Showing papers on "Calcium oxide published in 2003"

A New Mechanism for Cement Hydration Inhibition: Solid-State Chemistry of Calcium Nitrilotris(methylene)triphosphonate

Abstract: The reaction of the cement retarder nitrilo-tris(methylene)phosphonic acid, N[CH2PO(OH)2]3 (H6ntmp) with calcium oxide, tricalcium silicate (C3S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF) has been studied individually, and in the case of C3A in the presence of gypsum, to gain an understanding of the effect on the individual minerals prior to studying a typical sample of Portland cement. The reaction of H6ntmp with calcium oxide results in the initial formation of soluble [Ca(Hnntmp)](4-n)-, which precipitates over time as [Ca(H4ntmp)(H2O)]∞, whose sheetlike structure has been confirmed by single-crystal X-ray diffraction. The study of the hydration of C3S in the presence of H6ntmp indicates that no C−S−H forms, and the surface changes from silicon-rich to calcium-rich associated with the formation of various calcium phosphonates. The hydration of C3A is severely inhibited in the presence of H6ntmp, with the phosphonic acid reacting primarily with calcium as opposed to aluminum to...

Sorbent for separation of carbon dioxide (CO2) from gas mixtures

Abstract: A reaction-based process has been developed for the selective removal of carbon dioxide (CO 2 ) from a multicomponent gas mixture to provide a gaseous stream depleted in CO 2 compared to the inlet CO 2 concentration in the stream. The proposed process effects the separation of CO 2 from a mixture of gases (such as flue gas/fuel gas) by its reaction with metal oxides (such as calcium oxide). The Calcium based Reaction Separation for CO 2 (CaRS-CO 2 ) process consists of contacting a CO 2 laden gas with calcium oxide (CaO) in a reactor such that CaO captures the CO 2 by the formation of calcium carbonate (CaCO 3 ). Once “spent”, CaCO 3 is regenerated by its calcination leading to the formation of fresh CaO sorbent and the evolution of a concentrated stream of CO 2 . The “regenerated” CaO is then recycled for the further capture of more CO 2 . This carbonation-calcination cycle forms the basis of the CaRS-CO 2 process. This process also identifies the application of a mesoporous CaCO 3 structure, developed by a process detailed elsewhere, that attains >90% conversion over multiple carbonation and calcination cycles. Lastly, thermal regeneration (calcination) under vacuum provided a better sorbent structure that maintained reproducible reactivity levels over multiple cycles.

Process for producing polysiloxanes and use of the same

Abstract: A process for the preparation of an organosilicon condensate which comprises reacting together (A) at least one silicon containing compound having at least one silanol group; and (B) at least one silicon containing compound having at least one -OR group in the presence of (C) a calcium or magnesium catalyst selected to allow the reaction to proceed and (D) at least one solvent. Advantageous catalysts include calcium hydroxide, calcium oxide, magnesium hydroxide or magnesium oxide. Advantageously the solvent may be a protic solvent such as water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol. The invention also relates to condensates, such as siloxanes, prepared by the process.

Effectiveness of Lime in Hot-Mix Asphalt Pavements:

Abstract: The pavement community has recognized that moisture damage of hot-mix asphalt (HMA) has been a serious problem since the early 1960s. Numerous additives have been evaluated with the objective of reducing the potential of moisture damage in HMA mixtures; lime has been one of the most common ones. The Nevada Department of Transportation has been using lime in HMA mixtures since the mid-1980s. The objective of this research was to quantify the improvements in pavement performance that have been realized through the addition of lime to HMA mixtures. The program evaluated field samples and pavement performance data from untreated and lime-treated pavements. The properties of untreated and lime-treated mixtures from field projects in the southern and northwestern parts of Nevada indicate that lime treatment of Nevada's aggregates significantly improves the moisture resistance of HMA mixtures. The study showed that lime-treated HMA mixtures become significantly more resistant to multiple freeze-thaw cycles than ...

