High Resolution Microscopy of Carbon Fibers

1970 ◽  
Vol 28 ◽  
pp. 468-469
Author(s):  
David F. Harling
Keyword(s):  
High Resolution ◽  
Carbon Fiber ◽  
Physical Properties ◽  
Carbon Fibers ◽  
Structural Composites ◽  
The Past ◽  
Reinforcing Material ◽  
High Resolution Microscopy

Much interest has been shown over the past few years in carbon fibers, a novel reinforcing material included in the growing field of structural composites. Typical carbon fiber products can easily match the physical properties of steel but with only one-fifth the weight. These unusual properties are attributed to the microstructure of the fibers and the orientation of extremely long graphitic crystallites more or less parallel to the long axis of the fiber. Variations in fiber strengths have been attributed to, among other things, voids between these crystallites.

Pitch-based carbon fiber reinforced cements: structure, performance, applications, and research needs

1992 ◽  
Vol 19 (1) ◽  
pp. 26-38 ◽  
Author(s):  
Nemkumar Banthia
Keyword(s):  
Carbon Fiber ◽  
Physical Properties ◽  
Mechanical Behavior ◽  
Key Words ◽  
Carbon Fibers ◽  
Fiber Reinforcement ◽  
Performance Characteristics ◽  
Future Research ◽  
Cement Composites ◽  
Research Needs

The improvements in the performance characteristics of cements due to carbon fiber reinforcement are described. In particular, the structure, the physical properties, the mechanical behavior, and the durability aspects of carbon–cement composites using pitch-based fibers are discussed. The various possible applications of these composites in structural and nonstructural applications are enumerated. The future research needs are identified. Key words: cements, carbon fibers, microstructure, strength, toughness, durability, applications.

HREM of twin intersections in Silicon

1989 ◽  
Vol 47 ◽  
pp. 132-133
Author(s):  
C.J.D. Hetherington ◽  
U. Dahmen ◽  
P. Pirouz ◽  
K.H. Westmacott
Keyword(s):  
High Resolution ◽  
Local Stress ◽  
Local Deformation ◽  
Maximum Information ◽  
The Past ◽  
High Resolution Images ◽  
Twin Band ◽  
Secondary Twinning ◽  
Local Distortions ◽  
High Resolution Microscopy

A twin band is an effective barrier to the propagation of another, noncoplanar twin band. However, under conditions of sufficiently high local stress, twin intersections are possible. The geometric configuration of intersecting twin bands has been considered in the past in the context of dislocation mechanisms and deformation behavior. Observations on plane-strain deformed Co-8wt%Fe single crystals showed that intersecting twins gave rise to highly complex local deformation structures and led to the conclusion that the strain in the region of intersection was accommodated either by slip or by (secondary) twinning. The recent discovery of hexagonal ribbons of Si in hot-indentation experiments on silicon has renewed the interest in twin intersections as an integral part of the deformation microstructure, and prompted their study by high resolution microscopy.It is frequently necessary to record high resolution images under less than optimum conditions, e.g. because of radiation damage or local distortions. It then becomes desirable to devise methods for extracting the maximum information from such imperfect images.

Processing-Microstructure-Tensile Property of Vapor Grown Carbon Fiber Reinforced Carbon Composite

1995 ◽  
Vol 383 ◽  
Author(s):  
Jyh-Ming Ting
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Carbon Fiber ◽  
Physical Properties ◽  
Tensile Properties ◽  
Gas Phase ◽  
Thermal Management ◽  
Carbon Fibers ◽  
Carbon Composite ◽  
Carbon Composites

ABSTRACTIn contrast to the form in which other carbon fibers are produced, vapor grown carbon fiber (VGCF) is produced from gas phase precursors in the form of individual fibers of discrete lengths. VGCF can be harvested as a mat of semi-aligned, semicontinuous fibers, with occasional fiber branching and curling. The use of VGCF mats as reinforcement result in composites which exhibit unique microstructure and physical properties that are not observed in other types of carbon composites. This paper describes the processing of VGCF mats reinforced carbon composites, and its unique microstructure and properties. Utilization of fiber tensile properties, as well as thermal conductivity, in the composites is discussed. Comparison of experimental results from various VGCF composites to theory indicates that mechanical properties are more strongly affected by characteristics of VGCF mat than are thermal conductivity. The implications of this relationship favors applications for thermal management where structural demands are less stringent.

