Nanovoid morphology and distribution in deformed HDPE studied by magnified synchrotron radiation holotomography

The individual morphology and size distribution of nano-cavities in a necked tensile specimen made of semicrystalline high-density polyethylene (HDPE) have been observed and quantified in three dimensions using magnified synchrotron radiation holotomography. Here, using a voxel size of 59.7 nm, permanent voids in the unloaded state after yielding are observed that can only be assessed in averaged manner at finer length scales using small angle X-ray scattering (SAXS) techniques. Observation of the same sample using typical synchrotron radiation tomography with micron resolution is also given highlighting the novel opportunities arising with magnified synchrotron radiation holotomography in comparison. Two populations of voids elongated in loading direction are observed: A population of large cavities that has nucleated around inclusions and a population of small cavities. All cavities are equiaxed in radial directions and elongated in loading direction which is consistent with SAXS findings of other studies. Void volume fraction, void size distributions and characteristic dimensions of the voids are assessed using 3D image analysis.     

Reactions of ethylbenzene in the presence of toluene over external surface passivated MFI zeolite

The reactions of ethylbenzene in the presence of toluene were studied over external surface passivated MFI zeolite. With increase in extent of external surface passivation the para selectivity of both transalkylation and disproportionation reactions enhanced. The effects of mole ratio of ethylbenzene to toluene, reaction temperature and WHSV on the performance of the modified zeolite are discussed. It was observed that the high para selectivity feature of the modified zeolite is not influenced by changes in reaction conditions.     

XPS studies of radiation grafted PTFE‐g‐polystyrene sulfonic acid membranes

Structural investigations of PTFE‐g‐polystyrene sulfonic acid membranes prepared by radiation grafting of styrene onto PTFE were conducted by X‐ray photoelectron spectroscopy (XPS). The analyzed materials included original PTFE film as a reference material, grafted film, and sulfonated membrane samples having various degrees of grafting. Interest is focused on C1s, F1s, O1s, and S2p of narrow XPS spectra as the basic elemental components of the membrane. The original PTFE film was found to undergo structural changes in terms of chemical composition and shifting in binding energy induced by incorporation of sulfonated polystyrene grafts, and the amount of such changes depends on the degree of grafting. The atomic ratio of F/C was found to decrease with the increase in the degree of grafting, while that for S/C and O/C were found to increase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 336–349, 2000     

Chemical interaction of D9 alloy clad with B4C in liquid sodium: Studies employing XPS,XRD, and SEM

A cell representing typical control rod subassembly of the prototype fast breeder reactor is designed to probe the liquid sodium-mediated chemical interaction of boron carbide (B₄C) control rod with the D9 alloy clad. The cell was equilibrated at 973 K for 5000 hours with liquid sodium in the annular gap. XRD shows the formation of Cr₃C₂ and Fe₂B along with oxides of Ni, Cr, and Fe. XPS studies reveal the diffusion of boron and carbon up to a depth of about 160 and 120 μm, respectively. A boron-rich region is observed up to a depth of about 40 μm which consists of B³⁺ arising from oxides and a nearly constant elemental boron region, extending up to a depth of 160 μm. The highly reacted zone extends up to a depth of about 40 μm consisting of oxides of most of the elements of D9 clad exhibiting a higher valence states. As the cell is helium leak tested, oxygen out gassed from B₄C at 973 K played a major role in chemical oxidation of the constituents of the D9 alloy which can be minimized by using high-density B₄C.     

沸石填料电化学反应器处理氨氮污水的研究

采用填充沸石的电化学反应器对20 mg/L的氨氮模拟污水进行处理研究,考察了影响氨氮去除效果的主要因素及处理效果。结果表明:当采用不锈钢板作为阴阳极、电流密度8 m A/cm2、电源电压60 V、初始p H=5、载铁斜发沸石填充量为200 g/L、曝气量为7 L/min、反应时间20 min时,废水中氨氮质量浓度能从20 mg/L降低到5 mg/L左右,达到国家城市污水处理厂一级A的排放标准(GB 18918—2002)。     

微波辐射法氢交换Naβ分子筛催化合成蒽醌及其分离

用微波辐射法对Naβ分子筛进行氢交换,并对微波辐射条件进行了优化.通过对微波辐射法与常规加热方法氢交换Naβ分子筛的催化性能比较,发现利用微波辐射法省时,节能,高效.用溶剂法对产物进行了分离,通过对不同溶剂的筛选,发现N,N-二甲基甲酰胺是较合适的溶剂,分离得到蒽醌的纯度为97.98%,回收率为93.90%.     

