Ceramic Blends Research Articles

Nature inspired dough processing of alumina-zirconia composites: Rheology, plasticity and weibull analysis towards net shaping

Advanced ceramic composites of alumina/zirconia are widely used in structural, functional and biomedical applications owing to superior physico-mechanical properties and biocompatibility. Unlike clays/bread dough, green shaping of ceramics was limited to slip casting due to insufficient plasticity. Herein, we introduce a ceramic dough forming inspired by the natural chemistry and mechanism of wheat flour dough. Ceramic blends were kneaded into a soft visco-plastic dough with vinyl polymer assuming the role of gluten matrix. A weakly linked dough matrix with a higher loss modulus enhanced the rate of powder deagglomeration and homogeneous distribution of the different phases during kneading. High plasticity index of the dough offers replication of intricate features with good dimensional retention. Dental prosthesis like root form implant, dental crown and bridge were successfully machined on a dried blank. Shape forming by this route is a viable alternative for dental prosthesis as evidenced by microstructure, strength and Weibull modulus values.

Features of Obtaining Multicomponent Magnetron Targets for the Formation of Non-Porous Transformation-Hardenable Coatings of a Given Composition

The technological process of thin-film sputtering significantly depends on the quality of the target for magnetron sputtering. This paper presents the features of obtaining the multicomponent magnetron target for the formation of non-porous transformation-hardenable coatings by the method of impact electric pulse consolidation. Special considerartion is given to the blend preparation and technological parameters of compaction. Blend powder consolidation under impact electric pulse compaction at different speeds of the striker has been investigated. At high speeds of the drop-hammer striker, the time parameters of the dynamic impact and electric pulse heating of the powder billet are shown to superpose, which leads to the final consolidation of the ceramic blend of the target for magnetron sputtering. The use of the technology of impact electric pulse compaction has made it possible to obtain multicomponent magnetron targets for formation of non-porous transformation-hardenable coatings of a given composition.

Incorporation of sulphidic mining waste material in ceramic roof tiles and blocks

The demand for building and construction materials increases as the world population keeps growing, thus increasing the need of shelter, as a basic human need. This increasing demand for building and construction materials not only leads to higher demand for primary raw materials, such as clay or sand, but also to higher emissions of carbon dioxide that contribute to the greenhouse effect, leading us to the biggest and ongoing threat to life on earth: global warming. The potential use of secondary raw material sources, such as mining waste, in building and construction products not only minimises the ecological footprint of this sector but also minimises the pressure on the primary raw material sector, hence fostering the transition towards a more resource efficient and sustainable world. The goal of this study is to evaluate the potential use of uncleaned sulphidic mining tailing material from two inactive Pb-Zn (Plombières, Belgium) and Cu-Zn-Pb (Freiberg, Germany) mines, and uncleaned sulphidic mining waste rock material from an active Cu-Zn mine (Neves-Corvo, Portugal), in ceramic roof tiles and blocks taking into account production parameters (shaping, drying, and firing processes), product quality (technical, aesthetical, and chemical properties) and environmental compliance of secondary raw materials for use as building products. After a detailed physical, mineralogical, chemical, and thermal characterisation of the materials, blends for ceramic roof tiles and blocks were made by partly or totally replacing some primary raw materials (mainly clay and sand) by 4 different mining waste materials. Roof tile and block blends containing 5 wt% and 10 wt% mining waste materials, respectively, were produced on a lab scale. The required technical, aesthetical, and chemical properties for each ceramic product were evaluated. Freiberg tailing and Neves Corvo waste rock materials presented considerable amounts of sulphur and metal(loid)s. Moreover, technical, aesthetical, and chemical properties of the blends using these mining waste materials were not satisfying and the Neves Corvo waste rock materials have the disadvantage of needing a mechanical treatment (grinding and sieving) before integrating them into the ceramic blends. Therefore, the Freiberg tailing and both of the Neves Corvo waste rock materials are less suitable to replace primary raw materials in ceramic roof tile and block blends, even in smaller amounts (5 wt% and 10 wt%, respectively). In contrast, the Plombières fine tailing material was characterised by a low sulphur and metal(loid) content, as well as satisfying environmental performance. The roof tile and block blends, in which the Plombières tailing material was integrated, showed satisfying technical, aesthetical, and chemical properties. Consequently, the Plombières tailing material can be considered as the best fit to partly or totally replace primary raw materials in both ceramic roof tile and block blends.

Femtosecond Laser Fabrication of Engineered Functional Surfaces Based on Biodegradable Polymer and Biopolymer/Ceramic Composite Thin Films.

