Effect of the mineralogical composition of the initial clay on the properties of ceramic articles

The regular features in the variation of molding, drying, and the physicomechanical properties of ceramic articles as a function of the mineralogical composition of the clays and coal cleaning waste are determined. The proportions of the basic clay minerals required for preparing high-quality building articles are established.     

The influence of raw materials composition on the properties of fired clay products

One factor controlling formation of ceramic structures is the initial mineralogical composition which has a great influence on processing and fabrication stages and the properties of the product. This paper investigates the relationship between the mineral content of raw compositions and the product properties after thermal treatment. Optimum compositions have been established for binary and ternary systems of kaolinite, hydromica, montmorillonite and also their genetic varieties. The trends have been used to develop new ceramic compositions with improved properties.     

The influence of phosphate on the properties of clay bricks

The fabrication, properties and composition of heated phosphate-bonded clay bricks are reported. The strength of phosphate-bonded clay bodies is shown to be related to the equilibrium pH of the clay mix. The highest strengths were obtained for mixes with equilibrium pH 7 fired at 500°C which gave a modulus of rupture 60% higher than the unmodified clay heated under similar conditions but at 800°C firing temperature. The phosphate-bonded products were also of low porosity and improved dimensional stability. An insight into the probable mechanism of strength development of the heated product has been obtained from XRD, SEM and DSC studies. The results show that the properties of the phosphate-bonded clay bodies are critically affected by new mineral phases resulting from the reactions of phosphates with clay which subsequently undergo physico-chemical changes above 550°C.     

The influence of ultrasound on the thermal behaviour of clay minerals

The aim of this work is to compare the influence of sonication on the thermal behaviour of kaolinites (KGa-1, KGa-2), pyrophyllite, talc and muscovite. Sonication produces a significant increase of the specific surface area due to particle size reduction. As sonication time increases and the particle size decreases, the thermal behaviour of these clay minerals is strongly modified. Thus, there is a significant increase of the weight loss at low temperature which is related to the loss of some outer hydroxyl groups and protonated hydroxyls whose proportion in the minerals increase as the new surface generated increases. Additionally, the original endothermic dehydroxylation effects of all these minerals shift to lower temperatures. Disordered kaolinite shows the smallest shift (9 °C) while muscovite presents the largest (184 °C). A linear relation has been established between the temperature shift of the dehydroxylation and the percentage of increase in the specific surface area. The influence of sonication on the high temperature DTA effects of kaolinite, pyrophyllite, and muscovite is also studied.     

Different shades of red: The complexity of mineralogical and physico-chemical factors influencing the colour of ceramics

Different techniques (X-ray diffraction, field emission scanning electron microscope, colorimetry, visible-near infrared reflectance spectroscopy) were carried out to investigate the cause of colour changes of traditional ceramic materials. Two clayey materials of different composition, collected in the Bay of Naples, were fired in oxidising atmosphere at different temperatures resulting in different shades of red colour.Hematite is responsible of the reddish hue of ceramics and its nucleation is strictly related to firing temperature and chemical composition of the raw materials. A low CaO concentration allowed hematite to form in higher amounts providing a more intense reddish hue at high firing temperatures (over 950 °C). At the highest temperature (1100 °C) all samples showed darker colour due to increased size of iron oxide particles. Black core developed in Ca-rich ceramics fired at low temperatures as the short time of firing is insufficient to complete iron oxidation within the matrix, except in those containing high temper amounts. Indeed, microstructural modification occurs due to the presence of discontinuities among temper grains and matrix, which improves the circulation of oxygen in the core of ceramics.     

Phosphorus status of Philippine rice soils with different clay mineralogical characteristics

In an effort to relate clay mineralogies of some tropical rice soils to their P supplying status, clay mineral compositions of 214 wetland rice soils from the Philippines were determined by x-ray diffractometry, followed by Olsen P estimations on the airdried soil samples.Soils containing halloysite, kaolinite, and x-ray amorphous components (allophane and imogolite) were found deficient in available P (Olsen P < 10 mg per kg), whereas those containing montmorillonite, beidellite, vermiculite, and hydrous mica were adequate in available P (Olsen P > 10 mg per kg).     

Influence of chemical and mineralogical composition on color for commercial talcs

Commercial talcs are pulverized mineral products with a variable chemical and mineralogic composition, widely used in industry. Although generally white, they have color variations. The aim of this study was to establish relationships between color parameters and the chemical and mineralogic composition of commercial talc samples, in order to investigate the causes of color. Chlorite, dolomite, magnesite, and calcite were the most abundant accessory minerals. Fe, Mn, Ti, and Ni were the most abundant chromophore chemical elements. Factor statistical analysis (89.8% of total variance explained) revealed that the influence of each mineral species on the different color parameters a*, b*, and L* is well defined (the highest loading factors). Chlorite associated with Fe, Mn, Ti, Zr, Cu, Zn, and V, and calcite associated with Zn, Cu, Sr (and, to a lesser degree, Fe, Mn, Ni, and Co) affect the color parameters a* and b* by inducing chromatic variations (greening and yellowing). Dolomite and magnesite associated with Fe, Sr, Ni, Co, V (and, to a lesser extent, Mn and Cu) affect L* by inducing darkening.     

