Mssbauer在测定Al—V—Fe纳米晶合金中相组成的应用

采用机械合金方法制备Al—V—Fe纳米晶合金粉末,合金粉末由纳米尺度的铝晶粒加非晶颗粒组成。利用Mossbauer测定表明合金由单铁组态、双铁组态固溶体以及非晶相组成,三者的含量分别为22.644%,16.746%,60.610%。     

Ni-Zn铁氧体纳米晶的机械化学合成

以α－Fe₂O₃、ZnO及NiO粉体为原料,在高能球磨的作用下,通过机械化学反应合成了Ni－Zn铁氧体纳米晶．用XRD、TEM及Mossbauer谱学方法对样品进行了表征．结果表明,球磨所得纳米晶的晶粒尺寸为5～20nm,表现为超顺磁性．经800℃热处理后,晶粒长大到约50nm;表现为亚铁磁性．     

非水介质中制备纳米氧化铁

在严格无水的条件下,制备了氧化铁纳米粒子,采用FTIR、XRD、TEM、TG-DTA、Mossbauer谱等方法对所得的纳米粒子进行了表征和分析.实验结果证明:室温晾干后,得到无定形的FeOOH超细粉体;通过控制热处理的温度;可以得到不同晶型的氧化铁纳米粒子.即:在300℃热处理1h,主要得到约30nm的Fe_3-xO₄,450℃处理1h,可得到粒径约为98nnm的α-Fe₂O₃粒子.     

固相法合成Li铁氧体纳米粒子

以Li₂CO₃和α-Fe₂O₃粉体为原料,通过高能球磨的机械化学处理,制备出具有固溶体结构的Li铁氧体的前驱体．将前驱体在远低于固相反应所需的温度下进行热处理,得到Li铁氧体粉体,这一反应是通过LiFeO₂作为中间相完成的．用Mossbauer谱、XRD、IR光谱、TEM及VSM方法对制得的Li铁氧体粉体进行了表征．结果表明,所得铁氧体为纳米粒子,具有有序结构,其比饱和磁化强度高于用湿化学方法所得的纳米粒子,且具有较高的矫顽力．     

低频脉冲磁场对非晶合金Fe78Si9B13稳定性的影响

对非晶合金Fe78Si9B13进行了低频脉冲磁场处理,用Mossbauer谱仪、透射电镜等方法,观察处理试样的微观结构变化,用DTA方法研究了低频脉冲磁场对非晶合金Fe78Si9B13稳定性的影响;结果表明低频脉冲磁场可促进非晶合金发生纳米晶化,且处理后的试样与制备态相比其表观激活能有所提高,从而改善了原始非晶合金的稳定性.     

Quantitative Mossbauer Study on Retained Austenite and Carbide in High Speed Steel

The retained austenite in high speed steel oftwo different heat treatment regimes wasquantitatively,determined by transmissionMssbauer spectroscopy (TMS),backscatteringX-ray geometry,Mossbauer spectroscopy (BXMS)and X-ray diffraction technique.The results meas-ured by these methods were in agreement with eachother.It was demonstrated that the concentrationof carbides in high speed steel could be measured bytransmission Mossbauer spectroscopy or Mossbau-er spectroscopy in backscattering X-ray geometryaccurately.     

棒状γ-Fe2O3纳米粒子的制备及表征

在聚乙二醇(PEG-400)存在的条件下,在溶液中FeCl3与NaOH反应所得的沉淀物经抽滤后,在空气中60℃干燥6h后再在不同温度下热处理.所得的各样品用XRD、Mossbauer谱、TEM及FTIR等手段进行了表征.结果表明,沉淀经60℃干燥6h后得到结晶较差的γ-Fe2O3粉体(含少量结晶较好的α-FeOOH).经300℃热处理1h后得长径比约为5的棒形γ-Fe2O3纳米粒子.     

