Reflectance Of Films Research Articles

Performance studies of novel all-glass heat pipe evacuated collector tube integrating numerical simulation and experiment method

Metal heat pipe evacuated collector tube (ECT) suffer from cracks in the joint between the glass outer layer and the metal heat pipe due to the large difference in thermal expansion coefficients of glass and metal, resulting in non-industrialization. In this paper, the metal heat pipe is replaced with a glass heat pipe to form an all-glass heat pipe ECT to address the air-tight sealing problem, and a reflective film was added to the lower part of the outer tube to improve energy. According to these results, the thermal stress of 0.279 MPa is well below the bearing range of 40–120 MPa, and the maximum thermal strain of 0.175 mm/mm is also far less than the affordable value of 120 mm/mm, inducting the all-glass structure fully copes with the transient local heating changes. The optical efficiency is increased by 0.17 % by the addition of the reflective film, and yielding an energy output of 87 W and a maximum volume fraction of 4.8 % for liquid–water in the quasi-thermal equilibrium state. At the same time, the evaporation operating speed of the vapor can be increased by improving the solar radiation flux density and reducing thermal losses, and optimizing the multi-level and cross-scale vapor vortices can also improve the convective heat transfer rate, so they are future directions for development. However, there are the limitations of decreasing the thermal conductivity and increases the resistance due to the heat pipe conversion from metal to glass.

Effects of Upward Reflective Film Applied to Window Glass on Indoor and Outdoor Thermal Environments in a Mid-Latitude City

The effect of upward reflective film applied to a window on the thermal environment inside and outside the window was investigated, considering the reflection and transmission characteristics depending on the angle of incident solar radiation. In terms of controlling the amount of solar radiation on a building’s windows, it is sufficient if the reflected solar radiation returns upward and does not need to be retroreflected in the azimuthal direction. Therefore, in this study, only the incident angle was considered and treated in two dimensions. The amount of incident solar radiation on the vertical façade is greater around 9:00 and around 16:00. Therefore, it is important to take measures in the morning for east-facing windows and in the afternoon for west-facing windows. The indoor MRT in front of upward reflective film is lower than in front of a transparent window due to lower transmittance. The outdoor MRT in front of upward reflective film is suppressed to the same level as in front of a transparent window, because the downward reflectance does not increase as much as in transparent windows. Upward reflective films applied to windows can improve the indoor thermal environment without worsening the outdoor thermal environment compared to thermal barrier films.

Broadband reflection induced by chiral dopant-loaded mesoporous polystyrene-divinylbenzene microspheres via diffusion in polymer stabilised cholesteric liquid crystals

ABSTRACT A new method to construct polymer stabilised cholesteric liquid crystal (PSCLC) films with broadband reflection in the near infrared region (NIR) has been proposed which utilises the chiral dopant-loaded mesoporous polystyrene-divinylbenzene (PS-DVB) microspheres. The diffusion time, UV intensity and temperature during polymerisation were investigated to control the diffusion of chiral dopant and the polymerisation process which could affect the non-uniform pitch distribution and thus the reflection bandwidth. The optimised reflection bandwidth was broadened from 300 nm to 860 nm. Potential application fields of broadband reflective films include smart windows for the control of the solar-light irradiation, and military infrared shielding devices.

High-Performance Optical Fiber Fabry–Perot Sensor Based on a Sawtooth Spectrum and Its Application in Acoustic Sensing

An optical fiber sensor based on Fabry–Perot (F–P) resonance with sawtooth spectral shape can break the mutual constraint of sensitivity and response range through simultaneously demodulating intensity variation of lasers working on the two asymmetric spectral lines. Here, theoretical solution and practical approach for obtaining the F–P resonance with a sawtooth spectrum have been proposed. The linear range and slope of the asymmetric spectrum are first calculated based on the proposed theoretical model, which regulates the spectral shape variation. Then, the composite film on fiber end face has been solved to fulfill the model parameters required for the sawtooth spectrum through reversely utilizing an equivalent interface approach, which has been theoretically and experimentally demonstrated by using a composite film of platinum and germanium (Pt/Ge) as the first reflective mirror and gold film as the second mirror. Finally, an optical fiber F–P sensor with sawtooth spectral characteristics is prepared for underwater acoustic sensing application, which demonstrates an average of 10-dB improvement in dynamic range at the frequency range of 20–800 Hz.

