Amorphous Fibers Research Articles

Synthesis of amorphous carbon fiber from a new organosilicon precursor

Synthesis of amorphous carbon fiber with atomic scale dispersed silicon was investigated. An organosilicon precursor (MSP), which was developed as heat resistant plastics in recent years, was used as a precursor. Temperature control during the melt-spinning was important in order to tailor precursor fibers having thin diameters. For the fiber curing, γ-ray irradiation previous to pyrolysis in an O2 atmosphere was available. The effect of irradiation on the MSP fiber was investigated with mass change, FT-IR and SEM observation after pyrolysis. During the irradiation, oxygen was introduced in the fiber in proportion to the total dose, but the irradiation curing formed microscopic defects on the fiber surfaces at the same time which limited the resultant fiber strength.

What Is the Most Transparent Polymer?

The development of polymer optical fiber (POF) leads to the fundamental question about the transmission loss limit of amorphous polymer glasses. The two important intrinsic loss factors in amorphous polymer optical fibers are molecular vibration absorption and scattering due to fluctuation. In this paper, we have investigated the lower limit of the inherent light transmission loss of amorphous polymer glass from its molecular structure by using the Morse potential theory for absorption and the fluctuation theory for scattering. The theoretical lower limit of the attenuation of the amorphous perfluoropolymer is 0.3 dB km-1 at 1.3 μm, and is comparable with that of silica fiber. Amorphous perfluoropolymer seems to be a most transparent polymer.

Synthesis of silicon nitride fibers from ferrosilicon

Silicon nitride occurs in two crystalline forms: α-Si3N4 and β-Si3N4 and as amorphous material. There is a current interest in making silicon nitride fibers with a high tensile strength for use in composite materials especially, at high temperature (≈1400 ◦C) and in various atmospheres. Chollon et al. [1, 2] have recently produced amorphous silicon nitride (oxide) fibers from a starting mixture of amorphous silica and titanium powders spread over a silicon carbide substrate. The resulting fibers had a diameter of 1–6 μm and an average strength of 2.38 GPa. However, they contained about 11 (at.%) oxygen which is present not as free silica but as an integral component in the silicon oxide nitride phase, hence this is a ternary phase material. Osendi and Miranzo [3] have prepared β-Si3N4 monocrystalline fibers by a self-propagating-high-temperature method (SHS). The fibers showed ribbon like aspects, but no oxygen analysis was given. A simple high temperature method for producing colorless and predominantly amorphous silicon nitride fibers with a very low oxygen content from relatively inexpensive ferrosilicon (FeSi) alloy has been discovered and is reported here. 3 g of ferrosilicon (FeSi) powder (−45 μm) was placed in an alumina crucible and introduced into the working tube of an electrically heated tube furnace. The tube was sealed with silicon bungs and connected to associated gas flow apparatus to allow ammonia to flow through the tube with a flow rate of 80 ml/min. The furnace was heated at a rate of 5 ◦C/min and the sample held at the independently measured temperature of 1370 ◦C for 24 h. This temperature was selected since it is just 40 ◦C below the melting point of FeSi. After cooling to room temperature (5 ◦C/min) the furnace was flushed with argon and the sample examined. A similar experiment was performed in which the sample was heated to the much lower temperature of 400 ◦C. Upon opening the end of the furnace working tube a highly expanded mat of very fine colorless fibers was found in and above the crucible. This mat had a pronounced rubbery texture such that the fibers were held intimately together with very little loose material. In the bottom of the crucible lay the remains of a grey powder with some evidence of partial fusion. By comparison, no reaction was evident from the experiment run at 400 ◦C. The fibers were removed, ground and analyzed by powder X-ray diffractometry using a Philips diffractometer PW1710 with Cu Kα1 radiation (λ= 1.54050 A). The diffraction pattern (Fig. 1) showed two very broad regions between approximately 20–40 and 60–80 ◦2θ which is characteristic of amorphous material and when integrated indicated that this is the major phase. The sharp diffraction peaks in the pattern all correspond to α-Si3N4 (ICDD card 41-360) which is present as the minor phase. No other material was detected. The fibers were analyzed by infra-red spectroscopy and comparison made with a silica glass reference material to see if they contained any silicon-oxygen bonds. Fig. 2 shows clearly the two large infra-red absorbance peaks for the silica glass (≈470 and≈1100 cm−1). The coincidence of the 1100 cm−1 peak with the Si3N4 sample does not exclude the presence of Si-O bonds in the silicon nitride sample, but the absence of the

