Dielectric and energy storage properties of PbO–SrO–Nb2O5–Na2O–Si thin films by annealing

Dielectric and energy storage properties of PbOSrO-Na₂O-Nb₂O₅-SiO₂（PSNNS） thin films with annealing temperature from 700 to 850 ℃ were investigated by measuring their capacitance-electric filed curve and hysteresis loops.The results show that the highest dielectric constant and energy density are 81.2 and 17.0 J·cm^-3,respectively,which is obtained in the sample with annealing temperature of 800 ℃.Annealed from 700 to800 ℃,the dielectric constant and energy storage performance of PSNNS films are continuously improved.However,with annealing temperature up to 850 ℃,their dielectric constant decreases,which might be related with the removal of interfacial defects as a function of annealing temperature.Defect is one of the causes of space charge phenomenon,resulting in the increase in dielectric constant.Moreover,the micro structure analysis by X-ray diffraction（XRD） and transmission electron microscope（TEM） indicates that the change of crystallization phase and interfacial polarization takes responsibility to the results.     

Effect of substrate temperature on structural properties and photocatalytic activity of TiO2 thin films

Titanium dioxide （TiO2） films with anatase structure were prepared on quartz glass substrates by pulse laser ablating titanium （99.99%） target under oxygen pressure of 10 Pa at substrate temperature of 500-800 ℃. The structural properties of the films were characterized by X-ray difffactometry（XRD）, X-ray photoelectron spectroscopy（XPS） and field emission scan electron microscopy（FESEM）. The results show that, as the substrate temperature is increased from 600 ℃ to 800 ℃, the anatase structure of the films changes from random growth to （211）-oriented growth. The absorption edge tested by UV-Vis Spectrometer has a blue shift. The photocatalytic activity of the films was tested on the degradation of methyl orange. It is found that the film with random growth structure exhibits better photo-degradation efficiency than that with （211）-oriented growth structure.     

Nb2O5掺杂NiFe2O4陶瓷材料的显微结构和导电性能

以NiO、Fe2O3和Nb2O5为原料,采用固相烧结法合成陶瓷粉体,通过等静压-气氛烧结法制备Ni1-xNbxFe2O4(x=0,0.02,0.05,0.07,0.10,0.20)陶瓷试样,并对其进行导电性能测试。通过XRD、SEM、EDX、FTIR和XPS等分析手段对材料的物相组成、显微结构和微区成分进行表征,研究Nb2O5掺杂对陶瓷材料显微结构和导电性能的影响。结果表明:Nb2O5掺杂抑制NiFe2O4基体中NiO相的出现,过量时生成FeNbO4相;适量掺杂(x=0.05)有利于消除晶界孔隙,提高陶瓷的烧结密度;与未掺杂试样相比,掺杂Nb2O5的NiF2O4陶瓷材料的导电性均得到很大改善,其中掺杂量x=0.05的Ni0.95Nb0.05Fe2O4陶瓷试样在1 233 K的电导率较纯NiFe2O4的提高60%。     

Lu2O3/TiO2/Nb2O5共稳定ZrO2热障涂层材料研究

采用Lu2O3/TiO2/Nb2O5作为ZrO2热障涂层材料的稳定剂,研究Lu2O3/TiO2/Nb2O5共稳定ZrO2(15%LTNSZ)热障涂层材料在900℃、40 mol%V2O5+60 mol%Na2SO4熔盐中的热腐蚀行为。结果表明:8%YSZ热障涂层材料热腐蚀2 h后,t相ZrO2全部相变为m相ZrO2,热腐蚀产物为尺寸较大的YVO4晶体;15%LTNSZ热障涂层材料热腐蚀20 h后,m相ZrO2的比例仅为5.5%,热腐蚀产物为尺寸较小的LuVO4晶体。与Y2O3稳定剂相比,Lu2O3/TiO2/Nb2O5稳定剂使ZrO2在40 mol%V2O5+60 mol%Na2SO4熔盐中的抗热腐蚀性能提高1个量级以上。     

