Liquid Potassium Research Articles

Modeling the molecular dynamics of liquid metals at high pressures: Liquid potassium

A way of building potassium models by molecular dynamics using the embedded atom model (EAM) is developed. The contribution from pairwise interaction is presented as power series at an interpartial distance. Embedded potential parameters are determined by the experimental dependence of pressure on volume for a static compression of potassium at 300 K to a pressure of 53 GPa (potential A). By using potential A to describe shock compression and choosing the appropriate temperature at given degree of compression (up to 40000 K at compression to 0.29 of initial volume) it is shown that the model pressure can be made equal to the pressure indicated by the Rankine-Hugoniot relations. The model energy is lower than the actual energy determined by the relations, and the difference in energies increases with temperature almost linearly; such growth corresponds to an excess average heat capacity of about 11.6 J/(mol K), compared to the model heat capacity. It is established that the reasons for this divergence are the inability of the EAM potential to describe the temperature dependency of metal properties precisely, and the appearance of an energy contribution upon heating that is dependent on temperature but not on atom coordinates. Adding another summand to the potential energy (which is dependent on temperature only) allows us to match the heat capacities of real potassium and the models. The dependence of potassium’s melting temperature on pressure is calculated. The calculated melting temperature at 41.2 GPa is 1231 K. Additional data (e.g., the actual temperature on the Rankine-Hugoniot curve and precise quantum mechanics calculations of heat capacity at extreme conditions) is required to eliminate potential ambiguity.

Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons

► Proposed hybrid solar thermoelectric (HSTE) system using a thermosyphon for heat transfer to a bottoming cycle. ► Developed and optimized the HSTE model showing efficiencies as high as 52.6%. ► Comparable efficiency for low cost thermosyphons with k as low as 1.2 W/mK and C < 4 suns. ► Proposed five bottoming cycle applications for potential HSTE integration. We present the modeling and optimization of a new hybrid solar thermoelectric (HSTE) system which uses a thermosyphon to passively transfer heat to a bottoming cycle for various applications. A parabolic trough mirror concentrates solar energy onto a selective surface coated thermoelectric to produce electrical power. Meanwhile, a thermosyphon adjacent to the back side of the thermoelectric maintains the temperature of the cold junction and carries the remaining thermal energy to a bottoming cycle. Bismuth telluride, lead telluride, and silicon germanium thermoelectrics were studied with copper–water, stainless steel–mercury, and nickel–liquid potassium thermosyphon-working fluid combinations. An energy-based model of the HSTE system with a thermal resistance network was developed to determine overall performance. In addition, the HSTE system efficiency was investigated for temperatures of 300–1200 K, solar concentrations of 1–100 suns, and different thermosyphon and thermoelectric materials with a geometry resembling an evacuated tube solar collector. Optimizations of the HSTE show ideal system efficiencies as high as 52.6% can be achieved at solar concentrations of 100 suns and bottoming cycle temperatures of 776 K. For solar concentrations less than 4 suns, systems with thermosyphon wall thermal conductivities as low as 1.2 W/mK have comparable efficiencies to that of high conductivity material thermosyphons, i.e. copper, which suggests that lower cost materials including glass can be used. This work provides guidelines for the design, as well as the optimization and selection of thermoelectric and thermosyphon components for future high performance HSTE systems.

Optimal algorithm for constructing the embedded atom method potential for liquid metals

An optimal algorithm has been developed for calculating the embedding potential in the embedded atom method (EAM) with the aim of describing not only the temperature-dependent density of a liquid metal but also its energy up to its critical temperature. The algorithm is based on the unification of the form of the potential and calculation of its parameters from known density and energy data for the liquid metal. The basis of the algorithm is the use of least squares fitting of the pressure and energy in molecular dynamics simulations to data for a series of states of the liquid along an isobar. To describe liquid potassium, the pair contribution to the potential is represented by a power series in interparticle distance. Data on the properties of potassium at 343, 473, 723, 1000, 1500, 2000, and 2200 K were used. The embedding potential was expanded in terms of 1 − ρ, where ρ is the effective electron density in the EAM. In least squares fitting, fifteen equations were included: eight for the energy and seven for the pressure. The number of unknown coefficients was seven. Iterative calculations allow one to find optimal expansion coefficients and construct equilibrium models through molecular dynamics simulations. It is shown that the discrepancy in energy between simulations and the real metal at high temperatures can be eliminated by taking the electron excitation energy into consideration. The difference between the actual energy of a metal and the energy obtained in EAM simulations is very close to the contribution of the electron heat capacity.

