High Vacuum Conditions Research Articles

High vacuum applied during malaxation in oil industrial plant: Influence on virgin olive oil extractability and quality

Vacuum technology was applied for the first time at industrial scale to the mechanical extraction processes of virgin olive oil (VOO). The study was carried out using an industrial plant with a working capacity of 4 tons of olives. The use of high vacuum conditions during the malaxation process induced an intense mass transfer into the olive paste that improved the coalescence phenomena of oil droplets with a significant increase in oil extractability for four different cultivars (Arbequina, Arbosana, Koroneiki and Picual). The evaluation of the quality characteristics of the Picual VOO showed an enhancement in the hydrophilic phenol fraction mainly related to the oleacein content. The low temperature set during the vacuum treatment (16 ± 1 °C for 30 min of malaxation) limited the stripping process of the main aldehydes, alcohols and esters. In contrast, other negative volatile compounds related to off-flavoured VOO (ethanol, 3-methyl-1-butanol, ethyl acetate and acetic acid) were significantly reduced.

Hydrogen Degassing of Zirconium under High-Vacuum Conditions

Micromechanics techniques, such as nano-indentation and micro-pillar compression, can be applied to study hydrogen-charged zirconium alloys at elevated temperatures, which is highly relevant for the nuclear industry. Such experiments are often conducted inside a scanning electron microscope (SEM) under high-vacuum conditions (10−5 mbar). The combination of a high-temperature and high-vacuum environment causes some hydrogen to escape from the sample into the chamber. Although this effect is evident at temperatures above 600 °C, the extent of hydrogen desorption at lower temperatures is still unclear. In the presented study, the desorption of hydrogen was assessed in zirconium cladding tube material under temperature and hydrogen content conditions comparable to those faced by used nuclear fuel during dry storage. The measured hydrogen loss due to the high vacuum was compared to the simulations obtained using an extended version of a hydrogen behavior tool developed at PSI.

Monitoring of silicone adhesive in space solar cells with an embedded multi-parameter TFBG sensor in a simulated space environment

In this research the ageing of a silicone adhesive in a simulated space environment is monitored through an embedded three parameter tilted fibre Bragg grating (TFBG) sensor. Here, the silicone is used as an adhesive between two thin cover glasses, and the space environmental ageing is simulated by thermal cycles in high vacuum conditions (better than 10−5 mbar). These operational conditions can induce variations in the silicone adhesive with respect to its original properties such as dimensional stability, chemical composition, generated contaminants, discoloration and, mechanical or optical degradation. Therefore, surrounded by the adhesive, in the centre of the cover glass sandwich, a weakly tilted FBG sensor was placed to obtain information from its spectra on the state of the polymer during the test. Specifically, the temperature, strain and refractive index (RI) of the silicone can be, simultaneously and separately, measured from the spectrum of a single TFBG from selected resonance peaks. These parameters can be used to evaluate the ‘health’ state of the silicone during the vacuum thermal cycles. The simultaneous TFBG thermomechanical measurements gave a solution to the non-localized measuring issues when using classical fibre optic or electrical strain-gauges and a thermocouple to compensate the temperature and to better understand the material behaviour. The trends of the measured parameters are reported during the entire testing time, and at the end of the test, the optical fibre sensor measured a negative strain of ∼100 μϵ and a positive RI variation of ∼0.002.

Structural characterisation of Cu-Zr thin film combinatorial libraries with synchrotron radiation at the limit of crystallinity

We report for the first-time combinatorial synthesis of thin film metallic glass libraries via magnetron co-sputtering at the limit of crystallinity. Special care was taken to prepare extremely pure CuZr films (1–2 µm thickness) with large compositional gradients (Cu18.2Zr81.8 to Cu74.8Zr25.2) on X-ray transparent polymer substrates in high-vacuum conditions. Combined mapping of atomic structure (synchrotron radiation) and chemical composition (X-ray fluorescence spectroscopy) revealed that over the entire composition range, covering multiple renowned glass formers, two phases are present in the film. Our high-resolution Synchrotron approach identified the two phases as: untextured amorphous Cu51Zr14 (cluster size 1.3 nm) and textured, nanocrystalline α-Zr (grain size 1–5 nm). Real space HR-STEM analyses of a representative composition substantiate our XRD results. Determined cluster and grain sizes are below the resolution limit of conventional laboratory-scale X-ray diffractometers. The presented phase mixture is not permitted in the Cu-Zr phase diagram and contrary to existing literature. The phase ratio follows a linear trend with amorphous films on the Cu-rich side and increasing amounts of α-Zr with increasing Zr content. While cluster size and composition of the amorphous phase remain constant thorough the compositional gradient, crystallite size and texture of the nanocrystalline α-Zr change as a function of Zr content.

