纳米CuO的制备及对NH4ClO4热分解的催化性能

研究了快速液相沉淀条件对纳米CuO结构和形貌的影响。并用热分析法考察了不同形貌的纳米CuO对高氯酸铵(AP)分解的催化作用。结果表明,当反应物Cu(NO₃)₂和NaOH的浓度均增大到1.00mol·L^-1或者反应介质乙醇和水的体积比增大到3∶1时,纳米CuO(111)晶面的XRD峰强度弱于其(111)晶面的XRD峰强度;用Na₂CO₃作沉淀剂可获得平均粒径11nm的球形CuO,但团聚严重,添加聚乙二醇(PEG)可改善其分散性。不同形貌的纳米CuO均能强烈催化AP的分解,其中分散性良好的球形纳米CuO,催化活性最强,可使AP的高温分解温度降低99.13℃,分解放热量由590.12J·g^-1增至1380J·g^-1。     

一维CuO纳米棒的微乳-均匀沉淀耦合法制备与结构表征

以CuSO4和NH3·H2O为原料,采用微乳-均匀沉淀耦合法制备了一维CuO纳米棒。用XRD、SEM、TEM、HRTEM和FTIR对产物的结构和形貌进行了表征。结果表明:产物为单斜晶相结构的CuO纳米棒,内部具有孔洞结构,其直径为40～110nm,长度为800～3000nm。可通过改变水核比(ω)、反应物的浓度、反应时间、反应温度等条件实现对CuO纳米棒形貌和尺寸的调控。探讨了可能的反应机理,并用热分析方法考察了CuO纳米棒对高氯酸铵(AP)分解的催化作用。     

草酸铜原位催化高氯酸铵热分解的研究

通过TG-DTA-MS联用技术研究了草酸铜对高氯酸铵的催化过程。研究发现,草酸铜分解生成的氧化铜对高氯酸铵有较强的催化作用,添加2%的草酸铜使高氯酸铵的高温分解温度提前112℃。分解的气相产物主要有H2O,NH3,O2,HCl,Cl2,HNO,NO,N2O和NO2。在草酸铜原位分解生成的CuO表面吸附生成氧的过氧化离子(O2-)和氧离子(O-,O2-)是加速AP热分解反应的主要原因。     

纳米Cu2O的制备及其对高氯酸铵热分解的催化性能

 以Cu(NO3)2和NaOH为原料,以水合肼为还原剂,通过沉淀法在室温下制备了纳米Cu2O. 采用X射线衍射、透射电镜和X射线光电子能谱等手段对产物进行了表征,并用热分析法考察了不同形貌的纳米Cu2O对高氯酸铵热分解的催化作用. 结果表明,通过改变NaOH溶液的加入量可分别得到长针形和多边形的纳米Cu2O. 通过调节反应物浓度可以将纳米Cu2O粒径控制在19～68 nm. 不同形貌的纳米Cu2O均能强烈催化高氯酸铵的热分解,其中分散性良好的多边形纳米Cu2O的催化活性较高,添加2%的多边形纳米Cu2O可使高氯酸铵的高温分解温度降低103 ℃,分解放热量由590 J/g增至1350 J/g.     

Y2O3纳米粒子/碳纳米管复合体的制备及其催化高氯酸铵热分解

采用化学液相沉淀法制备Y2O3纳米粒子/碳纳米管复合体(Y2O3/CNTC),利用扫描电镜(SEM)和X 射线光电子能谱(XPS)对其结构和成分进行了表征. 结果表明, Y2O3纳米粒子能负载在碳纳米管上,且负载效果较好. 采用差热分析研究了Y2O3/CNTC 对高氯酸铵热分解的催化性能, 结果表明, Y2O3 /CNTC 可显著降低高氯酸铵(AP)的高温分解峰温,表现出对AP 高温分解良好的催化性能. 相同量的Y2O3/CNTC 和纯Y2O3纳米粒子进行对比, Y2O3 /CNTC表现出更强的催化性能.当Y2O3/CNTC的质量分数为4%时,使AP的高温分解峰温提前131.14C[deg].     

