Kurzwegdestillation

Among serveral processes of vacuum distillation the so-called Short Path Distillation has proven as the most efficient process for laboratory, pilot plant and production use. Especially in pharmacy, cosmetics and plastic resins where sensitive mixtures have to be separated, the Short Path Distillation has made itself indispensable.     

Kondensation: Ein unterschätzter Aspekt der Kurzwegdestillation

Condensation: an underestimated aspect of Short Path Distillation Since many years, Short Path Distillation has earned its place amongst the various thermal separation methods available. Especially for substances with high boiling points and accordingly low vapor pressures there are few techniques which can keep up with Short Path Distillation regarding the mild process conditions and economic efficiency. In this article a short introduction into Short Path Distillation is given. A new development called Washing Condenser for achieving better residue purities is described as well as an industry‐scale example for its application.     

On the compositional,optical and electrical characteristics of vacuum‐deposited GaAs1‐xPx films prepared by a successive evaporatron method

Abstract

GaAs_1‐xP_x thin films have been deposited onto glass substrates at a rate of 50Å/min. in a vacuum of 5 x 10^‐5 Torr using a successive evaporation method. Thin films of various compositions (X = 0.3–0.9) were obtained at gallium source temperature T_Ga = 870°C, arsenic source temperature T_As = 275°C, phosphorus source temperature T_P = 330°‐363°C and substrate temperature T_sub = 265°‐330°C. Compositional, optical (absorption) and electrical properties of the films in a thickness range of 1300–1900 Å were determined by using an X‐ray diffractometer, a grating spectrometer and an electrometer respectively. The experimental results were compared with those for simultaneous evaporation and discussed from the atomistic viewpoints.

The values of △X/△T_sub are ‐ 7 x 10^‐3 and ‐1 x 10^‐3 °C^‐1 for successive and simultaneous evaporation respectively, the difference of which can be explained by the absorption effect of a predeposited Ga layer in successive evaporation. The value of △X/△Tp is about +7 x 10^‐3°C^‐1 for the two evaporation methods, however, it levels off more distinctly at higher substrate temperatures. Absorption edge shift and relatively low resistivity suggest that successively vacuum‐deposited films have much more phosphorus vacancies and/or impurities than simultaneously vacuum‐deposited and chemically vapor‐deposited films.     

Vacuum-Aided Recovery Technology of Spent Ni-Cd Batteries

Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions.The fundamental research on a process of disassembling and recovering selected materials from Ni-Cd batteries was conducted ,The impacts of temperature,pressure and time were studied respectively ,The mechanism of vacuum thermal recovering was laso discussed,The results show that:Ni-Cd batteries can be recovered effectively by vacuum-aided recovering system at 573-1173K.At constant pressure,the increase of temperature can improve the separating efficiency of cadmium ,When the temperature is 1173K, the cadmium can evaporate completely from the residue during 3 h at 10 Pa ,The reduction of pressure in the certain range is effective to separate cadmium by vacuum distillation .Distillation time is a very important factor affecting separation of cadmium.     

In‐situ‐Sauerstoffmesszellen für den Einsatz im Vakuum. In‐situ oxygen sensors for the use in vacuum

The use of galvanic cells with oxide‐ion‐conducting solid electrolytes as sensors in vacuum allows to measure directly the oxygen partial pressure deciding for redox processes at the surface of workpieces during heat treatments. The oxygen exists either as a free molecular gaseous component or in the thermodynamic equilibrium with other gases. The bases of the known gas potentiometry are valid also in vacuum. Reducing gases are indicated in redoxquotients as Q_H = p(H₂O)/p(H₂). For the technique of measurements with solid electrolytes in vacuum special requirements arise. Probes with air reference electrode are already offered commercially. A solid reference electrode formed with Cu and Cu₂O was tested now in the range of pressure from 1 to 10^‐7 bar. It is usable at sensor temperatures between 400 and 650 centigrades. Important disturbances by oxygen permeability of the solid electrolyte were not observed in this temperature range. Changes of the composition of rest gases in vacuum, often arising as a result of wall reactions are indicated by alterations of p(O₂) or Q_H respectively. The accuracy of measurements is improved by consideration of temperature differences between the electrodes.     

