Showing papers on "Calcium oxide published in 1999"

Effectiveness of Portland Cement and Lime in Stabilizing Clay Soils

Abstract: Pavement subgrades constructed with clay soils can cause significant pavement distress because of moisture-induced volume changes and low subgrade support values. Lime is well known for its ability to stabilize plastic clays; however, portland cement also provides highly effective clay stabilization, usually with the added benefit of higher strength gain. Stabilizing clays with cement or lime can improve subgrade properties at a lower cost than either removing and replacing material or increasing the base thickness to reduce subgrade stress. The clay soil stabilization mechanism for the calcium-based stabilizers portland cement and lime is reviewed. These materials modify soil properties through cation exchange, flocculation and agglomeration, and pozzolanic reaction. Additionally, cement provides hydration products, which increase the strength and support values of the subgrade materials as well as enhance the permanence of the treatment. Comparative laboratory and field performance studies by others, fo...

Product Layer Diffusion during the Reaction of Calcium Oxide with Carbon Dioxide

Abstract: The carbonation rate of 15−20 μm, nonporous, calcium oxide crystals has been studied over a temperature range of 550−1100 °C and a CO2 pressure range of 1−11.7 atm. At temperatures greater than 600 °C, the carbonation rate decreases more rapidly with time than would be expected from diffusion through a uniform product layer and the activation energy is initially low but increases with conversion. The product layer consists of crystalline grains, and these product layer grains grow by coalescence from less than one μm diameter to the approximate dimension of the particle. The carbonation rate can be described by a model where CO2 pressure-independent grain boundary diffusion and diffusion through the carbonate crystals act in parallel. The relative importance of bulk diffusion through the product layer crystals increases with time relative to transport through the grain boundaries and has an effective activation energy of 57 kcal/mol. Diffusion through the crystal boundaries has low activation energy and l...

Influence of sodium oxide content on bioactive glass properties

Abstract: The rate of in vivo degradation and level of bioactivity of bioactive glasses are composition dependent [1]. By altering bioactive glass composition, the rate of resorption can be controlled. The network connectivity of a glass can be used to predict various physical properties of the glass including its solubility and, hence, its bioactivity [2]. Glass solubility increases as network connectivity is reduced. Glasses in the soda-lime phosphosilicate system were studied. The initial choice of composition was based on phosphate content and low network connectivity. A systematic substitution of calcium oxide for sodium oxide on a molar basis was made in order to examine the influence of sodium oxide content on the glass properties while keeping the network connectivity constant. The glass transition temperature and the peak crystallization temperature were seen to decrease linearly with increasing sodium oxide content. Thermal expansion coefficient and glass density were also seen to be related to sodium oxide content. Preliminary in vitro biocompatibility studies revealed that the glasses of higher sodium oxide content were associated with a cytotoxic response. The measurement of media pH indicated that this cytotoxic effect was due to ion exchange reactions at the glass surface.

Modification of titanium by ion implantation of calcium and/or phosphorus

Abstract: Pretreatment of titanium by implantation of P and Ca is of interest in order to improve the quality of hydroxyapatite coatings used to enhance its biocompatibility. A near surface implantation of high doses of calcium results in an oxidation of the modified layer and the formation of CaO. By post-implantation annealing also Ca4Ti3O10 is formed. For deeper calcium implantations, precipitation of the metastable hexagonal modification of calcium has been observed instead of the cubic equilibrium phase. By high dose implantation of phosphorus, the implanted layer becomes partly amorphized. This hinders the reaction with oxygen during implantation and room temperature aging. The thickness of the surface oxide corresponds to the native oxide layer. For high dose double implantation with both elements, due to the strong swelling effect and the incorporation of oxygen, the second implant is shifted to the surface, if the energies are chosen so that the profiles should be overlapping by implantation into pure titanium. No indication for compound formation besides calcium oxide has been found as a result of the implantation.

