Dy2O3掺杂对(Ba,Sr)TiO3基高压电容器陶瓷性能的影响

研究了(Ba,Sr)TiO3基电容器陶瓷中掺杂稀土氧化物Dy2O3对材料介电性能的影响,得到了Dy2O3影响其性能的规律,即随着Dy2O3加入量的增加材料的介电常数开始增大随后减少,当W(Dy2O3)=0.5%时介电常数最大,而介质损耗逐渐减少.得到了介电常数为5245,介质损耗为0.0026,耐压为5.5kV/mm的高压低损耗陶瓷电容器瓷料.探讨了Dy2O3掺杂改性的机理.这些结果为Dy2O3掺杂改性电容器陶瓷提供依据.     

Dy2O3掺杂（Ba，Sr）TiO3基电容器陶瓷的研究

采用单因素变量法研究了(B a,S r)T iO3基电容器陶瓷中掺杂稀土氧化物D y2O3对材料介电性能的影响,得到了D y2O3影响其性能的规律,即随着D y2O3加入量的增加材料的介电常数开始增大随后减少,当W(D y2O3)=0.5%时介电常数最大,而介质损耗逐渐减少。得到了介电常数为5245,介质损耗为0.0026,耐压为5.5kV/mm的高压低损耗陶瓷电容器瓷料。利用SEM分析了不同D y2O3加入量样品的表面形貌。结果表明:D y2O3有强烈的偏析晶界、抑制晶粒生长和细晶、形成固溶体等来影响BST性能。这些结果为D y2O3掺杂改性(B a,S r)T iO3基电容器陶瓷提供依据。     

工业化(Ba,Sr,Ca)(Ti,Zr)O3基电容器陶瓷的研究

采用正交设计试验研究了配方对（Ba,Sr,Ca)(Ti,Zr)O3（BSCTZ）基电容器陶瓷介电性能的影响，得到了影响BSCTZ基陶瓷介电性能的主次因素，各因素水平影响基性能的趋势，同时得到了介电常数最大的配方和介质损耗最小的配方，在实验过程中晶相料均是工业纯，这样极大降低电容器陶瓷制造成本，通过正交设计实验得到综合性能佳的BSCTZ基陶瓷，利用SEM研究了BSCTZ陶瓷的显微结构，探讨了各组分对BSCTZ基陶瓷介电性能影响机理，为研制高介，低损耗，高耐压电容器陶瓷提供了依据。     

BaO-Nd2O3-PbO-TiO2微波介质陶瓷的研制

本文介绍了BaO－Nd2O3－PbO－TiO2微波介质陶瓷的研制结果,εr＝90,Q＝2000（2GHz）,τf＝0ppn／℃。此材料有一非常高的介电常数,它适用于频率小于1GHz的应用。另外,我们对此材料作了电镜和X衍射等结构分析,证明此材料生晶相为（Ba、Pb）Nd2Ti5O14。     

镧掺杂量对Pb(1-2x/3)Lax(Ti0.99Mn0.01)O3压电陶瓷性能的影响

采用固相烧结法制备了Pb(1-2x/3)Lax(Ti0.99 Mn0.01)O3压电陶瓷,研究了镧掺杂量(x=0.005,0.045,0.075,0.150,物质的量分数)对压电陶瓷晶格常数、压电各向异性、介电常数、介电损耗、居里温度以及机械品质因数的影响.结果表明:随着镧掺杂量增加,压电陶瓷晶格的轴向比(c/a)减小,各向异性和四方相结构减弱,介电损耗减小,机械品质因数增大;镧的掺杂有利于压电性能的改善,但会造成压电各向异性减弱,居里温度降低,介电常数增大.     

掺杂CuO的（1-x）Ca0.61Nd0.26TiO3+xNd(Mg1/2Ti（1/2）)O3复合陶瓷的微波介电性能

采用固相合成法制备了掺杂CuO的(1-x)Ca0.61Nd0.26TiO3+xNd(Mg1/2Ti1/2)O3微波介质复合陶瓷材料,研究了不同成分复合陶瓷烧结后的密度、微观结构以及介电性能的变化规律。结果表明:随着x值的增大,复合陶瓷的介电常数呈下降趋势,Q.f值逐渐升高,谐振频率温度系数由正变为负,且在0.3相似文献   

V2O5掺杂对ZnNb2O6介质陶瓷性能的影响

采用传统的固相反应法制备了V2O5掺杂ZnNb2O6介质陶瓷,借助XRD、SEM和LCR测试仪等研究了陶瓷的烧结特性及介电性能.结果表明V2O5掺杂能有效地降低ZnNb2O6陶瓷的烧结温度,提高介电常数,改善频率温度系数,但介电损耗有所增加.经1050℃烧结,1.0%V2O5掺杂的ZnNb2O6陶瓷具有较好的介电性能,εr=28,tanδ=0.000 6,τf=-42.50×10-6℃-1.     

