Additive manufacturing of alumina parts by indirect selective laser sintering and post processing

Innovative powder preparation and post-processing techniques can be employed to obtain high density ceramic parts by means of indirect selective laser sintering. Thermally induced phase separation (TIPS) was used to produce polymer and polymer–ceramic composite particles. The effect of polymer concentration, cooling rate, stirring and alumina particles on polymer and polymer–ceramic composite particles was investigated. Homogeneous spherical alumina–polypropylene (PP) composite powder was synthesized by TIPS for selective laser sintering (SLS). Green Al₂O₃–PP component parts with a density of 34% could be produced by conventional SLS of the polymer under optimized laser power, scan speed, scan spacing and powder preheating temperature. Various post-processing techniques like pressure infiltration (PI), warm isostatic pressing (WIPing) or a combination of both were applied to increase the green density of the Al₂O₃–PP SLM parts. Infiltrating the open porosity green SLS parts with a 30 vol% alumina-powder based ethanol suspension allowed to increase the sintered density, i.e. after polymer debinding and pressureless sintering in air at 1600 °C, from 38 to 64% of the theoretical density (TD). WIPing of the SLS and SLS/infiltrated green parts at 135 °C and 64 MPa allowed raising the green density up to 93 and 83% TD and a sintered density up to 89 and 88% TD, respectively.     

Self-assembled polyaniline nanotubes and nanoribbons/titanium dioxide nanocomposites

Self-assembled polyaniline (PANI) nanotubes, accompanied with nanoribbons, were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous medium, in the presence of colloidal titanium dioxide (TiO₂) nanoparticles of 4.5 nm size, without added acid. The morphology, structure, and physicochemical properties of the PANI/TiO₂ nanocomposites, prepared at various initial aniline/TiO₂ mole ratios, were studied by scanning (SEM) and transmission (TEM) electron microscopies, FTIR, Raman and inductively coupled plasma optical emission (ICP-OES) spectroscopies, elemental analysis, X-ray powder diffraction (XRPD), conductivity measurements, and thermogravimetric analysis (TGA). The electrical conductivity of PANI/TiO₂ nanocomposites increases in the range 3.8 × 10^?4 to 1.1 × 10^?3 S cm^?1 by increasing aniline/TiO₂ mole ratio from 1 to 10. The morphology of PANI/TiO₂ nanocomposites significantly depends on the initial aniline/TiO₂ mole ratio. In the morphology of the nanocomposite synthesized using aniline/TiO₂ mole ratio 10, nanotubes accompanied with nanosheets prevail. The nanocomposite synthesized at aniline/TiO₂ mole ratio 5 consists of the network of nanotubes (an outer diameter 30–40 nm, an inner diameter 4–7 nm) and nanorods (diameter 50–90 nm), accompanied with nanoribbons (a thickness, width, and length in the range of 50–70 nm, 160–350 nm, and ～1–3 μm, respectively). The PANI/TiO₂ nanocomposite synthesized at aniline/TiO₂ mole ratio 2 contains polyhedral submicrometre particles accompanied with nanotubes, while the nanocomposite prepared at aniline/TiO₂ mole ratio 1 consists of agglomerated nanofibers, submicrometre and nanoparticles. The presence of emeraldine salt form of PANI, linear and branched PANI chains, and phenazine units in PANI/TiO₂ nanocomposites was proved by FTIR and Raman spectroscopies. The improved thermal stability of PANI matrix in all PANI/TiO₂ nanocomposites was observed.     

Conducting polymer embedded with nanoferrite and titanium dioxide nanoparticles for microwave absorption

The present paper deals with the synthesis of conducting ferrimagnetic polyaniline nanocomposite embedded with γ-Fe₂O₃ (9–12 nm) and titanium dioxide (70–90 nm) nanoparticles via a micro-emulsion polymerization. The microwave absorption properties of nanocomposite in 12.4–18 GHz (Ku-band) frequency range shows shielding effectiveness due to absorption (SE_A) value of ?45 dB, which is much higher than polyaniline composite with iron oxide and polyaniline–TiO₂ composites. The higher EMI shielding is mainly arising due to combined effect of γ-Fe₂O₃ and TiO₂ that leads to more dielectric and magnetic losses which consequently contributed to higher values of shielding effectiveness. XRD analysis of the nanocomposite reveals the incorporation of nanoparticles in the conducting polymer matrix while the thermal gravimetric analysis (TGA) demonstrates that the nanocomposite is stable up to 250 °C.     

