PERSPEKTIVNYE MATERIALY
2020, №11
Formation of oxygen bubbles in K-208 glass under electron irradiation
R. Kh. Khasanshin, L. S. Novikov
The formation of gas-filled bubbles, which is one of the indicators and quantitative criteria for radiation degradation of the surface layer of K-208 glass irradiated by 20-keV electrons, and the effect of ITO (Indium tin oxide) film deposited on the glass, are investigated. Using atomic force microscopy, the nucleation of oxygen bubbles in the surface layer of glass irradiated with a fluence (Φ) of the order of 1015 cm–2 at a particle flux density (φ) of 2·1010 cm–2·s–1was detected. Gas-filled bubbles appear on the surface of samples with an ITO film at Φ ≥ 4·1015cm–2 in smaller amounts but larger sizes than on glass without a film. The formation of oxygen bubbles is explained by the formation of a negative charge region in the surface layer of the irradiated glass, in the field of which sodium ions migrate, which plays a key role in the release of non-bridge oxygen atoms. Migration and aggregation of liberated oxygen atoms in defective places in the glass grid leads to the formation of gas-filled bubbles.
Keywords:glass; electron radiation; sodium migration; oxygen bubble.
DOI: 10.30791/1028-978X-2020-11-5-14
Khasanshin Rashid —Joint-stock company Kompozit (4, Pionerskay str., 141070 Korolev, Moscow region, Russia), PhD, head of laboratory, associate professor of chair of physics with Bauman Moscow State Technical University (5, 2-ay Baumanskay ul., 105005 Moscow, Russia), specialist in the field of interaction of ionizing radiation with matter, mathematical modeling. E-mail: rhkhas@mail.ru.
Novikov Lev — Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University (Leninskie gory 1, p. 2, Moscow, GPS-1, 119991), head of department, professor, specialist in the field of radiation materials science and space physics. E-mail: novikov@sinp.msu.ru.
Reference citing:
Khasanshin R. Kh., Novikov L. S. Formirovanie kislorodnyh puzyr'kov v stekle K-208 pri elektronnom obluchenii [Formation of oxygen bubbles in K-208 glass under electron irradiation]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 5 – 14. DOI: 10.30791/1028-978X-2020-11-5-14
Thermoelectric properties of germanium telluride
with fine-grained structure
L. D. Ivanova, Yu. V. Granatkina, I. Yu. Nikhezina, A. G. Malchev,
S. P. Krivoruchko, T. S. Vekua, M. I. Zaldastanishvili
The microstructure and thermoelectric properties of materials based on germanium telluride p-type conductivity doped with copper and bismuth obtained by hot pressing of three types powders prepared by grinding an ingot to a size of hundreds microns (0.315 mm) to hundreds of nanometers (mechanical activation) in planetary high-energy mill and melt spinning were investigated. The microstructure of the samples were analyzed by optical and electron scanning microscopies. The nanoscale grain structure of these samples was established. The thermoelectric characteristics of the materials: Seebeck coefficient, electrical and thermal conductivities, were measured both at room temperature and in the temperature range of 100 – 800 K. The slopes of these dependencies are estimated. The coefficient of thermoelectric figure of merit is calculated. The higher thermoelectric efficiency (ZT = 1.5 at 600 K) was received for the samples hot-pressed from granules, prepared by melt spinning.
Keywords: germanium telluride, melt spinning, mechanical activation, hot pressing, microstructure, thermoelectric properties.
DOI: 10.30791/1028-978X-2020-11-15-25
Ivanova Lidia — Baikov Institute of Metallurgy and Materials Sciences of RAS (119334, Russia, Moscow, Leninsky prospect, 49), PhD (Eng), leading researcher, specialist in the field of semiconductor materials science, technologies for obtaining and researching thermoelectric materials. E-mail: ivanova@imet.ac.ru.
Granatkina Julia — Baikov Institute of Metallurgy and Materials Sciences of RAS (119334, Russia, Moscow, Leninsky prospect, 49), researcher, specialist in the field of semiconductor materials science and research of properties of thermoelectric materials. E-mail: granat@imet.ac.ru.