废铝合金真空蒸馏脱锌的研究

首先分析了用真空蒸馏的方法脱除废铝合金中金属Zn的可行性。对二种含Zn质量分数为10%,12.25%的废铝合金进行了真空蒸馏脱除锌的实验。最终的实验结果与理论分析是紧密一致的。本文利用真空蒸馏法脱除含锌废铝中的金属Zn,解决了废铝脱锌难的问题,且对环境友好,不会造成二次污染。     

Stabile Vakuumprozesse mit Dreh‐/Schiebedurchführungen

Stable vacuum processes despite rotary/sliding feedthroughs – Effects of motion speed and direction using the MeTraVac system as an example Components for ultra‐high (p < 1 · 10^?7 mbar) and extreme high vacuum (p < 1 · 10^?11mbar) conditions must have very clean surfaces with low outgassing rates. The determination of outgassing characteristics for static components is common practice. However, it is unusual to investigate the influence of the outgassing rates of dynamic components when they move in a vacuum. Various experiments with a self‐designed and built rotary/sliding feed‐through were carried out. The aim of these investigations was to monitor the pressure increases during movements and thereby draw conclusions on the quality of the vacuum conditions. One rotary and two translational movement types were selected exemplarily for practical vacuum applications. Each experiment was performed in an unconditioned and conditioned (in‐situ bake‐out) state. For the experiments a heatable test setup was assembled. The rotary motion does not affect the process vacuum perceivable. Two translational movements were carried out, which differed in the speed. The pressure increases during slower and faster translatory movements show that the speed of movement has no significant influence on the vacuum. Nevertheless, a significant change in pressure was observed with translational movements. By bake‐out, the amount of water released per movement will significantly be reduced. Most kind of vacuum‐sided movements do not affect the process pressure at all or only to a small extent.     

Modifiziertes Bayard‐Alpert‐ Ionisationsmanometer für Druckmessungen von 10‐9 ... 10+1 mbar

Generally, the requirements for the design and the operating parameters of hot filament ionisation gauges for high and low pressure measurement are incompatible. Nevertheless it is possible to construct an ionisation gauge with a wide measuring range. For that purpose the electrode configuration and its operating parameters of a suitable gauge have to be optimised in this way that the contrary requirements are met with minor restrictions. With the help of computer simulations and experimental investigations a vacuum gauge was developed which combines the main features of both different types of ionisation gauges in one gauge construction. According to our ideas a gauge geometry similar to the ordinary Bayard Alpert gauge enables to measure the pressure in an extended operation range by using not only the pressure dependence of the formation of ions but additional the pressure dependence of the ion drift velocity in an electric field in the upper pressure range too. The upper pressure limit of this ionisation gauge can be shifted up to the rough vacuum range without changing the lower pressure limit of 10^‐9 mbar as usual for Bayard‐Alpert gauges. Thus, the operation range of this modified gauge cover nearly ten decades of pressure.     

High Detectivity Graphene‐Silicon Heterojunction Photodetector

A graphene/n‐type silicon (n‐Si) heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity, which can be utilized for the development of high‐performance photodetectors. However, graphene/n‐Si heterojunction photodetectors reported previously suffer from relatively low specific detectivity due to large dark current. Here, by introducing a thin interfacial oxide layer, the dark current of graphene/n‐Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n‐Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 10¹³ cm Hz^1/2 W^‐1 at the peak wavelength of 890 nm in vacuum, which is highest reported detectivity at room temperature for planar graphene/Si heterojunction photodetectors. In addition, the improved graphene/n‐Si heterojunction photodetectors possess high responsivity of 0.73 A W^?1 and high photo‐to‐dark current ratio of ≈10⁷. The current noise spectral density of the graphene/n‐Si photodetector has been characterized under ambient and vacuum conditions, which shows that the dark current can be further suppressed in vacuum. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors.     

Selbsttrocknende Membran‐ Vakuumpumpen für feuchte Gase

Diaphragm vacuum pumps have proved their superiority as dry‐running systems over other types of vacuum pumps in many applications, and in particular in the medical, analysis, and process engineering sectors, as well as in the chemical industry. These pumps deliver the media without any contamination of content, have a high gas tightness, and can be designed as chemically resistant with regard to those parts which come in contact with the media. Although they are in principle relatively insensitive towards condensates which may be formed or conveyed with the media, liquids in the vapor or gas flow may be the cause for the prolongation of a vacuum process, which can be considerable and is certainly undesirable. This applies in particular to applications involving multi‐user vacuum systems in chemical laboratories, which under certain circumstances may contain very substantial volumes of condensates, and to the use of pumps in steam sterilizers (autoclaves) and vacuum drying cabinets. These examples of applications will be considered in greater detail hereinafter. The condensates which occur in the pump head of a diaphragm vacuum pump cause interference in that — due to re‐evaporation during the suction cycle — they incur a substantial reduction in the usable suction capacity of the pump. This problem can be resolved by means of a drying system for diaphragm vac uum pump heads. The drying system makes use in this case of the pressure differential which pertains between the pump chamber and the atmosphere outside the pump. The function of the drying system can be described as follows: A solenoid valve vents the pump head in a cyclic manner, with the result that liquid in the pump head will be blown out, while the process vacuum in the process engineering system will continue to be maintained. Diaphragm vacuum pumps equipped with this drying system have provided excellent results, for example in the chem ical laboratory, both in individual diaphragm vacuum pumps as well as in multi‐user vacuum systems. Extremely good experience has also been gained in the evacuation of sterilizer autoclaves and vacuum drying cabinets with the use of diaphragm vacuum pumps fitted with the drying system. When using the drying system on steam sterilizer autoclaves, another favorable effect is also encountered: The vapor fraction in the pumping medium is cooled in the diaphragm pump head to below the evaporation or boiling temperature, with the result that the vapour condenses. This reduces its volume to a fraction of the initial value, which is the equivalent of an additional suction capacity, in the same manner as with a condenser. The condensate which occurs with this process is blown out of the pump heads by the drying system, and, as a result, can no longer cause interference due to re‐evaporation.     

