Institute of Fundamental Technological Research

The changes in the optical, structural, mechanical properties, and chemical composition of Y3Fe5O12/Gd3Ga5O12 (YIG/GGG) single crystal structures grown by liquid phase epitaxy, particularly at the interface between the film (Y3Fe5O12) and the substrate (Gd3Ga5O12), are studied. Different complementary techniques, including optical microscopy, local spectrophotometry, electron probe microanalysis, micro-Raman spectroscopy, and nanohardness analysis are used. The main finding of the study is an experimental approach, in which the probe of the measuring device (light beam, electron beam, nanoindenter) is directed to the surface of the studied sample in a direction perpendicular to the direction of structure growth, and the surface is scanned along this direction. It allows to obtain the profiles of changes in refractive properties, nanohardness, optical absorption, chemical composition, and intensity of phonon spectrum bands at the transition from the GGG to YIG. It is established that the lengths of the scanning intervals, at which the changes of various properties of a specimen occur, differ significantly. The obtained results are affected by the size of the probes and by the sensitivities of both the particular measuring method and the particular physical property of the material to changes in the chemical composition and crystalline structure of the sample.

electron probe microanalysis, gadolinium gallium garnet, interface, nanohardness, Raman scattering, spectrophotometry, yttrium iron garnet

Spatial changes of optical and mechanical properties of doped lithium niobate (LN, LiNbO3) single crystals are investigated. The crystals are doped with copper ions by thermal diffusion at elevated temperatures. LiNbO3 crystal absorption spectra are recorded in a direction perpendicular to the direction of diffusion. The concentrations of copper ions are calculated using the Smakula–Dexter formula. To determine a relation between changes of optical and mechanical properties, the hardness profiles of the doped crystals are investigated by the nanoindentation technique. Young's modulus and hardness are specified in accordance with the Oliver–Pharr method.

The results of X-ray diffraction studies on structural changes in the near-surface layers in the NiTi alloy caused by nitrogen-ion implantation with the energy E = 50 keV and the fluence D = 1018cm°2 are presented. X-ray diffractometry, using the Philips diffractometer type X’Pert in the Bragg–Brentano geometry, was used to identify the phase composition of NiTi alloy. For layer by layer analysis of structural changes in the near-surface layers, the D8 Discover Bruker diffractometer with polycapilar beam optics was used. The ion-implanted NiTi alloy in the near-surface layer exhibits five phases: the dominating austenite phase, two martensitic phases and a small amount of the Ni4Ti3 and NTi phases. Along with the decreasing thickness of the near-surface layer investigated in material an increasing fraction of the Ni4Ti3 and NTi phases was observed. With the thickness of this layer about 340 nm, besides still existing the austenite, Ni4Ti3 and NTi phases, only one martensitic phase is present in the alloy. Further decrease of the thickness of the near-surface layer to about 170 nm leads to the increasing fraction of the Ni4Ti3 and NTi phases.

X-ray diffraction, ion implantation, shape memory alloy, nitinol, phase composition

In the present study we report the changes in the modified near-surface layer on NiTi shape memory alloy, caused by ion implantation as well as their influence on the structure and mechanical properties of this material. Experimental results of an inhomogeneous structure and tribological properties of implanted NiTi are discussed in this paper.

shape memory NiTi alloy, Ion implantation, DSC, X-ray diffractometry, TEM

A new setup for light depolarization measurements was designed. Two innovative elements have been introduced. The first is an electronic system which enables depolarization ratio to be registered directly. The second is a system of temperature control allowing effective implementation of a temperature–time program according to the particular requirements. Direct registration of depolarization ratio instead of intensity of depolarized light for individual components (parallel and perpendicular), as is performed in the usual apparatus, allows elimination of light scattering effects because of the insensitivity of depolarization ratio to the scattering level. Application of the new setup was shown for crystallization and melting of isotactic polypropylene (i-PP). Comparison of phase transitions in i-PP, as registered by light depolarization and DSC, indicates some differences. Possible sources of the observed differences are discussed.

Light depolarization, Polymers, Crystallization, Melting, Kinetics of phase transitions

This paper reports the application of nitrogen ion implantation for modification of a shape memory alloy. It is known that the problem of creating a protective surface coating for the shape memory alloy is the most acute for potential applications of this material. Thus, the problem of increasing surface protective properties and, at the same time, simultaneous preservation of functional properties of shape memory materials is a subject of research and development [Pelletier H, Muller D, Mille P, Grob J. Surf Coat Technol 2002;158:309.]. The surface characterization of nitrogen implanted (fluence 1018 cm−2 and energy 50 keV) equiatomic commercial NiTi alloy samples was performed with the assistance of high resolution transmission electron microscopy (HTEM) techniques and modifications of phase composition before and after irradiation are studied at room and martensitic transformation temperatures by X-ray diffraction methods. Differential scanning calorimetry (DSC, TA Instruments) was used to characterize the transformation sequence and transformation temperatures for the initial and surface-modified materials. Experimental results of an inhomogeneous structure of near-surface layers in the ion-implanted NiTi alloy are discussed in this paper

Shape memory NiTi alloy, Ion implantation, DSC, X-ray diffractometry, TEM