Ceramic Pigments Research Articles

Anatase-to-rutile transition in co-doped TiO2 pigments

In this paper, cobalt-doped titanium dioxide green ceramic pigments were synthesized by the polymeric precursor method. In order to investigate the obtainment of a crystalline rutile phase and particles in nanoscale, a chromophore doping was made with fixed concentrations of 1, 2, and 4 mol%, utilizing a calcination temperature of 600oC. The products were investigated by thermal analysis, X-ray diffraction, diffuse reflectance, scanning and transmission electron microscopies. The titanium dioxide:cobalt crystallite size was about 65–100 nm. A broad reflectance band around 540 nm (green region) was observed for all doped samples, indicating the appearance of a deep green pigment. Furthermore, the results have shown that cobalt-doped titanium dioxide promotes greater phase conversion of anatase to rutile. Samples submitted at a temperature of 600 °C, pure titanium dioxide contains 22% rutile, whereas titanium dioxide: 4% of cobalt contains 78% rutile. The mechanism of phase transition in presence of cobalt is attributed to the lower valences of the dopant (II or III) when compared to the titanium valence (IV). Ionic substitution leads to the generation of oxygen vacancies that promote phase transitions at lower temperatures than expected in pure titanium dioxide.

Karrooite green pigments doped with Co and Zn: Synthesis, color properties and stability in ceramic glazes

Abstract The solid-state synthesis and stabilization of Co doped ( Mg 1−x Co x Ti 2 O 5 ), Zn doped ( Mg 1−x Zn x Ti 2 O 5 ) and Co- and Zn-codoped karrooite solid solutions ( Mg 0.8−x Zn 0.2 Co x Ti 2 O 5 and (Mg 0.5 Zn 0.5 ) 1−x Co x Ti 2 O 5 ) were investigated. In addition, the optical spectra, color properties and technological performance of (Co,Zn)-karrooite compositions as new green ceramic pigments were also analyzed. XRD characterization revealed for the first time the high solid solubility of Zn 2+ in MgTi 2 O 5 karrooite at 1200 oC (between 60 and 80 mol% per Mg or karrooite formula unit). In contrast, the reactivity and stabilization of karrooite phase decreased in the case of Co 2+ doping. Interestingly, codoping with Zn 2+ ions at high molar ratios (Zn:Mg ratio equal to 1:1) enhanced the reactivity and enabled the stabilization of (Co,Zn)-MgTi 2 O 5 karrooite solid solutions, even with high Co 2+ loadings (20 mol% per karrooite formula unit). The (Co,Zn)-MgTi 2 O 5 pigments exhibited yellowish-green colors associated to Co 2+ ions allocated in octahedral M1 and M2 sites of karrooite lattice, and becoming more intense and less yellow the higher the Co content. However, Zn 2+ codoping produced less saturated green colors with similar green but lower yellowish hues. The obtained pigments were not stable enough within the tested ceramic glazes, giving rise to turquoise colorations due to cobalt leaching and incorporation into tetrahedral sites of the glassy phase. The stability of Co-karrooite green pigments was higher in a Ca- and Zn-enriched ceramic glaze (B) fired at a higher temperature (1050 °C).

Functionalized pink Al2O3:Mn pigments applied in prosthetic dentistry

Statement of problemThe color of dental poly(methyl methacrylate) (PMMA) is conventionally rendered by organic and inorganic pigments, which are usually not bonded to the polymer network. Functionalized ceramic pigments can be used to color PMMA, allowing improved chemical interaction with the resin matrix. PurposeThe purpose of this in vitro study was to synthesize, functionalize, and characterize pink manganese-doped alumina ceramic pigments. The hypothesis tested was that functionalized ceramic pigments would render pink coloration to a translucent PMMA without jeopardizing its mechanical properties. Material and methodsPink alumina powders doped with 1 or 2 mol% of manganese (Al2O3:Mn) were prepared by means of a polymeric precursor method. Pigment (Pig.) particles were functionalized with a silica coating method followed by silanation before preparation of PMMA-based composite resins (5 wt% pigment). The color of composite resins (Pig.1% and Pig.2%) and PMMA controls (Pink and translucent [Trans]) was evaluated (CIELab color coordinates), and their mechanical properties were tested (3-point bending). ResultsThe microstructure of the pigment particles showed approximately 55-nm nanocrystals of manganese-doped α-alumina clustered into irregular porous particles up to 60 μm. The composite resins and pink PMMA showed similar color parameters (CIE a* pink=20.1, Pig.1%=14.6, Pig.2%=16.0, Trans=0.19, P<.001; CIE b* Pink=17.0, Pig.1%=18.6, Pig.2%=19.0, Trans=2.52, P<.001). No statistical differences were observed in mechanical properties among groups (σf pink=98.4, Pig.1%=98.1, Pig.2%=98.8, trans=89.1, P=.136). ConclusionsThe addition of the functionalized pink ceramic pigments to a translucent PMMA yielded similar coloration to that of the regular pink PMMA used in dentistry and did not jeopardize its mechanical properties.

