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71.
以Fe(NO3)3.9H2O和Cd(NO3)2.4H2O为原料,以柠檬酸为还原剂,采用燃烧法制备了CdFe2O4纳米粉体,用X射线粉末衍射仪(XRD)、透射电子显微镜(TEM)、红外光谱(IR)和振动样品磁强计(VSM)等手段对样品进行了表征,结果表明,样品为尖晶石型铁酸镉纳米粉体,其粒径大约为20—50nm,且具有超顺磁性。 相似文献
72.
73.
DS Zhulai SA Bugaychuk GV Klimusheva TA Mirnaya VN Asaula VI Handziuk 《Liquid crystals》2017,44(8):1269-1276
The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC8) and of the cobalt octanoate (CoC8). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained. 相似文献
74.
In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal (P63/mmc) and orthorhombic (Pmmn) structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B (Ru-B) than those of Re-B (Os-B). All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength. 相似文献
75.
V. G. Shpak S. A. Shunailov M. R. Ul'maskulov M. I. Yalandin N. S. Ginzburg I. V. Zotova A. S. Sergeev I. V. Konoplev A. D. R. Phelps A. W. Cross S. J. Cooke P. Aitken 《Russian Physics Journal》1996,39(12):1233-1240
We have theoretically and experimentally investigated the process of induced coherent emission (superradiance) in an electron
bunch rotating in a homogeneous magnetic field. We have shown that this process makes it possible to generate ultrashort microwave
pulses. In this case, the optimum conditions are found under group synchronism conditions, when the translational velocity
of the bunch matches the group velocity of the radiation propagating in the waveguide circuit. For experimental investigation
of the superradiance, we used a RADAN accelerator with subnanosecond electron pulse sharpener. In the 35 GHz range, we obtained
microwave pulses with record short duration, down to 0.4 nsec for a peak power level up to 200 kW.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 89–97, December, 1996. 相似文献
76.
催化光度法测定钒已有报道[1~3],在0.45 mol·L-1磷酸介质及加热条件下,过氧化氢氧化溴甲酚紫褪色反应非常缓慢,而痕量钒对此反应具有较高的催化活性,且在一定浓度范围内,钒量与褪色反应程度呈线性关系,据此可建立测定痕量钒的方法.方法的检出限为1.9×10-6g·L-1,测定范围为0.003~1.8 mg·L-1.方法操作简便,重现性好,用于钢样中痕量钒的测定,结果满意. 相似文献
77.
78.
V. G. Shpak M. I. Yalandin S. A. Shunailov M. R. Ul'maskulov 《Russian Physics Journal》1996,39(12):1257-1263
The excitation of superbroad-band TEM antennas with a high-voltage subnanosecond modulator permitting a pulse-repetition frequency
of up to 100 Hz is experimentally investigated. The modulator consists of a RADAN-303B nanosecond driver and a pulse amplifier
based on gas discharges. The instrument generates unipolar and bipolar pulses of tunable length and amplitude. The amplitude
and power of the pulses sent to the antenna reach 100 kV and 200 MW. Data are obtained on the stability of the parameters
of the subnanosecond modulator pulses. Information is given on the electrical strength of the air insulation in the matching
interval between the modulator and the antenna. The superbroad-band pulses emitted are recorded at distances of up to 25 m.
The characteristics of the instrument permit the spatial resolution of reflections from conducting objects with a shape-inhomogeneity
scale of no more than 25 cm. Emitters with increased directionality in the E or H (E and H) planes based on two (four) TEM
antenna supplied with split modulator pulses are investigated. In-phase and antiphase antenna configurations are considered.
Institute of Electrophysics, Ural Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii,
Fizika, No. 12, pp. 119–127, December, 1996. 相似文献
79.
通过固定化酶Novozyme435(NV435)催化聚乙二醇(PEG)开环聚合己内酯(CL)得到端基带有羟基的ABA型三嵌段聚合物,用2,2-二氯代乙酰氯将聚合物的端羟基功能化形成H型大分子引发剂,在CuCl/HMTETA体系中引发4-乙烯基吡啶(4VP)进行原子转移自由基聚合反应(ATRP),得到了具有两亲性的H型五嵌段聚合物(PVP)2-b—PCL-b.PEG-PCL-(PVP)2,用红外光谱(FT IR),核磁共振(^1H NMR),凝胶渗透色谱(GPC)对其结构与分子量及其分子量分布进行了表征,结果表明:H型五嵌段聚合物分子量46121g/mol,分子量分布1.30.并利用动态光散射(DLS)和原子力显微镜(AFM)对聚合物在水溶液中的自组装行为进行了研究,H型嵌段聚合物的胶束呈球形结构,平均直径为70nm左右. 相似文献
80.
Mixed-metal carbonyl clusters of W2Ir2(CO)10(η^5-C5H4Me)2 1 and W2Ir2(μ-L)(CO)8(η^5-C5H4Me)2 (L = dppe 2, dppf 3) have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude (βtot-10×10^-30 esu). The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p (π*) electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values. 相似文献