In a new two-phase system (tetrahydrofuran/saturated NaCl aqueous solution) monolayer protected clusters (MPCs) were prepared. The AuCl4 − anion in saturated electrolyte aqueous solution was transferred into the organic phase of tetrahydrofuran by tetra-n-butylammonium bromide ((C4H9)4NBr) and was reduced quickly by sodium borohydride in the presence of alkanethiol. The functionalized MPCs were characterized by solubility, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX) analysis and UV-vis spectroscopy. Electrochemical measurements of MPCs in CH2 Cl2 exhibited 7 pairs of reversible voltammetric waves within the potential range of −1.0 to 1.0V (vs Ag/AgCl), which was ascribed to the quantized capacitance charging of nanoparticle double layers. All the results show that the new preparing method is feasible.
Suspended gold nanorods have been synthesized via an electrochemical method. The absorption spectrum features show two peaks at 520nm and 650nm, which result from the transverse and longitudinal surface plasmon resonance. The spectra at different growth stages indicate that the absorption peaks split and shift after electrolysis, which correspond to the anisotropy growth of nanorods. The quasi-static calculation results indicate that with increasing the mean aspect ratio of the nanorods, the longer wavelength absorption peak decreases and red shifts obviously, whereas the shorter wavelength absorption peak blue shifts slightly.
The phase-separation glasses with composition of Na2O (9.0) B2O3 (25.0)-SiO2 (66.0) (in mode ratio) were leached with hydrochloric acid, and porous glasses were prepared. The dynamis of the acid treatment was investigated. The effects of treatment time, temperature and acid concentration on the acid treatment process were studied using HCl as treatment solution. The dynamics equation and apparent activation energy obtained in acid treatment process were
By means of an inherent elevated-temperature of poured liquid steel, a Ti-C-30 wt% Fe preform, which was pre-placed in a mould cavity, was directly ignited and a combustion synthesis reaction took place. As a result, a TiC−Fe cermet coating with a thickness of about 10 mm was simutaneously synthesized on the solidified steel matrix. The synthesized coating exhibits a feature of graded composite structure, in which both the amount and size of TiC particles decrease gradually with an increasing distance from the furface of the coating. Moreover, by a proper casting technique, the pores formed during the combustion synthesis of the preform could be centrally distributed in 2–3 mm in outer layer of the coating. When this outer porous layer was worn off, the rest coating with a thickness of about 8 mm possesses a dense structure and a high abrasive wear resistance.
Two kinds of nanopowders were studied. One is NiFe2O4 spherical nanopowders which have different particle sizes. Another is ZnO nanopowders including two series of spherical particles and tetrapod nanowhiskers. Through measuring the infrared diffuse reflection spectra of nanopowders, it can be found that the particle size and morphology affect the infrared diffuse reflection spectra. For the NiFe2O4 nanopowders the smaller the particle size, the larger the K-M value. And when the particle size is large enough, the effect of the particle size on infrared diffuse reflection spectra would disappear. For the ZnO nanopowders the effects of the particle size and morphology are more special. The effect of the particle sizes of tetrapod whisker nanopowders on infrared diffuse reflection spectra is more than that of spherical nanopowders.
High-yielding low-cost vanadium oxide nanotubes were prepared by the hydrothermal self-assembling process from vanadium pentoxide and organic molecules as structure-directing templates. Moreover, a new method was discovered for determining the content of V (IV) in vanadium oxide nanotubes by thermogravimetric analysis (TGA). This method is simple, precise and feasible and can be extended to determine the content of low oxidation state in the other transition metal oxide nanomaterials.
