球磨干湿环境对原位硫掺杂氮化碳可见光催化性能的影响

以硫脲为原料,通过简单绿色的球磨法提高原位硫掺杂g-C3N4的光催化活性。利用X射线衍射、扫描电子显微镜、元素分析、X射线光电子能谱、紫外-可见漫反射光谱及光致发光光谱等测试方法对其结构和光学特性进行表征。以亚甲基蓝为目标污染物,评价了在不同物料溶剂比下球磨的硫掺杂g-C3N4的可见光催化性能。结果表明,湿式球磨后的硫掺杂g-C3N4光催化剂比表面积增大,反应活性位点的数量增加,带隙宽度也适当增大,氧化还原能力增强。另外,湿式球磨后样品的表面缺陷减少,聚合度增加,促进了光生电子-空穴的有效分离和转移,从而降低其复合率,协同提高了硫掺杂g-C3N4的可见光催化性能。湿式球磨后的样品在可见光照射下对亚甲基蓝的降解速率分别比未球磨的样品和干式球磨后的样品提高了1.5和3.6倍。     

Characterisation of δ-VCl3, a highly active ziegler-natta catalyst obtained by ball-milling. Dependence of polymerisation activity upon milling time

A new structural form, δ-VCl₃, a highly active Ziegler-Natta catalyst, showing disorder due to stacking faults, has been obtained by ball-milling. To elucidate the structure of δ-VCl₃, a known disorder function developed for triply layered structures contining stacking faults has been applied. In this way, the experimental X-ray diffraction pattern of δ-VCl₃ for different periods of ball-milling has been well reproduced and agreement between the calculated and experimental patterns is good (standard error less than 5%). Like TiCl₃ and MgCl₂, VCl₃ exhibits structural modification when subjected to ball-milling. The strikingly similar behaviour and structural properties of these three chlorides indicate that they belong structurally and chemically to the same family. The relationship between grinding time and polymerisation activity of VCl₃ has been confirmed. Further, the increase in activity of the samples for the first 2 hr of grinding is mainly due to a decrease in crystallite dimension (i.e. an increase in surface area). However the contribution of structural disorder to polymerisation activity is still not well defined. We would expect different activities for the samples ground for 6 and 12 hr and having the same crystallite dimension but different structural disorder parameters; but that was not the case however. Although it was not possible to establish a relationship between structure and activity, we think that structural disorder must influence polymerisation activity. We have taken into account only the crystallite dimension but other significant parameters such as porosity are probably important.     

Magnesium chloride-supported,high-mileage catalysts for olefin polymerization. V. BET,porosimetry, and x-ray diffraction studies

The physical state of the material obtained during the various stages of preparation of a typical MgCl₂-supported, high-mileage propylene polymerization catalyst was studied by BET, mercury porosimetry, and x-ray diffraction techniques. The starting MgCl₂ and the substance after HCl treatment have negligible BET surface areas. Mercury porosimetry showed that they have large pores with radii > 200 nm which are probably crevices between MgCl₂ crystallites. The most pronounced physical changes occur during dry porcelain ball milling in the presence of ethyl benzoate. After 60 h or more of ball milling the material had a 5.1–7.3 m² g^?1 BET surface area, twice the pore surface area, and a smaller pore radius than before ball milling and a large reduction in crystallite sizes to almost ultimate dimensions. The crystallites were probably held together by complexation with ethyl benzoate in the form of large agglomerates. Subsequent reactions with p-cresol and triethyl aluminum had minor effects in further reduction of the MgCl² crystallite size but efficiently brokeup the agglomerates. The final refluxing with TiCl₄ increased the BET surface area to 110–150 m² g^?1 but may have increased the crystallite size somewhat due to cocrystallization of TiCl₃ and AlCl₃ with MgCl₂. There may have been only 8–10 crystallites in each catalyst particle. The surface structure of the catalyst resembled those of the classical Ziegler-Natta γ-TiCl₃·0.33 AlCl₃ catalyst.     

