Laser Ignition of Nano‐Composite Energetic Loose Powders

Laser ignition experiments were conducted to better understand parameters that influence ignition of energetic materials. A Nd:YAG laser (10 ms, 1.5 J, 3 mm spot diameter) was used to heat the top surface of an energetic powder composed of nanometric aluminum (Al) combined stoichiometrically with an oxidizer (copper oxide (CuO), iodine pentoxide (I₂O₅), polytetrafluoroethylene (C₂F₄), molybdenum trioxide (MoO₃) or iron oxide (Fe₂O₃)). Ignition delay time was calculated as the difference between first light of the laser’s flash lamp and the energetic material. Results show that laser energy required for ignition is dependent on pre‐ignition reactions, phase change/decomposition temperatures, confinement, and laser absorbance.     

A comparative study on dielectric,structure, and thermal behavior of micro‐ and nano‐sized CCTO in nylon 6,9 matrix

Calcium copper titanium oxalate CaCu₃Ti₄O₁₂ (CCTO) particles as a filler with both micro‐ and nano‐sized into nylon 6,9 polymer have been investigated under structural, thermal, and dielectric properties to find that particle satisfy all the same. Micro‐sized CCTO particles (point out as mCCTO) was synthesized using solid‐state route using ball milling and nano‐sized CCTO particles (point out as nCCTO) was synthesized using complex oxalate precursor route. Fabrication of nylon 6,9/CCTO composite for both micro‐ and nano‐sized CCTO particles were employed separately into nylon 6,9 matrix and examined comparatively. The composite containing 20 vol% of nCCTO achieve 24.5 dielectric permittivity at 100 Hz in room temperature that was significantly higher than mCCTO which was 14 at the same condition. From the structural analysis, we obtained that the nCCTO was well dispersed in the matrix medium, whereas the mCCTO were also dispersed with some agglomeration that was the reason for the interaction failure between the particles and matrix material. The dielectric permittivity results obtained from this study specify that the composite containing nano‐sized CCTO particles may be suitable for energy storage devices and in the higher temperature sensor applications. POLYM. COMPOS., 38:927–935, 2017. © 2015 Society of Plastics Engineers     

Modifying Aluminum Reactivity with Poly(Carbon Monofluoride) via Mechanical Activation

Modification of the reactivity of micrometer‐sized aluminum through inclusion of low levels of poly(carbon monofluoride) (PMF) using mechanical activation (MA) is reported. Resulting composite particle combustion enthalpy, average particle size, and specific surface area depend on MA intensity, duration, and inclusion level, and range from 18.9 to 28.5 kJ g⁻¹, 23.0 to 67.5 μm, and 5.3 to 34.8 m² g⁻¹, respectively. Differential scanning calorimetry experiments in O₂/Ar indicate that MA reduces the exotherm onset from 555 to 480 °C (70/30 wt‐%). Particles are sensitive to electrostatic discharge stimulus (11.5–47.5 mJ) but not to impact (>213 cm) or friction (>360 N) and some low energy MA particles are ignitable by optical flash. With their altered reactivity and high combustion enthalpy, these nanofeatured, micrometer‐sized particles may have use as replacements for aluminum in energetic applications.     

Highly Insensitive/Reactive Thermite Prepared from Cr2O3 Nanoparticles

Thermites prepared from nanoparticles are currently the subject of growing interest due to their increased performances compared to classical micrometer‐sized thermites. Here, we studied the combustion behavior of energetic composite composed of Al and chromium (III) oxide (Cr₂O₃) as function of the oxide particle size. Homogeneous composites were prepared by mixing Al nanoparticles (Φ≈50 nm) with Cr₂O₃ micro‐ and nanoparticles (Φ≈20 nm), respectively, in hexane solution. The dried Cr₂O₃/Al composite powders were ignited by using a CO₂ laser beam. The use of nanosized Cr₂O₃ particles incontestably improves the energetic performances of the Al/Cr₂O₃ thermite since the ignition delay time was shortened by a factor 3.5 (16±2 vs 54±4 ms) and the combustion rate (340±10 mm s⁻¹) was significantly accelerated in contrast to those reported until now. Interestingly, the sensitivity to friction of the Al‐based thermites formulated from Cr₂O₃ is two orders of magnitude lower than the thermite prepared from other metal oxide nanoparticles (MnO₂, WO₃). Finally, our study shows that the decrease of Cr₂O₃ particle size has an interesting and beneficial effect on the energetic properties of Cr₂O₃/Al thermites and appears as an alternative to tune the properties of these energetic materials.     