Nikhezina Irina — Baikov Institute of Metallurgy and Materials Sciences of RAS (119334, Russia, Moscow, Leninsky prospect, 49), researcher, specialist in the field of semiconductor materials science and research of properties of thermoelectric materials. E-mail: nihezina@imet.ac.ru.
Malchev Alexey — Baikov Institute of Metallurgy and Materials Sciences of RAS (119334, Russia, Moscow, Leninsky prospect, 49), junior researcher, specialist in the field of semiconductor materials science and research of properties of thermoelectric materials. E-mail: wilkanaris@gmail.com.
Krivoruchko Sergey — Sukhumi Institute of Physics and Technology of Abkhazia Academy of Sciences (384990, Abkhazia, Sukhum, Sinop, Kodori highway, 665), head of laboratory, LLC “Era-Istok”, specialist in physics and technology of thermoelectric materials.
Vekua Tamara — Sukhumi Institute of Physics and Technology of Abkhazia Academy of Sciences (384990, Abkhazia, Sukhum, Sinop, Kodori highway, 665), researcher of laboratory 430, LLC “Era-Istok”, specialist in the field of X-ray structural analysis of thermoelectric materials.
Zaldastanishvili Merab — Sukhumi Institute of Physics and Technology of Abkhazia Academy of Sciences (384990, Abkhazia, Sukhum, Sinop, Kodori highway, 665), deputy head of laboratory 430, LLC “Era-Istok”, specialist in physics and technology of thermoelectric materials.
Reference citing:
Ivanova L. D., Granatkina Yu. V., Nikhezina I. Yu., Malchev A. G., Krivoruchko S. P., Vekua T. S., Zaldastanishvili M. I. Termoelektricheskie svojstva tellurida germaniya s melkozerennoj strukturoj [Thermoelectric properties of germanium telluride with fine-grained structure]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 15 – 25. DOI: 10.30791/1028-978X-2020-11-15-25
Adhesion of plasma coatings of hydroxyapatite
D. I. Komlev, V. I. Kalita, A. A. Radiuk, A. Iu. Ivannikov, A. S. Baikin
Hydroxyapatite coatings were sprayed with an arc plasma torch argon-nitrogen plasma at a power of 25 kW from a powder with a particle size of 25 – 63 μm at a distance of 95 mm. The samples to which the coatings were applied were preheated in a resistance furnace in an air atmosphere to temperatures in the range of 20 to 600 °C before being sprayed. The adhesion of the plasma coating from hydroxyapatite to the titanium substrate was determined on the pin specimens. The maximum average adhesion value was recorded when the titanium substrate was preheated to a temperature of 550 °C. The results of the study were discussed on the basis of the mechanism for increasing the activity of the titanium substrate during its preheating in order to increase the adhesion of the coating HA and the formation of an equilibrium phase state in the HA coating required for the prolonged use of implants. The received results will be used for formation of optimum structure of the bioactive covering consisting from three-dimensional capillary-porous titanium coatings (3D CP Ti) coating in the form of crests and hollows with porosity of 50% and HA coating applied on its free surface at a temperature of 550 °C. Such process of spraying to provide dense strong and stable a HA coating on implants.
Keywords:hydroxyapatite coating, adhesion, pin technique, plasma spraying, titanium substrate, heating.
DOI: 10.30791/1028-978X-2020-11-26-33
Komlev Dmitrii — Baikov Institute of Metallurgy and Material Science RAS (Moscow, 119334, Leninsky Prospect, 49), PhD, leading researcher, specialist in the field of plasma spraying. E-mail: imet-lab25@yandex.ru.
Kalita Vasilii — Baikov Institute of Metallurgy and Material Science RAS (Moscow, 119334, Leninsky Prospect, 49), Dr Sci (Eng), chief scientific officer, specialist in the field of plasma spraying. E-mail: vkalita@imet.ac.ru.
Radiuk Aleksei — Baikov Institute of Metallurgy and Material Science RAS (Moscow, 119334, Leninsky Prospect, 49), junior researcher, specialist in the field of plasma spraying. E-mail: imet-lab25@yandex.ru.
