ZIF-8-SiO2的制备及其对U(Ⅵ)的吸附

以沸石咪唑酯骨架结构材料ZIF-8及硅酸四乙酯(TEOS)为原料制备ZIF-8-SiO2复合材料,并采用XRD、SEM、EDS等方法对ZIF-8-SiO2的结构及吸附U(Ⅵ)前后的形貌进行表征,结果表明ZIF-8-SiO2成功制备且对U(Ⅵ)具有良好的吸附作用.以静态吸附实验,分别考察了pH值、时间、温度、溶液初始铀浓...     

ZIF-8/PVA静电纺丝膜的制备及其吸附性能

采用静电纺丝技术成功制备出沸石咪唑骨架材料(ZIF-8)/聚乙烯醇(PVA)静电纺丝膜。分别探究和优化了PVA浓度、纺丝电压、接收距离等参数对纤维膜形态结构的影响。对复合纳米纤维膜进行了形貌表征和成分分析。实验发现在ZIF-8的浓度为10wt%条件下,当PVA的浓度为7wt%、电压为40kV、接收距离为16cm时,可得到可纺性最好、形态均匀的纳米纤维膜,膜纤维的平均直径在240nm左右。将已经制备成功的ZIF-8/PVA复合纳米纤维用于吸附刚果红,在12h内吸附容量可达86mg/g,显示出良好的吸附能力。     

聚苯乙烯-SiO2/NiFe2O4磁性微球的制备与表征

以NiFe2O4纳米粒子作磁性载体、苯乙烯(ST)、正硅酸乙酯(TEOS)为原料,KH-570为交联剂,采用乳液聚合法制备了聚苯乙烯-SiO2/NiFe2O4磁性微球材料。通过VSM、FT-IR、SEM、TG-DTA、溶剂抽提等方法对磁性微球材料进行了测试。制备的NiFe2O4粒子为面心立方结构,NiFe2O4纳米颗粒及聚苯乙烯-SiO2/NiFe2O4磁性微球具有超顺磁性。聚苯乙烯-SiO2/NiFe2O4磁性微球以SiO2/NiFe2O4为核、PS为壳,通过KH-570接枝到SiO2/NiFe2O4上,核壳间以共价键相接的包覆型纳米粒子,平均直径为100nm左右,具有良好的热稳定性和耐溶剂性能。热重(TG)分析表明,磁性聚苯乙烯微球磁性物质质量分数为28.8%。     

UiO-66/壳聚糖的制备及其对U(VI)的吸附机制

铀矿开采和冶炼等工艺产生大量低浓度铀废水,危害着生态环境和人类健康,从含铀废水中去除铀(VI)迫在眉睫。本文以UiO-66、壳聚糖(CS)为原料,采用交联法制备UiO-66/CS新型复合材料,通过静态吸附实验,考察不同pH值、吸附剂投加量、吸附时间及铀初始浓度等外部因素对U(VI)去除率的影响。通过SEM、FTIR、XPS等对UiO-66/CS材料进行表征分析,揭示吸附剂去除U(VI)的机制。结果表明：在铀初始浓度为5 mg/L,温度为298 K,p H为5,投加量为0.15 g/L,吸附时间120 min条件下,UiO-66/CS对U(VI)的去除率可达90.24%。吸附过程符合准二级动力学模型和Freundlich等温吸附模型。U(VI)吸附去除机制主要是-NH、-COOH、Zr-O、-OH等官能团与U(VI)发生络合作用。     

ZrW2O8 / ZrO2 可控热膨胀复合材料的制备

采用分步加热固相法成功制备了纯度较高的各向同性负热膨胀材料ZrW₂O₈ 。将ZrW₂O₈ 与ZrO₂ 按一定比例混合, 在1200 ℃烧结24 h 制备了热膨胀系数可控的ZrW₂O₈ / ZrO₂ 复合材料。研究结果表明, 通过改变ZrW₂O₈ 的体积分数, ZrW₂O₈ / ZrO₂ 复合材料的热膨胀系数可以控制为负、正或零。当ZrW₂O₈ 的体积分数为37 %时, 复合材料的热膨胀系数接近零。为了得到致密的ZrW₂O₈ / ZrO₂ 复合陶瓷, 采用Al₂O₃ 作为烧结剂, 取得了较好的效果。0. 35 wt % Al₂O₃ 的加入可以在不影响复合材料热膨胀性能的前提下, 显著提高复合材料的致密度。      

