Search for: All records

Solar panels contributed to over 115,000 GWh of energy being produced in the United States and solar panel energy consumption has increased by 27 % at the start of the 21st century. Given the decrease of photovoltaic efficiency at higher temperatures and the increasing demand for clean energy, the development of an economical technology for solar panel cooling is necessary. Passive cooling can be achieved by infrared radiating into space. Typical solar arrays require large functional areas in order to supply a significant amount of power as compared to other sources. As such, any method to help reduce the temperature of the solar panel surfaces needs to maintain manufacturing scalability for sustainable use. We demonstrate a rapid, low-cost, template-free roll coating method to fabricate photonic composite film with SiO2 nanoparticles which possess high emissivity in the atmospheric transparent window while passing visible and near infrared light to photovoltaics beneath. When facing direct sunlight at summer noon, the coatings show a 3.5°C temperature decrease without loss of photovoltaic efficiency while having hydrophobic and contamination-resistance merits. 

Abstract The understanding of domain dynamics in ferroelectric materials is crucial for optimizing their performance in piezoelectric and electro‐optic applications. Although previous studies have focused on static domain structures and macroscopic characteristics, the time‐resolved approach of domains remains largely unexplored. In this study, we compare the dynamic responses of direct current (DC) and alternating current (AC) poled [001]‐oriented rhombohedral Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃(PMN–PT) single crystals using X‐ray photon correlation spectroscopy (XPCS) during the application of external electric fields. Our results demonstrate that the AC‐poled sample exhibit enhanced reconfiguration of domain variants in response to driving fields compared to the DC‐poled counterpart, as evidenced by accelerated correlation decay and faster relaxation time. This phenomenon is attributed to enhanced reversible domain wall motion achieved through AC poling, which facilitates field‐induced domain realignment. These findings provide insight into the relationship between dynamics and macroscopic properties in relaxor‐PT single crystals for high‐performance applications. 

Abstract Bio-inspired, micro/nanotextured surfaces have a variety of applications including superhydrophobicity, self-cleaning, anti-icing, antibiofouling, and drag reduction. In this paper, a template-free and scalable roll coating process is studied for fabrication of micro/nanoscale topographies surfaces. These micro/nanoscale structures are generated with viscoelastic polymer nanocomposites and derived by controlling ribbing instabilities in forward roll coating. The relationship between process conditions and surface topography is studied in terms of shear rate, capillary number, and surface roughness parameters (e.g., Wenzel factor and the density of peaks). For a given shear rate, the sample roughness increased with a higher capillary number until a threshold point. Similarly, for a given capillary number, the roughness increased up to a threshold range associated with shear rate. A peak density coefficient (PDC) model is proposed to relate capillary number and shear rate to surface roughness. The optimum range of the shear rate and the capillary number was found to be 40–60 s−1 and 4.5 × 105–6 × 105, respectively. This resulted in a maximum Wenzel roughness factor of 1.91, a peak density of 3.94 × 104 (1/mm2), and a water contact angle (WCA) of 128 deg.