Rainbow piezoelectric ceramics are a new type of stress-biased, oxide-reduced composite ferroelectric ceramics, which have a special dome structure. The have shown excellent properties such as ultra-high displacement under an applied electric field and enhanced load-bearing capability. In this article, their manufacture, structures and properties were discussed in detail by combining experiments and theory analysis. The resuts show that the optimal conditions for producing Rainbow samples from PLZT ceramics were determined to be 900°C for 1 to 1.5 hours. A number of different phases have been found in the reduced layer of Rainbow ceramics by XRD analyses. The phases found include metallic lead and other oxide phases, such as PbO, ZrO2 and TiO2. The original PLZT phase was not observed. The reduced layer was transgranularly fractured while the unreduced ceramic was intergranularly fractured. Two kinds of fracture types can be seen at the interface, which denotes the different degrees of reduction. It is shown that the Pb grains (about 0.2μm) constitute a continuous phase in the reduced layer, which accounts for the good electrical conductivity
Several effective numerical techniques, based on a finite element analysis, have been developed and computed independently. Results are presented describing the impacting process, and the subsequent temperature and residual stress fields of a molten nickel particle impacting onto a flat substrate. Problems of this type, especially the prediction of the thermal residual streses, are of major practical interest in thermal spray operations as a pioneering approach.
Oscillating combustion is one of classic phenomenon in SHS. But the cause of its formation in a set of complex processes is unclear yet. With a two-step chemical reaction assumption and effects of other thermal dynamic factors, an auto-oscillating combustion has been gained in a solid SHS process on the macro-homogenous and micro-heterogonous model. Numerical solution shows that the change of chemical reaction is the main cause of the oscillating combustion.
A n-Hexyl NH3Sr2Nb3O10 is obtained by the stepwise ion-exchange reaction, then is dispersed in aqueous solution of trinuclear acetato-hydroxo iron (III) nitrate, [Fe3(OCOCH3)7OH·2H2O]NO3, and the interlayer potassium cations of the perovskite niobate are exchanged with the partially hydrolyzed trinuclear acetato complex ions. On heating, the exchanged complex ions are converted into iron oxide pillars which keep the perovskite sheets apart. The product is characterized by XRD, SEM, EDAX and surface area measurement respectively.
The ceramic/metal gradient thermal barrier coatings (CMGTBCs) which combined the conceptions of thermal barrier coatings (TBCs) and functional gradient materials (FGMs) are investigated. The structure model studied in this paper is a general model which includes four different layers: pure ceramic layer, ceramic/metal gradient layer, pure metal layer, and substrate layer. The microstructures of gradient layer have different ceramics and metal volume fraction profile along with the direction of thickness. The profile function used to describe the gradient microstructures can be expressed in power-law or polynomial expression. The mechanical properties of CMGTBCs are obtained by means of microscopic mechanics. As special cases, the interactive solutions are given by Mori-Tanaka method, and the non-interactive solutions by dilute solution. The Young's modulus calculated by these methods are compared with those by other methods, e g, the rule of mixtures.
The recent development of polymer optical fiber (POF) at home and abroad was summarized. The special characteristics of the perfluorinated POF were introduced and its wide potential application was predicted. POF is the most suitable in conjunction network project, especially using with quartz optical fibers. Facing this market opportunity, it is a right choice to unit colleges, research institutions and manufacture corporations to accelerate the industrialization of POF.
The purpose of this study was to find a kind of new artificial bone for anterior spinal fusion. ZrO2 stabilized by Y2O3(Y-PSZ), porous hydroxyapatite (HA) and bone morphogenetic protein (BMP) were used to make artificial compound bone (Y2O3) ZrO2-HA/BMP(Z-H/BMP), whose function was tested, microstructure and mineralogic composition constitution were analysised by SEM and XRD, and the corresponding animal tests were porformed. Osteogenesis of the material was observed by eyes, histology and SEM. Experimental results show that the component and ossific activity of Z-H/BMP were satisfactory.
(PEO) x−(V0.85Mo0.15)2O5(x=0,0.5,1.0) nanocomposite films were prepared by a modified sol-gel method. The structure of the films was analyzed by XRD, and the DC electrical conductivity. Cyclic voltammogram and optical spectral transmittance were investigated. The results show that the (V0.85Mo0.15)2O5 xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1.7897 nm at x=1.0. The introduction of MoO3 improved the DC electrical conductivities of the films due to the generation of V4+ to maintain the electrical neutrality of the oxides. PEO intercalated in the interlayer of (V0.85Mo0.15)2O5 oxides has interaction with the oxides, enhancing the amount of Li+ ions inserted into the interlayer of the oxides. Moreover, the intercalation of PEO into the interlayer of (V0.85Mo0.15)2O5 oxides improved the cathodic electrochromic property in near ultraviolet region and anodic electrochromic property in visible range.
