Black Ceramic Pigments Research Articles

Novel Co and Cr free, high-temperature black ceramic pigment based on (Ni, Mn) co-doping (CuFe)Fe4O8

Novel Co and Cr free, high-temperature (Ni, Mn) co-doping (CuFe)Fe4O8 black ceramic pigment was synthesized. The results indicate that the brightness (L*) values of the synthesized pigments decrease first, then reach an optimal value, and then increase with the doping amounts increasing of both Ni2O3 and MnO2. The optimized Ni2O3 and MnO2 doping amounts are 0.20 (molar ratio to (CuFe)Fe4O8) and 0.75 (molar ratio to (CuFe)Fe4O8), respectively. L*, a* and b* values of the optimized pigment (0.20Ni, 0.75Mn) co-doping (CuFe)Fe4O8 are 21.36, 1.10 and −0.24, respectively. The crystal phase of the optimized pigment is (CuFe)Fe4O8 (JCPDS73–2314). The crystal size of the pigment is 0.8–1.5μm with excellent dispersivity. The glazing temperatures have little effect on the coloration of the pigment when used at 1000℃, 1150℃ and 1300℃. The results show that the pigments have excellent high-temperature resistance and are expected to be widely used in high-temperature glazing coloration.

Minimizing the cobalt content in black ceramic pigments by Design of Experiments

This paper presents a comprehensive optimization strategy for the synthesis of new black ceramic pigments with low cobalt content while maintaining a single-phase spinel structure. The aim is to achieve comparable hues to those of an industrial benchmark containing five transition metals while minimizing the environmental impact. Exploring all possible compositions deriving from a five–component system (Cr, Mn, Fe, Co and Ni), through traditional methods would be extremely time consuming to guarantee an efficient sampling, requiring high experimental efforts. Hence, to identify the best black compositions, we employed a chemometric approach, the Design of Experiments, aiming to investigate the compositional domain derived by varying the metals stoichiometry within fixed boundaries to identify optimal pigment compositions. The resulting pigments (comprising Cr, Fe and Co), despite the lower cobalt content, exhibited optimal colorimetric properties comparable to the standard benchmark, with experimental ΔE values comparable to the ones predicted by the model. In particular, the pure spinels Cr1.05Fe1.05Co0.9O4 and Cr1.2Fe1.05Co0.75O4 displayed low lightness and chroma (L∗ = 2.4; C∗ = 5 and L∗ = 1.12; C∗ = 1.1, respectively), providing deep and dark black tonality. These compositions exhibit promising colorimetric performance and chemical stability, offering potential benefits for industrial applications.

SrMn1-xFexO3-δ (x = 0–1) black ceramic pigment: Synthesis, color properties, and application

In this work, SrMn1-xFexO3-δ (x = 0–1) black ceramic pigments were synthesized by the solid-state method. The research explores the influence of calcination temperature and iron ion doping on the color properties of the pigments. Furthermore, the potential applications of SrMn1-xFexO3-δ pigments in ceramic glaze and heat-absorbing materials are also discussed. The findings reveal that the synthesized SrMnO3 pigment exhibits the lowest L*-value (22.30) at 1100 °C, although it displays a slight blue hue. To optimize the color properties of the SrMnO3 pigment, iron ion doping is employed. When the doping level of iron ions is 50 mol.% (i.e., x = 0.5), the L*-value of the SrMn0.5Fe0.5O3-δ pigment calcined at 1000 °C significantly decreases to 19.77, while the a*- and b*-values approach 0, resulting in a pure black color. This is attributed to the high surface roughness, low band gap energy, and substantial oxygen vacancies present in the SrMn0.5Fe0.5O3-δ pigment. The tinting mechanism of the SrMn1-xFexO3-δ pigment in the ceramic glaze is classified as "ion tinting", wherein the glaze color relies on the concentrations of Mn and Fe ions. When the pigment content reaches 36 wt%, the L*-value of the glaze drops to 4.94, showing a deep black shade. Additionally, the SrMn0.5Fe0.5O3-δ pigment exhibits excellent sunlight absorption capabilities, with a near-infrared reflectance (R*) of only 5.04%. This research presents a black ceramic pigment with various advantages, such as simplified processing, affordability, environmental friendliness, and exceptional color performance.

