Liquid Vacuum Research Articles

<em>In Situ</em> Characterization of Boehmite Particles in Water Using Liquid SEM

In situ imaging and elemental analysis of boehmite (AlOOH) particles in water is realized using the System for Analysis at the Liquid Vacuum Interface (SALVI) and Scanning Electron Microscopy (SEM). This paper describes the method and key steps in integrating the vacuum compatible SAVLI to SEM and obtaining secondary electron (SE) images of particles in liquid in high vacuum. Energy dispersive x-ray spectroscopy (EDX) is used to obtain elemental analysis of particles in liquid and control samples including deionized (DI) water only and an empty channel as well. Synthesized boehmite (AlOOH) particles suspended in liquid are used as a model in the liquid SEM illustration. The results demonstrate that the particles can be imaged in the SE mode with good resolution (i.e., 400 nm). The AlOOH EDX spectrum shows significant signal from the aluminum (Al) when compared with the DI water and the empty channel control. In situ liquid SEM is a powerful technique to study particles in liquid with many exciting applications. This procedure aims to provide technical know-how in order to conduct liquid SEM imaging and EDX analysis using SALVI and to reduce potential pitfalls when using this approach.

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS.

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) and their roles in environmental microbiology. This study outlines a method to cultivate biofilm attachment to the System for Analysis at the Liquid Vacuum Interface (SALVI) and achieve in situ chemical mapping of a living biofilm by time-of-flight secondary ion mass spectrometry (ToF-SIMS). This is done through the culturing of bacteria both outside and within the SALVI channel with our specialized setup, as well as through optical imaging techniques to detect the biofilm presence and thickness before ToF-SIMS analysis. Our results show the characteristic peaks of the Shewanella biofilm in its natural hydrated state, highlighting upon its localized water cluster environment, as well as EPS fragments, which are drastically different from the same biofilm's dehydrated state. These results demonstrate the breakthrough capability of SALVI that allows for in situ biofilm imaging with a vacuum-based chemical imaging instrument.

Isolation of Piperin from The Fruit of Piper retrofractum

This paper will described the isolation of major compound from MeOH extract from the fruit of Piper retrofractum . Using several chromatography technique including liquid vacuum chromatography and thin layer chromatography, and further purification using re-cristalization technique, Piperine, an alkaloids compound, was isolated from this extract. The structure of this compound was determined using spectroscopic methods including FTIR, 1D-NMR and 2-D NMR. Keywords : P.retrofractum , alkaloids, piperine, structure elucidation

Surface-Induced Changes in the Thermochromic Transformation of an Ionic Liquid Cobalt Thiocyanate Complex.

We demonstrate that a thermodynamic complex equilibrium within an ionic liquid film can be significantly influenced by the presence of the liquid–vacuum interface. Using surface-sensitive X-ray photoelectron spectroscopy, we find that the temperature-driven transition from the blue-colored tetrahedral [Co(II) (NCS)4]2– to the red-colored octahedral [Co(II) (NCS)6]4– complex already occurs within the outermost nanometers at around +4 °C as compared with −25 °C in the bulk. This thermochromic transformation in the near-surface region goes along with a loss in preferential surface orientation of free [SCN]− anions and with a pronounced decrease in the complex density; both effects are attributed to the formation of a weakly bound solvation shell around the [Co(II) (NCS)6]4– anion, leading to an effective complex dilution. Our results are not only relevant for high-surface area thin film systems, such as in sensor and catalysis applications, but also shed light on the role of ionic liquid surfaces in particular and liquid surfaces in general.

Conducting Nanopaper: A Carbon-Free Cathode Platform for Li–O2 Batteries

For a lithium–oxygen (Li–O2) battery air electrode, we have developed a new all-in-one platform for designing a porous, carbon-free conducting nanopaper (CNp), which has dual functions as catalyst and current-collector, composed of one-dimensional conductive nanowires bound by a chitin binder. The CNp platform is fabricated by a liquid diffusion-induced crystallization and vacuum filtration methods. Employing less than 1 wt % chitin to connect the conductive skeleton, pores and active sites for reactions have become maximized in self-standing CNp. The carbon-free CNp enables the Li–O2 air electrode to be more stably operated compared to carbon nanofibers and other CNps bound by PVDF and PMMA; side reactions are largely suppressed on the CNp. The versatile chitin is highlighted for diverse conducting nanopapers that can be used in various applications.

