JP2006306644A - Porous fluorescent ceramic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous fluorescent ceramic realizing the utilization of mud discharged on the ground in accordance with a construction work, contributing to the prevention of environmental destruction and the reduction of treatment cost, and further utilizable in various fields such as heat insulating materials, decorative materials, building materials and road materials. <P>SOLUTION: The porous fluorescent ceramic is a sintered mixture composed of mud essentially consisting of silicon dioxide, aluminum oxide and calcium oxide, glass and a fluorescent substance, and the coefficient of volume expansion thereof is 105 to 250%. Preferably, the mud is discharged on the ground by a soil column method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a porous fluorescent ceramic having both foaming properties and fluorescent properties.

  Conventionally, porous bodies have been applied to various fields and applications. For example, a heat insulating material, a cushion material, a levitation material, a carrier water-permeable material, and the like have been developed and used using a polymer, a ceramic, a metal material, and the like.

  In addition, since phosphors can generate light without consuming electric power, energy consumption can be suppressed as much as possible. In the future, it will be applied to various fields such as decoration materials, building materials, road materials, etc. Application development is expected.

  In addition, industrial waste is required to be reused from the standpoints of preventing environmental destruction and reducing processing costs.

Conventionally, “inorganic fluorescent porous particles and method for producing the same” (Patent Document 1), “method for producing fluorescent particles” (Patent Document 2), and “fluorescent glass and method for producing the same” (Patent Document 3) has been proposed.
JP-A-11-61113 JP-A-9-241634 JP 2004-224604 A.

  The invention described in each of the patent documents described above relates to fluorescent foamed particles, and there is no description of porous fluorescent ceramics, and none of them reuse industrial waste.

  The present invention finds a new field of use from mud that is still rarely used, especially by reusing mud discharged to the ground during construction work, contributing to prevention of environmental destruction and reduction of treatment costs In addition, an object is to provide a porous fluorescent ceramic that can be used in various fields such as heat insulating materials, decorative materials, building materials, road materials, and the like.

  In order to solve the above-mentioned problems, the present invention is a sintered mixture composed of mud, glass and fluorescent material mainly composed of silicon dioxide, aluminum oxide and calcium oxide, and has a volume expansion coefficient of 105 to 250%. (Claim 1). Preferably, the mud is drained to the ground by a soil column method (Claim 2).

  According to the present invention, ceramics having moderate porosity and excellent fluorescent properties can be obtained from mud discharged to the ground with construction work such as buildings, which has wear resistance, hardness, and compressive strength. It has excellent mechanical strength such as tensile strength and high elastic modulus, and has antibacterial properties, so it can be used for applications such as heat insulating materials, decorative materials, building materials, road materials and the like.

  So far, mud generated from construction work such as soil column method, which has been rarely used, can be effectively utilized, enabling waste treatment while protecting the environment, and the cost at that time Can be reduced.

  The mud used in the present invention is mainly composed of silicon dioxide, aluminum oxide and calcium oxide, and these three kinds of oxides are contained in the mud at 60% by mass or more, preferably 70% by mass or more. Is done. It is desirable that silicon dioxide occupies 60% by mass or more, preferably 65% by mass or more in these main components.

  When these three types of oxides are within the above ranges, a porous body excellent in mechanical strength such as wear resistance, hardness, tensile strength, and high elastic modulus can be obtained. The mud may further contain various oxides such as iron oxide and magnesium oxide in addition to the oxides.

  The inorganic substance derived from the mud is contained in the sintered mixture in an amount of 4 to 30% by mass, preferably 5 to 25% by mass. When in this range, a porous body having excellent mechanical strength can be obtained. As an example of such mud, one generated from a construction site such as a building can be used. Also, what is called sandy soil can be used.

  Currently, when cutting down the underground construction of buildings and other structures, a method of forming a continuous wall with soil columns at the boundary to prevent the impact on adjacent land and buildings, that is, the soil column method is adopted. Therefore, it is possible to suitably use the mud generated in the implementation of this construction method.

  The soil column forming the continuous wall is formed in the ground by mixing a cementing material such as cement and bentonite and water, and further the soil at the site of the creation site simultaneously with or after the drilling. When soil columns are formed at the same time as the perforations, a simple calculation shows that a mixture of the cement, bentonite and other consolidated materials added at the time of forming the continuous wall and the amount of earth and sand corresponding to the amount of water on the ground. Will be discharged.