Two-step hot pressing of bimodal micron/nano-ZrB2 ceramic with improved mechanical properties and thermal shock resistance

The densification and grain growth behaviors for micron- and nano-sized ZrB₂ particles were investigated. The densification on-set temperature (T_d-micron) and grain growth on-set temperature (T_g-micron) for micron-sized ZrB₂ particles were about 1500 °C and 1800 °C, respectively. And the densification on-set temperature (T_d-nano) and grain growth on-set temperature (T_g-nano) for nano-sized ZrB₂ particles were about 1300 °C and 1500 °C, respectively. A bimodal micron/nano-ZrB₂ ceramic was therefore prepared using a novel two-step hot pressing. A high relative density of 99.2%, an improved flexural strength of 580.2 ± 35.8 MPa and an improved fracture toughness of 7.2 ± 0.4 MPa·m^1/2 were obtained. The measured critical thermal shock temperature difference (ΔT_c) for this bimodal micron/nano-ZrB₂ ceramic was as high as 433 °C.     

Unusual spectroscopic properties of PPE/TiO2 composite and its sensor response to TNT

A composite from a broad bandgap polymer, poly(phenylene ethylene) (PPE), and nano-sized TiO₂ particles was found to be able to sense 2,4,6-trinitrotoluene (TNT) for TNT sensor. Fluorescence quenching induced by charge transfer from PPE to nano-sized TiO₂ was observed in toluene solution. At high TiO₂ composition, a strong exciplex band occurred at 550 nm. Under prolonged light irradiation at 400 nm, unusual fluorescence gains took place at 460 nm, companied with a very small change in the UV–vis absorbance. After 30 min light irradiation, the fluorescence at 460 nm reached a maximum, but the peak at 550 nm disappeared. This composite showed amplified sensor response to TNT compared to the pristine PPE film, which can be potentially used as sensing material for detecting TNT based explosives.     

Titanium-supported Ce-, Zr-containing oxide coatings modified by platinum or nickel and copper oxides and their catalytic activity in CO oxidation

A combination of plasma electrolytic oxidation (PEO) and impregnation techniques followed by annealing in air has been used to obtain composites Pt/nZrO₂ + pTiO₂/Ti, Pt/nZrO₂ + pTiO₂ + zCeO_x/Ti, NiO + CuO/nZrO₂ + pTiO₂/Ti, NiO + CuO/nZrO₂ + pTiO₂ + zCeO_x/Ti with different zirconium and titanium contents and ZrO₂/TiO₂ phase ratio. The composites have been investigated by means of XRD, XPS and SEM/XSA methods. According to the XPS data, the platinum content on the coating surface is ~ 0.4 at.%, whereas the XSA measurements have shown that the nickel and copper contents in coatings attain 16 and 8 at.%, respectively, depending on the initial oxide coatings composition. Nickel and copper oxides form either extended islets or solid layers (“crusts”) on the coating surface. Both the composites promoted with platinum and those with the “crust” built from nickel and copper oxides are active in CO oxidation at the temperatures above 200 °C and 300 °C, respectively.     

Semiconductor TiO2–Ga2O3 thin film gas sensors derived from particulate sol–gel route

Nanostructured and mesoporous TiO₂–Ga₂O₃ thin films with various Ti:Ga atomic ratios were prepared by a new straightforward particulate sol–gel route. Titanium isopropoxide and gallium (III) nitrate hydrate were used as precursors, and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the specific surface area (SSA). XRD and TEM analysis of the powders revealed that the Ga₂O₃ formed from the nitrate precursor retarded anatase-to-rutile transformation, crystallization and crystal growth. The average crystallite size of pure TiO₂ powder annealed at 600–1000 °C were in the range 4–10 nm; the values that could be decreased to 2–6 nm for TiO₂–Ga₂O₃ powders. Furthermore, one of the highest SSA was obtained by introducing Ga₂O₃ into TiO₂, being 305 m² g⁻¹ for TG11 (Ti:Ga = 50:50 atomic ratio) binary oxide annealed at 600 °C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of CO and NO₂ gases at low operating temperature of 200 °C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. TG11 sensor showed the highest response towards all CO and NO₂ concentrations operated at 200 °C. The response magnitude of 13.7 and 4.3 with response times of 30 s and 108 s were achieved for TG11 sensor towards 400 ppm CO and 10 ppm NO₂, respectively. Furthermore, calibration curves revealed that TiO₂–Ga₂O₃ sensors follow the power law (S = A[gas]^B) (where S is sensor response, coefficients A and B are constants and [gas] is gas concentration) for the two types of gases, and they have excellent capability for the detection of low gas concentrations (25 ppm CO and 0.5 ppm NO₂). The maximum response of TiO₂–Ga₂O₃ sensors towards CO and NO₂ was measured at 450 and 400 °C, respectively. The sensor response decreased with increasing film annealing temperature owing to sintering of the particles. The response magnitude and response time of the sensors obtained in this work is superior to TiO₂-based sensors reported in previous studies.     

