Granite as flux in stoneware tile manufacturing

Natural granite was used to completely replace both feldspathic and inert components of a traditional ceramic body. Raw material from Sinai (Egypt) was added (in the range 20-35 wt%) to a commercial Egyptian ball clays (from Aswan, Egypt) in order to obtain laboratory tiles sintered at 1220 °C.Densification was studied according to ISO rules, while sinterability was estimated by optical dilatometry. Chemical, physical and microstructural analyses were accomplished to find the relationship between both the phase composition and microstructure of the fired bodies properties. The fired samples show moderate thermal expansion as well as reasonable bending strength. Therefore, as a nonconventional raw material in the modern ceramic production, the studied batches are recommended for the production of industrial fast firing tiles showing properties similar to commercial ceramic floor and/or wall tiles.     

Spodumene-bearing rock as flux for triaxial ceramic bodies

Abstract

Abstract

In this work, spodumene-bearing rock, a waste from mineral processing, was used as a flux in ceramic bodies, and its reactivity to other raw materials such as quartz and kaolin was analysed. The petrology properties of the pegmatite (parent rock) from which the flux is extracted were characterised. The grindability, fluxing strength and pyroplastic deformation of the spodumene-bearing rock were investigated. In addition, the influence of spodumene-bearing rock on technological properties of the final pieces, mainly in relation to the firing temperature, phases formation and microstructure was also analysed. Then, the firing behaviour to other commercial fluxes such as albite and feldspar was compared. The spodumene-bearing rock was considered an effective flux, capable of reducing the firing temperatures of the tested bodies by viscous flow.     

Melting behaviour of raw glazes

Melting behaviour of raw and inhomogeneous glazes influences the appearance and the properties of the final glaze surface. The melting behaviour was estimated from the sintering curves and characteristic samples measured with hot-stage microscopy. The glaze compositions were statistically chosen to cover the glaze-forming systems used in traditional ceramic industries. Altogether seventy-five compositions were mixed and ball-milled from seven different raw materials. The temperatures describing the sintering and melting of the glazes were mathematically modelled as functions of the raw material compositions. All the compositions were then also applied on raw floor tiles and fired in an industrial kiln for fast-firing (50 min) of dense floor tiles. The gloss of the fired glazes was mathematically modelled as a function of both the raw material and the oxide compositions. The resistance to abrasion and the crystalline phases of the fired surfaces were also determined.     

Untreated coffee husk ashes used as flux in ceramic tiles

The agro-industrial activities are responsible for the production of large amounts of solid wastes, which, so far, have found scarce reuse alternatives. Among the former, coffee bean beneficiation generates an equal amount of coffee husks whose highest reuse potential is as fuel. The resulting ashes are frequently an object of illegal covert disposal and a serious source of environmental impact. However, coffee husk ashes (CHA) are particularly rich in alkaline and alkaline-earth metals, and might be adequate to replace the traditional feldspars, which are used in high content as fluxes in clay-based ceramic formulations but are becoming scarce and costly. In this work, the fluxing effect of CHA additions to an industrial clay-based mixture was evaluated. Based on the characterization results and the mullite–silica–leucite phase diagram, additions of 5 to 20 wt.% CHA were made to the clay-based mixture and the resulting compositions were evaluated after sintering at temperatures between 1100 and 1200 °C (60 min soaking time). The results obtained show that firing temperatures near 1180 °C and ~ 10 wt.% CHA addition lead to linear shrinkage, water absorption and flexural strength values that fall within the range specified by floor tile standards (NBR 13817, EN 176 and ISO 13006), requiring no significant changes in processing parameters. Coffee husk ashes can thus advantageously replace feldspars in the role of fluxing material, with the potential to reduce not only natural ceramic raw material consumption, but also production and landfill costs as well as waste disposal area requirements.     

