Glass Vacuum Research Articles

Carbonization, Hydrogenation, Oxidation and Electromagnetic Absorption of TiOx‐Pyrrole Compounds

This work presents a morphologic, structural and electromagnetic absorption study in plasma‐synthesized organometallic hybrid compounds based on titanium oxide and pyrrole, which could potentially be used as photoconductive materials in solar cells. The synthesis was carried out with the combination in liquid phase of titanium tetra isopropoxide and pyrrole with 1:1 mass ratio in a glass vacuum tubular reactor with resistive electric discharges and reaction intervals from 60 to 240 min. Films and particles were formed with mean particle diameter of 438 nm. The hybrid compounds presented functional groups with multiple bonds related with pyrrole and TiOx structures. Organic and inorganic phases were detected in the hybrid matrices in which carbonization, hydrogenation, oxidation and nitridation were quantified which suggested strong dehydrogenation and the formation of multiple bonds in the plasma reactions. The compounds absorbed electromagnetic radiation in two regions with different intensity. The first and most intense one was between 190 and 350 nm wavelength, the second one was identified from 350 to 800 nm, this effect suggests that the titanium oxide is the dominant fraction in the first region and pyrrole in the second.

High Vacuum Glass Units Application for Solar Radiation Thermal Conversion

This work was carried out with the aim to investigate a new concept of high-vacuum glazing application in flat structures designed for solar radiation conversion into thermal energy of a fluid. The research includes studies of performance characteristics of flat-structure solar collector samples manufactured on the base of vacuum glazing (VG) (or vacuum insulating glass unit) in which liquid fluid has direct contact with VG. Results of thermal stability tests, performance tests and tests of stability against aging in natural environment conditions have been presented.

New Cooled Feeds for the Allen Telescope Array

We developed a new generation of low-noise, broadband feeds for the Allen Telescope Array at the Hat Creek Observatory in Northern California. The new feeds operate over the frequency range 0.9 to 14 GHz. The noise temperatures of the feeds have been substantially improved by cooling the entire feed structure as well as the low-noise amplifiers to 70 K. To achieve this improved performance, the new feeds are mounted in glass vacuum bottles with plastic lenses that maximize the microwave transmission through the bottles. Both the cooled feeds and their low-noise amplifiers produce total system temperatures that are in the range 25–30 K from 1 GHz to 5 GHz and 40–50 K up to 12.5 GHz.

Hydrocarbon source for oil and gas indication associated with gas hydrate and its significance in the Qilian Mountain permafrost, Qinghai, Northwest China

Since gas hydrate was sampled by drilling in the Qilian Mountain permafrost in 2008, to investigate the source of the gas hydrate and the relationship between gas hydrate and the concomitant oil and gas indication (OGI) have become an important research focus. The rocks bearing gas hydrate and OGI from the Middle Jurassic strata in the Qilian Mountain permafrost, Qinghai, Northwest China were extracted by organic solvent and thermally treated (300 °C and 400 °C) in vacuum glass tubes. The hydrocarbons from the extracts and cracked products of the rocks and the stable carbon isotope of the gas hydrocarbons were studied. The results showed that the OGIs can be classified into two types according to different biomarker characteristics. The I-type of OGIs, which suffered from the process of early biodegradation and later-hydrocarbon input and featured high concentrations of 17α(H)-diahopane and αββ-regular steranes, mainly originated from the shallow source rocks of the Middle Jurassic strata, while the II-type one with a series of long-chain alkylnaphthalene may originate from the lower portion of Middle Jurassic or deeper source rocks than the Middle Jurassic strata. The adsorbed gas (300 °C) of the Middle Jurassic rocks was very wet, had a normal carbon isotope sequence, and can be regarded as an organic thermogenic gas derived from Middle Jurassic source rocks. Comparing the adsorbed (300 °C) and cracked (400 °C) gases from the rocks with gases from the gas hydrate and drilling core, we found they had similar stable carbon isotope distributions but different relative contents of methane (C1), ethane (C2), and propane (C3). The Middle Jurassic source rocks are mainly deposited in a freshwater paleo-environment, similar to the parent biomass of the gas hydrate and drilling core gas. The difference of the relative concentrations of C1-C3 may result from different formation processes between the adsorbed and cracked gases and the gas hydrate and drilling core gas. The II-type OGI, which possibly originated from deeper strata than the Middle Jurassic, were closely associated with the gas hydrate under the drilling well and had a similar parent biomass and depositional environment as the gas hydrate, showing they have a closely correlated hydrocarbon origin.

