Advances and challenges of ceramic pigments for inkjet printing

In the last decades, the development of new ceramic pigments has been a very pursuit goal, mainly since the emergence of the inkjet technology applied to ceramic tiles. The digital decoration of industrial ceramics has contributed to a notable reduction of pigment consumption and an aesthetical decoration improvement, which makes more flexible the production processes, enhancing the reproducibility and cost savings. The nanopigment requirements of the inkjet technology demand submicronic particle size, ink rheology, stability, drop resolution, etc. Although the up-down procedure by micromilling contributed firstly to the particle size reduction of existing pigments, novel approaches are developed to obtain directly high-quality particles of suitable size with the aim of providing a higher optical efficiency. Thus, in this work, a comprehensive review about the existing crystalline structures, novel compositions, and synthesis methods as well as new coloring mechanisms is addressed, giving an overview of all these advances while considering the four-color process required for inkjet technology. The inkjet technology has the challenge of evolving towards a sustainable technology by eliminating the use of critical raw materials, removing the use of synthesis aid fluxes, and reducing the energy consumption, to approximate to a circular economy which is predominant in this sector.     

Ceramic pigments and dyes beyond the inkjet revolution: From technological requirements to constraints in colorant design

The advent of digital decoration has changed the technological requirements of colorants and the way they are applied onto ceramic substrates. This technological revolution has introduced additional steps in colorant production (ink micronization) and new constraints in application (ink-jet printing) that cannot be reproduced in a standard ceramic laboratory, so stretching the distance between academic and industrial research. The goal of this work is to provide an up-to-date picture of ceramic pigments, dyes and effects, with emphasis on their behavior in the current decoration technologies, which are shortly reviewed. Technological performance expected for ceramic colorants and new requirements imposed by digital decoration are discussed in detail. An extensive overview of both industrially used and candidate pigments, dyes and effects is focused on the suitability to different ceramic applications and firing conditions. Finally, lines of future research are outlined and commented.     

Review: An investigation of single particle breakage tests for coal handling system of the gladstone port

Aspects of the literature on single particle breakage test have been reviewed in this article. The test procedures that are commonly used by the researchers in examining and measuring the breakage characteristics of the ore and coal particles are also discussed. It appears that most of the common size distribution function fitting techniques were not suitable for accurate representation of the size distributions obtained from a pendulum breaking process. The single impact test, double impact test (drop weight test, pendulum test) and slow compression test can be used to study the behaviour of the single particle breakage events. The single impact test, slow compression test and drop weight test cannot measure the energy utilization pattern in single particle breakage events, but this can be determined from the pendulum test.The energy utilized for breakage was predominantly dependent upon the size and shape of the specimen, level of input energy and the breakage properties of the specimen. This review highlights that the size distribution curves were linear in the fine particle region and have varying curvature in the coarser region, the gradient of the linear fine particle region of the size distribution curves increases with an increase in the specific comminution energy. The comminution energy increases with input energy at lower levels of input energy but at the higher levels of input energy the comminution energy did not show the same proportional increase. At a given level of input energy, the size distribution resulting from the breakage of the particles by the pendulum apparatus can be represented by a one-parameter family of curves.     

Energy and population balances in comminution process modelling based on the informational entropy

The results of theoretical and experimental studies of a comminution process are presented. There are two random functions: the selection function and the breakage function in the stochastic model based on a population balance. This model enables prediction of particle size distributions of comminution products after determination of both random functions. Maximum entropy method is used in the entropy model for determining the breakage function. Two cases are analysed, based on continuous and discrete particle size distribution functions of the fed material. Apart from mass balance, the energy balance of comminution process is also used. Searched form of breakage function is determined with the application of methodology of calculus of variations. The results of experimental identification of both models are presented. The parameters that occur in the discrete form of the selection and breakage functions were the identification objects. The results of experimental investigations of quartz sand single comminution in a laboratory jet mill provided an identification base. The experimentally identified results of the entropy model confirmed the adequacy of the theoretical analysis and demonstrated the possibility of adequate prediction of particle size distributions resulting from single comminution.     

