双离子(40Ar+, C2H+6)辐照合成金刚石纳米晶颗粒

用双离子(⁴⁰Ar⁺，C₂H⁺₆)辐照实验完成了从多壁碳纳米管向金刚石纳米晶颗粒的转变.对转变机理进行了初步探讨.这一探索有望能成为一种金刚石纳米晶合成的新途径.由此可知，多重荷能离子辐照用于其他材料纳米结构的制备也不是凭空设想. 关键词： 金刚石纳米晶 离子辐照 透射电子显微镜     

Ar+轰击石墨表面生成碳纳米管和碳纳米多面体

报道了一种用60keV Ar⁺轰击石墨生成碳纳米管和纳米碳壳层多面体颗粒的方法.高分辨透射电子显微镜研究指出，这些纳米多层结构物的尺寸约在20nm到0.4μm之间，碳原子层之间的距离为0.34nm.基于高分辨透射电子显微镜图像，建议了一个关于“组合碳多面体”的生长模型. 关键词：     

Ar+离子束轰击在石墨表面形成六方金刚石纳米晶的研究

在0.6keV Ar⁺高剂量(～10²²/cm²)辐照石墨表面,借助于高分辨透射电子显微镜(HRTEM),发现有六方金刚石纳米晶产生.它们的平均直径介于1—50nm之间,而且晶粒个数约随其直径的增大而直线减少.有趣的是,晶粒具有两种结构模式：直径小于10nm的晶粒为单晶结构,而直径大于10nm的为多晶结构.基于受离子轰击过程特点制约的六方金刚石晶粒成核和成长观点,讨论了这种双重结构的形成性质. 关键词： 离子轰击 六方金刚石纳米晶     

La3PO7:Eu3+纳米晶的制备和光谱性质

通过燃烧法合成了Eu³⁺掺杂的含氧磷酸镧(La₃PO₇:Eu³⁺)纳米晶颗粒材料。样品的结构、形貌和粒径分别由X射线衍射、扫描电镜和透射电子显微镜得到。测量了样品的发射光谱、激光选择激发光谱和时间分辨光谱。实验结果表明:样品展示的较强红光发射来自于Eu³⁺ 的⁵D₀→⁷F₂辐射跃迁,Eu³⁺在La₃PO₇基质中至少占据两种不同的格位,且具有较低的格位对称性。     

Na+离子掺杂Gd2O3 ∶ Sm3+纳米晶的发光增强

采用柠檬酸作燃烧剂,在柠檬酸-硝酸盐体系下制备了Gd₂O₃ ∶ Sm³⁺和Gd₂O₃ ∶ Sm³⁺,Na⁺纳米晶。用X射线衍射仪、透射电子显微镜、荧光光谱仪等对样品的结构、形貌和光致发光性能进行了分析。结果表明:所得纳米样品为纯立方相,晶粒尺寸约为30 nm。在室温下,用275 nm激发光激发各样品时,可观测到Sm³⁺离子 的较强发光,其主发射峰位分别位于561.5,603.5,651.5 nm,分别对应着Sm³⁺离子的⁴G_5/2→⁶H_5/2 , ⁴G_5/2→ ⁶H_7/2 和⁴G_5/2 →⁶H_9/2的电子跃迁, 其中以⁴G_5/2→⁶H_7/2 跃迁的光谱强度最强。实验表明:Na⁺离子的掺入使得Sm³⁺离子的光发射强度显著增强。对引起样品荧光强度变化的原因进行了分析。     

水溶性β-NaY(Gd)F4:Yb3+/Er3+纳米棒的水热合成及生物偶联

以聚乙烯亚胺(PEI)为表面活性剂,采用水热合成法,制得了表面氨基修饰的水溶性β-NaY(Gd)F₄:Yb³⁺/Er³⁺纳米棒,并对β-NaY(Gd)F₄:Yb³⁺/Er³⁺上转换纳米棒的制备方法、条件等进行了考察.结果表明,当Gd³⁺的引入摩尔分数为40%时,200 ℃下反应8 h即可获得纯β-NaY(Gd)F₄:Yb³⁺/Er³⁺纳米棒.利用X射线粉末衍射仪(XRD)、扫描电子显微镜 (SEM)、透射电子显微镜(TEM)、荧光光谱(PL)对样品的结构、形貌及光谱特性进行了表征.结构和形貌分析结果表明,制得的样品为单相β-NaY(Gd)F₄:Yb³⁺/Er³⁺纳米棒,纳米棒的截面粒径约为40 nm,平均长度约为210 nm.在980 nm波长激发下,样品的上转换发光光谱中出现了4个发射中心位于407,529,546,660 nm的发射带,分别对应于Er³⁺离子的²H_9/2→⁴I_15/2、²H_11/2→⁴I_15/2、⁴S_3/2→⁴I_15/2和⁴F_9/2→⁴I_15/2跃迁.采用戊二醛法,使β-NaY(Gd)F₄:Yb³⁺/Er³⁺上转换纳米棒表面的氨基与牛血清蛋白(BSA)分子中的氨基成功偶连在一起.利用紫外光谱分析(UV)和考马斯亮蓝法,对二者的偶联进行了证明.     

