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Electrophoretic deposition of biocomposite ceramic coatings of hydroxyapatite and chitosan with silver and gentamicin on titanium for medical applications
No full textBiocomposite ceramic coatings hydroxyapatite (HAP), silver/hydroxyapatite (Ag/HAP) and
silver/hydroxyapatite/graphene (Ag/HAP/Gr) are obtained on titanium by electrophoretic
deposition (EPD). The goal of this research was to develop multifunctional composite
coatings as a suitable strategy to improve the surface properties of metallic implants.
The deposition was performed on titanium electrodes with specific geometry suitable for
implantation in the frontal bone of rabbits for in vivo experiments. The effect of deposition
parameters on deposited mass was investigated by varying different values of constant
voltage for various deposition time. Uniform and compact HAP coatings were successfully
deposited at applied voltage of 30 V for 45 s, whereas Ag/HAP and Ag/HAP/Gr coatings
with satisfying adhesion and coverage were deposited at applied voltage of 60 V for 1 min.
Bearing in mind certain toxic effects of the nanoparticle silver, the deposition of the coating
of hydroxyapatite/chitosan/graphene (HAP/CS/Gr) of the same composition with the
addition of the antibiotic gentamicin was performed, in order to replace the silver
nanoparticles. The antimicrobial activity of the coating HAP/CS/Gr without and with
gentamicin against Staphylococcus aureus and Escherichia coli was examined by agar
diffusion test. Moreover, disc diffusion test showed improved bactericidal effect of
gentamicin-loaded composite coatings against Staphylococcus aureus and Escherichia coli
compared to control non-gentamicin-loaded coatings
The crystal structure of the Ba-Hexacelsian phases doped with Ca2+ and Pb2+
No full textThe ion-exchange procedure is used for doping
the Ba-hexacelsian structure with Ca 2+ and Pb 2+ cations.
The hexacelsian doped with Ca 2+ has a composition of
Ba 0.64 Ca 0.36 Al 2 Si 2 O 8, and hexacelsian doped with Pb 2+
has a composition Ba 0.9 Pb 0.1 Al 2 Si 2 O8 . The crystal structure
of both doped hexacelsians was refined by Rietveld
refinement procedure. The crystal structure of Ca-hexac-
elsian is refined in the space group P 3c1, and results
indicate ordering distribution of Si and Al (unit cell
parameters is a = 5.2995, c = 15.594 A˚ and agreement
factors: Rexp = 15.3 Rp = 19.9, Rwp = 19.0, RB = 15.0
RF = 4.08). Structural model for Pb-hexacelsian samples is
described in the space group P6 3/mcm with disorder dis-
tribution Si/Al (unit cell parameter is a = 5.2973,
c = 15.591 A˚ and agreement factors Rexp = 21.5 Rp = 21.5,
Rwp = 19.0, RB = 5.74 RF = 4.08). The results of Rietveld
refinements indicate that Ca 2+ and Pb 2+ cations are
incorporated into hexacelsian structure in different
position
Possibility Of Using Limestone From “Gigovići”-Ulcinj Deposit As Filler In Various Industry Branches
No full textThis paper presents results of investigations of the possibility of using “Gigovići”-Ulcinjlimestone (Republic Montenegro) as filler in various industry branches. Micronization methods, granulometric composition, oil and water absorption and degree of whiteness were investigated, and chemical and thermal analyses (DT/TG) were performed. Physico-chemical properties of this limestone classify it among high quality carbonate raw materials with relativelyhigh CaCO3 content of 98.16%, as well as low MgCO3 content of 1.53% and low silicate content (SiO2 0.30%). Its quality satisfies requirements of standards on using of calcium carbonate as filler in industry of paints and coatings; paper industry, rubber and PVC industry; glass industry; production of mineral fertilizers; foundry industry; sugar industry and metallurgy. Due to the low degree of whiteness (85,25%) “Gigovići” limestone cannot be used in pharmaceutical and cosmetics industry. Due to relatively high content of MgO (0,73%) and Fe (340ppm), as well as high content of heavy metals, Cu (18 ppm), Ni (24 ppm) and Cd (9 ppm), “Gigovići” limestone cannot be used, in production of cattle feed and for neutralization of acidic soils
Pyrophyllite-mineral of the future for application in agriculture