Synthesis and color properties of MnTiO3 black ceramic pigment

In this paper, MnTiO3 powder has synthesized by solid-state method, and its color properties were also investigated. Research indicates that the L*-value of the prepared MnTiO3 powder was only 25.85, showing a pure and deep black hue, which indicates that MnTiO3 can be used as a black ceramic pigment and coating. The color mechanism of MnTiO3 pigment is attributed to the 6A1g→4A1g and 6A1g→4T2g crystal field transition of octahedral Mn2+ site. Besides, the MnTiO3 pigment exhibited outstanding tinting performance in ceramic glaze. The L*-v alue of the glaze sample with 8 wt% MnTiO3 pigment added was only 11.44, which is the minimum value reported in the literature. Moreover, the MnTiO3 pigmented coating shows an excellent solar energy utilization performance. This work demonstrates the promising application of MnTiO3 pigment in ceramic decoration and solar absorber.

Preparation and coloring mechanism of cobalt-free black ceramic pigments from stainless steelmaking dust

In order to improve the recovery of Fe, Cr, Mn and Ni in stainless steel dust and efficiently recycle of stainless steel dust, this study supplies a novel method for the development of high-quality, low-cost and environmentally friendly cobalt-free black ceramic pigments. The results show that the optimal parameters for preparing the cobalt-free black ceramic pigments from stainless steelmaking dust are Fe/Cr/Mn/Ni molar ratio of 1:1:1:1 in the mixture of stainless steelmaking dust and chemical reagents, sintering temperature and holding time of 1125 °C and 30 min respectively, and cooling in the furnace to room temperature. Under this condition, the material undergoes high-temperature sintering reaction to produce Fe 3 O 4 , FeCr 2 O 4 and NiFe 2 O 4 , which results in the black color of prepared pigment. Meanwhile, the prepared pigments have uniform and superior coloring properties ( L* = +36.43, a* = +2.61, b*= +1.70 and C *= +3.11), which are better than those of commercial cobalt pigments.

Effect of the nickel molar content on the preparation and properties of spinel-type black ceramic pigment by microwave processing from stainless steelmaking dust

The transformation of stainless steel dust(SSD) rich in transition metal elements into Fe-Cr-Ni series spinel-type black ceramic pigment can solve a number of problems associated with traditional high-temperature SSD treatment while also maximizing resource efficiency and harmlessness utilization. Microwave heating and calcination at 900 °C using SSD, Cr2O3, and NiO as the main raw materials, altering the molar ratio of Fe and Cr in the raw materials to 1, and gradually adding NiO, were used to make black spinel ceramic pigments in this study. The solid solution phase is gradually replaced by the spinel phase as the amount of NiO added increases, and the primary phases are Ni(FeCr)O4 and NiCr2O4. The generated pigment phases are completely transformed to spinel when the Fe/Cr/Ni molar ratio is altered to 1:1:0.5. Because NiO can react with spinel in SSD, increasing the NiO content of the raw material will increase the intensity of the spinel phase diffraction peak. According to morphological examination, the prepared spinel pigments have a characteristic polyhedral shape. Furthermore, as the amount of NiO increases, so does the average grain size of the spinel phase, the orbital hybridization effect, the degree of atomic inversion in tetrahedra and octahedra, and oxygen vacancies and deficiencies, resulting in an increase in visible light absorbance and a decrease in band gap width. The prepared spinel pigments are fired in ceramics and exhibit good color rendering and adaptation properties.

Nanoparticle Black Ceramic Pigment Obtained by Hydrotalcite-like Compound Microwave Treatment

Development of ceramic pigments with controlled particle sizes below 1 µm is essential for the preparation of ceramic inks used in inkjet digital decoration that is currently being applied in the ceramics sector. A black ceramic pigment based on NiCoCrFe composition has been prepared using thermal decomposition of hydrotalcite-like compounds. The stoichiometry ratio between different cations was studied to obtain the blackest pigment, giving Ni0,5Co0,5CrFeO4 the better cation ratio, also the thermal treatment, comparing traditional firing in an electric furnace with microwave treatment. Samples have been characterized by X-ray diffraction, Scanning Electron Microscopy and Lab colour measurement. Microwave treatment showed the best way to obtain a pigment with spinel-type structure and a homogeneous size distribution near to 150 nm, with a high intensity and colorimetric data, reducing drastically the temperature and energy consumption to obtain a black ceramic pigment suitable to be utilized in digital ceramic inks.