多孔纳米CoFe2O4的制备及其对高氯酸铵的热分解催化性能

采用胶晶模板法制备出具有三维多孔结构的纳米CoFe₂O₄。利用X射线衍射仪(XRD)、傅里叶变换红外(FT-IR)光谱仪、扫描电镜(SEM)、透射电镜(TEM)和N₂吸附-脱附对样品的晶型和形貌结构等进行表征,采用差示扫描量热法(DSC)对比研究多孔纳米CoFe₂O₄和球形纳米CoFe₂O₄对高氯酸铵(AP)的热分解性能的影响,并考察这两种催化剂对AP催化热分解的动力学参数。结果显示,制备出的多孔纳米CoFe₂O₄样品具有典型的尖晶石结构,孔径约200 nm;比表面积明显高于40 nm球形CoFe₂O₄,达到55.646 m²·g^-1。DSC测试结果表明：多孔纳米CoFe₂O₄的加入促进了AP的热分解,最高使AP的高温分解峰温降低91.46℃,能量释放最高达1120.88 J·g^-1,是纯AP分解放热量的2.3倍;多孔纳米CoFe₂O₄具有较高的比表面积,能提高催化反应的接触面积,使AP的高温分解峰温度更低,反应活化能较小,从而表现出比球形纳米CoFe₂O₄更高的催化活性。此外,对多孔纳米CoFe₂O₄催化AP的热分解机理进行初步探索,纳米多孔催化剂对气态中间产物的作用促进了AP的热分解。     

纳米Co-B非晶态合金对高氯酸铵分解的催化性能

 利用化学还原法制备了纳米 Co-B 非晶态合金,并用透射电镜、X射线衍射、差示扫描量热和N2吸附表面积测试等技术对样品进行了表征. 运用差热分析研究了纳米 Co-B 非晶态合金对高氯酸铵(AP)分解的催化性能. 结果表明,加入 Co-B 非晶态合金后AP的高低温放热峰相连,合并成一个高而大的放热峰,且峰温有很大程度的降低, 这说明纳米 Co-B 非晶态合金对AP热分解有很好的催化活性. 同时, Co-B 非晶态合金能使AP的表观分解热显著增大.     

直形碳纳米管、分叉碳纳米管负载纳米NiO及其对高氯酸铵热分解的影响

采用射流进样催化裂解法制备了直形碳纳米管(CNTs)、分叉碳纳米管, 分别以二者为载体, 用化学沉积法制备了负载纳米NiO的复合粒子, 并研究了纳米NiO和CNTs的单一纳米粒子、简单混合物、复合物对高氯酸铵(AP)热分解的催化性能, 对催化效果的差异作了初步探讨. 结果表明: NiO/直形CNTs和NiO/分叉CNTs复合粒子比表面积大, 表面负载层的纳米NiO结晶好、粒子均匀、粒径小、分散性好. 复合粒子对AP热分解的催化效果比单一纳米粒子和简单混合物好, 其中NiO/分叉CNTs复合粒子催化效果最好, 使AP高温分解峰温降低了94.6 ℃, 使表观分解热增加了819 J/g. CNTs的载体支撑作用, 可防止NiO纳米粒子的团聚, 增大比表面积, 增加反应活性中心, 增加催化效果, 载体分叉CNTs的枝杈形结构, 有利于纳米NiO/分叉CNTs复合粒子催化性能的提高.     

