Li2CO3掺杂BaTiO3无铅压电陶瓷的低温烧结

以Li2CO3作为烧结助剂,采用传统固相烧结法制备BaTiO3陶瓷。研究了烧结温度(1000~1150℃)和Li2CO3添加质量分数(0%~5%)对BaTiO3陶瓷结构和电学性能的影响。结果表明:Li2CO3的掺入有效地促进了陶瓷的烧结,使BaTiO3的烧结温度从1300℃以上降低到1050℃。X射线衍射结果表明:未掺Li2CO3的BaTiO3陶瓷样品为四方相结构,掺Li2CO3的BaTiO3陶瓷样品为正交相结构。Li2CO3掺量为1%的陶瓷样品具有较高的致密度,且在1050℃时获得最大值,其相对密度可达94%。当烧结温度为1100℃时,BaTiO3陶瓷的压电常数d33获得最大值,且d33随着Li2CO3掺量的增加而降低。其中Li2CO3掺量为1%时陶瓷具有较好的电性能:d33=200pC/N,εr=1322,TC=115℃。     

Three-point bending behavior of surface composite Al2O3/Ni on bronze substrate produced by vacuum infiltration casting

Al₂O₃/Ni surface infiltrated composite layer is a protective surface layer. It was fabricated on bronze substrate through vacuum infiltration casting technique using Ni-based powder and Al₂O₃ powder with different content as raw materials. With an appropriate choice of processing condition, a compact infiltrated layer is achievable as conformed through SEM observation. The infiltrated layer consists of surface composite layer and transition layer, and the thickness of transition layer decreases with increasing content of Al₂O₃. Metallurgical fusion formed at the interface between the surface infiltrated composite layer and substrate. Three-point bending tests were carried to investigate the mechanical and bonding properties of the surface infiltrated layer. It was found that load-holding circumstance appeared on the load–displacement curve of specimen with surface infiltrated layer comparing with that of the substrate. The peak load reduces with increasing content of Al₂O₃. The fracture extended to the substrate for specimen with Al₂O₃ content less than 20 (wt%). The fracture direction of specimen more than 30% with Al₂O₃ (wt%) is along with the interface of the surface composite and the substrate because of the thinner transition layer.     

Er~(3+)掺杂位置对Er~(3+):BaTiO_3薄膜上转换发光的影响(英文)

采用溶胶-凝胶法在LaNiO3/Si衬底上制备Er3+掺杂BaTiO3薄膜。通过XRD、AFM和PL图谱分别研究薄膜的晶体结构、形貌以及上转换发光性能。结果表明,薄膜的微观结构和发光性能与Er3+掺杂晶格的位置有关。A位掺杂薄膜较B位掺杂薄膜具有较小的晶格常数和较好的结晶。PL光谱表明:A位掺杂的薄膜和B位掺杂的薄膜都于528nm和548nm处获得较强的绿色上转换发光以及在673nm处获得较弱的红光,分别对应Er3+离子的2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2能级跃迁。相对于B位掺杂的薄膜,A位掺杂样品有较强的绿光发射积分强度以及较弱的红光发射相对强度。这种差异可以通过薄膜的结晶状况和交叉弛豫机制来进行解释。     

Influence of sintering schedule on the electrical properties of Mn（NO3）2-doped Ba0.92Ca0.08TiO3 PTCR ceramics

The relationship of electrical properties of Mn-doped Ba0.92Ca0.08TiO3 PTCR (positive temperature coefficient resistance) ceramics with two sintering schedules was discussed. Using TEM (transmission electron microscope) combined with EDS (energy dispersive X-ray spectrometer), the Mn ions distributed at grain boundaries were analyzed. The results show that the PTCR effect of Mn-doped PTCR ceramics is more dependent on the sintering schedule than those of Mn free. The phenomenon may be caused by the valence states variance of Mn ions segregated at the grain boundaries.     

碳化铬/Ni3Al复合堆焊层组织及摩擦磨损分析

采用光学显微镜、扫描电镜、电子探针及X射线衍射分析钨极氩弧堆焊碳化铬增强Ni3Al基复合堆焊层的组织结构,并采用销盘式干摩擦磨损试验机对堆焊层与活塞环用蠕墨铸铁材料的干摩擦磨损性能进行试验比较.结果表明,复合堆焊层内形成Ni3Al金属间化合物基体,其中弥散分布有大量细小的块状和条状碳化物硬质相Cr3C2和Cr7C3;焊接时焊丝中Cr3C2颗粒溶解析出,重新析出的碳化铬颗粒中包含Fe和Ni元素,碳化铬颗粒与Ni3Al基体形成良好的冶金结合;弥散分布的碳化铬颗粒和Ni3Al基体固溶强化的Cr元素决定了堆焊层具有较高的硬度.室温条件下,复合堆焊层具有优异的耐干摩擦磨损性能,其摩擦系数为0.23,远低于活塞环蠕墨铸铁的0.39;磨损率仅为蠕墨铸铁材料的43%.     