Ivannikov Alexander — Baikov Institute of Metallurgy and Material Science RAS (Moscow, 119334, Leninsky Prospect, 49), PhD, senior researcher, specialist in the field of plasma spraying. E-mail: imet-lab25@yandex.ru.
Baikin Alexander — Baikov Institute of Metallurgy and Material Science RAS (Moscow, 119334, Leninsky Prospect, 49), PhD, scientific researcher, specialist in the field of mechanical testing of materials. E-mail: baikinas@mail.ru.
Reference citing:
Komlev D. I., Kalita V. I., Radiuk A. A., Ivannikov A. Iu., Baikin A. S. Adgeziya plazmennyh pokrytij gidroksiapatita [Adhesion of plasma coatings of hydroxyapatite]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 26 – 33. DOI: 10.30791/1028-978X-2020-11-26-33
Peculiarities of the formation of high-coercivity structure
of (Sm,Zr)(Со,Cu,Fe)zalloys in varying
the (4f-,4d-)/(3d-) element relationship
N. A. Dormidontov, N. B. Kolchugina, Yu. V. Milov, A. G. Dormidontov
Processes of the formation of high-coercivity state of Sm0.85Zr0.15(Co0.702Cu0.088Fe0.210)zalloys with different z = 6.0, 6.5 and 6.8, which is the value characterized the relationship of (4f-,4d-)/(3d-) elements in these alloys, are studied. It is shown the interrelation of the chemical composition of samples and their microstructure with the coercive force formed in the course of isothermal tempering and tempering during slow cooling (or stepped tempering). The interrelation of the high-coercivity state of the alloys and quantitative ratio (volume fractions) of the main structural components based on the 2:17R and 1:5H phases is discussed. It is shown that the cellular morphology of the alloy, which corresponds to the high-coercivity state, forms during isothermal tempering, whereas the final phase compositions of the main structural components form in the temperature range from the isothermal aging temperature to 400 °С during stepped (slow) cooling or upon quenching. The magnetic properties of sample in the high-coercivity state are determined by the degree of completeness of phase transformations of the main structural components; this directly depends on their quantitative relationships and the relationship of the (4f-,4d-)/(3d-) elements, i.e., on the z value in the alloy formula (Sm,Zr)(Со,Cu,Fe)z.
Keywords: Sm-Co alloys, coercive force, phase transformations, thermal treatment, high-coercivity state.
DOI: 10.30791/1028-978X-2020-11-34-44
Dormidontov Nikolai — Magnetoelectromechanics LLC (123458, Moscow, Tvardovskogo
str. 8, bld. 1), process engineer, specialist in the field of rare earth hard magnetic materials. E-mail: ontip@mail.ru.
Kolchugina Natalia —Magnetoelectromechanics LLC (123458, Moscow, Tvardovskogo str. 8, bld. 1), Dr Sci (Eng), leader of project in terms of grant, specialist in the field of high-purity rare earth materials, as well as rare earth hard magnetic materials. E-mail:
natalik014@yandex.ru.
Milov Yury —Magnetoelectromechanics LLC (123458, Moscow, Tvardovskogo str. 8, bld. 1), physicist, specialist in the field of rare-earth hard magnetic materials. E-mail:
milov.yv@mail.ru.
Dormidontov Andrey —Magnetoelectromechanics LLC (123458, Moscow, Tvardovskogo str. 8, bld. 1), PhD (Phys-Math), leading engineer, specialist in the field of rare-earth hard magnetic materials. E-mail: doremi.andr@gmail.com.
