Showing papers on "Calcium oxide published in 1993"

Low-cost, high early strength, acid resistant pozzolanic cement

Abstract: A low cost cement composition that can be admixed with water and hydrothermally closed cured to give acid-resistant products of high compressive strength consisting essentially of, in parts by weight, 1 to 1.5 parts of a calcium oxide material containing at least about 60% CaO, 10 to 15 parts of pozzolanic material containing at least about 30% by weight amorphous glass or vitreous silica, and 0.025 to 0.075 parts by weight of an alkali metal catalyst and building materials made therefrom as well as the method of making such building materials by closed curing.

Destructive adsorption of chlorinated hydrocarbons on ultrafine (nanoscale) particles of calcium oxide. 2

Abstract: As a one-step approach to the safe destruction of chlorocarbons, the reaction of carbon tetrachloride with ultrafine particles of calcium oxide to give calcium chloride and carbon dioxide (CCl4(g) + 2CaO(s) → CO2(g) + 2CaCl2(s)) has been studied in detail. Calcium oxide prepared by an aerogel/hypercrytical drying method (AP−CaO) is superior to a conventionally prepared (CP−CaO) sample, and both are vastly superior to commercial CaO (CM−CaO). Optimum temperature for this gas−solid reaction is 450 °C, although AP−CaO reacted with reasonably high capacity as low as 300 °C. The effects of surface −OH, added water, CCl4 pressure, and a wide range of temperatures are discussed. Conditions for the suppression of byproducts C2Cl4 and Cl2CO are presented. Morphological changes in the particles after CCl4 reaction were studied by atomic force microscopy. A wide range of other techniques have been applied toward complete characterization of the process and products, including FT-IR, pulsed U-tube reaction studies, g...

Production of purified calcium carbonate

Abstract: A method of producing relatively pure calcium carbonate from a relatively impure source of calcium oxide, characterised in that the method comprises the steps of slaking the calcium oxide source in water to produce an aqueous hydrated lime slurry; treating the slurry by the addition thereto of a water soluble source of anions which anions are capable of forming a salt with calcium ions which salt has a dissociation constant greater than the dissociation constant of calcium hydroxide; separating the solid content of the slurry from the liquid fraction content thereof to obtain a substantially solids-free solution of calcium ions and anions; intimately contacting the solids-free liquid fraction with carbon dioxide gas at a selected rate to maintain the temperature of the solution within a specific range and to lower the pH of the solution to a pre-set value conducive for the formation of a precipitate of calcium carbonate in which one of the crystalline forms, selected from the group consisting of calcite, vaterite and aragonite, predominates; and separating the precipitated calcium carbonate from the mother liquor.

Reactions between calcium oxide and flue gas containing sulfur dioxide at lower temperatures

Abstract: An experimental study has been performed of the reactions occurring when the reactive particles of calcium oxide are exposed to sulfur dioxide bearing flue gas. Using a differential, fixed-bed reactor, kinetic measurements have been made in the temperature range of 170 and 580C. A relatively simple correlation based on the amassed data has been proposed. This correlation allows the estimation of the reaction rate as a function of temperature, conversion of the solids and concentration of sulfur dioxide in the gas phase. The proposed rate law equation makes it possible to predict in a straightforward manner the rate of sorption which would be required to design the performance of a desulfurization unit.

Lead-free crystal glass with the refractive index higher than 1,52

Abstract: Lead-free cyrstal glass with the refractive index higher than 1,52, designated for the production of man-made and machine-made utility glass especially of luxurious character with high light transmittance, perfect clearness and elevated hydrolitical resistance which is suitable particularly for decorating by cutting, engraving and other decorating techniques and is well polishable by using both chemical and mechanical processes, containing in % by weight from 50 to 75 of silicon dioxide SiO2, from 0,05 to 10 of aluminium oxide Al2O3, from 0,05 to 15 of zirconium dioxide ZrO2, from 0,001 to 2,5 of hafnium dioxide HfO2, from 0,001 to 5 of titanium dioxide TiO2, from 2 to 9 of calcium oxide CaO, from 0,001 to 6 of magnesium oxide MgO, from 0,05 to 10 of zinc oxide ZnO, from 0,1 to 10 of potassium oxide K2O, from 5 to 16 of sodium oxide Na2O, from 0,05 to 2,5 of entimony trioxide Sb2O3 and the total amount of iron expressed as iron trioxide Fe2O3 ranges from 0,005 to 0,035 % by weight, while this glass further contains in % by weight from 0,001 to 1,25 of sulphates SO42- and chlorides Cl- and from 0,000005 to 0,8105 at least one component from the group comprising erbium oxide Er?2?O3, neodymium oxide Nd2O3, ceric oxide CeO2, cobaltous oxide CoO, nickel oxide NiO, manganese oxides and selenium compounds. In any case, sum of all components mentioned totals at lest 99,6 % by weight.