纳米Fe2O3/高氯酸铵复合粒子的制备及其热分解性能研究

用溶剂-非溶剂法制备了纳米Fe2O3／高氯酸铵(AP)复合粒子，并用TEM，SEM，XRD和ICP对其进行了表征．为了研究纳米复合粒子中纳米Fe2O3对AP热分解的催化性能，将相同比例的微米Fe2O3和纳米Fe2O3与AP分别简单混合后作对比，并用DTA对三种样品进行了热分析．结果表明，三种样品中的Fe2O3粒子都能催化AP的热分解；但纳米Fe2O3粒子的催化性能优于微米Fe2O3粒子，纳米Fe2O3／AP复合粒子中纳米Fe2O3对AP的催化性能优于纳米Fe2O3与AP简单混合物．与纳米Fe2O3与AP简单混合的样品相比，纳米复合粒子中的AP高温分解峰温降低20．1℃，低温分解峰几乎消失，表观分解热由850．2J／g提高到1080．8J／g．证明纳米Fe2O3与AP的复合处理能显著提高纳米Fe2O3对AP热分解的催化性能．并用不同样品中AP热分解的动力学参数对所得结果进行了理论分析．     

溶剂热合成Cu2O微球及其对高氯酸铵热分解的催化作用

以聚乙烯吡咯烷酮(PVP)为添加剂,利用溶剂热法合成了Cu2O微球.考察了PVP用量以及反应温度对产物形貌的影响,并在反应时间为2.5与4.5h时分别合成了直径为100-200nm和1μm的Cu2O微球.同时,利用差热分析(DTA)技术考察了不同直径的Cu2O微球对高氯酸铵(AP)热分解的催化效果,结果表明:添加2%(w)的直径为100-200nm和1μm的Cu2O微球使得AP的高温分解温度分别降低了116和118°C,AP在低温阶段的分解量也明显提高.     

Singlet-triplet energy separations in divalent five-membered cyclic conjugated C5H3X, C4H3SiX, C4H3GeX, C4H3SnX, and C4H3PbX (X = H, F, Cl, and Br)

Singlet-triplet energy gaps in cyclopenta-2,4-dienylidene, as well as its 2- or 3-halogenated derivatives, are compared and contrasted with their sila, germa, stana, and plumba analogues; at HF/6-31G* and B3LYP/ 6-311++G(3df, 2p) levels of theory. Energy gaps (ΔG_t-s), between triplet (t) and singlet (s) states, appear linearly proportional to: (i) the size of the group 14 divalent element (M = C, Si, Ge, Sn and Pb), (ii) the angle ∠C-M-C, and (iii) the ΔG_(LUMO-HOMO) of the singlet state involved. The magnitude of ΔG_t-s, for each 2- and/or 3-substituted species studied, increases with an order of: carbenes < silylenes < germylenes < stanylenes < plumbylenes. This order reverses for the barriers of the ring puckering. The puckering occurs with more ease for every singlet, compared to its corresponding triplet form.Regardless of the group 14 element (M) employed, every 3-halo-substituted species is more stable than the corresponding 2-halo-substituted isomer. For M = Pb, Sn and/or Ge; 3-halo-substituted species have higher ΔG_t-s than their corresponding 2-halo-substituted analogues. For M = Si, similar ΔG_t-s are found for 2- and 3-halogenated isomers. For M = C, 3-halo-substituted species have lower ΔG_t-s than their corresponding 2-halo-substituted analogues.Every cyclic singlet has a larger ∠C-M-C angle, than its corresponding cyclic triplet state, except for 3-halosilacyclopenta-2,4-dienylidenes where triplet has a larger ∠C-M-C angle than its corresponding singlet state.     

Electronic structures of the boron cage molecules B4H4, B4Cl4 and B4F4

Ab initio calculations have been performed on B₄H₄, B₄Cl₄ and B₄F₄ in order to aid our understanding of the bonding in these compounds, which is presumably based on a tetrahedral boron cage. This cage has only 8 electrons and so is less than that expected on the basis of the usual framework electron counting rules. Basis sets with polarisation functions were used at the SCF, CI and CPF levels of theory to confirm that the T _d structures are indeed more stable than the D _4h ones. Davidson-Roby population analyses were able to show that many factors, including 3-centre 2-electron bonding and backbonding from the ligand to the boron cage, are of importance in determining the relative stability of the three compounds, of which B₄Cl₄ is the only one that has yet been observed experimentally.     