English

A foliar application of soluble silicon (liquid potassium silicate) was tested for the control of powdery mildew of tomato for 2 years in the field conditions on susceptible cultivar Alida F1. Powdery mildew in field-grown staked tomato, caused by Leveillula taurica was significantly controlled by a foliar spray of either K2SiO3 or Bayleton + sulfur. Potassium silicate applied on a 12 day schedule was highly protective against natural infection by the mildew fungus in the field conditions. The disease severity indexes (DSI) were 77.5 and 74.7% in control plots in 2006 and 2007, respectively, and were significantly different (P < 0.05) from those in the K2SiO3 plots with 5.8 and 4.6% in 2006 and 2007, respectively. Potassium silicate concentration (1 g/1 L water) used in the present study were not phytotoxic to plant foliage. The inhibitory effectiveness of potassium silicate makes it a useful biocompatible fungicide and possibly ideal foliar fertilizer for disease control in the field.

EFFECT OF DIFFERENT POTASSIUM FERTILIZER RATES AND FOLIAR APPLICATION WITH SOME SOURCES OF POTASSIUM ON GROWTH, YIELD AND QUALITY OF CARROT PLANTS (Daucus carota L.)

Two field experiments were carried out at Barramoon experimental farm, Hort. Res., Institute, Dakahlia Governorate, Egypt, during the two winter seasons of 2007/2008 and 2008/2009 to study the effect of different rates of potassium fertilization (0, 25, 50 and 75 kg K2O /fad.) as potassium sulfate in addition to foliar application by water (control), liquid potassium (3 ml/ L), potassium borate citrate (3 ml/ L) and NPK- humate (3 ml/ L) and their interaction on production and quality of carrot cv. “Chantenay Red Core. Potassium foliar applications were made 3 times at 20 days intervals with the same doses during the growing period (20, 40 and 60 days after sowing). The highest potassium fertilization rate (75 kg K2O /fad.) gave the tallest shoot, the highest number of leaves per plant and the highest fresh weight of shoots as well as the highest total yield per fadden in both seasons. Also, the obtained results reported that the root measurements expressed as (root length, root diameter, root weight, TSS and carotenoids content, as well as leaves chemical composition (N, P and K concentrations) were increased with increasing potassium fertilization rate in both seasons. On the other hand, spraying carrot plants with potassium humate at a rate of 3 ml/ L markedly increased vegetative growth, yield, root quality and chemical composition in both seasons. The favorable effects of the potassium on the growth, total yield and root parameters were obtained when carrot plants fertilized with 75 kg K2O /fad. as potassium sulfate plus foliar application of potassium humate (3 ml/ L) followed statistically by 75 kg K2O /fad. with foliar application of potassium borate citrate (3 ml/ L) in both seasons.

On the occurrence of two-stage combustion in alkali metals

Pool combustion experiments have been conducted for three alkali metals, namely, lithium (Li), sodium (Na) and potassium (K). Lithium and sodium are found to show a two-stage combustion behaviour which has been reported for a number of other metals. Here, the combustion is characterized by a sporadic rise in the flame temperature accompanied by a bright glow. Potassium is found to burn in vapour phase combustion in all cases without sporadic temperature excursions. In the present study, this different burning behaviour is attributed to the formation of thick oxide agglomerates in the case of Li and Na through the pores of which oxygen/metal vapour has to diffuse for combustion to occur. In such cases, a second stage of vapour phase combustion occurs when the oxide agglomerate is heated sufficiently so that the vapour of the liquid metal trapped in the pores breaks through to the surface. In the case of potassium, a self-cleaning mechanism, attributable to the high solubility of the metal oxides in liquid potassium and the relatively low melting point of the potassium oxides, enables a clear liquid surface to be exposed throughout for vapour phase combustion to prevail always. Recorded temperature profiles, SEM analysis of the oxide agglomerates as well as calculations of the metal–oxygen equilibrium thermo-chemistry for the three metals confirm this scenario.