Abrasive grain comprising calcium oxide and/or strontium oxide

Abstract: Alumina-based abrasive grain comprising rare earth oxide and calcium oxide and/or strontium oxide, and a method of making the same. The abrasive grain is useful in abrasive articles, such as coated abrasives, three-dimensional, low density abrasives, and bonded abrasives.

Carbon dioxide absorbent packet and process

Abstract: An absorbent packet for absorbing carbon dioxide at a rapid rate from a closed container, such as a package or can containing coffee and water vapor, including a porous envelope containing calcium oxide and a hydrating agent, such as silica gel with water adsorbed therein. The water vapor from the container permeates the envelope at a relatively rapid rate because of the affinity of silica gel for the water vapor in the container, and the silica gel becomes supersaturated and gives off water. The carbon dioxide from the environment also permeates the envelope because of its concentration outside of the envelope and because of the pressure gradient between the outside and inside of the envelope. The water given off by the supersaturated silica gel combines with the calcium oxide in the envelope to form calcium hydroxide. The carbon dioxide and the calcium hydroxide react to produce calcium carbonate and water. Any other suitable metal oxide may be used, including but not limited to the oxides of sodium, potassium, magnesium and barium. Also other hydrating agents may be used instead of silica gel.

Nonmagnetic ferrite for composite laminated component, and composite laminated component

Abstract: PURPOSE:To contrive reduction in the difference of linear expansion coefficient between the magnetic materials used by a method wherein MgO, Bad, SiO2 B2O3 SnO2 and CaO are added to the ferrite, containing Fe2O3, CuO and/or ZnO, in such a manner that the total quantity of the adding material is in the prescribed range. CONSTITUTION:To the nonmagnetic ferrite composition, containing iron oxide, oxidized. copper and/or a zinc oxide, of fe2O3 and/or ZnO of 100mol%, four kinds of oxide component of magnesium oxide, barium oxide, silicon oxide and boron oxide, or five or six kinds of oxide component, consisting of the above-mentioned four kinds of oxide component and one or more kinds selected from tin oxide, calcium oxide, is added. As a result, the difference of the linear expansion coefficient of the magnetic ferrite and the like used can be made small and the deterioration of characteristics can be prevented.

Revision of the enthalpies and gibbs energies of formation of calcium oxide and magnesium oxide

Abstract: Major revisions in the enthalpies and Gibbs energies of formation of calcium oxide and magnesium oxide are presented. In free-evaporation experiments over the temperature range of 1830 to 2070 K, the kinetics of vaporization of calcium oxide and magnesium oxide have been studied. Conditions of local equilibrium were established. The results lead to new values for the standard enthalpies of formation of CaO and MgO. The ΔfH298 0 of CaO is ≈33 kJ/mol more positive than the currently tabulated value, whereas that for MgO is ≈34 kJ/mol more negative. The currently tabulated values could not account for these observations nor for other recent studies. These significant changes result in a reversal of the relative thermodynamic stabilities of CaO and MgO, with MgO now indicated as the more stable oxide at lower temperatures on Ellingham diagrams. These results are consistent with recent work on the formation of CaC2, solubility product measurements in liquid iron, and with theoretical models based on ionic radii.

Translucent polycrystalline alumina and process for producing the same

Abstract: Translucent polycrystalline alumina made of aluminum oxide containing magnesium oxide in an amount of larger than 0.01% by weight and less than 0.03% by weight, zirconium oxide in an amount of larger than 0.01% by weight and less than 0.06% by weight and calcium oxide in an amount of less than 0.001% by weight, all based on the weight of aluminum oxide, which alumina has good light transmittance and mechanical strength.