In situ nuclear magnetic resonance microimaging of live biofilms in a microchannel.

Biofilms are comprised of microbial cells and an extracellular polymeric substance (EPS) matrix that supports interactions between community members and with the local environment. The highly hydrated EPS matrix makes the application of many biofilm visualization techniques difficult. Hence, to better visualize how biofilms interact with their environment, there is a need for imaging techniques to monitor hydrated state biofilm dynamics. We employed an in situ dynamic approach to construct label-free images of biofilms. In situ imaging was conducted using a vacuum compatible microfluidic reactor, SALVI (System for Analysis at the Liquid Vacuum Interface), for biofilm growth; real-time confocal laser scanning microscopy analysis; and nuclear magnetic resonance (NMR) microimaging and spectroscopy. We integrated SALVI microchannel fluids and live biofilms to demonstrate in situ measurement capabilities, including velocity mapping, diffusion coefficient mapping, relaxometry, localized spectroscopy, relaxation times, porosity, and two- and three-dimensional imaging within the microchannel at high spatial resolution. We monitored organic acids adjacent to biofilms, suggesting that kinetic rate and substrate-product yield ratio studies are possible using the SALVI microfluidic reactor for growth characterizations. The integration of NMR microimaging studies into the SALVI platform demonstrates that a multimodal microfluidic platform can serve as an avenue to explore complex biological phenomena, such as biofilm attachment to surfaces, with detailed quantitative physical and chemical mapping. The further incorporation of other SALVI-compatible technologies, such as liquid time-of-flight secondary ion mass spectrometry imaging, with NMR microimaging will produce a powerful correlative approach to monitor in situ biofilm chemistry and dynamics at different spatial scales.

Hiding the Headgroup? Remarkable Similarity in Alkyl Coverage of the Surfaces of Pyrrolidinium- and Imidazolium-Based Ionic Liquids

The liquid–vacuum interfaces of a series of ionic liquids (ILs) containing 1-alkyl-1-methylpyrrolidinium ([Cnmpyrr]+) cations of different alkyl chain lengths have been studied by reactive-atom scattering with laser-induced fluorescence detection (RAS-LIF) and molecular dynamics (MD) simulations. A direct, quantitative comparison has been performed between [Cnmpyrr]+ and the previously better-characterized 1-alkyl-3-methylimidazolium ([Cnmim]+) ILs with the same chain lengths, n, and common anion, bis(trifluoromethylsulfonyl)imide ([Tf2N]−). Both RAS-LIF experiments, using O(3P) as the projectile and monitoring OH yield, and MD simulations indicate that the coverage of the surface by alkyl chains is almost independent of the identity of the cation headgroup. Moreover, the potentially abstractable H atoms of the saturated pyrrolidinium ring do not contribute appreciably to the experimental OH yield. In both these senses, therefore, the headgroup is “hidden” from the probe particles approaching from vacuum....

Site-Specific Preparation of Intact Solid-Liquid Interfaces by Label-Free In Situ Localization and Cryo-Focused Ion Beam Lift-Out.

Scanning transmission electron microscopy (STEM) allows atomic scale characterization of solid-solid interfaces, but has seen limited applications to solid-liquid interfaces due to the volatility of liquids in the microscope vacuum. Although cryo-electron microscopy is routinely used to characterize hydrated samples stabilized by rapid freezing, sample thinning is required to access the internal interfaces of thicker specimens. Here, we adapt cryo-focused ion beam (FIB) "lift-out," a technique recently developed for biological specimens, to prepare intact internal solid-liquid interfaces for high-resolution structural and chemical analysis by cryo-STEM. To guide the milling process we introduce a label-free in situ method of localizing subsurface structures in suitable materials by energy dispersive X-ray spectroscopy (EDX). Monte Carlo simulations are performed to evaluate the depth-probing capability of the technique, and show good qualitative agreement with experiment. We also detail procedures to produce homogeneously thin lamellae, which enable nanoscale structural, elemental, and chemical analysis of intact solid-liquid interfaces by analytical cryo-STEM. This work demonstrates the potential of cryo-FIB lift-out and cryo-STEM for understanding physical and chemical processes at solid-liquid interfaces.

