有机前躯体浸渍对凝胶注模RBSiC的弥散强化

针对凝胶注模成型的反应烧结Si C空间反射镜材料,进行有机物前驱体浸渍处理,制备了具有细小次生β-Si C均匀分布于基体的Si C陶瓷。研究了浸渍工艺对Si C密度及微观结构的影响。未经浸渍处理的样品反应烧结后密度为2.945g/cm3,一次浸渍后密度增至2.969g/cm3,二次浸渍后密度增至3.011g/cm3。并随浸渍次数的增加,显微结构中细小Si C所占比例随之增加,即在反应烧结过程中,通过浸渍引入的碳与硅反应生成细小的β-Si C弥散于基体。对样品进行了三点弯曲性能测试,未经浸渍处理的样品抗弯强度为308MPa,一次浸渍处理强度为339MPa,强度提高10.1%,二次浸渍处理强度为380 MPa,强度提高23.4%,大幅提高了力学性能。     

纳米碳化硅对浆料流变学及碳化硅性能的影响

研究纳米碳化硅颗粒对凝胶注浆料流变学特性及反应烧结碳化硅性能的影响。利用凝胶注模(gel-casting)成型工艺制备碳化硅素坯,经过脱模、干燥、预烧结和反应烧结等工艺,制备含有纳米碳化硅颗粒的反应烧结碳化硅(RBSC),总结了固含量、球混时间和纳米碳化硅含量对浆料流变学特性的影响机制。实验结果表明:加入纳米碳化硅颗粒后,浆料流变学特性由剪切变稀转变为先剪切增稠后剪切变稀。随着纳米碳化硅的加入,反应烧结碳化硅的力学性能不断提高,当纳米碳化硅颗粒含量达到7%时,反应烧结碳化硅的抗弯强度和弹性模量分别提高到345 MPa和339 GPa,与未加纳米碳化硅颗粒相比,分别增加了18.1%和13.8%。纳米碳化硅的加入改变了浆料的流变学特性,提高了反应烧结碳化硅的力学性能。     

AlF_3-MgF_2-SiO_2系低温共烧氧氟玻璃陶瓷性能研究

制备了AlF3-MgF2-SiO2系低温共烧氧氟玻璃陶瓷材料,用XRD、SEM和阻抗分析仪等分析其烧结特性、显微结构、介电性能以及与Ag电极浆料共烧等性能。结果表明:该材料可以在900℃烧结致密化,烧成后的样品具有低的介电常数(6.2)和介质损耗(<0.002)、较低的热膨胀系数(7.4×10–6/K)、较高的弯曲强度(220 MPa)和热导率[2.4 W/(m.K)],能够与Ag电极浆料共烧,是一种很有应用前景的低温共烧陶瓷基板和无源集成介质材料。     

绝缘导热浆料制备和性能

以低熔玻璃粉、金刚石粉及有机载体制备成浆料,丝网印刷在硬铝LY12基材上,烧结后制成导热绝缘层。分析了浆料中的金刚石粉含量对绝缘导热涂层导热参数和与基片附着力的影响,测试分析了浆料的流变性和触变性。结果表明,绝缘导热浆料的最佳配方为:w(有机载体)为18%;w(金刚石粉)为30%;w(低熔玻璃粉)为52%。静止时浆料中形成弱的絮凝,是剪切变稀体,有一定触变性,具有较好的丝网印刷适性。所制备绝缘涂层的热导率最高可达2.47W/(m·K)。     

真空反应烧结大尺寸碳化硅反射镜

利用高温真空烧结炉对凝胶注模(Gel-casting)成型的SiC素坯进行反应烧结(RB-SiC),可制备得到光学级别的碳化硅反射镜镜体.测试结果表明,镜体内部结构均匀致密,机械性能优异,烧结线收缩率＜0.23%,直接抛光后的表面粗糙度RMS值优于3 nm,适用于空间大尺寸碳化硅反射镜的制备.     

压力对W-Cu合金电场快速烧结的影响

采用Gleeble—3500D热模拟机,用电场快速烧结的方法制得W-Cu合金。通过对烧结压坯的密度、显微结构以及硬度的分析,研究了压力对W-Cu合金烧结的影响。结果表明:W-Cu合金在800℃、3 min内快速烧结可获得晶粒较细小、显微组织较均匀的烧结体;在10~30 MPa范围内加压能有效促进烧结体的致密化,可获得相对密度为92.60%~94.84%的W-Cu合金烧结体。但是随着压力的增加,烧结体的相对密度增加不明显。压力可使该烧结体显微硬度增高。     

