Relationship between the Local Vibration Mode Characteristics and the Charge State of Carbon Acceptor in GaAs

The local vibration mode(LVM)of carbon acceptor in GaAs is studied by measuring directly the changein LVM absorption with a NIC-170 SX FT-IR spectrometer.The change in the charge state of carbon acceptorand the temperature dependence of the LVM absorption were investigated also.The contents of the impuritiesother than carbon were estimated by secondary ion mass spectrometry.It is observed that the frequency,thespectral form and the integrated absorption of the LVM are not affected by the change in charge state of car-bon acceptor.     

Attenuated total refection spectroscopy under conditions weak absorption: New method for determination of integrated intensities

The basic principles of attenuated total reflection (ATR) spectroscopy are briefly described and its main areas of application are listed. It is shown using symbolic calculations that in the case of ATR spectra measured under conditions of weak absorbance, the area under the curve of absorbance of an isolated Lorentz absorption band is directly proportional to the integral band intensity. It is shown that the proportionality factor between these quantities contains a single a priori unknown parameter, i.e., the real part of dielectric constant of the studied medium in the maximum of the studied band. This fact offers a new scope for determining the integrated intensities of isotropic condensed media directly based on experimental ATR data.     

Attenuated total reflection spectroscopy under conditions of weak absorption: Further development of a new method for determination of integrated intensities

Development of a new method for the determination of the integrated intensities in isotropic condensed media is suggested. In a previous publication, with the use of analytical calculations, it is shown that, for the ATR spectra measured under conditions of weak absorption, the area under the absorbance curve of an isolated Lorentzian band is directly proportional to the integrated intensity of this band. It is also shown that the proportionality coefficient between these two parameters contains only one unknown parameter: the real part of the complex dielectric constant for the studied medium at the maximum of the studied band. In order to determine the numerical value of this parameter and, at the same time, to find the integrated intensity value, it is suggested to carry out two experiments; in these experiments, the same band is studied while the most important parameters are varied, such as the IRE refractive index, the angle of incidence, and the polarization. The main random and systematic errors of the suggested method are considered: ways to minimize these errors are discussed. The approach developed in this work is compared with other methods for determination of the integrated intensities.     

Absorption and fluorescence spectra of gallium phosphide（GaP） nanoparticles

The optical absorption spectrum ranging from 200 to 800 nm and fluorescence spectra ranging from 300 to 650 nm of GaP nanoparticles at room temperature were reported. From the optical absorption spectrum it is inferred that the GaP nanoparticles exhibit a direct transition of about 410 nm （3.02 eV） and an indirect transition around 480 nm （2.58 eV）. In addition, an absorption peak at about 308 nm （4.02 eV） corresponding to the direct transition at higher energy was observed. The absorption peak was attributed to the transition from the spin-orbit-split valence band to the lowest conduction band along the A direction. By observing the fluorescence of the GaP nanoparticles, it follows that multiple emission bands corresponding to the violet, blue, and yellow light are shown peaking at about 400.4-414.1 nm （3.097-2.994 eV）, 450.1-466.8 nm （2.755-2.656 eV）, and 582.4 nm （2.129 eV）, respectively. The violet and blue light emissions are ascribed to the direct and indirect transitions from conduction band to valence band of the GaP nanoparticles. As to the weak yellow emission, it may be attributed to the radiative recombination from defect centers. The spin-orbit-splitting of the GaP nanoparticles is determined as about 100 meV.     

金芯-银壳复合纳米微粒光学吸收光谱分析

通过液相还原法制备出金．银复合纳米颗粒。透射电镜图像显示所制备金-银复合纳米颗粒呈球状的芯-壳结构。光学吸收谱的实验表明：金芯．银壳复合结构纳米微粒具有双峰的等离子体吸收带。一个峰值的波长位于纯银纳米颗粒的等离子体吸收带附近；另一个介于纯银和纯金纳米颗粒的等离子体吸收峰之间，且随着反应试样中银的摩尔分数的增加发生蓝移，基于实验分析和Mie散射理论的定量计算。结果认为：该吸收峰的蓝移可归因于银壳层厚度的增加。     

SIDEBANDS OF X-RAY DIFFRACTION IN AGE-HARDENED Cu-Ti ALLOY

ＳＩＤＥＢＡＮＤＳＯＦＸ－ＲＡＹＤＩＦＦＲＡＣＴＩＯＮＩＮＡＧＥ－ＨＡＲＤＥＮＥＤＣｕ－ＴｉＡＬＬＯＹ￥ＷｅｉＹｉｎｇｈｕｉ；ＷａｎｇＸｉａｏｔｉａｎ（ＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，Ｘｉ＇ａｎＪｉａｏｔ...     