The attachment structure of the guinea pig tympanic membrane

Objective: The attachment structure between the tympanic membrane and the surrounding structures, the annular ring and the manubrial part, has not been described fully. We examined the relationship between the tympanic membrane and the tympanic annulus or the handle of the malleus in guinea pigs using light microscopy as well as transmission and scanning electron microscopy (SEM). Methods: We used the temporal bone of the guinea pig and examined the relationship between the tympanic membrane and the surrounding structures using light microscopy and transmission electron microscopy. In the examination of scanning electron microscopy, we used the special method such as alkali–water maceration/SEM method. Results: The results showed that the radial fibers of the tympanic membrane continued directly into the annular ring and the manubrial part. The histological structure of the annular ring was amorphous and collagen fibers were seen in the amorphous matrix. The manubrial part histologically resembled the annular ring. These structures were associated with the cartilage structure. Our observations indicated that the collagen fibers of the tympanic membrane are a special type of cartilage collagen fibers. Conclusion: In conclusion, we propose that the surrounding structures of the tympanic membrane such as the tympanic annulus and manubrial part play an important role in the maintenance and the vibration of the tympanic membrane.

Automatic image analysis and morphology of fibre reinforced concrete

Automatic image analysis is an efficient tool to quantify the morphology of materials. Moreover, it can aid to understand their mechanical behaviour. Several applications of automatic methods are presented to investigate concrete reinforced by ribbon shaped amorphous cast iron fibres. Introducing ribbons into the plain matrix entrapped air voids. This affected the workability and, later on, the compressive strength of the fibre reinforced concrete (FRC). Both were improved by additions of superplasticizer in order to keep the water to cement ratio constant. The influence of the superplasticizer and fibre contents on the compactness of the FRC was characterized by the dimensional and the spatial distributions of the air voids. The orientations of fibres and microcracks were quantified by Fourier image transforms. Due to the casting procedure of the FRC, the fibres were located in “horizontal layers”, perpendicular to the casting axis. Whatever the direction of compression with respect to the layers of fibres, the microcrack network was getting more and more oriented in the direction of compression as stresses increased. The analysis of fibre and microcrack orientations suggests that, under uniaxial compression, the inelastic strain domain should be characterized by an anisotropic biaxial damage model, whose principal axes are the orthogonal and parallel directions to the layers of fibres.

High temperature erosion of fibrous ceramic components by solid particle impact

Low-density fibrous ceramic components (e.g., aluminosilicates) are widely used as insulating materials in boilers and furnaces. In practical applications the impact of hard particles such as ash or clinker may result in serious damage. The high temperature erosive wear of fibrous aluminosilicate ceramics has been studied to verify whether the mechanisms of damage change with temperature. The effects of temperature on erosive wear were examined with a gas-blast erosion rig and silica sand particles. For a vacuum-shaped board not subjected to an ageing heat treatment, a significant increase of erosion rate with temperature was observed, caused by the embrittlement of the initially amorphous fibres by mullite formation, which occurs rapidly at above 990°C. For materials previously aged for 1000 h at 1260°C, no variation of erosion with temperature was observed between 20 and 1000°C. It was concluded that erosion rates measured at room temperature for these materials can be used to predict erosion at temperatures up to ca. 1000°C.

Peripheral vascular resistances during total left heart bypass with an oscillated blood flow.

For development aimed at a totally implantable type ventricular assist device (VAD), the vibrating flow pump (VFP) has been developed at Tohoku University. A transcutaneous energy transmission system (TETS) using amorphous fibers was developed to power the totally implantable VAD system. The VFP works at a high frequency compared to that of a natural heart of a biological system. It is a frequency of 10-50 Hz. In this research, animal experiments with left heart bypass were carried out with healthy adult goats. For comparison between nonpulsatile flow and oscillated flow, a rotary pump (RP) and the VFP were used in the experiments. For the achievement of total left heart bypass, left ventricular approaches were carried out, and blood was pumped from the left ventricle to the descending aorta. Adequate support of the left heart was provided by both pumps. In terms of the results, the vascular resistances tended to decrease during the use of both pumps during 100% bypass driving. When we compared these pumps at the same flow rate, the resistances during RP driving were significantly smaller than those during VFP driving. These results may suggest that the influences of the VFP upon the peripheral vessels may be relatively small compared to those of the RP. This may be an important result when a stable hemodynamic condition is required during artificial circulation. The VFP was considered as a candidate for a totally implantable VAD as a result.

