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Oxygen concentration dependence of microstructure formed on Ni by backward pulsed laser deposition
摘要： In the automotive industry, direct joining between resin and metal without additional material is expected due to a growing need for hybrid structures composed of resin and metal. Roughening the metal surface before joining can improve the adhesion with the resin, and forming a microstructure on the metal surface by backward pulsed laser deposition could be a useful method. In the present study, we investigated the dependence of microstructure on the oxygen concentration in the ambient gas during surface processing for controlling the morphology of the microstructure. In the experiments, the oxygen concentration in the ambient gas composed of nitrogen and oxygen was controlled under atmospheric pressure, and microstructure characteristics, such as the shape and hardness, were analyzed. As a result, it was demonstrated that the formation range of the microstructure was constant regardless of the oxygen concentration, whereas a rougher microstructure was formed at higher oxygen concentrations, and a dense, flat microstructure was formed at lower oxygen concentrations. These results implied that the oxidation between the nanoparticles in the laser-induced plume and the ambient gas affects the mobility of the nanoparticles on the metal surface, leading to a transmutation in the morphology of the microstructure. Finally, it was shown that it is important to reduce the surface mobility of nanoparticles, such as processing under high oxygen concentration, to form a microstructure that improves adhesion.
关键词： Resin-metal joining,Backward pulsed laser deposition,Oxygen concentration,Microstructure,Nanosecond pulsed laser
更新于2025-09-23 15:21:01
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Effect of light absence or attenuation on biaxial flexural strength of dual-polymerized resin cements after short- and long-term storage
摘要： Objective: To evaluate whether biaxial flexural strength (BFS) of dual resin cements is affected by light absence or attenuation, storage time, or cements' chemical nature. Materials and methods: One hundred and twenty disk-shaped specimens were made from each cement (non-self-adhesive cement and self-adhesive cement) using Teflon molds on a controlled temperature surface (35°C). Specimens were polymerized as follows (N = 30): self-cured, directly light-cured, light-cured at a distance of 6 mm between the light tip and the specimen, and through a 6-mm thick composite resin barrier (indirectly light-cured). Each group was divided (N = 10) for storage purposes (15 minutes, 24 hours, and 6 months). Specimens were placed into a biaxial-flexure jig and a vertical load was applied until failure. The BFS values were subjected to generalized linear models statistical analysis and Weibull distributions (α = 0.05). Results: After 15 minutes aging, neither material achieved enough polymerization to perform the BFS test when polymerized using the self-curing mode. The self-adhesive product demonstrated much lower variation in strength with storage time than did the non-self-curing cement. Conclusions: Attenuated/light-curing reduced BFS values only for 15-minutes storage period for both materials. Flexural strength of the self-adhesive cement was less affected by light absence/attenuation and storage time.
关键词： resin cements,Weibull analysis,biaxial flexural strength,physical properties,polymerization
更新于2025-09-23 15:21:01
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Optical properties and colorimetric evaluation of resin cements formulated with thio-urethane oligomers
摘要： Objective: The aim of this study was to evaluate the color parameters and optical properties of resin cements (RCs) formulated with thio-urethanes (TUs). Materials and methods: Six TUs were synthesized by combining thiols (pentaerythritol tetra-3-mercaptopropionate [PETMP] or trimethylol-tris-3-mercaptopropionate [TMP]) with di-functional isocyanates (1,6-Hexanediol-diissocyante [HDDI] [aliphatic-AL] or 1,3-bis(1-isocyanato-1-methylethyl) benzene [BDI] [aromatic-AR] or Dicyclohexylmethane 4,40-Diisocyanate [HMDI] [cyclic-CC]). TUs (20 wt%) were added to a BisGMA/UDMA/TEGDMA matrix. Filler was introduced at 60 wt%. Fluorescence was evaluated through an UV-light emitting equipment. Coordinates L*, a*, and b* were obtained in the black and white reflectance to evaluate the contrast ratio (CR) and translucency parameter (TP00). The coordinates obtained from transmittance were used to evaluate lightness (L*), chroma (C*), color difference (ΔE00) after 6 month, and whiteness index for Dentistry (WID). Results: RCs formulated with TUs presented significantly higher CR, and fluorescence (with T_AR). Significantly lower C*, L*, and TP00 (except for P_AR and T_AL) were also observed in RCs containing TUs. ΔE00 were not significant among the materials. WID was not influenced. Conclusion: RCs composed by TU oligomers present higher CR and lower translucency. The material also present higher fluorescence depending on the oligomer used. Clinical Significance: The use of thio-urethanes to formulate resin cements can ensure a luting material with improved potential to mask colored substrates due to the higher contrast ratio and lower translucency obtained. A final higher fluorescence of restoration is also expected with the use of specific oligomer.
