AFI (AlPO4-5, CoAPO-5, SAPO-5, CrAPO-5, FeAPO-5 and MnAPO-5) molecular sieves were synthesized by hydrothermal method, and then single-walled carbon nanotubes (SWCNTs) with a diameter of 0.4 nm were prepared in the channels of these kind molecular sieves by low-temperature hydrocracking. The effect of the type and the amount of active metals, the hydrocracking temperature and the carbon content of template agents was investigated by means of XRD, NH3-TPD and micro-Raman spectroscopy. The results show that the addition of Si or active metal can improve the quantities of acid sites in the AFI molecular sieves, which can improve the density and quality of the SWCNTs in the channels of the hydrocracked AlPO4-5 molecular sieves. Besides, the hydrocracking temperature and the carbon content of template agents are also key influence factors for the preparation of SWCNTs.
The effects of solution treatment and aging treatment on microstructures and mechanical properties of Ti-3Al-8V-6Cr-4Mo-4Zr alloy bars have been investigated. The results show that the highest hardness and the highest tensile strength can be achieved by the solution and aging treatment (800℃×30 min/AC+510℃×16 h/AC), and an insignificant decline on elongation rate and necking rate is also acquired. The quantity and size of the ω-phases and α-phases result in the increase of hardness and strength of Ti-3Al-8V-6Cr-4Mo-4Zr alloy bars. A lot of dimples exist in the tensile fractures of the hot rolling alloys and heat treatment alloysdemonstrating a typical ductile fracture.
Nanostructure tungsten materials were successfully prepared by He plasma assisted methods. The effects of ions fluences and discharge power on the surface morphology of tungsten were investigated. Scanning electron microscopy and tapping mode atomic force microscopy were used to characterize the sample topography and surface roughness under different discharge condition. At the discharge power of 6 kW and ion energy of 220 eV, it showed that the tungsten surface formed the nano pinhole structure and then the pore size gradually increased with increasing ion fluences. When the ion fluence increased to 1.0×1026 ionsm-2, the sample surface formed nano tungsten fuzz. The cross section analysis also showed that the nano structure layer thickness increases with the increase of irradiation ion flunece. High-resolution scanning electron microscope analysis found that there are a large number of nanoHe bubble at the interface of tungsten fuzz root and tungsten bulk, which gives the direct evidence that the tungsten fuzz forming is derived from He bubble. This work is of great significance for the further understanding the formation mechanism of nano tungsten fuzz.
The influence of inert solid particles SiO2 on electrochemical characteristics of carbon steel was studied by using the array electrode technique and the electrochemical impedance spectroscopy. It was found that the spreadability of droplets increased with the increase of the amount of SiO2,as well as the corrosion activity area.In addition, the impedance spectra showed two capacitive loops with the deposition of SiO2 particles, and the capacitive loop in the high frequencies was attributed to the blocking effect of the SiO2 particles. The corrosion behavior of carbon steel was affected by these two aspects, the spreadability of droplets and the blocking effect of the SiO2 particles. With the increase of the amount of SiO2, the average current value decreased firstly and then increased. There was a critical value in the deposition amount of SiO2 particles. When the amount was lower than the critical value, it could hinder corrosion. While, when the amount was higher than the critical value, it would accelerate corrosion owing to the expansion of droplets.
The composite particles of mSiO2/CeO2(330-340 nm in size) were prepared by applying CeO2 nanoparticles coating (15-20 nm in thickness) on core material of mesoporous silica (mSiO2, ca. 300 nm in size) with radial mesochannels (ca. 2.6 nm in pore size). The prepared composite particles were characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The results show that the oxidized silicon wafer substrates was polished comparatively with when taking mSiO2/CeO2 composite particles or sSiO2/CeO2 composite particles(solid silica core) as polishing paste, the polished pre-oxidized silicon wafer presented had a lower root-mean-square roughness(RMS=0.267 nm) and a higher material removal rate(MRR=45 nm/min) for the former paste, in the contrast, than those of the sSiO2/CeO2 composite particles with solid silica cores(RMS=0.309 nm and MRR=24 nm/min for the later one. Furthermore, the mSiO2/CeO2 composite particles may be beneficial were attributed to the elimination of mechanical damages (such as scratches) on the wafer surface. The very structure of silica core of mSiO2/CeO2 composite particles presented obvious effects for their polishing characteristics.
Fly ash based geopolymer were prepared with fly ash as raw material and several compounds of heavy metals as additives. Then the effect of the type, content and chemical form of the heavy metal on the compressive strength, reaction products, and pore structure of the prepared geopolymers was investigated. The results show that the incorporation of Pb2+、Cr3+ and Cu2+ has great effect on the late compressive strength and results in formation of reinhardbraunsite in the solidified body. Moreover, the Pb2+ reduces the total pore volume of the solidified body, while Cr3+ and Cu2+ increase it. The content of the heavy metal compounds should be controlled within a reasonable range. When the content of the heavy metal compounds is relatively small, the total pore volume is small and the solidified body is much compact. Besides, the different chemical forms of chromium have different effect on the stability of the geopolymers. The single addition of chromium oxide or elemental Cr may reduce the total pore volume of the geopolymers, whereas the average pore size increases obviously for the geopolymers with addition of a variety of other heavy metal compounds.