Development of supported iron oxide catalyst for destruction of PCDD/F.

Abstract: Studies on the development of supported iron oxide catalysts for PCDD/F decomposition using 2-monochlorophenol as a surrogate test compound are presented. Iron oxide catalysts supported on titania were prepared by two methods: impregnation and the sol−gel method. The latter preparation method resulted in better dispersion of iron oxide on the surface and the formation of γ-Fe2O3. This is in contrast to the impregnated samples where α-Fe2O3 crystallites were formed. Formation of γ-Fe2O3 resulted in improved reducibility of the active phase that favorably affected the catalytic oxidation properties of the catalyst, i.e., the light-off curves for the sol−gel samples were shifted toward lower temperature. Addition of calcium oxide to iron oxide catalyst further improved the performance of the system through stabilization and increase in the concentration of γ-Fe2O3 in the sol−gel prepared samples. Addition of calcium oxide has a dual effect on the performance of the catalyst. First, it creates oxygen vacanci...

Evaluation of Moisture Susceptibility of Asphalt Mixtures Containing Bottom Ash

Abstract: Bottom ash, as a by-product of coal-fired electric power plants, has recently been used in constructing transportation facilities. However, the use of bottom ash in asphalt mixtures is still in an early stage. The moisture resistance of asphalt mixtures containing bottom ash, which has not been adequately researched, is investigated in this study. Eight asphalt mixtures produced with one type of asphalt cement, two types of aggregate, three sources of bottom ash, and lime additive were evaluated using the principles in AASHTO T283. Analysis of test data indicated that granite mixtures had higher tensile strength values than did limestone mixtures in dry conditions. Addition of lime or bottom ash did not substantially change these values. All mixtures tested met the Superpave volumetric mix design requirement of tensile strength ratio (TSR) after one freeze-thaw cycle. The addition of lime significantly improved the moisture resistance of the asphalt mixtures as measured by the TSR. With lime addition, aggregate type, bottom ash addition, and bottom ash source were all insignificant with respect to TSR. On the basis of TSR rate (TSRR), the addition of lime significantly improved the moisture resistance of the asphalt mixtures subjected to multiple freeze-thaw cycles. Without lime addition, bottom ash played a role similar to that of lime in improving the TSRR for the materials tested.

Encapsulated organic electronic device

Abstract: In a first embodiment of the invention, an organic electronic device is encapsulated using an epoxy that includes a desiccant The epoxy is around a perimeter of the organic electronic device The epoxy bonds an encapsulation lid to a substrate and also absorbs oxygen and/or moisture The desiccant in the epoxy is: barium oxide, calcium oxide, magnesium oxide, cobalt chloride, calcium chloride, calcium bromide, lithium chloride, zinc chloride, zinc bromide, sodium molevular, silicon dioxide, aluminum oxide, calcium sulfate, copper sulfate, potassium carbonate, magnesium carbonate, titanium dioxide, bentonite, acidic clay, montmorillonite, diatomaceous earth silica alumina, zeolite, silica, zirconia, activated carbon, or a mixture thereof

The electrochemical deoxidation of metal oxides by calcium using a solid oxide membrane

Abstract: The reduction of a metal oxide by calcium in a CaCl2 melt produces metal and calcium oxide (CaO) dissolved in the molten chloride. To minimize waste salts, the reacted salts have to be regenerated. This can be done either by converting CaO to CaCl2 by chlorination with Cl2 and adding calcium metal or by electrochemical deoxidation of CaO. In the first method, the addition of calcium metal increases the amount of reacted salts, and consequently the waste salts, while in the second method the quantity of reacted salts remains constant. The electrochemical deoxidation of CaO occurs in one step and the produced oxygen is evacuated. This article describes a study of the electrochemical deoxidation of CaO using a solid oxide membrane.

