Laser applications in semiconductor industry, metrology and medical applications call for improvement and reliable optical coatings in the short wavelength range. Especially, optical coatings for ArF and F2 laser syst...
详细信息
Aluminum film reflectors can yield a high reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. The reflectors, however, cou...
Aluminum film reflectors can yield a high reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. The reflectors, however, could deteriorate under the irradiation by charged particles in the Earth radiation belt. To understand the deterioration mechanisms, the change in surface morphology of an Al film reflector irradiated with 60 keV protons was studied in liquid nitrogen cooled vacuum environment. Proton irradiation affected strongly the Al film reflectors forming a rough surface covered with hillocks and valleys that caused an increase in the RMS roughness and light scattering that, in turn, contributed to the decrease of specular reflectance in UV and visible wavelength ranges. The studies on the changes in surface morphology of Al film reflectors induced by proton irradiation would help to understand the damage mechanism and predict the performance evolution of optical equipment used in spacecrafts under space radiation environment.
The microstructure and morphology of polypropylene grafted polyurethane (PP-g-PU) copolymer have been investigated by dynamic mechanical thermal analysis (DMTA), transmission electron microscopy (TEM) and polarized li...
详细信息
The microstructure and morphology of polypropylene grafted polyurethane (PP-g-PU) copolymer have been investigated by dynamic mechanical thermal analysis (DMTA), transmission electron microscopy (TEM) and polarized light optical microscopy (PLOM). It is shown that the microphase-separated structure of the PP-g-PU copolymer is consist of continuous domain formed by the polypropylene (PP) component and dispersed domains of polyurethane (PU). A complex microstructure was observed for the dispersed phase, which was believed to be formed by the hard segments and soft segments of the PU branches. The microstructure and morphology were also affected by the length of PU chains, the content of PU and the crystallization process of the copolymer.
The heat dissipation of six different types of microchannel networks integrated in LTCC based microsystems has been investigated by experimental measurement and simulation analysis, including straight, serpentine, spi...
详细信息
The heat dissipation of six different types of microchannel networks integrated in LTCC based microsystems has been investigated by experimental measurement and simulation analysis, including straight, serpentine, spiral and fractal-shaped microchannel networks of curve, I-shaped and parallel. The cross section of microchannel is 200 ¿m × 200 ¿m and the total length is about 200 mm. The water mass flow rate at the inlet was controlled at 7.5 ml/min by a powerful micro-bump and the heat flux of surface heating area was supplied from 0.2 W/cm 2 to 1 W/cm 2 by an array of chip resistors. The simulated maximum temperature rise by finite volume method agrees well with the experimental results. It is found that the spiral microchannel has the best cooling ability and reduces 86.8% of the maximum temperature rise at 1 W/cm 2 . The microchannels are proved to have little effect on the strength of the substrate by finite element analysis method due to the small size of cross section.
La 2 Ce 2 O 7 (LCO) is a promising candidate material for thermal barrier coatings (TBCs) application because of its higher temperature capability and better thermal insulation property relative to yttria stabilized z...
详细信息
La 2 Ce 2 O 7 (LCO) is a promising candidate material for thermal barrier coatings (TBCs) application because of its higher temperature capability and better thermal insulation property relative to yttria stabilized zirconia (YSZ). In this work, La 2 Ce 2 O 7 TBC with segmentation crack structure was produced by atmospheric plasma spray (APS). The mechanical properties of the sprayed coatings at room temperature including microhardness, Young's modulus, fracture toughness and tensile strength were evaluated. The Young's modulus and microhardness of the segmented coating were measured to be about 25 and 5 GPa, relatively higher than those of the non-segmented coating, respectively. The fracture toughness of the LCO coating is in a range of 1.3–1.5 MPa m 1/2 , about 40% lower than that of the YSZ coating. The segmented TBC had a lifetime of more than 700 cycles, improving the lifetime by nearly two times as compared to the non-segmented TBC. The failure of the segmented coating occurred by chipping spallation and delamination cracking within the coating.
The electronic structures and formation energies of the Ni 9Mn4Ga3-xAlx and Ni 9Mn4Ga3-xInx alloys have been investigated using the first-principles pseudopotential plane-wave method based on density functional theory...
详细信息
The NiAl alloys modified by reactive element(RE), dysprosium(Dy), were produced by arc melting. The microstructures of the modified alloys were investigated by field emission-scanning electron microscope(FE-SEM) equip...
详细信息
The NiAl alloys modified by reactive element(RE), dysprosium(Dy), were produced by arc melting. The microstructures of the modified alloys were investigated by field emission-scanning electron microscope(FE-SEM) equipped with energy dispersive spectroscope(EDS) and back scatter detector. Cyclic oxidation tests at 1 200 ℃ were conducted to assess the cyclic oxidation performance of the alloys. The Dy dopant prevents the surface rumpling of the oxide scale and the formation of cavities beneath the oxide scale. The pegs consisting of Dy-rich oxide inclusion core and an outer alumina sheath develop deeply in the alloy and improve the oxide scale adhesion. 0.05%-0.1% (molar fraction) Dy dramatically improves the cyclic oxidation resistance of the NiAl alloy. Too high concentration of Dy is deleterious because of the fast oxidation rate caused by severe internal oxidation.
We calculate the second harmonic generation (SHG) from an antiferromagnetic film (AFF) embedded in a one-dimension photonic crystal. The electromagnetic wave localization in the AFF leads to a giant enhancement of the...
We calculate the second harmonic generation (SHG) from an antiferromagnetic film (AFF) embedded in a one-dimension photonic crystal. The electromagnetic wave localization in the AFF leads to a giant enhancement of the SHG. The numerical results based on three typical structures show that the highest power of SH outputs reaches several hundred times that of a single AFF for the same incident power. The SH outputs depend sensitively on the structural geometry and symmetry, and the best structure and the best layer-thickness matching for it are found. The SHG nonreciprocity is very obvious; i.e., if the direction of incident radiation is reversed, the SH output powers can be changed by several dozens times. Three narrow and obvious SHG bands are found.
The longitudinal ultrasonic velocity （V1）, attenuation （α1）, magnetization and resistivity of single phase polycrystalline La1/3Sr2/3CoO3 were measured as a function of temperature from 20 K to 300 K. The resisti...
详细信息
The longitudinal ultrasonic velocity （V1）, attenuation （α1）, magnetization and resistivity of single phase polycrystalline La1/3Sr2/3CoO3 were measured as a function of temperature from 20 K to 300 K. The resistivity shows metallic behavior in the whole temperature range and a kink at 235 K was observed, which coincides with the ferromagnetic transition temperature （Tc）. As the temperature cools down from Tc, the V1 softens conspicuously at beginning and reaches a minimum at 120 K. After that the V1 dramatically stiffens below 120 K accompanied by a wide attenuation peak. The analysis of the results suggests that these ultrasonic anomalies ;nay correspond to local lattice distortions via the Jahn-Teller effect of intermediate spin Co^3＋.
暂无评论