Polymer nanocomposite dielectrics with high electrocaloric effect for flexible solid-state cooling devices

Nanocomposite dielectrics show great promising application in developing next generation wearable all-solidstate cooling devices owing to the possessed advantages of high cooling efficiency, light-weight and small volume without the induced greenhouse effect or serious harm to ozone layer in the exploited refrigerants. However, low electrocaloric strength in nanocomposite dielectric is severely restricting its wide-spread application because of high applied operating voltage to improve electrocaloric effect. After addressing the chosen optimized ferroelectric ceramic and ferroelectric polymer matrix in conjunction with the analysis of crucial parameters, recent progress of electrocaloric effect(ECE) in polymer nanocomposites has been considerably reviewed. Subsequently, prior to proposing the conceptual design and devices/systems in electrocaloric nanocomposites, the existing developed devices/systems are reviewed. Finally, conclusions and prospects are conducted, including the aspects of materials chosen, structural design and key issues to be considered in improving electrocaloric effect of polymer nanocomposite dielectrics for flexible solidstate cooling devices.

Effect of misfit strain on the electrocaloric effect of polydomain epitaxial ferroelectric thin films

The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTi03 thin films at room temper- ature is investigated using the Ginzburg^Landau Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca1/ca2/ca1/ea2 phase is much larger than that in the mon- odomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.

Effect of an electric field on the electrocaloric response of ferroelectrics

The electrocaloric effect of the model ferroelectric BaTiO3was investigated using phenomenological theory. The results indicate that the applied electric field strength is a key factor for the induced electrocaloric response and there are two distinguishing electrocaloric responses. When a moderate electric field is applied, the electrocaloric temperature variation is small but the electrocaloric strength is high. In contrast, the electrocaloric temperature variation is large but electrocaloric strength is low when a very high electric field is applied. These results are consistent with the experimental observations on BaTiO3based bulk and thin film ferroelectric materials.

Composition and misfit strain dependence of electrocaloric effect of Pb_(1-x) Sr_xTiO_3 thin films

A Landau-Devonshire thermodynamic theory is employed to investigate the effects of composition and misfit strain on the room-temperature electrocaloric effect of epitaxial Pbl-xSrxTiO3 thin films. The ＂temperature-misfit strain＂ phase diagrams with the Sr composition x of 0.1, 0.3, and 0.5 are constructed. The introduction of Sr composition reduces the Curie temperature greatly, and enhances the electrocaloric effect. Moreover, the electrocaloric effect largely depends on the misfit strain. Therefore, the Sr composition and the misfit strain can be controlled to obtain the giant room-temperature electrocaloric effect.

Electrocaloric effect and pyroelectric properties of organic–inorganic hybrid （C2H5NH3）2CuCl4

The organic–inorganic hybrid(C2H5NH3)2 CuCl4(EA2CuCl4) single crystals are prepared by the solvothermal condition method. The x-ray diffraction, scanning electron microscopy, dielectric permittivity, pyroelectric current, and heat capacity are used to systematically investigate the electrocaloric performances of EA2CuCl4. The pyroelectric currents are measured under various voltages, and the electrocaloric effect(ECE) is calculated. Its ECE exhibits an isothermal entropy change of 0.0028 J/kg·K under an electric field of 30 kV/cm associated with a relatively broad temperature span. Further, the maximum pyroelectric coefficient(p) is 4× 10^-3 C/m^2·K and the coefficient β for generating ECE from electric displacement D is 1.068× 10^8 J·cm·K^-1·C^-2 at 240 K. Our results indicate that the ECE behavior of organic–inorganic hybrid EA2CuCl4 is in accordance with Jona and Shirane’s opinion in which the ECE should occur both below and above the Curie temperature Tc.

