Metal nanofibers with highly tunable electrical and magnetic properties via highly loaded water-based electrospinning

Nanofibers are synthesized by electrospinning highly loaded water-based precursor-polymer hybrid solutions followed by thermal treatment to control crystal structure. Electrical conductivity and magnetic coercivity, as shown, are tested displaying independent magnetic and electrical property control from coercive to superparamagnetic and resistive to near-bulk conductivity at room temperature.     

Novel highly luminescent europium dinitrosalicylates

A series of lanthanide dinitrosalicylates M₃Ln(3,5-NO₂-Sal)₃ · nH₂O (Ln = Eu, Gd; M = Li, Na, K, Cs) was synthesized. It was found that the luminescence efficiency of some M₃Eu(3,5-NO₂-Sal)₃ · nH₂O compounds was near to the high efficiency of europium dibenzoylmethanate with 1,10-phenanthroline, Eu(DBM)₃ · Phen. The luminescence excitation spectra, electron-vibrational luminescence spectra, and vibrational IR spectra were investigated. The energy of the lowest excited triplet state of the ligand was obtained from phosphorescence spectra of M₃Gd(3,5-NO₂-Sal)₃ · nH₂O, M(3,5-NO₂-HSal) · nH₂O, and M₂(3,5-NO₂-Sal) · nH₂O. The details of the structure of compounds were discussed. The influence of different M-cations on the Eu³⁺ luminescence efficiency and on the processes of excitation energy transfer to a Eu³⁺ ion was analyzed. The presence of large alkali metal cations in lanthanide dinitrosalicylates and an increase in the temperature weaken the network of hydrogen bonds and, to some extent, the “ligand–metal” bonds. This is a cause of a long-wavelength shift of the intraligand charge transfer (ILCT) band in Eu³⁺ excitation spectra arising at inclusion of Cs⁺ instead of Li⁺ cations in the crystal lattice and at the heating of compounds. A change of the energies of ligand electronic states at substitution of Li⁺ and Na⁺ for Cs⁺ can give a tenfold enhancement of the Eu³⁺ luminescence efficiency at 300 K.     

Novel highly luminescent europium dinitrosalicylates

A series of lanthanide dinitrosalicylates M₃Ln(3,5-NO₂-Sal)₃ · nH₂O (Ln = Eu, Gd; M = Li, Na, K, Cs) was synthesized. It was found that the luminescence efficiency of some M₃Eu(3,5-NO₂-Sal)₃ · nH₂O compounds was near to the high efficiency of europium dibenzoylmethanate with 1,10-phenanthroline, Eu(DBM)₃ · Phen. The luminescence excitation spectra, electron-vibrational luminescence spectra, and vibrational IR spectra were investigated. The energy of the lowest excited triplet state of the ligand was obtained from phosphorescence spectra of M₃Gd(3,5-NO₂-Sal)₃ · nH₂O, M(3,5-NO₂-HSal) · nH₂O, and M₂(3,5-NO₂-Sal) · nH₂O. The details of the structure of compounds were discussed. The influence of different M-cations on the Eu³⁺ luminescence efficiency and on the processes of excitation energy transfer to a Eu³⁺ ion was analyzed. The presence of large alkali metal cations in lanthanide dinitrosalicylates and an increase in the temperature weaken the network of hydrogen bonds and, to some extent, the “ligand–metal” bonds. This is a cause of a long-wavelength shift of the intraligand charge transfer (ILCT) band in Eu³⁺ excitation spectra arising at inclusion of Cs⁺ instead of Li⁺ cations in the crystal lattice and at the heating of compounds. A change of the energies of ligand electronic states at substitution of Li⁺ and Na⁺ for Cs⁺ can give a tenfold enhancement of the Eu³⁺ luminescence efficiency at 300 K.     

Preparation of highly exchangedLaHZSM-5 zeolite

This paper describes the result obtained when ZSM-5 zeolite was exchanged with the lanthanum ionby the hydrothermal method.     

无硫高倍膨胀石墨的制备及影响因素探讨

以鳞片石墨、硝酸、乙酸酐、高锰酸钾为原料，采用化学法经氧化酸化插层、水洗、干燥、高温膨胀过程制备膨胀石墨，利用正交试验方法确定最佳工艺条件，并对相关影响因素及插层机理作了初步探讨。结果表明：按鳞片石墨：硝酸：乙酸酐：高锰酸钾(质量比)=1：0．7：1．5：0．4，反应时间90min，反应温度30℃～40℃的条件可以制备出膨胀体积达478mL/g的高倍无硫膨胀石墨。相关影响因素的大小依次为：高锰酸钾、硝酸、乙酸酐、反应时间，其中高锰酸钾的影响程度远大于其他三个因素。     

Mechanical anisotropy of highly oriented polymers

Recent progress on the understanding of the mechanical anisotropy of orientedpolymers is reviewed. The key issues that are discussed include theexperimental validation of theoretical predictions for the elastic constantsof fibres, quantitative interpretations of the mechanical anisotropy of chain-extended polyethylenes and liquid crystalline polymers using aggregate models,the analysis of anisotropic polymers and fibre/resin composites and compositemodels for specially oriented polyethylene sheets and high moduluspolyethylene fibres.     

