Influence of field evaporation treatment on the field emission properties of carbon nanotubes array

Field evaporation was used in the post-fabrication treatment of a carbon nanotubes (CNTs) array and effectively modified the CNTs morphology in favor of the field emission under a moderate field. After the field evaporation treatment, the uniformity of the emission site distribution improved but the onset voltage rose. Using the Fowler-Nordheim theory, the actual onset field and the evaporation field around the CNT were calculated to be −4.6-5 and 9-12 V/nm, respectively. These values are close to those obtained from the individual CNT samples. The above results have provided an alternative to modify the configuration of an array sample and demonstrated the feasibility of tackling the problem of the disparity in the field emission capability of different CNTs in an array.     

热蒸发YbF3薄膜的机械特性

 实验研究了热蒸发YbF₃薄膜在大气中的应力和附着力。利用Veeco干涉仪,测试了各种工艺条件下单层YbF₃薄膜的应力。结果发现:YbF₃薄膜的残余应力为张应力,热应力在残余应力中的比重较大;沉积方式对薄膜应力的影响不大;薄膜应力在大气中有一个释放的过程。热处理后,YbF₃薄膜应力增大。     

Al掺杂四针状ZnO纳米结构的制备及其光致发光和场发射特性

采用热蒸发法成功制备了Al掺杂四针状ZnO纳米结构(T-AZO),利用扫描电子显微镜、X射线衍射仪、荧光光谱仪和场发射测试系统分别研究了不同Al摩尔分数对T-AZO纳米结构表面形貌、微结构、光致发光谱和场发射特性的影响。实验结果表明:T-AZO纳米结构呈现六角纤锌矿结构,Al掺杂对四针状ZnO纳米结构的形貌产生明显影响并且使紫外发射峰产生蓝移。实验中,当Al掺杂摩尔分数为3%时,场发射性能最好,其开启场强为1.33 V/μm,场增强因子为8 420。     

Encapsulation and characterization of flurbiprofen loaded poly(є-caprolactone)–poly(vinylpyrrolidone) blend micropheres by solvent evaporation method

Flurbiprofen loaded PCL/PVP blend microspheres were prepared by o/w solvent evaporation method using various concentrations of gelatin as emulsifying agent. Microsphere recovery decreased with a decrease in the concentration of the emulsifier in the dispersion. Encapsulation efficiency and drug loading of microspheres increased with decrease in concentration of emulsifying agent. Hydration rate, encapsulation efficiency and drug loading of microspheres increased with increase in concentration of PVP. Rheological properties showed free flowing nature of microspheres. SEM (Scanning electron microscope) revealed microspheres were discrete, spherical and became porous with decrease in concentration of emulsifying agent but smooth with higher concentration of emulsifying agent. FTIR (Fourier transform infrared spectroscopy) spectra of pure and encapsulated flurbiprofen in all formulation showed no significant difference in characteristic peaks, suggesting stability of flurbiprofen during encapsulation process. X-RD (X-ray powder diffractometry) of pure flurbiprofen shows sharp peaks, which decreases on encapsulation, indicating dispersion at molecular level and hence decrease in the crystallinity of drug in microspheres. Microspheres showed an enteric nature at pH 1.2 and a sustained release pattern at pH 6.8. Rapid drug release was observed in microspheres with higher concentration of PVP (polyvinylpyrrolidone), PVP acts as channeling agent. Formulation with low concentration of emulsifying agent also showed a fast release due to porous structure. Drug release kinetics followed zero order at pH 1.2 while at pH 6.8 Higuchi model was best fitted and was found non fickian.     

A Preliminary experimental study of the boron concentration in vapor and the isotopic A preliminary experimental study of the boron concentrationin vapor and the isotopic fractionation of boron betweenseawater and vapor during evaporation of seawater

A laboratory experiment was undertaken to investigate the behaviour of boron at theseawater-air interface under air flow conditions. Dried air at 25 and 35℃ was passed over or bub-bled through seawater at the same temperature. A combination of ice-chilled condensers and KOHimpregnated cellulose fibre filters was used to collect boron from the reacted air. When air strippedof boron was passed over the seawater, boron was found in the reacted air, and its concentrationwas higher in the higher temperature test. In the tests where air was bubbled through seawater theconcentration of boron in the reacted air was directly proportional to the air flow rate. In this situa-tion the boron in the reacted air was mainly introduced as a spray of microdroplets. Isotopic analy-sis of the collected boron in the non-bubbled tests yields fractionation factors which demonstratethat the lighter isotope, 10B, is enriched in the reacted air. The size of the fractionation changeswith temperature, ruling out a purely kinetic effect.     