The effect of inorganic soil stabilizer, as soil modifier, on the compression strength, water resistance, freeze-thaw resistance of the raw soil materials was assessed, whilst the prepared materials were characterized by means of scanning electron microscope and X-ray diffractometer. The results show that the compressive strength, softening coefficient and freeze-thaw resistance (BDR) are 8.78 MPa, 0.85 and 38.38% respectively for the raw soil material with addition of 20%~25% inorganic soil stabilizer after maintenance for 60 days, which indicates that the material has an excellent performance. The inorganic soil stabilizer reacts with SiO2 and Al2O3 in the soil to generate new products such as Ca1.7MgO3SiO4, 2CaOAl2O3SiO2 and Na2CaSiO4, in the meanwhile, α-C2S and γ-C2S within the modified admixture may react with water to produce C-S-H gel, which are the main causes responsible to the enhancement of the performance of the raw soil material.
The mol ratio between Bi element and Fe element was determined to be 1.03:1. The influences of co-precipitation time on the preparation of its precursor powders and properties of single-phase BiFeO3 ceramics were researched when other conditions were fixed. The results indicated that: the pure single-phase BiFeO3 powders was obtained at the reaction time of 95 h and the particle size was uniform. The high density BiFeO3 (the relative density 98.3%) ceramics samples were prepared by spark plasma sintering (SPS) and then their dielectric properties and ferroelectric properties were measured. And the result showed that it also had the maximum dielectric constant 106.5 and the minimum dielectric loss 0.006 at the frequency of 30 MHz. The saturated electric hysteresis loop was detected at room temperature too, the saturated polarization is 0.4 μC/cm2.
In order to evaluate the acoustic-radiation performance of two functional materials, the vibro-acoustic radiation of a typical cylindrical shell with stiffened ring ribs is calculated based on FEM and BEM method, and the results agree well with the experimental results. According to the equivalent principle of temperature and frequency, the dynamic mechanical parameters of viscoelastic core material for acoustic absorption were acquired from the results of dynamic thermodynamic experiments. The coupling effect of water and the shell was simulated by finite element method. Finally, the acoustic radiation field of sandwich-shells with different core materials excited by a point source was calculated by means of indirect boundary method. The results show that the circumferential mode has an important influence on the modal damping ratio of both the sandwich shell with buoyancy core and sandwich shell with sound-absorption core, whilst axial mode just has a significant effect on the modal damping ratio of the sandwich shell with sound-absorption core. The peak value of the acoustic power of the sandwich shell with buoyancy core and sandwich shell with sound-absorption core is 21.38 dB and 56.55 dB lower than that of the steel shell respectively. When the combination of the above two functional materials in different proportion were used as the core material, the radiation acoustic power decreases with the increasing proportion of the sound-absorption material, but the decrease amount diminishes gradually.
Flowability is a prerequisite for the applicability of powders for thermal spraying. Nanoscale feedstock of NiCrCoAlY-TiB2MMCs (metal matrix composites) was synthesized by high energy ball milling method with NiCrCoAlY and TiB2 powders as raw material, and argon as shielding gas. The milled powder was characterized by scanning electron microscope, X-ray diffraction, apparent density tester, tap-density tester, repose angle tester and laser scattering. The results show that after wet-milled at 320 r/min for 20 h and dry-milled at 220 r/min for 5 h, a stable nanoscale feedstock of NiCrCoAlY-TiB2 MMCs was obtained. The particle size ranges from 5 to 50 μm and a majority of the powders shows ellipsoidal morphology which is expected to have good fluidity during HVOF spraying. Compared with the initial mixed powders, the repose angle of milled powders reduces from 38.4° to 32.9°, HR value reduces from 1.925 to 1.248, indicating the flowability has been improved obviously.
Copper pastes with different glass powders were prepared and then printed on Al2O3 substrate and finally sintered at 850℃ to produce Cu film on the Al2O3 substrate surface. The produced Cu-films and glass powder were characterized by means of metallographic microscope, X-ray diffractometer, scanning electron microscope and thermo gravimetric analyzer. While the effect glass powder on the conductivity and adhesive performance of Cu films was also assessed. The results show that glass powder G3 composited of SiO2-B2O3-ZnO possesses appropriate transition temperature, with which a compact copper film with flat surface and good electrical conductivity can easy be made. When the Cu-paste with 4.8 mass% of glass powder G3, the produced Cu-film presents electrical resistance of 9.5 mΩ/□ and adhesive strength of 24 N/mm2 to the Al2O3 substrate. In order to verify the reliability of Cu-film in service, the oxidation resistance and aging properties of Cu-film G3-3 were examined. It was found that the average mass gain rate of the Cu-film was 3.5% after 28 days oxidation at room temperature, the resistance change average rate was 0.79%. After aging test at 20~160oC for 12 h, the average change rate of the Cu-film resistance was 12.63% and the average mass gain rate was 4.63%, which demonstrated that film has the good oxidation resistance and anti-aging performance.