Zur wirkung von zusatzstoffen bei der bildung von geordneten graphit-FeCl3-einlagerungsverbindungen

Intercalation compounds with strong disturbances in the stacking sequences of the layers are normally formed in the reaction of ferric chloride vapour with graphite [6]. Fully periodic sequences can be prepared, however, by addition of either chlorine, oxygen or water vapour [5]. The effect of these added substances has been investigated. Oxygen and water vapour do not act directly but liberate chlorine from ferric chloride in a preliminary reaction. The produced chlorine was detected quantitatively by spectrophotometry. If no additional time is allowed for the preliminary reaction, the ordering effect of oxygen (Table 2) and of water vapour is less than that of chlorine. The stacking order has been determined by X-ray diffraction [6]. It is quantitatively represented by the “degree of order” (“Bildungsgrad”) of a stage, with a value between zero (completely random sequence) and one (strictly periodical sequence).If chlorine is added only in the initial phase of the intercalation, then the ordering effect will be lost with progressive reaction. Thus the effect of chlorine does not result in any permanent change of the graphite. The rate of intercalation is reduced a little by the addition of chlorine (Fig. 2), probably as the result of the diffusioncontrolled kinetics. Thus the chlorine does not act like a catalyst causing an acceleration of an otherwise slow reaction step. The ordered compounds cannot be interpreted as secondary products of the disordered ones. therefore, and also not as alternative products which are kinetically promoted by addition of chlorine.X-Ray diffractometer recordings (Fig. 1) show that the effect of chlorine is much stronger in the final phase than in the initial phase. Following up quantitatively the degree of order, it became evident that with additional chlorine in the final phase a supplementary increase in order is possible. This works as long as the graphite takes up ferric chloride. A subsequent annealing with additional chlorine does not affect the order any more.For the model conception of the effect of chlorine the following conclusions can be drawn: a close connection exists between the motion of ferric chloride in the interior of the crystal and the eventual formation of periodic arrangements. We assume that the chemisorbed chlorine at the surface of graphite weakens the bond of ferric chloride to graphite by charge transfer. Thereby the mobility of ferric chloride between the graphite layers increases. In each small region (domain) periodical arrangements then can be formed more easily.     

Zur Kinetik der photoinduziertenRadikalpolymerisation mit Elektronendonator/Elektronenakzeptor-Initiatorsystemen

Kinetics of Photoinduced Radical Polymerization with Electron Donor/Electron Acceptor Initiator Systems By means of benzyltriphenylphosphonium tetrafluoroborate (P^⊕) and anthracene (An) as photoinitiator system and methylmethacrylate (MMA) as monomer the influences of several reaction parameters on the polymerization quantum yield Φ_p, were studied. The following principal reactions proceed: electron transfer between excited An (¹An) and P^⊕ salt (k_q = 2,5 · 10⁹ M⁻¹ s⁻¹), quenching of ¹An by MMA (k = 1,3 · 10⁷ M⁻¹ s⁻¹), reaction between a ¹An…P^⊕ salt complex and MMA. The last reaction is assumed, since from the disappearance of An and the formation of An cation radical, respectively, rate constants k > 10⁸ M⁻¹ s⁻¹ have been calculated. Furthermore, it is assumed, that only the quenching of ¹An by MMA (Φ_p = 3,8) and the addition of free radicals, produced by the photoinduced electron transfer, lead to polymer formation. Kinetic equations were developed, which can explain the effect of P^⊕-salt concentration, light intensity and MMA concentration on Φ_p data. The quotient obtained for k_p/k is in the range of 0,053 to 0,087 M^−0,5 s^−0,5, depending on the used experimental parameters. Polymerization degrees P_n of 260–590 were found, which also depend on the experimental parameters.     

Das redox-standardpotential von Co3+/Co2+

The standard potenial of the process Co³⁺+e=Co²⁺ has been calculated on the basis of the calorimetric determination of the thermal effect of the reaction Fe²⁺+Co³⁺=Fe³⁺+Co²⁺. The standard potential has also been estimated by extrapolating the cathode and anode tafel curves to intersection. The data available concerning the value of E^o_{Co³⁺/Co²⁺} have been thoroughly analysed, and the average value E^o from all independent methods of estimating the standard potential an acidic medium has been shown to be + 1·45. It has been found from the data on potentials of cobalt oxides in an alkali medium that the standard potential Co³⁺/Co²⁺ must be within the range 1·40–1·53 V. This value agrees with the value 1·45 V obtained in acidic media.     

