Si添加物对Li掺杂的Mg2(Ge,Sn)热电性能的影响

Mg₂(Ge, Sn)固溶体是一种环境友好型的中温(500~800 K)热电材料。目前n型Mg₂(Ge, Sn)热电材料的ZT值已经高达1.4,但p型Mg₂(Ge, Sn)的ZT值仅为0.5。本文在p型Mg_1.92Li_0.08Ge_0.4Sn_0.6中添加了少量Si元素以在材料中形成富Si相,利用其与基体的界面过滤低能载流子、降低热导率。采用两步固相反应、球磨和热压的方法制备Mg_1.92Li_0.08Ge_0.4Sn_0.6-xSi_x (x=0, 0.025, 0.05, 0.075, 0.1)样品,通过测试样品的热电输运参数,分析Si添加物对样品热电输运和性能的影响。结果表明:Si添加物能显著提高基体的功率因子,同时有效降低晶格热导率和电子热导率;最终,Mg_1.92Li_0.08Ge_0.4Sn_0.525Si_0.075的ZT最大值在723 K达到0.75。     

H原子对Gd5Si1.72Ge2.28合金低场磁性能和磁熵变的影响

为了提高Gd5(SixGe1-x)4(0.2<x≤0.5)系合金的居里温度同时保持该类合金的大磁热效应,使用商业蒸馏Gd为原材料,用非自耗电弧炉熔炼出Gd5Si1.72Ge2.28母合金,然后将该合金粉末在贮氢合金用PCT设备上进行吸氢,获得了Gd5Si1.72Ge2.28Hx合金.磁性测量结果表明,H原子的引入,使合金的居里温度从246 K提高到297 K;同时,合金在居里温度附近的最大磁熵变从-7. 6 J*kg-1*K-1下降到-4.2 J*kg-1K-1(0～1.5 T),但与同纯度的Gd相比,Gd5Si1.72Ge2.28Hx合金的磁熵变仍然比Gd的磁熵变(-3.1 J*kg-1*K-1,0～1.5 T)高出35%.     

Mg70(A0.25Ni0.75)30合金结构及储氢性能

为研究稀土元素Ce、Y对非晶储氢合金催化及其性能的影响,采用快淬法制备Mg70(A0.25Ni0.75)30(A=Ce,Y)合金,使用Sievert’s气体吸附技术和差示热扫描技术研究其储氢性能和热力学稳定性。XRD衍射分析显示,快淬制备的合金为非晶合金,但在573K、2MPa的氢压下,氢化后的Mg70(Y0.25Ni0.75)30会产生MgH2、Mg2NiH4和2相,Mg70(Ce0.25Ni0.75)30会产生Mg2NiH4、CeNi5和MgH2相。不同温度的动力学测试结果表明,快淬法制备的Mg70-(Ce0.25Ni0.75)30和Mg70(Y0.25Ni0.75)30合金分别获得的最大吸氢量为质量分数4.42%和3.09%,Mg70(Ce0.25Ni0.75)30和Mg70(Y0.25Ni0.75)30合金前100s吸氢量分别达到各自最大吸氢量的97%和87%。通过对DSC曲线的分析发现,Mg70(A0.25Ni0.75)30的脱氢活化能较低,分别为111.025±2.790kJ/mol(A=Ce)、84.843±2.057kJ/mol(A=Y)和152.207±6.764kJ/mol(A=Y)。实验结果表明,Y元素对Mg70(A0.25Ni0.75)30合金催化及储氢性能的改善要优于Ce元素。     

通过Cu/Ti液相扩散反应进行Si_3N_4/Cu的连接

用 Ti粉作中间层在 12 73K直接进行 Si3 N4 / Cu的连接 .用四点弯曲方法测定了不同保温时间下的连接强度 ,并对连接界面进行了 SEM、EPMA和 XRD分析 .结果表明 :通过 Cu- Ti二元扩散促使液相与氮化硅发生界面反应 ,形成 Si3 N4 / Ti N/ Ti5Si3 Ti5Si4 / Cu3 Ti2 (Si) / Cu的梯度层界面 .接头弯曲强度随着保温时间的增加 ,先增后降 .微观分析表明 :Si3 N4 与 Ti的界面反应以及 Cu、Ti、Si的相互扩散决定了接头的力学性能     

