Investigation of the Influence of Grinding on Regions near the Surface of Steel by Ultrasonic Surface Waves

The applicability of surface wave velocity measurements as a nondestructive test method to investigations of deformation layers with preferred orientations and residual stresses has been examined at steel C70W2. The residual stresses in various directions parallel to the surface have been detected from changes of velocity caused by a stress-free annealing. From the anisotropy and the frequency dependence of velocity the existence of a surface layer with preferred orientations has been deduced and such characteristic parameters as preferred orientation and depth have been estimated. The results have been compared and completed with X-ray texture investigations and data from Barkhausen noise.     

Optical and X-ray studies of a four component cyano liquid crystal mixture: Comparison of properties with that of a similar mixture

Optical and X-ray studies have been conducted on a four component liquid crystal mixture (code name 2013) with cyano–end groups in all the four components and a lateral substitution of fluorine atom in one of them. The variations in the optical birefringence with temperature, have been investigated and the thermal dependence of polarisability anisotropy and orientational order parameter have been evaluated. X-ray studies have been conducted to determine the effective molecular characteristics such as apparent molecular length and inter molecular distance and their variations with temperature. From nature of molecular alignment as envisaged from X-ray photographs the order parameter variation with temperature has been determined and compared with macroscopic order parameter variation as determined from birefringence studies. The results have been compared with these obtained for another structurally similar four-component liquid crystal mixture (code name 2014) with isothiocyanato end group in place of cyano.     

Effect of neutron irradiation on stratigraphy in calcium fluoride single crystals

Natural single crystals of calcium fluoride have been cleaved along {111} planes and a number of matched pairs have been obtained. One piece from etch pairs have been irradiated with thermal and pile neutrons, the flux varying from 1.3 × 10⁴ to 3.0 × 10¹³ neutrons cm⁻². After irradiation, the irradiated and their non-irradiated counterparts have been matched. They were then etched simultaneously in 0.2 N hydrochlorid acid for the same period. The stratigraphical etch patterns produced have been studied optically. There is no exact correspondence of the stratigraphical etch patterns have been observed on the irradiated and non-irradiated matched pairs. The disappearing in the stratigraphical pattern of the irradiated crystals increases with increase in the dose of irradiation. The implications are dicussed.     

Growth, phase transitions and properties of Li2Ti3O7 crystals

Metastable crystals of Li₂Ti₃O₇ of dimensions up to a diameter of 20 mm and a length of 20 mm have been grown by the Czochralski method from oriented seeds. The effects of seed orientation, growth atmosphere and dopant on crystal growth have been studied. Phase transition processes in the crystals and the H phase structure have been measured. Optical and acoustic properties of the crystals have also been determined.     

The growth of single crystals of langbeinites Rb2Cd2(SO4)3, Tl2Cd2(SO4)3, K2Co2(SO4)3, and their phase transitions

Single crystals of dicadmium dirubidium sulphate and dicadmium dithallium sulphate have been grown from non-stoichiometric aqueous solutions by various methods. Optical and thermal properties in the vicinity of their phase transitions have been studied. Polycrystalline samples of dicobalt dipotassium sulphate have been prepared using Bridgman method. Optical and specific heat measurements have shown a new phase transition at −148°C.     

Carbonaceous Mesophase and Carbon Fibers

I esteem it a great honor to have been invited to this meeting. On the other hand, I am a little confused by the invitation, because I am not a specialist in liquid crystals but only in carbon materials. The main reason why I have been invited to this meeting is, I think, probably because I first originated the fundamental procedure for producing carbon fibers from pitches and have been developing this field for the past 15 years. I also presume that the preparation of carbon fibers from mesophase pitches especially claims your interest. From these points of view I have prepared the subject matter of my lecture.     

Bulk crystals of PbTe synthesized by the iodide method

Bulk crystals have been prepared for the first time from PbTe synthesized by low-temperature iodide method. Their basic structural, physico-chemical and electrical parameters as a result of certain technology conditions have been investigated.     

Growth and characterisation of Na3Sb2F9 single crystals

Optically clear single crystals of Na₃Sb₂F₉ have been grown from solution by slow evaporation technique at constant temperature. Crystals of sizes upto 30 × 8 × 8 mm have been grown in a period of three months. Vickers microhardness measurements have been carried out on these crystals. Attempts have also been made to understand the nature of the cracks developed around the microindentation. Single crystal X-ray diffraction studies have been carried out and cell parameters are determined.     

Growth of different habits of lead bromide crystals in silica gel by the new gel technique

Lead bromide crystals of high optical perfection and of different habits have been grown in silica gel by new gel technique starting from colloidal lead tartrate and KBr solution. pH is found to be not a factor for habit modification. Certain habits of the grown crystals exhibit interesting surface features. The growth conditions have been optimized and the various aspects of the growth process have been widely investigated.     

Micro- and nanostructures in lithium niobate single crystals doped with lanthanides

Lithium niobate single crystals doped with lanthanides (Gd, Er) and nominally pure single crystals of congruent and stoichiometric compositions have been grown under time-dependent thermal conditions. Regular growth domain microstructures and periodic nanostructures have been investigated by optical microscopy and atomic force microscopy with a step from 10 to 100 nm. Comparative investigations of the Raman spectra of lithium niobate single crystals of different compositions have been performed.     

