A simple chemical method for deposition of electrochromic potassium manganese oxide hydrate thin films

A new chemical method for fast deposition of electrochromically active thin films of birnessite-type potassium manganese oxide (K_0.27MnO₂·xH₂O) has been developed. The chemical deposition has been performed at room temperature by a reaction of aqueous solutions of potassium permanganate and manganese(II) chloride. The prepared thin films have thickness from 50 to 250 nm depending on the number of the deposition cycles. The composition and the structure of the K-birnessite films are studied by XRD, IR spectroscopy and TG/DTA analyses. Electrochemical studies using four different electrolytes such as aqueous K₂SO₄, Li₂SO₄, KNO₃, and LiClO₄ in PC have been performed. The electrochromic activity has been explored by cyclic voltammetry and VIS spectrometry. The best electrochromic properties are obtained using aqueous KNO₃, where the difference in the transmittance at 400 nm between the bleached and colored state is 40% for both as-deposited and annealed films. The obtained data allow the prepared K-birnessite thin films in aqueous KNO₃ electrolyte to be proposed as a promising system for electrochromic applications.     

Chemical bath deposition and characterization of electrochromic thin films of sodium vanadium bronzes

Thin yellow-orange films of sodium vanadium oxide bronzes have been prepared from a sodium–vanadium solution (1:1) at 75 °C and pH = 3. The composition, structure and morphology of the films have been studied by XRD, IR spectroscopy, TG and SEM–EDX analyses. It has been established that the prepared films are a phase mixture of hydrated NaV₆O₁₅ (predominant component) and Na_1.1V₃O_7.9 with total water content of 10.58%.The sodium vanadium bronze thin films exhibit two-step electrochromism followed by color change from yellow-orange to green, and then from green to blue. The cyclic voltammetry measurements on the as-deposited and annealed vanadium bronze films reveal the existence of different oxidation/reduction vanadium sites which make these films suitable for electrochromic devices. The annealing of the films at 400 °C changes the composition, optical and electrochemical properties     

Experimental study of the copper thiosulfate system with respect to thin-film deposition

An experimental study of the copper-thiosulfate system in mild acidic (pH 5) aqueous solutions, with respect to thin-film formation, was undertaken. Thin films of Cu_xS (1 x 2) were deposited by a simple electroless technique on glass or transparent polyester films, at 50 °C. Thin films were deposited from chemical baths in which the ratios of copper to thiosulfate were varied from 1:1 to 1:10. Thin films of different compositions (Cu₂S, Cu_1.8S, Cu_1.4S and CuS) were prepared and then characterized for morphological, optical and electrical properties. The deposited films chemically close to Cu₂S were found to be amorphous, while the CuS films were a mixture of both amorphous and polycrystalline phases. The optical spectra of the Cu₂S films exhibited high transmission both in the visible region of the spectrum (beyond 600 nm) and throughout the near-infrared region (800 to 2500 nm), while CuS films were found to be highly absorptive throughout the near-infrared region, with peaked transmission in the visible region at about 560 nm. The sheet resistances of the films, determined by the standard four-probe measurements, were between 100 and 650 Ω/square.     

A simple chemical method for preparation of hydroxyapatite coatings on Ti6Al4V substrate

A novel, simple and economical chemical bath method for deposition of calcium hydroxyapatite coating has been developed. The coatings were prepared from EDTA solutions in alkaline media on Ti6Al4V substrates. The method is based on thermal dissociation of the Ca(EDTA)^2- complex at 65–95 °C. Two chemical baths with and without presence of Na⁺ and Cl^- were used for the deposition. The Rutherford back scattering study shows that the coating material from bath which contained sodium and chlorine ions have their presence in the coated material. The bath which has been prepared with potassium substituting sodium and nitrate substituting chlorine produced coatings with better stoichiometry, with Ca/P=1,67. The X-ray analysis revealed that the calcium hydroxyapatite coatings have preferred crystal orientation in the 002 direction. © 2001 Kluwer Academic Publishers     

Chemical solution method for fabrication of nanocrystalline iron(III) oxide thin films

A chemical solution technique for preparation of nanocrystalline iron(III) oxide thin films is developed. The deposition process is essentially based on the thermal decomposition of urea. The as-deposited and post-deposition heat-treated materials were characterized by X-ray analysis and Fourier transform infrared (FTIR) spectroscopy. Basic optical and electrical investigations were also performed. X-ray analysis confirmed that post-deposition heat-treated material is nontextured -iron(III) oxide, with an average crystal size of 22 nm. The optical investigations show that the absorption of films (as-deposited and post-deposition treated) gradually decreases with an increase of the wavelength in the 390–820 nm region. The optical band gap for the as-deposited and post-deposition heat-treated films was determined to be 3.2 eV and 2.0 eV, respectively. The obtained -Fe₂O₃ thin films exhibit a rather high resistivity at room temperature. However, our preliminary qualitative investigations have shown that the room temperature resistivity of -Fe₂O₃ thin films is highly sensitive to moisture, indicating their potential applicability in moisture sensing systems.