复合氟化物中钐离子价态与基质的相关性

本文通过不同基质中钐离子光谱特征的研究,发现钐离子的存在价态与基质密切相关。讨论了被取代阳离子电荷、半径等化学因素对基质中钐离子价态的影响,利用能带理论建立了基质中变价稀土离子的价态与基质间关系的能带模型。     

Cu—ZSM—5分子筛表面铜离子的价态研究

以吸附ＣＯ红外光谱结合ＴＰＲ谱详细表征了经真空自还原及用不同还原剂还原的Ｃｕ－ＺＳＭ－５分子筛样品，考察了表面铜离子的价态分布情况及其影响因素，得知铜在Ｃｕ－ＺＳＭ－５是还原的。用不同方法进行氧化和还原时的难易程度不同。研究了用不同方法进行氧化还原时铜的价态转变条件和铜离子在不同价态间氧化还原循环的可逆性。     

钙钛矿型复合氟化物中钐离子的格位取代及价态

以掺钐氟化镁钾为例,通过实验确证了钐离子在基质中的取代格位。利用荧光光谱研究了钐离子在基质中的价态与取代格位的关系,发现不同阳离子格位上的钐离子具有不同价态。讨论了基质中钐离子的价态与占据格位之间的内在联系。     

丙烷在负载型催化剂上脱氢反应的研究——Ⅰ.原位Mssbauer谱表征不同载体负载铂锡催化剂中锡组分状态

应用原位M(?)ssbauer谱考察了Al_2O_3、MgO、SiO_2及AC(活性炭)等载体负载的铂锡催化剂中锡组分的存在状态。结果发现:(1)PtSn/Al_2O_3还原后,锡组分仍为氧化态;(2)PtSn/MgO及PtSn/SiO_2还原后有部分零价锡生成并与金属铂形成了Sn~o/Pt~o合金;(3)PtSn/AC还原后所生成的零价锡则以游离态存在。这些结果为进一步了解催化剂中锡组分价态及存在方式对负载型铂锡催化剂反应性能的影响奠定了基础。     

MF2-MgF2(M=Ca,Sr,Ba)体系中钐离子的价态及光谱

高温固相反应合成了钐离子激活的MF_2-MgF_2磷光体,考察了合成条件及基质组成对钐离子价态的影响,并讨论了荧光光谱与基质及钐离子价态间的关系.     

铈离子价态和OH~-根浓度对Tb~(3+)掺杂磷酸盐玻璃发光性能的影响

通过控制熔制气氛获得了Ce/Tb离子共掺磷酸盐玻璃样品,利用吸收光谱判断Ce离子在玻璃中的价态,并研究了不同Ce离子价态下的激发光谱和发射光谱,进而分析了Ce离子价态对Tb3+离子发光性能的影响。通过除水工艺的控制,获得不同OH-根浓度的Ce/Tb离子共掺磷酸盐玻璃样品,研究了OH-根浓度对Tb3+离子发光性能的影响。结果表明,在Ce/Tb离子共掺磷酸盐玻璃中,采用还原气氛熔制和通气除水工艺,可大大提高Tb3+离子在545 nm处的发光强度。     

低钼锡比催化剂中钼的价态对甲醇氧化制甲缩醛反应性能的影响

采用两步水热合成法制备了一系列低Mo/Sn比(1∶20,物质的量比)催化剂,并考察了锡前驱体焙烧温度对甲醇氧化制甲缩醛反应性能的影响。通过XRD、Raman、FT-IR、XPS、NH₃-TPD及H₂-TPR等表征手段对催化剂的晶体结构、表面性质、氧化还原性及钼物种价态等进行了分析。结果表明,在Mo1Sn20-600℃Sn催化剂上,反应温度为140℃时,甲醇转化率及甲缩醛选择性分别达30.0%及90.0%。锡前驱体焙烧温度的变化主要影响了Mo1Sn20催化剂的结构、钼物种的价态及存在状态,进而影响其催化活性;高温焙烧的锡前驱体更有利于Mo1Sn20催化剂中甲醇活化的活性位点Mo⁶⁺物种的生成。     

钐的氟化物体系中钐离子价态及其转换

H_2气流中多次还原SmF_3,合成了非整比系列SmF_x(2.0≤x≤3.0),并获得了接近整比的二氟化钐,讨论了各类非整比氟化钐化合物的结构及钐离子的价态,考察了在不同气氛中二氟化钐中钐离子价态的高温转换过程。     

