Flammability limits of the system CH3ClCH2Cl2HClCl2

In this paper, experimental work to determine flammability limits of the four-component system CH₃ClCH₂Cl₂HClCl₂ is reported. The limit determinations were carried out at atmospheric pressure and at temperatures of 20–30°C in a 50-mm internal-diameter vertical flame tube. The temperature of 30°C was needed to prevent condensation of methylene chloride from the gaseous mixture. The results show an irregular rich-flammability limit. The limits agree well with the literature data for two-component systems. Measurements of flammability limits at higher temperatures and pressures will be carried out in the near future.     

The preparation and characterization of Ba3Te2O9; a new oxide structure

The structure of Ba₃Te₂O₉ has been determined from x-ray powder diffraction data and by profile refinement of neutron diffraction data. We find tellurium octahedrally coordinated as expected and the same face-shared [B₂O₉]^6? unit as observed in Ba₃W₂O₉. The phase Ba₃Te₂O₉ has, however, a Cs₃Fe₂F₉ type structure ($\text{P}\text{6}{}_3\text{mmc}$, $\text{a}\text{=}\text{5}\text{.8603(1)}\text{A}\text{?}$, $\text{c}\text{=14.3037(6)}\text{A}\text{?}$) rather than the Cs₃Tl₂Cl₉ structure (R3c) found for the tungsten analogue. The two oxide structures have the same BaO₃ layer sequence but differ only in the spatial arrangement of the [B₂O₉] groups in the lattice. Infrared and Raman spectra confirm the different site symmetries associated with the different packing of the tungstate and tellurate anions in their respective structures.     

Preparation and properties of Y3Si2O8Cl; Ce phosphor

A new phosphor Y₃Si₂O₈Cl; Ce was prepared by firing the mixture of Y₂O₃, CeF₃, colloidal SiO₂ and NH₄Cl in an argon atmosphere at around 1100°C. The luminescence properties, crystal structure and formation processes of the phosphor are presented and discussed.     

New pnictides with Ce2O2S-type structure

The compounds EuMn₂P₂, EuMn₂As₂, EuMn₂Sb₂, YbMn₂As₂, and YbMn₂Sb₂ were prepared for the first time. Their crystal structure corresponds to that of Ce₂O₂S (ordered “anti-”La₂O₃ or CaAl₂Si₂-type structure). Their lattice constants are reported. Attempts to prepare isotypic compounds with typically three-valent rare earth metals have failed so far. The new compounds can be rationalized as normal valence compounds with the expected oxidation numbers e.g. Eu²⁺Mn²⁺Mn²⁺P^3?P^3?.     

Vapour growth and structural characterization of the new indium bismuth sulphide halides InBi2S4Cl and InBi2S4Br

The title compounds were prepared for the first time, and ledge-shaped single crystals were grown by chemical vapour transport. InBi₂S₄Cl(Br) crystallizes in the space group $\text{C}\text{2}\text{m}$ with lattice parameters a = 12.383 (12.55), b = 3.899 (3.90), $\text{c}\text{= 8.514 (8.58)}\text{A}\text{?}$, and β = 115.30 (115.2)°; Z = 2. The crystal structure of InBi₂S₄Cl was determined from 816 independent reflexions and refined to R = 4.0%. The indium atoms occupy the center of distorted sulphur octahedra which are linked to chains running in y-direction. They are interconnected by bands of bismuth and chlorine atoms. Bismuth is irregularly surrounded by six sulphur and two chlorine atoms.     

The preparation of high purity Mg2Ni

The intermetallic compound Mg₂Ni has been prepared by the vapour exchange/diffusion reaction of the elements sealed in a stainless steel container. The product has been characterised by powder X-ray diffractometry with Mo-K_α radiation, using step-scanning and profile refinement techniques. The hexagonal unit cell has constants a = 5.2117(4), $\text{c}\text{= 13.2538(9)}\text{A}\text{?}$.     

