A suitable combustion synthesis and densification process was designed to fabricate dense NiAl/TiB2 composites from Ni−Al−Ti−B system. Combustion synthesis processing and microstructure characteristics of products were studied in detail. The results show that the amount of TiB2 ceramics has a great influence on the combustion synthesis processing and microstructure; with the increase of the amount of TiB2 ceramics, the combustion temperature and combustion velocity increase rapidly. The volume of synthesized products and the grain size of ceramics particle size are also affected by the amount of TiB2 ceramics. TiB2 ceramics fiber can be produced in this synthesis system. The dense NiAl/TiB2 composites with residual porosity of no more than 1% are fabricated by the combustion synthesis and hot pressing, the mechanical properties of the dense NiAl/TiB2 composites increase with increase of the amount of TiB2 ceramics.
Infrared radiant powder was synthesized by conventional ceramic processing techniques by using Fe2O3, MnO2, CuO, Co2O3 and kaolin as raw materials. A novel infrared radiant glaze was developed by introducing the infrared radiant powder into glazing as a functional additive. Infrared radiant characteristics of the powder and the glaze were investigated. The optimum content of infrared radiant powder in glazing was ascertained to be 5%. The infrared radiant glaze exhibits significant antibacterial and antifungal functions due to the thermal effect of infrared radiation. Antibacterial percentages of the glaze reach 91%–100% when Escherichia coli, Staphylococcus aureus and Bacillus subtilis are used as model bacterium respectively, while antifungal percentage of the glaze exceeds 95% when Penicillum citrinum is used as model fungus.
The complexation reaction between borate ions and phenol-formaldehyde resol resin in aqueous solution was studied by pH measurement, small model molecules and infrared spectroscopy. The results show that the complexation can proceed completely and rapidly at room temperature. Borate ion attacks phenol hydroxyl groups and adjacent position hydroxymethyl groups on the phenol ring of the resin, and forms the coordinate bond between boron atom in borate ion and oxygen atom in the hydroxyl groups. The complexation is a quantitative reaction. The complex is a six member ring containing two oxygens and one boron. The complexation can release hydrogen ions resulting in the decreasing pH in the resin solution.
In order to form the apatite nuclei on a surface of the substrate, the substrate was placed on or in CaO, SiO2-based glass particles which were soaked in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma, and to make the apatite nuclei grow on the substrate in situ, the substrate was soaked in another solution highly supersaturated with respect to the apatite. The induction period for the apatite nucleation varied from 0 to 4 days depending on the kind of the substrate. The thickness of the apatite layer increases linearly with increasing soaking time in the second solution. The rate of growth of the apatite layer increases with increasing degree of the supersaturation and temperature of the second solution, reaching 7 um/d in a solution with ion concentrations which is as 1.5 times as those of the simulated body fluid at 60°C. The adhesive strength of the apatite layer to the substrate varies depending on the kind and roughness of the substrate. Polyethyleneterephthalate and polyethersulfone plates abraded with No. 400 diamond paste show adhesive strengths of as high as 4 MPa. This type of composite of the bone-like apatite with metals, ceramics and organic polymers might be useful not only as highly bioactive hard tissue-repairing materials with analogous mechanical properties to those of the hard tissues, but also as highly biocompatible soft tissue-repairing materials with ductility.
The characteristic of combustion wave and its change were analyzed by numerical value calculation and computer simulation, based on the combustion dynamical model of SHS process. It is shown that with the change of condition parameters in SHS process various time-space order combustion waves appear. It is concluded from non-linear dynamical mechanism analysis that the strong coupling of two non-linear dynamical processes is the dynamical mechanism causing the time-space order dissipation structures.
Pb (Mn1/3Sb2/3) x (Zn1/3Nb2/3) y (Zr0.535Ti0.465)1-x-yO3 (PMZN) piezoelectric ceramics were fabricated. The effects of sintering temperature and heat-treatment time on properties were discussed, the optimum preparation technology parameters were obtained. In this case, the ceramics have the highest electromechanical coupling coefficients and mechanical quality factor and the least dielectric loss. It is revealed that the PMZN piezoceramics material can be utilized for high-power ultrasound transducers.
Composite particles consisting of polyaniline (PAn) core and barium titanate (BaTiO3) layer shell were synthesized. The PAn-BaTiO3 composites particles were characterized with TEM and XRD. The dielectric behavior of particles was tested and the electrorheological (ER) behavior of the suspensions of PAn/BaTiO3 particles in chlorinated paraffin oil with a 20 vol% was investigated under DC electric field. The results show that the ER effect of composite particle is far stronger than that of pure polyaniline and barium titanate which were synthesized by the same method. pH and thickness of BaTiO3 have an important influence on the ER effects.