Solution-processable exfoliation and photoelectric properties of two-dimensional layered MoS2 photoelectrodes

MoS2 based photoelectrodes with different thickness have been fabricated by liquid phase exfoliation and vacuum filtration method. Absorption spectra clearly demonstrated two splitting absorption peaks due to the spin-orbit coupling and first principle calculation also indicate the spin-orbit coupling effect. These results combined with the SEM and TEM measurement suggests that the randomly stacked MoS2 films can maintain the properties of few-layered materials with good quality. As a proof-of-principle applications, photoelectrochemical experiments of MoS2 based photoelectrodes manifests that these MoS2 films are one kind of reversible and stable optoelectronic materials with tunable microampere photocurrent as the change of film thickness. The rising and decay response of photocurrent are in the scale of several seconds. The results will be useful for the MoS2 based scalable photovoltaic devices and photodetectors.

Repairs revitalize papermill system

The papermaking industry places heavy demands on liquid ring vacuum pumps to remove water throughout the process and repairs require considerable expertise. One pump distributor and systems builder undertook the repair of a pump which had been operating for over 45 years in a papermill in northern Finland.

ТЕОРЕТИЧЕСКИЙ АНАЛИТИЧЕСКИЙ МЕТОД РЕШЕНИЯ ЗАДАЧИ ПРОЦЕССА ВАКУУМНОГО ЗАМОРАЖИВАНИЯ ЖИДКОСТИ В СПОКОЙНОМ СОСТОЯНИИ

A generalized closed analytical solution of the problem of a quasi-stationary process in liquid vacuum freezing in a quiet state with regard to the thickness of the frosting layer ξ whereas heretofore numerical solutions of this problem occurred. The advantage of the analytical solutions obtained of the problem of a quasi-stationary vacuum freezing of moisture in a finedispersion state over existing numerical ones consists in the identification of an immanent tie between defining and determined parameters regarding a thickness of the frosting layer ξ. It is also possible to use them directly at the computation without resorting to the help of computers.

Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis.

In situ liquid secondary ion mass spectrometry (SIMS) enabled by system for analysis at the liquid vacuum interface (SALVI) has proven to be a promising new tool to provide molecular information at solid-liquid and liquid-vacuum interfaces. However, the initial data showed that useful signals in positive ion spectra are too weak to be meaningful in most cases. In addition, it is difficult to obtain strong negative molecular ion signals when m/z>200. These two drawbacks have been the biggest obstacle towards practical use of this new analytical approach. In this study, we report that strong and reliable positive and negative molecular signals are achievable after optimizing the SIMS experimental conditions. Four model systems, including a 1,8-diazabicycloundec-7-ene (DBU)-base switchable ionic liquid, a live Shewanella oneidensis biofilm, a hydrated mammalian epithelia cell, and an electrolyte popularly used in Li ion batteries were studied. A signal enhancement of about two orders of magnitude was obtained in comparison with non-optimized conditions. Therefore, molecular ion signal intensity has become very acceptable for use of in situ liquid SIMS to study solid-liquid and liquid-vacuum interfaces. Graphical Abstract ᅟ.

Performance Monitoring Analysis of Liquid Ring Vacuum Pumps

Liquid ring vacuum pump which uses rotating liquid as piston to abstract and compress gas is a kind of rotating positive displacement pump. Its running state implies some fault informantion. To capture performance levels of liquid ring vacuum pump, a comprehensive performance monitoring system includes data acquisition, data reprocessing, data storage, abnormal judgment and fault alarm, performance displaying is developed in this paper. Hence, the performance levels of liquid ring vacuum pump can be observed anytime by the monitoring system, the maintenance cost can be reduced, pumps can be operated at the highest performance level as far as possible, the reliability and the maintainability of liquid ring vacuum pump can be effectively improved by this monitoring system.

Design of a permeator against vacuum for tritium extraction from eutectic lithium-lead in a DCLL DEMO

One of the most important issues in future fusion power plants is the extraction of tritium generated in the breeders in order to achieve self-sufficiency. When the breeder is a liquid metal one of the most promising techniques is the Permeation Against Vacuum, whose principle is based on tritium diffusion through a permeable membrane in contact with the liquid metal carrier and its further extraction by a vacuum pump. A conceptual design of permeator has been developed, taking into account the features of a DEMO reactor with a Dual Coolant Lithium Lead (DCLL) breeder blanket. The study is based on the analysis of different membranes and geometries aiming at the overall efficiency (extraction capability) of the device, as well as its compatibility with the breeder material. The permeator is based on a rectangular section multi-channel distribution where the liquid metal channels and vacuum channels are alternated in order to maximize the contact area and therefore to promote tritium transport from the bulk to the walls. The resulting permeator design has an excellent estimated extraction efficiency, of 80%, in a relatively compact device.