The Effects of S-Chitosan on the Physical Properties of Calcium Phosphate Cements:

Abstract: Water-soluble disodium (1→4)-2-deoxy-2-sulfoamino-β-d-glucopyranuronan (S-chitosan) was prepared from chitin by successive N-deacetylation, specific carboxylation at C-6 and sulfonation. Its structure was characterized by IR spectra and elemental analysis. The S-chitosan was added to two easily developed calcium phosphate cements (CPCs). One cement was monocalcium phosphate monohydrate (MPCM) with calcium oxide (CaO) in a 1M phosphate buffer (pH 7.4)(CPC-I); the other cement was dicalcium phosphate dihydrate (DCPD) with calcium hydroxide [Ca(OH)2] in a 1M Na2HPO4 solution (CPC-II). In vitro experiments showed that when S-chitosan where added to the liquid phases that the resulting S-chitosan containing CPCs had higher mechanical strengths and slightly prolonged setting times. The polyanion enhanced the mechanical strength of the CPCs by increasing the dissolubility of the cement start materials and binding the calcium ions strongly afterwards. An excess of the polyanion destroys the balances of the formul...

Comparison of Calcite to Quicklime for Amending Partially Oxidized Sulfidic Mine Tailings before Flooding

Abstract: Flooding partially oxidized mine tailings for the purpose of mitigating further oxidation of sulfide minerals and generation of acid drainage is generally preceded by treatment with alkaline amendments to prevent releasing previously accumulated acidity to the water cover. This work compares the ability of calcite (CaCO 3 ) and quicklime (GaO), two common amendments, to establish and maintain pH conditions and dissolved metal concentrations within environmentally acceptable ranges over long time periods. Although higher initial pH values were obtained with quicklime, the pH of quicklime treated tailings decreased over time. This was attributed to the low buffering capacity of quicklime treated tailings and to the consumption of hydroxide ions by incongruent dissolution of water-insoluble iron oxyhydroxysulfate minerals. In contrast, the pH of tailings treated with calcite increased initially and then remained stable at pH 6.7. This pH behavior was due to the lower reactivity of iron oxyhydroxysulfates with calcite, the increased buffering capacity provided by bicarbonate ions, and the incomplete dissolution of calcite. Overall, calcite was found preferable to quicklime for maintaining long-term neutral pH conditions in the treated tailings. With the exception of zinc, acceptable dissolved metal concentrations were achieved with calcite treated tailings.

Reducing odor in absorbent products

Abstract: Hydrogen sulfide is removed or reduced in absorbent products by the use of a particulate material attached to pulp fiber by a retention aid. The particulate material can remove or reduce the hydrogen sulfide in the environment surrounding the fiber. Suitable materials are zinc oxide, calcium oxide, cupric oxide, magnesium oxide, manganese dioxide, manganese oxide and aluminum oxide. Zeolites are also suitable. The particulate material may be combined with a filler prior to attachment to the fiber.

Thermoneutral Coproduction of Calcium Oxide and Syngas by Combined Decomposition of Calcium Carbonate and Partial Oxidation/CO2-Reforming of Methane

Abstract: The calcination of limestone to produce lime and cement is characterized by its high-energy consumption and concomitant CO2 emissions to the atmosphere. By combining the calcination reaction with the partial oxidation and CO2-reforming of methane, an overall thermo-neutral process can be designed, with high-quality syngas as a useful byproduct, and a substantial decrease in CO2 release. The thermochemical boundary conditions for such a combined process are established. The thermodynamics are also examined with coal instead of methane as the fuel and carbon source. Adding H2O in the reaction mixture results in the coproduction of CaO and syngas with a H2/CO molar ratio of 2, suitable for methanol synthesis. A preliminary economic analysis indicates favorable competitiveness, even before the application of credit for CO2 avoidance. The fuel saving of the proposed coproduction vs the separate production may amount up to 70%, and the avoidance of CO2 emissions may reach 74%.