Rare‐earth‐doped SiO2‐CaF2 glass ceramic nano‐particle with upconversion properties

Rare‐earth‐doped upconversion nano‐phosphor shows new possibilities in the field of bioimaging because of its unique properties like higher penetration depth, low signal to noise ratio (SNR), good photo stability, and zero auto fluorescence. The oxyfluoride glass system is the combination of both fluoride and oxide where fluoride host offers high optical transparency due to low phonon energy and oxide network offers high physical stability. Thus, in the present work, an attempt has been made to synthesize 1 mol% Er³⁺ doped SiO₂‐CaF₂ glass ceramic nano‐particles through sol‐gel route. The synthesized glass ceramic particles were heat treated at 4 different temperatures starting from 600°C to 900°C.The X‐ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) analysis confirmed the formation of CaF₂ nano‐crystals in the matrix which is 20‐30 nm in size. The vibrational spectroscopic analysis of the glass ceramics sample has been investigated by Fourier transform infrared (FTIR) spectroscopy. The UV‐Visible‐NIR spectroscopy analysis was carried out to analyze the absorption intensity in the near infrared region. Upon 980 nm excitation, the sample shows red emission corresponds to ⁴F_9/2→⁴I_15/2 energy level transition. The prepared nano‐particles showed excellent biocompatibility when tasted on MG‐63 osteoblast cells.     

Cage Compounds as Potential Energetic Oxidizers: A Theoretical Study of a Cage Isomer of N2O3

Ab initio electronic structure calculations are employed to investigate the cage isomer of N₂O₃ (c‐N₂O₃) as a viable energetic oxidizer. c‐N₂O₃ is vibrationally stable with a large heat of formation of 7.95 kJ g⁻¹ and can produce larger enthalpies of combustion than other commonly used oxidizers such as ammonium perchlorate, O₂(l) and N₂O₄. c‐N₂O₃ is shown to have a unimolecular decomposition barrier of 24.4 kJ mol⁻¹ at the CCSD(T)/CBS(Q‐5) level of theory, and a dimer‐induced decomposition barrier of 100.8 kJ mol⁻¹. Although c‐N₂O₃ is predicted to perform well as an oxidizer, the low barrier to unimolecular decomposition is likely to render it impractical as an energetic oxidizer.     

Polarizer effect and structure of iodinated before and after casting poly(vinyl alcohol) film

Poly(vinyl alcohol) (PVA)/iodine polarizing film was manufactured as follows: PVA iodinated in solution before casting (IBC film) and iodinated again after casting (IBC + IAC film) and then the IBC + IAC film was drawn in boric acid aqueous solution (IBC + IAC polarizing film), to improve the durability of the polarizing film under a humid and warm atmosphere. These effects were examined by investigating the structural and optical properties of the IBC, IBC + IAC, and IBC + IAC polarizing films. In the IBC state, the PVA chain segments that combined boric acid and iodine were regarded as defects of the crystal, the formation of I₃⁻ decreased with respect to weight gain of boric acid. In the IBC + IAC state, the strength of the peak corresponding to I₃⁻ decreased and the I₅⁻ peak increased. The iodine ions penetrated into crystal of the IBC state during the IAC process and formed a new PVA/iodine complex crystal at the 2θ = 20° in the X‐ray diffraction curves. In the IBC + IAC polarizing film state, another type of polarizing film (IBC + IAC polarizing film‐H) containing I₃⁻ ions mainly was manufactured as well as the IBC + IAC polarizing film to compare the effects of the I₃⁻ and I₅⁻ ions on the durability of the polarizing films. The durability of the I₃⁻ ions that were complexed with the PVA chain was higher than the I₅⁻ ions, which could possibly be separated to I₃⁻ and I₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of boric acid and heat treatment for the formation of poly(vinyl alcohol)/iodine complex films iodinated at solution before casting

