Nodular Structure Research Articles

Liquid reagent CVD of carbon. I. Processing and microstructure

The processing and microstructure of carbon coatings deposited using liquid reagent CVD were studied. High density pyrolytic carbon coatings were successfully deposited on graphite and molybdenum substrates from benzene and cyclohexane precursors. Very high deposition rates were obtained. Examination via transmission electron microscopy showed that the deposits were of the desired turbostratic nodular structure with low texture.

Density‐based phase‐separation asymmetric polyethylene–poly(dimethyl siloxane) blend membranes: Preparation and properties

AbstractA new concept of density‐based phase separation for the preparation of asymmetric membranes from polyethylene (PE) blended with liquid poly(dimethyl siloxane) (PDMS) has been tried. The PE/PDMS membranes were prepared via high‐temperature solution casting. The purpose of incorporating PDMS was to utilize its flexibility, relatively high density in comparison with PE, and dissolution in common solvent for the formation of asymmetric PE/PDMS membranes. The study has been carried out with 1.25, 2.5, 5, and 10% (v/w) loading of PDMS. A host of techniques were used to study morphology of PE/PDMS blend membranes. The membranes show nodular structure on surfaces in contact with solvent vapor environment, whereas the opposite surfaces have smoother texture devoid of nodules. Although differential scanning calorimetric (DSC) melting endotherms indicate enhancement of crystallinity with PDMS addition, chemical etching and subsequent scanning electron microscopic (SEM) observations show increasingly ordered spherulitic pattern on individual nodules with the incorporation of PDMS up to 2.5%. The density of the films also increases with the addition of PDMS as compared to the control. ATR‐FTIR data revealed asymmetric distribution of PDMS in membranes with more PDMS retention toward lower surface of membranes. Membrane cross sections were indicative of graded porosity with increasing pore size toward the bottom surface of membranes. The results were explained in terms of density‐based phase separation.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:2278–2287, 2004

Ultrafiltration hollow fiber membranes from poly(ether imide): preparation, morphologies and properties

Ultrafiltration hollow fiber membranes were prepared from poly(ether imide) (PEI) with a wet spinning method. Effects of N, N-dimethylacetamide (DMAc) as a solvent additive in internal coagulant and acetic acid as a nonsolvent additive in dope solution on the morphologies and performances of the membranes were investigated respectively. Scanning electron microscope (SEM) study indicated that the addition of DMAc into the internal coagulant changed the inner fiber surface from dense skin layer to porous structure. However, the pure water flux of the membrane decreased with the increase of DMAc content. On the other hand, the addition of acetic acid into casting solution promoted the spinodal demixing of the membrane-forming system and suppressed the macrovoid formation in the membrane. Nodular structure was formed in the fiber skin layer. With the increase of acetic acid ratio, the pure water flux of the membrane increased about four times, and the solute retention showed a slight decrease. The mechanical properties could also be improved slightly by this additive. The influences of PEI dope concentration on membrane morphologies and properties were also studied. It was found that tighter structure was formed for higher PEI concentration, in turn, the pure water flux of the membrane decreased from 23.4 l/(m 2 h) 100 kPa for 17 wt.% PEI concentration to 7.2 l/(m 2 h) 100 kPa for 25 wt.% PEI concentration. The thermal resistance of the PEI ultrafiltration membranes prepared in this work was examined using a hot water treatment up to 80 °C. No change was observed for the permeation performances of the membranes, while the study of mechanical properties showed that the elongation at break of the membrane decreased slightly.