Electrocaloric effect in ferroelectric materials:From phase field to first-principles based effective Hamiltonian modeling

Electrocaloric effect(ECE)of ferroelectrics has attracted considerable interest due to its potential application in environmentally friendly solid-state refrigeration.The discovery of giant ECE in ferroelectric thin films has greatly renewed the research activities and significantly stimulated experimental and theoretical investigations.In this review,the recent progress on the theoretical modeling of ECE in ferroelectric and antiferroelectric materials are introduced,which mainly focuses on the phase field modeling and first-principles based effective Hamiltonian method.We firstly provide the theoretical foundation and technique details for each method.Then a comprehensive review on the progress in the application of two methods and the strategies to tune the ECE are presented.Finally,we outline the practical procedure on the development of multi-scale computational method without experiemtal parameters for the screening of optimized electrocaloric materials.

Electrocaloric effect enhanced thermal conduction of a multilayer ceramic structure

The electrocaloric effect of ferroelectric ceramics has been studied extensively for solid-state caloric cooling.Generally,most ferroelectric ceramics are poor thermal conductors.In this work,the possibility of enhancing the thermal conduction of ferroelectric ceramics through the electrocaloric effect is studied.A multilayer ceramic structure is proposed and the proper sequential electric field is applied to each ceramic layer.The result shows that the thermal conduction of the multilayer structure is significantly enhanced because of the electrocaloric effect of the ferroelectric ceramics.As a result,the work finds an alternatively way of applying the electrocaloric effect,prompting thermal conduction.

On the parameters for electrocaloric effect predicted by indirect method

The influences of specific heat capacity CP, temperature step ？T, electric field step ？E, and initial electric field E1 on predicted electrocaloric（EC） temperature ？T of monodomain Ba TiO3 are examined by combining the Maxwell equation and phenomenological theory. Since the procedure is similar to indirect measurement of the EC effect, the results can serve as a reference for experiments. The results suggest that（i） it is reasonable to use zero-field CP,（ii） optimized ？T should be 2 K,（iii） it is better to keep △E 〈 EC, and（iv） E1〈 EC. Here, EC is the coercive field of material.

Compact Thermal Management Device Using Electrocaloric Effect

The electrocaloric effect (ECE) is defined as the fact that the temperature of dielectric material changes, when an electric field is applied to or removed from the material [1]. It might be a possible solution for the increasing energy consumption for thermal management because of its high effectiveness. Previous research on the ECE has investigated several possible methods to build a model based on ECE and feasibilities to increase the efficiency of the model. But there has been no study on all the factors that may affect the performance of the device. Thus, in this paper, we designed a cooling device based on ECE and simulated it by using the control variates method showing that a high efficiency can be reached through stated model.

西黄丸联合免疫及EC化疗一线治疗广泛期小细胞肺癌的临床效果及安全性

目的探讨西黄丸联合免疫及EC化疗一线治疗广泛期小细胞肺癌的临床效果及安全性。方法选取2021年8月至2023年2月江西省胸科医院收治的126例广泛期小细胞肺癌患者作为研究对象,按照随机信封法分为研究组和对照组,每组63例。对照组患者采用免疫及EC化疗,研究组在对照组的基础上联用西黄丸,比较两组患者的临床疗效、血钠浓度、胃泌素释放肽前体(proGRP)、肿瘤标志物、生存质量、不良反应发生情况。结果研究组治疗客观缓解率(ORR)高于对照组,差异有统计学意义(P<0.05)。治疗结束后7 d,两组患者肿瘤卡氏评分(KPS)高于本组治疗前,且研究组KPS评分高于对照组,差异有统计学意义(P<0.05)。研究组无进展生存期(PFS)高于对照组,差异有统计学意义(P<0.05)。治疗结束后7 d,两组患者血钠浓度高于本组治疗前,proGRP、癌胚抗原(CEA)、神经元烯醇化酶(NSE)和糖类抗原125(CA125)水平低于本组治疗前,且研究组血钠浓度高于对照组,proGRP、CEA、NSE和CA125水平低于对照组,差异有统计学意义(P<0.05)。研究组不良反应总发生率低于对照组,差异有统计学意义(P<0.05)。结论西黄丸联合免疫及EC化疗方案治疗广泛期小细胞肺癌有效率高,能够延缓肿瘤进展,降低肿瘤标志物表达水平,改善生存质量,治疗安全性和实用性较高。

Effect of misfit strain on the electrocaloric effect of polydomain epitaxial ferroelectric thin films

The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO 3 thin films at room temperature is investigated using the Ginzburg–Landau–Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca 1 /ca 2 /ca 1 /ca 2 phase is much larger than that in the monodomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.