Fe—SiO2颗粒膜的磁和隧道磁电阻效应

采用射频共溅射方法制备了不同金属体积分数fv的Fe-SiO2颗粒膜,利用X射线衍射、透射电镜、Mossbauer效应和振动样品磁强计详细研究了薄膜的结构、磁性及磁电阻效应.结果表明fv为0.33时,得到磁电阻最大值-3.3%.Fe033(SiO2)067样品在室温下表现出超顺磁性,对该样品的变温Mossbauer谱研究表明颗粒的尺寸分布满足对数正态分布.探讨了TMP与Fe的依赖关系.     

棒状γ-Fe_2O_3纳米粒子的制备及表征

在聚乙二醇(PEG-400)存在的条件下, 在溶液中FeCl₃与NaOH反应所得的沉淀物经抽滤后, 在空气中60℃干燥6h后再在不同温度下热处理. 所得的各样品用XRD、Mossbauer谱、TEM及FTIR等手段进行了表征. 结果表明, 沉淀经60℃干燥6h后?得到结晶较差的γ-Fe₂O₃ 粉体(含少量结晶较好的α-FeOOH). 经300℃热处理1h后得长径比约为5的棒形γ-Fe₂O₃纳米粒子.     

中国纳米科技与产业发展路径

纳米技术和信息技术、生物技术被列为21世纪世界经济发展的三大支柱。纳米科技和纳米材料一度成为国内产业热点问题，这两年国内纳米产业的声音稍有降温，大批纳米企业仍然在生存和发展边界线上孜孜以求。如何做大做强中国的纳米产业已成为政府产业决策部门、企业界、科学界共同面临的问题。中国纳米产业应该深入认识产业发展规律，有规划、有目标、有策略地进行产业组织创新、企业商业模式创新，走出中国纳米科技和纳米材料的产业自主创新之路。     

Mechanically Driven Alloying and Structural Evolution of Nanocrystalline Fe_(60)Cu_(40) Powder

Highly supersaturated nanocrystalline fcc Fe60Cu40 alloy has been prepared by mechanical alloying of elemental powders. The phase transformation is monitored by X-ray diffraction (XRD),Mossbauer spectroscopy and extended X-ray absorption fine structure (EXAFS). The powder obtained after milling is of single fcc structure with grain size of nanometer order. The Mossbauer spectra of the milled powder can be fitted by two subspectra whose hyperfine magnetic fields are 16 MA/m and 20 MA/m while that of pure Fe disappeared. EXAFS results show that the radial structure function (RSF) of Fe K-edge changed drastically and finally became similar to that of reference Cu K-edge, while that of Cu K-edge nearly keeps unchanged in the process of milling. These imply that bcc Fe really transforms to fcc structure and alloying between Fe and Cu occurs truly on an atomic scale. EXAFS results indicate that iron atoms tend to segregate at the boundaries and Cu atoms are rich in the fcc lattice. Annealing experiments show that the Fe atoms at the interfaces are easy to cluster to α-Fe at a lower temperature, whereas the iron atoms in the lattice will form γ-Fe first at temperature above 350℃, and then transform to bcc Fe     

Superparamagnetic Behavior of Zinc-Substituted Nickel Ferrite Nanoparticles and its Effect on Mossbauer and Magnetic Parameters

Zinc-substituted nickel ferrite (Ni _1?x Zn _x Fe ₂ O ₄ with x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) nanoparticles were synthesized by solgel auto-combustion technique at low temperature and characterized by using X-ray diffraction, scanning electron microscopy, pulse field hysteresis loop technique, and Mossbauer spectroscopy. X-ray diffraction studies confirmed the formation of single-phase spinel structure of the prepared ferrite samples with average crystallite size of 30 nm, very close to that of the critical size for nanoparticles exhibiting superparamagnetism. Scanning electron micrographs of the ferrite samples showed uniform spherical morphology of nanograins with homogenous microstructure. Further investigations on magnetic properties by pulse field hysteresis loop technique and Mossbauer spectroscopy indicated the presence of superparamagnetic phases in the ferrite samples attributed to occupation of octahedral [B] sites by zinc ions in these Ni–Zn samples and also to the nanometer sizes of the ferrite particles. Magnetic behavior of the Ni–Zn ferrite system is in agreement, initially, with Neel’s two-sublattice collinear model and then with the Yafet–Kittel model for samples with higher zinc content (x ≥ 0.4). Value of hyperfine splitting is found to decrease with increase in zinc content and is attributed to the reduction in particle size giving rise to superparamagnetism. Other Mossbauer parameters like quadrupole splitting and the isomer shift are within the reported range for those of ferrites with spinel structure.     

