弹性体/无机纳米粒子复合体系增强增韧回收ABS树脂

分别研究了弹性体和无机纳米粒子对回收丙烯腈-丁二烯-苯乙烯共聚物(ABS)的增韧。结果表明:弹性体能使回收ABS树脂的韧性得到恢复,但导致刚性下降;无机纳米粒子对ABS树脂的增韧能力有限,但能增加ABS的刚性。最后采用弹性体/无机纳米粒子复合体系改性回收ABS树脂,添加质量分数5%~8%的高胶粉和质量分数2%~3%无机纳米粒子时,实现了对回收ABS树脂的增强增韧。     

聚丙烯/弹性体/纳米高岭土三元复合材料的研究

以新型聚烯烃弹性体POE为增韧剂，以纳米高岭土为增强剂，将传统的弹性体增韧方法和新型的纳米粒子增韧增强手段相结合；采用合金化技术和填充复合工艺，制得高性能的聚丙烯复合材料。研究结果表明，纳米高岭土和弹性体POE对PP增韧具有协同作用，呈现的并不是二者独立增韧作用的简单加和，纳米无机粒子对复合体系PP／POE还有增强作用并大大减缓了因POE的加入而导致复合体系强度的降低。     

热塑性聚氨酯/无机纳米粒子增韧改性聚甲醛研究

采用热塑性聚氨酯弹性体(TPU)和无机纳米粒子复合增韧改性聚甲醛(POM),制备了刚韧平衡的POM/TPU共混物。讨论TPU及无机纳米粒子种类、稳定剂体系及注塑工艺对复合材料力学性能的影响。结果表明,聚酯型TPU-2对POM增韧效果较好;纳米Ca CO3可以有效提高共混材料强度;添加抗氧剂Irganox 245制备的复合材料具有更高的断裂伸长率和冲击韧性;注塑工艺对POM/TPU复合材料性能影响较大。     

无机纳米粒子改性聚氨酯弹性体的研究进展

介绍了用无机纳米粒子改性聚氨酯弹性体的制备方法,综述了纳米Si O2、纳米Zn O、纳米蒙脱土、纳米Ca CO3、纳米Ti O2、碳纳米管以及其他无机纳米粒子改性聚氨酯弹性体的研究进展,指出了无机纳米粒子改性聚氨酯弹性体目前存在的问题。     

聚氨酯/无机粒子纳米复合材料的制备与应用进展

综述了国内外关于纳米层状硅酸盐和无机刚性纳米粒子改性聚氨酯的最新研究进展,其中纳米层状硅酸盐包括蒙脱土、累托石、海泡石、滑石粉等,无机刚性纳米粒子包括二氧化钛、二氧化硅、碳酸钙、氧化锌、氢氧化镁、纳米铋掺杂二氧化锡、碳纳米管、纳米金、纳米纤维素晶等。同时介绍了聚氨酯/无机粒子纳米复合材料在弹性体、泡沫塑料、涂料和胶黏剂等行业的应用研究现状,并对其发展前景做出展望。     

PA6基"沙袋结构"复合材料的形态及力学性能

研究了弹性体种类、预混料中纳米CaCO3的质量分数对纳米CaCO3/弹性体/PA6三元复合体系中纳米粒子的分布、分散相形貌以及力学性能的影响.研究发现,纳米CaCO3/弹性体预混料中纳米粒子质量分数为30%时,纳米CaCO3粒子及其团聚体被弹性体所包覆,形成比较完整的"沙袋结构",利用沙袋结构内粒子团聚体的变形吸收能量,三元复合材料的冲击强度明显提高.     

