I.L.B.装置在小电网下大型管磨机启停控制中的应用

大型管磨机启停时电压会波动，常规方法是采用一台液体电阻启动器来保证电机启动过程平滑、无冲击。而在小电网下，此法却不尽人意。在越南某水泥粉磨站的水泥磨主电机的供电系统中，成功地将I.L.B装置与液体电阻启动器结合起来，收到事半功倍的效果。     

单萜烯的超临界液相色谱法研究

用(超)临界液相色谱法分析了单萜烯混合物。该方法操作简单、灵敏度较高、重复性好，在单萜烯的研究中有一定的参考价值。     

Comparison of surface properties of carbons gasified in nitrous oxide and in oxygen

Surface structures and reactivities of carbons gasified in N₂O and in O₂ are compared in this study. The carbon employed was derived from pyrolysis of phenol-formaldehyde resins. It was found that greater surface area and pore volume are created for the carbon gasified in O₂ than that in N₂O. At high extents of burn-off the carbon gasified in N₂O shows a larger mesopore volume than that in O₂. The reactivity per unit surface area of the carbon in N₂O decreases with the extent of burn-off, while that in O₂ remains relatively constant at various extents of burn-off. Surfaces in carbon micropores do not appear to be fully utilized in the N₂O-carbon reaction. It is confirmed that standard N₂ or CO₂ surface area is not a proper characterization of the reactive surface area of carbon gasified in N₂O.     

Preparation of self-reinforcement of porous mullite ceramics through in situ synthesis of mullite whisker in flyash body

Self-reinforced porous mullite ceramics were fabricated by a starch consolidation method with flyash, different aluminium sources (Al(OH)₃ and Al₂O₃) and the additive AlF₃ as raw materials. The reinforcement mechanism of needle-like mullite whiskers through in situ synthesis in ceramic body was investigated. The bulk density, apparent porosity and bending strength of the samples were tested. Phase compositions and microstructures of the sintered samples were measured by XRD and SEM, respectively. It showed that AlF₃ as additive was helpful to the formation of mullite whiskers at a low temperature. As the aluminium sources, Al(OH)₃ was more suitable for the preparation of mullite whiskers than Al₂O₃. The in situ synthesized mullite whiskers formed an interlocking structure, which enhanced the mechanical strength of the porous mullite ceramics. Porous mullite ceramics with bending strength of about 100 MPa and apparent porosity of about 55% were made at 1550 °C.     

Temperature and composition dependent excitonic luminescence and exciton-phonon coupling in CdSeS nanocrystals

ABSTRACT: The yellow- and red-emitting CdSeS nanocrystals (NCs) synthesized through one-step organometallic synthesis method are uniformly assembled in polymethyl methacrylate (PMMA). A higher-energy emission band originates from band-edge excitonic state appeared at low temperature. With the Se dopant concentration increasing, the luminescent spectra of CdSeS NCs have a red-shifted emission peak and a shorter luminescent lifetime, which is attributed to the existence of trapping state caused by surface defect and Se dopant. CdSeS NC shows a shorter luminescence lifetime and higher energy emission peak in PMMA matrix than that in toluene, indicating that the former is more favorable to transfer energy through exciton-phonon coupling. The upconversion luminescence (UCL) is observed using 800nm femtosecond laser excitation. The pump power dependence demonstrated UCL spectra of yellow-emitting CdSeS NCs has a slope of 2.2, while that of red-emitting CdSeS NCs has a slope of 1.4. The results demonstrate that the two-photon absorption plays a dominating role when Se concentration of CdSeS NCs is lower, while phonon-assisted UCL by one-photon excitation gradually takes place with the amount of Se dopants increasing.     

Sealants in the automotive industry

This paper outlines the use and test requirements of adhesives and sealants in the automotive industry. The application and typical properties required by automotive manufacturers are listed. Accelerated ageing test methods and conditions are described. Test results for Elastosol products are used to illustrate the values expected and obtained with these products on a wide range of metal substrates. All bonds failed cohesively after all conditions (for initial tests and after ageing).     

Estimation of compound classes in coal hydrogenation liquids by thin-layer chromatography

Compound classes in coal liquids were investigated by thin-layer chromatography coupled with a flame ionization detector (t.l.c.-f.i.d.). Individual t.l.c. peaks for coal liquids were identified as paraffins, aromatics, polar compounds and more strongly polar compounds or asphaltenes in order of increasing R_f values by comparison with specific compounds separated previously by conventional liquid chromatography. Concentrations of compound classes for a series of samples obtained by varying the hydrogenation time were estimated and good agreement was found with the results obtained by the USBM-API 60 liquid chromatography procedure. By using the t.l.c.-f.i.d. method, the relation of distribution of compound classes to the reaction conditions of coal hydrogenation could be derived quantitatively with relative ease.     

