Crystal Fiber Structure Research Articles

Research on Improving the Pre‐Oxidation Process of the Excellent Mechanical Strength Carbon Fiber

AbstractThis study uses synchrotron wide‐angle X‐ray diffraction (WAXD) and synchrotron small angle X‐ray scattering (SAXS) to carry out an in situ study of the pre‐oxidation process of polyacrylonitrile (PAN) fibers with two different preparation processes. Through analysis of 2D WAXD/SAXS data, this study divides the evolution of PAN fiber's crystal and microporous structures during pre‐oxidation into three and two stages, respectively. The evolution of PAN fiber's crystal structure during pre‐oxidation can be divided into three stages: 1) Initial stage: small‐sized crystals melt, crystal orientation decreases, and no cyclization reactions occur. 2) Intermediate stage: cyclization reactions happen in the amorphous region, leading to increased crystal size, crystal orientation, and crystallinity. 3) Final stage: cyclization reactions occur in the crystal region, resulting in reduced crystal size and orientation. The evolution of microporous structure can be divided into two stages: microporous shrinkage stage and microporous expansion stage. These features are analyzed using 2D WAXD/SAXS techniques. This study provides valuable references and guidance for the industrial production of PAN fibers by exploring the mechanism of the pre‐oxidation process in‐depth.

Localized Surface Plasmon Resonance based Photonic Crystal Fiber for Cadmium Detection

In this work, fabrication of Localized Surface Plasmon Resonance based fiber optic sensing probe for cadmium detection in an aqueous solution is reported. Multimode fiber-photonic crystal fiber-multimode fiber structure coated with gold nanoparticles make up this probe. The proposed sensor's sensitivity is 1.564 nm/ppm. Furthermore, the sensor is small in size, immune to electromagnetic interference, making it ideal for a wide range of harsh environments and real-time measurement.

Multi-Core Surface Plasmon Resonance Refractive Index Sensor on Photonic Crystal Fiber

In this research work, low refractive index (RI) detection done on multi-core photonic crystal fiber (PCF) based highly sensitive surface plasmon resonance (SPR) sensor is propounded. Sensing the changes in neighboring medium’s refractive index is done by placing the plasmonic material i.e. Silver (Ag) over the crystal structure of fiber. On top of the Silver, a threadlike film of titanium dioxide (TiO2) is deposited to prevent oxidation of plasmonic material silver. Peak wavelength sensitivity thus achieved by this sensor is 127,600 nm/RIU and similarly, peak amplitude sensitivity achieved is 2561 RIU-1, respectively. Subsequently making this sensor suitable candidate for various applications such as biosensing, sensing organic compounds and chemicals, inspecting pharmaceuticals and other detections.

Single-Crystalline Fibers of Deuterated Potassium Dihydrogen Phosphate

Single-crystalline fibers have distinct structures and optical properties comparing with the bulk crystals. In this article, two types of single-crystalline fibers of deuterated potassium dihydrogen phosphate (K(H1−xDx)2PO4, DKDP) are obtained by rapid growth in room-temperature supersaturated solution. X-ray diffraction analysis reveals that these DKDP single-crystalline fibers belong to tetragonal (I-42d) and monoclinic (P21/c) phases, respectively. The crystal structure of the tetragonal DKDP single-crystalline fiber is identical to that of the bulk DKDP tetragonal crystal reported. The lattice parameters of the monoclinic DKDP fiber (with the deuterium content of 55%) are a = 14.6571 Å, b = 4.5187 Å, c = 18.6962 Å, and β = 108.030°, which is a new crystal phase of DKDP. The monoclinic DKDP single-crystalline fiber is metastable at the present experimental condition and readily transit to the corresponding DKDP tetragonal phase in solution and in solid by grinding. The optical experiment shows that the highly deuterated tetragonal DKDP single-crystalline fiber possesses excellent optical guided-wave and effective second-harmonic generation properties. DKDP single-crystalline fibers are expected to be the suitable candidates for fabrication of the miniaturized nonlinear optical devices.

Effects of Combined Acid-alkali and Heat Treatment on the Physiochemical Structure of Moso Bamboo

To improve the performance of bamboo and increase its utilization value, this study aimed at investigating the effects of impregnation pretreatment and thermal treatment on the structural changes of bamboo. The samples were pretreated in sodium hydroxide or zinc chloride solution, and then treated at 160 °C. The pretreated and control samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), and Fourier transform infrared spectroscopy (FTIR). The results showed that the cellulose crystallinity and intensity of samples pretreated by ZnCl2 could be reduced, but the crystal structure remained the same. As for samples pretreated in NaOH, the crystal structure of fiber was destroyed and the crystallinity was increased significantly. High temperature treatment has little effect on the thermal stability of bamboo. However, after treatment with NaOH and ZnCl2, the thermal degradation temperature changed obviously and moved to a lower temperature. ZnCl2 pretreatment had influence on the chemical structure of bamboo, while NaOH pretreatment had greater influence on the chemical structure of bamboo.

