异丁烷-丁烯烷基化反应催化剂的研究Ⅳ.Zr(SO_4)_2和Zr(SO_4)_2/Al_2O_3(SiO_2)

制备了一系列不同焙烧温度的 Zr(SO4) 2 及 Zr(SO4) 2 负载量不同的 Zr(SO4) 2 / Al2 O3(Si O2 )固体强酸催化剂 ,用 XRD、IR、BET、TG- DTA、NH3- TPD、Hamm ett指示剂等方法研究了该催化体系的晶型、结构、比表面、酸量及酸强度随负载量和焙烧温度的变化规律 .将 Zr(SO4) 2 负载在 Al2 O3和 Si O2 两种载体上呈现不同的特性 .在 Al2 O3上明显地延缓了 Zr(SO4) 2 的分解和 Zr O2的晶相转变 .并且使酸量和酸强度有所提高 .研究了异丁烷 -丁烯烷基化反应 ,结果表明 ,对 973和 10 2 3K焙烧的 Zr(SO4) 2 样品 ,活性最好 ,而对 Zr(SO4) 2 / Al2 O3,负载量在 m(Zr(SO4) 2 ) /m(Al2 O3) =0 .5 / 1.0左右时活性最好 .各种样品均具有较高的 C08选择性.

储热材料 AlNH_4(SO_4)_2 . 12H_2O 的过冷性实验研究

对储热材料AlNH4（SO4）2·12H2O添加成核剂CaF2及C时在不同冷却条件下进行了过冷性实验研究

异丁烷/丁烯烷基化新型固体强酸催化剂的研究

异丁烷和丁烯在酸催化剂的作用下反应生成的烷基化油，是车用汽油的理想调合组分。工业上的烷基化过程采用硫酸和氢氟酸为催化剂，存在着设备腐蚀、废酸处理和毒性等问题，因此开发对环境友好的固体酸催化剂对于推动传统催化剂的改革具有重要意义。本文研究了WO_3/ZrO_2、Zr(SO_4)_2/Al_2O_3(SiO_2)及M_xO_y/Hβ分子筛等固体酸催化剂的制备、性质表征及其在异丁烷—丁烷基化反应中的催化性能。结果表明WO_3的加入对稳定ZrO_2的四方晶相起着重要作用，分散于ZrO_2表面上的氧化钨主要呈单层分散和析出的WO_3晶粒，部分可能与ZrO_2作用形成Zr-O-W键起强酸作用。与其它固体酸相比，具有较好的起始活性和i-C_8~0选择性。用过渡金属M (M = Pt、Co、Ni、Mn、Fe、Cu)活化的M-WO_3/ZrO_2固体强酸催化剂与WO_3/ZrO_2相比，结构、表面状态和酸量均有不同和度的改变。从反应机理上分析了添加过渡金属元素无显著效果的原因。以超细ZrO_2为载体的WO_3/ZrO_2等催化剂，具有更大的比表面、酸强度和对金属氧化物的负载能力，因而具有更好的反应活性，在烷基化产物中C_5～C_7裂解产物较多，使i-C_8~0的选择性有所下降。阐明了不同焙烧温度的Zr(SO_4)_2及Zr(SO_4)_2负载量不同的Zr(SO_4)_2/Al_2O_3(SiO_2)固体强酸催化剂的晶型结构、比表面、酸量及酸强度随焙烧温度和负载量变化的规律。将Zr(SO_4)_2负载在Al_2O_3和SiO_2两种载体上，呈现不同的特性。尤其在Al_2O_3上明显地延缓了Zr(SO_4)_2的分解和ZrO_2的晶相转变。并且使酸量、酸强充和反应活性有所提高，各种样品均具有较高的i-C_8~0选择性。负载各种氧化物的M_xO_y/Hβ(M = Li, Ca, La…)样品仍然保持Hβ的基本特性，但酸性和催化性能也发生了不同程度的改变，其中在Tm_2O_3/Hβ等样品上具有更好的稳定性，烷基化产物i-C_8~0的比例也有所增加。

