The growth of titanium dioxide nanotubes (TiO2) via anodization process depends on the controlling parameters such as applied potential, anodization time, and electrolyte composition. In the present work, the Taguchi method was applied to evaluate statistically the influence of the anodization parameters on the morphology of anodized TiO2 films. Mixture of ethylene-glycol and glycerol was used as an electrolyte and the settings of the experimental design were parameterized on the basis of four important anodization factors consisting of chemical pretreatment, amount of fluoride, water content and applied potential. Samples were characterized by XRD and FEG-SEM. Based on 4 variables at 3 different settings, full factorial plan requires 34 = 81 tests. In this work the experiment was designed on the basis of an L9 (34) orthogonal array (4 variables, 3 levels, 9 tests). The optimum conditions were found on the basis of smaller-is-better and larger-is-better analyses. The signal-to-noise ratio was employed to find optimal process parameters levels and to analyze the influence of these parameters on the tubular length, internal and external diameters and formation of nanograss on the film surface. Hence, it is clearly shown that the performance of TiO2 nanotubes can be evaluated by the Taguchi method.

The evolution of TiO2 nanotubular morphology, synthesized in a mixture of fluorinated ethylene glycol and glycerol electrolyte, was studied as a function of the anodization time. The samples were characterized by FEG-SEM, XRD, XPS, UV-Vis and EIS. The formation of single-or double-walled TiO2 nanotube structure can be efficiently controlled by the anodization time. For anodization times less than 30 minutes, a compact oxide layer is formed, followed by double-walled nanotube formation up to 120 minutes and single-walled nanotubes up to 240 minutes. XPS analyses show that the samples obtained with short anodization time have a high carbon content and oxygenated surface species compared to the longer-time anodized sample; however, binding energy peaks for Ti 2p remained invariant. The performances of TiO2 nanotubular photoelectrodes were evaluated in photoelectrochemical water splitting where TiO2 nanotubes anodized for 120 minutes presented the best performance that was related to their optimal morphology and charge transportation.

<title>Abstract</title><p>Large buildings situated in hot regions of the Globe need to be agreeable to their residents. Air conditioning is extensively used to make these buildings comfortable, with consequent energy consumption. Absorption of solar visible and infrared radiations are responsible for heating objects on the surface of the Earth, including houses and buildings. To avoid excessive energy consumption, it is possible to use coatings formulated with special pigments that are able to reflect the radiation in the near- infrared, NIR, spectrum. To evaluate this phenomenon an experimental study about the reflectivity of paints containing infrared-reflective pigments has been made. By irradiating with an IR source and by measuring the surface temperatures of the samples we evaluated: color according to ASTM D 2244-14, UV/VIS/NIR reflectance according to ASTM E 903-12 and thermal performance. Additionally, the spectral reflectance and the IR emittance were measured and the solar reflectance of the samples were calculated. The results showed that plates coated with paints containing IR-reflecting pigments displayed lower air temperature on the opposite side as compared to conventional coatings, indicating that they can be effective to reflect NIR and decrease the temperature of buildings when used in roofs and walls.</p>