Open Bath Research Articles

Synthesis and characterization of porous ZnO nanoparticles by hydrothermal treatment of as pure aqueous precursor

The presence of the complexing agents in the growth solution poses risk of the unintentional doping in the synthesized product and hence is likely to adversely affect the intrinsic properties. Herein we report the synthesis of ZnO nanoparticles with porous microstructure using pure aqueous precursor. Crystalline ZnO nanoparticles were synthesized by thermal treatment of aqueous solution of zinc acetate in an open bath. The size of the nanocrystals was controlled by changing the initial precursor concentration. The structural and optical properties of the synthesized nanocrystals were analyzed by X-ray diffraction, high resolution transmission electron microscopy, UV–vis absorption and room temperature photoluminescence measurement techniques. The TEM and UV–vis spectral signature analyses confirmed the formation of dispersed single crystalline ZnO nanoparticles. The nanopowders were found to have disordered mesoporous structure. The synthesized nanocrystals exhibited characteristic band edge emission as well as to surface defect related deep level visible luminescence.

Development of a new radiation detector utilizing carbon nanotube as anode

A new gas-multiplication radiation detector utilizing carbon nanotube (CNT) as anode is proposed. With CNT anode, a very compact radiation counter with a good spatial resolution might be built. Two test chambers have been built and are being tested. Each detector body, a chamber with a volume of 100 cm - 3 , is purged of air beforehand and then supplied with argon gas. At room temperature, the chamber works as a traditional proportional counter filled with argon gas. The chamber can be dipped in an open bath of liquid argon (LAr) and cooled to the vapor point of argon, 87 K. Within 1 h of deposition, the chamber will be filled with LAr. The background noise has been reduced to a level that the charge produced by 60 keV photons from 241Am is successfully detected, although a gas-multiplication around CNT is not yet confirmed.

Experimental Study of Boiling Phenomena of Liquid Nitrogen Around a Thin Wire Heater in Open Bath and Inside Capillary Tubes

The heat transfer characteristics of liquid nitrogen around a thin wire heater immersed in open bath and confined in glass capillary tubes were experimentally studied in the present article. A thin wire heater of 50 μm in diameter, which was placed in open bath and in the center of the capillary tubes with the diameters of 0.24–3.8 mm, was employed as both the heating element and thermometer. The temperature of the thin wire heater was measured to evaluate the heat transfer performance. The experiments were conducted at the inclination angles from 0 to 90° with an interval of 30°. It was found that the presence of the capillary tube could decrease the superheat of the thin wire heater in the nucleate boiling regime when the diameter of the capillary tube was larger than 0.6 mm. The visualization pictures showed that the boiling appearance in the capillary tube was very different from that in open bath. The inclination angle and the diameter size of the capillary tube have significant effect on the critical heat flux (CHF).

Experimental Investigation of the Heat Transfer Characteristics of Liquid Nitrogen in the Capillary Tubes

The heat transfer characteristics of liquid nitrogen in both capillary tubes and open bath are experimentally investigated in the present study. The experiments are conducted by using a thin wire heater as both the heating element and the thermometer under the inclination angles of 0deg to 90deg with the interval of 30deg. The diameters of the capillary tubes are 3.8 mm and 1.2 mm. It is found that the nucleate boiling heat transfer can be enhanced with the capillary tube in some cases. The heat transfer enhancement increases with the decrease of the diameter of the capillary tubes. The visualization shows that the appearance of the boiling phenomenon in the capillary tube is different from that in the open bath. The measurement results show that the critical heat fluxes (CHFs) were affected by the inclination angle and the diameter of the capillary tube

Reduction of occupational exposure to perchloroethylene and trichloroethylene in metal degreasing over the last 30 years: influences of technology innovation and legislation.

Occupational exposure to trichloroethylene (TRIC) and perchloroethylene (PERC) in metal degreasing is analyzed by calculating airborne concentrations for a large set of possible exposure scenarios (Scenario-Based Risk Assessment, SceBRA). Different types of degreasing machines ranging from open-top machines used until the 1980s to closed-loop nonvented machines used since the 1990s are investigated; the scope of the study is Germany. Concentrations are calculated for different kinds of releases (emissions from open baths, leakage, release of contaminated air during loading and unloading) with a dynamic two-box model for the near-field and the far-field. The concentration estimates are in good agreement with measured data. The airborne concentrations are compared to maximum workplace concentrations (MAK values). The full set of scenarios shows for which situations MAK values were exceeded and how the transition to newer degreasing machines reduced the occupational exposure by more than one order of magnitude. In addition, numbers of exposed workers are estimated for different years. While more than 25,000 workers in the near-field were exposed to TRIC and PERC in 1985, the number is below 3000 since 1996, which is mainly due to technology changes, rationalization, automatization, and replacement of TRIC and PERC by nonchlorinated solvents.