Role of core diameter and silica content in photocatalytic activity of TiO2/SiO2/Fe3O4 composite

Magnetically separable TiO₂/SiO₂/Fe₃O₄ composites of different core (Fe₃O₄) diameters and silica contents have been prepared by sol–gel technique for both silica and titania coatings. Energy dispersive X-ray fluorescence (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area analysis and scanning electron microscope (SEM) have been used for characterization of prepared samples. Photocatalytic activity of the prepared samples has been investigated by photodegradation of methyl orange. Obtained results have shown that 25–45 μm core diameter exhibits the maximum activity since it possesses a convenient surface area and light transmittance. Silica content has a significant effect on the activity of composite. Silica content of more than 10 wt% has reduced the catalyst activity because of the increase in particle diameter and reduction of surface area.     

X-Ray absorption spectroscopy and diffraction study of miscible and immiscible binary metallic systems prepared by ball milling

A series of copper-based alloys (CuTi, CuV, CuMn, CuCo of equiatomic composition) were obtained by ball milling under a protective atmosphere with the aim of exploring the effect of milling on systems showing very different miscibilities in the solid state. The alloys were studied by means of X-ray spectroscopy (EXAFS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The mechanical treatment produces an amorphous phase in CuTi. The other systems, displaying a positive heat of mixing, cannot be amorphized, although enhanced reactivity leads to the formation of supersaturated solid solutions. The effect of milling time has been studied on Cu₅₀V₅₀ following the increase in lattice parameters of both fcc and bcc solutions. The fragmentation of the crystallites to a size as low as 300 Å represents a necessary condition for the solid state reaction in Cu₅₀V₅₀.     

Comparison of sample preparation methods for determination of free carbon in boron carbide by X-ray powder diffraction

Several sample preparation methods were evaluated for determination of free carbon in boron carbide powders by quantitative X-ray diffraction method, including ultrasonication, wet ball milling and dry ball milling–wet mixing. Quantitation was based on measuring the integral peak area ratio of the diffraction lines of graphite (002) to boron carbide (012) in samples spiked with pure graphite. The dry milling–wet mixing method provided the best precision and accuracy in all the measurements as well as in determination of free carbon in a boron carbide reference material. There was a linear relationship between the integral peak area ratios and graphite added to boron carbide samples which were purified from their free carbon content. The method provided a low detection limit of 0.05 wt% free carbon.     

Mechanosynthesis of zinc ferrite in hardened steel vials: Influence of ZnO on the appearance of Fe(II)

Nanocrystalline ZnFe₂O₄ spinel powders are synthesized by high-energy ball milling, starting from a powder mixture of hematite (α-Fe₂O₃) and zincite (ZnO). The millings are performed under air using hardened steel vials and balls. X-ray diffraction and Mössbauer spectrometry are used to characterize the powders. A spinel phase begins to appear after 3 h of milling and the synthesis is achieved after 9 h. Phase transformation is accompanied by a contamination due to iron coming from the milling tools. A redox reaction is also observed between Fe(III) and metallic iron during milling, leading to a spinel phase containing some Fe(II). The mechanism for the appearance of this phase is studied: ZnO seems to have a non-negligeable influence on the synthesis, by creating an intermediate wüstite-type phase solid solution with FeO.     

Tailoring materials by high-energy ball milling: TiO2 mixtures for catalyst support application

We carried out a rational design of catalyst supports by high-energy ball milling. Tailored mixtures of TiO₂ crystalline phases were obtained using rotational speed and milling time as variable parameters. Polymorphic transformation from anatase to rutile through high-pressure TiO₂ (II) as intermediate was confirmed by X-ray Diffraction (XRD), Raman Spectroscopy and Transmission Electron Microscopy (TEM). Also, starting material doubled its specific surface area due to particle fragmentation, as confirmed by surface area of Brunauer-Emmet-Teller (S_BET) and Scanning Electron Microscopy (SEM). Defects introduced during milling process generated oxygen vacancies in the surface and bulk of supports, as evidenced by X-ray Photoelectron Spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR). Furthermore, longer milling time increased reducibility and oxygen mobility of supports, as observed by H₂ Temperature Programmed Reduction (H₂-TPR) and O₂ Temperature Programmed Desorption (O₂-TPD). Phase composition remained unchanged even under extreme conditions, highlighting the stability of unusual TiO₂ (II) phase. Properties achieved in present materials could benefit metal-support interactions and play a major role in supported catalysts.     