伯胺N_(1923)萃取过渡金属离子机理的研究

伯胺由于其特殊的结构（R-NH_2），使它具有和仲、数胺不相同的一些性质。有较强的和矿物酸HX结合形成RNH_3X的能力，从而以离子交换机理萃取金属离子；也可以-NH_2上的氮、氢原子同以高价存在的过渡金属含氧酸以氢键方式相结合；另外，RNH_2也可通过氮原子以配位键形式与一些属于软酸类的过度金属离子形成配合物。通过伯胺萃取金属离子行为的研究，可发现新的萃取体系，扩大我国自行设计的伯胺N_(1923)萃取剂的应用领域，为金属离子的分离提纯工艺提供基本参数。我们实验室过去曾对伯胺N_(1923)萃取稀土（III）、Fe（III）、Zn （II）、Cd（II）、Ag（I）、Sc（III）等的机理进行了比较系统的研究。本工作是在此基础上，进一步完善及扩大N_(1923)对周期表中各族元素的萃取及应用。为此，我们选择了文献尚未报道的Ti（IV）、HgCl_2、Hg(CH_3COO)_2、Cu(CH_3COO)_2为研究对象，对它们的萃取机理进行了较详细的研究。结果表明，自由的N_(1923)或其盐对上述体系具有良好的萃取性能，并初步讨论了N_(1923)在金属离子萃取分离中的应用。一、伯胺N_(1923)萃取HgCl_2的机理 微量汞的萃取及分离对环境保护具有重要的实际意义。我们的研究结果表明，在pH值为3-4.5范围内，即使Cl~-浓度很低时，伯胺N_(1923)也能几乎定量地萃取HgCl_2，其盐酸盐亦能有效地萃取Hg（II），但两者的萃取机理不同。自由伯胺RNH_2可与HgCl_2形成配合物，其萃取机理为：RHN_(2(0)) + HgCl_2 <-> Hg(RNH_2)Cl_(2(0))对伯胺盐，实验证明其机理主要为加合反应，但当Cl~-浓度较高时，则为阴离子交换反应：加合反应：2RNH_3Cl_((0)) + HgCl_2 <-> (RNH_3Cl)_2HgCl_(2(0))交换反应：2RNH_3Cl_((0)) + HgCl_4~(2-) <-> (RNH_3)_2HgCl_(4(0)) + 2Cl~-通过考察温度对配位萃取反应的影响，求得反应的热效应ΔH = -48.82 KJ/mol，并分析了萃合物的IR、NMR谱。二、伯胺N_(1923)萃取Hg(CH_3COO)_2的机理 与HgCl_2体系相似，自由伯胺或其盐均能萃取Hg(CH_3COO)_2，萃取机理分别为：RNH_(2(0)) + Hg(CH_3CCO)_2 <-> Hg(RNH_2)(CH_3COO)_(2(0)) (CH_3COONH_3R)_(2(0)) + Hg(CH_3COO)_2 <-> (CH_3COONH_3R)_2Hg(CH_3COO)_(2(0))。在不同的萃取剂浓度下，上述反应的表观平衡常数基本不随萃取剂浓度的变化而改变，其对数值分别为：11.85、8.11。三、伯胺N_(1923)萃取Cu(CH_3COO)_2的机理 水相酸度对萃取反应的影响表明，RNH_2在近中性体系中具有很好的萃取性能，而在乙酸浓度较高的条件下，Cu（II）几乎不被RNH_2所萃取。说明自由伯胺能以配位机理的形式萃取Cu(Oh_3coo)_2，经确定，萃取反应式为：2RNH_(2(0)) + Cu(CH_3COO)_2 <-> Cu(RNH_2)_2(CH_3COO)_(2(0))并对该反应的表观平衡常数及热力学函数进行了计算。通过分析萃合物的IR谱，认为Cu(RNH_2)_2(CH_3COO)_2为平面型四配位的配合物。四、(RNH_3)_2SO_4从硫酸溶液中萃取Ti（IV）的研究 在低酸度（pH：0.84）的H_2SO_4溶液中，伯胺N_(1923)对Ti（IV）具有很强的萃取能力。用化学平衡法确定其反应式为：3(RNH_3)_2SO_(4(0)) + Ti(OH)_3~+ + SO_4~(2-) <-> 2(RNH_3)_3Ti(OH_3)(SO_4)_(2(0))我们用正十二胺代替N_(1923)，合成了上述萃合物的模拟物，经元素分析确定了萃合物的分子式：(RNH_3)_3Ti(OH)_3(SO_4)_2。并较详细地分析了萃合物的NMR、IR谱。变温NMR的结果表明，萃合物中存在两种含有活泼氢的基团，用D_2O交换后的NMR的结果亦证明了这一点。从萃合物的IR谱中，可得到SO_4~(2-)是以单齿配位形式同Ti（IV）相结合的信息。这些结果为所提出的萃取机理提供了直接的证据。并求出了上述萃取反应的表观平衡常数，其对数值为10.15，该值基本不随萃取剂浓度的变化而发生改变。反应的热效应ΔH = 66.49 KJ/mol，由计算得出的ΔG值可知，上述萃取反应有很大的向右进行的趋势。五、伯胺N_(1923)在萃取分离中的应用 为了扩大N_(1923)的应用，通过上述研究，我们对其在萃取分离中的应用进行了讨论，认为在以下几方面有可能得到应用：1、从环境废水中除Hg(II)；2、Hg(II)和Zn(II)、Cd(II)在CH_3COOH体系中的分离；3、CH_3COOH体系中Cu(II)、Co(II)、Ni(II)的萃取分离；4、在较高浓度的H_2SO_4体系中，应用(RNH_3)_2SO_4进行了Ti(IV)-Fe(II)的分离。

