Temperature analysis of driver and optical behavior of LED lamps

This exploratory study was carried out with the objective to know the optical behavior of light-emitting diode (LED) lamps used and the temperature reached by electronic components that compose the driver (electronic circuit situated inside the body LED lamp) responsible to convert electrical alternating current from power line to direct current to operate the LED devices. Then, two different experiments were carried out with LED lamps. In the first experiment, 131 LED lamps used were chosen randomly and bought from household appliances store (bargain market product) presenting different nominal powers, 8, 10, 12 and 15 watts. All LED lamps were polarized at the power line at 127 V and revealed different optical behaviors, such as: not turn-on; flashing light (as strobe effect); flashing light (as strobe effect) with high intensity (more intense than normal); flashing light (as strobe effect) with low intensity (less intense than normal); fast turnon and turn-off only; and turn-on with low intensity of light (less intense than normal). The hypothesis for these behaviors can be attributed by three different behaviors: in lamps not turn-on, this failure can be attributed for dark spots that are created on the surface of LED device. In these lamps, all LED devices are electrically connected in serial. When a LED is inoperative, the electrical current is interrupted for all LED devices; damage to the electronic components caused by internal high temperature confined inside the lamp body during the operation causing electrical oscillations, as observed from different behaviors from flashing light, flashing light with high intensity, flashing light with low intensity and fast turn-on and turn-off only; swelling of the electrolytic capacitors causing low energy storage and varying the electrical current flow, the electrical current for other electronic components altered the normal optical behavior of the LED lamps. In the second experiment, the temperatures of electronic components located in driver were obtained out of body lamp revealing: from 33 (lowest temperature attributed to inductor) to 52.5ºC (highest temperature attributed to electrolytic capacitor). These temperature values represent the ideal or normal condition of operation for electronic components, but, when they are operating inside the lamp body, the found temperature values increased considerably. This characteristic can be better evidenced by strong color change (caused by accumulative temperature during the elapsed days used) on the printed circuit board used in the driver.

Análise de dados de um espectrômetro óptico

Um espectrômetro óptico é um equipamento capaz de determinar as características de filmes finos, tais como espessura e constantes ópticas, pela sua interação com a luz. As constantes ópticas descrevem como a luz é refletida ou se propaga através de um material. Neste trabalho, utilizou-se um espectrômetro óptico portátil (Ocean Optics USB 4000), com o objetivo de analisar a curva de transmitância óptica em função do comprimento de onda de um filme fino de carbono amorfo hidrogenado. Esse filme possui alta transmitância na região próxima a 800 nm e baixa transmitância para comprimentos de onda abaixo de 400 nm. O índice de refração encontrado (ns) foi de 1,513, e a espessura do filme depositado (h), de 2.369 nm.

Assembly of UV-Ozone Reactor to Combat of Coronavirus and Other Pathogenic Microorganisms

The contamination on the surface of objects caused by: fungi, microbes, bacteria and viruses (and also coronavirus) can be solved using UV rays and/or ozone gas. For this reason, a UV-Ozone reactor apparatus with low cost was mounted to test two different types of HID (high intensity discharge) lamps: high pressure mercury vapor lamp (HPMVL) and metal halide lamp (MHL), both with nominal power of 400 watts and E-40 (base, screw) were studied as possible method of disinfection. Each lamp used the respective electromagnetic ballasts and both were manufactured by Osram Company. These lamps have two bulb types: the outer bulb which was removed and it is responsible for filtering the ultraviolet wavelengths and the internal bulb (where there is mercury, argon or metal halide confined at high pressure) that is the main source of ultraviolet rays. The complete apparatus was assembled using: aluminum reflector (used as a chamber), two microcomputer fans and a wooden base covered by an aluminum foil. A rubber strip was placed at the edge of the reflector for better adhesion on the aluminum foil (for better confinement ozone gas). The ozone concentration inside the reactor was measured with a monitor, the temperatures were measured near lamps with a thermocouple and a spectroradiometer with optical fiber was used to obtain the wavelengths. The results revealed to the elapsed time of 2 minutes a maximum peak of ozone concentration of 23 ppm for LVMAP, while the MHL presented 4.5 ppm only. The temperature obtained by HPMVL was lower with 31.5 ºC, while the MHL presented 48.0 ºC. The HPMVL presented higher amount of wavelengths at the ranges: UV-A, UV-B and UV-C, while the MHL presented only UV-A. For these reasons, it is suggested to be most promissory the use of HPMVL to combat the coronavirus and other pathogenic microorganisms.

