Sr3YCo4-xMgxO10.5+δ(0≤x≤0.04)多晶的制备和热电输运性质研究

采用固相反应法制备Sr3YCo4-xMgxO10.5+δ(0≤x≤0.04)系列多晶,研究了Mg掺杂对体系结构、电输运和热电性质的影响.结果表明系列多晶为四方晶系,由于掺入的Mg2+(0.066 nm)部分替代了Co3+/4+(0.053 nm/0.061 nm),使晶格膨胀;多晶热电势在340~830 K随温度升高而下降,且Mg掺杂对热电势影响不大,表明Mg掺杂对体系载流子浓度影响不大;多晶电阻率在100~300 K随温度升高而降低,且随着掺杂量增加电阻率降低,结合扫描电镜观察到多晶的气孔数目减少、晶粒连接紧密和热电势的结果认为Mg掺杂对体系电输运性质的影响机制主要是使气孔、晶界散射作用减弱、载流子迁移率变大,而Mg掺杂对载流子浓度的影响是次要的.     

Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method

As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results.     

稳定同位素比质谱法测定苹果和浓缩苹果汁的δ13C值

用从国际原子能机构溯源得到的橄榄油标准物质[Cat No.B 2172-Batch 3130,其δ13CPDB为(-28.51±0.16)‰]作标准,应用稳定同位素比质谱法测定了苹果和苹果汁的δ13 C值,并以此确定国产苹果的δ13 C值的范围和鉴定制成的果汁的质量。苹果样品去皮后切碎,打成糊状,离心后取其上清液,在75℃加热2～3h至呈黏稠状液体,冷却至室温。此时其糖度约为70Brix。浓缩苹果汁样品是黏稠液体,其糖度一般也在70Brix左右。取2μL上述样品置于锡杯中,按方法处理后供质谱分析。标准物质的进样量为2μL。按所测得碳的稳定同位素13C与12C的比值代入所给公式计算δ13 C值。结果表明:方法的精密度较好,其相对标准偏差(n=11)均小于0.021%。根据测定结果发现,我国苹果的δ13C值在-29.1‰～-23.33‰之间。     

On the ground state of quantum graphs with attractive δ-coupling

We study relations between the ground-state energy of a quantum graph Hamiltonian with attractive δ coupling at the vertices and the graph geometry. We derive a necessary and sufficient condition under which the energy increases with the increase of graph edge lengths. We show that this is always the case if the graph has no branchings while both energy increase and decrease are possible for graphs with a more complicated topology.     

利用H3PO4液层侧面红外热像研究YBCO高温超导薄膜的激光辅助刻蚀特性

利用红外热像实时监测系统,获取钇钡铜氧激光辅助化学刻蚀中H₃PO₄液层的侧面红外热像,研究了其溶液温度分布与热对流特性,并对红外监测数据与钇钡铜氧薄膜激光化学刻蚀特性的关系进行了分析.主要实验结论包括:红外灰度图可真实反映溶液的温度分布和热对流情况,为激光化学刻蚀的热环境分析提供有价值的红外监测数据;通过任意时刻钇钡铜氧表面生成热流所到达高度的分布情况和该时刻的红外灰度图,分析出钇钡铜氧薄膜表面各区域的腐蚀启动先后和刻蚀程度差异等重要信息,为钇钡铜氧及其它材料的激光化学刻蚀特性的实时监测提供了一种新的技术手段.     

δ-Jordan李超代数的交换扩张

通过δ-Jordan李超代数T的表示和上同调理论,构造δ-Jordan李超代数T■V.证明了δ-Jordan李超代数的等价交换扩张给出相同的表示.通过δ-Jordan李超代数的表示和其交换扩张得到2-上圈.     

Synthesis of pyranoid δ-sugar amino acids and their oligomers from per-benzylated β-C-vinyl glucoside

Two pyranoid δ-sugar amino acids were prepared from the common per-benzylated β-C-vinyl glucoside and easily oligomerised using solution-phase coupling methodology.     

A sulfonating ionic liquid for one-pot pseudo four-component synthesis of novel 3-chlorosulfonyl-δ-sultones: A novel class of fluorescent compounds

An active imidazolium-based ionic liquid mixture was developed for efficient synthesis of some novel 4,6-diaryl-3-(chlorosulfonyl)-1,2-oxathiine-2,2-dioxides (chlorosulfonyl-δ-sultones) from simple acetophenones at room temperature. The ionic liquid mixture acts as a catalyst to condense two molecules of an acetophenone derivative and as a mild sulfonating agent to convert the resulting condensate into 4,6-diaryl-1,2-oxathiine-2,2-dioxides, and finally as a chlorosulfonating reagent to deliver the desired fully unsaturated chlorosulfonyl-δ-sultones in onepot. The products were separated easily from the reaction mixture and showed valuable fluorescence properties. The structures of these products are in good agreement with their ¹H NMR, ¹³C NMR, and mass spectral data. All rights reserved.     

Enantioselective organocatalytic approach to δ-lactones bearing a fused cyclohexanone scaffold

A new method based on the cascade reaction between β,γ-unsaturated-α-ketophosphonates and cyclic 1,3-dicarbonyls is reported for the synthesis of highly enantiomerically enriched δ-lactones bearing a fused cyclohexenone scaffold. The target products bearing a δ-lactone moiety and one stereogenic center were obtained in good to excellent yields (83–96%) and enantioselectivities (63:32–95:5 er). The best results were obtained in the presence of a chiral Brønsted base catalyst derived from the cinchona alkaloid quinine and modified by a squaramide moiety.     

Effects of Praseodymium Doping on Conductivity and Oxygen Permeability of Cobalt-Free Perovskite-Type Oxide BaFeO3-δ

Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation.In order to stabilize the cubic perovskite structure of BaFeO_3-δ material at room temperature, iron was partially substituted by praseodymium.BaFe_1-yPr_yO_3-δ powders were synthesized by a solid state reaction method, and sintered samples were prepared from the synthesized BaFe_1-yPr_yO_3-δ powders.X-ray diffraction results reveal that the BaFe_1-yPr_yO_3-δ samples remain cubic structure at praseodymium substitution amount of y=0.05, 0.075, 0.1.Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe_1-yPr_yO_3-δ increase monotonically with the increase of the praseodymium doping amount, praseodymium doping promotes the grain size growth.Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe_1-yPr_yO_3-δ and BaFe_0.9Pr_0.1O_3-δ composition has an electrical conductivity of 6.5 S/cm and an oxygen permeation of 1.112 mL/(cm²·min) at 900 ℃, respectively.High temperature XRD investigation shows that the crystal structure of BaFe_0.975Pr_0.025O_3-δ membrane completely transform to cubic phase at 700 ℃.The present test results have shown that partially substitution of Fe by praseodymium in BaFeO₃ can stabilize the cubic structure and improve the properties.