On the crystal chemistry of three copper(II)-arsenates: Cu3(AsO4)2-III,Na4Cu(AsO4)2, and KCu4(AsO4)3

The three copper(II)-arsenates were synthesized under hydrothermal conditions; their crystal structures were determined by single-crystal X-ray diffraction methods:Cu₃(AsO₄)₂-III:a=5.046(2) Å,b=5.417(2) Å,c=6.354(2) Å, =70.61(2)°, =86.52(2)°, =68.43(2)°,Z=1, space group ,R=0.035 for 1674 reflections with sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a=4.882(2) Å,b=5.870(2) Å,c=6.958(3) Å, =98.51(2)°, =90.76(2)°, =105.97(2)°,Z=1, space group ,R=0.028 for 2157 reflections with sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a=12.234(5) Å,b=12.438(5) Å,c=7.307(3) Å, =118.17(2)°,Z=4, space group C2/c,R=0.029 for 1896 reflections with sin / 0.80 Å^–1.Within these three compounds the Cu atoms are square planar [4], tetragonal pyramidal [4+1], and tetragonal bipyramidal [4+2] coordinated by O atoms; an exception is the Cu(2)^[4+1] atom in Cu₃(AsO₄)₂-III: the coordination polyhedron is a representative for the transition from a tetragonal pyramid towards a trigonal bipyramid. In KCu₄(AsO₄)₃ the Cu(1)^[4]O₄ square and the As(1)O₄ tetrahedron share a common O—O edge of 2.428(5) Å, resulting in distortions of both the CuO₄ square and the AsO₄ tetrahedron. The two Na atoms in Na₄Cu(AsO₄)₂ are [6] coordinated, the K atom in KCu₄(AsO₄)₃ is [8] coordinated by O atoms.Die drei Kupfer(II)-Arsenate wurden unter Hydrothermalbedingungen gezüchtet und ihre Kristallstrukturen mittels Einkristall-Röntgenbeugungsmethoden ermittelt:Cu₃(AsO₄)₂-III:a = 5.046(2) Å,b = 5.417(2) Å,c = 6.354(2) Å, = 70.61 (2)°, = 86.52(2)°, = 68.43(2)°,Z = 1, Raumgruppe ,R = 0.035 für 1674 Reflexe mit sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a = 4.882(2) Å,b = 5.870(2) Å,c = 6.958(3) Å, = 98.51(2)°, = 90.76(2)°, = 105.97(2)°,Z = 1, Raumgruppe ,R = 0.028 für 2157 Reflexe mit sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a = 12.234(5) Å,b = 12.438(5) Å,c = 7.307(3) Å, = 118.17(2)°,Z = 4, Raumgruppe C2/c,R = 0.029 für 1896 Reflexe mit sin / 0.80 Å^–1.Die Cu-Atome in diesen drei Verbindungen sind durch O-Atome quadratisch planar [4], tetragonal pyramidal [4 + 1] und tetragonal dipyramidal [4 + 2]-koordiniert; eine Ausnahme ist das Cu(2)^{[4 + 1]}-Atom in Cu₃(AsO₄)₂-III: Das Koordinationspolyeder stellt einen Vertreter des Übergangs von einer tetragonalen Pyramide zu einer trigonalen Dipyramide dar. In KCu₄(AsO₄)₃ haben das Cu(1)^[4]O₄-Quadrat und das As(1)O₄-Tetraeder eine gemeinsame O—O-Kante von 2.428(5) Å, was eine Verzerrung der beiden Koordinationsfiguren CuO₄-Quadrat und AsO₄-Tetraeder bedingt. Die zwei Na-Atome in Na₄Cu(AsO₄)₃ sind durch O-Atome [6]-koordiniert, das K-Atom in KCu₄(AsO₄)₃ ist [8]-koordiniert.