Effect of sol–gel method on colour properties of the classical cobalt olivine (Co2SiO4) ceramic pigment

A sol–gel method based on (H 2 S 2 5) a q as silicon precursor in the presence of NaCl and KCl mineralizers was used for the synthesis of the classical cobalt olivine (Co 2 SiO 4 ) ceramic pigment. The effect of this synthesis route on the colour properties was studied. Highly pure olivine phase was obtained after firing at 1200 ∘ C for 3 h. The resulting powders exhibited very intense violet colour, while their addition at only 1 wt% to an industrial transparent glaze was enough to produce a very intense blue–violet colouration. Based on the aspect of glazed ceramics, addition of pigments even at 0.5 wt% to the glaze resulted in a very interesting colour and opacity. By this appropriate minimization of the used pigment amount without compromising the colouring properties required during application, the obtained Co olivine could be more efficient, less toxic and less expensive.

Gelatin synthesis and color properties of (La, Pr, Nd) lanthanide aluminates

This work aimed to synthesize (LnAlO3, Ln=La, Pr, Nd) lanthanide aluminates with perovskite structure in order to study their application as ceramic pigments. Effects of the lanthanide ions on the color properties of the powders were evaluated. Perovskites were synthesized by a method, which makes uses of gelatin as an organic precursor and thermally treated at 800 and 1000°C for 4h. The resulting powders were characterized using thermal analysis, X-ray diffraction, scanning electron microscopy, UV–visible diffuse reflectance spectroscopy and CIELab colorimetry. The calcined powders were single-phase and exhibited a well-developed rhombohedral perovskites structure. Pigments presented high percentage of reflectance and a light violet color. The crystal field transitions of lanthanide ions were the only source of colors of the pigments.

Micronization of Ceramic Pigments for Digital Ink-Jet Printing Process

Ink-jet printing techniques with ceramic ink, which contains ceramic pigments as colorant, are in increasingly use in the ceramic industry. Generally, ceramic pigments that are produced by conventional method show diameters of several micrometers; these micrometer sized particles in the ink-jet printing process can cause undesirable behavior such as print head nozzle clogging. To prevent this problem, a particle size reduction process is required. In this study, CMYK (cyan, magenta, yellow, black) pigments were synthesized via solid state method. Each pigment particle was milled to submicron size by an attrition mill. The effects of micronizing on the morphology, mechanical property, crystal structure and color property of the CMYK ceramic pigments were investigated by field emission scanning electron microscopy (FE-SEM), particle size analysis (PSA), X-ray diffraction (XRD) and CIE L*a*b*.

Red-brown ceramic pigments based on chromium doped ferrian armalcolite, effect of mineralizers