关键词： colorimetric evaluation,resin cements,thio-urethane oligomers,optical properties
更新于2025-09-23 15:21:01
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Microencapsulation of energy conversion photochromic materials with epoxy resin shell by interfacial polymerization
摘要： In this study, a novel type of photochromic spirooxazine microcapsule was prepared by interfacial polymerization between epoxy resin and polyamine compound. The effects of different process parameters on the formation, microstructure and performance of microcapsules, such as curing reaction temperature, emulsification shear rate and the addition of silica nanoparticles were studied in this paper. The morphology, microstructure, diameter and distribution, as well as the thermal stability of microencapsulated photochromic spirooxazine were also investigated by field emission scanning electron microscope, laser particle size analyzer and thermogravimetric analysis systematically. In addition, the photochromic performance of microcapsule was studied as well.
关键词： microencapsulation,photochromic,epoxy resin,spirooxazine,interfacial polymerization
更新于2025-09-23 15:21:01
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Outdoor manufacture of UV-Cured plastic linings for storm water culvert repair: Chemical emissions and residual
摘要： Storm water culverts are integral for U.S. public safety and welfare, and their mechanical failure can cause roadways to collapse. To repair these buried assets, ultraviolet (UV) light cured-in-place-pipes (CIPP) are being installed. Chemical emission and residual material left behind from the installation process was investigated in New York and Virginia. Samples of an uncured resin tube and field-cured styrene-based resin CIPPs were collected and analyzed. Also collected were air and water samples before, during, and after installations. Chemicals were emitted into air because of the installation and curing processes. Particulates emitted into the air, water, and soil contained fiberglass, polymer, and contaminants, some of which are regulated by state-level water quality standards. The uncured resin tube contained more than 70 chemical compounds, and 19 were confirmed with analytical standards. Compounds included known and suspected carcinogens, endocrine disrupting compounds, hazardous air pollutants, and other compounds with little aquatic toxicity data available. Compounds (14 of 19 confirmed) were extracted from the newly installed CIPPs, and 11 were found in water samples. Aqueous styrene (2.31 mg/L), dibutyl phthalate (12.5 μg/L), and phenol (16.7 μg/L) levels exceeded the most stringent state water quality standards chosen in this study. Styrene was the only compound that was found to have exceed a 48 hr aquatic toxicity threshold. Newly installed CIPPs contained a significant amount volatile material (1.0-6.8 wt%). Recommendations provided can reduce chemical emission, as well as improve worksite and environmental protection practices. Recommended future research is also described.
关键词： VOC,styrene,Plastic lining,sewer pipe,cured in place pipe,resin
更新于2025-09-23 15:21:01
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Development of a composite polymer-dye medium for tunable laser emission
摘要： We demonstrate optically pumped laser medium with emission in the visible spectral range from binary solutions of Rhodamine 6G and Rhodamine B in epoxy resin as matrix without appending additional scattering centers. A frequency doubled Q-switched Nd: YAG laser was used for pumping. The generation’s behavior is similar to random laser (RL) with no external optical resonator. The in?uence of the nanostructured morphology of the medium on the laser properties was investigated by means of SEM, AFM, TEM, SAED, Spectro?uorimetry and Spectrometry. The laser emission is characterized by high intensity – energy per pulse – 300 μJ, threshold pump energy 1.7 mJ, relatively low beam divergence of 70 mrad (for RL) and spectrally narrowed major peak at 597 nm. The new gain medium was also investigated in a conventional tunable resonator. Generation with continuous tuning in the spectral range 590–610 nm was obtained. This new e?ective nanostructured medium, which shows with high optical and energy parameters, can be used in speckle-free laser imaging, time-resolved microscopy, high speed optical converters and others photonics applications.
关键词： Dye laser,Tunable laser,Broadband laser,Random laser,Epoxy resin
更新于2025-09-23 15:19:57
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Semiquantitative Atomic Force Microscopy-Infrared Spectroscopy Analysis of Chemical Gradients in Silicone Optical Waveguides
摘要： Crossing losses in silicone optical waveguides are related to the magnitude and spatial extent of the waveguide refractive index gradient. When processing conditions are altered, the refractive index gradient can vary substantially, even when the formulation remains constant. Controlling the refractive index gradient requires control of the concentration of small molecules present within the core and clad layers. Developing a fundamental understanding of how small molecule migration drives changes in crossing loss requires the ability to examine chemical functionality over small length scales, which is a natural fit for atomic force microscopy-infrared spectroscopy (AFM-IR). In this work, AFM-IR spectra from model bilayer stacks are initially examined to understand molecular migration that occurs from heating the core and clad layers. The results of these model studies are then applied to photopatterned waveguide builds, where structure?function relationships are constructed between values of crossing loss and the concentration of C?H and O?H functionalities present in the core and clad layers. Results show that small molecule evaporation and migration are competing processes that need to be controlled to minimize crossing loss.