The crystal structure of the intercalates SnTaS2 and SnNbS2

The crystal structure of SnTaS₂ was determined by X-ray and neutron powder diffraction. SnTaS₂ is hexagonal, $\text{a}\text{=3.307}\text{A}\text{?}$, $\text{c}\text{=17.442}\text{A}\text{?}$, space group P6₃/mmc with Ta and Sn at special positions. Ta is in trigonal-prismatic coordination by sulfur forming TaS₂ slabs; Sn is linearly coordinated by sulfur atoms of adjacent TaS₂ slabs. X-ray powder diffraction showed that SnNbS₂ is isostructural with SnTaS₂.     

The crystal structure of LiScS2 and NaScS2

LiScS₂ and NaScS₂ were prepared and the structure was determined by X-ray powder work. The observed α-NaFeO₂ structure for these compounds is discussed in relation to other ABS₂ compounds.     

The crystal structure of Li2MoF6

Crystals of Li₂MoF₆ are tetragonal P4₂2₁2 with a_o = 4.6863(7) and c_o = 9.191(2)A, Z = 2 and the calculated density is 3.687 g/cc. The Li⁺ and Mo⁴⁺ ions are octahedrally coordinated. The Li-F distances range from 2.017(2) to 2.102(7)A and the Mo-F distances range from 1.927(2) to 1.945(2)A. The MoF₆^-- ion is coordinated by 10 Li⁺.     

Crystal data on ytterbium chlorosilicate,Yb3(SiO4)2Cl

Ytterbium chlorosilicate, Yb₃(SiO₄)₂Cl, was obtained in the form of single crystals up to 1.5 × 1.5 × 0.5 mm³ as by-product of the synthesis of ytterbium oxychloride. The compound has orthorhombic symmetry (space group Pnma - D_2h¹⁶). The unit cell parameters are: $\text{a}\text{= 6.753}\text{A}\text{?}\text{, b}\text{= 17.583}\text{A}\text{?}\text{, c}\text{= 6.137}\text{A}\text{?}$. The substance is characterized by means of morphology and X-ray powder data.     

Luminescent properties of Ca2BO3Cl:Eu yellow-emitting phosphor for white light-emitting diodes

The Ca₂BO₃Cl:Eu²⁺ phosphor was synthesized by the general high temperature solid-state reaction and an efficient yellow emission under near-ultraviolet and blue excitation was observed. The emission spectrum shows a single intense broad emission band centered at 573 nm, which corresponds to the allowed f-d transition of Eu²⁺. The excitation spectrum is very broad extending from 350 to 500 nm, which is coupled well with the emission of UV LED (350-410 nm) and blue LED (450-470 nm). The measured emission of In-GaN-based Ca₂BO₃Cl:Eu²⁺ LED shows white light to the naked eye with a chromatic coordinate of (0.33, 0.36). The Ca₂BO₃Cl:Eu²⁺ is a very appropriate yellow-emitting phosphor for white LEDs.     

Synthesis and characterization of europium(II)-holoborates,Eu2B5O9Cl and Eu2B5O9Br

Europium(II)-haloborates, Eu₂B₅O₉Cl and Eu₂B₅O₉Br, were synthesized and characterized by X-ray analysis, magnetic susceptibility and luminescent spectral measurements. The chloroborate Eu₂B₅O₉Cl crystallizes in the tetragonal system, D⁶₄-P4₂2₁2, with cell dimensions: a=11.349(4), $\text{c}\text{=6.500(4)}\text{A}\text{?}$ and Z=4, and Eu₂B₅O₉Br in the orthorhombic system, C¹⁰_2v-Pnn2 or D¹²_2h-Pnnm, with cell dimensions: a=11.503(3), b=11.382(3), $\text{c}\text{=6.484(2)}\text{A}\text{?}$ and Z=4. Both of them were paramagnets with paramagnetic Curie temperature at about ?1 K, and band emissions peaking at about 430 and 435 nm which were based on a 4f⁷-4f⁶5d transition of Eu²⁺ ion were observed on Eu₂B₅O₉Cl and Eu₂B₅O₉Br, respectively.     