无机盐对辛基酚聚氧乙烯醚乙基磺酸钠临界胶束浓度的影响研究

在(25±0.2)℃的实验温度下,通过用表面张力法确定了辛基酚聚氧乙烯醚(10)乙基磺酸钠(OPS)在无机盐氯化物(LiCl,NaCl,KCl,MgCl2,CaCl2,BaCl2,AlCl3,FeCl3和SmCl3)水溶液中的临界胶束浓度(cmc)值,根据cmc值的变化得出无机盐反离子对非离子-阴离子型表面活性剂OPS的cmc值影响规律.实验数据分析表明,虽然非离子-阴离子型表面活性剂OPS分子中增加了一个非离子氧乙烯单元的亲水性基团,但其cmc值和无机盐反离子浓度[M]之间具有与离子型表面活性剂相似的线性关系:lgcmc=-4.242-(0.2980-0.0102Z/r)lg[M]([M]1mol/L),其中Z和r分别为反离子的价态和范德华原子半径的平均值.无机盐对OPS的cmc的影响具有离子型表面活性剂的性质,不具有非离子型或两性表面活性剂的性质.该关系式亦说明了水溶液中非离子-阴离子型表面活性剂OPS的cmc值与无机盐反离子的浓度、价态和范德华原子半径的平均值有关,反离子对胶束的结合度的大小取决于反离子的价态与范德华原子半径平均值的比值.最后就无机盐反离子对OPS的cmc影响机理进行了简要分析.     

交换沸石催化剂上乙烯聚合反应的研究——Ⅳ.PdY沸石上乙烯双聚反应中活性中心的价态和位置的考察

用XPS、ESR及高分辨固体NMR考察了在PdY沸石上乙烯双聚反应中活性中心钯离子的价态和位置。XPS的实验结果表明,双聚反应的活性价态为一价的Pd~+离子。同时,ESR的结果表明,用乙烯对样品进行预处理,在诱导期消失,双聚反应开始时,ESR谱上出现一新信号,它可能是乙烯与Pd~+配位形成的表面活性物种所引起的,它的生成导致诱导期的消失。NMR的结果证实了PdY沸石中阳离子在沸石笼之间的迁移现象,而XPS的实验结果又证实了钯离子在催化剂体相和表面间的迁移。提出了乙烯双聚反应中PdY催化剂的活化图式。     

Mössbauer investigation of the reaction between HCl and tin dopant ions located on the surface of Cr2O3 microcrystals

The chemical behavior of surface-located tin dopant ions depends strongly on their valence state. At room temperature all Sn(II) ions readily react with gaseous hydrogen chloride while, under similar conditions, the predominant part of Sn(IV) ions is not affected by this gas. The results of this study, along with those previously obtained for both valence states of tin dopant exposed to a H₂S atmosphere, suggest that lower reactivity of Sn(IV) ions is essentially due to their higher coordination number and concomitant steric hindrance effects.     

Effect of Glass Substrates on the Formation of Gold-Silver Colloids in Nanocomposite Thin Films

A sol-gel route to synthesize nanocomposite thin films containing phase separated metal colloids of gold (Au) and silver (Ag) was developed. Ag—Au colloids were prepared in silica films using dip coating technique. The annealing of the samples in air results in the formation of phase separated Ag and Au colloids in SiO₂ thin films, showing the surface plasmon peaks at 410 nm and 528 nm. For the synthesis of phase separated Ag and Au colloids on float glass substrates, formation of the silver colloids was found strongly dependent on the surface of the float glass. On the tin rich surface formation of both gold and silver colloids took place, whereas, on the tin poor surface the formation of only gold colloids was observed. The surface dependence of the formation of silver colloids was attributed to the presence of tin as Sn²⁺ state on the glass surface, which oxidizes into Sn⁴⁺ during heat treatment, reducing Ag⁺ into silver colloids.     

Tin ions in float glass cause anomalies

There are two anomalies at the tin bath side of silicate float glasses caused by the in-diffusion of tin into the glass melt, the tin hump in the micrometer region and the phenomenon of bloom, a microscopic wrinkling at the glass surface after reheating in air. A diffusion–reaction model is developed to explain the tin hump and it is shown that it occurs only for Fe₂O₃-rich (> 0.5 wt%) silicate float glasses. The bloom effect, on the other hand, is found only for Fe₂O₃-poor (< 0.13 wt%) silicate float glasses. It could be demonstrated that these float glasses have a high tin peak already near the surface (< 100 nm) and that after annealing its height is strongly increased. The drastically altered surface properties lead to a buckling at the surface.     

An optical spectroscopic study of borate glasses containing uranium ions

An optical spectroscopic investigation has been performed on some borate glasses containing 1mol % UF(4), UO(2) and UO(3). The optical data confirm the presence of uranium ions in valence stages of +6, +5 and +4. The influence of the composition of the glass matrix and of the gamma-irradiation on the redox equilibrium of uranium ions was discussed.     

Stabilization of the unhybridized Sn2+ stannous ion in the BaClF structure and its characterization by119Sn Mössbauer spectroscopy

In divalent tin halides, when the halogen is small and highly electronegative (F, Cl), the tin valence orbitals are hybridized, the tin(II) non-bonded electron pair is located on one of the hybrid orbitals, and the resulting large electric field gradient gives a large quadrupole splitting. The reaction of barium chloride and tin difluoride in aqueous solutions, for large BaCl₂.2H₂O/SnF₂ ratios (>10) results in the precipitation of a white powdered material, which is identified by X-ray diffraction to be BaCIF. However, Tin-119 Mossbauer spectroscopy shows the material contains a fairly large amount of divalent tin in the Sn²⁺ ionic form, with unhybridized orbitals, like in SnCl₂. Using X-ray diffraction, we have established that Sn²⁺ ions substitute 15% of the Ba²⁺ ions at random, and chemical analysis shows the material has the formula Ba_5.66SnCl_7.30F_6.04 and thus is enriched in chlorine.     