Δ E effect in amorphous microwires and fibres

The field dependence of the Young's modulus (Δ E effect) has been studied in amorphous microwires, with their glass cover and after glass removal, and magnetic fibres based on Fe. The study of the Δ E effect can provide valuable information about the domain structure and internal stresses in these samples. The different magnetization processes in this kind of small sized samples are also discussed.

Comparative study of the magnetic behavior of Co-rich amorphous fibers and amorphous glass-covered wires

Co-rich amorphous glass-covered wires and wires after glass removal with small magnetostriction are magnetically softer in the axial direction, while Co-rich amorphous fibers have better soft magnetic properties in the circumferential direction. The obtained results reveal the importance of intrinsic creep-induced anisotropy in such materials.

Metacarpophalangeal Arthroscopy

Summary: Although small joint arthroscopy has become commonplace over the past decade, relatively little attention has been paid to the investigation and clinical utility of metacarpophalangeal (MP) joint arthroscopy. The literature is scant in this area and consists of only a handful of case reports. In addition, the arthroscopic anatomy of the MP joint has not as yet been reported. Six cadaveric hands (24 joints) were rigorously studied in the laboratory using standard 2.5-mm small joint arthroscopic instrumentation and 5 lb of overhead traction. Radial and ulnar portals were used with care not to injure the extensor tendons. Arthroscopic anatomic landmarks include: (1) A consistent tripartite configuration of the main radial and ulnar collateral ligaments with characteristic changes in relative fiber orientation as the digit goes from extension to flexion, (2) nonvisualization of the accessory collateral ligament from inside the joint, (3) transitional amorphous capsular fibers connecting the collateral ligaments to the volar plate and dorsal capsule, (4) four synovial recesses (radial, ulnar, volar, and dorsal-proximal), (5) metacarpal head and proximal phalanx, (6) a consistent circumferential meniscal equivalent around the margin of the proximal phalanx articular surface, and (7) the sesamoid-metacarpal articulation in the thumb MP joint. There are published case reports on the utility of MP joint arthroscopy for synovectomy in rheumatoid arthritis and hemachromatosis and realigning Stener lesions in gamekeepers' thumbs. The current clinical series reveals preliminary experience with the technique. MP joint arthroscopy was useful in relieving a locked MP joint from a loose osteochondral body and sagittal tear in the volar plate that enfolded into the joint surface. Intra-articular release of post-traumatic volar plate and dorsal capsular contracture were readily accomplished using this technique. Juxta-articular bone lesions such as osteoid osteomas can be removed with careful preoperative planning. Gamekeeper's thumbs that are unstable on stress radiographs can undergo arthroscopy with excellent sensitivity to determine the presence of a Stener lesion before an open or arthroscopic repair. The advantages of arthroscopic versus open techniques are similar to those experienced in larger joints. With time, more indications will emerge. Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 15, No 3 (April), 1999: pp 333–337

An Amorphous Ceramic Fiber with Large Viscous Flow Deformation at 1193 K

An Al 31 Gd 9 O 60 ceramic continuous fiber with a fiber diameter of about 20 μm and an amorphous structure could be made successfully by using the melt extraction method. This ceramic continuous fiber can be freely shaped by viscous flow deformation in the supercooled liquid state (about 1193 K). similar to glass The ceramic continuous fiber strength is about 2 GPa and this strength is maintained up to around 973 K This amorphous ceramic is promising as a ceramic that can be easily shaped at relatively low temperatures (about 1193 K) in agreement with temperature range of superplastic processing of Ti alloys.

