Electroless deposition and some properties of Ni–Cu–P and Ni–Sn–P coatings

In this review, a summary of our published results, completed with new unpublished data are considered together with some of other authors’ publications, making an attempt to reveal the mechanism of the third element co-deposition in electroless Ni–P plating and to define its influence on the ternary coatings’ properties. A model explaining the triple role of Cu added to the solution for electroless (EL) Ni–P plating is described: as a stabilizer [Cu(I)]; as an accelerator; and as a stability-affecting agent, forming a dispersed solid phase in the solution. The disproportionation reaction of Cu(I) has been taken into account. A planned experiment was performed using full-effect factorial design with two levels of three process variables, and the response surfaces were constructed. The interaction between the factors was revealed. The results are in harmony with the aforementioned model. In low-tin Ni–Sn–P coatings, the alloy components are uniformly distributed both on the surface and through the thickness. In contrast, high-tin coatings exhibit three-dimensional areas enriched in Sn and impoverished in Ni and P. As the reason for their formation, the disproportionation reaction of Sn(II) is suggested, supposed to be locally predominant over the hypophosphite oxidation. EL deposition of pure Sn onto Ni–Sn–P substrates is shown. The inclusion of Cu or Sn in EL Ni–P increases the thermal stability of amorphous state, ensures the preservation of a paramagnetic behavior and improves the corrosion resistance. Dedicated to the 70th birthday of Professor A. Vaskelis.     

Electrical resistivity feature of Cu–Sn–(Bi) alloy melts

The temperature dependence of electrical resistivity of Cu–Sn alloys, along with Cu–Sn–Bi alloys, has been investigated in a wide temperature range using the DC four-probe technique. Evidently abnormal changes are observed on ρ–T curves of these alloys. The result reveals that the irreversible and reversible changes on these ρ–Tcurves indicate the existence of the metastable microinhomogeneous structure and microheterogeneous structure (including some short range orders) of the Cu–Sn and Cu–Sn–Bi alloy melts, respectively. Furthermore, the addition of Bi increases the metastable microheterogeneity in the first heating process of Cu–Sn melts.     

The role of the He I and He II metastables in the population of the Sn II,Sn III and Sn IV ion levels

On the basis of the temporal evolutions of the singly, doubly and triply ionized tin (Sn II, Sn III and Sn IV, respectively) spectral line intensities, in the pulsed helium and nitrogen plasmas, the important role of the He I and He II metastables has been observed in the Sn II, Sn III and Sn IV ionization and population processes. According to these processes, one can expect realization of several laser levels in the Sn II (11.07, 11.20, 12.44 and 13.11 eV), Sn III (15.91, 17.82, 19.13 and 20.19 eV) and Sn IV (20.51 eV) spectra. The modified version of the linear, low-pressure, pulsed arc was used as a plasma source operated in helium with tin atoms, as impurities, evaporated from tin cylindrical plates located in the homogenous part of the discharge tube. This plasma source provides good conditions for a generation of the Sn III, Sn IV and Sn V ions at relatively low electron temperatures (below 18,000 K) providing low background radiation around the intense Sn IV and Sn III spectral lines in the helium plasma. The 222.613 ± 0.0005 nm Sn IV line, not observed up to now, has been identified. The marked, but not classified 243.688 nm Sn spectral line is sorted by ionization stages. The shapes of Sn III and Sn IV lines, ranged between 207 nm and 307 nm, have been obtained. At a 17,500 K electron temperature and 1.07 × 10²³ m^− 3 electron density the Stark broadening was found as the dominant mechanism in the mentioned lines broadening. The measured Stark widths of the prominent nine Sn IV and seven Sn III lines are the first data in the literature. The Stark widths of the intense 229.913 nm and 288.766 nm Sn IV lines can be used for the plasma electron density and temperature diagnostics purposes.     

共掺La3+对Sr2SnO4∶Sm3+的余辉增强

研究了以La3+离子为辅助激活剂,对Sm3+掺杂的发光材料Sr2SnO4:Sm3+余辉性能的影响。采用传统的高温固相法合成Sr2SnO4∶Sm3+,La3+红色长余辉发光材料。利用X射线粉末衍射仪、荧光光谱仪、热释光剂量仪等手段对粉末样品进行了表征。分析结果表明,在1400℃得到了单相Sr2SnO4,Sr2SnO4∶Sm3+,La3+发光粉末有563、599和646 nm 3个发射峰,与Sm3+单掺杂的Sr2SnO4∶Sm3+相比,其光谱发射峰位没有明显变化。余辉亮度衰减曲线表明适量的La3+掺杂可以延长Sr2SnO4∶Sm3+的余辉时间。通过对热释光谱的分析,解释了双掺杂发光粉余辉性能增强的原因,La3+掺杂增加了更多适宜深度的陷阱(VSr″),可以有效存储光能,增强余辉的时间和强度。     

