In this work studies of barrier height local values are presented. Distribution of the gate-oxide EBG(x, y) and semiconductor-oxide EBS(x, y) barrier height local values have been determined using the photoelectric measurement methods. Two methods were used to obtain the local values of the barrier heights: modified Powell-Berglund method and modified Fowler method. Both methods were modified in such a way as to allow determination of the EBG(x, y) and EBS(x, y) distribution over the gate area using a focused UV light beam of a small diameter d = 0.3 mm. Measurements have been made on a series of Al-SiO2-Si(n+) MOS structures with semitransparent (tAl = 35 nm) square aluminum gate (1 x 1 mm2). It has been found that the EBG(x, y) distribution has a characteristic dome-like shape, with highest values at the center of the gate, lower at the gate edges and still lower at gate corners. On the contrary, the EBS(x, y) distribution is of a random character. Also, in this paper, both barrier height measurements have been compared with the photoelectric effective contact potential difference fMS(x, y) measurements. These results show good agreement between distribution of the barrier heights EBG(x, y) and EBS(x, y) measurements and independently determined shape of the effective contact potential difference fMS(x, y) distribution.
The addition of hard ceramic particles of nc-(Ti,Mo)C in carbon network into Ti matrix has been proved to be an efficient way to enhance their properties. The purpose of this work was to analyze the corrosion, tribological, mechanical and morphological effects of combining nc-(Ti,Mo)C/C with titanium metal, to create a unique composite via selective laser melting technique (SLM). Composites with different weight percentage (5, 10 and 20 wt %) of ceramic phase were produced. The samples of pure Ti and Ti-6Al-4V alloy were also tested, as a reference. These composites were examined for corrosion resistance in body fluid (artificial saliva solution). Moreover, the properties of titanium composites reinforced with nc-TiC powders were compared. It was stated that mechanical properties were significantly improved with increasing amount of nc-(Ti,Mo)C/C in Ti matrix. In terms of corrosion resistance, the composites showed worse properties compared to pure titanium and Ti-6Al-4V alloy, but better than TiC-reinforced composites.
Code Excited Linear Prediction (CELP) algorithms are proposed for compression of speech in 8 kHz band at switched or variable bit rate and algorithmic delay not exceeding 2 msec. Two structures of Low-Delay CELP coders are analyzed: Low-delay sparse excitation and mixed excitation CELP. Sparse excitation is based on MP-MLQ and multilayer models. Mixed excitation CELP algorithm stems from the narrowband G.728 standard. As opposed to G.728 LD-CELP coder, mixed excitation codebook consists of pseudorandom vectors and sequences obtained with Long-Term Prediction (LTP). Variable rate coding consists in maximizing vector dimension while keeping the required speech quality. Good speech quality (MOS=3.9 according to PESQ algorithm) is obtained at average bit rate 33.5 kbit/sec.
The report presents research efforts on the synthesis of Zn/MoS2 composite coatings by electrochemical reduction from a sulphate-borate bath containing MoS2 powder as a dispersion phase at various concentrations. The structure of the Zn/MoS2 composite coatings was characterised and the effect of MoS2 particles embedded on their microhardness was evaluated. The coatings produced are characterized by a compact, homogeneous structure and a good connection to a steel substrate. The incorporation of MoS2 particles into the zinc matrix has an influence on the structure and morphology of the Zn/MoS2 composite coatings. It was found that the presence of MoS2 particles increases surface roughness along with coating hardness. The incorporation of the MoS2 particles into the zinc matrix slightly improves the corrosion resistance compared to Zn coatings, making the corrosion potential shift towards more electropositive values.