Reference citing:
Dormidontov N. A., Kolchugina N. B., Milov Yu. V., Dormidontov A. G. Osobennosti formirovaniya vysokokoercitivnoj struktury splavov (Sm,Zr)(So,Cu,Fe)z pri var'irovanii sootnosheniya (4f-,4d-)/(3d-) elementov [Peculiarities of the formation of high-coercivity structure of (Sm,Zr)(Со,Cu,Fe)z alloys in varying the (4f-,4d-)/(3d-) element relationship]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 34 – 44. DOI: 10.30791/1028-978X-2020-11-34-44
Thermophysical properties of glass-ceramic material during thermal insulation of pipelines of heating mains and utilities
A. S. Apkaryan, S. N. Kulkov
It is proposed to use porous heat-insulating glass-ceramic material (SCM) in the form of segments based on glass, plasticizer, organic additives and a gas generator for thermal insulation of pipelines of heating mains and utilities. Research on the use of SCM in pipelines was carried out according to the key methodology for studying new materials: composition, structure, properties, their changes under the influence of external factors, application. The basis for determining the effectiveness of thermal insulation materials for thermal insulation of pipes was on the physical and technical characteristics of the coolant, pipes and thermal insulation materials. During the study, heat losses and thermal resistances through the insulated surface of the supply and return pipelines of heat networks were determined when installed on the surface. When calculating the heat loss through the pipe using various heat insulators, the layer thickness was assumed to be the same value. Studies have shown that when using a shell made of granular SCM, the heat loss transmitted by thermal conductivity is 1.36 times less than that of a vermiculite shell, 2.45 times than that of mineral wool segments and 2.11 times than that of brand 500 sovelite shells. The use of products made of granular glass-ceramic material (SCM) significantly reduces heat loss and the thickness of the heat-insulating layer of pipelines, and saves fuel and energy resources.
Keywords: Broken glass, ecology, wastes, foamed glass ceramic, charge, granular, density, thermal conductivity, flux density, thermal resistance, temperature, water absorption, thermal insulation, pipe, pores, organic matter.
DOI: 10.30791/1028-978X-2020-11-45-51
Apkaryan Afanasy — Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences (ISPMS SB RAS, 634021 Tomsk, Russia, prospekt Akademicheskij 8/2); Tomsk State University of Control Systems and Radioelectronics (TUSUR, 40 Lenina Prospect, Tomsk, 634050 Russia), Dr Sci (Eng), associated professor, specialist in the field of thermal physics. E-mail: asaktc@ispms.tsc.ru.
Kulkov Sergey — Tomsk State University (TSU, 36, Lenin Avenue, Tomsk, 634050, Russia); Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences (ISPMS SB RAS, 634021 Tomsk, Russia, prospekt Akademicheskij 8/2), Dr Sci (Phys-Math), professor, specialist in the field of mathematics, physics, materials science, ceramics. E-mail: kulkov@ms.tsc.ru.
Reference citing:
Apkaryan A. S., Kulkov S. N. Issledovanie teplofizicheskih svojstv steklokeramicheskogo materiala pri teploizolyacii truboprovodov teplotrass i inzhenernyh kommunikacij [Thermophysical properties of glass-ceramic material during thermal insulation of pipelines of heating mains and utilities]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 45 – 51. DOI: 10.30791/1028-978X-2020-11-45-51
Study of reversibility of electrolytic tin powder obtained from ionic liquid
M. S. Lipkin, N. I. Yalyushev, V. M. Lipkin, M. A. Burakov, A. V. Semenkova,
D. N. Kuznetsov, R. M. Bachayev, V. V. Novoselov
In this paper, a promising new high-capacity anode material for lithium-ion batteries based on a highly dispersed search is considered. The powder was obtained using pulsed electrochemical cathodic reduction in an electrolyte from an ionic liquid choline chloride-ethylene glycol on a titanium vibrocathode. The discharge capacity of the anode material was 817 (mA·h)/g, which is close to the theoretically specific electrochemical capacity of tin 924 (mA·h)/g. The powder of the researchers for the dispersion and morphology of tin crystals. The particle size distribution of the particles with an increased fraction ratio of less than 0.1 μm and SEM-photographs of grains with a rhombohedral particle shape are presented. For research, we turned to this anode material the applied methods of electrochemical analysis: cyclic voltammetry, galvanostatic cycling and impedance spectroscopy in the process of charge and discharge of the electrode. Consideration of changes in the characteristics of the electrode under study using circuits for impedance spectroscopy during the formation of the lithium-tin intermetallic compound, as well as a change in the ratio It is shown that when the charging capacity is reached, close to theoretical intercalation can go through two ways: through SEI and intermetallic compound.
Keywords: tin electrode, lithium-ion battery, tin powder, intermetallic compound.