PI/ZIF-8杂化膜的制备及CO_2/N_2分离性能研究

以BTDA-ODA型聚酰亚胺为基质膜材料,2-甲基咪唑锌(ZIF-8)为掺杂剂,制备了聚酰亚胺基杂化膜(PI/ZIF-8)。运用FT-IR、XRD、SEM和EDS等表征方法,对ZIF-8含量不同的杂化膜的化学结构和微观结构进行了分析,并对杂化膜进行了CO_2和N_2单一气体渗透测试。结果表明,ZIF-8与PI两相完全相容且杂化膜对CO_2表现出很高的渗透选择性。当ZIF-8质量分数为7%(PI/7Z)时,CO_2的渗透系数为2.79×10~(-9) mol·m~(-2)s~(-1)Pa~(-1),相应的CO_2/N_2理想选择性系数达到最大值13.6,远大于努森扩散的分离系数0.79。     

化学共沉淀法合成低热膨胀ZrW2O8/ZrO2复合材料

采用化学共沉淀法合成前驱体,前驱体经1150℃烧结得到ZrW₂O₈/ZrO₂复合材料。对ZrW₂O₈/ZrO₂前驱体进行傅里叶变换红外光谱、热重-差示扫描量热分析;通过X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)和热膨胀仪对合成样品的晶体结构、断面形貌和热膨胀性能进行表征。研究结果表明:合成的复合材料的组元为α-ZrW₂O₈和m-ZrO₂相,化学均匀性良好且易烧结;随着ZrW₂O₈质量分数增加,复合材料的热膨胀系数减小,其中26%ZrW₂O₈/ZrO₂复合材料在30~600℃的平均热膨胀系数为-0.5649×10-6K-1,近似为0。      

基于ZIF-8的中空立方体的制备及锂离子电池应用

材料的结构形貌对其应用起到至关重要的作用, 中空结构因其独特的结构特征广泛应用于催化, 气体储存, 锂离子电池等领域。本文首先通过调控表面活性剂CTAB制备出大小一致的沸石咪唑骨架 (ZIF-8) 立方体, 然后利用TEOS和多巴胺来固定立方体ZIF-8的形貌, 接着通过退火以及刻饰的方法获得SiO₂@C的中空立方体结构。通过X射线衍射、扫描电镜、透射电镜等一系列表征方法可知, 采用模板法制备出的SiO₂@C不仅在尺寸上保持大小的高度一致并且具有规则的立方体结构。作为中空结构在实际应用中的典型例子, 将SiO₂@C作为模板制备出的中空SiO₂@C@MoS₂结构, 具有优异的锂离子储存性能。在100 mA/g恒流充放电下循环100次后保持着930 mAh/g的放电比容量, 且在此过程中充放电循环效率均在95%以上。     

Variation of the An-O bond lengths in NaAnO2(OOCCH3)3 and (NH4)4AnO2(CO3)3, An = U(VI), Np(VI), and Pu(VI)

For studying actinide contraction in triacetate and tricarbonate complexes of hexavalent actinides in the series U-Np-Pu, single crystals were prepared and crystal structures of NaPuO₂(OOCCH₃)₃ and (NH₄)₄. AnO₂(CO₃)₃ (An = Np, Pu) were determined. These compounds are isostructural with NaAnO₂(OOCCH₃)₃ (An = U, Np) and (NH₄)₄UO₂(CO₃)₃ studied previously. The coordination surrounding of An(VI) is a distorted hexagonal bipyramid. The actinide contraction in An(VI) triacetate and tricarbonate complexes is manifested in shortening of the bond lengths in the AnO ₂ ²⁺ cation in the series U-Np-Pu. In triacetate complexes NaAnO₂(OOCCH₃)₃, the average bond lengths in AnO ₂ ²⁺ decrease by approximately 2.3% in passing from Np(VI) to Pu(VI). In tricarbonate complexes (NH₄)₄AnO₂(CO₃)₃, the bond lengths in AnO ₂ ²⁺ decrease by approximately 0.7% in passing from U to Np and by approximately 0.4% in passing from Np to Pu. The actinide contraction is less noticeable in the equatorial planes of the bipyramids. The lengths of the An-O bonds with oxygen atoms located around actinyl groups depend on the ligand nature and also on participation of oxygen atoms in the coordination with Na⁺ cations in the triacetate complexes or in hydrogen bonds with NH ₄ ⁺ ions in the tricarbonate complexes. Original Russian Text ? I.A. Charushnikova, N.N. Krot, Z.A. Starikova, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 6, pp. 495–499.     

