Microstructural Welding Engineering of Carbon Nanotube/Polydimethylsiloxane Nanocomposites with Improved Interfacial Thermal Transport

Carbon nanotube (CNT) reinforced polymer nanocomposites with high thermal conductivity show a promising prospect in thermal management of next-generation electronic devices due to their excellent mechanical adaptability, outstanding processability, and superior flexibility. However, interfacial thermal resistance between individual CNT significantly hinders the further improvement in thermal conductivity of CNT-reinforced nanocomposites. Herein, an interfacial welding strategy is reported to construct graphitic structure welded CNT (GS-w-CNT) networks. Notably, the obtained GS-w-CNT/polydimethylsiloxane (PDMS) nanocomposite with a GS loading of 4.75 wt% preserves a high thermal conductivity of 5.58 W m⁻¹ K⁻¹ with a 410% enhancement as compared to a pure CNT/PDMS nanocomposite. Molecular dynamics simulations are utilized to elucidate the effect of interfacial welding on the heat transfer behavior, revealing that the GS welding degree plays an important role in reducing both phonon scattering in the GS-w-CNT structure and interfacial thermal resistance at the interfaces between CNT. The unique welding strategy provides a new route to optimize the thermal transport performance in filler reinforced polymer nanocomposites, promoting their applications in next-generation microelectronic devices.     

Polymer/Carbon Composites with Versatile Interfacial Interactions for High Performance Carbon-Based Thermoelectrics: Principles and Applications

The urgent demand for renewable energy has attracted widespread interest in polymer-based thermoelectric materials due to easy fabrication, high flexibility, low toxicity, low thermal conductivity, and great potential in industrial applications. However, the power factors of the polymers are still quite low compared with those of their inorganic counterparts, resulting in a low energy conversion efficiency. Highly conductive carbon materials, including graphene and carbon nanotubes, have recently been incorporated into the polymer matrix through intrinsic chemical intimacy, providing new opportunities to tune the thermoelectric properties. In particular, the characteristic π-π coupling and other interactions between the two components have contributed to unique mechanisms for better thermoelectric performance beyond the simple rule of mixtures. This paper aims to review the up-to-date progress in polymer/carbon nanocomposites along with various compositions and novel synthetic strategies. The salient aspects of this review are characteristic interactions and various mechanisms, which might result in enhanced thermoelectric properties and subsequent potential applications in energy harvesting, wearable electronics, photo-thermoelectrics, and other devices.     

Sulfate‐Assisted Interfacial Engineering for High Yield and Efficiency of Triple Cation Perovskite Solar Cells with Alkali‐Doped TiO2 Electron‐Transporting Layers

Facile electron injection and extraction are two key attributes desired in electron transporting layers to enhance the efficiency of planar perovskite solar cells. Herein it is demonstrated that the incorporation of alkali metal dopants in mesoporous TiO₂ can effectively modulate electronic conductivity and improve the charge extraction process by counterbalancing oxygen vacancies acting as nonradiative recombination centers. Moreover, sulfate bridges (SO₄^2?) grafted on the surface of K‐doped mesoporous titania provide a seamless integration of absorber and electron‐transporting layers that accelerate overall transport kinetics. Potassium doping markedly influences the nucleation of the perovskite layer to produce highly dense films with facetted crystallites. Solar cells made from K:TiO₂ electrodes exhibit power conversion efficiencies up to 21.1% with small hysteresis despite all solution coating processes conducted under ambient air conditions (controlled humidity: 25–35%). The higher device efficiencies are attributed to intrinsically tuned electronic conductivity and chemical modification of grain boundaries enabling uniform coverage of perovskite films with large grain size.     

Interfacial Reactions of Si Die Attachment with Zn-Sn and Au-20Sn High Temperature Lead-Free Solders on Cu Substrates

The interfacial reaction of Si die attachment with a high temperature lead-free solder of Zn-xSn (x = 20 wt.%, 30 wt.% and 40 wt.%) was investigated, and the currently used high temperature lead-free solder of Au-20Sn was compared. A sound die attachment to a Cu substrate can be achieved with Zn-Sn solder. No intermetallic compound (IMC) phase was observed in the solder layer, and only primary α-Zn and Sn-Zn eutectic phases were observed. At the interface with the Si die, with a metallization of Au/Ag/Ni, an AgAuZn₂, IMC layer was formed along the interface, and the Ni coating layer did not react with the solder. At the interface with the Cu substrate, CuZn₅ and Cu₅Zn₈ IMC layers were confirmed, and their thicknesses can be controlled by soldering conditions. During multiple reflows, the growth of these IMC layers was observed, but no additional voids or cracks were observed. For more reliable die attachment, a titanium nitride (TiN) coating layer was applied to suppress the formation of Cu-Zn IMCs. The Si die attached joint on the TiN-coated Cu was quite stable during the multiple reflows, and no visible IMC phase was confirmed in the interfacial microstructure.     

