二氧化钛纤维表面担载Pt纳米结构的原子力显微镜研究

通过原子力显微镜研究了二氧化钛纤维表面担载Pt的表面形貌及其结构.结果表明,TiO2纤维表面担载的Pt具有微米尺度的近似六边形或者近似长方形的结构,与在单晶TiO2(110)表面的Pt纳米簇形貌相似,但尺度较大.TiO2纤维担载的Pt表面明显存在不同高度的台阶结构,台阶高度以2~4倍Pt(111)晶面面间距的高度为主.由Pt在TiO2纤维表面的形貌与纤维的纳米晶粒排布有序性推测可知,Pt与TiO2纤维存在强的相互作用,可能正是这种强相互作用和表面台阶结构才使TiO2表面担载的Pt虽是微米尺寸但仍具有高光催化活性.     

26Al的加速器质谱测量及其应用

26Al是一个在多个学科都非常有意义的放射性核素。主要介绍了国内外在利用加速器质谱技术测量26Al时所开展的各种测量方法、各自的优缺点和测量灵敏度，并介绍了目前利用^26Al在地球科学、生物医学、核物理以及天体物理等诸多方面的应用研究工作。     

Polarization spectra of Rb atoms and their application in laser frequency stabilization

Polarization spectra of rubidium atoms were investigated with different uncrossed angles between the polarizer and the analyzer. The variation of the spectra was derived theoretically as a function of arbitrary angle, and measured experimentally for different angles. The spectral profile of D2 line of rubidium was further used to stabilize the frequency of a diode laser. It was demonstrated that the laser linewidth was reduced to 2 MHz.     

用HI-13串列加速器质谱装置测量182Hf的研究

¹⁸²Hf的半衰期为(8.90±0.09)Ma, 是一个接近灭绝的放射性核素. 超新星爆炸是自然界中已知的惟一能产生¹⁸²Hf的途径. 因此¹⁸²Hf是研究近1亿年来在地球附近可能发生的超新星事件的理想核素. 另外, ¹⁸²Hf是核工程中特别感兴趣的一个长寿命放射性核素. 精确测量超痕量的¹⁸²Hf对反应堆的设计和核天体物理学以及其他研究领域都是非常重要的. 用加速器质谱有可能实现对超低含量¹⁸²Hf的测量. 在中国原子能科学研究院的HI-13加速器质谱装置上对¹⁸²Hf的测量方法以及样品的化学去钨方法进行了研究, 分别得到了空白样品以及系列标准样品的¹⁸²Hf和¹⁸³W的能量-飞行时间双维谱. ¹⁸²W对¹⁸²Hf计数的贡献是通过测量¹⁸³W的计数归一扣除的. 目前本工作对¹⁸²Hf的测量灵敏度为4.15±10^－11 (¹⁸²Hf/¹⁸⁰Hf比值).     

Tl系超导薄膜金属涂层的生长与特性研究

我们研究了Tl-2212超导薄膜在带有YSZ/CeO2缓冲层和带有CeO2/YSZ/CeO2缓冲层的Ni金属RABiTS基带上的生长情况.基带上的缓冲层是采用PLD方法制备的,Tl-2212薄膜的制备采用了磁控溅射和后热处理两步方法.XRD 实验结果表明,Tl-2212薄膜都具有很好的C轴垂直于膜面的织构,并具有双向外延生长特性.在CeO2/YSZ/CeO2/Ni基带上制作的Tl-2212薄膜的Tc达到102.8 K,Jc(77 K,0 T)达到2.6 MA/cm2;在YSZ/CeO2/Ni基带上薄膜Tc可达97.7 K,Jc(77 K,0 T)也可以达到0.45 MA/cm2.     

氧含量对Tl-1212薄膜超导特性的影响

通过在氩气中的低温热处理降低氧含量 ,可使富氧的Tl 12 12薄膜的超导电性明显得到提高 .富氧的Tl 12 12薄膜是在氧气中高温下生成的 ,超导转变温度Tc 一般为 80～ 90K .去氧处理后 ,当氧含量为最佳值时 ,Tc 可以升高到 10 0K ;临界电流密度Jc 也有显著提高 ,77K温度下Jc 最高可以达到 1.8× 10 6A/cm2 .伴随Tc 和Jc 的提高 ,薄膜的晶格常数和表面形貌也有相应变化 .     

Measurements of 79Se with AMS based on extracting molecular negative ions

A new method for measuring selenium-79 with AMS, which is based on extracting molecular negative ions, is described in this paper. According to the experimental results, the extraction ion form SeO₂^－ could depress the interference of Bromine-79 as much as 5 order levels, that is to say, the background of ⁷⁹Br can be deducted to ⁷⁹Br/Se≈10^－10. By the way, the chemical form of sample and preparation flow was also developed. Finally, three ⁷⁹Se AMS calibration standard samples with theoretical ⁷⁹Se/Se ratios of 5.06×10^－7, 6.87×10^－8, 5.40×10^－10 were obtained and the method of ⁷⁹Se measurement was set up, which actualized transmission and detection of ⁷⁹Se. By using our Bragg curve detector, the two isobars ⁷⁹Br and ⁷⁹Se could be partly identified to a certain extent and ⁷⁹Se can be identified from ⁷⁹Br about 1 order level. AMS measurements of the three calibration standard samples above were performed and good linearity was obtained. The sensitivity of the measurement is (5.16±1.80)×10^－11.     

AMS measurement of In-situ produced cosmogenic 10Be in Loess Quartz in Luochuan

Loess is the most important and the most typical continental classic sediments of Quaternary. So the measurement of In-situ produced cosmogenic ¹⁰Be is expected to be used for the Loess stratigraphic age. But the production rate of In-situ produced cosmogenic ¹⁰Be in Loess quartz is very low. It requires very high sensitivity and accuracy of measurement. This work has measured the concentrations of ¹⁰Be of two layers in Loess section of Luochuan including L8, L9 and the concentrations of ¹⁰Be in (of) blank sample with the HI-13 AMS system at China Insitute of Atomic Energy(CIAE), then calculated the content of ¹⁰Be in loess quartz for each layer. The ratio of ¹⁰Be/⁹Be was found in the range of 10^－13. The background of ¹⁰Be/⁹Be was about 3×10^－14.     

高中数学考试命题中的改题方法

考试命题就是命制考试题目,其环节、方法众多为体现公平性,需尽量避免陈题,因此,原创试题和改编试题就成为命题的要事．诚然,原创试题难度颇大,且在一份试卷中的比重亦较小,于是,改编试题就是命题的主要工作之一．