Ceramic Pigments Research Articles

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.

In situ formation of coloured M(II)–doped Zn2SiO4–willemite in ceramic glazes (M=Mn, Co, Ni, Cu)

The family of M(II) substituted ZnO–wurtzite was investigated as potential new ceramic pigments. When MxZn1−xO or (MM׳)xZn1−xO with (M/M′=Mn, Co, Ni, Cu) oxides are incorporated to industrial frits the development of new colour hues is observed. This is attributed to the in situ formation of coloured M(II)–doped Zn2SiO4–willemite in ceramic glazes. The pigments were prepared by solid state reaction through the traditional ceramic route. Prior to enamelling, the materials were characterized by XRD analysis and FTIR spectroscopy. The colour performance and technological properties of the enamels were evaluated by enamelling in batches containing 5wt% with a transparent frit, representative of single firing industrial procedures, and submitting them to thermal treatment at 1000°C. The colours obtained, once the glazes were formed are attributed mainly to the formation of crystalline Zn2SiO4 within the glassy matrix, when chromophore M(II) ions enter into the tetrahedral coordination Zn(II) site available in willemite. The colorimetric CIELab parameters measured are in good agreement with the structural and spectroscopic analyses. The colour of some glassy coatings was interpreted by analysing the reflectance UV–visible electronic spectra of the samples. This study demonstrates that this family of pigment is capable of forming its own Zn-based crystals in a conventional transparent ceramic frit giving rise to a wide palette of colours. When Mn, Co, Ni and Cu are present in the Zn(II) site light brown, deep blue, pale yellow and green, are achieved respectively. Furthermore the simultaneous doping with a combination of MM′ results in various nice new shades of colours, enlarging the palette of green, yellow, brown and blue hues. The homogeneity of the enamels was confirmed by SEM–EDX microscopy. These materials are promising for ceramic applications since a low amount of pigment would be necessary to achieve intense colouration.

Study of thermal behaviour and stability of Co-doped malayaite ceramic pigments

This contribution deals with the preparation and characterization of Co-doped malayaite pigments. Pigment samples were prepared by solid-state reaction at different firing temperatures (1200–1400 °C). For characterization of thermal behaviour, pigment formation and thermal stability were studied by the methods of thermal analyses. The compounds were evaluated from standpoint of their phase composition and particle size distribution. The XRD analysis of samples prepared at 1,300–1,400 °C indicates the occurrence of two-phase compounds, i.e. the malayaite and the cassiterite. Average value of mean particle size of tested malayaites is moved ~10 μm. The great attention was focused on determination of impact of firing temperature on the pigment-application properties. Because the malayaite compounds belong into ceramic pigments, the pigment-application properties were observed after application into organic matrix in mass tone and middle-temperature glaze in different pigment amounts. Generally, the colour appearance of tested malayaites is dependent on the firing temperature and it moves in different shades of blue colour. From pigmentary point of view, it is possible to recommend 15 % of mass pigment for sufficient colouring of middle-temperature glaze. The higher firing temperature provides the formation of pigment samples with the higher saturation and the higher values of hue angle. For preparation of Co-doped malayaite pigments with the excellent colour properties, the firing temperature 1,350 °C is necessary.

Ceramic Pigments Based on Raw Materials from Uzbekistan

Green, blue and turquoise ceramic pigments have been obtained by means of heterovalent substitution of atoms based on calcium aluminosilicate (anorthite) with calcium and silicon ions replaced by transition elements and aluminum using quartz sand from the Navoinskoe deposit, Samarkand chalk and alumina-containing wastes from the Shurtanskii Gas-Chemical Complex. The physical-chemical properties of the pigments were studied. The new ceramic pigment compositions were used to produce a commercial test lot of decorative majolica.