Broadband Coverage Optical Sensor with Liquid Crystalline Materials and Pyroelectrics

ABSTRACTBy utilizing a thin layer of supertwisted liquid crystal and potassium sodium strontium barium noibate crystal material with excellent pyroelectric effect, a broadband coverage optical sensing concept was proposed. Coating the pyroelectric substrate with a carbon layer of excellent absorption in the frequency range of interest, the intensity of an incident mid- or far-IR radiation can be converted to a corresponding intensity variation of a reflected near-IR beam via optical modulation of the liquid crystal film. As the result, the spatial intensity distribution of an incident mid- or far-IR radiation can thus be perceived directly by a low-cost semiconductor sensor/ sensor array. With flexible design of wave collecting arrangement, the broadband coverage sensor is suitable for viewing IR-giving objects with a large field-of-view.

THE INFLUENCE OFAPPLICATION METHODS OF POTASSIUM FERTILIZATION ON GROWTH, PODS YIELD AND ITS QUALITY OF PEA PLANTS

Two field trails were conducted out during the season of 2006/2007 and 2007/2008 to study the influence of soil dressing of potassium fertilizer at rates of 100, 200 and 300 kgs./fed. as potassium sulphate (48.5 % K2O) as well as foliar application of liquid potassium contained K2O 36.5 % and sulphure 26.0 % as twice and/or 3 times) on growth, yield and its quality of pea plant. The important findings are as follows: 1. All plant growth parameters recorded their highest values when pea plants received 300 kgs. /of potassium sulphate. The increments in fresh and dry weight of whole plant over that plants which supplied 100 kgs/fed. amounted by 34.9 and 56.9 respectively in 1st season and by 48.6 and 49.3 % for the same respective in 2nd season. Also that pea plants which received liquid potassium 3 time by 10 day intervals gained the vigor plant growth. 2. Pea plants which fertilized by the highest rate of K (300 kgs./fed.) recorded an increase in total and early pods yield over than that plants received medium and low potassium level. The enhancement in total pods weight amounted by 10.01, 34.4 % in 1st season and by 16.1 and 31.1 in 2nd one respectively. 3. The best physical quality of pea pods expressed as average number/plant length and diameter recorded their highest significant values when soil was dressed by 300 kgs./fed. Of potassium sulphate. Moreover, foliar application of pea plant by liquid potassium 3 times gained the heaviest total and early pods yield as well as its best physical quality of pods. 4. With increasing potassium fertilizer of soil dressing and/or the numbers of liquid spraying gained an increase in the nutritional values of pea pods as expressed by protein and carbohydrate content as well as N, P and K.

UV-B RADIATION FOR CONTROL OF STRAWBERRY POWDERY MILDEW

Powdery mildew of strawberry (Fragaria × ananassa) caused by Sphaerotheca aphanis var. aphanis is one of the serious airborne diseases in Japan. We have used various methods in an attempt to control this disease. Among these methods, liquid potassium silicate was found to be a very useful liquid fertilizer for suppressing powdery mildew. However, various types of cultivating style are used in strawberry production, and it is difficult to apply the silicate using each cultivating type. Recently, we focused on the use of UV-B radiation as an alternative method of disease control. Many reports have described how UV-B induces plant resistance against many stresses. However, there are no examples of its practical application in horticulture. In the present study, radiation conditions were determined in order to prevent the disease in an experimental booth. The suppressive effect of UV-B radiation against powdery mildew was evaluated in a vinyl house from October to June using three susceptible cultivars: 'Akihime', 'Toyonoka', and 'Sachinoka'. All cultivars were protected from powdery mildew by UV-B radiation. For example, in 'Akihime' control plots, 41% of fruits were diseased, whereas in the UV-B plots, 0% of fruits were diseased. Similar results were obtained for the other cultivars. In a laboratory experiment, RT-PCR analysis revealed that UV-B radiation induced the expression of a disease-resistance gene (the gene encoding the PR-protein). These results indicate that UV-B prevents powdery mildew development by inducing disease resistance in the plants as one of its modes of action.

