Papers by Keyword: Ultraviolet Radiation

Abstract: The objective of this study was to evaluate the effect of three types of surface protectors: Protector with and without ultraviolet pigment and hydrophobic protector, on cracking and discoloration of Pinus radiata wood, after accelerated aging caused by temperature variation, UV-A radiation and humidity. For the tests, a QUV/Spray model accelerated aging chamber was used, which simulates the spectrum of radiation emitted by the sun under controlled climatic conditions in accordance with the EN 927-6 standard. The main results show that after 11 cycles (1848 hours) of testing, the color change decreased and the presence of the number and size of cracks occurred in the order of samples with Hydrophobic protection, followed by samples with UV pigment protector. and finally, in sample with protector without UV pigment. When wood is exposed to UV radiation, it undergoes photo-oxidation, causing an alteration of the properties and the original colour. This radiation burns the surface cells (lignin) of the wood, this effect produces cracking and flaking of the wood.

Abstract: Polyethylene (PE) has an exclusive set of properties, such as good toughness and mechanical resistance as well as high flexibility, and ease conformation. However, when exposed to degrading agents, such as heat, humidity and radiation, macromolecular changes can be observed and consequently affect the PE. This work evaluated for the first time the thermomechanical and fracture behavior of low-density polyethylene (LDPE) subjected to degradation at different times of exposure to ultraviolet (UV) radiation. The changes induced in the chemical structure and the highlighted behavior were investigated through thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transformed infrared spectroscopy (FTIR), reticulation content, tensile test, and scanning electron microscopy (SEM). The results suggest that UV radiation modify the failure of the polymer by reducing its crystallinity and dramatically increasing its degree of crosslinking. These modifications impair the LDPE mechanical performance as well as its thermal stability.

Abstract: Miscible transparent blend consist of poly (methylmethacrylate) with cellulose acetate phthalate was prepared in order to get more transparent blend for ultraviolet rays. The blend was prepared by melt-blending and examined using UV-VIS spectroscopy. The structural, mechanical and thermal properties of selected samples were studied using X-ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and thermos-gravimetric analysis. The UV-VIS spectrum exhibited the best blend ratio which has low absorbency to ultraviolet rays, On the other hand, high optical transparency within visible region. The results also showed that the blend has an amorphous structure as X-ray diffraction diffractogram. Moreover, thermal stability happened with the presence of cellulose acetate phthalate in the blend.

Abstract: The paper provides a brief review of modern sources of ultraviolet (UV) radiation used in fluorescent penetrant testing (FT). The differences in implementation of the method with different radiation sources (excilamps, mercury UV lamp and LED UV lamp) are revealed experimentally. It is shown that the XeCl excilamp is not inferior to other sources of UV radiation used in FT.

Abstract: Thin films of ZnO, ZnO coated with TiO₂ and ZnO modified with titania were prepared by using simple spray pyrolysis of zinc and titanium containing solutions. The photicatalytic activity of the obtained films was determined by degradation of MB solution under UV and simulated solar illumination. The photocatalytic activity of ZnO/TiO₂ films depended on the content of titania, substrate surface roughness, surface area and deposition cycles. The highest activity under simulated solar light was detected for ZnO films containing 3 wt.% of TiO₂.

Abstract: The possibility of modification of mineral extenders with a specific surface of 350 m²/kg with ultraviolet irradiation is considered. Infrared spectroscopy confirmed that under the influence of ultraviolet irradiation, the bonds of OH-groups with SiO₂ tetrahedra are weakened, that contributes to the formation of extenders of the acid centers of Lewis and Bronsted on the surface. The optimum time of ultraviolet exposure is determined, at which the concentration of active Lewis and Bronsted acid sites on the extenders surface increases by more than 100%. It was found that replacing 10% of cement mass with a modified extenders makes it possible to produce concretes with strength values 20-30% higher than for composites without extenders. Obtaining equal strength concrete is possible with replacing 20% of cement with modified extenders.

Abstract: Recently, diamonds have been utilized gradually for sliding parts and wear-resistant parts because of their excellent properties. The shape of diamond applied to these parts is not only plane but also arc-shaped inner surface. Therefore, development of diamond polishing technology is required. In this study, ultraviolet assisted polishing was thought to develop to polish polycrystalline diamond (PCD) on arc-shaped inner surface. The authors investigated effect of ultraviolet radiation on polishing efficiency and surface roughness. As a result, the surface roughness Ra of PCD showed less than 15 nanometers. In addition, polishing efficiency was improved about 30 percent due to ultraviolet assisted polishing.

Abstract: A fundamental study on finishing aided by an ultraviolet ray (generally mashining:referred to as U-RAM^R) was conducted to evaluate its applicability to the polishing of aluminum alloy. Qualitative analysis with X-ray photoelectron spectroscopy (XPS) was used to estimate the chemical reaction induced on Al surfaces that were immersed in some solutions. Inductively coupled plasma spectroscopy (ICPS) was employed to quantitatively analyze the amount of oxidized/dissolved Al, Mg and Fe. The following conclusions were obtained by investigation of the aluminum alloy polishing process. Aluminum does not dissolve in TiO₂-solution, whereas a small amount of Al dissolves into cathilon dye solution. Although only a small amount of Al dissolves in TiO₂-cathilon dye solution in the absence of UV irradiation, the amount of Al dissolved increases slightly under UV irradiation with the formation of oxide, nitrogen oxide and nitride on the Al surface. In addition, a small amount of an aluminum chloride dissolves into TiO₂-cathilon dye solution. An Al alloy (A5052) surface was made flat by polishing with TiO₂-cathilon dye slurry under UV irradiation.

Abstract: Solid-phase chemical reaction speed control is one of the most essential problems of physics and chemistry of solid bodies. Special attention is paid to the studies of sensitivity and stability of explosive substances (ES). Fundamental issues of studies of azides of heavy metals (AHM) are connected with developing ways of controlling new chemical reactions – solid-phase chain reactions in which electron excitations of a crystal lattice serve as active particles. Applied value is determined by safety issues of ES that include such wide range of problems as storage, transfer, destruction, etc.The result of this work is the use of the experimental results for purposeful change of energetic material

Abstract: In order to improve the hydrophilic performances, the surface of poly films was modified through grafting polymerization of styrene (ST) initiated by ultraviolet (UV) in ethanol/water mixture solution. The effects of irradiation time, concentration of inhibitor (ferrous ammonium sulfate) on the grafting degree of ST will be investigated. The original and grafted poly films were characterized by scanning electron microscopy (SEM) and Static contact angle (CA), to characterize the chemical changes of the poly film surface. The results showed that the hydrophilic of poly films was improved significantly than that of the original film. The contact angle of PO-g-ST increased from 70° to 120.4° over a critical grafting degree of 26.35%, the hydrophilic of PP membranes improved dramatically.