BaTiO_3/γ-Fe_2O_3颗粒膜的介电性质和磁电性质

本文利用高真空磁控——离子束复合溅射系统在单晶n型Si(100)面上生长了Ag/[BaTiO3/?-Fe2O3]/ZnO结构的复合薄膜,对比研究了BaTiO3/γ-Fe2O3颗粒膜在真空退火温度300°C,400°C和500°C下的介电性质、磁性质以及铁电特性.实验研究发现,随着退火温度的升高,样品的电容和介电常数逐渐变大,在500°C退火的样品,其电容为633.93 pF,介电常数为10.233.所有样品都具有良好的铁磁性和铁电性,其中在400°C退火的样品具有最大的饱合磁化强度103.3 emμ/cm3,而在500°C时具有最大的剩余电极化强度9.13?10?1μm/cm2.同时,在零磁场和1.0 T的磁场下,矫顽电场和剩余电极化强度都没有明显的变化.在200 K时,电滞回线却发生了明显的变化.     

Effects of Ti additive on HPHT diamond synthesis in Fe-Ni-C system

Diamond crystals with low nitrogen concentration were synthesized from the Fe-Ni-C system with Ti additive at high pressure and high temperature （HPHT） in a china-type cubic high pressure apparatus （CHPA）. The synthesis pressure range was 4.8-5.2 GPa, and the temperature range was 1420-1600 K. The lowest synthesis pressure for diamond fell first and then rose with the increase of Ti additive. The color, shape, surface morphology and nitrogen impurity concentration of the synthesized diamond crystals were characterized using optical microscopy （OM）, scanning electron microscopy （SEM） and micro Fourier transform infrared （FTIR） spectrometry. The results show that the Ti additive has significant effects on color, growth rate, crystal shape, surface morphology and nitrogen impurity con- centration of the synthesized diamond crystals. The color of diamond crystals synthesized without Ti additive is yellow, while that with Ti additive becomes light and nearly colorless. The growth rate without Ti additive is higher than that with Ti additive. The crystal shapes of as-grown diamond crystals vary with the increase of Ti additive. The {111} crystal faces become dominant and some {311} crystal faces appear with the increase of Ti additive. The concentration of nitrogen impurity in diamond crystals without Ti additive is higher than that with Ti additive.     

Spatial separation of spectrum inside the tapered metamaterial optical waveguide

In this work,the optical metamaterials based on silver dendritic cells are prepared by electrochemical deposition,and its transmission and focusing behaviors are investigated.The experimental results show that the optical metamaterials reveal a multiple pass-band transmission spectrum and a prominent focusing effect at the wavelength corresponding to the maximum transmission coefficient.Two optical metamaterial samples are combined into a tapered optical waveguide,and the spectra of transmitted light at the surface of the tapered optical waveguide is measured by using the fiber spectrometer along the light propagation direction.The results demonstrate that each frequency component of the wave packet is stopped at a different waveguide thickness,leading to the spatial separation of its spectrum.The spatial separation of spectrum can be effectively tuned by adjusting the inclination of the tapered optical waveguide,which can be used for storing photons and slow-light research.     

Mechanism of diamond-to-graphite transformation at diamond-stable conditions

The diamond-to-graphite transformation at diamond-stable conditions is studied by temperature gradient method （TGM） under high pressure and high temperature （HPHT）, although it is unreasonable from the view of thermodynamic considerations. It is found that, at diamond-stable conditions, for example, at 5.5 GPa and 1550 K, with fine diamond grits as carbon source and NiMnCo alloy as metal solvent assisted, not only large diamond crystals, but metastable regrown graphite crystals would be grown by layer growth mechanism, and the abundance of carbon source in the higher temperature region is indispensable for the presence of metastable regrown graphite crystals. From this transformation, it is concluded that, with metal solvent assisted, although the mechanism of crystal growth could be understood by the macro-mechanism of solubility difference between diamond and graphite in metal solvents, from the point of micro-mechanism, the minimum growth units for diamond or graphite crystals should be at atomic level and unrelated to the kinds of carbon source （diamond or graphite）, which could be accumulated free-selectively on the graphite with Sp2Tr or diamond crystals with sp3 bond structure.     

