SiC Die Attach for High-Temperature Applications

Eutectic solders AuIn19 and AuGe12 and nanosilver paste were investigated for SiC die attach in high-temperature (300°C) applications. The soldering or sintering conditions were optimized through die shear tests performed at room temperature. In particular, application of static pressure (3.5 MPa) during sintering resulted in greatly improved mechanical behavior of the nanosilver-based joint. Microstructural study of the eutectic solders showed formation of Au-rich grains in AuGe die attach and significant diffusion of Au and In through the Ni layer in AuIn19 die attach, which could lead to formation of intermetallic compounds. Die shear tests versus temperature showed that the behaviors of the studied die attaches are different; nevertheless they present suitable shear strengths required for high-temperature applications. The mechanical behavior of joints under various levels of thermal and mechanical stress was also studied. Creep experiments were carried out on the eutectic solders to describe the thermomechanical behavior of the complete module; only one creep mechanism was observed in the working range.     

金刚石薄膜高温器件

本文详细地论述了低压气相生长的金刚石薄膜作为一种新型半导体材料的研究进展,讨论了金刚石薄膜与金属的欧姆接触和整流接触,以及可以在高温区工作的金刚石薄膜Schottky二极管和MESFET器件。最后,讨论了目前金刚石薄膜作为半导体材料所遇到的两个尚无法实现的问题:n型掺杂和异质外延单晶膜的生长。     

New Ternary Arsenides for High-Temperature Thermoelectric Applications

Two isostructural materials Mo₃(Sb,Te)₇ and Re₃(Ge,As)₇ were synthesized and characterized in our laboratories during the past decade. Both crystallize in the Ir₃Ge₇ type, possessing the space group . They show excellent potential for thermoelectric energy conversion at high temperatures. Our recent physical properties measurements revealed a higher Seebeck coefficient for the new ternary Re₃Sn_0.2As_6.8, as compared with Re₃(Ge,As)₇, while the power factors are comparable. Rietveld refinements indicate an increasing unit cell volume with increasing Sn content. It has also been found that intercalation of an additional transition-metal atom (Co, Ni) into the cubic void of Re₃(Ge,As)₇ can significantly alter the Seebeck coefficient.     

Polydopamine Encapsulation of Fluorescent Nanodiamonds for Biomedical Applications

Fluorescent nanodiamonds (FNDs) are promising bioimaging probes compared with other fluorescent nanomaterials such as quantum dots, dye‐doped nanoparticles, and metallic nanoclusters, due to their remarkable optical properties and excellent biocompatibility. Nevertheless, they are prone to aggregation in physiological salt solutions, and modifying their surface to conjugate biologically active agents remains challenging. Here, inspired by the adhesive protein of marine mussels, encapsulation of FNDs within a polydopamine (PDA) shell is demonstrated. These PDA surfaces are readily modified via Michael addition or Schiff base reactions with molecules presenting thiol or nitrogen derivatives. Modification of PDA shells by thiol terminated poly(ethylene glycol) (PEG‐SH) molecules to enhance colloidal stability and biocompatibility of FNDs is described. Their use as fluorescent probes for cell imaging is demonstrated; it is found that PEGylated FNDs are taken up by HeLa cells and mouse bone marrow‐derived dendritic cells and exhibit reduced nonspecific membrane adhesion. Furthermore, functionalization with biotin‐PEG‐SH is demonstrated and long‐term high‐resolution single‐molecule fluorescence based tracking measurements of FNDs tethered via streptavidin to individual biotinylated DNA molecules are performed. This robust polydopamine encapsulation and functionalization strategy presents a facile route to develop FNDs as multifunctional labels, drug delivery vehicles, and targeting agents for biomedical applications.     

High-Temperature Superconducting Homopolar Inductor Alternator for Marine Applications

This paper describes a high power density high-temperature superconducting (HTS) electric machine topology that is scalable for marine propulsion and power generation. The design, currently being pursued for airborne applications, is based on homopolar inductor alternator (HIA) technology, which is new within HTS applications. The basic machine design configuration of the HTS HIA is based on a stationary HTS field excitation coil, a solid rotor, and an advanced but conventional stator comprising liquid-cooled air-gap armature winding and an advanced iron core. High power density is obtained by the enhanced magneto-motive force capability of the HTS coil, the increased airgap flux density and armature current loading, and the high tip velocity of the rotor. Preliminary scaled up designs look attractive for three marine applications: propulsion drive, primary ship power generation, and power generation modules. The generators are driven directly by the turbines without the additional complexity of a clutch and gear system. A conceptual design study of a 36-MW 3600-r/min generator, a 4-MW 7000-r/min auxiliary generator, and a 36-MW 120-r/min and 4-MW 132-r/min propulsion motor are summarized.     