Microstructural evolution during high-temperature oxidation of Ti2AlC ceramics

Microstructural development during high-temperature oxidation of Ti₂AlC below 1300 °C involves gradual formation of an outer discontinuous TiO₂ layer and an inner dense and continuous α-Al₂O₃ layer. After heating at 1400 °C, an outer layer of mixed TiO₂ and Al₂TiO₅ phases and a cracked α-Al₂O₃ inner layer were formed. After heating to 1200 °C and cooling to room temperature, two types of planar defect were identified in surface TiO₂ grains: twins with (2 0 0) twin planes, and stacking faults bounded by partial dislocations. Formation of planar defects released the thermal stresses that had generated in TiO₂ grains due to thermal expansion mismatch of the phases (TiO₂, α-Al₂O₃ and Al₂TiO₅) in the oxide scale. After heating to 1400 °C and cooling to room temperature, crack propagation in TiO₂ grains resulted from the thermal expansion mismatch of the phases in the oxide scale, the high anisotropy of thermal expansion in Al₂TiO₅ and the volume changes associated with the reactions during Ti₂AlC oxidation. An atomistic oxidation mechanism is proposed, in which the growth of oxide scale is caused by inward diffusion of O^2? and outward diffusion of Al³⁺ and Ti⁴⁺. The weakly bound Al leaves the Al atom plane in the layered structure of Ti₂AlC, and diffuses outward to form a protective inner α-Al₂O₃ layer between 1100 and 1300 °C. However, the α-Al₂O₃ layer becomes cracked at 1400 °C, providing channels for rapid ingress of oxygen to the body, leading to severe oxidation.     

Characterization and dielectric behavior of V2O5-doped 0.9Mg0.95Co0.05TiO3–0.1Ca0.6La0.8/3TiO3 ceramic system at microwave frequency

The microwave dielectric properties and the microstructures of Mg_0.95Co_0.05TiO₃–Ca_0.6La_0.8/3TiO₃ ceramics, prepared by a mixed oxide route, have been investigated. With small amount of V₂O₅ additions, the sintering temperatures of 0.9Mg_0.95Co_0.05TiO₃–0.1Ca_0.6La_0.8/3TiO₃ ceramics can be lowered to 1250 °C. The microwave dielectric properties are found strongly correlated with the sintering temperature as well as the amount of V₂O₅ additions. The Q × f value of 0.9Mg_0.95Co_0.05TiO₃–0.1Ca_0.6La_0.8/3TiO₃ increased with increasing temperature to 1250 °C and decreased thereafter. The decrease in Q × f value was coincident with the abnormal grain growth. A maximum Q × f value of 58,000 (GHz) associated with a dielectric constant (?_r) of 21.7 and a temperature coefficient (τ_f) of ?10 ppm/°C, was achieved for 0.25 wt.% V₂O₅-doped samples at 1250 °C. Moreover, a cross-coupled compact hairpin filter with designed center frequency of 2.0 GHz is designed and fabricated using the proposed dielectric ceramic to study its performance. It also showed a substantial reduction in both insertion loss and size in comparison with other dielectrics FR4 and alumina.     

Microstructure and stress rupture property of titanium-containing 11Cr ferritic/martensitic steels

The microstructure and stress rupture behavior of 11Cr ferritic/martensitic steels with 0.02 wt.%Ti (low Ti) and 0.14 wt.%Ti (high Ti) have been studied. The steels are prepared by vacuum induction melting followed by hot forging and rolling into plates. The results show that titanium is easy to combine with oxygen and other elements to form complex inclusions. Large MX particles with 1–3 μm are found in the high titanium steel. Most of the large MX particles have a TiO₂ cored structure. After normalizing at 1100 °C for 1 h, cooled in air and tempering at 750 °C for 1 h, nano-sized MX precipitates distribute densely near martenstic lath boundaries in the high titanium steel. The large MX particles cannot be dissolved even at austenitizing temperature up to 1300 °C. Creep cracks nucleate at the interface between matrixes and the large MX particles or titanium-containing oxide inclusions.     

