Naim Aslan, Necati Başman, Orhan Uzun, Mustafa Erkovan and Fahrettin Yakuphanoğlu
Diamond-like carbon (DLC) films were electrochemically deposited onto indium tin oxide (ITO) substrates using acetic acid and deionized water as electrolyte at low deposition voltages (2.4 V and 60 V). The transmittance of the films was investigated by UV spectrometry. Transmittance measurements versus wavelength revealed that the films transmit 86 % to 89 % light in visible region and band gap of the films varies between 3.87 eV and 3.89 eV. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used for structural characterization to evaluate surface morphology of the DLC films. The grain size and the surface roughness increased for the films prepared at higher deposition potential, while their measured average height decreased. The mechanical properties (hardness H and elastic modulus Er) were determined from load-displacement curves which were obtained by using nanoindentation method. Hardness and elastic modulus of the films increased as the deposition voltage of the films increased from 2.4 V to 60 V.
Moniruddoza Ashir, Andreas Nocke and Chokri Cherif
Considering their energy and resource efficiency, fiber-reinforced plastics (FRPs) have been displacing metals and metal alloys for lightweight constructions. During the semiautomated manufacturing process of FRPs, and in particular during the laying of reinforced fabric layers, foreign bodies are enclosed within them, which in turn reduce the mechanical performance of FRPs. The research project presented in this article investigated if the loss in mechanical properties, such as tensile, flexural, and impact strengths, depends on the position of defined local defects, polytetrafluorethylene (PTFE) in this case, in the thickness direction of FRPs. In order to achieve this aim, PTFE was placed in different layers of reinforcing fabric before infusion. Subsequently, the mechanical performance of the fabricated FRPs was tested and evaluated. On the basis of the experiment, it can be concluded that the loss in mechanical properties was maximal if PTFE was laid in the middle position of FRPs in the thickness direction.
This study deals with experimental thermodynamic and rheological characterization of kaolin. Water sorption isotherms of kaolin were determined for three temperatures (30, 50 and 70°C). Desorption isotherms were fitted by using five models (GAB, BET, Henderson modified, Adam and Shove, Peleg) among the most used ones in literature. The GAB model was found to be the most suitable for describing the relationship between equilibrium moisture content and water activity for the whole range of temperature (30-70°C) and relative humidity(0-100%). Desorption enthalpy and entropy were determined. The desorption enthalpy decreases with increasing moisture content. The density and the shrinkage of the material and the Young’s modulus variations as a function of moisture content were determined experimentally. The Young modulus varies between 0.1 MPa and 14 MPa. The viscoelastic parameters of kaolin were also determined by using a series of Prony.
Liliana-Laura Badita, Gheorghe Gheorghe, Vasile Bratu, Valentin Gornoava, Marian Vocurek, Aurel Zapciu and Iulian Sorin Munteanu
Taking into account the importance of mechatronic applications, researches regarding the possibility to improve the lifetime of mechatronic components were made. Nanostructured metallic thin films (Ti, Cr, Al and Ti/Al multilayer) were deposited on different types of steel substrates, because nanomaterials have exceptional properties in relation to the common materials. In this paper a part of the results obtained after mechanical and topographic characterization of the thin films are presented. Cr is the deposited thin film showing the highest hardness on the surface of steel substrate type OSC. After the scratch tests realized, Ti layer presented the best adhesion on all types of steel substrates used in experiments. The results of these researches could be extremely useful for engineers in the mechatronic field.
, D. G. Papadopoulos, P. J. Dunn, A. C. Bentham, J. C. Mitchell and M. J. Snowden, Mechanicalcharacterization of powders using nanoindentation, Powder Tech. 143-144 (2004) 179-185; DOI: 10.1016/j.powtec.2004.04.012.
87. L. J. Taylor, D. G. Papadopoulos, P. J. Dunn, A. C. Bentham, N. J. Dawson, J. C. Mitchell and M. J. Snowden, Predictive milling of pharmaceutical materials using nanoindentation of single crystals, Org. Process Res. Dev. 8 (2004) 674-679; DOI: 10.1021/op0300241.