The use of the embedded atom model for liquid metals: Liquid potassium

The method for calculations the embedded atom potential for liquid metals based on the diffraction data on the structure close to the melting temperature was applied to potassium. The embedded atom potential parameters were adjusted using the data on the structure of potassium at 343, 473, and 723 K and the thermodynamic properties of potassium at temperatures up to 37240 K. The use of the molecular dynamics method and the embedded atom potential gave close agreement with the experimental data on the structure, density, and potential energy of liquid metal along the p ≅ 0 isobar at temperatures up to 2200 K and along the shock adiabat up to a pressure of ∼85 GPa and 37240 K. The calculated bulk compression modulus at 343 K was close to its actual value, and the self-diffusion coefficients increased under isobaric heating conditions following a power law with an exponent of 1.6478. The melting temperature of body-centered potassium with the embedded atom potential was (319 ± 1) K, which was close to the actual melting temperature. The potential obtained incorrectly described crystalline potassium.

A conceptual configuration of the lunar base bioregenerative life support system including soil-like substrate for growing plants

The paper presents a conceptual configuration of the lunar base bioregenerative life support system (LBLSS), including soil-like substrate (SLS) for growing plants. SLS makes it possible to combine the processes of plant growth and the utilization of plant waste. Plants are to be grown on SLS on the basis of 20 kg of dry SLS mass or 100 kg of wet SLS mass per square meter. The substrate is to be delivered to the base ready-made as part of the plant growth subsystem. Food for the crew was provided by prestored stock 24% and by plant growing system 76%. Total dry weight of the food is 631 g per day (2800 kcal/day) for one crew member (CM). The list of candidate plants to be grown under lunar BLSS conditions included 14 species: wheat, rice, soybean, peanuts, sweet pepper, carrots, tomatoes, coriander, cole, lettuce, radish, squash, onion and garlic. From the prestored stock the crew consumed canned fish, iodinated salt, sugar, beef sauce and seafood sauce. Our calculations show that to provide one CM with plant food requires the area of 47.5 m 2. The balance of substance is achieved by the removal dehydrated urine 59 g, feces 31 g, food waste 50 g, SLS 134 g, and also waters 86 g from system and introduction food 236 g, liquid potassium soap 4 g and mineral salts 120 g into system daily. To reduce system setup time the first plants could be sowed and germinated to a certain age on the Earth.

Stochastic dynamics in liquid potassium as explored by polarized neutron scattering

The coherent Sc(Q,ω) and single particle Ss(Q,ω) dynamic structure factors which contribute to the low-energy spectrum of molten potassium are separated by means of neutron polarization analysis. The linewidth and amplitude of the single-particle spectra follow an apparent Fickian behavior with a diffusion coefficient well below the value found by macroscopic means. Once this is accounted for, the results are found to conform with predictions made from kinetic theory. In contrast, the available theoretical recipes to account for the coherent quasielastic intensity are seen to be semiquantitative, at best.

Direct alkaline fuel cell for multiple liquid fuels: Anode electrode studies

A direct alkaline fuel cell with a liquid potassium hydroxide solution as an electrolyte is developed for the direct use of methanol, ethanol or sodium borohydride as fuel. Three different catalysts, e.g., Pt-black or Pt/Ru (40 wt.%:20 wt.%)/C or Pt/C (40 wt.%), with varying loads at the anode against a MnO 2 cathode are studied. The electrodes are prepared by spreading the catalyst slurry on a carbon paper substrate. Nickel mesh is used as a current-collector. The Pt–Ru/C produces the best cell performance for methanol, ethanol and sodium borohydride fuels. The performance improves with increase in anode catalyst loading, but beyond 1 mg cm −2 does not change appreciably except in case of ethanol for which there is a slight improvement when using Pt–Ru/C at 1.5 mA cm −2. The power density achieved with the Pt–Ru catalyst at 1 mg cm −2 is 15.8 mW cm −2 at 26.5 mA cm −2 for methanol and 16 mW cm −2 at 26 mA cm −2 for ethanol. The power density achieved for NaBH 4 is 20 mW cm −2 at 30 mA cm −2 using Pt-black.