Synthesis of amorphous manganese borohydride in the(NaBH_4–MnCl_2) system,its hydrogen generation properties and crystalline transformation during solvent extraction

The mixture of(2NaBH_4+ MnCl_2) was ball milled in a magneto-mill. No gas release was detected. The XRD patterns of the ball milled mixture exhibit only the Bragg diffraction peaks of the Na Cl-type salt which on the basis of the present X-ray diffraction results and the literature is likely to be a solid solution Na(Cl)x(BH4)(1-x), possessing a cubic Na Cl-type crystalline structure. No presence of any crystalline hydride was detected by powder X-ray diffraction which clearly shows that NaBH_4 in the initial mixture must have reacted with MnCl_2 forming a Na Cl-type by-product and another hydride that does not exhibit X-ray Bragg diffraction peaks. Mass spectrometry(MS) of gas released from the ball milled mixture during combined MS/thermogravimetric analysis(TGA)/differential scanning calorimetry(DSC) experiments, confirms mainly hydrogen(H2) with a small quantity of diborane gas, B_2H_6. The Fourier transform infra-red(FT-IR) spectrum of the ball milled(2NaBH_4+ MnCl_2) is quite similar to the FT-IR spectrum of crystalline manganese borohydride, c-Mn(BH_4)_2, synthesized by ball milling, which strongly suggests that the amorphous hydride mechano-chemically synthesized during ball milling could be an amorphous manganese borohydride. Remarkably, the process of solvent filtration and extraction at 42 °C, resulted in the transformation of mechano-chemically synthesized amorphous manganese borohydride to a nanostructured,crystalline, c-Mn(BH_4)_2hydride.     

Chloride substitution in sodium borohydride

The dissolution of sodium chloride and sodium borohydride into each other resulting in formation of solid solutions of composition Na(BH₄)_1−xCl_x is studied. The dissolution reaction is facilitated by two methods: ball milling or combination of ball milling and annealing at 300 °C for three days of NaBH₄-NaCl samples in molar ratios of 0.5:0.5 and 0.75:0.25. The degree of dissolution is studied by Rietveld refinement of synchrotron radiation powder X-ray diffraction (SR-PXD) data. The results show that dissolution of 10 mol% NaCl into NaBH₄, forming Na(BH₄)_0.9Cl_0.1, takes place during ball milling. A higher degree of dissolution of NaCl in NaBH₄ is obtained by annealing resulting in solid solutions containing up to 57 mol% NaCl, i.e. Na(BH₄)_0.43Cl_0.57. In addition, annealing results in dissolution of 10-20 mol% NaBH₄ into NaCl. The mechanism of the dissolution during annealing and the decomposition pathway of the solid solutions are studied by in situ SR-PXD. Furthermore, the stability upon hydrogen release and uptake were studied by Sieverts measurements.     

Phase transformations in nanocrystalline TiO2 milled in different milling atmospheres

The structural evolution of nanocrystalline TiO₂ milled in different milling atmospheres was studied by X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy. Rietveld refinements of the XRD data showed that high-energy ball milling induced the transformations from anatase to srilankite and rutile at room temperature and ambient pressure. The milling atmospheres with different oxygen partial pressures had an influence on the transformation kinetics of anatase. When the nanocrystalline TiO₂ powders were, respectively, milled in oxygen, air and nitrogen atmospheres, the transformation rates of anatases in turn increased with a decrease in oxygen partial pressure of the milling atmosphere, due to the reducing concentration of oxygen vacancies in the milled TiO₂ lattice.     

