Ideality of pressure‐sensitive paint. II. Effect of annealing on the temperature dependence of the luminescence

This article reports the effect of annealing on a pressure‐sensitive paint (PSP) consisting of platinum tetra(pentafluorophenyl)porphine (PtTFPP) in a fluoroacrylic polymer called FIB (Puklin, E.; Carlson, W. B.; Gouin, S.; Costin, C.; Green, E.; Ponomarev, S.; Tanji, H.; Gouterman, M. J Appl Polym Sci 2000, 77, 2795). Samples annealed at 150°C, 75°C, annealed by a heat gun, and dried at room temperature are compared to nonannealed samples. Temperature dependences of luminescence intensity and lifetime are studied as a function and pressure and temperature and fit with Arrhenius and Stern–Volmer equations. We find that heating above T_g is more important than drying at room temperature in lowering the temperature dependence and obtaining ideal PSP, ideal meaning independent effect of pressure and temperature on luminescence properties of the paint. Ideality is achieved by lowering the activation energy for oxygen diffusion, presumably by relaxation of the polymer network. It is shown that ideal behavior occurs only over a limited temperature region. This range is more useful for PtTFPP in FIB than for ruthenium bathophenanthroline in polydimethylsiloxane (PDMS), another common PSP formulation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2805–2814, 2000     

Effect of elevated annealing temperature on electrical conductivity and magnetic properties of iron phthalocyanine polymer

A novel iron phthaocyanine (FePc) polymer was prepared via the polymerization of phthalonitrile with ferrous chloride and investigated for morphology, crystallinity, conductivity, dielectric and magnetic properties at different annealing temperatures from 300 °C to 700 °C. The results showed that the elevating annealing temperature could significantly change the morphology and microstructure of FePc polymer, leading to the formation of the turbostratic carbon, α-Fe phase and cemetite, and enhance electrical conductivity and magnetic properties. It was worth noting that the dramatic transition of conductivity, dielectric and magnetic properties appeared when the annealing temperature was 550 °C. The electrical conductivity of the samples exhibited a transition of electrical behavior from an insulator to semiconductor. And the saturation and remanent magnetization of the annealed FePc polymer increased from 0.24 to 6.18 emu/g and from 0.03 to 2.38 emu/g, respectively. The pyrolysis of FePc polymer annealed at high temperature was believed to become a good way to get electrical or magnetic materials.     

Growth of Mg2GeO4 nano-crystals on Si substrate and modulation of Seebeck coefficient by post growth annealing technique

We have reported the successful growth of Mg₂GeO₄ nano-crystals by simple thermal evaporation technique. The Mg and Ge metal powders were evaporated on the Si substrate and kept the oxygen flow rate of 100 sccm. The modulation of structural, morphological, thermoelectric and electrical properties was performed by controlling the thermal energy of carriers using different annealing temperatures. XRD data showed a peak at 61.8⁰ which was related to (212) plane of Mg₂GeO₄. XRD data further suggested that sample annealed at 700 °C has stable crystal structure while sample annealed at 800 °C posses degraded structure because the presence of highest density of donors defects. This defect concentration causes an increase in the conductivity of annealed samples as evident by the Hall data. This argument was also supported by Raman spectroscopy which showed that sample annealed at 700 °C has strongest Mg₂GeO₄ Raman peak. SEM images also verified the smooth surface of the sample annealed at 700 °C. The temperature dependent (25–100 °C) Seebeck effect measurements were performed to calculate the Seebeck coefficient of Mg₂GeO₄ nano-crystals at different measurement temperatures. The highest value of room temperature Seebeck coefficient (397 μV/⁰C) for the sample annealed at 800 °C is due the high density of carrier concentration.     

Effect of process parameters on residual stress distribution in poly(ethylene terephthalate) fibers and films as revealed by chemical etching

Poly(ethylene terephthalate) fibers and films produced by varying process parameters, such as production speed and medium, temperature and rate of drawing, were annealed at temperatures between 100 and 250°C in the free-to-shrink and constant-length conditions. The as-spun, as-drawn, and drawn and annealed samples were etched in 40% aqueous methylamine at room temperature for 4 h. The etch patterns were examined on a scanning electron microscope and were found to be related mainly to residual stress and its distribution in the samples and thereby to sample morphology. The studies clearly bring about the important role played by the processing history. © 1995 John Wiley & Sons, Inc.     

