The evolution of display technologies is rapidly transitioning from traditional screens to advanced augmented reality (AR)/virtual reality (VR) and wearable devices, where quantum dots (QDs) serve as crucial pure-color emitters. While solution processing efficiently forms QD solids, challenges emerge in subsequent stages, such as layer deposition, etching, and solvent immersion. These issues become especially pronounced when developing diverse form factors, necessitating innovative patterning methods that are both reversible and sustainable. Herein, a novel approach utilizing lipoic acid (LA) as a ligand is presented, featuring a carboxylic acid group for QD surface attachment and a reversible disulfide ring structure. Upon i-line UV exposure, the LA ligand initiates ring-opening polymerization (ROP), crosslinking the QDs and enhances their solvent resistance. This method enables precise full-color QD patterns with feature sizes as small as 3 µm and pixel densities exceeding 3788 ppi. Additionally, it supports the fabrication of stretchable QD composites using LA-derived monomers. The reversible ROP process allows for flexibility, self-healing, and QD recovery, promoting sustainability and expanding QD applications for ultra-fine patterning and on-silicon displays.
Recently, the handling of waste industrial resources has become an issue, and the importance of sustainable resources has increased. Among these waste industrial materials are glass wool and mineral wool, which are fibrous materials used as insulation materials with characteristics such as sound absorption, insulation, and non-flammability. However, after their service life, glass wool and mineral wool used for insulation are generally buried or incinerated, causing problems such as air and soil contamination. This research was conducted to examine the applicability of waste glass wool and mineral wool obtained from expired insulation as fiber reinforcement in cement concrete. The research aimed to evaluate the fresh concrete properties, strength properties, and durability properties by adding waste glass wool and waste mineral wool up to 0.5–2.0% of the cement weight. Regarding the slump and air content of fresh concrete, the results showed that the addition of waste fibers within this range did not significantly affect the air content. However, the slump decreased as the addition amount increased due to the high absorption, which is a characteristic of the fibers. In addition, the evaluation of strength revealed that the incorporation of fibers decreased the compressive strength compared to the reference concrete. However, the tensile strength increased due to the load-supporting function of the waste fibers. In the evaluation of freezing–thawing resistance and chloride ion penetration resistance, it was confirmed that the freezing–thawing resistance improved in all cases where waste glass wool was added. The chloride ion penetration resistance was found to be similar to that of the reference concrete. However, in the case of waste mineral wool, it was observed that an addition rate of more than 2.0% of fibers was required to ensure freezing–thawing resistance. As the addition rate increased, the total charge passed (permeability) increased significantly, leading to a decrease in chloride ion penetration resistance.
The global desire to improve the performance of road pavements and move towards a sustainable transportation system has immensely encouraged the usage of fibers in asphalt paving materials. In this study, glass fibers trademarked as ESGFIBER produced by the ESG Industry company Limited from Daejeon, Korea were added in dense-graded asphalt mix. The purpose of this study was to evaluate effects that fibers have on volumetric properties, mechanical properties, and long-term performance of asphalt concrete mixes. ESGFIBER were mixed together with aggregates and asphalt binder in asphalt mix and five different asphalt mixes with different dosage of fibers were evaluated in this study. The Marshall mix design method was used for designing all asphalt mixes, and laboratory tests indirect tensile strength test, deformation strength test and Hamburg wheel tracking test were conducted to evaluate moisture susceptibility, fatigue cracking behavior and rutting resistance of asphalt concrete mixes. The results showed that when ESGFIBER were added in asphalt mix moisture susceptibility, fatigue cracking and rutting resistance were both improved. The usage of ESGFIBER in asphalt concrete mixes can be very beneficial since the mechanical and long-term performance were improved upon the addition of fibers.