Synergistic Effect of Cottonseed Oil EC and Soybean Oil EC on Imidacloprid and Avermectin

[Objective] The study aimed to investigate the synergistic effect of vegetable oil EC on chemical pesticides. [Method] Cottonseed oil EC and soybean oil EC were mixed with 20% imidacloprid EC and 0.5% avermectin WE respectively, Schizaphis graminum were handled with dipped method,synergistic effects of vegetable oil EC on imidacloprid and avermectin were analyzed. [Result] Cottonseed oil EC and soybean oil EC had obvious synergistic effect on 20% imidacloprid EC and 0.5% avermectin WE. Corrected mortality of 20% imidacloprid EC＋cottonseed oil EC（0.10＋10.00, 0.10＋5.00, 0.10＋3.33 and 0.05＋10.00 ml/L）, 0.5% avermectin WE＋cottonseed oil EC（1.00＋10.00, 1.00＋5.00, 0.50＋10.00 and 0.50＋5.00 ml/L）and 20% imidacloprid EC＋soybean oil EC（0.10＋10.00, 0.10＋5.00, 0.10＋10.00 and 0.05＋5.00 ml/L） were all over 90%. [Conclusion] Considered from control effect and economy angle, the mixture of cottonseed oil EC or soybean oil EC with 20% imidacloprid EC, and the mixture of cottonseed oil EC with 0.5% avermectin WE could be used to control S. graminum.

Giant negative electrocaloric effect measured by indirect method in X-ray irradiated P(VDF-TrFE)films

Flexible solid-state cooling devices with high efficiency are attracted to ferroelectric polymers with excellent negative electrocaloric(EC)effects.It is challenging to obtain a large negative EC effect in ferroelectric polymers due to the lack of tunable techniques.A giant negative EC response was obtained in the poly(vinylidene fluoride-trifluoroethylene)copolymers(P(VDF-TrFE),70/30,in mole ratio)irra-diated with high-energy X-ray.The irradiated P(VDF-TrFE)films showed an adiabatic temperature change of-13.5 K at 40 MV/m under a dose of 5 Mrad(1 Mrad=10^(4) J/kg)obtained by the indirect method.This significant negative EC effect is attributed to the enhancement of crystalline due to the entry of polymer molecules into the amorphous to crystalline structure and the reduction of heat ca-pacity due to the increase of crosslinking.In addition,X-ray irradiation improves the dielectric coefficient from 15 to 22.This research indicates that irradiation can modify the negative EC properties of ferro-electric polymers for solid-state cooling.

A study on effective parameters of electric cortical stimulation for motor-sensory brain mapping

Objective The purpose of the study was to investigate the effective parameters of electric cortex stimulation (ECS) for functional brain mapping. Methods We collected 21 subjects who underwent epilepsy surgeries consecutively in Beijing Institute of Functional Neurosurgery with the epileptogenic zone located in perirolandic areas from

Simultaneous achievement of large electrocaloric effect and ultrawide operating temperature range in BaTiO_(3)-based lead-free ceramic

The electrocaloric effect(ECE),known for its environmentally friendly characteristics,holds significant promise for advancing next-generation solid-state refrigeration technologies.Achieving a large ECE along with a wide working temperature range near room temperature remains a key developmental goal.In this study,we successfully obtained a substantial ECE of 1.78 K and an extensive working temperature range of 103 K(AT>1.52 K)near room temperature in CaZrO_(3)-modified BaTiO_(3) lead-free ferroelectric ceramics.Furthermore,this achievement was verified using direct methods.The piezoresponse force microscopy(PFM)results suggest that the broad temperature range is attributed to the formation of ferroelectric microdomains and polar nanoregions(PNRs).Furthermore,X-ray photoelectron spectroscopy(XPS)and ultraviolet-visible(UV-Vis)spectroscopy reveal a decrease in the oxygen vacancy concentration and an increase in the bandgap for higher CaZrO_(3) doping levels.These changes synergistically enhance the maximum applied electric field,helping to achieve a high-performance EcE near room temperature.This research presents a straightforward and effective approach for achieving high-performance ECEs in BaTiOg lead-free ceramics,offering promising prospects for application in next-generation solid-state refrigeration technologies.