Physical properties and self-setting mechanism of calcium phosphate cements from calcium bis-dihydrogenophosphate monohydrate and calcium oxide

Abstract: An apatitic calcium phosphate cement was developed from calcium bis-dihydro-genophosphate monohydrate (or monocalcium phosphate monohydrate, MCPM) and calcium oxide (CaO). The powder had a Ca/P molar ratio of 1.67, and the liquid was either pure water or 0.25 M–1 M sodium phosphate buffer, pH 7.4. The influence of the powder-to-liquid (P/L) ratio on the setting time and the mechanical strength were studied. The best results were obtained for the 1 M phosphate buffer with a P/L ratio of 1.53; the setting time was 7 min and the compressive strength was 25 MPa after 24 h and 33 MPa after 11 d. The mechanism and kinetics of the setting reaction were investigated by X-ray diffraction, differential scanning calorimetry, 31P magic angle spinning–nuclear magnetic resonance and infrared spectrometry. The setting reaction was found to be biphasic: in the first step, during the mixing time, MCPM reacted with CaO immediately to give calcium hydrogenophosphate dihydrate (or dicalcium phosphate dihydrate, DCPD) which, in the second step, reacted more slowly with the remaining CaO to give hydroxyapatite. The conversion of the starting materials to hydroxyapatite was complete within 24 h when the liquid was water, but was slower and incomplete with the phosphate buffers. Of the starting materials, 30% remained after 3 d. © 1999 Kluwer Academic Publishers.

Dry soda lime markedly degrades sevoflurane during simulated inhalation induction.

Abstract: We have investigated gas composition during simulated inhalation induction with sevoflurane to elucidate possible mechanisms of incidental prolonged induction times and airway irritation. Using a circle system, 8% sevoflurane in oxygen 6 litre min-1 was washed into an absorbing canister filled with fresh soda lime containing 2.9% KOH (Draegersorb, 'D') or no KOH ( 2.5 mg, S > 0.6 mg). In summary, the use of moist soda lime is of crucial importance during inhalation induction. With dry soda lime, the patient may inhale potentially toxic degradation products in significant amounts. Sevoflurane degradation is aggravated by a high KOH content of the lime. The observed airway irritation may be caused by formic acid, which is generated in isomolar concentrations with methanol (Cannizzaro reaction). The amount of compound A found with dry KOH-containing lime is unlikely to be noxious.

Silicone rubber composition for producing cables or profiles with retention of function in the event of fire

Abstract: A composition which is useful for producing profiles and cable insulation which retain their function in the event of fire, comprise peroxidically crosslinking or condensation-crosslinking silicone rubber, metal oxides selected from magnesium oxide, aluminum oxide, tin oxide, calcium oxide and barium oxide and metal compounds of this class which produce oxides on heating, boric acid, zinc borate, and a platinum complex having at least one unsaturated group.

Mineral Composition of Build-up in Cement Kiln Preheater

Abstract: Use of a short rotary kiln with a cyclone preheater allowed the internal recirculation of volatile constituents, essentially consisting of compounds of potassium, chlorine and sulphur. These compounds underwent partial condensation on the raw material grains, composed mainly of calcite. The increasing concentration of volatile constituents created convenient conditions for the crystallization of new phases, particularly sylvite. Beautiful crystals of this phase were formed, probably by the VLS mechanism. Thermal analysis revealed that a liquid phase was formed in the system at the relatively low temperature of about 630°C, which enhanced the reaction of silica with calcium carbonate, and spurrite was formed. Thus, the build-ups were composed mainly of calcite, sylvite and spurrite, and in some cases also of calcium oxide and anhydrite. Sulphospurrite, gehlenite, calcium langbeinite, dicalcium silicate and calcium aluminate, 12CaO·7Al2O3 were found as minor components.

Stabilizer combination for halogen-containing thermoplastic resin compositions

Abstract: The invention relates to a stabilizer combination for halogen-containing thermoplastic resins, comprising (a) calcium hydroxide and/or calcium oxide, which can possibly be surface-modified; and (b) an isocyanurate containing hydroxyl groups This stabilizer combination is especially suitable for weather-resistant halogen-containing resin compositions such as rigid PVC

Thermodynamic description of 'FeO'-MgO-SiO2 and 'FeO'-MnO-SiO2 melts: a model approach

Abstract: Activities of the oxide components in the 'FeO'-MgO-SiO2 and 'FeO'-MnO-SiO2 systems have been predicted based on the information of binary systems using a thermodynamic model. The model considers t ...