Thermal conductivity of calcium-doped aluminium nitride ceramics

Abstract: Aluminium nitride ceramics were prepared with the addition of up to 12wt% of calcium oxide as a sintering aid Both the oxygen and the calcium content of the samples decreased during sintering with increasing sintering temperature and soaking time Higher amounts of calcium oxide resulted in higher thermal conductivities, with values up to 142 W m−1 K−1 Moderate sintering temperatures, short temperature soaking times and the use of inexpensive Ca-based sintering additives should enable the production of aluminium nitride ceramics with sufficiently high thermal conductivity at relatively low cost

Crack inhibitor for tape joint compositions

Abstract: The use of calcium oxide or calcium hydroxide as a crack-inhibiting additive for tape joint compositions is disclosed. Tape joint compositions containing calcium oxide or calcium hydroxide maintain their workability while experiencing less cracking upon drying.

Solid detergent composition

Abstract: A solid detergent composition such as soap which contains 0.02 to 5.0% by weight of magnesium oxide and/or calcium oxide based on the total weight of the composition.

Porous particles of calcium carbonate and method for the preparation thereof

Abstract: A method is proposed for the preparation of porous calcium carbonate particles of which each of the particles is not an aggregate but has ink bottle-shaped pores each not communicating with the others. The method comprises: (a) blending particles of heavy calcium carbonate having a specific particle size distribution with from 0.1 to 0.3% by weight of a porosity-forming agent, e.g., sodium chloride; (b) calcining the powder blend at a temperature in the range from 800° C. to 1000° C. to decarbonate the calcium carbonate particles into particles of calcium oxide having pores developed therein; (c) slaking the particles of calcium oxide with steam to convert the calcium oxide particles into particles of calcium hydroxide; (d) drying the particles of calcium hydroxide at a temperature in the range from 100° C. to 350° C.; and (e) carbonating the dried particles of calcium hydroxide with carbon dioxide gas at a temperature in the range from 600° C. to 750°C.

Lime sludge amended fly ash for utilization as an engineering material

Abstract: Sludges generated from various water treatment operations are predominantly subject to the fate of land disposal. To prepare sludges for land disposal typically requires time consuming dewatering schemes, which can become extremely difficult to execute dependent upon the composition of the sludge and its affinity for water. Due to the pozzolanic properties of fly ash and its demonstrated ability to achieve relatively high strength in the presence to lime, the utilization of lime sludge amended fly ash may not only reduce the strain on continuously decreasing land space, but also provide a useful engineering material for possible utilization as a landfill cap, linear, or engineered fill. In the following study, lime sludge from a groundwater remediation project was added in various proportions to coal fly ash. The mechanical properties of the resulting mixtures were analyzed, and permeability and leachate data was studied.

Process and catalyst for converting methane into higher hydrocarbon products

Abstract: Methane is converted into higher hydrocarbon products by oxidative coupling, by bringing a gaseous mixture containing methane and oxygen into contact with a solid catalyst formed from calcium oxide, magnesium oxide, a lanthanide oxide plus possibly lithium oxide, wherein: the lithium content is between 0 and 0.20 wt %, the calcium/magnesium atomic ratio is between 0.08 and 0.7, and the (calcium+magnesium)/lanthanide atomic ratio is between 0.8/1 and 8/1, and preferably between 2/1 and 4/1.

High strength alumina porcelain.

Abstract: of EP0522343Alumina porcelains, such as are used especially in electrical insulators, involve the problem of the high-strength alumina porcelains containing a higher proportion of calcined alumina and consequently having a higher sintering temperature. The normal-strength alumina porcelain compositions are therefore not compatible with the high-strength porcelain compositions, so that a fluid transition in production from normal-strength to high-strength alumina porcelains was not possible. In this connection, the invention provides that, at a specific bending strength of more than 190 DEG N/mm on a glazed bending rod, only 33 to 45% by weight of calcined alumina and, as sintering aid, one or more of the substances magnesium oxide, calcium oxide and/or zinc oxide are present, the quantities of magnesium oxide and calcium oxide being each less than 1.5% by weight, and the quantities of zinc oxide being less than 0.8% by weight. The invention is applicable to industrial porcelain, in particular for electrical insulators.

