Self-doping Effects on the Superconducting Properties of Cu0.5Tl0.25M0.25Ba2Ca2Cu3O10−δ (M = Bi, Hg, Nb, Pd, Li, Na, K)

The effect of self-doping and substitution of elements of higher and lower electronegativity, such as Bi, Hg, Nb, Pd, Li, Na, K, on the superconducting properties of Cu_0.5Tl_0.5−x M _x Ba₂Ca₂Cu₃O_10−δ with x=0.25 is investigated. These experiments demonstrated that the elements of lower electronegativity such as Li, Na, and K can easily liberate their outer most s-electron that could be supplied to the conducting CuO₂ planes of Cu_0.5Tl_0.5−x M _x Ba₂Ca₂Cu₃O_10−δ superconductor, and as a result, we get enhanced superconducting properties. However, highly electro-negative elements hinder the transfer of carriers from charge reservoir layer to the conducting CuO₂ planes and promote inferior superconducting properties. In the present studies, we have investigated the effect of post-annealing in nitrogen and oxygen atmospheres for optimizing the carriers in conducting CuO₂ planes of Cu_0.5Tl_0.5−x M _x Ba₂Ca₂Cu₃O_10−δ (M=Bi,Hg,Nb,Pd,Li,Na,K) superconductor. These studies are important since the density of carriers in the conducting CuO₂ planes determines the Fermi-vector k _F and Fermi velocity v _F of the carriers, which ultimately brings about the final superconducting state of the system.      

Unified model of nucleation and growth of fatigue cracks. Part 1. Use of force parameters of fracture mechanics of materials in the stage of crack nucleation

According to the phenomenological model of nucleation of a fatigue macrocrack, the process is considered as a two-parameter process. The process is described by the local stress or strain range and a certain linear parameter of the material. We propose the corresponding parameters, namely, the local stress range Δσ _y ^* and the characteristic sized ^* of the prefracture zone. The formation of this zone is caused by the anomaly of the yield strength of the material in subsurface layers, the microstructure, the loading amplitude, the cyclic strain hardening, and the environment. The quantityd ^* is a constant of the material, which is independent of the geometry of notch and specimen. the boundary of the prefracture zone is considered as a macrobarrier that determines the growth of microstructurally short and physically small cracks. The moment when a physically small crack oversteps the boundary of the prefracture zone is defined by the quantitative criterion (a ₀=d ^*) of the initial sizea ₀ of a macrocrack in the material. The proposed dependences of (Δσ _y ^* ,N _i ),N _i ) and (d ^*,N _i ) can be regarded as a basis for the determination of characteristics of resistance of the material to the nucleation of a fatigue macrocrack. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 1, pp. 7–21, January–February, 1998.     

Deposition of zirconium oxynitride films by reactive cathodic arc evaporation and investigation of physical properties

The area of metal oxynitrides is poorly explored, and understanding of the fundamental mechanism that explains structural, mechanical, electrical, and optical properties is still insufficient. Therefore, the purpose of the present investigation is to analyze structural, electrical, and optical properties of ZrN_xO_y films deposited by reactive cathodic arc evaporation.Depending on the oxygen flow, cubic ZrN:O, monoclinic ZrO₂:N, and tetragonal ZrO₂:N phases films were prepared. The sheet resistance and the optical transmittance very much depend on the oxygen flow. Optical transparent ZrN_xO_y films with transmittance of 86% at 650 nm, the sheet resistance 1.1 · 10³ Ω/sq, and the figure of merit 2 · 10^− 4 Ω^− 1 are deposited with the 60 sccm oxygen flow.     

