Showing papers on "Calcium oxide published in 1976"

Modified electron-gas study of the stability, elastic properties, and high-pressure behavior of MgO and CaO crystals

Abstract: A theoretical study of the crystal structure and bonding in the simple inorganic oxide crystals magnesium oxide and calcium oxide is reported. An a priori method based on an electron-gas approximation is applied to an ionic description of these crystals. The quantities calculated are the equilibrium interionic separation, the elastic constants and their pressure derivatives, the transition pressures and volume changes in high-pressure-induced phase transitions, and the thermodynamic stability of the crystal structures. Comparison with available experimental data shows good agreement, without any adjustable parameters in the theory. We conclude that the ionic description of these crystals is rather accurate for energy calculations, provided that a suitably stabilized oxide ion is used in the theory.

Reduction of oxidative hardening of asphalts by treatment with hydrated lime -- a mechanistic study

Abstract: The paper reports on a study to compare the susceptibility of the untreated and lime-treated asphalts to oxidative hardening when subjected to laboratory aging and to suggest a mechanism explaining the action of lime. Four different asphalts were tested, along with four aggregate types, and solvents and hydrated lime. Testing procedures are outlined, and the discussion of results goes into such things as the effect of lime treatment and aggregate type on resilient modulus, chemistry of lime action, mechanism of lime action, and others.

Effect of lime treatment on the resilient behavior of fine-grained soils

Abstract: Lime treatment of fine-grained subgrade soils has definite potential for beneficially altering subgrades softening due to high moisture contents and freeze-thaw action. The effects of high moisture content and freeze-thaw cycles on the resilient response of a number of untreated and lime-treated soils are examined. A finite element procedure is used to evaluate the structural response of a flexible pavement on untreated and lime-treated subgrades. The analysis reveals that high moisture contents and freeze-thaw action in the subgrade have a detrimental effect on the magnitude of pavement response parameters and that lime treatment of the upper layer of the subgrade causes a substantial improvement in pavement response.

Curable composition comprising a calcium fluoro-alumino silicate glass and poly(carboxylic acid) or precursor thereof

Abstract: A novel calcium fluoroaluminosilicate glass consisting essentially of from 25 to 35% by weight of silicon calculated as silica, from 30 to 40% by weight of aluminum calculated as alumina, from 20 to 35% by weight calcium, calculated as calcium oxide, and up to 9% by weight fluorine (preferably 4-7%) can be associated with a poly(carboxylic acid) e.g. as an intimate mixture of glass and acid to constitute a composition curable on contact with water and useful, for example, as a loading on a splinting bandage. Such a bandage preferably has a ratio of set time to gel time from 4:1 to 8:1 with a minimum gel time of 60 seconds.

Solubility of magnesium oxide in calcium oxide-calcium chloride mixtures

Abstract: Measurements and theoretical calculations of the solubility product of magnesium oxide in calcium chloride-calcium oxide mixtures at 1133 K are reported. A filtration technique in an inert atmosphere was used to obtain samples for analysis by atomic absorption for magnesium content. At low concentrations of O-2, the data are in consonance with the very low solubility product of 10-6.2 predicted by a simple thermodynamic cycle first proposed by Flood, Fϕrland and Grjotheim.

Refractory fiber composition and intermediate temperature range fibrous insulation composed thereof

Abstract: Refractory fiber compositions are disclosed comprising 84% to 97% by weight total silica and alumina, with the silica-to-alumina weight ratio being in the range of 3:2 to 1:1, preferably approximatey 5:4, and 3% to 16% by weight of a dolomitic component comprising calcium oxide and magnesium oxide. The dolomitic component may be composed of burnt dolomite or lime and magnesia. The fibers made of these compositions are suitable for thermal insulation use at temperatures in the range of from 1400° F to 2000° F (760° C to 1100° C) and find particular use as insulating mats and blankets for furnaces, kilns and automobile catalytic mufflers.

Multilayer reflector for gas discharge laser

Abstract: A multilayer reflector of which the last layer most remote from the substrate and having a high refractive index is vapor-deposited from a mixture containing a metal or oxide of an element from group 4b of the periodic table and a metal oxide from the group of beryllium oxide, magnesium oxide and calcium oxide, is particularly resistant to hydrogen and ultraviolet light and is hence suitable for application in a laser which is to have a long life.