DOI: 10.30791/1028-978X-2020-11-52-58
Lipkin Mikhail — Platov South-Russian State Polytechnic University (NPI, 346428, Rostov Region, Novocherkassk, Prosveshcheniya, 132), Dr Sci (Eng), professor, head of Department of Chemical technologies, specialist in the field of technologies of electrochemical production. E-mail: lipkin@yandex.ru.
Yalyushev Nikolay — Platov South-Russian State Polytechnic University (NPI, 346428, Rostov Region, Novocherkassk, Prosveshcheniya, 132), associate professor, specialist in the field of technologies of electrochemical production.
Lipkin Valery — Platov South-Russian State Polytechnic University (NPI, 346428, Rostov Region, Novocherkassk, Prosveshcheniya, 132), associate professor, specialist in the field of technology of electrochemical production.
Burakov Mikhail — Platov South-Russian State Polytechnic University (NPI, 346428, Rostov Region, Novocherkassk, Prosveshcheniya, 132), postgraduate student, specialist in the field of electrochemical impedance spectroscopy mesuarements. E-mail: maburakov@mail.ru.
Semenkova Anastasia — Platov South-Russian State Polytechnic University (NPI, 346428, Rostov Region, Novocherkassk, Prosveshcheniya, 132), postgraduatestudent, specialist in electrochemical diagnostics E-mail: semenkovaanastasiya@mail.ru.
Kuznetsov Denis — Platov South-Russian State Polytechnic University (NPI, 346428, Rostov Region, Novocherkassk, Prosveshcheniya, 132), postgraduate student, specialist in the field of obtaining of ultrafine metal powders
Bachaev Roman — JSC Energy (Yelets, 399775 pos. Electric 1), engineer-technologist, specialist in the production of lithium-ion batteries.
Novoselov Valery — JSC Energy (Yelets, 399775 pos. Electric 1), deputy chief engineer, specialist in the production of lithium-ion batteries.
Reference citing:
Lipkin M. S., Yalyushev N. I., Lipkin V. M., Burakov M. A., Semenkova A. V., Kuznetsov D. N., Bachayev R. M., Novoselov V. V. Issledovanie obratimosti elektroliticheskogo poroshka olova, poluchennogo iz ionnoj zhidkosti [Study of reversibility of electrolytic tin powder obtained from ionic liquid]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 52 – 58. DOI: 10.30791/1028-978X-2020-11-52-58
Influence of carbon fibers and composite technologies
on the properties of PCM based
on polytetrafluoroethylene
M. A. Markova, P. N. Petrova
The given paper presents the results of studies on the development of various technological methods for producing composites based on polytetrafluoroethylene (PTFE) and UVIS-AK-P carbon fibers. The methods consist in the physical and ultrasonic actions on the components of polymer composites. The dependence of the physical-mechanical and tribotechnical properties on the production technology of polymer composite materials (PCM) based on PTFE and carbon fibers of the UVIS-AK-P brand is investigated. Two technological methods were applied in the present work to improve the distribution of discrete carbon fibers in the polymer matrix: ultrasonic treatment of the powder composition in a dry medium and the technology of introducing the filler into the polymer matrix through a polymer concentrate with carbon fibers (CF). Herewith, the influence of the filler content in the concentrate on the properties of polymer composites is considered. To increase the adhesive interaction of the polymer with filler, the technology of joint activation of the components was used at the stage of obtaining the concentrate. Afterward, the resulting mixture was mixed with a portion of the polymer to the required concentration of the filler. The positive effect of the technology of joint mechanical activation of components on the properties of PCM based on PTFE and UVIS-AK-P carbon fibers has been established. It has been revealed that the composite with a carbon fiber content of 5 wt. % obtained using combined mechanical activation of a polymer with CF at a rotational speed of planetary mill drums of 400 rpm with a mass ratio of 50 % concentrate and 50 % PTFE has optimal properties. The deformation and strength characteristics of this composite at the level of the initial factor, the wear resistance is higher than in 2020, compared with PTFE and 5, compared with a composite obtained by a simple mixed concentration with a polymer.
Keywords:polytetrafluoroethylene, carbon fibers, wear resistance, joint mechanical activation, ultrasonic treatment, laboratory rollers.
