Colour assays: An inside look into Alentejo traditional limewash paintings and coloured lime mortars

A series of colour assays were conducted taking into account old bibliographic recommendations and oral testimony regarding traditional lime painting technology from the Alentejo (South Portugal) region. The main objectives were: (a) the colorimetric analysis of paintings made with different limewash preparation methods; (b) the comparison between natural processed red and yellows ochre pigments (“home made” and from industrial origin) and synthetic iron oxides in different concentrations and lime proportions; (c) the evaluation of the colorimetric CIELAB coordinates during the lime carbonation process in coloured mortars and limewashes. The results shows that the evolution of L*, a*, and b* during the carbonation process is independent of pigment concentration and paint thickness but dependent of pigment composition and finishing technique (lime painting or coloured mortar). They also emphasize the importance of surface appearance attributes and its influence on the colorimetric parameters. © 2010 Wiley Periodicals, Inc. Col Res Appl, 36, 61–71, 2011     

Combined cathodoluminescence and X-ray analysis of paint pigments

The suitability of cathodoluminescence (CL) measurements for differentiating between different paint pigments is demonstrated with an example of a combined energy-dispersive X-ray (EDX) and CL analysis of different zinc oxide (ZnO) pigments in a paint fragment where the EDX spectra are virtually identical, but where the CL spectra show significant differences. Consequently, it is possible to distinguish different pigments on the basis of CL spectra and monochromatic CL micrographs.     

云母钛珠光颜料的正电子寿命谱研究

用正电子湮没技术测量了云母钛珠光颜料的正电子寿命和强度与煅烧温度，包覆量等的关系，并与Ｘ射线衍射，透射电镜等方法进行了比较。     

水介质中制备铝粉颜料的研究

以蒸馏水替代有机溶剂制备环保型铝粉颜料,通过优化组合获取一种优良的复合缓蚀剂,以抑制铝粉在球磨过程中与水发生反应;通过优化转速、球料比及球磨时间等工艺参数,获得制备铝粉颜料的最佳条件:转速为300r/min,球料比为25∶1,球磨时间为6h.     

Dislocation engineered silicon light emitting devices

The influence of boron-induced dislocation loops on the luminescence efficiency of silicon-based light-emitting diodes is investigated. Luminescence measurements and transmission-electron-microscopy images from devices fabricated by boron implantation into crystalline silicon, and subsequently processed under different conditions to form dislocation loops of different size and densities, were compared. Light emitting devices were also fabricated in an otherwise identical but a pre-amorphized substrate, to prevent boron-induced loop formation. The results demonstrate a strong correlation between the dislocation loop density and areal coverage, and the light emission efficiency. The devices produced in the pre-amorphized substrate, without dislocation loops, show strongly quenched light emission.     

Combined use of chitosan and alginate in the treatment of wastewater

This study examined the combined use of chitosan and sodium alginate in the treatment of wastewater containing heavy‐metal ions and dye. Wastewater samples were divided into two equal parts before chitosan and sodium alginate solutions were added to each part. When these two solutions were mixed together, the heavy‐metal ions and dye molecules were separated from the water as the positively charged chitosan and the negatively charged sodium alginate precipitated each other. The effects of the concentration and ratio of chitosan and sodium alginate, the treatment temperature, and the time on the efficiency of metal‐ion and dye removal were investigated. The results showed that when used in combination, sodium alginate and chitosan were effective in removing copper, cadmium, lead, and silver ions as well as acid dye molecules © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3581–3587, 2007     

Effect of acetaldehyde and several acids on the formation of vitisin A in model wine anthocyanin and colour evolution

Summary It was found that the reaction between malvidin 3-glucoside and added pyruvic acid (PA), leading to the formation of vitisin A in model wine solutions, was not prevented by the addition of either acetaldehyde (A) or several organic acids. The acylated forms of vitisin A (3-acetylvitisin A and 3- p -coumarylvitisin A) were formed through the interaction of malvidin 3-acetylglucoside and malvidin 3- p -coumarylglucoside. Disappearance of the three main anthocyanins (malvidin 3-glucoside, malvidin 3-acetylglucoside and malvidin 3- p- coumarylglucoside) from the model wine with time followed first order kinetics. Acetaldehyde had the effect of increasing the total amount of these losses but producing smaller amounts of vitisin A. During ageing model solutions developed some browness. The brownest solution was obtained without A and a reduced rate of browning was found in the presence of A. This latter result can be explained by the assumption of a superimposition of a blueing effect upon reactions of A with anthocyanins. In the presence of PA the formation of vitisin A compounds gave an intermediate colour, contributing a reddish hue to the solution. A good correlation (r²= 0.96) between the percentage of vitisin A, of the total anthocyanins and the hue angle was observed. The addition of large amounts of organic acids that are normally found in wine into the model solutions did not lead to the formation of new anthocyanins. The linear loss of PA in all model systems indicates that a first order reaction occurs and 35.35 times more PA than total anthocyanin was lost to form the new compounds.     