The influence of Ca2+ and Zn2+ doping on the development of sustainable pigments based on GdFeO3 perovskite: From a reddish colour towards a pure black

Black pigments are very commonly used and arouse widespread interest in the ceramic industry. Nevertheless, these pigments contain toxic elements that are detrimental to human health. In view of this, the present work is focused on the development of sustainable black pigments prepared by a coprecipitation method at 1200 °C. Samples with the nominal formula (Gd1–xCax)(Fe0.95Zn0.05)O2.975–x/2 (x = 0.00, 0.05, 0.10) showed single-phase orthorhombic perovskite. The presence of dopants played an important role in the reduction of Fe3+ to Fe2+ and caused different local distortions in the structure which explained the final black colouration of these pigments in comparison with the red GdFeO3 sample. The loss of symmetry and the increase in the number of d-d transitions of iron may explain the aforementioned changes. Co-doped pigments reached low C* values, improving on the purest black colour obtained in a commercial black ceramic pigment, which contains toxic elements. In addition to presenting good NIR solar reflectance values of up to 8%, the final colours of these pigments were also stable after their application in a commercial transparent glaze at 1080 °C that could be used for tiles.

Designing of technological scheme for conversion of Cr-rich electroplating sludge into the black ceramic pigments of consistent composition, following the principles of circular economy

Development of method for the complete conversion of Cr-containing electroplating sludge (ES) into the black inorganic pigment was presented. Difficulties related to the ES complex, variable composition and inhomogeneity, where the dominant presence of Cr was followed by: Fe, P, Zn, Ni, Cu, etc., can be overcome by determination of the precise amount of Fe2O3 necessary to be added in order to firmly embed all the heavy metals into the pigment structure (i.e. the Fe0.7Cr1.3O3/FePO4 nanocomposite), taking care not only about weight/molar ratios, but also about average particle size, apparent densities, and volume fraction of the starting materials. As a source of Fe2O3, commercial (p.a.) Fe2O3 and two different Fe-wastes were used, thus completely fulfilling the principles of the circular economy. The obtained black inorganic pigments have consistent composition, no leaching of toxic metals, color (CIE L*a*b* values) comparable with those of commercial pigments and thus have the potential commercial large scale application.

Selective leaching of vanadium over iron from vanadium slag.

A new comprehensive utilization of vanadium slag (VS) method focusing on inhibiting leaching of iron (Fe) during the leaching of vanadium (V) using sulfuric acid (SA) was proposed. In this process, Cr2O3 was added to VS to conjugate with Fe in the VS to form (Fex,Cr1-x)2O3 which is insoluble in SA, resulting in the decrease of leaching ratio (LR) of Fe to avoid the subsequent separation difficulty of V in leachate. The phase evolutions of VS during the roasting and SA leaching process, and the influences of roasting temperature, roasting time, and addition of Cr2O3 on the LR of V, Fe and chromium (Cr) from VS were studied. When the addition of Cr2O3 is 12 wt.%, the mass concentration of V in the leachate is 1 order magnitude higher than Fe and the mass ratio of V to Fe reaches 18.34. The LR of V, Fe and Cr are 91% 1.39% and 0.28%, respectively. The leaching residue can be reused as ironmaking raw material. More importantly, the (Fex,Cr1-x)2O3 and Fe2TiO5 can be separated from the leaching residue and recycled as raw materials for black ceramic pigments and titanium dioxide production by mineral processing technology, respectively.

Preparation of Zircon-Encapsulated Carbon Black Ceramic Pigment Using the Collapsed Mesoporous-Structure

The black zircon encapsulated carbon black (C@ZrSiO4) ceramic pigment is prepared using the collapsed mesoporous-structure to improve the coverage of carbon black. In the preparation process, the tri-block copolymer (Pluronic P123, EO20PO70EO20) is used as both the template of mesoporous zirconia and the source of carbon black under the calcination at 300 °C in Ar. Carbon black originated from P123 distributes uniformly in the mesoporous zirconia. After mixed with SiO2 sol and re-calcinated at over 800 °C, the procedure loses gradually the mesoporous structure and reacts with SiO2 to generate zircon. Carbon black is encapsulated completely by dense zircon. After calcined at 900 °C in air to remove the possible uncoated carbon black, the obtained pigment still has the deep black hue (L* = 24.14). This preparation method provides a simple way to prepare black ceramic pigment.

Facile non-aqueous synthesis of high color rendering C@ZrSiO4 encapsulation pigment with carbon-containing precursors as in-situ carbon sources