Metal catalysed intumescence: characterisation of the thermal decomposition of calcium gluconate monohydrate

Abstract: Calcium gluconate monohydrate is a member of a new class of base-catalysed intumescent compounds. It forms low-density closed-cell carbonaceous foam when exposed to heat. The volume expansion can be as high as two hundred times the original volume. At temperatures above 750°C this foam is transformed into a porous, yet cohesive, structure based on calcium oxide. The latter has only a slightly higher density and shows significant flame-resistance.

Water-repellent film-coated articles, water-repellent film-coating liquid composition and process for preparation of water-repellent film-coated articles

Abstract: There are provided articles coated with high-performance water-repellent films with high hardness that can withstand outdoor use, which are water-repellent film-coated articles that comprise a substrate and a water-repellent film composed mainly of silicon oxide and having a water-repellent group coated on the surface of the substrate, and are characterized by containing at least one type of metal oxide selected from the group consisting of magnesium oxide, calcium oxide, strontium oxide and boron oxide, as well as a process for preparation of such water-repellent film-coated articles at a high rate of productivity and a coating liquid composition for preparation of such water-repellent film-coated articles.

Mechanochemical Decomposition of an Aromatic Polyamide Film

Abstract: A film sample of aromatic polyamide, or so-called Aramid, was subjected to grinding in air with calcium oxide (CaO) powder by using a planetary ball mill, to investigate its mechanochemical decomposition. The reaction was found to proceed with an increase in the period of grinding time, and all chlorine in the film was transformed into inorganic chlorides in prolonged grinding. The process was characterized by X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopic observation, and Raman shift analysis. The main products after decomposition reaction were water-soluble calcium chloride hydrate, amorphous carbon, calcium carbonate, and a small part of calcium nitrite, as a result of a rupture in the covalent bonds of C−C, C−Cl, C−N, and C−H in aramid film construction into some new bondings. The most significant phenomenon was the formation of Ca(NO2)2, suggesting the strong oxidative ability of CaO during the mechanochemical reaction.

Method for preparing nano active calcium carbonate

Abstract: The preparation method of nano active calcium carbonate is characterized by that it uses the carbide slag as raw material, which includes the following steps: adding water into calcium oxide obtainedby cleaning carbide slag, digesting to obtain calcium hydroxide sturry liquor with a certain concentration, then introducing CO2 and at the same time adding additive to make carbonization reaction, and controlling a series of technological parameters to prepare nano calcium carbonate with a certain grain size, then adopting a certain surface treatment process to make the nano calcium carbonate undergo the process of organic surface modification and make it surface be oleophilic and have good dispersion property in oil phase.

additives for preparing rheology-modified aqueous fluids

Abstract: A rheology modified aqueous fluid composition comprising clay, water, magnesium oxide, aluminum oxide hydroxide, sodium carbonate or potassium carbonate, and calcium oxide or calcium hydroxide. The magnesium oxide and aluminum oxide hydroxide are prepared by a specific thermal treatment protocol involving heating of appropriate precursors within a specified temperature range. The pH of the composition is at least about 10. The composition is prepared by admixing the components and, optionally, sodium oxide or sodium hydroxide for pH adjustment as necessary. A substantially dry rheology modification agent comprising the enumerated components, not including the water, is also included. The resulting composition preferably exhibits shear-thinning capability including very rapid thinning upon application of shear forces and also rapid viscosification upon removal of such forces.

Antibacterial health ecologic nanopaint

Abstract: An antibacterial health-care nano paint is characterized by that the antibacterial agent (nano particles of the oxides of Ag, Zn and copper) is added to basic material, the far infrared particles (nano particles of aluminium oxide, calcium oxide and zinc oxide) are added to filler, and the photocatalytic TiO2 and RE activated zinc oxide are added to solidifying agent. Its advantages are low cost and durable action on bactericiding and cleaning air.

