双色流荧——基于氨气制备的鲁米诺双色荧光喷泉

基于氨气的制备、收集和尾气处理装置来设计溶液反应,利用氨气易溶于水导致瓶内外大气压瞬间失衡的性质实现喷泉实验。通过简单易行的操作,基于鲁米诺发光反应和无色酚酞溶液遇碱变色反应,成功实现了双色荧光喷泉实验。本实验的目的是普及基础化学中氨气的性质和鲁米诺遇血发出明亮的蓝光的特性,介绍鲁米诺发光的原理,让参观者解开悬疑侦探片中喷洒试剂就可以显示出肉眼不可见血迹的疑惑,切身感受化学之趣。

Investigation on relaxor-ferroelectric behavior of BNBT-KNN ceramics with Ta doping

In this study,BNBT-KNN-xTa_(2)O_(5)was designed and synthesized,successfully achieving a reduction in the relaxor-ferroelectric phase transition temperature.Synergy between temperature-dependent ferroelectric testing and dielectric spectroscopy confirmed that the depoling temperature gradually decreased with increasing doping concentration.Fitting of the relaxation parameter and freezing temperature substantiated that the incorporation of Ta_(2)O_(5)increased the degree of relaxation in BNBT-KNN-xTa_(2)O_(5),thereby effectively lowering the relaxor-ferroelectric phase transition temperature.

Enhanced energy-storage performance with optimized thermally stable dielectric property in BNT–BST ceramics modified by KNN doping

Developing environmental-friendly materials with high-density energy storage is of paramount importance to meet the burgeoning demands for energy storage.In this study,we harness the modulation of a multicomponent solid solution by introducing KNN as a third element into the BNT–BST system,thereby achieving a marked enhancement in both energy storage performance and the temperature stability of the dielectric constant.BNBST–4KNN stands out for its exceptional dielectric stability,with a dielectric constant variation rate within 10%across a broad temperature range of 40℃to 400℃,a feat attributed to the flattening and broadening of the Tm peak.BNBT–2KNN exhibits superior energy storage capabilities,with an energy storage density of 1.324 J/cm^(3)and an energy storage efficiency of 72.3%,a result of the P–E loop becoming more slender.These advancements are pivotal for the sustainable progression of energy storage technologies.

High strength-ductility and rapid degradation rate of as-cast Mg-Cu-Al alloys for application in fracturing balls

Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.

Mechanical properties and deformation mechanisms of a novel fine-grained Mg-Gd-Y-Ag-Zr-Ce alloy with high strength-ductility synergy

Grain boundary precipitation and segregation play an important role in determining mechanical properties of Mg alloys. In the present work, we studied work focuses on the strengthening and deformation mechanism of coarse-grained(CG) and fine-grained(FG) Mg-Gd-Y-Ag-Zr-Ce alloy. The CG alloy is strengthened by means of age-strengthening with the formation of both basal plate γ" and prismatic plate β’ precipitates in the grain interior. While the strengthening of FC alloy is completed by intergranular alloying segregation and intragranular precipitates γ" and β’. The segregation of alloying elements at the grain boundary and formation of sub-micron particles can stabilize the grain boundary and suppress the intergranular deformation. Consequently, dislocations could be trapped near γ" and β’ precipitates in the grain interior. Unlike CG alloys, the FG alloys exhibit a heterogeneous transition from elastic to plastic deformation via the Lüders plateau. The rapid gliding dislocation multiplications and fine-grained size are necessary and sufficient conditions for the Lüders strains. Our work provides the insights on the evolution of fine-grained microstructure and helps for the design of Mg alloys with good mechanical properties.

Current vortices and magnetic fields driven by moving polar twin boundaries in ferroelastic materials

Ferroelastic twin boundaries often have properties that do not exist in bulk,such as superconductivity,polarity etc.Designing and optimizing domain walls can hence functionalize ferroelastic materials.Using atomistic simulations,we report that moving domain walls have magnetic properties even when there is no magnetic element in the material.The origin of a robust magnetic signal lies in polar vortex structures induced by moving domain walls,e.g.,near the tips of needle domains and near domain wall kinks.These vortices generate displacement currents,which are the origin of magnetic moments perpendicular to the vortex plane.This phenomenon is universal for ionic crystals and holds for all ferroelastic domain boundaries containing dipolar moments.