Precipitate potential of highway subbase aggregates

Abstract: Tufaceous material has been observed clogging pavement drains along highways in northeastern Ohio. Previous studies suggest that the free lime (CaO) present in subbase materials is the source for the deposition of the tufa. Nine slag samples which consisted of air cooled blast furnace (ACBF), open hearth (OH), basic oxygen furnace (BOF), and electric arc furnace (EAF) and two recycled portland cement concretes (RPCC) were evaluated for the tufa precipitate research. An X-ray, SEM and physicochemical tests were conducted on the samples. In addition, leachate study and surface area measurements were performed to characterize the precipitate potential of the samples. The results of these tests indicate that all of the slags, except the ACBF slag, are prone to produce tufa. The solution of CaO in hot ethylene glycol ('sugar' test) revealed that the ACBF slag does not contain any residual free lime. The results of the X-ray diffraction and thermogravimetric (TG) analyses confirmed that ACBF slag does not contain either portlandite or calcium carbonate. X-ray diffraction analysis for both the OH and the BOF slags shows that these slags contain portlandite Ca(OH)2 and calcium carbonate. ODOT requires six months aging of slags before they are used. The 'sugar' test results show that the aging of slags for six months or more, does not decrease the free lime content enough to prevent the formation of tufa deposits. TG analyses and the results of the 'sugar' test permit the determination of original percentage free lime. Five groups, according to the calculated total percent free lime, are recognized: (1) 0%; (2) 3-5.5%; (3) 8-9%; (4) 10-12% and (5) 24-25%. The thermogravimetric and 'sugar' test methods used are excellent and economical ways to characterize the original free lime in slags and the susceptibility of the slags to precipitate CaCO3 in subdrains of highways. The RPCC samples contain both portlandite and calcium carbonate. X-ray diffraction and SEM analyses indicate that one RPCC sample does not contain free lime. The leachate study shows that both samples produce tufa. Therefore presence of free lime or portlandite in the cement paste of the concrete can result in tufa precipitation.

High purity resins for thiol-ene polymerizations and method for producing same

Abstract: A treatment method for polyene resins used in thiol-ene formulations, especially norbornene resins, significantly stabilizes thiol-ene compositions made from batches of polyene resin which otherwise give compositions with poor dark stability The treatment comprises contacting the polyene with an amphoteric treating agent selected from the group consisting of silicated magnesium oxide, basic aluminum oxide, silica gel, magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, barium oxide, and barium hydroxide, and then separating the resin from the treating agent prior to mixture with a polythiol to form a thiol-ene composition The treatment method significantly reduces ionic content in polyene resins, particularly chloride ion but also sodium and potassium ions Consequently, treatment is also beneficial with polyene resins which do not produce substantial dark stability problems Reduction of the ionic content of the resin is desirable to produce cured thiolene polymers with low electrical conductivity and low corrosiveness

Ceramic moldings composed of aluminum oxide having high metallization adhesion

Abstract: Ceramic moldings composed of aluminum oxide which have a proportion of intercrystalline fracture of more than 50%, an average pore radius of more than 4 μm and a porosity of more than 2%, are obtained by: a) grinding aluminum oxide which is at least 99.5% pure and has an average primary crystal size of 1 to 4 μm to an average fragment size of 2 to 7 μm, b) adding a source of magnesium oxide, silicon oxide and calcium oxide in amounts such that the magnesium oxide content is 0.2 to 2.5%, the silicon dioxide content is 1 to 6% and the calcium oxide content is 0.1 to 2.5%, in each case with respect to the amount of Al2 O3, c) shaping a green compact and d) sintering.

Prevention of sulfur gas emissions from a rotary processor using lime addition

Abstract: Oil sand is treated to prevent the production of sulfur dioxide ("SO2") from a known rotating kiln-type processor. Lime or calcium oxide ("CaO") is added with the oil sand feed to the kiln. In the kiln, the CaO is mixed with the sulfur-containing bitumen of the oil sand and preheated. The preheated mixture is then pyrolysed, forming coke which is modified by the added CaO to reduce its tendency to produce SO2 when combusted. The modified coke is then combusted with air, producing substantially no SO2.