Study of the Adsorption of CdCl2 Vapor on Various Minerals Using a Drop Tube Furnace

Abstract: Most of these studies were performed with fixed bed or thermogravimetric apparatus, and it is often difficult to correlate the results of these experiments with incineration flue gas conditions. To study more precisely the reaction between heavy metal vapor and suspended particles, the GRE laboratory has developed a drop tube furnace. With this experimental setup, it was possible to quantify the adsorption of cadmium chloride on different sorbents in conditions representative of incinerators; a dilute stream of particles was in contact with a counter current flow of metal vapors at high temperature during a few seconds. Leaching was done to quantify the physisorbed and chemisorbed fractions of the metal. Silica, alumina, alumina-silica, and calcium oxide were used, and the influence of sorbent surface area, gas temperature, and metal vapor concentration was studied. Alumina and calcium oxide were found to be more effective for cadmium capture. The leachable fraction of cadmium on each sorbent appears to be very low. This is in favor of a chemisorption mechanism. Results were correlated with Freundilch isotherms to get characteristic values of vapor chemisorption on these sorbents.

Glass composition and substrate for information recording medium

Abstract: A glass composition having a high Young's modulus and a low density is disclosed which can be mass-produced by a continuous process and easily made to have high surface smoothness. Also disclosed are a substrate including the glass composition and reduced in bending and resonance even upon high-speed rotation, a recording medium usable at a lower flying height, and an information recording device having a higher recording capacity and a shorter access time. The glass composition includes, in terms of mol %, 40 to 55% silicon dioxide (SiO2), 0.5 to 6% aluminum oxide (Al2O3), 2 to 20% lithium oxide (Li2O), 0 to 10% sodium monoxide ((Na2O), 2 to 30% R2O (R2O=Li2O+Na2O), 5 to 25% magnesium oxide (MgO), 0 to 25% calcium oxide (CaO), 0 to 10% strontium oxide (SrO), 10 to 40% RO (RO=MgO+CaO+SrO), 0 to 10% titanium dioxide (TiO2), and 0 to 5% zirconium oxide (ZrO2).

Process for preparing and modifying synthetic calcium carbonate

Abstract: The present invention concerns a process for preparing calcium carbonate-based pigment from calcium oxide and/or calcium hydroxide and carbon dioxide in the presence of water. According to the invention, the starting materials are reacted in fluid state containing at least 20 parts by volume of gas for each part by volume of a suspension formed by water and solid substances, and the amount of water is essentially equivalent to the amount which is evaporated during the reaction together with the amount left in a calcium carbonate product which behaves like a powder. By means of the present invention, PCC in powder form can be prepared without the product first having to be separated from a slurry.

Production of Zirconia from Zircon by Thermal Reaction with Calcium Oxide

Abstract: Thermal reaction of Zircon with lime is studied within the temperature range 1200-1500°C for periods up to 4h. The heating products are examined physically, chemically and mineralogically. The extent of reaction is determined from the solubilized silica obtained by leaching the sintered products in hydrochloric acid. A product assaying -91% ZrO2 in monoclinic form is obtained by HCl acid leaching of the product fired at 1400°C for 2h in presence of 1.2 stoichiometry calcium oxide. The thermal reaction of decomposition at the aforementioned temperature seem to follow a diffusion kinetic model in the form of x+(1-x)In(1-x)=kt, where x is the extent of solubilized silica in time t and k is the rate constant. The apparent activation energy of the process was calculated and found to be 205kJ/mole.

Method for making manufactured aggregates from coal combustion by-products

Abstract: This is a method for producing manufactured aggreates from coal combustion by-products having sulfur. Recycle fines containing calcium hydroxide, and aluminum-containing material, and water are mixed together to form a feed mix which is agglomerated into a an gglomerated product. The agglomerated product is combined with curing fines which contain calcium oxide which together form a blended mix. The blended mix is cured using the moisture in the blended mix which is used to exothermally hydrate the calcium oxide in the blended mix to form calcium hydroxide and which autogenically provides the required heat for curing and converts the calcium oxide in the blended mix to a dry calcium hydroxide-containing material to form aggregate products and dry fines. The aggregate products are separated from the dry fines, the dry fines are recycled to the mixing step and the aggregates are taken and used as a useful product for other purposes.

Raw coal treating agent

Abstract: The raw coal treating agent consists of sulfur-fixing agent, swelling agent, catalyst and oxidizing agent,and its adding quantity is 25%-4% of raw coal weight Said raw coal treating agent contains 76%-82% of powdered sulfur-fixing agent with grain size of 1 mm-6mm, 10%-13% of swelling agent which can be sodium chloride, potassium nitrate, sodium nitrate and calcium carbonate, 2%-3% of catalyst which can be ironic oxide, manganese dioxide, chromic oxide and cobaltous oxide and 5%-7% of oxidizing agent which can be potassium permanganate, potassium chlorate, potassium nitrate and sodium nitrate The above-mentioned sulfur-fixing agent contains 70%-85% of calcium oxide and 15%-30% of calcium carbonate, sodium carbonate and magnesium oxide It also possesses adhesive which can be paper-making waste liquor, aluminium-making waste slag or soap-making waste residue Its sulfur-fixing efficiency can be up to 70%, and the dust discharge also can be reduced

