铋基中间合金显微组织研究

介绍了Ｂｉ－Ｍｎ（及Ｂｉ－Ｍｎ－Ｆｅ）系和Ｂｉ－Ｎｉ（Ｂｉ－Ｎｉ－Ｆｅ）系高熔点铋中间合金的相及显微组织特征,以进一步建立含铋相的性质、数量与合金熔点间的定量关系。本文为Ｂｉ－Ｍｎ系、Ｂｉ－Ｎｉ系中间合金成份的优化提供了依据。     

Biomolecule-assisted Solvothermal Synthesis of Bismuth Sulfide Nanorods

A simple biomolecule-assisted synthetic route has been successfully developed to prepare bismuth sulfide(Bi 2 S 3 ) nanorods under solvothermal conditions.In the synthetic system,pentahydrate bismuth nitrate was employed to supply Bi source and L-cystine was used as sulfide source and complexing agent.The morphology,structure,and phase composition of the as-prepared Bi 2 S 3 products were characterized by X-ray diffraction(XRD),energy dispersion spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),field-...     

硅酸铋晶体的蚀像形貌

本文研究了提拉法生长的硅酸铋晶体(BSO)的蚀像形貌,比较了{100},{110},{211},{111}面族的腐蚀像特征和腐蚀速度,并用周期性键链(PBC)的形貌理论分析了腐蚀形貌。通过蚀像形貌特征便可方便地进行晶体定向,准确地确定各族晶面之间的相对位置和极轴的方向等。     

Effect of Annealing on Virgin and Recycled Carbon Fiber Electrochemically Deposited with N-type Bismuth Telluride and Bismuth Sulfide

N-type thermoelectric bismuth telluride (Bi₂Te₃) and bismuth sulfide (Bi₂S₃) were deposited on virgin carbon fiber (VCF) and recycled carbon fiber (RCF) substrates by electrodeposition. The effects of annealing on the surface morphology and the Seebeck coefficient of the Bi₂Te₃ and Bi₂S₃ films were investigated. A nearly stoichiometric N-type Bi₂Te₃ was obtained from an electrolyte solution of 8 mM of Bi(NO₃)₃.5H₂O and 10 mM of TeO₂, which displayed the highest Seebeck coefficient of ?20.01 and ?13.0 µV/K for VCF and RCF, respectively. The deposition of Bi₂S₃ was slightly off-stoichiometry, but the improvement was still significant with a Seebeck coefficient of ?16.3 and ?12.4 µV/K for VCF and RCF, respectively. The effect of varying the annealing temperature (275°C and 350°C) and annealing time (2 and 3 hours) was studied on a nearly stoichiometric N-type Bi₂Te₃. The result shows an improvement in the Seebeck coefficient by 1.51–1.24 times at 350°C for 2 hours.     

Physical characteristics of thermally evaporated Bismuth thin films

Thin films of bismuth with different thicknesses were produced by thermal evaporation from a molybdenum boat source onto cleaned glass substrates at room temperature. The material has been characterized using X-ray diffraction, electrical and optical measurements. A polycrystalline transition phase was observed. The resistivity was calculated for different film thicknesses and found to vary with thickness and temperature. An anomalous dependence of resistivity on temperature was observed during heating. The optical constants were determined from the transmission and reflection data of these thin films for normal incidence. The absorption coefficient revealed the existence of an allowed direct transition with energy gap (E_g) values ranging from 3.45 to 3.6 eV.     

半金属铋薄膜导电特性和粗糙度的研究

本论文利用真空镀膜方法在云母片上生长半金属Bi薄膜,测量了薄膜生长厚度与电阻之间的关系,并用原子力显微镜(AFM)研究了云母表面半金属薄膜电阻变化与薄膜粗糙度间的关系.生长初始阶段,薄膜先形成孤立的三维小岛(典型高度1 nm,直径10 nm,间距10 nm),随后互相聚结形成网状结构,薄膜不导通(R≥20 MΩ),粗糙度随膜厚增加而减小.当等效厚度d=1.74 nm时,薄膜导通(R≤13 MΩ),薄膜的形貌变为有小孔洞的连续状结构,粗糙度在此厚度附近达到最小值然后又增大.随着薄膜继续生长,连续状结构的厚度增加,薄膜电阻随之迅速减小,当d≥2.4 nm时薄膜电阻趋近于稳定值2kΩ.     

基片温度对射频磁控溅射碲化铋薄膜微结构和表面形貌的影响

碲化铋材料是目前已知的室温下性能优异的热电材料之一。本文利用射频磁控溅射在不同基片温度下制备了碲化铋薄膜。研究发现,基片温度对薄膜的微结构和表面形貌影响显著。随着温度的提高,薄膜内晶粒尺寸都不同程度地增加。基片温度100℃以上碲化铋薄膜为Bi2Te3相为主的多晶结构,并具有良好的c轴择优取向,形成了六角层状结构。基片温度250℃时薄膜转变为BiTe相,并在表面生成Te长条状颗粒。应力分析表明碲化铋薄膜与Si(100)基片之间的残余应力受温度影响明显。     

On the prediction of the orientation factor and fibre distribution of steel and macro-synthetic fibres for fibre-reinforced concrete

The orientation and distribution of the fibres is decisive in the mechanical behaviour of fibre-reinforced concrete. Several classical models have extensively been used for the case of rigid steel fibres. The increasing interest in structural synthetic fibres that can bend demanded new considerations in this matter. A probabilistic model considering the previous research with stereographical assumptions has been performed allowing the use of fibres that can bend. This paper also provides significant tools for design engineering in order to predict and confirm the number of fibres crossing a vertical surface using fibre reinforced concrete with steel and polyolefin fibres. Additionally, the proposed model coincides with the most accepted values and represents with accuracy the existence of boundaries.     