Spectroscopic properties of Yb in NaYbP2O7 diphosphate single crystals

Yb³⁺ absorption and fluorescent emissions were investigated for NaYbP₂O₇ diphosphate single crystals. The interpretation of electronic energy level positions has been done by using the comparison of absorption and emission spectra with those of vibronic sideband energy positions from Raman and IR absorption spectroscopies. The Yb³⁺ energy levels scheme in this host was drawn. The decay time for infrared Yb³⁺ (⁵F_5/2 excited state) fluorescence was in the range of 1–2 ms. The interest feature is leading to broad emission band at room temperature from 940 nm to 1100 nm, which seems of high interest for ultra-short laser pulse production.     

金属橡胶材料单层结构吸声特性研究

从理论上研究了金属橡胶材料单层结构吸声特性。根据金属橡胶材料声学特性参数计算式,推导出两种基本单层吸声结构——置于刚性墙和带有空气层吸声结构的声阻抗率和吸声系数计算式。确定了流阻率是决定金属橡胶材料声学特性的基本参数。分析了材料厚度、流阻率及空气层厚度对两种吸声结构的吸声性能影响关系,建立了金属橡胶材料单层吸声结构第一共振频率的计算方法。结果表明：通过优化设计材料厚度、流阻率及空气层厚度可有效提高金属橡胶材料单层吸声结构的吸声性能。     

Nd元素对Ce2Co17为基体的合金吸波性能的影响

目前,具有高效、宽、薄等特点的微波吸收材料已经引起了研究人员的广泛关注。在此文中,采用真空电弧熔炼和高能球磨法制备片状NdxCe2-xCo17合金粉末并且通过相关设备研究Nd含量和匹配厚度对相组成、形貌、电磁参数和微波吸收性能的影响。结果显示,Nd0.3Ce1.7Co17粉末的最大反射率可以达到-32.36dB,同时有效带宽能扩大4倍。此外,调整Nd含量能成功优化Ce2Co17合金粉末的微波吸收性能。随着Nd含量的增加,吸收峰有向低频段移动的趋势,并且当厚度为1.8mm时,Nd0.3Ce1.7Co17 粉末在7.28 GHz处,最大反射率可以达到-30.53 dB并且有效带宽为2.24 GHz,这些表明Nd-Ce-Co合金可以用作在C波段具有低厚度、宽频和高效等特点的理想吸收材料。     

纺锤状ZnO/还原氧化石墨烯异质结构及其微波吸收性能

目的调节石墨烯的电磁匹配,以实现最优的微波吸收性能。方法通过改进的Hummers法制备氧化石墨烯GO,以六水合硝酸锌、双六甲撑三胺、氧化石墨烯为原料,采用水热法在140℃获得了具有异质结构的包裹r-GO的纺锤状ZnO棒(S-ZnO/r-GO)。通过X射线衍射分析仪(XRD)、扫描电子显微镜(SEM)以及透射电子显微镜(TEM)测试,分别对S-ZnO/r-GO的组成成分、形貌特征以及微观结构进行了表征,同时采用同轴法,通过矢量网络分析仪测试分析了不同填充浓度下S-ZnO/r-GO复合材料在2~18 GHz范围内的电磁特性,并通过计算得到了材料的微波反射率损耗。结果尺寸均匀且相互交织的纺锤状ZnO棒被大量褶皱的还原氧化石墨烯所包覆,构建了一种相互连接的三维交织结构。纺锤状ZnO的引入以及三维结构的建立,明显改善了S-ZnO/r-GO异质结构在2~18 GHz频率范围内的电磁特性和微波响应。在厚度为2.0 mm,频率为14.8 GHz处,最大反射率损耗值达到−40 dB,有效吸收带宽几乎覆盖整个Ku波段。结论纺锤状ZnO/r-GO复合材料表现出优异的微波吸收性能和较宽的有效吸收频段,具有一定的应用前景。     

INTERACTION AMONG Si IN LEC GaAs AND B_2O_3 AND H_2O IN THE ENCAPSULANT

本文利用文献报道的LEC法GaAs晶体中的Si,B的红外LVM吸收光谱和SIMS分析数据,作出三条lg[Si]-lg[B]直线,其斜率分别接近于4/3,2/3,1/2.本文结合晶体生长的不同工艺条件试用熔体中Si与B_2O_3,H_2O间的相互作用,解释斜率的差异.     