Sintering behavior and mechanical properties of spark plasma sintered β–SiAlON/TiN nanocomposites

In this study, fully dense β-SiAlON/TiN composites were produced by Spark Plasma Sintering (SPS) method. Si₃N₄, Al₂O₃, AlN and TiO₂ powders were used as precursors. Starting powders were mixed with high energy ball milling and then were sintered by SPS method (at 1750 °C under pressure of 30 MPa for 12 min.). The milled powders had an average particle size of below ~ 155 nm. The XRD patterns of SPS-ed composites showed that the entire β-SiAlON phase constituent was in the form of Si₄Al₂O₂N₆ phase and cubic TiN phase can be formed by the phase transformation of TiO2 in relation with other precursors. FESEM micrographs confirmed that TiN particles were distributed homogeneously throughout β-SiAlON matrix. Mechanical properties evaluation revealed that by adding micro sized TiO₂, optimal mechanical properties with a hardness ~ 14.6 GPa and a fracture toughness ~ 6.3 MPa m^1/2 were obtained. The improvement in the fracture toughness was attributed to the presence of the crack deflection as the dominant toughening mechanism in the SPS-ed β–SiAlON/TiN composites.     

A facile synthesis of TiB2 nano-particles via mechano-thermal route

A mixture of TiO₂, B₂O₃ and Si powders was milled up to 50 h using a high energy planetary ball mill. The milling products were heat treated at 850, 1200 and 1300 °C. Effects of Si content and addition of catalyst on the phase evolutions and morphology of the products were investigated. XRD results showed that phase composition of the 50 h milled sample after heat treatment at 1300 °C consists of nano-crystalline TiB₂ with mean crystallite size of 50 nm together with some Ti₂O₃, Si and SiO₂ phases. Addition of 2 mol of NaCl in the same sample facilitates the process and resulted in the single phase TiB₂with a mean crystallite size of 30 nm. SEM and TEM micrographs exhibited the nano-sized particles of TiB₂.     

x(Mg0.7Zn0.3)0.95Co0.05TiO3-(1−x)(La0.5Na0.5)TiO3 ceramic at microwave frequency with a near zero temperature coefficient of resonant frequency

Dielectric properties of x(Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃-(1?x)(La_0.5Na_0.5)TiO₃ ceramic were investigated at microwave frequencies. A nearly 0 ppm/°C temperature coefficient of resonant frequency was realized at x = 0.9. A two-phase system was confirmed by XRD analysis. A dielectric material applicable to microwave devices with a Q × f of 20,000–87,000 GHz and a dielectric constant of 21.27–26.2 was obtained at 1100 °C after 4 h of sintering. The microwave dielectric material 0.9(Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃-0.1(La_0.5Na_0.5)TiO₃ sintered at 1150 °C for 4 h has a dielectric constant of 24.56, a Q × f of 68,000 GHz, and a τ_f value of 0 ppm/°C. It is proposed as a candidate dielectric for GPS patch antennas.     

Effects of processing parameters on density and electric properties of electric ceramic compacted by low-voltage electromagnetic compaction

In this research, low-voltage electromagnetic compaction (EMC) was applied to compact TiO₂ and PZT powders in the indirect way. After selecting the appropriate processing parameters, TiO₂ and PZT ceramics of higher density and better electrical properties were produced compared with traditional static compaction. The microstructures of two ceramics produced by two above-mentioned methods respectively show that, the average grain size of TiO₂ and PZT compacted by low-voltage EMC are about 8 μm and 4 μm which are smaller than that by static compaction respectively (15 μm and 7 μm) under the same sintered condition. Discharge voltage and charge capacitance are important factors to the green density and sintered part's density of each ceramics. Meanwhile, TiO₂ and PZT have their own discharge voltage range (700–1100 V for TiO₂ and 600–1000 V for PZT), during which each ceramic powder could be pressed effectively. With the same condition of charge capacitance, as the discharge voltage increases toward a peak value, the green density and sintered part's density increase, then tend to decrease after that peak value. The green density and sintered part's density of each ceramic increase and the above peak discharge voltage decrease slightly, as charge capacitance enlarges in the range investigated. In addition, effects of pancake coil turns and field shaper structure on the ceramic density were investigated. In most of cases investigated, the higher the ceramic part's density, the better the dielectric constants of TiO₂ parts and the piezoelectric constants of PZT parts.     