Synthesis and crystal structure of new U(VI) and Np(VI) benzoates, K11(AnO2)23(OOCC6H5)57(H2O)18+x

The structure of new double benzoates of hexavalent actinides, K₁₁(AnO₂)₂₃(O₂C₇H₅)₅₇(H₂O)_18+x (An = U, Np), was studied. There are five crystallographically independent actinide atoms in the crystals. The coordination polyhedra of An(1), An(3), An(4), and An(5) are distorted hexagonal bipyramids, and that of An(2) is a distorted pentagonal bipyramid. Ten crystallographically independent benzoate ions have been found in the crystals. All but one anions are bidentate chelating and form with AnO₂²⁺ cations either electrically neutral [AnO₂(O₂C₇H₅)₂(H₂O)₂][An(1)O₂²⁺ cations] or negatively charged [AnO₂(O₂C₇H₅)₃]⁻[An(3)O₂²⁺, An(4)O₂²⁺, An(5)O₂²⁺ cations] complexes. The bidentate bridging benzoate ion links two adjacent An(2)O₂²⁺ cations with the formation of peculiar electrically neutral cyclic fragments [AnO₂(O₂C₇H₅)₂(H₂O)]₆ arranged perpendicular to the c-axis. There are three independent K⁺ cations in the structure. The coordination surrounding of K(1)⁺ (coordination number CN 6) is formed by oxygen atoms of two electrically neutral [AnO₂(O₂C₇H₅)₂(H₂O)₂] fragments and of the complex anion [AnO₂(O₂C₇H₅)₃]⁻. The coordination surrounding of K(2)⁺ (CN 6) consists of oxygen atoms of three complex anions [AnO₂(O₂C₇H₅)₃]⁻. The disordered K(3)⁺ cation is arranged near the sixfold axis between the cyclic fragments [AnO₂(O₂C₇H₅)₂(H₂O)]₆. An important structure-forming factor in the crystals is hydrogen bonding involving coordinated water molecules. In the coordination polyhedra of actinides, the An-O bond lengths regularly decrease in going from U to Np owing to actinide contraction.     

Recording Resolution and Writability for (Co-Pt)-SiO2/Co-SiO 2 Hard/Soft-Stacked Granular Perpendicular Media

The magnetic properties and recording performance of hard/soft stacked media consisting of a magnetically hard 9-nm-thick (Co-Pt)-SiO ₂ layer underneath a thin (2-3 nm) soft granular layer were studied. Experimental results indicated that an increase in the mean value of saturation magnetization of the soft layer langM_s ^softrang was very effective at improving the recording resolution D₅₀ due to an increase in the slope of magnetization curve alpha. The use of a Co-SiO₂ layer, which has the highest langM_s ^softrang in the present study, resulted in the highest D₅₀ value. It is likely that the increase in alpha was mainly caused by the demagnetization field in grains due to the difference between langM _s ^softrang and the mean value of saturation magnetization of the hard layer, langM_s ^hardrang. Moreover, it was successfully demonstrated that the magnetization reversal of (Co-Pt)-SiO₂/Co-SiO₂ stacked media changed systematically as theoretically predicted on reducing the interfacial exchange coupling by using NiFeCr-SiO₂ or Pt-SiO₂ interlayers. The reduction of remanence coercivity H_r was achieved by controlling the thickness and film composition of the interlayer, moreover, a high-langM_s ^softrang enhanced the H_r reduction. The H_r reduction improved recording writability without degrading D₅₀, the signal to medium noise ratio SN_mR and thermal stability     

Synthesis and characteristics of double Np(VI) and Pu(VI) phthalates of the composition M2AnO2(C8H4O4)2· n H2O (M = NH4, K, and Cs)

Double salts of o-phthalic acid of the general composition M₂AnO₂(C₈H₄O₄)₂ nH₂O (M = NH₄, K, Cs and An = Pu, Np) were isolated from neutral aqueous solutions. The composition was determined by chemical analysis. The compounds were characterized by powder X-ray diffraction, and unit cell parameters of some salts were determined from the powder X-ray patterns. The optical absorption spectra of the crystal-line plutonium compounds were measured. Thermal behavior in heating to 800°C in air was studied. The differences in the behavior of U, Np, and Pu compounds under similar conditions were noted. Original Russian Text N.N. Krot, I.A. Charushnikova, A.A. Bessonov, M.S. Grigor’ev, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 3, pp. 202–206.     