Low‐Cost Manufacturing of Bioresorbable Conductors by Evaporation–Condensation‐Mediated Laser Printing and Sintering of Zn Nanoparticles

Currently, bioresorbable electronic devices are predominantly fabricated by complex and expensive vacuum‐based integrated circuit (IC) processes. Here, a low‐cost manufacturing approach for bioresorbable conductors on bioresorbable polymer substrates by evaporation–condensation‐mediated laser printing and sintering of Zn nanoparticle is reported. Laser sintering of Zn nanoparticles has been technically difficult due to the surface oxide on nanoparticles. To circumvent the surface oxide, a novel approach is discovered to print and sinter Zn nanoparticle facilitated by evaporation–condensation in confined domains. The printing process can be performed on low‐temperature substrates in ambient environment allowing easy integration on a roll‐to‐roll platform for economical manufacturing of bioresorbable electronics. The fabricated Zn conductors show excellent electrical conductivity (≈1.124 × 10⁶ S m^?1), mechanical durability, and water dissolvability. Successful demonstration of strain gauges confirms the potential application in various environmentally friendly sensors and circuits.     

Palm‐Sized Ag+ Ion Emission Gun Operated at Room Temperature in Non‐Vacuum Atmosphere

Ion implantation is an effective method for changing surface properties and inducing various functionalities. However, a high vacuum is generally necessary for ion implantation, which limits the range of applications. Here, we describe a palm‐sized Ag⁺ ion emission gun produced using a solid electrolyte. AgI–Ag₂O–B₂O₃ glass, known as a super‐ion‐conducting glass, has a Ag⁺ ion conductivity higher than 5 × 10^?3 S cm^?1 at room temperature. In addition, the melted glass has suitable viscous flow, and a sharp glass‐fiber emitter with a pyramid‐like apex can be obtained. Ag⁺ ion emission is observed from the tip of the glass fiber at accelerating voltages corresponding to electric fields above 20 kV cm^?1, even at room temperature in a non‐vacuum atmosphere. Ag nanoparticles of size 50–350 nm are precipitated on a Si target substrate. Other glass components such as boron and iodine are not detected. Electrochemical quartz crystal microbalance (EQCM) measurements show that the mass of Ag nanoparticles estimated from the emission current using Faraday's law of electrolysis is in good agreement with that estimated from the QCM frequency shift.

     

Process methodology for the small scale production of m6N5 purity zinc using a resistance heated vacuum distillation system

Ultra high purity Zn (m6N5) was obtained through triple vacuum distillation using an m4N5 Zn as input material. High-volatile impurities were removed from the zinc matrix by vacuum evaporation, while traces having lower volatility than the matrix remained in the residual material after finishing of the entire purification process. The time required for the removal of the main high-volatile impurity (Cd) was monitored using a connected gas source mass spectrometer. During distillation the Zn vapor of the distillate was condensed on the cap of a glassy carbon crucible which was water cooled by a movable copper block. The temperatures were optimized for the removal of the volatiles and for the distillation process using vapor pressure data. High resolution glow discharge mass spectrometry was applied for the analysis and purity evaluation of the distilled and input zinc. The analysis confirmed the reduction of the metallic impurities from 43 mg kg⁻¹ to 0.5 mg kg⁻¹ (m6N5) after three consecutive vacuum distillations. An increase in the grain size and a decrease in the micro-hardness were observed for the purified Zn material.     

Modeling of the evaporation of liquids and condensation of their vapor during distillation

This paper considers the evaporation process in an evaporator–connecting tube–condenser system under conditions such that the evaporation rate is determined by the evaporation and condensation mechanisms and the hydraulic resistances of the evaporation and condensation compartments and connecting tube. We present a mathematical model and numerical simulation results that demonstrate quantitative patterns of a steady-state evaporation process in a closed evaporation–condensation system. For a particular example of selenium vacuum distillation, we have determined the evaporation coefficient of selenium from experimental data on the temperature dependences of the selenium evaporation rate and saturated vapor pressure.     