A new niobate crystal Ba4Na2VNb9O30 was synthesized in BaO−Na2O−V2O5−Nb2O5 system for the first time. Its shape, optical properties, melting point and chemical stability wer estudied. X-ray powder diffraction study determined that this compound assumes a tetragonal tungsten bronze structure with space group P4 bm (100) and lattice parameters a=b=12.4275(2), c=3.970(3). The new compound may be one kinds of photorefractive crystals.
Electromagnetorheological (EMR) fluids containing CuPc−Fe3O4 nanopareticles composite were prepared and their properties were studied. The results show that Δτ of this kind of EMR fluids increases with the increments of applied electric field, magnetic field and volume fraction of the nanoparticles composite. Δτ has an approximate linear relationship with γ. When an electric and magnetic field are applied simulateously, the EMR fluids have a synergistic effect. The EMR fluids have a good long-term stability.
Gold colloids were prepared by citrate-induced reduction of hydrogen tetrachlorourate, and gold nanoparticles were electrostatically self-assembled with poly (diallyldimethylammonium chloride) into multilayer thin films on silicon and quartz substrates. The particulate thin films were characterized by UV-vis spectroscopy, surface enhanced Raman scattering, atomic force microscopy and resistivity measurements. Due to the interparticle coupling between individual gold particles, an obvious collective particle plasmon resonance was observed on UV-vis spectra, and the particulate thin films exhibited a strong SERS effect. For multilayer thin films with a high particle coverage on substrates, resistivity of the order of 10−4Ω·cm was yielded.
The Compressive strength, porosity and pore size distribution of high performance metakaolin (MK) concrete were investigated. Concretes containing 0.5%, 10% and 20% metakaolin were prepared at a water/cementitious material ratio (W/C) of 0.30. In parallel, concrete mixtures with the replacement of cement by 20% fly ash or 5 and 10% silica fume were prepared for comparison. The specimens were cured in water at 27°C for 3 to 90 days. The results show that at the early age of curing (3 days and 7 days), metakaolin replacements increase the compressive strength but silica fume replacement slightly reduces the compressive strength. At the age of and after 28 days, the compressive strength of the concrete with metakaolin and silica fume replacement increases. A strong reduction in the total porosity and average pore diameter were observed in the concrete with MK 20% and 10% in the first 7 days.
Mercury intrusion porosimetry was used to measure the pore structure of steel fiber reinforced polymer-cement-based composite. The results indicate that the large pore volume decreases by 57.8%–51.2% and by 87.1%–88% with the addition of steel fibers and polymers respectively. When both steel fibers and polymers are simultaneously added, the large pore volume decreases by 88.3%–90.1%. As a surface active material, polymer has a favorable water-reduced and forming-film effect, which is contributed to the decrease of the thickness of water film and the improvement of the conglutination between the fibers and the matrix. Polymers could form a microstructure network. This network structure and the bone structure of cement hydration products penetrate each other and thus the interpenetrating network with sticky aggregate and steel fiber inside forms.
In accordance with a fresh accident by severe expansion cracks of structural elements, based on systematic detection and analyses such as X-ray diffraction, differential thermal analysis, scanning electron microscory, chemical analysis, petrographic analysis, electronic probe analysis, and atomic absorption spectroscopy analysis, it is pointed out that the dominant reasons lie in the hydration reaction of magnesia in concrete aggregates, resulting in a volume expansion in structure members. A wholly new corresponding strengthening method is applied to the cracked elements and turned out to be effective.
A system of impact damage detection for composite material structures by using an intelligent sensor embedded in composite material is described. In the course of signal processing, wavelet transform has the exceptional property of temporal frequency localization, whereas Kohonen artificial neural networks have excellent characteristics of self-learning and fault-tolerance. By combining the merits of abstracting time-frequency domain eigenvalues and improving the ratio of signal to noise in this system, impact damage in composite material can be properly recognized.
The topological index F* is defined and obtained by the method of a non-dimensional unit calculation in which three matrices multiply with each other. These matrices represent the connective cases of atoms in a molecule, the structural features of atoms on top and the bonded cases of the adjacent atoms respectively. The standard formation enthalpies of ABn (g) molecules were correlated with F* (A=C, Al, Si, Ti, Zr, B=F, Cl, Br, I, H, n=1–4) and these correlation coefficients are all more than 0.96. Some molecules (e.g CH4, SiH4,etc.) can be preferably handled by F* but can not be dealt with by other topological indices. By contrast to traditional hydrogen suppressed graph, the contribution of hydrogen atoms to structures and properties of molecules is considered.
