spectra, a homogenous distribution of nickel, silicon, and carbon particles appeared into the nickel matrix coating. Finally, the experimental outcomes demonstrated that the surfactants have significant influence on the composition of coatings, surface morphology, and mechanical properties.
Among various biocompatible materials, hydroxyapatite (HA) is widely used in medical applications. Hydroxyapatite can be used as temporary substitute material for the human bone. Despite of the risk ...of contamination during milling, the mechanochemical method shows higher reproducibility and low processing cost. In this investigation, the mechanochemical method has been carried out to produce nanocrystalline powders of hydroxyapatite using two experimental procedures (HA1: CaHPO4 + Ca (OH) 2; HA2: CaCO3 + CaHPO4) in polymeric and metallic vials at different milling time. The Effects of milling time, milling media and also chemical composition of initial materials on the crystallinity and morphological properties of obtained materials using X-ray diffraction (XRD) and transmission electron microscopy (TEM) were studied. Appropriate equation and graphs for determining crystallinity degree were used. The obtained results show that the crystallites sizes are within the nanometer range and also indicated that nanocrystalline hydroxyapatite with spherical morphology and high crystallinity degree can be produced much better in polymeric vials; therefore using polymeric vials with high wear resistance can have better performance during the mechanochemical process for the production of high quality nanocrystalline hydroxyapatite. Further work is needed to expand the idea for mass production.
Hydroxyapatite (HAp) is an important bioactive ceramic that possessing beneficial biocompatibility and osteoconductivity resulting in bonding to human bone tissues. The dry mechanochemical process is ...widely used to prepare nanometer HAp. However, little research has been carried out concerning the correlation between adding alumina and the structural changes during the mechanochemical process. In this research, special attention was paid to the effect of alumina additive on the crystallite size and lattice strain of nanocrystalline HAp. Characterization was accomplished by using powder X-ray diffraction (XRD). The obtained data demonstrated that the diffraction lines corresponding to the HAp phase became broad and weak with increasing alumina additive. In fact, the nanocrystalline HAp with high crystallinity degree can be synthesized in the proper amounts of alumina additive via mechanochemical method. Furthermore, an increase of alumina additive led to increase in lattice strain and decrease in size of the powder grain.
The mechanically induced self-sustaining reactions (MSRs) in TiO
2
-B
2
O
3
-Mg-X (Al, C) quaternary system to synthesize various nanocomposite powders were investigated. Results showed that the ...phase compositions, structural features and morphological characteristics of the synthesized powders were notably influenced by the type and weight fraction of the reductants. Based on the morphological assessment, the mechanosynthesized nanocomposites had a unique flower-like cluster structure composed of loosely arranged nanosheets with a side length of about 400 nm and a thickness of about 25 nm.
ABSTRACT Background and Objective: Biofilms are community of bacteria that attach to inanimate surfaces or living tissues via production of extracellular polymers and exopolysaccharide ...matrix. Microbial biofilms on various surfaces of the hospital environment are considered as a reservoir of infection spread. The present study aimed to evaluate the disinfecting effect of benzalkonium chloride on some bacterial isolates causing nosocomial infections. Methods: First, 13 isolates from four bacteria including Pseudomonas aeruginosa, Staphylococcus aureus, Acinetobacter and Enterobacter were obtained from Microbiology Laboratory of Al-Zahra Hospital in Isfahan, Iran. The samples were transferred to Microbiology Laboratory of Faculty of Veterinary Medicine of Shahrekord University for testing. Evaluation of biofilm formation and determination of minimum inhibitory concentration (MIC) of the disinfectant and effect of the disinfectant on planktonic growth and biofilm formation were performed. Results: All bacterial isolates (52 cases) produced biofilm. Mean MIC of benzalkonium chloride for P. aeruginosa, S. aureus, Enterobacter and Acinetobacter was 0.14, 0.2, 0.18, 0.17 g/ml, respectively. Planktonic growth of all four bacteria was inhibited at concentrations of 2MIC, MIC and 1/2MIC. Biofilm was not produced in MIC and 2MIC concentrations, and biofilm formation capability increased by reducing the concentration of benzalkonium chloride. Conclusion: The results show that the use of appropriate concentration of benzalkonium chloride can prevent the growth of different bacterial species, but sub-MIC dose of this disinfectant may stimulate biofilm formation. Keywords: Biofilm, Benzalkonium Chloride, Pseudomonas Aeruginosa, Staphylococcus Aureus, Enterobacter, Acinetobacter.
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