Claudiu Nicolicescu

Hydroxyapatite–alendronate composite systems for biocompatible materials

In this study, hydroxyapatite–alendronate composites were synthesized from calcium nitrate, diammonium hydrogen phosphate and alendronate by chemical precipitation method. The obtained materials were analysed by physical–chemical methods, while the compositional and structural characteristics of hydroxyapatite–alendronate phases were determined by a combination of crystallographic, spectroscopic and thermal analysis investigations; moreover, the alendronate content, its maximal incorporation efficiency to hydroxyapatite and stability were determined. A two-level full factorial design was chosen to determine the optimum set of process parameters (synthesis temperature, reactant addition rate and ripening time) and their effects on various hydroxyapatite–alendronate characteristics: alendronate incorporation efficiency, hydroxyapatite crystallite size (XRD), hydroxyapatite particle size distribution (DLS). These effects were quantified using design of experiments. The in vitro release profile of alendronate from hydroxyapatite–alendronate tablets was assessed.

Research of the Milling Time Influence on Ag-Cu Powder Particles Size Processed by Mechanical Alloying Route

This research focuses on Ag-Cu powder particles processing by mechanical alloying (MA) route. The powder mixture is representative for the eutectic composition, respectively 72%wt. Ag + 28% wt. Cu. The milling process is developed in high energy ball mill Pulverisette 6, using different size for the milling balls, in wet conditions for 80 hours. One of the most important parameter studied in this research is the particle size distribution of the processed powder mixture. Thus, it changes along the milling time, from 10…75 µm at the beginning of MA process up to (60 – 80) nm at 80 h. The milling parameters will be optimized in future research depending on the particle size distribution related with thermophysical and thermodynamic properties focused on electrical and optical properties improvement.

Influences of the Elaboration Conditions and Addition of Ni and Co on the Some Properties of the W-Cu Electrical Contacts

This paper presents a study about the influence of some alloying elements like Ni and Co on the elaboration of W-Cu electrical contacts. For the experimental work four types of mixture were prepared using mechanical alloying (MA) technique for six hours. All the samples had the same Ni and Co content (2%) varying the W content as following: 88W-10Cu-Ni, 78W-20Cu-Ni, 68W-30Cu-Ni, 88W-10Cu-Co, 78W-20Cu-Co and 68W-30Cu-Co. The mixtures were pressed in a cylindrical die with 10 mm diameter at two pressures: 400MPa and 600 MPa. The sintering process was carried out in an electrical furnace at the 1180 OC and maintained at this temperature for three hours. For all the samples the electrical properties: resistivity, conductivity, resistance were measured and were made correlation between electrical contacts with Ni and the other with Co. It is observed that, the compaction pressure influence the electrical properties and better properties are obtained for the samples compacted at 600 MPa.

Study about the Influence of Two-Steps Sintering (TTS) Route for an Alloy Based on Titanium

This paper describes the influence of two-steps sintering regime temperatures concerning the final properties of titanium hydride based alloy obtaining by Two-Steps Sintering (TTS) route, which is a method that is part of the Powder Metallurgy (PM) technology. The initial titanium hydride powder has been mixed with some metallic powders as: Alumix, Mn, Zr, Sn and graphite was added in different proportions for improving the final mechanical properties. The Two-Steps Sintering (TTS) route have been applied for obtaining a low-cost Ti- alloy. The effect of the sintering regime temperatures on the height and diameter shrinkages and density for these alloys based on titanium hydride powder was studied

Synthesis of Cu/Cr and Cu/Cr/W Materials by Powder Metallurgy Techniques

Alloys based on Cu/Cr and Cu/Cr/W attract the attention due to their presence in different applications that require higher electrical properties which are combined with good mechanical properties. In order to synthesis the material based on Cu/Cr and Cu/Cr/W, mechanical alloying technique was used. Four mixtures, X1 (99%CuCr), X2 (97%CuCr), X3 (94%Cu1%CrW), X4 (92%Cu3%CrW – weight percent), were prepared using a vario planetary ball mill Pulverisette 4 made by Fritsch. The mixtures obtained after 10 hours were analyzed by scanning electron microscopy (SEM). It was found that the presence of chromium and tungsten influence the morphology and the particles tend to be flat. Sinter ability and microhardness are influenced by the chemical composition of the samples.

