Alkali Flux Research Articles

Effect of Addition of Talc on the Properties of Feldspar-Kaolinitic Clay Blends during Heating

Effects of low addition of talc (up to 8 wt%) on thermal transformations of feldspar-kaolinitic clay blends were investigated by X-ray diffraction, scanning electron microscope and Fourier-transform infrared spectroscopy. The variations of some properties (firing shrinkage, water absorption, density and bending strength) versus talc additions were measured. It was found that talc additions did not affect the presence of neoformed phases (mullite, spinel and glassy phase) but markedly influenced their contents. With up to 4 wt% talc addition, the amount of the formed phases increased with the increase of talc content; consequently shrinkage increased along with strength and density. Apparently, talc derivative oxide (MgO) facilitated the sintering process. For >4 wt% talc, the effect of alkali fluxes reduced because of the abundance of MgO, and consequently the glassy phase content decreased. Therefore, the variations of properties changed except for water absorption and total porosity, which manifested a continuous decline.

Characterization of Chalawa River Sand for Foundry Application

The characterization of Chalawa river sand with its suitability for foundry applications has been investigated. Chemical and sieve analyses and Green permeability were determined for the sand via standard procedure. Based on the result of the chemical and sieve analyses and permeability (the sand by its high silica content and low alkali fluxes) it needs small amount of binder, has moderate refractoriness and therefore, can be employed in foundry applications.

Undersized (12.5 mm diameter) glass beads with minimal amount (11 mg) of geochemical and archeological silicic samples for X‐ray fluorescence determination of major oxides

The small glass bead technique was developed to assay precious silicic samples for geochemical and archeological analyses. Undersized (12.5 mm diameter) glass beads were prepared for wavelength dispersive X‐ray fluorescence determination of major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3). Synthetic calibration standards were prepared by compounding chemical reagents (oxides, carbonates, and diphosphate). For reliable calibration, recipe compositions of standard specimens were constructed on the basis of the evenness of plot intervals on a calibration curve. Calibration curves showed good linearity (correlation coefficient: r > 0.998). Analytical results of major oxides in granitic and basaltic rocks, obsidian, and ancient pottery were obtained with good precision (relative standard deviations were the following: <3% for more than 10.0 mass% of analyte, <5% for 1.0–10.0 mass% of analyte, and <15% for 0.1–1.0 mass% of analyte). Lower limits of detection were roughly a sub‐percentage of analyte in an unprepared sample: 0.3 mass% for Na2O, 1.0 mass% for SiO2, 0.01 mass% for MnO, and so on. The present preparation reduced the following analytical scales: (1) amount of sample from 400 mg to 11 mg (97% cutting out), (2) amount of Li2B4O7 as an alkali flux from 4000 mg to 396 mg (90% cutting out), and (3) weight of platinum crucible from 80 g to 12.5 g (84% cutting out). This small‐scale preparation might enable us to conduct destructive pretreatment of valuable and limited silicic samples such as archeological ceramics and stone tools, geochemical minerals in rock, and sediments and sand. Copyright © 2012 John Wiley & Sons, Ltd.

Glass bead with minimized amount (11 mg) of sample for X‐ray fluorescence determination of archaeological ceramics

By using very small amount – 11‐mg – of sample powder, major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3) in ancient pottery (and igneous rocks) were determined with X‐ray fluorescence spectrometry. This minimized amount of sample was used to prepare a fused glass bead with 300 times the weight of lithium tetraborate as an alkali flux. Calibration standards were obtained by compounding chemical reagents (Na2CO3, MgO, Al2O3, SiO2, Na4P2O7, K2CO3, CaCO3, TiO2, MnO2, and Fe2O3) and the flux. Fewer 11 mg of reagents as oxides were able to give reliable calibration curves with good linearity (correlation coefficient: r > 0.995). Fewer 11 mg of sample was able to give reliable analytical results with good precision (relative standard deviation: <3% for more than 10.0 mass% of analyte, <10% for 1.0–10.0 mass% of analyte, and <20% for 0.1–1.0 mass% of analyte). Lower limits of detection were roughly a sub‐percentage of analyte in an unprepared sample (e.g. 0.3 mass% for Na2O, 0.5 mass% for MgO, 1.0 mass% for Al2O3, and 0.01 mass% for MnO). Composition of major oxides in artificial and natural aluminosilicate materials (including rock, stone, sand, sediment, and clay; and their products) should be fundamental information to be considered in detail. The present X‐ray determination based on very small amount of sample might be made readily accessible for destructive analysis of precious samples for archaeology (and geochemistry). Copyright © 2011 John Wiley & Sons, Ltd.