Vacuum conditions for tunable wettability transition on laser ablated Ti-6Al-4V alloy surfaces

This work investigates the mechanism of the controllable wettability transition on laser ablated Ti-6Al-4V alloy surfaces with the vacuum treatment. The effects of surface morphologies, vacuum conditions and joint mechanisms are discussed. To achieve stable and controllable wettability transitions, the laser ablated Ti-6Al-4V alloy surfaces were placed in a low vacuum environment to adsorb non-polar organic molecules. The sample appeared an unstable wettability transition, which manifested itself as a change in the apparent contact angle (ACA) with time. High vacuum conditions can accelerate the assembly of organic molecules on the sample surface and achieve a stable wettability transition. Furthermore, by varying the surface morphologies of laser ablated Ti-6Al-4V alloy and the adsorption time of organic molecules, stable and controllable wettability transitions can be achieved at high vacuum conditions.

Adjustment concept for compensating for stiffness and tilt sensitivity of a novel monolithic electromagnetic force compensation (EMFC) weighing cell

Abstract. This paper describes the new adjustment concept of novel planar, monolithic, high-precision electromagnetic force compensation weighing cells. The concept allows the stiffness and the tilt sensitivity of the compliant mechanisms that are dependent on the nominal load on the weighing pan to be adjusted to an optimum. The new mechanism is set up and adjusted according to the developed mechanical model. For evaluation of the concept the system is tested on a high-precision tilt table and under high vacuum conditions in the environment of a commercially available mass comparator.

VIS spectroscopy of NaCl – water ice mixtures irradiated with 1 and 5 keV electrons under Europa's conditions: Formation of colour centres and Na colloids

Recent laboratory efforts and telescopic observations of Europa have shown the relevance of a yellow colouration of sodium chloride (NaCl) caused by crystal defects generated by irradiation. We further investigate this process by irradiating (with energetic electrons) different types of analogues where NaCl is associated in different ways to water ice. We produce two types of icy analogues: compact slabs and granular particles where we investigate two particle sizes (5 and 70 μm). We perform electron irradiation at cryogenic temperatures (100K) and under high vacuum (10−7 mbar) conditions, with energies of 1 and 5 keV. We observe the formation of two different types of colour centres. The so-called F-centres (460 nm) were formed in every sample, but the intensity of the absorption band within the compact slabs surpassed any other icy analogues and was comparable to the intensity of the absorption band within pure NaCl grains. M-centres (720 nm) have not been detected at the surface of Europa so far, and were close to the detection limit during our irradiation of compact slabs. The slabs could be good analogues for Europa's surface as they produce mainly F-centres. Other notable differences have been observed between compact slabs and granular samples, such as the presence of an absorption band at 580 nm attributed to colloids of Na, exclusively within granular samples. Such absorptions have not been reported in previous studies.

Fabrication and mechanical property of three-dimensional carbon fiber reinforced Mg-based bulk metallic glass matrix composite

Carbon fiber (CF) reinforced bulk metallic glass matrix composites (BMGMCs) have received widespread attention due to their light weight, but subsequent development is facing urgent challenges of uncontrollable interface reaction and poor plasticity. Here, we report a three-dimensional CF-reinforced Mg-based BMGMC, which significantly improves the microstructure and compressive plasticity by adjusting the pressure infiltration parameters. It has been found that the electroless copper plating improves the wettability of the CF and the melt without inducing the crystallization of the matrix, in spite of the partially dissolving and diffusing of the coating to the matrix. Under a similar infiltration pressure difference, high vacuum conditions are beneficial to reduce the capillary resistance of the porous CF preform, thereby improving the formability of BMGMC. Compression test results prove that the introduction of three-dimensional CF effectively improves the plasticity of the composite material and reduces its brittleness tendency. It can be attributed to the fact that the carbon fibers distributed in different directions effectively bridge the multi-directional cracks and prevent the early rapid shear band propagation. The present work provides meaningful enlightenment for the development of CF-reinforced BMGMC materials.

