Strength, Structure, and Fracture Properties of Ceramic Fibers Produced from Polymeric Precursors: I, Base-Line Studies

ABSTRACTCeramics can be prepared by pyrolysis of organosilicon polymers. Advantages of this method of ceramics preparation are; the ability to prepare shapes difficult to achieve by other methods such as fibers and films; the ability to achieve high purity because reagents used to prepare the polymer can be purified by well established chemical methods; processing at lower temperature than conventional methods [2].

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A facile method to prepare ZrC ceramic fibers by centrifugal melt-spinning using zirconium-containing polymeric precursors

Materials Letters ◽

10.1016/j.matlet.2022.131693 ◽

2022 ◽

pp. 131693

Author(s):

Kai Wang ◽

Qingnan Meng ◽

Kang Zhao ◽

Xin Li ◽

Qian Bai ◽

...

Keyword(s):

Melt Spinning ◽

Ceramic Fibers ◽

Polymeric Precursors

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Development of Crystallinity in Turbostratic Boron Nitride Derived from Polymeric Precursors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089081 ◽

1991 ◽

Vol 49 ◽

pp. 954-955

Author(s):

X. Qiu ◽

A. K. Datye ◽

T. T. Borek ◽

R. T. Paine

Keyword(s):

Thermal Treatment ◽

Boron Nitride ◽

Diffraction Pattern ◽

Polymeric Precursors ◽

Polymer Precursors ◽

Diffuse Ring

Boron nitride derived from polymer precursors is of great interest for applications such as fibers, coatings and novel forms such as aerogels. The BN is prepared by the polymerization of functionalized borazine and thermal treatment in nitrogen at 1200°C. The BN powders obtained by this route are invariably trubostratic wherein the sheets of hexagonal BN are randomly oriented to yield the so-called turbostratic modification. Fib 1a and 1b show images of BN powder with the corresponding diffraction pattern in fig. 1c. The (0002) reflection from BN is seen as a diffuse ring with occational spots that come from crystals of BN such as those shown in fig. 1b. The (0002) lattice fringes of BN seen in these powders are the most characteristic indication of the crystallinity of the BN.

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Use of EDS mapping to characterize thermochemical stability of fibers in intermetallic matrix composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012120x ◽

1992 ◽

Vol 50 (1) ◽

pp. 160-161

Author(s):

John R. Porter

Keyword(s):

Spatial Information ◽

Beam Current ◽

Fiber Types ◽

Ceramic Fibers ◽

Dye Transfer ◽

Science Center ◽

Commercial Development ◽

Nih Image ◽

Intermetallic Matrix Composites ◽

Thermochemical Stability

New ceramic fibers, currently in various stages of commercial development, have been consolidated in intermetallic matrices such as γ-TiAl and FeAl. Fiber types include SiC, TiB2 and polycrystalline and single crystal Al2O3. This work required the development of techniques to characterize the thermochemical stability of these fibers in different matrices.SEM/EDS elemental mapping was used for this work. To obtain qualitative compositional/spatial information, the best realistically achievable counting statistics were required. We established that 128 × 128 maps, acquired with a 20 KeV accelerating voltage, 3 sec. live time per pixel (total mapping time, 18 h) and with beam current adjusted to give 30% dead time, provided adequate image quality at a magnification of 800X. The maps were acquired, with backgrounds subtracted, using a Noran TN 5500 EDS system. The images and maps were transferred to a Macintosh and converted into TIFF files using either TIFF Maker, or TNtolMAGE, a Microsoft QuickBASIC program developed at the Science Center. From TIFF files, images and maps were opened in either NIH Image or Adobe Photoshop for processing and analysis and printed from Microsoft Powerpoint on a Kodak XL7700 dye transfer image printer.