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Zur Kristallchemie dreier Kupfer (II)-Arsenate: Cu₃(AsO₄)₂-III, Na₄Cu(AsO₄)₂ und KCu₄(AsO₄)₃

     

Energetics of formation of alkali and ammonium cobalt and zinc phosphate frameworks

Alkali and ammonium cobalt and zinc phosphates show extensive polymorphism. Thermal behavior, relative stabilities, and enthalpies of formation of KCoPO₄, RbCoPO₄, NH₄CoPO₄, and NH₄ZnPO₄ polymorphs are studied by differential scanning calorimetry, high-temperature oxide melt solution calorimetry, and acid solution calorimetry.α-KCoPO₄ and γ-KCoPO₄ are very similar in enthalpy. γ-KCoPO₄ slowly transforms to α-KCoPO₄ near 673 K. The high-temperature phase, β-KCoPO₄, is 5-7 kJ mol⁻¹ higher in enthalpy than α-KCoPO₄ and γ-KCoPO₄. HEX phases of NH₄CoPO₄ and NH₄ZnPO₄ are about 3 kJ mol⁻¹ lower in enthalpy than the corresponding ABW phases. There is a strong relationship between enthalpy of formation from oxides and acid-base interaction for cobalt and zinc phosphates and also for aluminosilicates with related frameworks. Cobalt and zinc phosphates exhibit similar trends in enthalpies of formation from oxides as aluminosilicates, but their enthalpies of formation from oxides are more exothermic because of their stronger acid-base interactions. Enthalpies of formation from ammonia and oxides of NH₄CoPO₄ and NH₄ZnPO₄ are similar, reflecting the similar basicity of CoO and ZnO.     

The compounds KAs4O6 X (X=Cl,Br, I) and NH4As4O6 X (X=Br,I): Hydrothermal syntheses and structure determinations

The crystal structures of five isotypic hexagonal compounds with general formulaMAs₄O₆ X [M=K, NH₄;X=Cl, Br, I; space group: P622;Z=1] were determined from 370 single crystal X-ray data and refined toR values <0.05. The structure type is characterized by neutral charged [As₂O₃] sheets arranged parallel (00.1). The As atoms of neighbouring two sheets point to each other and the sheets are combined by interlayeredM andX atoms, respectively. TheM atoms are coordinated to twelve oxygen atoms, theX atoms are coordinated to twelve arsenic atoms. In both cases the coordination polyhedron is a hexagonal prism. The compounds were synthesized by thermal treatments of cubic As₂O₃ and potassium or ammonium haloids in a saturated aqueous solution of potassium acetate resp. ammonia [500 K, saturation vapour pressure].

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Die Verbindungen KAs₄O₆ X (X=Cl, Br, I) und NH₄As₄O₆ X (X=Br, I): Hydrothermalsynthese und Strukturbestimmung

Zusammenfassung Die Kristallstrukturen der fünf isotypen hexagonalen Verbindungen mit der allgemeinen FormelMAs₄O₆ X [M=K, NH₄;X=Cl, Br, I; Raumgruppe: P622;Z=1] wurden anhand von 370 Einkristall-Röntgendaten bestimmt und aufR-Werte <0.05 verfeinert. Der Strukturtyp ist ausgezeichnet durch neutrale [As₂O₃]-Schichten, die parallel (00.1) angeordnet sind. Die As-Atome zweier benachbarter Schichten weisen jeweils aufeinander zu, und die Schichten selbst werden durch zwischengelagerteM- bzw.X-Atome verbunden. DieM-Atome werden jeweils von zwölf O-Atomen, dieX-Atome von zwölf As-Atomen umgeben. Das Koordinationspolyeder ist in beiden Fällen ein hexagonales Primsa. Die einzelnen Verbindungen wurden unter Hydrothermalbedingungen aus kubischem As₂O₃ und dem jeweiligen Kalium- oder Ammoniumhalogenid in einer gesättigten wäßrigen Lösung von Kaliumacetat bzw. Ammoniak synthetisiert (500 K, Sättigungsdampfdruck).