反应烧结制备AlON-AlN复相陶瓷及其性能

以AlN和Al2O3为原料、Y2O3为烧结助剂,在氮气气氛下无压反应烧结制备了AlON-AlN复相陶瓷;用XRD及SEM等方法对复相陶瓷的物相组成和显微结构进行了表征;研究了烧结温度、Al2O3及Y2O3加入量对复相陶瓷的烧结性能、力学性能和热导率的影响。结果表明:在1 650~1 800℃范围内反应烧结可以得到AlON-AlN复相陶瓷;其抗弯强度和热导率均随着烧结温度的升高先增大后减小,分别在1 750℃与1 700℃时达到最大值(378 MPa,38 W.m-1.K-1);随着Al2O3加入量的增加,复相陶瓷的抗弯强度先增大后减小,当Al2O3加入量为30%时达到最大值,其热导率则随着Al2O3加入量的增加呈明显下降趋势;随着Y2O3加入量的增加,抗弯强度不断增大,而热导率则先增大后减小,在Y2O3加入量为3%时达到最大值41 W.m-1.K-1。     

闭式谐振腔法微波介质陶瓷介电常数测量

采用一种封闭式的圆柱形微波谐振腔,实现了微波介质陶瓷材料以及其他中低损耗材料介电常数的准确测量,通过模式匹配技术实现了介质加载条件下腔内电磁场问题的精确求解,得到了腔体谐振频率与材料介电性能之间的精确关系,对各类典型介质材料的测量结果以及多家比对数据表明,相比于传统方法,该方法的测量准确度更高,可达到0.1%;测量范围更宽,不仅能准确测量高介电常数的微波介质陶瓷,也适用于低介电常数的交联聚苯乙烯、聚四氟乙烯等材料,此外由于闭式腔不存在辐射损耗,金属表面电流损耗也较小,对低损耗材料的Q值测量更加准确,损耗角测量下限达10~(-6)以下。该方法适用于介电常数εr=1~100及以上,损耗角正切tanσ=1×10~(-3)~1×10~(-6)范围内各种材料介电性能的准确测量。     

ZrO_2-Al_2O_3质陶瓷轧辊材料性能的研究

以氧氯化锆、氯化钇和氯化铝为原料，采用化学共沉淀法制备高纯超细的ZrO2-Al2O3微粉。选用无压烧结制出ZrO2-Al2O3陶瓷。分析了Al2O3掺杂量对ZrO2陶瓷的抗弯强度、断裂韧性、维氏硬度和弹性模量等性能的影响。     

Rosen-type Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal piezoelectric transformer

In this study, a Rosen-type Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) single crystal piezoelectric transformer is presented. First, we simulate the operation of this transformer using the finite element method and ANSYS. By adjusting the dimensions of the piezoelectric transformer, a maximum voltage step-up ratio of 138 can be obtained at a frequency of 33.8 kHz when the output part is open. Second, we fabricate a transformer with the size of 20 mm length, 4 mm width, and 1 mm thickness to examine the simulation results. It is found that this transformer exhibits a maximum voltage step-up ratio of 134 at 37 kHz, with the efficiency over 95% when driving a liquid crystal display backlight, which shows good consistency with the numerical simulation results. Besides, we investigate the electrical properties under different frequencies and load resistances. When the input voltage increases, a maximum output power of 1 W is obtained with the temperature rise less than 10 degrees C.     

新型3-PCRNS球面3自由度并联机构

提出一种新型3-PCRNS球面3自由度并联机构,其分支运动链由一个带环形导轨的移动副PC,一个转动副RN (下标N表示三个分支中转动副的轴线都交于一点)和一个球铰S构成。运用约束螺旋理论,对该机构的自由度、奇异位形和输入选取进行分析。在一般非奇异位形下,该机构中三个PCRNS分支运动链对动平台施加三个汇交于机构中心点的约束力,约束机构动平台的3移动自由度,机构具有3转动自由度;在奇异位形下,三个PCRNS分支对动平台施加六个线性相关的约束力,其最大线性无关数为五,机构具有一个绕z轴的瞬时转动自由度。可选用带环形导轨的移动副PC作为主动副,此外该机构动平台绕z轴的转动自由度和其他转动自由度解耦。     

3DXpert金属3D打印斯特林发动机模型

宾夕法尼亚州立大学是世界领先的从事增材制造研究和教育的高等院校之一,拥有很有特色的增材制造与设计工程硕士(MEng AMD)项目。该项目的特色之一是它不仅招收全日制学生,还招收在职工程师,这些工程师可以用宾夕法尼亚州立大学世界校区(网络虚拟校区)在线完成学习。为帮助学生成为技术专家,将其所学的增材制造知识用于实践,该项目将多学科理论知识与亲身实践相结合,学生们可在宾夕法尼亚州立大学增材制造车间获得实践经验。     

Structural properties of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 relaxor ferroelectric thin films on SrRuO3 conducting oxides

Coating of 0.65Pb(Mg(1/3)Nb(2/3))O(3)-0.35PbTiO(3) (PMN-PT) relaxor ferroelectrics by a sol-gel method is followed by growth of epitaxial SrRuO(3) (SRO) metallic oxide electrodes on SrTiO(3) (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN-PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN-PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed.     