Kinetic parameters of silver electrodeposition from nitrate melts

The system Ag/KNO3–NaNO3–AgNO3is studied in an open bath in air by various experimental methods. The limiting diffusion currents of the silver electrodeposition are determined by a galvanodynamic method at various linear current sweep rates. The diffusion coefficient of Ag+ions in equimolar KNO3–NaNO3melt is determined by a potentiodynamic method at linear potential sweep. The exchange currents on a silver support are determined by the method of two current pulses.

Tip heater for minimum quench energy measurements on superconducting strands

Superconducting strands can be characterized by their minimum quench energy (MQE), i.e. the minimum heat pulse needed to trigger a quench in operation conditions (field, temperature, current), in the limit of a (temporally and spatially) /spl delta/-shaped disturbance. The sub-mm//spl mu/s range of perturbation space has only been achieved using the electrical graphite-paste heater technique. The present work has put this technique into practice for the strands of the LHC main magnets, which are designed to operate at 1.9 K in peak fields of up to 9 T. No way has been found yet to calibrate MQE measurements. To make relative statements on the MQE of different samples possible, the reproducibility of the measurements was emphasized. First heater prototypes did not come up to this stipulation. Finally the tip-heater configuration was found to meet the requirements. It generates a heat pulse in a thin resistive graphite paste deposit on top of a small tip that is pressed against the sample with a clamp. The clamp guarantees a maximum of exposure of the sample to the surrounding cryogen. The most striking aspect of repeated measurements on a reference sample is that in open bath conditions the MQE as a function of transport current in subcooled helium can reach hundred times the corresponding value in adiabatic conditions (i.e. with the sample potted in a low conductivity medium). This extraordinary cooling performance of superfluid helium, predicted by many has rarely been shown in superconductor stability experiments.

Electrochemical oxidation of cyanide in the hydrocyclone cell

A diluted electroplating cyanide rinse water has been used to test the use of the hydrocyclone cell (HCC) in batch recycle mode of operation for the simultaneous oxidation of cyanide during the electrodeposition of silver. The results obtained in this work with regard to the final products, current efficiency and the number of transferred electrons per CN − helped to establish a probable reaction scheme. According to this, the process occurs mainly with one-electron transfer, through cyanate and cyanogen as intermediate species. Meanwhile, under conditions where the electrolyte circulates in an open bath and flows successively through the cathodic and the anodic compartments, as in the case of the HCC system, the cyanate could be produced by the direct oxidation through air and/or generated peroxide and CN − could be lost as HCN (g).

Particle Deposition, Adhesion, and Removal

Physical forces control particle deposition on wafers in virtually all manufacturing environments: open air, liquid baths, and subatmospheric chambers. Physical forces also often dominate particle adhesion and removal. In aerosol systems, gravity and diffusion are important universal mechanisms contributing to particle deposition velocity (= particle flux to a surface/particle concentration adjacent to that surface). Under appropriate conditions, electrical and thermal forces are also important and sometimes dominating. Both these conditional mechanisms can be introduced so as to minimize particle deposition velocity and thus protect wafers from particulate contamination. In liquid systems where particle and liquid densities are similar, gravity is a less important particle deposition mechanism. Convective diffusion remains an important mechanism but typically contributes a much lower deposition velocity than in aerosol systems (particle diffusion coefficients are smaller in liquids than in gases). In many liquid systems, electrical forces, arising from particle and surface charging by ion adsorption from the liquid or ionization of surface groups, dominate particle deposition by introducing electrostatic double layer repulsion. The primary force binding a particle to a surface is van der Waals attraction which is universal and dominating when separation distances between a particle and a surface decrease below I to 2 nm. Van der Waals attractive forces are lower in liquids than in gases so particles are easier to remove in liquids, partly because of this reduced adhesion. Physical forces—centrifugal, hydrodynamic, vibrational—typically dominate particle removal technology as well. These forces depend directly on fluid density and hence are larger in liquid systems than in gases, another reason why liquid systems remain more successful at particle removal than dry methods.

Transient subcritical and supercritical helium heat transfer in an open bath and gaps

Transient heat transfer processes in subcritical and supercritical helium were investigated during the application of a heat pulse to a very thin (∼ 10 −3 mm) nickel film deposited on glass substrate. The nickel film served as a simultaneous heater and thermometer. Measurements of time-varying heated surface temperatures were taken in order to obtain the heat transfer rate in an open bath and gaps filled with helium. All experiments were performed at pressures between 100 and 250 kPa (0.44 < p/pc < 1.10).