Ag离子注入非晶SiO2的光学吸收、拉曼谱和透射电镜研究

能量为200keV的Ag离子，以1×10¹⁶，5×10¹⁶，1×10¹⁷ cm^-2的剂量分别注入到非晶SiO₂玻璃，光学吸收谱显示：注入剂量为1×10¹⁶ cm^-2的样品的光吸收谱为洛伦兹曲线，与Mie理论模拟的曲线形状一致；注入剂量较大的5×10¹⁶，1×10¹⁷ cm^-2的谱线共振吸收增强，峰位红移并出现伴峰. 透射电镜观察分析表明，注入剂量不同的样品中形成的纳米颗粒的大小、形状、分布都不同，注入剂量较大的还会产生明显的表面溅射效应，这些因素都会影响共振吸收的峰形、峰位和峰强. 当注入剂量达到1×10¹⁷ cm^-2时，Ag纳米颗粒内部可能还形成了杂质团簇. 关键词： 离子注入 纳米颗粒 共振吸收 红移     

CaF2：xYb3+, yEr3+纳米颗粒的合成及其上转换发光性质

采用水热合成法制备了CaF₂：xYb³⁺,yEr³⁺（x=0.1~0.8,y=0.01~0.08）纳米颗粒,利用X射线粉末衍射仪、透射电子显微镜和F-4600荧光分光光度计表征了样品的物相和形貌尺寸,并探究了Yb³⁺和Er³⁺掺杂浓度对样品的上转换发光性质的影响。结果表明,所合成的样品为立方相,球形颗粒,平均直径为 12 nm,敏化剂Yb³⁺的最佳掺杂摩尔分数为20%,而激活剂Er³⁺的最佳掺杂摩尔分数为6%。此时,绿光与红光的强度之比最大。     

掺铕纳米氧化锌的制备及其发光性质

以尿素为沉淀剂，与可溶性硝酸锌、硝酸铕反应制备纳米晶ZnO:Eu3+³⁺，通 过x射线粉末衍射、透射电子显微镜对纳米粒子的组成、结构、形貌及尺寸进行了分析和测定.研究 结果表明，制得的纳米粒子粒度均匀，粒径分布窄，最小粒径为8nm.详细研究了不同制备 方法、不同掺杂浓度及不同粒度等对ZnO:Eu3+³⁺发光性质的影响.为探讨纳米 掺杂材料的制备技术及发光方面的应用提供了可行的方法. 关键词： 光致发光 3+')" href="#">纳米晶ZnO:Eu3+³⁺ 均匀沉淀法     

Y2O3:Eu纳米晶中能量传递相互作用的研究

通过浓度猝灭曲线确定了引起Y₂O₃纳米晶中Eu³⁺发光浓度猝灭的是交换相互作用.测量了两种颗粒尺寸下Eu³⁺的⁵D₀—⁷F₂跃迁发光衰减曲线随掺杂浓度的变化,利用交换相互作用的理论衰减曲线对实验衰减曲线进行拟合.计算Eu³⁺离子的交换相互作用能量传递的效率,分析了Y₂O_{3关键词： 能量传递 2}O₃Eu纳米晶')" href="#">Y₂O₃Eu纳米晶 发光衰减     

GROWTH MODEL OF TEXTURED DIAMOND (111) FILM IN CH4/O2/H2 ATMOSPHERE

Partially oriented and highly textured diamond films on Si( 111 ) substrates were achieved by hot-filament chemical vapor deposition(HFCVD). High nucleation density greater than 5×10⁸cm^-2 was realiged in 3 min by near-surface glow discharge. The os-grown films were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD) and Raman spectroscopy. It was found that by adding a small amount of oxygen to the mixture of CH₄/H₂, the appearance of facet(111) was well controlled, and the secondary nucleation on the facet(111) was suppressed greatly. Growth feature of homoepitaxy on diamond (111) surface was demonstrated to be in Stranski-Krastanov model by SEM.     