High frequency collective dynamics in liquid potassium

We investigated by inelastic X-ray scattering the dynamical properties of molten potassium in a wide range of momentum transfer, Q, from 1nm−1 up to the main peak of the structure factor Q≈17nm−1. The observed increase of sound velocity in the low Q region (1<Q<3nm−1), has been described within a model characterized by two distinct relaxation processes for the collective dynamics. The obtained results are discussed and compared with those from previous neutron scattering experiments. In particular, we associate the speed-up of the sound velocity to the ‘instantaneous’ disorder of the liquid as opposed to the argument, supported by some neutron scattering studies, of a transition from a liquid to solid like response of the system.

Suppressive effect of liquid potassium silicate on powdery mildew of strawberry in soil

A soil drench of soluble silicon (liquid potassium silicate) was tested for the control of powdery mildew of strawberry in soil for 2 years in a vinyl house under growers' conditions on two cultivars: very susceptible Toyonoka and slightly susceptible Sachinoka. Soluble silicon suppressed the disease more effectively as a preventive control than as a control to reduce initial incidence. The suppressive effect against this disease was more effective for Toyonoka than for Sachinoka. The control value of soluble potassium silicate was 85.6% for Toyonoka in the first year and 60.2% in the second year, while for Sachinoka it was 58% in the first year and 40.6% in the second year. Strawberry leaf hardness was measured for the control and silicate-treated leaves. Although silicate-treated leaves seemed to be harder than control leaves, leaf hardness did not vary significantly between controls and silicate-treated leaves in either of the 2 years, and the mode of preventive action of liquid potassium silicate remains unknown. A factor other than a physical action may be involved.

Contradictions and new aspects of the bubble model of doped tungsten wires

The interpretation of a series of small angle neutron scattering studies on lamp grade tungsten rods and wires is in contradiction with an extended body of the results that were obtained by fractographic methods and thin foils studies by means of scanning microscopy and transmission electron microscopy. In order to facilitate the re-interpretation of the scattering studies, the state of agglomeration of potassium in the dope phase has to be clarified, due to the peculiar scattering properties of the two-phase inclusions. These efforts yielded to the following results: (1) There are independent pieces of experimental evidence that the dope inclusion are filled with liquid potassium in heavily drawn lamp grade tungsten wires and rods in various stages of the processing. (2) A slight volume compression of liquid inclusion upon wire drawing is compatible with the scaling laws of the Taylor model in a good approximation, because the expected deviations are less than the accuracy of the required measurements. (3) The size increase of the inclusion cannot be explained as the expansion of individual bubbles that do not interact with each other. One has to take into account also various sorts Ostwald type ripening processes.

Electrochemical and chemical redox doping of fullerene (C 60) peapods

Different types of redox doping of C 60@SWCNT were monitored by Raman spectroscopy. Chemical doping was carried out by gaseous potassium, liquid potassium amalgam and gaseous fluorine diluted with argon. Electrochemical doping was investigated by in situ Raman spectroelectrochemistry in LiClO 4 + acetonitrile solution and in 1-butyl-3-methylimidazolium tetrafluoroborate (ionic liquid). The peapods exhibit characteristic and complex feedback to chemical as well as to electrochemical doping. In contrast to chemical p-doping by F 2, the Raman scattering of intratubular fullerene is selectively enhanced during electrochemical p-doping. Similar selective enhancement is traced at chemical n-doping with gaseous potassium. Doping by gaseous potassium causes deep reduction of intratubular C 60 to C 60 6 - , which is not fully re-oxidizable upon contact to air. On the other hand, doping with liquid potassium amalgam causes reduction of intratubular C 60 to C 60 4 - or C 60 5 - , and complete re-oxidation to neutral fullerene occurs spontaneously upon contact to air. In general, the doping chemistry of peapods is significantly dependent on the applied redox potential, charge-compensating counterions and on the actual doping technique used. A critical review of the current data is provided.