Damage mechanics applied to concrete reinforced with amorphous cast iron fibers, concrete subjected to compression

The evolution of damage in compression, due to microcracking, is investigated in concrete reinforced by amorphous cast iron fibers and compared to damage in non reinforced concrete whose workability and strength were similar. As microcracking is anisotropic, two damage variables are defined, d 1 in the orientation of compression and d 2 in a perpendicular orientation. Damage values are calculated as a function of the loss of stiffness measured during loading-unloading cycles. Since the fiber arrangement is 2D (isotropic transverse), it is shown that damage is delayed in a reinforced concrete stressed in an orientation perpendicular to the fibers. On the other hand, due to fiber/concrete debonding, damage is greater when the compression is applied in an orientation parallel to the fibers. The damage behavior of the non reinforced concrete is intermediate.

Fiber Crystal Growth From the Melt

1 What Do We Want With Fiber Crystals? An Introductory Overview.- 2 Fundamentals of Growth Dynamics of the ?-Pulling Down Method.- 3 Theoretical Analysis of the Micro-Pulling-Down Process.- 4 Practice of Micro Pulling Down Growth.- 5 Crystal-Chemistry and Fiber Crystal Growth of Optical Oxide Materials.- 6 Oxide Eutectic Crystals for High-Temperature Structural Application.- 7 Oxide Fiber Crystals Grown by ?-PD and LHPG Techniques.- 8 Growth of Micro and Bulk Crystals by Modified Micro-PD and their Properties.

The generation of magnetic bistability in annealed Fe-Si-B fibre by hydrogenation

The magnetically bistable nature of as-quenched amorphous fibre disappeared when the material underwent stress-relief annealing at for 30 min. A reduction of internal stress leading to a lowering of the magnetoelastic anisotropy was the cause of such a change from bistable to normal ferromagnetic behaviour. Cathodic hydrogen impregnation caused the re-appearance of magnetic bistability, the magnitude of which was dependent on the duration of hydrogen charging (and hence on the hydrogen concentration). Perfect bistability was restored when the annealed fibre was charged for 120 min at the charging current density of . Owing to the positive molar volume of hydrogen, internal stresses were generated by hydrogenation, which increased the size of the longitudinal anisotropy region. When this longitudinal anisotropy region was big enough to act as a monodomain at the core of the fibre, bistability with a large switching field was observed.

Hydrothermal degradation of chemical vapour deposited SiC fibres

The interaction of chemical vapour-deposited (CVD) SiC fibres with H2O at 200 MPa and 400–700°C (673–973K), was investigated. With increasing temperature and time, the smooth surface of the amorphous SiC fibre becomes rough and sponge-like. This modification can be controlled by adjusting temperature and duration of the hydrothermal treatment. CVD SiC dissolves in supercritical water in a first order reaction with Ea=150 kJ mol-1. According to thermodynamic calculations, the main products are SiO2, CH4 and H2. The formation of carbon is also predicted. Films of amorphous and graphitic carbon have been observed, but only small areas of the fibres were coated with carbon. Amorphous silica, quartz, cristobalite and keatite were deposited on the surface of fibres in larger quantities © 1998 Kluwer Academic Publishers

Assessment of fibre orientation in reinforced concrete using Fourier image transform.

In this study, ribbon-shaped amorphous cast-iron fibres were used to reinforce a concrete matrix. X-ray photographs have been taken to detect fibres in situ. Their orientation has been investigated by automatic image analysis methods. However, this measurement should not be influenced by the digitization on the square frame of the analyser. For that purpose, the Fourier transform was used rather than the rose of direction method. This analysis revealed the transverse isotropic nature of the spatial arrangement of these fibres, whose axis of revolution corresponds to the concrete casting axis. Such a morphological characterization of the fibre-reinforced concrete reveals its mechanical behaviour.

Left heart bypass using the oscillated blood flow with totally implantable vibrating flow pump.

Aiming at a totally implantable ventricular assist device (VAD), a vibrating flow pump (VFP) was developed in Tohoku University. A transcutaneous energy transmission system (TETS) using an amorphous fiber was developed for the totally implantable VAD system. The VFP works with a higher frequency than the natural heart of a biological system, a frequency of 10-50 Hz. In this research, animal experiments on left heart bypass were performed with healthy goats. Blood from the apex of the left ventricle was received and was sent to the aorta so that an adequate supporting effect of the left heart was provided. In particular, the depression effect of the left ventricle was obvious. As a result, sufficient artificial heart flow was provided. For a totally implantable type VAD, left heart bypass of almost 100% may become necessary in some situations. Therefore, apex approaches of left heart bypass may be desirable. From an anatomical consideration, an apex of the heart is suitable for the VFP of this totally implantable type. In the left heart bypass for which the apex of the heart was used, an almost 100% bypass was possible. This is a requirement that is important when waiting for recovery of sufficient cardiac function. It is also important that left heart circulation is maintained fully by an artificial heart of the complete implantation type. The VFP was considered to be useful as a totally implantable type artificial heart from the results.