Ultrafiltration hollow fiber membranes of sulfonated polyetherimide/polyetherimide blends: preparation, morphologies and anti-fouling properties

Sulfonated polyetherimide/polyetherimide (SPEI/PEI) ultrafiltration (UF) hollow fiber membranes were prepared with phase inversion method and SPEI was used as a polymer additive. Scanning electron microscope (SEM) study revealed that the addition of SPEI could induce the formation of nodular structure and suppress the formation of finger-like macrovoids. With the increase of air gap distance, it was found that the micropores were formed in the outer fiber surface and the pore size increased accordingly. On the other hand, the pure water flux of the membrane reached a maximum and then decreased while the solute retention decreased at first and leveled off at longer air gap. Through bovine serum albumin (BSA) solution filtration test, it was found that the use of SPEI in the blend membranes increased its hydrophilicity. When SPEI with ion exchange capacity (IEC) of 2.88 mmol/g was blended with PEI by 15/85 weight ratio, 75% of the membrane flux reduction in the BSA solution (pH=8.0) filtration process was caused by reversible BSA adsorption, compared with 32% for PEI membrane. Increasing the pH value of the BSA solution, the membrane fouling tendency reduced and the reversible flux reduction ratio increased.

Surface morphology and nodule formation mechanism of cellulose acetate membranes by atomic force microscopy

AbstractBy the use of atomic force microscopy (AFM), formation mechanism of nodular structure in cellulose acetate membranes was systematically investigated. Elementary factors affecting the nodule formation were delineated on the basis of both kinetic and thermodynamic considerations. It was shown that (1) the exact nature of nodular structure is thermodynamic equilibrium glassy state; nodular structure will vanish in the rubbery state; (2) the thermodynamic factor affecting nodule formation is the membrane formation temperature; with the membrane formation temperature decreasing, more chain segments are able to form nodular structures; (3) nodule formation is dependent on the segment rearrangement; variation of the solvent environment is the major kinetic factor affecting the segment rearrangement and nodule formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1328–1335, 2003

Atomic force microscopy of cellulose membranes prepared from the N‐methylmorpholine‐N‐oxide/water solvent system

AbstractCellulose membranes were obtained by solutions of cellulose being cast into a mixture of N‐methylmorpholine‐N‐oxide (NMMO) and water under different processing conditions. Atomic force microscopy (AFM) was used to investigate the surface structures of the membranes. The AFM method provided information on both the size and shape of the pores on the surface, as well as the roughness of the skin, through a computerized analysis of AFM micrographs. The results obtained showed that the surface morphologies were intrinsically associated with the permeation properties. For the cellulose membranes, increasing the NMMO concentration and the temperature of the coagulation bath led to higher fluxes and lower bovine serum albumin rejection. These were always correlated with higher values of the roughness parameters and larger pore sizes of the membrane surfaces. When the cellulose concentration of the casting solution was 11 wt %, the membrane showed a nodular structure with interconnected cavity channels between the agglomerated nodules. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3389–3395, 2002

Polyetherimide/dicyanate semi-interpenetrating polymer networks having a morphology spectrum

The morphology, dynamic mechanical behavior and fracture behavior of polyetherimide (PEI)/dicyanate semi-interpenetrating polymer networks (semi-IPNs) with a morphology spectrum were analyzed. To obtain the morphology spectrum, we dispersed PEI particles in the precured dicyanate resin containing 300 ppm of zinc stear- ate catalyst. The semi-IPNs exhibited a morphology spectrum, which consisted of nodular spinodal structure, dual- phase morphology, and sea-island type morphology, in the radial direction of each dispersed PEI particle due to the concentration gradient developed by restricted dissolution and diffusion of the PEI particles during the curing process of the dicyanate resin. Analysis of the dynamic mechanical data obtained by the semi-IPNs demon- strated that the transition of the PEI-rich phase was shifted toward higher temperature as well as becoming broader because of the gradient structure. The semi-IPNs with the morphology spectrum showed improved fracture energy of 0.3 kJ/m 2 , which was 1.4 times that of the IPNs having sea-island type morphology. It was found that the partially introduced nodular structure played a crucial role in the enhancement of the fracture resistance of the semi-IPNs.