88. http://cdn.intechweb.org/pdfs/16971.pdf; access date
Corina Cheptea, Andreea Celia Benchea, Marius Gaina, Dana Ortansa Dorohoi and Valeriu Sunel
Two derivatives of glutamine were synthesized and the most convenient physical conditions for obtaining reactions were established in factorial experiments with temperature and time of reactions considered as relevant variables. A quantum-mechanical characterization for the new compounds was performed by using HyperChem 8.0.6 Programs and their physical and chemical properties were theoretically estimated. The toxicity of two new compounds was experimentally determined.
M. Suresh Kumar, K. Rajesh, G.V. Vijayaraghavan and S. Krishnan
Good quality diglycine perchlorate (DGPCL) single crystals were grown by slow evaporation solution growth method using the combination of glycine and perchloric acid in the ratio of 2:1. Single crystal X-ray diffraction and mechanical characterization of the grown single crystals of diglycine perchlorate were analyzed in this article. Lattice parameters, space group and crytal system were found from single crystal X-ray diffraction analysis. All the cell parameters and space group are in a good agreement with the reported values. Mechanical properties, such as Vicker’s microhardness number, work hardening index, standard hardness value, yield strength, fracture toughness, brittleness index and elastic stiffness constant values, were determined using Vicker’s microhardness tester.
Ni2MnGa is a ferromagnetic alloy that exhibits the shape memory effect either induced by an externally applied magnetic field or mechanical stress. Due to the former, the alloy is commonly called magnetic shape memory alloy or MSMA. The microstructure of the MSMA consists of tetragonal martensite variants (three in the most general case) that are characterized by a magnetization vector which is aligned with the short side of the tetragonal unit cell. Exposing the MSMA to a magnetic field causes the magnetization vector to rotate and align with the external field, eventually leading to variant reorientation. The variant reorientation is observed macroscopically in the form of recoverable strain of up to 6% [1, 2]. As the magnetic field induced reorientation happens instantaneously [1, 3], MSMAs are suitable for fast actuation, sensing, or power harvesting applications. However, actuation applications are limited by the maximum actuation stress of the material that is about 3.5MPa at approximately 2 to 3% reorientation strain. During MSMA fatigue magneto-mechanical characterization studies [4, 5] it was observed that cracks nucleate and grow on the surface of material samples, after a relatively small number of cycles, leading to loss in material performance. This triggered the need for understanding the mechanisms that govern crack nucleation and growth in MSMAs, as well as the nature of the material, i.e. ductile or brittle. The experimental study reported in this paper was carried out to determine material’s fracture toughness, the predominant crack growth directions, and the orientation of the cracks relative to the mechanical loading direction and to the material’s microstructure. A fixture has been developed to allow Vickers micro indentation of 3mm by 3mm by 20mm Ni2MnGa samples exposed to different levels of magnetic field and/or mechanical stress. Using the measured characteristics of the impression generated during micro indentation, the lengths of propagated cracks, and appropriate equations (introduced in the paper), and the fracture toughness was evaluated as a function of the magneto-mechanical loading experienced by the material. The influence of the magneto-mechanical loading on the growth of already nucleated cracks has also been evaluated.
Zhong Hua Luo, Alex Chung, Gibok Choi, Yih Huie Lin, Huajin Pang, Barry T. Uchida, Dušan Pavčnik, Miran Jeromel, Frederick S. Keller and Josef Rösch
1. Gralla J, Schroth G, Remonda L, Fleischmann A, Fandino J, Slotboom J, et al. A dedicated animal model for mechanical thrombectomy in acute stroke. AJNR Am J Neuroradiol 2006; 27: 1357-61.
2. Chueh JY, Wakhloo AK, Hendricks GH, Silva CF, Weaver JP, Gounis MJ. Mechanicalcharacterization of thromboemboli in acute ischemic stroke and laboratory embolus analogs. AJNR Am J Neuroradiol 2011; 32: 1237-44.
3. Luo ZH, Chung A, Choi G, Lin YH, Uchida BT, Pavcnik D, et al.. Creation of