铕（II）等低价稀土离子在氧化物基质中光谱特征及其变化规律

近年来，围绕低价稀土离子开展的研究工作越来越多，尤其重视铕(II)、钐（II）和镱(II)的研究，以期获得短波可调固体激光晶体或高效率发光材料。由于4f~n到4f~(n-1)5d'组态的d-f跃迁是属于宇称允许的跃迁，所以它的发射要比4f~n壳层内的受迫电偶极跃迁强得多。这可以保证对泵浦的有效吸收，提高光泵效率。而4f~n组态内部的f-f锐线发射可以实现激光振荡，有利于提高储能，降低阀值。所以深入了解4f~n和 4f~(n-1)5d'体系在基质晶场中的行为以及基质环境对稀土离子发光特征的影响，对于寻找和设计新的激光和发光材料有着极为重要的意义。 本文从理论上讨论了晶场效应和化学键性质对铕(II)、钐(II)等稀土离子发光性质的影响。采用高温固相反应的方法合成了一系列铕(II)、钐(II)激活的氧化物基质荧光材料。结合光谱实验数据建立了晶格环境对铕(II)的 4f~65d'能级影响的表观模型和定量计算公式。为了研究4f~65d'激发态的性质，我们采用改进的Slater法计算了铕(II)和配体氧的有关轨道能量。利用静电晶场模型讨论了4f~65d'能带劈裂幅度(△E)与Eu-O键距(R)的关系，量子化学计算表明5d能级在晶场中的劈裂(△E)与R~5成反比。碱金属和碱七金属磷酸盐基质中铕的光谱数据证实了上述结论。在该基质中铕的4f~65d'能带的劈裂幅度随Eu-O键距增加而变小。在MeSO_4:Eu~(2+) (Me = Ca, Sr，Ba)中，随碱七金属离子半径增大，其发射和激发截止波长均有规律地向短波区移动。这是由于当铕(II)占据较大半径阳离子格位时，将受到较小的晶场影响。其体系的荧光寿命数据也证实了这一点。运用统计热力学原理讨论了4f~(n-1)5d'与 4f~n激发态能级的相对位置对低价稀土离子d-f和f-f跃迁发射的影响。在Ba_(1-x)Mg_(1+x)(SO_4):Eu~(2+)中，适当增大Mg~(2+)离子含量，线一带两种发射强度比R = I (f-f)/I(d-f) 明显增大。Ba_(0.4)Mg_(1.6)(SO_4)_2:Eu~(2+)的f-f锐线发射强度最大。在Ba_(1-x)Sr_xMg(SO_4)_2:Eu~(2+)中，铕(II)的f-f强度随x增大而变小，d-f发射峰则随x增加而发生红移。运用“电子云扩展效应”和鲍林化学键原理解释了，在Na_(3-x)(PO_4)_(1-x)(SO_4)_x:Eu~(2+)和Na_(2-x)CaSi_(1-x)P_xO_4:Eu~(2+)体系中，随X值在固溶区内变大，铕(II)的发射光谱逐渐移向短波区的现象。为了研究稀七离子的取代格位对其光谱性质的影响，我们合成了K_2Mg_2(SO_4)_3:Eu~(2+)单晶化合物。并经四圆衍射仪解出了结构。铕(II)在单晶中占据Mg_1~(2+)格位，与KMgF_3:Eu~(2+)相比，它将受到更强的晶场作用使4f~65d'能带劈裂幅度变大，又通过计算可知，Eu-O键的共价性比Eu-F键更强，因而在K_2Mg_2(SO_4)_3中Eu~(2+) 4f~65d'重心更低一些。综上所述，K_2Mg_2(SO_4)_3:Eu~(2+)的发射能级(E_(em)~m)要比KMgF_3:Eu~(2+)的发射能级更低。光谱实验数据证实了这一结论。用245 nm激发， K_2Mg_2(SO_4)_3:Eu~(2+)发兰光，最大中心处于400 nm。而KMgF_3:Eu~(2+)发紫色或近紫外光(E_(em)~m = 363 nm)，并且在后者是观察到Eu~(2+)离子的f-f跃迁锐线发射。采用高温氢气还原法制备了SmF_2和SmCl_2作为离子激活源。钐(II)激活的硫酸盐材料的荧光光谱数据表明，在室温条件下该基质中钐(II)的荧光光谱均为4f~55d' → 4f~6跃迁的宽带发射。论文对铕(II)，钐(II)等低价稀土离子的4f~(n-1)5d'激发态性质和稀七离子在基质中的格位取代以及电荷补偿效应也作了较为详细的讨论。

