Rawlings, J. Wu, A. ABSTRACT Glass-ceramics are polycrystalline materials of fine microstructure that are produced by the controlled crystallisation devitrification of a glass. Numerous silicate based wastes, such as coal combustion ash, slag from steel production, fly ash and filter dusts from waste incinerators, mud from metal hydrometallurgy, different types of sludge as well as glass cullet or mixtures of them have been considered for the production of glass-ceramics.
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- Slag-sitall production by a hot-pressing method
- Use of waste materials in the construction industry
- Glass-Ceramics Their Production
- Construction materials examples. Construction materials
- Refractories and Industrial Ceramics (v.52, #2)
- US20020192422A1 - Glass ceramic composite of mirror blank - Google Patents
- Glass-ceramics: Their production from wastes—A Review
- GOST 9900-2013
Slag-sitall production by a hot-pressing methodVIDEO ON THE TOPIC: 304 stainless steel catherinetatetickets.comuction material catherinetatetickets.comng material supplier.
This application is a continuation of U. EP The invention primarily relates to lithium silicate materials which can be easily shaped by machining and subsequently converted into shaped products with high strength.
There is an increasing demand for materials which can be processed into dental restorative products, such as crowns, inlays and bridges, by means of computer controlled milling machines. A so-called chair-side treatment is thus possible for the dentist. First of all, they need to have in the finally prepared restoration appealing optical properties, such as translucence and shade, which imitate the appearance of the natural teeth.
They further need to show high strength and chemical durability so that they can take over the function of the natural tooth material and maintain these properties over a sufficient period of time while being permanently in contact with fluids in the oral cavity which can even be aggressive, such as acidic in nature.
Secondly and very importantly, it should be possible to machine them in an easy manner into the desired shape without undue wear of the tools and within short times. This property requires a relatively low strength of the material and is therefore in contrast to the desired properties mentioned above for the final restoration. DE-A 50 discloses lithium disilicate glass ceramics which are primarily intended to be shaped to the desired geometry by a hot-pressing process wherein the molten material is pressed in the viscous state.
It is also possible for these materials to be shaped by computer aided milling processes. However, it has been shown that the machining of these materials results in a very high wear of the tools and very long processing times. These disadvantages are caused by the high strength and toughness primarily imparted to the materials by the lithium disilicate crystalline phase. Moreover, it has been shown that the machined restorations show only a poor edge strength.
Further approaches of achieving easy machinability together with a high strength of the final restoration have also been made. Subsequently, the green bodys are sintered to increase the strength.
This leads to difficulties in preparing the restorations with exactly the dimensions as desired. The substantial shrinkage represents a particular problem if complicated restorations are manufactured, such as a multi-span bridge. From S. These Ag-particles serve as crystallization agent in a lithium metasilicate phase.
The areas which were exposed to light are in a subsequent step washed out by diluted HF. This procedure is possible since the solubility of the lithium metasilicate phase in HF is much higher than the solubility of the parent glass.
Also investigations of Borom, e. Borom, A. Turkalo, R. However, there also exist compositions which crystallize in the form of the disilicate phase from the beginning and the metasilicate phase is not present at all. A systematic investigation of this effect has not become known. From the investigations of Borom it is also known that the glass ceramic which contains lithium metasilicate as the main phase has a reduced strength compared to the one of a glass ceramic which only contains a lithium disilicate phase.
It has further been found out that the presence of ZnO in lithium silicate glass ceramics of the prior art is undesirable especially when highly translucent dental restorations are to be produced.
Under such circumstances, the strong opalescent effect caused by ZnO is apparent and results in unacceptable optical properties for a restoration which is to imitate the natural tooth material. It is, therefore, an object of the present invention to eliminate these disadvantages and in particular to provide a material which can be easily shaped by computer-aided milling and trimming processes and can subsequently be converted into a high-strength dental product which also displays a high chemical durability and excellent optical properties and exhibits a drastically reduced shrinkage during said final conversion, and achieves all these properties without the need for ZnO as a component.
This object is achieved by the lithium silicate glass ceramic according to the invention. It has surprisingly been shown that by using a starting glass of a very specific composition and a specific process it is possible to provide in particular a glass ceramic which has metastable lithium metasilicate Li 2 SiO 3 as main crystalline phase rather than lithium disilicate Li 2 Si 2 O 5.
