La2O3、Y2O3掺杂对(Na0.5Bi0.5)0.94Ba0.06TiO3无铅压电陶瓷性能的影响

以(Na0.5Bi0.5)0.94Ba0.06TiO3为基体,研究了单、双组分掺杂La2O3、Y2O3对BNBT6陶瓷的压电和介电性能及微观结构的影响。XRD分析表明:掺杂La2O3、Y2O3均得到钙钛矿结构。SEM分析表明,分别掺杂0.2%La2O3和0.2%Y2O3使得陶瓷晶粒增大,压电常数提高,双组分掺杂La2O3、Y2O3在掺杂量0.12%La2O3+0.08%Y2O3时,压电常数d33增大到最大值144.6×10-12C/N,介质损耗降低到最小值0.039。     

CO在SrO表面吸附的热脱附

在真空条件下,利用程序升温热脱附方法测量CO吸附在SrO表面的脱附谱.实验结果表明,SrO吸附C^18O后,在升温过程中可通过氧的同位素交换生成C^16O而脱附,同时伴随少量C^18O的直接脱附,其波峰温度分别为430 K和420 K,属于二级脱附过程.     

Luminescent properties of ZrO2:Tb nanoparticles for applications in neuroscience

In this paper a new generation of non-toxic nanoparticles based on the zirconium oxide doped with 0.5%Tb and co-doped by the range of 0–70% with Y was evaluated for the use as a fluorescent biomarker of neuronal trafficking. The ZrO₂:Tb nanoparticles were created by microwave driven hydrothermal method. Influence of the yttrium content and thermal processing on the Tb³⁺ related luminescence emission was discussed. The higher intensities were achieved, when host was cubic and for the nanoparticles with 33 nm. Presence of yttrium was associated with the energy coupling of the host and dopant, wide excitation band is present at 309 and 322 nm before and after calcination respectively.For the experiment on living primary neurons, nanoparticles doped with 0.5%Tb and 7%Y were chosen based on their luminescence emission intensity. Recently transfer of the nanoparticles through the barriers in the organism including blood–brain barrier following their alimentary absorption was confirmed (Godlewski and Godlewski, 2012). This raised the possibility of the nanoparticle application as a tool in the neuroscience, and the question of potential mechanisms of nanoparticle turnover in neurons. Concentration of 0.001 mg/ml of ZrO₂:0.5%Tb 7%Y in growth medium was added to the primary murine culture medium, and the intracellular trafficking of nanoparticles was observed following 15 min pre-incubation period. ZrO₂:0.5%Tb 7%Y nanoparticles were dynamically absorbed by the neurons and the dynamic passage of transport vesicles containing ZrO₂:0.5%Tb 7%Y nanoparticles was observed along the neuronal processes and in between two neighbouring neurons. Reassuming, the ZrO₂:0.5%Tb 7%Y nanoparticles proved to be biocompatible and a valid tool to assess intracellular trafficking dynamics in the neurobiology.     

主链含苯基均三嗪联苯型聚芳醚的热稳定性

利用热重分析(TG、DTG)研究了主链含苯基均三嗪联苯型聚芳醚在不同气氛和升温速率时的热降解动力学。比较了升温速率和气体气氛对热降解行为的影响,结果表明,该聚合物具有优异的耐热性和耐热氧化稳定性。用Flynn-Wall-Ozawa,Freeman-carroll等方法进行了动力学处理,计算得热降解反应活化能分别为291.19kJ/mol,286.83kJ/mol,与Kissinger法计算活化能值283.25kJ/mol非常接近。结合Coats-Redfern方法,推测出聚合物在氮气气氛中的热分解机理为F2机理,其机理函数积分式为g(α)=1/(1-α)。     

Cobalt basic salts as inorganic precursors of cobalt oxides and cobalt metal: Thermal behaviour dependence on experimental conditions

The influence of heating rates and environment conditions on the thermal behaviour of two cobalt basic salts,-Co₂(OH)₃Cl and Co₅(OH)_8.5Cl_1.5 · 2.5H₂O, have been studied. The processes were followed using thermogravimetric and differential thermal analysis, X-ray diffraction, and infrared spectroscopy. When decomposition reactions are carried out in a nitrogen atmosphere, Co₃O₄ is always formed in quantities that seem to depend on the heating rates. When decomposition processes are carried out in an X-ray high-temperature diffraction chamber, pure cobalt is obtained at 750° C as the final product. Green cobalt hydroxychloride, the composition of which determined from chemical analysis seems to correspond to the formula Co₅(OH)_8.5Cl_1.5 · 2.5H₂O or alternatively 4Co(OH)₂. CoCl_1.5(OH)_0.5 · 2.5H₂O, has been isolated as a stable compound and the evolution of this material during the ageing process has been followed by X-ray diffraction, electron microscopy and BET surface-area determination.     

