In this paper, the principle of Attenuated Total Reflection (ATR) is used to test and study the silicon nitride particle samples, and the influence of particle size, shape and crystal phase on its infrared spectral performance is emphatically analyzed. It is found that the larger the particle size of Si3N4 is, the more its extinction peak moves to the long wave. The smaller the particle size is, the lower the extreme value of infrared transmission in the characteristic spectrum segment is. For Si3N4 particles of the same scale, spherical like particles can obtain lower infrared transmittance, while cylindrical like ones show a wider range of infrared absorption bands. Under the same shape and similar scale, α phase Si3N4 particles have better infrared absorption than β phase.
Based on electromagnetic scattering mechanism, Mie scattering theory and Monte Carlo method are used to analyze the radiation characteristics of SiC particle swarm with different distribution forms. The study find that the form of particle size distribution has a significant impact on the spectral transmittance of particle swarms. The proportion of particles of different sizes in the particle size distribution, the dispersion of particle size distribution, and the span of particle size scale all affect the infrared extinction performance of particle swarms in varying degrees. Among them, the proportion of particles of specific size in the particle size distribution is the most one, which is a necessary factor to ensure the existence and amplitude of particle characteristic spectra. The relationship between particle size distribution and radiation characteristics was deeply analyzed, and the results showed that increasing the proportion of particles in the 0.16~2.5 µm particle size range of SiC particle swarm can comprehensively improve the extinction performance of SiC particle swarm, this is of practical significance for optimizing the infrared radiation performance of particle swarms.
Based on Mg/Na (NO3) 2 and Mg/Sr (NO3) 2, the combustion and radiation characteristics of pyrotechnics in vacuum were studied. The burning rate and visible light radiation characteristics of different samples were obtained, and the relationship between combustion performance (visible light intensity and burning rate) of the sample and vacuum environment pressure were further obtained. The results show that: 1) the linear burning rate and mass burning rate of the two formulations decrease with the decrease of pressure, and the burning rate has an exponential relationship with the pressure, and the sensitivity of Mg/Sr (NO3) 2 to ambient pressure is slightly higher than that of Mg/Na (NO3) 2; 2) Under the same vacuum pressure, the visible radiation intensity of Mg/Sr (NO3) 2 is significantly higher than that of Mg/Na (NO3) 2; 3) With the decrease of vacuum pressure, the visible light radiation intensity of the two formulations of pyrotechnic composition decreased. 4) According to the test data, the light intensity pressure index of Mg / Na (NO3) 2 is 1.07, which is more sensitive to environmental pressure than that of Mg/Sr (NO3) 2 system 0.598; 5) Based on the fitting formula, it is estimated that the visible light radiation intensity of Mg/Na (NO3) 2 system is 16cd, which is much less than that of Mg/Sr (NO3) 2 system 443cd.
Based on the principle of one-dimensional photonic crystal, ZnS and SiO2 were used as the main substrates to study the surface optical modification of various flexible fabric substrates. One dimensional photonic crystal coating structure system was constructed by extending the photonic band gap by multi heterojunction superposition and introducing disorder reasonably. Multilayer coating was carried out on the fabric surface by vacuum evaporation technology to realize the infrared selective spectrum regulation on the fabric surface. The surface spectral emissivity and coating adhesion of the fabric before and after coating were tested. The results show that the one-dimensional infrared photonic crystal structure based on flexible substrate can achieve the infrared radiation properties of infrared medium wave emissivity ≤ 0.3 and long wave emissivity ≥ 0.8; Based on this architecture, the infrared spectrum selectivity of flexible fabric surface can be realized by vacuum evaporation; For the surface of pure fabric, the bonding strength between the coating and the fabric surface is related to the surface density and surface smoothness of the fabric; Using adhesive layer to improve the surface smoothness of fabric, and further coating on this basis can effectively improve the adhesion of coating, and the adhesion level can be increased from grade 5 to grade 0; The results show that the medium wave incidence, long wave emissivity and emissivity difference are 0.15, 0.87 and 0.72, respectively; At the same time, the coating is stable in the range of 25 ℃ to 350 ℃ and has good thermal stability.
In this paper, a temperature control method of flexible composite film was proposed based on porous adsorption principle and phase change materials blending technology, the flexible composite film samples were developed accordingly, and the temperature control performance was tested experimentally. It was shown by the test results, the phase change of flexible composite film can be applied to a wide temperature range of 23-55 ℃, and also conducted heat well.
Based on LOS method ,combined with DSMC, the particle clouds movement model and the optical radiation transmission model were established, the dynamic radiation performance and transmittance of particle clouds in space within medium wave and long wave were analyzed accordingly, the results showed that the heat flux in space has a certain influence on the particle clouds radiation, but not on the extinction obviously; when the number density of particle clouds was greater than 1x107 , the transmittance of particle clouds in medium wave and long wave was less than 10%.
In this paper, terahertz (THz) characteristics of a direct current (DC) arc discharge uniform plasma are analyzed, which is of practical significance in plasma diagnostics with electromagnetic waves. A model for estimating total collision frequency of DC arc discharge plasma is built based on the Coulomb model and elastic scattering model. Explicit expressions for attenuation coefficient and transmission coefficient of THz wave propagating through a uniform plasma are obtained, which are expressed as a function of plasma frequency and collision frequency in the DC arc discharge. Detailed numerical analysis and discussions are conducted to reveal the influence of electron density, collision frequency, thickness of the plasma, and incident angle of the wave on the transmission characteristics of THz wave in plasma. Results show that the greater are the electron density, collision frequency and transmission length of a wave propagating in plasma, more power of the wave is attenuated. The attenuation energy of laser under horizontal sending and horizontal receiving (HH) polarity is as same as the vertical sending and vertical receiving (VV) polarity in underdense plasma.
Based on optical scattering theory of Aden–Kerker method, the extinction efficiencies of submicron hollow particles with 5 kinds of materials, such as graphite(C), brass powder (Cu), cupric oxide (CuO), cuprous oxide(Cu2O) and soot are given in this paper. Some influences of different materials, inner radius (x), outer radius (y), shell thickness (z) and x-z ratio(x/z) on the extinction efficiencies are studied respectively. Owing to lack of literature data, the optical constants of C, Cu, CuO, and Cu2O are firstly obtained by measuring infrared spectral transmittance of material piece and retrieving the equivalent optical constants combined with electromagnetic scattering theory and K-K relation. The results show that particle C, Cu, Cu2O and Soot have a good performance in stability of extinction efficiency distribution within 3-5μm; the extinction efficiencies of C, Cu, Soot decrease gradually with the shortening of the wavelength within 3-5μm; the extinction efficiency of all kinds of particles increase along with outer radius y increased when shell thickness z is fixed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.