稀土磁致冷Gd5Ge2(Si2-xMnx)化合物的结构及微观机制

利用X射线衍射和扫描电镜对Gd5Ge2(Si2-xMnx)结构及表面形貌进行了研究.并利用差示量热法对Gd5Ge2(Si2-xMnx)的磁热性能进行了研究.x射线衍射(XRD)测量分析表明Mn的替代不会影响母体Gd5Si2Ge2的晶体结构,样品中的主相仍然具有单斜结构(P1121/a),其晶体对称性不会随Mn含量的增加而改变.随着Mn含量的增加,晶粒逐渐变大,晶常数增大,体积膨胀,同时Mn和杂质相的析出量也在增加.少量的Mn元素替代Si可以提高Gd5Si2Ge2化合物的居里温度.     

Cu-Cr2O3/Al2O3催化剂上乳酸乙酯加氢制丙二醇研究

在间歇反应器上考察了通过共沉淀法制备得到的一系列不同负载的Cu-Cr2O3/Al2O3催化剂的催化加氢效果.研究结果表明:当n(Cu)∶n(Cr)=2∶1时有最佳的催化剂活性,n(Cu)∶n(Cr)=1∶1时有最佳的1,2-丙二醇选择性.在反应温度为200℃、氢气压力为3MPa、搅拌速率为500r/min和n(Cu)∶n(Cr)=2∶1的Cu-Cr2O3/Al2O3催化剂作用下,反应6h,实现了乳酸乙酯的完全转化,其中1,2-丙二醇的收率达到了95.3%.     

NOM组分对O3降解水中微污染有机物的影响

采用一系列不同截留分子量的超滤膜将提取的天然有机物(NOM)滤分为6种组分(NOM10K、NOM5K-10K、NOM3K-5K、NOM1K-3K、NOM500-1K、NOM500)组分,并研究了这6种NOM组分对臭氧(O3)氧化降解水中两种典型微污染有机物(双酚A和硝基苯)的影响.结果表明:对于与O3反应活性较高的有机物双酚A(BPA),NOM各组分的引入使得O3去除BPA效能有所下降;对于与O3反应活性较低的有机物硝基苯(NB),高分子量范围的NOM组分(NOM10K、NOM5K-10K、NOM3K-5K、NOM1K-3K)的存在能强化O3的自由基链式分解反应,从而促进O3对硝基苯的去除.低质量浓度的NOM对O3氧化降解水中有机物的影响与NOM的特性(所含的官能团的类型和数量)以及目标有机物与O3的反应活性有关.     

复合催化剂WO3/ZrO2-SiO2的制备及其在仲醇脱水制备α-烯烃中的应用

采用等体积浸渍法合成复合催化剂WO₃/ZrO₂-SiO₂,并通过XRD、NH₃-TPD、XPS等表征确定其结构和性能。在固定床反应器上通过仲醇脱水制备α-烯烃对催化剂活性进行评价。结果表明：在WO₃负载量(质量分数)为15%,n(Zr)/n(Si)为1/1、焙烧温度600℃、焙烧时间6 h时所制备的催化剂最具催化活性,在固定床反应器中进行仲醇脱水实验,当反应温度为350℃、空速0.3 h^-1时,α-烯烃的有效选择性可达到80%以上。     

Ag/CuWO4/g-C3N4复合光催化剂的制备及可见光下降解盐酸四环素

利用超声辅助水热法以及光还原法将Ag纳米颗粒与CuWO₄/g-C₃N₄光催化剂复合,并使用XRD、SEM、TEM、FT-IR、XPS、DRS和PL等表征手段对催化剂的表面特性和光化学性质进行了分析。通过Ag/CuWO₄/g-C₃N₄光催化剂在氙灯照射下降解盐酸四环素的实验,考察了Ag纳米粒子担载的二元复合材对催化剂光催化性能的影响。Ag/CuWO₄/g-C₃N₄复合光催化剂对盐酸四环素(TTCH)的光催化降解率达到95%,降解速率是CuWO₄/g-C₃N₄的1.39倍。Ag担载的CuWO₄/g-C₃N₄复合材料通过Ag表面的等离子共振效应和电子聚集能力促进电子空穴分离,提升了材料的光催化活性。     