Metallic glass fiber-reinforced Zr-based bulk metallic glass

A novel Zr-based bulk metallic glass composite was fabricated using stainless steel capillaries as the reinforcement. Large plasticity (14%) was achieved in the composite with a reinforcement volume fraction of 38%. The high plasticity observed can be attributed to the formation of small glass fibers encapsulated by the steel capillaries, which promotes multiple shear bands in both metallic glass matrix and the fibers themselves. A new parameter was also proposed to approximately evaluate the reinforcement efficiency.

A vibrational spectroscopic study of the silicate mineral normandite – NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2

We have studied the mineral normandite using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral normandite NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2 is a crystalline sodium calcium silicate which contains rare earth elements. Chemical analysis shows the mineral contains a range of elements including Na, Mn2+, Ca, Fe2+ and the rare earth element niobium. No Raman bands are observed above 1100 cm−1. The mineral is characterised by Raman bands observed at 724, 748, 782 and 813 cm−1. Infrared bands are broad; nevertheless bands may be resolved at 723, 860, 910, 958, 933, 1057 and 1073 cm−1. Intense Raman bands at 454, 477 and 513 cm−1 are attributed to OSiO bending modes. No Raman bands are observed in the hydroxyl stretching region, but low intensity infrared bands are observed at 3191 and 3450 cm−1. This observation brings into question the true formula of the mineral.

Glass forming ability and stability: Ternary Cu bearing Ti, Zr, Hf alloys

Four Cu bearing alloys of nominal composition Zr25Ti25Cu50, Zr34Ti16Cu50, Zr25Hf25Cu50 and Ti25Hf25Cu50 have been rapidly solidified in order to produce ribbons. All the alloys become amorphous after meltspinning. In the Zr34Ti16Cu50 alloy localized precipitation of cF24 Cu5Zr phase can be observed in the amorphous matrix. The alloys show a tendency of phase separation at the initial stages of crystallization. The difference in crystallization behavior of these alloys with Ni bearing ternary alloys can be explained by atomic size, binary heat of mixing and Mendeleev number. It has been observed that both Laves and Anti-Laves phase forming compositions are suitable for glass formation. The structures of the phases, precipitated during rapid solidification and crystallization can be viewed in terms of Bernal deltahedra and Frank-Kasper polyhedra.

Stability of Fe3+ -VO defect pairs in polycrystalline Pb(Ti,Zr)O3

The intensity of the EPR signal with g = 5.985 arising from a ferric ion â oxygen vacancy defect pair (Fe3+ â VO) in PbTiO3, varies with the extent of PbO nonstoichiometry at constant Fe3+ content due to an increased oxygen vacancy concentration. In PZT solid solutions, the signal intensity decreases with an increase in Zr. A lower intensity is also noticed for Fe3+ â VO signals in PbZrO3. This behaviour is explained on the basis of PbO nonstoichiometry arising from independent Pb- and O-vacancies as well as the randomly distributed crystallographic shear (CS) plane defects. The contribution to PbO nonstoichiometry from CS planes is larger in high zirconium compositions of PZT.

Stress-induced martensitic phase transformation in Cu-Zr nanowires

A novel stress-induced martensitic phase transformation in an initial < 100 >/{100} B2-CuZr nanowire is reported for the first time in this letter. Such behavior is observed in a nanowire with cross-sectional dimensions of 19.44 x 19.44 angstrom(2) over a temperature range of 100-400 K and at a strain rate of 1 x 10(9) s(-1) using atomistic simulations. Phase transformation from an initial B2 phase to a BCT (Body-Centered-Tetragonal) phase is observed via nucleation and propagation of {100} twinning plane under high strain rate tensile deformation. (C) 2009 Elsevier B.V. All rights reserved.