A new red-brown ceramic pigment based on chromium-doped ferrian armalcolite have been synthesized and characterized. (MgFe)(CrxTi3−xFe)O10 powders (x=0–0.3) fired at 1200°C crystallize ferrian armalcolite as the only crystalline phase detected. Samples fired at 1000°C show red-brown shades in glazes that darken and bluish (b* turns to negative values) at 1200°C. The x=0.2 sample fired at 1000°C shows the best red colour (L*a*b*=49.5/15.2/10.3). Assignment of bands in the UV–Vis–NIR spectra is difficult due to the overlapping of Cr3+, Cr4+ and Fe3+ absorptions in octahedral coordination. Analysis of UV–Vis–NIR spectra of powders shows that these spectra are dominated by the strong absorption associated to Fe3+ ions in octahedral sites. In contrast, an intense band at 520nm dominates the UV–Vis–NIR spectra of glazed samples, which should be associated to Cr4+ in octahedral coordination. This absorption increases when the amount of chromium increases, indicating that chromium is the real chromophore of the system. Finally, the weak shoulder at 600nm and the double weak band at 700nm, detected more evidently when chromium amount in sample increases, indicate the progressive presence of Cr3+ in octahedral sites. The entrance of Cr4+ in x=0.1 sample shrinks the crystalline cell, but when chromium amount in the samples increases, both Cr4+ and Cr3+enter simultaneously and the unit cell remains practically stable. The microstructure of the powders analysed by SEM microscopy indicates aggregates of 6–10 fine particles of 200–400nm of diameter. The addition of mineralizers (boric acid, sodium perborate, NaF and a mixture BaF2.4MgF2) does not modify significantly the reactivity of the system; at 1000°C hematite and rutile remain as residual crystalline phases, except in NaF additions where the crystallization of NaFeTi3O8 is detected. SEM-EDX mapping analyses of pigment powders confirm in all cases a homogeneous distribution of ions in the particles.

Structural characterization and colour of Ni3VxP2−xO8 (0 ≤ x ≤ 2) and Ni2VyP2−yO7 (0 ≤ y ≤ 2) materials

Structural characterization of Ni3VxP2−xO8 (0≤x≤2) and Ni2VyP2−yO7 (0≤y≤2) compositions was made and colour parameters of these materials measured. Ni(II) diphosphate and divanadate crystalline phases are not stables at high temperature. Solid solutions in Ni3P2O8 and Ni3V2O8 are obtained by incorporation of V(V) in Ni orthophosphate and P(V) in Ni orthovanadate structures. Solid solutions with Ni3V2O8 structure are formed in a greater compositional interval than solid solutions with Ni3P2O8 structure. These materials might be used as ceramic pigments because of its thermal and chemical stability. Tan brown colorations were obtained in glazed tiles when the fired compositions were 4% weight enamelled with a commercial glaze.

Synthesis of pigments of Fe2O3·SiO2 system, with Ca, Mg, or Co oxide additions

The present research work is based on the comparative evaluation of the Ca, Mg, and Co dopant impact on the properties of new ceramic pigments from the system Fe2O3·SiO2 obtained via classical ceramic technology. This approach enabled determination of the optimal temperature for the synthesis and the most appropriate mineralizer. The obtained specimens were submitted to systematical analysis, including X-ray Diffraction (XRD) spectroscopy, Electron Paramagnetic Resonance (EPR) analysis and Mössbauer spectroscopy for crystalline phase determination. The color characteristics are quantified by spectrophotometric measurements. The pigments particle size has been determined by Scanning Electron Microscopy (SEM), combined by Energy Dispersion X-ray spectroscopy (EDX). The obtained results enabled to determine the correlation between the calcination temperature and the phase compositions of the obtained pigments. In addition, some interesting magnetic properties were detected for the Co-doped composition.

Validation of Surface Temperature Measurements on a Combustor Liner Under Full-Load Conditions Using a Novel Thermal History Paint

The ever-increasing requirements on gas turbine efficiency and the simultaneous demand for reduced emissions, necessitate much more accurate calculations of the combustion process and combustor wall temperatures. Thermal history paints (THPs) is an innovative alternative to the established measurement techniques, but so far only a limited number of tests have been conducted under real engine conditions. A typical THP comprises oxide ceramic pigments and a water-based binder. The ceramic is synthesized to be amorphous and when heated it crystallizes, permanently changing the microstructure. The ceramic is doped with lanthanide ions to make it phosphorescent and as the structure of the material changes, so do the phosphorescent properties of the material. By measuring the phosphorescence, the maximum temperature of exposure can be determined, enabling postoperation measurements at ambient conditions. This paper describes a test in which THP was applied to an impingement-cooled front panel from a combustor of an industrial gas turbine. The panel was instrumented with a thermocouple (TC), and thermal paint was applied to the cold side of the impingement plate. The THP was applied to the hot-gas side of this plate for validation against the other measurement techniques and to evaluate its resilience against the reacting hot gas environment. The durability and temperature results of the three different measurement techniques are discussed. It is shown that the THP exhibited greater durability compared to the conventional thermal paint. Furthermore, the new technology provided detailed measurements indicating local temperature variations and global variations over the complete component.