Fe_(40)Co_(40)Zr_(10)B_9M_1(M=Cu,Ge,Ag)合金的热稳定性及微观结构研究

采用单辊快淬法制备Fe40Co40Zr10B9Cu1、Fe40Co40Zr10B9Ge1和Fe40Co40Zr10B9Ag1非晶合金薄带,并对3种合金在不同温度下进行热处理.利用差热分析仪(DTA)和X射线衍射仪(XRD)等测试手段对样品的热稳定性及微观结构进行研究.结果表明:Fe40Co40Zr10B9Cu1、Fe40Co40Zr10B9Ge1和Fe40Co40Zr10B9Ag13种合金的激活能分别为262.4、267.6和252.3 k J/mol,说明Cu元素、Ge元素和Ag元素的添加对合金的热稳定性影响不大,Ge元素的添加最有利于提高合金的热稳定性.3种合金的晶化过程相似:非晶→非晶+α-Fe(Co)→α-Fe(Co)+Zr Co3B2+Fe(Co)3Zr.     

硅锗超晶格结构热导率的分子动力学模拟

采用Stillinger-Webber势能函数描述硅锗超晶格结构原子间的相互作用,建立硅锗超晶格结构的热传导系统,利用非平衡分子动力学模拟方法计算了不同周期数、不同厚度、不同温度下的Si/Ge超晶格结构热导率.模拟结果表明：超晶格结构热导率随着周期长度和周期数的增加而逐渐增大.受界面热阻效应的影响,靠近高温热墙处导热层...     

Electrical conductivity of Cu/（10NiO-NiFe2O4） cermet inert anode for aluminum electrolysis

Cu/(10NiO-NiFe2O4) cermets containing mass fractions of Cu of 5%, 10%, 15% and 20% were prepared, and their electrical conductivities were measured at different temperatures. The effects of temperature and content of metal Cu on the electrical conductivity were investigated especially. The results indicate that the metallic phase Cu distributes evenly in 10NiO-NiFe2O4 ceramic matrix. The mechanism of electrical conductivity of Cu/(10NiO-NiFe2O4) cermets obeys the rule of electrical mechanism of semiconductor, the electrical conductivity for cermet containing 5% Cu increases from 2.70 to 20.41 S/cm with temperature increasing from 200 to 900 ℃. The change trend of electrical conductivity with temperature is similar with each other and it increases with increasing temperature and content of metal Cu. At 960 ℃, the electrical conductivity of cermet increases from 2.88 to 82.65 S/cm with the content of metal Cu increasing from 0 to 20%.     

Structure Electrical Conducting and Thermal Expansion Properties of Ln0.6Sr0.4Co0.8Fe0.2O3 (Ln=La,Pr,Nd,Sm)Ceramics

Ln0.6Sr0.4Co0.8Fe0.2O3 (Ln=La, Pr, Nd, Sm) perovskite-type complex oxides were synthesized using a glycine-nitrate process, and the structure, electrical conducting and thermal expansion properties of the resulting ceramics were examined with regard to the nature of the lanthanide cations. The results indicated that the La, Pr and Nd specimens had a rhombohedral symmetry, while an orthorhombic structure was determined for the Sm specimen. The pseudo-cubic lattice constant decreased with smaller lanthanide cations. It was found that the electrical conducting properties declined with decreasing lanthanide cation size. Fortunately, all the compositions remained rather high electrical conductivities exceeding 650Ω1.cm-1 in the intermediate temperature range (600-800℃). An appreciable thermal expansion increase at high temperatures was detected for all the compositions. Decreasing the size of the lanthanide cations resulted in an increase of thermal expansion. With respect to the high electrical conductivities, the Ln0.6Sr0.4Co0.8Fe0.2O3 oxides are considered to be acceptable as mixed conducting component in composite cathode designs together with doped ceria electrolytes.     