掺杂锗酸铋晶体(Bi_4Ge_3O_(12))的电子顺磁共振

用电子顺磁共振方法对 Fe、Cr 和 Mn 杂质在 Bi_4Ge_3O_(12)晶体中的位置和价态进行了研究。测试并分析了和 Fe~(3+)和 Cr~(3+)离子的 EPR 谱线位置随磁场方向的变化,确定了 Fe~(3+)和 Cr~(3+)主要进入氧四面体占据 Ge位。测试并分析了 Mn~(4+)和Mn~(2+)掺杂样品各向异性的 EPR 谱线,也测试了处于晶体粉末态及玻璃态的 Mn 掺杂样品的谱线,认为 Mn~(2+)离子进入氧八面体占据 Bi 位。紫外线辐照后 Mn 离子 EPR 信号降低表明辐照导致 Mn 离子价态改变。     

Bismuth doping effect on the phase-change characteristics of nitrogen-doped GeTe films

The microstructures and electrical properties of 8.4% nitrogen-doped GeTe and GeBi(6 at.%)Te films thermally annealed in N₂ atmosphere were investigated. With the addition of Bi to N-doped GeTe films, the initial crystallization temperature was reduced and crystallization speed slowed. The N-doped GeBiTe films showed a rapid increase in crystallite size compared to the N-doped GeTe films. The formation energy of the nucleus may be lower due to the Bi atoms and the growth speed may be slower.     

On flow properties,fibre distribution,fibre orientation and flexural behaviour of FRC

For improving the mechanical properties of fibre reinforced concrete one can either increase the fibre content, use hybrid fibre systems, or one can attempt to align fibres in the direction of stress. In this paper, it is attempted to use the flow-properties of the fresh (self-compacting) concrete to change the fibre distribution and orientation. Using a single mixture of fibre reinforced concrete, containing 3% of 30 mm long straight steel fibres, the fibre distribution and orientation was determined in three different parts of a ‘U-shaped specimen’ where the concrete could flow in three different directions. The fibre distribution and orientation was determined from a CT-scan. Flexural tests show that the mechanical behaviour depends on the fibre distribution and orientation, which can be affected by changing the viscosity of the fresh mixture.     

Passively Q-switched fibre laser utilizing erbium-doped fibre saturable absorber for operation in C-band region

In this paper, a stable and robust all-fibre passively Q-switched erbium-doped fibre laser (EDFL) emitting at 1558?nm is described. The proposed laser utilizes an 11?cm long erbium-doped fibre as saturable absorber (SA). The fibre SA features a linear optical absorption of about 13?dB in the Q-switched EDFL operating regime. By elevating the input pump power from the threshold of 60?mW to the maximum available power of 142?mW, a pulse train with a maximum repetition rate of 86?kHz, minimum pulse width of 3.39?µs, maximum average output power of 10.5?mW, maximum pulse energy of 122?nJ and maximum peak power of 36?mW are obtained. The signal to noise ratio (SNR) of the spectrum is measured to be around 70?dB. This fibre SA is simple, reliable, compact and alignment free. Thus it is suitable for making a portable pulse laser source.     

锗酸铋（Bi4Ge3O12）单晶热物理性质的研究

本文用不同的测试技术和方法测定了锗酸铋(BGO)单晶的比热(300～800K)热膨胀系数(100～1100K)和导温系数(140～700K),进而导出了 BGO 单晶不同温度下的导热系数、定容比热、德拜温度和格虑内森数。本文还对 BGO 单晶热物理性质的变化规律作了理论解释。     

On multiplicity of solutions in quasi-brittle fracture computations

The analysis of quasi-brittle fracture processes is formulated as a linear complementarity problem either in finite increments or in rates. Some time-stepping solution procedures and mathematical programming algorithms are discussed as for their ability to capture the whole set of possible alternative equilibrium paths. Potentialities and limitations of the proposed approach and of the relevant procedures are pointed out also by means of a numerical example.     

On crack tunneling and plane-strain delamination in laminates

Previous numerical work on crack tunnelling and plane-strain delamination in layered solids is evaluated with static and fatigue experiments and analysis. It is concluded that the translation of the theory derived for static fracture to fatigue loading is not as straightforward as initially assumed. Details such as delamination location, stress state, plasticity and mode-mixity need further consideration to obtain a theory that is sufficiently adequate to describe the static and fatigue phenomena observed in practice.