基于聚噻吩/WO_3的有机-无机复合材料低温NO_2传感器(英文)

通过化学氧化聚合法和胶溶法分别制备了聚噻吩(PTP)和纳米WO3,通过简单机械共混和PTP和WO3制备不同PTP质量分数的有机-无机PTP/WO3复合物。所制备的PTP/WO3复合物比纯的PTP具有更高的热稳定性。气敏测试结果表明,在低温检测NO2时,PTP/WO3复合物具有比纯的PTP和WO3更高的响应,这可能与PTP/WO3复合物中p-n异质节的存在有关系。PTP/WO3复合物的响应受PTP质量分数的影响显著,20%PTP/WO3复合物在低温(90°C)时对NO2显示出高的响应和好的选择性。因此,PTP/WO3传感器有望被用于低温检测NO2     

Morphology of M23C6 precipitation in L12-ordered Ni3(Al, Cr)

A transmission electron microscope investigation has been performed on the morphology of M₂₃C₆ precipitation in L1₂-ordered Ni₃(Al, Cr) containing 0.1–0.5 mol% of carbon. By aging at temperatures around 1073 K after solution annealing at 1423 K, fine octahedral-shaped precipitates of M₂₃C₆ bounded by {111} facets appear first on the dislocations and then in the matrix. The shapes of the precipitates are not always equilateral but tetragonal or elongated octahedral ones appear during aging. Planar growth faults were observed in some of the octahedral precipitates. After prolonged aging or by aging at higher temperatures, these shapes of precipitates become unstable. The M₂₃C₆ precipitates then adopt a rod-like morphology elongated parallel to the 100 directions and characterized by steps bounded by {111} facets.     

Si3N4/Ni/TiAl扩散连接接头界面结构及性能

采用厚度为80 μm的镍中间层实现了Si3N4陶瓷和TiAl合金的扩散连接.采用扫描电镜(SEM),能谱检测(EDS)等分析方法确定了TiAl/Ni/Si3N4扩散焊接头的典型界面结构为TiAl/Al5Ni2Ti3/AlNi2Ti/Ni3(Ti,Al)/Ni(s,s)+Ni3Si/Si3N4.重点分析了连接温度对接头界...     

Improvement in the properties of nickel by nano-Cr2O3 incorporation

Nano-ceramic composite coatings were prepared by the electrodeposition method using sulphamate electrolyte. Nickel was chosen as the metal matrix and nano-Cr₂O₃ particles were chosen as the reinforcement. The surface morphology and the particle distribution in the coating were analysed using field emission scanning electron microscope (FESEM). The particle content was obtained using energy dispersive X-ray analysis (EDAX). A change in the surface morphology of Ni was seen on the incorporation of Cr₂O₃ particles. The coatings were characterized for their structure and no change in the diffraction pattern was seen between plain Ni and Ni-Cr₂O₃ composite. The mechanical property like microhardness and tribological behaviour of the nano-composite coatings was studied and it was observed that the incorporation of Cr₂O₃ particles enhanced the mechanical properties of Ni matrix. The nano-composites were analysed for their thermal stability and corrosion resistance. An improvement in thermal stability was observed but no change in the corrosion behaviour of Ni was seen on the incorporation of nano chromium oxide particles.     

等离子熔凝Al2O3/GdAlO3共晶陶瓷的制备与组织

以77mol%Al2O3和23mol%Gd2O3的共晶配比混粉,以高温等离子为热源,加热粉体使其熔融,随后以空冷和水冷的不同冷却方式实现凝固,得到不同的冷凝试样。采用X射线衍射仪和场发射扫描电镜对试样的相组成和微观形貌进行表征。结果表明,采用不同冷却工艺制备的熔凝试样均具有部分连续的Al2O3/GdAlO3共晶组织,组织致密,相界面结合良好,没有气孔和杂质;与空冷试样相比,水淬试样组织得到细化,共晶间距达到0.2μm左右。     