导电银浆的制备和性能研究

采用商用微米银片为导电相,玻璃粉为粘结剂,乙基纤维素、松油醇和曲拉通为有机载体制备了烧渗型银浆。利用扫描电子显微镜、方阻仪和百格测试法对烧结银浆的显微结构、导电性和附着力进行表征和研究。实验结果表明:烧结温度、玻璃粉含量和导电相的性质对银浆烧结后的显微结构、导电性和附着力均有较大影响。其中,烧结温度不仅对玻璃粉的熔化情况有影响,而且对烧结后的银浆中银片间的接触程度和与基材的润湿性等也有影响;玻璃粉的含量是影响烧结银浆的导电性和附着力的主要因素;微米银片中掺杂纳米银会导致烧结体中导电颗粒间的致密性下降,进而导致烧结后的银浆的导电性和附着力均下降。     

微米银焊点的超快激光图形化沉积及其在芯片连接中的应用探索

集成电路(IC)芯片封装中小尺寸、细节距焊点采用的传统锡基钎料在服役过程中存在桥接、电迁移、金属间化合物等问题,在大电流、大功率密度的应用中受到限制。采用脉冲激光沉积(PLD)技术,在覆铜陶瓷(DBC)基板上图形化沉积了多孔微米银焊点,用于替代传统的钎料凸点,并将其应用于Si芯片与DBC基板的连接。结果表明:采用不锈钢作为掩模,可沉积出500μm及300μm特征尺寸的疏松多孔银焊点阵列,银焊点呈圆台形貌;在250℃温度、2 MPa压力下热压烧结10 min, Si芯片与DBC基板连接良好,连接后的银焊点边缘的孔隙率为42%左右,银焊点中心区域的孔隙率为22%; 500μm和300μm特征尺寸的银焊点的连接接头的剪切强度分别为14 MPa和12 MPa;接头断裂主要发生在银焊点与芯片或DBC基板的连接界面处。     

大尺寸轻型碳化硅反射镜的凝胶注模成型

利用凝胶注模（Gel-casting）成型技术制备碳化硅反射镜坯体,可以一次性地制备出较大尺寸、复杂结构的碳化硅镜坯,并使镜坯完成轻量化,较大程度地减少镜坯的机械加工难度。制备的碳化硅坯体内部组织均匀、表面平整、不产生裂纹,整体机械性能较强,并具有较好的反应烧结性能。本技术的浆料固相体积分数控制为66%,镜体收缩率〈1.28%,是一种制备大尺寸碳化硅反射镜镜体的良好工艺方法。     

无压烧结SiC-AlN复相陶瓷导热和介电性能的研究

添加10%(质量分数)BaO-SiO_2-Y_2O_3烧结助剂在氮气氛下无压烧结制备SiC-AlN复相陶瓷。研究了SiC含量、烧结温度对复相陶瓷烧结性能、显微结构、热导率和高频介电性能的影响。结果表明:样品中主晶相为6H-SiC和AlN,次晶相为Y_3Al_5O_(12)和Y_4Al_2O_9;当SiC质量分数为50%时,1850℃烧结1 h,显气孔率低于0.3%;而Si C含量继续增加,显气孔率显著上升。热导率、介电常数和介电损耗都随着烧结温度的升高而升高。当Si C质量分数为50%时,1900℃下复相材料呈现最好的热扩散系数和热导率,分别为26.3 mm~2·s~(–1)和61.5W·m~(–1)·K~(–1);1850℃下获得的Si C-Al N复相陶瓷在12.4~18 GHz频率范围内获相对介电常数和介电损耗分别为33~37和0.4~0.5,该频段内随频率升高,介电常数和介电损耗下降。     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks     

Call for Papers—Feature Topic,Vol.12,No.7,2015

正Information Centric Networking Information-Centric Networking(ICN) is an emerging direction in Future Internet architecture research,gaining significant tractions among academia and industry.Aiming to replace the conventional host-to-host communication model by a data-centric model,ICN treats data content as the first     

JOURNAL OF ELECTRONICS(CHINA)

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NEXT GENERATION WIRELESS NETWORKS–ESPECIALLY THE USE OF MILLI-MICROWAVE BANDS

The global bandwidth shortage of wireless communications has motivated the exploration of the naillimeter wave （ram-wave） frequency spectrum for the next generation wireless communications. Recent advances in RF CMOS technology and high speed baseband signal processing technologies have enabled tile extensive research and development of turn-wave wireless communications. The multi gigabit per second data rate of ram-wave system will lead to applications in many important scenarios, such as WPAN, WLAN,back-haul for cellular system. And the frequency bands include 28 GHz, 38 GHz, 45GHz, 60GHz, E-BAND and even beyond 100 GHz. The propagation and the imitation of the RF circuits design in these frequency bands make the directional antennas be inevitable for mm-wave communications.