TiO2@CoTiO3 complex green pigments with low cobalt content and tunable color properties

Green complex pigments with TiO₂@CoTiO₃ core–shell structure were prepared through calcination of precursors obtained from the precipitation of Co²⁺ on TiO₂ particles. The synthesized pigments were characterized by colorimetry, near-infrared diffuse reflectance spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet–visible (UV–vis) spectroscopy. The pigments were found to consist of a rutile TiO₂ core and outer ilmenite CoTiO₃ shell. The green pigments with good color properties could be obtained via calcination of the precursors at 800 °C. The pigments with Co/Ti ratio of 0.4 had the highest green component value and exhibited good color properties (L*=49.51, a*=−34.58, b*=5.53). The color properties could be tuned by just changing the Co/Ti ratio. The as-prepared complex pigments exhibited an enhanced near-infrared reflectance compared with pure CoTiO₃ pigments and also exhibited better color properties than the mixed pigments of TiO₂ and CoTiO₃. Further, the complex pigments had much lower consumption of cobalt compared to pure CoTiO₃ and Co₂TiO₄ pigments. The special core–shell structure was found to be responsible for the enhanced near-infrared reflectance and good color properties.     

聚丙烯基木塑复合材料的老化性能研究

以聚丙烯(PP)作为基体,以木粉作为填料,并分别加入炭黑、钛白粉、氧化铁红等,用注射成型法制备了PP基木塑复合材料(WPC),用烘箱热氧老化法和氙灯老化法研究了颜料对WPC老化性能的影响。结果表明,随着老化时间的增加,无论是否加入颜料,均出现了WPC的拉伸强度和氧化诱导时间减小,熔体流动速率和色差增大的现象;烘箱老化前后,添加钛白粉和氧化铁红的WPC的拉伸强度、氧化诱导时间和色差均较小,熔体流动速率均较大;在氙灯老化条件下,添加颜料的WPC老化后拉伸强度、熔体流动速率、颜色和氧化诱导时间的变化速度均较小。     

Structural analysis and characterization of doped spinel Co2−xMxTiO4 (M=Mg2+, Mn2+, Ni2+, Cu2+ and Zn2+) coated mica composite pigments

A new kind of composite mica pigments were prepared by coating Co_2−xM_xTiO₄ composite oxide nanoparticles onto mica, to investigate the effects of doping ions Mg²⁺, Mn²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ on the properties of the doped composite pearlescent pigments, such as the crystal structure, color and shading power. The structure, morphology, color and shading power of the coated pigments were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis spectrophotometer and CIE L*a*b* methods. SEM images of coated pigments showed that mica were coated uniformly with a single layer of dispersed nanoparticles. Research of the doped composite pigments showed that the doping ions had entered into the spinel crystal structure, forming a new kind of composite mica pearlescent pigments coated with Co_2−xM_xTiO₄. For the analysis of color and shading power of the pigments, doping of Ni²⁺ and Zn²⁺ can improve the color and shading power of the doped pigments, but the larger dosage of Zn²⁺ doping can weaken the color and shading power of the doped pigments. Doping of Mg²⁺, Mn²⁺ and Cu²⁺ metal ions can also weaken the color and shading power of the doped pigments.     

Allochroic effect of praseodymium doped neodymium molybdate pigment synthesized by solid-state reaction

This paper was to synthesize praseodymium-doped neodymium molybdate allochroic pigments with different molar ratios of molybdenum (Mo), neodymium (Nd) and praseodymium (Pr) through solid-state reactions. The pigments synthesized were investigated by X-ray diffraction (XRD), selected area electron diffraction (SAED), thermogravimetry and differential thermal analysis (TG-DSC), diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and colorimeter. The results show that a pure neodymium molybdate (i.e., Nd₂MoO₆) can be formed after sintering at 1000 °C for 3 h, and praseodymium-doped neodymium molybdate can be synthesized after sintering at 1000 °C for 3 h due to praseodymium ions entering in the lattice of Nd₂MoO₆. The crystal structure in the pigment synthesized can transform from cubic to tetragonal depending on the molar ratio of neodymium/molybdenum and sintering procedure. The color properties of pigments were measured in color space CIEL*a*b* under different standard illuminants (i.e., solar-light (D65), incandescent light (A), cool white fluorescent lamp (F2), and three-band fluorescent lamp (F11)). The results show that the colors of the pigments vary under different illuminants. According to the color difference (ΔE) analysis, neodymium molybdate pigment exhibits a maximum color difference of 10.69, and the maximum color difference of praseodymium-doped neodymium molybdate pigment with doping content of 0.2 increases to 17.63 due to the Pr³⁺ ions substitution for Nd³⁺ ions in the lattice. In addition, the color difference of the pigments with allochroic effect was discussed based on the colorimetry. The color difference of the pigments is due to a high reflectance region at 540–550 nm and a low reflectance region at 380–500 nm.     