Fe3Al合金与Q235钢扩散焊界面元素的扩散

对Fe3Al／Q235扩散焊界面附近元素的分布进行计算并通过电子探针进行测定。结果表明，界面附近Al、Fe元素分布计算值和实测值的扩散趋势一致。随着加热温度和保温时间的增加，Fe3Al／Q235扩散焊界面附近元素的扩散距离增大。Fe3Al／Q235扩散焊界面过渡区宽度与保温时间的关系符合抛物线生长规律，保温时间超过60min后界面过渡区宽度不再明显增加。     

Electrochemical properties of the MmNi3.55Mn0.4Al0.3Co0.4Fe0.35 compound

In this paper, the electrochemical properties of the MmNi_3.55Mn_0.4Al_0.3Co_0.4Fe_0.35 alloy used as a negative electrode in Ni–MH accumulators, have been investigated by different electrochemical methods such as cyclic voltammetry, chronopotentiometry, chronoamperometry and electrochemical impedance spectroscopy. The experimental results indicate that the discharge capacity reaches a maximum value of 260 mAh g⁻¹ after 12 cycles and then decreases to about 200 mAh g⁻¹ after 70 cycles. The value of the mean diffusion coefficient D_H, determined by cyclic voltammetry, is about 3.44 × 10⁻⁹ cm² s⁻¹, whereas the charge transfer coefficient , determined by the same method, is about 0.5 which allows us to conclude that the electrochemical reaction is reversible. The hydrogen diffusion coefficients in this compound, corresponding to 10 and 100% of the charge state, determined by electrochemical impedance spectroscopy, are, respectively, equal to 4.15 × 10⁻⁹ cm² s⁻¹ ( phase) and 2.15 × 10⁻⁹ cm² s⁻¹ (β phase). These values are higher, for the phase and less, for the β phase, than the mean value determined by cyclic voltammetry. We assume that this is related to the number of interstitial sites susceptible to accept the hydrogen atom, which are more numerous in the phase than in the β phase. The chronoamperometry shows that the average size of the particles involved in the electrochemical reaction is about 12 μm.     

烧结助剂Y2O3和Pr6O11对Al2O3陶瓷相对密度和热导率的影响

采用高分子网络法制备混合纳米粉体,研究稀土氧化物Y2O3和Pr6O11加入量对Al2O3陶瓷相对密度和热导率的影响。采用阿基米德方法测定样品的体积密度,利用激光脉冲法测量试样的热扩散率并计算得出热导率。结果表明:两种添加剂都可以降低Al2O3陶瓷的烧结温度,提高Al2O3陶瓷的热导率,其中Y2O3的促进作用较强;当保温时间相同、烧结温度为1 500~1 650℃时,Al2O3陶瓷的相对密度和热导率都随烧结温度的升高而增大;当烧结温度相同、保温时间为30~120 min时,Al2O3陶瓷的相对密度和热导率也随保温时间的延长而增大。     

MoSi2—Mo5Si3复合材料的低温氧化行为

通过热重分析（TGA）、X射线衍射（XRD）和扫描电镜（SEM）研究了MoSi2-Mo5Si3复合材料的低温氧化行为,指出材料低温氧化时,随Mo5Si3量增多,材料氧化加剧,当Mo5Si3含量超过16％（质量分数）时发生“PEST”现象,所形成的SiO2由于MoS3晶须的大量存在,使其不能均匀连续地分布于材料表面,从而加剧了氧化。     

Investigation on the corrosion and oxidation resistance of Ni-Al2O3 nano-composite coatings prepared by sediment co-deposition

Ni-Al₂O₃ composite coatings were prepared by using sediment co-deposition (SCD) technique from a Watt's type electrolyte containing nano-Al₂O₃ particles. The corrosion resistance and high temperature oxidation resistance of resulting composite coatings were investigated. It was found that the incorporation of nano-Al₂O₃ particles in Ni matrix refined the Ni crystal and changed the preferential orientation of composite coatings. Meanwhile, the corrosion and oxidation resistance were improved after the incorporation of nano-Al₂O₃ particles into Ni matrix. The nano-Al₂O₃ content in deposits plays an important role for improving the corrosion and oxidation protection. The corrosion and oxidation resistance of Ni-Al₂O₃ nano-composite coatings produced via SCD technique are superior to that of CEP technique. Compared to pure Ni and Ni-Al₂O₃ composite coatings fabricated using CEP technique, the Ni-7.58 wt.% Al₂O₃ composite coating obtained by SCD technique exhibits better corrosion resistance and enhanced high temperature oxidation resistance. Moreover, the mechanism of corrosion and high temperature oxidation resistance of Ni-Al₂O₃ nano-composite coatings are discussed.     

