Materials Literature
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By means of a sol–gel method, we prepare layered-perovskite samples of La2—2xCa1+2xMn2O7 (x = 0.3) at synthesis temperatures from 1000 to 1200 °C. The grain size changes from 20 to 45 nm. A magnetoresistance above 25% at low temperatures is acquired in a field of 0.8 T. We also find that decreasing grain size is deter…
Results of DC electrochemical measurements of four Ni‐base alloys are presented. The tests were conducted in 1 percent sulphuric acid, containing 0.2 percent chlorides at temperature 353K. Gravimetric test, performed in the same conditions, revealed excellent properties of alloy signed A3. Pitting corrosion of alloy A…
We report first-principle electronic structure calculations of the three representative minerals of the platinum group: cooperite (PtS), braggite (PdPt3S4) and sperrylite (PtAs2) using the Tight-Binding Linear Muffin Tin Orbital (TB-LMTO) technique. We predict non-metallic behaviour for all three minerals with semicon…
The paper deals with the detail investigation of the smooth motion of the single plane domain wall (PDW) in the vicinity of the initial/steady position and analysis of the mechanisms of Barkhausen noise generation during PDW jump-like motion.
Interest in the study of the dynamic properties of materials subjected to high-rate loading has been motivated by two circumstances. First, the design of structures and evaluation of technological processes require a correct consideration of the properties of the material to be used. Second, the study of the macroscop…
The creep behavior of three types of silicon carbide fibers that have been fabricated via chemical vapor deposition is described. The fibers exhibit only primary creep over the range of conditions studied (1200°–1400°C, 190–500 MPa). A transmission electron microscopy study of the microstructural development that is i…
Nano-grain sized β-SiC was prepared with various additives by hot-pressing in Ar. The relative bulk densities were more than 95 %. As-sintered bodies were composed of equiaxed grains. Amorphous phase existed at grain boundaries in each as-sintered material. Tension tests were performed at the initial strain rates from…
This study reports the influence of preforming on the final thickness distribution of superplastically formed domes. It is very common to see about 50% thickness difference between apex and periphery of domes formed from initially uniform blanks. If the initial shape of the blank is modified properly by preforming, th…
We show that the layer groups, describing the symmetry of compatible (coherent, permissible) ferroelastic domain walls, are polar. From this it follows that all compatible ferroelastic walls in dielectric crystals can be spontaneously polarized. We shortly discuss the feasibility of reversing the spontaneous polarizat…
Eu-and Ce-Eu-containing quartz glasses obtained by a direct sol-gel-glass transition are investigated. It is discovered that the conversion of a xerogel into a glass leads to lowering of the symmetry of the Eu3+ optical centers from hexagonal to orthorhombic and a many-fold increase in the efficiency of the excitation…
The incorporation of heavy metal ions into simulated corrosion films has been investigated using spectroscopic and electrochemical techniques. The films were formed by electrodeposition of the appropriate oxide (hydroxide) onto a graphite substrate. Synchrotron X‐ray absorption spectroscopy (XAS) was used to determine…
α-Chloromethyl-α-methyl-β-propiolactone (CMMPL) was synthesized by dehydrohalogenation of α,α-dichloromethyl-β-propionic acid which was obtained by chlorination of α,α-hydroxymethyl-β-propionic acid (DMPA). Due to high strain of the four-numbered ring, CMMPL can be polymerized by ring-opening with or without an initia…
The effects of applied strain on the resistivity of Al thin film metallization interconnects have been measured with a novel methodology that uses thermal expansion mismatch to produce the strain. The interconnect volumetric strain is induced by thermal cycling of passivated and unpassivated interconnects between ≈70…
Tests have been performed at about 25°C in both natural and chlorinated sea waters on couples of nickel–aluminium bronze (NAB) and Zeron 100 (Z100) superduplex stainless steel. Two NAB/Z100 area ratios (1 : 1 and 1 : 10) were used in exposures of 60 days. The results in natural sea water showed severe localised corros…
Circularly polarized photoluminescence (CPPL) was characterized for rod-like molecules of Exalite 428 helically arranged in a chiral-nematic liquid crystalline film. With an unpolarized excitation at 370nm, CPPL intensities measured at 428nm, and a selective reflection wavelength ranging from 7.2 to 72.6mum, the obser…
Lead zirconium titanate (Pb(Zr 0.5 Ti 0.5 )O 3 , PZT) ferroelectric thin films were successfully deposited on platinum‐coated silicon substrates and platinum‐coated silicon substrates with a PbTiO 3 interlayer by using a modified sol–gel spin‐coating process, using zirconium oxynitrate dihydrate as the zirconium sourc…
Boehmite powder has been prepared by hydrolysing aluminium iso-propoxide and peptising with nitric acid. This amorphous boehmite undergoes a series of phase transitions (γ-AlOOH → γ-Al2O3 → δ-Al2O3 → α-Al2O3 ) on heating. Thermal analysis and phase determination using XRD and IR spectra of powder calcined at different…
A simplified phenomenological theory of the temperature dependence of the second-order elastic constants of crystals is considered. The temperature dependences of the second-order elastic constants are calculated for a series of cubic crystals with various types of predominant chemical bonding. Satisfactory agreement…
Single crystals of KTiOPO 4 (KTP) and NaTiOPO 4 (NaTP) show pronounced pyroelectric behaviour. In order to determine the origin of this property on an atomic scale, X-ray diffraction measurements have been carried out at several temperatures between 100 and 600 K. Modelling of the electron density and the evolution of…
The results of measurements of spin correlations and magnetonuclear cross-correlations (MNCCs) in the system 154 Sm 1− x Sr x MnO 3 with the perovskite structure ( x =0.25,0.4) in the low-temperature phase in magnetic fields 0< H <1 kOe are presented. These are the first measurements performed by the small-angle polar…