Development of Vacuum Glass in China – Both Opportunity and Challenge Coexist

Development of Vacuum Glass in China – Both Opportunity and Challenge Coexist

Lateral MEMS-Type Field Emission Electron Source

This paper describes a microelectromechanical-system-type field emission electron source fabricated as a planar silicon structure bonded with a glass substrate. It consists of a carbon nanotube cathode, beam formation electrodes, and silicon glass vacuum housing, all made in a uniform technological process. The current–voltage characteristics obtained inside a reference vacuum chamber for the two-, three-, and four-electrode configurations have been presented. The possibility of generation of a focused electron beam as well as gas ionization has been investigated. In addition, the lateral electron source has been integrated on the chip with a miniature ion-sorption vacuum pump and hermetically sealed. The use of the micropump significantly improved the stability of field emission current.

Receiver shape optimization for maximizing medium temperature CPC collector efficiency

Low optical-concentration solar thermal CPC collectors for process heat at 150–300°C generally use thermal oil as the collector fluid. Thermal oils have low thermal conductivity and high viscosity, which leads to significant thermal resistance and hence reduced collector thermal efficiency. One way to minimize the thermal resistance is by having turbulent flow of the thermal oil within the receiver. For a given receiver area and mass flow rate of the fluid, this can be achieved by narrowing the flow passage but keeping the receiver area constant by adding external flat fins. In this paper a new receiver design for a compound parabolic concentrator is proposed which is a hybrid of a U-shaped tubular receiver and a bifacially irradiated flat receiver. To keep the receiver area constant, the fins are increased in width as the tube diameter is decreased. Its performance when enclosed in a glass vacuum tube and a CPC has been modelled. The transmission and absorption of solar energy, optical losses due to the receiver–reflector gap, heat transfer within the receiver, and the thermal losses have been modelled. Keeping the receiver area and fluid flow rate constant, the thermal resistance of the thermal oil flow within the receiver reduces when the flow passage is narrowed leading to increased thermal efficiency. On the other hand, the hybrid receiver has lower optical efficiency as compared to a tubular receiver due to its higher gap loss. Overall, the hybrid receiver has similar or better thermal efficiency than the tubular receiver. Thermal efficiency and effective thermal efficiency, which accounts for the pumping power penalty, shows that the performance improvement with thermal oil due to receiver shape optimization depends on the receiver area, concentration ratio, absorptivity and emissivity of the selective surface, the mass flow rate through the receiver and fluid temperature. Highest effective thermal efficiency is generally achieved in the laminar–turbulent transitional regime. For temperatures below 150°C, water has been found to give better performance than thermal oil at all mass flow rates with no significant improvement in collector performance achieved by reducing the tube diameter.

Finite Element Analysis of Glass Vacuum Windows of the “COMPASS” Tokamak in Prague

In this paper is described the mechanical stress analysis of glass vacuum windows of the COMPASS tokamak using Finite Element Method. As a reference test problem the problem of uniformly loaded glass vacuum window with circular shape has been chosen, which problem can be solved also analytically. In the case of Finite Element analysis we used two different mechanical models: 3-dimensional (3D) approach and shell modelling. For 3D approach an optimal finite element type - quadratic tetrahedron element with appropriate size - was chosen, and for shell modelling a thin axisymmetric shell element type - shell 209 - was applied. The analytic and both numerical results have been compared and summarized.

Insight into the loading temperature of sulfur on sulfur/carbon cathode in lithium-sulfur batteries

Lithium–sulfur batteries are highly desired because of their characteristics such as high energy density. However, the applications of Li-S batteries are limited because they exist dissolution of polysulfides into electrolytes. This study reports the preparation of sulfur cathodes by using bimodal microporous (0.5nm and 0.8nm to 2.0nm) carbon spheres with high specific area (1992m2g−1) and large micropore volume (1.2gcm−1), as well as the encapsulation of polysulfides via formation of carbon–sulfur bonds in a sealed vacuum glass tube at high temperature. Given that sulfur and polysulfides are well confined by the SC bond, the shuttle effect is effectively suppressed. The prepared S/C cathodes with a sulfur loading of up to 75% demonstrate high sulfur activity with reversible capacity of 1000mAhg−1 at the current density of 0.1Ag−1 and good cycling stability (667mAhg−1 after 100 cycles).