Effect of Bonding Temperature and Interlayer(s) on Microstructure Evolution, Hardness, and Shear Properties of Diffusion Bonded Ti-6Al-4V Alloys

Abstract The workhorse Ti-6Al-4V alloy has numerous applications under extreme conditions, and there is a necessity to produce metallic joints with the alloy for fabrication of some industrial components. In the present study, the solid-state diffusion bonding (DB) process was used to produce similar metal joints between Ti-6Al-4V alloy sheets with and without copper and nickel interlayers. The effect of the bonding temperature as well as the influence of interlayers on the joint interface microstructure and, subsequently, on the mechanical performance of the bonded joints were investigated. The DB was performed at three different bonding temperatures of 1,023, 1,123, and 1,223 K under high-vacuum conditions using a thermomechanical deformation simulator. The microstructure across interface of the joint was examined using optical and scanning electron microscopes. The joint strength was evaluated using both the nanoindentation technique and the shear test. The findings show the formation of intermetallic phases between titanium and interlayer(s) elements across the interface up to the bonding temperature of 1,123 K. Further increase in the bonding temperature led to a complete diffusion of the interlayers into the base metals, thereby forming the Widmanstätten microstructure across the interface. In the case of direct DB, there was a gradual closure of voids along with a homogenized joint interface with an increase in the bonding temperature. The variation of hardness across the bonding interface and the shear properties were found to be consistent with the resultant microstructural features evolved with the bonding temperature and type of interlayer(s).

Development of multi-frequency impedance scanning electron microscopy.

Nanometre-scale observation of specimens in water is indispensable in many scientific fields like biology, chemistry, material science and nanotechnology. Scanning electron microscopy (SEM) allows high-resolution images of biological samples to be obtained under high vacuum conditions but requires specific sample-preparation protocols. Therefore, there is a need for convenient and minimally invasive methods of observing samples in solution. We have developed a new type of impedance microscopy, namely multi-frequency impedance SEM (IP-SEM), which allows nanoscale imaging of various specimens in water while minimising radiation damage. By varying the frequency of the input voltage signal of the sine wave, the present system can detect dielectric properties of the sample’s composition at nanometre resolution. It also enables examination of unstained biological specimens and material samples in water. Furthermore, it can be used for diverse samples in liquids across a broad range of scientific subjects such as nanoparticles, nanotubes and organic and catalytic materials.

Chemical – crystallographic characterisation of cement clinkers by EBSD-EDS analysis in the SEM

Characterisation of cement clinkers is a prerequisite to optimise properties of cements and concretes. Therefore, the protocol to prepare and characterise cement clinkers using electron backscatter diffraction (EBSD) in combination with energy dispersive X-ray spectrometry (EDS) is described.It is shown that argon broad ion beam polishing delivers surfaces with high contrast electron backscatter diffraction patterns (EBSP). EBSD data quality in high and low vacuum SEM reveals that high vacuum conditions and state-of-the-art EBSD cameras deliver EBSPs of cement clinker at improved quality.Furthermore, exemplary EBSD-EDS analysis is discussed for two Portland cement clinkers. Results clearly show that differentiation between major phases can reliably be achieved. In addition, it is revealed that crystal distortion in belite is high. Analysis of C3A phases show that differentiation of orthorhombic and cubic polymorph is possible, and that Mg incorporation leads to amorphization.Results demonstrate that EBSD-EDS analysis allows reliable phase characterisation of cement clinkers.

Epitaxial Growth and Optical Properties of Laser Deposited CdS Thin Films

In this study, cadmium Sulfide (CdS) thin films were synthesized on quartz substrates using an infrared pulsed laser deposition (IR-PLD) technique under high vacuum (~10−6 Torr) conditions. X-ray diffraction was used to evaluate the structural features. According to X-ray analysis, the deposited CdS films are crystalline and have a favored orientation on a plane (110) of an orthorhombic. The peak intensity and the average crystallite size increases with increasing the film thickness. After annealing at 300 °C, the orthorhombic phase transformed into a predominant hexagonal phase and the same result was obtained by SEM photographs as well. Spectrophotometric measurements of transmittance and reflectance of the CdS films were used to derive optical constants (n, k, and absorption coefficient α). The optical band gap energy was found to be 2.44 eV. The plasma plume formation and expansion during the film deposition have also been discussed. The photocurrent response as a function of the incident photon energy E (eV) at different bias voltages for different samples of thicknesses (85, 180, 220 and 340 nm) have been studied, indicating that the photocurrent increases by increasing both the film thickness and photon energy with a peak in the vicinity of the band edge. Thus, the prepared CdS films are promising for application in optoelectronic field.

