新型热释电材料及其在高性能红外探测器中的应用

采用改进的Bridgman法生长出了大尺寸高质量的Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PMNT)单晶,并发现了PMNT单晶具有非常大的热释电响应。为探索高性能的热释电材料,提高现有红外探测器的性能,对PMN-PT的热释电性能、及其在红外探测器中的应用进行了系统的研究。研究表明：PMNT单晶具有优异的热释电性能,其综合性能优于传统的热释电材料。用PMNT单晶制备出了的红外探测器,电压响应率和比探测率分别为Rv = 211 V/W,D* = 1.06×108 cm·Hz^1/2·W^-1,器件性能能够基本满足使用要求,同时也表明PMNT单晶有望在高性能的红外探测及成像器件中得到实际应用。     

新型热释电材料及其在红外探测器中的应用

以(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3{PMNT[(1-x)/x}为代表的大尺寸、高质量弛豫铁电单晶具有非常高的热释电系数、探测优值和较低的热扩散系数,其综合热释电性能远优于传统的热释电材料.概述了PMNT[(1-x)/x]单晶、掺锰PMNT(74/26)单晶和0.42Pb(In1/2Nb1/2)...     

Chemical mechanical polishing of polymeric materials for MEMS applications

Polymeric materials such as polycarbonate (PC) and poly-methyl methacryate (PMMA) are replacing silicon as the major substrate in microfluidic system fabrication due to their outstanding features such as low cost and good chemical resistance. In this study, chemical mechanical polishing (CMP) of PC and PMMA substrates was investigated. Four types of slurry were tested on CMP of the polymers under the same process conditions. The slurry suitable for polishing PC and PMMA was then chosen, and further CMP experiments were carried out under different process conditions. Experimental results showed that increasing table speed or head load increased the material removal rates of the polymers. The polymeric surface quality after CMP was acceptable to most MEMS applications. Analysis of variance was also carried out, and it was found that the interaction of head load and table speed had a significant (95% confidence) effect on surface finish of polished PMMA. On the other hand, table speed had a highly significant (99% confidence) effect on surface finish of polished PC.     

Durability of polymeric encapsulation materials for concentrating photovoltaic systems

The durability of polymeric encapsulation materials was examined using outdoor exposure at the nominal optical concentration of 500 suns. The results for 12 months' cumulative field deployment are presented for materials including ethylene‐co‐vinyl acetate, polyvinyl butyral (PVB), ionomer, polyethylene/polyoctene copolymer, thermoplastic polyurethane, poly(dimethylsiloxane), and poly(phenyl‐methyl siloxane). Measurements during the experiment included optical transmittance (direct and hemispherical), mass, visual appearance, and fluorescence spectroscopy in addition to the initial thermogravimetry of the materials. Measurements of the field conditions and ultraviolet dose at the test site were facilitated by numerous laboratory instruments; characterization of the specimen temperature was performed using thermography. Discovery experiments identified the importance of a secondary homogenizer optic and the importance of contamination control. To date, the formal experiment verified a thermal‐runaway‐motivated combustion failure mechanism for one of the PVB formulations and identified densification, cracking, and haze‐formation behaviors in some of the silicone specimens. The behaviors observed for the silicone specimens may be facilitated by their greater thickness. Copyright © 2012 John Wiley & Sons, Ltd.     

Sorptive polymeric materials and photopatterned films for gas phase chemical microsensors

The selective layer on a gas phase chemical microsensor plays a critical role in the sensitivity and selectivity of the sensor's response. Polymers can rapidly and reversibly absorb vapor molecules. As sorptive layers on chemical sensors, polymers are useful for a variety of chemical microsensor types and transduction mechanisms, either as is or as composites with conductive particles or dyes. The performance requirements for polymers are described in terms of their chemical and physical properties. A versatile synthetic approach for preparing sensing polymers has been developed using hydrosilylation chemistry to prepare carbosiloxane polymers. Polymers with diverse chemical selectivities have been prepared by this method. Furthermore, sorptive polymer materials can be photopatterned into defined areas on surfaces using a photoactivated catalyst and hydrosilylation chemistry. Polymer films with diverse chemical selectivities have been patterned with this new method.     