RETRACTED ARTICLE: A Review on Nanoporous Gallium Nitride (NPGaN) Formation on P-Type Silicon Substrate with the Mather-type Plasma Focus Device (MPFD)

A Mather-type plasma focus device (MPFD) was unitized to fabricated porous gallium nitride (GaN) on p-type silicon (Si) substrate with a <100> crystal orientation for the first time in a deposition process. GaN was deposited on Si with four and seven shots. The samples went through a three phase annealing procedure. First, the semiconductors were annealed in the PFD with nitrogen plasma shots after their deposition, second, a thermal chemical vapor deposition (TCVD) annealed the samples for 1 at 1050?°C by nitrogen gas at 1 Pa pressure. Finally, an electric furnace annealed the samples for 1 h at 1150?°C with continues flow of nitrogen. Porous GaN structures were observed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Furthermore, X-ray diffraction (XRD) analyze was carried out to determine the crystallinity of GaN after the samples were annealed. Energy-dispersive X-ray spectroscopy (EDX) indicated the amount of gallium, nitrogen, and oxygen due to self-oxidation of the samples. Photoluminescence (PL) spectroscopy revealed emissions at 2.94 and 3.39 eV which shows hexagonal wurtzite crystal structures was formed.     

The effect of pre-annealing and post-annealing on the transparency of MgAl2O4, prepared by slip casting and spark plasma sintering (SPS)

The aim of this paper is to investigate the effect of slip casting process and the annealing before and after sintering to achieve a transparent MgAl₂O₄. To remove contaminants such as carbon from the structure of shaped spinel bodies, at first, the samples were annealed at temperature of 800?°C, 900?°C and 1000?°C for 2?h and then sintered at 1400?°C. By annealing the sample before sintering at 900?°C, the transmission increased (15% at IR region and 10% at visible region). Although by annealing the samples, the amount of carbon contamination reduced. Annealing the samples after sintering also had some desirable results. The samples annealed at temperature of 1200?°C for a time of 3, 5 and 10?h. The darkness of samples reduced due to the removal of carbon impurities and the sample was annealed at 1200?°C for 5?h had the most transparency in the visible and infrared regions.     

Strain‐induced crystallization in uniaxially drawn PETG plates

The copolyester poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG) is used industrially as an uncrystallizable polymer, whereas PET is an inherently crystallizable polymer. Nevertheless, a crystalline phase could appear in the material. To create a strain‐induced crystalline phase in an initially amorphous PETG material, plates were placed in the heating chamber of a tensile machine at 100°C and uniaxially drawn to obtain different samples with various draw ratios. During DSC analysis of highly drawn samples, perturbations of the baseline appear above the glass‐transition temperature, consisting of weak exothermic and endothermic phenomena. Comparison of DSC and X‐ray diffraction analysis of drawn PETG and PET shows that a strain‐induced crystalline phase appears in this copolyester. A spherulitic superstructure could also appear after lengthy annealing. Analysis of this semicrystalline material allowed estimation of the degree of crystallinity, about 3% after a drawing at high draw ratio and about 11% for undrawn annealed material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3405–3412, 2001     

X‐ray diffraction studies on reverse‐annealed polyethylenes

Linear low and high density polyethylene sheets were compression molded and crystallized at a 5–10°C/min cooling rate. Parts of the sheets were annealed at different temperatures up to 2°C below the melting temperature. The small angle X‐ray scattering (SAXS) and the wide angle X‐ray scattering intensities of the annealed samples were studied. SAXS intensities showed particle scattering with a bimodal size distribution. The estimated radii of gyration were 15–17 nm and 5–7 nm, respectively. The crystallinity and the radius of gyration increased slightly with increasing annealing temperature for some samples; others did not show any change. No peaks characteristic of intercorrelated lamellar crystallinity in the SAXS intensities developed during the annealing. The original broad peak of high density polyethylene disappeared from the SAXS recordings on annealing. The length of the perfect chain versus melting temperature was calculated by the Thomson‐Gibbs formula and Flory's concept of melting temperature depression where methyl groups and tertiary carbon atoms at the branches were regarded as second components (solvent). Linear relationships were found for both cases. Experimental data for a linear low density polyethylene obtained from the literature were in between the two functions. A lamellar model of crystallization corresponding to the data is proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 340–349, 2001     

Effects of annealing temperature on both radial supporting performance and axial flexibility of poly(L-lactic acid) braided stents

