Laser-induced graphene (LIG) is a highly porous carbon material with prospects for application in various fields of modern electronics, energy and medicine. In this work, LIG film samples with the size of 5 x 10 mm were synthesized on the surface of polyimide film using line-by-line scanning of focused radiation from a cw carbon dioxide laser. Studies using scanning electron microscopy and Raman spectroscopy revealed that the structure of the resulting material depends significantly on the laser power. Measurements of the specific surface area Ssa of the synthesized carbon material, carried out by the well-known BET method during adsorption and desorption of gaseous nitrogen, showed that Ssa significantly depends on the laser power. At a line scanning speed of 220 mm/ s, 25 mu m spacing between lines and a focused laser beam diameter of 120 mu m, an increase in power from -1.7 to 8.2 W leads to a decrease in Ssa from -370 to -100 m2/g. At the same time, the ratio of the total area of all LIG pores to the area of the obtained film varies in the range - 365-660 and reaches its maximum value of 660 at a power - 4.3 W.

X-ray, Mössbauer, and magnetic methods have been used to determine the structural-phase state of nanocomposites—carbide steels doped with chromium and nickel (Fe 0.90 – x Mn 0.10 Ni x ) 83 C 17 , where x = 0.05 and 0.10, obtained by mechanosynthesis followed by annealings. The magnetic (para- or ferro-) states of the phases and their influence on the formation of magnetic hysteresis properties of carbide steels have been studied.

The phase composition, magnetic state of the phases and their influence on the formation of the magnetic hysteresis properties of the nanocomposite with the (Fe0.85Mn0.10Ni0.05)83C17 composition after mechanosynthesis and subsequent annealing have been studied. It is shown that, although the dependences of the coercive force on the annealing temperature H_c(Tann) of the alloy, measured at room and liquid nitrogen temperatures, are curves with maxima, the formation of Hc is driven by different mechanisms. At room temperature measurements, the maximum Hc value of the composite is obtained when the size of the ferrite phase precipitates approaches to the critical single-domain state, whereas at low temperature maximum Hc value is caused by the change of the cementite structural state upon annealing. Keywords: Nanocrystalline Fe-C-Mn-Ni alloys, mechanical alloying, heat treatment, X-Ray diffraction, coercive force, magnetic susceptibility, Curie temperature, Mossbauer spectroscopy.

Новые технологии, Химическая промышленность, Химическая технология, Научные журналы, Защита от коррозии, Технология металлов, Свойства материалов, Технические журналы, Наука и технологии, Справочная литература, Научные разработки

The formation of phases in mechanically synthesized (Fe0.90−xMn0.10Nix)75C25 alloys, where х = 0.05 and 0.10, is studied via X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. It is shown that certain products form during the mechanosynthesis of the initial powders in a planetary ball mill: cementite doped mainly with manganese, ferrite, and an amorphous phase doped mainly with nickel. Annealing at 500°C and higher temperatures leads to the formation of a composite consisting of cementite and austenite doped mainly with nickel. Cementite regions with two different Curie temperatures form as the alloys cool after high-temperature (700°C) annealing, due to differences in the manganese doping of cementite in these regions.

Formation of phases in nanocomposites of composition of carbide steels alloyed with chromium and nickel obtained as a result of mechanosynthesis in a planetary ball mill and further annealing was studied. It was shown that the structure mainly consisting of nickel-alloyed austenite and chromium-alloyed cementite is realized in composite (Fe0.80Cr0.10Ni0.10)83C17 after annealing at temperatures of 700–800°C. The size of cementite grains is in the nanometer range.

The formation of phases in nanocomposites consisting of chromium- and nickel-doped carbide-steels obtained as a result of mechanical synthesis in a ball planetary mill and subsequent annealings has been studied. It was shown that after annealings at 700—800 °C in Fe0.80Cr0.10Ni0.10)83C17 composite the structure consisting mainly of nickel-doped austenite and chromium-doped cementite was realized. The cementite grain size is in the nanometer range.

Changes in the magnetic hysteresis properties of the (Fe 0.8 Cr 0.1 Ni 0.1 ) 75 C 25 alloy during the formation of the phase composition at different stages of mechanosynthesis and subsequent annealing are studied by means of X-ray diffraction and Mössbauer spectroscopy.

X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements have been used to study the phase formation and doping during mechanical synthesis (MS) and subsequent annealing of the alloy (Fe0.80Cr0.05Ni0.15)75C25. It has been shown that, after MS, the nanocomposite contains mainly two phases – an amorphous phase and cementite A. During annealing, as a result of crystallization of the amorphous phase, cementite B is formed, in which contains more nickel than in the mechanically synthesized cementite A. As the annealing temperature increases, austenite, which is inhomogeneous in nickel content, is formed. The Curie temperature of this austenite reaches 500 °C. It has been determined that cementite in the mechanosynthesized nanocomposite (Fe,Cr,Ni)75C25 has a higher temperature stabilitythan that in a MS composite (Fe,Ni)75C25.