Reactions of Aromatic Phosphate Esters with Metals and Their Oxides

Previous results obtained in this laboratory have shown that tricresyl phosphate vapors preferentially react with iron and its oxides in the order of the oxidation state (reaction rate of Fe3+≫Fe2+>Fe+>Fe). The reaction kinetics is attributed to a Lewis acid, FenOm, reacting with the basic phosphate ester, (ArO)3PO. The current research further investigates the role of the oxide in the reaction of the aryl phosphate lubricants, tricresyl phosphate and tertiary-butyl phenyl phosphate, with 1010 steel coupons. To measure the relative effect of iron oxides, some coupons were exposed to 400 °C air for 1 h and then sealed under vacuum in glass tubes with 25 mg of lubricant. Other samples were sealed under vacuum without the oxidation step. All of the sealed test tubes with lubricant and foil were heated to a temperature of 475 °C and held for different lengths of time. Afterwards, the coupons were analyzed with Fourier infrared microscopy, Auger electron spectroscopy, Raman spectroscopy, and scanning electron microscopy. In the case of the pre-oxidized sample, a nodular film was formed that contained organic species and iron polyphosphate. For samples that were not pre-oxidized, simple ionic iron phosphate was formed. In another work it was found that nodular structure formation is important to obtain good lubrication. This type of film forms on iron surfaces and not on surfaces passivated by inert oxide films, i.e., aluminum, nickel, and high chrome content alloys. The reaction of tricresyl phosphate with other metals and their oxides were also examined and found to correlate well with iron.

Analysis of blends of poly(styrene‐co‐acrylonitrile) with an epoxy/aromatic amine resin using scanning thermal microscopy

AbstractUsing a microthermal analyzer TA Instruments 2990 μTA, we have analyzed the morphologies developed for the resin tetraglycidyl‐4,4′‐diaminodiphenylmethane cured with an aromatic amine 4,4′‐diaminodiphenylsulphone modified with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic. The phase‐separation phenomenon induced by polymerization was also followed by scanning electron microscopy. Using the modulated local thermal‐analysis mode of μTA, the glass‐transition temperatures of different domains for each sample were evaluated. Dynamic mechanical analyzer experiments were made to evaluate the macroscopic thermal properties of the blends. A morphology was well established for all blends examined with these techniques showing a nodular structure, the epoxy‐rich phase, and a continuous phase, the SAN‐rich phase, that forms the matrix. From both microscopic and macroscopic thermal analyses, it is concluded that a phase separation exists for the blends investigated. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 284–289, 2002

Microstructure evolution of electroless Ni–P and Ni–Cu–P deposits on Cu in the presence of additives

The microstructures of electroless Ni–P and Ni–Cu–P deposits were investigated in the presence of thiourea and saccharin with AFM. The phosphorus contents and crystallinity of the deposits were investigated. Saccharin was found to refine the nodular structure of the Ni–Cu–P deposit, while not affecting the P% of the Ni–P and Ni–Cu–P deposits. On the other hand, thiourea was found to affect the P% and surface roughness of the Ni–P deposit. Thiourea does not exhibit nodular refining effect on the deposit.

Influence of the electropolymerisation time on the nucleation mechanism, structure and morphology of polyfurane/perchlorate doped films

The influence of electropolymerisation time, t p, on the synthesis, structure and morphology of polyfurane films doped with perchlorate anions, PFu/ClO 4, was analysed. The analysis of the nucleation mechanism revealed a mixture of progressive and instantaneous nucleation of small hemispherical nodules controlled by spherical diffusion. The morphological study revealed an ordered nodular structure and different levels of growth from the first seconds of synthesis untill higher t p values. Dendritic formations on the growth face and the cross-section pores implied alternating planar and normal growth of the films. FTIR spectra study verified that the structure of these polymers was influenced by t p, so that the film aromaticity differed according to this parameter.