Structural properties and kinetics of nitro-niobized steels

In the present study, structural characterization and kinetics of nitro-niobized AISI 1010, AISI D2, and AISI M2 steels by thermo-reactive deposition technique in the powder mixture consisting of ferro-niobium, ammonium chloride, and alumina at the temperatures of 1173, 1273, and 1373 K for 60–240 min were investigated. The thickness of the niobium nitride layers formed on the nitro-niobized AISI 1010, AISI D2, and AISI M2 steels are ranged from 2.80 ± 0.90 to 11.89 ± 1.10 μm, 3.16 ± 0.60 to 13.16 ± 1.51 μm, and 3.85 ± 0.91 to 16.77 ± 2.10 μm, respectively. The phases formed in the coating layer deposited on the surface of the steel substrates are NbN_0.95 and Nb₂CN. The hardness of the niobium nitride coating layers produced on AISI 1010, AISI D2, and AISI M2 steels are changing from 1151 ± 126 to 1446 ± 121 HV_0.005, 1359 ± 413 to 1594 ± 761 HV_0.005, and 1321 ± 51 to 1915 ± 134 HV_0.005, respectively. Diffusion constants of the coating layers were changing between 1.517 × 10⁻¹⁵ and 2.043 × 10⁻¹⁴ m²/s, depending on steel compositions, treatment time and temperatures, and activation energies of the AISI 1010, AISI D2, and AISI M2 steels for the process were calculated as 128.7, 123.8, and 132.5 kJ/mol, respectively. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of niobium nitride coating thickness variation, depending on process time and temperature.     

Photoluminescence and Electrical Conductivity of As<Subscript>2</Subscript>S<Subscript>3</Subscript>〈Au〉 and As<Subscript>2</Subscript>S<Subscript>5</Subscript>〈Au〉 Glasses

The 77-K photoluminescence spectra of (As₂S₃)_{100 − x} Au_x and (As₂S₅)_{100 −x} Au_x (0 ≤ x ≤ 0.04) semiconducting glasses are measured for the first time. At low doping levels, the spectra of the (As₂S₅)_{100 − x} Au_x glasses are split into two components, one of which arises from the Au dopant. The temperature-dependent conductivity of the glasses shows two breaks at low Au concentrations and anomalous behavior in the range 300–360 K. Qualitative analysis of the conductivity data suggests that most of the impurity atoms have saturated valence bonds and form solid solutions with host atoms, changing the band gap of the material. A small fraction of the impurity atoms, those having unsaturated valence bonds, produce an electrically active level responsible for impurity conduction.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 876–880.Original Russian Text Copyright © 2005 by Babaev, Kamilov, Sultanov, Askhabov, Terukov.     

Enhancing Superconductivity in Low-dimensional TlBa2Ca2Cu3O10?δ System

Mg-doped Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? (x=0, 0.25, 0.50, 0.75, 1.0, 1.25, 1.5) superconductors are synthesized at the normal pressure and the possible mechanism of superconductivity in these compounds is studied. Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? samples have shown an orthorhombic crystal structure and their c-axis length decreases up to Mg-doping of x=0.75 and then increases up to Mg-doping of x=1.50. In these studies we have investigated the role of decreased thickness of charge reservoir layer on the mechanism of superconductivity. The T _c (R=0) in as-prepared Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? (x=0, 0.25, 0.5, 0.75, 1.0, 1.25) samples was 100, 98, 101, 102, 100, 96?K and in the oxygen post-annealed samples the T _c (R=0) is observed around 99, 98, 108, 127, 109, 97?K, respectively. The magnitude of the superconductivity after Mg-doping is improved in Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? (x=0.25, 0.5, 0.75, 1.0, 1.25) samples. It was observed from the FTIR absorption measurements that the phonon modes related to CuO₂ planar oxygen atoms are hardened with the doping of Mg in the charge reservoir layer. These studies have shown that the thickness of charge reservoir layers decreases with Mg-doping, which most likely makes the charge transfer mechanism more efficient, which increases the magnitude of superconductivity in the final compound.     

Microstructures of high-J c melt-textured YBa2Cu3O7−x /Ag superconductors

Silver has been previously added to the melt-textured YBa₂Cu₃O_7?x in order to increase the critical current density (J _c ) of these materials. However, the effect of this addition on theJ _c is presently unclear. The purpose of this study is to investigate the effect of silver on both critical current density and the microstructure of the melt-textured YBa₂Cu₃O_7?x superconductors by means of X-ray diffraction, optical polarized microscopy, and transmission electron microscopy (TEM). TheJ _c of the MTG YBCO/Ag samples is more than 10⁴A/cm² under the 5 kOe magnetic field. It has been shown that as the concentration of silver increases, the fraction of the 211 phase dispersed within the 123 matrix decreases. Therefore, theJ _c slightly decreases. These results, together with the effect of the 211 phase, dislocations, and other structure defects on flux pinning, are described in this paper.     