基于儿童认知发展的学龄前儿童APP界面交互设计研究

目的基于3～6岁学龄前儿童认知发展的生理特点与心理特点,探讨学龄前儿童APP的界面交互设计原则,旨在为此类界面交互设计提出方法论指导,从而使学龄前儿童的综合学习能力得到更好的发展。方法通过对国内外学龄前儿童APP界面交互设计理论的归纳整理与优秀APP案例的比较研究,运用学龄前儿童的视觉、听觉、触觉和运动觉的认知发展,结合皮亚杰的认知理论及儿童认知发展心理学的相关理论研究,总结出优秀的学龄前儿童APP设计策略的五个方面,并将其应用于项目实践。结论通过具体案例的设计实践,在APP界面交互设计中初步验证了关于学龄前儿童的认知发展研究的适用性,提出符合儿童认知发展特征的设计策略,满足儿童在线学习的荣誉感和成就感,从而助推学龄前儿童在线学习的积极性和注意力。     

Formation of nano-sized Y2O3 dispersoids in mechanically alloyed Ni-(Cr, Y2O3, Y) alloys during heat-treatments

In the present work, the evolution of nanoparticles during annealing and hot-consolidation in mechanically alloyed Ni-22Cr-1.5Y, Ni-22Cr-1.5Y2O3 and Ni-3% Y2O3 was examined. The high-energy ball-milling of elemental powders resulted in the complete dissolution of the constituent Cr, Y, or Y2O3, forming a Ni-based solid solution. During the subsequent annealing, however, oxide particles precipitated from the solid solution. In the case of mechanically alloyed Ni-22Cr-1.5Y2O3, over-grown Cr2O3 precipitated at a temperature as low as above approximately 500 degrees C and ternary YCrO3 particles precipitated at 1100 degrees C. In the case of mechanically alloyed Ni-22Cr-1.5Y, on the other hand, the binary Y2O3 phase precipitated at 1100 degrees C during spark plasma sintering. The presence of Cr in the alloy composition facilitated the formation of Cr2O3 or YCrO3, and the precipitated oxides were highly prone to grain growth during hot-consolidation, sometimes reaching several micrometers. In Cr-exempt Ni-3%Y or Ni-3% Y2O3, however, the growth of nanodispersoids was restrained even at temperatures as high as 1000 degrees C and the resulting dispersoid was only nano-sized Y2O3.     

Nanoengineering Natural Leather for Dynamic Thermal Management and Electromagnetic Interference Shielding

Unpredictable and extreme weather conditions, along with increasing electromagnetic pollution, have resulted in a significant threat to human health and productivity, causing irreversible damage to society's well-being and economy. However, existing personal temperature management and electromagnetic protection materials lack adaptability to dynamic environmental changes. To address this, a unique asymmetric bilayer leather/a-MWCNTs/CA fabric is developed by vacuum-infiltrating interconnected a-MWCNTs networks into natural leather's microfiber backbone and spraying porous acetic acid (CA) on the reverse side. Such fabric achieves simultaneous passive radiation cooling, heating, and anti-electromagnetic interference functions without external energy input. The fabric's cooling layer has high solar reflectance (92.0%) and high infrared emissivity (90.2%), providing an average subambient radiation cooling effect of 10 °C, while the heating layer has high solar absorption (98.0%), enabling excellent passive radiative heating and effective compensation for warming via Joule heating. Additionally, the fabric's 3D conductive a-MWCNTs network provides electromagnetic interference shielding effectiveness of 35.0 dB mainly through electromagnetic wave absorption. This multimode electromagnetic shielding fabric can switch between cooling and heating modes to adapt to dynamic cooling and heating scenarios, providing a new avenue for sustainable temperature management and electromagnetic protection applications.     

Preparation and Thermal Transformations of a Hydrous Cadmium Diphosphate Ammine Complex

A solid hydrous cadmium diphosphate ammine complex of composition Cd₂P₂O₇ · 3.0NH₃ · 4.5H₂O is prepared, and its thermal transformations during constant-rate and quasi-isothermal heating are studied using chemical analysis, paper chromatography, and x-ray diffraction. The results are used to establish the mechanisms of the transformations.     

