The mixture for the manufacture of composite metal-ceramic materials and products

 

(57) Abstract:

Usage: the invention relates to the field of manufacturing metal-ceramic composite material by the method of thermosynthesis and can be used for the production of refractory ceramics, highly porous materials and materials for construction. The essence of the invention: a composition for manufacturing the metal-ceramic composite material by the method of thermosynthesis containing reaction mixture comprising iron oxide and aluminium powder, taken in stoichiometric ratio, the inert additive, a binder and a hydrocarbon additive. The composition of the charge provides for the regulation of the reaction of thermosynthesis, allowing to obtain a composite sintered material with predetermined physical and mechanical properties, structure and shape of the product. The hydrocarbon additive is introduced into the shaft in the amount of 0.75 to 2.75 wt. % and a binder in the amount of 1-2 wt. % to obtain a highly porous metal-ceramic composite material. It is proposed to use as inert components aluminum oxide, or clay, or sand, or a mixture. Encouraged to enter in the charge reinforcing perehodnogo metal into the reaction mixture to use iron oxide in the form of scale - waste of metallurgical production. table 2. 6 Il.

The invention relates to the field of production of metal-ceramic composite material by the method of thermosynthesis and can be used for the production of refractory ceramics in the form of bricks, crucibles, tubes, etc. highly porous materials for filter elements and aeration of sewage in environmental systems; highly porous nizkoteploprovodnye materials for construction, insulating panels, layers, overlays; cladding material in porous and malabarista performed in blocks, slabs, tiles, building bricks.

The known composition of the charge for carrying out oxidation-reduction reactions between oxides of transition metals and metals, reducing agents, taken in the stoichiometric ratio of /1/. In General, the redox reaction is:

< / BR>
wherei, j, k, l stoichiometric coefficients; Aithe oxide of the transition metal, for example Fe3O4, Fe2O3, Cr3O4etc. Bjmetal-reducing agent, such as Al, Mg; Dkthe metal oxide-reducing agent; Fe recovered metal oxide of the transition metal.

The disadvantage of the charge is the inability to obtain a compact of the final product due to the high exothermic effect redox reactions, leading to melting and dispersion of the final product.

Known exothermic refractory material containing 28-32% magnesite, 23-28% iron oxide, 10-13% aluminum, 18-22% of chromomagnetic, 5-6% of refractory clay, 6-9% liquid glass, is used as a prototype /2/. The disadvantage of this charge, taken as a prototype, is the inability to conduct controlled reaction kinetics by varying the concentration of inert components and the impossibility of obtaining a porous material. This composition can be used only for the lining of metallurgical units due to the fact that the relative amount of each component in the mixture, the reaction can be initiated only at temperatures close to 1000oC.

The objective of the invention is the creation of the charge, consisting of the reaction mixture and inert additives, taken in such quantities that would regulate the reaction of thermosynthesis, allowing produces uroy and shape of the product.

The objective of the invention is a mixture containing the additive, which would get, first, the metal-ceramic composite material with high porosity, second, refractory metal-ceramic composite material, thirdly, the metal-ceramic composite material for construction work.

In addition, the aim of the invention is the utilization of metallurgical wastes.

The task is solved in that the proposed charge for manufacturing metal-ceramic composite material by the method of thermosynthesis containing exothermic mixture consisting of oxides of iron and aluminum, are taken in stoichiometric ratio, inert additives, petroleum additives and a binder, in which, according to the invention, these components are contained in the following amounts, wt.

inert additive 20-70

binder 1-2

the hydrocarbon additive of 0.75 to 2.75

exothermic mixture rest.

The addition of inert components in the reaction mixture in such a quantity allows control of the reaction thermosynthesis by linking part of the heat released during the reaction. Taking part talfiq. 1 shows a graphical representation of the process thermosynthesis made with the assumption that the influence of inert components in a heat balance is performed linearly. For a given mass of the initial reaction mixture, taken as a constant, the amount of heat Qeffallocated during the exothermic reaction, too, constantly. In the coordinates of the amount of heat Q and the concentration of inert components this reflects a horizontal line 1. When changing the concentration of inert components (increase) the amount of heat associated with it, grows linearly. In Fig.1 this corresponds to direct 2, the slope of which is proportional to the specific heat of the inert additive. The intersection of the straight line 2 with a horizontal straight line 1 allows to determine the critical value of the concentration of inert additiveskrwhere in the charge completely stops the process of structuring. Intermediate concentrations of inert additives Ciallows only partially relate the amount of heat QStthe rest amount of heat Qpgoes on structuring, i.e., either by melting or sintering or sintering with partial melting of microvolumes. Using an external source telecast heat source charge increases due to heat an external source, that leads at a constant concentration of inert components to increase heat going on structuring, QNR. At the same time, the critical value of the concentration of the inert additive is increased to values . Structuring in the range of concentration is only due to external heat source. In Fig.3, 4, 5, 6 the physical-mechanical characteristics and structure of the obtained material.