The formation and doping of phases during mechanical synthesis followed by annealing in the (Fe0.80Cr0.05Ni0.15)75C25 alloy are studied by the method of X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. It is shown that after mechanical synthesis, the nanocomposite contains mainly two phases (amorphous phase and cementite A). During annealing, as a result of crystallization of the amorphous phase, cementite B is formed, in which the nickel concentration is higher than in mechanically synthesized cementite A. Upon an increase in the annealing temperature, austenite with a nonuniform nickel concentration is formed. The Curie temperature of such austenite reaches 500°C. It is established that cementite in mechanically synthesized nanocomposite (Fe,Cr,Ni)75C25 has a higher stability to temperature variations than mechanically synthesized composite (Fe,Ni)75C25.

In this paper, we propose a technique for additive manufacturing of bulk materials from electrically conductive powders, based on the method of point wise electro pulse sintering. This method consists of layer-by-layer consolidation of powders, each layer being formed as a result of successive sintering of small portions of powder compressed between the electrode and the substrate, or between the electrode and the previously sintered layer. Using the proposed method, bulk samples were obtained from powders having the different chemical composition (Cu, Ti, mechanically alloyed tin bronze), and particles of various shapes (dendritic, dumbbell, stone-shaped). Using X-ray diffraction, electron microscopy, and micro hardness measurements, the structural phase states, and porosity of the obtained bulk consolidated materials were studied. Sintering of powders using this method is greatly influenced by the heat release along the boundaries of the particles, which in turn depends on the electrical resistivity of the material. The porosity of the sintered samples mainly depends on the type of powder used and decreases with the decreasing size of the powder particles. Keywords: additive manufacturing, electro pulse sintering, metal powders, porous structure

Методами рентгеновской дифракции, мёссбауэровской спектроскопии и магнитных измерений исследованы фазовые превращения и особенности перераспределения легирующих элементов Ni и Cr в высокохромистых сплавах состава цементита в результате механосинтеза, после средне и высокотемпературных отжигов.

Based on the analysis of the literature data, the phase formation processes in alloys of the Fe-C system are compared in mechanical alloying and quenching of melts. It is shown that there are common features between these processes. In addition, the types of phases formed coincide. From this it is concluded that, as in the quenching of melts, thermally activated processes of nucleation and growth play an important role in the formation of phases during mechanical alloying. The heat required for these processes is stored by the alloy during deformation.

АННОТАЦИЯ.С помощью метода рентгенофазового анализа и температурных измерений магнитной восприимчивости исследовано формирование фаз в процессе механосинтеза порошков состава легированного хромом и никелем цементита (Fe 0.8 Cr 0.1 Ni 0.1 ) 75 C 25 в шаровой планетарной мельнице «Pulverizette-7».Показано, что измельчение исходных частиц порошков Fe, Cr, Ni и C происходит неравномерно.После помола в течение 2 ч было зафиксировано с помощью рентгеновской дифракции наличие суммарно более 40 об.% непрореагировавшего α-Fe и Cr.Необходимо отметить, что пластичность хрома резко ухудшается при незначительных загрязнениях примесями.Поэтому пластичность использованного в работе хрома (чистота 99,9 мас.%) существенно уступает пластичности α-Fe.Также около половины Ni, заложенного в виде порошка в исходный состав сплава, не прореагировало в течение первых двух часов помола.Вследствие этого аморфная фаза, первой образующаяся на начальном этапе механосинтеза, обеднена атомами легирующих элементов.С повышением времени механосинтеза запускается процесс образования цементита.Весь никель и хром переводятся в наноструктурное состояние и участвуют в легировании фаз.Но увеличение содержания цементита в составе сплава способствует появлению нежелательного намола железа со стенок размольных сосудов и поверхности мелющих тел, что изменяет химический состав сплавов.Поэтому оптимальным временем механосинтеза, при котором легирующие элементы полностью растворяются в композите при удовлетворительной однородности не только в составе отдельной порошинки, но и по всему объему сплава, является t мс = 8 -10 ч.При этом увеличение массы

Исследовано влияние легирования элементами замещения (Cr, Si) на формирование наноструктур в порошковых нанокристаллических сталях на основе Fe-1мас. % С, полученных механосплавлением исходных порошков железа и графита. Исследования проводили методами рентгеновской дифракции и магнитной структуроскопии. В наноструктуре сталей углерод распределен между объемами нанозерен феррита и зернограничными сегрегациями. Концентрация углерода в феррите изменяется в пределах 0,2 – 0,37 ат. % в зависимости от легирования. Cr и Si повышают концентрацию углерода в феррите по сравнению с нелегированной сталью. Концентрация углерода в зернограничных сегрегациях изменяется в пределах (1,1 – 1.7)•10-5 моль/м2. Сr понижает концентрацию углерода в сегрегациях, Si – изменяет мало. Концентрация углерода в сегрегациях определяется, главным образом, размерами зерен и связанной с ними протяженностью границ, достигаемыми при механосплавлении.