Effect of hydroxyl ions on chloride penetration depth measurement using the colorimetric method

In this paper, the effect of hydroxyl ions on chloride penetration depth measurement using the colorimetric method was studied. Equivalent silver nitrate solution (i.e. Ag⁺ = Cl⁻) was added to the NaCl + NaOH solution with different concentrations, then the amount of precipitated silver chloride and silver oxide were determined by chemical methods, and the color of the precipitated products was examined. Results show that the amount of silver chloride formed decreases linearly as OH⁻ to Cl⁻ ratio (r) increases. Thus, the chloride concentration at color change boundary changes with the pH value of the concrete. AgCl has a white color, while Ag₂O has a dark brown color. When the value of r exceeds 4, the color of the mixture looks brown, and color change boundary cannot be easily distinguished.     

Anticorrosive properties of the epoxy–cardanol resin based paints

An epoxy–cardanol resin was developed using epichlorohydrin, bisphenol-A and cardanol. On evaluation it was found that epoxy–cardanol resin exhibits better properties as compared to epoxy resin in terms of increase in tensile strength, elongation, bond with steel and lowering of water vapour transmission of the film. The improvement in these properties indicated that the paints based on modified resin would be more durable than the epoxy based paints. Accordingly, paints were formulated using the developed resin and their performance were compared with their counterparts made with unmodified epoxy resin. Zinc powder, zinc phosphate, micaceous iron oxide and synthetic iron oxide were used as pigments along with fillers, additives and an aromatic polyamine adduct hardener. For both types of paints similar doses of pigments and additives were used. Physico-mechanical properties, chemical resistance and corrosion protection efficiency of the formulated paints were determined. It was found that the anticorrosive properties of epoxy–cardanol resin based paints are superior to that of the paints formulated with the unmodified epoxy resin. Micaceous iron oxide based paints in epoxy–cardanol resin showed the best performance followed by zinc phosphate based paints. It is concluded that the developed resin is a better binder media for the formulation of paints.     

Prediction of splitting tensile strength of high-performance concrete

Splitting tensile strength (STS) is one of the concrete mechanical properties that are used in structural design. It can be related to numerous parameters, which include compressive strength, water/binder (W/B) ratio and concrete age. Until now, most researchers estimated the STS directly from compressive strength data. This paper suggests formulae that relate STS with that of compressive strength, W/B ratio and concrete age. The predicted STS can be obtained accurately using these formulae. It is proposed that the equation with the concrete age (t) parameter be used in predicting the STS of high-performance concrete (HPC).     

New red pigments based on Li3AlMnO5 for NIR reflective cool coatings

The exploration of new red pigments based on transition elements is of great practical value in the field of inorganic pigments, since the red coloured pigments have unique applications in paints, ceramic tiles, cosmetics, etc. Here we mainly reported a new class of eco-friendly red pigments based on substituted Li₃AlMnO₅ (LAMO) and briefly state about the other rock salt layered structure Li₃GaMnO₅ (LGMO). The solid-state synthesized powders were crystallized to monoclinic structure having Mn^IV(1)_2b and Mn^IV(2)_4g site. The absorption bands in the synthesized samples mainly arises due to the octahedrally coordinated Mn^IVO₆ in the 4g site. Among the synthesized samples, LAMO: 0.10Ti⁴⁺ showed exemplary chromatic properties. The doping of tetravalent Ti⁴⁺ ions in the Mn⁴⁺ sites altered the Mn^IV(2)O₆ bond lengths and increased the crystal field around the absorption band attributed to the ⁴A_2g→⁴T_2g transitions. The ball milled LAMO: 0.10Ti⁴⁺shows the a* value of 40.05, which is higher than that of the commercially available red iron oxide pigments (a* = 28.9). Meanwhile, the brighter red powder LAMO: 0.10Ti⁴⁺ demonstrated appreciable thermal and chemical stability. From the thermal evaluating study, we observed that, LAMO: 0.10Ti⁴⁺ pigment coated roof panels showed a temperature difference of (3.2 °C) compared to the bare roof panel (3.7 °C). We estimated the coating's performance of the LAMO: 0.10Ti⁴⁺ in concrete block, metal plate and ceramic tile. In these substrates, the pigment possesses distinctly elevated NIR‐reflectance, which makes these materials worthwhile for cool coating applications.     