球磨-溶剂热诱导法合成WS2纳米棒及其摩擦性能

采用行星式高能球磨机，将WS₂与S粉末混合球磨，得到纳米片状结构的前驱体，然后添加分散剂聚乙二醇(PEG)用溶剂热诱导的方法使纳米片状前驱体发生结构转变，制备了棒状结构的WS₂纳米材料。用XRD、SEM、TEM等方法对WS₂纳米棒进行了形貌和结构表征，并对其作为润滑油添加剂的摩擦性能进行了初步的研究。     

Preparation of a highly active nanocrystalline TiO2 photocatalyst from titanium oxo cluster precursor

Nanocrystalline TiO₂ (sample S1) was prepared from a titanium oxo cluster (Ti₇O₄(OEt)₂₀) precursor via a sol-gel route. This photocatalyst showed a higher photocatalytic activity than the TiO₂ (sample S2) obtained from titanium tetraisopropoxide. The samples were characterized by thermal analysis (TGA/DSC), X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, N₂ adsorption (BET surface area), infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy. The characterization results show that both samples are anatase nanocrystals with particle sizes of about 12 nm, but the more photocatalytically active sample S1 has more surface hydroxyl groups and larger surface area and pore volume than sample S2.     

Chelation-assisted method for the preparation of cathode material LiFePO<Subscript>4</Subscript>

LiFePO₄/C composite cathode material is prepared by ball milling with the assistance of EDTA chelation with using water as the media of ball mill procedure. FePO₄ and LiOH are used as starting materials; a certain amount of glucose is used as carbon sources and reduction agent. The structure and morphology of the composite are characterized by X-ray diffraction and scanning electron microscopy. Cyclic voltammetry, AC impedance measurements, and galvanostatic charge–discharge and cycling performances are used to characterize its electrochemical properties. The results indicate that the performances of composites prepared by chelation-assisted method are much better than common ball milling method which using alcohol or acetone as the media of ball mill procedure. The stable discharge capacity of the prepared composite is 150 and 105 mAh g⁻¹ at 1 and 10 C rate, respectively.     

Comments on: “Toward improved heat transfer performance of annular heat exchangers with water/ethylene glycol based nanofluids containing graphene nanoplatelets,Journal of Thermal Analysis and Calorimetry 126.3 (2016): 1427–1436”

The present study has investigated the complex mechanisms in the aluminum–titanium system with different percentages of titanium through a combination of thermal and X-ray analyses. Thermogravimetry, derivative thermogravimetric, X-ray diffraction, scanning electron microscope and transition electron microscope were used for characterization of the samples. Initially, different Al–Ti powder mixtures were produced by high-energy ball milling and after 30 h of milling the phases generated at different percentages of Ti were analyzed. The XRD results revealed that the intermetallic Al₃Ti powder is obtained after a certain duration of milling. In addition, L1₂ to D0₂₃ phase transformation is possible with increase of the Ti percent. Analyses of the powder annealed at different temperatures yielded interesting results, including the effect of stearic acid as the surface control agent on phase transformations of the aluminum–titanium system and also the formation of unexpected phases such as Al₄C₃ and TiC. Moreover, ductile to brittle transition during phase transformations of the intermetallic Al₃Ti powder was quite conspicuous, which could result in more homogeneity of the powders and the occurrence of more reactions in the system. For example, formation of D0₂₃-Al₃Ti powder which is more brittle compared to L1₂ resulted in the exit of Al from among its layers, leading to the increase of the chances for Al reaction with the system impurities.     

Preparation of Nanosized α-Fe2O3 Using Mechanical Activation

The processes occurring during the mechanical activation of a-Fe₂O₃ (hematite) in the presence of oleic acid in a centrifugal-planetary mill have been investigated. Mechanical activation for 10 h afforded hematite powder with particles size of 10–40 nm, as shown by means of X-ray diffraction analysis, FTIR spectroscopy, high-resolution transmission electron microscopy, and specific surface area measurements. Longer milling has led to mechanochemical transformation of hematite into Fe₃O₄ (magnetite).