Photoelectron spectroscopic studies of the interfacial reaction between glass and commercial adhesive

The valence band and core‐level photoelectron spectroscopy [using X‐ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS)] were used to probe the interfacial reaction between glass and a commercial adhesive (Loctite). The interaction was investigated by comparing experimental valence band spectra with spectra calculated for various possible interaction schemes. The valence band spectrum for the interfacial region between the glass and the adhesive was obtained using difference spectra on a thin film of adhesive on glass. This film was sufficiently thin that the adhesion interphase could be directly probed. Chemical interaction occurs at the interface as evidenced by the fact that the spectrum for the interfacial region could not be represented by the addition of the spectrum of the glass alone and the adhesive alone. The XPS valence band spectrum and the UPS spectrum showed that the shallow top surface layer is very much enriched in acrylic acid, which is a minor component in the adhesive. When the Loctite adhesive was coated on glass, the C1s and O1s regions of the adhesion interface region showed evidences of new chemistry at the adhesive–glass interface. The possible reactions were evaluated by comparison of the experimental spectra with calculated ones based on different models using ab initio molecular orbital calculations. The experimental spectra are well represented by models where the acrylic acid of the surface region of the adhesive reacts with the glass, suggesting chemical interaction occurred at the adhesion interphase. Copyright © 2009 John Wiley & Sons, Ltd.     

Surface Properties of the Sn-9Zn Alloy with the Trace Addition of Lanthanum

Summary. The surface properties of solders play an important role in its wettability. The poor wettability of the Sn-9Zn alloy has prohibited its commercial application. In this paper, the solid surface properties of the Sn-9Zn alloy were studied by using X-ray photoelectron spectroscopy (XPS). It was shown from the XPS analysis that zinc is highly enriched on the surface of the Sn-9Zn alloy. Although the zinc concentration on the surface is greater than 9%, lanthanum is accumulated on the surface of the Sn-9Zn-1La alloy. In addition, the analysis of the valence of tin and lanthanum indicated that tin and lanthanum could form complex oxygen-containing salts so that the anti-oxidation of the solder was enhanced, and the wettability of the solder was improved accordingly.     

K2ScSn(AsO4)3: an arsenate‐containing langbeinite

The title compound, dipotassium tri‐μ‐arsenato‐scandium(III)tin(IV), is the first arsenate‐containing langbeinite to be characterized by single‐crystal methods and crystallizes in the aristotype P2₁3 cubic symmetry for this structure type in which the K⁺ ions and the octahedral scandium and tin cations lie on crystallographic threefold axes. The Sc^III and Sn^IV ions show a slight segregation over the two octahedral sites, with Sc/Sn populations of 0.582 (5):0.418 (5) on one site and 0.418 (5):0.582 (5) on the other. Bond‐valence‐sum calculations indicate that the K⁺ ions are significantly underbonded in this structure and the O atoms show large anisotropic displacement parameters, as also seen in other langbeinites. The crystal studied was found to be a merohedral twin with a 0.690 (16):0.310 (16) domain ratio.     

Surface Properties of the Sn-9Zn Alloy with the Trace Addition of Lanthanum

The surface properties of solders play an important role in its wettability. The poor wettability of the Sn-9Zn alloy has prohibited its commercial application. In this paper, the solid surface properties of the Sn-9Zn alloy were studied by using X-ray photoelectron spectroscopy (XPS). It was shown from the XPS analysis that zinc is highly enriched on the surface of the Sn-9Zn alloy. Although the zinc concentration on the surface is greater than 9%, lanthanum is accumulated on the surface of the Sn-9Zn-1La alloy. In addition, the analysis of the valence of tin and lanthanum indicated that tin and lanthanum could form complex oxygen-containing salts so that the anti-oxidation of the solder was enhanced, and the wettability of the solder was improved accordingly.     

Energy loss of scattered ions at glancing-angle incidence on the crystal surface

Experimental findings of glancing-angle scattering of energetic ions are reviewed with particular emphasis on the energy loss of ion during scattering. The position-dependent stopping power of the surface which is derived from the angular dependence of observed energy loss is explained in terms of single and distance electron excitations of surface electrons. For the ions with velocities less than the Fermi velocity of target valence electrons, it is shown that the stopping power of a surface is determined only by the elastic collisions of the ion with valence electrons. From the analysis of the energy losses of 12–30 keV He ions reflected from the (001) surface of SnTe, a method is proposed to derive the electron density distribution averaged over the plane parallel to the surface from this position-dependent stopping power.