喷墨打印用陶瓷墨水的研究现状及其发展趋势

陶瓷数字喷墨打印技术是一种极具潜力的陶瓷装饰技术,它是现代计算机技术与陶瓷装饰材料技术相结合的产物,其独特的优势是传统陶瓷装饰工艺无可比拟的。本文主要对陶瓷墨水的制备工艺及目前国内外陶瓷墨水的研究现状进行了评述,同时,对陶瓷墨水今后的研究重点及发展趋势进行了分析。     

喷墨打印用陶瓷墨水的研究现状及其发展趋势(连载完)

陶瓷数字喷墨打印技术是一种极具潜力的陶瓷装饰技术,它是现代计算机技术与陶瓷装饰材料技术相结合的产物,其独特的优势是传统陶瓷装饰工艺无可比拟的。本文主要对陶瓷墨水的制备工艺及目前国内外陶瓷墨水的研究现状进行了评述,同时,对陶瓷墨水今后的研究重点及发展趋势进行了分析。     

Improving comminution efficiency using classification: An attainable region approach

The AR for the fundamental processes of breakage and mixing was constructed in an earlier paper (Khumalo, N.; Glasser, D.; Hildebrandt, D.; Hausberger, B.; Kauchali, S. (2006). The application of the attainable region analysis to comminution. Chem. Eng. Sci., 61, 5969-5980). This work presents the AR constructed when the process of classification is combined with the processes of breakage and mixing. The process of classification extends the AR. An additional variable of energy consumption is introduced, increasing the dimensionality of the geometric construction from 2-D to 3-D. The AR shows that there is a linear relationship between consecutive particle size distributions with grinding time. However total energy consumption results in concavities when plotted against mass fraction in the median size class.This work demonstrates the degree to which there is an advantage of including the additional fundamental process of classification to particle breakage. The attainable region (AR) of a three particle size distribution can easily be represented graphically. Process targets can be inferred from these graphs. In our chosen system, the classification process has the effect of reducing total energy consumption by 95% to reach an objective of producing 92% of the material in the fines size class. This has cost implications since energy is often the predominant operating cost in size reduction systems. This work also shows that the benefits of classification are a function of the grinding extent for a system which consists of mono-sized feed particles. This suggests that classification should be introduced after some grinding at some point which is easily identified by analysing the AR construction.     

Breakage probability of irregularly shaped particles

The investigation of breakage probability by compression of single particles was carried out. The spherical glass particles and irregularly shaped particles of NaCl, sugar, basalt and marble were subjected to a breakage test. The breakage test includes the compression up to breakage of 100 particles to obtain the distribution of the breakage probability depending on the breakage force or compression work. The breakage test was conducted for five particle size fractions from each individual material, at two stressing rates. Thus obtained 50 breakage force distributions and corresponding 50 breakage work distributions were fitted with log-normal distribution function.Usually, the breakage probability distribution can be found by means of stress or energy approach. The first one uses the stress to calculate the breakage probability distribution. The second approach uses the mass-related work done to break the particle. We prefer to use the breakage force and energy as essential variables. The correlation between the force and energy at their breakage points is obtained by integrating the characteristic force–displacement curve, i.e. the constitutive function of elastic–plastic mechanical behavior of the particle. The irregularly shaped particle is approximated by comparatively “large” hemispherical asperities. In terms of elastic–plastic deformation of the contacting asperities with the plate, a transition from elastic to inelastic deformation behavior was considered. Thus, one may apply the model of soft contact behavior of comparatively stiff hemispheres. Based on this model a relationship between the breakage force distributions and corresponding energy distributions was analyzed. Every tested material exhibits a linear relationship between average breakage energy and average breakage force calculated for every size fraction.For future consideration both force and energy distributions were normalized by division by average force or energy, consequently. The relationship between the fit parameters of normalized energy distribution and corresponding fit parameters of normalized force distribution was established. The mean value and standard deviation of normalized force distribution can be found from mean value and standard deviation of normalized energy distribution by means of system of two linear equations. The coefficients of those linear equations remain the same for all of the above tested materials; particle size fractions and stressing rates. As a result the simple transformation algorithm of distributions is developed. According to this algorithm the force distribution can be transformed into energy distribution and vice versa.     

Druckverhalten feuchter kugelförmiger Zeolith 4A‐Granulate

The material behavior of three particle sizes of elastic‐plastic zeolite 4A granules has been experimentally studied using compression tests. The recorded force‐displacement curves have been approximated by mechanical models from the literature. Moreover, the influence of particle size and moisture content on the material behavior has been investigated. Furthermore, the specific fracture energy distribution and the distribution of the equivalent impact velocity at fracture have been determined. At impact stressing the energetic equivalent breakage energy corresponds to the impact velocity of a particle on a rigid wall initiating breakage of the particle.     

