Фазовый состав и магнитная структура нанокомпозитов FeCoZr—(PbSrNaBi)(ZrTi)O₃

Изучены фазовый состав и магнитные свойства гранулированных нанокомпозитов FeCoZr—(PbSrNaBi)(ZrTi)O₃, синтезированных в кислородсодержащей среде с различным давлением кислорода. Анализ фазового состава выполнялся методами рамановской и ЯГР-спектроскопии, а магнитных свойств – методом вибрационной магнитометрии. Установлена взаимосвязь между условиями синтеза композитов, а также окислением металлических гранул, с одной стороны, и магнитными свойствами нанокомпозитов, с другой. Обнаружена возможность изменения положения порога перколяции и величины магниторезистивного эффекта в материале путём вариации давления кислорода при синтезе.Вивчено фазовий склад та магнетні властивості ґранульованих нанокомпозитів FeCoZr—(PbSrNaBi)(ZrTi)O₃, синтезованих у кисневмісному середовищі з різним тиском кисню. Аналіза фазового складу виконувалася методою Раманової та ЯГР-спектроскопії, а магнетних властивостей – методою вібраційної магнетометрії. Встановлено взаємозв’язок між умовами синтези композитів, а також окисненням металевих ґрануль, з одного боку, та магнетними властивостями нанокомпозитів, з іншого. Виявлено можливість зміни положення порогу перколяції та величини магнеторезистивного ефекту в матеріялі шляхом варіяції тиску кисню при синтезі.Phase composition and magnetic properties of FeCoZr—(PbSrNaBi)(ZrTi)O₃ granular nanocomposites synthesized in oxygen-containing ambient with different values of oxygen pressure are studied by Mössbauer spectroscopy, Raman spectroscopy, and vibrating sample magnetometry. Correlations between the synthesis conditions and oxidation of metallic granules and the magnetic properties of nanocomposites are determined. Possibility to tailor percolation threshold and modify magnetoresistive effect value in a material by varying oxygen pressure in a chamber during synthesis is revealed

Multi-phase nature of sintered vs. arc-melted CrxAlFeCoNi high entropy alloys - experimental and theoretical study

High entropy CrxAlFeCoNi alloys with x = 0, 0.5, 1.0 and 1.5 were synthesized using arc-melting and sintering preparation techniques. Three crystal structures (fcc, bcc and σ) were observed using XRD technique, while EDX measurements showed the presence of up to three chemically different phases (FeCr-rich phase with fcc structure, AlNi-rich phase with bcc structure and Cr-rich phase with bcc and/or σ structures). The reasons for the observed phase coexistence were addressed to total energy electronic structure calculations using KKR-CPA method accounting for chemical disorder effects. Such theoretical analysis confirmed that the multi-phase system was energetically more favorable than the single-phase one. Furthermore, DSC measurements allowed to identify two phase transitions in melted samples, unlike sintered ones due to high-temperature nitrogen corrosion. This process turned out to be highly selective, resulting in the formation of the scales consisting of AlnNm–phases at the cost of total Al loss in the HEA alloy

CVD graphene sheets electrochemically decorated with “core-shell” Co/CoO nanoparticles

The paper reports on the first successful fabrication of Co-graphene composites by electrochemical deposition of Co nanoparticles (NPs) on the sheets of twisted graphene. Characterization of the surface morphology and element mapping of twisted graphene decorated with Co NPs by transmission and scanning electron microscopy in combination with the energy-dispersive X-ray spectroscopy reveals the formation of isolated quasi-spherical oxidized Co NPs with the mean diameter h di _ 220 nm and core-shell structure. X-ray photoelectron spectroscopy indicates that the core of deposited NPs consists of metal Co while the shell is CoO. Composite Co-graphene samples containing core-shell NPs reveal an exchange bias field up to 160 Oe at 4 K as detected by vibrating sample magnetometry after the field cooling procedure

Mössbauer spectroscopy, magnetic and ab-initio study of the approximant Al76_{76}Ni9_{9}Fe15_{15} to a decagonal Al-Ni-Fe quaiscrystal

The structural, magnetic, and Mössbauer spectral properties of the approximant Al76Ni9Fe15 to a decagonal Al–Ni–Fe quasicrystal, complemented by ab-initio electronic structure and the hyperfine-interaction parameters calculations, are reported. The approximant studied crystallizes in the monoclinic space group C2/m with the lattice parameters a = 15.3898(3) Å, b = 8.0840(2) Å, c = 12.4169(2) Å, and β = 107.870(2)∘. The existence of a pseudogap in the calculated electronic density of states slightly above the Fermi level suggests electronic stabilization according to the Hume-Rothery-type mechanism. High metallicity of Al76Ni9Fe15 is predicted. Both the Mössbauer spectra and magnetic susceptibility data indicate that Al76Ni9Fe15 is a paramagnet down to 2.0 K. The presence of the distribution of the electric quadrupole splitting in the Mössbauer spectra measured in the temperature range 4.5–296.1 K is observed. The increase of the average quadrupole splitting with decreasing temperature is well described by a T3/2 power-law relation. The Debye temperature of Al76Ni9Fe15 is found to be 431(3) K

Alterations of costimulatory molecules and instructive cytokines expressed by dendritic cells in the microenvironment of an endogenous mouse lymphoma.

Costimulatory surface molecules and instructive cytokines expressed by dendritic cells (DCs) determine the outcome of an immune response. In malignant disease, DCs are often functionally compromised. In most tumors studied so far, the deficient induction of effective T cell responses has been associated with a blockade of DC maturation, but little has been known on DCs infiltrating malignant B cell lymphoma. Here, we investigated for the first time the phenotypic and functional status of DCs in B cell lymphoma, and we analyzed the network of DCs, tumor cells, natural killer (NK) cells and cytokines present in the tumor micromilieu. Therefor, we used an endogenous myc-transgenic mouse lymphoma model, because transplanted tumor cells foster an IFN-γ-driven Th1 antitumor response rather than an immunosuppressive environment, which is observed in autochthonous neoplasias. Lymphoma-infiltrating DCs showed a mature phenotype and a Th2-inducing cytokine pattern. This situation is in contrast to most human malignancies and mouse models described. Cellular contacts between DCs and tumor cells, which involved CD62L on the lymphoma, caused upregulation of costimulatory molecules, whereas IL-10 primarily derived from lymphoma cells induced an IL-12/IL-10 shift in DCs. Thus, alteration of costimulatory molecules and instructive cytokines was mediated by distinct mechanisms. Normal NK cells were able to additionally modulate DC maturation but this effect was absent in the lymphoma environment where IFN-γ production by NK cells was severely impaired. These data are relevant for establishing novel immunotherapeutic approaches against B cell lymphoma