低温陶瓷釉的制备

低温烧结工艺是目前陶瓷行业节约能源、降低燃耗、提高生产效率的有效途径,因此在低温条件下烧制陶瓷釉逐渐成为研究热点。为大幅度降低烧结温度,采用磷酸钠代替基础釉中的二氧化硅的方法,促使液相在低温形成,成功研制了烧成温度为890 ℃的基础釉。当磷酸钠质量分数达到33.25%时,基础釉的烧成温度降低了290 ℃。采用场发射扫描电镜分析了样品的表面和断口形貌,实验结果表明磷酸钠能够显著降低陶瓷釉的煅烧温度。通过在基础釉中加入显色剂,实现了在低温下制备红色陶瓷釉,并且烧成温度降低了350 ℃。实验结果表明,磷酸钠在低温陶瓷釉的制备过程中起到降低温度的重要作用。这些研究结果有助于彩色陶瓷釉的研制。     

Fe-Cr-Ni-Mn系黑色陶瓷颜料的制备及呈色性能分析

以Fe₂O₃、Cr₂O₃、MnO和NiO为原料,采用固相合成法制备Fe-Cr-Ni-Mn系黑色陶瓷颜料,并使用X射线衍射仪、色度仪、扫描电子显微镜、紫外-可见分光光度计等分析手段对所制备颜料进行了表征,研究了原料配比、烧结温度、保温时间和冷却方式等对颜料呈色性能的影响。结果表明:当原料中Fe₂O₃、Cr₂O₃、MnO和NiO的摩尔比为6:1:1:1,烧结温度为1 150 ℃,保温时间为45 min,采用随炉冷却时,颜料颗粒细小,粒度分布均匀,其L^*、a^*与b^*值分别为18.02、0.20和0,禁带宽度为1.25 eV,呈纯正黑色,且物相主要由NiFe₂O₄、NiCr₂O₄和Ni[Mn_0.5Cr_1.5]O₄组成;将所制备颜料应用于黑色陶瓷釉,釉面呈纯正黑色,且光滑致密,表明所制备颜料具备优异的着色性能和应用潜力。     

缩点釉的研究与应用

利用陶瓷活性材料和添加剂等原料磨制成釉料施于坯体上,上釉的坯体釉层干燥后产生裂纹,经煅烧后釉层因张力大而收缩产生缩点现象,形成缩点釉。本文通过对原料的运用、施釉方法、施釉厚度、烧成制度等方面论述了缩点釉形成的机理。     

煅烧过程中二氧化钛微结构参数的变化和相变

采用X射线衍射研究室温到1273K煅烧过程中TiO2微结构特征和相变。结果发现：锐钛型TiO2向金红石型TiO2的转变出现在1223-1273K的高温区,此结果为高温烧结附着力强的锐钛型TiO2薄膜和将TiO2水溶胶直接加入釉料中制备光催化活性的釉面陶瓷提供了理论依据。773～973K之间的锐钛型TiO2基体中出现了质量分数小于12％的板钛型TiO2。锐钛型TiO2微晶尺寸分布在低温比在高温的均匀,其应变能量密度随煅烧温度升高明显降低。     

Life cycle assessment of a ceramic glaze containing copper slags and its application on ceramic tile

Even though copper slags have many possible applications, their disposal is still practiced, creating long-term waste management problems. This led to the investigation of new products for residential applications, taking advantages of the interesting chemical properties of copper slag. This study aims to assess the environmental impact of the use of copper slag as secondary raw material in a ceramic glaze composition and to compare it with a traditional glaze. A manufacturing process was designed, through an industrial scale up operation from experimental laboratory data and the entire life cycle of the products was analyzed using the Life-cycle assessment (LCA) methodology. Considering the production of a ceramic glaze containing copper slag, the most impacting process resulted the one related to frit production, due to the large amount of thermal energy necessary for the raw materials melting. The comparative LCA analysis carried out between the frit obtained from metallurgical slags and a traditional one, demonstrated that the innovative ceramic frit has a greater environmental advantage. The LCA analysis allowed to highlight the most impactful stages of an industrial process using copper slag as a secondary raw material for glaze production and to quantify the potential environmental advantages of this operation.     