Tracking the same fast-LGSO crystals by changing surface treatments for better coincidence timing resolution in PET

Achieving fast coincidence timing resolution (CTR) is an important issue in clinical time-of-flight positron emission tomography (TOF-PET) to improve the reconstructed image quality. One of the major factors affecting the CTR is the crystal surface treatment, which is often parameterized as surface roughness. However, previous studies on the crystal surface treatment optimization had two limitations of crystal-by-crystal variation and worse CTR over 200 ps. Here, we report the effects of the crystal surface treatment on the performance of a 20 mm long fast-LGSO crystal based TOF detector by tracking the same crystals in the sub-180 ps CTR regime. The light collection efficiency (LCE), energy resolution (ER) and CTR of the TOF detector were evaluated with six different crystal surface treatments of chemically polished (C.P), C.P half side roughened (1/2S) treatment, and then the C.P one side roughened (1S) treatment, mechanically polished (M.P) treatment, M.P 1/2S treatment, and M.P 1S treatment. The four lateral surfaces of each crystal were wrapped by using enhanced specular reflector film while the top surface was covered by using Teflon tape. The bottom surface of the crystal was optically coupled to a silicon photomultiplier. The timing and energy signals were extracted by using a custom-made high-frequency readout circuit, and then digitized by using a waveform digitizer. All the experimental conditions were same except the crystal surface treatment. Among the six different crystal surface treatments, the M.P 1S would be the optimal crystal surface treatment which balanced enhancements in the CTR (165 ± 3 ps) and ER (10.5 ± 0.5%). Unlike the M.P 1S, the C.P 1S did not enhance the CTR and ER. Hence, the C.P without roughening would be the second-best optimal crystal surface treatment which balanced the CTR (169 ± 3 ps) and ER (10.5 ± 0.5%).

Reflective mulch films a boon for enhancing crop production: A review

Mulches are materials that are put to the surface of the soil for a variety of reasons. Plastic mulches of various colours have been developed and employed in a variety of agricultural production methods. Colored plastic mulches are used to modify the radiation budget and prevent soil water loss. It also helps with weed and insect infestation, as well as soil temperature regulation, water efficiency, plant development, yield, and quality. This paper reviews and discusses the understanding and prospective application of coloured plastic mulches to improve soil physical attributes growth, yield, and crop quality. Colored plastic mulches' effectiveness in minimising the detrimental impacts of environmental stress on crops is also explored. The impact of coloured plastic mulches on soil temperature has been documented by several researchers to vary from area to area and crop to crop. Various physicochemical mechanisms have also described that result in increased crop productivity when coloured plastic mulches are employed. Colored plastic mulches have a significant impact on soil temperature, moisture, and water holding capacity, according to the study. Clear and white plastics lower the temperature of the soil, but black and blue plastics raise it. A higher number of fruits, roots, tubers, and bulbs were produced when coloured plastic mulches were used. TSS, Vitamin C, and the proportion of liquid in diverse plants all improved significantly. Infestation of weeds and viral diseases has also been found to be significantly reduced. Reduced plant growth and yield, increased pest infestation, microplastic pollution, soil puddling, soil structural loss, and reduced soil-microorganism activity are some of the disadvantages of coloured plastic mulches. As a result, using coloured plastic mulches demands a detailed investigation of interactions with factors such as cropping season, root zone temperature, crop type, insect pest infestation, and water use efficiency.