Synthesis and characterization of CeO2·α-Fe2O3 and CeO2·Pr6O11 ceramic pigments through the solid state reaction and modified sol–gel method

Ceramic pigments, CeO2·α-Fe2O3 and CeO2·Pr6O11 systems, were synthesized through the solid state reaction at 1300 °C/3 h and modified sol–gel method at 1300 °C/3 h. Pigments presented shades from brown to reddish-orange for the system CeO2·α-Fe2O3, and light-brown to earth-brown for the system CeO2·Pr6O11, and a tendency to the red color in the reflectance spectrum was observed in all pigments. The CeO2·Pr6O11 system, synthesized through both methods, and the CeO2·α-Fe2O3 system, synthesized through modified sol–gel, presented only cerianite phase. The lattice of CeO2·α-Fe2O3 system presents a tendency to expand with the addition of Fe3+ ions, through both methods of synthesis, suggesting an interstitial solid solution formation. The Fe3+ ion solubility limit within the CeO2 lattice is between 2 and 3% in mol. The 57Fe Mössbauer spectroscopy analysis revealed that the sample with 2 and 3 mol% α-Fe2O3, synthesized by the solid state reaction or by the modified sol–gel method presented hematite signals, together with Fe3+ signals within the cerium oxide lattice. For the system CeO2·Pr6O11, changes in the mechanism of solid solution formation depends on the oxidation number of praseodymium reagent.

Production and characterization of colored feldspathic enamel for dental application

In this work we synthesized pigments capable of developing dental shades when mixed with dental porcelain and fired at appropriate temperatures. TiO2-xCeO2 pigments (x = 2, 6, 10, 13 and 18 mol%) were synthesized by the Pechini method. Characterization by thermal analysis revealed the stability of the material at temperatures up to 1200 ºC. X-ray diffraction showed stable crystalline phases (rutile to TiO2 and cerianite to CeO2) for all pigments studied. Color of pigments was characterized by colorimetric coordinates according to the CIELAB method and reflectance measurements in the visible region. Through colorimetric analysis it was possible to verify the potential use of these pigments in dental ceramics.

Study of ceramic pigments based on cobalt doped Y2O3–Al2O3 system

Ceramic pigments based on Y2O3–Al2O3 system doped by cobalt as a colourant agent were synthesized by solid-state reaction at temperatures up to 1,400 °C. The reactivity of initial mixtures of components was improved by the mineralizer LiF and the mechanical activation in a planetary ball mill. The temperature region of the product formation was followed by the method of thermal analysis. The effect of the synthetic method on the phase composition of the products was studied by X-ray diffraction analysis. Studied pigment-application properties of the product include the measurement of optical properties in the visible region of light and particle size distribution. The simple solid-state reaction led to the formation of turquoise samples that contain mainly blue CoAl2O4 spinel and next to it also YAlO3 perovskite and Y3Al5O12 garnet phases. The mineralizer LiF promotes the formation of yttrium aluminium double oxides of sandy-yellow to grey–brown colour hue, although the samples also contain small amount of blue CoAl spinel phase. Intensive milling process did not results in CoAl spinel phase and the samples contain yttrium aluminium perovskite and cobalt oxide. Evaluation of Kubelka–Munk absorption as a function of the pigment concentration was found that hiding is complete by adding of 5 mass% of pigment to the ceramic glaze. Resulting colour hue of all pigment applications into ceramic glaze is blue. The size of particles lies in the range of 7–26 μm.