In this paper, the effects of annealing temperature on both radial supporting performance and axial flexibility of poly(L-lactic acid) (PLLA) braided stents are studied. Stents are annealed at a series of temperatures ranging from 80 to 160°C for 1 h, then indicators of shaping effect, radial supporting performance, and axial flexibility are compared. Stents not annealed and annealed at 80°C cannot be completely shaped. In contrast, stents annealed at 100 to 160°C are well shaped showing radial shrinkage rate of 1.0 ± 0.2% and almost no axial elongation. The radial compressive force and axial force are gradually increased by 51.2% and 89.2%, respectively with the annealing temperature gradually increasing from 80 to 160°C, indicating that the radial supporting performance is improved but axial flexibility is weakened by a higher annealing temperature. Taken together, PLLA braided stents can be annealed at 100 to 120°C to obtain sufficient radial force and lower axial force simultaneously for clinical applications. Moreover, tensile test, X-ray diffraction, and differential scanning calorimetry are performed for monofilaments annealed at different temperatures to further explore the effect mechanism of annealing temperature on the mechanical properties of stents. This study may provide helpful suggestions for the manufacture of biodegradable braided stents.     

Properties of syndiotactic-rich poly(vinyl alcohol) thin film in water. III. Contraction and extension of drawn and annealed thin film in water

Contraction and extension behaviors in water for drawn (four times original length) and annealed (at 60–215°C) thin films of poly(vinyl alcohol) (PVA_VTFA) derived from vinyl trifluoroacetate have been examined. At a constant temperature of 25°C, drawn films annealed at 60–190°C contracted after a certain standing time. Length of films annealed at 200°C did not change after standing of 20 min and film annealed at 215°C extended very little. As the temperature was raised, the drawn films annealed at 60–190°C contracted further until a certain temperature and then extended. The drawn film annealed at 200°C first started contraction at 70°C. The drawn film annealed at 215°C extended further very little until 75°C and then contracted very little until 99°C (in boiling water). In standing at 99°C, it contracted very little with standing and resisted without breaking for 300 min.     

Temperature-independent physical properties of electrophoretic Ti5NbO14 films for high-temperature capacitors

Ti₅NbO₁₄ (T5NO) films were developed on Pt/Ti/SiO₂/Si substrates by electrophoretic method by using T5NO³⁻ nanosheets. The film deposited at room temperature (RT) contained organic defects, which were almost eliminated in the film annealed at 700 °C. The film deposited at RT revealed (100) planes with an inter-planar distance of 1.1 nm because of the existence of TBA⁺ defects. However, for the films annealed at higher temperatures (≥400 °C), two types of structures formed: (100) planes with 0.55 nm inter-planar distance (group-1 structure), and (100) planes with 1.42 nm inter-planar distance (group-2 structure). The dielectric constant (ε_r) of the film annealed at 700 °C was 61 with a low dielectric loss of 1.0%. Variations in the ε_r according to the film thickness, electric field, and temperature were small. This film displayed a high insulating property up to 300 °C with a small temperature coefficient of capacitance (−56.7 ppm/K) up to 400 °C.     

In situ studies on the temperature‐related deformation behavior of isotactic polypropylene spherulites with uniaxial stretching: The effect of crystallization conditions

The deformation behavior of isotactic polypropylene (iPP) spherulites with uniaxial stretching was investigated at different drawing temperatures via in situ polarized optical microscope (POM) observation. The iPP spherulites were prepared by two procedures: cooled to the room temperature from melt and annealed at 135, 140, and 145°C for 3 h. It was found that the crystallization conditions dominate the crystalline morphology and even the tensile properties of iPP. For iPP which crystallized during cooling progress, the spherulites were imperfect and the boundaries of the spherulites were diffuse, displaying good toughness at various drawing temperatures. For iPP annealed at high temperatures displayed the brittle fracture‐modes and the crack happened between spherulites, which due to the large and perfective spherulites have thick lamellas and weak connection at interspherulitic boundary. The shape and size of the iPP spherulites formed at 140 and 145°C are affected with uniaxial stretching till to the fracture of the samples at different drawing temperatures. The spherulites obtained at 135°C are deformed along the drawing direction at 100°C but not affected at low drawing temperatures, indicating the toughness increased with the increase of the drawing temperatures. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Properties of blends containing petroleum jelly and 4-methyl-pentene-1 (TPX-RT-D30)