Self-standing conductive ITO-silica nanofiber mats for use in flexible electronics and their application in dye-sensitized solar cells

For the realization of flexible electronics, we proposed a nonwoven mat of inorganic electrospun nanofibers (NFs) of amorphous silica that is flexible and heat-resistive as a candidate to replace a glass or plastic substrate. We attempted to add electrical conductivity using indium tin oxide (ITO) to create self-standing, nonwoven flexible mats completely composed of inorganic ceramic materials. Two methods were tested to make the ITO-silica NF mats: electrospun silica-NF mats drop coated by ITO and hybrid mats composed of ITO NFs and silica NFs fabricated by the dual-spinneret electrospinning technique. Our produced ITO-silica NF mats exhibited both mechanical flexibility and thermal stability, even after heat treatment at 450–650 °C. The sheet resistance was 15–113 Ω/sq. We attempted to apply the obtained nonwoven conductive mats to the flexible photoanode of dye-sensitized solar cells (DSSCs) and highlighted the problems in the existing application.     

Synthesis of polyynes in a submerged electric arc in organic solvents

The products formed by the electric arc between graphite electrodes submerged in organic solvents like acetonitrile, n-hexane and methanol consist of a series of polyynes having the general chemical structure: H(CC)_mH (with m an integer 1,2,3,…m). The polyynes were separated through liquid chromatography (HPLC) and identified through their characteristic electronic absorption spectra recorded by a diode-array detector. When acetonitrile was arced at −40 °C, the entire polyynes series to m=9 (chain with 18 carbon atoms) were produced. Instead, at room temperature the entire polyynes series to m=8 (chain with 16 carbon atoms) were obtained. Similar results were obtained by arcing graphite electrodes in n-hexane and in methanol. The purest polyynes mixture is obtained in methanol while in n-hexane and in acetonitrile by-products are formed together with the polyynes series. In particular, in acetonitrile, a series of monocyanopolyynes was detected together with the normal polyynes series.The polyynes are formed by the vaporization of the elemental carbon from the graphite electrodes and dissolved in the solvent where the electrodes are submerged. The demonstration that the polyynes series H(CC)_mH is hydrogen-capped is based on several experimental data from electronic and FT-IR spectroscopy as well as their reactivity with a specific reagent for terminal acetylenes. Some chemical properties of the polyynes solutions (hydrogenation, oxidation) are also treated and discussed.     

高质量磷酸三钠生产工艺控制要点

阐述了磷酸三纳生产中关键岗位工艺指标的控制及为降低产品消耗采取的主要措施。通过工艺控制与降低消耗,使产品一级品率达到了１００％,纯碱消耗３４４ｋｇ／ｔ（１００％）,烧碱消耗１６９ｍｇ／ｔ（１００％）。     

Hydrogen in fullerites

The peculiar kind of fullerene molecule structure is also reflected in the crystal structure of fullerites. The cubic lattices of metal fullerides and hydrofullerenes behave similarly to the cubic lattices of different metals and alloys. They form interstitial solid solutions when impurity elements are distributed in octahedral and tetrahedral interstitial sites. By replacement of C₆₀ and C₇₀ molecules in lattice sites they make up substitution solid solutions. Forming exo- and endohedral compounds, the fullerene molecules, located in sites of the crystal lattice, can modify greatly the crystal properties with no change of crystalline structure. Some peculiarities of fullerite crystalline structures will be discussed in the present paper.     

Pitting corrosion behavior of stainless steel in ultrasonic cell

Under potentiostatic conditions on stainless steel electrodes in chloride solution, a novel electrochemical cell equipped with an ultrasonic transducer has been designed to evaluate the metastable and stable pitting corrosion behaviors. The advantage of the cell is that the rupture of pit cover can be controlled during the metastable or stable pitting growth periods, and in which the effect of the cover on pitting stability is affirmed. Some shallower stable pits, which were formed at higher anodic potential, were found to repassivate after ultrasonic cover rupture due to their shorter diffusional length. In terms of the relative susceptibility to localized corrosion, repassivation potential (E_r) determined by the cyclic potentiodynamic polarization curve was found to describe more properties of the occluded pit cover than the others.     

Cluster size distribution of charged nanopowders in suspensions

In order to control the aggregation phenomena in suspensions of nanoparticles, one often charges the particles electrically in order to delay or even suppress the aggregation process. The resulting cumulative size distribution of agglomerates of monopolarly charged nanoparticles suspended in liquid nitrogen is measured experimentally. The distribution is compared to results obtained by mean field theory. The relative width of the distribution obeys the lower bound predicted by theory. The results are discussed with respect to technical applications, e.g. stabilization of suspensions against aggregation.     