Synthesis of high quality type-Ib diamond crystals in carats grade

High quality type-Ib tower-shape gem-diamond crystals in carats grade were synthesized in cubic anvil high pressure apparatus (SPD-6×1200) at 5.4 GPa and 1250-1450°C. The relationship between the growth time and the weight of growth diamond has been gained. The faces of {110} and {113} were found in the synthetic diamond crystals frequently. We found that the relative growth rate of {113} face was descending with the increase of growth temperature, and that of {110} face had no obvious change with the incre...     

Preparation and thermal stability on non-vacuum high temperature solar selective absorbing coatings

Spectrally selective TiAl/TiAlN/TiAlON/TiAlO coating was deposited on stainless steel and copper substrates using a multiarc ion plating system.The structure,morphology,optical reflectance and electrical resistivity were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),spectrophotometer and four-point probe meter,respectively.The results show that the coating exhibits high absorptance(―0.9) and low emittance(0.09―0.19).The coating remains stable in air up to 650℃ for 1h.These propert...     

Photoelectron spectroscopy of terpenoids and prediction of their rate constants in atmospheric oxidation reactions

The electronic structures of six mono-terpenoids and two of their oxygenated derivatives were studied by He I photoelectron spectroscopy (PES). The observed bands were interpreted on the basis of empirical arguments and theoretical calculations. The first vertical ionization potentials for β-pinene, α-terpinene, terpinolene, γ -terpinene, limonene, myrcene, citral, and terpinene-4-ol were determined to be 8.73, 7.57, 8.26, 8.30, 8.53, 8.68, 8.71, and 8.77 eV, respectively. Most of these values have not been determined by PES before. The correlations of the first vertical ionization potentials of these compounds to the natural logarithms of rate constants for their reactions with the radicals OH, NO3, and O3 were determined. The correlation coefficients for their reactions with OH, NO₃, and O₃ were 0.97, 0.91, and 0.95, respectively. This method is a powerful technique for predicting the rate constants for the atmospheric oxidation reactions of terpenoids.     

Study on growth of coarse grains of diamond with high quality under HPHT

The growth of coarse grains of diamond was observed with graphite as carbon source and Fe₈₀Ni₂₀ alloy powder as catalyst at HPHT in a China-type SPD 6×1670T cubic high-pressure apparatus with highly exact control system. To synthesize coarse grains of diamond crystal with high quality, advanced indirect heat assembly, powder catalyst technology and catalyst with optimal granularity were used. Especially the nucleation of diamond and the growth rate were strictly controlled by the optimized synthesis craft. At last, diamond crystals (about 0.85 mm) in the perfect hex-octahedron shape were successfully synthesized at ~5.4 GPa and ~1360℃ in 60 min. The characteristic of crystal growth with powder catalyst technology under HPHT was discussed. The results and techniques might be useful for production of coarse grains of diamond.     

Dependence of nitrogen concentration in type Ib diamonds on synthesis temperature

Type Ib diamonds were grown by the temperature gradient method (TGM) at 5.5 GPa and 1500－1560 K in a china-type cubic anvil high pressure apparatus using Ni₇₀Mn₂₅Co₅ alloy as solvent/catalyst. The concentration of nitrogen (C_N) in type Ib diamonds synthesized at different synthesis temperatures was measured by a Fourier transform infrared (FTIR) spectrometer. The dependence of C_N in diamond on synthesis temperature was studied. For the type Ib diamonds synthesized using Ni₇₀Mn₂₅Co₅ as catalyst, its C_N decreases along with the increase of synthesis temperature.     

Characterization of nanoscale iron and its degradation of 2,4-dichlorophenol

Nanoscale iron was detected by TEM, X-ray diffraction and X-ray photoelectron spectroscopy. It was found that the size of the nanoscale iron particles is in the range of 30–40 nm according to TEM image, and it contains abundant Fe₃O₄ as passivating layers on the surface of the core-shell structure. To improve its performance, dilute HCl was used for the removal of the passivating layers, and the degradation of 2,4-dichlorophenol (2,4-DCP) was measured for the nanoscale iron samples treated and untreated. Experimental results demonstrated that the removal of 2,4-DCP by untreated nanoscale iron is mainly due to the adsorption of 2, 4-DCP by nanoscale iron, and there are no degradation products detected by HPLC in the process. However, excellent dechlorination of 2,4-DCP was gained by HCl-treated nanoscale iron, and 2-chlorophenol, 4-chlorophenol and phenol were detected during the process. It was concluded that dechlorination is the key reaction pathway for the degradation of 2,4-DCP by activated nanoscale iron, and phenol is found to be the main product.