A zircon encapsulated carbon black (C@ZrSiO4) pigment with high color rendering was synthesized via facile non-aqueous acetic acid (NAA) assisted sol-gel method using carbon-containing precursors (zirconium n-propoxide and tetraethoxysilane) as in-situ carbon sources. The effects of the NAA amount and heat treatment temperature on the structure and properties of the synthesized encapsulation pigments were characterized by XRD, FT-IR, FE-SEM, HR-TEM, EDS, XPS and CIELAB colorimeter, respectively. The results showed that the C@ZrSiO4 encapsulated pigments heating at 1000 °C for 2 h in N2 atmosphere presented a dense and stable encapsulation structure as well as deep dark hue when the mole ratio of NAA and Zr (NAA/Zr) was 3:1, and the chromaticity values were L* = 21.20, a* = 0.56, b* = −0.09 and Cab = 0.57, respectively, which were contributed to the high homogeneity at atomic level in ZrSiO4 sol and the tight bonding between carbon black carbonized by carbon containing group and zircon matrix. In addition, the pigment exhibited excellent chemical stability, thermal stability and tinctorial strength when it was used in water, acid, alkali, organic solvents and ceramic glaze. Especially, these pigments improved the utilization of raw materials and avoided the use of heavy metals or transition metals as coloring agent, which was an environment-friendly black ceramic pigment.

Recycling of Cr/Ni/Cu plating wastes as black ceramic pigments

The non-ferrous metal industry, such as Cr/Ni/Cu plating, produces acid sludge which is usually neutralized with lime slurry in batch processes, and the resulting waste is dewatered by vacuum filtration or filter-pressing. Dewatered sludge contains calcium sulphate (CaSO4) coming from the neutralization process, as well as transition metals (Cr, Ni and Cu), oil, grease and suspended solids. In this communication, two residual sludges from Cr/Ni/Cu plating have been dried (110 °C) and fired (1100 °C), and both dried (gray coloured) and fired powders (black coloured) have been characterized by DTA-TG, XRD and SEM-EDX techniques. XRD shows only quartz crystallization in dried samples, while NiCr2O4 chromite spinel and NiO periclase crystallize in fired powders, along with CaSO4 anhydrite and CaSiO3 wollastonite. The powders have been introduced as ceramic pigments into three different conventional glazes: a) a lead bisilicate (PbO.2SiO2) double fire frit (1000 °C), b) a double fire frit with low lead content (1000 °C), and c) a double fire frit without lead (1050 °C). Glazed samples were characterized by UV-Vis-NIR (diffuse reflectance) and CIEL∗a∗b∗ (color parameters). Dried powders induce glaze defects (pin-holing and crawling), but fired powders did not show these faults exhibiting more intense (higher L∗) and yellowish (higher b∗) black colors than the standard spinel.

Synthesis and characterization of black ceramic pigments by recycling of two hazardous wastes

In this study, two different industrial wastes, namely vanadium tailing and leather sludge, were used as less expensive alternative raw materials for the synthesis of black ceramic pigments to be used in commercial glazes. The pigments were based on hematite structure (FexCr1-x)2O3 and prepared by the common solid-state reaction method, under optimal formulation and processing conditions. The synthesized pigments were characterized in typical ceramic glazes and ceramic tile bodies. Optimal color development was achieved when the Fe/Cr mole ratios were 2.0 with 40 wt% content of vanadium tailing at 1200 °C. The coloring properties were similar to those imparted by a commercial black pigment.

Influence of variables on the synthesis of CoFe2O4 pigment by the complex polymerization method

Synthetic inorganic pigments are most widely used in ceramic applications due to their excellent chemical and thermal stability and their lower toxicity to both human and environment as well. In the present work, black ceramic pigment CoFe2O4 has been synthesized by the complex polymerization method (CPM) with good chemical homogeneity. In order to study the influence of variables on the process of obtaining pigment through CPM, 2(5-2) fractional factorial design with resolution III was used. The variables studied in the mathematical modeling were: citric acid/metal concentration, pre-calcination time, calcination temperature, calcination time, and calcination rate. Powder pigments were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible (UV-Vis) spectroscopy. Based on the results, the formation of cobalt ferrite phase (CoFe2O4) with spinel structure was verified. The color of pigments obtained showed dark shades, from black to gray. The model adjusted to the conditions proposed in this study due to the determination coefficient of 99.9% and variance (R 2) showed that all factors are significant at the confidence level of 95%.

Synthesis of black pigments containing chromium from leather sludge

The black ceramic pigments with spinel structure have been prepared by using Cr-rich leather sludge in this paper. The washed Cr-rich leather sludge calcined at 1100°C for 1h as chromium oxide precursor (named as CA) was mixed with an appropriate proportion of other industrial metallic oxides, followed synthesizing black ceramic pigment by sintering. Both non-washed and washed sludge fired at 1100°C were characterized by X-ray fluorescence (XRF) in order to determine their chemical compositions and X-ray diffraction (XRD) analysis to confirm that CA mainly contains Cr2O3 crystal phase. The results show that CA could be used as a source of chromium to prepare black pigment. The crystalline phases of obtained pigments were characterized by XRD. Furthermore, the morphology as well as the composition of pigments was investigated by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The color coordinates of pigments were examined and compared with the commercial pigments based on CIE-L* a* b* values measured using UV–vis spectroscopy. The obtained pigments sintered at 1200°C with 35–55wt% content of CA possess the excellent black spinel structure and color effect. Under optimized conditions, the pigment has low average spectral reflectance (7%).