Zur passivierung von blei in Schwefelsäure keimbildung und wachstum der PbSO4-Deckschicht

The examination of the morphological structure (scanning electron microscopy), the crystal structure (X-ray-diffraction) and the electrochemical potential of the PbSO₄-film on lead, grown in sulfuric acid, leads to an hypothesis about the mechanism of the film nucleation and growth: A primary stage is the formation of a film, amorphous to X-rays and which is not in the range of the resolution of the scanning electron microscope. After this, in a second stage the well-known PbSO₄-crystals develop with linear dimensions of about 1 μm.Antimony solved in the electrolyte causes a more porous primary film and changes the equilibrium potential.Air-atmosphere accelerates the velocity of film growing and influences the equilibrium potential.     

Spectral pure RGB up-conversion emissions in self-assembled Gd2O3: Yb3+, Er3+/Ho3+/Tm3+ 3D hierarchical architectures

Self-assembled three-dimensional Yb³⁺(Ln = Er, Ho, Tm) co-doped Gd₂O₃ up-converted (UC) phosphors were synthesized by a facile co-precipitation method, and their morphologies and microstructures were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis. Under the excitation at 980 nm, spectral pure three primary colors red, green and blue (RGB) emissions were respectively achieved in Yb³⁺/Er³⁺, Yb³⁺/Ho³⁺ and Yb³⁺/Tm³⁺ co-doped Gd₂O₃ phosphors, in which spectral color purities were tuned by adjusting the doping concentration, annealing temperature, excitation power density and the pulse-width of 980 nm laser. These results provide deeper insights into modulating spectral color purities of up-converted emission, and the potential applications of spectrally pure RGB up-converted materials in fingerprint recognition and multi-color printing were also investigated.     

Sr2+–Mg2+-Doped SiAlON Ceramics

In the present work, multi-cation-doped (Sr²⁺–Mg²⁺) SiAlON ceramics were investigated. MgO and SrO were used in 100:0 and 50:50 molar ratios. The mixture was sintered at 1800° and 1830°C for 1 h in a gas pressure-sintering furnace. The results showed that sintered samples were composed of mainly α- and β-SiAlON phases and small amounts of some Sr-containing phases and SiAlON polytypes. According to Rietveld analysis of X-ray diffraction patterns, Mg is incorporated into the α-SiAlON structure. However, the incorporation of Sr is limited.     

Improvement of photoluminescence properties of Ce3+- doped CaSrAl2SiO7 phosphors by charge compensation with Li+ and Na+

In this work, we prepared CaSr_1-xAl₂SiO₇:xCe³⁺ (0.03 ≤ x ≤ 0.12) and CaSr_0.94Al₂SiO₇:0.03Ce³⁺,0.03 M⁺ (M⁺ = Li⁺ and Na⁺) phosphors via solid-state reaction method. Structural and photoluminescence (PL) properties of the phosphors were also investigated. The prepared phosphors formed an orthorhombic crystal structure with the P2₁2₁2₁ space group. CaSr_1-xAl₂SiO₇:xCe³⁺ phosphors were effectively excited by near-ultraviolet (UV) light (345 nm), which is suitable with the emission of near-UV light emitting diode chips. A broad blue emission (402 nm) was detected in CaSr_1-xAl₂SiO₇:xCe³⁺ and CaSr_0.94Al₂SiO₇:0.03Ce³⁺,0.03 M⁺ phosphors; this was attributed to the 4f⁰5d¹ → 4f¹ transition of Ce³⁺. To maintain charge equilibrium, charge compensators, such as monovalent Li⁺ and Na⁺ ions, were doped into the CaSr_0.97Al₂SiO₇:0.03Ce³⁺ phosphor, significantly improving its PL properties. The strongest emission intensity was achieved in CaSr_0.94Al₂SiO₇:0.03Ce³⁺,0.03Li⁺ phosphor. Addition of Li⁺ charge compensator was highly effective in improving PL properties of CaSr_0.97Al₂SiO₇:0.03Ce³⁺ phosphors.     

稀土固体超强酸SO2-4/TiO2/La3+催化合成醋酸丁酯

研究了以固体超强酸SO24-/TiO2/La3+催化剂,醋酸和正丁醇为原料合成醋酸丁酯,并考察了影响反应的因素.结果表明醇酸物质的摩尔比为1.61、催化剂用量0.6 g、带水剂甲苯7 mL、反应时间2.5 h是最适宜的反应条件,其酯化率可达96.2%.     