关键词： migration,silicone resin,low-loss,photopatterned,PTIR,waveguides
更新于2025-09-23 15:19:57
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Laser cleaning performance and mechanism in stripping of Polyacrylate resin paint
摘要： Laser cleaning is a high-efficient, newly emerging and environmentally friendly technology. Removing paint from aircraft skin is an important application of this technology. This paper describes how a high repetition frequency fiber laser of 1064 nm was used to remove the 50-μm-thick polyacrylic resin primer paint layer on an aircraft skin (LY12 aluminum alloy plate). Experiments were conducted to study the cleaning performance by varying process parameters such as scanning speed, pulse frequency, scanning line interval and laser power. This paper found that the quality and efficiency could be improved by selecting the appropriate combination of scanning speed and pulse frequency. The amount of paint stripped by the single pulsed laser increased with an increase in laser power. By analyzing the cleaned surface and the particles collected from the process, we propose three different kinds of possible stripping mechanisms: combustion reaction, thermal stress vibration effect and plasma shock effect.
关键词： Law,Polyacrylate resin,Paint stripping,Mechanism,Pulsed laser
更新于2025-09-23 15:19:57
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Polymerization pattern characterization within a resin-based composite cured using different curing units at two distances
摘要： Objectives To investigate the relationship of the irradiance-beam-profile areas from six different light-curing units (LCUs) with the degree of conversion (DC), microhardness (KH), and cross-link density (CLD) throughout a resin-based composite (RBC) cured at two clinically relevant distances, and to explore the correlations among them. Materials and methods A mapping approach was used to measure DC using micro-Raman spectroscopy, KH using a Knoop indentor on a hardness tester, and %KH reduction after ethanol exposure, as an indicator for CLD within a nano-hybrid RBC increment (n = 3) at various depths. These sample composites were cured from two distances while maintaining the radiant exposure, using six different light-curing units: one quartz-tungsten-halogen; two single and three multiple-emission-peak light-emitting-diode units. Irradiance beam profiles were generated for each LCU at both distances, and localized irradiance values were calculated. Points across each depth were analyzed using repeated measures ANOVA. Correlations across multiple specimen locations and associations between beam uniformity corresponding with polymerization measurements were calculated using linear mixed models and Pearson correlation coefficients. Results Significant non-uniform polymerization patterns occurred within the specimens at various locations and depths. At 2-mm curing distance, the localized DC = 52.7–76.8%, KH = 39.0–66.7 kg/mm2, and %KH reduction = 26.7–57.9%. At 8-mm curing distance, the localized DC = 50.4–78.6%, KH = 40.3–73.7 kg/mm2, and %KH reduction = 28.2–56.8%. The localized irradiance values were weakly correlated with the corresponding DC, KH, and %KH reduction, with only a few significant correlations (p < 0.05). Conclusions Although significant differences were observed at each depth within the specimens, the localized irradiance values for all LCUs did not reflect the polymerization pattern and did not seem to have a major influence on polymerization patterns within the RBC, regardless of the curing distance. Clinical relevance Commonly used LCUs do not produce uniform polymerization regardless of the curing distance, which may contribute to the risk of RBC fracture.
关键词： Microhardness,Light-curing unit,Beam profile,Resin composite,Cross-link density,Degree of conversion
更新于2025-09-19 17:15:36
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A New Dealcoholization Method in the Synthesis of Vinyl Methyl Phenyl Silicone Resins for LED Encapsulation
摘要： The oligosiloxane resins were synthesized through hydrolytic sol-gel reaction and remained many hydroxyl groups, which did great harm to the curing process and resulted in poor performance of the cured products. In previous works, epoxy-modified silicone resins were synthesized by dealcoholization, a reaction between 3-glycidoxypropylmethyldimethoxysilane and terminal hydroxyl groups in phenyl silicone resins. Although this method eliminated the hydroxyl groups, it caused a large loss of vinyl groups inevitably and a poor stability of cured products. In this study, methyltrimethoxysilane (MTMS) was used to eliminate hydroxyl groups containing in vinyl methyl phenyl silicone resins, which were synthesized through hydrolytic sol-gel reaction. Most of residual hydroxyl groups were deleted effectively and the great loss of vinyl groups were avoided in the dealcoholization reaction. Then, the methyl phenyl silicone materials were fabricated by hydrosilylation reaction between the synthesized vinyl methyl phenyl silicone resins and hydrogen-containing ones. The cured silicone materials showed excellent optical performance (~ 89.1% at 450 nm) and good adhesion performance. In addition, due to less vinyl loss in the vinyl methyl phenyl silicone resins, the cured methyl phenyl silicone materials exhibited higher cross-linking density, better thermal resistance (5% mass loss at 435 °C) and better mechanical properties (50 shore D) compared with the epoxy-modified phenyl silicone materials. The lumen depreciation (working 168 h at 50 mA) and reflow soldering tests further demonstrated the methyl phenyl silicone materials possessed good thermal stability. These results indicated that the methyl phenyl silicone materials could be used as a LED encapsulant with a good performance.
关键词： LED packaging,Methyltrimethoxysilane,Non-hydrolytic sol-gel,Hydrolytic sol-gel,Vinyl methyl phenyl silicone resin
更新于2025-09-19 17:13:59