Influence of Potsdam sandstone on the trace element signatures of some 19th‐century American and Canadian glass: Redwood, Redford, Mallorytown, and Como–Hudson

AbstractPotsdam sandstone from quarries and outcrops near 19th‐century glassworks sites in Redwood, NY, and Saranac, NY, Mallorytown, ON, and Como and Hudson, QC, commonly contains _97% silica, so in terms of its purity can compete with other historical producers of silica sand (e.g., Cheshire quartzite, MA; southern New Jersey sand). Exploratory analysis of trace element data using multidimensional scaling (MDS) shows that geographically distinct sources of Potsdam sandstone can be distinguished from one another and from competing sources of silica sand, particularly in terms of high field strength elements (e.g., Nb, Y, Ti, Zr), the rare earth elements, and radioactive elements (U, Th), and this geochemical signature is carried through to the glass it was used to manufacture. Other trace elements (e.g., Ba, Sr, Rb) are concentrated in various batch ingredients (e.g., limestone, alkali fluxes). The Hf/Nb, La/Ce, Nb/Th, and La/Zr ratios for each type of glass and nearby Potsdam sandstone sources cluster together in distinct fields on MDS plots. These data confirm the use of Potsdam sandstone in these important historical glassworks, and show that except for material sampled from neighboring communities (Mallorytown and Redwood), trace elements can be used to identify specific sources of silica historically used by the glassmaking industry. © 2008 Wiley Periodicals, Inc.

The production technology of Egyptian blue and green frits from second millennium BC Egypt and Mesopotamia

The microstructures and chemical compositions of some 55 Egyptian blue and green frit samples from New Kingdom Egypt and 15th century BC Mesopotamia are determined using analytical scanning electron microscopy, the main focus being on frit cakes, powder residues, and frit vessel and bead fragments from one of the “factory areas” at Amarna in Middle Egypt. Replicate Egyptian blue frits produced in the laboratory are similarly investigated. Comparison of the microstructures of the ancient and replicate samples suggest that frit cakes are the primary product, and that these were ground to produce the powder, and then moulded to shape and refired to produce the vessels and beads. Egyptian blue and green frits are shown to be distinct pigments, the pigment produced depending on the relative proportions of copper oxide and lime in the mixtures. The bulk and glass phase compositions are used to try to infer the different sources of the quartz, lime, copper and alkali flux used in the production of frits from Egypt and Mesopotamia. An estimate is made of the scale of production of Egyptian blue frit in New Kingdom Egypt.

Low temperature synthesis and characterization of rare earth orthoferrites LnFeO 3 (Ln=La, Pr and Nd) from molten NaOH flux

Rare earth orthoferrites of the general formula LnFeO 3 (Ln=La, Pr and Nd) phases have been synthesized for the first time in molten NaOH flux at a temperature as low as 400 ∘C. The flux-grown oxides were characterized by XRD, SEM, EDX, FT-IR and temperature dependent electrical resistivity measurements. The crystal structures of these materials have been refined by the Rietveld profile analysis method using powder XRD data. All these oxides crystallize in the orthorhombic structure (space group P b n m , no. 62) and exhibit insulating behavior. As-synthesized samples show three active IR absorption bands for Fe–O stretching vibration ( ν 1 mode) and O–Fe–O deformation vibration ( ν 2 mode). In the KOH flux on the other hand, no product formation is observed, thus providing evidence for the differences in the two alkali fluxes.

The production technology of Iznik pottery—a reassessment*

Previous research has established that Iznik pottery differs from other Islamic stonepaste pottery in that its stonepaste bodies contain lead oxide as well as soda and lime, and that a significant proportion of the tin oxide in its glaze is present in solution rather than as tin oxide particles. In order to better understand these distinguishing features, the chemical compositions and microstructures of Iznik pottery and tile samples, together with those of lumps of glass found in association, were investigated using both scanning electron and optical microscopy. These data have been supplemented by the study of replicate lead–alkali glazes produced in the laboratory with a range of different compositions. The results demonstrate that separate soda–lime and high‐lead glasses were used in the production of Iznik stonepaste bodies, and that the total glass contents of the bodies were significantly higher than those quoted by Abū’l‐Qāsim, who was writing in about ad 1300. The very high purity of the lead–soda Iznik glazes indicated that the alkali flux used was either a purified plant ash or an as yet unidentified mineral source of soda. Replication experiments established that the high solubility of tin oxide in the glaze was due to the high purity of the glaze constituents. Furthermore, it is suggested that tin oxide was added to the glaze in order to give it a very slight opacity and thus obscure any blemishes in the underlying body.