ИССЛЕДОВАНИЕ ХАРАКТЕРИСТИК РАЗВЕРТЫВАЕМОЙ КОСМИЧЕСКОЙ ЗЕРКАЛЬНОЙ АНТЕННЫ С РАЗРЕЖЕННОЙ ОТРАЖАЮЩЕЙ ПОВЕРХНОСТЬЮ

The article presents the results of a study of the characteristics of a space parabolic mirror with a deployable reflector. A model of the reflector truss structure formed by two asymmetric parabolic networks with tension cables is presented. Three variants of the sparse structure of the reflecting film of the reflector are presented, differing in periodically repeating hexagonal holes with different sizes. A complex electrodynamic modeling of the radiation characteristics of a parabolic mirror antenna with a developed model of a truss-bearing structure and the proposed structures of reflective films, allowing to reduce the mass of the reflector and increase the reliability of the antenna system, are carried out. The estimation of the frequency dependences of the characteristics of the variants of the parabolic mirror antenna model is given. Recommendations on the use of sparse reflective films for small, medium and large apertures of deployable reflectors are proposed.

Flexible omnidirectional reflective film for CO2 laser protection

In this Letter, we presented a flexible omnidirectional reflective film made of polymer substrates and multiple alternating layers of two chalcogenide glasses for full-angle CO2 laser protection. The structure parameters of the device were simulated for theoretical prediction of best device structure. The reflector was fabricated by alternate thermal evaporation of two chalcogenide glasses with large refractive index contrast. The reflectivity was greater than 78% at 10.6 µm. The flexible reflective film can provide an effective solution for full-angle CO2 laser protection of the moving targets, such as laser operators and mobile optical components, with potential applications for wearable laser protective clothing.

SOLAR STOVES AS AN ALTERNATIVE SOLUTION FOR THE USE OF RENEWABLE ENERGY IN INDONESIA

Along with the development of technology, the need for fossil energy for cooking purposes using conventional stoves is increasing. The limitations of fossil energy reserves that cannot be renewed have resulted in an energy crisis starting to hit. Solar energy is an energy source that is environmentally friendly and available free of charge. Solar energy is utilized using the system. Concentrating solar power (CSP) focuses solar radiation to a point to get a higher temperature. This type of box-type solar cooker has a long history dating back to the 18th century when Nicholas-de-Saussure first made this type of solar cooker. A parabolic solar cooker is a solar-powered stove that uses reflections from the sun's radiation which is concentrated directly on the pan. A trough solar cooker collects sunlight and reflects it to a focal point using a reflective film. A box-type solar cooker has an important part between the reflectors which use aluminum foil with a diameter of 41 cm and a thickness of 0.2 mm. The collector was made of brass copper for cooking with a diameter of 41 cm and a thickness of 0.2 mm. The parabolic type of solar cooker has important parts, including a collector that uses a parabola with a diameter of 140 cm and a depth of 40 cm and a reflector that uses a reflective film with an emissivity value of 0.91. The trough-type solar cooker performs better than the box and parabola types because it has a higher temperature where the ambient temperature is 25.5 ℃, the focal point temperature is 164℃, and the load temperature is 163℃.

Fourier-transform infrared spectroscopy for characterization of liquid protein solutions: A comparison of two sampling techniques

Whereas industrial laboratory systems for Fourier-Transform Infrared (FTIR) spectroscopic characterization have been available for decades, dedicated FTIR solutions for in-line process control or for industrial at-line analysis of protein quality are still scarce. Thus, the present study aimed to compare two industrially viable sampling techniques, namely attenuated total reflectance (ATR) and dry film FTIR spectroscopy, for qualitative and quantitative analysis of liquid protein solutions. For this purpose, two sample sets were acquired: set 1 consisted of 95 protein hydrolysate samples produced in the laboratory from salmon processing by-products, and set 2 consisted of 133 protein hydrolysate samples obtained from an industrial processing plant of poultry by-products. Average molecular weights (AMW) and Brix measurements of protein hydrolysates were used as reference values for obtaining regression models. AMW was predicted with higher accuracy and lower estimation errors using dry film FTIR compared to ATR measurements for both sample types. The difference in predictive performance was higher in poultry hydrolysates because the protein and tissue complexities are higher than in salmon hydrolysates, and information from the amide I region in the FTIR spectra is needed to provide good calibration results. ATR, on the other hand, was more reliable for the prediction of Brix values of protein hydrolysates. The study also showed that FTIR spectroscopy can be used to predict protein quality features of industrially produced protein hydrolysates with a sensitivity of high industrial relevance. Therefore, developing industrially viable portable instruments for at-line process analysis in the food, feed, and biotech industries is a natural next development stage.