花型结晶釉的制备及显微结构表征

针对传统结晶釉产品普遍存在的烧成温度高、保温时间长、连续化生产难等问题,以钾长石、方解石、氧化锌、玻璃粉为主要原料,在1 220 ℃成功烧成K₂O-Na₂O-CaO-ZnO-SiO₂-Al₂O₃系陶胎结晶釉,重点研究了窑炉冷却制度和着色剂对釉面效果的影响。结果表明:冷却过程中,1 100 ℃“定点保温”3 h,2%(质量分数)NiO和2%(质量分数)CuO的着色剂组合可使陶胎釉面呈现直径约4.5 cm、白色花边、绿色内簇的花状粗晶;在速率为125 ℃/h的“缓速冷却”制度下,可生成内部绿色放射状晶簇、宏观尺寸约8 mm、美观自然且边界清晰的“梅花状”晶体。采用场发射扫描电镜(FESEM)、能谱仪(EDS)、XRD等分析对典型“梅花状”晶体的显微结构、化学组成等进行了表征,发现其内部存在着六边形柱状、针状等同晶异构硅锌矿晶体。六边形柱状晶体主要聚集在“梅花”中心,由于垂直釉面方向空间受限而长大缓慢,其尺寸普遍在2 μm左右;针状晶体主要平行于釉面并向“花瓣”放射生长。底釉非晶玻璃相中存在大量纳米级分相微球结构,呈现出豆绿乳浊效果。Fe₂O₃、CuO、MnO、NiO的两两组合可使陶胎釉面呈现窑变多色的釉面结晶效果,其中Fe₂O₃与MnO,以及NiO与CuO的着色组合效果最佳。     

二氧化钛对黑色Al2O3陶瓷性能的影响

以超微细a-氧化铝粉为主要原料,添加适量过渡金属氧化物以及不同分量的TiO2粉末,采用传统粉末冶金技术、干压烧结法制备了黑色Al2O3陶瓷。对制备工艺中的原料准备、压制成型、烧结过程进行了讨论,并对其导电性能进行了测试分析。实验结果表明：TiO2是一种良好的添加剂,它不仅可以降低烧成温度,还有利于Al2O3陶瓷黑色的形成,改善其电气性能。     

陶瓷砖装饰用釉料——微晶玻璃釉

近年来，微晶玻璃材料引起众多行业的关注，主要原因在于其具有一些特殊的性能，如良好的耐腐蚀性能、机械强度高、表面硬度高、热膨胀系数低以及适应性强等特性。微晶玻璃铀应用陶瓷行业的变化是，传统的二次烧成工艺逐渐被—次快速烧成替代和传统的铀料配方有了很大的改变。     

Technological features of Renaissance pottery from Deruta (Umbria, Italy): An experimental study

This work is focused on the assessment of the basic technological features of the pottery production in Deruta in the Renaissance period. For this purpose, clay samples and two kinds of ceramic products (tiles and wares) dating back to the XVIth century were characterized using different analytical techniques: optical, cathodoluminescence and electron microscopy on thin sections, X-ray fluorescence and X-ray diffraction on the bulk powdered samples. Then two clays best representing the chemical composition of the ceramic products underwent laboratory experimental firing tests at different conditions following the procedure of firing applied in the XVIth century as reported in the ancient historical documents. The firing products underwent textural, chemical and mineralogical characterization by the same analytical techniques in order to be compared with the clays and the shards. Archaeometric investigation of the ceramic bodies led to the identification of two different clay raw materials, both of local provenance, for the tile and the ware production. Archaeometric investigation of the glazes showed some differences between the wares from different workshops. In this respect the typology and the quality of the glaze resulted to be much more effective than the texture and composition of the ceramic body in characterizing the wares from different coeval workshops. Results of the experimental tests evidenced the firing products result from a complex mix of physical and chemical variables strictly correlated to one another. Above all, the heating rate and the amount of calcite in the clay raw material are crucial driving forces of the kinetics of firing. Comparison between the original and the experimental ceramic products indicated ranges of biscuit firing temperature of 850–1050 °C and of 950–1050 °C for the tiles and the wares, respectively, and a low heating rate in both cases.     