改性海泡石对废水中Pb2^＋、Hg2^＋、Cd2^＋1吸附性能的研究

用盐酸溶液对海泡石进行处理和在450C灼烧，制备出改性海泡石。在动态条件下，研究了改性海泡石对重金属离子Pb2^ 、Hg2^ 、Cd2^ 的吸附效果及吸附条件。同时探讨了改性海泡石对重金属离子Pb2^ 、Hg2^ 、Cd2^ 的吸附机理。合Pb2^ 、Hg2^ 、Cd2^ 的冶金废水经改性海泡石吸附后，重金属离子含量显著低于国家排放标准。     

+ alumina—A novel Li+ solid electrolyte

Li⁺ is one of several monovalent cations known to completely replace Na⁺ in Na⁺ beta alumina. The exchange occurs readily to approximately 50% producing a physically stable Li⁺ solid electrolyte having a conductivity of approximately 10^?3 (Ωcm)^?1 at 25°C. The Li⁺ transport number through Li⁺-Ni⁺ beta alumina is nearly 1 for compositions having Li⁺/Na⁺ greater than 1. Li⁺ ions migrate through the solid electrolyte lattice without significantly altering its Na⁺ content. This paper discusses our work examining ionic equilibrium, Li⁺ transport, ionic conductivity, and stability of Li⁺-Na⁺ beta alumina. The extraordinary preferential Na⁺ occupation of the beta alumina structure even in the presence of high Li⁺ activity is discussed and similar behavior predicted for another beta alumina composition.     

Graphite trifluoromethylsulfate C12+SO3CF3−

Graphite trifluoromethylsulfate C₁₂SO₃CF₃, a new binary graphite salt is formed by the irreversible solvolysis of C₈SO₃F in a large excess of trifluoromethylsulfuric acid. The salt is identified as a stage one intercalation compound with a C₀ value of 8.12 Å and characterised by microanalysis, epr and ¹⁹F NMR spectroscopy. Both Raman spectra, in the back scattering configuration, and IR spectra, in transmission as well as reflection geometries, are used to support an ionic formulation as C₁₂⁺SO₃CF₃^?.     

Spectroscopic Properties and Energy Transfer Mechanism of Er^3＋/Yb^3＋/Ce^3＋ Codoped Tellurite-based Glasses

为进一步揭示多稀土离子共掺低声子能量玻璃中Er3＋的光谱特性及其发光机理,采用高温熔融法制备了Er3＋/Yb3＋/Ce3＋共掺组分为（72.5–x）TeO2–20ZnO–5La2O3–0.5Er2O3–2Yb2O3–xCe2O3（x=0,0.4,0.7,1.0,摩尔分数x%）的碲酸盐玻璃,通过测量吸收光谱、荧光光谱和无掺杂样品的Raman光谱,以及计算相应能级间的吸收截面和受激发射截面,研究并分析了Yb3＋和Ce3＋离子掺杂对于Er3＋的1.55μm波段荧光特性的影响。结果显示：Yb3＋和Ce3＋的引入能显著增强975nm泵浦下Er3＋的1.55μm波段荧光强度。分析表明：Er3＋在1.55μm波段荧光强度的增强主要归结于Yb3＋/Yb3＋、Yb3＋/Er3＋离子间的共振能量传递过程以及基于单声子和双声子辅助的Er3＋/Ce3＋离子间的能量传递过程,并通过计算得到了相应稀土离子间的能量传递微观参数和声子所作的贡献比。     

Lower power dependent upconversion multicolor tunable properties in TiO2:Yb3+/Er3+/ (Tm3+)

Multicolor tunable upconversion luminescence materials could be applied to polychromatic LED and anti-counterfeit due to their superiority in abundant color and security feature. However, the harsh terms to achieve emission tuning associated with the drawbacks, including changing the concentration or types of doping ions, higher temperature, and higher excitation power, limit the range of its application. In this paper, a convenient and versatile approach for multicolor-emitting is realized via simply lower power modulating in TiO₂:Yb³⁺/ Er³⁺ and TiO₂: Yb³⁺/Er³⁺/Tm³⁺. The emission color is tuned from pink to yellowish green in TiO₂:Yb³⁺/ Er³⁺ and tuned from white to yellowish green in TiO₂: Yb³⁺/Er³⁺/Tm³⁺. It's found that there is no apparent temperature variation at lower power. Meanwhile, the mechanism of the emission and the multicolor tunability is discussed.     

Mechanical properties of Al2O3 + ZrO2 + nano-SiCp ceramic composites

The mechanical properties of Al₂O₃ matrix composites reinforced by ZrO₂(2 mol% Y₂O₃) and nanometre scale SiC dispersions have been investigated. It is shown that the Al₂O₃ matrix is simultaneously strengthened and toughened by both ZrO₂(2 mol% Y₂O₃) and nano-SiC particles. The maximum flexural strength and fracture toughness of the composites are 945 MPa and 7.3 MPam^1/2, respectively. The reinforcing effect of both t-m phase transformation of ZrO₂ (2 mol% Y₂O₃) and nano-SiC particles appears to be synergetic.     