Synthesis of New Pb-Based 1222 Cuprates Containing Phosphorus, (Pb0.75P0.25)Sr2(RE2–x–y Ce x Sr y )Cu2O z (RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y)

New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (Pb_0.75P_0.25)Sr₂- (RE_2–x–y Ce _x Sr _y )Cu₂O _z (RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. The almost-single phase samples are obtained for 0.5≤x≤1.0 and y=0.1 in the cases of RE = Nd, Dy, Ho, Er, Tm, Yb and Y, while for 0.3≤x≤1.0 and y=0.1 in the cases of RE = Sm, Eu and Gd. The samples crystallize in a tetragonal lattice, the lattice parameters a and c are decreasing with the decrease of the ionic radius of the RE element. Even after annealing under 143 atm O₂ atmosphere at 400 °C, almost all the samples with the common values x=0.5 and y=0.1 are semiconductors with a transport process followed by three-dimensional variable range hopping. However, the samples of RE = Sm, Eu and Gd, which are of almost single 1222 phase, even for x=0.3 and y=0.1, show superconductivity with the onsets at about 25 K, 20 K and 22 K, respectively. Through this study, we find very important procedure for discovery of new superconducting 1222 compound.     

The exact shape of a deformed internal slant crack under biaxial loading

A theoretical investigation has been performed to determine the exact geometrical features of an inclined, biaxially loaded, crack in an infinite elastic plate. It has been shown that the shape of the deformed Griffith crack, as this follows from the exact linear elastic displacement field at the lips of the crack, is always an ellipse in opposition to the singular and two-term solutions which give a parabolic shape for the deformed lips of the crack. The combined effect of the mode of loading, the load biaxiality and the crack orientation on the lengths of the semiaxes of the ellipse, and the orientation of its major axis with respect to the initial crack was studied in detail. It is also shown that in general the positions of the initial crack tips after deformation on the curve of the ellipse do not coincide with the points of the maximum curvature of the ellipse. The case, where the ellipse presents overlapping lips and where the elastic solution becomes invalid, has been examined and the configurations of the problem-parameters for which this phenomenon happens has been established.These important features of the deformed shape of the loaded crack may have a considerable influence on the mode of loading and the behaviour in yielding and fracture of the cracked bodies.

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Résumé On a procédé à une étude théorique en vue de déterminer les caractéristiques géométriques exactes d'une fissure inclinée et sollicitée en biaxialité dans une plaque élastique infinie. Ainsi qu'il résulte du champ de déplacements élastiques linéaires aux lèvres de la fissure, on a montré que la forme d'une fissure de Griffith déformée est toujours une ellipse. Ceci est en opposition avec les solutions singulières et en deux termes, qui attribuent aux lèvres déformées de la fissure une forme parabolique. On a étudié en détail l'effet combiné du mode de mise en charge, de sa biaxialité et de l'orientation de la fissure sur la longueur des demi-axes de l'ellipse, ainsi que sur l'orientation de l'axe principal par rapport à la fissure initiale.On a également montré que, en général, les positions après déformations des extrémités de la fissure initiale sur l'ellipse ne coïncident pas avec les points de courbure maximum de l'ellipse. On a examiné le cas où la fissure présente des lèvres qui se recouvrent, et où la solution élastique n'est plus valable, et on a établi les configurations des paramètres du problème pour lesquelles ce phénomène se produit.Ces caractéristiques importantes de la déformation d'une fissure sous sollicitation peuvent avoir une influence déterminante sur le mode de sollicitation et sur le comportement à l'écoulement plastique ou à la rupture des corps fisurés.

     

The Distribution of the Maximum Sum of Rank

In this paper a c-sample slippage analogue of the Wilcoxon [11] test is considered. Given a sample of size n for each of c populations, the test rejects the hypothesis that the c populations are identical when max_1≤i≤c σ _k r _ik > λ, where r _i1, …, r _in are the ranks of the observations from the i-th population in the combined sample of size cn. The small and large sample distributions of the test statistic are derived. Tables of the exact distribution are given for c = 2(1)5, n = 2(1)5. Tables of critical values are given for c = 2(1)6, n = 2(1)8 for values of α = 0.001, 0.005, 0.01, 0.025, 0.05, 0.10, and 0.20.     