Ni-Doped Hibonite 파란색 안료의 합성과 발색기구

Abstract NiO-doped hibonite pigments were synthesized by the solid state method to get stabilized blue color pigment inboth oxidation and reduction atmospheres. Optimum substitution condition with NiO for hibonite blue pigment was investigated.Experimental results were comparable to those of previous cobalt-minimization studies performed with other phosphate- oroxide-based cobalt-containing ceramic pigments (having olivine (Co 2 SiO 4 ), spinel (CoAl 2 O 4 ), or with co-doped willemite((Co,Zn) 2 SiO 4 ) structures). Composition was designed varying the NiO molar ratio increasing with SnO 2 . The optimumsubstitution content is 0.93 mole NiO with 0.75 mole SnO 2 . The characteristics of the synthesized pigment were analyzed byXRD, Raman spectroscopy, SEM, and UV-vis. Synthesized pigment was applied to a lime-barium glaze with 10 wt% each andfired at an oxidation atmosphere of 1250 o C/1h and a reducing atmosphere 1240C/1h. Blue color was obtained with L*a*b*values at 43.39, −6.78, −18.20 under a reducing atmosphere and 41.66, −6.36, −14.7 under and oxidation atmosphere, respectively.Key wordshibonite, blue pigment, NiO, SnO

Ceramic pigments based on doped strontium stannates

This study reports the development of red-shade inorganic pigments based on chromium- and terbium-doped strontium stannate. Perovskite compounds belong to group of high-temperature pigments. Powder samples were prepared by the conventional ceramic method, i.e. solid-state reaction. Pigments were characterized by X-ray diffraction analysis and thermal analysis. Powder morphology was analysed by scanning electron microscopy. The colouring mechanism seems to result from the combined contribution of octahedral Cr(III) and tetrahedral Cr(IV) species replacing Sn4+. Colorimetric parameters were evaluated by measuring the reflectance in the visible region of light, and their colouring performance was tested in an organic matrix and transparent ceramic glazes. Intense reddish brown hues were developed with optimized formulations, i.e. containing 0.1 Cr and 0.1 Tb at 1,350 °C.

Vanadium Catalyst Waste in the Synthesis of Heat-Resistant Ceramic Pigments

Ceramic pigments with mullite structure were obtained using waste vanadium catalyst. The ion-chromophores were introduced to the initial mixture in the quantity of 5-15 wt. % in the form of nickel, chromium, iron, and cobalt oxides. It was established that the phase composition of the obtained pigments was complex and consisted of mullite and corundum. But it does not effect on the properties of the obtained pigments, in particular, on heat resistance.

酸化鉄を導入したセリアジルコニア材料の合成と光学的特性の評価

Iron oxide-doped ceria Ce1-yFeyO2-δ (where y=0, 0.01, 0.05, 0.10, and 0.20) and iron oxide-doped ceria-zirconia ZrxCe0.95-xFe0.05O2-δ (where x=0, 0.20, 0.40, 0.60, 0.80, and 0.95) powder samples were synthesized by a coprecipitation method and heated at 900℃ and 1230℃. The samples were characterized by XRD, colorimetric assessment and UV-Vis diffuse reflectance spectroscopy. Furthermore, the color glazes obtained by adding the samples to the basic glaze were heated at 1230℃ in air, and evaluated by colorimetric assessment. X-ray diffraction data revealed that Ce1-yFeyO2-δ samples with y ≥ 0.05 were composed of Fe-doped CeO2 solid solution and Fe2O3. The powders of Ce1-yFeyO2-δ showed dark red color and the glazes containing them also showed yellowish red color. In Fe-doped ceria zirconia samples heated at 900℃, the red color varied to orange and yellow with increasing x in ZrxCe0.95-xFe0.05O2-δ. However, the glazes containing them (with Zr) changed from warm color into pale like celadon. These warm colored materials show high durability against high temperature and environmental friendly properties, so the application as ceramic pigments can be expected.

Synthesis of Ceramic Pigments ACr<sub>2</sub>O<sub>4</sub> Using the Non-Conventional Method of Co-Precipitation Assisted by Ultrasound and High Energy Milling

In this research ceramic pigments have been synthesized with crystalline spinel structure and chromium based with a stoichiometry ACr2O4. A was an element with +2 valence metal, in this case, metals were zinc and iron, these pigments have been synthesized by non-conventional methods like the co-precipitation assisted by ultrasound and high milling energy. Pigments were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), spectrophotometry, and colorimetric CIELab method. Results showed that it was possible to obtain a crystallin desired structure at temperatures below 900&#176C by non-conventional methods. These results showed the advantages of ceramic pigments obtained by alternative routes, because it was possible to have a better control over stoichiometry and colorimetric structure properties. Furthermore, they were obtained at temperatures lower than those used by the traditional ceramic route.