This lithium metasilicate glass ceramic has a low strength and toughness and hence can be easily machined into the shape of even complicated dental restorations, but can after such machining be converted by a heat treatment into a lithium disilicate glass ceramic product with outstanding mechanical properties, excellent optical properties, in particular a strongly reduced opalescence, and very good chemical stability thereby undergoing only a very limited shrinkage.
The lithium silicate glass ceramic according to the invention comprises the following components:. Component wt. It is surprising that even without presence of ZnO the glass ceramic according to the invention fulfils the mentioned multiple requirements. This was possible by the selection of the other components and their amounts and preferably by the ratios of some of these components to each other.
Preferred glass ceramics are those which comprise lithium metasilicate as main crystalline phase. Such glass ceramics are also referred to in the following as lithium metasilicate glass ceramics.
It has also been found out to be beneficial if the glass ceramic comprises 0 to 2. Particularly preferred glass ceramics comprise 0. It serves to induce formation of lithium metasilicate crystalls and is preferably P 2 O 5. Further, it was shown that a specific molar ratio of SiO 2 to Li 2 O serves to ensure that upon the necessary heat treatment of a corresponding starting glass mainly lithium metasilicate and lithium disilicate, respectively, is produced.
This is of particular importance. While a lithium metasilicate glass ceramic essentially free of lithium disilicate results in particular in an excellent machinability, a lithium disilicate restoration essentially free of the easily dissolvable lithium metasilicate has a very good chemical stability. Thus, it was found preferable that the molar ratio of SiO 2 :Li 2 O is at least 2.
Moreover, investigations revealed that the molar ratio of Al 2 O 3 :K 2 O is of significance for obtaining the desired tranclucence and the predominant crystallization of lithium metasilicate. It is preferred that the molar ratio of Al 2 O 3 :K 2 O is in the range of There also exist preferred ranges for the amounts of components of the glass ceramic according to the invention.
These can be used independently from each other. It is preferred that the glass ceramic comprises 2. It is also preferred that the glass ceramic comprises It is also preferred that the glass ceramic comprises 0 to 4. If the emphasis is on the achieving of a high strength of the final lithium disilicate ceramic, then 0 to 2.
It is further preferred that the glass ceramic comprises at least one of the following components in an amount of:. The colouring or fluorescent oxides ensure that the colour of the final dental product matches that of the natural tooth material of the patient in question.
Further, the glass ceramic may comprise as additional component Na 2 O in an amount of 0 to 2. Additional components to enhance the technical processability of the glass may also be present. Such additional components may therefore be in particular compounds such as B 2 O 3 and F which in general amount to 0 to 5. Generally the amount of lithium metasilicate is 20 to 80 vol. It has surprisingly been shown that a specific volume portion of lithium metasilicate should be present to achieve excellent processing properties.
Such a part of the volume leads to the crystals being present rather remote from each other and hence avoids a too high strength of the glass ceramic. If the emphasis is on the achieving of a high strength of the lithium disilicate ceramic, then the lithium metasilicate phase preferably forms more than 50 and up to 80 vol. The lithium metasilicate crystals are preferably of lamellar or platelet form.
This leads to a very good machinability of the lithium metasilicate glass ceramic without use of high energy and without uncontrolled breaking. The latter aspect of uncontrolled breaking is for example known from glasses which are generally unsuitable for machining.
It is assumed that the preferred morphology of the lithium metasilicate crystals is also responsible for the surprisingly high edge strength of products, e. The lithium silicate glass ceramic according to the invention preferably is in the form of a blank. The blank usually takes the form of a small cylinder or a rectangular block. The exact form depends on the specific apparatus used for the desired computer-aided machining of the blank. After the machining, the lithium silicate glass ceramic has preferably the shape of a dental restoration, such as an inlay, an onlay, a bridge, an abutment, a facing, a veneer, a facet, a crown, a partial crown, a framework or a coping.
A lithium silicate glass ceramic according to the invention which comprises lithium disilicate as main crystalline phase is a further preferred embodiment of the invention.
It is preferred that this lithium disilicate glass ceramic is formed in a process wherein the lithium metasilicate of a glass ceramic according to the invention is converted to lithium disilicate crystals. A dental product made from lithium disilicate glass ceramic according to the invention is a further preferred embodiment of the invention. It is preferred that such product is formed in a process wherein the lithium metasilicate of a glass ceramic according to the invention is converted to lithium disilicate crystals.
