Synthesis of osmium borides by mechanochemical method

Transition metal osmium borides were synthesized by mechanochemical method using high‐energy ball‐milling with Os (Osmium) and B (Boron) powders as raw materials. The formation process, reaction mechanism, and thermal stability of the mechochemically synthesized osmium borides were studied. Almost pure Os₂B₃ phase was obtained when the Os‐to‐B molar ratio was 1:2; while ReB₂‐type hexagonal OsB₂ with a small amount of RuB₂‐type orthorhombic OsB₂ was obtained when the Os‐to‐B molar ratio was 1:3. Stoichiometry OsB₂ was obtained from boron rich starting mixture powders due to the B loss during the high‐energy ball‐milling process. It was also found that WC and osmium oxide were present as contaminants after ball milling for 40 hours. Heat treatment results revealed that the as‐synthesized Os₂B₃ powders are thermally stable in flowing Ar up to 800°C, but a transformation from hexagonal to orthorhombic structure partially occurred for the OsB₂ powders as low as 600°C.     

8-氟-5-甲氧基-1,2,4-三唑并[4,3-c]嘧啶-3(2H)-硫酮的合成

以5-氟尿嘧啶为起始原料,经氯代反应、醇解反应、肼解反应和环合反应合成了高效除草剂双氟磺草胺的关键中间体—8-氟-5-甲氧基-1,2,4-三唑并[4,3-c]嘧啶-3(2H)-硫酮。以5-氟尿嘧啶计,产品总收率达70.1%,产品结构经核磁共振分析验证。探讨了原料配比、反应温度、时间等因素对反应收率的影响。     

少量共单体对丙烯腈在DMF中溶液聚合的影响

研究了丙烯腈与少量衣康酸、丙烯酸、丙烯酸甲酯、甲基丙烯酸甲酯、丙烯酰胺等共单体在N,N-二甲基甲酰胺(DMF)中溶液共聚时的云点阈值。提出共单体云点迹线斜率的概念,用以比较不同共单体对丙烯腈聚合物的改性作用,发现相比其他几种烯类单体衣康酸更适合于用作碳纤维原丝的共单体。同时考察了衣康酸与丙烯腈在DMF中溶液共聚时,其含量对聚合动力学的影响。发现随衣康酸用量的增加,聚合速率与分子量都降低。分析了间歇共聚中共单体含量随转化率的变化,并拟合了该单体对溶液共聚时的竞聚率,发现接近于理想共聚:rIA=2.0、rAN=0.5;且在低共单含量时,共聚物的累积平均共单组成随转化率线性地下降。     

Synthesis,calcination and characterization of Nanosized ceria powders by self-propagating room temperature method

Nanometric ceria powders with fluorite-type structure were obtained by applying self-propagating room temperature method. The obtained powders were subsequently thermally treated (calcined) at different temperatures for different times. Powder properties such as specific surface area, crystallite size, particle size and lattice parameter have been studied. Roentgen diffraction analysis (XRD), BET and Raman scattering measurements were used to characterize the as-obtained (uncalcined) powder as well as powders calcined at different temperatures.It was found that the average diameter of the as-obtained crystallites is in the range of 3–5 nm whereas the specific surface area is about 70 m²/g. The subsequent, 15 min long, calcination of as-obtained powder at different temperatures gradually increased crystallite size up to ～60 nm and reduced specific surface down to 6 m²/g. Raman spectra of synthesized CeO_2?y depicts a strong red shift of active triply degenerate F_2 g mode as well as additional peak at 600 cm^?1. The frequency of F_2 g mode increased while its line width decreased with an increase in calcination temperature. Such a behavior is considered to be the result of particle size increase and agglomeration during the calcination. After the heat treatment at 800 °C crystallite size reached value larger than 50 nm. Second order Raman mode, which originates from intrinsic oxygen vacancies, disappeared after calcination.     

Preparation of a ternary hybrid of P-g-C3N4@PGS-Ti and its enhancement of the flame retardancy of epoxy resins

A novel ternary hybrid flame retardant named P-g-C₃N₄@PGS-Ti was prepared through step-by-step method. First, titanium dioxide was loaded on PGS to make PGS-Ti (where PGS = palygorskite), and then, PGS-Ti was decorated by phosphor-doped g-C₃N₄ (abbreviated as P-g-C₃N₄) to prepare a ternary flame retardant of P-g-C₃N₄@PGS-Ti. It showed that P-g-C₃N₄@PGS-Ti could efficiently improve the flame retardancy of epoxy resins (EP). The structure and the morphology of P-C₃N₄@PGS-Ti were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scaanning electron microscopy and hermogravimetric analysis (TGA). The flame retardancy and the burning behavior of 5 wt% P-g-C₃N₄@PGS-Ti composited EP were well investigated through TGA, limiting oxygen index (LOI), cone calorimeter test (CCT) and vertical burning test (UL-94 standard). It was found that the peak heat releasing (pk-HRR) of the EP/P-g-C₃N₄@PGS-Ti composite reduced 36% (from 1459 to 852 kW/m²) with the addition of 5 wt% of P-g-C₃N₄@PGS-Ti flame retardant to the matrix of EP. The combustion residue analysis showed that the EP/P-g-C₃N₄@PGS-Ti composite gained the most continuous and firmest char yield due to the synergistic effect of PGS, TiO₂ and the introducing of P element. The mechanism proved that the combination of gas phase and condensed phase flame-retardant processes were well coordinated to improve the fire retardancy for EP. We tested and studied the mechanical properties of EP/P-g-C₃N₄@PGS-Ti composites. Only 2.4% decreasing of flexural strength and 23.5% decreasing of impact strength in EP/P-g-C₃N₄@PGS-Ti composites compared to pure EP, respectively. But according to the test results of EP/P-g-C₃N₄@PGS-Ti composite material and the control sample in the system, EP/P-g-C₃N₄@PGS-Ti composite material had the highest flexural modulus and impact strength.     

