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1.
J Colloid Interface Sci ; 606(Pt 2): 913-919, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34487938

RESUMO

With the development of mobile terminals, tunable capacitors for signal processing and memristors for calculation have received a lot of attention. Combining a tunable capacitor and a memristor can improve the performance of mobile terminals and reduce space requirements. In this article, we report on Bi2NiMnO6 (BNMO) films with high dielectric tuning and nonvolatile resistive switching (RS) effects. The BNMO films are fabricated by the sol-gel method and annealed at different temperatures. It exhibits a dielectric tunability of up to 92%. This high dielectric tunability may be attributed to the modulation of the interface dipole by the electric field. When an electric field is applied, the interface dipole of the BNMO film is far away from the interface of the BNMO, and then forms a conductive channel where anions and cations are mixed. The BNMO films are found to have a double-set type effect due to its dielectric tunability properties. This work introduces an ultra-high dielectric tuning material and a new type of RS effect on BNMO thin film, which can achieve tuning and memory behavior on a device.

2.
Nanomaterials (Basel) ; 11(10)2021 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-34685146

RESUMO

Herein, Bi4Ti3O12 (BIT) ferroelectric thin films were fabricated into Au/BIT/LaNiO3/Si structures to demonstrate their memristor properties. Repeatable and stable bipolar resistive switching (RS) characteristics of the device are first reported in this work. The switching ratio of the device annealed in air reached approximately 102 at 0.1 and -0.1 V. The RS performance was not significantly degraded after 100 consecutive cycles of testing. We also explored the factors affecting the RS behavior of the device. By investigating the RS characteristics of the devices annealed in O2, and in combination with XPS analysis, we found that the RS properties were closely related to the presence of oxygen vacancies. The devices annealed in air exhibited a markedly improved RS effect over those annealed in O2. According to the slope fitting, the conduction mechanism of the device was the ohmic conduction and space charge limited current (SCLC). This study is the first to successfully apply BIT ferroelectric films to the RS layers of memristors. Additionally, a theory of conductive filaments is proposed to adequately explain the relationship between RS behavior and oxygen vacancies, providing meaningful inspiration for designing high-quality resistive random access memory devices.

3.
Artigo em Inglês | MEDLINE | ID: mdl-33201657

RESUMO

As an important method to further improve the storage density of resistive memory, multistage resistive switching devices have become an important research direction. However, no stable and controllable multistage resistive switching device has been prepared, and the working mechanism is still unclear. Here, a sandwich-structured device is simply prepared by spin coating, with the work layer is the Bi2FeCrO6 thin film. The device can realize bidirectional controllable multistage resistive switching behavior, the biggest on/off ratio is 104, and it can maintain stability without attenuation at 100 times slow loop and 104 times pulse cycle. The analyzes showed that the charged ions formed by defects in the device migrated under the action of an external electric field lead to the Schottky barrier height reversible changed. Which is the key to cause multistage resistive switching behavior. This work is the first report about the voltage control of bidirectional adjustable multistage resistive switching behavior in the Bi2FeCrO6 thin film. The principle of generation is analyzed, and important ideas and insights are provided for the preparation and treatment of related multistage resistive problems.

4.
Nanomaterials (Basel) ; 9(12)2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31847505

RESUMO

Double perovskite Bi2NiMnO6 (BNMO) thin films grown on p-Si (100) substrates with LaNiO3 (LNO) buffer layers were fabricated using chemical solution deposition. The crystal structure, surface topography, surface chemical state, ferroelectric, and current-voltage characteristics of BNMO thin films were investigated. The results show that the nanocrystalline BNMO thin films on p-Si substrates without and with LNO buffer layer are monoclinic phase, which have antiferroelectric-like properties. The composition and chemical state of BNMO thin films were characterized by X-ray photoelectron spectroscopy. In the whole electrical property testing process, when the BNMO/p-Si heterojunction changed into a BNMO/LNO/p-Si heterojunction, the diode behavior of a single diode changing into two tail to tail diodes was observed. The conduction mechanism and temperature stability were also discussed.