Development of guarded hot plate apparatus utilizing Peltier module for precise thermal conductivity measurement of insulation materials

In this paper, a guarded hot plate (GHP) apparatus utilizing a Peltier module is proposed and developed to precisely measure the thermal conductivity of insulation material. The Peltier module is used to detect a temperature difference with high sensitivity and to precisely measure heat flux. To develop the GHP apparatus, a two-dimensional axisymmetric heat conduction analysis and calibration experiments of thermistors and Peltier module were conducted. In addition, to assess the reliability of the developed apparatus, thermal conductivity measurements for a high-density glass wool and vacuum insulation panel (VIP) were conducted. Based on the results, the expanded uncertainties of the measurements were estimated. Therefore, the apparatus was found to be reliable for conducting precise thermal conductivity measurements not only for conventional insulation materials but also for a VIP.

Establishment of regression model for estimating shape parameters for vacuum-sealed glass panel using design of experiments

Presently, the technique of edges sealing of vacuum glass panels is being utilized in a variety of industrial applications, such as in displays and home appliances. The sealing conditions of a vacuum glass panel strongly affect its key performance parameters, such as its insulation and strength. In the present study, edges of two glass panels were melted and sealed using a hydrogen mixed gas torch. The edges were sealed after appropriately setting process parameters that affected the shape of the sealed edges. Regression models were established for estimating the edge thickness, deflection, and maximum radius of the sealed part, which were considered as shape parameters. The effects of the process parameters on the shape parameters, as well as the interactions among the process parameters, were analyzed, and a polynomial regression model that considered these interactions was established. The feasibility of all the regression models was verified through analysis of variance.

Solid-State Fabrication of SnS2/C Nanospheres for High-Performance Sodium Ion Battery Anode.

Tin disulfide (SnS2) has emerged as a promising anode material for sodium ion batteries (NIBs) due to its unique layered structure, high theoretical capacity, and low cost. Conventional SnS2 nanomaterials are normally synthesized using hydrothermal method, which is time-consuming and difficult to scale up for mass production. In this study, we develop a simple solid-state reaction method, in which the carbon-coated SnS2 (SnS2/C) anode materials were synthesized by annealing metallic Sn, sulfur powder, and polyacrylonitrile in a sealed vacuum glass tube. The SnS2/C nanospheres with unique layered structure exhibit a high reversible capacity of 660 mAh g(-1) at a current density of 50 mA g(-1) and maintain at 570 mAh g(-1) for 100 cycles with a degradation rate of 0.14% per cycle, demonstrating one of the best cycling performances in all reported SnS2/C anodes for NIBs to date. The superior cycling stability of SnS2/C electrode is attributed to the stable nanosphere morphology and structural integrity during charge/discharge cycles as evidenced by ex situ characterization.

In situ formed carbon bonded and encapsulated selenium composites for Li–Se and Na–Se batteries

Carbon bonded and encapsulated selenium composites were synthesized in a sealed vacuum glass tube at a high temperature. Because selenium is bonded and encapsulated by carbon, the shuttle reaction of selenium was effectively suppressed. The C/Se composites exhibit a superior cycling stability and rate capability in commercial carbonate based electrolytes.

Thermomechanical coupling of geometrically non‐coherent interfaces

AbstractAn evacuated tube collector is composed of a vacuum glass tube forged to a metal tube creating an interface which undergoes thermomechanical cyclic loading. To numerically model such a thermomechanical and geometrically non‐coherent interface, a decohesion element with mixed‐mode capability, based on a normal‐shear decomposition of the displacement discontinuity vector is used, exploiting exponential traction‐separation laws. In addition to the classical strategies, interfacial elements are allowed to have an in‐plane stretch resistance by assuming a thermohyperelastic interface Helmholtz energy, a function of the rank‐deficient interface deformation gradient $\overline{\bf F}$ and temperature $\overline{\Theta}$ , as an extension of the surface/interface elasticity theory. The nonlinear governing equations are given and solved using the finite element method. The results are illustrated through a series of numerical examples for different material parameters. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Experimental investigation of the effect of using thermosyphon heat pipes and vacuum glass on the performance of solar still