Crystallization and solidification studies in calcia-alumina fibres formed via inviscid melt spinning (IMS)

Differential thermal analysis (DTA) is used to study solidification phenomena in 46.5 wt% CaO-53.5wt% Al 2O 3 (m.p. = 1392 °C) fibres formed via inviscid melt spinning (IMS). After an initial heating cycle at 20 °C min −1 in nitrogen to 1600 °C showing crystallization of the amorphous fibres, cooling curves indicate a solidification exotherm at 1403 °C, followed by two small exotherms, believed to be solidification of sub-solidus liquid. Subsequent heating cycles show no crystallization transformations, indicating near complete crystallization upon cooling between heating cycles. XRD results obtained after a final cooling step show two anhydrous calcium aluminate phases are present: CaAl 2O 4 and Ca 3Al 2O 6.

Synthesis and Thermogravimetric Analysis of Amorphous Boehmite Fibres

Amorphous fibres of boehmite OH—Al=O are synthesised using an electrochemical surface oxidation reaction of an amorphous Al plate in open air at room temperature. The microstructures of the samples, measured at selected periods of time of reaction, demonstrate a very rapid growth in the separated fibres with a highly exothermic reaction. Two broad haloes occur in the X-ray diffractogram of the sample, at scattering vectors k1 = 25.5 nm—1 and k2 = 6.3 nm—1, intrinsic to amorphous solids. Thermogravimetric analysis together with infrared studies determine the chemical composition of the sample to be AlO(OH) · xH2O, with x ≈︂ 0.25. The water in this example is hydrogen bonded with the AlO(OH) molecule in a particular fashion so that they form a correlated structure at molecular scale. As a result, its controlled thermal desorption at 320 to 350 K modifies the 2 AlO(OH) → Al2O3 + H2O thermal desorption transformation, which occurs at subsequently higher temperatures. The presence of the hydrogen bonding is clearly evidenced by a significantly modified (lowered) value for the symmetric or asymmetric stretching vibration frequency of the Al—OH=O group in the IR spectrum at 1022 or 1125 cm—1 in comparison to 1070 or 1150 cm—1 found for a gel derived boehmite sample. The OH functional group in the AlO(OH) molecule exhibits three characteristic vibration bands at ≈︂600, 1640 and 3460 cm—1.

Synthesis and Thermogravimetric Analysis of Amorphous Boehmite Fibres

Amorphous fibres of boehmite OH—Al=O are synthesised using an electrochemical surface oxidation reaction of an amorphous Al plate in open air at room temperature. The microstructures of the samples, measured at selected periods of time of reaction, demonstrate a very rapid growth in the separated fibres with a highly exothermic reaction. Two broad haloes occur in the X-ray diffractogram of the sample, at scattering vectors k1 = 25.5 nm—1 and k2 = 6.3 nm—1, intrinsic to amorphous solids. Thermogravimetric analysis together with infrared studies determine the chemical composition of the sample to be AlO(OH) · xH2O, with x ≈︂ 0.25. The water in this example is hydrogen bonded with the AlO(OH) molecule in a particular fashion so that they form a correlated structure at molecular scale. As a result, its controlled thermal desorption at 320 to 350 K modifies the 2 AlO(OH) → Al2O3 + H2O thermal desorption transformation, which occurs at subsequently higher temperatures. The presence of the hydrogen bonding is clearly evidenced by a significantly modified (lowered) value for the symmetric or asymmetric stretching vibration frequency of the Al—OH=O group in the IR spectrum at 1022 or 1125 cm—1 in comparison to 1070 or 1150 cm—1 found for a gel derived boehmite sample. The OH functional group in the AlO(OH) molecule exhibits three characteristic vibration bands at ≈︂600, 1640 and 3460 cm—1.