The properties of 4-methyl-pentene-1 polymer (TPX-RT-D30) were altered by blending petroleum jelly (P.J.) with the polymer. The polymer was blended with up to 40% by weight P. J. The plasticization of the polymer by the P. J. apparently allows high molecular weight fractions of the polymer to crystallize and influences the crystalline size and perfection. Tensile properties of the blends showed both a break and yield value in all ratios as compared to only a break value for the pure polymer. Breaking strength ranged from 4000 psi for the polymer to 1000 psi at 40% P. J. The samples had a “necking down” effect at 10% P. J. Modulus decreased from 1.8 × 10⁴ (literature value 2.1 × 10⁵) to 2.3 × 10⁴ at 40% P. J. Brittle point values varied from above room temperature to 5°C at 40% P. J. The Vicat softening point ranged from 181°C for the polymer to 87°C at 40% P. J. Differential thermal analysis (Stone) showed a melting point depression from 235°C to 218°C at 40% P. J.     

Effect of Annealing Temperature on TiO2 Nanorod Films Prepared by dc Reactive Magnetron Sputtering for Dye-Sensitized Solar Cells

Anatase TiO₂ nanorod films have been prepared on ITO coated glass substrates at room temperature by dc reactive magnetron sputtering technique. The nanorods are highly ordered and are perpendicular to the substrate. XRD measurements show that the anatase nanorods have a preferred orientation along the [110] direction. The prepared nanorods were annealed at different temperatures (200?C500 °C) in air for 1 h. The dye-sensitized solar cells (DSSC) have been made using the as-deposited and annealed TiO₂ nanorods as working electrodes. It has been found that annealing improves the efficiency of the DSSC. An optimum conversion efficiency of 2.13%, at 100 mW/cm² light intensity has been achieved with TiO₂ nanorods annealed at 300 °C.     

Improved Schottky contacts to annealed 4H-SiC using a protective carbon cap: Investigated using current voltage measurements and atomic force microscopy

Schottky contacts on 4H-SiC surfaces, annealed at high temperature in the presence of a protective carbon cap, are compared to contacts fabricated by the same process, without the protective layer. Annealing at 1600 °C is required to electrically activate implanted dopants, but causes severe surface damage. We show using surface morphology studies, based on atomic force microscopy (AFM), that carbon-cap protected 4H-SiC had a considerably lower surface roughness than surfaces annealed without the protective cap.Nickel diodes fabricated on 4H-SiC samples, after removal of the carbon-cap using oxygen plasma etching, showed similar Schottky I(V) forward bias characteristics to contacts on samples that had not been annealed, and displayed similar reverse blocking voltages. Carbon cap protected samples also displayed lower reverse leakage currents than un-annealed samples. In contrast, contacts fabricated on unprotected surfaces, damaged by annealing at 1600 °C, displayed non-rectifying behaviour.     

Thermal and mechanical properties of the precursor polymers: Comparison of their properties with poly(amic acid)

The DSC thermograms of P-PHA show a large endothermic peak at 450–550°C. As the annealing temperature increases from 250°C to 400°C, the endothermic peaks become smaller and then disappear for samples annealed above 450°C. As observed for P-PHA, the endothermic enthalpy of PHA and PAA became smaller with an increasing annealing temperature. The cyclization onset temperature (T₁) of the three precursors increases linearly with an increasing annealing temperature at a constant annealing time (30 min). Otherwise, the initial decomposition onset temperature (T₂) was shown to be constant. T₂ of P-PHA, PHA, and PAA were observed in the temperature ranges of 601–603°C, 576–577°C, and 532–534°C, respectively. These TGA results confirm that all of the samples are thermally stable. Increasing the annealing temperature of the three precursor polymers significantly increases the tensile properties of the films. The tensile properties of all annealed precursors were much higher than those of the unannealed films. In contrast, the initial modulus of PAA is improved only slightly when compared with the other two polymers regardless of the heat treatment. The biaxial stresses in the PHA and PAA films were investigated by holographic interferometry. The stresses in the films were 6.85–7.61 MPa for PHA and 27.01–27.70 MPa for PAA.     

