温度对Ib型和IIa型金刚石大单晶(100)表面特征的影响

本文在5.6 GPa, 1250–1340 ℃的条件下, 利用温度梯度法, 以FeNiMnCo 合金为触媒, 沿籽晶的(100)晶面成功合成了不同晶形的优质Ib型和IIa型金刚石大单晶. 利用激光拉曼附件显微镜, 分别对上述不同温度下合成的两类金刚石样品上表面(100)面的中心区域及棱角区域进行观察分析. 研究发现, Ib型和IIa型金刚石大单晶(100)晶面上从中心到棱角处黑色纹路的分布逐渐变黑变密集; 另外, 随着金刚石合成温度的升高, Ib型金刚石大单晶(100)面上黑色纹路由稀疏逐渐变稠密, 而IIa型金刚石大单晶的黑色纹路较为稀疏; Ib型金刚石大单晶的形貌特征表现为从低温晶体的不规则分布过渡到中温、高温晶体的典型树枝状分布. IIa型金刚石大单晶(100)面特征随温度变化规律与Ib型的类似. 这两类金刚石大单晶表面特征的差异可能是由于IIa 型金刚石具有比Ib型更小的生长速度和更少的氮含量. 最后, 对两类塔状金刚石大单晶进行拉曼光谱测试分析, 结果表明IIa型金刚石大单晶的品质较Ib型金刚石大单晶好.     

Grow Large High-Quality Diamonds with Different Seed Surfaces

Large high-quality type Ib diamond crystals have been grown with different seed surfaces by temperature gradient method at 5.5 CPa, 1500-1600K, with NiMnCo alloy as the metal solvent. Compared with {100} as the growth surface, the growth region of large high-quality diamond crystals with {111} as the growth surface at a higher growth rate shifts markedly from lower temperatures （suitable for {100}-facet growth） to higher temperatures （suitable for {111}-facet growth）. However, regardless of different growth surfaces, {100} or {111}, the grown crystals of sheet-shaped shape are most difflcult for metal inclusions to be trapped into, and whether or not matched growth between the seed surfaces and the growth temperatures determines the crystal shapes. In view of the growth rates, large high-quality diamond crystals of sheet-shaped shapes can be grown at a growth rate of above 2.5 mg/h, while the growth rate of large high-quality diamond crystals should not be beyond 1.5 mg/h for tower-shaped crystals.     

双反馈光学双稳态

提出了采用双反馈来提高光学双稳系统静态稳定度的方法。理论分析和实验均表明，采用这种方法可命名稳定度获得大幅度提高，非常明显地改善了系统输出的稳定性。     

Measurement of Ultrashort Laser Pulse Width in a Wide Spectrum Range Using Dimethyl Sulfoxide by Optical Kerr Effect Technique

We illustrate that applying the optical Kerr effect technique to dimethyl sulfoxide （DMSO） can determine the width of laser pulses in a wide spectrum range that is transparent. Different from many other simple molecular liquids, such CS2, and toluene, DMSO responds to both 130 fs 800 nm laser pulses and 248 fs 400 nm laser pulses with electronic motions only. Therefore, the observed signal as a function of time reflects the temporal distribution of the intensity. We verify our illustration by both the autocorrelation technique and spectra analysis.     

Hetero-Epitaxial Diamond Single Crystal Growth on Surface of cBN Single Crystals at High Pressure and High Temperature

We report a new diamond synthesis process in which cubic boron nitride single crystals are used as seeds, FesoNi20 alloy powder is used as catalyst/solvent and natural flake-like graphite is used as the carbon source. The samples are investigated using laser Raman spectra and x-ray diffraction （XRD）. Morphology of the sample is observed by a scanning electron microscope （SEM）. Based on the measurement results, we conclude that diamond single crystals have grown on the cBN crystal seeds under the conditions of high temperature 1230℃ and high pressure 4.8 GPa. This work provides an original method for synthesis of high quality hereto-semiconductor with cBN and diamond single crystals, and paves the way for future development.     

高压合成La填充型CoSb3方钴矿热电材料及其电输运性能

 采用高温高压手段,在压力3.5 GPa、温度900 K的条件下,成功合成出La填充型方钴矿热电材料La_xCo₄Sb₁₂（0相似文献   

Ib型金刚石大单晶的限形生长

金刚石的限形生长有利于其后续加工.对于磨料级金刚石限形生长的研究已经比较透彻,但金刚石大单晶的限形生长尚缺乏全面系统的研究.本文以Fe Ni(64wt%:36wt%)合金为触媒,利用高温高压下的温度梯度法在5.6 GPa时对不同温度下分别沿(100)面和(111)面生长的Ib型金刚石大单晶的晶形进行了研究.研究表明:随着温度的升高,沿(100)晶面生长的金刚石大单晶的晶形分别为板状、塔状直至尖塔状,而沿(111)面生长的金刚石大单晶的晶形则分别为塔状和板状;分析了不同温度下分别沿(100)面和(111)面生长金刚石大单晶不同晶形高径比的变化情况.利用不同压力和温度下的金刚石大单晶合成实验绘制了沿(100)和(111)面生长金刚石大单晶的晶形在V形生长区域内的分布示意图,表明沿(111)面生长的金刚石大单晶V形区温度下限明显比以(100)面生长的高,而沿这两面生长金刚石大单晶的V形区温度上限差别并不明显.对不同生长面V形区温度上下限的差别进行了解释,据此实现了Ib型金刚石大单晶的限形生长.     

硼氢协同掺杂Ib型金刚石大单晶的高温高压合成与电学性能研究

在压力6.0 GPa和温度1600 K条件下, 利用温度梯度法研究了(111)晶面硼氢协同掺杂Ib型金刚石的合成. 傅里叶红外光谱测试表明: 氢以sp³杂化的形式存在于所合成的金刚石中, 其对应的红外特征吸收峰位分别位于2850 cm^-1和2920 cm^-1处. 此外, 霍尔效应测试结果表明: 所合成的硼氢协同掺杂金刚石具有p型半导体材料特性. 相对于硼掺杂金刚石而言, 由于氢的引入导致硼氢协同掺杂金刚石电导率显著提高. 为了揭示硼氢协同掺杂金刚石电导率提高的原因, 对不同体系进行了第一性原理理论计算, 计算结果表明其与实验结果符合. 该研究对金刚石在半导体领域的应用有重要的现实意义.     

有序介孔碳的简易模板法制备与电化学电容性能研究

0引言电化学电容器(Electrochemical Capacitors),又称为超级电容器(supercapacitors)是介于传统电容器和二次电池之间的一种新型储能装置,它具有循环寿命长、比容量高、能快速充放电等优点[1,2]。近年来随着电子、电气设备的日趋小型化以及电动汽车工业的不断发展,作为后备电源和记忆候补装置的超级电容器日益引起了人们的广泛关注。碳材料由于具有成本低、比表面积大、导电性优良、制备电极工艺简单等特点,一直是超级电容器电极材料的首选。其中,活性炭是最早采用的多孔电极材料,其比表面积可高达2500￣3000m·2g-1[3]。然而,活性炭材料…