Experimental Studies for the VVER-440/213 Bubble Condenser System for Kola NPP at the Integral Test Facility BC V-213

In the frame of Tacis Project R2.01/99, which was running from 2003 to 2005, the bubble condenser system of Kola NPP (unit 3) was qualified at the integral test facility BC V-213. Three LB LOCA tests, two MSLB tests, and one SB LOCA test were performed. The appropriate test scenarios for BC V-213 test facility, modeling accidents in the Kola NPP unit 3, were determined with pretest calculations. Analysis of test results has shown that calculated initial conditions and test scenarios were properly reproduced in the tests. The detailed posttest analysis of the tests performed at BC V-213 test facility was aimed to validate the COCOSYS code for the calculation of thermohydraulic processes in the hermetic compartments and bubble condenser. After that the validated COCOSYS code was applied to NPP calculations for Kola NPP (unit 3). Results of Tacis R2.01/99 Project confirmed the bubble condenser functionality during large and small break LOCAs and MSLB accidents. Maximum loads were reached in the LB LOCA case. No condensation oscillations were observed

СВОЙСТВА НАНОСТРУКТУРНЫХ КЕРАМИКО-МЕТАЛЛИЧЕСКИХ ПОКРЫТИЙ TiN–Ni, ПОЛУЧЕННЫХ ИОННО-ПЛАЗМЕННЫМ ВАКУУМНО-ДУГОВЫМ МЕТОДОМ

There were investigated physical and mechanical, as well as tribological properties of TiN–N surface coatings, obtained by means of ion-plasma vacuum-arc deposition. There was established that hardness (Н) grow up from 23 to 54 GPa at content Ni from 0 to 12 at.%, and it is defined by influence of nanopattering of coatings’ nitride constituent. Herewith coefficients НЕ–1 and Н3Е–2, characterized resistance of material to elastic and large deformation of rupture, attain values of 0,104 and 0,567 GPа, correspondingly. Further increment of nickel concentration in coatings until 26 at.% leads to increasing of H to 23–25 GPа, due to influence of increasing quantity of mild plastic metal and forming of marked porosity in coating volume. Friction coefficient of investigated coatings is characterized by value of 0,45, contrast to 0,58 (for TiN coating) and 0,72 (for the base from sintered hard alloy). There was established cohesive mechanism of nanostructured coatings TiN-N’s fracture (СNi = 2,8÷12,0 at.%) and defined critical loads, characterized occurrence of the firs crack (13,5–14,2 N) and in-situ fletting until template (61,9–64,4 N). There was not observed complete flatting of coatings up to stress 90 H, that showed about its high adhesion strength. Developed nanostructured ceramic-metallic coatings are characterized by high heat-resisting quality up to temperature 800 °C. Исследованы физико-механические и трибологические свойства керамико-металлических покрытий TiN–Ni, полученных ионно-плазменным вакуумно-дуговым осаждением, Установлено, что их твердость (Н) растет с 23 до 54 ГПа при содержании Ni от 0 до 12 ат.%, и это определяется влиянием наноструктурирования нитридной составляющей покрытий. При этом коэффициенты НЕ–1 и Н3Е–2, характеризующие сопротивление материала упругой и пластической деформациям разрушения, достигают значений 0,104 и 0,567 ГПа соответственно. Дальнейшее возрастание концентрации никеля в покрытиях до 26 ат.% приводит к уменьшению Н до 23–25 ГПа, что связано с влиянием увеличивающегося количества мягкого пластичного металла и формированием заметной пористости в объеме покрытий. Коэффициент трения исследованных покрытий характеризуется значением 0,45, против 0,58 (для покрытия TiN) и 0,72 (для основы из твердого сплава). Установлен когезионный механизм разрушения наноструктурных покрытий TiN–Ni (СNi = 2,8÷12,0 ат.%) и определены критические нагрузки, характеризующие появление первой трещины (13,5–14,2 Н) и локальное истирание покрытия до подложки (61,9–64,4 Н). Полного истирания покрытий не происходит вплоть до нагрузки 90 Н, что говорит об их высокой адгезионной прочности. Разработанные наноструктурные керамико-металлические покрытия характеризуются высокой жаростойкостью до температуры 800 °С

УПРОЧНЕНИЕ ТВЕРДОСПЛАВНОГО ЛЕЗВИЙНОГО ИНСТРУМЕНТА, ИСПОЛЬЗУЕМОГО ДЛЯ РЕЗАНИЯ ТРУДНООБРАБАТЫВАЕМЫХ ТИТАНОВЫХ СПЛАВОВ И ХРОМОНИКЕЛЕВЫХ СТАЛЕЙ, МНОГОСЛОЙНЫМИ НАНОСТРУКТУРНЫМИ ПОКРЫТИЯМИ