Optical and Structural Properties of Lanthanum Chromite Synthesized by Microwave Assisted Self-Combustion Method

Lanthanum chromite is a perovskite oxide type, which exhibit high mechanical and chemical stability, high electric conductivity for use in SOFC and catalytic activity for the oxidation reaction. However, their optical properties have not yet been studied. The aim of this study was to synthesize lanthanum chromite by the microwave assisted self-combustion method for use as ceramic pigment. The resulting precursor powders were calcined at 800 to 1000 ° C to obtain the perovskite phase and characterized by X-ray diffraction, followed by Rietveld refinement, UV-Visible and colorimetry. The results revealed porous powders, nanometric, and single-phase with orthorhombic perovskite structure. There was few change in the colorimetric parameters, the chromites presented colours with gray tones which became darker in the calcined powder at higher temperatures.

디지털 잉크젯 프린팅용 흰색 세라믹 안료의 고온 및 화학적 안정성 평가

고온 및 화학적 안정성이 높은 세라믹 안료는 타 소재 대비 우수한 내구성을 가지며, 최근 잉크젯 프린팅 기술의 발전과 함께 산업적인 응용영역이 점점 확대되고 있다. 세라믹 잉크젯 프린팅 공정은 다양한 이미지를 인쇄 가능하고 높은 효율성을 가지는 친환경 공정이라는 장점으로 인해 다양한 분야에 적용이 시도되고 있어, 디지털 4원색인 CMYK(cyan, magenta, yellow, black) 세라믹 안료를 비롯하여 다양한 색상 및 기능성을 가지는 세라믹 안료에 대한 관심이 커지고 있다. 본 연구에서는 세라믹 잉크젯 프린팅에 적합한 white 세라믹 안료를 선정하기 위해 고온에서의 화학적 안정성 및 혼합 발색 거동에 대해 연구하였다. MgO, <TEX>$Al_2O_3$</TEX>, <TEX>$MgAl_2O_4$</TEX>, <TEX>$CeO_2$</TEX> 조성의 세라믹 안료가 가지는 미세구조 및 결정구조를 분석하고 유약과의 반응성을 평가하였다. 또한 세라믹 잉크젯 프린팅에서 요구되는 고온 안정성을 평가하기 위해 CMYK 발색 세라믹 안료와 혼합한 뒤 열처리 공정을 거쳐 색상 혼합에 따른 화학적 안정성을 CIE <TEX>$L^*a^*b^*$</TEX> 측정을 통해 분석하여 디지털 프린팅 공정으로의 적용가능성을 평가하였다. Ceramic pigments, which show good thermal and chemical stabilities, have been applied for various industry with development of digital printing technology. Ceramic inkjet printing has advantages of high efficiency of ink usage and eco-friendly process. Thus, the interest of the ceramic pigments with various function and color including CMYK (cyan, magenta, yellow, black) digital primary color is increasing. Here, we investigated the thermal and chemical stabilities of white ceramic pigment for digital inkjet printing process. The microstructure and crystal structure of MgO, <TEX>$Al_2O_3$</TEX>, <TEX>$MgAl_2O_4$</TEX>, <TEX>$CeO_2$</TEX> were analyzed, and the stability with glaze were evaluated. In order to evaluate the applicability for digital inkjet printing, the chemical stability of white ceramic pigments at high temperature was investigated by characterization of the mixed color properties with CMYK ceramic pigments after firing process.