Rapid solidifiation is a kind of new process for enhancing the hardness and electrical conductivity of Cu−Cr−Zr copper alloy. The use of BP neural network (NN) is presented to model the non-linear relationship between parameters of age hardening processes and the mechanical and electrical properties of rapdily solidified Cu−Cr−Zr alloy. The improved model is developed by the Levenberg-Marquardt training algorithm and the good generalization performance is demonstrated. So, an important foundation has been laid for optimisticaly controlling the rapidly solidified aging processes of Cu−Cr−Zr alloy.
The crystallization behavior of desulfurization product is directly related to its high-temperature-resistant ability. Effects of the additive on the sulfur-fixation efficiency of the Ba-sulfur-fixation agent and also on the crystallization behavior of the sulfur-fixation product were studied when CaCO3 and BaCO3 were used as the desulfurization agent and MgO and SrCO3 used as the assistant sulfur-fixation agent. The result shows that increase of sulfur-fixation capability for the additive is not owe to their directly react to form sulfate or interact with CaCO3 and BaCO3 to form composite mineral heat-resistant in high temperature, but owe to their activation to sulfur-fixation reaction of the sulfur-fixation agent.
The friction and wear properties of the nylon coating, prepared by hot-extrusion, used to protect the surface of the flexible continuous sucker rod were studied by using a pin-on-disc wear tester in the simulated oil well environment. The effects of sliding speed and load were considered. The wear mechanism was also studied by using a scanning electron microscope (SEM). The result shows that the friction coefficients of both kinds of materials, JKPA and ZZ7024B, used to protect the surface of the flexible continuous sucker rod decrease with sliding speed increase, but change little with load increase in the simulated oil well environment. The value of friction coefficient of ZZ7024B is smaller than that of JKPA. The minimum value of friction coefficient of ZZ7024B is about 0.05. The wear volume of ZZ7024B is smaller than that of JKPA under the same conditions of experimentation.
The influence of Mo on the microstructure, bending strength and HV of Ti/Al2O3 composite was studied, and the influence mechanism was analyzed. The results indicate that after the addition of Mo, the composite organization is finer and phases distribution is better-proportioned which make the microstructure denser, the bending strength and HV of composite are also increased to a degree. But the bending strength increases first then decreases with the increasing of Mo content, so the appropriate Mo content for the Ti/Al2O3 composite is to be further confirmed.
Phenolic resin/montmorillonite intercalation composites were prepared by using the methods of pressing intercalation and melt intercalation. Properties and structure of the composites were investigated by using XRD, TG and test of softening point. It is indicated that both the pressing intercalation and melt intercalation can be used to prepare the phenolic resin/ organo-montmorillonite intercalation nanocomposites. Compared with phenolic resin, the intercalation nanocomposites have better heat-resistance, higher decomposition temperatures and less thermal weight-loss. However, these two intercalation methods have different effects on the softening point of the intercalation nanocomposites. Pressing intercalation almost does not affect the softening point of the intercalation nanocomposites, while melt intercalation significantly increases the softening point of the intercalation nanocomposites, probably due to the chemical actions happening in the process of melt intercalation.
The optimal parameters for flow grooves and supply grooves were determined by a series of experiments, and the influences of various molding conditions on the mold filling process were analyzed. Furthermore, the whole VIMP procedure based on grooves was introduced in detail taking the manufacture of a sandwich panel as an example.
The hydration process, hydration product and hydration heat of blended cement paste mixed with mineral admixture and expansive agent at low W/B ratio are studied by XRD, thermo analysis, and calorimetry instrument, and they were compared with those of pure cement paste. The results show that pure cement and blended cement at low W/B ratio have the same types of hydration products, but their respective amounts of hydration products of various blended cements at same ages and the variation law of the amount of same hydration products with ages are different; The joint effect of tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore and rift caused by the crystalloid ettringite is the impetus of the volume expansion of cement paste, and the former effect is much greater than the latter one.