A new method for the direct flame calibration of nebulized additive concentrations

A new technique is described to calibrate the flame delivery flux of an aerosol-producing nebulizer. The method is based on flame deposition. It centers on the nature of deposition onto a cooled surface immersed in the burned flame gases that contain an alkali salt (Na, K, Rb, or Cs) that has been nebulized into the flame. This deposition process has been shown to be controlled solely by the alkali concentration in the flame and for the same alkali flux the rates of deposition are invariant being independent of the nature of the alkali flame speciation, the fuel, equivalence ratio, flame or probe temperature (in the 350-800 K range for the latter), probe material, or the deposit’s molecular composition. In flames containing, for example, sodium and sulfur or chlorine, there is a pronounced preferential ranking of Na 2SO 4 > NaCl > Na 2CO 3 > NaOH for the resulting composition of the deposit. This dominance of sulfate formation is so pronounced that it produces a linear titration method for the alkali, and fractional addition of sulfur reflects into a corresponding fractional formation of Na 2SO 4. In flames containing solely sodium and sulfur additives, insufficient sulfur for a Na 2SO 4 formulation will result in a fractional mixture of the sulfate, with the remaining sodium forming carbonate. Collecting a deposit from a flame containing a nebulized alkali salt solution aerosol and a known trace addition of SO 2, and then analyzing the deposit using an inductively coupled plasma/atomic emission spectrometer (ICP/AES) for its alkali to S ratio, provides a measure of the extent of sulfate formation. This then translates into an absolute calibration of the nebulizer delivery flux of alkali in the burned gases. A variation of the method is to use instead a Raman scattering spectrometer to measure the ratio of sulfate to carbonate in a deposit, in this case for flames free of halogens. The method has the advantage that it can be used in any flame, turbulent or laminar, requires only a trace of deposit for ICP analysis, and is accurate. Moreover, the probe can intercept any partial part of the flame gases. A limited number of other techniques currently are available for nebulizer calibration. However, other than the curve of growth method, these have not been discussed in combustion texts. Their various limitations and accuracies are outlined together with that of the presently suggested method.

Extraction of silicon dioxide from waste colored glasses by alkali fusion using potassium hydroxide

A process of extraction of SiO2 from waste colored glasses by alkali fusion using KOH was investigated. In the present study, the waste colored bottles of green, blue, brown or black were selected as sample waste glasses. These colored bottles were qualitatively confirmed to contain the elements of Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe and Cu from energy dispersive X-ray spectroscopic analysis. The condition for alkali fusion of KOH and the waste glasses was optimized, i.e., for each bottle, the composition was KOH:crushed glass bottle = 90:10 wt%, melting temperature was 360°C and melting time was 2 h. For each waste colored bottle, the potassium silicate solution was prepared by using the potassium silicate obtained by alkali fusion. After mixing HCl with the obtained potassium silicate solution, Si(OH)4 was then precipitated by boiling the solution which became to be a very strong acid. After drying the Si(OH)4 separated from the solution, the SiO2 powder with purity of 99.9% was obtained. The yield of 97.75 ± 1.05% for the SiO2 powder extracted from the bottles was confirmed from quantitative analysis, indicating that the bottles selected in the present study contain about 60 wt%SiO2. From the results of the yield and purity, the established process was found to have a potential applicability as a recycling process of waste glasses. Particularly, for alkali fusion of KOH, the melting temperature of 360°C was lower than those for alkali fusion of NaOH (500°C) and carbonate fusion of Na2CO3 (900°C). This suggested that the energy consumption during alkali fusion of KOH and the glasses in an electric furnace was lower than those for the fusions of NaOH and Na2CO3. In addition, ideal recycling and reusing processes of waste glasses and the final wastes produced after extracting SiO2 from the waste glasses were also discussed. For the KCl solution which is obtained after extracting SiO2, the KCl can be resolved into K and Cl by electrolysis (: 2KCl → 2K+ − 2Cl− and 2K + 2H2O → 2KOH + H2 ↑) and the HCl can be also prepared by the chemical reaction of the H2 and Cl2 (: H2 + Cl2 → 2HCl). These reactions suggested that the KOH and HCl can be reused as the alkali flux and acid solution, respectively. From these results and discussions, the established recycling process of waste glasses was expected that cost reduction would result from selection of KOH as an alkali flux and reuse of the final wastes.