Lifetime and optical analyses of LED lamps

In this study, optical and lifetime analyses of commercial light-emitting diode (LED) lamps were carried out with the objective to better understand these characteristics. Lamps of different manufacturers and powers were used: Ourolux of 9 watts, Kian of 9 watts, Black+Decker of 9 watts, FLC of 8 watts, Galaxy of 7 watts and Brilia of 7 watts. These LED lamps remained on by 24 hours/day for 4,291.16 hours. Illuminance measurements were analyzed once a week by each lamp inside the integrating sphere with a sensor of lux meter coupled. Results showed decrease of illuminance by elapsed time, due to the degradation. Results of the illuminance obtained between the initial moment of the experiment and the final one were calculated, revealing degradation of 19% to Ourolux, 20% to FLC, 26% to Black+Decker, 28% to Kian, 29% to Galaxy and 33% to Brilia. This study suggests that the diffusers can have different transmittance values interfering on the illuminance, since the FLC LED lamp presented illuminance with highest values than the other LED lamps tested with similar electrical and optical characteristics. This experiment showed that the nominal power of the LED lamp has no direct relation to the illuminance and, comparing the lifetime, the LED lamp manufactured by Black+Decker was the only one to reach 5,521 hours, that is a lifetime much shorter than the one described at the packages (25,000 hours) for all LED lamps tested

Circular economy of ITO thin films deposited on glass obtained from degraded OLED devices

In this work, circular economy was investigated for commercial indium tin oxide (ITO) thin films deposited on glass substrates obtained from degraded organic light-emitting diodes (OLED). These devices were assembled and polarized at laboratory in a previous work. For each substrate, with geometry 2.5 × 2.5 cm, four OLEDs with active area of 3 × 3 mm were set up. These OLED devices were assembled with ITO as the electrode anode and successive depositions of other materials (layer-by-layer), to form the complete structure. To obtain the recovered ITO, all layers were removed from the samples containing the OLEDs previously mounted, remaining only the ITO thin films, that were cleaned with commercial product together with the received ITO/glass samples. Both samples were compared using some techniques, such as: colorimetry, electrical resistance, and Raman spectroscopy. A methodology with light-emitting diode (LED) device polarized emitting light crossing the ITO thin films was used, and the luminance with chromaticity coordinates was obtained, revealing the good transparency of the thin films. Electrical resistance of recovered ITO revealed five higher orders of magnitude in comparison to the one of received ITO. This fact can be tributed to a poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) layer, causing corrosion of the ITO thin films during the assembly of OLEDs or loss of the field lines created during the electrical measurements by probes of four-point probe. Raman spectroscopy did not show satisfactory results in the chemical composition analyses of the samples, but it indicated good cleaning process of the samples before the analyses.

Different electrode anodes used in OLED devices Diferentes eletrodos anodos usados em dispositivos OLEDs

Transparent conductive oxides (TCOs) known as indium tin oxide (ITO) and fluorine tin oxide (FTO) deposited on glass were compared by different techniques and also as anodes in organic light-emitting diode (OLED) devices with same structure. ITO produced at laboratory was compared with the commercial one manufactured by different companies: Diamond Coatings, Displaytech and Sigma-Aldrich, and FTO produced at laboratory was compared with the commercial one manufactured by Flexitec Company. FTO thin films produced at laboratory presented the lowest performance measured by Hall effect technique and also by I-V curve of OLED device with low electrical current and high threshold voltage. ITO thin films produced at laboratory presented elevated sheet resistance in comparison with commercial ITOs (approximately one order of magnitude greater), that can be related by a high number of defects as discontinuity of the chemical lattice or low crystalline structure. In the assembly of OLED devices with ITO and FTO produced at laboratory, neither presented luminances. ITO manufactured by Sigma-Aldrich company presented better electrical and optical characteristics, as low electrical resistivity, good wettability, favorable transmittance, perfect physicalchemical stability and lowest threshold voltage (from 3 to 4.5 V) for OLED devices.

