NiMn2O4纳米粉体的相变过程和晶粒生长行为研究

采用溶胶凝胶法（Ｓｏｌ－Ｇｅｌ）制备ＮｉＭｎ２Ｏ４纳米粉体．用Ｘ射线衍射（ＸＲＤ）法，热分析仪研究ＮｉＭｎ２Ｏ４纳米粉体的相变过程．用Ｘ射线衍射线线宽法，透射电子显微镜（ＴＥＭ）研究晶粒长大行为．研究结果表明：热处理温度小于６７０°Ｃ，存在非晶晶化过程和向ＮｉＭｎ２Ｏ４尖晶石主晶相转变等相变过程，晶粒尺寸缓慢增大，热处理温度在于６７０°Ｃ，粉体的相结构为ＮｉＭｎ２Ｏ４尖晶石相．晶粒尺寸较快增长．相变过程严重影响了晶粒长大行为．     

Graphite powder and multiwalled carbon nanotubes chemically modified with 4-nitrobenzylamine.

We demonstrate that graphite powder and multiwalled carbon nanotubes (MWCNTs) can be derivatised by 4-nitrobenzylamine (4-NBA) simply by stirring the graphite powder or MWCNTs in a solution of acetonitrile containing 10 mM 4-NBA. We propose that 4-NBA partially intercalates at localised edge-plane or edge-plane-like defect sites and this hypothesis with a range of experimental data provided by electrochemistry in both aqueous and nonaqueous media, electron microscopy and X-ray powder diffraction.     

Degree of coherence and dimensions of the generation region of powder lasers

A degree of coherence of powder-laser radiation of 10–20% is estimated by the magnitude of the image contrast for a speckle, although cases are recorded where it attains 40–50%. It is found that as the average speckle intensity increases, the contrast decreases. It is established that the minimum, dimensions of the generation region in powders are 20–30 μm. Cases of existence of several generation centers simultaneously are noted. An attempt to interpret the results obtained is made. Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 11, Mokhovaya St., Moscow, 103907. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 780–786, September–October, 1998.     

Synthesis,Crystal Structure Determination from X‐Ray Powder Diffractometry and Vibrational Spectroscopic Properties of Mg[N(CN)2]2 · 4 H2O

Magnesium dicyanamide tetrahydrate Mg[N(CN)₂]₂ · 4 H₂O was synthesized by aqueous ion exchange starting from Na[N(CN)₂] and Mg(NO₃)₂ · 6 H₂O. The crystal structure was solved and refined on the basis of powder X‐ray diffraction data (P2₁/c, Z = 2, a = 737.50(2), b = 732.17(1), c = 971.67(2) pm, β = 98.074(1)°, wR_p = 0.059, R_p = 0.046, R_F = 0.075). In the crystal there are neutral complexes [Mg[N(CN)₂]₂(H₂O)₄] which are only connected via hydrogen bonds. Above 40 °C the tetrahydrate decomposes into anhydrous Mg[N(CN)₂]₂.     

Pre-equilibrium effects in (n, 2n) reactions at 14.2 MeV+

With a view to study the pre-equilibrium effects in neutron-induced reactions, the activation cross-sections for (n, 2n) reactions at 14.2±0.2 MeV in the heavy mass region have been measured using the versatile mixed powder technique and high resolution Ge(Li) detection. The experimental cross-sections are found to be consistently smaller than the predictions based on the statistical theory and this is attributed to the effect of pre-equilibrium decay in these reactions. The cross-sections due to pre-equilibrium decay were estimated using exciton, hybrid and unified models. When this cross-section was included in comparing the experimental cross-sections with theory, we obtained better agreement, within the limitations of the present-day preequilibrium theories. Preliminary results of this work were reported at the Nuclear Physics and Solid State Physics Symposium, Pune (1978).     

Determination of peptide φ angles in solids by relayed anisotropy correlation NMR

A solid state NMR method is presented for determination of a backbone dihedral angle φ in peptides, being based on the previously reported method, relayed anisotropy correlation (RACO) NMR [Y. Ishii et al., Chem. Phys. Lett. 256 (1996) 133]. In the present method, the and the dipolar tensors in the system are two-dimensionally (2D) correlated via polarization transfer from to under magic angle spinning (MAS). This method was applied to N-acetyl , -valine, and the H–C–N–H dihedral angle was determined to be 154.0±1.4° or 206.0±1.4°, the former agreeing with the X-ray value of 154±5°.     

Synthesis and Characterization of Monodisperse Spherical Zirconia Particles

Monodisperse zirconia spherical particles are prepared by hydrolysis of zirconium propoxide in 2-methoxyethanol in presence of decanoic acid as a shape stabilizer. The powder is analyzed by computer image analysis on TEM micrographs, TG-DSC, FTIR, X-ray diffraction and nitrogen adsorption isotherms. A competition phenomenon between aggregation and individual growth of the particles during precipitation is deduced from the observations.     

悬浮粒子对电沉积Zn粉缓蚀性能的影响

在ＺｎＣｌ２镀槽中悬浮一定量的不溶性粒子，如石墨ＰｂＣ２，ＳｎＯ２，ＴｉＯ２，ＳｉＯ２等，电沉积制备Ｚｎ粉，并对其结构，形貌及腐蚀行为进行分析，ＳＥＭ的结果表明使用悬浮法可阻止Ｚｎ枝晶生长，悬浮ＰｂＯ２，ＳｎＯ２，ＴｉＯ２，ＳｉＯ２或Ｉｎ２Ｏ３等能明显地提高Ｚｎ粉在５ｍｏｌ／ＬＫＯＨ溶液中的缓蚀能力此外，文中还应用于分形理论对结果作了进一步讨论。     

活血逐瘀颗粒剂中芍药甙的含量测定

本文采用了薄层色谱法将复方制剂活血逐瘀颗粒中的芍药甙与其他成分分离，用紫外分光光度法测定芍药甙的含量，其平均回收率为９８．７４％，变异系数为１．４３％，本文方法抗干扰能力强，适合于中药复方制剂中芍药甙的定量分析。