This study examined the role of boric acid and the effect of heat treatment on PVA‐iodine polarizing films prepared in the solution state before casting (IBC) of PVA/iodine/boric acid films. The films were prepared by casting aqueous solutions of 10 wt % poly(vinyl alcohol) (PVA) containing boric acid with 0, 0.1, 0.3, and 0.5 mol/l of I₂/KI aqueous solution, and I₂/KI(1 : 2) with 5 wt % of PVA. The effect of boric acid and heat treatment on the durability of the IBC PVA polarizing sheet films was investigated by UV–vis absorption spectroscopy. Boric acid was found to be essential for the complex formation in PVA/iodine solutions at relatively low I₂/KI concentrations and high temperatures. The strength of the complex peak at ∼ 600 nm in UV–vis absorption spectra increased with increasing boric acid concentration. With increasing heating temperature over 90°C the intensity of the peak at 600 nm corresponding to the complex decreased due to the evaporation of I₂ decomposed from I₅⁻, but the peak at 355 nm corresponding to free I₂·I₃⁻ was remained unchanged. From heat treatment at 150°C, the intensity of the peak at 600 nm decreased but the intensity of the complex peak (600 nm) of the sample with 0.5 mol/l boric acid was unaffected. The transmittance and degree of polarization for the films increased and decreased with increasing heat treatment time under heat and a humid atmosphere, respectively. However, this tendency decreased with increasing boric acid concentration and heat treatment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Altering Reactivity of Aluminum with Selective Inclusion of Polytetrafluoroethylene through Mechanical Activation

Micrometer‐sized aluminum is widely used in energetics; however, performance of propellants, explosives, and pyrotechnics could be significantly improved if its ignition barriers could be disrupted. We report morphological, thermal, and chemical characterization of fuel rich aluminum‐polytetrafluoroethylene (70–30 wt‐%) reactive particles formed by high and low energy milling. Average particle sizes range from 15–78 μm; however, specific surface areas range from approx. 2–7 m² g⁻¹ due to milling induced voids and cleaved surfaces. Scanning electron microscopy and energy dispersive spectroscopy reveal uniform distribution of PTFE, providing nanoscale mixing within particles. The combustion enthalpy was found to be 20.2 kJ g⁻¹, though a slight decrease (0.8 kJ g⁻¹) results from extended high energy milling due to α‐AlF₃ formation. For high energy mechanically activated particles, differential scanning calorimetry in argon shows a strong, exothermic pre‐ignition reaction that onsets near 440 °C and a second, more dominant exotherm that onsets around 510 °C. Scans in O₂‐Ar indicate that, unlike physical mixtures, more complete reaction occurs at higher heating rates and the reaction onset is drastically reduced (approx. 440 °C). Simple flame tests reveal that these altered Al‐polytetrafluoroethylene particles light readily unlike micrometer‐sized aluminum. Safety testing also shows these particles have high electrostatic discharge (89.9–108 mJ), impact (>213 cm), and friction (>360 N) ignition thresholds. These particles may be useful for reactive liners, thermobaric explosives, and pyrolants. In particular, the altered reactivity, large particle size and relatively low specific surface area of these fuel rich particles make them an interesting replacement for aluminum in solid propellants.     

High-pressure glass-ceramics for iodine nuclear waste immobilization: Preliminary experimental results

Several matrix types have been considered for the immobilization of iodine radioisotopes from which glass-ceramics represent a serious candidate; however, I-bearing glass-ceramics are challenging owing to the iodine volatility. We have synthesised glass-ceramics from the partial crystallization of a parental glass enriched with different iodine sources (I₂ and I₂O₅) under high-pressure conditions (up to 1.5 GPa). The samples were characterized using Scanning and Transmission Electron Microscopy and X-ray Diffraction. Using standard synthesis protocol: melting, nucleation and crystal growth, we have obtained glass-ceramics showing the coexistence between I-bearing glass (<0.8 mol.% I), nepheline (NaAlSiO₄) and iodosodalite (Na₈Al₆Si₆O₂₄I₂ with up to 14 mol.% I). For several samples, we observed also the presence NaPt₃O₄ witnessing a chemical reaction between the container walls and the inside experimental charge. The structure of iodosodalite is entirely resolved by Rietveld refinement of the XRD pattern for I₂ experiments whereas it cannot be solved for I₂O₅ experiments suggesting a change in the iodosodalite structure probably due to the β cage filling by IO₃⁻ clusters instead of I⁻. Our present work could represent a potential solution to tackle the problem of iodine radioisotopes immobilization.     