Performance of a novel Ni/Nb cathode material for molten carbonate fuel cells (MCFC)

In this work the performance of NiO and a novel cathode material preoxidized nickel–niobium alloy were investigated. It is found that under a cathode atmosphere of p(CO2)/p(O2) = 0.67 atm/0.33 atm, the equilibrium solubility of nickel ions in (Li0.62, K0.38)2CO3 melt at 650 °C is about 17 ppm for the nickel oxide electrode and 8 ppm for the preoxidized nickel–niobium alloy electrode. The improvement in the stability of material in the melt may be attributed to the formation of a more dense nodular structure for the nickel–niobium alloy electrode when compared with a Ni electrode during preoxidation. The formation of a dense nodular structure for the nickel–niobium alloy electrode depresses the dissolution of NiO from the electrode into the carbonate melt and, accordingly, enhances the stability of the electrode material in the melt. The polarization performance of the NiO cathode was improved by electrodeposition of niobium. As far as the thermal stability and the polarization performance are concerned, the preoxidized nickel–niobium alloy can be considered as a candidate for the cathode material of MCFCs.

Influence of synthesis conditions on the morphology of perchlorate doped polyfuran films

Polyfuran films doped with perchlorate anions (PFu/ClO 4 ) were studied by scanning and transmission electron microscopies under different synthesis conditions. However, an electropolymerization overpotential equal to at least 2.1 V was needed to obtain stable PFu/ClO 4 films. In the synthesis conditions analysed, the film growth face presented an ordered nodular structure oriented 45 ° with respect to the lengthwise axis of the electrode. The nodule size and film rugosity were affected by the ratios between furan and NaClO 4 concentrations. When the furan concentration was double that of perchlorate, the films were less rough and more homogeneous.

UV–ozone induced growth of a SiO x surface layer on a cross-linked polysiloxane film: characterization and gas separation properties

A thin SiO x surface layer was formed on porous Nylon ® membranes coated with a cross-linked polysiloxane by exposure to ultraviolet light at room temperature in the presence of atmospheric oxygen. The transformation of the cross-linked polysiloxane to SiO x was monitored by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR-IR), contact angle analysis and atomic force microscopy (AFM). A continuous surface layer of SiO x formed after about 1 h of UV exposure. AFM analysis revealed that a nodular structure with a characteristic size less than 0.5 nm formed after extended UV exposure. Gas permeation measurements on the composite membranes documented interesting gas separation properties: the CO 2 permeance of the cross-linked polysiloxane/Nylon ® composite membrane before irradiation was 8.9×10 −8 mol m −2 s −1 Pa −1, and the CO 2/N 2 selectivity was 22; after UV–ozone induced formation of the SiO x surface layer, the permeance decreased to 5.1×10 −8 mol m −2 s −1 Pa −1 while the selectivity for CO 2/N 2 increased to 48.

Morphological and phytochemical features of secretory structures in Hypericum richeri (Clusiaceae)

Structural and complementary chemical studies were carried out on Hypericum richeri, a lesser known species amongst those reported for folk medical use. We found only one type of secretory glands consisting of black dots which are present even in early emerging leaves. In the fully expanded leaves the nodular structure appears to be composed by a cluster of cells. These become unfunctional and disassembled towards the end of their development, and are used only as reservoirs of secretion products. HPTLC analyses showed that flower buds and flowers are the plant parts richest in active compounds. However, the spectrum of active compounds accumulated by H. richeri was both quantitatively and qualitatively similar to those reported for the pharmaceutically utilized, H. perforatum, and thus could potentially represent a possible alternative to this species.

Polyether‐segmented nylon hemodialysis membrane. VII. Studies on surface structures of various poly(ethylene oxide)‐segmented nylon membranes

The relationships of the surface morphologies to the surface chemical compositions in poly(ethylene oxide)-segmented nylon (PEO–Ny) membranes prepared by the phase-inversion method were studied using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and static secondary ion mass spectrometry (SSIMS). The PEO–Ny's used were high semicrystalline PEO-segmented polyiminosebacoyliminohexamethylene (PEO–Ny610), low semicrystalline PEO-segmented poly(iminosebacoylimino-m-xylylene) (PEO–NyM10), and amorphous PEO- segmented poly(iminoisophthaloyliminomethylene-1,3-cyclohexylenemethylene) (PEO–NyBI). SEM observation showed that the surfaces of the PEO–Ny610 and PEO–NyM10 membranes were composed of crystalline spherulite and that the PEO–NyBI membrane surface had a nodular structure. ESCA analysis exhibited the enrichment of the PEO segment at the surfaces of the PEO–Ny610 and PEO–NyM10 membranes. On the other hand, the enrichment of the Ny segment was observed in the case of the PEO–NyBI membrane. SSIMS analysis revealed that the outermost surfaces of the PEO–Ny membranes except the PEO–NyBI membrane were almost covered with the PEO segment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 517–528, 2000