真空蒸馏法从粗铟中脱除镉锌铊铅的研究

利用纯度为99.7%粗铟为原料,采用真空蒸馏的方法从粗铟中直接脱除镉、锌、铊、铅。分别进行了蒸馏温度、蒸馏时间、投料量等的条件实验。结果表明,控制真空度1~5 Pa,蒸馏温度950℃,蒸馏120 min,可将粗铟中镉、锌、铊、铅可除至6N高纯铟要求。并且以实验结果为依据计算出产物中各种杂质的挥发系数、分离系数、活度系数,对铟的热力学数据的完善有一定的参考意义。     

Epitaxial Growth of 6 in. Single‐Crystalline Graphene on a Cu/Ni (111) Film at 750 °C via Chemical Vapor Deposition

The future electronic application of graphene highly relies on the production of large‐area high‐quality single‐crystal graphene. However, the growth of single‐crystal graphene on different substrates via either single nucleation or seamless stitching is carried out at a temperature of 1000 °C or higher. The usage of this high temperature generates a variety of problems, including complexity of operation, higher contamination, metal evaporation, and wrinkles owing to the mismatch of thermal expansion coefficients between the substrate and graphene. Here, a new approach for the fabrication of ultraflat single‐crystal graphene using Cu/Ni (111)/sapphire wafers at lower temperature is reported. It is found that the temperature of epitaxial growth of graphene using Cu/Ni (111) can be reduced to 750 °C, much lower than that of earlier reports on catalytic surfaces. Devices made of graphene grown at 750 °C have a carrier mobility up to ≈9700 cm² V^?1 s^?1 at room temperature. This work shines light on a way toward a much lower temperature growth of high‐quality graphene in single crystallinity, which could benefit future electronic applications.     

Herstellung funktionaler organischer Dünnschichten durch Vakuumverdampfung

Depositing of functional organic thin films by vacuum evaporation Material evaporation under high or ultra‐high vacuum conditions has been a well known method of thin film coating since nearly a hundred years. Since discovery of semiconducting organics in the 1970s and 1980s, this technology has been increasingly applied to deposit organic molecular compounds. At the moment especially materials for organic LEDs (OLEDs) and for thin‐film solar cells are in the focus of interest. While organics evaporation makes use of advantages of high‐vacuum coating (purity, compatible processing, masking etc.) there are also dedicated demands on process control coming up. The article describes basic requirements, capabilities of present temperature‐controlled evaporation sources, material‐related features, as well as typical applications.     

Plasmachemische Gasphasenabscheidung und Plasmaätzen bei Atmosphärendruck

Plasma enhanced Chemical Vapour Deposition and plasma etching at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are, e.g. coatings to achieve an improved corrosion and scratch protection, or surface cleaning and texturising. Since these processes, however, usually take place in vacuum, they are unfortunately not applicable for large area industrial use. Plasma enhanced CVD processes at atmospheric pressure enable the deposition of functional coatings on components and semi‐finished parts with in a continuous air‐to‐air process without the use of expensive vacuum systems. By their integration into in‐line production processes the substrate handling and the coating costs are definitely reduced. A thermal plasma source, basing on a linearly extended DC arc discharge at atmospheric pressure, has been tested for the deposition of silicon nitride at substrate temperature of less than 300° in a continuous PECVD process. Furthermore this source has been tested for plasma‐chemical etching and texturising of silicon as well.     

Technisch‐wirtschaftlicher Review der Herstellung tetraedrisch‐amorpher Kohlenstoffschichten durch Lichtbogenverdampfen

Technical and economical review of the production of tetrahedral‐amorphous carbon films by vacuum arc evaporation Due to the high energy of the depositing species, vacuum arc evaporation is suited for the production of tetrahedral‐amorphous carbon coatings (ta‐C). As besides, the process allows for high deposition rates, it seems to be ideal for the deposition of ta‐C in industrial mass production. However, during the evaporation process inevitably macroparticles are formed, which also deposit on the parts to be coated, degrading the coating properties considerably. Therefore, measures are necessary in order to counter the formation and/or deposition of these particles. The following article intents to give an overview of possible measures and to subject them to a technical and economical evaluation in regard to their application in industrial mass production.     

Removal of barium impurities from selenium by vacuum distillation

We have studied the behavior of barium impurities in the form of BaF₂ and BaO during vacuum distillation of selenium. The effective Ba partition coefficient is shown to depend on the impurity concentration and evaporation rate. At initial barium contents in the range 3 × 10⁻³ to 2 × 10⁻⁵ wt %, the effective Ba partition coefficient is 600 and 1.5 at distillation rates of 4.7 × 10⁻⁶ and 1.5 × 10⁻³ cm³/(cm² s), respectively. The chemical form of barium has no significant effect on its partition coefficient. Using a Rayleigh distillation equation, we have determined the equilibrium partition coefficient and the thickness of the diffusion boundary layer in the system.