Vapor-solid growth of Sn nanowires: growth mechanism and superconductivity

A noncatalytic and template-free vapor transport process has been employed to prepare single-crystalline Sn nanowires with diameters of 10-20 nm. The growth of one-dimensional Sn nanowires follows the mechanism similar to the vapor-solid (V-S) mechanism. Two-dimensional square-shaped nanostructures were also found to form in the region of lower deposition temperatures. The rich morphology may be attributed to the competition in growth rate among different crystallographic planes. Structural characterization with high-resolution transmission electron microscopy showed that the nanowires and nanosquares grew in a preferential direction of [200]. The superconducting transition temperatures for Sn nanowires and Sn nanosquares were about 3.7 K, which was very close to that of bulk beta-Sn. Magnetization measurements showed that the critical magnetic fields for both Sn nanowires and Sn nanosquares increased significantly as compared to that of bulk Sn.     

Influence of the anion on lone pair formation in Sn(II) monochalcogenides: a DFT study

The electronic structure of SnO, SnS, SnSe, and SnTe in the rocksalt, litharge, and herzenbergite structures has been calculated using density functional theory. Comparison of the distorted and undistorted structures allows for an explanation of the unusual experimentally observed structural transitions seen along the Sn(II) monochalcogenides. Analysis of the electronic structure shows a strong anion dependence of the Sn(II) lone pair, with the Sn(5s) and Sn(5p) states too far apart to couple directly. However, the interaction of Sn(5s) with anion states of appropriate energy produce a filled antibonding Sn(5s)-anion p combination which allows coupling of Sn(5s) and Sn(5p) to occur, resulting in a sterically active asymmetric density on Sn. While the interaction between Sn(5s) and O(2p) is strong, interactions of Sn with S, Se, and Te become gradually weaker, resulting in less high energy 5s states and hence weaker lone pairs. The stability of the distorted structures relative to the symmetric structures of higher coordination is thereby reduced, which induces the change from highly distorted litharge SnO to highly symmetric rocksalt SnTe seen along the series.     

Ca6Cu2Sn7: novel 3D open framework with unusual Sn4 tetramers

The new ternary polar intermetallic phase, Ca6Cu2Sn7, has been synthesized by the solid-state reaction of the stoichiometric mixture of the pure elements in welded Ta tubes at high temperature. Its structure was established by single-crystal X-ray diffraction studies. Ca6Cu2Sn7 crystallizes in the monoclinic space group C2/m (No. 12) with cell parameters of a=14.257(7), b=4.564(2), and c=12.376(7) A, beta=93.979(6) degrees, V=803.3(7) A3, and Z=2. The structure of Ca6Cu2Sn7 belongs to a new structure type and features a 3D anionic open-framework composed of [Cu2Sn3] layers interconnected by unusual Sn4 tetramers, forming large tunnels along the b axis which are composed of Cu4Sn12 16-membered rings. The calcium atoms are located in these large tunnels. Ca6Cu2Sn7 is metallic and exhibits temperature-independent paramagnetism.     

超音速流动条件下Sn/N2O(O2)化学发光反应动力学的实验研究

在温度低于900 K和1—10乇腔压范围内, 首次采用等离子加热方法产生金属Sn蒸气, 并利用超音速流动反应装置, 研究了载气为N_2和N_2+Ar时Sn+N_2O和Sn+O_2的化学发光反应。首次采用光学多通道分析仪(OMA Model 1450)获得了不同腔压下SnO(a~3∑~+—X~1∑~+)跃迁的化学发光光谱, 得出了不同腔压下SnO(a~3∑~+)态的相对振动布居, 并将本实验结果与低亚音速高温快速流动反应器(HTFFR)中所得的结果做了比较。     

铽锰基化合物TbMn6Sn6的结构和磁性

研究了重稀土金属化合物ＴｂＭｎ６Ｓｎ６的晶体结构、内禀磁性及其矫顽力随和外场变化的规律。ＴｂＭｎ６Ｓｎ６为ＨｆＦｅ６Ｇｅ６型六角型结构，晶格常数为：ａ＝０．５５６１ｎｍ，ｃ＝０．９０４７７ｎｍ，单胞体积为０．２４１ｎｍ＾３，居里温度ＴＣ＝４２１Ｋ。ＴＭｎ６Ｓｎ６化合物在外场较弱时，热磁曲线呈亚铁磁性；当外场较强时，则表现出铁磁行为，具有变磁性，ＴｂＭｎ６Ｓｎ６的矫顽力随温度变化，当温度Ｔ＝２００Ｋ     

Effect of plasmochemical modification on electro-optical and surface properties of zinc sulfide electroluminescent phosphors

Method for improving the brightness of photo- and electroluminescence from ZnS:Cu and ZnS:Cu, Al phosphors by their treatment in a low-temperature gas-discharge plasma was developed. The relationship between the luminescence brightness and spectra and surface properties of the phosphors was studied. The mechanism of processes that occur on the surface and in the bulk of phosphor particles during their bombardment with plasma ions was determined.     