No full textFrequently repeated phrases are that mining is a low-accumulative activity, with high production expenses and low prices of final products, which puts mining at a disadvantage compared to other, less demanding activities. We often point out that employees in the field of mining have been taking into account production expenses much more than generated profit for a long time. At the same time, capacities have not been sufficiently utilised. Non-metallic mineral raw materials, such as pyrophyllite (Al2Si4O10(OH)2), have an important role in economic development, whether as final products or as raw materials in manufacturing in processing and other industries. By its available quantities, pyrophyllite is one of the most important domestic natural non-metallic mineral raw materials in BiH (18.000.000t), [1-2]. There are almost no economic sectors that do not use pyrophyllite. In other words, it is used in the majority of industries, including civil engineering, agriculture, and lately increasingly in technologies for environmental protection. The existence of potential raw material base, pyrophyllite, in significant quantities, provides extensive possibilities for the development of manufacture with a wide product range. This paper will attempt to point out the possibilities for prospective processing and application of high- quality concentrates of pyrophyllite for new materials with added value, with special emphasis on agriculture
The influence of mechanical activation of talc-filler on the quality of the refractory coatings
No full textFor development of the refractory coatings with controlled rheologic properties, for application in new Lost Foam casting process, the influence of the mechanical activation on the talc-based filler’s properties change was examined. The test referred to the change of filler particles’ size and shape, as well as to dispersion ability and stability of the coating suspension. Optimization of the coating composition was attained chosing the right size and grain shape factor of the activated filler. In addition, different coating components were applied and the coating production procedure was altered. It was shown that application of this type of the water-based refractory coatings had a positive influence on surface quality, structure and mechanical properties of the aluminium alloy castings
The Chemometric Study of Limestone Physico-chemical Properties and Thermal Behavior for Application in Construction Composites
No full textThe limestone, as an economically sustainable and easily available basic raw material, is frequently utilized in the building industry for resolving of the environmental protection issues. The limestone is incorporated in a cementitious system either by grinding with cement clinker, or by blending with the binder during concrete production. The employing of powdery limestone as partial cement replacement gives the construction composites with properties comparable to that of conventional concrete. The study of limestone thermal behavior and its chemistry is crucial for the prognosis of the designed composites properties. In this work, the instrumental techniques (atomic emission spectroscopy, differential thermal and thermo-gravimetric analysis, Fourier transform infrared spectroscopy) and the Principal component analysis were employed to discriminate and classify 22 limestone types. The PCA statistical method, as a means of spectra and experimental data fingerprinting, grouped the samples in a multi-dimensional factor space producing four graphical prognosis - one for each instrumental method. DTA/TG peak values varied the most in a short range between 830-870 degrees C, while FTIR spectra showed the highest diversity in the 867-887 cm(-1) and 1237-1647 cm(-1) ranges. This research was governed by an idea to reveal whether it is possible to differentiate various limestone types and to predict the possibility of their employment in construction composites on the basis of the results of instrumental and mathematical analyses
Reaction mechanism and kinetics of sulfide copper concentrate oxidation at elevated temperatures
No full textSulfide copper concentrate from domestic ore deposit (Bor, Serbia) was subjected to oxidation in the air atmosphere due to a better understanding of reaction mechanism and oxidation of various sulfides present in the copper concentrate at elevated temperatures. Results of the initial sample characterization showed that concentrate is chalcopyrite-enargite-tennantite type, with an increased arsenic content. Characterization of the oxidation products showed the presence of sulfates, oxysulfates, and oxides. Based on predominance area diagrams for Me-S-O systems (Me = Cu, Fe, As) combined with thermal analysis results, the reaction mechanism of the oxidation process was proposed. The reactions which occur in the temperature range 25 -1000 degrees C indicate that sulfides are unstable in the oxidative conditions. Sulfides from the initial sample decomposed into binary copper and iron sulfides and volatile arsenic oxides at lower temperatures. Further heating led to oxidation of sulfides into iron oxides and copper sulfates and oxysulfates. At higher temperatures sulfates and oxysulfates decomposed into oxides. Kinetic analysis of the oxidation process was done using Ozawa's method in the non-isothermal conditions. The values for activation energies showed that the reactions are chemically controlled and the temperature is the most influential parameter on the reaction rates