Polymorphism of BaTiO3 Acceptor Doped with Mn3+, Fe3+, and Ti3+

The effect of Mn doping on the cubic to hexagonal phase transition temperature in BaTiO₃ has been determined by quenching samples with different Mn contents from a range of temperatures. Under conditions of equilibrating samples in air over the range 1000°–1400°C, cubic solid solutions BaTi_{1− x} Mn _x O_3−δ form over the range 0≤ x ≤0.015(5), whereas hexagonal solid solutions form for x ≥0.02, depending on the temperature. The results are compared with those on doping BaTiO₃ with Fe³⁺ and observations made concerning acceptor doping with Ti³⁺.     

Upconversion Luminescence in Er3+ Doped and Yb3+/Er3+ Codoped Yttria Nanocrystalline Powders

Y_1.9Er_0.1O₃ and Y_1.7Yb_0.2Er_0.1O₃ nanocrystalline powders were prepared via a reverse-strike coprecipitation method using nitrates and ammonia as raw materials. The obtained powders were of cubic-phase structure of Y₂O₃ and the particle size was in the range of ∼60–80 nm. Strong red (⁴F_9/2–⁴I_15/2) and green (²H_11/2/⁴S_3/2–⁴I_15/2) upconversion luminescence were observed in all the samples when excited with a 980-nm continuous wave diode laser. The possible upconversion mechanisms in Y_1.9Er_0.1O₃ and Y_1.7Yb_0.2Er_0.1O₃ were discussed. Power studies indicated that two-photon processes are responsible for the green and red upconversion luminescence in these systems. The codoping of Yb³⁺ greatly enhanced the red (⁴F_9/2–⁴I_15/2) upconversion emission.     

Largely enhanced mechanoluminescence properties in Pr3+/Gd3+ co-doped LiNbO3 phosphors

Pr³⁺/Gd³⁺ co-doped LiNbO₃ phosphors were prepared by a traditional solid-state reaction method and their structure, photoluminescence, mechanoluminescence and thermoluminescence were investigated. The results showed that the LiNbO₃ phase with a rhombohedral structure and an R3c space group was successfully prepared. Mechanoluminescence intensity in nonstoichiometric LiNbO₃:Pr³⁺ was largely increased by introducing Gd³⁺ ions. The optimal co-doped concentration of Gd³⁺ was 1?mol% and the enhanced ML intensity of LiNbO₃:0.01Pr³⁺, 0.01Gd³⁺ was about 177% times compared with that of LiNbO₃:0.01Pr³⁺. The effect of Gd³⁺ co-dopants on trap levels were explored through thermoluminescence curves. The enhancement of mechanoluminescence intensity was suggested to be ascribed to the regulated trap quantities caused by co-doped Gd³⁺ ions. Appropriate co-dopants are proved to be effective sensitizers for mechanoluminescence materials.     

Ferromagnetic coupling of Fe3+-VO-Fe3+polarons in Fe-doped ZnO

Room temperature ferromagnetic Fe-doped ZnO with hexagonal wurtzite structure was synthesized by a hydrothermal method under 4 T high pulsed magnetic field. Detailed studies were carried out to survey the effect of magnetic field on morphological, structural and magnetic properties of samples. The results showed that the concentration of oxygen vacancies (VOs) and amount of Fe³⁺ doping in ZnO were improved due to the high magnetic field processing. It proposed that the inherent exchange interaction is mediated by magnetic ions (Fe³⁺) through VOs assist to produce bound magnetic polorans (BMPs), which is responsible for RTFM in Fe-doped ZnO matrix.     

Sc3+–Lu3+-Doped α-SiAlONs

Sc³⁺ and dual Sc³⁺–Lu³⁺-doped α-SiAlON compositions were sintered by hot pressing, and the formation behavior, microstructure, and mechanical properties were assessed. It was found that the small cation Sc³⁺ could not be accommodated into the α-SiAlON structure alone. The addition of Lu₂O₃ in the composition induces the Sc³⁺ cation to enter the α-SiAlON structure, and leads to the production of α-SiAlON with an elongated-grain microstructure. Transmission electron microscopy analysis shows that α-SiAlON grains always contain an α-Si₃N₄ core, implicating heterogeneous nucleation to be in present in a mixed lutetium/scandium-doped α-SiAlON system.