利用高分遥感工程助推地球系统科学载体生态发展

针对我国高分工程,再对接北斗导航战略,介绍了一种可助推"世界级地球仪"发展的可计算系统,并以"Point Earth"再次阐述了高分工程助推下的地球系统发展以及主体需要由高中低分辨率全球遥感数据来说明由探索、探测和监测等全球数据所能够表达的一个极其重大的地球认知体系。通过以高分遥感完善以往的RS、GIS、PS观察、观测和观点,便可展现一个精彩的认知世界。高分工程将会为地球人文发展服务,形成地球系统科学载体的生态发展。     

高方块电阻发射区单晶硅太阳电池的性能优化

通过提高发射区的方块电阻和优化发射区的磷杂质浓度纵向分布,制备了性能优良的单晶硅太阳电池。I-V测量分析表明:高表面活性磷杂质浓度浅结发射区太阳电池短路电流密度、开路电压和填充因子分别提高了0.32mA/cm2,1.19mV和0.22%,因此转换效率提高了0.22%。内量子效率分析表明:高表面活性磷杂质浓度浅结发射区太阳电池短路电流密度的提高是由于短波光谱响应增强了。SEM分析表明:高表面活性磷杂质浓度浅结发射区太阳电池在发射区硅表面沉积的Ag晶粒分布数量更多、一致性更好,从而更容易收集光生电流传输到Ag栅线,改善了太阳电池的性能。     

Active Regulation Volume Change of Micrometer-Size Li2S Cathode with High Materials Utilization for All-Solid-State Li/S Batteries through an Interfacial Redox Mediator

Low electronic and ionic transport, limited cathode active material utilization, and significant volume change have pledged the practical application of all-solid-state Li/S batteries (ASSLSBs). Herein, an unprecedented Li₂S-Li_xIn₂S₃ cathode is designed whereby In₂S₃ reacts with Li₂S under high-energy ball milling. In situ electron diffraction and ex situ XPS are implanted to probe the reaction mechanism of Li₂S-Li_xIn₂S₃ in ASSLSBs. The results indicate that Li_xIn₂S₃ serves as a mobility mediator for both charge-carriers (Li⁺ and e⁻) and redox mediator for Li₂S activation, ensuring efficient electronic and ionic transportation at the cathode interface and inhibiting ≈ 70% relative volumetric change in the cathode, as confirmed by in situ TEM. Thus, the Li₂S-Li_xIn₂S₃ cathode delivers an initial areal capacity of 3.47 mAh cm⁻² at 4.0 mg_Li2S cm⁻² with 78% utilization of Li₂S. A solid-state cell with Li₂S-Li_xIn₂S₃ cathode carries 82.35% capacity retention over 200 cycles at 0.192 mA cm⁻² and a remarkable rate capability up to 0.64 mA cm⁻² at RT. Besides, Li₂S-Li_xIn₂S₃ exhibits the highest initial areal capacity of 4.08 mAh cm⁻² with ≈74.01% capacity retention over 50 cycles versus 6.6 mg_Li2S cm⁻² at 0.192 mA cm⁻² at RT. The proposed strategy of the redox mediator minimized volumetric change and realized outstanding electrochemical performance for ASSLSBs.     

Solid Free‐Form Fabrication of Tissue‐Engineering Scaffolds with a Poly(lactic‐co‐glycolic acid) Grafted Hyaluronic Acid Conjugate Encapsulating an Intact Bone Morphogenetic Protein–2/Poly(ethylene glycol) Complex

Despite wide applications of bone morphogenetic protein–2 (BMP‐2), there are few methods to incorporate BPM‐2 within polymeric scaffolds while maintaining biological activity. Solid free‐form fabrication (SFF) of tissue‐engineering scaffold is successfully carried out with poly(lactic‐co‐glycolic acid) grafted hyaluronic acid (HA‐PLGA) encapsulating intact BMP‐2/poly(ethylene glycol) (PEG) complex. HA‐PLGA conjugate is synthesized in dimethyl sulfoxide (DMSO) by the conjugation reaction of adipic acid dihydrazide modified HA (HA‐ADH) and PLGA activated with N,N′‐dicyclohexylcarbodiimide (DCC) and N‐hydroxysuccinimide (NHS). BMP‐2 is complexed with PEG, which is encapsulated within the PLGA domain of the HA‐PLGA conjugate by SFF to prepare tissue‐engineering scaffolds. In vitro release tests confirm the sustained release of intact BMP‐2 from the scaffolds for up to a month. After confirmation of the enhanced osteoblast cell growth, and high gene‐expression levels of alkaline phosphatase (ALP), osteocalcin (OC), and osterix (OSX) in the cells, the HA‐PLGA/PEG/BMP‐2 scaffolds are implanted into calvarial bone defects of Sprague Dawley (SD) rats. Microcomputed tomography (μCT) and histological analyses with Masson's trichrome, and hematoxylin and eosin (H&E) staining reveal effective bone regeneration on the scaffolds of HA‐PLGA/PEG/BMP‐2 blends.