Enhanced blue emission and EPR study of LaMgAl11O19:Eu phosphors

Europium doped LaMgAl₁₁O₁₉ phosphor was prepared by the combustion method. The as-prepared and post-treated (1350 °C 10 h 5% H₂+95% N₂) phosphors were investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques. XRD patterns show that LaMgAl₁₁O₁₉:Eu phosphors have hexagonal structure. FT-IR spectrum exhibits absorption bands corresponding to the stretching vibration of AlO₄ and AlO₆. Morphological studies reveal that this phosphor has faceted plates of varying sizes and shapes. The as-prepared LaMgAl₁₁O₁₉:Eu phosphor consists of both Eu³⁺ and Eu²⁺ ions. The phosphor exhibits a bright blue emission at 450 nm (4f⁶5d→4f⁷ transition of Eu²⁺). On post-treating the phosphor we are able to enhance the blue emission efficiency by 330%. The process was detected from the evolution of excitation, emission and EPR spectra and the results are discussed.     

Splitting of X-ray diffraction peak in (Ge:SiO2)/SiO2 multilayers

(Ge:SiO₂)/SiO₂ multilayers were fabricated for exploring the influence of the stress on the structure of Ge nanocrystals. When annealed at 800 °C, the multilayers show a clear splitting (fine structure) of the Ge (220) X-ray diffraction peak and have a preferred orientation. Similar effects cannot take place in the multilayers annealed at higher or lower temperature. Analyses of Raman scattering, X-ray diffraction spectroscopy, and transmission electron microscope observations suggest that the observed phenomena arise from compressive stress exerted on Ge nanocrystals, which is induced by the confinement of both the SiO₂ matrix in the cosputtered layer and neighboring SiO₂ layers. The stress may cause an orthorhombic distortion of the diamond structure of bulk Ge. This will lead to the disappearance of the (111) and (311) diffraction peaks and the splitting of the (220) peak. This kind of (Ge:SiO₂)/SiO₂ multilayers enables us to control the sizes of the Ge crystallites and enhance the stress, and is thus promising in forming new nanocrystal structures.     

Eu activated M6AlP5O20 (M=Sr/Ba/Mg) novel red phosphors

Eu³⁺ activated M₆AlP₅O₂₀ (where M=Sr/Ba/Mg) phosphors prepared by combustion synthesis and the completion of the synthesis was confirm by XRD (X-ray diffraction) patterns. The surface morphology studied by scanning electron microscopy (SEM) and photoluminescence (PL) properties has been reported in this paper. The Eu³⁺ PL emission spectrum was observed in M₆AlP₅O₂₀ phosphors (where M=Sr/Ba/Mg) at 592 (orange) and 618 nm (red) region, the spectrum due to ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at mercury free excitation, respectively. Its considerable emission intensity under 350 nm excitations makes it possible candidate materials as red component of tricolor luminescence materials and for near ultra violet light emitting diode (n-UVLED) phosphors.     

Al2O3-Y2O3-ZrO2三相复合陶瓷的介电谱研究

采用传统的固相反应法,在1400–1500 ℃下烧结,制备得到Al₂O₃-Y₂O₃-ZrO₂三相复合陶瓷.样品的结构、形貌和电性能分别用X射线衍射(XRD)、扫描电子显微镜(SEM)及介电谱表征.XRD表明此三相复合体系无其他杂相,加入Y₂O₃及ZrO₂后使得Al₂O₃成瓷温度降低;SEM表明此体系晶粒直径为200–500 nm,并且样品随烧结温度的升高而变得更加致密,晶界更加清晰;介电损耗谱中出现峰值弛豫现象,根据Cole-Cole复阻抗谱得出其为非德拜弛豫. 关键词： 2O₃-Y₂O₃-ZrO₂三相陶瓷')" href="#">Al₂O₃-Y₂O₃-ZrO₂三相陶瓷 介电弛豫 阻抗谱 热导率     

