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The main electrical and dielectric properties of Au/TiO 2 /n-4H-SiC (MIS) type Schottky barrier diodes (SBDs) have been investigated as functions of frequency and applied bias voltage. We believe that the use of high dielectric interfacial layer between metal and semiconductor can improve the performance of Schottky diodes. From the experimental data, both electrical and dielectric parameters were found as strong function of frequency and applied bias voltage. The Fermi energy level (E F ), the concentration of doping donor atoms (P), barrier height (Φ B ) and series resistance (R s ) values were obtained from reverse and forward bias C-V characteristics. The changes in E F and N D with frequency are considerably low. Therefore, their values were taken at about constant. The real and imaginary parts of dielectric constant ( , e e ¢  ), tangent loss (tanδ), ac electrical conductivity (σ ac ), and real and imaginary parts of electric modulus (M′ and M″) values were also obtained from reverse and forward bias C-V and G/ω-V characteristics. In addition, the voltage dependent profiles of all these electrical and dielectric parameters were drawn for each frequency. These results confirmed that both electrical and dielectric properties of Au/TiO 2 /n-4H-SiC (MIS) type SBD are quite sensitive to both the frequency and applied bias voltage due to surface polarization, density distribution of interface traps (D it ), and interfacial layer.

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The Ni-based superalloy Inconel 625 is extensively used owing to its high strength, excellent fabricability, good weldability and outstanding resistance to high temperature corrosion against aggressive environments. However, despite its unique properties and extensive use, its wear resistance is in some cases unsatisfactory. In this study, Inconel 625 was subjected to boriding treatments at different temperature and different durations. Microstructural characterization was made by conventional methods (scanning electron microscopy, optic microscopy, X-ray diffraction analysis) and mechanical characterization was made by microhardness and micro-abrasion wear test. Micro-abrasion wear tests were conducted against a AISI 52100 steel under 5, 7.5 and 10 N load in a 25 wt.% SiC slurry at room temperature. Microstructural results revealed that multi-phase boride layer (nickel boride, chrome boride and iron boride) and silicide layer were formed. The hardness and thickness of the boride layers were found to be 1175-2432 HV 0.1 and, 6.61-92.03 μm, respectively. Depending on the boriding temperature and time. In spite of silicide layer formation the wear resistance of borided Inconel 625 alloy increased up to 8 times thanks to the increase in the surface hardness which was caused by boriding process. The boriding treatment caused a transition in the wear mechanism. While grooving was observed in the untreated Inconel 625 samples, mixed (grooving and rolling) and rolling type wear was predominant in the borided samples.

A ceramic sample of a layered cuprate of Tl2Ba2Ca2Cu3Ox and Tl2Ba2Ca1Cu2Ox, so-called Tl-based 2223 and 2212 compounds, was investigated by the measurement of the dielectric constants (ε′ and ε′′), the dielectric loss (tanδ), and the conductivity (σac) as a function of temperature (80–300 K) and frequency (100 Hz–10 MHz). A negative capacitance phenomenon has been observed and it is believed that the negative capacitance effect is due to the polarization effect. The negative dielectric constant has been calculated from the negative capacitance. The dielectric constant (ε′) and the dielectric loss (tanδ) show strong dispersions at lower frequencies. The dielectric properties of the sample were found to have strong frequency and temperature dependence.

Wear behavior of four kinds of thermally sprayed coatings on steel tooth drill bits have been investigated by micro-abrasion wear test. The fixed ball micro abrasion wear test was applied for bare substrate and for thermal sprayed substrate of each sample. SiC and Al2O3 abrasive powders with grain size of 5 µm were used in the abrasion experiments. Ball rotational speed values of 140 rpm and applied loads of 1, 2 and 3 N were used. Experimental results show that the wear mechanisms of the coatings are micro-grooving and micro-rolling. Application of the coatings was found to have an influence on the wear mechanism of the samples. The results also indicate that wear resistance of thermally sprayed coatings can be correlated to porosity, hardness, plasticity, toughness, and cohesion properties of the coatings. In addition, wear resistance of the coated samples had increased in accordance with the increasing coating thickness.