热处理温度对CuInS2粉体物相、形貌及光吸收性能的影响

采用溶剂热法在不同反应体系和温度下,制备了一系列Cu In S2(CIS)粉体。CIS粉体的物相、形貌、光吸收性能分别用X射线衍射(XRD)仪、场发射扫描电镜(FESEM)、透射电镜(TEM)、紫外-可见光谱仪(UV-Vis)等手段进行了表征。结果表明,180℃时乙醇-硫脲体系所得"绣球"状CIS粉体为黄铜矿结构,而乙二胺-硫化钠体系则为"花簇"状纤锌矿结构,升高溶剂热温度,两者形貌均往"球体"演变;结合XRD,差热(DSC)分析表明纤锌矿CIS具有往黄铜矿CIS转变的趋势,物相转变温度约为453℃;受物相转变影响,纤锌矿CIS的带隙值由黄铜矿的1.43 e V减小至1.35 e V,其可见光吸收能力增强。同时探讨了CIS物相的转变机理。     

激光增材制造Ti6Al4V点阵结构的抗压吸能特性

人体骨骼受到碰撞后的断裂过程伴随着能量吸收,多孔骨植入体的设计需考虑结构的抗压吸能特性。在空间尺寸（20 mm×20 mm×30 mm）内,通过拓扑优化设计和激光增材制造技术制备不同胞元尺寸和相对密度的Ti6Al4V点阵结构,采用熔池监控、单向压缩实验和有限元仿真方法,探究了点阵结构的表面质量、断裂形变规律和吸能特性。结果表明,点阵结构的结构参数受熔池温度场和粉末支持力的影响;点阵结构的抗压行为遵循弹脆性变化规律,断裂带与制造方向呈45°;点阵结构的断裂机制为韧性断裂,裂纹沿内部微孔洞分布方向扩展;能量吸收能力随着相对密度增大呈递增趋势,随着胞元尺寸增大呈递减趋势;能量吸收效率随着相对密度增大呈递减趋势,随着胞元尺寸增大呈递增趋势。     

用多轮置换/生长法调节银纳米盘的SPR吸收峰(英文)

以双还原剂法制备的单晶三角形银纳米盘为模板,在室温溶液相与HAuCl4发生多轮置换反应,反应9轮后纳米盘的面内偶极表面等离子体共振峰从初始的700 nm逐步红移到1100 nm,形貌从实心盘状逐渐变为空心纳米环.改变每轮加入的HAuCl4的量即可精细调节面内偶极峰的红移步进量.在只进行一轮反应时,若加入的HAuCl4少于一定量,面内偶极峰会发生小幅度的蓝移.在银纳米盘模板溶液中用抗坏血酸还原AgNO3,银原子沉积到纳米盘上使其生长,若采用多轮还原生长的方法,生长8轮后纳米盘的面内偶极峰逐步蓝移至650 nm,形貌从三角形盘状逐渐变为更大更圆滑的圆盘状.以上方法实现了在温和反应条件下在可见光至近红外光区方便地逐步调节银纳米结构的吸收峰.     

Cu靶功率和衬底温度对Cu-SiO_2纳米复合膜的相结构与光吸收性能影响

实验利用直流和射频磁控溅射方法交替沉积Cu-SiO2纳米复合膜,研究不同Cu靶功率和衬底温度对纳米复合膜的相结构和光吸收性能的影响。结果表明:随着Cu靶功率的增加,金属Cu纳米颗粒尺寸增大,导致光吸收峰峰位发生红移;随着衬底温度的升高,由于Cu再蒸发效应致使金属Cu纳米颗粒尺寸减小,引起光吸收峰峰位发生蓝移;与室温下沉积态Cu-SiO2纳米复合膜相比,在衬底加热条件下沉积的纳米复合膜在可见光波段出现了明显的表面等离子体共振吸收峰。因此,Cu靶功率和衬底温度对Cu-SiO2纳米复合薄膜的结晶状况和光吸收性能有显著影响。     

Synthesis of Flowerlike MoS2/CoNi Composites for Enhancing Electromagnetic Wave Absorption

The hierarchical MoS₂/CoNi composites were successfully synthesized by a two-step hydrothermal method. The large surface area of the MoS₂ enhances the dispersivity of the CoNi nanoparticles and the formation of abundant MoS₂/CoNi interfaces, which make an important contribution to the dielectric loss, and the introduction of the CoNi improves impedance matching and introduces magnetic loss, which can improve the absorption performance to electromagnetic waves. Through the calculation of the electromagnetic parameters, the minimum reflection loss (RL) value of the MoS₂/CoNi composites achieves -41.44 dB at 13.53 GHz under a thickness of 2.0 mm and the corresponding effective absorption bandwidth (RL below -10 dB) is 5.6 GHz. The MoS₂/CoNi composite has the potential to be applied to microwave absorption due to its strong absorption and wide bandwidth.     