并联双三角机构精度分析

并联双三角机构是Stewart平台的一种特殊型式。由于其结构的特点 ,直接精确测量该机构的结构误差有一定困难。文中采用一种有效的误差正解分析方法 ,分析包含球铰、驱动杆长在内的全部结构参数误差以及平台半径的变化对主轴端位姿误差的影响。应用这种误差正解方法可定量地确定结构参数设计精度 ,并能找出特定位姿下的敏感结构参数。为这类并联机器人的设计、制造及装配提供了一种有效的途径     

O.9Pb(Mg1/3Nb2/3)O3-O.1PbTiO3功能铁电薄膜的制备及其电性能研究

利用溶胶凝胶(sol-gel)技术制备Pb(Mg1/3Nb2/3)O3-PbTiO3(PMNT)铁电薄膜,研究了不同的溶剂对溶胶的配制和溶胶稳定性的影响,得到了可以长期稳定放置的溶胶;采用热重分析和差热分析的方法研究了凝胶的热解过程,确定了420℃为溶胶的热解温度,750℃为合理的结晶温度;以Pt/Ti/Si(100)为衬底,成功地制备了0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3铁电薄膜.通过X射线衍射分析了热处理温度对薄膜相的影响.通过高倍显微镜研究了薄膜的表面形态,通过ZT-Ⅱ型铁电参数测试仪对PMNT薄膜进行了铁电性能测试.测试结果表明,制备的PMNT铁电薄膜为具有完全钙钛矿相的弛豫性PMNT铁电薄膜,薄膜无裂纹,致密性好,其剩余极化和矫顽场分别可达到2.5μC/cm2和45kV/cm.     

Evidence of multimicrometric coherent γ′ precipitates in a hot‐forged γ–γ′ nickel‐based superalloy

This paper demonstrates the existence of large γ’ precipitates (several micrometres in diameter) that are coherent with their surrounding matrix grain in a commercial γ–γ’ nickel‐based superalloy. The use of combined energy dispersive X‐ray spectrometry and electron backscattered diffraction (EBSD) analyses allowed for revealing that surprising feature, which was then confirmed by transmission electron microscopy (TEM). Coherency for such large second‐phase particles is supported by a very low crystal lattice misfit between the two phases, which was confirmed thanks to X‐ray diffractograms and TEM selected area electron diffraction patterns. Dynamic recrystallization of polycrystalline γ–γ’ nickel‐based superalloys has been extensively studied in terms of mechanisms and kinetics. As in many materials with low stacking fault energy, under forging conditions, the main softening mechanism is discontinuous dynamic recrystallization. This mechanism occurs with preferential nucleation on the grain boundaries of the deformed matrix. The latter is then being consumed by the growth of the newly formed grains of low energy and by nucleation that keeps generating new grains. In the case of sub‐solvus forging, large γ’ particles usually pin the migrating boundaries and thus limit grain growth to a size which is determined by the distribution of second‐phase particles, in good agreement with the Smith–Zener model. Under particular circumstances, the driving force associated with the difference in stored energy between the growing grains and the matrix can be large enough that the pinning forces can be overcome, and some grains can then reach much larger grain sizes. In the latter exceptional case, some intragranular primary γ’ particles can be observed, although they are almost exclusively located on grain boundaries and triple junctions otherwise. In both cases, primary precipitates have no special orientation relationship with the surrounding matrix grain(s). This paper demonstrates the existence of high fractions of large γ’ precipitate (several micrometres in diameter) that are coherent with their surrounding matrix grain, in a commercial γ–γ’ nickel‐based superalloy. Such a configuration is very surprising, because there is apparently no reason for the coherency of such particles.     

Molecular dynamics simulation of dislocation nucleation and motion at γ/γ′ interface in Ni-based superalloy

Molecular dynamics simulations are conducted on the dislocation behavior at the apices and edges of cuboidal Ni₃Al precipitate in a pure Ni matrix, or the idealized γ/γ′ microstructure in a Ni-based superalloy. A tensile simulation of the [001] direction is implemented with a periodic cell that has eight cubic precipitates in order to investigate the nucleation site of dislocation in the idealized microstructure with no defects other than the γ/γ′ interfaces. The effect of residual internal stresses on the stability of the interfaces is also discussed. Other simulations are conducted on the behavior of edge dislocations nucleated from a free surface and proceeding in the γ matrix toward γ′ precipitates under shear force. Dislocation pinning at γ′ precipitates, bowing-out in the γ channel, pile-up and nucleation of superdislocation in the γ′ precipitate are simulated and inspected in detail. Discussions on the size of the γ/γ′ microstructure and the sharpness of the edge of the γ′ precipitate are also presented.