Zirconium dioxide based material, surgical cutting tools made of zirconium dioxide based material, tools made of zirconium dioxide based material

Abstract: A on zirconium dioxide based material stabilised by an yttrium oxide, contains an additional metal oxide as a stabilising component selected from a group consisting of calcium oxide, magnesium oxide, strontium oxide, scandium oxide, and oxides of rare-earth elements from europium to lutetium. The proportion of said components is as follows (mole %): yttrium oxide: 0.5-4.5; stabilising component: 0.1-4.5; zirconium oxide: the rest. The inventive surgical cutting tool comprises a blade with a stem and a blade holder for rigid fixing thereof. The blade is made of one crystal of the zirconium dioxide based material. The crystal has a nanocrystal structure with domain dimensions of 200 nm without phase interfaces. The material is stabilised by the yttrium oxide and contains the additional stabilised component such as metal oxide selected from a group consisting of calcium oxide, magnesium oxide, strontium oxide, scandium oxide, and oxides of rare-earth elements from europium to lutetium. The proportion of said components is as follows (mole %): yttrium oxide: 0.5-4.5; stabilising component: 0.1-4.5; zirconium oxide: the rest. Said material can also be used for manufacturing technological tools, for example rollers, dies, plain bearings.

Lightweight non-sintered bricks made from coal cinders

Abstract: A fire-free light brick is made up of calcined garbage, powdered coal ash, slag or sandstone, cement, calcium oxide, calcium sulfate, sodium sulfate, sodium silicate, and sodium fluosilicate through press shaping. It features simple manufacture process, low cost and reducing environmental polution.

Glass for precision press molding, optical parts and method for production thereof

Abstract: PROBLEM TO BE SOLVED: To provide optical glass suitable for obtaining optical parts having high refractive indices and low dispersions by precision press molding. SOLUTION: This glass for precision press molding consists of, by weight, 26-39% boron oxide, 16-26% lanthanum oxide, 4-11% yttrium oxide, 3-17% silicon oxide, 3-7% lithium oxide, 2-17% calcium oxide, 5-18% zinc oxide and 0.5-12% sum total of 0-7% gadolinium oxide and/or 0-7% zirconium oxide and has 1.67-1.71 refractive index nd, 50-55 Abbe's number νd, <950°C liquid phase temperature L.T and ≤545°C transition temperature Tg of the glass. COPYRIGHT: (C)2001,JPO

Process for preparing super-high basicity-value calcium alkyl salicylate

Abstract: The invented preparation method uses alkyl salicylic acid and calcium oxide as raw material, and uses methyl alcohol and ammonia type compound as accelerator to synthesize the calcium alkyl salicylate with extra high base number. Said invented synthesis process is applicable to industrial calcium oxide with different activity, and the invented synthetic product possesses a certain antioxidative and corrosion-resisting property as well as high-temp. cleaning property, so that it is an excellent additive for lubricating agent.

Phosphate glass for precision molding, optical element using the same, and production of optical element

Abstract: PROBLEM TO BE SOLVED: To miniaturize an image pickup device utilizing a solid image pickup element and reduce the production cost by making the phosphate glass include a specific amount of phosphorus oxide and copper oxide SOLUTION: This phosphate glass for precision molding is obtained by mixing 35-50 wt% phosphorus oxide with 17-48 wt% zinc oxide, 0-18 wt% alkali metal oxide comprising 0-5 wt% lithium oxide, 0-10 wt% sodium oxide, 0-18 wt% potassium oxide and 0-15 wt% cesium oxide and 0-15 wt% alkaline earth metal oxide comprising 0-5 wt% magnesium oxide, 0-7 wt% calcium oxide, 0-7 wt% strontium oxide and 0-10 wt% barium oxide (with the provide that total amount of the alkali metal oxide and the alkaline earth metal oxide is 1-35 wt%), 0-5 wt% aluminum oxide, 0-7 wt% scandium oxide, 0-20 wt% lead oxide and 02-10 wt% copper oxide so that total content thereof becomes >=80 wt% and heating and melting the mixture at 900-1,280 degC and carrying out stirring, defoaming and homogenization of the mixture The phosphate glass has <=500 degC yield point