Doped oxides of cerium as inorganic colorants

The colour of inorganic colorants is based on metal ions such as cadmium, lead, chromium or cobalt, the majority of which are unfortunately potentially toxic. Thus, there is in a need to introduce alternative metal or metal oxides, which would be environmentally friendly and economically viable as a replacement for potentially toxic inorganic colorants. Rare earth-based colorants offer an additional opportunity for the development of optically pure colours. In this study, a replacement for potentially toxic colorants has been sought through the use of a rare earth metal ion, cerium. Appropriate doping of cerium oxides with molybdenum and iron gives an orange–red colorant. The conditions ideal for optimal colour have been standardised and the resultant colorant characterised through powder X-ray diffraction techniques, particle size measurement, etc. The colorants exhibit good hiding power and tinting strength.     

Untersuchung des Prall‐ und Druckverhaltens feuchter γ‐Al2O3‐Granulate

The material behavior of dominant elastic‐plastic γ‐Al₂O₃ granules has been experimentally studied by means of quasi static compression tests and dynamic impact tests until fracture. The obtained distributions of breakage velocity and specific breakage energy are compared. Thus, velocity‐dependent influences at stressing like viscous behaviour can be derived. Additionally, the influence of particle size and moisture content are investigated.     

The application of the attainable region analysis to comminution

The aim of any comminution circuit is to produce material of a desired particle size distribution (PSD) at a minimum operational cost. Currently, the comminution process is energy intensive and operates at very low efficiency when the input energy is compared to the breakage achieved. The attainable region (AR) technique has been successfully used to solve optimization problems simultaneously with the process synthesis formulation of reactor systems. The AR looks at the fundamental processes of a given system and determines all the possible outputs to which the objective function can be applied and an optimal process solution selected.Particle breakage, separation (classification) and mixing are identified as the three fundamental processes of interest taking place during comminution. Breakage and mixing processes are used in this paper to illustrate the applicability of the AR theory in comminution. We develop a fundamentally based model which is equipment independent to describe breakage. Specific energy is the independent variable and the production of particles with a certain PSD is the objective function. We use geometric construction to represent this PSD as a point in an n-dimensional space in relation to an input specific energy. Output PSDs are dependent on the input PSDs, allowing connectivity of the batch grinding stages to form a pseudo-continuous process.Specific energy is used as the control variable to obtain sharper product PSDs. It is shown that the same net energy consumed in the system can produce different product PSDs. Therefore, this implies that the design of comminution circuits should achieve better control of the specific energy. Once the candidate AR is constructed, operational process targets can be defined more accurately. This establishment of targets permits a measure of the actual process efficiency against a theoretical target. The advantage of the AR method lies in its ability to develop not only the performance of the optimal circuit but also the operational conditions to be used in the optimal process circuit. This also answers the process synthesis question of the type of equipment to be used which is a function of the specific energy.     

Compression Behavior of Moist Spherical Zeolite 4A Granules

The material behavior of elastic‐plastic zeolite 4A granules has been experimentally studied using compression tests. The influence of particle size and moisture content has been investigated. Furthermore, the specific fracture energy distribution and the distribution of the equivalent breakage velocity at impact on a rigid target have been determined.     

塑料着色剂特性及生产发展

本文综述了塑料着色剂的特性、种类、生产与应用情况。重点介绍塑料着色剂选用原则和主要品种，并提出国内今后发展趋势。     

Semiclosed-Cell Mullite Foams: Preparation and Macro- and Micromechanical Characterization

The preparation and characterization of the properties of mullite ceramic foams suitable for diesel exhaust filtration systems are described. Two foams of different cell sizes, 32 and 61 ppi (pores per inch), were prepared from slurries by the replication process with polyurethane sponges as the templates. The microstructure and the dependence of the porosity and the mechanical properties on the preparation and resulting foam cell size and normalized density are discussed. In addition the micro- and macromechanical properties have been characterized using instrumented indentation techniques; with sharp (Berkovich) and small spherical-tipped indenters the hardness and modulus of the dense strut materials have been measured. The macroproperties have been measured with a large sapphire indenter, ∼5 mm radius using a load partial-unloading technique. The latter enables the modulus and the contact pressure versus penetration to be measured. These values are compared with traditional bulk measurements for crushing strength and elastic modulus. The results are discussed in terms of available theoretical treatments of the indentation of brittle porous materials.     

