Tatiana N. Sokolova

Microspectral investigation of hair of one girl during six years by laser emission analysis

Multiple chemical elements of clinical and nutritional interest were measured in the hair of a girl - cerebral palsy patient. Sixteen samples of hair were cut and investigated to determine time and nutrition trends by using laser and arc emission spectroscopy.

Studies of rejected dental Ti-implants by laser microspectral analysis

The surface of rejected dental implants was studied. It was clarified that the implant rejection happened in a case of incomplete osteointegration of implants, incomplete proliferation of a bone tissue in holes. In a turn, osteointegration depends on uniformity of deposition of a titanium-hydroxyapatite (Ti/HA) coating and the impurities composition of used materials. The excess of exterior elements imported at technological processes also influences on adhesion.

Prospects for the LIBS study of films using an axicon optical system

The features of the application of an axicon optical system for the LIBS sampling are described. For the axicon sampling, the crater depth is less than that for a conventional spherical lens. The zone of thermal effect around a sampling point is also reduced. The results obtained indicate that the axicon optical system is promising for the thin-film study.

Laser forming of emitting structure of metal-porous cathodes

Metal-porous cathode is an electrovacuum EHF device, providing a high density of emission current. The emitting surface of the device is usually obtained by ion etching. The emitting layer is made of a porous sponge of a refractory metal, usually tungsten. Through the pores of the sponge alkaline earth metals and their oxides are delivered to the emitting surface. One of the most important parameters of the cathode is a uniformity of emission, depending on regularity of the location of pores. We describe a method of laser modification of metal-porous cathode surface, instead of traditional ion etching. The preferences of laser etching are uniformity of pores, absence of deformation of surface, opportunity to specify the necessary size of the pores and the distance between them. Laser structuring of the cathode surface was implemented by laser micrograving. The resulting structure is a field of pores, diameter 15 μm, with spacing of 20 μm.

Laser formation of tip emitting structures with high aspect ratio on glass-carbon field-emission cathodes

Paper describes the method of creating the sharp emitting tips on the surface of a field- emission cathode. The needle-shaped structures with a high aspect ratio on the glass-carbon plate are produced by means of nanosecond laser micromachining. The operations of laser scribing, milling and cleaning were applied for fabrication of the single- and multi-tip field-emission cathode. The special technique of laser rough and fine milling provided high tips with sharp and smooth apexes. As a result we obtained the tips with aspect ratio up to 600. The tests of cathodes showed that high density of current emission and a shorter technological route of production to be reached.

Model of mechanical effect of nanosecond laser radiation upon monolithic glassy carbon on formation of an emitting structure

A mathematical model of the mechanical effect of nanosecond laser pulse radiation on brittle materials is suggested. An analytic technique is developed for estimating the strength of monolithic glassy carbon on formation on its surface of an emitting structure by a series of nanosecond laser pulses with high energy density.

Spectroscopic study of demineralization and restoration processes in dental enamel

The spectroscopic study of dental enamel by LIBS (laser induced breakdown spectroscopy), FTIR (Fourier transform infrared) and XRD (X-ray diffraction) are represented. The changes of enamel structure and composition in process of natural (caries) and artificial demineralization and restoration were studied. In comparison of sound and carious enamel LIBS showed a decrease of the content of Ca, P and change of the content of some other macro-and trace elements (Mn, Na, Fe, Zn etc). The character of the elemental composition variation was stipulated by the concrete disease. Analysis of FTIR and XRD spectra of dental samples, subjected to artificial demineralization and restoration, showed that restoration action reveals slower, than demineralization. And in some cases the damage of crystals after restoration is more significant than after demineralization.

Application of scanning sampling for studying coatings

LIBS is one of the best methods of multilayer coatings studying. Special laser technique-scanning sampling-was developed for studying of different kinds of objects (technical and biomedical coatings). The scanning sampling is based on the scanning of analyzed object during the exposition time. The velocity of scanning is defined by the diameter of laser crater and pulse repetition rate. It allows to increase the volume part of a coating substance in a sample. Some special applications of LIBS and scanning sampling with Q-switched Nd:YAG-laser in the field of technics and biomedicine are described. The layer-by-layer elemental analysis of multilayer components was performed for finding-out the probable non-uniformity. That could appear the reason of wrong work of components. Special layer characteristic calculated as a ratio of spectral lines intensities for elements contained in different layers of a coating was defined for estimation non-uniformity. LIBS in investigation of dental tissues allows to define preliminary the nature of pathology. Scanning sampling used for such tissues as debris and odontolith, allows to find out the stage of lesion and to predict carious conditions.

Laser microspectral analysis of superthin evaporations of unknown composition

Laser microspectral analysis is an effective method for determination of composition of thin films and evaporations. In the paper results on investigation of accidental superthin evaporations are described. The composition of evaporations allows one to make conclusion about their source.