Unique pore selectivity for Cs+ and exceptionally high NH4+ exchange capacity of the chalcogenide material K6Sn[Zn4Sn4S17

Highly selective ion-exchange properties and -exchange capacities of the open framework chalcogenide material K(6)Sn[Zn(4)Sn(4)S(17)] (1) with Cs(+) and NH(4)(+) are reported. Because the structure of this framework is known in great detail, these studies are a rare example where structure/property relationships can be directly drawn. 1 possesses three types of micropore cavities. The largest pore of 1 presents an exact fit for Cs(+) and exhibits high selectivity for this ion, as demonstrated by competitive ion-exchange experiments. The next largest pore has a greater capacity (up to four cations) and is well suited for NH(4)(+) ions. This leads to a high ammonium-exchange capacity for 1 of 3.06 mequiv/gr, which is close to the NH(4)(+)-exchange capacities of natural zeolites. The single-crystal structures of ammonium-exchanged products at various stages reveal an unusual mechanism for the exchange process of 1 which involves diffusion of ammonium cations from the large cavity to the small ones of the framework. Thermal analysis of one of these ammonium-exchanged products, in combination with mass spectroscopy, showed the decomposition of NH(4)(+) cations to NH(3) and H(2)S with the parallel transformation of the exchanged product to a mixture of crystalline phases. Since K(6)Sn[Zn(4)Sn(4)S(17)] can be grown in suitably large crystals (much larger than most zeolites), it defines an excellent model system in which ion-exchange processes and products can be characterized and studied in detail in various reaction stages.     

Enantiospecific Sn(II)- and Sn(IV)-catalyzed cycloadditions of aldehydes and donor-acceptor cyclopropanes

A cycloaddition strategy for the synthesis of highly enantioenriched 2,5-cis-disubstituted tetrahydrofurans has been developed. In the presence of catalytic Sn(OTf)2 or SnCl4, a range of aldehydes will undergo formal [3 + 2] cycloadditions with a scalemic donor-acceptor cyclopropane to form optically active heterocycles. Mechanistic studies support an unusual SN2 attack by the aldehyde on the activated cyclopropane. Through this mechanism, stereochemical information contained in the cyclopropane is effectively transferred to the tetrahydrofuran products.     

Synthesis, structure, characterization, and calculations of two new Sn2+ -W6+-oxides, Sn2WO5 and Sn3WO6

Two new Sn2+-W6+-oxides, Sn2WO5 and Sn3WO6, have been synthesized hydrothermally, and their structures have been determined by single-crystal X-ray diffraction methods. Both materials exhibit layered structural topologies consisting of two edge-shared WO6 octahedra connected to SnO3 and SnO4 polyhedra. Both the W6+ and Sn2+ cations are in locally asymmetric coordination environments attributable to second-order Jahn-Teller effects. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis were also performed on the reported materials. Theoretical calculations using the tight binding linear muffin tin orbital method agree with the observed electronic properties of these materials and indicate that the stereoactive lone pair on the Sn2+ is similar for both materials. Crystal data: Sn2WO5, monoclinic, space group P21/n (No. 14), a = 7.994(2) A, b = 13.712(4) A, c = 10.383(3) A, beta = 110.507(3) degrees , V = 1066.0(5) A3, and Z = 4; Sn3WO6, monoclinic, C2/c (No. 15), a = 12.758(3) A, b = 8.0838(16) A, c = 13.865(3) A, beta = 112.49(3) degrees , V = 1321.2(5) A3, and Z = 8.     

Specific Features of the Structure of the Electrical Double Layer on Intermetallic Compound Ag3Sn in Aqueous Surface-Inactive Electrolytes

The behavior of a polycrystalline electrode of intermetallic compound Ag₃Sn in aqueous NaF solutions is studied using an impedance method. At potentials of –1.3 to –0.6 V (SCE), the electrode may be viewed as ideally polarizable. The Gouy–Chapman–Stern–Grahame model quite satisfactorily describes capacitance curves obtained at various electrolyte concentrations. Experimental capacitance curves for an Ag₃Sn electrode are compared with those for polycrystalline Ag and Sn electrodes renewed by cutting. Characteristics of an Ag₃Sn electrode are unique and its capacitance curves cannot be simulated from the data for Ag and Sn electrodes within the known phenomenological approaches.     

