Pavel Švanda

Magnetic and transport properties of the V2–VI3 diluted magnetic semiconductor Sb2−xMnxTe3

We have measured electrical and magnetic properties of single crystals of Sb2−xMnxTe3 with x=0–0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2–VI3 diluted magnetic semiconductors, at least in the range of magnetic impurity and carrier concentrations studied here.

Improving the strength of adhesively bonded joints through the introduction of various surface treatments

Abstract The aim of this paper is to model an interface adhesion and failure mechanism of single lap joints, subjected to tensile loading, focusing on the effects of various surface treatments, including surface characterization parameters, such as surface roughness and contact angle of adherend surfaces. The applied surface treatments are sandblasting, etching, anodic oxidation and hybrid processes. The influence of surface treatment techniques and conditions on single lap joint strength and interfacial properties is investigated by performing a static tensile test. A numerical approach, which is a cohesive zone model, is implemented using ABAQUS™ and introduced to create a correlation between maximum interface traction and surface processing parameters, such as surface roughness and work of adhesion. As a result of experiments, an etching plus sanding process was found to provide the best single lap joint performance (8726 N), having surface roughness of Ra = 2.93 μm and work of adhesion, Wa = 119.4 mJ/m2. Based on numerical solutions, a correlation between maximum interface traction and type of surface treatment process has been established, taking certain assumptions into consideration.

Mechanism of degradation of stabilized corrosion‐resistant steel during the welding cycle

Purpose – The purpose of this paper is to clarify the destabilisation mechanism that occurs with two types of ferritic corrosion‐resistant steel during the welding cycle.Design/methodology/approach – A series of experimental weld joints was made to verify the actual response of non‐stabilised corrosion‐resistant steel, and of the same steel that had been stabilised by added titanium. The character and extent of the ensuing structural changes were analysed. The essential characteristics of degradation in the heat‐affected zone are evaluated using optical and scanning electron microscopy; individual phases are identified by means of EDX microanalysis. The underlying mechanism for the loss of stability is induced experimentally in several stages; depending on the thermal doping level and interaction with the environment during the welding process, phases of various types are precipitated. These phases subsequently are studied in connection with the original microstructural characteristics of the steel and th...

Magnetic and transport properties of the V[sub 2]–VI[sub 3] diluted magnetic semiconductor Sb[sub 2−x]Mn[sub x]Te[sub 3]

We have measured electrical and magnetic properties of single crystals of Sb2−xMnxTe3 with x=0–0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2–VI3 diluted magnetic semiconductors, at least in the range of magnetic impurity and carrier concentrations studied here.

Testing of pigmented coatings on thermal sensitised stainless steel

Purpose – The purpose of this paper is to verify the capability of pigmented coatings to mitigate the effects of thermal sensitisation of 430 stainless steel.Design/methodology/approach – Experimental weld joints of non‐stabilised ferritic corrosion resistant steel type AISI 430 were prepared. Protective coatings in several variants were applied to a number of weldments, subsequently subject to corrosion tests in SO2 and NaCl. The anticorrosive efficiency of the coatings was evaluated by means of normative visual assessment and metallographic analysis of the mechanism and depth of corrosion damage.Findings – Anticorrosive efficiency of the tested coatings was experimentally established under conditions where differences were identified in structural changes caused by welding, or resulting from mechanical damage to the coating. Differences in the progress of corrosion damage caused by phase changes in the heat‐affected zone were established.Practical implications – Tests of anticorrosive efficiency of coat...

Transport coefficients of titanium-doped Sb/sub 2/Te/sub 3/ crystals

Titanium-doped single crystals (c/sub Ti/ = 0 to 2/spl times/10/sup 20/ atoms cm/sup -3/) were prepared from the elements Sb, Ti, and Te of 5N purity by a modified Bridgman method. The obtained crystals were characterized by measurements of the temperature dependence of the electrical resistivity, Hall coefficient, Seebeck coefficient and thermal conductivity in the temperature range of 5-300 K. It was observed that with an increasing Ti content in the samples the electrical resistance, the Hall coefficient and the Seebeck coefficient increase. This means that the incorporation of Ti atoms into the Sb/sub 2/Te/sub 3/ crystal structure results in a decrease in the concentration of holes in the doped crystals. For the explanation of the observed effect a model of defects in the crystals is proposed.

Magnetic and transport properties of the V2–VI3V2–VI3 diluted magnetic semiconductor Sb2−xMnxTe3Sb2−xMnxTe3

We have measured electrical and magnetic properties of single crystals of Sb2−xMnxTe3 with x=0–0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2–VI3 diluted magnetic semiconductors, at least in the range of magnetic impurity and carrier concentrations studied here.

Magnetic and transport properties of the V 2-VI 3 diluted magnetic semiconductor Sb 2-xMn xTe 3

We have measured electrical and magnetic properties of single crystals of Sb2−xMnxTe3 with x=0–0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2–VI3 diluted magnetic semiconductors, at least in the range of magnetic impurity and carrier concentrations studied here.