Cerium magnesium aluminate luminescent compositions, and lamps utilizing same

Abstract: Cerium magnesium aluminate luminescent compositions containing from about 1.25 to about 6.25 mole percent of cerium oxide, from about 1.25 to about 6.25 mole percent of magnesium oxide and from about 87.5 to about 97.5 mole percent of aluminum oxide and compositions containing from about 1.25 to about 4.5 mole percent of cerium oxide, from about 6.25 to 14 mole percent of magnesium oxide and from about 81.5 to about 92.5 mole percent of aluminum oxide, the percentage being calculated on the basis of CeO1.5, MgO and AlO1.5, are efficient ultraviolet light emitting materials when excited by 254 nanometer energy. Up to 50 mole percent of the cerium oxide (on a CeO1.5 basis) content can be replaced by an equivalent molar amount of strontium oxide, calcium oxide or barium oxide. The materials are self-activating due to the presence of trivalent cerium. The good temperature dependence of these materials and their emission characteristics enable the production of high quality lamps useful for the treatment of psoriasis as well as conventional high loaded fluorescent lamps.

Regeneration of sulfated metal oxides and carbonates

Abstract: Alkali metal or alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate found in dolomite or limestone are employed for removal of sulfur dioxide from combustion exhaust gases The sulfated carbonates are regenerated to oxides through use of a solid-solid reaction, particularly calcium sulfide with calcium sulfate to form calcium oxide and sulfur dioxide gas The regeneration is performed by contacting the sulfated material with a reductant gas such as hydrogen within an inert diluent to produce calcium sulfide in mixture with the sulfate under process conditions selected to permit the sulfide-sulfate, solid-state reaction to occur

Method of producing expansive and high strength cementitious pastes, mortars and concretes

Abstract: Expansive and high strength cementitious pastes, mortars and concretes are produced by adding to a mix of water, cement and aggregates a mixture containing calcium oxide and/or magnesium oxide, a water-reducing agent and an additive for reducing or eliminating bleeding of the fresh mix.

Use of fly-ash in road construction

Abstract: At the present time, 34 power plants produce approximately 4000000 t of fly ash per year. Fly ash can be combined with lime to form a binder which sets in the presence of water. The composition of a subbase would be: 91% fly ash, 4% quick lime, 5% industrial gypsum (phosphogypsum). This mixture has a compressive strength of 30 bars at 7 days and 140 bars after one year. When manufactured in a plant, it is compacted with pneumatic-tyred rollers. The composition of a roadbase would be: 0/20 gravel (85%), 12% fly ash, 3% hydrated lime. The grading curve of gravel-ash mixtures is a bolomey curve. The composition of the binder (lime/fly ash = 1/4) is that giving optimum performance, the optimum proportioning being 15%. After one year, gravel-ash mixtures containing some limestone, have the highest strength, approximately 300 bars; with quartzite or siliceous limestone, the strength reaches 250 bars. These values decrease by approximately 16% when the density decreases from 100 to 95% of the optimum density. These gravel-ash mixtures are produced exclusively in mixing plants. Compaction is carried out by means of a heavy vibrating roller followed by a pneumatic-tyred roller. /TRRL/

Process for the production of elemental phosphorus and iron from phosphate rock

Abstract: A process for the production of phosphorus from low-grade phosphate rock containing at least 5% by weight of each of iron and aluminum (calculated as their oxides) by heating a mixture of the rock, calcium oxide and a carbonaceous reductant in a reaction chamber at a temperature of at least 1400° C to produce molten reaction products containing ferrophosphorus and a calcium aluminate slag which is liquid at the reaction temperature, and gaseous reaction products containing elemental phosphorus. The gaseous reaction products are withdrawn from the reaction chamber and elemental phosphorus is recovered therefrom. The ferrophosphorus is separated from the liquid calcium aluminate slag and subjected to an oxidizing treatment in the presence of a calcium-containing material to produce metallic iron and calcium phosphate. Calcium phosphate this produced is recycled to the reaction chamber.

Pressure-injected lime for treatment of swelling soils

Abstract: The pressure-injected lime technique for treating swelling soils is described and evaluated. Basic mechanisms of soil-lime reactions and pressure-injected lime are considered, and the effects of treatments with pressure-injected lime are discussed. Typical field experiences with pressure-injected lime are summarized, and the factors that appear to influence the effectiveness of the technique are identified. There are conflicting reports concerning the effectiveness of pressure-injected lime treatment of expansive soils. The condition most favoring the achievement of successful pressure-injected lime treatment of expansive soils is the presence of an extensive fissure and crack network into which the lime slurry can be successfully injected. The proposed treatment mechanisms (prewetting, development of soil-lime moisture barriers, and effective swell restraint with the formation of limited quantities of soil-lime reaction products) have validity. The relative significance of the prewetting and soil-lime pozzolanic reaction aspects of pressure-injected lime treatment has not been established. The various statements and reports in the literature and the information presented in the paper suggest that pressure-injected lime may not be effective under all circumstances but that in appropriate conditions it can be satisfactorily and economically used. It is indicated that appropriate guidelines and principles should be developed for evaluating (on a site-by-site basis) the potential effectiveness of pressure-injected lime treatment.