Dense nanocrystalline UO2+x fuel pellets synthesized by high pressure spark plasma sintering

Nanocrystalline UO_2+x powders are prepared by high‐energy ball milling and subsequently consolidated into dense fuel pellets (>95% of theoretical density) under high pressure (750 MPa) by spark plasma sintering at low sintering temperatures (600°C‐700°C). The grain size achieved in the dense nano‐ceramic pellets varies within 60‐160 nm as controlled by sintering temperature and duration. The sintered fuel pellets are single phase UO_2+x with hyper‐stoichiometric compositions as derived by X‐ray diffraction, and micro‐Raman measurements indicate that random oxygen interstitials and Willis clusters dominate the single phase nano‐sized oxide pellets of UO_2.03 and UO_2.11, respectively. The thermal conductivities of the densified nano‐sized oxide fuel pellets are measured by laser flash, and the fuel stoichiometry displays a dominant effect in controlling thermal transport properties. A reduction in thermal conductivity is also observed for the dense nano‐sized pellets as compared with micron‐sized counterparts reported in the literature. The correlation among the SPS sintering parameters—microstructure control—properties is established, and the nano‐sized UO_2+x pellets with controlled microstructure can serve as the model systems for fundamental understandings of fuel behaviors and obtaining critical experimental data for multi‐physics MARMOT model validation.     

Preparation and Properties of an AP/RDX/SiO2 Nanocomposite Energetic Material by the Sol‐Gel Method

A nanocomposite energetic material was prepared using sol‐gel processing. It was incorporated into the nano or submicrometer‐sized pores of the gel skeleton with a content up to 95 %. AP, RDX, and silica were chosen as the energetic crystal and gel skeleton, respectively. The structure and its properties were characterized by SEM, BET methods, XRD, TG/DSC, and impact sensitivity measurements. The structure of the AP/RDX/SiO₂ cryogel is of micrometer scale powder with numerous pores of nanometer scale and the mean crystal size of AP and RDX is approx. 200 nm. The specific surface area of the AP/RDX/SiO₂ cryogel is 36.6 m² g⁻¹. TG/DSC analyses indicate that SiO₂ cryogel can boost the decomposition of AP and enhance the interaction between AP and RDX. By comparison of the decomposition heats of AP/RDX/SiO₂ at different mass ratios, the optimal mass ratio was estimated to be 6.5/10/1 with a maximum decomposition heat of 2160.8 J g⁻¹. According to impact sensitivity tests, the sensitivity of the AP/RDX/SiO₂ cryogel is lower than that of the pure energetic ingredients and their mixture.     

Temperature-dependent transport properties of micro and nano-sized zinc cobalt oxide (ZnCo2O4) and zinc manganese oxide (ZnMn2O4) particles synthesized by a hydrothermal route

In the present work, a hydrothermal method has been adopted to synthesize micro (~150 nm), and nano (~20 nm) particles of Zinc based, cobalt, and manganese oxide structures, i.e., ZnCo₂O₄ (ZCO) and ZnMn₂O₄ (ZMO). These structures have been examined by X-ray diffraction, Field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. The effect of different reducing agents and solvents have been ascertained on the morphological and the crystalline nature of the samples. The highly crystalline and micron-sized particle formation has been observed with the usage of NaBH₄ as the reductant in the water solution, and a polycrystalline structure with nanosized particle formation has been found with NaOH as the reductant in the water and DMF solution. The electrical properties have been investigated between 100 Hz and 1 MHz by varying the temperature from 303 K to 513 K. The micro and nano sized particles of ZCO and ZMO have shown frequency dependence, thermally activated and relaxation-type dielectric behavior confirming the semiconducting nature. The variation of ac conductivity with frequency at different temperatures is according to Jonscher's power law for micro and nano sized particles of the ZCO and ZMO but supporting different conduction mechanisms. The conduction mechanism in microparticles and nano-particles is according to an overlapping-large polaron tunneling (OLPT) model, and the Non-overlapping small polaron tunneling (NSPT) model, respectively.     