Experimental study on fire behaviors of external thermal insulation composite system under vertical radiation

Using a vertical thermal radiator, we perform a set of experiments on the external thermal insulation composite system (ETICS) and pure extruded polystyrene (XPS). Several important parameters, including time to ignition, mass loss, and sample temperature, were measured. The combustion degree of XPS used during the experiments was B1 and B2. Results show that the whole burning process can be divided into 3 typical stages. Because of the protection effect of the outer layer of ETICS, the burning process of ETICS was noticeably different from that of pure XPS. The experimental results indicated that the protection effect of the outer layer weakened the difference between B1 and B2 flame‐retardant XPS. The time to ignition was increased under the effect of outer layer, while the core material (XPS) was easier to be ignited when the outer layer falls out. The research results are useful to the theoretical and numerical study on the fire characteristics of foamed polymer under vertical thermal radiation condition.     

AlN微粉表面结合状态的XPS研究

通过X射线光电子能谱 (XPS)分析研究了碳热还原氮化法制备的AlN微粉的表面结合状态。结果表明 :AlN微粉的表面有明显的氧化层存在 ;AlN微粉表面结合状态为Al—O和Al—N复合型结合 ;杂质元素W主要是由球磨介质中的WC引入的 ,并以WO2 - 4形式分布于AlN微粉表面。     

ICP-AES法测定Beta沸石中常量和微量组分

研究了沸石分子筛中主要和微量组分电感偶合等离子体发射光谱（ICP-AES）测定方法。考察了溶样酸度、仪器条件对测定的影响,以及共存元素间的干扰情况,优化了工作条件。实验结果表明,常量元素相对标准偏差（RSD）<1%,回收率为98.6%;杂质元素RSD<7%,回收率为85%~112.1%。     

Effect of pressure on TiO2 crystallization kinetics using in‐situ high‐temperature synchrotron radiation diffraction

The phase transformation behavior of TiO₂ sol‐gel synthesized nanopowder heated in a sealed quartz capillary from room temperature to 800°C was studied using in‐situ synchrotron radiation diffraction (SRD). Sealing of the capillary resulted in an increase in capillary gas pressure with temperature. The pressures inside the sealed capillary were calculated using Gay‐Lussac's Law, and they reached 0.36 MPa at 800°C. The as‐synthesized material was entirely amorphous at room temperature, with crystalline anatase first appearing by 200°C (24 wt% absolute), then increasing rapidly in concentration to 89 wt% by 300°C and then increasing more slowly to 97 wt% by 800°C, with there being no indication of the anatase‐to‐rutile transformation up to 800°C. The best estimate of activation energy for the amorphous‐to‐anatase transformation from the SRD data was 10(2) kJ/mol, which is much lower than that observed when heating the material under atmospheric pressure in a laboratory XRD experiment, 38(5) kJ/mol. For the experiment under atmospheric pressure, the anatase crystallization temperature was delayed by ~200°C, first appearing after heating the sample to 400°C, after which crystalline rutile was first observed after heating to 600°C. The estimated activation energy for the anatase‐to‐rutile transformation was 120(18) kJ/mol, which agrees with estimates for titania nanofibers heated under atmospheric pressure. Thus, heating the nanopowders material under pressure promoted the amorphous‐to‐anatase transformation, but retarded the anatase‐to‐rutile transformation. This behavior is believed to occur in an oxygen‐rich environment and interstitial titanium is also expected to form when the material is heated under high gas pressure. This suggests that atmospheric oxygen appears to accelerate the amorphous‐to‐anatase transformation, whereas interstitial titanium inhibits TiO₂ structure relaxation, which is required for the anatase‐to‐rutile transformation.     