Rheology based modeling and design of particle laden polymeric thermal interface materials

Most of the research on particle laden polymeric (PLP) thermal interface materials (TIM) have been primarily focused ob understanding the thermal conductivity of these types of TIMs. For thermal design reduction of the thermal resistance is the end goal. Thermal resistance is not only dependent on the thermal conductivity, but also on the bond line thickness (BLT) of these TIMs. This paper introduces a rheology based model for the prediction of the BLT of these TIMs from very low to very high pressures. BLT depends on the yield stress of the particle laden polymer and the applied pressure. The model is based on the concept of finite size scaling of physical properties of particle laden systems at very thin length scale due to percolation phenomenon in these materials. This paper shows that the yield stress of the PLP increases with decreasing thickness of the TIM and therefore it is size dependent. The BLT model combined with the thermal conductivity model can be used for modeling the thermal resistance of these TIMs for factors such as particle volume faction, substrate/die size, pressure and particle diameter.     

Interface microstructure effects in Au thermosonic ball bonding contacts by high reliability wire materials

Palladium-doped and (Cu, Pt)-doped high reliability gold wires were used to form wire bond interconnects on aluminum IC metallization. By isothermal annealing of wire bond samples the formation of intermetallic Au–Al phases was stimulated. SEM/EBSD investigations of the phase regions exhibited significantly slower isothermal growth rates compared to a reference gold wire. Correlated TEM, STEM–EDXS and nanobeam diffraction analyses revealed that Pd is preferentially incorporated into the Au₈Al₃ intermetallic forming a new stable phase but additionally can obviously form a new Pd-rich ternary intermetallic. In comparison, Cu dopants are also accumulated into a new Al–Au–Cu phase while Pt is rather found agglomerating within grain boundaries and interfaces. These results suggest a diffusion barrier model that allows discussing how wire doping can affect the bond contact microstructure, thus increasing the lifetime of bond contacts.     

高频高速印制板材料导热性能的研究进展

随着电子技术的发展,对高频高速印制板导热性越来越高的要求。除了开发高成本的高导热性聚合物材料外,在聚合物中填充高导热性的无机材料也是提高高频高速印制板基材导热性能的有效方法,而且填充型复合材料可以用理论模型预测其导热系数。主要综述了填料的形貌、分布与表面改性对填充型复合材料导热系数的影响等方面的研究进展。     

电子塑封材料的高温界面强度研究

为了研究最常见的电子封装失效模式之一——高温下的界面破坏机理,在传统剪切拉拔实验的基础上进行了改良,运用焊接力测试机(Dage 4000)、拉伸机、热控制仪和热烘箱等辅助仪器,实现了电子塑封材料在高温下的界面强度测试.结果表明,界面强度随着温度的升高而降低,特别是在跨越塑封材料的玻璃转换温度时,界面强度有显著降低.比较...     

Durability of polymeric encapsulation materials in a PMMA/glass concentrator photovoltaic system

The durability of polymeric encapsulation materials was examined using outdoor exposure at the nominal geometric concentration of 500 suns. The results for 36‐month cumulative field deployment are presented for materials including: poly(ethylene‐co‐vinyl acetate), (EVA); polyvinyl butyral (PVB); ionomer; polyethylene/polyoctene copolymer (PO); thermoplastic polyurethane (TPU); poly(dimethylsiloxane) (PDMS); poly(diphenyl dimethyl siloxane) (PDPDMS); and poly(phenyl‐methyl siloxane) (PPMS). Measurements of the field conditions including ambient temperature and ultraviolet (UV) dose were recorded at the test site during the experiment. Measurements for the experiment included optical transmittance (with subsequent analysis of solar‐weighted transmittance, UV cut‐off wavelength, and yellowness index), mass, visual photography, photoelastic imaging, and fluorescence spectroscopy. While the results to date for EVA are presented and discussed, examination here focuses more on the siloxane materials. A specimen recently observed to fail by thermal decomposition is discussed in terms of the implementation of the experiment as well as its fluorescence signature, which was observed to become more pronounced with age. Modulated thermogravimetry (allowing determination of the activation energy of thermal decomposition) was performed on a subset of the siloxanes to quantify the propensity for decomposition at elevated temperatures. Supplemental, Pt‐catalyst‐ and primer‐solutions as well as peroxide‐cured PDMS specimens were examined to assess the source of the luminescence. The results of the study including the change in optical transmittance, observed failure modes, and subsequent analyses of the failure modes are described in the conclusions. Copyright © 2016 John Wiley & Sons, Ltd.     

On solution schemes for time-independent thermomechanical analysis for structures containing polymeric materials

Contradicting ideas about implementing temperature-dependent Young’s modulus in a time-independent quasi-static thermomechanical analysis can be found regularly in the literature. The incremental (quasi-static evolution) and the non-incremental (Hookean) solution schemes represent simplifications of the viscoelastic behavior of polymeric materials according to different theoretical disciplines. These two schemes lead to completely different solutions when Young’s modulus is a function of the temperature. In this paper we review the ideas about implementing temperature-dependent Young’s modulus in a time-independent quasi-static thermomechanical analysis. Differences of the ideologies are highlighted using bimaterial beam solutions. Thermomechanical deformations of a bimaterial structure, which resembles a plastic ball grid array package assembly, at different temperatures are measured using shadow Moiré interferometry. Numerical solutions from different schemes are compared with measurement results.     