The effect of ground steel-making slag on microstructure and composition of hydration products of ordinary Portland cement (OPC) was investigated by mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and differential thermal analysis (DTA). Results show that ground steel-making slag is a kind of high activity mineral additives and it can raise the longer-age strength of OPC mortar. The total porosity and average pore diameter of OPC paste with ground steel-making slag increase with the increase of the amount of ground steel-making slag replacing OPC at various ages, while after 28 days most pores in OPC paste with ground steel-making slag do not influence the strength because the diameter of those pores is in the rang of 20 to 50 nm. The hydration mechanism of ground steel-making slag is similar to that of OPC but different from that of fly ash and blast furnace slag. The hydration products of ground steel-making slag contain quite a lot of Ca(OH)2 in long age.
The hydration characteristics and expansion impetus of three kinds of cement paste under free-and confined-curing conditions were investigated, which were respectively mixed with three different kinds of expansive agent at low W/B ratio. The results show that the hydration products of pure cement paste and paste mixed with expansive agent are same, but the amount of hydration products, un-hydrated C3S and C2S are obviously different at the same hydration age. At 3 d age, the amount of CH in pure cement paste is less than that of paste mixed with expansive agent, but it is reverse when at 28 d age. The amount of AFt at 3d and 28d age in pure cement paste is less than those of paste mixed with expansive agent. Regardless of under free- or confined-curing condition, the amount of ettringite produced varies little since 3d age. The joint effect of the tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore caused by the crystalloid ettringite is the cause of the volume expansion of cement paste, and the former effect is much greater than the latter.
Low-grade fly ash (rejected fly ash, rFA), a significant portion of the pulverized fuel ash (PFA) produced from coal-fired power plants and rejected from the ash classifying process, remains unused due to its high carbon content and large particle size (>45 μm). But it is thought that the rejected ash may have potential uses in chemical stabilization solidification (S/S) processes which need relatively lower strengths and a lower chemical reactivity. Flue Gas Desulphurisation (FGD) sludge is a by-product of air pollution control equipment in coal fired power plants whose chemical composition is mainly gypsum. As there is no effective usage of both of these two materials, it is of interest to research on the possible activation of rFA using FGD. This paper presents experimental results of a study on the properties of rFA activated by the FGD in rFA-cement pastes. Different percentages of FGD were added into the mix to study the effects of the FGD on the reaction of the rFA blended cement pastes. The results show that FGD takes effect as an activator only at late curing ages. Adding Ca(OH)2 enhances the effect of FGD on activating the hydration of rFA. Also, 10% FGD by weight of rFA is the optimal addition in the rFA-cement pastes. The results of the compressive strength measurements correlate well with the porosity results.
Fracture energy in strain softening regime was investigated analytically by considering microstructures interaction and interplay. Based on gradient-dependent plasticity, the thickness of localized band was determined completely and strictly by characteristic length in relation to average grain diameter. After obtaining the plastic shear displacement of the band, the formula on axial response of concrete was proposed and the analytical post-peak fracture energy was deduced. A comparison between present theoretical results and earlier experimental results was carried out and the analytical result is reasonable and has a plausible foundation as considering the localized failure theoretically. Decreasing the relative stress leads to increasing the fracture energy non-linearly. The large the shear elastic modulus and shear softening modulus, the lower the post-peak fracture energy. A larger fracture energy is caused by a larger thickness of shear band or a larger characteristic length of concrete material. If the inclination angle of the shear band and the compressive strength are not concerned with structural size of specimen, the post-peak fracture energy is size independent.
The effect of the composite of natural zeolite and fly ash on alkali-silica reaction (ASR) was studied with natural alkali-reactive aggregate and quartz glass aggregate respectively. The expansive experiment of mortar bar and concrete prism was completed. The results show that ASR can be suppressed effectively by the composite of natural zeolite and fly ash.
The feasibility of producing graphite gangue wall body materials was discussed by the experiments of four kinds of hardeners solidifying graphite gangue. The result demonstrates that the physical performances of graphite gangue solidified brick samples with 8% hardener D reach the senior grade or the special grade in JC422-91. The study of solidification mechanism indicates that the hardeners produced pastes while being hydrated. In addition, they can activate the mineral compositions in clay to joint in the reaction to produce pastes and intensive framework.