有机/无机纳米复合粒子平衡型态的热力学计算——粒子型态的转化率依赖性

有机/无机纳米复合粒子是一种性能优异的纳米复合材料,基于分裂/融合过程的细乳液聚合是制备此类复合粒子的新型方法。从热力学角度出发,基于界面Gibbs自由能最低原理推导了核壳型、半球型、夹心型和分离型有机/无机纳米复合粒子平衡型态的界面Gibbs自由能方程,考虑了聚合过程中单体转化率对纳米复合粒子热力学平衡型态的影响,扩展了上述方程应用范围。将这些热力学方程用于炭黑/（聚）苯乙烯/水体系中,发现当无机颗粒体积分数小于0.2时,核壳型纳米复合粒子的界面Gibbs自由能最低;随着单体转化率的增加,核壳型、半球型和夹心型复合粒子的界面Gibbs自由能略有下降,这可能是由于聚苯乙烯/水相的界面张力略低于苯乙烯/水相的数值造成的。     

电纺丝技术制备无机/有机复合纳米纤维的研究进展

静电纺丝法是一种利用聚合物溶液或熔体在强电场中进行喷射纺丝的加工技术,是获得纳米尺寸长纤维的有效方法之一。目前电纺丝技术逐渐转移到无机/有机纳米复合纤维的制备方面。回顾了近年来电纺丝技术制备无机/有机复合纳米纤维的研究进展,包括:半导体纳米粒子/聚合物复合纳米纤维的制备,无机氧化物纳米粒子/聚合物复合纳米纤维的制备以及贵金属纳米粒子/聚合物复合纳米纤维的制备。     

纳米技术在弹性体增韧环氧树脂中的应用

综述了弹性体与无机纳米粒子协同增韧改性环氧树脂以及纳米弹性体粒子增韧环氧树脂的应用进展,并且对纳米技术在弹性体增韧环氧树脂中的应用进行了展望。     

纳米无机粉体对PP／POE共混物力学性能和形态结构的影响

采用纳米无机粒子对茂金属聚乙烯（POE）弹性体增韧聚丙烯（PP）二元共混体系进行改性。从而制得PP／POE／无机纳米粒子三元复合材料。分别探讨了纳米高岭土和纳米碳酸钙对复合材料拉伸性能和冲击性能的影响，并考察了不同纳米粉体的增强效果。     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Thin-Layer Dielectrics in the Pb[(Mg1/3Nb2/3)1-xTix]O3 System

Thin layers of Pb[(Mg_1/3Nb_2/3)_{1– x} Ti _x ]O₃ (PMNT) were prepared by spin casting alkoxide-based solutions on platinized Si. The effects of additives, heat treatment, and composition ( x = 0 to 0.9) on perovskite phase development, ceramic microstructure, and dielectric properties are reported. Depending upon the processing conditions, ceramic thin layers could be formed in a nonferroelectric pyrochlore phase (A₂B₂O₆) or in a ferroelectric perovskite phase (ABO₃). The dimensions of the pyrochlore and perovskite units cells were related and increased with Mg and Nb contents. To minmize pyrochlore formation, the most effective processing method involved rapid heat treatment between successive solution depositions. Phase development and microstructure were also affected by solution additives. Additions of benzoic acid were found to affect the structure in solution and the later organic pyrolysis behavior from thin layers. The effect of composition on the dielectric and ferroelectric properties is also reported.     

Thermochemistry of MgAl2O4-Al8/3O4 Defect Spinels

Solution calorimetry of MgAl₂O₄-Al_8/3O₄ solid solutions was performed in a molten 2PbO · B₂O₃ solvent at 975 K. The results indicate small negative heats of mixing, relative to spinel standard states for both end-members. These data were combined with information on the energetics of the α-γ transition in Al₂O₃ and on the MgAl₂O₄-Al_8/3O₄ (MgO-Al₂O₃) subsolidus phase relations to estimate the partial molar entropy of mixing of γ-Al_8/3O₄ in the solid solution. This entropy is much less positive than that calculated from several models for the configurational entropy of mixing of magnesium, aluminum, and vacancies on octahedral and/or tetrahedral sites. The data suggest a good deal of local order to be present in the solid solutions, consistent with negative enthalpies of mixing and entropies of mixing far less than ideal configurational values.     