Nondestructive testing of highly inhomogeneous materials

Nondestructive testing (NDT) of highly inhomogeneous materials, such as carbon-filled plastics, composites, especially fiber-reinforced and using coarse-grain fillers, etc., is a quite difficult problem. Thus, when these materials are scanned by sensitive elements of conventional systems for NDT, the instability of initial signals caused by the structure of the material may exceed the signal emitted by the defect which, therefore, remains undetected. We investigate a principal possibility of detecting defects by representing them in the form of finite regions whose spatial signals are characterized by distribution functions whose shapes differ from the shape of the same function for the intact material. We analyze the most difficult case of complete overlapping of these functions. By applying both theoretical methods and numerical simulation, we demonstrate the possibility of detection of defect zones in highly inhomogeneous materials which are not visible in the process of human inspection even under the most favorable conditions for observation. We present a method for the calculation of the optimal statistical filter and a system of scanning of the investigated material in local zones. The experimental data of automatic detection are compared with the data of human control according to the Neumann-Pearson risk criterion. The regions of the optimal application of automatic and manual inspection are indicated. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 4, pp. 97–108, July–August, 1996.     

NMR spectra of highly polarized lithium

No Heading We have studied the magnetic resonance of the nuclear spin system in lithium down to spin temperatures well below 1 K. The observed emergence of a distinguished low frequency maximum at low fields indicates clear disparity from the paramagnetic behavior.     

Accurate calibration with highly distorted images

Camera calibration is a two-step process where first a linear algebraic approximation is followed by a nonlinear minimization. The nonlinear minimization adjusts the pin-hole and lens distortion models to the calibrating data. Since both models are coupled, nonlinear minimization can converge to a local solution easily. Moreover, nonlinear minimization is poorly conditioned since parameters with different effects in the minimization function are calculated simultaneously (some are in pixels, some in world coordinates, and some are lens distortion parameters). A local solution is adapted to parameters, which minimize the function easily, and the remaining parameters are just adapted to this solution. We propose a calibration method where traditional calibration steps are inverted. First, a nonlinear minimization is done, and after, camera parameters are computed in a linear step. Using projective geometry constraints in a nonlinear minimization process, detected point locations in the images are corrected. The pin-hole and lens distortion models are computed separately with corrected point locations. The proposed method avoids the coupling between both models. Also, the condition of nonlinear minimization increases since points coordinates are computed alone.     

Peelback of highly oriented cellulosic fibres

An original study of peelback of cellulosic fibres spun using the N-methylmorpholine N-oxide (NMMO) process was performed. 13 micrometre diameter fibres were peeled under a microscope. Due to the high orientation of the material, the rupture could propagate in the centre of the fibres. Fibres presenting very different Fibrillability Index (FI = 0 or FI = 5) and hydration (swollen in water or freezedried) were studied. The resulting surfaces were analysed using Scanning Electron Microscopy (SEM). They showed the original formation of regularly spaced ribs corresponding to tearing of a homogeneous oriented material for the non fibrillable fibres. The structure of fibrillable fibres appeared through the creation of fibrils. Measurements of the energy release rate were performed with a set of each kind of fibres. Low values of this energy were obtained, corresponding to the formation of small ribs, due to the high orientation of the cellulose molecules. The energy values can be increased by the occurence of fibrils in the case of fibrillable fibres.     

Printing highly efficient organic solar cells

The technological attraction in organic solar cells is their compatibility to printing processes. However, up to today, nearly no literature on "printed" organic solar cells have been published and the major body of the research work was done by spin coating or blading techniques. Transferring the spin-coating or doctor blading process currently used for the fabrication of bulk heterojunction solar cell to a printing process holds morphological challenges that have not been observed or reported up to today. We highlight these challenges and we show that inkjet printing of organic bulk heterojunction solar cells requires completely novel approaches and skill sets compared to the current state of the art. By adjusting the chemical properties of the poly(3-hexylthiophene) polymer donor and by using our recently developed inkjet solvent mixture, we have gained control over the nanomorphology of poly(3-hexylthiophene):fullerene blends during the printing process and report a new record power conversion efficiency of 3.5% for inkjet printed poly(3-hexylthiophene):fullerene based solar cells.     

Synthesis of highly conductive polyaniline nanofibers

Polyaniline nanofiber product synthesized by using both potassium biiodate, KH(IO₃)₂, and sodium hypochlorite oxidant shows high electrical conductivity of greater than 100 S cm^− 1. The nanofiber product also shows not only a long nano-size fibril structure with average diameter of ~ 50 nm and length of ~ 4 μm but also high crystallinity. It was observed that the nanofibers synthesized using the two oxidants give both high electrical conductivity and high crystallinity compared to polyaniline synthesized using commonly known ammonium peroxydisulfate (APS) oxidant. We also found that dimensional and morphological uniformity of PANI nanofibers were greatly improved when the two oxidants were used. The long length and high crystallinity will probably be the contributing factors to have high conductivity. Order of the oxidant addition for the synthesis has no effect on quality of the product. Characterization study was made via UV/Vis absorption spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as conductivity measurement.     

Dislocation behavior in highly impurity-doped Si

The dynamic behavior of dislocations in highly impurity-doped Si crystals is investigated. Suppression of the generation of dislocations from a surface scratch is found for Si doped with B and P with a concentration higher than 1×10¹⁹cm^-3 and the critical stress for dislocation generation increases with B and P concentration which is interpreted in terms of dislocation locking due to impurity segregation. The velocity of dislocations in B- and P-doped crystals increases with increasing B and P concentration, respectively.     

高吸油树脂材料的研究进展

介绍了高吸油树脂的分类和性能.系统阐述了高吸油树脂的合成方法,讨论了单体,引发剂,交联剂和分散剂对高吸油树脂吸油性能的影响,并对未来的发展趋势进行了展望.