Method for producing titanium oxide containing slag

Abstract: A method for producing a titanium containing slag, which comprises heating a raw material mixture containing a titanium oxide, an iron oxide and a carbonaceous reducing agent or another raw material mixture further containing a calcium oxide source in addition to the above in a reducing furnace to reduce the iron oxide in the mixture to a reduced iron, supplying the product to a heating type melting furnace, heating the product in the melting furnace to melt said reduced iron and separate it from a slag containing a titanium oxide, and discharge the resultant titanium oxide containing slag to the outside of the furnace for recovery. The method can be used for producing a titanium oxide containing slag from a material containing a titanium oxide and an iron oxide with good efficiency, while suppressing the reduction of titanium dioxide and minimizing electric power consumption.

Biodegradable and bioactive glass-ceramics, and method for fabricating the same

Abstract: Disclosed herein is a biodegradable and bioactive glass-ceramic fabricated by mixing a slowly biodegradable glass-ceramic and a highly biodegradable glass-ceramic in a predetermined mixing ratio wherein the bioactivity is maintained to be constant, and the biodegradation rate is controlled by the mixing ratio. The biodegradable and bioactive glass-ceramic is fabricated from a composition consisting of calcium oxide (CaO), silica (SiO 2 ), boron oxide (B 2 O 3 ), magnesium oxide (MgO), calcium fluoride (CaF 2 ) and phosphorus pentoxide (P 2 O 5 ).

Clinical application of calcium hydroxide in dental pathology and endodontics.

Abstract: Calcium hydroxide has a hard tissue inducing effect. It is a powder, that can be mixed with a physiological saline to a paste. The paste is highly alkaline with a pH 12.5 and its application to the pulp results in necrosis of the part of coronal pulp tissue shows no or only a milled inflammatory reaction. Analyzing the pH and the concentration of calcium ions in the periapical area, it is obvious that at least 2 weeks are necessary for calcium hydroxide bactericide activity. Calcium hydroxide retains its anti-bacterial properties for about two months when placed under a restoration, after which it degrades to calcium oxide and other less effective calcium salts. All calcium hydroxide preparations have a limited shelf life as they eventually turn into calcium oxide. Calcium hydroxide can be used as linings, for indirect and direct pulp cupping, root dressing, root canal sealant, apical closure. The vehicles play a supportive role, giving pastes chemical characteristics such as dissociation and diffusion as well as favoring the correct filling of the root canal which are decisive factors for antimicrobial potential and tissue healing. The mechanism of action of calcium hydroxide on tissues, inducing the deposition of mineralized tissue, is an extremely important aspect for the indication of calcium hydroxide, because it demonstrates biological compatibility of calcium hydroxide.

Method and apparatus for hydration of calcium oxide

Abstract: An improved system for slaking of lime which does not rely on the weighing of materials delivered to the vessel where the mixing takes place. A control system is utilized to control the volume of lime and water delivered to insure that a preselected temperature is obtained during the chemical reaction in the vessel. In a batch process the volume of lime and water is controlled based on the temperature sensed to maintain the temperature at the desired level. Once the reaction is complete the resultant slurry is discharged from the vessel for further processing. The vessel is then cleansed and prepared for the next batch.

Packaging material used for a display device and method of forming thereof

Abstract: A packaging material used for a display device which is a desiccative-containing adhesive agent The desiccative-containing adhesive agent is composed of a liquid-state organic material selected from a group including epoxy resin, polyurethane, bakelite, polyamide, acrylic resin and polysiloxane, and a solid-state desiccative selected from a group including alkaline metal oxide, alkaline-earth metal oxide, metallic halide, barium oxide, calcium oxide, calcium sulfate, calcium chloride, lithium chloride, calcium bromide, potassium Carbonate, aluminum oxide, magnesium oxide, copper sulfate, zinc chloride, zinc bromide, cobalt chloride, silica gel, zeolite and molecular sieve