Сравнительный структурно-динамический анализ ультратонких волокон поли-(3-гидроксибутирата), модифицированного комплексами тетрафенилпорфирина с металлами

Проведены комплексные исследования, сочетающие рентгеноструктурный анализ, термофизические, динамические измерения зондовым методом и сканирующую электронную микроскопию. Рассмотрена особенность кристаллической и аморфной структуры ультратонких волокон на основе поли(3-гидроксибутирата) (ПГБ), содержащего минорные концентрации (0–5%) комплексов тетрафенилпорфирина (ТФП) с марганцем (в форме MnCl2 ), цинком и железом (в форме FeCl3 ). Показано, что при добавлении в волокна ПГБ указанных комплексов меняется морфология волокон, наблюдается изменение кристалличности и замедление молекулярной подвижности в плотных и рыхлых аморфных областях ПГБ в следующей последовательности: ПГБ/ТФП, ПГБ/Zn–ТФП, ПГБ/MnCl2 –ТФП, FeCl3 –ТФП. Температурное воздействие на волокна (их отжиг при 140°С) приводит к резкому росту кристалличности и молекулярной подвижности в аморфных областях волокон. Их экспозиция в водной среде при 70°С приводит к росту энтальпии плавления и замедлению молекулярной динамики только в исходном ПГБ, но к значительному снижению энтальпии в модифицированных волокнах. Молекулярная подвижность цепей в аморфных областях при этом возрастает. Полученные волокнистые материалы обладают бактерицидными свойствами и должны найти применение при создании новых терапевтических систем антибактериального и противоопухолевого действия.

Highly birefringent large mode area photonic crystal fiber-based sensor for interferometry applications

In this work, highly birefringent large mode area (LMA) photonic crystal fiber (PCF) structure for interferometric sensor applications is proposed. The effective mode area, birefringence and the sensitivity coefficient of the proposed PCF structure by employing the full vectorial finite element method (FV-FEM) have been thoroughly investigated. The numerical results have shown that proposed structure simultaneously offers high birefringence of order 10[Formula: see text], adequately LMA and high sensitivity for various liquid analytes by employing the elliptical liquid core holes.

Temperature-dependent bending loss characteristics of W-type photonic crystal fibres: design and analysis

The temperature-dependent bending loss characteristics of two solid-core W-typephotonic crystal fibres have been reported by employing full-vectorial finite element method. The bending loss characteristics of W-type-I photonic crystal fibrestructure have been found better than that of the W-type-II photonic crystal fibre structure. The proposed photonic crystal fibrestructures show significant nonlinearity and hence can be used in telecommunication and nonlinear applications such as visible to near-infrared supercontinuum generation. Macro-bend insensitive nature of the proposed photonic crystal fibres makes them suitable candidates for fibre-to-the-home applications.

Effects of Silane Debonder on the Properties of Fluff Pulp and the Study of Relevant Mechanism

The influence of silane debonder on the properties of fluff pulp fibers was investigated. The results showed that the burst index and internal bond strength of pulp sheet decreased with the increasing debonder loading. The density and zero-span tensile strength didn't change significantly when the debonder was added. The absorption capacity of fiber increased with increasing the de-bonder loading and achieved a maximum value of 10.3 g·g-1 when the debonder loading was 2.5%. The relevant mechanism was studied by X-ray Diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and energy dispersive X-ray analysis (EDAX). XRD analysis indicated that the debonder had no great influence on the crystal structure of fiber. FT-IR analysis results showed that it was easier to break the intermolecular hydrogen bond than the intramolecular hydrogen bond with the incorporation of debonder. Therefore, the proportion of intramolecular hydrogen was increased. The EDAX results indicated that the debonder can decrease the binding force of fiber by shielding the hydroxyl groups and preventing the formation of hydrogen bonds.