Resistance Spot Welding of some Sintered Steels

The aim of the paper is to study the possibility of welding some sintered steels, which were obtained from mixtures of iron with different concentrations of graphite powders (between 0.2 and 0,8% weight). The sintered steels were resistance spot welded using different parameters and were investigated by optical microscopy in order to study the evolution of microstructures of the welded areas and base materials. There were perform studies regarding the evolution of microhardness respectively the evolution of tensile strength too.

Hydroxyapatite-ciprofloxacin delivery system: Synthesis, characterisation and antibacterial activity

Abstract The main objective of this study was to synthesize hydroxyapatite-ciprofloxacin composites using a chemical precipitation method and to evaluate the properties and in vitro release profile of the drug from the hydroxyapatite-ciprofloxacin composites. Composite characterization was achieved by FT-IR, XRD and DLS. Ciprofloxacin determination was accomplished by HPLC, resulting in good incorporation efficiency of the drug (18.13 %). The in vitro release study (Higuchi model C = K t1/2 and Ritger-Peppas model, C = K t0.6) showed a diffusion-controlled mechanism. The antibacterial activity showed that the bacterial growth inhibition zones were approximately equal for the synthesis composites and for the mechanical mixture on the Staphylococcus aureus germ. The use of hydroxyapatite, which is a biocompatible, bioactive and osteoconductive material, with ciprofloxacin, which has good antibacterial activity in this composite, makes it suitable for the development of bone grafts. Furthermore, the synthesis process allows a slow local release of the drug.

Aspects about Sintering Behaviour of a Titanium Hydride Powder Based Alloy Used for Automotive Components

For this study with high originality, some aspects about the sintering behaviour of Titanium based alloy used for automotive components are presented. This paper presents the experimental results concerning the processing of Ti based alloy by Powder Metallurgy (PM) technology. The initial powder mixture consists in TiH2 micrometric powder particles that have been combined with some metallic powders for improving the final mechanic-chemicals and functional properties for using in the automotive industry. The classical PM route have been applied for obtaining a low-cost Ti- alloy.As a result it was compulsory to study the parameters that influence the densification process and the sintered properties, depending on the sintering temperature. The experimental test results were processed using the STATISTICA program. Therefore the influence of these sintering temperatures on the height and diameter shrinkages, density and hardness for the alloys based on Ti micrometric powders has been studied.

RESEARCH REGARDING THE INFLUENCE OF COPPER POWDERS ON TENSILE STRENGTH OF SINTERED STEELS

The aim of this paper is to present experimental results on the evolution of tensile strength of some low alloyed steels function the copper content. There are prepared six types of mixtures as following: A1 (Fe), A2 (Fe+1.5%Cu), A3 (Fe+3%Cu), A4 (Fe+0,2%C), A5 (Fe+0,2%C+1.5%Cu), A6 (Fe+0,2%C+3%Cu). All six mixtures were pressed at 400, 500 respectively 600 MPa and the green parts were subjected to CARBSINT and SINTCARB thermal treatments. The influence of copper content, pressures and type of thermal treatments on the tensile strength was studied.

RESEARCH OF THE Fe2O3 POWDER GRANULATION EFFECT ON BaFe12O19 FIRING TEMPERATURE

In the paper is presented the study of the Fe2O3 powders granulation effect on the firing parameters for the BaCO3+6Fe2O3 powder mixture. The Fe2O3 powders were milled in a ball mill in wet medium. The results indicated that the granulation of Fe2O3 powders decreased rapidly with the increase of milling time. The Fe2O3 milled powders were then mixed with unmilled barium carbonate powders in order to form barium hexaferrite. After mixing, the powders were analized by thermogravimetric point of view and then the obtained barium hexaferrite samples were investigated by XRD analysis. It was observed that the firing temperature of the hexaferrites decreases with 10 degrees when we introduce in the mixture Fe2O3 milled powders with a fine granulation.