진공상온분사 공정을 이용한 세라믹 도료 분말의 장식용 코팅 및 패터닝 제조

진공상온분사 공정을 이용한 세라믹 도료 분말의 장식용 코팅 및 패터닝 제조

Synthesis of Ceramic Pigment Based on Crystal Structure of Wollastonite

In the ceramic industry, color is of great importance to product development. Parameters such as hue, brightness and color intensity influence the visual appearance of the ceramic surface and its market value. Research on the development of new pigments is ongoing, with focus on cost reduction, environmental suitability and color innovation. Different studies have shown the feasibility of using industrial by-products to obtain pigments. Many of these waste products have calcium carbonate and nickel oxides in their composition. This study investigates the synthesis of ceramic pigment with the structure of wollastonite - CaSiO3, with the use of nickel as chromophore ion. In order to evaluate the effect of adding nickel to the formation of crystalline phases X-ray diffraction was used. Particle size analysis was performed by Laser diffraction technique and a colorimetric study was conducted through the analysis of the pigment applied to a commercial enamel, by determining colorimetric parameters L*, a* and b*. The results showed that wollastonite combined with nickel acts as pigment and that its presence may interfere with the performance of new pigments depending on the nickel content and synthesis temperature.

Visible photon excited photoluminescence; photometric characteristics of a green light emitting Zn2TiO4:Tb3+ nanophosphor for wLEDs

A novel green light emitting Zn2TiO4:Tb3+ nanophosphor was synthesized via solution combustion synthesis and the final product was well characterized. From diffused reflectance spectra the energy band gap of the sample was estimated to be in the range 3.16–3.19 eV and the effect of Tb3+ on the electronic structure was calculated based on absolute electronegativity. The characteristic photoluminescence emission peak observed at 493 nm in the blue region was due to 5D3 → 7F3 and peaks at 515, 541, 579 and 620 nm corresponding to 5D4 → 7Fj (j = 6, 5, 4, 3), respectively, were due to f–f transitions of Tb3+ cations in the given host lattice upon 415 nm high energy visible photon excitation. Photometric characteristics suggest that the phosphors have a long lifetime, excellent color purity, color chromaticity coordinates and correlated color temperature values, so it is clearly evident that the optimized phosphor is quite useful for the green region of wLEDs, a ceramic pigment and for solid state display applications.

In-situ Cr-doped Alumina Nanorods Powder Prepared by Hydrothermal Method

Cr-doped ammonium aluminum carbonate hydroxide nanorods were prepared by a hydrothermal method, with Al(NO3)3·9H2O, Cr(NO3)3·9H2O, and urea as raw materials and PEG-20000 as surfactant. In-situ Cr-doped alumina nanorods powder was obtained through calcining its precursors (Cr-doped ammonium carbonate hydroxide nanorods) at 1200 °C. The crystal composition, the structure and the morphology of the as-prepared products were characterized by XRD, SEM and FTIR. Besides, the color performances of the products were analyzed by UV/Vis/NIR spectrometer and automatic color measurement. Results show that the precursors of Cr-doped alumina nanorods powder prepared by the hydrothermal method are composed of uniform nanorods. After its calcinations at 1200 °C, the in-situ doping of Cr in the alumina substrate is achieved. In the Cr-doped alumina nanorods powder, a continuous solid solution of Cr2O3 and Al2O3 is formed, which has a corundum crystal structure. With the increasing Cr content, Cr-doped ammonium aluminum carbonate hydroxide nanorods gradually become short, and the melting phenomenon occurs in calcined products. UV-Vis spectroscopy analysis shows that Cr-doped alumina nanorods powder has three strong absorption bands at 562, 406 and 372 nm, thus leading to a pink color for samples which is in agreement with chromatic data. In the present study, Cr-doped alumina nanorods powder prepared by the hydrothermal method can reduce the formation temperature of corundum crystal structures and resolve the problem of mixing homogeneity of Al2O3 and Cr2O3, which will contribute to the preparation and the application of alumina-chrome refractory, pink corundum abrasive and ceramic pigment.

Using extraction and sorption processes to obtain nanosized powders of calcium silicates and functional materials on their basis

The review presents summary data on extracting agents and the application of sorption processes during the cycle of studies on the joint processing of calcium and silicon-containing raw materials on the production of calcium silicates and composite materials on their basis. It is found that, in processes of the production of synthetic calcium silicates from various types of calcium and silicon-containing raw materials, ionic and nonionic surfactants, including extractants, serve as structuring additives that hinder crystal growth and impede their agglomeration. The sorption properties of amorphous and crystalline nanopowders of calcium silicates and hydrosilicates synthesized from water-soluble materials are studied with respect to cations of base and rare metals. It has been found that the studied samples have high sorption capacity for cations of Eu3+, Pr3+, Tb3+, Er3+ and may be used as the basis for producing functional composite materials. The efficiency of applying the extraction-pyrolytic method has been shown to provide homogeneity and predetermined composition of the desired products, for the production of ceramic pigments and luminescent materials based on calcium silicates.