Mechanical interactions and their effects on chemical mechanicalpolishing

Mechanical interactions, such as contact stress and fluid pressure are of extreme importance in silicon wafer polishing, especially for the wafer-scale planarity of the finished surfaces. In this paper, the measurements of interfacial fluid pressure and friction, as well as their dependence on some major process variables, are presented. A nonuniform subambient fluid pressure was measured, and the resulting wafer/pad contact stress, obtained by combining the effects of both applied normal load and interfacial fluid pressure, is determined. An analytical model was developed to predict the magnitude and distribution of the interfacial fluid pressure. The results of polishing experiments show good evidence of the effects of this subambient fluid pressure on with in-wafer nonuniformity (WIWNU). By properly designing the polishing process variables, the fluid pressure may be tailored, and a relatively uniform material removal can be achieved     

络合剂对NASICON材料的影响

摘要:采用以无机盐为基础的新型溶胶-凝胶法合成了固体电解质NASICON材料。合成过程中,通过向原溶液中添加草酸作络合剂,有效降低了烧结温度,缩短了烧结时间。实验中,利用XRD、TEM等分析测试手段对草酸络合剂以及合成产物的影响情况进行了对比研究,对络合剂的作用机理进行了讨论。     

Chalcogenide materials and their application to Non-Volatile Memories

Chalcogenide materials are chemical compounds consisting of at least one chalcogen ion, i.e. a chemical element in column VI of the periodic table also known as the oxygen family. More precisely the term chalcogenide refers to the sulphides, selenides, and tellurides. Among the various applications of this class of materials, we review here two types of Non-Volatile Memories (NVM): the Phase Change Memories (PCM) which rely on the rapid crystallisation and high electrical contrast between the amorphous and crystalline phases of some of these compounds, and the Current Bridging Random Access Memories (CBRAM) which make use of the ionic conduction of compounds containing metallic ions.     

Curing shrinkage effects of UV-curable materials on fiber losscharacteristics

The curing shrinkage effect in the radial direction of ultraviolet UV-curable coating on fiber-loss characteristics is investigated theoretically and experimentally. It is shown that curing shrinkage causes lateral forces to the fiber and leads to microbending loss increases at low temperatures. A model for pressure caused by curing shrinkage in the radial direction is discussed. According to this model, the radial pressure to the optical fiber in the coating can be estimated by measuring the fiber pulling force from the coated optical fiber. Based on the agreement of theoretical and experimental results, the allowable range of curing shrinkage percentages of primary and secondary coatings to prevent fiber-loss increase is obtained. Design strategies to prevent fiber loss increases at low temperatures are described     

Window materials for high power gyrotron

The room temperature application of sapphire as window material at higher frequencies is not feasible since its absorption coefficient increases almost linearly with increasing frequency in the millimeter wavelength region. At cryogenic temperature the absorption coefficient value decreases only by a few factors (factor of 2 to 3) in the 90 – 200 GHz region. The earlier reported temperature squared dependence (decrease) in the absorption coefficient or the loss tangent value is totally absent in our broad band continuous wave data we are reporting here (at 6.5 K, 35K, 77K and 300K) and one we reported at conferences earlier. Our results are verified by another technique. We utilize our precision millimeter wave dispersive Fourier transform spectroscopic techniques at room temperature and at cryogenic temperatures The extra high resistivity single crystal compensated silicon is no doubt the lowest loss material available at room temperature in the entire millimeter wavelength region At higher millimeter wave frequencies an extra high resistivity silicon window or an window made with extra high resistivity silicon coated with diamond film would certainly make a better candidate in the future. A single free standing synthetic diamond window seems to have higher absorption coefficient values at millimeter wavelength region at this time although it is claimed that it possesses good mechanical strength and higher thermal conductivity characteristics. It certainly does not rule out the use of diamond film on a single crystal high resistivity silicon to improve its mechanical strength and thermal conductivity     

含能材料激光点火的氧平衡问题研究

实验研究了含能材料激光点火的氧平衡问题。对Zr/KClO4 等的临界激光点火能量的测定实验表明,锆与高氯酸钾的质量比对Zr/KClO4 的临界激光点火能量阈值有明显影响,在其他条件、因素相同的情况下,当偏富氧配比时,有利于激光点火,即点火的阈值能量低,或者说含能材料的激光感度较高。