Mean field modelling of NOx storage on Pt/BaO/Al2O3

A mean field model, for storage and desorption of NO_x in a Pt/BaO/Al₂O₃ catalyst is developed using data from flow reactor experiments. This relatively complex system is divided into five smaller sub-systems and the model is divided into the following steps: (i) NO oxidation on Pt/Al₂O₃; (ii) NO oxidation on Pt/BaO/Al₂O₃; (iii) NO_x storage on BaO/Al₂O₃; (iv) NO_x storage on Pt/BaO/Al₂O₃ with thermal regeneration and (v) NO_x storage on Pt/BaO/Al₂O₃ with regeneration using C₃H₆. In this paper, we focus on the last sub-system. The kinetic model for NO_x storage on Pt/BaO/Al₂O₃ was constructed with kinetic parameters obtained from the NO oxidation model together with a NO_x storage model on BaO/Al₂O₃. This model was not sufficient to describe the NO_x storage experiments for the Pt/BaO/Al₂O₃, because the NO_x desorption in TPD experiments was larger for Pt/BaO/Al₂O₃, compared to BaO/Al₂O₃. The model was therefore modified by adding a reversible spill-over step. Further, the model was validated with additional experiments, which showed that NO significantly promoted desorption of NO_x from Pt/BaO/Al₂O₃. To this NO_x storage model, additional steps were added to describe the reduction by hydrocarbon in experiments with NO₂ and C₃H₆. The main reactions for continuous reduction of NO_x occurs on Pt by reactions between hydrocarbon species and NO in the model. The model is also able to describe the reduction phase, the storage and NO breakthrough peaks, observed in experiments.     

The structures of VOx/MOx and alkali-VOx/MOx catalysts and their catalytic performances for soot combustion

Vanadium oxides supported on γ-Al₂O₃, SiO₂, TiO₂, and ZrO₂ were studied on their molecular structures and reactive performances for soot combustion. To investigate the effect of different alkali metals on the structures and reactivities of supported-vanadium oxide catalysts, they were doped into the V₄/TiO₂ catalyst which had the best intrinsic activity for soot combustion in the selected supported vanadium oxide catalysts. The experimental results demonstrated that the catalytic properties of these catalysts depended on the vanadium loading amount, support nature, and the presence or the absence of alkali metals. The spectroscopic analysis (FT-IR and UV–vis) and H₂-TPR results revealed that the higher activity of alkali-promoted vanadium oxide catalysts could be related to the ability of alkali metal promoting the redox cycle of the active vanadyl species. TG results showed that adding alkali to V_m/TiO₂ catalyst was beneficial to lowering their melting points. Low melting points could ensure the good surface atom migration ability, which would improve the contact between the catalyst and soot. Due to the alkali metal components promoting the redox ability and the mobility of the catalysts, alkali-modified vanadium oxide catalysts could remarkably improve their catalytic activities for soot combustion. The catalytic activity order for soot combustion followed Li > Na > K > Rb > Cs in the catalyst system of alkali-V₄/TiO₂, and the reason why it followed this sequence was discussed.     

A-Site and B-Site Order in (Na1/2La1/2)(Mg1/3Nb2/3)O3 Perovskite

(Na_1/2La_1/2)(Mg_1/3Nb_2/3)O₃ undergoes a series of phase transitions that involve cation order on the A- and B-sites of the parent perovskite structure. At high temperatures both sites contain a random distribution of cations; below 1275°C a 〈111〉 layering of Mg and Nb leads to the formation of a 1:2 ordered structure with a monoclinic supercell. A second transition was observed at 925°C, where the Na and La cations order onto alternate A-site positions along the 〈001〉 direction of the parent subcell. By quenching samples from above 1275°C to preserve the disorder on the B-site, a fourth variant of this compound was obtained by inducing A-site order through a subsequent anneal at 900°C. Although the changes in structure do not produce significant alterations in the relative permittivity (ɛ_r∼ 35), they do have a significant effect on the value of the temperature coefficient of the capacitance.     