Formation and Characterization of Nano‐sized RDX Particles Produced Using the RESS‐AS Process

It has been shown that nano‐sized particles of secondary explosives are less sensitive to impact and can alter the energetic performance of a propellant or explosive. In this work the Rapid Expansion of a Supercritical Solution into an Aqueous Solution (RESS‐AS) process was used to produce nano‐sized RDX (cyclo‐1,3,5‐trimethylene‐2,4,6‐trinitramine) particles. When a saturated supercritical carbon dioxide/RDX solution was expanded into neat water, RDX particles produced from the RESS‐AS process agglomerated quickly and coarsened through Ostwald ripening. However, if the pH level of the suspension was changed to 7, particles were metastably dispersed with a diameter of 30 nm. When the supercritical solution was expanded into air under the same pre‐expansion conditions using the similar RESS process, RDX particles were agglomerated and had an average size of approximately 100 nm. Another advantage of using a liquid receiving solution is the possibility for coating energetic particles with a thin layer of polymer. Dispersed particles were formed by coating the RDX particles with the water soluble polymers polyvinylpyrrolidone (PVP) or polyethylenimine (PEI) in the RESS‐AS process. Both PVP and PEI were used because they have an affinity to the RDX surface. Small and well‐dispersed particles were created for both cases with both PVP and PEI‐coated RDX particles shown to be stable for a year afterward. Several benefits are expected from these small polymer coated RDX particles such as decreased sensitivity, controlled reactivity, and enhanced compatibility with other binders for fabrication of bulk‐sized propellants and/or explosives.     

Evaluation of Nano‐Co3O4 in HTPB‐Based Composite Propellant Formulations

Different propellant compositions were prepared by incorporating nano‐sized cobalt oxide from 0.25 % to 1 % in HTPB/AP/Al‐based composite propellant formulations with 86 % solid loading. The effects on viscosity build‐up, thermal, mechanical and ballistic properties were studied. The findings revealed that by increasing the percentage of nano‐Co₃O₄ in the composition, the end of mix viscosity, the modulus and the tensile strength increased, whereas the elongation decreased accordingly. The thermal property data envisaged a reduction in the decomposition temperature of ammonium perchlorate (AP) as well as formulations based on AP. The ballistic property data revealed an enhanced burning rate from 6.11 mm s⁻¹ (reference composition) to 8.99 mm s⁻¹ at 6.86 MPa and a marginal increase in pressure exponent from 0.35 (reference composition) to 0.42 with 1 % nano‐cobalt oxide.     

Facile synthesis of pseudocapacitive Mn3O4 nanoparticles for high-performance supercapacitor

In this work, a facile method to produce the ultrafine (4–14 nm) and mixed valence Mn₃O₄ nanoparticles from low-cost MnSiO₃ (manganese silicate) particles were introduced. The best NaOH concentration in hydrothermal treatment has been determined after a series of experiments. Also, the as-synthesized Mn₃O₄ material with good specific capacitance has been investigated attentively at a high mass loading (∼3 mg cm⁻²). The particles size and the pore size distribution is found to be refined and optimized, respectively. This increased the crystallinity and the capacitive contribution in the energy process. Thereby improving the rate capability and cycling stability, which result in significant improvement of specific capacitance (401 F g⁻¹ at 10 mV s⁻¹). The aqueous asymmetric supercapacitor device AC//Mn₃O₄ with a stable working voltage window up to 2.0 V has been fabricated, and it is found to have an energy density of 40.2 W h kg⁻¹ at 500 W kg⁻¹ power density. This could sustain 5000 cycles galvanostatic charge/discharge with 96.9% retention.     

Effect of Nano‐Copper Oxide and Copper Chromite on the Thermal Decomposition of Ammonium Perchlorate

The catalytic effect on the thermal decomposition behavior of ammonium perchlorate (AP) of p‐type nano‐CuO and CuCr₂O₄ synthesized by an electrochemical method has been investigated using differential scanning calorimetry as a function of catalyst concentration. The nano‐copper chromite (CuCr₂O₄) showed best catalytic effects as compared to nano‐cupric oxide (CuO) in lowering the high temperature decomposition by 118 °C at 2 wt.‐%. High heat releases of 5.430 and 3.921 kJ g⁻¹ were observed in the presence of nano‐CuO and CuCr₂O₄, respectively. The kinetic parameters were evaluated using the Kissinger method. The decrease in the activation energy and the increase in the rate constant for both the oxides confirmed the enhancement in catalytic activity of AP. A mechanism based on an electron transfer process has also been proposed for AP in the presence of nano‐metal oxides.     