Neutron diffraction study of magnetic ordering of the manganese bismuth chloro-sulfide: MnBiS2Cl

In quaternary compounds of Mn²⁺PnQ₂X (Pn = Sb, Bi; Q = S, Se; X = Cl, Br, I), Mn atoms in octahedral coordination (4 Q and 2 X) form waved layers separated by Pn atoms. The magnetic structure of the manganese bismuth chloro-sulfide MnBiS₂Cl has been determined by neutron powder diffraction, revealing a magnetic ordering with an incommensurate wave-vector along b-axis (k = [0, 0.3978, 0]) at 1.6 K. Two modulation models, sinusoidal and helicoidal, give quite equivalent magnetic reliability factors (R_mag = 0.0450 and 0.0481, respectively). The magnetic moment decreases with increasing temperature, to zero at T_N = 32 K. The evolution of the propagation wave-vector shows an irregularity at about 28 K. It could evidence two-phase transitions in agreement with the specific heat measurements. These results are compared to those of manganese antimony chloro-sulfide MnSbS₂Cl, isotypic with MnBiS₂Cl.     

The crystal structure of Ni5TiB2O10

The crystal structure of Ni₅TiB₂O₁₀ was determined by single crystal X-ray analysis. The compound has the same structure as the mineral ludwigite. The orthorhombic celldimensions and space group are $\text{a}\text{=9.206(7)}\text{A}\text{?}$, $\text{b}\text{=12.224(9)}\text{A}\text{?}$, $\text{c}\text{=2.994(2)}\text{A}\text{?}$, Pbam z=2. Ti and Ni are disordered on one equipoint.     

The preparation of SnO2 film by electrodeposition

SnO₂ is an interesting material for a wide array of applications. In this report, pure SnO₂ films were deposited on Cu substrates by one-step cathodic electrodeposition without any pretreatment of the electrolyte or post-treatment of the deposit. It was found that the concentration of HNO₃ in the electrolyte, ageing of the electrolyte, the electrodeposition temperature, and the electrodeposition voltage are critical to obtain SnO₂ films and avoid co-deposition of Sn. By carefully controlling those processing parameters, pure SnO₂ films composed of fine particles with good adherence to the Cu substrate have been successfully prepared.     

The crystal structure of lithium tantalum oxyfluoride LiTaO2F2

A structural analysis of lithium tantalum oxyfluoride LiTaO₂F₂ has been carried out by means of single-crystal diffraction methods. The symmetry is tetragonal, space group I4/mmm, with a cell having the dimensions : a = 3.903 ± 0.003, $\text{c}\text{= 25.380 ± 0.008}\text{A}\text{?}$ and containing five formula units. The structure was solved by Patterson and Fourier techniques and was refined by full-matrix least squares to an R value of 0.056. The structure consist of infinite ReO₃ type blocks three units-cells thick stacked perpendicularly to the c axis and shifted along the [110] direction with respect to each other. These blocks are connected together by the lithium atoms in a squarepyramidal coordination.     

Preparation and electrical conductivity of Cr2V2WO10 and Cr2Nb2WO10 with the rutile structure

Polycrystalline samples of Cr₂V₂WO₁₀ and Cr₂Nb₂WO₁₀ isostructural with the rutile type FeNbO₄ have been prepared. The compounds are nonstoichiometric with respect to all the constituent metal ions. Their crystallographic parameters and electrical resistivities have been characterized. The stabilization of rutile structure in these compounds is attributed to electronic effects.     

苯乙烯-丙烯酸酯树脂/纳米SiO2核壳乳液的制备及性能

以聚乙烯醇为保护胶体,以含双键的纳米SiO2粉体与丙烯酸酯类单体通过原位无皂乳液聚合合成了苯乙烯-丙烯酸酯树脂/纳米SiO2核壳乳液。通过红外光谱(FT-IR)、透射电镜(TEM)、扫描电镜和接触角测试对杂化材料进行表征,结果表明纳米SiO2和丙烯酸酯之间产生了化学键的结合,两者复合达到分子水平。材料力学性能和耐水性均好,其中拉伸强度最高可达5.5N/mm2,断裂伸长率可达到102%;耐水性最低为12.5%。