橙红色荧光粉YPO4:Gd3+,Eu3+的制备及发光特性

采用高温固相法在1100℃下合成了橙红色荧光粉YPO₄:Gd₃₊,Eu₃₊,研究了Eu₃₊离子掺杂浓度、碱金属碳酸盐、助熔剂、敏化剂对荧光粉发光性能的影响。XRD检测结果显示：合成荧光粉为单相的YPO₄。Eu₃₊离子较佳掺杂浓度为2.5%,碱金属碳酸盐 Na₂CO₃能有效提高荧光粉的发光强度。添加助熔剂NH₄F可将荧光粉的煅烧合成温度从1100℃降低到800℃,并可促进发光中心进入晶格。Gd₃₊离子能将吸收的激发能有效传递给发光中心Eu₃₊离子,提高荧光粉的发光强度。色坐标分析显示,合成YPO₄:0.025Eu₃₊荧光粉色坐标为(0.61,0.39) ,位于橙红光的色坐标范围内。     

原位合成Cr7C3激光熔覆陶瓷涂层的显微组织及腐蚀性能

采用激光熔覆技术在Q235钢表面原位合成了Cr7C3陶瓷熔覆层,并采用光学显微镜、X射线衍射仪、扫描电子显微镜及静态浸泡法结合极化曲线分析,对熔覆层的显微组织及耐腐蚀性能进行研究。结果表明,熔覆层表面平整、无裂纹、无孔洞且与基体呈冶金结合,陶瓷Cr7C3形状多为条状和块状;熔覆层腐蚀电流密度约为基材的1/2,表明其具有良好的耐腐蚀性能。     

氧化铝掺杂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3陶瓷介电性能的影响

Zr4+取代Ti4+的Ba0.6Sr0.4(Zr0.2Ti0.8)O3固溶体在降低介电常数的同时,保持了BST固溶体优异的可调性。为降低BST材料的介电损耗和介电常数,以氧化铝为改性剂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3材料(BSZT材料)进行了掺杂。随着氧化铝掺杂质量分数从1%到10%增加,BSZT材料的介电常数从5000降低到了1550(100kHz),介电损耗降低到0.001(100kHz)以下,而材料的介电可调性保持在35%左右(1.5kV/mm)。X射线衍射图谱表明,烧结后得到的BSZT材料具有典型的钙钛矿结构。扫描电子显微镜观察表明,氧化铝的掺杂使得陶瓷致密度较高,晶粒均匀。     

一种可内生Al2O3扩散障的δ-Ni2Al3-Cr2O3/ Ni-Cr2O3涂层体系

通过对Ni-Cr₂O₃复合镀层620 ℃部分渗铝制备了δ-Ni₂Al₃-Cr₂O₃/Ni-Cr₂O₃涂层体系。Cr₂O₃颗粒在渗铝的过程中和Al反应生成更为稳定的Al₂O₃。1000 ℃恒温氧化20 h后发现,铝化物涂层和复合镀层内掺杂的Cr₂O₃颗粒完全转化为Al₂O₃,并在铝化物涂层/Ni镀层界面自发形成了一层Al₂O₃富集层,该富集层起扩散障作用,阻碍铝化物涂层因互扩散所致的退化。     

Kinetic Monte Carlo simulation of growth of BaTiO3 thin film via pulsed laser deposition

Considering the characteristics of perovskite structure, a kinetic Monte Carlo（KMC） model, in which Born-Mayer- Huggins（BMH） potential was introduced to calculate the interatomic interactions and the bonding ratio was defined to reflect the crystallinity, was developed to simulate the growth of BaTiO3 thin film via pulsed laser deposition（PLD）. Not only the atoms deposition and adatoms diffusion, but also the bonding of adatoms were considered distinguishing with the traditional algorithm. The effects of substrate temperature, laser pulse repetition rate and incident kinetic energy on BaTiO3 thin film growth were investigated at submonolayer regime. The results show that the island density decreases and the bonding ratio increases with the increase of substrate temperature from 700 to 850 K. With the laser pulse repetition rate increasing, the island density decreases while the bonding ratio increases. With the incident kinetic energy increasing, the island density decreases except 6.2 eV〈Ek〈9.6 eV, and the bonding ratio increases at Ek〈9.6 eV. The simulation results were discussed compared with the previous experimental results.