Table 1 shows in accordance with the calculation and experiment, the preheating temperature of the mixture before the reaction and reaction kinetics. These data show that there is a tight coupling between the charge and the preheating temperature.

Thus, the content of inert additives and the temperature of the external source act as effective adjustable parameters, you can use them purposefully to shape the structure and properties of the synthesized material and products.

The influence of the content of inert additives on the mechanical properties of composite cermet material shown in Fig.2, where the generalized data on physico-mechanical properties of the synthesized materials. Basic physico-fur the EO FF, characterizing the ability of the resulting material to retain the shape. The form factor is measured on a seven-point system, under which the 1 point corresponds to a complete loss of the given shape of the charge during thermosynthesis due to the melting of the reaction products, and 7 points correspond to the full preservation of the specified form.

From the graphical representation of the influence of the content of inert components on the physico-mechanical properties of the obtained composite material, when the content of inert components is less than 20 wt. the material melts, the form factor is equal to 1 point, and when the content is higher than 70 wt. decreases the strength of the resulting material below the required. The porosity of the resulting material decreases with increasing inert components.

Thus, the metal-ceramic composite material with the desired properties can be obtained when the content of the inert additive in 20-70 wt. The optimal set of properties is limited to the interval 40-60 wt. However, depending on operating conditions and material requirements necessary options dominated melting point above the sintering and, on the contrary, sintering above the melting. Then in the range of 20-40 wt. you can select the charge mode for structuring procedimentos sintering.

It is also proposed to introduce a charge hydrocarbon additive in the amount of 0.75 to 2.75 wt. and a binder in amounts of 1 to 2 wt.

The hydrocarbon additive during thermosynthesis fade (decomposes), and gas emissions form an open porous structure. As hydrocarbon additives you can use engine oil, spun oil, diesel oil, etc. as a binder, you can use liquid glass, sulfite-alcohol bard, etc. in Addition, it is proposed to use as inert components aluminum oxide and put in charge of the binder in the amount of 1-2 wt. This allows during the reaction of thermosynthesis to obtain refractory materials, representing Al2O3-the matrix and the dispersed-distributed reduced iron.

It is proposed to use clay or sand or sand and clay as an inert additive and optionally type in charge of the reinforcing elements in the form of nets and rods, as well as a binder in the amount of 1-2 wt.

Use as inert components of sand, clay allows you to reduce the cost of obtaining highly porous metal-ceramic materials.

It is also proposed as an oxide of the transition metal in R>
To obtain a highly porous structure of the synthesized composite cermet material to prepare a mixture consisting of iron oxide and aluminum taken in accordance with the stoichiometry 3Fe3O4+8Al ___4Al2O3+9Fe inert components, a binder and hydrocarbon components. As inert components take the powder of Al2O3as the binder liquid glass, and hydrocarbon additives engine oil or spun oil. The percentage of the component, as well as the porosity of the material obtained are shown in table 2. The synthesis is conducted in either the SAF or thermosynthesis. As follows from the table, the value of porosity is clearly correlated with the content of hydrocarbon additives. The upper boundary of the range is limited to 2.75 wt. because more content leads to loss of heat to the sublimation and decomposition, making it difficult to carry out reaction in the CBC mode. Below 0.75 wt. the hydrocarbon content of the additive in the mixture reduces the porosity of the end Assembly and does not allow you to use it as highly porous (porosity below 15%, see table.2).

In addition, the optimal concentration interval was chosen composition of the initial charge and prepared samples in the form paralleled the rod 2.5 mm, the grid cell size is 2.0 mm, the diameter of the wire mesh 1 mm

In the synthesis process at the indicated concentrations component reduced iron in the form of droplets of different sizes had to be welded to a reinforcing rod that increases the surface interaction of the reinforcing element with the matrix and increased the strength of coupling. TTT

1. The charge for manufacturing metal-ceramic composite material or products by the method of thermosynthesis containing exothermic mixture containing oxides of iron and aluminum, are taken in stoichiometric ratio, inert additive and a binder, characterized in that it further comprises a hydrocarbon additive in the following ratio, wt.

Inert additive 20 70

Binder 1 2

The hydrocarbon additive 0,75 2,75

Specified exothermic mixture Rest

2. The charge under item 1, characterized in that as inert additives it contains aluminum oxide, or clay, or sand, or a mixture of sand and clay.

3. The charge on the PP. 1 and 2, characterized in that it further comprises reinforcing elements in the form of nets or rods.

4. The charge on the PP. 1-3, characterized in that as oxides

 

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