Research on reflection-mode InxGa1-xN thin film photocathode

The ternary nitride alloy InxGa1-xN, characterized by tunable band gap, can be used in photoelectric devices to achieve a wide spectrum response of UV-infrared light. A complete photoemission theoretical model of reflective InxGa1-xN thin film vacuum photocathode is established based on the “Spicer's model” and “Andachi model”. The simulation experiment of InxGa1-xN thin film photocathode is constructed by COMSOL Multiphysics software based on the finite element method. By analyzing the optical absorption and the distribution of photogenerated carrier concentration of photocathode, it is found that the photoconversion performance of photocathode can be enhanced by optimizing the thickness of emission layer and the angle of polarized light. The peak quantum efficiency and peak spectral responsivity of In0.5Ga0.5N photocathode with a thickness of 400 nm are 63.13% and 240.83 mA/W, respectively. The quantum efficiency of In0.5Ga0.5N photocathode with an incidence angle of 50° of TM mode polarized light can be increased to 65.99% compared with that with normal incidence. Therefore, the simulation results of this paper can provide reference for the design of wide spectrum photodetectors and vacuum electron sources.

Deterioration of Novel Silver Coated Mirrors on Polycarbonate Used for Concentrated Solar Power

The lifetime of mirrors in outdoor conditions is crucial in the correct operation of any concentrating solar power (CSP) installation. In this work, the corrosion behavior of two types of metallized surfaces was studied. The first was made of a flexible polymer having a deposited reflective silver metallic film. The second was made of the same surface type with a dielectric SiO2 protection coating by an atmospheric pressure plasma jet. Polycarbonate sheets were used as substrates on which metallic silver was deposited by the Dynamic Chemical Deposit technique. This electroless technique allowed producing the mirror finishing under environmental conditions by sequentially spraying; as aerosols projected towards the substrate surface, the activation and reducing-oxidizing solutions with rinsing after each one. The silver coatings were about 100 nm thick. Environmental and accelerated weathering degradation and salt and sulfide fogs were carried out. XPS analyses show that the corrosion products formed were Ag2S, AgCl, and Ag2O. It was observed that the tarnishing was initiated locally by the formation of Ag2S columns as eruptions on the surface. Subsequently, the ions diffused through the protective layer and into the silver reflective layer, chemically reacting with the silver. The main atmospheric agents were H2S, chloride particles, and HCl. High reflectance was initially obtained of about 95%. The obtained results suggest mechanisms for the degradation of exposed silver surfaces to moisturized atmospheres with corrosive compounds.

Environmentally robust Ag–Cu based low-e coatings

Low emissivity (low-e) coatings minimise heat transmittance through the coating and emission of infrared light from hot surfaces. They are used in space applications to reduce overheating of the spacecraft, in architectural applications and automotive windows to block heat from entering a building or vehicle. Typically, in window applications the low-e coatings consist of a multilayer coating, which combine metallic films (approx. 10 nm); responsible for the heat reflection and dielectric films (approx. 40 nm); used to protect the metallic films and enhance their visible transmittance. Commercially available low-e coatings can contain more than 15 layers, with Ag typically used as the metallic layer. However, Ag is soft and tends to tarnish, making Ag-based low-e coatings vulnerable to degradation when exposed to environmental conditions. In this study we demonstrated environmentally durable low-e coatings based on Ag–Cu alloyed thin films. The thin film alloys showed higher level of scratch resistance than conventional pure Ag coatings with high level of transmittance of visible light. The multilayer coating consisting of a dielectric film, metal alloy film and a protective coating was demonstrated as robust, long-life, first surface low-e coating. • Ag–Cu thin films have been co-evaporated onto glass substrates. • 30 at.% Cu in Ag film exhibits the most neutral colour and good adhesion to TiO 2 . • Ag and Ag 70 Cu 30 based multilayer low-e coating have been grown on polycarbonate. • Cu in Ag film elevates the durability and barely compromising optical performance.