Effect of Al doping on electrochemical performance of NaTi2(PO4)3/C anode for aqueous sodium ion battery

The Na_1+xAl_xTi_2?x(PO₄)₃/C (x?=?0, 0.05, 0.10, 0.20) composites serving as anode for aqueous sodium ion battery are successfully synthesized through a facile sol–gel route. The results indicate that introduction of proper amount of aluminum has no obvious effect on the structure and morphology of NaTi₂(PO₄)₃/C. Among the four synthesized samples, Na_1.1Al_0.1Ti_1.9(PO₄)₃/C (NATP-0.10) exhibits the best electrochemical performance. NATP-0.10 delivers a discharge specific capacity of 115.8, 106.9, 98.4, and 89.1 mAh g^?1 at 2, 5, 10, and 20 C rate, respectively, and still retains 114.7 mAh g^?1 when the current density comes back to 2 C. Additionally, NATP-0.10 exhibits an initial discharge capacity of 102.9 mAh g^?1 and still retains a reversible capacity of 90.1 mAh g^?1 at 10 C rate after 200 cycles. Cyclic voltammetry and electrochemical impedance spectroscopy demonstrate the better electrochemical performance of NATP-0.10 is due to the faster sodium migration and enhanced electrochemical kinetics.

Graphical abstract

Al doping Na_1+xAl_xTi_2?x(PO₄)₃/C (x?=?0, 0.05, 0.10, 0.20) composites were firstly used as anodes in aqueous SIBs. The electrochemical performance of NaTi₂(PO₄)₃/C has been improved by introducing a proper amount of Al.

     

A ternary mechanism for the facilitated transfer of metal ions onto metal–organic frameworks: implications for the ‘‘versatility’’ of these materials as solid sorbents

Although metal–organic frameworks offer a new platform for developing versatile sorption materials, yet coordinating the functionality, structure and component of these materials remains a great challenge. It depends on a comprehensive knowledge of a “real sorption mechanism”. Herein, a ternary mechanism for U(VI) uptake in metal–organic frameworks was reported. Analogous MIL-100s (Al, Fe, Cr) were prepared and studied for their ability to sequestrate U(VI) from aqueous solutions. As a result, MIL-100(Al) performed the best among the tested materials, and MIL-100(Cr) performed the worst. The nuclear magnetic resonance technique combined with energy-dispersive X-ray spectroscopy and zeta potential measurement reveal that U(VI) uptake in the three metal–organic frameworks involves different mechanisms. Specifically, hydrated uranyl ions form outer-sphere complexes in the surface of MIL-100s (Al, Fe) by exchanging with hydrogen ions of terminal hydroxyl groups (Al-OH₂, Fe-OH₂), and/or, hydrated uranyl ions are bound directly to Al(III) center in MIL-100(Al) through a strong inner-sphere coordination. For MIL-100(Cr), however, the U(VI) uptake is attributed to electrostatic attraction. Besides, the sorption mechanism is also pH and ionic strength dependent. The present study suggests that changing metal center of metal–organic frameworks and sorption conditions alters sorption mechanism, which helps to construct effective metal–organic frameworks-based sorbents for water purification.     

薄互层剩余油压裂挖潜工艺技术研究与应用

鄂尔多斯盆地某特低渗透油藏纵向上主要发育K1、K2两层,层内隔夹层发育。但经历20多年的开发后,受层间隔夹层和非均质性影响,前期采用以老裂缝充填和延伸为主的重复压裂工艺动用层间剩余油不明显,措施后含水率上升且单井增油量逐年下降。基于储层剩余油分布类型,剖析了储层纵向上剩余油分布界限和增产潜力,开展了储层纵向上地应力和储层物性变化研究,采用正交试验设计原理对比评价了影响重复压裂裂缝高控制的主要影响因素,提出了“水力喷射器+K344单底封”重复压裂工艺,并应用全三维压裂软件优化了储层关键参数。在某区特低渗透油藏现场应用10口井,试验井日产油是投产初期的近1.5倍。     

Epoxidation of n-hexene and cyclohexene over titanium-containing catalysts

TS-1, Ti-beta and Ti-MCM-41 molecular sieves have been prepared by direct hydrothermal synthesis method and applied to the epoxidation of n-hexene and cyclohexene with H₂O₂ under mild conditions. Ti-beta with extremely low Al content was synthesized by using a seed method to suppress the formation of diol produced by Brønsted acid sites present in Ti-beta. It was also found that a large amount of by-products (1-ol and 1-one) formed over hydrophilic Ti-MCM-41. We further modified Ti-MCM-41 by silylation with bis(trimethylsilyl) trifluoroacetamide (BSTFA). Among these catalysts, the Ti-beta with low content of Al enhanced the yield of epoxide and suppressed the formation of diol markedly. The silylated Ti-MCM-41 reduced the formation of by-products and promoted the yields of epoxide significantly. Based on experimental results, a reaction mechanism with two parallel and competitive reactions was proposed.     

PET扩链/支化改性及其微孔发泡研究进展

介绍了采用反应挤出法,增加PET分子链长度/支化度和分子量的研究现状。综述了国内外有关PET微孔发泡的研究进展,并阐述了影响其微孔发泡的主要工艺参数。