Synthesis of Spinel Ceramic Pigments and Glazes Based on Them

The results of research on the synthesis of ceramic pigments based on titanomagnetite with modifying additives zinc, magnesium, cobalt and manganese oxides are presented. X-ray phase analysis is used to determine the phase compositions of the pigments as a function of the composition and synthesis temperature. The optimal compositions and synthesis conditions of pigments are determined.

Effective synthesis route for red-brown pigments based on Ce – Pr – Fe – O and their potential application for near infrared reflective surface coating

New cerium-based ceramic pigments, displaying Ce2Pr0.2FexO4.3+y stoichiometry, were obtained at low temperature using a sol–gel method. The powder precursor dissolved in 80% ethylene glycol was precipitated using ammonia and the obtained gel calcined at 800°C for 2 h to yield homogeneous and crystalline particles with a diameter of around 150 nm. The oxide was composed of cerium in its +4 oxidation state and Pr in its +3 oxidation state. The oxides with varying Fe content had an intense red-brown colour, with bandgap energy of around 2.2 eV at 0.1 mol% Fe doping. The near infra red reflectance from these pigments, a measure of their ability to reflect rather than absorb heat waves from sunlight was found to be 82.7%, even in the absence of a white reflective base. Such high near infra red reflectance from these pigments qualify them for being ideal cool pigments for surface coating applications.

Novel Inorganic Products Based on Industrial Wastes

This contribution reports the use of industrial wastes, red mud and tionite, obtained upon refining and extraction of bauxite and titania ores, respectively. For red mud, two applications were explored: geopolymers and clinker/cement. According to this study, only after 14 days the effects of addition of red mud are translated into technological properties of geopolymers. Moreover, in small proportions the mechanical strength was improved at 28 days curing, certainly due to the high alkaline nature of the waste. Belitic clinkers with balanced amounts of cementitious phases were produced at 1,350 °C. Mortars cured for 10 days produced from those clinkers/cements show mechanical strength that tends to increase when high amounts of C3S are formed. The relative content of C2S is also important in the hardening process. With the addition of red mud, the technological properties of the mortars were enhanced due to the pozzolanic reactivity of this sludge. The tionite was selected to be recycled as ceramic pigment. The colorimetric parameters of tionite pigment calcined at 1,200 °C and its application in transparent glaze show a light brownish colour, due to the strong brightness (L*). This colour should be exalted by the intercalation of metal ions present in the sludge that could form a metal bearing rutile phase. In the glaze, the yellow component (+b*) doubled and responds for the final beige coloration .

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.

