Acta Energiae Solaris Sinica•2026•DOI: 10.19912/j.0254-0096.tynxb.202608_9659
The utilization of medium-deep geothermal energy is primarily achieved through deep buried pipe closed-loop heat exchange systems, where the heat transfer efficiency is governed by the coupled effects of pipe depth, pump power, and heat pump energy consumption. Based on a casing-type deep buried pipe heat exchange project in Xi'an, three-dimensional full-scale numerical models with depths of 2039, 2539, 3039, and 3539 m were established to simulate heat extraction, pump power, and heat pump energy consumption over a 121-day operational period, thereby evaluating the comprehensive heat transfer performance. Results indicate that the comprehensive heat transfer power, accounting for pump power, increases approximately linearly with depth, with a maximum deviation of no more than 1.5% from the net heat transfer power. The pump pressure drop required to achieve a flow rate of 4.88 kg/s increases linearly with depth, reaching 622, 774, 924, and 1074 kPa for the four depths, respectively. The per-unit-depth pump power decreases with increasing depth, indicating that greater burial depth reduces the pump power proportion and enhances the overall heat transfer efficiency. The numerical model was validated against field experimental data, showing a maximum relative error of 4.26% in heat transfer power over a 72-hour period. These findings provide a quantitative basis for optimizing deep buried pipe system design and assessing the trade-offs between heat extraction and parasitic energy consumption in medium-deep geothermal applications.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4257-y
Hafnia-based ferroelectrics exhibit a distinctive reverse size effect and exceptional scalability, positioning them as critical candidates for CMOS-compatible non-volatile memory and ferroelectric transistors, with substantial promise for advancing hardware acceleration in artificial intelligence and large-data storage technologies. However, their practical deployment is constrained by a longstanding dilemma: the difficulty in simultaneously stabilizing metastable polar phases and ensuring long-term reliability under the high electric fields required for polarization switching. This review reinterprets this challenge through the lens of defect physics and advocates a paradigm shift from stochastic, disorder-mediated defect incorporation toward ordered, multiscale defect engineering. We systematically discuss the collective influence of point defects, line defects, planar defects, and defect-coupled structures on the phase stability, switching kinetics, and failure mechanisms in hafnia-based ferroelectrics. Controlling oxygen-vacancy states, engineering dopants via Fermi-level and chemical pressure, deploying periodic dislocation arrays, designing topological domain walls, functionalizing interfaces, and leveraging flexoelectric strain gradients constitute the core strategic toolkit. Through such ordered defect architectures, scalable performance metrics, including high remanent polarization, low coercive field, fast switching speed, and endurance exceeding 10^12 cycles, become attainable. These approaches establish a set of design principles for next-generation low-power, high-reliability ferroelectric electronics.
SCIENCE CHINA Materials•2025•DOI: 10.1007/s40843-024-3291-3
Multiferroic van der Waals heterostructures offer a route to atomically thin spintronic memory and logic, yet the simultaneous attainment of large tunnel magnetoresistance (TMR), stable multi-resistance states, and low resistance-area (RA) product remains unresolved. This work employs first-principles calculations to design a Fe3GaTe2/α-In2Se3/Fe3GaTe2 multiferroic tunnel junction (MFTJ). The device exhibits TMR exceeding 10^5%, nonvolatile multistate operation, and RA product below 1 Ω μm2, satisfying high-density memory cell requirements. The exceptionally low RA product arises from the narrow bandgap of the ultrathin ferroelectric barrier, while the high TMR and near-perfect spin polarization stem from enhanced momentum-selective tunneling at the Fe3GaTe2/α-In2Se3 interface. A low energy barrier for ferroelectric switching enables efficient voltage-driven polarization control. These findings establish a pathway for integrating low-RA, high-TMR, multistate MFTJs into spintronic architectures, accelerating high-density, energy-efficient data storage and processing technologies.