Dehydration rate of the glycine‐MgSO4·5H2O complex and the stability of glycine expelled from the complex by in situ Raman spectroscopy under Mars‐relevant conditions

AbstractIn this work, we studied the dehydration process of the glycine‐MgSO4·5H2O complex under Mars‐relevant conditions (99% CO2 and 0.6% H2O under ultra violet (UV) irradiation exposure at 7‐mbar pressure and high vacuum conditions: 8 × 10−5 and 5 × 10−5 mbar) by in situ Raman spectroscopy inside a planetary atmosphere and surface chamber (PASC). This work provides quality Raman spectra taken under simulated planetary conditions (to be integrated in a database), as Raman spectroscopy forms part of the current and upcoming NASA and ESA Mars planetary missions. The results demonstrate that Raman spectroscopy can be used to calculate rates of dehydration of the glycine‐MgSO4·5H2O compound to study the chemical stability with respect to photodecomposition (1) of metal‐bound glycine molecules forming the complex and (2) glycine expelled from the complex, both under Mars‐simulated conditions; finally, Raman spectroscopy can also be used to quantify intermolecular interactions in terms of local pressures. Importantly, advanced detection of water molecules as part of a complex with astrobiological interest under planetary conditions plays a crucial role in planetary missions.

VACUUM BRAZING OF A HIGH-FREQUENCY WAVEGUIDE OF A RECTANGULAR SECTION AND MINIMAL REFLECTION WITH A FLANGE

The technology of vacuum brazing of a long high-frequency waveguide with variable cross-section and minimal reflection with a flange made of a composite material based on copper is presented. When developing the technology, experiments were carried out under different temperature conditions, and materials with different properties were also used. Oxygen-free copper was chosen as the material for the waveguides. Due to its properties, oxygen-free copper is easily processed on metal-cutting machines and is widely used in accelerator technology. The BVAg-8 alloy was selected as the filler, which satisfies the conditions corresponding to the vacuum brazing process with its composition. Filler is an alloy of silver and copper. Brazing of a rectangular waveguide and a flange was performed under high vacuum conditions, in a vacuum brazing unit, which was restored and modernized at the CANDLE Synchrotron Research Institute.

In situ x-ray photoelectron spectroscopy analysis of electrochemical interfaces in battery: Recent advances and remaining challenges

An in-depth understanding of charge transfer processes at the electrochemical interfaces is a critical knowledge gap impeding the design of energy storage materials. X-ray photoelectron spectroscopy plays an important role in analyzing electronic structures of heterogeneous interfaces, such as electrode-electrolyte interphases. Correspondingly, ex situ studies based on postmortem analysis of electrode materials using x-ray techniques are widely reported in the literature but often fail to capture intermediate and transient species, which are critical for a predictive understanding of the charge transfer process. The lack of extensive in situ/operando x-ray analysis of buried interfaces in energy storage systems can be mainly attributed to technical limitations, such as the requirement of high vacuum conditions. However, in the past decade, considerable efforts have been devoted to overcoming these technical barriers and enable investigation of the solid/solid and solid/liquid interfaces. This review catalogs some of the recent progresses and new experimental designs in the application of in situ and operando x-ray photoelectron spectroscopy toward characterizing interfacial processes and emergent properties, which can help build the design strategy for advanced batteries. The remaining challenges and future research directions are also discussed, as potential paths forward in this field.