Development of Integrated Thermionic Circuits for High-Temperature Applications

This paper describes a class of microminiature, thin-film devices known as integrated thermionic circuits (ITC) capable of extended operation in ambient temperatures up to 500°C. The evolution of the ITC concept is discussed. A set of practical design and performance equations is demonstrated. Recent experimental results are discussed in which both devices and simple circuits have successfully operated in 500°C environments for extended periods of time (greater than 11000 h).     

Titanium Disilicide as High-Temperature Contact Material for Thermoelectric Generators

Thermoelectric devices can be used to capture electric power from waste heat in a variety of applications. The theoretical efficiency rises with the temperature difference across the thermoelectric generator (TEG). Therefore, we have investigated contact materials to maximize the thermal stability of a TEG. A promising candidate is titanium disilicide (TiSi₂), which has been well known as a contact material in silicon technology for some time, having low resistivity and thermal stability up to 1150 K. A demonstrator using highly doped silicon as the thermoelectric material has been integrated. A p- and an n-type wafer were oxidized and bonded. After cutting the wafer into pieces, a 200-nm-thick titanium layer was sputtered onto the edges. After a 750°C rapid thermal annealing step, the TEG legs were connected by a highly conductive TiSi₂ layer. A TEG with 12 thermal couples was integrated, and its joint resistance was found to be 4.2 Ω. Hence, we have successfully demonstrated a functional high-temperature contact for TEGs up to at least 900 K. Nevertheless, the actual thermal stability will be even higher. The process could be transfered to other substrates by using amorphous silicon deposited by plasma-enhanced chemical vapor deposition.     

High-Temperature Electronics Applications in Space Exploration

One of the most exciting applications of high-temperature electronics is related to the exploration of the planet Venus. On this planet the atmospheric temperatures range from about 170 K at elevations of 100 km to a searing 730 K near the surface. Mechanisms for exploring the atmosphere might include balloons, airplanes, surface landers, and surface-launched probes. Balloons, for example, could fly in the region from 20(320°C at 22 bars) to 60 km (-20°C at 0.2 bar). Suitable balloon fabrics presently exclude excursions to lower altitudes; however, adequate electronic systems could survive to 325°C. Small airplanes would require more sophisticated electronics for guidance and control. Long life surface landers would most likely be developed first, as these could be used to measure long-term variations in weather. Ranging transponders would be important for ephemeris development, measurement of spin state, and studies of general relativity. Surface temperatures of 460°C and pressures of 90 bars present a challenge to the developers of such instruments.     

Fabrication and Evaluation of a Skutterudite-Based Thermoelectric Module for High-Temperature Applications

We report a straightforward methodology for the fabrication of high-temperature thermoelectric (TE) modules using commercially available solder alloys and metal barriers. This methodology employs standard and accessible facilities that are simple to implement in any laboratory. A TE module formed by nine n-type Yb _x Co₄Sb₁₂ and p-type Ce _x Fe₃CoSb₁₂ state-of-the-art skutterudite material couples was fabricated. The physical properties of the synthesized skutterudites were determined, and the module power output, internal resistance, and thermocycling stability were evaluated in air. At a temperature difference of 365 K, the module provides more than 1.5 W cm^?3 volume power density. However, thermocycling showed an increase of the internal module resistance and degradation in performance with the number of cycles when the device is operated at a hot-side temperature higher than 573 K. This may be attributed to oxidation of the skutterudite thermoelements.     

Recent Advances in Gallium Phosphide Junction Devices for High-Temperature Electronic Applications

Recent advances in gallium phosphide technology are reviewed as they relate to high-temperature (T > 300°C) device applications. The electronic properties and materials aspects of GaP are summarized and compared to silicon and gallium arsenide. Minority-carrier unction devices are discussed as one area where this technology could have wide application. In this light, the high-temperature operation of two junction devices, a diode and a bipolar junction transistor (BJT), are displayed. The GaP diode is observed to provide excellent rectification properties with very low leakage over the full temperature range from 20°C to 400°C (< 3x10 -3A/cm2 at VR = 3 V, T = 400°C) and has demonstrated stable operation under bias for over 1000 h at 300°. The bipolar transistor has demonstrated constant current gain (6 < ? B < 10) and very low collector-base leakage for temperatures up to 450°C (ICO 80 μA at VCB = 3 V, T = 450°C). The contacting technology to GaP is identified as one area where additional work is necessary.     