Crystal structure of complexes of Np(VI) and Pu(VI) perchlorates with triphenylphosphine oxide, [NpO2(OP(C6H5)3)4](ClO4)2 and [PuO2(OP(C6H5)3)4](ClO4)2

Single crystals of [NpO₂(TPPO)₄](ClO₄)₂ and [PuO₂(TPPO)₄](ClO₄)₂ isostructural to the complex [UO₂(TPPO)₄](ClO₄)₂ [TPPO = OP(C₆H₅)₃] studied previously were prepared, and the structures of these compounds were determined. The coordination polyhedron of these compounds is a tetragonal bipyramid. The geometric characteristics of the tetragonal bipyramids in the compounds are practically the same despite the actinide contraction of the central atoms, whereas the unit cell volume decreases in the series U-Np-Pu. The equality of the volumes of the coordination polyhedra of the U, Np, and Pu atoms is attributed to the influence of TPPO containing phenyl radicals with negative effective charge. Original Russian Text ? I.A. Charushnikova, N.N. Krot, Z.A. Starikova, I.N. Polyakova, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 407–411.     

K2(Rb2,Cs2,Tl2)TeBr6(I6) and Rb3(Cs3)Sb2(Bi2)Br9(I9) perovskite compounds

We systematize available experimental data on the crystal structure of the ternary halides K₂(Rb₂,Cs₂,Tl₂)TeBr₆(I₆) and Rb₃(Cs₃)Sb₂(Bi₂)Br₉(I₉), analyze the general trends in the properties of their single crystals, and examine the key features of the physicochemical interaction in related systems.     

Treatment of electrostatic interactions at the Si(1 0 0)-SiO2 interface

Silica in equilibrium with silicon is known to be partly crystalline. Because of crystallographic constraints, models proposed so far (cristobalite as well as tridymite) deal with polar surfaces of silica, which are expected to be highly unstable. In this paper, using both exact treatments of simplified models and Monte-Carlo simulations of the real system with effective potentials, we show how the system compromises to decrease the electrostatic energy. We also investigate the role of electrostatic interactions on the formation of oxygen vacancies at the Si-SiO₂ interface. Using a tight binding approach, implications of these interactions on mid-gap surface states in silica are also discussed.     

Crystal Structure of (H3O)6[(UO2)5(SeO4)8(H2O)5](H2O)5

Crystals of (H₃O)₆[(UO₂)₅(SeO₄)₈(H₂O)₅](H₂O)₅ were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 13.835(2), b = 13.4374(16), c = 14.310(3) Å, β = 108.004(14)°, V = 2530.1(7) Å ³] was solved by the direct method and refined to R ₁ = 0.090 for 4409 reflections with |F _hkl ≥ 4σ|F _hkl |. The structure is based on [(UO₂)₅(SeO₄)₈(H₂O)₅]⁶⁻ layers arranged parallel to the (101) plane; these layers have a unique topological structure. The U(1)O₆(H₂O) and U(3)O₆(H₂O) linked through selenate groups form chains running along [ [`1]\bar 1 01] direction. The chains are combined in layers by U(2)O₆(H₂O) bipyramids. The layers are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups located between the layers.     

Use of semi-empirical potentials to simulate the Si(1 0 0)-SiO2 interface

The rapid development of ab initio methods makes possible the test of semi-empirical potentials which retain some advantages in the simulation of large systems. Even systems involving oxygen vacancies can be studied with semi-empirical methods. Modelling of the Si(1 0 0)-SiO₂ interface raises some specific problems due to charge transfers and severe simplifications are still necessary.     

Structural and thermochemical properties, and energetics of C8(NO2)8 and C20(NO2)4n (n = 0–4)

Density-functional-theory calculations, at the B3LYP level with the 6–31 G basis set, have been performed to investigate the structural and electronic properties of octanitrocubane, C₈(NO₂)₈, and polynitrofullerenes of type C₂₀(NO₂)_4n, with n = 0–4, in their ground states. Having determined their energetically optimized geometric structures, energetics, and vibrational frequencies, we have calculated the enthalpies of combustion and decomposition of these molecules. Extrapolating from the so-obtained data, we have also estimated, as a by-product, the enthalpy values of C₂₀(NO₂)₂₀.