Process of desulfurizing liquid melts

Abstract: A method for the rapid desulfurization of steel melts having oxygen available for reaction of less than 001% wherein the temperature of the melt is raised above 1500° C, and a desulfurizing slag is injected into the melt using a non-oxidizing carrier gas The slag is in a finely divided state and is specially prepared by mixing calcium oxide, calcium fluoride and aluminum oxide with silicane dioxide and heavy metal oxides, melting the mixture and cooling the melt to prefuse the slag Thereafter, the prefused slag is comminuted into the finely divided state This slag has a liquidous temperature such that the particles thereof become liquid at a temperature at least 150° C below that of the steel melt and the particles are sufficiently small such that they become liquid immediately on contacting the melt The process is advantageous in that it provides more rapid desulfurization and more complete desulfurization than prior art techniques

Powder for continuous casting

Abstract: A flux powder for use in the continuous casting of steels, particularly aluminum killed steels in the form of a mechanical mixture of components and has the following chemical analysis by weight % :- silicon dioxide 20 - 60, calcium oxide source 20 - 60, calcium fluoride 3 - 20, alkali metal carbonate 3 - 20, carbon source 4 - 20 and aluminum oxide 0 - 10. At least the inorganic components of the mixture are substantially pure, whereby the properties of the powder may be made substantially uniform and reproducible. The components preferably have a uniform grain size and calcium carbonate is disclosed as a calcium oxide source and natural graphite is a preferred carbon source.

Process for removing sulfur dioxide and nitrogen oxides from gases

Abstract: Process for removing sulfur dioxide and nitrogen oxides from gaseous mixtures which comprises contacting such mixtures, in the presence of a reducing agent comprising carbon monoxide, hydrogen, or mixtures thereof, with a solid reagent comprising calcium oxide, magnesium oxide, or mixtures thereof at temperatures in excess of about 700° C

Investigation of accelerated curing of soil-lime and lime-fly ash-aggregate mixtures

Abstract: : The objectives of this investigation were to examine current mix design procedures for soil-lime and lime-fly ash-aggregate mixtures and to develop accelerated curing test procedures for estimating long-term field strengths. Unconfined compression tests were conducted on Vicksburg silt (ML) plus 3 and 5 percent lime, Vicksburg buckshot clay (CH) plus 5 and 8 percent lime, and 90 percent clay gravel and 90 percent sandy gravel plus 3 or 6 percent fly ash, respectively. Representative groups of specimens were normally cured at 50 F and 72 F each for 7, 28, and 56 days, while other groups were accelerated cured 1, 3, and 5 days at 90 F, 105 F, and 120 F each. The soil-lime mixtures could be judged to be reactive or nonreactive. Accelerated curing times equivalent to 28-day normal-cure strengths depended upon curing temperature, soil type, and to a lesser extent on lime content or lime: fly ash ratio. Hence, no universally applicable equivalent 28-day curing time exists for accelerated-cured soil-lime or lime-fly ash-aggregate mixtures. Because none of the existing 'maturity' rules for concrete were found to be applicable to soil-lime mixtures, a method was developed based upon normal-cure 7-day and accelerated-cured 105 F strengths for estimating 28-day strengths. Procedures for mix design evaluation of soil-lime and lime-fly ash-aggregate mixtures are presented.

Process for preparing a 3-exomethylenecepham sulfoxide from penicillin sulfoxides

Abstract: A penicillin sulfoxide ester is reacted with an N-chloro halogenating agent at a temperature of from about 75° C to about 135° C and in the presence of an alkylene oxide and calcium oxide to produce a 2-chlorosulfinylazetidin-4-one intermediate The intermediate, upon separation from the alkylene oxide, calcium oxide, and any conversion products of both the alkylene oxide and calcium oxide, can be treated with stannic chloride to produce a 3-exomethylenecepham sulfoxide

Pigment preparation and use in coating compositions

Abstract: A new and useful pigment is prepared by reacting an inorganic silicofluoride and an inorganic calcium compound selected from the group consisting of calcium oxide, calcium hydroxide and calcium carbonate. The product is especially useful in protective coating compositions which are applied to metals in order to enhance adherence to and corrosion resistance of metals such as aluminum, zinc, magnesium, steel and alloys of said metals.

Method for the disposal of waste water containing ammonium ions, sulfate ions and organic substances

Abstract: Disclosed is a method whereby a waste water containing ammonium ions, sulfate ions and organic substances is subjected to combustive disposal subsequent to addition of calcium hydroxide or calcium oxide thereto.

Process for stabilizing lime mud

Abstract: There is provided a process for stabilizing lime mud so as to eliminate balling during calcination of the same by incorporating a surface active agent decomposable at a temperature below 1500° F into lime mud comprising calcium carbonate, filtering said treated lime mud, and thereafter calcining said treated lime mud to recover calcium oxide absent any balling during calcination.