Surface functionalization introduced by precisely-defined surface structures depended on the surface texture and quality. Laser treatment is an advanced, non-contact technique for improving the biomaterials surface characteristics. In this study, femtosecond laser modification was applied to fabricate diverse structures on biodegradable polymer thin films and their ceramic blends. The influences of key laser processing parameters like laser energy and a number of applied laser pulses (N) over laser-treated surfaces were investigated. The modification of surface roughness was determined by atomic force microscopy (AFM). The surface roughness (Rrms) increased from approximately 0.5 to nearly 3 µm. The roughness changed with increasing laser energy and a number of applied laser pulses (N). The induced morphologies with different laser parameters were compared via Scanning electron microscopy (SEM) and confocal microscopy analysis. The chemical composition of exposed surfaces was examined by FTIR, X-ray photoelectron spectroscopy (XPS), and XRD analysis. This work illustrates the capacity of the laser microstructuring method for surface functionalization with possible applications in improvement of cellular attachment and orientation. Cells exhibited an extended shape along laser-modified surface zones compared to non-structured areas and demonstrated parallel alignment to the created structures. We examined laser-material interaction, microstructural outgrowth, and surface-treatment effect. By comparing the experimental results, it can be summarized that considerable processing quality can be obtained with femtosecond laser structuring.

Thermal conductivity of MgO-C refractory ceramics: Effects of pyrolytic liquid and pyrolytic carbon black obtained from waste tire

In the present study, thermal conductivity and mechanical properties of MgO-C refractory ceramic bricks were investigated. Pyrolytic liquid and pyrolytic carbon black obtained from pyrolysis of waste tires were used as a resin and carbon source, respectively. The pyrolysis of the tires was conducted in a fixed bed reactor at the temperature of 500 °C with a 15 °C/min heating rate under nitrogen flow (0.5 lt/min). Before using in MgO-C refractory ceramic blends, pyrolytic products were purified with the acidic extraction methods which resulted in 61and 66 wt%. decreases in sulfur and ash contents in pyrolytic carbon, respectively. After this treatment of pyrolytic liquid, the sulfur content was reduced by 24 wt%. Eight different blends of MgO-C refractory ceramics consisting of different pyrolytic product contents were prepared, pressed, and tempered at 250 °C, and then characterized in terms of porosity, thermal conductivity, and density. The mechanical behavior of the samples was tested using a three-point bending test. Archimedes test was employed to determine the porosity and density. Surface properties of the bricks were analyzed by scanning electron microscopy (SEM). The obtained results were compared with a reference consisting of graphite and resin. The results revealed that mechanical and thermal properties of the developed bricks were highly sensitive to the porosity and the carbon source as well as the type of binder.

Study of formulations and the manufacturing variables of a ceramic weld backing

This paper presents a methodology for the in-lab manufacturing of a ceramic backing for the one-sided steel welds. Formulations were prepared using cordierite, bauxite, and magnesite as refractory minerals. Bentonite and sodium silicate were used as additives for the ceramic blend. The manufacturing process included dry mixture, compressing, drying, and sintering of the specimens. The weld backings were characterized by X-ray diffraction, optical microscopy of the surface, water absorption, and flexible voltage. They were also submitted to the welding of the root pass with the MIG–MAG process. The results show that the conventional ceramic manufacturing process is adequate for the production of the ceramic weld backing. Among the tested formulations, cordierite showed better integrity both during its manufacturing and during the welding operation, producing well-shaped weld beads, free from discontinuities. Manufacturing variables were evaluated such as compacting pressure, sintering temperature, and the amount of water added to the ceramic mass.

Improving the composition of ceramic blends in coke-furnace repair at Evraz Koks Sibir’

Experience in the hot repair of coke furnaces by ceramic surfacing over 12 years at OAO ZSMK is reviewed. It is established that the calculation method for ceramic repair blends adopted at Chernogolovke must be employed. At OAO ZSMK, ceramic blends are produced from the initial components on special equipment. The ceramic patches obtained from these mixtures last 4–4.5 years. Since 2004, original equipment covered by Russian patents has been used for hot repair by ceramic surfacing.

Modeling of thermal explosion in constrained dies for B 4C–Ti and BN–Ti powder blends

The process of reactive in-situ synthesis of dense particulate reinforced TiB 2/TiC and TiB 2/TiN ceramic matrix composites from B 4C–Ti and BN–Ti powder blends with and without the addition of Ni has been modeled. The objective of modeling was the determination of optimal thermal conditions preferable for production of fully dense ceramic matrix composites. Towards this goal heat transfer and combustion in dense and porous ceramic blends were investigated during heating at a constant rate. This process was modeled using a heat transfer–combustion model with kinetic parameters determined from the differential thermal analysis of the experimental data. The kinetic burning parameters and the model developed were further used to describe the process of combustion synthesis in a constrained die under pressure. It has been shown that heat removal from the reaction zone affects the ignition temperature of thermal explosion.