铀吸氘和氚的动力学同位素效应

应用反应速率分析方法,在高真空金属系统中测定了金属铀在恒容体系和150～300℃范围内吸收氘和氚的p-t曲线。由p-t曲线可知,在同一温度下,铀吸氚的速率与铀吸氘的速率基本相同;而随着温度的升高,由于解吸逆反应的影响,铀吸氚(氘)的反应速率降低。根据p-t曲线计算了吸气反应在不同温度的速率常数,得到铀吸氘和氚的表观活化能分别为(-42.8±0.3)和(-43.2±1.2)kJ·mol-1。从活化能数据可以看出,铀吸氘和氚的反应动力学同位素效应不明显。     

高性能铁电吸波材料

铁电材料由于具有高极化以及良好的化学、热稳定性等性质,在微波吸收领域得到了广泛关注。过去二十年,开展了大量关于铁电吸波材料的研究。系统地综述了铁电材料微波吸收的损耗机制与几类典型铁电材料的微波吸收性能。在损耗机制方面,详细论述了铁电材料的电损耗机制,包括介电损耗、电导损耗及界面损耗机制,同时对于多铁材料与铁电-磁杂化复合材料,分析了磁损耗机制以及磁-介电损耗协同机制,并对各类损耗的形成原因及作用机理进行了总结。在微波吸收性能方面,重点阐述了近些年BiFeO3基与BaTiO3基等铁电材料的微波吸收表现,包括单相材料、掺杂材料及复合材料,并对其在室温及高温下的微波吸收性能进行了比较,同时基于材料的结构、微结构与微波吸收强度及有效吸收带宽等参数的演变联系,对其微波响应机制进行了归纳。最后详细分析了影响铁电微波吸收材料发展所面临的关键问题,并对其未来的研究方向进行了展望。     

LaNixMn0.26Aly合金的吸放氢性能研究

对LaNixMn0.26Aly合金的储氢性能进行了研究。结果表明,与LaNi4.61Mn0.26Al0.13合金相比,LaNi4.5Mn0.26Al0.13合金的晶格常数和晶胞体积均变大,吸氢平台压力略有降低,放氢平台压力基本不变,滞后因子有所改善,储氢容量略有减少,氢化物生成焓绝对值变大,氢化物稳定性增加;对于LaNi4.4Mn0.26Al0.34合金,Al替代部分Ni使合金的晶格常数和晶胞体积变大,吸放氢平台压力明显降低,滞后因子明显改善,吸氢动力学性能显著提高,氢化物生成焓绝对值变大,氢化物更加稳定,但储氢容量有所减少。     

High-Frequency Absorption Properties of Three Kinds of Hollow Multiphase Ceramic Microspheres

Al-TiO₂-Fe₂O₃-MnO₂-Fe-Sucrose-Epoxy Resin as reaction system and self-reactive quenching technology which combines flame thermal spraying, self-propagating high-temperature synthesis and rapid solidification, were used to prepare three kinds of hollow multiphase ceramic microspheres (HMCMs) in different feeding gas (N₂, O₂) and dimension (coarse, fine). The characteristic results of three kinds of HMCMs indicated that various process parameters containing feeding gas and initial agglomerate size in this study can result in the change of surface organization, composition, morphology, and dimension. Investigation of microwave electromagnetic (EM) characteristics of three kinds of HMCMs showed that intrinsic characteristics play an important role in the determining the resulting properties. At 10-14.5 GHz, No. 3 HMCMs possess weak absorption intensity and narrow effective bandwidth (<?10 dB) owing to smaller dimension, but in higher-frequency band (14.5-17 GHz), an obvious absorption peak appears due to good EM match and nano-effects. Compared with No. 1 (O₂ coarse) and No. 3 (O₂ fine) HMCMs, enhanced absorption intensity and effective bandwidth (<?10 dB) were observed in No. 2 (N₂ coarse) HMCMs. Enhancements of absorption intensity and effective bandwidth are associated with extra nitride (AlN, FeN), partial open microspheres, M-hexagonal crystal and micro-nano thick dendrite. No. 2 HMCMs presented excellent microwave-absorption property, with the minimum reflectivity (R _L) of ?27.7 dB at 12.9 GHz. The effective bandwidth (<?10 dB) could reach to 4.1 GHz (10.9-15 GHz). This may be ascribed to the increased conductance loss, multiple scattering, magnetocrystalline anisotropy, and shape anisotropy.