Thermal expansion study of plasma-sprayed oxide coatings

The thermal expansion characteristics of overlay coatings is of considerable importance when the coated parts are exposed to thermal cycling. In this study we investigated the thermal cycling behavior of oxide coatings plasma sprayed onto mild steel. Thermal expansion measurements were carried out on Al₂O₃TiO₂ and zirconia coatings under different conditions of coating-substrate adherence and on coatings that were substrate free. A study was initiated of the effects on the expansion coefficient of variations in composition, porosity, heating rate and thermal cycling. In addition, metallographic and acoustic emission methods were employed to examine the compatibility of these oxide coatings with steel substrates under varying conditions.     

Analytic Thermal Modeling for dc-to-Midrange Modulation Frequency Responses of Thin-Film High- T c Superconductive Edge-Transition Bolometers

Thin-film superconductive edge-transition bolometers are modeled with a one-dimensional analytic thermal model with joule heating, film and substrate materials, and the physical interface effects taken into consideration. The results from the model agree well with the experimental results of samples made of large-meander-line Yba(2)Cu(3)O(7-x) films on crystalline SrTiO(3), LaAlO(3), and MgO substrates up to 100 kHz, the limits of the experimental setup. Compared with the results of the SrTiO(3) substrate samples, the results from the model of the LaAlO(3) and the MgO substrate samples deviate slightly from the measured values at very low modulation frequencies (below ~10 Hz). The deviation increases for higher thermal-conductive substrate materials. When the model was used, the substrate absorption and the thermal parameters of the devices could also be investigated.     

Joining of Zirconia and Ti-6Al-4V Using a Ti-based Amorphous Filler

Polycrystalline ZrO2-3 mol.%Y2O3 was brazed to Ti-6Al-4V by using a Ti47Zr28Cu14Ni11(at.%) amorphous ribbon at 1123-1273 K in a high vacuum. The influences of brazing temperature on the microstructure and shear strength of the joints were investigated. The interfacial microstructures can be described as ZrO2/TiO+TiO2+Cu2Ti4O+Ni2Ti4O/α-Ti+(Ti,Zr)2(Cu,Ni) eutectic/acicular Widmanst¨aten structure/Ti-6Al-4V alloy. With the increase in the brazing temperature, the thickness of the TiO+TiO2+Cu2Ti4O+Ni2Ti4O layer reduced, the content of the α-Ti+(Ti,Zr)2(Cu,Ni) eutectic phase decreased, while that of the coarse α-Ti phase gradually increased. The shear strength of the joints did not show a close relationship with the thickness of the TiO+TiO2+Cu2Ti4O+Ni2Ti4O layer. However, when the coarse (Ti,Zr)2(Cu,Ni) phase was non-uniformly distributed in the α-Ti phase, or when α-Ti solely situated at the center of the joint, forming a coarse block or even connecting into a continuous strip, the shear strength greatly decreased.     

Thermal decomposition of acetic anhydride-nitric acid mixtures

The adoption of Ac2O/HNO3 mixtures for the nitration of organics or the preparation of nitric esters is not free from some risks of explosion. The behaviour of these mixtures at varying Ac2O/HNO3 molar ratios is studied by means of adiabatic and scanning calorimetry. A simplified kinetic model, based on two lumped reactions (one of which leads to the formation of tetranitromethane) is developed to simulate the thermal decomposition of the investigated system under adiabatic conditions. The use of this model allows satisfactory prediction of the temperature profiles in the reactor whereas calculated pressures are generally overestimated due to some model inadequacies to account for the absorption of gaseous decomposition products into the reacting solution.     

氦注入铝的热解吸谱

用氦热解吸谱(THDS)研究了10keV,4.0×1017cm-2剂量He+辐照(200)择优取向Al的氦热解吸行为及其与升温速率的关系。结果显示,He解吸开始于270℃附近,THDS中无干扰峰存在。He解吸行为与升温速率密切相关,其解吸峰个数及峰位随升温速率的变化而改变,且不遵循通常的一级化学反应模型,而可能是多级或一级与多级化学反应的混合模型。     

Specific Heat and Thermal Transport Measurements of Reactive Metallic Alloys by Noncontact Calorimetry in Reduced Gravity

Experimental concepts, application, and recent results of noncontact calorimetry inculding ac-specific heat and thermal transport property measurement of reactive metallic specimens are described. The method is based on induction heating in an electromagnetic levitation device. Experiments have been performed in reduced gravity onboard Spacelab. A heat flow model is discussed regarding conditions for precise specific heat determination from the temperature response to modulated heating power input as well as determination of thermal transport properties from the transient temperature response. Modulation techniques were developed for application in the metastable regime of the undercooled melt, where processing time is a critical issue. Results to be discussed include the total hemispherical emissivity of a bulk metallic glass-forming alloy revealing effects of surface segregation, thermal conductivity measurements, and application of ac calorimetry in the two-phase region.     