Enhancing radiative cooling performance for bifacial photovoltaic module using two kinds of polycarbonate films

Radiative cooling, as a cooling method that does not consume any energy during operation, has become a hot topic in recent years. Unlike passive daytime radiative cooling in buildings, radiative coolers used in photovoltaic modules must also have high light transmittance, which undoubtedly makes relevant research more difficult. Currently, bifacial photovoltaic modules are widely available on the market, if traditional cooling methods are employed in the back of them, including passive cooling such as heat sink and active cooling such as air cooling and water cooling, it will block the rear irradiance into the module. Hence, radiative cooling is an excellent solution. In this paper, polycarbonate (PC) film and one composed with a high reflective layer are proposed. The former has high emissivity in the atmospheric window and the latter has high reflectivity in the near-infrared band. Both achieve a good cooling effect without affecting the normal operation of the module. We also prepared the reflective film on PC by magnetron sputtering, and its optical characteristics were also measured and compared with simulation results. We innovatively use PC material and combine the reflective film with quite simple structure. Compared with other research results, they are simpler and stabler film structures and have the advantages of low cost, easy installation, good cooling effect, and can be directly pasted on the surface of the photovoltaic module. It turns out that the cooling effect can reach 6.02°C with R-PC film and photoelectric conversion efficiency can be improved by 0.27% with PC film when hc = 20 W · m − 2 · K − 1 and Ta = 27 ° C. Given its excellent performance, they have a broad application prospect in the daytime passive radiative cooling of bifacial photovoltaic modules.

Experimental Study of a Tubular Solar Distillation System with Heat Exchanger Using a Parabolic Trough Collector

One way to overcome the scarcity of clean water through sustainable approach is by utilizing a solar distillation system. This easy-to-use technology is adopting tubular solar distillation. The three main components, which are the most essential for producing the amount of permeate, are the solar collector, tubular and heat exchanger (HE). This study aims to determine the performance of a tubular solar distillation device equipped with HE using a parabolic trough collector (PTC). The PTC has an area of 5.1 m2 covered with a solar reflective chrome film. Aluminum tubular acts as the feedwater heater. The HE is placed inside the tubular, which acts as a coolant to convert the steam phase into freshwater/permeate and as a feedwater heater to flow into the tubular. In the present study, several parameters were tested: comprise temperature, solar radiation, pressure, humidity, mass flow rate, permeate productivity and efficiency. This study demonstrated the production of a sufficient amount of permeate, which was 5.32 L for 6 h. The efficiency of this device yielded a peak of 48.2% during solar radiation of 813 W/m2 in an average ambient temperature of 32 °C, with an overall average of 44.59%.

Laser Protection Properties of Multi-Band Non-Regularized Highly Reflective Films

With the increasing exploitation of lasers, single-band laser protection has been extensively studied. However, single-band laser protection techniques have remained expensive and failed to meet protection requirements for multi-band lasers. In addition, the actual use of protective films requires a specific transmittance, which is generally not met by regular films. Here, we deposited three non-regularized highly reflective films using SiO2 as the low-refractive-index material and TiO2, HfO2, and Ta2O5 as the high-refractive-index materials by thermal evaporation for achieving multi-band laser protection. To verify the effectiveness of the films, the variation in transmittance, damage threshold, standing-wave electric field, and damage morphology of the films were analyzed at two laser wavelengths, and their protection mechanisms were evaluated based on optical properties and damage resistance. The results showed that the reflectances of the prepared non-regularized films at 1064 nm and 532 nm were greater than 99%, and the laser-induced damage thresholds for TiO2/SiO2, HfO2/SiO2, and Ta2O5/SiO2 films were 5.99, 5.89, and 9.99 J/cm2 at 1064 nm and 3.04 J/cm2, 1.48 J/cm2, and 4.93 J/cm2 at 532 nm, respectively, demonstrating good laser protection. The present work provides a practical and effective solution for multi-band laser protection and the prepared films may be used in numerous laser applications.