偶联剂对高岭土增韧聚丙烯的影响

考察了偶联剂的种类及用量、高岭土的含量等对高岭土增韧聚丙烯的影响,结果表明,NDZ-401是高岭土增韧聚丙烯的最佳偶联剂,当NDZ-401含量为1.0%、高岭土含量为30%时,高岭土/聚丙烯复合材料的冲击韧性最佳。     

生物柴油的组成对低温流动性的影响

生物柴油的化学组成是影响其低温流动性的重要因素。通过用气质联用仪和多功能低温试验器分别测定常见的6种生物的组成分布和浊点、倾点、冷滤点等低温流动性指标,用控制变量法研究生物柴油的组成和冷滤点的关系。结果表明,生物柴油中饱和脂肪酸甲酯的含量越高,饱和脂肪酸甲酯的脂肪酸碳链越长,生物柴油的低温流动性越差;不饱和脂肪酸甲酯的含量越高,脂肪酸甲酯的不饱和度越大,生物柴油的低温流动性越好;与饱和脂肪酸甲酯相比,不饱和脂肪酸甲酯对生物柴油低温流动性的影响可以忽略。     

生物柴油的组成对低温流动性的影响

生物柴油的化学组成是影响其低温流动性的重要因素。通过用气质联用仪和多功能低温试验器分别测定常见的6种生物的组成分布和浊点、倾点、冷滤点等低温流动性指标,用控制变量法研究生物柴油的组成和冷滤点的关系。结果表明,生物柴油中饱和脂肪酸甲酯的含量越高,饱和脂肪酸甲酯的脂肪酸碳链越长,生物柴油的低温流动性越差;不饱和脂肪酸甲酯的含量越高,脂肪酸甲酯的不饱和度越大,生物柴油的低温流动性越好;与饱和脂肪酸甲酯相比,不饱和脂肪酸甲酯对生物柴油低温流动性的影响可以忽略。     

The influence of composition ratio on the morphology of biomedical polyurethanes

Two series of thermoplastic polyurethane elastomers were synthesized from 4,4′‐methylenediphenyl diisocyanate (MDI), 1,4‐butanediol (BDO) chain extender, and each of poly(tetramethylene oxide) (PTMO) and poly(hexamethylene oxide) (PHMO) macrodiols. The PTMO and PHMO molecular weights were kept constant at 993 and 852 g/mol, respectively. In the PTMO‐based series, the composition ratio was varied between 48 and 58% (w/w) of macrodiol; 2 commercially available PTMO‐based polymers were also included. These were Pellethane 2363 80A® and its harder counterpart, Pellethane 2363 55D®. In the PHMO‐based series, the composition ratio was varied between 50 and 60% (w/w) of macrodiol. The materials were characterized by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS). Mechanical performance was also assessed by tensile testing, stress hysteresis, and hardness testing. Altering the composition ratio had a similar effect on morphology and properties for both the PTMO and PHMO‐based series. An increase in hard segment content was associated with increased hard microdomain crystallinity, hardness, and stiffness. In both series, he beginning of hard microdomain interconnectivity was observed at a composition ratio of 52% soft segment. That is to say, for the processing and annealing conditions employed, macrodiol contents of 52% and below began to produce continuous, rather than discrete, hard microdomains. Pellethane 80A® was shown to have a discrete hard microdomain morphology, while Pellethane 55D® was shown to incorporate interconnecting hard microdomains. It is suggested that the superior biostability performance of Pellethane 55D relative to Pellethane 80A may be related to its interconnecting hard microdomain texture. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 937–952, 1999     

The influence of shear forces on clay modification with oppositely charged polyelectrolytes

The interaction between the oppositely charged polymers poly(dimethyldiallylammonium chloride) (PDADMAC) and poly(maleic acid‐co‐styrene) in the presence of clay can be used for strong surface modification. Different methods were applied for characterizing each step of the reaction and the properties of the modified material. By characterizing the formation of the pure polyelectrolyte complex in solution as well as the three component system (two polyelectrolytes in presence of clay) with polyelectrolyte titration and comparing these results with the total carbon content, it was shown that a significant quantity of a soluble, positively charged polyelectrolyte complex is formed in the system. The strong cationic surface charge is obtained by precipitation of this complex on clay. It was found that the conditions of reaction (type of stirrer, time) strongly influence the particle properties like particle size and adsorption behavior/surface charge. The higher surface charge and the greater diameter of particles was obtained with an anchor stirrer, whereas the formation of larger particles and the precipitation of the complex is prevented by the stronger shear forces of the leaf stirrer.     

Influence of mineralogical composition of applied ball clays on properties of porcelain tiles

Relations between quality of ball clays applied in raw materials batches for manufacture of porcelain tiles, and physical properties and microstructure of obtained tiles, were investigated. Studied clays constituted 35% of the batch, while the other components were unchangeable. Stoch index, new IR 3620/3700 index and XRIR index (Stoch index multiplied by IR 3620/3700 index), were proposed to take into account crystallinity of kaolinite and contents of illite and smectites in studied clays. Relationship between XRIR index value of clay, and water absorption and abrasion resistance of the obtained ceramic material, was found. Water absorption of the tile is also correlated with grain size distribution and bending strength of used clay. Optimal ball clay for porcelain tile production should exhibit: Stoch index - min. 4.3; IR 3620/3700 index - min. 1.2; XRIR index - min. 4.8; grain size median - max. 0.27 μm; bending strength after drying - min. 8.0 MPa.