Process for the removal and the recovery of ammonia from liquid waste

Abstract: A process for the removal and recovery of ammonia from liquid waste, characterized essentially by the following operations: reacting the liquid waste with pure carbon dioxide, or with a gaseous mixture rich in carbon dioxide, or with at least one carbonate, to give ammonium carbonate reacting the resulting ammonium carbonate with calcium chloride to give calcium carbonate and ammonium chloride; causing the resulting calcium carbonate to undergo thermal decomposition to give calcium oxide and carbon dioxide; using, optionally, the carbon dioxide formed after thermal decomposition of calcium carbonate for said reaction with the liquid waste; and using the calcium oxide, formed after thermal decomposition of calcium carbonate, for the production of pure ammonia, by reaction with the ammonium chloride obtained in said reaction between ammonium carbonate and calcium chloride The figure shows a flow sheet of a plant allowing the operations of an embodiment of the above process

Long-term effects of gypsiferous coal combustion ash applied at disposal levels on soil chemical properties

Abstract: Currently, there is renewed interest in the agricultural utilization of coal combustion byproducts. Field sites where high rates (112 Mg ha−1) of high gypsum coal combustion spent bed ashes were surface applied in 1980 within fruit tree orchard rows were identified and sampled with depth. The objective of this study was to examine the effects on long-term exposure/leaching of these materials on soil profile chemical properties. When applied, the material had an aqueous pH of 12.5 and consisted of about 52% calcium sulfate, 33% calcium oxide and 15% coal ash residues. Eleven years after ash application, soil pH is significantly higher in the top 66 cm of the treated sites compared to unamended sites. This has been accompanied by increases in extractable and total calcium and total boron and sulfur with a concomitant reduction in extractable magnesium. Remaining pieces of the applied spent bed material are composed primarily of calcite and quartz with some gypsum associated with large pieces.

Enzyme enhanced stabilization of soil and fly ash

Abstract: The purpose of this research was to determine if enzymes could be utilised to increase the strength and stability of soil mixed with fly ash. Samples were prepared with and without the enzyme by varying the percentages of fly ash in the soil-fly ash mixture and subjected to unconfined compression test, freeze thaw test and compaction test. The results indicated that addition of very small amount of enzyme (about 5%) increased the unconfined compression strength significantly. The UC strengths of enzyme stabilized soil-fly ash mixture was found to be higher than the UC strengths of lime stabilized soil and gained higher strengths earlier. Enzyme stabilized soil-fly ash mixture was found to be as stable as the lime stabilized soil-fly ash mixture under freeze- thaw cycles. No change in the compaction characteristics of soil-fly ash mixture was observed because of the enzyme. For the covering abstract see IRRD 863991.

An electric discharge machining fluid

Abstract: An electric discharge machining fluid comprising a mixture of a liquid dielectric and a powder of polycrystalline silicon and a small amount of inorganic oxide, provided for forming smooth workpiece surfaces having a carbon-iron-silicon alloy. The powder is present in an amount from 0.1 to 5.0 wt % of the liquid dielectric. The inorganic oxide includes silicon oxide, iron oxide and/or calcium oxide. Further, a concentrate made by kneading the powder with oil mainly composed of an aromatic hydrocarbon or aromatic hydrocarbons having a density of more than 0.93 g/millilitre at 15°C, is added to the dielectric whereby the powder is dispersed uniformly.

Plant oil clarifying agent and its preparing method

Abstract: The clarifying agent contains calcium oxide 5-15%, calcium sulfate 10-30%, expansive soil 15-30%, active white soil 10-20%, active carbon 5-10%, silica-gel G 2-3%, anhydrous calcium chloride 5-7%, dewatering alum 2-5%, citric acid 1-3%; it can effectively remove harmful gel, pigment, smell, free acid and soap slag in vegetable oil.

Topical compositions for protection against ultraviolet radiation

Abstract: Disclosed are compositions useful for topical application to protect skin from ultraviolet radiation, which comprise effective amounts of the reaction product of a calcium compound such as calcium hydroxide, calcium oxide, or calcium carbonate, with citric acid, the reaction product exhibiting a calcium:citrate molar ratio of 2.50:2 to 2.95:2 and a 1% slurry of the reaction product in water at 25° C. exhibiting a pH value of about 4 to below 7.