A study of the structure and properties of certain aluminides

Experimental data are presented on the structure and heat resistance of the aluminides ZrAl3, Fe2Al5 and Co2Al9, considering sp. wt., type of combination, and resistance to oxidation at high temperatures. Co2Al9 possesses a relatively high heat of formation, attributed to its high heat resistance characteristics

Large magnetic anisotropy in Ferrihydrite nanoparticles synthesized from reverse micelles

Six-line ferrihydrite(FH) nanoparticles have been synthesized in the core of reverse micelles, used as nanoreactors to obtain average particle sizes $$ $\approx$ 2 to 4 nm. The blocking temperatures $T_B^m$ extracted from magnetization data increased from $\approx 10$ to 20 K for increasing particle size. Low-temperature \MOS measurements allowed to observe the onset of differentiated contributions from particle core and surface as the particle size increases. The magnetic properties measured in the liquid state of the original emulsion showed that the \FH phase is not present in the liquid precursor, but precipitates in the micelle cores after the free water is freeze-dried. Systematic susceptibility \chi_{ac}(\emph{f},T) measurements showed the dependence of the effective magnetic anisotropy energies $E_{a}$ with particle volume, and yielded an effective anisotropy value of $K_{eff} = 312\pm10$ kJ/m$^3$.Comment: 8 pages, 10 figures. Nanotechnology, v17 (Nov. 2006) In pres

Every apple has a voice: using stable isotopes to teach about food sourcing and the water cycle

Agricultural crops such as fruits take up irrigation and meteoric water and incorporate it into their tissue (fruit water) during growth, and the geographic origin of a fruit may be traced by comparing the H and O stable isotope composition (δ2H and δ18O values) of fruit water to the global geospatial distribution of H and O stable isotopes in precipitation. This connection between common fruits and the global water cycle provides an access point to connect with a variety of demographic groups to educate about isotope hydrology and the water cycle. Within the context of a 1-day outreach activity designed for a wide spectrum of participants (high school students, undergraduate students, high school science teachers) we developed introductory lecture materials, in-class participatory demonstrations of fruit water isotopic measurement in real time, and a computer lab exercise to couple actual fruit water isotope data with open-source online geospatial analysis software. We assessed learning outcomes with pre- and post-tests tied to learning objectives, as well as participant feedback surveys. Results indicate that this outreach activity provided effective lessons on the basics of stable isotope hydrology and the water cycle. However, the computer lab exercise needs to be more specifically tailored to the abilities of each participant group. This pilot study provides a foundation for further development of outreach materials that can effectively engage a range of participant groups in learning about the water cycle and the ways in which humans modify the water cycle through agricultural activity

Влияние гафния на литую микроструктуру в сплаве 1570

The issue is devoted to the study of the influence of hafnium on the structure and properties of alloy 1570. Ingots from alloy 1570 were cast into the steel coquille, including those with additives of hafnium 0.1, 0.2 and 0.5 %. To determine the size of the grain structure in the obtained ingots, an Axionovert-40 MAT optical microscope was used, chemical analysis of intermetallic particles was carried out using JEOL 6390A SEM. In addition, for the alloy 1570 and 1570–0.5Hf, the presence of nanoparticles with the L12 structure was studied using transmission electron microscope JEM-2100. Studies showed that hafnium additives make it possible to achieve a significant modification of the cast structure. For example, when introducing hafnium into the initial alloy in an amount of 0.5 % of the total weight, it was possible to achieve a reduction in the average grain size by 2 times. Scanning microscopy data showed that hafnium partially dissolves in particles containing scandium and zirconium as well. The addition of hafnium increases the number of large particles formed during crystallization. Transmission microscopy showed the presence of coherent aluminum matrix nanoparticles in alloy 1570 and having a superstructure of L12, which were most likely formed during intermittent decay during ingot cooling. When 0.5 % Hf was added, no nanoparticles with the L12 superstructure were detected. To explain the latter fact, it is necessary to study the surface of the liquidus of the Al–Hf–Sc system, as well as to study the effect of hafnium on the diffusion coefficient of scandium in aluminum.Изучено влияние гафния на структуру и свойства сплава 1570. В стальной кокиль были отлиты слитки из сплава 1570, в том числе с добавками гафния (0,1, 0,2 и 0,5 %). Для определения размеров зеренной структуры в полученных слитках применялся оптический микроскоп «Axionovert-40 MAT», химический анализ интерметаллидных частиц проводился с помощью сканирующего электронного микроскопа JEOL 6390A. Кроме того, для сплавов 1570 и 1570–0,5Hf на просвечивающем электронном микроскопе JEM-2100 изучалось наличие наночастиц, имеющих структуру L12. Исследования показали, что добавки гафния позволяют добиться существенной модификации литой структуры. Например, при введении в исходный сплав 0,5 % Hf (от общей массы) достигнуто уменьшение среднего размера зерна в 2 раза. Согласно данным сканирующей микроскопии, гафний частично растворяется в частицах, содержащих также скандий и цирконий. Добавка гафния увеличивает количество крупных частиц, образующихся при кристаллизации. Просвечивающая микроскопия показала наличие в сплаве 1570 наночастиц, когерентных алюминиевой матрице и имеющих сверхструктуру L12, которые с большой долей вероятности образовались в ходе прерывистого распада при остывании слитков. При добавке 0,5 % Hf наночастиц, имеющих сверхструктуру L12, не обнаружено. Для объяснения этого факта необходимы исследования поверхности ликвидуса системы Al–Hf–Sc, а также изучение влияния гафния на коэффициент диффузии скандия в алюминии