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A TEM investigation of silicon nitride whiskers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125737 ◽

1987 ◽

Vol 45 ◽

pp. 160-161

Author(s):

Tapan Roy

Keyword(s):

Silicon Nitride ◽

High Resolution ◽

Ceramic Matrix Composites ◽

High Resolution Electron Microscopy ◽

Molten Silicon ◽

Matrix Composites ◽

Ceramic Fibers ◽

Resolution Electron ◽

Point To Point ◽

Technological University

Ceramic fibers are being used to improve the mechanical properties of metal matrix and ceramic matrix composites. This paper reports a study of the structural and other microstructural characteristics of silicon nitride whiskers using both conventional TEM and high resolution electron microscopy.The whiskers were grown by T. E. Scott of Michigan Technological University, by passing nitrogen over molten silicon in the presence of a catalyst. The whiskers were ultrasonically dispersed in chloroform and picked up on holey carbon grids. The diameter of some whiskers (<70nm) was small enough to allow direct observation without thinning. Conventional TEM was performed on a Philips EM400T while high resolution imaging was done on a JEOL 200CX microscope with a point to point resolution of 0.23nm.

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Some Base Line Data on School Mental Health Services

PsycEXTRA Dataset ◽

10.1037/e575802011-001 ◽

2013 ◽

Keyword(s):

Mental Health ◽

Mental Health Services ◽

Health Services ◽

School Mental Health ◽

Base Line ◽

Base Line Data

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Some base line data on school mental health services

PsycEXTRA Dataset ◽

10.1037/e578532011-004 ◽

2006 ◽

Keyword(s):

Mental Health ◽

Mental Health Services ◽

Health Services ◽

School Mental Health ◽

Base Line ◽

Base Line Data

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Ceramic fibers from hydridopolysilazane

Journal de Chimie Physique ◽

10.1051/jcp/1986830869 ◽

1986 ◽

Vol 83 ◽

pp. 869-873 ◽

Cited By ~ 4

Author(s):

Gary E. Legrow ◽

F. Lim ◽

J. Lipowitz ◽

Ronald S. Reaoch

Keyword(s):

Ceramic Fibers

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On the Fibrinolytic System in Aged Rats, and Its Reactivity to Endotoxin and Cytokines

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648525 ◽

1992 ◽

Vol 67 (06) ◽

pp. 697-701 ◽

Cited By ~ 6

Author(s):

J J Emeis ◽

A Brouwer ◽

R J Barelds ◽

M A Horan ◽

S K Durham ◽

...

Keyword(s):

Plasminogen Activator ◽

Fibrinolytic Activity ◽

Fibrinolytic System ◽

Tissue Type ◽

High Dose ◽

Base Line ◽

Aged Rats ◽

Tissue Type Plasminogen Activator ◽

Young Rats ◽

Type Plasminogen Activator

SummaryAged rats are more susceptible to endotoxin-induced effects, including microthrombosis and platelet aggregation, than are young rats. To investigate whether changes in the fibrinolytic system might be involved, we investigated the fibrinolytic activity in plasma euglobulin fractions and tissues (lung and heart) of young (6-months old) and aged (24-months old) rats under baseline conditions and after challenge with endotoxin. Aged rats had lower plasma levels of tissue-type plasminogen activator (t-PA) and of urokinase-type PA (u-PA) activity. PA inhibitor (PAI) activity was higher in the plasma of aged rats, as was t-PA activity in lung and heart.Rats were treated with either a low dose (1 μg/kg) or a high dose (10 mg/kg) of endotoxin. Both treatments induced a transient phase of increased blood fibrinolytic activity, as evidenced by higher levels of tissue-type plasminogen activator (t-PA) activity and decreased levels of PA inhibitor (PAI) activity. Over time, the fibrinolytic activity decreased, probably due to increased levels of PA inhibitor.Both the early increase in t-PA activity, and the subsequent increase in PAI activity, were more pronounced in the aged rats, as compared with the younger rats, after the high dose of endotoxin. The aged rats also responded to an injection of interleukin-1β or tumor necrosis factor-α with a larger increase of PAI activity than did the younger rats.Together the data suggest that, compared to young rats, aged rats have a decreased base-line plasma fibrinolytic activity, while their fibrinolytic system is more responsive to challenge by endotoxin and cytokines.

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