Metallurgy of open-bath plasma processes

Abstract

Heat transfer and stability characteristics of cable bundles in He I and subcooled He II

Results from two experiments aimed at understanding the stability of cabled composite superconductors are reported. The first is a heat transfer study of stainless steel tubular bundles. The peak heat flux from these test sections is investigated as a function of number of bundle tubes and gap between each tube. Experiments are performed in both He I at 4.2 K and subcooled He II at approximately 2 K. Results indicate that the peak heat flux is supressed substantially as the gap between tubes is reduced. With zero gap the surface averaged heat flux is only about 20% of that achieved with large gaps roughly equivalent to an open bath. The second experiment consists of a stability measurement on a bundled composite conductor. The test section is made up of a 66.3 cm length of a 7 wire bundle. The six outer wires are copper-NbTi composites while the core is an insulated resistance wire. Normalization of the conductor, either achieved by exceeding I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> or by pulsing the heater, is detected by voltage taps across the inductively wound test section. Stability measurements made in both He I and He II are correlated with the heat transfer results in the first experiment.

A pipetting device for staining electron microscopic grids.

SUMMARYA simple device for staining EM grids in small batches is described. The device easily produces high quality well‐stained grids and is adaptable to most stain techniques.The most common method for staining EM grids is certainly the droplet technique (Kay, 1965) in which grids are individually floated, section‐side down, on droplets of stain. Since this requires repeated handling, electron microscopists have devised various methods for batch staining. These generally fall into two categories: partitioned grid boxes which are either immersed in, or filled with stain (Sjostrom et al., 1973; Polysciences Inc., EM Multiple Grid Staining Unit*), and clamp arrangements which grip a number of grids while they are placed in various baths (Baratz, 1976; Fisher, 1972; Gorycki, 1966; Hiraoka, 1972; Robertson &amp; Roberts, 1972; Springer, 1974). These types of devices increase contrast and detail, over the droplet technique, by staining both section surfaces (Shalla et al., 1964). However, these require large and/or open baths of stain which are wasteful and prone to contamination. Contamination is especially critical with lead stains which precipitate lead carbonate on exposure to air (Peachy, 1959).Recently, Forsdyke (1979) described a flow‐through tube for staining. The device consists of an S‐tube with an internal grid holder. Stains are introduced into the tube by siphon. This arrangement greatly reduces the amount of stain required as well as the air‐stain interface. This paper details an adaptation of Forsdyke's device designed for easier handling, flexibility in use, and further improved staining quality.The device described herein is used to draw a few millilitres of stain directly from their containers, thus reducing contamination, air exposure, and waste. The device is used as the first receptacle for freshly cut sections on grids. The grids remain in the closed device until all sectioning and staining is completed. Since the device is closed all the sections remain damp, including those first prepared, until stained. In our laboratory we have observed that epoxy embedded tissue sections stain more evenly and intensely with uranyl acetate and lead citrate when kept moist prior to staining. Shalla et al. (1964) also reported improved staining of moist sections for another stain and different embedding plastics.

Anodizing Aluminium in Molten Nitrates

SummaryA preliminary, but fundamental study has been undertaken of the anodizing of pure aluminium in molten eutectic mixtures of alkali metal nitrates. These media have sufficiently low melting temperatures, ∼ 100°-140°C, to ensure that high strength alloys and aluminium clad alloys can be safely anodized without significant over-ageing. However, they are very hygroscopic even at these elevated temperatures and the presence (or absence) of dissolved water in the melt has been found to affect drastically the morphology of the anodic oxide films grown onto the substrate, as shown by a series of electron micrographs taken under a range of experimental conditions. Thin, amorphous alumina films were formed in anhydrous melts at all voltages below the breakdown voltage. In contrast, in wet melts, such as might pertain to open bath operation, amorphous films were evident only at > 50 V. Thick white friable films were obtained at lower voltages. The growth of the thin amorphous films was accompanied by significant changes in the luminium substrate microstructure; as yet, this remains unexplained.

The continuous measurement of molten steel temperature in the open hearth bath

The continuous measurement of molten steel temperature in the open hearth bath

The oxygen content of the slag and the yield of liquid steel in blowing an open hearth bath with oxygen

The oxygen content of the slag and the yield of liquid steel in blowing an open hearth bath with oxygen

BIAXIAL DEFORMATION OF SPHERULITE AND MULTI-LAYER STRUCTURE IN THE BIAXIALLY STRETCHED POLYPROPYLENE FILMS

In this report effects of spherulite size and of various stretching processes on the characteristics of the deformation and fracture of polypropylene spherulites were investigated at both the room and higher temperature in connection with the stretchability of films. The exfoliatical property of biaxially stretched film is discussed in terms of spherulite deformation.Film containing spherulite of various sizes were prepared by hot-press technique under the various cooling conditions. These films were stretched with the film-stretcher, in the open bath or the hot-air bath. The following stretching methods were adopted: uniaxial stretchings under the free or constant width, and two-way successive or simultaneous biaxial stretchings.The biaxial stretchability is higher in the films with small size spherulites than in the films with large size.The deformation and the fracture mechanisms of spherulite could be phenomelogically classified as follows: (1) brittle break-down, (2) fracture with the cleavage of interfacial boundary, (3) uniaxial plastic deformation, (4) deformation with necking, (5) deformation with pleating, (6) deformation into fibril structure, and (7) biaxial plastic deformation.The characteristis of the deformation and the fracture of spherulites are summarized in Table 1.We have deduced that the appearance of exfoliatical property as mica was owing to the multilayer structure of the spherulite and the planar orientation of molecular chains and crystalls in the film.