The effects of gradation and admixture on the pumice lightweight aggregate concrete

The usage of lightweight concrete, which has some advantage over ordinary concrete, has increased to a remarkable level in recent years. Many researchers have investigated the possible uses of lightweight concrete in terms of its strength, density and other mechanical and physical properties. The desired quality for lightweight concrete can be obtained through the proper selection of admixtures and proper grading of the lightweight aggregate.In this article, an experimental investigation on the production of moderate-strength lightweight concrete with pumice, according to the ACI standard, is presented. The gradation curves' (which fall within A16-C16 gradation curves, Turkish Standard Code, TS706) performances were investigated in terms of strength and density. The addition of superplasticizer and air-entraining admixtures improved the strength-to-density ratio of the hardened concrete and the workability of fresh concrete. As a result of this study, lightweight concrete blocks having a minimum compressive strength of 6.56 N/mm² and a density of 1300 kg/m³ were obtained.     

Influence of heat curing on the pore structure and compressive strength of self-compacting concrete (SCC)

The mechanical properties of self-compacting concrete (SCC) are well understood. But there are no scientific investigations available on the influence of a heat treatment on the properties of SCC. To evaluate the influence on the compressive strength, SCCs as powder type, combination type and viscosity-agent type in the strength classes between C20/25 and C70/85 were designed and exposed to heat treatment with different maximum temperatures. It has been found that there is an influence of the composition of the concrete, especially the (w/c)_eq ratio, on the compressive strength after heat treatment. The reason for the substantial loss of strength in some cases compared to the strength of the concrete, which was stored under standard conditions, is a change of the pore size distribution. An empirical formula is presented to calculate the influence of the heat treatment on the compressive strength of the SCCs.     

外墙乳胶漆耐候性研究

采用天然曝晒和人工老化方法研究了各种纯丙乳液和硅丙乳液的耐候性,由该类乳液制备的不同PVC白色乳胶漆的耐候性,以及白色乳胶漆与各色色浆配制的浅色乳胶漆的耐候性。结果表明:硅丙乳液和核壳型纯丙乳液具有较好的耐候性,高PVC乳胶漆容易变色,炭黑和氧化铁系色浆适合于配制浅色外墙乳胶漆,有机颜料色浆应用在外墙时应谨慎。     

Synthesis and optical properties of Ce0.95Pr0.05−xMxO2 (M = Mn,Si) as potential ecological red pigments for coloration of plastics

Ecological red pigments Ce_0.95Pr_0.05?xM_xO₂ (M = Mn, Si) have been synthesized by conventional solid-state route and characterized by X-ray diffractometer, scanning electron microscope and UV–vis spectroscopy. Mn⁴⁺/Si⁴⁺ was incorporated into the CeO₂–PrO₂ system to tune the color properties of the pigments by shifting the optical absorption edge. Si⁴⁺ substitution blue shifts the absorption edge of Pr-doped ceria and shows bright reddish brown color. Mn⁴⁺ substitution stabilizes the absorption edge and exhibits dark brown hue. The coloring mechanism is based on the shift of charge transfer band of CeO₂ to higher wavelength by co-substitution of Pr⁴⁺ and tetravalent metal ions in ceria. Si co-doped pigments possess smaller particles and hence exhibit more lightness compared to Mn co-doped samples. The reddish brown pigments exhibit very good coloring performance in polymer matrix. These Ce_0.95Pr_0.05?xM_xO₂ (M = Mn, Si) pigments have potential to be used as ecological red pigments for coloration of plastics.     

