Waveband Range Research Articles

Flowability and Infrared Interference Properties of Modified Graphite Flake with Hydrophobic Nano-silica

To research the dispersion properties and infrared (IR) interference efficiency of graphite flake particulates modified by hydrophobic nano-silica, the flowability of graphite flake particles before and after modification was measured by a powder property tester. The smoke was formed by dispersing the graphite flake particles into the smoke box using air flow dispersion way. The mass concentration and IR spectrum transmission of the smoke were measured. On the basis of stir settlement model, the settling velocity of smoke was calculated. Results show that the Carr′s flowability index of graphite flake particulates modified with hydrophobic nano-silica in mass ratio of 4.0 % is the highest, reaching 61 and at the same time, the settling velocity decreases from 2.288×10 -3 m·s -1 before modification to 1.125×10 -3 m·s -1 after modification. Average IR spectrum transmission of the smoke formed in the wave band range of 3-5 μm and 8-12 μm decreases from 0.3895 % and 0.7288% to 0.072% and 0.176%. The physical modification of hydrophobic nano-SiO 2 on graphite flake surface effectively improves the flowability and dispersion properties and significantly increases the duration of the smoke formed by graphite flake particles and IR interference performance.

Study of the rapid detection of γ-aminobutyric acid in rice wine based on chemometrics using near infrared spectroscopy.

Rice wine, in which γ-aminobutyric acid is present, is beneficial to human health and is one of the three most well-known fermented wines in the world, and is very popular in China. The rapid detection of γ-aminobutyric acid was studied in rice wine using near infrared spectroscopy with an optical fibre probe. Through the selection of detection conditions, including a waveband range of 12500-4000cm(-1), a scanning duration of 16 scans and a resolution of 8cm(-1), the near infrared spectrum of rice wine was acquired three times, for every wine sample, with an optical fibre probe. The resulting average value of the spectrum was obtained and the corresponding data were analysed via normalization. By adopting a multivariate calibration partial least squares method (PLS) and establishing a calibration model, the highest precision for γ-aminobutyric acid in rice wine was predicted when the factor coefficient was 17. The overall results demonstrating the content of γ-aminobutyric acid in rice wine was predicted to be between 157.6696-317.5813mg/L, with a relative standard deviation of prediction between 0.01-5%, as well as the fact that the single sample measuring time was less than 20s, prove that near infrared spectroscopy is a rapid, accurate and effective method to adopt for detecting the content of γ-aminobutyric acid in rice wine.

Preparation, dielectric property and infrared emissivity of Fe-doped ZnO powder by coprecipitation method at various reaction time

Fe-doped ZnO powders have been synthesized by the coprecipitation method at 600°C with various reaction time, using zinc nitrate as the staring material, urea as the precipitator, and ferric nitrate as the doping source, respectively. The phase and morphology of the prepared powders have been characterized by X-ray diffraction and scanning electron microscopy, respectively. It was found that the prepared product synthesized for 1h had a pure ZnO wurtzite structure and was a ZnO(Fe) solid solution powder. The real part, imaginary part, and dielectric loss of complex permittivity of prepared powders in the frequency range of 8.2–12.4GHz decreased with increasing reaction time. The average infrared emissivities of prepared powders at the waveband range of 8–14μm increased with extending reaction time.

Effect of synthesized temperature on microstructure, infrared emissivity and dielectric property of Fe-doped ZnO powder

Fe-doped ZnO powder has been synthesized by coprecipitation method under different synthesized temperature, using zinc nitrate as the staring material, urea as the precipitator, and ferric nitrate as the doping source, respectively. The prepared powders have been characterized by XRD and SEM. Results show that when the synthesized temperature is below 700 °C the prepared powders are ZnO(Fe) solid solution powders and the ZnFe2O4 impurity phase appeared for the Fe-doped ZnO powder synthesized at 700 °C. The electric permittivities in the frequency range of 8.2–12.4 GHz and average infrared emissivity at the waveband range of 8–14 μm of prepared powders have been determined. The real part and imaginary part of electric permittivities of prepared powders have increased firstly and then decreased with increasing synthesized temperature. The average infrared emissivity has presented the opposite changing trend.

Optimization of highly nonlinear dispersion-flattened photonic crystal fiber for supercontinuum generation

A simple type of photonic crystal fiber (PCF) for supercontinuum generation is proposed for the first time. The proposed PCF is composed of a solid silica core and a cladding with square lattice uniform elliptical air holes, which offers not only a large nonlinear coefficient but also a high birefringence and low leakage losses. The PCF with nonlinear coefficient as large as 46 W−1 · km−1 at the wavelength of 1.55 μm and a total dispersion as low as ±2.5 ps · nm−1 · km−1 over an ultra-broad waveband range of the S—C—L band (wavelength from 1.46 μm to 1.625 μm) is optimized by adjusting its structure parameter, such as the lattice constant Λ, the air-filling fraction f, and the air-hole ellipticity η. The novel PCF with ultra-flattened dispersion, highly nonlinear coefficient, and nearly zero negative dispersion slope will offer a possibility of efficient super-continuum generation in telecommunication windows using a few ps pulses.

CdSe/ZnSe/ZnS量子点在单晶太阳能电池中的应用

The luminescent down-shifting characteristics of CdSe /ZnSe /ZnS core /shell /shell quantum dots( QDs) were studied by incorporating the QDs as the down-shifting luminescent material into polymethyl-methacrylate( PMMA). Firstly,the optical high-pass filter with threshold 420 nm was used to cover the solar cell,so as to make the spectral response of the cell almost zero in the waveband range of 300 ~ 420 nm. Then the luminescent down-shifting( LD) layer of QDs was prepared on the external surface of the optical filters,we found the external quantum efficiency( EQE) of solar cell improved. This indicates that LD layer can realize the down-shifting of frequency spectra at300 ~ 420 nm,which is out of the spectral response region of the normal cell. Finally,in order to analyze the possibility of applying quantum dots to solar cells,the minimum fluorescence quantum efficiency( FQE) of the quantum dots was calculated to be 87. 8% according to the measured EQE of solar cell.

Millimeter waveband signal conversion in S-c-S Josephson junctions with self-pumping

The temperature sensitivity of a radiometer with a Josephson junction mixer at the input was experimentally determined to be better than that of existing radiometers with Shottky diode mixers in the short millimeter waveband range, but worse by 10 to 15 db than follows from the theory. The temperature sensitivity can be reduced by approximately an order of magnitude by optimization of the amplifier parameters and by shunting the junction with a ''cold'' resistance. (auth)