The usage of modified asphalt binder in road pavements has been increasing in the past few decades. Therefore, quality control and understanding of modified asphalt binders have become an important issue. This study was conducted as a part of a larger study on the efficient management of these modified asphalt binders by evaluating the characteristics of asphalt binders mixed with styrene–butadiene–styrene (SBS), ethylene-vinyl acetate (EVA), and wax-based warm-mix additives using Fourier transform infrared (FTIR) analysis. For original asphalt binders modified with SBS, response wavenumbers were 700 and 966 cm−1, which means a particular wavenumber of polybutadiene and polystyrene, while in the case of binders modified with EVA, peak response wavenumbers were at 1242 and 1739 cm−1, which represents a particular wavenumbers of a single stretching bond between carbon and hydrate and a double stretching bond between carbon and oxygen. Asphalt binders modified with wax-type additives showed peak response at 730 and 1540 cm−1, which represents a double stretching bond of carbon and a single stretching bond between nitrogen and oxygen. It was also found that peak values increased as addition rates also increased. The results showed that the additives used in this study have particular wavenumbers that show peak responses even when mixed into asphalt binders. Using these characteristics of the additives, FTIR analysis confirms that it is possible to determine whether or not a binder has been modified.
Spurred by the increasing market needs for big data and cloud services, global server suppliers and hyper- scalers are looking to adopt high-speed and large-capacity memory modules. To fulfill this trend, the brand- new low-voltage operable DDR5 (double data rate 5th generation) memory can be an appropriate solution, with the highest speed of 7.2 Gbps and the largest capacity of 512 GB. However, some critical obstacles, such as increased capacity and high-speed I/O requirements, unstable power noise occurrences, high power consumption, and increase in operating temperature, must be overcome. This poster will cover various technical pathfinding solutions for world's first DDR5 512 GB module with an advanced DRAM process and I/O schemes, package technology, and module architecture regarding improvements in the following four aspects: performance, speed, capacity, and power. This will unveil the industry's first high-performance and large-capacity memory product with 8-stacked DDR5 DRAMs. Samsung believes that this product will pave the way for achieving both higher bandwidth and lower power consumption to inaugurate the era of terabyte DRAM modules for next-gen servers.
Surface-textured polymer nanocomposite (PNC) films are utilized in many device applications, and therefore understanding the relaxation behavior of such films is important. By extending an in situ wrinkle relaxation method, we observed that the thermal stability of wrinkled PNC films, both above and below the glass transition temperature (Tg), is proportional to a film's nanoparticle (polymer grafted and bare) concentration, with a slope that changes sign at a compensation temperature (Tcomp) that is determined to be in the vicinity of the film's Tg. This provides unambiguous confirmation of entropy-enthalpy compensation (EEC) as a general feature of PNC films, implying that the stability of PNC films changes from being enhanced to becoming diminished by simply passing through this characteristic temperature, a phenomenon having evident practical ramifications. We suggest EEC will also arise in films where residual stresses are associated with the film fabrication process, which is relevant to nanotech device applications.
Understanding the effects of polymer brush architecture on particle interactions in solution is requisite to enable the development of functional materials based on self-assembled polymer-grafted nanoparticles (GNPs). Static and dynamic light scattering of polystyrene-grafted silica particle solutions in toluene reveals that the pair interaction potential, inferred from the second virial coefficient, A(2), is strongly affected by the grafting density, sigma, and degree of polymerization, N, of tethered chains. In the limit of intermediate sigma (similar to 0.3 to 0.6 nm(-2)) and high N, A(2) is positive and increases with N. This confirms the good solvent conditions and can be qualitatively rationalized on the basis of a pair interaction potential derived for grafted (brush) particles. In contrast, for high sigma > 0.6 nm(-2) and low N, A(2) displays an unexpected reversal to negative values, thus indicating poor solvent conditions. These findings are rationalized by means of a simple analysis based on a coarse-grained brush potential, which balances the attractive core-core interactions and the excluded volume interactions imparted by the polymer grafts. The results suggest that the steric crowding of polymer ligands in dense GNP systems may fundamentally alter the interactions between brush particles in solution and highlight the crucial role of architecture (internal microstructure) on the behavior of hybrid materials. The effect of grafting density also illustrates the opportunity to tailor the physical properties of hybrid materials by altering geometry (or architecture) rather than a variation of the chemical composition.