Sensitization of Eu3+ luminescence with titanium(IV) oxide in the composition of nanoparticles in porous glasses

A series of modified porous glasses with a fixed europium content Q(Eu³⁺) = 30 μmol/g and a variable titanium oxide content Q(TiO₂) = 15–375 μmol/g are synthesized. The luminescence properties of the prepared glasses are investigated as a function of the component ratio in the composition of oxide nanoparticles. The specific features of the luminescence quenching in a wet medium are analyzed. It is shown that titanium(IV) oxide substantially sensitizes the photoluminescence of Eu³⁺ ions and shields them against the water adsorption.     

Production of brown pigments for porcelain insulator applications

In this study, production of brown pigment for the ceramic insulator applications by using inexpensive natural raw materials or waste materials was undertaken. Different pigment compositions were designed, synthesised and examined. As a source of chromium, chromite, Cr₂O₃ and ferrochrome were used. Limonite, grinding waste, flotation waste and iron oxide scale were used as an iron source whereas manganese oxide and ferromanganese were used as a manganese source. The colour of glazed insulator bodies change from dark brown to light brown depending on the pigment composition. The pigments prepared with ferrochrome, manganese oxide, flotation waste (C6) or iron oxide scale (D4) and calcined at 1300 °C have a darker brown colour and possess suitable L*a*b* values as 30.1, 2.7, 1.6 for C6 and 30.9, 2.1, 0.3 for D4, which are closer to the L*a*b* values (30.1, 2.9, 0.1) of commercial MnFeCr pigments. The results indicate that waste materials containing iron can be used to produce brown pigments to be used in the insulator application in ceramic industry and as a result of this waste material can be converted into a value-added product. Also, ferrochrome can be used successfully as chromium source and help to reduce the cost of the pigment.     

Chromatographic and colorimetric characterizations of brominated indigoid dyeings

The major indigoids constituting modern and archaeological purple pigments produced from molluskan species include, in varying compositions, indigo, 6-bromoindigo, and 6,6′-dibromoindigo. Though woolen Tyrian Purple dyeings produced from these pigments were the most prized and precious of all dyeings in antiquity, a full chromatographic and colorimetric analysis of multi-fibered textiles dyed with these indigoids has not been previously performed. This current study reports on high-performance liquid chromatographic (HPLC) analyses conducted on the indigoid pigments and on woolen dyeings individually produced from them. In addition, comparative colorimetric analyses via reflectance spectrophotometry were performed on standard multifiber fabric swatches, each consisting of 13 different synthetic and natural fibrous materials. Each swatch was dyed with one of the cited indigoids. These colorimetric properties included the Kubelka-Munk spectral curves, color strengths at the wavelengths of maximum absorptions, color coordinates of the CIE L*a*b* and L*C*h* color spaces, and the color differences. Excellent functional correlations were observed among these properties and these relationships should be applicable to similar dyeings on other fabric materials. The results show that filament triacetate and nylon-66 possess the most remarkable color strengths of all the fiber materials investigated in all the dyeings, and of the natural fibers studied, wool possessed the highest color strength and cotton the poorest with all three dyes. Such chromatographic and colorimetric analyses would further our understanding of the colors produced from ancient, and modern, purple-dyed textiles.     

钙硅比对生物质灰渣加气混凝土性能的影响

生物质灰渣含有较高的SiO2和CaO,与水泥、石灰等按一定的比例混掺,制备生物质灰渣加气混凝土砌块.实验通过改变生物质灰渣、粉煤灰和石灰的相对含量,调节加气混凝土砌块的钙硅比,并研究了钙硅比对其水化产物、机械力学性能和微观结构的影响.结果显示,随着钙硅比的增大,生物质灰渣加气混凝土砌块的干密度逐渐增大,钙硅比为0.86时,强度达到峰值,其抗压强度和抗折强度分别为2.5 MPa和1.8 MPa,且托勃莫来石的生成量也达到最大.干燥收缩图也表明钙硅比为0.86时,生物质灰渣加气混凝土砌块的体积性能最好,其最大干燥收缩率为0.44 mm/m,优于国家标准(0.5 mm/m).水化产物电镜图谱表明随着钙硅比的增加,生物质灰渣加气混凝土砌块的水化产物形貌由针棒状结构转变为片状结构.     