     

不同氮源溶剂热合成N-TiO2纳米颗粒及其光催化降解气相苯（英文）

采用三种不同的氮源溶剂热合成了锐钛矿-板钛矿混晶的N-TiO2催化剂.采用X射线衍射、N2吸附-脱附、X射线光电子能谱和透射电子显微镜等手段对催化剂进行了表征.重点研究了不同氮源对催化剂的相组成、晶粒尺寸、微观结构以及比表面积的影响.采用紫外光降解气相苯测试了合成材料的催化活性.结果表明,以水合肼为氮源合成的N-TiO2表现出最优的光催化活性,其活性明显高于P25,且能够循环使用15次以上.采用气相色谱-质谱技术分析了光降解过程的中间产物,基于此提出了相应的降解机理.     

A crystallographic study of disorder in titanium trichloride,a component of Ziegler-Natta catalysts for stereospecific polymerization

The profiles of X-ray diffraction patterns have been examined for several powder samples of δ-TiCl₃, obtained by mechanical activation of γ-TiCl₃ and presenting different catalytic activities in the Ziegler-Natta stereospecific polymerization of propylene to isotactic polypropylene. Particular attention has been paid to the δ-TiCl₃ samples showing the best catalytic properties.On the basis of a previous investigation by Allegra, a mathematical treatment has been developed and a disorder function has been elaborated taking into account, in calculating the profiles of the X-ray diffraction intensities, not only the disorder effects but also the sizes of the δ-TiCl₃ crystallites. The selected experimental pattern (δ-TiCl₃, highly activated) has been well reproduced in this way and fitted by overlapping the calculated spectra of two disordered forms, labelled ?₁ and ?₂, which differ in the relative amounts cubic and hexagonal sequences of the Cl-Ti-Cl layers constituting the violet forms of TiCl₃. The best fit was achieved by introducing into the calculations crystallite sizes of about 70 Å.The results of the structural investigation are also discussed in terms of activity of the δ-TiCl₃ based catalyst for the stereospecific polymerization of propylene.     

Effect of the Ni/Cu ratio on the composition and catalytic properties of nickel-copper alloy in anisole hydrodeoxygenation

The activity of NiCu-SiO₂ catalysts with a metal content of 90% and different Ni/Cu ratios has been investigated in the hydrodeoxygenation of anisole, a model compound of bio-oil, at 280°C and 6 MPa. A homogeneous phase composition of the active component has been synthesized by the co-decomposition of nickel and copper nitrates followed by the introduction of SiO₂ as a stabilizer. The resulting catalysts have been characterized by temperature-programmed reduction, X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy combined with energy-dispersive microanalysis. The bulk and surface composition of active-component particles has been determined by XPS and X-ray diffraction. In all of the catalysts containing 15–85 wt % Ni, there are two types of solid solutions. One has a constant composition, Cu_0.95Ni_0.05, which is independent of the Ni/Cu ratio in the catalyst; in the other, the nickel stoichiometry increases with an increasing Ni content of the active component. A correlation has been established between the Ni/Cu ratio and the rate constants of the reaction examined and between the Ni/Cu ratio and the degree of hydrodeoxygenation for all samples. The most active catalyst is Ni85Cu5-SiO₂.     

Low temperature synthesis and luminescence investigations of YAG:Ce,Eu nanocomposite powder for warm white light-emitting diode

The preparation of the cerium and europium co-doped YAG materials as well as the study for their synthesis and emitting mechanism of the energy transfer between Ce³⁺ and Eu³⁺ were investigated in the present study. YAG:Ce³⁺, Eu³⁺ powders were synthesized using a high-energy ball milling method in different sintering temperature and atmosphere: air and H₂/N₂. The effects of the synthesis procedure on the crystallinity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy, and photoluminescence spectroscopy. The europium co-doped YAG:Ce³⁺ phosphors is improved the chromaticity coordinates.