  However, since the added caking material and a part of the water penetrate into the surrounding formation, the substantial amount of the mixture is not discharged to the ground. However, when a continuous wall is constituted by a large number of soil columns, the mixture of the above-mentioned consolidated material, water and earth and sand discharged to the ground becomes large. The mixture is mud mixed with a binder such as cement and bentonite, and is used in the form of dry powder in the production of the porous fluorescent ceramic of the present invention.

Table 1 below shows an example of the chemical composition (content) of the mud dry powder (hereinafter referred to as “RS powder”), although it varies depending on the soil quality at the site.

  The sintered mixture according to the present invention further contains glass. The glass may be glass generally used for plate glass or the like, or waste glass once used. Using the latter results in waste recycling. In the production of the sintered mixture, the glass is used after mixing into dry powder.

  This glass is contained in the sintered mixture in an amount of 10 to 75% by mass, preferably 15 to 70% by mass. When the glass content is within this range, it becomes a binder of various oxides in the mud when sintering the mixture, and it has a large coefficient of thermal expansion compared to other components, so it will foam moderately It also acts as a foaming agent that can be magnified, and imparts high mechanical strength to the sintered mixture.

Moreover, the fluorescent substance which can be used for this invention can contain what kind of thing as long as it is the fluorescent substance which has a high luminous intensity and a long persistence time, and has the luminous property. A preferred fluorescent material is a compound represented by the general formula MAl ₂ O ₄ , where M is an alkaline earth metal such as Sr, Ca, Ba, Mg. Examples of the compound represented by such a general formula include SrAl ₂ O ₄ and CaAl ₂ O ₄ .

If necessary, the MAl ₂ O ₄ may be used as a main component, and a rare earth metal element such as europium Eu as an activator and a rare earth metal element such as dysprosium Dy as a coactivator may be contained. In the production of the sintered mixture, it is used in the form of each oxide, for example Eu ₂ O ₃ , Dy ₂ O ₃ .

Each of the activator and the coactivator is generally contained in the range of 0.1 to 10 mol% with respect to the compound represented by MAl ₂ O ₄ . By containing them, the luminescent properties of the sintered mixture are improved better.

In addition, as a fluorescent substance, the fluorescent characteristic is weaker than that of a compound represented by MAl ₂ O ₄ , but ZnS can also be contained. In this case, oxides such as Mn, Ag, Zn and Cu can coexist.

Phosphor substances such as MAl ₂ O ₄ and ZnS are contained in a mixture containing mud, glass and the like in an amount of 3 to 50% by mass, preferably 10 to 45% by mass. When the content of the fluorescent material is within the above range, strong fluorescence can be imparted to the sintered porous body. The fluorescent substance also acts as a foaming agent that imparts an appropriate foaming ratio when producing the sintered mixture.

  The sintered mixture according to the present invention may further contain various oxides such as boric acid and / or boron oxide, titanium oxide, nitric pentoxide, bentonite and the like. They can be contained in the sintered mixture in an amount of 5 to 60% by mass, preferably 5 to 50% by mass.

  Inclusion of boric acid and / or oxidized boric acid further enhances the fluorescence characteristics such as increasing the initial fluorescence intensity and extending the afterglow time, and also changes the expansion ratio in a wide range during the production of the sintered mixture. It can also act as a foaming agent.

  When an oxide such as titanium, molybdenum, chromium, phosphorus, potassium hydroxide, or bentonite is contained, it acts as an auxiliary agent for adjusting the expansion ratio during the production of the sintered mixture. Titanium dioxide exhibits an antibacterial effect due to its photocatalytic action.

  In sintering the raw material mixture, first, the raw material mixture is pulverized into a fine particle size powder, dried and mixed, and then sintered using a heating furnace such as an electric furnace. The heating temperature is preferably in the range of 600 to 750 ° C., and is usually slowly cooled after heating in air or in vacuum for 10 minutes to 3 hours. As a result, porous and fluorescent ceramics can be produced.

  In the raw material mixture, there is clearly no component called a foaming agent, but components other than mud play a role as a foaming agent during sintering. The expansion ratio changes depending on the content and sintering conditions, and the volume expansion coefficient. Of porous ceramics in the range of 105 to 250%, preferably 110 to 240%. Moreover, mechanical strength physical properties, such as a compressive strength, an elasticity modulus, and hardness, can be adjusted with the volume expansion coefficient.