Ionic conductivity studies in KCl–NaCl mixed crystals

Single crystals of KCl and a few compositions of KCl-NaCl mixed crystals were grown from melt by Kyropoulos technique. Ionic conductivity measurements have been carried in these crystals in the temperature range 100 to 400 °C. The activation energy for the migration of charge carriers have been calculated from the conductivity-temperature plots of these crystals and the results obtained were discussed.     

Field-assisted ion exchange between molten alloys and soda lime glass

Using molten alloys, the electrolysis of soda lime glass has been studied. Ions from a molten anode can be driven into soda lime glass by applying a modest electric potential. The anode current densities have been measured. The temperature and potential dependences have also been measured. The current-time behavior depends on the ion exchange. In a molten alloy the most easily oxidized metal is suited for exchange.     

Similar quartz crystallographic textures in rocks of continental earth’s crust (by neutron diffraction data): I. Quartz textures in monomineral rocks

Quartz crystallographic textures in different rocks have been investigated by neutron diffraction. Various types of crystallographic textures of quartz-bearing mineral associations in monomineral and multiphase rocks from a representative collection of samples have been revealed and classified. Experimental investigations have been performed on special neutron texture diffractometers designed at the Frank Laboratory of Neutron Physics and mounted in the seventh channel of the IBR-2 reactor at the Joint Institute for Nuclear Research (Dubna).     

电子辐照对VO2薄膜热致相变过程中光学性能的影响

利用能量为1.7MeV,注量分别为10^13-10^15/cm^2,的电子束辐照二氧化钒薄膜,对辐照及未辐照样品进行了UV－VIS,XPS参数测试,并测量900nm处光透射性能随温度的变化,发现电子辐照导致了VO2薄中的V离子价态由V^4向V^5 转变,薄膜热致相变前后的光透射比随注量增加变化较小,只在注量为10^14/cm^2时光透射比减小得较明显,相变温度点及热滞回线宽度随注量增加出现显著变化,并对有关的结果进行了讨论。     

Determination of the crystallite size in epitaxial layers of PbTe by means of X-ray diffraction rocking curves

To prove the influence of the crystallite size (dimension of coherent regions parallel to the reflecting lattice planes) on the rocking curve of single crystals, half widths measured on epitaxial layers of PbTe have been evaluated. It results from statistical analysis of the data that there exist a significant influence of the crystallite size. The crystallite sizes have been calculated from these data using two simple models. The values have orders of magnitude as expected and agree with data from electron microscopy. The method as described here can be applied in suitable cases to get an additional parameter for characterizing the structural perfection.     

Enhanced Eu emission by non-radiative energy transfer from Tb in zinc phosphate glass

Energy transfer studies have been made in terbium-europium-doped zinc phosphate glass at room temperature. Enhancement of the Eu³⁺ (⁵D₀→⁷F manifold) emission and a decrease in the Tb³⁺ emission (⁵D₄→⁷F manifold) have been observed as a result of energy transfer from Tb³⁺ ions to europium ions. The energy transfer mechanisms have been found to be mainly electric dipole-dipole in nature. The energy transfer efficiencies, transfer probabilities and average donor-acceptor distances have been calculated.     

Comparative Study of the Thermal Dependence of the Birefringence and Order Parameter of Two nOCB Compounds

The optical properties, birefringence and order parameter of two alkoxycyanobiphenyls (nOCBs, where n = 5 or 8) have been studied as a function of temperature. The variation of orientational order parameter has been determined experimentally. Theoretical order parameter values have also been computed in the smectic range using McMillan potential and in the nematic range using Maier–Saupe potential and compared with the experimentally obtained values. The variations of polarizabilities with temperature have also been evaluated from density variation and birefringence studies.     

Application of the iodide synthesis to the preparation of indium arsenide bulk crystals and epitaxial layers

Bulk crystals and epitaxial layers have been prepared from iodidely synthesized InAs. Their parameters have been studied and compared with those of high-temperature synthesized InAs. The synthesis mixture composition substantially effects the electrical parameters of the samples. Iodine is supposed to be a donor-acting impurity in iodidely synthesized InAs.     

Photoconductivity of amorphous CdS films

The photoconductivity of amorphous CdS films, vacuum evaporated onto cooled substrates, has been investigated. The conditions and possible reasons for the appearance of a low temperature maximum in the photoconductivity temperature dependence of chalcogen rich samples have been found. The presence of a slow recombination centre related to the lone pair level of the one-fold coordinated negative chalcogen has been assumed. The energy necessary for both the electron (2 eV) and hole (0.4 eV) escape from this centre has been determined. Photoinduced changes in photoconductivity have been examined as well.     

Oblique Phonons in Raman Scattering and IR Reflection of TeO2 Crystal

The Raman scattering and IR reflectivity have been investigated for different crystal configurations. The contours of reflectivity spectra have been calculated. The angle dependence of polar vibrational modes in both reflectivity and Raman spectra have been investigated. The peculliarities of the transition from longitudinal mode to transverse one and vice versa both with and without changing of symmetry have been obtained. The phonon parameters and effective ionic charges of the anions and cations have been determined. It has been shown that there exists an effective ionic charge anisotropy of the oxygen and tellurium ions.