Hydrogen interaction with Zr-based getter alloys in high vacuum conditions: In situ SIMS-TPD studies

The paper summarizes the results of combined SIMS-TDS measurements of hydrogen interaction with the alloys Zr2Fe, Zr(V0.75Fe0.25)2, Zr65V30Ti5, Zr37.7Ti4.7Mn20.2Fe37.4 at hydrogen pressures below 1 × 10−2 Pa, and in temperature range ∼300 ÷ 1100 K. Hydrogen is readily chemisorbed on the sputter-cleaned surface of the alloys. Besides chemisorption, substantial hydrogen uptake into the bulk was observed for Zr2Fe, Zr(V0.75Fe0.25)2, Zr65V30Ti5, but almost no uptake for Zr37.7Ti4.7Mn20.2Fe37.4. Temperature increase above 300 K resulted in the increase of the hydrogen absorption effectiveness and its dissolution rate from the surface into the bulk indicating the surface-to-bulk transition and/or bulk diffusion rate as the absorption limiting steps. Hydrogen release from the alloys was observed at temperatures above 600 K. Its beginning temperature depended on the amount of hydrogen absorbed and the alloy composition. The comparative effectiveness of hydrogen absorption by the alloys decreased in the sequence Zr65V30Ti5 > Zr(V0.75Fe0.25)2 > Zr2Fe.

In situ observation of the capillary infiltration of molten silicon in a SiC/SiC composite by X-ray radiography

Capillary infiltration is an innovative fabrication method for metal and ceramic-matrix composites. SiC/SiC composites can be infiltrated by molten silicon to decrease residual porosity. Physical and chemical mechanisms involved during Liquid Silicon Infiltration (LSI) are complex to analyse. An in situ observation setup for capillary infiltration of molten silicon has been designed for synchrotron observations. The setup reproduces the extreme high temperature and high vacuum conditions used in the LSI process. It is also designed for X-ray observations in synchrotron beamlines and tomography stages. Sets of 2D X-ray absorption radiographs were acquired at high frequency during the LSI process. The study outlines the capillary infiltration mechanisms of molten silicon inside SiC/SiC composites. It proves that full saturation of the composite is not directly achieved after the rise of molten silicon. It is a two step mechanism. First, the infiltration occurs inside the intra granular porosity of the SiC powder matrix. Then, larger scale porosities such as cracks are filled. These phenomena have been discussed previously in the literature but never observed in situ.

Cryo secondary ion mass spectrometry for wood component visualization: a mini review

Abstract Various phenomena in living physiological systems are conducted on the hydrated conditions, and in many cases, they do not work in a dry state. Imaging mass spectrometry is one of the direct detection methods scanning the sample surface with some focused and pulsed energy and analysing the sputtered components. However, under the high vacuum conditions required for usual imaging mass spectrometry, the sample surface is rapidly dried. It is difficult for the target cell to survive, and the original situation are lost soon. Here, the combination of a freeze-fixation and a cryo sample stage is a promising method to do mass spectrometry while maintaining the original situation. By rapidly freezing the cells, the momentary situation as a living cell is fixed. The situation in a living cell can be captured as still images by cryo imaging mass spectrometry. This mini-review introduces the outline of imaging mass spectrometry especially for low molecular weight components and recent results for frozen-hydrated samples by cryo secondary ion mass spectrometry.

Electrical performance of ZrC ceramics

AbstractIn the present study it was possible to provide evidence that ZrC ceramics – regarding their electrical‐mechanical and thermal properties – are an attractive substitute for tungsten and molybdenum in the field of refractory materials and heating elements. For this purpose, the heating behavior of ZrC materials was investigated in a specific test stand under high vacuum conditions (10−6 mbar) at temperatures above 2000 °C. In addition, the applicability of ZrC as an electrical heating element was investigated in terms of geometric design and long‐term behavior. Examinations after the heating tests did not reveal any significant changes in the material.

An Analysis of Kikuchi Lines Observed with a RHEED Apparatus for a TiO2-Terminated SrTiO3 (001) Crystal.

In this study, electron diffraction patterns observed under high vacuum conditions for an SrTiO3 surface were interpreted in detail while paying special attention to the features of inelastic effects. The surface of the SrTiO2 was carefully prepared to enforce its termination with single domains of TiO2 layers at the top. The inelastic patterns were interpreted using analytical models. Two types of Kikuchi lines are recognized in this paper: those which can be described with the Bragg law and those which appear due to surface wave resonance effects. However, we also discuss that there exists a formal connection between the two types of the Kikuchi lines observed.