Fracture of foamed portland cements

The effects of microstructural parameters such as pore size, pore wall thickness, grain size, and bulk density on the mechanical behavior of foamed Portland Type I and Type III cements with densities ranging from 0.28 (18 lb/ft³) to 0.72 g/cm³ (45 lb/ft³) were studied.For both types of cements the elastic modulus and notched-beam fracture surface energies were found to increase with increasing bulk density.The strength of notched specimens varied as a function of the inverse square root of the notch depth indicating that the Griffith criterion of failure is applicable. The strength was found to increase with increasing bulk density which correlated with changes in the elastic modulus and fracture surface energy. The maximum in the strength as a function of refining time correlated with a minimum in the pore size.     

An experimental validation of a specific energy-based approach for comminution

In a recent paper [Khumalo, N., Glasser, D., Hildebrandt, D., Hausberger, B., Kauchali, S., 2006. The application of the attainable region analysis to comminution. Chemical Engineering Science 61, 5969-5980] it was shown that the attainable region approach could prove useful in designing better comminution circuits. Fundamental to this approach was the assumption that the rate of comminution was only determined by the specific energy within the device. This paper shows experimentally that this assumption holds for a batch ball mill.The system presented here considered breakage of mono-sized feed particles in a laboratory ball mill into two distinct progeny size classes. The population balance model was successfully used to model the experimental products and the results were represented geometrically in a two-dimensional space. The resulting geometric structure can be used to solve process synthesis and optimization problems simultaneously.It was found that the breakage rate parameter out of size class 1 changes with time but exhibits an exponential relationship with an asymptote. It is hypothesized that this asymptote is the rate of breakage at long grind times or in well-mixed, steady-state continuous systems. It is shown that the parameters of the process depend only on the specific energy. This was one of the assumptions that was made in the construction of the attainable region. Thus, equipment selection and operating conditions only require one to match the required specific energy.     

Breakage behaviour of spherical granulates by compression

This paper describes the deformation and breakage behaviour of granulates in single particle compression test. Three industrial spherical granulates—γ-Al₂O₃, the synthetic zeolite Köstrolith^® and sodium benzoate (C₆H₅COONa) were used as model materials to study the mechanical behaviour from elastic to plastic range. The elastic compression behaviour of granulates is described by means of force-displacement curves, by application of Hertz-Huber contact theory and continuum mechanics. An elastic-plastic contact model was proposed to describe the deformation behaviour of elastic-plastic granules. The effects of granulate size and stressing velocity on the breakage force and contact stiffness during elastic and elastic-plastic displacement are examined. It is shown that the zeolite granulates with elastic-plastic behaviour have viscous properties as well. Breakage mechanisms of granulates during elastic, elastic-plastic and plastic deformation are also explained. The breakage probability is approximated by Weibull distribution function. The behaviour of the granulate during compression under the repeated loading-unloading conditions was investigated.     

Crushing characteristics

A method of measuring the basic characteristics of comminution was developed. These characteristics are expressed by the major comminution functions: crushing probability function, energy function and breakage function. The crushing probability function is the strength distribution of particles of a given size. The energy function is the strength of the particles as a function of their sizes. And finally, the breakage function is the size distribution of the crushed material. The functions are defined mathematically. Several natural minerals were tested by drop tests in order to determine their individual comminution functions. From the tests, several crushing properties of the particulate materials can be derived. The comminution functions given in this paper would be the basic elements in developing mathematical models for various crushing and grinding processes.     

Optimizing inkjet printing process to fabricate thick ceramic coatings

This article describes the use of Taguchi optimization and ANOVA techniques on inkjet printing process to determine optimal parameters for fabrication of thick ceramic coatings over glass substrates. Stable nanoparticle suspensions are synthesized through high energy milling of precursor powders with adequate quantities of binder and suspending solvent. Most often, inkjet printing process is being used for developing fine and thin layers (<10 µm). However, an attempt is made to fabricate thick ceramic films by varying only IJP process parameters and without multiple layer deposition, thereby reducing efforts in ink synthesis and processing time of coated substrates. Three parameters of IJP were varied for developing a model that was used for precisely predicting the printed layer thickness under varying process parameters. ANOVA technique showed that open time interval in combination with nano particle concentration in the ink could potentially lead to thick coatings. The higher volume % of solvent in the diluted suspension ink under the influence of substrate heating contributed significantly to coffee stain effect with irregular surface coatings. However, increasing the concentration of nanoparticles in the diluted ink resulted in substantial improvement in thickness of the layer with simultaneous control of coating defects.