Nicanor Cimpoeşu

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.

Heating rate effects on reverse martensitic transformation in a Cu – Zn – Al shape memory alloy

Abstract Different fragments of martensitic Cu-14.86 Zn-5.81 Al-0.5 Fe (mass.%) shape memory alloy were subjected to heating, up to 453 K, with different rates ranging from 1.66 ×10−2 K s−1 to 54.6 × 1.66 × 10−2 K s−1, performed by means of a differential scanning calorimeter. In all cases, during heating, an endothermic peak was observed which was associated with the martensite reversion to parent phase. By means of the differential scanning calorimeter charts the critical transformation temperatures of martensite reversion were determined using the tangent method. The effects of heating rate were evaluated from the point of view: (i) of variation tendencies of critical transformation temperatures; (ii) of deviations of experimental values from linear fit and extrapolation to zero heating rate; and (iii) of corroborating morphological changes of martensite (sub)plates with heat flow variation particularities. The results prove that there is an obvious tendency of critical transformation temperatures, of reverse martensitic transformation, to linearly increase with heating rate. The effectiveness of the linear relationships was checked for two heating rate values located inside and outside the above mentioned range, respectively and the difference between the experimental and calculated values of critical transformation temperatures fell within the range (−3 … +4) ‰.

Biomaterials with controlled release of geranium essential oil

This research aimed to produce personal care biomaterials with an antimicrobial and flavoring effect that allowed the controlled release of biologically active constituents. We investigated the manufacturing conditions of oil-in-water-type chitosan emulsions encapsulating geranium essential oil and the influence on controlled release and antimicrobial effect of the biologically active compounds. The materials were obtained by applying the polymeric matrix/biologically active principal system on a 100% cotton textile substrate. Seven treatment variants that differ one from another by the concentrations of the two components of the system (the polymer and the biologically active compound) were used. The release profile of the biologically active principal from the treated textile substrate was analyzed according to the Peppas kinetic models. The results suggest that the forming of emulsions should be processed under the following conditions: a concentration of chitosan of 0.250% (w/v), geranium essential oil 0.450% (w/v), Tween 80 1% (w/v) and glycerine 2% (w/v), so that we could obtain biomaterials with the best controlled release of biologically active compounds.

Preliminary Results of FeMnSi+Si(PLD) Alloy Degradation

In this study, nano-silicon (Si) thin films were deposited on biodegradable Fe–1.5Mn–1Si substrate by pulsed laser deposition (PLD) method. Biodegradable metallic materials represent a good solution in implantology field based on the elimination of the second surgical operation required for the extraction of the material. Also, using biodegradable materials medical complications between the metallic implant and the human body that might appear during the recovery period are excluded. In this sense we propose a metallic material based on iron with a longer degradation period compared to Mg-Ca based materials. Scanning electron microscopy (SEM) and X-ray dispersive energy analyze (EDAX) were use to analyze the implant material surface before and after Si thin film deposition and before and after implantation.

Preliminary Results of Copper Based Shape Memory Alloys Analyze Used for MEMS Applications

Shape memory alloys (SMAs) are commonly used in micro-electro-mechanical systems (MEMS). Having the unique shape memory, super-elastic affects and now damping capacity SMAs have become an important smart material for a broad range of engineering applications in last years. Copper based SMAs are promising alloys, based on the obtaining price and good characteristic properties. Shape memory alloys as thin films are used for fast actuation in applications due to their high surface to volume ratio comparing to bulk SMAs. In this paper two shape memory alloys based on copper, proposed as targets in different deposition processes to obtain MEMS and with different chemical composition, are analyzed through scanning electrons microscope (SEM), XRD and EDAX considerations after water quenching and recovery heat treatments. The martensite variants are dimensioned and 3D aspects are also analyzed for both metallic materials. The metallic phases obtained after heat treatment are determined and compare in both thermal influenced cases.

Preliminary Results on Microstructural, Chemical and Wear Analyze of New Cast Iron with Chromium Addition

A new cast-iron material was obtained by melting in an induction furnace. The material was microstructural and chemical characterized before and after a wear test. We analyze the chemical composition of the material at macro-scale using a Spark Spectrometer and at micro-scale using Dispersive Energy Spectrometer. Microstructure before and after the external solicitations was observed using a Scanning Electron Microscope. We also evaluate the influence of external force on the dendrites microstructural and chemical modification.

Quantification of Fe-Base Alloy Degradation after Immersion Test

A new FeMnSi metallic alloy is proposed as biodegradable material with applications in medical field. The corrosion behavior in simulated body fluids is evaluated after immersion for 14 days. The metallic biodegradable material surface was analyzed with a SEM (2 and 3D)+EDAX equipment. The effects of the solution on the metallic surface present an area with pitting corrosions, marks around 10 µm in depth, and a different one with new chemical compounds form from biological solution with good stability on the surface. Even if is a new biodegradable material based on iron simmilar results about the surface behavior were obtain by other researchers on different FeMnSi chemical compositions.

A Potential Biodegradable Metallic Material with Shape Memory Effect Based on Iron

FeMnSi alloys are promising shape memory alloys which have been used for pipe joints but no previous work pays any attention to their biomedical application. Following the outline of the aforementioned development of biodegradable Fe-based alloys, we believe that it is worthwhile to investigate the feasibility of FeMnSi alloy as biodegradable metal candidate, since element Si is widely used in biomedical metallic materials as an alloying element. A shape memory metallic material based on FeMnSi was obtained through classical melting method. The material was analyzed as cast and plastic deformed through rolling concerning materials microstructure (scanning electrons microscopy - SEM), chemical analyses (X-ray analyze by EDAX) and corrosion resistance (or biodegradation rate) in an artificial saliva electrolytic solutions (Fusayama) artificial aerated by linear and cyclic curves determination (potentiometry - VoltaLab).

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.

NiTi Shape Memory Alloy Used for Multiple-Resetting Actuator for Fire Protection

The paper introduces the possibility to replace the “wet alloy”, used for sprinkler-triggering within automatic fire protection systems, with a shape memory alloy (SMA) type. The idea of the present application is based on the thermoelastic reversible martensitic transformation, governing SMA functioning, which has completely reversible character, and enables the occurrence of two-way shape memory effect (TWSME) after the application of a thermomechanical treatment called “training”. For this purpose a commercial NiTi rod, which was martensitic at room temperature, was subjected to thermal analysis tests, performed by differential scanning calorimetry (DSC) and dilatometry. Martensite (M) reversion to parent phase (A), during heating, was emphasized by an endothermic peak on the DSC thermogram and by a length shrinkage, on the dilatogram. The capacity to develop TWSME was revealed by the change in displacement-temperature variation, with increasing the number of training cycles. This stabilized fully reversible behavior recommends NiTi rods as executive elements of a new concept of resettable sprinkler for fire protection.