Electrical properties of TiO2-filled polyimide nanocomposite films prepared via an in situ polymerization process

To fully understand the reliable electrical properties of the nanocomposite films, their physical and chemical behaviors as well as dielectric properties were analyzed. Polyimide/TiO₂ (PI/TiO₂) nanocomposite films were prepared using in situ dispersion polymerization process. Influences of frequency, temperature and the nano-TiO₂ particles loading concentration on dielectric permittivities of the PI/TiO₂ nanocomposite films were studied. The dielectric relaxation behavior of the PI/TiO₂ nanocomposite films has been investigated with dielectric relaxation spectrum. It was found that interfacial polarization, namely Maxwell–Wagner–Sillars, existed in the PI/TiO₂ nanocomposite films with different loading concentration of the nano-TiO₂ particles. Dielectric permittivities of the PI/TiO₂ nanocomposite films fluctuation with temperature (?50–150 °C) were attributed to the mobility and thermal expansion of the polymer matrix, for which the Cole–Davidson model, or modified Cole–Cole model, was brought to account.     

Colored nanoparticles dispersions as electronic inks for electrophoretic display

Phthalocyanine green (CuPcCl) nanoparticles was successfully prepared by anti-solvent recrystallization method and combined with in situ modification to improve the electrophoretic properties and dispersion ability in organic medium. The produced particles were characterized by SEM, FT-IR and ζ-potential test. It was found that the particles exhibited 120 nm with spherical shape and narrow size distribution when the modifier was mixture of CTAB and PVP. Sedimentation ratio of the prepared CuPcCl particles in tetrachloroethylene was nearly down to zero within 30 days and the ζ-potential was 26.8 mV. In addition, stable TiO₂/C₂Cl₄ dispersion was prepared by coated TiO₂ surface with trimethoxyoctylsilane. The sedimentation ratio of the modified TiO₂ was nearly 7.6% within 30 days, and the ζ-potential value was ?28.9 mV. The particle size was about 300 nm with spherical morphology. The results demonstrated that green CuPcCl and white TiO₂ dispersions were suitable as electronic ink and showed potential value in the application of electrophoretic display.     

Stability and dewetting kinetics of thin gold films on Ti,TiOx and ZnO adhesion layers

We present an in situ high-temperature confocal laser microscopy study on the thermal stability of 40 nm thick gold thin films grown on 40 nm Ti, TiO_x and ZnO adhesion layers on (0 0 1) Si. In situ observation of the dewetting process was performed over a wide range of set temperatures (400–800 °C) and ramp rates (10–50 °C min^?1) for each gold/adhesion layer combination. We found that significant dewetting and subsequent formation of gold islands occurs only at and above 700 °C for all adhesion layers. The dewetting is driven to equilibrium for gold/ZnO compared to gold/Ti and gold/TiO_x as confirmed by ex situ X-ray diffraction and scanning electron microscopy characterization. Quantification of the in situ data through stretched exponential kinetic models reveals an underlying apparent activation energy of the dewetting process. This energy barrier for dewetting is higher for gold/Ti and gold/TiO_x compared to gold/ZnO, thus confirming the ex situ observations. We rationalize that these apparent activation energies correspond to the underlying thermal stability of each gold/adhesion layer system.     

Microstructure,dielectric response and electrical properties of polypyrrole modified (poly N-vinyl carbazole–Fe3O4) nanocomposites