Removing UV‐A and UV‐C Radiation from UV‐B Fluorescent Lamp Emissions. Differences in the Inhibition of Photosynthesis in the Marine Alga Dunaliella tertiolecta Using Chromate Versus Cellulose Acetate‐Polyester Filters¶

ABSTRACTUltraviolet‐B (UV‐B; 280‐320 nm)‐emitting lamps unavoidably emit ultraviolet‐A (UV‐A; 320‐400 nm) and ultraviolet‐C (UV‐C; &lt; 280 nm) radiation. Short‐wavelength‐blocking filters are generally used to limit the wave bands of UV under investigation. The widespread use of such filters means that all exposures to UV‐B radiation will have a significant UV‐A component. Therefore, the physiological effects unique to UV‐B exposure are difficult to clearly isolate. This study presents a method to remove the UV‐A and UV‐C “contamination” using a liquid potassium chromate (K2CrO4) filter, thus allowing more direct assessment of the effects of UV‐B exposure. Cultures of the green marine alga Dunaliella tertiolecta were grown in the absence of UV radiation. Sunlamps supplied the UV radiation for a 24 h exposure (solar radiation was not used in this study). The UV radiation was filtered either by the standard method (i.e. cellulose acetate (CA) with polyester = Mylar controls) or by a liquid filter of potassium chromate. Photosynthetic responses were compared. Major decreases in the ratio of variable to maximal fluorescence in dark‐adapted cells and photosynthetic capacity were observed in CA‐filtered cultures, whereas no change was observed in cells exposed to the same UV‐B flux with the UV‐A removed by K2CrO4. The use of a CA filter with a Mylar control does not link results unequivocally to UV‐B radiation. Such results should be interpreted with caution.

Management of powdery mildew in flowering dogwood in the field with biorational and conventional fungicides

In a 2 yr study, control of powdery mildew on flowering dogwood (Cornus florida L.) by four biorational and four conventional fungicides was assessed on seedlings and on 3 yr liners in the field. Biorational fungicides applied were three household soaps containing 0.2% triclosan (Irgasan® DP 300)—Ajax® liquid hand soap, Equate® liquid dish soap and Palmolive® liquid dish soap-and potassium bicarbonate salt. Conventional fungicides applied were propiconazole, thiophanate methyl, azoxystrobin and copper sulfate pentahydrate. All products controlled powdery mildew compared with water controls. Application of the biorational fungicides on a weekly basis was as effective as propiconazole and thiophanate methyl and more effective than azoxystrobin and copper sulfate pentahydrate. Application of some biorational products at semi-monthly intervals was slightly less effective. Of the biorational fungicides, Palmolive® was the most effective but was phytotoxic, whereas Ajax®, Equate® and potassium bicarbonate were not. When three applications of any biorational fungicide were rotated with one application of propiconazole, the incidence of powdery mildew was less than when a fungicide rotation was not included. Plant growth was enhanced with either biorational or conventional fungicides compared with water controls. Propiconazole treatments resulted in the highest growth rates, whereas biorational products were as effective in promoting growth as thiophanate methyl, azoxystrobin or copper sulfate pentahydrate. The incorporation of biorational fungicides in a powdery mildew disease management program may have economic and environmental benefits because they are less costly than conventional fungicides and presumed safer to the environment and the applicators. Key words: Cornus florida L., Erysiphe (sect. Microsphaera) pulchra, Microsphaera pulchra, Oidium spp, Phyllactinia guttata

Collective dynamics in molten potassium: an inelastic x-ray scattering study.

The high-frequency collective dynamics of molten potassium has been investigated by inelastic x-ray scattering, disclosing an energy/momentum transfer region unreachable by previous inelastic neutron scattering (INS) experiments. We find that a two-step relaxation scenario, similar to that found in other liquid metals, applies to liquid potassium. In particular, we show how the sound velocity determined by INS experiments, exceeding the hydrodynamic value by approximately 30%, is the higher limit of a speedup, located in the momentum region 1 < Q < 3 nm(-1), which marks the departure from the isothermal value. We point out how this phenomenology is the consequence of a microscopic relaxation process that, in turn, can be traced back to the presence of "instantaneous" disorder, rather than to the crossover from a liquid to solidlike response.