Complex investigations into physicomechanical properties and adhesion strength in the «coating–carbide cutting insert» system of monolayered (Ti–Al–N) and multilayered (Ti–Al–N/Cr–N, Ti–Al–N/Zr–N/Cr–N) are performed. The advantage of using the latter; which is associated with the passage from the adhesion mechanism of coating destruction to the cohesion mechanism; with an increase in parameters H3/E2 and H/E that characterize the material resistance to plastic and elastic deformation, respectively; is shown. The introduction of chromium into the composition of Ti–Al–N coatings provides a decrease in friction coefficient (from 0,52 to 0,45) and a decrease in probability of adhesion interaction with the treated material. Comparative operational tests of carbide cutting insets (CCI) with coatings under study in the course of continuous cutting steel 12H18N10Т showed that largest wear resistance of Ti–Al–N/Zr–N/Cr–N coatings. Wear tests of CCIs made of VK6NST and TT10K8B alloys with Ti–Al–N/Zr–N/Cr–N coatings in the course of longitudinal turning steel 12H18N10Т and VT20 alloy evidence an increase in their resistance up to a factor of 3,0–3,5 both at low and high cutting rates. These coatings provide an increase in resistance of cutting tool and in milling operations of VT20 titanium alloy at cutting velocity up to 40 m/min.Проведены комплексные исследования физико-механических свойств и адгезионной прочности в системе «покрытие – твердосплавная подложка» монослойных (Ti–Al–N) и многослойных (Ti–Al–N/Cr–N, Ti–Al–N/Zr–N/Cr–N) покрытий. Показано преимущество использования последних, которое связано с переходом от механизма адгезионного разрушения покрытия к когезионному, с повышением параметров H3/E2 и H/E, характеризующих сопротивление материала пластической и упругой деформации соответственно. Введение в состав покрытий Ti–Al–N хрома обеспечивает снижение коэффициента трения (c 0,52 до 0,45) и уменьшение вероятности адгезионного взаимодействия с обрабатываемым материалом. Сравнительные эксплуатационные испытания твердосплавных сменных многогранных пластин (СМП) с исследуемыми покрытиями при непрерывном резании стали 12X18H10Т показали наибольшую износостойкость покрытий Ti–Al–N/Zr–N/Cr–N. Стойкостные испытания СМП из сплавов ВК6НСТ и ТТ10К8Б с покрытиями Ti–Al–N/Zr–N/Cr–N при продольном точении стали 12Х18Н10Т и сплава ВТ20 свидетельствуют об увеличении их стойкости до 3,0–3,5 раз как при низких, так и высоких скоростях резания. Данные покрытия обеспечивают повышение стойкости режущего инструмента и на операциях фрезерования титанового сплава ВТ20 при скорости резания до 40 м/мин

ТВЕРДОСТЬ, АДГЕЗИОННАЯ ПРОЧНОСТЬ И ТРИБОЛОГИЧЕСКИЕ СВОЙСТВА АДАПТИВНЫХ НАНОСТРУКТУРНЫХ ИОННО-ПЛАЗМЕННЫХ ВАКУУМНО-ДУГОВЫХ ПОКРЫТИЙ (Ti,Al)N–Mo2N

The article reviews the properties of nanostructured multilayer coatings (Ti, Al)N–Mo2N obtained by plasma-ion vacuum arc deposition method (arc-PVD). The thickness of coating layers was comparable to the size of a grain, which was about 30–50 nm. Coating hardness reached 40 GPa with relative plastic work of deformation of about 60 %. It was found by the measuring scratching method that cohesive nature of coating destruction takes place entirely by a plastic strain mechanism, which was the evidence of its high viscosity. Local coating abrasion to a substrate level occurred at a load in the order of 75 N. Under test conditions as per «pin-on-disk» scheme using the opposing Al2O3 element at a load of 5 N, coating friction factor was equal to 0,35 and 0,50 at 20 °C and 500 °C respectively. Besides, it was practically not worn due to formation of MoO3 oxide in the friction zone (Magneli phase) which served as a solid lubricant. The increase in friction factor and appearance of significant wear were observed with further rising of test temperature. Such effect was due to intensified sublimation of MoO3 from friction surfaces with subsequent reduction of its lubricating efficiency.Исследованы свойства наноструктурных мультислойных покрытий состава (Ti,Al)N–Mo2N, полученных методом ионно-плазменного вакуумно-дугового осаждения (arc-PVD). Толщина слоев покрытия сопоставима с размером зерна, который составлял порядка 30–50 нм. Твердость покрытий достигала 40 ГПа с относительной работой пластической деформации около 60 %. Методом измерительного царапания установлено, что когезионный характер разрушения покрытия происходит исключительно по механизму пластического деформирования, что свидетельствует о высокой его вязкости. Локальное истирание покрытия до подложки происходило при нагрузке порядка 75 Н. Коэффициент трения покрытия в условиях испытаний по схеме «стержень–диск» с применением контртела из Al2O3 при нагрузке 5 Н составлял 0,35 и 0,50 при температурах 20 и 500 °C соответственно. При этом оно практически не изнашивалось из-за образования в зоне трения оксида MoO3 (фазы Магнели), работающего в качестве твердого смазывающего материала. При дальнейшем повышении температуры испытания наблюдалось повышение коэффициента трения и появление заметного износа, что связано с интенсификацией процессов сублимации MoO3 с рабочих поверхностей и снижением эффективности его работы как смазывающего материала