Insight into the influence of liquid paraffin for methanol synthesis on Cu(110) surface using continuum and atomistic models

Methanol synthesis from CO/CO2 hydrogenation and water-gas shift (WGS) reaction on Cu(110) in liquid paraffin and vacuum have been systematically researched with density functional theory calculation (DFT). For methanol synthesis from CO hydrogenation, the reaction pathways in liquid paraffin and vacuum are CO+H→HCO→H2CO→H3CO→H3COH; in the case of WGS, the reaction pathways in liquid paraffin and vacuum are CO+2H2O→CO+2OH+2H→CO+H2O+O+H2→CO2+H2O+H2; the reaction pathways of methanol synthesis from CO2 hydrogenation in liquid paraffin and vacuum are CO2+H→HCOO→H2COO→H2CO→H3CO→H3COH and CO2+H→HCOO→HCOOH→H2COOH→H3CO→H3COH, respectively. The result shows that liquid paraffin does not affect the reaction mechanisms of methanol synthesis from CO and WGS, but it changes the reaction mechanisms of methanol synthesis from CO2 hydrogenation. Hirshfeld charge and the d-band centers indicate that the catalytic activity of Cu(110) in liquid paraffin is smaller than that in vacuum. Our results also show that it is necessary to consider both continuum and atomistic models in the slurry bed.

Comparative study of degassing membrane modules for the removal of methane from Expanded Granular Sludge Bed anaerobic reactor effluent

Abstract The feasibility of an emergent technology for in situ removal/recovery of methane from the effluent of an Expanded Granular Sludge Bed (EGSB) anaerobic reactor has been studied. For this purpose, the performances of two commercial hollow fibre degassing contactors with different membrane materials – microporous (polypropylene, PP) and non-porous (polydimethylsiloxane, PDMS) – were compared. The influence of water fluxes (Q L /A membrane ranging from 22.6 to 377.4 L h −1 m −2 ), vacuum pressure (140–800 mbar), sweep gas fluxes (Q N2 /A membrane ranging from 0.14 × 10 3 to 4.44 × 10 3 L h −1 m −2 ), and mode of operation (liquid flowing in the lumen side or the shell side) was studied. Both materials showed different behaviours with the variations in operational conditions. In liquid flowing in the lumen mode operation, PP microporous membrane was slightly more efficient under soft or mild operational conditions (low liquid flow and/or vacuum pressure) but showed a wetting phenomenon when operational conditions were harder. In shell side mode, PDMS was more efficient and no wetting phenomenon was observed with this contactor. The differences have been explained, taking into account the material properties (porosity, material resistance …) of the membrane and structure (packing density, fibre diameter …) of the modules. Methane removal efficiencies of up to 98% could be achieved, showing the viability of methane removal/recovery using this technology. Simultaneous degassing of CO 2 was also monitored in both modules, showing that the removal efficiency of this gas was considerably lower than for methane. In general terms, the removal of dissolved CO 2 followed a quite similar behaviour from that described for methane. Experimental overall mass transfer coefficients were also obtained.

Switchable 1,8-diazabicycloundec-7-ene and 1-hexanol ionic liquid analyzed by liquid ToF-SIMS

Switchable ionic liquids (SWIL) play an important role in green chemistry. Due to the nature of SWIL chemistry, such as air sensitivity, pressure, and temperature dependence, it is difficult to characterize SWIL using vacuum-based surface techniques. The fully CO2 loaded 1:1 mixtures of 1,8-diazabicycloundec-7-ene (DBU) and 1-hexanol (a SWIL system) and non-CO2 loaded DBU and 1-hexanol mixture were analyzed by in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) coupled with the system for analysis at the liquid vacuum interface (SALVI), respectively. The DBU/1-hexanol/CO2 SWIL was injected into the microchannel before liquidsecondary ion mass spectrometryanalysis. Bi3+ primary ion beam was used. The positive and negative spectra of the SWIL chemical components are presented. The characteristic peaks m/z 153 (protonated DBU) in the positive mode and m/z 101 (deprotonated 1-hexanol) in the negative mode were observed. In addition, ion pair peaks including m/z 253, 319, 305, and 451 in the positive mode and m/z 145, 223, and 257 in the negative mode are first observed using this approach. These results demonstrate that the SALVI microfluidic reactor enables the vacuum-based surface technique (i.e., ToF-SIMS) for in situ characterization of challenging liquid samples such as ionic liquids.