  An example of implementation will be described below.

  As a raw material, the following powdery dry substance was sufficiently mixed using a mortar, and then a pellet was produced by applying a pressure of 20 MPa using a press molding machine. Then, using an electric furnace, it was heated in the atmosphere at a constant temperature for 20 minutes to obtain a porous body. The heating temperature was 600, 650, 700, 750, and 800 ° C. each time.

RS powder ... 0.4g
Waste glass ... 1.6g
Boron oxide ... 1.5g
Titanium oxide 0.25g
Bentonite ... 0.5g
Potassium hydroxide ... 0.5g
Fluorescent substance ... 1.9g
SrAl ₂ O ₄ ..
Eu ₂ O ₃ ... 5 mol% of SrAl ₂ O ₄
Dy ₂ O ₃ ... 5 mol% of SrAl ₂ O ₄
After sintering, 5.9 g of a hard porous body was obtained. The density was 1.39 (g / cm ³ ) and the volume expansion coefficient was 122.4%.

  In order to investigate the fluorescence, the fluorescence spectrum of the porous phosphor was measured. The result is shown in FIG. In addition, the said measurement was performed using the fluorescence spectrophotometer (Shimadzu RF-5300PC). For reference, the fluorescence spectrum of the fluorescent material used in this example was also shown in FIG.

An absorption peak corresponding to green was measured at 520 nm and coincided with the absorption peak of SrAl ₂ O ₄ which is a fluorescent substance. From the results shown in FIG. 1, it was found that the sample sintered at 600 to 750 ° C. showed strong fluorescence intensity, but when sintered at 800 ° C., the fluorescence intensity decreased significantly.

Further, X-ray diffraction analysis of the obtained porous phosphor was performed using Philips product APD1700, and the results are shown in FIG. In the figure, the X-ray diffraction peak of the fluorescent substance SrAl ₂ O ₄ is also shown for reference.

According to the above, the X-ray diffraction peak position and diffraction intensity sintered at 650, 750 and 800 ° C. were almost the same as those of the fluorescent material SrAl ₂ O ₄ . Although there is no change in the X-ray diffraction analysis result when sintered at 800 ° C., the fluorescence is lowered according to the result of FIG. The cause is considered to be that europium contained in the fluorescent material is oxidized from Eu ²⁺ ions to Eu ³⁺ ions.

In addition, the density measurement was performed using the Archimedes method. That is, the density P was calculated from the mass W ₁ of the dried sample of the sintered body, the mass W ₂ of the sintered body in distilled water, and the density Pw of distilled water using the following formula.

P = (W ₁ × Pw) / (W ₁ −W ₂ )
The volume expansion coefficient was calculated by the following method after first preparing a preform from the raw material mixture by pressure molding and determining its volume V ₀ .

Volume after sintering V = Total weight (g) / P
Volume expansion rate (%) = (V / V ₀ ) × 100

  The following powdery dry substances as raw materials were sufficiently mixed using a mortar, and then pellets were produced by applying a pressure of 20 MPa using a press molding machine. Then, it heated for 20 minutes at 650 degreeC in air | atmosphere using the electric furnace, and obtained 12.5g of porous bodies.

Sandy soil ... Silicon dioxide ... 66%
Aluminum oxide: 17%, total: 3.0 g
Calcium oxide ... 17%
Glass ... 5.0g
Boron oxide ... 1.0g
Niline pentoxide 0.5g
Potassium hydroxide ... 0.5g
Fluorescent substance ... 3.0g
SrAl ₂ O ₄ ..
Eu ₂ O ₃ ... 5 mol% of SrAl ₂ O ₄
Dy ₂ O ₃ ... 5 mol% of SrAl ₂ O ₄
The density of the obtained sintered body was 0.95 (g / cm ³ ), and the volume expansion coefficient was 230%. In addition, fluorescence was confirmed by fluorescence spectroscopic analysis.

It is a fluorescence spectrum measurement figure of porous fluorescent substance. It is a X-ray diffraction analysis figure of porous fluorescent substance.

Claims (2)

Porous fluorescent ceramics, characterized in that it is a sintered mixture comprising mud, glass and fluorescent material mainly composed of silicon dioxide, aluminum oxide and calcium oxide, and has a volume expansion coefficient of 105 to 250%. . The porous fluorescent ceramic according to claim 1, wherein the mud is discharged on the ground by a soil column method.

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