Comparative Analysis of the Subventricular Zone in Rat, Ferret and Macaque: Evidence for an Outer Subventricular Zone in Rodents

The mammalian cerebral cortex arises from precursor cells that reside in a proliferative region surrounding the lateral ventricles of the developing brain. Recent work has shown that precursor cells in the subventricular zone (SVZ) provide a major contribution to prenatal cortical neurogenesis, and that the SVZ is significantly thicker in gyrencephalic mammals such as primates than it is in lissencephalic mammals including rodents. Identifying characteristics that are shared by or that distinguish cortical precursor cells across mammalian species will shed light on factors that regulate cortical neurogenesis and may point toward mechanisms that underlie the evolutionary expansion of the neocortex in gyrencephalic mammals. We immunostained sections of the developing cerebral cortex from lissencephalic rats, and from gyrencephalic ferrets and macaques to compare the distribution of precursor cell types in each species. We also performed time-lapse imaging of precursor cells in the developing rat neocortex. We show that the distribution of Pax6+ and Tbr2+ precursor cells is similar in lissencephalic rat and gyrencephalic ferret, and different in the gyrencephalic cortex of macaque. We show that mitotic Pax6+ translocating radial glial cells (tRG) are present in the cerebral cortex of each species during and after neurogenesis, demonstrating that the function of Pax6+ tRG cells is not restricted to neurogenesis. Furthermore, we show that Olig2 expression distinguishes two distinct subtypes of Pax6+ tRG cells. Finally we present a novel method for discriminating the inner and outer SVZ across mammalian species and show that the key cytoarchitectural features and cell types that define the outer SVZ in developing primates are present in the developing rat neocortex. Our data demonstrate that the developing rat cerebral cortex possesses an outer subventricular zone during late stages of cortical neurogenesis and that the developing rodent cortex shares important features with that of primates

HARDENING OF THE ELECTRODESIEGED IRON CHEMICAL HEAT TREATMENT

Summary. Currently in the repair and manufacture at the stage of recovery of steel parts, widely used special coatings formed by electrolytic effects on ferrous ions. This technique offers high performance, ease of implementation, low cost of technological equipment and materials used, as well as easy automation of the process. However, this method has several disadvantages: low fatigue strength of reconditioned parts, insufficiently strong grip of the iron coating to the substrate, particularly in alloy steels, insufficient wear resistance. For the purpose of increasing durability and wear resistance of parts, restored through electrochemical action, it is proposed to use chemical-heat treatment, consisting in the application of carbonitriding. Investigated the efficacy of different modes of carbonitriding in the highly carburizing paste-and their influence on the structure and properties of iron plating. It is established that the nitrocarburizing both low and high temperatures repeatedly (6-7.5 times) increases the microhardness of the coatings. The highest hardness is obtained by low-temperature carbonitriding with direct quenching in water. Conducting the carbonitriding process at low temperatures (650 °C), significantly increases the hardness of the iron coatings, increasing the limit of its fluidity, a and also greatly increases its endurance limit. Nitrocarburized fatigue strength of samples with iron precipitation on the surface, as shown by our studies, not only higher strength of the same samples without carbonitriding (more than 2 times), but higher than the fatigue strength of the base metal without coatings. Raising the temperature of the carbonitriding did not increase the hardness of electrolytic iron. Developed a rational technology of hardening of steel parts, re-chain iron fortification. Selected optimum conditions for carbonitriding hardening restored iron fortification, with the purpose of increasing durability of machine parts Optimal process temperature re-benching of the process of carbonitriding in which is possible to obtain maximum fatigue strength and wear resistance from the restored detail, is the process of carbonitriding at 650°C, followed by quenching and tempering at 150 °C

Determining a Dependence of the Effect of Inert Electrolyte on a Difficultly Soluble Salt Under Different Conditions

We examined the impact of various factors on the salt effect, which enhances the solubility of difficultly soluble salt, exerted by the presence of inert electrolyte that has neither common cation nor anion. It was conducted experimentally, by examining the ratios of solubility products of different salts in different solvents, as well as at different ionic strength. The goal was to select such ionic strength where the activity coefficient is minimal, that is, the enhancing effect is maximal.It was established that such factors as dielectric permittivity of the solvent, the anion charge affect enhancing coefficients but do not affect the value of ionic strength at which the salt effect is maximal. It was found that dielectric permittivity of the solvent has a direct impact on the multiplying factor of the “salt effect”; we also established dependence of the anion charge and the magnitude of the “salt effect”. In addition, it was influenced by the degree of bond ionicity between the cation and the anion, in other words, the difference in electronegativities according to Pauling (EN).The obtained data are of high theoretical interest for physical chemistry, as well as for the design of new adsorbents and in other situations where it is required to improve the solubility of a difficultly soluble salt