Plasma polymerization coating of silica fillers for Epoxy Molding Compounds (EMCs)

Silica fillers for Epoxy Molding Compounds (EMCs) were modified via plasma polymerization coating of acrylonitile, acrylic acid and dimethyl phosphite with RF plasma (13.56 MHz). The resulting samples were characterized by DSC, FT-IR and contact angle measurements. EMC samples were prepared from silica fillers, biphenyl epoxy resin, phenol novolac and triphenyl phosphine, and cured at 175°C for 4 h. Flexural strength of the EMC samples was evaluated in a 3-point bending mode with an Instron 5567 at a crosshead speed of 1 mm/min both at RT and 250°C, and failure surfaces were analyzed by SEM. Some samples were exposed to 121°C, 2 atm pressure and 100% RH for 12, 24 and 32 h, and then to 250°C for 10 min prior to testing at RT. Plasma polymer coating of silica with acrylonitrile greatly improved the flexural strength of EMC at RT as well as at 250°C, followed by acrylic acid and dimethyl phosphite. Exposing EMC samples to 121 °C, 2 atm pressure and 100% RH for 32 h decreased the flexural strength by 13% when the silica was coated with acrylonitrile plasma polymer, compared to the 21% decrease in the control sample. Plasma polymer coating of silica also increased the Tg of the EMC, and lowered water absorption and CTE in the rubbery region. Therefore, enhanced properties by plasma polymer coating of silica with acrylonitrile or acrylic acid can be attributed to nitrile or carboxylic acid groups, as confirmed by FT-IR, which can react with epoxy groups in the base resin, as evidenced by DSC analysis.     

Doubly oriented β-form films of poly(vinylidene fluoride)

PVDF sheets, rapidly quenched, were (1) two-step transversely stretched at various temperatures and (2) stretched at various temperatures, rolled at room temperature and then annealed. The orientation patterns of the β-form crystal (which contains the polar b-axis) in these films were analysed on the basis of X-ray diffraction photographs taken with flat and cylindrical cameras. In the case of (1), when both of the two-step transversely stretching temperatures were below 100°C, a doubly oriented film with the plar b-axis oriented parallel to the film surface was obtained. In the case of (2), when the stretching temperature was below 100°C, the sheets then rolled without annealing, another doubly oriented film with the polar b-axis preferentially oriented at 30° to the film surface was obtained. On the other hand, when these films were annealed above 100°C, or the stretching temperatures were above 100°C, orientation patterns in which the polar b-axis was partially rotated through 60° were obtained. The orientation mechanisms of these films are discussed using the measurements of the lattice spacings of the β-form crystal.     

Temperature dependent dielectric properties of (na,K) NbO3, near equimolar composition

Pellet samples of Na_1-xK_xNbO₃ (0.490 ≤ x ≤ 0.510) were prepared using solid state reaction method with double sintering. Dielectric measurements were carried out on the prepared samples, from 30 to 500 °C, at 1 MHz. Dielectric constant and electrical conductivity were found minimum, for x = 0.500 among all the prepared compositions, at room temperature and at all the measured frequencies. Three distinguished phase transitions, at 200, 380 and 460 °C, were observed in dielectric measurements of the prepared compositions. The high temperature X-ray diffraction (HT- XRD) of the samples with x = 0.500, shows monoclinic phase between room temperature and 200 °C, tetragonal between 200 and 380 °C, tetragonal with increased lattice parameters, between 380 and 460 °C, and cubic phase beyond 460 °C. The tetragonal to tetragonal phase transition at 380 °C, and tetragonal to cubic at 460 °C was distinctly observed from dielectric and HT- XRD measurements in the present study.     

Properties of syndiotactic-rich poly(vinyl alcohol) thin film in water. V. Effect of initial temperature of heating on elongation

The effect of the initial temperature of heating on the elongation of syndiotactic-rich poly(vinyl alcohol) thin films was investigated in water under a load. The elongation ratios E_i after 4 h at fixed temperatures increased roughly with an increase in the initial temperature T_i and a decrease in the annealing temperature. E_i after 4 h was the smallest at T_i = 45°C for the films annealed at temperatures below 100°C. E_i was 6.8 at T_i = 60°C for the unannealed film and 1.12 at T_i = 70°C for the film annealed at 200°C. The elongation at break decreased and the temperature at break increased with an increase in annealing temperature, but those at the annealing temperature of 100°C were the smallest. The films annealed at 200°C did not break even at 98°C (boiling temperature) in water and the elongation ratio was 1.42–1.97 in the initial temperature range of 10–70°C. From these results, the relation between the elongation in water and the state of polymer chains in film was discussed.