Corneliu Munteanu

Low cost adsorbents obtained from ash for copper removal

We investigated the utilization of ash and modified ash as a low-cost adsorbent to remove copper ions from aqueous solutions such as wastewater. Batch experiments were conducted to determine the factors affecting adsorption of copper. The influence of pH, adsorbent dose, initial Cu2+ concentration, type of adsorbent and contact time on the adsorption capacity of Cu2+ from aqueous solution by the batch adsorption technique using ash and modified ash as a low-cost adsorbent were investigated. The optimum pH required for maximum adsorption was found to be 5. The results from the sorption process showed that the maximum adsorption rate was obtained at 300 mg/L when a different dosage of fly ash was added into the solution, and it can be concluded that decreasing the initial concentration of copper ion is beneficial to the adsorption capacity of the adsorbent. With the increase of pH value, the removal rate increased. When the pH was 5, the removal rate reached the maximum of over 99%. When initial copper content was 300 mg/L and the pH value was 5, the adsorption capacity of the zeolite Z 4 sample reached 27.904 mg/g. The main removal mechanisms were assumed to be the adsorption at the surface of the fly ash together with the precipitation from the solution. The adsorption equilibrium was achieved at pH 5 between 1 and 4 hours in function of type of adsorbent. A dose of 1: 25 g/mL of adsorbent was sufficient for the optimum removal of copper ions. For all synthesized adsorbents the predominant mechanism can be described by pseudo-second order kinetics.

The Estimation of Corrosion Behavior of NiTi and NiTiNb Alloys Using Dynamic Electrochemical Impedance Spectroscopy

Linear anodic potentiodynamic polarization and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out for NiTi and NiTiNb alloys in physiological 0.9 wt% NaCl solution in order to assess their corrosion resistance. DEIS measurements were performed from open circuit potential to dissolution potential. It was shown that the impedance measurements in potentiodynamic conditions allow simultaneous investigation of changes in passive layer structure. The impedance spectra of various potential regions were fitted and also discussed. The surface morphology of the alloys after linear anodic polarization test was studied using scanning electron microscopy (SEM) technique.

XRD and Microstructural Analyses on Biodegradable Mg Alloys

Stainless steels, titanium and titanium alloys are the most widely used artificial surgical biomaterials for a long time. These alloys with non-degradability properties present long-term adverse effects or stress shielding and require a second surgery for a complete healing. The ongoing scientific research to avoid this problem found a new kind of biocompatible alloys for implants made of biodegradable materials witch should be used as alternative. Among the various biodegradable materials, magnesium alloys have unique biodegradability properties in the physiological environment, have stimulatory effects on new bone formation and have an elastic modulus similar to that of human bone. Roentgen structural analysis was used to detail the global chemical composition analysis, especially the analysis to determine the phase-pick sites characteristic diffraction and crystallographic orientation parameters Miller constituent phases. On studied alloys Mg and Mg2Ca type compounds with different crystallographic orientations were identified. The results obtained on the Mg-Ca and Mg-Ca-Si systems will be correlated with results from previous tests and analyses, to finally obtain an alloy with biodegradability that may be controlled.

New Titanium Alloys Potentially Used for Metal-Ceramic Applications in Medicine

Titanium alloys corresponding to Ti-Nb-Zr-Ta system represent a new generation of biomaterials, which were developed for medical applications like metal-ceramic. They are composed of non-toxic and non-allergenic elements and have lower values of modulus of elasticity compared to that of the current biomaterials used in dentistry or orthopedics. In this paper are presented two new titanium alloys (Ti-21Nb-6Zr-15Ta and Ti-25Nb-10Zr-8Ta), which were characterized from structural aspect, mechanical and surface properties point of view using scanning electron microscopy, X-ray diffraction, wear properties, Vickers microhardness measurement. Also, was tested the cytotoxicity of these alloys using direct contact method. The results showed that the investigated alloys have a biphasic structure composed of β-solid solution with intragranular lamellar structures specific to α”. The experimental results shown that new titanium alloys from the system Ti-Nb-Zr-Ta present much better properties compared to that of the metallic biomaterials used currently.

Structural Characterization of Mg-0.5Ca-xY Biodegradable Alloys

In recent years, researchers have been able to identify new materials with special properties that can be used in major medical fields. Magnesium-based materials used in orthopedics are an important alternative, being the third generation of biocompatible materials. A biodegradable magnesium-based material has the ability to degrade at a certain rate, is biocompatible, and together with other alloying elements ensures osteointegration. Mg-0.5Ca-xY biodegradable alloys will be developed in an induction melting furnace using ceramic crucibles, melting at 710-720 °C in the controlled atmosphere of 5.0 Ar. SEM analyses and X-ray diffraction reveals the size distribution of Mg-sized grains, with a hexagonal lattice and formation of compounds with the two alloying elements: Mg2Ca, Mg2Y, Mg24Y5 uniformly arranged in the α-Mg matrix. The alloying elements influence the microstructure, the size of the α-Mg grains decreasing considerably.