Harmful nitrogen oxides (NOX) are produced by vehicles, factories, mines, and power plants. In fact, over one million tons of NOX are emitted into the atmosphere every year, making it the most prevalent air pollutant. Approximately 45% of the emitted NOX in Korea is associated with the transportation sector. In this paper, the application of a new TiO2 photocatalyst on the asphalt roads to remove combustion-produced NOX was studied. In an effort to overcome the known constructability, adhesion, cost, and dispersion problems associated with TiO2 photocatalysts, the liquid polyurethane (PUD) was added with TiO2 to form a mixture later known as liquid PUD-TiO2. Laboratory and field tests were conducted to determine the optimum amount of photocatalyst to be used and the performance of asphalt pavement coated with PUD-TiO2 in terms of indirect tensile strength, water susceptibility, and rutting resistance. Additionally, the performance of PUD-TiO2 under different humidity, wind speed, and temperature conditions was also evaluated. The results showed that the application of PUD-TiO2 photocatalyst on the asphalt pavements road reduces the NOX available on the surface of the road. The PUD-TiO2 also was found to have no effects on the performance of asphalt pavement. Meanwhile, under different weather conditions, the reaction between the photocatalyst and NOX is mainly affected by the humidity.
Acid mine drainage (AMD) is a pervasive source of metal pollution that severely impacts freshwater ecosystems and has a direct impact on human health. Conventional active and passive methods work very well for removing iron in AMD remediation, which is typically the highest metallic impurity. However, conventional passive remediation fails to remove all aluminum, which has severe ecological implications. Removal of aluminum ions using chelation, which traditionally uses small molecules that bind metals tightly for sequestration, holds promise. Yet, chelation strategies are limited because once introduced into surface water, small molecules are difficult to reclaim and often persist in the environment as pollutants. To address this, we have designed six unique scaffolds based on functional graphenic materials (FGMs) to create nonsoluble materials that could be placed at the end of a passive remediation process to remove persistent aluminum. When tested for efficacy, all six FGMs successfully demonstrated a reversible capacity to remove aluminum from acidic water, chelating up to 21 μg of Al/mg of FGM. Furthermore, when they were exposed to E. coli as an approximation for environmental compatibility, viability was unaffected, even at high concentrations, suggesting these FGMs are nontoxic and viable candidates for passive chelation-based remediation.
A strategy to synthesize SiO2-g-PMMA/PMMA-b-PS mono- and bimodal block copolymer particle brushes by surface-initiated atom transfer radical polymerization (SI-ATRP) from silica particles is presented. First, PMMA blocks were prepared by normal ATRP with controlled degree of polymerizations and grafting density. In a second step, the PS block was synthesized through a chain extension using low parts per million of Cu catalyst. Variation of the SiO2-g-PMMA-Br macroinitiator concentration had a pronounced effect on the modality of the chain extension product. In the limit of small concentration, partial termination resulted in bimodal brush architectures, while more uniform brush architectures were observed with increasing concentration of macroinitiator. Brush nanoparticles with bimodal architectures assembled into string-like aggregates that bore a resemblance to structures found in systems comprised of sparse (homopolymer) brush particles. The unexpected effect of modality on structure formation points to opportunities in controlling microstructures in brush particle materials.
Photothermal energy conversion is of fundamental importance to applications ranging from drug delivery to microfluidics and from ablation to fabrication. It typically originates from absorptive processes in materials that-when coupled with non-radiative dissipative processes-allow the conversion of radiative energy into heat. Microstructure design provides versatile strategies for controlling light-matter interactions. In particular, the deliberate engineering of the band structure in photonic materials is known to be an effective approach to amplify absorption in materials. However, photonic amplification is generally tied to high optical contrast materials which limit the applicability of the concept to metamaterials such as microfabricated metal-air hybrids. This contribution describes the first observation of pronounced amplification of absorption in low contrast opals formed by the self-assembly of polymer-tethered particles. The dependence of the amplification factor on the length scale and degree of order of materials as well as the angle of incidence reveal that it is related to the slow photon effect. A remarkable amplification factor of 16 is shown to facilitate the rapid "melting" of opal films even in the absence of "visible" absorption. The results point to novel opportunities for tailoring light-matter interactions in hybrid materials that can benefit the manipulation and fabrication of functional materials.