The influence of pretreatment of fibre on interfacial and mechanical properties of glass fibre/polypropylene composites was investigated. Firstly, the glass fibres were coated with the blends of m-IPP (maleic anhydride grafting isotatic polypropylene) and m-APP (maleic anhydride grafting amorphous polypropylene) in different ratios. Secondly, the interfacial reaction of the coated composites was analysed by FTIR, which shows that the interfacial chemical reaction between m-IPP/m-APP in the fibre coating and the fibre surface-bound coupling agent is in existence. Thirdly, the microstructure of the coated composites was studied by SEM. The results indicate that the coating treatment is effective on improving interfacial adhesion of the fibre-matrix and the right amount of m-APP added to the coat impels the plastic deformation surrounding the point of cracks, which makes cracks turn to region and prevents from further interface debonding. Lastly, the mechanical properties were evaluated by measurement of the flexural strength and impact strength of the composites. It was found that the flexural strength and impact strength of the composites with coating fibre are higher than those of uncoating fibre composite. The results of these investigations draw the conclusion that the pretreatment of fibre with m-IPP/m-APP blends can form an optimize interlayer between the fibre and the PP matrix, which improves both the strength and toughness of the composites.
The polypropylene was modified by ultraviolet irradiation. The polypropylene-montmorillonite nanocomposites were prepared by direct melting intercalation of polypropylene powders. The structure of polypropylene, the polyproprlene irradiated, montmorillinote and polypropylene-montmorillonite composites were studied by XRD, IR and DSC. The results show that the PP molecules can are oxidized during ultraviolet irradiation, melt polypropylene can intercalate into montmorillonite layer. As a result, the layered distance (d001) of montmorillonite increases, and the melt absorption peak of polypropylene in layer is eliminated.
A Kind of homogeneous resin, which can be used as thermal resistant adhesive and matrix for composite, was prepared by bis (4-maleimidophenyl) methane (BMI), 4, 4′-diaminodiphenylmethane (DDM), aniline (An), phenol type epoxy resin (F-51) and nitrile-butadiene rubber (NBR) through solution copolymerization. The reaction from prepolymerization to curing of the resin system was studied. And the factors such as raw material ratio and curing temperature, which affect thermal resistance and adhesives of cured product, were also analyzed. SEM and IR spectra were utilized to discuss the mechanisms of toughness and reaction of modified BMI.
Coal’s volatile component, ash and fixed carbon content have different functions in different stages of a combustion process, but the traditional coal classification can precisely show its combustion property. In this experiment coal’s evaluation indexes (ignition index Di), (burn off index Df) were used to qualitatively show the ignition property and combustion ending property of coal samples. Meanwhile, considering actual heating circumstances in calciner (in cement plants), this thesis established the relationship among the ignition index, burn off index and coal’s industrial analysis value, which makes it possible for the user to predict the quality of coal before using it and is very valuable in practice.
Yttrium isopropoxide was prepared directly by the reaction between yttrium and isopropyl alcohol using mercuric chloride and iodine as catalyst. Yield is above 83%. This method possesses the merits of easy operational approach, high product purity, high reaction rate and high production rate. Compared with the previous reported results, the period needed was shortened by 19h and the yield increased by 8%. The period needed for preparation is about 5 hours. These results are better than the present report. The dehydrolysis method of isopropyl alcohol and the composition of catalyst were presented.
There are many difficulties in concrete endurance prediction, especially in accurate predicting service life of concrete engineering. It is determined by the concentration of SO4 2−/Mg2+/Cl−/Ca2+, reaction areas, the cycles of freezing and dissolving, alternatives of dry and wet state, the kind of cement, etc., In general, because of complexity itself and cognitive limitation, endurance prediction under sulphate erosion is still illegible and uncertain, so this paper adopts neural network technology to research this problem. Through analyzing, the paper sets up a 3—levels neural network and a 4—levels neural network to predict the endurance under sulphate erosion. The 3—levels neural network includes 13 inputting nodes, 7 outputting nodes and 34 hidden nodes. The 4—levels neural network also has 13 inputting nodes and 7 outputting nodes with two hidden levels which has 7 nodes and 8 nodes separately. In the end the paper give a example with laboratorial data and discussion the result and deviation. The paper shows that deviation results from some faults of training specimens: such as few training specimens and few distinctions among training specimens. So the more specimens should be collected to reduce data redundancy and improve the reliability of network analysis conclusion.