利用地方原料研制红坯内墙釉面砖

以地方劣质红坭为主要原料，添加７％的瓷砂作助熔剂，添加１２％石灰石以减少坯体收缩，缩短烧成时间，并施用锆高乳白釉则可在辊道窑快速烧成生产出符合国家标准的红坯内墙釉面砖。     

High-alumina composite concretes and coatings based on modified phosphate binder suspensions

Coatings and materials based on aluminum phosphate suspensions are studied that have high strength in a raw state and are suitable for carrying out combined firing of a refractory and coating. An aluminum phosphate binder provides preparation of high physicomechanical properties in the firing temperature range. Use of traditional mixes with a protective aluminum phosphate coatings, and also ceramic concrete based on this binder provide increased material corrosion resistance, and consequently an increase in object operating life and period between repairs for metallurgical and glass melting units.     

Sintering of anorthite ceramic body based on interstratified illite-smectite clay

The effects of the different properties of plastic raw materials for whitewares based on different clay minerals (kaolinite vs interstratified illite/smectite [I/S]) on the sintering process (according to vacuum water absorption) was studied for anorthite porcelain body creation after firing in the range of 950–1500 °C to achieve optimal sintering temperature. The mineralogical composition of the fired bodies was observed from the firing temperature of 950 °C to the sintering temperature. Calcium carbonate decreases the sintering temperature and creates a new mineralogical phase in the fired body – anorthite – which decreases the linear thermal expansion coefficient and increases the strength (modulus of rupture) of the sintered bodies. All the described effects take place at lower firing temperatures when the I/S plastic raw material is compared with kaolin.     

结晶釉的研究进展

结晶釉以它独有的艺术风格,享有广泛的声誉,颇得消费者的青睐。传统结晶釉主要用于工艺品以及日用陶瓷上,而在建筑陶瓷上的应用较晚亦较少。为了使结晶釉在建筑陶瓷中的装饰应用更广泛,迫切需要我们在传统结晶釉配方的基础上,研制出一种符合现代建筑陶瓷产品低温快速烧成要求的新型结晶釉。本文简要介绍了结晶釉的定义以及研究现状,重点阐述硅锌矿结晶釉的历史背景、国内外研究进展和存在的问题,并指出可能的发展趋势。     

广州沙边窑出土窑具及瓷器化学组成研究

利用能量色散X射线荧光光谱仪,对广州沙边窑出土的窑具、青釉、酱釉瓷进行成分分析.结果显示,样品的胎都使用了含铝较高的原料,窑具中杂质较多,而瓷胎中还含有一定量的钾.瓷釉中的钙和钾含量相近,同为主要助熔剂,所以瓷釉多为钙碱釉.通过与西村窑同类型瓷器样品成分的比较,发现二者虽具有相似的制瓷工艺,但西村窑产品的胎、釉具有明显...     

烧结合成镁锆熟料的研究

采用轻烧氧化镁和锆英石粉为原料,研究了锆英石配合量、粉料细度及烧成温度对合成料的烧结及显微结构的影响。结果表明：在氧化镁与锆英石反应烧结过程中,锆英石分解后在初始锆英石颗粒内形成的气孔是阻碍合成料烧结致密化的不良因素;粉料细度,特别是锆英石的细度,对合成料的致密化有决定性的影响     

Utilization of energy in recuperative counterflow furnaces

Conclusions Recuperative counterflow furnaces are based on a thermotechnically ideal scheme of heat exchange and are the most promising systems for firing ceramic materials on a large scale. The thermodynamic quality of such furnaces is governed by their exergetic characteristics, which are based on the first and second laws of thermodynamics.The formation of an isothermal area of sintering in a recuperative counterflow furnace is possible on account of a small fraction of the energy of the fuel, which decreases with rise in the firing temperature. Improvement of the energy relations of the furnace and the quality of firing of the material involves optimization of the sintering parameters and reduction of the resultant heat fluxes in the high-temperature holding section.Translated from Ogneupory, No. 2, pp. 24–30, February, 1980.