PVP-Assisted Sb-Doped SnO<sub>2</sub> Nanofibers Synthesized by Electrospinning Process

Well-defined Sb-doped tin oxide (ATO) nanofibers were synthesized by electrospinning technique. Polyvinylpyrrolidone (PVP), SnCl4·5H2O and SbCl3 were chosen as suitable precursors for preparing ATO nanofibers. All of precursors were homogeneously dissolved with the mixture solvent of dimethylformamide (DMF) and absolute ethanol. Electrospinning process was carried out at applied voltage of 10 kV and distance between needle tip to aluminium foil collector was fixed at 10 cm. The injection rate of precursor solution was controlled at 0.5 ml/hr. The as-spun nanofibers were calcined at 600°C with heating rate of 5 °C/min in order to remove the PVP template and improve the crystallinity of ATO structure. Effect of Sb doping concentration on their crystal structure was investigated. The morphology and crystal structure of the electrospun fibers were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). In this work, the obtained ATO nanofibers had average range diameter from 150 to 350 nm with rough surface. Sb doping concentration in ATO nanofibers plays a key role on their network morphology. The excellent doping concentration of Sb that offered the continuous fibrous and porous ATO nanofibers was 7%.

Dark Plasmon-Solitons in Plasmonic Photonic Crystal Fiber Induced by Thermo-Modulational Nonlinearity of Metal

In this paper, formation of dark plasmon-soliton in a plasmonic photonic crystal fiber (PPCF) structure is predicted and analyzed by the use of the generalized nonlinear Schrodinger equation (GNLSE). Linear analysis of the plasmonic guided modes in the proposed structure offers a lower attenuation and dispersion values compared with the conventional core metallic fiber. Kerr coefficient of the silica background and the thermo-modulational nonlinearity of the gold are considered as the origins of nonlinear behavior. A delicate balance between normal dispersion and nonlinear characteristics of the structure provides the necessary condition for the formation of dark plasmon-soliton. Moreover, the thermo-modulational nonlinearity of metal is accompanied by the delayed propagation of the guided modes which is well justified throughout the simulations. Undistorted and time-delayed propagation of solitary plasmonic modes is a key point for the potential applications in the future all-optical devices, sensing platforms, and frequency conversion.

Structure and Properties of In-Situ Reactive Compatibilized Polypropylene/Poly (Butyl Methacrylate-Co-Hydroxyethyl Methacrylate) Blend Fibers

In this study, in-situ compatibilized polymer blends of polypropylene (PP) and poly (butyl methacrylate-co-hydroxyethyl methacrylate) P(BMA-co-HEMA) were prepared in a corotating twin screw extruder through the reactive extrusion of mixtures of PP, P(BMA-co-HEMA), butyl methacrylate, and benzoyl peroxide. In the process of reactive extrusion, butyl methacrylate and benzoyl peroxide were used as the monomer and the initiator, respectively. Thereafter the polymer blend was made into fibers via melt spinning. The miscibility of PP and P(BMA-co-HEMA) in the blend fibers was investigated using field emission scanning electron microscopy. The absorption percentage of the blend fibers for organic liquids and their remaining ratios after the absorption tests were also determined and used to prove the generation of the third phase. The changes in the fiber morphology during organic liquid absorption were observed using polarized light microscopy. In addition, the effect of the miscibility on the crystal structure and melting characteristic of the blend fibers were analyzed using wide-angle X-ray diffractometry and differential scanning calorimetry. Finally, the thermal stability of the blend fibers that was associated with the miscibility of PP and P(BMA-co-HEMA) in the blend fibers were characterized by using thermogravimetry and dynamic thermomechanical analysis.

Preparation and photoelectric properties of indium tin oxide depositional optical fiber by centrifugal spinning

The purpose of this paper is to prepare an integrating light propagative, transparent and conductive optical fiber. This optical fiber is made by the coating of a thin layer of indium tin oxide (ITO) nanofibers. ITO nanofibers are fabricated via centrifugal spinning process and wrap around the quartz optical fiber. Field emission scanning electron microscopy, X-ray diffraction analysis, UV–Vis spectrophotometer, Avometer and Luminance colorimeter are used to characterize the morphology, crystal structure and photoelectric properties of ITO-coated optical fiber. Results show that the resistivity of ITO-coated optical fiber is around 0.87 (Ω cm); the average optical transmittance is more than 85 % in the visible range, and the ITO-coated optical fiber has a certain light propagation. This work laid the groundwork for future application in fiber sensors.

Structure and Properties of Hydrolyzed Cyclization-Crosslinking Flame-Retardant Polyacrylonitrile Fiber

As flame-retardant Polyacrylonitrile (PAN) fibers was one of the most important differential fibers, it was of great importance to make research on the modification of flame-retardant PAN fibers to improve its characteristics. In this present study, the flame-retardant PAN fiber with good moisture absorption and mechanical properties has been prepared treated by blending solution of sodium hydroxide and hydrazine hydrate. FTIR spectra presented that new amide and cyclization-crosslinking pyridine group band peaks appeared. X-ray diffraction showed that the crystal structure of PAN fibers has been converted from quasi-crystalline structure into partially crystallized structure after modification treatment. SEM micrographs indicated that the original longitudinal surface microgroove has changed to layered structure by surficial etchant.