Morphologies and electrochemical properties of 0.6Li2MnO3·0.4LiCoO2 composite cathode powders prepared by spray pyrolysis

Nanosized 0.6Li₂MnO₃·0.4LiCoO₂ composite cathode powders are prepared by spray pyrolysis. The micron-sized composite powders are converted into nanosized powders by a simple milling process. The mean sizes of the composite powders measured from the TEM images increase from 20 to 170 nm when the post-treatment temperatures increase from 650 to 900 °C. The Brunauer–Emmett–Teller surface areas of the composite powders post-treated at 650 and 900 °C are 24 and 3 m² g⁻¹, respectively. The XRD patterns indicate that the layered composite powders post-treated at 800 and 900 °C have high crystallinity and low cation mixing. The mean crystallite sizes of the powders, measured from the (003) peak widths of the XRD patterns using Scherrer's equation, are 35 and 56 nm at post-treatment temperatures of 800 and 900 °C, respectively. The initial discharge capacities of the 0.6Li₂MnO₃·0.4LiCoO₂ composite are 262, 267, 264, and 263 mAh g⁻¹ when the post-treat temperatures of the powders are 650, 700, 800, and 900 °C, respectively. The discharge capacity of the composite powders post-treated at 900 °C abruptly decreases from 263 to 214 mAh g⁻¹ by the seventh cycle and then slowly decreases to 198 mAh g⁻¹ with increasing cycle number, up to 30.     

Hydrogen-induced phase transformations in alloys based on Sm Co<Subscript>5</Subscript> under pressures of up to 650 kPA

The interaction of alloys based on SmCo₅ with hydrogen is studied by the methods of differential thermal and X-ray phase diffraction analyses under initial pressures of hydrogen of 200, 300, 400, 500, and 650 kPa at temperatures of up to 1223°K. The hydride of the alloy is formed up to a temperature of 343°K. Within the temperature ranges 388–408°K and 488–523°K, hydrogen is released from the hydrides of phases of the alloy. Within the temperature range 823–863°K, the alloy partially disproportionates into Sm H_x and Co. At 1008–1053°K, SmH_x undergoes partial decomposition and the SmCo₅ and Sm₂Co₁₇ phases are detected. The Co, SmCo₅, and Sm₂Co₁₇ phases exist at temperatures above 1168–1188°K. The compositions of the phases depend on the duration of interaction of the alloy with hydrogen. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 1, pp. 94–98, January–February, 2007.     

Synthesis of biopolymeric particles loaded with phosphorus and potassium: characterisation and release tests

The authors synthesised nanoparticles (NPs) loaded with P and K from KH₂ PO₄ using gelatin type‐A and type‐B, and sodium alginate as carriers. Using type‐A and type‐B gelatin, quasi‐spherical particles were obtained, with average sizes of 682 and 856 nm, respectively; with sodium alginate, the resulting NPs exhibited spherical shapes and 600 nm particle average size. The authors found an interaction between KH₂ PO₄ and alginate via the hydrogen bonds existent among the carboxylic groups of the carbohydrate and the OH‐groups of the H₂ PO₄ ‐; interactions among gelatin types with the OH‐groups and the H₂ PO₄ ‐ion were also observed. Adding trypsin to the distilled water solutions of the NPs coated with type‐A gelatin increased the concentration of P in the solution by threefold, while increasing that of K increased by 2.6‐fold. Conversely, adding α ‐amylase to the water solutions with sodium alginate increased the P and K concentrations in the solution by nearly 1.3‐ and 1.1‐fold, respectively. Thus, sodium alginate resulted in NPs with smaller sizes and better spherical formations, though with a high polydispersity index and lower release rate of P and K. This low release rate represents an advantage since plants demand nutrients for long periods, and conventional fertilisers display low use efficiency.Inspec keywords: nanofabrication, nanoparticles, hydrogen bonds, gelatin, biomedical materials, particle size, enzymes, molecular biophysics, biochemistry, nanobiotechnology, polymer films, potassium compoundsOther keywords: sodium alginate, biopolymeric particles, release tests, type‐B gelatin, spherical shapes, carboxylic groups, OH‐groups, distilled water solutions, type‐A gelatin, quasi‐spherical particles, particle average size, hydrogen bonds, trypsin, spherical formations, high polydispersity index, plants, α‐amylase, size 682.0 nm, size 856.0 nm, size 600.0 nm, H₂ PO₄ , KH₂ PO₄      

