Influence of High-Pressure Induced Lattice Dislocations and Distortions on Thermoelectric Performance of Pristine SnTe

As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and Σpositions and high thermal conductivity. Using high-pressure and high-temperature technology, we synthesized the pristine SnTe samples at different pressures and systemically investigated their thermoelectric properties.High pressure induces rich microstructures, including the high-density dislocations and lattice distortions, which serve as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduces the harmful high carrier concentration, due to the depression of Sn vacancies.Moreover, pressure induces the valence band convergence, reducing the energy separation between the L and Σpositions. The band convergence and suppressed carrier concentration increase the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds do not deteriorate significantly under the condition of decreasing electrical conductivity. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 is achieved at 750 K, representing a 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology is demonstrated as an effectively approach to optimize thermoelectric performance.

Simultaneously removal of P and B from Si by Sr and Zr co-addition during Al–Si low-temperature solvent refining

To remove the key impurity elements,P and B,from primary Si simultaneously,Sr and Zr co-addition to Al-Si alloy systems during solvent refining has been investigated.Sr reacts with Al,Si,and P in the melt to form a P-containing Al_(2)Si_(2)Sr phase and Zr reacts with B to form a ZrB_(2) phase.In the Al-Si-Sr-Zr system,high removal fractions of P and B in the primary Si,with 84.8%-98.4%and 90.7%-96.7%,respectively,are achieved at the same time,respectively.The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000μg·kg^(-1),and the removal fractions of P and B in the purified Si reach 98.4%and 96.1%.Compared with the Sr/Zr single-addition,the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend,indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent.Finally,an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases,which reveals the interaction between the impurity phases and the primary Si.

Porous polyimide-based phase change materials with enhanced mechanical properties, thermal conductivity, and thermal shock resistance through precisely designed triple-functional layers

Numerous scenarios of direct contact between electronic components and skin appear in wearable electronic devices. As the “second skin” that lies next to the biological skin of the human body, flexible wearable devices need to be equipped with thermal protection. However, the use of flexible phase change materials(PCMs) for wearable devices remains a challenge due to their low thermal conductivity, weakened mechanical strength, and liquid leakage. Herein, we developed a multilayered polyimide(PI) composite film integrating stable latent heat absorption, high thermal conductivity, and enhanced mechanical strength. This single piece of material achieved more prominent hotspot protection than traditional foams. The in-plane thermal conductivity of the resultant substrate layer is up to 2.655 W/(m K), which provides a fast response and in-plane dissipation for heat flow. The deliberately arranged interlayer of the material significantly improved the tensile strength(37.6 MPa) of the composite film,representing 128.9% greater strength than that of a bilayer film without a dense layer. The top layer with abundant pores provides reversibly latent heat storing and releasing function after being well infiltrated with paraffin wax. The resulting synergistic effect between three functional layers shows superb heat-suppressing performance in the thickness direction in both thermal shockresistant tests and simulation results. Impressively, the maximum temperature drop reached 40.2℃ compared with the pure PI film. The heating time was delayed by 12 s, providing sufficient warning time for human emergency response. This strategy can potentially pave the way for the design and fabrication of multifunctional films for wearable electronics in thermal protection applications.

Real-time quantification of nuclear RNA export using an intracellular relocation probe

Nuclear RNA export into the cytoplasm is one of the key steps in protein expression to realize biological functions.Despite the broad availability of nucleic acid dyes,tracking and quantifying the highly dynamic process of RNA export in live cells is challenging.When dye-labeled RNA enters the cytoplasm,the dye molecules are released upon degradation of the RNA,allowing them to re-enter the cell nucleus.As a result,the ratio between the dye exported with RNA into the cytoplasm and the portion staying inside the nucleus cannot be determined.To address this common limitation,we report the design of a smart probe that can only check into the nucleus once.When adding to cells,this probe rapidly binds with nuclear RNAs in live cells and reacts with intrinsic H_(2)S.This reaction not only activates the fluorescence for RNA tracking but also changes the structure of probe and consequently its intracellular localization.After disassociating from exported RNAs in cytoplasm,the probe preferentially enters lysosomes rather than cell nucleus,enabling real-time quantitative measurement of nuclear RNA exports.Using this probe,we successfully evaluated the effects of hormones and cancer drugs on nuclear RNA export in live cells.Interestingly,we found that hormones inhibiting RNA exports can partially offset the effect of chemotherapy.

Skin mimicking-sweating evaporation polyimide cooling film for electronic devices

In hot environments,the human body shows an efficient capability to maintain a stable temperature by benefiting from sweating behavior.Inspired by this skin perspiration strategy,in this study,we demonstrated an innovative polyimide foam(PIF)-based mimetic skin with excellent cooling capability by integrating a silver coating and reusable hydrogel for the first time.Because of the hybrid thermal dissipating system,the successive silver coating quickly transferred heat to the inside of the polyacrylamide hydrogel.Meanwhile,the hydrogel absorbed a large amount of heat due to its large enthalpy and effectively dissipated heat to the environment through the evaporation of moisture,similar to the sweating of skin.Thus,the temperature of the skin-like film was reduced by 25.4℃compared with pure PIF under a high-power laser heating source.Identical and remarkable cooling effects were also obtained in mobile phone and battery applications,far better than commercially available thermally conductive polyimide(PI).This outstanding performance paves a new way for the thermal management application of PI in wearable electronics,microprocessors,and flexible electronics.