Mossbauer study of the effect of oxygen stoichiometry on the highTc superconductor Y1Ba2(Cu0.97Fe0.03)3O7?x

The Mossbauer effect of oxygen-depleted YBa₂Cu₃O_7-x and PrBa₂Cu₃O_7-x doped with 3%⁵⁷Fe has been investigated at room temperature. A manifold of quadrupole-split spectra has been found, whose parameters are in general agreement with those found by other workers. In addition, the Mossbauer spectra show that a fraction of the Fe sites develop magnetic order at room temperature when the oxygen content is reduced. It is demonstrated that the observed asymmetries in the Mossbauer spectra can be the result of a preferential alignment of the platelike crystallites that arises during the normal sample preparation process. The tendency to bond with the oxygen atoms is presumed to be responsible for the discreteness of the Mossbauer spectra as a function of oxygen depletion.     

非晶Fe_(77)Cr_7B_(16)晶化过程的Mssbauer谱学研究

测量了Fe77Cr7B16非晶晶化过程居里温度Tc变化和Mossbauer透射谱．计算了磁超精细场分布P（H）．讨论了Fe77Cr7B16非晶晶化过程中非晶基体交换作用的变化     

Mossbauer study of the effect of oxygen stoichiometry on the highT c superconductor Y1Ba2(Cu0.97Fe0.03)3O7−x

The Mossbauer effect of oxygen-depleted YBa₂Cu₃O_7-x and PrBa₂Cu₃O_7-x doped with 3%⁵⁷Fe has been investigated at room temperature. A manifold of quadrupole-split spectra has been found, whose parameters are in general agreement with those found by other workers. In addition, the Mossbauer spectra show that a fraction of the Fe sites develop magnetic order at room temperature when the oxygen content is reduced. It is demonstrated that the observed asymmetries in the Mossbauer spectra can be the result of a preferential alignment of the platelike crystallites that arises during the normal sample preparation process. The tendency to bond with the oxygen atoms is presumed to be responsible for the discreteness of the Mossbauer spectra as a function of oxygen depletion.     

MÖssbauer Study of Mechanical Alloying Fe-Ti and Fe-Ti-N Alloys

Mossbauer spectrometry was used to study the peculiarity of formation of nonequilibrium phase in Fe-Ti and Fe-Ti-N systems by mechanical alloying. Mossbauer spectra of powders show the formation of nonequilibrium crystalline phase and intermetallic compounds during a mechanical alloying process depending on the alloy composition and the milling time.     

■ SPECTROSCOPY STUDY OF THE CRYSTALLIZATION OF AMORPHOUS Fe_(77)Cr_7B_(16)

测量了Ｆｅ７７Ｃｒ７Ｂ１６非晶晶化过程周期温度Ｔｃ变化和Ｍｏｅｓｓｂａｕｅｒ秀射谱，计算了磁超精细场发布Ｐ（Ｈ）讨论了Ｆｅ７７Ｃｒ７Ｂ１６非晶晶化过程中非晶基体交换作用的变化。     

氢对YFe10V2的结构和磁性的影响

吸氢使ＹＦｅ１０Ｖ２晶格膨胀，磁化强度和居里温度增加，但Ｆｅ－Ｆｅ的交换作用系数减小。吸氢不改变铁亚晶格的单易轴磁结构，但使单轴向向异性减弱。氢使各铁晶位的超精细场和同质异能移位都增加。     

Mossbauer Study of Mechanica Aloying Fe-Ti and Fe-Ti-N Alloys

Mossbauer spectrometry was used to study the peculiarity of formation of nonequilibrium phase in Fe-Ti and Fe-Ti-N systems by mechanical alloying. Mossbauer spectra of powders show the formation of nonequilibrium crystalline phase and intermetallic compounds during a mechanical alloying process depending on the alloy composition and the milling time.