静态法和动态法测量乙醇饱和蒸气压的比较

物质的蒸气压是化学、化工、冶金、医药等领域的重要基础数据。测量饱和蒸气压是大学物理化学实验教学中的一个基础实验,测量方法主要有静态法和动态法,但两种方法的比较尚未见报道。本文通过比较,得出了两种方法的优缺点以及注意事项。     

Structural transitions under high-pressure in a langasite-type multiferroic Ba3TaFe3Si2O14

The iron containing langasite family compound Ba₃Ta⁵⁷Fe₃Si₂O₁₄ was studied at high pressure up to 30 GPa at room temperature by means of in situ X-ray diffraction, Raman and Mössbauer spectroscopies in diamond anvil cell. Two structural transitions at pressures ∼5 and ∼20 GPa are observed. At ∼5 GPa, the low-pressure trigonal P321 phase undergoes phase transition to the most likely P3 structure as manifested by slight increase in the c/a ratio and by anomalies of the Mössbauer and Raman spectra parameters. At ∼20 GPa, the first order phase transition to monoclinic structure occurred with a drop of unit cell volume by 9%. The appearance of the ferroelectric state at such transitions is discussed in connection with the multiferroic properties.     

Direct analysis in real time mass spectrometry (DART‐MS) of highly non‐polar low molecular weight polyisobutylenes

Low molecular weight polyisobutylenes (PIB) with chlorine, olefin and succinic acid end‐groups were studied using direct analysis in real time mass spectrometry (DART‐MS). To facilitate the adduct ion formation under DART conditions, NH₄Cl as an auxiliary reagent was deposited onto the PIB surface. It was found that chlorinated adduct ions of olefin and chlorine telechelic PIBs, i.e. [M + Cl]^? up to m/z 1100, and the deprotonated polyisobutylene succinic acid [M? H]^? were formed as observed in the negative ion mode. In the positive ion mode formation of [M + NH₄]⁺, adduct ions were detected. In the tandem mass (MS/MS) spectra of [M + Cl]^?, product ions were absent, suggesting a simple dissociation of the precursor [M + Cl]^? into a Cl^? ion and a neutral M without fragmentation of the PIB backbones. However, structurally important product ions were produced from the corresponding [M + NH₄]⁺ ions, allowing us to obtain valuable information on the arm‐length distributions of the PIBs containing aromatic initiator moiety. In addition, a model was developed to interpret the oligomer distributions and the number average molecular weights observed in DART‐MS for PIBs and other polymers of low molecular weight. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterizing Pressure‐Induced Uranium CH Agostic Bonds

The diuranium(III) compound [UN′′₂]₂(μ‐η⁶:η⁶‐C₆H₆) (N′′=N(SiMe₃)₂) has been studied using variable, high‐pressure single‐crystal X‐ray crystallography, and density functional theory . In this compound, the low‐coordinate metal cations are coupled through π‐ and δ‐symmetric arene overlap and show close metal? CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic‐type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms‐in‐molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa.     

Ba3P5N10Br:Eu2+: A Natural‐White‐Light Single Emitter with a Zeolite Structure Type

Illumination sources based on phosphor‐converted light emitting diode (pcLED) technology are nowadays of great relevance. In particular, illumination‐grade pcLEDs are attracting increasing attention. Regarding this, the application of a single warm‐white‐emitting phosphor could be of great advantage. Herein, we report the synthesis of a novel nitridophosphate zeolite Ba₃P₅N₁₀Br:Eu²⁺. Upon excitation by near‐UV light, natural‐white‐light luminescence was detected. The synthesis of Ba₃P₅N₁₀Br:Eu²⁺ was carried out using the multianvil technique. The crystal structure of Ba₃P₅N₁₀Br:Eu²⁺ was solved and refined by single‐crystal X‐ray diffraction analysis and confirmed by Rietveld refinement and FTIR spectroscopy. Furthermore, spectroscopic luminescence measurements were performed. Through the synthesis of Ba₃P₅N₁₀Br:Eu²⁺, we have shown the great potential of nitridophosphate zeolites to serve as high‐performance luminescence materials.     