5.
ACS Omega ; 4(11): 14650-14654, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31528821

RESUMO

A giant electrocaloric effect is reported in (Pb0.97La0.02)(Zr0.95Ti0.05)O3 anti-ferroelectric ceramics. These samples were fabricated by a solid-state mixed oxide technique. Dielectric analyses were employed to investigate the anti-ferroelectric (AFE) and ferroelectric (FE) phase transitions of the sample. During the heating process, the phase transition from the orthorhombic anti-ferroelectric phase (AFEO) to the tetragonal anti-ferroelectric phase (AFET) occurs at 155 °C, and the phase transition from AFET to PE occurs at 225 °C. Using the Maxwell relationship, the entropy change ΔS and adiabatic temperature change ΔT were obtained at different electric fields ranging from 40 to 65 kV/cm. The maximum adiabatic temperature change (ΔT max = -7.47 K) was obtained at 50 kV/cm, which was attributed to the field-induced phase transformation between the anti-ferroelectric and ferroelectric phases. These results showed that PLZT2/95/5 ceramics possess a large negative electrocaloric effect value, which could be applied in achieving cooling power as refrigerants.

6.
Nanomaterials (Basel) ; 9(8)2019 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-31382660

RESUMO

The resistive switching (RS) characteristics of flexible films deposited on mica substrates have rarely been reported upon, especially flexible HfO2 films. A novel flexible Au/HfO2/Pt/mica resistive random access memory device was prepared by a sol-gel process, and a Au/HfO2/Pt/Ti/SiO2/Si (100) device was also prepared for comparison. The HfO2 thin films were grown into the monoclinic phase by the proper annealing process at 700 °C, demonstrated by grazing-incidence X-ray diffraction patterns. The ratio of high/low resistance (off/on) reached 1000 and 50 for the two devices, respectively, being relatively stable for the former but not for the latter. The great difference in ratios for the two devices may have been caused by different concentrations of the oxygen defect obtained by the X-ray photoelectron spectroscopy spectra indicating composition and chemical state of the HfO2 thin films. The conduction mechanism was dominated by Ohm's law in the low resistance state, while in high resistance state, Ohmic conduction, space charge limited conduction (SCLC), and trap-filled SCLC conducted together.

7.
Sci Rep ; 8(1): 396, 2018 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29321638

RESUMO

The unique properties and great variety of relaxer ferroelectrics make them highly attractive in energy-storage and solid-state refrigeration technologies. In this work, lanthanum modified lead titanate ceramics are prepared and studied. The giant electrocaloric effect in lanthanum modified lead titanate ceramics is revealed for the first time. Large refrigeration efficiency (27.4) and high adiabatic temperature change (1.67 K) are achieved by indirect analysis. Direct measurements of electrocaloric effect show that reversible adiabatic temperature change is also about 1.67 K, which exceeds many electrocaloric effect values in current direct measured electrocaloric studies. Both theoretical calculated and direct measured electrocaloric effects are in good agreements in high temperatures. Temperature and electric field related energy storage properties are also analyzed, maximum energy-storage density and energy-storage efficiency are about 0.31 J/cm3 and 91.2%, respectively.

8.
Nanomaterials (Basel) ; 7(9)2017 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-28885579

RESUMO

Sr(Ti1-xFex)O3-δ (0 ≤ x ≤ 0.2) thin films were grown on Si(100) substrates with LaNiO3 buffer-layer by a sol-gel process. Influence of Fe substitution concentration on the structural, ferroelectric, and magnetic properties, as well as the leakage current behaviors of the Sr(Ti1-xFex)O3-δ thin films, were investigated by using the X-ray diffractometer (XRD), atomic force microscopy (AFM), the ferroelectric test system, and the vibrating sample magnetometer (VSM). After substituting a small amount of Ti ion with Fe, highly enhanced ferroelectric properties were obtained successfully in SrTi0.9Ti0.1O3-δ thin films, with a double remanent polarization (2Pr) of 1.56, 1.95, and 9.14 µC·cm-2, respectively, for the samples were annealed in air, oxygen, and nitrogen atmospheres. The leakage current densities of the Fe-doped SrTiO3 thin films are about 10-6-10-5 A·cm-2 at an applied electric field of 100 kV·cm-1, and the conduction mechanism of the thin film capacitors with various Fe concentrations has been analyzed. The ferromagnetic properties of the Sr(Ti1-xFex)O3-δ thin films have been investigated, which can be correlated to the mixed valence ions and the effects of the grain boundary. The present results revealed the multiferroic nature of the Sr(Ti1-xFex)O3-δ thin films. The effect of the annealing environment on the room temperature magnetic and ferroelectric properties of Sr(Ti0.9Fe0.1)O3-δ thin films were also discussed in detail.