TIOx/Al2O3 Multilayer Ceramic Thin Films

Titanium oxide/aluminum oxide films have been deposited using molecular beam epitaxy methods and characterized by reflection high-energy electron diffraction and transmission electron microscopy techniques. Growth on silicon substrates below 973 K resulted in primarily amorphous multilayers. At 1323 K, the deposition of titanium in an oxygen atmosphere on (0001) Al₂O₃ substrates resulted in films of Ti₂O₃. These films consisted of small domains, up to 60 nm, slightly misoriented from a [1120] ∥ [1120] orientation relationship. Two variants of Ti₂O₃ were observed due to multiple positioning during growth. Closing the titanium shutter during growth resulted in an oriented TiO₂ film.     

The System HfO2-Y2O3-Er2O3

A mathematical model of the liquidus surface based on a reduced polynomial method was proposed for the system HfO₂-Y₂O₃-Er₂O₃. The results of calculations according to this model agree fairly well with the experimental data. Phase equilibria in the system HfO₂-Y₂O₃-Er₂O₃ were studied on melted (as-cast) and annealed samples using X-ray diffraction (at room and high temperatures) and micro-structural and petrographic analyses. The crystallization paths in the system HfO₂-Y₂O₃-Er₂O₃ were established. The system HfO₂-Y₂O₃-Er₂O₃ is characterized by the formation of extended solid solutions based on the fluorite-type (F) form of HfO₂ and cubic (C) and hexagonal (H) forms of Y₂O₃ and Er₂O₃. The boundary curves of these solid solutions have the minima at 2370°C (15. 5 mol% HfO₂, 49. 5 mol% Y₂O₃) and 2360°C (10. 5 mol% HfO₂, 45. 5 mol% Y₂O₃). No compounds were found to exist in the system investigated.     

Kinetic modelling of sulfur deactivation of Pt/BaO/Al2O3 and BaO/Al2O3 NOx storage catalysts

In this work, a kinetic model is constructed to simulate sulfur deactivation of the NO_x storage performance of BaO/Al₂O₃ and Pt/BaO/Al₂O₃ catalysts. The model is based on a previous model for NO_x storage under sulfur-free conditions. In the present model the storage of NO_x is allowed on two storage sites, one for complete NO_x uptake and one for a slower NO_x sorption. The adsorption of SO_x is allowed on both of these NO_x storage sites and on one additional site which represent bulk storage. The present model is built-up of six sub-models: (i) NO_x storage under sulfur-free conditions; (ii) SO₂ storage on NO_x storage sites; (iii) SO₂ oxidation; (iv) SO₃ storage on bulk sites; (v) SO₂ interaction with platinum in the presence of H₂; (vi) oxidation of accumulated sulfur compounds on platinum by NO₂. Data from flow reactor experiments are used in the implementation of the model. The model is tested for simulation of experiments for NO_x storage before exposure to sulfur and after pre-treatments either with SO₂ + O₂ or SO₂ + H₂. The simulations show that the model is able to describe the main features observed experimentally.     

Comment on "Effect of Al2O3 and Bi2O3 on the Formation Mechanism of Sn-Doped Ba2Ti9O20"

in a recent article of the Journal , Yu et al .¹ reported their experimental results on the effect of Al₂O₃ and Bi₂O₃ on the formation mechanism of Sn-doped Ba₂Ti₉O₂₀. They claimed that both Al₂O₃ and Bi₂O₃ can dramatically assist the formation of Sn-doped Ba₂Ti₉O₂₀ but are based on different mechanisms. They concluded that first, Bi₂O₃ melts above 830°C and accelerates the migration of the involved reactants to form Ba₂Ti₉O₂₀; second, Al₂O₃ can reduce the height of the potential energy barrier of the formation of Ba₂Ti₉O₂₀ due to the intergrowth of BaAl₂Ti₆O₁₆ phase. They explained their results from a point of view that the formation of Ba₂Ti₉O₂₀ is controlled by (1) the migration of reactants to the interfaces and (2) the height of the potential-energy barrier of the reaction at the interfaces. However, based on their results, we feel their conclusions are incautious and may be misleading, as will be discussed later.