Thermal and electrical properties of TiB2–MoSi2

The present communication reports the effect of MoSi₂ addition on high temperature thermal conductivity and room temperature (RT) electrical properties of TiB₂. The thermal diffusivity and the thermal conductivity of the hot pressed TiB₂–MoSi₂ samples were measured over a range from room temperature to 1000 °C using the laser-flash technique, while electrical resistivity was measured at RT using a four linear probe method. The reciprocal of thermal diffusivity of TiB₂ samples exhibit linear dependence on temperature and the measured thermal conductivity of TiB₂-2.5% MoSi₂ composites correlate well with the theoretical predictions from Hashin’s model and Hasselman and Johnson’s model. A common observation is that the thermal conductivity of all the samples slightly increases with temperature (up to 200 °C) and then decreases with further increasing temperature. It is interesting to note that both the thermal conductivity and electrical conductivity of TiB₂ samples enhanced with the addition of 2.5 wt.% MoSi₂ sinter additive. Among all the samples, TiB₂-2.5 wt.% MoSi₂ ceramics measured with high thermal conductivity (77 W/mK) and low electrical resistivity (12 μΩ-cm) at room temperature. Such an improvement in properties can be attributed to its high density and low volume fraction of porosity. On the other hand, both the thermal and electrical properties of TiB₂ were adversely affected with further increasing the amount of MoSi₂ (10 wt.%).     

Effect of ambient oxygen pressure on structural, optical and electrical properties of SnO2 thin films

PolycrystaUine SnO2 thin films were deposited on sapphire substrates at 450℃ under different ambient oxygen pressures by pulsed laser deposition technique. The effect of ambient oxygen pressure on the structural, optical and electrical properties of SnO2 thin films was studied. X-my diffraction and Hall measurements show that increasing the ambient oxygen pressure can improve crystallization of the films and decrease resistivity of the films. A violet emission peak centered at 409 nm was observed from photoluminescence measurements for SnO2 films under deposition ambient oxygen pressure above 5 Pa, which is related to the improvement of crystalline of the films.     

B2O3含量对SiO2–B2O3–Al2O3–Na2O系陶瓷结合剂结构与性能的影响

制备不同B₂O₃含量的SiO₂–B₂O₃–Al₂O₃–Na₂O系玻璃试样和陶瓷结合剂试样,利用电子多功能实验机、扫描电镜、显微硬度仪、平面流淌法、热膨胀系数测试仪等分别测试不同玻璃试样的密度和显微硬度,陶瓷结合剂试样的抗折强度、微观形貌和热膨胀系数等,并用X射线衍射仪、傅里叶变换红外光谱仪对陶瓷结合剂的结构和成分变化进行分析。结果表明：将B₂O₃引入陶瓷结合剂中可有效降低其烧结温度,提高其热稳定性并调节其热膨胀系数等。在陶瓷结合剂中加入摩尔分数为15%的B₂O₃时,其样条抗折强度最高为78.11 MPa,密度和硬度最高分别为2.45 g/cm³和856 MPa,且该陶瓷结合剂的热膨胀系数与金刚石最匹配。X射线衍射分析结果表明陶瓷结合剂是典型的玻璃相结构,且对磨料有良好的包覆效果。     

Microstructure and nanomechanical properties of Mn-rich Ni–Mn–Ga thin films

We report the effect of post-annealing on the crystalline phase, grain growth, magnetic and mechanical properties of Ni–Mn–Ga thin films deposited at room temperature followed by post-annealing at different temperatures. The phase and microstructural analysis reveal that amorphous to crystalline transformation occurs in as-deposited films after post-annealing above 873 K. The transformation of disordered phase into nanocrystalline phase by the influence of annealing has been confirmed by transmission electron microscopy. The crystalline films exhibit soft magnetic behavior with the Curie temperature of 314 K, while the amorphous films exhibit the Pauli-paramagnetic behavior even down to 4 K. The mechanical properties like hardness and elastic modulus of the films also show a strong dependence on the annealing temperature with crystalline film exhibiting maximum values of 6 GPa and 103 GPa, respectively. The Ni–Mn–Ga film annealed at 873 K exhibits enhanced nanomechanical properties and room temperature ferromagnetism which make this a potential candidate for use in MEMS devices.     

Nb2O5/TiO2微弧氧化复合膜层微观组织和高温性能的研究

为了研究Ti6Al4V钛合金微弧氧化膜层的抗高温氧化性能,在硅酸钠电解液中添加纳米铌(Nb)颗粒制备了Nb₂O₅/TiO₂复合膜层。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析膜层的微观结构和相组成。结果表明：随着纳米Nb浓度增加,膜层表面微孔直径增大、数量减小,膜层中Nb元素含量逐渐增加至5at%,膜层厚度由42.28μm增加至55.48μm;膜层由锐钛矿型TiO₂、金红石型TiO₂、Al₂TiO₅、Nb₂O₅及Nb-Ti化合物组成,金红石型TiO₂峰值和Nb₂O₅峰值逐渐上升;试样增重由基体10.25 mg/cm²降低至Nb浓度为6 g/L制备膜层的2.281 mg/cm²,平均氧化速率由2.8472×10^-5 mg·cm^-2     

