Controlled variation of the refractive index in ion-damaged diamond

A method of the formation of nanoporous structures in metallic materials by pulse-periodic laser treatment was developed. In this study, the multicomponent aluminum–iron brass was considered and the nanoporous structure across the entire cross section of the material with a thickness of 50 µm was formed. The method was implemented using a CO2 laser processing unit. The pulse-periodic laser treatment of the Cu–Zn–Al–Fe alloy with pulse frequency of 5 Hz has led to the formation of nanosized cavities due to accumulation of internal stresses during cyclic heating and cooling at high speeds. It was determined that the pores of a channel type with average widths of 80–100 nm are formed in the central region of the heat-affected zone during laser action with thermocycling. When implementing the chosen conditions of the pulse-periodic laser processing, the localness in depth and area of the physical processes occurring in the heat-affected zone is ensured, while maintaining the original properties of the material and the absence of significant deformations in the rest of the volume. This patented process is perspective for the production not only catalysts for chemical reactions, but for ultrafiltration and microfiltration membranes as well.

Formation of nanoporous structures in metallic materials by pulse-periodic laser treatment

We considered possibilities of an application of diffractive free-form optics in laser processing of metallic materials in aerospace production. Based on the solution of the inverse problem of heat conduction, an algorithm was developed that calculates the spatial distribution of the power density of laser irradiation in order to create the required thermal effect in materials. It was found that the use of diffractive optics for the laser beam shaping made it possible to obtain specified properties of processed materials. Laser thermal hardening of parts made of chrome–nickel–molybdenum steel was performed. This allowed us to increase the wear resistance due to the creation in the surface layer of a structure that has an increased hardness. In addition, a method of laser annealing of sheet materials from aluminum–magnesium alloy and low-alloy titanium alloys was developed. Application of this method has opened opportunities for expanding the forming options of these materials and for improving the precision in the manufacturing of aircraft engine parts. It was also shown that welding by a pulsed laser beam with a redistribution of power and energy density makes it possible to increase the strength of the welded joint of a heat-resistant nickel-based superalloy. Increasing the adhesion strength of gas turbine engine parts became possible by laser treatment using diffractive free-form optics.

Analysis of the Advantages of Laser Processing of Aerospace Materials Using Diffractive Optics

A use of laser technology it is progressive in the welding of dissimilar materials. Pulsed laser welding of an aluminum alloy AK4 and a titanium alloy VT5-1 was performed. Processing conditions were determined, the  realization of  which during melting of materials in the heat-affected zone  makes it possible to obtain a homogeneous structure without voids  and shells, potentially producing sufficiently sound welded joints. To  create the required power density distribution across the laser beam, it was found expedient to use diffractive optical elements. Aluminum  and copper were welded by continuous laser beam. It is determined  that laser action with its welldefined and precise localized heat input makes it  possible to significantly reduce the growth of intermetallic compound layers.

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Лазерная сварка разнородных металлических материалов с использованием дифракционных оптических элементов

Formation of ZnO / CuO Heterostructure Caused by Laser-induced Vibration Action☆

The fabrication of diamond-based optical elements for high-power CO2 lasers is of particular interest because of low optical absorption, high thermal conductivity and weak temperature dependence of the refractive index of diamond. In earlier publications, we presented the results of the implementation of ion-chemical etching technology for generating a diffraction grating on the surface of a diamond film. The results on generating diamond diffractive optical elements and a sub-wavelength antireflection structure by plasma etching were also presented. In this paper, we study the generation of the grating on the diamond surface by ion-chemical etching. The choice of (Ar+O2) mixture as a working gas and use of niobium as a masking layer are substantiated. The results of studying a diffraction microrelief generated on the diamond-film surface through ion-chemical etching are discussed.

Formation of diffractive microrelief on diamond film surface

In the last decade, the negative impact of hydraulic fracturing fluids on the reservoir properties has been noted, which has led to the new trend of improving characteristics and developing new hydraulic fracturing fluids. As an alternative option to the traditionally used cross-linked fluids based on guar solution, in our laboratory we have tested fluids having a branched spatial structure, which allowed them to hold and transport proppants, despite the low viscosity of this kind of fluids (100–200 mPa·s measured at 100 s−1). Existing theoretical models of hydraulic fracture (HF) propagation have some limitations in predicting the influence of fracturing fluids on reservoir properties. Unfortunately, in situ experiments in the target reservoir are difficult and expensive. Thus, laboratory experiments can be considered as a reasonable alternative for testing new fluids, since they can provide comprehensive information about the properties of the created HF before the application of a new hydraulic fracturing technique in the field conditions. This paper presents the results of an experimental study of hydraulic fracturing of granite samples in laboratory conditions. The injection of water- and oil-based unconventional fracturing fluids was performed to study the influence of fluid rheology on the dynamics of the hydraulic fracture propagation process and parameters of the created HF. We have found that the fracturing fluid viscosity affects the parameters of the created HF, such as aperture, propagation velocity, breakdown pressure, and HF surface tortuosity. The obtained relationships can be taken into account for Hydraulic Fracture modelling, which may increase the efficiency of the hydraulic fracturing in the field conditions.

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Laboratory Study of the Influence of Fluid Rheology on the Characteristics of Created Hydraulic Fracture

The paper presents a complex study of compositions based on pseudo-dimeric surfactants. Rheological and oscillation studies, proppant test (proppant drop rate and static proppant settling), composition’s influence on clay swelling were carried out.In the course of research, it was found that hydraulic fracturing fluids based on pseudo-dimeric surfactants have advantages over similar systems.

S. A. Borodin

Papers

Formation of diffractive microrelief on diamond film surface

Laboratory Study of the Influence of Fluid Rheology on the Characteristics of Created Hydraulic Fracture

Complex Study of a Hydraulic Fracturing Fluid Based on a Pseudo-Dimeric Surfactant

Methods for evaluating the technological properties of water-based fracturing fluids

Complex Study of a Hydraulic Fracturing Fluid with a Pseudo-Dimeric Surfactant