A Thyristorized Proportional Controller for a Constant Temperature Bath

The paper deals with the design consideration and the working principle of a thyristorized proportional temperature controller for an open top bath with ordinary glass wool insulation. A thermistor is used as a sensing element and a temperature stability better than ±0·01°C. has been achieved at any set temperature from ambient to 100°C. An expression for open loop sensitivity of the controller has been derived and the theoretical sensitivity using actual circuit parameters has been compared with that one obtained experimentally.

Life of refractory structures during intensive oxygen blow of the open hearth bath

When the oxygen blow intensity in a bath of a 250-ton open-hearth furnace was increased (13–15 m3/h·ton) the rate of wear of the roof brick and the irregularity of the erosion of the main roof were greater, the resistance of the roof lower, and the specific consumption of brick for building it greater, than when the oxygen was fed to the flame.

A Canadian plant for the direct reduction of iron

The Canadian company "Quebec South Steel Corpora t ion" has recent ly announced the proposed construction of a steel plant near Montreal. Construction on the new plant should start in the early part of 1961. The planned capac i ty of the plant is 91 thousand tons of iron and semifinished product per year; there will be provision for future expansion. The main raw mater ia l will be magnet i te ores from the Ironsides Deposit, situated 7 km from Ottawa. The reserves of ores from this deposit with a 47% iron content will provide normal operat ion of the plant for about 17 years. In addit ion, ores will be used ~om the group of deposits at the Big Three Lake (Quebec Province). The reserves of ores from this group of de posits is compara t ive ly smal l (14-22 mi l l ion tons). The average iron content in the ore is 40-50%. It is expected that the plant wil l operate for 330 days in the year with an average output of 975 tons of meta l per day. This pIant wil t be the first on the American continent to use the so -ca l l ed "S t ra teg ic -U@" process for the d i rec t reduction of iron. An exper imenta l plant working with this process is operating at Niagara Fails. About 10 thousand tons of various ores have been processed in this plant . At the exper imenta l plant at Niagara Fails there are three t r iple-phase modernized e l ec t r i ca l "Volta" furnaces of 1000 kv-a , a rotating roasting furnace of d iameter 1872 ram, length 24.4 m,f i t ted with a dust trap and vent i la t ion device and operating on gas or off,and also auxi l iary equipment . In the "St ra tegic-Udy" process a mixture of iron ore, flux and carbon reducing agent is continuously fed into a rotating furnace in which the materials are dried, the volat i les are removed and the iron is par t ia l ly reduced from the ore. Depending on the type of ore, the furnace temperature is 1100-1300 ~ If the temperature system is distributed it is possible to have sintering of the charge and the formation of incrustations on the inner surface of the furnace. To ensure the desired degree of reduction of the iron from the ore the required amount of carbon is introduced into the roasting furnace. In addition, gas obtained in the e lec t r ica l inching furnace is brought i n , The carbon monoxide in the gas is fully used up in the ini t ia l stages of the reduction. To save the thermal and e lec t r i ca l power, the hot mass leading the roasting furnace passes through a special feeder di rect ly into the fusion zone of the e lec t r ica l furnace. In the e lec t r ica l furnace the "S t ra teg ic -U@" process is set up on the principle of the so-ca l led open bath ("floating charge"). The height to which the e l ec trode is raised is fixed in dependence on the conditions: from 12.5 cm above the level of the mohen slag to 87.5 cm below this level . In the bath of the furnace, a constant e l ec t r i ca l resistance is provided which makes it possibIe to operate with the maximum power of the furnace. The carbon reacts compara t ive ly quickly with the iron oxides which were not comple te ly reduced in the roasting furnace. Because of this, good quali ty meta l is obtained from the e lec t r ica l furnace. The /u rnace output is fairly high. The meta l and slag are tapped per iodica l ly from the e lec t r ica l furnace in the usual way. The main advantage of the "Strategic-Udy" process is its continuity from the moment the ore is charged until the finished meta l is tapped, In this process the mass leaving the roasting furnace is not cooled ; this mass does not have to be ground or have magnet ic separation, nor is it necessary to sinter the semifinished product obtained from the separators.