Key Engineering Materials Vol. 495

Abstract: Biosensors using the mechanisms of electrochemical, optical, mass sensitive thermometric and magnetometric have been intensively investigated [1], and molecularly imprinted polymers (MIPs) has been used as recognition elements in sensors reviewed in numerous articles [1-3]. A severe challenge for MIP sensors is detection in chemically diverse environments, such as biological fluids [4-7]. There are many biomarkers discovered in biological fluid, like cerebrospinal fluid (CSF), saliva, serum and urine. Important biomarkers such as creatinine [4], urea, and albumin [8], urine contains non-protein nitrogen metabolites, carbohydrates [9], proteins and amino acids [10]; detection of analytes must be made amid this complex chemical background.

Abstract: Nitrogen-doped 6H-SiC single crystals irradiated with neutrons up to a fluence of 5.74×1018 n/cm2 at the temperature of 60-80°C were investigated by means of X-ray diffractometer and metallurgical microscope. The experimental results showed the X-ray diffraction peak (0006) was broadened due to the lattice distortion resulting from irradiation-induced defects, and then narrowed linearly when isochronally annealed over the temperature of 700°C. Meanwhile, from the chemical etching photomicrographs, the characteristic was accompanied by the changes of the dislocation density after the process of irradiation and post-irradiation annealing. According to this characteristic of irradiated 6H-SiC crystals, a novel temperature sensor suitable for the temperature range of 700-1300°C or more is developed, which depends on the linear relationship between XRD FWHM (the full width at the half maximum of X-ray diffraction peak) and isochronal annealing temperature over about 700°C. The subsequent application test demonstrated that the sensor remained no damage in the very harsh conditions as well as possessed a less than +5% of the relative temperature error. Therefore, the neutron-irradiated 6H-SiC can be employed as a kind of non-invasive temperature measurement sensor to determine the temperature of closed, high-speed rotating and difficult-to-access parts on a running machine such as internal-combustion engine pistons, turbine blades and so on.

Abstract: Thin films of Cu-In-Se (CISe) photoabsorber with overall composition of CuIn3Se5 were deposited onto glass/ITO substrates by using physical vapour deposition (PVD) technique. Thermal conditions for the substrates during deposition process and following thermal annealing were selected with the purpose to prepare polycrystalline n-CuIn3Se5 photoabsorber layers for the hybrid photovoltaic structures based on inorganic photoabsorber and conductive polymer functional layers. It was found, that the CISe layers deposited at the temperature of substrate of 200 °C and annealed at the temperature range of 450-500 oC in vacuum and double annealed in argon and vacuum at 500 oC demonstrate high photosensitivity and photoconductivity under white light illumination of 100 mW/cm2 intensity. Obtained results show the chalcopyrite structure of prepared photoabsorber films with good adhesion to the glass/ITO substrate.

Abstract: Due to the inertness of the intrinsic (nondoped) amorphous SiC (i-aSiC) material to the chemical impact, for making it porous by the electrochemical etching method, one must use the electrolyte solution with an appropriate composition. For this purpose we have found that besides the use of solutions containing surface activation agent (Triton X-100 for example), one can use also solutions containing oxidation agent. In this report we present the results obtained with electrolyte solution in which H₂O₂ plays the role of oxidation agent. Results showed that with appropriate ratio of components in the HF/H₂O/H₂O₂ solution, we can manufacture a porous layer in the i-aSiC thin film with the porosity similar to the porosity of the porous layer obtained by etching in the HF/H₂O/Triton X-100 solution with optimal composition. Thin film of i-aSiC material with porous surface layer can be used in different types of sensors.

Abstract: IR spectra of mixtures of light and heavy water seem to provide a clear evidence for the existence of substructures, each of which may be assigned to a particular kind of water molecule on the basis of their correlation with the local environment. These substructures have been related to three different populations named correlated, non correlated and intermediate according to their degree of correlation. Experimental data analysis show that, in a mixture of H2O-D2O, each population participates differently to the solution process.

Abstract: Magnetostrictive/piezoelectric hybrid composites have recently attracted renewed interest as high sensitivity sensors and actuators. One of the most common used geometry consists in laminated amorphous magetostrictive metal/piezoelectric layers, and the maximum magnetoelectric effect has been found at the electromechanical resonance of the system. Here we present results concerning the fabrication of such laminate composites sensor by using Vitrovac 4040^® (Fe₃₉Ni₃₉Mo₄Si₆B₁₂) as the magnetostrictive amorphous component and two different piezoelectric polymers: poly (vinylidene fluoride) (PVDF) and 2,6(β-CN)APB/ODPA (poli 2,6) polyimide, a new high temperature piezoelectric polymer. We have measured room temperature induced magnetoelectric voltages of 79.6 and 0.35 V/cm.Oe at the magnetoelastic resonance of the laminate when using PVDF and poli 2,6 polyimide as piezoelectric components. We have also tested the magnetoelectric response of both laminated composites at temperatures up to 85 °C, and we have observed that the PVDF polymer piezoelectric response quickly decays. Even if the induced magnetoelectric voltage is low, we discuss the advantage of using new piezoelectric polymers due to their good performance at high temperatures, up to 200 °C, making these laminate composites suitable for high temperature applications.

Abstract: Multiwall carbon nanotubes (MWCNT) network “Buckypaper” was made by the vacuum filtration method of MWCNT aqueous suspension. The sensitivity of multi-wall carbon nanotube (MWCNT) networks of randomly entangled pure nanotubes to various organic solvent vapors (tetrahydrofuran, methyl ethyl ketone, and ethanol) has been investigated by resistance measurements. The results demonstrate that the network electrical resistance increases when exposed to organic solvent vapors, and a reversible reaction is observed when the sample is removed from the vapors. The investigated MWCNT networks could be potentially used as sensing elements for sensitive and selective organic vapor detection.