高综合性能电卡复合材料及大功率制冷器件

通过制备BaZr_(0.2)Ti_(0.8)O_(3)-P(VDF-TrFE-CFE)复合材料来改善聚合物基电卡材料的综合性能,设计基于流固耦合传热的大功率制冷器件并通过有限元仿真来评估以不同电卡材料为制冷核心元件的器件制冷能力和效率。结果表明:相较于基础聚合物,BZT质量分数为10%的复合材料T-BZT-10%具有显著优异的电卡制冷性能和导热性能。在10 K的温度跨度下,以T-BZT-10%为制冷核心元件的电卡器件可实现31.0 W/cm^(3)的制冷功率密度和1060.4 W的总制冷功率为基础电卡制冷器件的10倍),且COP达到5.2。

柔性薄膜复合形状记忆合金弹簧驱动器

针对形状记忆合金(shape memory alloy,简称SMA)材料在使用过程中因其较低的响应频率而很难应用于高频率场所问题,在聚偏氟乙烯(polyvinylidene fluoride,简称PVDF)薄膜中引入锆酸铅钡(Pb_(0.8)Ba_(0.2)ZrO_(3),简称PBZ)纳米陶瓷纤维制备柔性薄膜,并与NiTi合金弹簧复合制得PBZ/PVDF@SMA复合驱动器,通过薄膜的电卡效应加热及冷却SMA丝,与传统电流加热及自然冷却方式进行了对比。结果表明,缩短了SMA丝循环周期,提高了其响应频率,有利于扩大SMA的适用场所。

纳米线电卡效应的表面应力与固溶改性相场模拟

以铁电纳米线为填料的复合薄膜表现出了满足固态制冷需求的高绝热温变,其平行分布填充的纳米线因和传统垂直分布的取向不同,被认为是获得大电卡效应的关键因素,然而其大电卡效应的内在机理尚不十分明确.因此本文以PbTiO_(3)纳米线为研究对象,建立平行分布纳米线模型,通过相场模拟研究表面应力和固溶改性对其电卡效应的影响.结果表明,表面应力和固溶改性能够分别调控纳米线相变温度并获取大的绝热温变,并最终实现了在600 kV/cm电场下,0-300℃的宽温度区间获得大于6 K绝热温变的效果.同时结合三维畴结构的演变,揭示了诱发不同畴翻转类型是平行分布纳米线结构获得大电卡效应的内在机理.通过本研究为基于平行分布铁电纳米线电卡效应的固态制冷技术发展提供了有益的理论指导.

α-细辛醚对人食管癌Ec-109细胞的体外抑制作用初探

α-细辛醚是中药石菖蒲挥发油中的主要活性成分,具有平喘、解痉、抗痫[1]、醒脑、杀虫、抗真菌等作用,临床主要用于治疗癫痫、支气管炎、小儿肺炎、老年性痴呆等。据文献资料,自1986年国内学者胡伯渊等率先报道α-细辛醚对SGC-701、HeLa细胞株有抗癌活性以来,至今,对于其它肿瘤细胞的研究以及其抗肿瘤的机制研究尚未见报道。1材料与方法1.1材料人食管癌Ec-109细胞株2010年2月购于中国医学科学院肿瘤研究所细胞库;

50g/L唑啉草酯EC防除春小麦田野燕麦药效及对作物的安全性研究

为明确50 g/L唑啉草酯EC在青海省春小麦田防除野燕麦药效、适宜剂量及对作物的安全性,在田间进行50 g/L唑啉草酯EC不同剂量的除草效果试验。于小麦3～5叶期、野燕麦2～4叶期对水喷雾处理。结果表明,50 g/L唑啉草酯EC是春小麦田防除野燕麦的优良除草剂,适宜剂量为900 mL/hm2,对野燕麦防效达90%以上,对小麦安全,增产率12%以上。