Some Tribological Aspects of Mg-0.5Ca-xY Biodegradable Materials

Biodegradable materials are a further development of new medical applications, such as orthopedic implants and vascular stents, or the tissue scaffold. The variety of alloying elements introduced into magnesium alloys lead to superior corrosion resistance and mechanical properties similar to the biological bone. From a mechanical point of view, increasing the percentage of calcium leads to decreased strength and elongation resistance, and Yttrium addition greatly improves tensile strength and favors a slower degradation process. Three different Mg-0.5Ca-xY alloys were obtained, varying the concentration of the Y-element. The Mg-0.5Ca-xY system was tested from the point of view of micro-scratch and micro-indentation with three determinations each, obtaining results for Youngs mode, micro-hardness, COF and stiffness. These alloys possess mechanical properties for use as orthopaedic applications. As future studies, mechanical properties can be improved by performing heat treatments.

Preliminary results on complex ceramic layers deposition by atmospheric plasma spraying

In this article we obtain thin layers from complex ceramic powders using industrial equipment based on atmospheric plasma spraying. We analyze the influence of the substrate material roughness on the quality of the thin layers using scanning electron microscopy (SEM) and X-ray dispersive energy analyze (EDAX). Preliminary results present an important dependence between the surface state and the structural and chemical homogeneity.

Increasing Wear Resistance of Power Steering Pump Cam Using Ni-Cr-Fe and Ni-Cr-Fe-B Coatings

Thermal depositions are very wide spread in the industry of coating techniques. The materials used as coatings for several applications must have the ability to produce a stable, slow-growing surface coating, in order to provide good service behavior. This paper presents a method to increase the wear resistance of steering pump cam, strongly stressed having premature wear effects. The method that the authors use is atmospheric plasma deposition with Ni-Cr-Fe and Ni-Cr-B-Fe powders on steel substrate. It was investigated the morphology and physico-mechanical properties (scratch and micro-indentation analysis). Results showed a comparison between those two coatings with the metallic substrate. It has been found that the deposited coatings have an adherent, dense and uniform layer with a typically molten morphology. By increasing the coefficient of friction we can obtain higher wear resistance and recommend the optimum solution for further researches.

Coating of Liquid Wood Sheets

Liquid wood is one of the newly discovered green polymer materials, being a biodegradable and recyclable thermoplastic, made from cellulose, lignin and natural additives, currently used in commerce as ARBOFIL, ARBOROM and ARBOBLEND. The applications of this material (aeronautics, automotive, construction, consumer goods etc.) are limited by two major drawbacks: higher weight compared to ordinary plastic materials and low melting point (≈ 175° C). In this work was studied the possibility of changing some mechanical and thermal properties of this material by applying superficial coatings. For this process were prepared specimens from two types of material: ARBOBLEND and ARBOFIL. The resulted samples were analyzed in terms of microstructural changes both longitudinally (in order to evaluate the quality of the deposited layer) and on cross section (in order to evaluate the changes produced at the interface substrate - coating). For this purpose were used the QUANTA 200 3D (FEI, Holland, 2009) scanning electron microscope and the X`PERT PROMD diffractometer (Panalitycal, Holland, 2009). Using the UMTR 2M-CTR Micro-tribometer were evaluated the elasticity modulus of the coatings through microindentation and its adhesion to the substrate through scratch method, applied both longitudinally and on cross section.

IMAQ Vision Builder Applications in SEM Image Processing of Pharmaceutical Powders

IMAQ Vision includes a set of optimized functions for image processing (filtering and geometric transformations) and analysis of different areas of interest (perimeter, area, orientation, height, length and width). Also with this program, it may determine the edges of objects, distances and angles between the edges, an object can be searched based on its shape. Particle analysis provides the ability to count objects within the pharmaceutical or biological applications. Image calibration is done to give the user instead of the unit pixel measurements, in units such as millimeters, inches, microns. This paper aims to examine the pharmaceutical powder containing ketoprofen in order to determine the quality of the particles and if this are optimal for pharmaceutical applications. It aims to detect surface defects in the deposited layer such as cracks or clusters of particles that cause surface irregularity. IMAQ Vision by processing images, increase productivity, versatility and reproducibility also reducing manufacturing costs.