A novel class of phosphorescent gold(III) alkynyl-based organic light-emitting devices with tunable colour

A novel class of luminescent cyclometalated gold(III) alkynyl complexes has been demonstrated to possess EL properties and has been employed in the roles of electrophosphorescent emitters or dopants of organic light-emitting diodes (OLEDs) with high brightness and efficiency.     

Synthesis of Cu3Sn Alloy Nanocrystals through Sequential Reduction Induced by Gradual Increase of the Reaction Temperature

Cu₃Sn alloy nanocrystals are synthesized by sequential reduction of Cu and Sn precursors through a gradual increase of the reaction temperature. By transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), UV/Vis spectroscopy, and X‐ray diffraction (XRD) analyses, the alloy formation mechanism of Cu₃Sn nanocrystals has been studied. The incremental increase of the reaction temperature sequentially induces the reduction of Sn, the diffusion of Sn into the preformed Cu nanocrystals, resulting in the intermediate phase of Cu–Sn alloy nanocrystals, and then the formation of Cu₃Sn alloy nanocrystals. We anticipate that the synthesis of Cu₃Sn alloy nanocrystals encourages studies toward the synthesis of various alloy nanomaterials.     

(tBu2MeSi)2Sn=Sn(SiMetBu2)2: a distannene with a >Sn=Sn< double bond that is stable both in the solid state and in solution

((t)Bu(2)MeSi)(2)Sn=Sn(SiMe(t)Bu(2))(2) 1, prepared by the reaction of (t)Bu(2)MeSiNa with SnCl(2)-diox in THF and isolated as dark-green crystals, represents the first example of acyclic distannene with a Sn=Sn double bond that is stable both in the crystalline form and in solution. This was proved by the crystal and NMR spectral data of 1. Distannene 1 has these peculiar structural features: a shortest among all acyclic distannenes Sn=Sn double bond of 2.6683(10) A, a nearly planar geometry around both Sn atoms, and a highly twisted Sn=Sn double bond. The reactions of 1 toward carbon tetrachloride and phenylacetylene also correspond to the reactivity anticipated for the Sn=Sn double bond. The one-electron reduction of 1 with potassium produced the distannene anion radical, the heavy analogue of alkene ion radicals, for which the particular crystal structure and low-temperature EPR behavior are also discussed.     

Dependence of Performance of Organic Light-emitting Devices on Sheet Resistance of Indium-tin-oxide Anodes

IntroductionIndium-tin-oxide(ITO) has been widely used asthe anode material in organic light-emitting devices(OLEDs) because of its high transmittance in the visi-ble region and low electrical resistivity. In the pastyears, many investigations focused on …     

A Guide to Brighter Phosphors-Linking Luminescence Properties to Doping Homogeneity Probed by NMR

Crystalline powders of Ln³⁺ doped LaPO₄ (Ln=Nd, Gd, Dy, Ho, Er, Tm, Yb) have been synthesized to serve in a case study for linking doping homogeneity as determined by NMR to luminescent properties. Samples obtained via different synthesis methods act as examples of homo- and inhomogeneous doping. The sample quality was verified by X-ray diffraction. The homogeneously doped samples show improved luminescent properties in terms of brightness and lifetime which is consistent with the interpretation that, NMR visibility curves probe the distribution of paramagnetic dopants on a similar length scale as necessary for an efficient energy transfer in crystalline phosphors i. e. between sensitizers and activators, and to killer sites. Thus “NMR homogeneity” as observed by visibility curves may serve as a tool to optimize luminescent materials.     

Monoclinic Cu2Se3Sn

A previously unknown modification of dicopper(I) triselenostannate(IV), Cu₂Se₃Sn, has been obtained from the Cu₂Se–SnSe₂ quasi‐binary system and investigated using X‐ray single‐crystal diffraction. The Se atoms are stacked in a closest‐packed arrangement with the layers in the sequence ABC. The Cu atoms occupy one‐third of the tetrahedral interstices, whereas the Sn atoms are located in one‐sixth of the tetrahedral interstices. All the atoms occupy general positions. The structure possesses pseudo‐inversion symmetry. The Cu₂Se₃Sn structure investigated in this paper (96 atoms per unit cell, ordered distribution of Cu and Sn over 12 cation positions) is a superstructure of the reported cubic (eight atoms per unit cell, random distribution of Cu and Sn over one cation position) and monoclinic (24 atoms per unit cell, ordered distribution of Cu and Sn over three cation positions) modifications.