Effects of hydrated lime on the behaviour of mastics and on their construction ageing

Abstract: This work concerns the influence of calcium hydroxide added to limestone filler: this addition may be comparable to modifying the bitumen. Experiments were performed on mixes containing different combinations of two bitumen, two fillers (one 'active filler' containing 25 wt-% of hydrated lime) and two aggregates. To study the interaction bitumen/filler, properties of fresh and aged binders and mastics have been determined and compared: stiffness and phase angle between -30 degrees C and +60 degrees C, asphaltenes content, generic composition, infrared spectra, the rate of 'construction' ageing. Also were determined the amount of adsorbed/absorbed bitumen to fillers and the size distributions of 'bitumen-molecules' solved in different solvents after having been in contact with the two filler materials. Mix behaviour has been investigated by retained Marshall and Cantabro tests on different asphalt mixes. It was found that specific physico-chemical interactions between bitumen and filler exist, leading to a reconfiguration of the bitumen molecules. Hydrated lime improves the rheological behaviour particularly at higher temperature and reduces construction ageing by 10 to 30%. Retained Marshall tests on dense asphalt mixes showed no effect (void contents were too low), but retained Cantabro tests on porous asphalt mixes showed beneficial efffects of active filler from 30 to 50% (in lifetime expectancy). Asphalt mixes can thus still be improved by selecting components that are 'compatible' by nature or that are made compatible by using additives. It has been proved that hydrated lime added to limestone filler is an active additive: it may, in these respects, lengthen the lifetime of pavements considerably (some 30 to 50% in case of porous asphalt). Therefore it is recommended, for wearing courses and especially for porous asphalt mixes, to account for the origin of the components in mix design and production. If the components are not compatible, it is advised to use adequate additives. (A) For the covering abstract see ITRD E104741.

Bindemittel für Spachtelmassen und Dünnbettmörtel

Abstract: A binder contains calcium sulphate, calcium hydroxide and/or calcium oxyde and a calcium sulfoaluminate cement with a Fe2O3 content of between 0.1 and 12 wt %. The ratio between calcium sulfoaluminate cement and calcium hydroxide or calcium oxide equals 5 to 25 and the ratio between calcium sulfoaluminate and calcium sulphate equals 1.5 to 4.5.

System for thermo-chemical accumulation of heat

Abstract: not available for EP1071915Abstract of corresponding document: WO9953257The invention relates to a system for thermo-chemical accumulation of heat and for exploiting the same, comprising a calcium oxide regeneration section (10) and a heat generation section (1), said calcium oxide regeneration section (10) comprising an energy production central able to provide overheated vapour (11) at about 600 DEG C or electric energy to a regenerator (10), calcium hydroxide feeding means, to feed calcium hydroxide within said regenerator (10), and means for the separated extraction of calcium oxide and water generated by said regenerator (10), said heat generation section (1) comprising a reactor (5) within which calcium oxide and water are fed, and from which heat produced by the reaction between calcium oxide and water is extracted by a heat exchanger (2).

Supercritical water and heat supply system

Abstract: PROBLEM TO BE SOLVED: To provide a heat-supply system for supplying heat required in a large amount for supercritical water and calcining calcium carbonate when using a reaction system as a fuel reformer or raw material reformer in a practical scale SOLUTION: In a system for supplying supercritical water 24 and heat 28 to an apparatus for producing hydrogen and methane by fixing carbon dioxide to calcium oxide 23 as calcium carbonate by reacting a carbon-containing solid fuel 21 with supercritical water 22, a device for supplying high temperature supercritical water which supplies supercritical water by heating and a device for supplying heat which supplies heat 2 required to calcine calcium carbonate 27 and regenerate the calcium oxide 23 are installed

Flux for steelmaking, production thereof and steelmaking method using it

Abstract: PROBLEM TO BE SOLVED: To provide a flux for steelmaking containing calcium-ferrite as an effective component instead of fluorspar and a producing method thereof. SOLUTION: The flux for steelmaking is the one which coats at least a part of the surface of grains obtd. by sintering calcium oxide, particularly lime stone 2A with the calcium-ferrite layer. Aqueous slurry containing iron oxide 1A and the lime stone is stuck on the surface of grains obtd. by crushing the lime stone and charged together with the lime stone grains into a rotary kiln and sintered at 1200-1400 deg.C, and after producing the calcium-ferrite by reacting between the iron oxide and calcium oxide, the calcium oxide grains are separated.