Studies on LiNi0.7Al0.3−xCoxO2 solid solutions as alternative cathode materials for lithium batteries

A series of phase-pure Co- and Al-substituted lithium nickel oxide solid solutions of the composition LiNi_0.7Al_0.3−xCo_xO₂ with x=0.0, 0.1, 0.15, 0.2, and 0.3, has been synthesized by adopting urea-assisted combustion (UAC) route. The structure and the physico-electrochemical features of the doped materials have been evaluated through PXRD, FTIR, SEM, CV, and charge/discharge studies. The stabilization of Ni in the +3 state and the existence of enhanced 2D-layered structure without any cation mixing have been substantiated from XRD. The results of the XRD and FTIR studies have established the complete mixing of Al and Co with Ni, especially at the various levels and the combinations of the dopants attempted in the present study. The enhanced electrochemical performance of LiNi_0.7Al_0.3−xCo_xO₂ may be attributed to the “synergetic effect” resulting from the presence of both Al³⁺ and Co³⁺ dopants in the LiNiO₂ matrix. From CV studies, it was understood that the addition of 10% Co is effective in suppressing the phase transformation during Li⁺ intercalation process that leads to better electrochemical properties. The effect and the extent of substitution of Ni with Al and Co on the structural and electrochemical performance of LiNi_0.7Al_0.3−xCo_xO₂ are discussed elaborately in this communication.     

Crystallographically oriented W-type barium hexaferrite BaZn2Fe16−xScxO27 with high squareness ratio

A series of oriented W-type barium hexaferrites of composition BaZn₂Fe_16?xSc_xO₂₇ (where x?=?0, 0.1, 0.2, 0.3, 0.4) has been synthesized by conventional ceramic methods and characterized by XRD, SEM, EDS, FTIR, and VSM. In this work, the effect of trivalent Sc substitution for trivalent Fe on the structure and magnetic properties of Zn₂W has been studied. The XRD results showed that all the specimens consisted of single phase of W-type ferrites. EDS analysis confirmed that the content of Ba, Zn, Sc, and Fe were closed to the elemental composition of BaZn₂Fe_16?xSc_xO₂₇. The SEM revealed the hexagonal platelet-like structure of the BaZn₂Fe_16?xSc_xO₂₇ and the average grain sizes of all samples remain in the range of single domain dimension (0.5 µm?~?1 µm). The SEM also demonstrated that the samples maintained high crystallographic c-axis texture when Sc³⁺ content was less than 0.4. The SEM results were consistent with magnetic hysteresis loops. As the function of Sc substitution, the squareness ratio (M_r/M_s) ranged from 0.78 to 0.82, which was critical for self-biased application. Moreover, the magnetocrystalline anisotropy field (H_a) decreased. The saturation magnetization (M_s) increased from 53.61 to 54.04 emu/g as x increased from 0 to 0.1, and then it decreased to 46.50 when x > 0.1. The samples showed other excellent magnetic properties, such as appropriate anisotropy field (~?9 kOe),and high coercive fields (~?1300 Oe). Therefore, the prepared Zn₂W ferrites are suitable candidate for the microwave devices operated at low frequency.