Xanthylium salts formation involved in wine colour changes

Summary The reaction of (+)-catechin in wine-like model solution was investigated. First appearance of colourless dimeric compounds consisting of two flavanol units linked by carboxy-methine bridge was observed. Their isolation and further incubation was found to yield two types of yellowish pigments showing visible absorption maxima at 440 and 460 nm, respectively. Mass spectroscopy (MS) spectral analysis showed that the first type were xanthylium salt pigments formed by dehydration of the colourless compounds followed by an oxidation process. The loss of a water molecule was shown to take place between two A ring hydroxyl groups of the colourless dimers. The second type were shown to be ester derivatives of the first ones. Thus ethylester of xanthylium salt was obtained and fully characterized by mass and nuclear magnetic resonance (NMR) spectroscopy. Esterification was found to involve the colourless compound before dehydration and thus a general scheme for xanthylium salt formation was postulated. The proposed scheme constitutes a new xanthylium formation pathway as up to now only anthocyanin-flavanol reactions were supposed to form xanthylium salt derivatives during wine ageing. This work also provides new support to the contribution of xanthylium salt in colour evolution observed during wine ageing which is generally expressed in an increase of absorption in the 400–500 nm, region of xanthylium salt absorption maxima.     

Modern mass spectrometry for coatings

For the analysis of polymers soft ionization mass spectrometry, in which only molecular ions are observed, can provide the complete distribution of chains (length, composition, end-groups) in under ten minutes on microgram quantities of material. Moreover, molecular ion information of neat organic pigments or those present in crosslinked networks can also be furnished. No other analytical technique can supply these data in such a short time. The application of mass spectrometry to the characterization of materials used in today's high performance automotive coatings is presented. These include functional monomers, several acrylic copolymers, organic pigments and an epoxide prepolymer. While there are a variety of mass spectrometric techniques, in this paper we will highlight the techniques that we have found useful for the characterization of organic coating components. The selection of the mass spectrometric technique is dictated by the molecular weight of the material and to a lesser extent the chemical composition. We used potassium ionization of desorbed species (K⁺IDS) performed on a quadrupole mass spectrometer for materials under 1000 Daltons (Da). However, many of the ingredients used in current automotive finishes fall between 1000 and 10 000 Da. For these materials we used a Fourier transform mass spectrometer (FTMS) which is well suited for this mass range and boasts the highest resolution and mass accuracy available. Direct desorption/ionization using a carbon dioxide laser is our standard method of sample introduction. Recently, we coupled a gel permeation chromatograph to our FTMS using an electrospray ionization interface. This hyphenated technique offers one of the most powerful characterization methods for the coatings chemist.     

Synthesis of poly(styrene-co-maleimide) and poly(octadecene-co-maleimide) nanoparticles and their utilization in paper coating

Aqueous polymer dispersions comprising of poly(styrene-co-maleimide) (SMI) or poly(octadecene-co-maleimide) (OMI) nanoparticles were synthesized by thermal imidization of the corresponding maleic anhydride copolymer precursors with ammonia using an organic solvent free process. Different reaction parameters such as temperature, time, agitation speed and stirrer geometry, and molar ratio of ammonia-to-anhydride were investigated in order to find optimal conditions. The obtained copolymer nanoparticles exhibited glass transition temperatures (T_g's) between 140 and 170 °C with particle sizes ranging from 50 to 230 nm. The compositional analysis was conducted by recording ¹H NMR and ATR-FTIR spectra. In addition, SMI dispersions were successfully spray dried and analyzed by SEM. Finally, the polymer dispersion's utility as auxiliary organic pigment in paper coating formulations was evaluated.