A distinctive HPHT platform with different types of large-volume press subsystems at SECUF

Large-volume presses(LVPs)providing large volumes,liquid media,deformation capability,jump compression,and in situ measurements are in great demand for high-pressure research,particularly in the fields of geoscience,condensed matter physics,material science,chemistry,and biology.A high-pressure and high-temperature(HPHT)platform with different LVP subsystems,both solid-state and liquid environments,and nonequilibrium subsystems,has been constructed at the Synergetic Extreme Condition User Facility,Jilin University.This article describes the construction of the different subsystems and provides an overview of the capabilities and characteristics of the different HPHT subsystems.A large sample volume(1000 mm^(3))at 20 GPa is achieved through the use of a belt-type apparatus in the solid-state subsystem.HPHT conditions(1.8 GPa and 1000 K)are realized in the liquid subsystem through the use of a piston-cylinder-type LVP with optical diamond windows for in situ spectroscopic measurements.A maximum pressure jump to 10.2 GPa can be reached within 20 ms in the nonequilibrium subsystem with the use of an improved bladder-pressurization jump press.Some typical results obtained with different LVPs are briefly reviewed to illustrate the applications and advantages of these presses.In summary,the platform described here has the potential to contribute greatly to high-pressure research and to innovations in high-pressure technology.

Cold sintering process:A green route to fabricate thermoelectrics

Cold sintering is a newly developed low-temperature sintering technique that has attracted extensive attention in the fabrication of functional materials and devices.Low sintering temperatures allow for a substantial reduction in energy consumption,and simple experimental equipment offers the possibility of large-scale fabrication.The cold sintering process(CSP)has been demonstrated to be a green and cost-effective route to fabricate thermoelectric(TE)materials where significant grain growth,secondary phase formation,and element volatilization,which are prone to occur during high-temperature sintering,can be well controlled.In this review,the historical development,understanding,and application of thermoelectric materials produced via cold sintering are highlighted.The latest attempts related to the cold sintering process for thermoelectric materials and devices are discussed and evaluated.Despite some current technical challenges,cold sintering provides a promising and sustainable route for the design of advanced high-performance thermoelectrics.

High-pressure synthesis,mechanical properties,and oxidation behavior of advanced boron-containingα/β-Si_(3)N_(4)/Si ceramics using polymer-derived amorphous SiBN ceramics

The preparation of dense Si_(3)N_(4)-based ceramics has attracted great attention because of the achievable improvements in their mechanical properties and high-temperature oxidation resistance.In this work,advanced dense boron-containingα/β-Si_(3)N_(4)/Si monoliths were prepared via a high pressure‒high temperature technique in which polymer-derived amorphous SiBN powders were used as raw materials.The crystallization behavior and phase transformation of the polymer-derived amorphous samples were studied in the temperature range from 1400 to 1800℃.The results demonstrate that the incorporation of boron in the Si_(3)N_(4)matrix suppresses the phase transformation fromα-Si_(3)N_(4)toβ-Si_(3)N_(4).Furthermore,the mechanical properties of the as-prepared samples were measured,and the maximum hardness and fracture toughness of boron-rich SiBN samples reached 14.8 GPa and 7.96 MPa·m1/2,respectively.The hardness of the obtained boron-rich SiBN samples is stable up to 300℃.In addition,the oxidation behavior of the samples prepared at 1400 and 1600℃ was investigated at 1400℃ for 50 h.The results show that the incorporation of boron significantly improved the oxidation resistance of the samples because of the formation of borosilicate/cristobalite.This work provides guidance for the synthesis of boron-containingα/β-Si_(3)N_(4)-based ceramics with excellent mechanical properties and oxidation resistance.