N-vinyl carbazole (NVC) was polymerized in the presence of nanodimensional Fe₃O₄ in solid state at ～65 °C and a nanocomposite of poly N-vinyl carbazole with Fe₃O₄ (PNVC–Fe₃O₄) was isolated. This composite was further modified by encapsulation with polypyrrole (PPY) via oxidative polymerization of pyrrole in an aqueous dispersion of the PNVC–Fe₃O₄ composite in the presence of potassium persulfate (KPS). The presence of PNVC and of PPY in the PPY–PNVC–Fe₃O₄ composite was confirmed by FTIR spectroscopic analyses. TGA and DTA analyses showed the overall thermal stability trend as: Fe₃O₄ > PNVC–Fe₃O₄ > PPY–(PNVC–Fe₃O₄) > PNVC. HRTEM images revealed that the PPY–(PNVC–Fe₃O₄) nanocomposites have an average grain size of ≈37 nm in good agreement with the values estimated from XRD data. SEM analysis indicated the preponderance of spherical particles embedded in the matrix. The dielectric constants of PNVC–Fe₃O₄ and the PPY–Fe₃O₄ systems were low (110–400) whereas the PPY encapsulated PNVC–Fe₃O₄ nanocomposites showed significantly higher values of dielectric constant (>1000), suggested that the interfaces between grain and grain boundary of the composite play a dominant role for enhancing dielectric properties of the system. Relaxation behaviors for the nanocomposite system were explained considering Maxwell–Wagner two-layered dielectric models. The ac conductivity was found to be independent on frequency in the range 10²–10³ Hz for all the nanocomposites implying contribution of free charges and rise thereafter appreciably in the frequency range of 1–25 kHz due to trapped charges in the grain boundary.     

Surface modification of NiTi/PZT heterostructure thin films using various protective layers for potential MEMS applications

The present study explored the in-situ deposition of hard and adherent nanocrystalline protective coatings on NiTi/PZT/TiO_x thin film heterostructure prepared by dc/rf magnetron sputtering. Protective layers (AlN, CrN and TiCrN) of approximate thickness (~ 200 nm) were used to improve the surface, mechanical and corrosion properties of NiTi/PZT/TiO_x heterostructure without sacrificing the shape memory effect and ferroelectricity of the NiTi and PZT layers, respectively. The influence of the protective layer on structural, electrical and mechanical properties of NiTi/PZT/TiO_x heterostructure was systematically investigated and the results were compared. Nanoindentation studies were performed at room temperature to determine the hardness and reduced modulus. The surface modified NiTi/PZT/TiO_x heterostructures were found to exhibit high hardness, high elastic modulus and thereby better wear resistance as compared to pure NiTi/PZT/TiO_x films. From the results of potentiodynamic polarization test conducted in 1 M NaCl solution, the CrTiN coated NiTi/PZT/TiO_x heterostructure showed the best corrosion resistance with the lowest corrosion current density (1.52 × 10^? 8 A cm^? 2) and the highest protective efficiency (96.8%). The results presented here prove the potential of a surface modified NiTi/PZT/TiO_x heterostructure to be used in various microelectromechanical (MEMS) applications.     

A study of thermal,optical and electrical properties of new branched triphenylamine-based polyazomethines

A series of branched aromatic polyazomethines have been obtained by high temperature solution polycondensation of 4,4′,4″-triformyltriphenylamine with 3,3′-dimethoxybenzidine with different feed molar ratio. For three polymers additional condensation of chain end groups with monofunctional monomers such as 4-formyltriphenylamine or 2-naphthylamine was carried out. Moreover, two model compounds were prepared and investigated for comparison with branched polymers. The structures of polymers and models were characterized by means FTIR, ¹H, ¹³C NMR spectroscopy, elemental analysis and gel permeation chromatography (GPC). UV–vis properties of the thin films of the polymers and compounds were investigated on the glass substrate. Eg of the branched polymers was found about 2.47 eV. UV–vis and FTIR spectroscopy for iodine doped compounds were investigated. Doping decreased the value of Eg of the branched polyazomethines to about 1.71 eV. Refractive index (n) for branched polyazomethines was found about 1.97, while for the doped compounds was a little higher (～2.48). Absorption (UV–vis) properties of the doped with iodine branched imines were investigated additionally after heating in different temperatures from 50 to 200 °C. Intensity of photoluminescence of branched imines in relation to 9,10-diphenylanthracene was found in the range 0.2–1.0% and 2.7–43.7% in dependence on the excitation wavelengths. Current–voltage (I–V) measurements were performed on ITO/TiO₂/polymer/Al, ITO/polymer/Alq₃/Al and ITO/TiO₂/polymer/Alq₃/Al devices in the dark and during irradiation with light (under illumination 1000 W/m²). The sol–gel technique was applied to prepared TiO₂ layer. TiO₂ layers and devices were investigated by Atomic Force Microscopy (AFM). Moreover, properties of these branched polymers were compared with the linear polyazomethine based on 3,3′-dimethoxybenzidine and 4,4′-diformyltriphenylamine.