Effect of moulding pressure on sink-mark defects of injection-moulded ceramics

Injection moulding is an attractive method for fabricating ceramic articles. The advantages include high precision forming in dimensional control and the freedom in achieving complex shapes. A prerequisite in obtaining moulded ceramics with an accurate dimensional tolerance is that the moulded products should be free from any shrinkage defect. It has been pointed out that non-uniform shrinkage in injected moulded ceramics often results in defects such as voids, sink marks, curve deformations, weld lines and even cracks [1, 2]. The shrinkage defects are reported to be closely related to moulding parameters and sample size, as well as to the blend compositions of compounded mixtures [3]. However, the details about the relative significance of each potential factor and the interactions between factors remain unclear. This letter is therefore aimed at providing such information by designing a statistical L162 experiment to investigate the dominant factors for the formation of sink marks on injection moulded ceramics. Other shrinkage-related defects will be discussed elsewhere. The injection moulding process is often divided into filling, packing and cooling cycles [4]. Thermal contraction is most pronounced at the cooling stage, and the moulding ceramics are subject to nonuniform volume shrinkage. It is plausible that at least two conditions must be met for the formation of sink marks. Firstly, the channel (such as the sprue) which feeds fresh molten suspension into the shrinking mould core to compensate for the volume reduction solidifies earlier than the core. Secondly, the wall surface of the moulded sample is still soft as the core contracts, i.e. voids will form instead of the sink mark if the wall surface hardens. Hunt et al. [5, 6] have suggested that buckling of the skin of moulded bars arising from non-uniform shrinkage and local difference in the coefficient of heat transfer are two possible causes for the formation of the sink mark. Separation of the moulding ceramics from the mould wall leads to local temperature inhomogeneity and has been suspected to be the main cause [3]. Undoubtedly, solidification-related parameters should be the main focal point for tackling the underlying mechanism. However, process parameters are often interdependent in injection moulding; in fact, the interaction effect may end up influencing the overall behaviour. We therefore conducted a two-level, 15factor designed experiment to account for the most probable individual factors as well as interaction parameters. The controlling factors, as well as the selected levels, are shown in Table I. The ceramic used in this study was HSY3.0 zirconia powder with an average particle size of about 0.25 im. Low molecular weight organic vehicles composed of paraffin wax and vinyl acetal polymer in weight ratios of 50:50 and 80:20 (as shown in Table I) were used as major and minor binders, respectively. Ceramic blends with solid loading of 45 and 65 vol% were prepared, compounded and kneaded through an extruder (model 70-20 vex-6, KCK Industrial Co.), followed by injection moulding. A Battenfeld BA 250=50 CDC with a replaceable wear resistant barrel liner was used with barrel temperature series of 70–120–140– 130 8C (or 180 8C) from feed to nozzle. The screw diameter of the injection moulding machine was 18 mm. The mould temperature was controlled at either 40 or 60 8C by a water-circulating HB-Therm CW90. The nominal injection pressure was set at 80 MPa. The holding pressure varied at either 80 or 190 MPa and pressure decay time was controlled at 10 or 30 s. The moulded bars of dimensions 4 mm 3 5 mm 3 60 mm were prepared, and stored in a controlled humidity of 55–60% relative humidity (RH) at room temperature for three days, and the sink marks of the green bars were inspected visually or under polarized microscopy.

Rheological behaviour of a polymer ceramic blend

The rheological behaviour of an alumina injection moulding suspension was studied. A capillary rheometer allowing working under accurate injection moulding conditions has been developed. The main result concerns the observed slip phenomenon. It was shown that wall slip is reinforced with higher temperatures and decreasing shear rates. An attempt was made to correlate the results of the rheological study with the emergence of injection moulding defects. Normal filling was observed at low temperature, but solid jetting appeared under high temperatures and low shear rates. This unusual behaviour is a consequence of the wall slip mechanism. At low temperatures, when no slip was detected on rheological measurement, a steady front flow takes place. At higher temperatures, wall slip is favoured to shearing and unsteady front flow is obtained.

Modification of ceramic dispersions using zirconium hydrogel

Zirconium hydrogel is an effective dispersing aid and binder for slip casting zirconia. The hydrogel interacts with the ceramic particles in dispersion to form a surface layer on each particle that provides stability for the slip. Removal of the suspending medium causes the hydrogel to undergo further chemical reaction to form an effective binder. The highest green densities and strengths are achieved when samples are cast at the isoelectric point of the ceramic dispersion. During sintering the hydrogel crystallizes to become part of the base ceramic. Zirconium hydrogel facilitates casting of ceramic blends such as yttria stabilized zirconia.

Explosively consolidated PVC-alumina powder mixtures

The ever-increasing interest in the manufacture of cheap, highly abrasive, but, at the same time, very strong materials possessing good wear-resistant properties has focused attention on the explosive powder-consolidating technique. This particular route has been exploited industrially in the areas of metallic and ceramic blends, but it is only more recently that the possibility of using polymeric particulate matrices has been investigated. The main attraction of dynamic consolidation lies in its ability to create conditions under which, as a result of the passage of a shock wave, inter-particle bonding becomes possible where, in consequence, the strength of the compact is enhanced. A relatively soft polymeric matrix, in conjunction with a hard, abrasive alumina material, forms a blend that combines strength with low manufacturing costs.