9.
Bioresour Technol ; 241: 726-734, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28628976

RESUMO

In this study, dilute alkali salts (0.6% NaClO, 0.067% Na2S) pretreatment at 10% sulfidity under the autoclave system at 120°C for 40min was used for pretreating bamboo shoot shell (BSS). Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated BSS solid residue. After 72h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50g/L pretreated BSS in dilute NaClO/Na2S media could be obtained at 31.11 and 20.32g/L, respectively. Finally, the obtained BSS-hydrolysates containing alkalic salt NaClO/Na2S resulted in slightly negative effects on the ethanol production. Glucose in BSS-hydrolysates was fermented from 20.0 to 0.17g/L within 48h, and an ethanol yield of 0.41g/g glucose, which represents 80.1% of the theoretical yield, was obtained. This study provided an effective strategy for potential utilization of BSS.


Assuntos
Hipoclorito de Sódio , Sulfetos , Celulase , Etanol , Fermentação , Hidrólise , Ácido Hipocloroso , Espectroscopia de Infravermelho com Transformada de Fourier
10.
Appl Biochem Biotechnol ; 182(4): 1341-1357, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28120241

RESUMO

Effective utilization of winter bamboo shoot shell (BSS) is of great interest, since BSS provides a renewable and inexpensive bioresource for the production of biofuels. In this study, an effective combination pretreatment by the sequential aqueous ammonia (25 wt%) extraction at 50 °C for 24 h and LiCl/N,N-dimethyl formamide (LiCl/DMF) (6 wt% of LiCl) pretreatment at 50 °C for 8 h was used for pretreating BSS. SEM, FTIR, and XRD results indicated that combination pretreatment could effectively remove lignin and change the crystal structure of cellulose for promoting enzymatic saccharification. Additionally, significant linear correlations were found about solid recovery-delignification (R 2 = 0.9235), delignification-reducing sugars (R 2 = 0.9552), and delignification-hemicellulose removal (R 2 = 0.9779) during the combination pretreatment. The reducing sugars and glucose from the hydrolysis of 100 g/L pretreated BSS could be obtained at 72.3 and 40.5 g/L, respectively. Using the recovered BSS-hydrolysates containing 20-50 g/L glucose as carbon source, the ethanol yields at 48 h could be obtained at 84.5-86.1% of the theoretical yield. In conclusion, the sequential ammonia extraction and LiCl/DMF pretreatment has high potential application in future.


Assuntos
Amônia/química , Carboidratos/química , Celulase/metabolismo , Dimetilformamida/química , Cloreto de Lítio/química , Poaceae/química , Água/química , Carboidratos/isolamento & purificação , Fracionamento Químico , Fermentação , Hidrólise
11.
Sci Rep ; 6: 31960, 2016 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-27628266

RESUMO

The behavior of ferroelectric domain under applied electric field is very sensitive to point defects, which can lead to high temperature dielectric relaxation behaviors. In this work, the phases, dielectric properties and ferroelectric switching behavior of strontium lead titanate ceramics were investigated. The structural characterization is confirmed by X-ray diffraction. The high dielectric tunability and high figure of merit of ceramics, especially Sr0.7Pb0.3TiO3 (SPT), imply that SPT ceramics are promising materials for tunable capacitor applications. Oxygen vacancies induced dielectric relaxation phenomenon is observed. Pinched shape hysteresis loops appeared in low temperature, low electric field or high frequency, whereas these pinched hysteresis loops also can become normal by rising temperature, enhancing electric field or lowering frequency. The pinning and depinning effect can be ascribed to the interaction between oxygen vacancies and domain switching. A qualitative model and a quantitative model are used to explain this phenomenon. Besides, polarization and oxygen treated experiment can exert an enormous influence on pinning effect and the machanisms are also discussed in this work.

12.
Nanoscale Res Lett ; 8(1): 207, 2013 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-23639007

RESUMO

Double-perovskite La2NiMnO6 (LNMO) nanoparticles were synthesized by co-precipitation process, and the adsorption of bovine serum albumin (BSA) protein on these nanoparticles was carried out. The powder samples were annealed at 750, 850, 950, and 1,050°C, respectively. X-ray diffraction (XRD) results reveal that there are double perovskites and exhibit mixed orientations, without any impurity phases. Transmission electron microscopy results as well as the XRD estimate results show that the crystalline size is about 34 to 40 nm. The adsorption of BSA on the magnetic nanoparticles was analyzed using a UV spectrophotometer at room temperature. The results show that the as-prepared LNMO nanoparticles display a good adsorbing ability for BSA, and the nanoparticle sintered at 850°C has the highest value of 219.6 mg/g, which is much higher than others.

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