Characterization of the glaze and in-glaze pigments of the nineteenth-century relief tiles from the Pena National Palace, Sintra, Portugal

The glaze and in-glaze pigments of the historical nineteenth-century glazed tiles from the Pena National Palace (Sintra, Portugal) were characterized using a multi-analytical approach. Chemical composition and microstructural characterization were ascertained by µ-PIXE, µ-Raman, optical microscopy and VP-SEM–EDS. The manufacturing technique and colour palette in these tiles were found to be close to the ceramic pigments used in traditional majolica. The blue and purple colours derive from cobalt oxide and manganese oxide, respectively. A mixture of Pb–Sn–Sb yellow with cobalt oxide and iron oxide was used for green and dark yellow, respectively, while grey tonalities consist of a complex mixture of cobalt oxide, manganese oxide and Pb–Sn–Sb yellow in different proportions. Results obtained allowed the determination of the oxides and elements used in pigments as well as production techniques, resorting to traditional majolica manufacture, although the tiles were produced by the end of the nineteenth century.

Synthesis and characterization of pigments of the LaAl1−xFexO3 system – Application in ceramic and polymer

Pigments from the LaAl1−xFexO3 (x = 0.00 to 1.00) system were synthesized through the citrate method and thermally treated at 910 °C for 4 h. The samples obtained were characterized through X-ray diffraction (XRD), Mössbauer spectroscopy (MS), field effect scanning electronic microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and diffuse reflectance spectroscopy in the UV–Visible (DRS UV–Vis). The XRD analysis revealed the formation of perovskite as a single phase, crystallizing in the rhombohedral crystalline system with values 0.00 ≤ x ≤ 0.80, and in the orthorhombic system with x > 0.80 value. Through the Mössbauer spectroscopy, it was possible to follow the phase transformation and determine at which iron concentrations the coexistence of the perovskite rhombohedral and orthorhombic phases occurred. The electronic microscopy enabled to identify that the pigments presented particles of ideal size to be applied as ceramic pigments. Regarding coloration, the increase in Fe3+ concentration in the LaAl1−xFexO3 system provoked lattice distortions, altering the pigment band gap values and consequently their color. The pigments obtained presented coloration varying from white (LA), greenish-yellow (LAF1 to LAF5) and orange (LAF6 to LF). The pigments were applied to the enameling of ceramic pieces at 850 °C, decorative burning temperature and presented good color and opacity. Thus, the system under study presented suitable properties to be used as pigment to ceramic and polymer, in addition to presenting low toxicity, a fundamental characteristic in the current scenery of environmental and human health concerns.

Preparação de pigmentos de aluminatos de cobalto para aplicação em vidrados cerâmicos

Resumo Os pigmentos inorgânicos são os mais utilizados industrialmente, pois apresentam maior estabilidade química e térmica e podem ser produzidos com um elevado grau de pureza e uniformidade. Essas características levaram ao desenvolvimento de diferentes cores intensas, estáveis e adequadas ao uso como pigmentos. O presente trabalho tem por objetivo sintetizar materiais cerâmicos com estrutura espinélio para uso como pigmento cerâmico e aplicá-los em fritas cerâmicas. O processo de síntese foi realizado pela rota da gelatina e com os pós obtidos foram conduzidos um estudo de evolução de fases cristalinas por meio de difração de raios X, refinamento das estruturas por meio do método Rietveld, espectroscopia na região do infravermelho, microscopia eletrônica de varredura, espectroscopia na região do UV-visível e colorimetria. Foram observadas nos difratogramas reflexões características da estrutura espinélio. O tamanho médio de cristalito e a cristalinidade aumentou com o aumento da temperatura de calcinação. A coloração dos pigmentos variou do azul claro ao violeta azul.