海藻酸钠-氢氧化镧改性Y型分子筛颗粒除氟研究

为解决除氟吸附剂分离困难、有效成分流失等问题,以海藻酸钠（SA）与氢氧化镧改性Y型分子筛（LHMS）为原料,采用滴球法制备了SA@LHMS颗粒吸附剂,并采用模拟废水对其进行了除氟研究。通过正交实验确定了吸附剂最佳制备条件,并通过间歇吸附实验测试了吸附剂投加量、pH、共存离子等因素对吸附的影响,探究了吸附速率、吸附等温线等吸附性能。结果表明,SA@LHMS吸附速率曲线符合拟二级反应速率方程;吸附等温线符合Ⅱ型等温线,为多分子层吸附;初始pH（3~12）对吸附效果没有显著影响;高浓度共存阴离子（50 mg/L）对吸附过程有一定抑制;1 mol/L和2 mol/L氢氧化钠溶液对SA@LHMS再生效果较好,经3次再生仍然保留较高的吸附能力。SA@LHMS颗粒表面和截面形态以及吸附前后颗粒的表面形态差异明显;吸附前后颗粒表面能谱（EDS）分析以及红外光谱（FT-IR）分析结果显示,吸附过程中溶液中的氟离子（F^-）与颗粒表面及内部的羟基（—OH）发生配体交换。     

红辉沸石两步水热法合成A型分子筛机理研究

以红辉沸石为原料,采用两步水热法将其转化为A型分子筛,系统地探讨A型分子筛的转化机理。对不同晶化时间的样品进行系统表征,深入解析天然红辉沸石转化A型分子筛的成核机制、生长控制、晶型稳定转化等结构基础问题。研究表明,A型分子筛的生长可分为3个阶段：在成核诱导期（晶化时间≤0.5 h）,凝胶中的β笼通过双四元环构筑成α笼,生成较多晶核及少量1μm小晶体;此后为快速生长期（晶化时间1～4 h）,大量晶核通过聚集生长形成2μm大晶体;在生长稳定期（晶化时间5～8 h）,通过二次成核凝胶将会转化为更多的分子筛晶体。A型分子筛的形成遵循：铝硅酸盐凝胶→四元环、六元环→双四元环、β笼→α笼的晶化过程,因而其转化过程符合液相转化机理。     

Structure of molybdenum oxide clusters prepared in zeolite cages

Molybdenum hexacarbonyl entrapped in NaY zeolite was oxidized with molecular oxygen by UV-irradiation at room temperature or by thermal treatment at 343–373 K. Both oxidation procedures resulted in the identical molybdenum(VI) oxide; molybdenum dimer species (Mo-Mo distance: 0.321 nm). The Mo-Mo bonding of the oxide species was degraded on an evacuation at 673 K, while it was considerably stable in the presence of gaseous oxygen.     

Sizing removal and functionalization of the carbon fiber surface studied by combined TOF SIMS and XPS

Time-of-flight secondary ion mass spectrometry (TOF SIMS) and X-ray photoelectron spectroscopy (XPS) have been jointly used to study a two-step surface processing of AS4 carbon fiber: extraction of sizing in CH₂Cl₂ and functionalization with trimellitic anhydride. The combined information on molecular specificity obtained with TOF SIMS and quantification obtained with XPS allows us to follow qualitatively and quantitatively the changes in functional groups on the carbon surface. The results show that the sizing on AS4 contains at least four different compounds. These compounds can be extracted in CH₂Cl₂ and the elimination is almost complete for silicone. The functionalization of AS4 with trimellitic anhydride has been realized. The reaction takes place between the amine groups on the carbon fiber and the two types of functional groups in trimellitic anhydride.     

Thermal and structural properties of sn-1,3-dipalmitoyl-2-oleoylglycerol and sn-1,3-dioleoyl-2-palmitoylglycerol binary mixtures examined with synchrotron radiation X-ray diffraction

Thermodynamic and polymorphic behavior of POP (sn-1,3-dipalmitoyl-2-oleoylglycerol) and OPO (sn-1,3-dioleoyl-2-palmitoylglycerol) binary mixtures was examined using differential scanning calorimetry and conventional and synchrotron radiation X-ray diffraction. A molecular compound, β_C, was formed at the 1:1 (w/w) concentration ratio of POP and OPO, giving rise to two monotectic phases of POP/compound and compound/OPO in juxtaposition. β_C has a long-spacing value of 4.2 nm with a double chainlength structure and the melting point of 31.9°C. A structural model of the POP-OPO compound is proposed, involving the separation of palmitoyl and oleoyl chain leaflets in the double chainlength structure. In the polymorphic occurrence of the POP-OPO mixtures, the POP fraction transformed from α to β′ with no passage through γ, then transformed to β. The presence of OPO in POP promoted the β′-β transformation of POP during the melt-mediated crystallization.     