A desalination system consumes energy for production of freshwater. Since the solar energy is a low-cost, environmentally clean, and available energy throughout the world, it could be the best source of energy for such systems. In this work, a modified desalination system is presented which uses advantages of thermosyphon heat pipes as a fast and high performance thermal conducting device, and at the same time, employs the advantages of evacuated tube collectors (ETCs) which are flexible and have high performance in adverse weather conditions. Results show considerable increase in the production rate of desalinated water and system efficiency with a maximum production rate of 1.02 kg/(m2 h) and maximum efficiency of 22.9%. Furthermore, the optimum water depth in the basin is measured to be 2 cm, which is the same as the length of the heat-pipe's condenser section in the basin.

Routine application of Raman spectroscopy in the quality control of hospital compounded ganciclovir

This study compares the performance of a reference method of HPLC to Raman spectroscopy (RS) for the analytical quality control (AQC) of therapeutic objects. We assessed a model consisting of a widely used antiviral drug, i.e., ganciclovir, which was compounded in a medical device and then transferred in a vacuum glass vial prior to analyses. As the aim of the alternative RS method is to replace the destructive, time-consuming HPLC method, requiring sample preparation, it needs to be demonstrated that RS performs at least as good as the HPLC method. Therefore, the two methods were validated by calculating the accuracy profile and provided excellent results for the analytical validation key criteria, i.e., trueness, precision and accuracy, ranging from 0.8 to 10mg/mL. The Spearman and Kendall correlation tests (p-value<1.10–15) and the statistical studies performed on the graphs confirm a strong correlation in the results between RS and the standard HPLC under the experimental conditions. These results confirmed the potential of this option for future applications, owing to its analytical and practical quality and its contributions to the safety of the medication circuit. This method also greatly contributes to the protection of caregivers and their working environment.

The Energy-Saving Design and Construction Study on Exterior Windows in the Building

Doors and windows,especially the exterior windows, are the weak parts to preserve or insulate heat in the exterior protected construction of a building, and the main contents in energy-saving architectural designs. The energy-saving design of exterior windows should start from such aspects as size, shape, frame form, glass type, gap sealing, etc. The size of the exterior window holes should be determined according to the window-wall area ratio specified in the relevant rules. It is priority to choose side-hung window in energy-saving design, to choose the low heat transferring window frame, to take measures to break the “thermal bridge”, and to select the energy-saving glass such as decalescence glass, coated glass, hollow glass and vacuum glass. The gaps should be sealed tightly between wall and window frame, window frame and sash, glass and window sash to reduce the air permeable.

Thermal performance evaluation of a conical solar water heater integrated with a thermal storage system

In the present research, a conical solar water heater (CSWH) with an attached thermal storage tank, with or without a vacuum glass absorber, was analyzed under different operating conditions. For maximum solar radiation of the system, the collector was equipped with a dual-axis tracking system and sun sensor, which kept the system oriented towards the sun at every instant during its operation. A forced cooling system circulated fluid to remove the solar heat from the absorber surface. Performance analyses with and without the vacuum glass absorber were conducted at different mass flow rates, inlet temperatures, and solar irradiation values. The influence of the vacuum glass cover and all operational parameters on the collector efficiency, outlet temperature, and thermal stratification were investigated. The efficiency increased with increasing inlet flow rate, and the maximum efficiency was obtained at a critical flow rate of 6L/min. When the flow rate was increased beyond this critical value, the efficiency began to decrease. The temperature rise of the working fluid with vacuum glass at a high rate of insolation was considerably higher than without a vacuum glass for all flow rates. Use of a high flow rate deteriorated the thermal stratification process in the storage tank, while it increased the efficiency of the conical solar water-heating system. It can be concluded that the CSWH operates more efficiently if the fluid is heated slightly at a critical flow rate.

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

Laboratory drop towers for the experimental simulation of dust-aggregate collisions in the early solar system.

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.