Thermal behaviors and kinetic analysis of two natural kaolinite samples selected from Qingshuihe region in Inner Mongolia in China

Journal of Thermal Analysis and Calorimetry - The thermal characteristic behaviors of two kaolinite samples selected from Qingshuihe region in Inner Mongolia in China were studied through...     

Sparse representation-based image restoration via nonlocal supervised coding

Sparse representation (SR) and nonlocal technique (NLT) have shown great potential in low-level image processing. However, due to the degradation of the observed image, SR and NLT may not be accurate enough to obtain a faithful restoration results when they are used independently. To improve the performance, in this paper, a nonlocal supervised coding strategy-based NLT for image restoration is proposed. The novel method has three main contributions. First, to exploit the useful nonlocal patches, a nonnegative sparse representation is introduced, whose coefficients can be utilized as the supervised weights among patches. Second, a novel objective function is proposed, which integrated the supervised weights learning and the nonlocal sparse coding to guarantee a more promising solution. Finally, to make the minimization tractable and convergence, a numerical scheme based on iterative shrinkage thresholding is developed to solve the above underdetermined inverse problem. The extensive experiments validate the effectiveness of the proposed method.     

Two New Neolignans from the Stems of Syringa pinnatifolia Hemsl. var. alashanensis

Two new neolignans, syripinnalignins A and B ( 1 and 2 , resp.), were isolated from the 95% EtOH extract of the stem of Syringa pinnatifolia Hemsl . var. alashanensis. The structures of 1 and 2 were elucidated by spectroscopic methods, including UV, IR, HR‐ESI‐MS, and extensive 1D‐ and 2D‐NMR techniques.     

Adsorption of 2‐amino‐5‐cyanopyridine on a gold surface as probed by surface‐enhanced Raman spectroscopy

The adsorption of 2‐amino‐5‐cyanopyridine (2‐ACP) was investigated in solution at different pH values by i n situ surface‐enhanced Raman scattering (SERS) spectroscopy combined with the electrochemical method. The assignments of the main bands were first performed on the basis of the spectral features of similar compounds and with the help of density functional theory calculations. The results revealed that the adsorption and the interfacial structure of 2‐ACP on the Au electrode depended on the applied potential and the pH values of the solution. In the natural solution, 2‐ACP was adsorbed on the surface with a vertical orientation by the CN group from − 0.4 to − 1.0 V, whereas in the − 0.4 to 0.8 V range, the N atom of the pyridine ring was bound to the surface. A transition region for the reorientation of the two adsorption modes was observed from − 0.8 to − 0.4 V. A flat configuration was preferred at an extremely negative potential. A similar surface adsorption behavior was observed in the alkali environment, while the Stark effect slope decreased because of the adsorption of OH⁻. Due to the protonation of N atom in the acidic solution, the potential region for the coexistence of two configurations ranged from − 0.4 to 0.2 V. Additionally, a similar adsorption configuration was proposed on the Au colloids at various pH values. The results revealed that the adsorption behavior became more complex on colloidal surfaces than that on a rigid electrode surface. Copyright © 2010 John Wiley & Sons, Ltd.     

北京同步辐射软X光反射率计装置及其物理工作

介绍了安装在北京同步辐射装置上专门用于软X光多层膜研究的反射率计系统,给出了在该装置上测量得到的Al滤光片的软X光透射谱和Nb/Si多层膜的高角反射谱,用磁控溅射方法自制的Nb/Si多层膜样品在17.59um附近得到的反射率为32%.     

Low-temperature preparation of F-doped TiO2 film and its photocatalytic activity under solar light

A novel and simple method for preparing F-doped anatase TiO₂ (defined as FTO) film with high photocatalytic activity was developed using titanium-n-butoxide and NH₄F as TiO₂ and fluorine precursors under mild condition, i.e. low temperature (lower than 373 K) and ambient pressure. The prepared samples were characterized by XRD, SEM, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectrum (DRS), photoluminescence spectrum (PL) and TG-DSC analysis. The photocatalytic activity was evaluated by decomposing X-3B under artificial solar light. The results showed that the crystallinity of TiO₂ was improved by F-doping. F⁻ ions can prevent the grain growth, and the transformation of anatase to rutile phase was also inhibited. The doped fluorine atoms existed in two chemical forms, and the ones incorporated into TiO₂ lattice might take a positive role in photocatalysis. Compared with surface fluorination samples, FTO film exhibited better photocatalytic activity. The high photocatalytic activity of FTO may due to extrinsic absorption through the creation of oxygen vacancies rather than the excitation of the intrinsic absorption band of bulk TiO₂. Furthermore, the FTO can be recycled with little photocatalytic activity depression. Without any further treatment besides rinsing, after 6 recycle utilization, the photocatalytic activity of FTO film was still higher than 79%.     