     

Near infrared study of aqueous lanthanide perchlorates

The near infrared spectra of water in aqueous solutions of La(ClO₄)₃, Pr(ClO₄)₃, Nd(ClO₄)₃, Gd(ClO₄)₃, Er(ClO₄)₃, Yb(ClO₄)₃, Lu(ClO₄)₃, and NaClO₄ have been measured in the concentration range from 0.3 to 2.5 mol-dm^–3, at 25°C. The relative contents of free OH groups in the 1.0, 1.6, and 2.2M solutions have been calculated from extinction coefficients for water at 1160 nm. They increase with increasing salt concentration and are greater in solutions of the lighter lanthanide perchlorates at any fixed molarity. The results are discussed in terms of the stoichiometry and structure of hydrated cations of trivalent lanthanides.     

Correlation between thermodynamic properties and coordination states of aqueous bivalent transition metal sulfates

The osmotic coefficients for CoSO₄, NiSO₄, CuSO₄, MnSO₄, and ZnSO₄ have been found to be approximately the same up to very highest concentrations, while they are significantly higher for MgSO₄. Negligible changes in the visible spectra of CoSO₄ and NiSO₄ induced by increasing concentration indicate little, if any, coordination of the sulfate anion, while the UV spectral effects indicate outer-sphere association. More distinct spectral effects are observed for CuSO₄. However, the free sulfate anion concentration is found to be the same in equimolal solutions of CoSO₄, NiSO₄, and ZnSO₄, and probably also in CuSO₄, while it is higher in the solutions of MgSO₄. The conclusion is drawn that the four isopiestic transition metal sulfates at any given molality are in corresponding coordination states. The general problem of correlation between thermodynamic properties of solutions and the coordination states of the dissolved salts is discussed.     

The synthesis and structural characterization of the new ternary nitrides: Ca4TiN4 and Ca5NbN5

The ternary nitrides, Ca₄TiN₄ and Ca₅NbN₅, were synthesized in sealed niobium tubes using lithium nitride as a flux at 900 and 1050 °C, respectively. The structures of both compounds were solved from single-crystal X-ray diffraction data. Ca₄TiN₄ is the first example of a calcium group IV nitride; it crystallizes in the triclinic space group (No. 2) with cell parameters a=5.9757(5) Å, b=6.0129(5) Å, c=6.0116(12) Å, α=71.565(4)°, β=79.471(4)°, γ=68.258(4)° and Z=2. Ca₄TiN₄ is isostructural with Na₄TiO₄ and contains tetrahedral TiN₄ units connected through edges and corners to CaN₄ tetrahedra and CaN₅ square pyramids. Ca₅NbN₅ crystallizes in the monoclinic space group C2/m (No. 12) with cell parameters a=11.922(7) Å, b=6.878(5) Å, c=8.936(7) Å, β=101.22(3)° and Z=4. Ca₅NbN₅ is isostructural with Ba₅NbN₅; the structure contains NbN₄ tetrahedra that share vertices with CaN₅ trigonal bipyramids.     

Interaction Between Two Similar Plane Parallel Double Layers for (NH4)2Fe(SO4)2 or (NH4)2Cu(SO4)2 Type Complex Salt Electrolytes at Positive Surface Potential

Interaction energies between two similar plane parallel double layers for (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y _e  < y ₀ ≤ 20. The general expressions were given for the interaction energies of A _ν +B _ν′ +C_ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl₂, Na₂SO₄, FeCl₃, Na₃PO₄, Mg₃(PO₄)₂, Al₂(SO₄)₃, and complex salts (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ at y ₀ = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH₄)₂Fe(SO₄)₂ was close to that for simple salt Na₃PO₄.

Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

Molecular orbitals studies on two limiting structures of conjugated vinyl cation,C4H4F+

Nonempirical LCAO-MO-SCF calculations employing STO-3G minimal basis set have been carried out to examine the two limiting, open and bridged, structures of a conjugative fluorovinyl cation system and the interconversion of these two structures. The bridged ion is found to be 37.6 kcal/mole higher in energy than the open ion. Three pathways of converting the open ion to bridged ion were investigated. The pathway in which conjugation is preserved along the reaction profile gives the lowest energy barrier and depicts the bridged ion as a transition state.