Varying duty operation of air-cooled condenser units

Results of experimental investigations of operation modes of air-cooled condensers (ACC) under design and varying duty conditions are presented. ACCs with varying cooling airflow rates under constant heat load and with constant cooling airflow under varying heat load are examined. Diagrams of heat transfer coefficients and condensation pressures on the heat load and cooling airflow are obtained. It is found that, if the relative heat load is in the range from 0.6 to 1.0 of the nominal value, the ACC heat transfer coefficient varies insignificantly, unlike that of the water-cooled surface condensers. The results of the determination of “zero points” are given, i.e., the attainable pressure in air-cooled condensing units (ACCU), if there is no heat load for several values of working water temperature at the input of water-jet ejectors and liquid ring vacuum pump. The results of the experimental determination of atmospheric air suction into the ACC vacuum system. The effect of additional air suctions in the steam pipe on ACCU characteristics is analyzed. The thermal mapping of ACC heat exchange surfaces from the cooling air inlet is carried out. The dependence of the inefficient heat exchange zone on the additional air suction into the ACC vacuum system is given. It is shown that, if there is no additional air suction into the ACC vacuum system, the inefficient heat exchange zone is not located at the bottom of the first pass tubes, and their portion adjacent to the bottom steam pipe works efficiently. Design procedures for the ACC varying duty of capacitors are presented, and their adequacy for the ACCU varying duty estimation is analyzed.

Chemical imaging of molecular changes in a hydrated single cell by dynamic secondary ion mass spectrometry and super-resolution microscopy.

Chemical imaging of single cells at the molecular level is important in capturing biological dynamics. Single cell correlative imaging is realized between super-resolution microscopy, namely, structured illumination microscopy (SIM), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) using a multimodal microreactor (i.e., System for Analysis at the Liquid Vacuum Interface, SALVI). SIM characterized cells and guided subsequent ToF-SIMS analysis. Lipid fragments were identified in the cell membrane via dynamic ToF-SIMS depth profiling. Positive SIMS spectra show intracellular potassium and sodium ion transport due to exposure to nanoparticles. Spectral principal component analysis elucidates differences in chemical composition among healthy alveolar epithelial mouse lung C10 cells, cells that uptake zinc oxide nanoparticles, and various wet and dry control samples. The observation of Zn(+) gives the first direct evidence of ZnO NP uptake and dissolution by the cell membrane. Our results provide submicron chemical mapping for investigating cell dynamics at the molecular level.

The BioCRACK Process - A Refinery Integrated Biomass-to-Liquid Concept to Produce Diesel from Biogenic Feedstock

Second generation biofuels, especially fuels from lignocellulose biomass, which are manufactured from non-food feedstock play a key role to reduce greenhouse gas emissions and the dependency on fossil oil. The bioCRACK process represents a new biomass-to-liquid concept to generate advanced biofuel by liquid-phase pyrolysis. As liquid heat carrier vacuum gas oil (VGO), an intermediate heavy oil product from the vacuum distillation, is used. Since autumn 2012 a fully integrated pilot plant at the refinery in Schwechat/Austria with a nominal biomass capacity of 100 kg/h is in continuous operation and generates data for up-scaling the technology to an industrial scale. This paper reports the results of the continuous operation. The influence of various reaction parameters, such as the reaction temperature, on yield and composition of the reaction products were investigated. As expected from previous results with a semi batch lab-scale reactor, within the selected range of temperature (350 °C to 400 °C), elevated temperature leads to decreasing amount of biochar and rising liquefaction. Based on the results could be shown that 10 to 20 % of the biogenic carbon can be transferred directly into raw fuels with the bioCRACK concept. Additionally 11 to 18 % of the bio-carbon merges into the remaining heat carrier.