On-line matrix addition for detecting aerosol particles

Single aerosol particles were measured by matrix-assisted laser desorption/ionization (MALDI) with an aerosol time-of-flight mass spectrometer (ATOFMS). The inlet to the ATOFMS was coupled with an evaporation/condensation flow cell that allowed matrix addition by condensation onto the particles. The coated particles entered the ion source through three-stage differentially pumped capillary inlet and were then ionized by a focused 266 nm Nd:YAG laser. The mass spectra and aerodynamic size of the single particles can be obtained simultaneously. The on-line matrix addition technique makes it possible to identify biological aerosols in real-time.     

Mesoscale Surface Patterning of a Laterally‐Grafted Rod Amphiphile: Rings And Fibers

An aromatic amphiphilic molecule based on branched oligo(ethylene oxide) was synthesized. Evaporation‐driven ring formation and Langmuir–Blodgett films are investigated by utilizing this rigid–flexible block molecule. The size of the rings is strongly dependent on the solvent evaporation rate and the concentration of the molecule. In case of fast evaporation, volcano‐like rings are formed by evaporating solution of high concentration. Perfectly symmetrical rings with diameters in the range of 2–6 μm are obtained by evaporating solution of low concentration. The formation mechanism of the ring is briefly discussed. The molecule at the air–water interface exhibits excellent amphiphilic properties. Upon transferring the monolayer onto solid substrates, AFM revealed the formation of fine and long, straight fibers. By combining the data obtained from the isotherms, AFM, water contact angle measurements, and UV/Vis and fluorescence spectra, the fibers are suggested to be formed by π–π stacking interaction of the aromatic rod segments as the oligo(ethylene oxide) branches are submerged in the water subphase upon compression. The fiber formation is associated with the transformation of the aromatic rod segments from the face‐on conformation to the edge‐on conformation.     

无沸腾喷雾冷却技术的研究进展

文中简述了无沸腾喷雾冷却技术近年来国内外的研究进展。着重介绍了关于影响无沸腾区换热各参数的实验研究,如壁面温度、介质体积通量、喷雾流量、喷雾倾角和喷雾高度等,为寻求最佳换热提供了指导。并对无沸腾区的理论研究内容进行了归纳,主要是模拟不同喷雾条件下的换热过程及特性参数(如液膜厚度)的大小和分布,并将理论值与实验数据进行比较分析;总结了影响无沸腾区换热的喷雾特性参数和外部特性。     

MAPLE deposition of Mn(III) metalloporphyrin thin films: Structural, topographical and electrochemical investigations

We report the deposition by MAPLE of metallized nanostructured (5,10,15,20-tetraphenyl)porphinato manganese(III) chloride thin films onto gold screen-printed electrodes, or 〈1 1 1〉 Si substrates. The deposited nanostructures were characterized by atomic force microscopy and exhibited globular structures with average diameters decreasing with laser fluence. Raman spectroscopy showed that no major decomposition appeared. We have investigated the Mn(III)-metalloporphyrin thin films by cyclic voltammetry in order to evaluate the potential bio/chemosensing activity on dopamine neurotransmitter analyte. We have found that the manganese(III)-porphyrin is appropriate as a single mediator for dopamine sensing in the specific case of gold screen-printed electrodes.     

氧化镍薄膜的制备及电化学性质

分别采用真空蒸镀_热氧化(VE_TO)及脉冲激光沉积(PLD)技术制备氧化镍(NiO)阳极薄膜材料,并利用XRD、SEM、循环伏安、充放电等方法对薄膜的结构和电化学性能进行了表征。结果表明,两种方法均制备了厚度均匀、表面光滑、与基片结合紧密、无缺陷、致密的纳米晶形NiO薄膜。采用PLD技术制备的薄膜颗粒更小、结构更有序,具有更高的电化学比容量,并且能承受大电流充放电。因此,这两种方法制备的NiO薄膜可根据充放电电流密度的要求有选择的应用于全固态薄膜锂离子电池中。