Low-temperature preparation of anatase titania-coated magnetite

A composite photocatalyst with an anatase titania shell and a magnetite core was prepared in a novel way at low temperature (75 °C at most) by coating photoactive titanium dioxide onto a magnetic Fe₃O₄ core. The photocatalytic activity of the prepared photocatalyst was evaluated by the degradation of model contaminated water of phenol and compared to single-phase titania (either Degussa P25 or prepared titania without magnetic Fe₃O₄). The results showed that the photoactivity was slightly depressed. Then, a remarkable improvement in photoactivity was achieved by modifying the photocatalyst with a SiO₂ layer between the Fe₃O₄ core and TiO₂ shell. The repetitive using of the modified photocatalyst was also investigated, and experimental results illustrated that the photocatalytic-degraded ratio of phenol was still higher than 80% after six cycles.     

Double dehydrogenation of carbocyclic β-dicarbonyl compounds:Koser's reagent can do what iodine(V) reagents can

Koser's reagent is found to be effective in the oxidative double dehydrogenation of various carbocyclic β-dicarbonyl compounds,which constitutes the first example on dehydrogenation reactivity of hypervalent iodine(Ⅲ) reagents for carbocyclic carbonyl compounds. DFT calculations reveal that the rate-determining step is the electrophilic addition of PhI+OH onto enolate of monodehydrogenated product.     

一种生物柴油代用品在HZSM-5分子筛催化剂上的催化热解

为了深入了解生物柴油在ZSM-5沸石上的催化反应机理,在常压的流动反应器中进行了生物柴油代用品丁酸甲酯在氢型ZSM-5(HZSM-5)催化剂上的热解和催化热解. 热解产物使用气相色谱-质谱法定性和定量测量. 动力学模型和实验表明,气相中氢提取反应是热解过程中丁酸甲酯分解的主要途径,但在HZSM-5上,丁酸甲酯则主要通过解离生成烯酮和甲醇消耗;与无催化反应相比,丁酸甲酯在HZSM-5上的初始分解温度降低了约300 K. 并且通过Arrhenius方程获得了在催化热解和均相热解条件下丁酸甲酯消耗的表观活化能. 明显降低的表观活化能证实了HZSM-5对丁酸甲酯热解的催化性能. 此外催化剂的活化温度对HZSM-5的某些催化性能具有一定的影响. 该研究对进一步的实际生物柴油燃料的催化燃烧具有一定的指导意义.     

聚丙烯腈基碳纤维原丝在纺丝过程中纳米孔变化规律与机理研究

应用小角X射线散射等方法, 系统、定量地测试表征了聚丙烯腈基碳纤维原丝中纳米孔的尺寸、形状、体积分数、单位体积中纳米孔绝对数量以及纤维总孔洞率等形态结构参量, 并对这些参量在水洗、水洗牵伸、热致密化、高压蒸汽牵伸及热稳定化等工艺过程中的变化规律及原因进行了研究. 结果表明, 纺丝过程中牵伸及高温热处理均可使纤维总孔洞率逐步下降. 纳米孔尺寸体积分数V_i测试表明, 对于小于10 nm³的小纳米孔和大于10³ nm³的较大纳米孔, 两者的V_i在纺丝初期水洗牵伸工艺中分别为0.217和0.369, 而在纺丝后期热稳定化处理后发生大幅度改变, 分别为0.948 与0.015. 其原因并不是在高压蒸汽牵伸及热稳定处理中较小纳米孔含量的增加, 而是较大纳米孔含量的大幅度减少. 纳米孔形状研究表明, 纺丝工艺中的多次牵伸处理均使纳米孔的长短轴比加大, 而大于玻璃化温度的热处理均使纳米孔长短轴比收缩, 并且对于较小纳米孔来说这种收缩更为显著.