Catalytic Effect of Two Shapes of Nano‐Fe2O3 on Hexanitrohexaazaisowurtzitane Using a Non‐Isothermal Decomposition Kinetic Method

Nanosized Fe₂O₃ particles (nano‐Fe₂O₃) with two shapes (tetrakaidecahedral and grainy) were synthesized by hydrothermal methods. The morphologies and structures were characterized using a combination of experimental techniques including X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Two composites containing CL‐20 (hexanitrohexaazaisowurtzitane, HNIW) and tetrakaidecahedral nano‐Fe₂O₃ [nmT‐Fe₂O₃/CL‐20] or grainy nano‐Fe₂O₃/CL‐20 (nmG‐Fe₂O₃/CL‐20) were prepared. The thermal behaviors of the two composites and pure CL‐20 were investigated using differential scanning calorimetry (DSC). Non‐isothermal decomposition kinetic parameters and the thermal decomposition mechanism of the two composites and CL‐20 were obtained. The apparent activation energy (E_a) of the main thermal decomposition reaction of CL‐20, nmT‐Fe₂O₃/CL‐20 and nmG‐Fe₂O₃/CL‐20 are 181.94, 179.17, and 176.18 kJ mol⁻¹, respectively. The thermal decomposition mechanism of CL‐20 as well as nmT‐Fe₂O₃/CL‐20 was controlled by the Avrami‐Erofeev equation (n=2/5) assumed as random nucleation and subsequent growth, while, the reaction mechanism of the composite nmG‐Fe₂O₃/CL‐20 was controlled by the Mample Power law (n=1/2). The reason for this difference may be due to the different morphology and particle size of the two nano‐Fe₂O₃ particles.     

Preparation of nano‐reinforced thermal conductive natural rubber composites

Natural rubber (NR) composites highly filled with nano‐α‐alumina (nano‐α‐Al₂O₃) modified in situ by the silane coupling agent bis‐(3‐triethoxysilylpropyl)‐tetrasulfide (Si69) were prepared. The effects of various modification conditions and filler loading on the properties of the nano‐α‐Al₂O₃/NR composites were investigated. The results indicated that the preparation conditions for optimum mechanical (both static and dynamic) properties and thermal conductivity were as follows: 100 phr of nano‐α‐Al₂O₃, 6 phr of Si69, heat‐treatment time of 5 min at 150°C. Furthermore, two other types of fillers were also investigated as thermally conductive reinforcing fillers for the NR systems: (1) hybrid fillers composed of 100 phr of nano‐α‐Al₂O₃ and various amounts of the carbon black (CB) N330 and (2) nano‐γ‐Al₂O₃, the particles of which are smaller than those of nano‐α‐Al₂O₃. The hybrid fillers had better mechanical properties and dynamic performance with higher thermal conductivity, which means that it can be expected to endow the rubber products serving under dynamic conditions with much longer service life. The smaller sized nano‐γ‐Al₂O₃ particles performed better than the larger‐sized nano‐α‐Al₂O₃ particles in reinforcing NR. However, the composites filled with nano‐γ‐Al₂O₃ had lower thermal conductivity than those filled with nano‐α‐Al₂O₃ and badly deteriorated dynamic properties at loadings higher than 50 phr, both indicating that nano‐γ‐Al₂O₃ is not a good candidate for novel thermally conductive reinforcing filler. POLYM. COMPOS., 37:771–781, 2016. © 2014 Society of Plastics Engineers     

Film formation from nano‐sized polystrene latex covered with various TiO2 layers

Steady‐state fluorescence technique was used for studying film formation from TiO₂ covered nano‐sized polystyrene latex particles. The composite films were prepared from pyrene (P)‐labeled PS particles by covering them with various layers of TiO₂ at room temperature. These films then annealed at elevated temperatures in 10 min time interval above glass transition (T_g) temperature of polystyrene. Five different composite films were studied in various TiO₂ layer contents. Fluorescence emission intensity, I_P from P was measured after each annealing step to monitor the stages of film formation. Films present significant increase in I_P above the certain onset temperature called minimum film forming temperature, T₀. However, at higher annealing temperatures, I_P showed a decrease. Increase and decrease in I_P were modeled by void closure and interdiffusion processes and related activation energies were determined, respectively. Dissolution of annealed PS film, with high TiO₂ content presented a nice, ordered nano‐sized ceramic structure, which may predict the construction of nano‐layer photonic crystals. POLYM. COMPOS., 27:651–659, 2006. © 2006 Society of Plastics Engineers