We combine in situ heated atomic force microscopy (AFM) with automated line-by-line spectral analysis to quantify the relaxation or decay phenomenon of nanopatterned composite polymer films above the glass-transition temperature of the composite material. This approach enables assessment of pattern fidelity with a temporal resolution of ≈1 s, providing the necessary data density to confidently capture the short-time relaxation processes inaccessible to conventional ex situ measurements. Specifically, we studied the thermal decay of nanopatterned poly(methyl methacrylate) (PMMA) and PMMA nanocomposite films containing unmodified and PMMA-grafted silica nanoparticles (SiO2 NP) of varying concentrations and film thicknesses using this new approach. Features imprinted on neat PMMA films were seen to relax at least an order of magnitude faster than the NP-filled films at decay temperatures above the glass transition of the PMMA matrix. It was also seen that patterned films with the lowest residual thickness (34 nm) filled with unmodified SiO2 NP decayed the slowest. The effect of nanoparticle additive was almost negligible in reinforcing the patterned features for films with the highest residual thickness (257 nm). Our in situ pattern decay measurement and the subsequent line-by-line spectral analysis enabled the investigation of various parameters affecting the pattern decay such as the underlying residual thickness, type of additive system, and temperature in a timely and efficient manner.
Elucidation of the mutual influence of composition and architecture of polymer canopies on the assembly and mechanical properties of brush particle-based materials holds the promise of advancing the understanding of the governing parameters controlling interactions in hybrid materials and the development of novel functional materials. In this work, the elastic properties of three series of brush particle systems were investigated, differentiated by grafting density as dense, intermediate, and sparse brush systems. Dense and intermediate systems displayed uniform microstructures; the degree of order (measured using Voronoi cell area analysis) increased with grafting density. For dense and intermediate brush particle systems, instrumented indentation analysis revealed an increase of the elastic modulus with the degree of polymerization of tethered chains, in contrast to effective medium predictions. Furthermore, the contribution of ligands to particle interactions increased with decreasing grafting density. The results indicated that the response behavior of particle brush films in tensile-type deformations depends on dispersion interactions between ligands of adjacent brush particles. The more pronounced brush interdigitation in the case of intermediate graft densities enhanced the dispersion interactions between brush particles and hence the modulus of films. A reversed trend in modulus was observed in films of sparse brush particles that also featured the formation of string-like superstructures. Here, the elastic modulus was substantially increased for low-molecular ligands and continuously decreased with increasing degree of polymerization of tethered chains along with a transition from string-like to uniform morphologies. Independent of grafting density, the elastic modulus of the pristine polymer was recovered in the limit of a high degree of polymerization of polymer ligands.
Nowadays, in order to improve asphalt pavement performance and durability and reduce environmental pollution caused by hydrocarbon materials, many researchers are studying different ways of modifying asphalt concrete (AC) and finding alternative paving materials to extend the service life of pavements. One of the successful materials used in the modification of AC is fibers. Different types of fibers have been reinforced in AC mixtures and improvements have been observed. This research studies the performance of glass wool fibers reinforced in a dense-graded asphalt mixture. Generally, glass fibers are known to have excellent mechanical properties such as high tensile modulus, 100% elastic recovery and a very high tolerance to heat. Glass wool fibers are commonly used as a thermal insulation material. In this research, to evaluate the performance of glass wool fibers in AC, laboratory tests, the Marshall mix design test, indirect tensile strength (IDT), tensile strength ratio (TSR) and the Kim test were conducted to determine a proper mix design, tensile properties, moisture susceptibility, rutting and fatigue behaviors. Results show that the addition of glass wool fibers does affect the properties of AC mixtures. The use of glass wool fibers shows a positive consistence result, in which it improved the moisture susceptibility and rutting resistance of the AC. Additionally, results show that the addition of fiber increased tensile strength and toughness which indicates that fibers have a potential to resist distresses that occur on a surface of the road as a result of heavy traffic loading. The overall results show that the addition of glass wool fibers in AC mixtures is beneficial in improving properties of AC pavements.
The kinetics and mechanism of the synthesis of SiO2-g-poly(methyl methacrylate) (SiO2-g-PMMA) and SiO2-g-polystyrene (SiO2-g-PS) nanoparticles were investigated through studies conducted at very low concentrations of the ATRP initiator functionalized silica particles (SiO2-Br) in the presence of reducing agent (tin(II) 2-ethylhexanoate) and low ppm loadings of the Cu-II catalyst (25 ppm) complex. In the SiOrg-PMMA system, the grafting density decreased under very low concentrations (<100 ppm) of SiO2-Br. However, in the SiO2-g-PS system, the initiation efficiency, defined through the grafting density of polymer chains on the particle surface, decreased significantly for lower concentrations of the initiator SiO2-Br. In addition, model systems with linear polymer chains (untethered) were studied to investigate the difference in initiation efficiency between polymers attached to nanoparticle surfaces and untethered chains. Because of the localization of initiating sites on the surface of nanoparticles and lower probabilities of collisions between nanoparticles, as compared to small initiator molecules, particle brush systems exhibited less interparticle termination. This observation was employed to synthesize very high molecular weight (M-n> 500K) particle brushes with relatively narrow molecular weight distribution (M-w/M-n < 1.3).