Amorphous-SiCBN-Based Metal–Semiconductor–Metal Photodetector for High-Temperature Applications

A photodetector (PD) with metal-semiconductor-metal (MSM) structure has been developed using an amorphous SiCBN film. The amorphous SiCBN film was deposited on the silicon substrate using reactive RF magnetron sputtering. The optoelectronic performance of the SiCBN MSM devices has been examined through photocurrent measurements. Temperature effect, with respect to photocurrent ratios, has been studied. The detector sensitivity factor, which is determined through the PD current ratio, was greater than five at room temperature. Furthermore, the device showed an excellent current sensitivity factor that is greater than two even at a higher temperature of 200 ^oC . The improved performance of the device at higher temperatures could open avenues for high-temperature PD applications.     

军用微波多层板的选材

随着高性能军用微波应用的发展,许多设计要求采用多层PCB。文章给出了在选择军用射频材料时的选择要点。从常规的PTFE材料的局限性、新的陶瓷粉填充以及它对材料的热膨胀系数、介电常数的温度稳定性影响等,同时讨论多层板材料加工中可能碰到的对微波特性的影响。     

印制电路板用双酚A型氰酸酯树脂

国产双酚A型氰酸酯树脂研制成功,目前通过了部级技术鉴定,于2000年年底批量投产。 专家认为,该树脂是目前制作印制电路板最理想的基体树脂,可替代目前通用的FR—4环氧树脂,满足微波信号传输向GHz方向发展的趋势。在通讯技术日新月异发展的今天,氰酸酯树脂这种新型电介质材料,必将获得越来越多的应用,产生越来越多的社会与经济效益。 双酚A型氰酸酯树脂是由双酚A与溴化氰或氯化氰反应,通过二步法合     

保偏光纤耦合器新型封装材料的稳定性研究

分析了以往保偏光纤耦合器封装工艺存在的一些技术缺陷,以及在试验过程中这些缺陷对保偏光纤耦合器造成的不良影响.针对存在的问题,提出了一种新的高稳定性的材料——低温玻璃封装用于耦合器的封装,经过一系列实验(工作温度,高温寿命,交变湿热,温度冲击),并对实验结果分析,新的封装基本达到预期目标.     

In-Line Fabry–Perot Etalons Based on Hollow-CorePhotonic Bandgap Fibers for High-Temperature Applications

In this paper, we report a novel in-line fiber Fabry–Perot (F-P) etalon, consisting of a section of hollow-core photonic bandgap fiber (HC-PBGF) spliced between two single mode fibers. The fabrication process of such a sensor is simple and straightforward, including only cleaving and splicing. The sensing characteristics of the F-P etalon based on HC-PBGF, including high temperature, strain, bend, and transverse load, are fully investigated by experiments, for the first time to our knowledge. It is found that such a F-P etalon can be used under high temperatures of up to 600 $ ,,^{circ}{hbox {C}}$, and has a low cavity-length-to-temperature sensitivity of $sim {1.4}~{hbox {nm}}/^{circ}{hbox {C}}$, while it has a relatively high strain sensitivity of $sim {5.9}~{hbox {nm}}/mu varepsilon$. Moreover, this F-P etalon is insensitive to bend or transverse load. Furthermore, the long cavity length ($> {1}~{hbox {cm}}$) of the sensor makes it suitable for multiplexing. These characteristics would make this HC-PBGF-based F-P etalon to be an excellent strain sensor or gas sensor for use in high-temperature environments.      

GaN材料的特性与应用

本介绍了GaN材料的特性、生长及应用，并展望了其应用前景。     

光子学在材料加工中的应用

光子学应用于材料加工已经三十多年,但是就其应用的深度和广度而言,相对于传统技术仍是一门新兴技术。评述了最近几年中光子学在材料加工的常规加工、激光成型、溶胶一凝胶技术、微加工和光学平版印刷术应用中的最新进展。     

SuperPower's YBCO Coated High-Temperature Superconducting (HTS) Wire and Magnet Applications

Recent developments in second-generation (2G) HTS wire and coil technology are presented highlighting the ability of 2G HTS wire to function under demanding operating conditions associated with many applications including linear motors for transportation. The challenges of use in various coil constructions and applications are discussed. The 2G wire architecture of a structural substrate, buffer stack, HTS layer, and stabilization enables the 2G wire to tolerate high stress levels while providing the high current density required for lightweight, compact magnets. The high winding current density that is available with SuperPower's thin (0.1 mm) 2G HTS wire has been utilized in several coil demonstrations, including one generating central fields in excess of 26.8 T. The ability of the wire to be tailored (stabilization, insulation, ac losses) to fit various operating parameters will also be discussed.      

光子学在材料工业中的应用

评述光子学在材料工业的光学硅、纳米材料、光子晶体和集成光路中的应用。