scholarly journals A Review on the Usage of Continuous Carbon Fibers for Piezoresistive Self Strain Sensing Fiber Reinforced Plastics

2021 ◽  
Vol 5 (4) ◽  
pp. 96
Author(s):  
Patrick Scholle ◽  
Michael Sinapius
Keyword(s):  
Carbon Fiber ◽  
Literature Review ◽  
Carbon Fibers ◽  
Fiber Reinforced ◽  
Strain Sensing ◽  
Carbon Fiber Reinforced Plastics ◽  
Reinforced Plastics ◽  
The Past ◽  
Experimental Approaches ◽  
Fiber Reinforced Plastics

This literature review examines the application of carbon fibers and their reinforced plastics for Self-Strain-Sensing structures and gives an up-to-date overview of the existing research. First, relevant basic experimental approaches that can be found in the literature are presented and discussed. Next, we propose to cluster the available articles into 5 categories based on specimen size and ranging from experiments on bare carbon fiber via impregnated fiber rovings to carbon fiber laminates. Each category is analyzed individually and the potential differences between them are discussed based on experimental evidence found in the past. The overview shows, that the choice of carbon fiber and the specific experimental setup both significantly influence the piezoresistive properties measured in Self-Strain-Sensing carbon fiber reinforced plastics. Conclusively, based on the conclusions drawn from the literature review, we propose a small number of measurements that have proven to be important for the analysis of Self-Strain-Sensing carbon fiber structures.

High-resolution scanning electron microscopy of carbon fiber

1989 ◽  
Vol 47 ◽  
pp. 704-705
Author(s):  
Deborah L. Vezie
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Carbon Fiber ◽  
Field Emission ◽  
Carbon Fibers ◽  
Low Voltage ◽  
Electron Gun ◽  
Scanning Electron

As part of an extensive study of polyacrylonitrile (PAN) and mesophase pitch-based carbon fibers, high resolution scanning electron microscopy (HRSEM) is shown to provide additional insight into understanding and modelling microstructural origins of mechanical properties of carbon fiber. Although carbon fiber has been studied extensively, no sufficiently clear relationship between structure and mechanical properties such as elastic modulus and compressive strength has yet been developed from quantitative TEM and WAXS investigations.In this study, HRSEM data of selected carbon fibers is used to illustrate the power of HRSEM to elucidate structural differences likely accounting for changes in mechanical properties not sensitively probed either by TEM or WAXS. The three-dimensional nature of SEM imaging with accompanying high resolution permits a clearer visualization and more detailed examination of regional structures within carbon fiber over two-dimensional TEM and globally averaged WAXS data.The design of the high resolution, field emission SEM permits low voltage imaging of poorly conducting samples with resolution an order of magnitude greater than a conventional tungsten hairpin filament SEM under the same operating voltage and sample preparation conditions. Although carbon fiber is a relatively conductive material, charging effects can be seen in uncoated PAN fibers above 3.0 keV in a conventional SEM. Lower accelerating voltages are necessary for uncoated imaging of these fibers, but become impractical due to degradation of conventional SEM performance at these voltages. Uncoated sample imaging is preferred to prevent conventional evaporation or sputter coating techniques from obscuring or altering the sample surface, although charging effects may then be a problem. The high resolution, field emission SEM solves these competing voltage/ charging/ resolution issues for poorly conducting materials with the very nature of its design; the high brightness of the electron gun at low voltage coupled with the “in lens” sample placement and above the objective lens detector dramatically improve the resolution of these instruments, especially at low voltage.

scholarly journals Multifunctional Braided Composite Rods for Civil Engineering Applications

2010 ◽  
Vol 123-125 ◽  
pp. 149-152 ◽  
Author(s):  
Emilijia Zdraveva ◽  
Cristiana Gonilho-Pereira ◽  
Raul Manuel Esteves Sousa Fangueiro ◽  
Senentxu Lanceros-Méndez ◽  
Saíd Jalali ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Carbon Fibers ◽  
Electrical Resistance ◽  
Fiber Content ◽  
Resistance Change ◽  
Reinforced Composite ◽  
Composite Rod ◽  
Reinforcing Material ◽  
Concrete Elements ◽  
Versus Strain