Retro-reflective target with high accuracy for industrial photogrammetry

Retro-reflective targets (RRTs) are important for obtaining the coordinates of the surface points of objects measured using industrial photogrammetry systems. Targeting the low measurement accuracy caused by the poor roundness of the conventional RRT, a novel RRT was designed in this study by covering a die-cut slice with round holes and high roundness on a glass bead reflective film. The roundness of this novel RRT was on average 0.03 mm higher than that of the conventional RRT. The accuracy of the novel RRT was evaluated in terms of both internal and external coincidence accuracies. The measurement repeatability accuracy of the novel RRT was improved by 25.0% compared with that of the conventional RRT. The thinner the die-cut slice thickness, the higher the repeatability in a certain range. Similarly, the plane fitting, flatness measurement, and standard length measurement accuracies were improved by 30.7%, 34.1%, and 28.1%, respectively.

Modelling sustainable transparent metasurfaces for tunable near infrared reflectance

Transparent conducting oxide (TCO) nanodisk metasurfaces on polymer substrates were modelled for high visible transmittance (400–750 nm) of more than 97%. An increase in the nanodisk diameter tuned the resonant wavelength between 840 and 1200 nm based on the transparent oxide material and the plasmonic metasurface geometry. The optical properties of ethylene tetrafluoroethylene (ETFE) and polyethylene terephthalate (PET) polymer substrates were imported for simulating the reflectance, transmittance and near field distributions for a TiO2/Ag/TiO2 metasurface. A high reflectance of 92.33% was observed for a specific three tier titanium dioxide (TiO2)/silver (Ag)/TiO2 geometry at a resonant wavelength of 1130.6 nm. High electric field localisation was exhibited at the resonant wavelength, which was compared at three interfaces, TiO2-air, TiO2-Ag and TiO2-polymer, for varying nanodisk diameters. A red shift in the resonant wavelength was recorded with a change in polymer substrate and nanodisk geometry. The use of fully recyclable polymers and the long-lasting nature of TiO2 can be beneficial for the fabrication of sustainable heat reflective films or coatings.

Reflectivity enhancement of full color tri-layer electrowetting display with polymer cholesteric liquid crystal films

Electronic paper display has received increasing attention due to its outstanding properties of wide viewing angle, bistable state and lower energy consumption. Among various electronic paper display technologies, electrowetting e-paper (EWD) is the most promising as it can achieve full-color display by using stacked layers or RGB color filter. However, the EWD is faced with several challenges, including poor color brightness, low contrast ratio and small color gamut. To improve the performance of the EWD, we proposed a new configuration of EWD consisting of three independent PCLC reflection films based on the cholesteric liquid crystal materials. We designed and experimentally fabricated three types of reflection films, and then added the PCLC films to the tri-layered EWD device. We experimentally characterized the reflectivity and color gamut of the sample in the dark room. It is found that the experimental results and simulation results match with each other. It is demonstrated that with the PCLC films, the reflectivity is improved by 20%, while the color gamut is improved by 80%, which is sufficient for the daily display demand of E-paper. The proposed EWD device containing PCLC reflection films provide a new strategy to improve the brightness and color gamut of current EWD device, and is promising for realizing the full-color E-paper display.

Preparation of polymer stabilised cholesteric broadband reflection films based on ZIF-8 assisted bidirectional diffusion method

ABSTRACT The polymer-stabilised cholesteric liquid crystal (PSCLC) broadband reflective films are prepared by zeolite imidazole framework-8 (ZIF-8)-assisted bidirectional diffusion combined with light curing, altering the single pitch of cholesteric liquid crystals (CLCs). By changing temperature, chiral compounds and ultraviolet (UV) absorbing dyes adsorbed on porous ZIF-8 are able to diffuse bidirectionally into the CLCs’ system and produce concentration gradients, thereby inducing a pitch gradient, and the structure of broad reflection bandwidth can be fixed through UV irradiation. In addition, the effects of various factors, such as UV irradiation intensity, UV irradiation time, mass fraction of polymerisable monomers and curing temperature on the pitch gradient of the films are systematically investigated, and the maximum reflection bandwidth of the prepared films is 1274 nm. There is no doubt that new and modified processes and techniques provide significant possibilities for preparing and applying PSCLC films.