جستجوی مقالات مرتبط با کلیدواژه « laser » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

 Poly(m-phenylenediamine) and barium titanate nanoparticles have promising physical and chemical properties in the electrical and optical fields. One of the attractive properties of these materials is their nonlinear optical behavior. This property allows these materials to be used in high-tech systems, the manufacture of various optical parts as well as lasers.

Poly(m-phenylenediamine/barium titanate) nanoparticles (PmPDA/BaTiO3) nanocomposite was prepared by in situ polymerizations. The prepared materials were characterized by various methods. Nonlinear optical studies of materials were investigated by the Z-scan technique with open aperture and closed aperture to obtain the absorption coefficient and nonlinear refractive index at different concentrations 0.3, 0.5, and 0.7 mg/L with four different intensities at a wavelength of 532 nm.

X-ray diffraction and field emission electron microscopy results showed a semi-crystalline pattern and an irregular aggregate structure for PmPDA/BaTiO3 nanocomposite, respectively. The thermal stability of the nanocomposite increased due to the presence of BaTiO3 nanoparticles relative to PmPDA. The presence of BaTiO3 nanoparticles in the nanocomposite shifted the absorption peak of PmPDA to a shorter wavelength (325 nm). The optical results show that at concentrations of 0.3, 0.5, and 0.7 mg/L with varying intensity of moderate light on PmPDA, BaTiO3, and PmPDA/BaTiO3 samples, the values of nonlinear refractive index (n2) and the nonlinear absorption coefficient (β) are obtained differently. In addition, the results show that by changing the intensity, the samples have a nonlinear refractive index with a negative sign (n2 <0). This result shows that the samples are self-focal in nature and can play an important role in the correction of laser pulses. The samples also have a saturation absorption (SA) nature. This feature plays an important role in the fabrication of optical switches and optical limiters in lasers.

The reduction of laser reflectivity is important as an effective defense to protect people and sensitive equipment. Reducing the reflectivity of surfaces is the most important strategy for decreasing the damages of laser radiation. In this research, the porous pigments are prepared to achieve the lowest percentage of reflection which were used to fabricate antireflective coatings for laser radiation. The porous carbon pigments containing CMK-1 and CMK-3 were prepared and the resulting black pigments were characterized using XRD, FE-SEM and DR-UV-Vis-NIR. The prepared paints were applied on aluminum substrate and the general tests of paints were investigated. The laser reflectivity was evaluated at wavelength of 532 nm that shows these coatings are effective antireflective coating for laser beam.

One of the best non-intrusive methods for concentration measurement in fluid flow is Laser Induced Fluorescence (LIF). In this technique, a laser used to excite the fluorescent component. Usually, fluorescent dyes such as Rhodamine B and fluoerscein are used as flow tracers. These tracers absorb the laser's energy and then emit a portion of the absorbed energy at the different wavelength. The emitted energy, after passing an optic filter reaches to a CCD sensor which could be quantified for dye concentration measurement. Additionally, this technique is used to whole field temperature measurement. In this article, the fluorescence phenomena, equipments for LIF system, basic theory and some literatures about concentration measurement in fluids have been reviewed.