     

Superconductivity in transition metal-germanium systems

The variation in the superconducting properties of various binary alloys of the transition metal-germanium system was surveyed by studying sputter-deposited samples prepared under various conditions. Radiofrequency cosputtering was used to form samples of the form T _x Ge _1–x , where T represents a transition metal, Y, La, Ti, Zr, Hf, V, Nb, Ta, Mo, W, and Re. The primary interest has been to study the formation of A-15 compounds. While sputtered V ₃ Ge hadT _cs close to bulk sample values, Nb ₃ Ge (T _c=21.7 K) and Mo ₃ Ge (T _c=5.7 K) showed a considerable enhancement inT _c over the bulk values. The formation of the metastable A - 15 modification of Ta ₃ Ge, Ti ₃ Ge, Zr ₃ Ge, and Hf ₃ Ge was attempted, without success. Superconductivity was observed in samples of ZrGe ₂ , HfGe ₂ , YGe ₂ , and LaGe ₂ , the highestT _c being that of ZrGe ₂ (T _c=8.0 K). Annealing studies indicated that superconducting ZrGe₂ and HfGe₂ were metastable, depending on the conditions of synthesis. Superconductivity was also observed in mixtures of semiconducting Ge and metallic NbGe ₂ , the highestT _c observed being 16 K. Several explanations are considered to account for the observedT _cbehavior among the various alloys.Supported in part by the National Science Foundation.     

Investigation of YBa2Cu3O x , Bi(Pb)-HTSC and Nd(123)-Particles in a Running Magnetic Field Near the Superconducting Transition Temperature

A novel system of electromagnetic separation (EMS) employing an alternating magnetic field (RMF) of suspended HTSC-particles in liquid nitrogen is described (Broide in Supercond. Cryoelectron. Summer:33, [1998]; Broide in Superconductor Week 12, No. 21, [1998]; Broide in US Patent 5,919,737, [1999]; Broide et al. in International Conference, Barcelona, Spain, [1999]). The EMS method is realized at temperatures close to those of the HTSC transition by extracting particles of YBaCuO, BiSrCaCuO, BiPbSrCaCuO, and NdBaCuO with optimal physical properties from the powders, concentrating particles with a greater critical current at one side. This process has shown great promise in its ability to produce high quality superconducting materials, being also an effective method of testing and analyzing powders to determine if synthesis adjustments are necessary in order to achieve optimal materials properties. In addition, a correlation between the speed of YBa₂Cu₃O _x particles and the percentage of oxygen (O _x ) was discovered. Since the temperature of the superconducting (SC) transition (T _c ) practically has a linear dependence on the oxygen percentage, the knowledge of the speed of the HTSC-particles during the separation, one may immediately give (within 10 s) the percentage of the oxygen in the chemical structure of the new HTSC materials. The EMS method enables statistical improvement in the uniformity of HTSC powders by decreasing the quantity of defective zones in the separated powders, the number of nonvalid admixtures, and thus, an increase in T _c and I _c (critical current). At the same time, ΔT _c the width of the SC-transition is decreased. Three YBa₂Cu₃O _x thick films have been produced by the paint method on MgO substrates from the source material, the separated high-quality concentrate, and the low-quality remnant (tail). The films exhibit different structural and electrical properties, in particular, different I _c , and ΔT _c . For the film that was made from the high-quality concentrate, ΔT _c is decreased from 5–7 K to 1–2 K. I _c is increased by a factor of 2–5 from the I _c of the source material (before EMS) and T _c is changed from 89 K to 93 K. Thick films, which had been produced from low-quality remnant (tail) do not have SC transition down to 77 K.      

Microstructure,fluidity, and mechanical properties of semi-solid processed ductile iron

This research is directed towards studying the effect of semi-solid processing (using cooling plate technique) on the microstructure, fluidity, and mechanical properties of ductile iron (DI). Sand mold castings with constant width of 25 mm and length of 150 mm with the thicknesses of 6, 12, 18, and 25 mm were used in this study. Microstructure, fluidity, and tensile strength properties were investigated as a function of fraction of solid. The results indicated that by increasing fraction of solid microstructure becomes finer and more globular. However, increasing primary fraction of solid increases the cementite content in the matrix. Above a certain fraction of solid (f _s = 0.28, f _s = 0.1, and f _s = 0.05 for 25, 18, and 12 mm wall thickness, respectively), the fluidity of semi-solid processed DI decreases steeply. For low fraction of solid (f _s ≤ 0.15), increasing the fraction of solid results in an increment in the tensile strength, comparing with the ordinary DI due to the fine and globular structure formation. Any further increment of fraction of solid (f _s > 0.15) leads to the cementite increment and gas porosity formation, consequently the tensile strength decreased. The fraction of solid of DI and casting wall thickness should be considered in order to obtain the best combination of microstructure, fluidity, and mechanical properties of semi-solid processed DI.     