Processing and properties of Ti-15Zr-15Mo-(1-3)Ag alloys for applications as biofunctional materials

Titanium (Ti) is employed as a biomaterial because of its superior biocompatibility and favorable mechanical properties that can be changed with the addition of alloying elements, such as zirconium and molybdenum. Silver is an alloying element recognized for its antibacterial action, which can improve the mechanical strength and decrease Young’s modulus of Ti. This work studies the effect of silver addition (1 and 3 wt%) on the crystalline structure, microstructure, Vickers microhardness and Young’s modulus of Ti-15Zr-15Mo (wt%) alloy, targeting for a potential application as a biofunctional material. The ingots were produced by argon arc melting and subsequently subjected to a heat treatment of homogenization, hot-rolling and solubilization heat treatment. Chemical composition indicated good quality on the processing of the alloy. Crystalline structure and microstructure analyzed by X-ray diffraction, optical microscopy and scanning electron microscopy showed only titanium’s β phase. Finally, mechanical properties studied by Vickers microhardness and Young’s modulus measurements presented that the addition of low content of silver did not significantly modify the alloy’s mechanical properties, but it can include antibacterial properties on the bulk.

Development of a methodology for measuring the evolution of duplex stainless-steel low-temperature plasma nitrided phases expansion using confocal laser scanning microscopy

Samples of duplex stainless steel SAF 2507 were low-temperature plasma nitrided to characterize separately, on the surface, the behavior of its ferrite and austenite phases in relation to two competing processes, that is, one caused by enrichment by nitrogen, resulting in possible expansion, and the other caused by the removal of superficial atoms via sputtering, which may lead to the retraction of the studied phases. Since these phases have different different compositions and crystalline structures, of which the diffusivity and solubility of nitrogen in them are dependent, a different response for each type of phase can be expected. In this article, an innovative methodology has been developed to quantify and clarify which effects are predominant in the course of nitriding for each of these phases. The results indicate that phase expansion prevails over sputtering.

Comparison of different organic solvents used in the luminescent material for OLED devices

In this work, organic light-emitting diode (OLED) devices were mounted using the structure: glass (as substrate)/indium tin oxide (ITO) (as anode)/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) (as hole transport layer)/poly[9,9-dioctifluorene-alt-bis-tienilene(benzotiadiazole)] (PFTB) (as luminescent material)/aluminum-doped zinc oxide (AZO) (as electron transport layer)/aluminum (as cathode). The PFTB was synthetized at laboratory and diluted in different organic solvents as chloroform and trichlorobenzene. The I-V curves of OLED devices showed that the trichlorobenzene used to dillute the PFTB improved the performance for OLED devices promoting the highest electrical current of ≈50 mA and the lowest range of thresold voltage from ≈2.5 to 5 volts, while the device OLEDs mounted with PFTB dilutted in chloroform presented maximum electrical current of ≈23 mA and range of thresold voltage from ≈5 to 8 volts. A hypothesis that explain these results can be attributed to the boiling point of the organic solvent of trichlorobenzene (≈214.4ºC) to be higher than the one of the chloroform (≈61.1ºC), favoring better rearrangement of the polymer chains of PFTB and interfaces between thin films PFTB/PEDOT:PSS and PFTB/AZO improving the injection of charges (holes and electrons) inside the OLEDs devices.

Effects of vacuum exposure on mechanical properties of thermoplastic materials

The present paper proposes the study of the behavior of three thermoplastic materials: acrylonitrile butadiene styrene (ABS), poly(lactic acid) (PLA), and polyethylene glycol terephthalate (PETG), processed by additive manufacturing type fused deposition modelling (FDM) when exposed to low vacuum. The experiment was composed of three moments consisting of tridimensional modeling and manufacturing of the specimens, drying process and vacuum exposure for 24 hours, according to American Society for Testing and Materials (ASTM) D6653/D6653M standards, and bending test for the determination of mechanical properties, based on ASTM D790 standards. The vacuum chamber tests exposed oscillations in the pressure indicating gases releasing from the specimen, but none of the samples showed visible deformations. Subjecting the materials exposed to low vacuum to bending tests and comparing them to the unexposed material, we observed a significant increase in the calculated modulus of elasticity and a change in the slope of graphic force versus deflection in all materials. This behavior demonstrates that it is possible to submit polymeric materials to vacuum, and low vacuum exposure can be a treatment for thermoplastic materials. In the future, a study using a spectrometer will be necessary to verify which gases are present during pressure oscillation in the chamber, thus making it possible to understand which factor has increased the mechanical properties of the materials. In sequence, experiments will be necessary to validate the vacuum exposure as a form of treatment of materials and to verify the possibility of applying thermoplastics commonly used in additive manufacturing for low-impact space applications.