Porous asphalt has been used for permeable pavement to improve safety of roadways and the effectiveness of storm water management. As a surface drainage layer with frequent exposure to water, this material is affected by moisture. In this study, dynamic modulus tests were performed on both moisture unconditioned and conditioned specimens to characterize viscoelastic properties of porous asphalt mixture. The dynamic modulus values of porous asphalt materials with air void content of 9.0% and 20.5% were investigated at dry condition and after specified moisture conditioning cycles. One cycle of moisture conditioning procedure included placing specimens in water tank at 60 °C for 24 h, and then in another water tank at 25 °C for additional 2 h. The results showed that porous asphalt mixture with lower air void content resulted in higher values of dynamic modulus, and these values of porous asphalt with air void content of 9.0% was about 1.5 to 3.0 times that of porous asphalt with air void content of 20.5%. Higher value of the first number of performance graded binder (average 7-day maximum pavement design temperature) seems to make the dynamic modulus values at high temperatures larger. After moisture conditioning, the dynamic modulus of porous asphalt mixture increased, overall, especially at low temperatures. The appropriated selection of asphalt binder, a weakening of asphalt due to moisture damage can be reduced.
According to deplete natural resources and need to protect the environment,the demand of a usage of waste material has significantly increased.Many studies are currently being carried out on the development of innovative and environmentally friendly materials for securing the safety of road users and improving the performance and durability of roads.For example,studies are currently being conducted on the use of waste tires as a substitute for currently used fuels.Since the development of the automobile industry,the amount of waste tire has continuously increased in accordance with the increased vehicle numbers.Tire-derived fuel (TDF) has been used as a fuel source with generated TDF fly ash.Mineral filler,made of fine mineral particles of a physical size passing the number 200 standard mesh sieve (75 micron),plays an important role in asphalt mixtures properties.This paper presents an application of TDF fly ash as filler in hot mix asphalt (HMA).In this study,the performance of TDF fly ash was confirmed through a comparison with three other mineral fillers:stone dust,cement,and hydrated lime.Various tests including Marshall stability test,moisture sensitivity test,dynamic immersion test,and a wheel tracking test were performed to investigate the difference in the behaviors of the samples with different parameters considered in this study.The results show that the mechanical performance of hot mix asphalt using TDF fly ash satisfied the quality standard specification of the Ministry of Land,Infrastructure and Transport (MOLIT),Korea.It can be concluded that the use of TDF fly ash as a mineral filler in HMA not only satisfied the mechanical properties,but also reduced the volume of the pollutants waste in the environment.
Linear poly(n-butyl acrylate)-gradient-poly(methyl methacrylate) (PBA-grad-PMMA) copolymers and SiO2-g-PBA-grad-PMMA particle brushes were synthesized by activator regenerated by electron transfer atom transfer radical polymerization via a semibatch copolymerization method in which the methyl methacrylate (MMA) monomer was slowly fed to the polymerizing n-butyl acrylate (BA) solutions. The effects of initial BA concentration and the MMA feeding rate on the polymerization were investigated. Controlled gradient compositions were achieved at relatively low conversion, <20%. Two gradient copolymer particle brushes, with grafting densities of 0.55 and 0.126 chains/nm(2), and one linear gradient copolymer were prepared with the same composition. Significant changes were observed after attaching the gradient copolymer ligands onto the surface of SiO2 nanoparticles, in both thermal and mechanical properties. Greater heterogeneity and microphase separation were introduced after the addition of SiO2 nanoparticles, and the nanocomposites displayed more complex glass transition temperature (T-g) behavior and a broader T-g range. An improvement in mechanical properties (strength and stiffness) was observed as the SiO2 nanoparticle content increased in gradient copolymer particle brushes; however, the damping property was compromised with increasing stiffness of the materials, especially under low frequency conditions.