Experimental study on thermophysical properties of C/C composites at high temperature

Ablationthermalprotectivecompositesarethekeystructureofspacevehiclesprotectingthemfromaerody namicheatingduringtheirreentryintotheaerosphere.Thecarbonmatrixcompositesarethemostpromisingablationmaterialsusedinthisenvironmentduetotheirpotentiallyfavorablepr…     

Thermoelectric properties of Ca3Co4O9 ceramics

Ca₃Co₄O₉ ceramics were prepared using the sol-gel process with ordinary pressing sintering and their thermoelectric properties were measured from room temperature to 673 K. The experimental results show that single phase Ca₃Co₄O₉ can be fabricated at 750–900 °C in different citrate acid molar proportions for 0.2–1.0. For all the oxides, both the Seebeck coefficients S and the electrical conductivities κ increase with the increasing temperature. The Seebeck coefficients S are all positive. The thermal conductivities k increase with the increasing temperature also and the lattice thermal conductivity κ _l plays an important role to the thermal conductivity κ. The citrate acid molar proportions have a large influence on the particle sizes, which influences the thermoelectric properties of the ceramics. The figure of merit increases with the increasing temperature and reaches 4.5×10⁻⁵ K⁻¹ at 573 K for the sample in the citrate acid molar proportion of 0.46.     

SiCp/Cu复合材料的热膨胀性和导热性

采用热等静压的方法制备了SiCp／Cu电子封装复合材料．材料热膨胀系数（CTE）和导热率的测定表明,增加SiC体积分数和减小SiC颗粒的尺寸有利于降低CTE值;SIC质量分数超过26％这一临界值后,材料导热率会明显下降．减小残余应力有利于降低材料的CTE值．     

辛醇接枝碳纳米管复合相变材料的导热性能研究

通过将碳纳米管（CNTs）用混酸进行处理后在其表面以正辛醇（C8H17OH）进行接枝处理,制得接枝C8H17O-CNTs。经红外光谱分析,所得接枝产物出现区别于C8H17OH上的C-O键特征吸收峰,表明接枝成功。在熔融的石蜡（PW）中加入接枝产物并进行搅拌和恒温超声后制得均匀复合物。复合物导热系数的测量结果表明,随温度的升高纯PW和各个组成的复合物的导热系数基本呈现下降趋势。复合物的导热系数基本随C8H17O-CNTs的含量的增加而增大。其中含质量分数为1.0%C8H17O-CNTs的复合物的导热系数较纯PW的导热系数在各个测量温度都提高了大约0.06 Wm-1K-1。     

Effects of Microstructure Modification on Properties of AIN/BN Composites

It is very difficult to prepare full-densified aluminum nitride-boron nitride(AIN/BN)composite ceramics with homogeneous microstructure and high thermal conductivity.Spark plasma sintering(SPS)was used to fully densify the AIN/BN composites in this work.Microstructure,mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated.The results show that the microstructure of composites is fine and homogenous,and the AIN/BN composites exhibit high mechanical properties.To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites,a heat treating methodology was introduced through gas pressure sintering(GPS).This processing was significantly beneficial to enhancing the thermal conductivity of the specimen.The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.     

Effects of Mierostructure Modification on Properties of MN/BN Composites

It is very difficult to prepare full-densified aluminum nitride-boron nitride(AIN/BN) composite ceramics with homogeneous microstructure and high thermal conductivity.Spark plasma sintering (SPS)was used to fully densify the AlN/BN composites in this work.Microstructure,mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated.The results show that the microstructure of composites is fine and homogenous,and the AIN/BN composites exhibit high mechanical properties.To promote the growth of AlN grains and modify the distribution of grain boundary in AIN/BN composites,a heat treating methodology was introduced through gas pressure sintering(GPS).This processing was significantly beneficial to enhancing the thermal conductivity of the specimen.The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.