Thermodynamic optimizations of the ternary Fe-B-Mo system and its binary sub-system B-Mo are presented. The Fe-B-Mo description is then extended to the quaternary Fe-B-Cr-Mo system by assessing the ternary B-Cr-Mo system. The thermodynamic descriptions of the other binaries (Fe-B, Fe-Cr, Fe-Mo, B-Cr, and Cr-Mo) and the other ternaries (Fe-B-Cr and Fe-Cr-Mo) are taken from earlier studies. In this study, the adjustable parameters of the B-Mo, Fe-B-Mo, and B-Cr-Mo systems were optimized using the experimental thermodynamic and the phase equilibrium data from the literature. The solution phases of the system (liquid, bcc and fcc) are described with the substitutional solution model, and most borides are treated as stoichiometric phases or semistoichiometric phases, using a simple two-sublattice model for the latter. The system’s intermetallic phases, Chi, Mu, R, and Sigma (not dissolving boron) as well as boride M3B2, based on a formulation of (Cr,Fe)(Cr,Fe,Mo)2(B)2, are described with a three-sublattice model. Reasonable agreement is obtained between the calculated and measured phase equilibria in all four systems: B-Mo; Fe-B-Mo; B-Cr-Mo; and Fe-B-Cr-Mo.
The aim of this paper is to present the procedure test for calibration and validation of the numerical model for X22CrMoV12-1 steel multilayer welding. On the real multilayer weld was described how to arrange the whole experiment in order to obtain not only relevant input data but also verification data. Tests on a specially prepared specimen, welded with 8 beads in 4 layers, allows to determine the actual geometry of the single welded beads, registration of welding thermal cycles and the hardness distribution in successively deposited beads together with determining the heat influence of subsequent layers. The results of the real welding tests were compared with the results obtained from the numerical simulations and extended by the calculated stresses and distortions distributions of the tested specimen. A new, improved hardness prediction algorithm for high-alloy martensitic and bainitic steels was also proposed.
The paper presents results of investigation of microstructure and micro-hardness for material of ZnO varistors applied to 110 kV surge arrester and surge arrester counter. The research combined two pairs of varistors, each consisted of one varistor subjected before to operation, while the other one was brand new unit and constituted a reference. All varistors were made of the same material by the reputable manufacture. The tests revealed a different degree of the material degradation for varistors subjected before to operation. This also refers to different degradation mechanism observed for the material of these varistors, if typical effects of degradation of aged ZnO varistors were considered as a reference. Physical state of spinel in the microstructure had a significant impact on the material degradation, however a considerable loosening of the microstructure associated with bismuth oxide was observed too. It was surprising, since the precipitates of the bismuth oxide phase most often showed very good binding to the ZnO matrix and high resistance to associated electrical, thermal and mechanical effects. The degradation effects in the ZnO matrix proved to be limited only.
In this study, microstructural and crystallographic properties of phase transformations occurring with thermal effect in Fe-XMn-Mo-Si (X = 15.14wt.% ve 18.45wt.%) alloys have been investigated. The effects of (wt.%) Mn rates in the alloy on the characteristics of phase transformations were investigated by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). SEM and TEM investigations was observed that two different martensite (ε and α') structures were formed in austenite grain. In addition, in TEM observations, the interface regions were selected over the bright field image. Crystallographic orientation relationships were obtained by the analyses of electron diffraction patterns from the interface regions. γ → α' type transformation was observed for α' particle formation, and orientation relationship was found as (1–11)γ // (011)α', [101]γ // [1–11–]α' and, γ → ε type transformation was observed for ε martensite plate formation, and the orientation relationship was found as (1–11–)γ // (0002–)ε, [1–1–0]γ // [2–110]ε. It was noticed that this orientation relationships were compatible with the literature (Kurdjumov-Sachs and Shoji-Nishiyama orientation relationship). Precipitation phase (carbide) formation was observed in microstructure analyses. The changes in the magnetic properties of the alloys having different rates of Mn as a consequence of thermal effect phase transformations was investigated by using Mössbauer Spectroscopy. The internal magnetic field, volume fractions (transformation rates), isomer shift values and magnetic characteristics of the main and product phases were revealed by Mössbauer Spectroscopy. In the Mössbauer Spectrum, it was noticed that ε-martensite and γ-austenite structures showed paramagnetic single-peak, and α'-martensite showed ferromagnetic six-peaks.