The banded spherulites of iPP induced by pressure vibration injection molding

Isotactic polypropylene(i PP) samples obtained by pressure vibration injection molding(PVIM) and conventional injection molding(CIM) were studied by polarized-light microscopy(PLM), respectively. It was found that the alternating bright and dark banded spherulites were generated in the transitional region of PVIM parts. It is the first time that the banded spherulites of isotactic polypropylene were observed in polymer processing. What's more, the banded spherulites were proved to be constituted of ?-form crystal by hot stage polarized-light microscopy(HT-PLM) and wide angle X-ray diffraction(WAXD). Morphology of the banded spherulites was also studied by scaning electronical microscopy(SEM).     

Characterization of Diamond Nanoparticles by High-Speed Micro-Thermal Field-Flow Fractionation

Micro-thermal field-flow fractionation was used to characterize the particle size distribution of nanometer-sized diamond nanoparticles. Although the experimental conditions were chosen to perform high-speed separation, and, consequently, the resolution achieved experimentally was not very high, the application of the original correction method for the zone spreading allowed for obtaining of very good calculated particle size distribution or, explicitly, a true polydispersity index of the diamond nanoparticle sample. The future use of several samples of diamond nanoparticles of different average sizes and different surface chemistries should allow deeper insight into the effect of these particulate characteristics on the retention in micro-thermal field-flow fractionation.     

Rattling in the Quadruple Perovskite CuCu3V4O12

Of particular interest is a peculiar motion of guest atoms or ions confined to nanospace in cage compounds, called rattling. While rattling provides unexplored physical properties through the guest–host interactions, it has only been observed in a very limited class of materials. Herein, we introduce an A‐site‐ordered quadruple perovskite, CuCu₃V₄O₁₂, as a new family of cage compounds. This novel AA′₃B₄O₁₂‐type perovskite has been obtained by a high‐pressure synthesis technique and structurally characterized to have cubic Im$\bar 3$ symmetry with an ionic model of Cu²⁺Cu²⁺₃V⁴⁺₄O₁₂. The thermal displacement parameter of the A‐site Cu²⁺ ion is as large as U_iso≈0.045 Ų at 300 K, indicating its large‐amplitude thermal oscillations in the oversized icosahedral cages. Remarkably, the presence of localized phonon modes associated with rattling of the A‐site Cu²⁺ ion manifests itself in the low‐temperature specific heat data. This work sheds new light on the structure–property relations in perovskites.     

Locating Gases in Porous Materials: Cryogenic Loading of Fuel‐Related Gases Into a Sc‐based Metal–Organic Framework under Extreme Pressures

An alternative approach to loading metal organic frameworks with gas molecules at high (kbar) pressures is reported. The technique, which uses liquefied gases as pressure transmitting media within a diamond anvil cell along with a single‐crystal of a porous metal–organic framework, is demonstrated to have considerable advantages over other gas‐loading methods when investigating host–guest interactions. Specifically, loading the metal–organic framework Sc₂BDC₃ with liquefied CO₂ at 2 kbar reveals the presence of three adsorption sites, one previously unreported, and resolves previous inconsistencies between structural data and adsorption isotherms. A further study with supercritical CH₄ at 3–25 kbar demonstrates hyperfilling of the Sc₂BDC₃ and two high‐pressure displacive and reversible phase transitions are induced as the filled MOF adapts to reduce the volume of the system.     

Supercritical fluid extraction of lipids from linseed with on-line evaporative light scattering detection

Supercritical fluid extraction (SFE) is a green alternative method of extraction for neutral lipids in seeds compared to conventional methods utilizing organic solvents. In this work, a novel method where SFE is hyphenated with an evaporative light scattering detector is presented. The method was subsequently applied to determine lipid content in crushed linseed. The new method enables rapid quantification of extracted lipids as well as be ability to continuously monitor the extraction rate in real-time, thus being able to determine the time point of completed extraction.