Cathodoluminescence and scanning tunnelling spectroscopy of ZnO single crystals

Bulk ZnO single crystals grown by the hydrothermal (HTT) and alkali flux methods have been investigated by means of scanning tunnelling spectroscopy (STS) and time resolved cathodoluminescence (CL). Measurements were performed in the different crystalline faces. The results from these measurements show that both, surface electrical properties and luminescent characteristics depend on the face studied. Polar O-terminated surfaces show an intrinsic conduction behaviour with a surface band gap ranging from 0.4 to 0.8 eV. Zn-terminated surfaces show mainly n-type conduction. The non-polar faces present either intrinsic or p-type behaviour. CL spectra show that the relative intensity of the different components of the deep level band also depends on the atomic structure of the face under study. This complex behaviour is clearly revealed from the time resolved spectra. The differences observed are attributed to the nature of the defects present in each case and, in particular, to different impurity incorporation processes that could be mainly controlled by the atomic configuration and polarity of the planes.

Cathodoluminescence microscopy of hydrothermal and flux grown ZnOsingle crystals

Bulk ZnO single crystals grown by the hydrothermal and flux methodshave been characterized by steady-state and time resolved cathodoluminescencemeasurements performed on the different crystalline faces. A shift of thepeak near band edge towards lower energies is observed in spectrarecorded with increasing delay times. This behaviour is often observed in theetch pit regions in alkali flux grown crystals, which suggests the presence ofa band related to dislocations or to the point defects surrounding thedislocations. In the low-energy region, cathodoluminescence spectra show thatthe relative intensity of the different components of the deep level band alsodepends on the atomic structure of the face under study. This complexbehaviour is clearly revealed from the time resolved spectra. The differencesobserved are attributed to the nature of the defects present in each face and,in particular, to different impurity incorporation processes that could bemainly controlled by the atomic configuration and polarity of the planes.

Seed Eaters of the Ancient Near East: Human or Herbivore?

On aborde ici la question de la domestication des plantes et des animaux au moment du passage du Mesolithique au Neolithique ancien au Moyen Orient L'A pose la question de l'expansion ou pas de l'habitat naturel des cereales et par consequence, s'il y a expansion, la question se pose alors des traces economiques et sociales reperables archeologiquement. Est-ce le manque de nourriture, la famine, qui a favorise le developpement de la culture intensive ?

Synthesis of High-Tc Superconductors by Alkali Flux Method

Synthesis of High-Tc Superconductors by Alkali Flux Method

Synthesis of High-Tc Superconductors by Alkali Flux Method

Synthesis of High-Tc Superconductors by Alkali Flux Method

Modification in the aluminum silicon system

Alloys in the range 0 to 24 wt pct Si have been examined by careful thermal analysis, macroand microscopical study with modification by a mixed alkali fluoride flux, and by separate additions of sodium, potassium, lithium, and strontium. Sodium and strontium exert similar effects and potassium and lithium differing and minor effects; with a mixed alkali flux the influence of sodium is dominant. The normal and modified eutectic arrests in the presence of primary aluminum both show comparable supercoolings and recalescence behavior relative to the horizontal growth temperatures, but this is not observed in hypereutectic alloys containing primary silicon. Both normal and modified eutectics grow radially inward from crucible walls, but the details of the growth fronts are very different: there is no nucleation from the bulk liquid in modified alloys and it is uncertain if this occurs in normal alloys. It is concluded that the structural modification in furnace cooled ingots, as in directionally grown samples, is primarily caused by modified growth of silicon. The mechanism(s) for such modification are briefly discussed.

Some investigations of fusing and dissolving samples

Alkali flux cakes are placed together with a beaker containing hydrochloric acid in a vacuum desiccator and after partial evacuation the acid is allowed to isothermally diffuse into the cake. Dissolution takes place without danger of loss by splattering and at the same time the acid is highly purified. Also other samples like alloys of magnesium and aluminium can in this way be dissolved in high purity hydrochloric acid. Brass is opened by isothermal diffusion of fuming nitric acid. Teflon crucibles and dishes are investigated to perform fusions under overhead radiation from focused projection lamps. The best flux was found to be potassium hydroxide containing about 15% water.

Seeded supersonic alkali atom beams

A seeded supersonic beam source for alkali atoms is described which provides velocities up to ∼ 5 km/sec. Potassium or rubidium vapor at ∼ 0.02 to 0.2 Torr is mixed with a diluent gas of H2, He, or Ar at ∼ 800 Torr and expanded through a pinhole nozzle. The beam properties are found to compare well with the simple theory of isentropic expansions. Typically, the alkali flux is ∼ 1016 atoms sr−1 sec−1 and the velocity spread is ∼ 8% (FWHM).