Utilization of secondary lead slag as construction material

Secondary lead slag, a waste product from battery smelting using CaCO₃ as flux, has been investigated for its use as an admixture and/or aggregate in the production of concrete blocks. The slag was added as partial replacements of cement and/or aggregate. The results revealed that the oxide components of the slag were similar to those of ordinary Portland cement (OPC). The CaO content in the slag is 6.2 times less than that in OPC, while its iron content, as FeO, is 15.1 times higher. Interestingly, it also possesses magnetic property. All samples exhibited higher compressive strengths than that of the sample without slag (STD) which increased with increasing the slag contents and ages. The highest compressive strength was of the sample containing 20% slag as cement substituent and 100% slag as aggregate replacement owing to 259% of that of the STD at 60 days. All samples showed higher water absorption than that of the STD. The higher the slag contents, the more the water absorption. The absorption was, as expected, decreased with ages. Magnetic property of the slag plays an important role in the properties of the concrete blocks. For environmental concern, leachability of lead (Pb) from all samples was also carried out.     

Characterization of selected pigments for exterior poly(vinyl chloride) applications

Pigments selected from the iron oxide, chromium oxide and furnace black families, which offer the possibility of preferred earthtone colors, were characterized for: their stability at PVC processing temperatures; their effect on long-term ultraviolet exposure, and their infrared absorption properties that relate to heat buildup and buckling in the composite. This study has basically ranked the pigments into three categories in terms of their overall performance. Besides the earthtone color, the added economics of these pigments makes them of prime interest for external applications.     

Weathering performance of rigid PVC pigmented with iron-containing pigments: The relationship between weathering and the chemical nature of the iron contained

Weathering performance of rigid PVC pigmented with iron oxide or some complex inorganic pigments (CIP) containing iron can be poor. Consideration of iron-containing CIP's for use in exterior PVC leads to the common question: “How much ‘free iron’ is present in the pigment?” It has been unclear what “free iron” means and therefore difficult to know which iron-containing pigments will weather well and which will not. Some formulators may avoid iron-containing pigments altogether by electing not to formulate in a color space only achievable with those pigments. We compare the weathering performance of a series of iron-containing CIP's to the amount of iron contained, the crystal phases, and the amount of acid-extractable iron. We see a strong correlation between the weathering performance and the extractable iron content. Many iron-containing pigments have good weathering performance in PVC, so one shouldn't exclude iron-containing pigments from consideration based solely on the iron content. The acid-extractable iron is an indicator of the expected weathering performance. Careful evaluation and selection of pigments may allow consideration of previously avoided pigment combinations.     

The interaction of water-soluble iron porphyrins with DNA films and the electrocatalytic properties for inorganic and organic nitro compounds

The electrochemistry of water-soluble iron porphyrins (Fe(n-TMPyP)) (where n=2 and 4) was studied as an electrochemically active film on DNA modified glassy carbon, gold, platinum, and transparent semiconductor tin oxide electrodes in solutions of various pH values. The two layers of the modified electrode containing the iron porphyrin and the DNA film were prepared by depositing the iron porphyrin on a DNA film modified electrode. The Fe(4-TMPyP)/DNA film was electrocatalytic reductive for p-nitrobenzoic acid in a weak acidic, or neutral aqueous solution through an Fe^II species, and the electrocatalytic reduction peak potential became more negative than the cathodic peak of the Fe^III/II redox couple. The electrocatalytic reduction properties by the Fe(2-TMPyP)/DNA film as catalysts for nitrite reduction have also been determined, and shown to be active through an Fe^I species and to be pH-dependent. The electrocatalytic oxidation properties of nitrite by Fe(n-TMPyP)/DNA (for n=2 and 4) film have also been determined and shown to be active through an Fe^IV species with the electrocatalytic oxidation efficiency of NO₂⁻ with Fe^IV(O)(n-TMPyP) being higher than with (HO)Fe^IV(O)(n-TMPyP). The electrocatalytic oxidation efficiency of NO₂⁻ by iron porphyrin is pH-dependent. The electrocatalytic reduction of p-nitrophenol by Fe(2-TMPyP)/DNA film are also discussed.