Magnetic properties of RE x Mo6Se8 compounds between 0.7 and 295 K

Magnetization measurements are reported for seven members of the series of compounds RE _x Mo ₆ Se ₈ (x1; RE=La, Ce, Pr, Eu, Gd, Yb, and Lu). These measurements establish that Ce, Pr, and Gd ions are trivalent in these compounds, but that Eu and Yb are primarily divalent, in agreement with crystallographic data. Large deviations of the susceptibilities for CeMo ₆ Se ₈ , PrMo ₆ Se ₈ , and YbMo ₆ Se ₈ from Curie-Weiss behavior above 10 K are attributed predominantly to crystal field effects, and quantitative agreement between crystal field theory and the experimental data was obtained for CeMo ₆ Se ₈ above 25 K. Further, we find for Gd _1.2 Mo ₆ Se ₈ an unusually small spin exchange interaction between the Gd ions and conduction electrons, consistent with previous estimates of this quantity based on superconductivity data. For the Gd, Eu, and Ce compounds, the low-temperature data indicate very small Curie-Weiss temperatures of –1.7, –0.6, and +0.4 K, respectively. No evidence for magnetic ordering of the RE ions in any of the above compounds was observed, with the exception of CeMo ₆ Se ₈ , for which the magnetization data at 0.7–1.3 K suggest the onset of ferromagnetic order.Research sponsored by the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under AFOSR Contract No. AFOSR/F-44620-72-C-0017.     

Effect of Ag‐NPs synthesised by Chamaemelum nobile extract on the inflammation and oxidative stress induced by carrageenan in mice paw

An environmentally friendly and rapid procedure was developed to synthesise silver nanoparticles (Ag‐NPs) by Chamaemelum nobile extract and to evaluate its in vivo anti‐inflammatory and antioxidant activities. The ultraviolet–visible absorption spectrum of the synthesised Ag‐NPs showed an absorbance peak at 422. The average size of spherical nanoparticles was 24 nm as revealed by transmission electron microscopy. Fourier transform infra‐red spectroscopy analysis supported the presence of biological active compounds involved in the reduction of Ag ion and X‐ray diffraction confirmed the crystalline structure of the metallic Ag. The anti‐inflammatory and antioxidant activity of the Ag‐NPs was investigated against carrageenan‐induced paw oedema in mice. The levels of malondialdehyde (MDA) and antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase and inflammatory cytokines tumour necrosis factor (TNF‐α), interferon gamma and interleukin (IL)‐6, IL‐1β were assessed in this respect. The results demonstrated that anti‐inflammatory activity of the Ag‐NPs might be due to the ability of the nanoparticles to reduce IL‐1β, IL‐6 and TNF‐α. Moreover, reduction of antioxidant enzymes along with an increase in MDA level shows that the anti‐inflammatory activity of the synthesised Ag‐NPs by C. nobile is attributed to its ameliorating effect on the oxidative damage.Inspec keywords: silver, nanoparticles, nanofabrication, ultraviolet spectra, visible spectra, particle size, transmission electron microscopy, Fourier transform infrared spectra, X‐ray diffraction, crystal structure, enzymes, molecular biophysics, tumours, biomedical materials, nanomedicineOther keywords: Chamaemelum nobile extract, oxidative stress, mice paw, silver nanoparticles, antiinflammatory activity, antioxidant activity, ultraviolet‐visible absorption spectrum, spherical nanoparticle size, transmission electron microscopy, Fourier transform infrared spectroscopy, biological active compounds, X‐ray diffraction, crystalline structure, carrageenan‐induced paw oedema, malondialdehyde, antioxidant enzymes, superoxide dismutase, catalase, glutathione peroxidase, inflammatory cytokines, tumour necrosis factor, interferon gamma, interleukin, IL‐1β, IL‐6, TNF‐α, MDA level, Ag