어트리션밀을 이용한 CoAl2O4나노 무기 안료의 제조 및 특성 평가

<TEX>$CoAl_2O_4$</TEX>는 열적 및 화학적으로 매우 안정한 물질이며 독특한 광학적 특성으로 인해 도자기 제품, 유리, 페인트, 플라스틱을 장식하는 세라믹 착색제로 사용되어져 왔다. 본 연구에서는 착체중합법(Polymerized complex method)과 고상합성법(Solid state reaction)을 이용하여 단상의 <TEX>$CoAl_2O_4$</TEX> 청색 무기 안료를 합성하였고, 잉크젯 프린팅용 잉크로의 응용 시 노즐 막힘 및 분산안정성과 같은 문제점을 방지하기 위해 고에너지 밀링 공정 중 하나인 어트리션밀을 이용하여 입자를 미세화하였다. 밀링 공정은 직경 1 mm의 지르코니아 볼을 이용하여 BPR(Ball to powder weight ratio) 100 : 1, 800 rpm의 조건에서 3시간 동안 진행되었다. 합성된 안료는 XRD, FE-SEM, TEM, PSA, 그리고 CIE <TEX>$L^*a^*b^*$</TEX> 측정을 통하여 어트리션밀링 전후의 특성을 분석하였다. XRD 측정 결과 단상의 <TEX>$CoAl_2O_4$</TEX> 청색 무기 안료가 합성되었고, 고에너지 밀링 공정을 통하여 100~200 nm의 입자 크기를 가지는 청색 나노 무기 안료를 얻었다. Cobalt aluminate (<TEX>$CoAl_2O_4$</TEX>) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, <TEX>$CoAl_2O_4$</TEX> is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, <TEX>$CoAl_2O_4$</TEX> pigments were synthesized by polymerized complex method and solid state reaction. Then <TEX>$CoAl_2O_4$</TEX> pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE <TEX>$L^*a^*b^*$</TEX>. The XRD patterns of <TEX>$CoAl_2O_4$</TEX> show single phase spinel structure. The particle size of <TEX>$CoAl_2O_4$</TEX> measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained <TEX>$CoAl_2O_4$</TEX> pigments could be confirmed through CIE <TEX>$L^*a^*b^*$</TEX> measurement.

Electrocoagulation of yogurt industry wastewater and the production of ceramic pigments from the sludge

In this study, the treatment of strained (condensed) yogurt wastewater using a uniquely designed iron reactor with electrocoagulation and the sludge produced during the electrocoagulation as a raw material in the production of ceramic pigment were investigated. A rectangular iron cathode compartment and parallel plate anodes were used, and various operating parameters, such as the current density, the electrolysis time, the supporting electrolyte concentration, the initial pH and the polyelectrolytes addition, were examined in order to determine the best conditions for intensifying the performance of the process. It was seen from the experiments that the COD removal efficiency was increased with the increasing current density from 20 to 30mA/cm2 and time while it was decreased with the increasing Na2SO4 concentration from 0.05 to 0.2M. The best treatment efficiency was observed at the original pH of the wastewater (pH 4.53) and the cationic polyelectrolyte showed better performance than the anionic polyelectrolyte. The strained yogurt wastewater, with a COD concentration of 6500mg/L, was treated with a removal efficiency of 84% after 90min of electrocoagulation with the addition of 0.75g/L cationic polyelectrolyte. The sludge produced during the electrocoagulation was characterised and used as an iron source to produce brown and black inorganic ceramic pigments because of their high iron oxide content. The results show that this specially designed electrochemical reactor is an effective alternative for the treatment of strained yogurt wastewater. It also shows that the sludge produced during electrocoagulation can be used as a raw material in the ceramic industry and that it can be converted from waste to a value-added product.

Optical Properties of the MoO3-TiO2 Particulate System and Its Use as a Ceramic Pigment

Mo-doped TiO2 powders were prepared using a dry mixture of TiO2 and MoO3 oxides with several compositions, followed by a calcination step at several temperatures. The resulting oxide system develops yellow and green tones. The XRD patterns showed only traces of MoO3; however, EDS results, combined with TG/DTA data, confirmed the presence of molybdenum ions, suggesting that the changes in optical properties of the oxide system is due to the incorporation of Mo ions into the TiO2 matrix, substituting Ti+4 with Mo+6 ions. The band gap decreased with increasing of MoO3 content; on the other hand, the band gap reached a maximum value at about 850°C to 910°C when plotted as a function of the calcination temperature. The glazes produced showed that the oxide system under study is a potential material for use as abinary ceramic pigment.

Improvement of the Compositions and Properties of Gray Ceramic Pigments

A comparative analysis of the optical and color characteristics of well-known gray ceramic pigments is performed and the effectiveness of different opacifying components in them is evaluated. Gray pigments with stable optical indicators are synthesized using open hearth slag. It is shown that zirconium compounds, characterized by inertness with respect to the coloring components in the pigment and by high resistance to dissolution by glass melts, are shown to be effective opacifiers for obtaining these pigments.