This paper presents the development of a braided reinforced composite rod (BCR) able to both reinforce and monitor the stress state of concrete elements. Carbon fibers have been used as sensing and reinforcing material along with glass fiber. Various composites rods have been produced using an author patented technique based on a modified conventional braiding machine. The materials investigated were prepared with different carbon fiber content as follows: BCR2 (77% glass/23% carbon fiber), BCR3 (53% glass/47% carbon fiber), BCR4 (100% carbon fiber). BCRs have been tested under bending while the variation of the electrical resistance was simultaneously monitored. The correlations obtained between deformation and electrical resistance show the suitability of the rods to be used as sensors. The fractional resistance change versus strain plots show that the gage factor increases with decreasing carbon fiber content.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Transmission electron microscopy of composite materials

1988 ◽  
Vol 46 ◽  
pp. 1012-1015
Author(s):  
K.P.D. Lagerlof
Keyword(s):  
Composite Materials ◽  
Physical Properties ◽  
Structural Defects ◽  
Structural Composites ◽  
Multiphase Materials ◽  
Structural Reinforcement ◽  
Transmission Electron ◽  
Reinforced Fiber ◽  
Particulate Reinforced Composites ◽  
Definition Of

Although most materials contain more than one phase, and thus are multiphase materials, the definition of composite materials is commonly used to describe those materials containing more than one phase deliberately added to obtain certain desired physical properties. Composite materials are often classified according to their application, i.e. structural composites and electronic composites, but may also be classified according to the type of compounds making up the composite, i.e. metal/ceramic, ceramic/ceramie and metal/semiconductor composites. For structural composites it is also common to refer to the type of structural reinforcement; whisker-reinforced, fiber-reinforced, or particulate reinforced composites [1-4].For all types of composite materials, it is of fundamental importance to understand the relationship between the microstructure and the observed physical properties, and it is therefore vital to properly characterize the microstructure. The interfaces separating the different phases comprising the composite are of particular interest to understand. In structural composites the interface is often the weakest part, where fracture will nucleate, and in electronic composites structural defects at or near the interface will affect the critical electronic properties.

High Resolution Observations of Ion-Milling Induced Transformation in Synthetic Hollandses

1981 ◽  
Vol 39 ◽  
pp. 114-115 ◽  
Author(s):  
T. J. Headley
Keyword(s):  
High Resolution ◽  
Radioactive Waste Disposal ◽  
Ion Milling ◽  
Minor Elements ◽  
Waste Forms ◽  
Carbon Substrates ◽  
Structural Differences ◽  
Oxide Phases ◽  
Argon Ions ◽  
High Resolution Microscopy

Oxide phases having the hollandite structure have been identified in multiphase ceramic waste forms being developed for radioactive waste disposal. High resolution studies of phases in the waste forms described in Ref. [2] were initiated to examine them for fine scale structural differences compared to natural mineral analogs. Two hollandites were studied: a (Ba,Cs,K)-titan-ate with minor elements in solution that is produced in the waste forms, and a synthesized BaAl2Ti6O16 phase containing ∼ 4.7 wt% Cs2O. Both materials were consolidated by hot pressing at temperatures above 1100°C. Samples for high resolution microscopy were prepared both by ion-milling (7kV argon ions) and by crushing and dispersing the fragments on holey carbon substrates. The high resolution studies were performed in a JEM 200CX/SEG operating at 200kV.

Design of a new objective lens for an HB-501A STEM

1991 ◽  
Vol 49 ◽  
pp. 416-417
Author(s):  
Earl J. Kirkland ◽  
Robert J. Keyse
Keyword(s):  
High Resolution ◽  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Microscopy

An ultra-high resolution pole piece with a coefficient of spherical aberration Cs=0.7mm. was previously designed for a Vacuum Generators HB-501A Scanning Transmission Electron Microscope (STEM). This lens was used to produce bright field (BF) and annular dark field (ADF) images of (111) silicon with a lattice spacing of 1.92 Å. In this microscope the specimen must be loaded into the lens through the top bore (or exit bore, electrons traveling from the bottom to the top). Thus the top bore must be rather large to accommodate the specimen holder. Unfortunately, a large bore is not ideal for producing low aberrations. The old lens was thus highly asymmetrical, with an upper bore of 8.0mm. Even with this large upper bore it has not been possible to produce a tilting stage, which hampers high resolution microscopy.

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