The lithium metasilicate glass ceramic according to the invention is preferably prepared by a process which comprises. In step a , usually a melt of a starting glass is produced which contains the components of the glass ceramic.
In order to obtain a particularly high degree of homogeneity, the glass melt obtained may be poured into water to form glass granules and the glass granules obtained are melted again. It is further preferred that the melt of the starting glass is cooled, such as to room temperature, before subjecting it to step b.
The melt of the starting glass is also usually poured into a mould to form a starting glass blank. In some cases it is convenient to control a cooling procedure such that it not only relaxes the glass, but also effects the first heat treatment of step b. In step b the starting glass is subjected to a first heat treatment at a first temperature to cause formation of nuclei for lithium metasilicate crystals. This results in formation of a great number of nuclei that ensure a very satisfactory crystal growth.
It also ensures that in the further processing after step c to give a lithium disilicate glass ceramic a very homogeneous lithium disilicate structure can be obtained. It has further surprisingly been shown that relatively high temperatures lead to high amounts of lithium metasilicate which in turn lead to a high amount of lithium disilicate in the third heat treatment. Such high amounts of lithium disilicate impart a high strength to the ceramic. Depending on the specific composition of a selected starting glass, it is possible for the skilled person by means of differential scanning calorimetry DSC and x-ray diffraction analyses to determine suitable conditions in steps b and c to result in glass ceramics having the desired morphology and size of the crystals of lithium metasilicate.
Moreover, these analyses allow also the identification of conditions avoiding or limiting the formation of undesirable other crystalline phases, such as of the high-strength lithium disilicate, or of cristobalite and lithium phosphate.
Usually, the starting glass of step a , the glass product of step b , or preferably the lithium metasilicate glass ceramic of step c is shaped to a desired geometry by machining or by hot pressing. This allows a so-called chair-side treatment of the patient by the dentist.
It is a particular advantage of the lithium metasilicate glass ceramic according to the invention that it can be shaped by machining without the undue wear of the tools observed with the tough and high-strength prior art materials.
This is in particular shown by the easy possibility to polish and trim the glass ceramics according to the invention.
Such polishing and trimming processes therefore require less energy and less time to prepare an acceptable product having the form of even very complicated dental restorations. Further, the lithium metasilicate glass ceramic according to the invention can advantageously be processed to a lithium disilicate glass ceramic of high strength, which usually has a content of 50 to 85 vol.
This heat treatment can also be effected when hot-pressing the lithium metasilicate glass ceramic to achieve a shaping. Thus, the lithium metasilicate glass ceramic can be further processed to the lithium dilsilicate glass ceramic of desired shape e. This is very advantageous for the user.
It is also possible to use for these purposes a corresponding lithium silicate glass which comprises nuclei suitable for formation of lithium metasilicate crystals.
From Wikipedia, the free encyclopedia Jump to navigation Jump to search This is a list of building materials. Many types of building materials are used in the construction industry to create buildings and structures. These categories of materials and products are used by architects and construction project managers to specify the materials and methods used for building projects. Some building materials like cold rolled steel framing are considered modern methods of construction, over the traditionally slower methods like blockwork and timber. Many building materials have a variety of uses, therefore it is always a good idea to consult the manufacturer to check if a product is best suited to your requirements.
Use of waste materials in the construction industry
Following the successful edition in , the Symposium is devoted to academic and industrial partners working on the substitution and recyclability of critical raw materials CRM in electronic, magnetic and energy harvesting devices. Raw materials are the basic, but fundamental, elements for a wealth of current technological applications. New research and development activities are required to improve the fundamental understanding of new material solutions containing reduced or no critical content while maintaining or enhancing the performance of the materials, components and products. The symposium provides an interdisciplinary platform to discuss about CRM alternatives from the modelling, synthesis, characterization, processing and device integration viewpoints. Bringing together researchers from academia and industry we aim at increasing the interaction among scientists, engineers, and students working on different areas of the CRM field that are too often treated separately.
Glass-Ceramics Their Production
Year of fee payment : 4. Year of fee payment : 8. Year of fee payment : A method for fabricating composite light-weighted glass ceramics, suitable for use as, e. Component pieces are polished then joined at low temperature using a silicate-containing joining liquid. Assembly is then performed in such a way that the joining liquid forms an interface between each component.