The room temperature fracture strength of sintered UO2 rings containing deliberately introduced impurities

Abstract: A ring test has been used to measure the room temperature fracture strength of sintered UO2 and of UO2 deliberately doped with either silica, calcium oxide or iron oxide. The maximum observed flaw size and the minimum measured fracture strength in a group of nominally identical specimens was found to be related for some of the materials tested. It is shown that the additions of silica and calcium oxide do not appear to alter the energy for fracture initiation. Fracture strength measurements obtained using the ring test, where the applied stress is relatively uniform over the specimen cross-section, and the three-point bend test where it is not, fit the same strength/flaw size relationship provided minimum measured strength is associated with maximum flaw size.

Soil stabilization using a western coal high calcium fly ash

Abstract: Fly ash, a pozzolanic by-product of coal burning power plants, is an abundant potential source of highway and embankment construction material. Some fly ashes are suitable for use as a supplement or replacement for lime and portland cement in soil stabilization applications. The paper discusses a study made of fly ash produced from Wyoming coal, which contains 20% CaO, causing it to react something like quick lime. In addition, the fly ash takes a pozzolanic set when mixed with water. Reported are the engineering properties of this fly ash and fly ash-soil mixtures.

Stabilisation of deep cuts with lime columns

Abstract: IN SWEDEN A NEW SOIL STABILIZATION METHOD HAS BEEN DEVELOPED WHICH REPLACES SHEET PILE RETAINING WALLS BY LIME STABILIZED CLAY COLUMNS FOR THE LATERAL SUPPORT OF DEEP CUTTINGS IN SOFT CLAY SOILS. THE CHALK COLUMNS ARE MADE UP IN-SITU BY MIXING IN UNSLAKED LIME AND SUITABLE ADDITIVES. THE SPACES BETWEEN THE COLUMNS SHOULD BE SO SMALL THAT THEY INTERACT WITH ONE ANOTHER AND THUS FORM A SOLID BLOCK OF STABILIZED SOIL. A 5.2 M DEEP TEST CUTTING WAS SECURED WITH A STABILIZED COLUMN WALL. IN THIS PAPER THE MEASUREMENT RESULTS ARE PRESENTED AS WELL AS METHODS FOR THE DIMENSIONING OF SUCH COLUMN WALLS. THE COVERING ABSTRACT FOR THE CONFERENCE IS IRRD NO 306088.

Manufacture of aziridinocarboxylic acid esters

Abstract: Aziridinocarboxylic acid esters of polyols are manufactured by trans-esterification of the corresponding esters of lower alcohols, using magnesium oxide or calcium oxide as the trans-esterification catalyst; this method gives a higher yield and a purer product.

Molecular Cluster Approach to Magnesium and Calcium Oxide Crystals

Abstract: The model of the molecular duster (MC) which has been applied for perfect MgO and CaO crystals is applied now to F+ and F centres in these crystals. A method is proposed to estimate the optical transition energies within the SCCC technique. The calculated values of the absorption maxima of the F+ and F centres are in reasonable agreement with experimental data. The procedure is also suggested to estimate the location of the defect levels within the forbidden gap of the perfect crystal. For comparison the analogous calculations of the ionic KCl crystal (perfect and with F centre) are given. Das Model1 des Molekulclusters (MC), das bereits fur perfekte MgO- und CaO-Kristalle benutzt wurde, wird nun auf F+-Zentren und F-Zentren in diesen Kristallen ausgedehnt. Eine Methode wird vorgeschlagen, um die optischen mergangsenergien innerhalb der SCCC-Technik zu berechnen. Die berechneten Werte der Absorptionsmaxima der F+- und F-Zentren befinden sich in verniinftiger Obereinstimmung mit experimentellen Werten. Es wird vorgeschlagen, mit dieser Methode auch die Storstellenniveaus innerhalb der verbotenen Zone des perfekten Kristalls zu berechnen. Zum Vergleich werden analoge Berechnungen des KC1-Ionenkristalls (perfekt und mit F-Zentren) angegeben.

Fired refractory brick and process for preparing the same

Abstract: A fired refractory brick composed of magnesia, 2 to 10% alumina, calcium oxide and up to 1.5% silica, the weight ratio of calcium oxide to silica being more than 1.4, and at least 2.2 (CaO - 1.4 SiO2) % zirconia, calcium and zirconium forming a cal-cium zirconate phase in the brick and the content of the calcium zirconate phase being from 0.5 to 8%, all percentages being by weight. This brick is prepared from a mixture of the components by pressing the mixture into the shape of a brick and firing the brick at a temperature of 1600°C to 1800°C until the brick contains the indicated amount of the calcium zirconate phase.