Preparation and characterization of large diameter pitchbased carbon fiber/ABS resin composites with high thermal conductivities

Parallel, stretched and evenly arranged mesophase pitch based graphitized carbon fibers with diameters of 50–53 μm were coated with different amounts of acrylonitrile butadiene styrene (ABS) resin, and hot-pressed to produce carbon fiber/ABS resin composites. The morphology, optical texture and crystal structure of the carbon fibers and their composites were characterized by scanning electron microscopy, polarized light microscopy and X-ray diffraction. The influence of the graphitization temperature and fiber content on the thermal conductivity of the composites was investigated. The thermal diffusivity and thermal conductivity of the composites along both fiber axial and radial directions showed an obvious difference, owing to the high orientation of the graphite crystals along the axial direction of the carbon fibers. The thermal diffusivity of the composites along the carbon fiber axial direction increased both with the graphitization temperature and fiber content. The composite with 54 vol.% carbon fibers graphitized at 2900 °C showed the highest thermal conductivity. [New Carbon Materials 2015, 30(1): 63–70]

Design of Ultra-Low Loss Highly Nonlinear Dispersion Flattened Octagonal Photonic Crystal Fibers

In this study, Octagonal Photonic Crystal Fiber (O-PCF) structures are designed for different air filling fractions with fixed pitch length of 2.2 μm. The light propagating characteristics of PCF structures such as effective refractive index, confinement loss, chromatic dispersion mode effective area and nonlinear coefficient are numerically analyzed. The simulation results show that the fibers have dispersion flattened, ultra-low loss highly nonlinear nature in the wavelength region 1.3 μm to 1.7 μm.

Preparation and Luminescence Properties of Rare Earth Magnesium Strontium Silicate Luminescent Fiber

The polypropylene luminescent fiber containing Sr2MgSi2O7: Eu2+, Dy3+ phosphors was prepared by melt-spinning method. Crystal phase structure, spectral features and afterglow properties of the luminescent fiber were tested and analyzed. The results show that the fiber has independent superposition phase features of both Sr2MgSi2O7: Eu2+, Dy3+ and polypropylene; the range of its excitation light wavelength locates among 250~450 nm; it can emit blue light of 460 nm wavelength; its initial luminescent intensity is more than 600 mcd/m2, and afterglow time lasts 7 h; the process of afterglow decay consists of fast stage and slow stage.

Crystal Structure Analysis on Aramid Fiber/Fibrids and Paper by Polarized Light Microscopy

The crystal structure of aramid fibers is highly orientated. The structure of aramid fibers with various manufacturing processes and aramid paper sheets were analyzed and observed by using polarized light microscope (PLM). The change and its law of aramid fiber crystal structure in such processes as aramid fiber mamufaturing of aramid fiber/fibrids, forming of aramid paper sheets, and heat treatment were analysed. The relationship between the structural feature of aramid fibers and the performance of aramid paper was also discussed.

Facile fabrication of conductive ultrahigh molecular weight polyethylene fibers via mussel‐inspired deposition

AbstractThe conductive ultrahigh molecular weight polyethylene fibers are fabricated by electroless silver plating. The extremely inert and smooth surfaces of fibers are first activated by dopamine self‐polymerization. Then, metallic silver layers are deposited on the surface via electroless silver plating. The chemical composition, surface topography, and crystal structure of fibers are studied by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy, and X‐ray diffraction (XRD), respectively. The XPS spectra certify the existence of polydopamine layer on surface. The XPS spectra and the XRD spectra prove that the silver particles deposited on the surface are pure in zero‐value state and of high crystallinity. The resistance of the silver‐coated fibers is 0.15 Ω/cm per bundle measured by two‐point method. These conductive fibers with high conductivity are expected to use as the electrical wires. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Study on Structure and Properties of Polyacrylonitrile Fiber Modified by Hydrazine Hydrate

In this study, the flame-retardant PAN fiber with good moisture absorption, good mechanical properties and better thermal properties has been prepared by blending solution of sodium hydroxide and hydrazine hydrate. FTIR spectra presented that new amide and cyclization-crosslinked pyridine group band peaks appeared. X-ray diffraction showed that the the crystal structure of PAN fibers has been converted from quasicrystalline structure into partially crystallized structure after modification treatment. SEM micrographs indicated that the original longitudinal surface microgroove has changed to layered structure by surfical etchant.