DOI: 10.30791/1028-978X-2020-11-59-68
Markova Marfa — Institute of Problems of Oil and Gas, Siberian branch of RAS (Yakutsk 677000, Avtodorojnaya, 20), PhD student, engineer, specialist in the field of composite materials based on polytetrafluoroethylene. E-mail: markovamusya@mail.ru.
Petrova Pavlina — Institute of Problems of Oil and Gas, Siberian branch of RAS (Yakutsk 677000, Avtodorojnaya, 20), PhD (Eng), associate professor, leading researcher, specialist in the field of composite materials based on polytetrafluoroethylene and supermolecular polyethylene. E-mail: ppavlina@yandex.ru.
Reference citing:
Markova M. A., Petrova P. N. Issledovanie vliyaniya uglerodnyh volokon i tekhnologij polucheniya kompozitov na svojstva polimernyh kompozicionnyh materialov na osnove politetraftoretilena [Influence of carbon fibers and composite technologies on the properties of PCM based on polytetrafluoroethylene]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 59 – 68. DOI: 10.30791/1028-978X-2020-11-59-68
Development of welding fluxes for hardfacing based
on the mineral raw materials of the far eastern region
V. M. Makienko, A. V. Atenyaev, T. V. Belous
This paper presents the results of the research aimed at the creation of the ilmenite-fluorite welding flux using mineral raw materials of the Far Eastern region. The authors have performed thermodynamic calculation based analysis of the possible physical and chemical processes in the slag system. The experimental research we have conducted resulted in the mathematical dependencies that allow selecting flux components that would ensure the desired properties of the hard facing surfaces formed. Experimental overlay welding sessions were performed to determine the welding-technological characteristics and properties of the welded deposit. The results of the research show that the flux, consisting of 50 % of the mineral components extracted in the Far Eastern region and of 50 % of the standard flux АN22 is basic (В = 1.46) and has a low oxygenation capacity (А = 0.22). This facilitates reduction processes in the slag bath and, as a consequence of, results in obtaining high quality weld deposit. High level mechanical and performance properties of the coatings formed is maintained due to the reduction of alloying elements and possible formation of carbides (CrFe)7C3 or (CrFe)23C6, alloyed cementite (CrFe)7C3 and other substances. As an example, overlay welding under AN22PK-DMS flux produces the maximum content of chrome in the welded deposit of 12 – 15 %, and the maximum content of manganese of 6 %.
Keywords:welding flux; charge; mineral raw materials; properties; microstructure; elemental and phase composition; thermodynamic calculation; metallurgical process; calculation of flux components; base-to-acid ratio and activity of the flux; alloying elements.
DOI: 10.30791/1028-978X-2020-11-69-82
Makienko Viktor — Far Eastern State Transport University (FESTU, 47, Serysheva St., 680021, Khabarovsk, Russia), Dr Sci (Eng), professor, department of transport and technology complexes, specialist in materials science, mechanical engineering, welding (related processes and technologies), metal technology, metallurgy of non-ferrous, rare and refractory metals. E-mail: mvm_tm@festu.khv.ru.
Atenyaev Alexander — Far Eastern State Transport University (FESTU, 47 Serysheva St., 680021, Khabarovsk, Russia), leading engineer, specialist in material science, mechanical engineering, metal technology, metallurgy of non-ferrous, rare and refractory metals. E-mail: atenia@mail.ru.
Belous Tatyana — Far Eastern State Transport University (FESTU, 47, Serysheva St., 680021, Khabarovsk, Russia), PhD, associate professor of department of transport and technology complexes, specialist in foundry production, metal technology, metallurgy of non-ferrous, rare and refractory metals. E-mail: belous_tatvic@mail.ru.
Reference citing:
Makienko V. M., Atenyaev A. V., Belous T. V. Sozdanie flyusov dlya formirovaniya pokrytij na osnove mineral'nogo syr'ya Dal'nevostochnogo regiona [Development of welding fluxes for hardfacing based
on the mineral raw materials of the far eastern region]. Perspektivnye Materialy — Advanced Materials (in Russ), 2020, no. 11, pp. 69 – 82. DOI: 10.30791/1028-978X-2020-11-69-82