高压下Al0.77Mn0.19Yb0.04合金准晶T相形成及结构

 利用静高压（4.2 GPa）熔态（1 300 ℃）淬火（10² ℃/s）方法，对含稀土的铝锰合金Al_0.77Mn_0.19Yb_0.04进行了研究。首次发现了准晶T相得形成。利用选区透射电子衍射技术，对合金中准静态的结构对称性进行了观察和分析。根据X射线和电子衍射对其衍射峰进行了指标化。使用扫描电镜和能谱技术进行了成份分析。     

Preparation and properties of nanocrystalline powders in (Y1−xCex)3Al5O12 system

Nano-sized cerium-doped yttrium aluminum garnet (YAG:Ce) phosphors were synthesized via a simple sol-gel process using metal nitrate precursors. The prepared phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy, respectively. Pure cubic garnet phase was formed at temperatures ∼900 ^οC. The particle sizes of as-prepared powders were mostly in the range of 17-27 nm. The crystalline YAG:Ce showed broad emission peaks in the range of 400-700 nm and maximum intensities at 500 and 520 nm. It is found also that the emission intensity decreased with increasing Ce doping concentration from 0.1 to 1.5 at%. With increasing Ce doping concentration, the PL intensity was shifted towards shorter wavelengths.     

H2O2氧化法制备Fe3O4纳米颗粒及与共沉淀法制备该样品的比较

在近中性条件下，利用H₂Ｏ₂氧化Fe(OH)2胶体成功制备了Fe₃ Ｏ₄纳米颗粒.分别利用透射电镜(TEM)，x射线衍射仪(XRD)，振动样品磁强计(VSM)和超导量子干涉仪（SQUI D）对样品的形貌，结构，宏观磁性进行了表征和测量.TEM图像表明样品为球形颗粒，直径 大小约18nm，且分布较均匀.XRD结果表明样品为立方尖晶石结构.穆斯堡尔谱测量表明样品 室温下对应两套六线谱，样品的晶体结构存在缺陷，内磁场略小于块体Fe₃Ｏ4的值. 宏观磁测量表明样品的饱和磁化强度可达67×10^-3A·m²/g，在20 K出现了Verw ey转变.选择该法制备的Fe₃Ｏ₄纳米颗粒与共沉淀法得到的样品作 了磁性比较.宏观磁 测量表明共沉淀法制备的样品在外磁场为1T时仍未饱和，磁化强度仅为46×10^-3A·m²/g，在178K出现了超顺磁转变温度，且在测量温度范围内没有发现Verwe y转变. 关键词： 亚铁磁 超顺磁 穆斯堡尔谱     

Magnetic properties and charge ordering in Pr0.75Na0.25MnO3 manganite

The structural and magnetic properties of Pr_0.75Na_0.25MnO₃ have been investigated experimentally. At room temperature, the compound shows paramagnetic characteristic. Along with decreasing temperature, a peak appears in the magnetization versus temperature curve around 220 K. To clarify whether this peak is associated with the ordering arrangement of Mn³⁺ and Mn⁴⁺ ions, electron diffraction experiments were carried out below and above 220 K respectively. Only basic Brag diffraction spots can be observed at high temperatures, however, superlattice diffraction appears below 220 K. This provides direct evidence for the existence of charge ordering in Pr_0.75Na_0.25MnO₃. We find the Mn³⁺ and Mn⁴⁺ cations form zigzag chains in a-c plane by analyzing the diffraction patterns. Combining with the magnetization measurements and the results of electron spin resonance, we confirm the antiferromagnetic phase and ferromagnetic component coexist in Pr_0.75Na_0.25MnO₃ below 120 K.     

Industrial diamonds grown in Ni70Mn25Co5--graphite--sulfur system under HPHT

This paper reports that diamond single crystals were synthesized from sulfur-added Ni70Mn25Co5+C system under high pressure and high temperature(HPHT).It was found that additive sulfur had inhibited the nucleation and growth of diamond to some extent.X-ray diffraction of the collected sample indicated that under the synthesis conditions,a new compound MnS had been formed through the reaction of additive sulfur with manganese in the catalyst.The MnS has a fcc structure,and its average crystal size was about 30 nm.By scanning electron microscope,the {111} surface of diamond was found to be flat,while there was usually a large depression on the central region of {100}.Further observation showed that there were many small upside-down pyramidal pits in the expression.The results of x-ray photoelectron spectroscopy shows that MnS can only be detected in the depression in the range of detection precision.It was inferred that MnS had been dissolved in the melted alloy during the growth experiment,and precipitated in the sequent quenching process.