Catalytic graphene formation in coal tar pitch- derived carbon structure in the presence of SiO2 nanoparticles

A simple and effective way to manufacture graphene from a coal tar pitch (CTP) is demonstrated. Silica (SiO₂) nanoparticles were used to modify the CTP as carbon precursor. A silica nanofiller introduced into the CTP matrix underwent carboreduction during heat treatment to 2000 °C, resulting in the formation of silicon carbide. Surfaces of SiC grains were sites for graphene formation. The influence of SiO₂ on the structure and microstructure of CTP- based carbon matrix, after annealing up to 2800 °C, was studied. Carbon samples were analyzed using X- ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy. Crystallite sizes (L_a, L_c) and interplanar distance (d₀₀₂) were determined. The presence of SiO₂ in CTP carbon precursor favored the crystallites’ growth in the ‘a′ crystallographic graphite direction, and inhibited their growth on the ‘c′ axis. The crystallites composing of graphene layers, were characterized by an elongated dimension in the ‘a′ axis direction. Above 2000 °C silicon carbide decomposed, followed by the sublimation of silicon from the carbon matrix.     

Spin-orbit coupling in manganese doped calcium molybdato-tungstates

The manganese doped calcium molybdato-tungstates with the formula of Ca_1-xMn_x(MoO₄)_0.50(WO₄)_0.50 (x = 0.01, 0.03, 0.05, 0.10, 0.125, and 0.15) were successfully obtained by two-step synthesis using in both steps a solid state reaction route. All ceramics show scheelite-type tetragonal structure with space group I4₁/a. The electrical and magnetic studies within the temperature range of 2–300 K showed a weak p-type electrical conductivity and the paramagnetic state of Mn-doped ceramic materials. With increasing Mn content in samples under study, a change in the short-range interactions from ferromagnetic to antiferromagnetic as well as an increase in the orbital contribution to the magnetic moment, resulting in a strong spin-orbit coupling, were observed. The Brillouin procedure was used to estimate the Landé factor.     

Computational modeling in processing flows of carbonaceous mesophases

Carbonaceous mesophases are liquid crystalline precursor materials that can be spun into high performance carbon fibers using the melt spinning process, which is a flow sequence consisting of capillary, diverging, porous media, converging, and extensional flows that modifies the precursor molecular orientation structure. Carbon fiber property optimization requires a better understanding of the principles that control the structure development during the fiber formation processes and the rheological processing properties. This paper presents the elastic and continuum theory of liquid crystals and computer simulations of structure formation for pressure-driven capillary flow of carbonaceous mesophase precursors used in the industrial carbon fiber spinning process. The simulation results capture the non-Newtonian rheology of mesophase and the formation of characteristic fiber macro-textures.     

DC-field-induced synthesis of ZnO nanowhiskers in water-in-oil microemulsions

ZnO nanowhiskers were successfully fabricated using DC-field induced water-in-oil microemulsions method. Phase structure, morphology and microstructure of the product were investigated by X-ray diffraction and transmission electron microscopy. Parameters in preparation process such as electric field intensity and surfactant were discussed and the product formation mechanism was studied. XRD and TEM results showed that the obtained ZnO particle was hexagonal wurtzite-type with 1-3 nm in diameter and 20-70 nm in length, and morphology of the particles was shown to be correlated not only with the electric field intensity but also with the surfactant. There was a threshold when the electric field intensity was 80 V/mm. The morphology of the particles was basically spherical before the threshold, while L/D increased with the raise of electric field intensity. ZnO nanowhiskers were obtained under mixed surfactants but spherical particles were got with a single surfactant.     

Layer disorder in carbon anodes

Inter- and intra-layer disorder in a representative hard carbon derived from epoxy novolac resin at 1000°C have been investigated by comparing both the elastic structure factor S(Q) and radial distribution function obtained from pulsed neutron time-of-flight measurements with calculations from simple hypothetic systems with specific disorder characteristics. The spatial relationship between these building blocks, planar graphene fragments with length scale of 1 nm, is probed in terms of inter-layer alignment and intra-layer connectivity. Coupled with the density of dangling bonds obtained from ESR and residual hydrogen concentration, these simulations provide sufficient information to construct an overall model of the carbon structure. Of special interest is the physical origin of the ubiquitous broad (002)-like reflection frequently interpreted as that from layers with a uniform interlay spacing (d₀₀₂) It is found to be directly related to the misalignment between layers with an average interlayer spacing as that in crystalline graphite (3.35 Å).     

Orderly evolution in the morphology of the anode deposit in hydrogen arc discharge

A layer of carbonaceous deposit with spectacular morphologies was obtained on the anode surface in a hydrogen DC arc-discharge. Pure graphite rods were used in the synthesis process without use of catalytic materials. Along the rod, the deposit product presented many different morphologies such as nanofibers, microfibers, pillars and trees, and was approximately divided into five regions with distinct features. The temperature gradient along the anode was thought to be responsible for the orderly change in deposit morphology.