Microstructure and mechanical properties of ZrB2–Nb composite

The high relative density of the ZrB₂-based composite toughened by 25 vol.%Nb (ZN) was hot-pressed at reduced temperatures with low pressure of 30 MPa. Compared with the toughness of 2.3–3.5 MPa m^1/2 and strength of 350 MPa of the monolithic ZrB₂, the toughness and strength of the ZN composite were improved to 6.7 MPa m^1/2 and 773 MPa, respectively, due to the addition of ductile Nb. The toughening mechanisms are crack deflection and branching as well as stress relaxation near the crack tip. Furthermore, the densification mechanism was analyzed and discussed. The results here pointed to a potential method for improving fracture toughness and strength of ZrB₂-based ceramics.     

Synthesis and characterization of nanosized urchin-like α-Fe2O3 and Fe3O4: Microwave electromagnetic and absorbing properties

Urchin-like α-Fe₂O₃ and Fe₃O₄ nanostructures were prepared from the precursor urchin-like α-FeOOH under reducing atmosphere. The dependence of reduction temperature on their morphology, microstructure, and microwave electromagnetic and absorbing characteristics were systematically studied. It is found that the reduction temperature plays an important role in the microstructure and electromagnetic characteristics of the resulting products. In present study, the urchin-like α-Fe₂O₃ with dual absorption peaks can be formed at the relatively low temperature (e.g. 300 °C). Urchin-like Fe₃O₄ can be obtained just at 350-400 °C, which presents excellent microwave absorption property, with the minimum reflection loss of −29.96 dB and below −20 dB in 3.76-8.15 GHz corresponding to 3-4 mm thickness. The excellent microwave-absorption properties are a consequence of a proper electromagnetic matching and enhanced absorbing abilities resulting from the urchin-like shape and inverse spinel-type crystal structure.     

Crystallization process and shape memory properties of Ti–Ni–Zr thin films

The crystallization process of as-deposited Ti–Ni–(10.8–29.5)Zr amorphous thin films was investigated. The Ti–Ni–Zr as-deposited films with a low Zr content exhibited a single exothermic peak due to the crystallization of (Ti,Zr)Ni with a B2 structure. In contrast, a two-step crystallization process was observed in the Ti–Ni–Zr thin films with a high Zr content. Shape memory behavior of Ti–Ni–Zr thin films heat treated at 873–1073 K was investigated by thermal cycling tests under various stresses. The martensitic transformation start temperature increased with increasing Zr content until reaching the maximum value, then decreased with further increasing Zr content. The inverse dependence of transformation temperature on Zr content in the thin films with a high Zr content is due to the formation of a NiZr phase during the crystallization heat treatment. The formation of the NiZr phase increased the critical stress for slip but decreased the recovery strain.     

Nb2O5含量对颗粒增强型钛基复合材料力学性能的影响

通过粉末冶金的方法制备了一种新型钛基复合材料,研究了其成分及烧结温度对力学性能的影响。结果表明,加入Nb2O5后,钛基复合材料的屈服强度得到显著提高,弹性模量有一定程度降低。     

Optical constants of new amorphous As–Ge–Se–Sb thin films

The present paper reports the effect of replacement of selenium by antimony on the optical constants of new quaternary chalcogenide As₁₄Ge₁₄Se_72−xSb_x (where x = 3, 6, 9, 12 and 15 at.%) thin films. Films of As₁₄Ge₁₄Se_72−xSb_x glasses were prepared by thermal evaporation of the bulk samples. The transmission spectra, T(λ), of the films at normal incidence were obtained in the spectral region from 400 to 2500 nm. A straightforward analysis proposed by Swanepoel, based on the use of the maxima and minima of the interference fringes, has been applied to derive the real and imaginary parts of the complex index of refraction and also the film thickness. Increasing antimony content is found to affect the refractive index and the extinction coefficient of the As₁₄Ge₁₄Se_72−xSb_x films. Optical absorption measurements show that the fundamental absorption edge is a function of composition. With increasing antimony content the refractive index increases while the optical band gap decreases.     