GOST Inorganic glass and glass crystal materials. Methods for the determination of elastic module at cross static bending. GOST General specification. GOST Bars, strips and reels of tool unalloyed steel. General specifications. GOST Technical rectified ethyl alcohol. GOST R
Construction materials examples. Construction materials
Zirconium silicate is an important raw material for ceramics. In this article, the author is going to have a brief introduction of the zirconium silicate which includes the raw material zircon, the grinding processing, the application and the future development. Request Permissions.
The risk of the increased levels of radioactive radiations determines a special attitude to the atomic energy and radwastes RW and demands the acceptance of cardinal and operative measures on their isolation from people. As regards the glass matrixes, they allow to reduce the volume of the conditioned waste products and to improve sharply physical and chemical properties of the matrix, but at the same time due to an amorphous structure have a number of disadvantages such as: high fragility, presence of numerous structural defects, low homogeneity and density and also rather low radiation resistance. During the last stage the optimal regimes of the extraction of radioactive nuclides by zeolites have been specified on the pilot machine. Thus, in the static and dynamic conditions the significant reduction of LRW volumes up to times with their transformation into a hard phase has been achieved. At the same time, the reduction of LRW volumes was considered by the participants of the above mentioned project as a temporary measure till the development of the technology of sitallization of sorbents with high concentration of radioactive nuclides and slurries got from the Deep Evaporation Machine. This direction of works, on which the prediscovery had been carried out, demands much more time and new financial support. In the suggested project the high-competent personnel will participate. Particularly the participants of the project made the following steps:.
Refractories and Industrial Ceramics (v.52, #2)
The main finishing materials in modern construction include finishing mortars and concretes ; natural and artificial masonry materials ; decorative ceramics ; materials and items made from wood, paper, glass, plastic, and metals; and paints and varnishes. Finishing materials are usually designed for interior or exterior finishing ; some materials are used for both for example, natural decorative stone, ceramic materials, and architectural glass. A special group consists of materials and items for covering floors , which must meet a number of specific requirements negligible wear , high impact strength, and so on. Finishing materials also include acoustic materials , which are used simultaneously as sound-absorbing coatings and as a decorative finish for the interiors of theaters, concert halls, and motion-picture theaters. An arbitrary distinction is made between finishing materials proper, which are used mainly to form decorative and protective coatings varnishes and paints, wallpaper, polymeric films, linoleum, and so on , and structural finishing materials , which also perform the functions of enclosing members and are components of such members decorative concrete , facing brick , glass blocks , and molded glass. A large group of finishing materials consists of facing materials , which are produced in the form of sheets, slabs, and tiles for example, asbestos-cement sheets, Stemalit, ceramic mosaic slabs and tiles, and decorative laminated-paper plastic and which are generally distinguished by their good service and architectural qualities. Under modern industrial construction conditions it is expedient to produce the facing during the manufacture of prefabricated units and to deliver the units to the assembly point with finished surfaces for example, ceramic mosaic tiles are laid in a form and concreted together with the wall panels or staircase landings. The most important finishing materials are discussed below. A traditional finishing material is natural stone , which is durable and has an attractive appearance.
US20020192422A1 - Glass ceramic composite of mirror blank - Google Patents
United States. Central Intelligence Agency. Foreign Documents Division. Studies on the Coulometric Determination of Caffeine. The Ammoniadimethyl Ether Liquidvapor Equilibrium.
Glass-ceramics: Their production from wastes—A Review
The structural materials used in chemical engineering are conventionally divided into four classes:. In addition, the composition of the steel contains impurities of silicon, manganese, as well as sulfur and phosphorus.
This application is a continuation of U. EP The invention primarily relates to lithium silicate materials which can be easily shaped by machining and subsequently converted into shaped products with high strength. There is an increasing demand for materials which can be processed into dental restorative products, such as crowns, inlays and bridges, by means of computer controlled milling machines.
Когда они снова двинулись в путь, Элвин не замедлил задать Хилвару множество вопросов. Он не мог представить себе природу любви в телепатическом обществе, и, выждав для приличия, затронул эту тему.
Хилвар охотно пустился в объяснения, хотя Элвин подозревал, что заданный им вопрос заставил его друга прервать долгое и нежное мысленное прощание. В Лисе, судя по всему, любовь начиналась с мысленного контакта; могли пройти месяцы и годы прежде чем пары встречались в действительности.
Второй раз сделать это ему уже не удастся. -- Вы что же -- хотите сказать, что Вэйнамонд только что родился. -- -- По его меркам --. Его истинный возраст невероятно велик хотя он, очевидно, и моложе Человека.