Hydrothermal preparation of Ba(Ti,Zr)O3 fine powders

Fine powders consisting of aggregated submicron crystallites of Ba(Ti,Zr)O3 in the complete range of Ti/Zr ratios are prepared at 85–130°C by hydrothermal method, starting from TiO2 + ZrO2 · xH2O mixed gel and Ba(OH)2 solution. The products obtained below 110°C incorporate considerable amounts of H2O and OH− within the lattice. As-prepared BaTiO3 is cubic and converts to tetragonal phase after the heat treatment at 1200°C, accompanied by the loss of residual hydroxyl ions. TEM investgations of the growth features show a transformation of the gel to the crystallite. Ba2+ ions entering the gel produce chemical changes within the gel, followed by dehydration, resulting in a cubic perovskite phase irrespective of Ti/Zr. The sintering properties of these powders to fine-grained, high density ceramics and their dielectric properties are presented.

Formation of Pb(Ti,Zr)O3, from thermal decomposition of oxalate precursors

Lead zir conyl oxalate hexahydrate (LZO) and lead titanyl zirconyl oxalate hydrate (LTZO) are prepared and characterized. Their thermal decompositions have been investigated by thermoanalytical and gas analysis techniques. The decomposition in air or oxygen has three steps — dehydration, decomposition of the oxalate to a carbonate and the decomposition of carbonate to PbZrO3. In non oxidising atmosphere, partial reduction of Pb(II) to Pb(0) takes place at the oxalate decomposition step. The formation of free metallic lead affects the stoichiometry of the intermediate carbonate and yields a mixture of Pb(Ti,Zr)O3 and ZrO2 as the final products. By maintaining oxidising atmosphere and low heating rate, direct preparation of stoichiometric, crystalline Pb(Ti,Zr)O3 at 550°C is possible from the corresponding oxalate precursor.

An electron spectroscopic study of the surface oxidation of glassy and crystalline Cu-Zr alloys

Surface oxidation of three metglasses in the Cu-Zr system has been investigated by employing X-ray photoelectron spectroscopy and Auger electron spectroscopy with a view to comparing their oxidation behaviour with that of the corresponding crystalline states of the alloys. Surface oxidation of pure Zr metal has also been examined in detail using these techniques. Sub-oxides of Zr are formed during the initial stages of oxidation of Zr (at oxygen exposures <10L), while at higher exposures, ZrO2 is formed together with the highest possible sub-oxide which the authors designate as 'ZrO'. The relative proportion of 'ZrO' goes through a maximum in the range 25-50 L. Both the glassy and the crystalline states of the Cu-Zr alloys exhibit preferential oxidation of Zr. The glassy alloys exhibit a higher rate of oxidation at intermediate exposures compared with the crystalline states of the alloys; the extent of oxidation at higher oxygen exposures is, however, higher for crystalline alloys. Interatomic Auger transitions have been found in the Zr+O2 system as well as in Cu-Zr alloys.

Comment on "Pseudoelasticity of Cu-Zr nanowires via stress-induced martensitic phase transformations"

Recently, a novel stress-induced phase transformation in an initial < 100 >/{100} B2-CuZr nanowire has been reported for the first time [Sutrakar and Mahapatra, Mater. Lett. 63, 1289 (2009)]. Following this, a martenisitic phase transformation in Cu-Zr nanowire was shown [Cheng et al., Appl. Phys. Lett. 95, 021911 (2009)] using the same idea (Sutrakar and Mahapatra, Mater. Lett. 63, 1289 (2009)]. The pseudoelastic recovery of the bct phase of Cu-Zr by unloading has also been shown [Cheng et al., Appl. Phys. Lett. 95, 021911 (2009)]. They also tested the epitaxial bain path [Alippi et al., Phys. Rev. Lett. 78, 3892 (1997)] and reported that the bct phase in the nanowire is metastable, whereas the bulk counterpart is unstable. This aspect is re-examined in this comment with corrected results.

Are Metallocene-Acetylene (M = Ti, Zr, Hf) Complexes Aromatic Metallacyclopropenes?

The bonding nature of metallocene acetylene complexes Cp2M(eta(2)-H3SiC2SiH3) 1M and CP2M (eta(2)- HC2H) 1M' (M = Ti, Zr, Hf) wits studied by density functional theory method. It is found that this acetylene complex has indeed it metallacyclopropene moiety with two in-plane M-C sigma-bonds and one out-of-plane pi-bond interacting with the metal center, resulting in the formation of it delocalized three-center and two-electron (3c-2e) system. Along with its delocalized out-of-plane bonding, this complex has been characterized its aromatic on the basis of the computed stabilizing energy and negative nucleus-independent chemical shifts (NICS). The aromatic stabilization increases from Ti to Zr and Hf, and this is because of the increased charge separation between the CP2M fragment and the H3SiC2SiH3 (also HC2H) unit. The decrease of the M-C bond length from Zr to Hf is ttributed to the increased s character of both M and C hybridization of the M-C a-bonds.