孔道Al2O3/SiO2对NaAlH4-Tm2O3体系储氢性能的影响

以机械球磨法制备具有可逆吸放氢性能的NaAlH4-Tm2O3储氢材料体系。利用相同制备方法进一步研究两种不同孔道材料(大孔Al2O3与介孔SiO2)对NaAlH4-Tm2O3体系储氢性能的影响,测试样品的循环吸放氢性能,并对样品吸放氢前后的结构进行表征。结果表明:大孔Al2O3材料的添加并不能明显改善NaAlH4-Tm2O3体系的放氢速率和放氢量,而介孔SiO2的加入使NaAlH4-Tm2O3体系在150℃条件下5 h内的首次放氢量(质量分数)达到4.61%,高于NaAlH4-Tm2O3体系的4.27%,增加了约8.0%。此外,添加介孔SiO2的NaAlH4-Tm2O3体系放氢速率也有所提高。     

Magnetic properties of mechanochemically synthesized γ-Fe2O3 nanoparticles

The synthesis of mono-dispersed γ-Fe₂O₃ nanoparticles by mechanochemical processing was demonstrated for the first time, via the solid-state exchange reaction Fe₂(SO₄)₃ + 3Na₂CO₃ → Fe₂(CO₃)₃ + 3Na₂SO₄ → Fe₂O₃ + 3Na₂SO₄ + 3CO₂(g) and subsequent heat treatment at 673 K. The nanoparticles had a volume-weighted mean diameter of 6 nm and a narrow size distribution with the standard deviation of 3 nm. The particles showed a superparamagnetic nature with the superparamagnetic blocking temperature of 56.6 K. The anisotropy constant was 6.0 × 10⁶ erg/cm³, two orders of magnitude larger than the magnetocrystalline anisotropy constant of bulk γ-Fe₂O₃. The detailed analysis of the magnetic properties indicated that the γ-Fe₂O₃ nanoparticles had a core-shell structure, consisting of a ferrimagnetic core of ∼4 nm in diameter having a collinear spin configuration and a magnetically disordered shell of ∼1.2 nm in thickness.     

Effects of ZrO2 on the structure and magnetic properties of CoPt thin films

[CoPt 1.5 ml/ZrO2 xnm]10 multilayer films were deposited on glass substrates by magnetron sputtering and then annealed in vacuum at 600℃ for 30 min. Their structures and magnetic properties were investigated as a function of ZrO2 content. The results show that the grain size and coercivity first increase and then decrease with the increase in ZrO2 content. The maximum coercivity and grain size are obtained at 37 vol.% of ZrO2. The content of ZrO2 in the film plays an important role in the separation of CoPt grains and in the reduction of intergrain exchange interaction. On the basis of the studies of angular dependent coercivity, it is found that the magnetization reversal of CoPt films with （111 ） texture is different from either the domain wall motion or the S-W type of rotation mode.     

Preparation and oxygen-sensing properties of TiO2 porous thin films on alumina substrate

The titanium dioxide sols were synthesized with tetrabutyl titanate as precursor, diethanolamine（DEA） as complexing agent , polyethylene glycol （PEG） as organic template. The porous films were prepared by sol-gel method, The structures and morphology of the titanium dioxide porous films were characterized by FE-SEM. The formation mechanism of TiO2 porous films and the relation between the porous structure and oxygen-sensing properties of TiO2 films were studied. Ordered structure was formed by assembling between TiO2 colloid particles and the template molecules. PEG molecules acted on TiO2 colloid particles by hydrogen bond and bridge oxygen. The porous structure was formed after the organic template was decomposed when calcining the films. The diameter, amount and distribution of the pores in the films are related with the content of PEG. The pore diameter increases with increasing of content of PEG and the pore density reaches the maximum at certain content. Oxygen-sensitivity and response speed of porous TiO2 films are improved compared with films without pores. Both the sensitivity and response speed increase with the increasing of pore diameter and pore density. Oxygen-sensitivity reaches 3 order of magnitude at 800 ℃. Its response time from H2/N2 to O2/N2 atmosphere and vice versa is about 0.11 s and 0.12 s respectively. Although the sensitivity and response speed increase, the resistance-temperature properties of porous films are not notably improved with the increasing of the content of PEG.     

Effect of annealing treatment on the structural, optical, and electrical properties of Al-doped ZnO thin films

Highly conductive and transparent Al-doped ZnO (AZO) thin films were prepared from a zinc target containing Al (1.5 wt.%) by direct current (DC) and radio frequency (RF) reactive magnetron sputtering. The structural, optical, and electrical properties of AZO films as-deposited and submitted to annealing treatment (at 300 and 400 ℃, respectively) were characterized using various techniques. The experimental results show that the properties of AZO thin films can be further improved by annealing treatment. The crystallinity of ZnO films improves after annealing treatment. The transmittances of the AZO thin films prepared by DC and RF reactive magnetron sputtering are up to 80% and 85% in the visible region, respectively. The electrical resistivity of AZO thin films prepared by DC reactive magnetron sputtering can be as low as tering have better structural and optical properties than that prepared by DC reactive magnetron sputtering.