微波合成锂离子电池正极材料LiCoO2的研究

为了研究锂离子电池的正极材料LiCoO2的新型制备方法,考查了反应原料配比、微波输出功率、微波合成温度和微波加热时间对LiCoO2结构和性能的影响.以LiOH·H2O和Co2O3为反应原料的最佳合成条件:Li/Co摩尔比为1.05∶1,微波输出功率为360W,反应时间为14min,合成温度为800℃.所合成LiCoO2样品均采用XRD和SEM进行表征,结果表明,采用微波合成的LiCoO2样品为单一相层状结构且晶体结构发育良好;样品的充放电循环性能良好,首次循环放电容量为130mAh/g.     

A Method for Thermal Diffusivity Determination of Thermal Insulators

A so-called “three-point” (3P) method has been developed for thermal diffusivity measurements of thermal insulating materials. One side of a cylindrical specimen, sandwiched between two thin metal plates, is subjected to intense light from an incandescent lamp to generate a thermal perturbance. The temperature response is measured in three locations along the test specimen. Thermocouples are located at the front and rear faces of the specimen, and the third is placed inside the specimen at a known location. The two outside temperatures are used as boundary conditions, and the unknown thermal diffusivity is calculated from the third temperature versus time curve. The method combines the advantages of rapid transient non-contact heating methods with the well-defined boundary conditions of steady-state methods. The results of the 3P method are compared with those from steady-state methods for a micro-porous insulation material and for a honeycomb structure.     

Thermal expansion of composites

Coefficient of thermal expansion (CTE) has been determined for selected composite materials using differential thermal analysis. Variables evaluated were: type of material, with particular emphasis on filler content; annealing; thermal history, with particular attention being payed to the effects of multiple heating and cooling cycles; ageing in wet or dry conditions. Filler content was a major factor involved in controlling CTE, although clearly other factors such as the type of filler, resin and degree of conversion are important. For an inlay material, annealing at 120°C significantly reduced the value of coefficient of thermal expansion and this is most likely due to an increase in conversion of methacrylate groups. The findings of this study confirm those of previous studies regarding the reduction in CTE following an initial heating. This is most likely due to the relief of internal stress. New information reported here relates to the fact that stress release can occur slowly without heating and that rapid stress release can be achieved through water storage at mouth temperature. These results suggest that, clinically, internal stresses induced by polymerization will be dissipated rapidly. A further finding was that long-term water storage causes an increase in CTE, which may reflect changes at the resin-filler interface.     

Thermal Stability of Fe2O3 Nanowires

The thermal stability of α-Fe203 and γ-Fe2O3 nanowires was studied by post annealing the samples at different temperatures. Before and after annealing, the samples were characterized by X-ray diffraction and scanning electron microscopy. The α-Fe2O3 nanowires are stable at the temperatures up to 600℃, and the crystalline structure becomes more perfect after annealing. This behavior supplies a way to improve the quality of the α-Fe2O3 nanowires. The γ-Fe2O3 nanowires become unstable when annealed at 350℃. Raman spectra of both nanowires have been measured, which also indicate that the γ-Fe203 nanowires are transformed into α-Fe2O3 under the strong laser beam.     

采用旋转镀膜技术的溶液沉积法合成的LiMn2O4薄膜形貌与合成条件之间的关系研究

通过旋转镀膜技术的溶液沉积法制备LiMn2O4薄膜,详细讨论了影响LiMn2O4薄膜形貌的各种因素.研究表明前驱体溶液溶剂、溶液浓度、匀胶速度、升温速度以及加热分解温度和时间等对薄膜形貌有重大影响.实验表明LiMn2O4前驱体溶液浓度为0.2mol/L,匀胶速度为3000r/min,匀胶时间为30s,加热分解温度350℃,加热分解时间20min,升温速度为10℃/min为较为理想的一组合成条件.