Combustion of Metallurgical Wastes Using Secondary Aluminum Foils
No full textSimulating the reactions in a complex system can lead to self-sustaining and energy efficient treatment of wastes in recycling promoting manner. In this contribution, the synergic combination of electric arc furnace dust (EAFD), mill scale, and secondary aluminum, in a form of waste foil, was researched aiming to use exothermal energy of reactions and to obtain environmentally favorable products. The secondary aluminum in the form of foil was prepared in different ways in order to develop aluminum surface and to be suitable for aluminothermic reactions. The commercial aluminum powder was used to determine optimal conditions using full factorial experiment design. After that, research was performed on aluminothermic reactions with the aluminum powder obtained from secondary aluminum foils. Results show that the secondary aluminum can be successfully used for a treatment of oxides bearing hazardous wastes in an energy efficient and environmentally friendly manner. The comparative life-cycle assessment revealed several advantages of using the secondary aluminum foil as a reduction agent compared to the conventional recycling of the secondary aluminum foil
Geochemical Properties of the Sediments of the Great War Island, Belgrade (Serbia)
No full textRivers, which approximately deliver 20 billion
metric tons of transported sediment to oceans every
year, play a key role in Earth surface processes.
Determining the content of potentially harmful
heavy metals in rivers sediments is essential for
estimating the environmental risk. The main sources
of heavy metals in drainage basins are weathering
of rocks and anthropogenic activities.
The aim of this study is to determine the
geochemical properties in river sediments in order
to assess the intensity of possible anthropogenic
influence. Sediments were collected from the Great
War Island in Belgrade, located at the confluence of
Sava and Danube River (Fig. 1).
Number of authors analyzed Danube and Sava
sediments [e.g. 1, 2], but so far no studies have been
conducted on the confluence of these two rivers.
Contents of Cr and Ni are of particularly interest
since high concentrations of these two elements
were reported in previous studies, but their origin is
still not completely understood.
For the purpose of this study sediment samples
were collected on five locations: 3 locations along
the shore of the island (Kalemegdan, Lido and
Small port) and 2 inland locations (at the Big and
Small Galijas channels) (Fig. 1).
Mineralogical and geochemical properties were
determined on 27 samples. Grain size composition
was determined using the Laser Microsizer 2000,
contents of major and minor elements using X-ray
fluorescence diffraction (XRF). Content of organic
carbon (Corg) was determined with CHNOS
Elemental analyzer.
Grain size analysis shows that analyzed sediments
form four groups: sands, silty sands, sandy silts
and clayey silts. Sediments from the shores show
very high variation in dominant grain size, while
sediments from the inner part of the island are
clayey silts. This is in accordance with hydrological
conditions since Island shores and the Big Galijas
are under constant sediment input, although very
low energy flows occur in the channel. Sediment
deposition in the Small Galijas occurs only during
extreme floods and consequently fine grain
sediments are deposited.
Clay content and Corg content have positive
correlation. Sediments from the Small Galijas have
highest Corg (~5%) and lowest carbonate content
indicating calm reduce deposition environment.
Future organic geochemical analyses will give
important insight into distribution of organic
compound at the molecular level.
Contents of Cr and Ni in all samples have a positive
correlation indicating the same geogenic origin.
Content of Cr is grain size controlled in sediments
that are under constant water flux, meaning higher
Cr concentration in coarser sediments. Sediments
in the Small Galijas do not obey this rule due to its
specific depositional environment
Effects of different sintering routes on the properties of steatite-based ceramics
No full textThis study provided insights into relations between sintering mechanism and behavior of two types of steatite-based ceramics. Experimental steatite samples were synthesized from low-cost natural raw materials. The sintering was conducted via dilatometer and SPS method. The thermally induced changes in the steatites and its properties were monitored by instrumental analyses: mineral phase transition was investigated via XRD, and the thermal stability was observed using DTA. The investigation highlighted the optimal combinations of the raw materials for production of the steatite ceramics for advanced electrical engineering applications