Structure Formation of Isotactic Polypropylene from the Glass

The structure formation process of isotactic polypropylene (itPP) from the glass into the “smectic” mesophase has been studied by small-angle x-ray scattering, wide-angle x-ray scattering and differential scanning calorimetry. The structure of the smectic phase was unaltered during the transition process, which indicates no spinodal decomposition process is present in the formation of the smectic phase from the supercooled melt in itPP. The long period of the nodular structure was 5 nm to 6 nm independent of annealing temperature lower than -15°C. The glass transition temperature increased by the formation of the smectic phase from -30°C to +1°C. The mechanism of structure formation is discussed and a possible model is proposed.

Polyether-segmented nylon hemodialysis membrane. VII. Studies on surface structures of various poly(ethylene oxide)-segmented nylon membranes

The relationships of the surface morphologies to the surface chemical compositions in poly(ethylene oxide)-segmented nylon (PEO–Ny) membranes prepared by the phase-inversion method were studied using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and static secondary ion mass spectrometry (SSIMS). The PEO–Ny's used were high semicrystalline PEO-segmented polyiminosebacoyliminohexamethylene (PEO–Ny610), low semicrystalline PEO-segmented poly(iminosebacoylimino-m-xylylene) (PEO–NyM10), and amorphous PEO- segmented poly(iminoisophthaloyliminomethylene-1,3-cyclohexylenemethylene) (PEO–NyBI). SEM observation showed that the surfaces of the PEO–Ny610 and PEO–NyM10 membranes were composed of crystalline spherulite and that the PEO–NyBI membrane surface had a nodular structure. ESCA analysis exhibited the enrichment of the PEO segment at the surfaces of the PEO–Ny610 and PEO–NyM10 membranes. On the other hand, the enrichment of the Ny segment was observed in the case of the PEO–NyBI membrane. SSIMS analysis revealed that the outermost surfaces of the PEO–Ny membranes except the PEO–NyBI membrane were almost covered with the PEO segment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 517–528, 2000

Extraction of Quantitative Three-Dimensional Information from Ultrasonic Volumetric Images of Cirrhotic Liver

The cirrhotic liver has many fibrotic tissue structures known as nodule structures. Understanding this characteristic in diseased tissue is important for quantitative diagnosis. In this paper, we present a technique to extract quantitative three-dimensional information from a cirrhotic liver. Consecutive two-dimensional images acquired by fan like scanning were processed using constant false alarm rate (CFAR). The 2D processed images are accumulated to obtain 3D information. The nodular structure is clear in the constructed images.

Dynamic mechanical modeling of PEI/dicyanate semi‐IPNs

AbstractThe dynamic mechanical behavior of polyetherimide(PEI)/dicyanate semi‐interpenetrating polymer networks (semi‐IPNs) was analyzed by using the conventional Takayanagi model for the sea‐island morphology (PEI content of 10% or below) and a polyhedron model, which we developed for the dicyanate nodular structure (PEI content of 20% or above). The model parameters for the Takayanagi model were determined by the volume fraction of the PEI dispersed phase and Kerner's equation, while the model parameters for the polyhedron model were simply calculated by introducing a phase continuity factor. Both models correlate well with the morphology revealed in the micrographs except near the transition temperature of the PEI‐rich phase. The additional shift toward higher temperature found in the nodular structure was due to the intermixed phase composition, and the effect was quantified by measuring the calorimetric transition temperature. The dynamic mechanical modeling for the dual‐phase morphology (PEI content of 15%) and for the semi‐IPNs showing a morphology spectrum were also successfully accomplished by combining the Takayanagi model and the polyhedron model.