XPS and SEM study of UV laser surface modification of polymers

Several commercial polymers—poly(ethylene) (PE), poly(propylene) (PP), poly(vinylidene fluoride) (PVF₂), poly(vinyl chloride) (PVC) and polystyrene (PS)—were treated in air with an argon-fluorine UV excimer laser (λ = 193 nm). The polymer etch rate was investigated by two methods: quartz crystal microbalance (QCM) and piercing of films. X-ray photoelectron spectroscopy (XPS) analysis was performed on the modified surfaces after laser exposure at various fluences. Samples were subsequently analysed by scanning electron microscopy (SEM). From our results, polymers may be classified into two categories concerning their reactivity towards UV laser light. — the weakly absorbing polymers (e.g. PE, PP, PVF₂) where a photothermal process (thermal degradation) dominates the interaction. — the strongly absorbing polymers (e.g. PVC, PS) where a photochemical process (photoablation) dominates the interaction.     

XPS法研究表面活性剂、碱和聚合物在固体颗粒表面吸附的协同效应

利用光电子能谱法(XPS)研究了表面活性剂、碱和聚合物在固体颗粒表面上的吸附量及相互之间的协同效应。表面活性剂和碱在S iO2固体颗粒上的最大吸附量随着浓度的增大而增加,分别在1 200,5 000 mg/L达到最大吸附量1.15 mg/g和1.65 mg/g,吸附量达到最大值后趋于稳定;聚合物的平衡吸附曲线随着浓度的增大吸附量先增加后减少,600 mg/L达到最大吸附量1.30 mg/g,后减小至0.40 mg/g基本不变;在表面活性剂、碱和聚合物复合吸附体系中,碱的存在大大降低了表面活性剂在固体表面上的吸附量,在一定程度上增加了聚合物在固体表面上的吸附量,聚合物和表面活性剂在共存竞争吸附影响下S iO2表面上的吸附量都有了较大的减少;在表面活性剂、碱和聚合物复合体系中,聚合物与碱协同吸附的固体表面吸附层比其它情况下厚。     

Structural development of natural rubber during uniaxial stretching by in situ wide angle X-ray diffraction using a synchrotron radiation

Structural development of natural rubber during uniaxial stretching was examined by an in situ wide angle X-ray diffraction measurement using a synchrotron. During stretching, the amorphous part showed little change, i.e. an amorphous halo remained clear even at 500% strain. The fraction of induced crystals was very small, though a clear crystalline pattern was observed at 400% strain. Some polymer chains were oriented and crystallized, but most of the chains were not oriented at all in spite of large deformations of the specimen. Only a small amount of polymer chains contributes to the stress and hysteresis loss during elongation.     

Determination of Positions of Zeolitic Calcium Atoms and Water Molecules in Hydrothermally Formed Aluminum-Substiqtuted Tobermorite-1.1nm Using Synchrotron Radiation Powder Diffraction Data

The crystal structure of hydrothermally formed Al-substituted tobermorite-1.1nm (Ca_4.9Si_5.5Al_0.5O_16.3(OH)_0.7·5H₂O) has been analyzed using synchrotron radiation powder diffraction data. Crystallographic positions of a zeolitic Ca atom and three water molecules in the channel of the framework were determined by the Monte Carlo method and subsequent Rietveld refinement. The Ca atom splits into two sites at a distance of 0.161 nm apart, and it is coordinated with the three water molecules and the three oxygen atoms belonging to the framework. Al atoms preferably substitute a part of the Si atoms at the "bridging SiO₄" tetrahedra rather than at those of the "chain middle group SiO₄" tetrahedra.