크롬 치환에 따른 흑색 세라믹 안료의 발색 특성 연구

The properties of black ceramic pigments including thermal and glaze stability were systematically investigated so that these pigments could be used to decorate porcelain products. Various compositions of (Ni,Mn)(Fe,Cr,Mn)₂O₄ and Co(Fe,Cr)₂O₄ powders were synthesised using a solid state reaction method. The obtained Co(Fe,Cr)₂O₄ and (Ni,Mn)(Fe,Cr,Mn)₂O₄ powders showed single phases of spinel structure after calcination processes at 1000℃ and 1200℃, respectively. CIE L*a*b* colourimetric parameters of glazed Co(Fe,Cr)₂O₄ and (Ni,Mn)(Fe,Cr,Mn)₂O₄ pigments were analyzed according to the different amounts of Cr substitution. In addition, the amount of Cr +6 remaining in the Co(Fe,Cr)₂O₄ and (Ni,Mn)(Fe,Cr,Mn)₂O₄ pigments was also measured.

Magnetic and colouring performaces of Co2+ ion doped magnetite powders synthesised using isothermal gaseous reduction

Co2+ ion doped magnetite Fe3O4 powders were synthesised through isothermal gaseous reduction of hematite Fe2O3. X-ray diffraction results indicated that a single magnetite phase formed with 20CO–80CO2 (%) gas composition annealed at 1000°C for 2 h. The phase accompanied with a minor amount of cobalt ferrite CoFe2O4 with varying the Co2+ ion content from 1·0 to 7·0%. The cobalt incorporation strongly influenced on the crystallite size, microstructure, magnetic properties and colorimetric performance. Vibrating sample magnetometer (VSM) evinced that pure magnetite phase as a soft magnetic material changed to hard magnetic material as the result of cobalt ferrite (CoFe2O4) phase formation. A saturation magnetisation (60·0 emu g−1) achieved for the pure magnetite phase. The coercive force increased from 41·7 Oe for pure phase to 476·7 Oe at 7%Co2+ ion doped magnetite. Meanwhile, addition of 2% Co2+ ion found to enhance the coloring properties of the magnetite. The colouring properties of CIE-L*a*b* and X, Y, Z colour measurements were near a commercial black pigment. However, the results demonstrated the visibility of using 2%Co2+ doped magnetite spinel powders as black magnetic ceramic pigments.

Encapsulated carbon black prepared by sol–gel-spraying: A new black ceramic pigment

As a new black ceramic pigment, encapsulated carbon black pigment has been prepared by a sol–gel-spraying method. The obtained pigment sintered at 900 °C for 2 h in air has a deep black hue (L* = 19), indicating carbon black can be fully covered. In the pigment, a dense coating layer on carbon black is formed due to the fast transformation from sol into gel by rapid extraction of solvent. The transparent silica phase spaces out the fine crystalline (zirconia or zircon), which permits to display the color of carbon black. This preparation method provides a way to prepare the encapsulated pigments. It will provide more colorful ceramic pigment applied in ceramic decoration by encapsulating.

Porcelain stoneware tiles with antimicrobial action

This work reports the development of extruded porcelain stoneware tiles that show antimicrobial (to act as a barrier to the bacteria's growth during a long period of time), and anti-stain (easy to clean) actions, and possess high chemical resistance.The antimicrobial action was proven through the reduction of Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. Staining and chemical resistance were tested according to ISO 10545-14 and 10545-13 standards, respectively. The tiles promote a population reduction of over 77% and 81% for the S. aureus and the E. coli bacteria, respectively. The optimized product was obtained by adding 2.5wt% of a black ceramic pigment to the industrially-prepared paste, followed by the application of a small quantity of glaze (by jet spraying). Chemical (solution of 98wt% NaNO3 and 2wt% AgNO3) and thermal (2h at 430°C) treatments were finally applied to get the active surface.In terms of anti-staining characteristics the tiles belong to class 5, while their chemical resistance is excellent (UA, ULA and UHA) against almost all aggressive agents, except for chloridric acid, 18% (v/v), for which a small surface attack (UHB) was observed. Furthermore, the treatments used (chemical and thermal) do not change the surface aspect of the product, and thus fulfil the industrial/commercial requirements.