All joints in the human body are subject to destruction by disease and trauma. Although the modem concept of joint replacements dates back to 1800's, polymeric material were not utilized till 1940's [1]. Early experiments were conducted with polymethacrylate and polytetrafluoroethylene. The results were disappointing with the polymeric material either quick fracturing or wearing at an extreme rapid rate. Microstructures were not well investigated as a function of processing conditions.

The goal of this research is to eliminate the presence of oxygen within the components during its processing operations, which is responsible for early failure of polytetrafluoroethylene. One approach to eliminate or reduce the amount of oxygen would be processing the PTFE resin in vacuum conditions. This research is aimed towards investigating the microstructure of PTFE when processed under vacuum conditions using SEM and TEM along with EDXS.

The fabricated PTFE billet samples were received from Dewal Industries, NJ and the PTFE components in vacuum conditions, processed at University of Massachusetts Lowell (UML) were studied using microscopic techniques.

Summary:

The polypropylene growth process on silica supported metallocene catalysts was examined by electron microscopy and kinetic investigations. It was possible to identify different polymerization stages with different characteristic kinetic data in the slurry phase which led to the development of a refined polymer growth model [1-2]. Tomographical reconstruction of shortly polymerized catalyst particles obtained by electron micrographs of serial microtome sections turned out to be a useful tool to achieve a better understanding of the heterogeneous polymerization process and the influence of the support structure on polymer growth.

1. Introduction

Single-site metallocene catalysts produce extremely uniform polymers with molecular weight distributions (MWD) of 2 or less and very narrow compositional distributions in comparison to conventional Ziegler-catalysts. For industrial gas phase or bulk polymerization in existing plants (drop-in-technology) it is necessary to fix the catalytically active components on a heterogeneous support.

Nanostructured polymers constitute an increasingly important class of materials. Investigations into the formation of nanostructural elements in microphase-ordered block copolymers have elucidated universal mechanisms of self-organization in soft-condensed matter, since topologically comparable nanostructures develop in biological and surfactant systems. Emerging applications of such polymers include nanotemplates for inorganic materials, optical switches and nanoreactors. Despite all the efforts that have focused on these materials in previous years, basic questions regarding the characteristics of these nanostructures, especially those exhibiting bicontinuity, persist. While most attempts to address these questions have relied on small-angle scattering, a real-space approach to this problem compares slices of simulated nanostructures to 2-D transmission electron microscopy (TEM) images. An alternate strategy is transmission electron microtomography (TEMT), which utilizes 3-D images (reconstructed from a series of 2-D images collected at sequential tilt angles) for detailed structural analysis. Using this method, we have, for instance, recently confirmed that packing frustration,

The photopolymerizable, conductive, and chromatic behavior of diacetylene containing films has lead to a number of investigations into possible applications. For example, when diacetylene films were investigated as photoresists it was demonstrated that 50 nm resolution could be achieved by electron lithography. Polymerized diacetylene layers display enviromentally dependent chromatic transitions and thus have been studied for sensor applications. Single crystals of polymerized diacetylene films belong to a class of one-dimensional semiconductors. Thus, conductive materials have been constructed using extended multilayers and monolayer of such polymers. For example, the conductive and self-supportive nature of films containing polymerized diacetylene makes them ideal for imaging large embedded molecules. The purpose of this article is to report the details of preparation of ultrathin Langmuir-Blodgett deposited phospholipid films containing polymerized diacetylene groups and analysis of the energy filtered electron diffraction spot intensities. This work shows promise that useful structural information of such systems can be obtained by TEM where owing to their finite grain size and radiation sensitivity,

Summary: In recent years the SEM has advanced from an instrument used primarily for imaging to a tool for performing precise and accurate measurements of features. The SEM has been widely adapted by workers in diverse technical fields such as: integrated circuit (IC) processing, micro electro-mechanical devices (MEMs) design and molecular biology research. The SEM user in need of acquiring accurate dimensional information about their samples normally relies on the magnification readings and settings provided by the instrument maker. Tools to evaluate the precision of these physical dimensions or to assist in understanding the state of the SEM are not currently available. This paper presents a new methodology based on novel software and hardware to provide the user with capability of diagnosing the magnification stability and non-linearity of their SEMs prior to attempting accurate and precise feature measurements. Examples will be presented demonstrating the diagnosis of magnification stability and non-linearity in SEMs located at 4 independent sites.

The Detective Quantum Efficiency (DQE) is one of the best parameters to characterize the performance of a charge-coupled device (CCD) camera when electron dose is an issue. This can be when there are beam source brightness limitations as in high-resolution applications or when specimen dose must be limited. For single parameter detectors such as a backscatter detector in a SEM, the DQE is defined as the square of the signal-to noise ratio (SNR) at the output divided by the square of the signal-to-noise ratio at the input:

where S, N, and n are respectively the signal, the noise and the electron dose. This definition is not valid to describe the performance of a multi-component device as an imaging detector. In fact a CCD camera is composed of many elements or pixels.

Biological transmission electron microscopy (TEM) has evolved over the past 50 to 60 years in concert with the instrumentation available. As beam acceleration energies have increased to 100-200 keV, specimen preparation protocols have been modified and tailored to fit the capabilities and constraints of new TEMs. Higher voltage allows improved resolution, (Fig. 1) but as acceleration voltage increases, contrast decreases. Vacuum levels required for conventional TEM prevent specimen contamination which protects specimen details from being obscured , but lower contrast requires heavy metal post staining which may lead to specimen contamination. Specimen thickness can increase with higher voltage (up to lOOnm at 200keV) because penetration is much increased, however, the chance of specimen - electron interaction of the type that causes heat build-up and specimen damage increases rapidly with thickness. It seems that these limitations and others must be tolerated in order to enjoy the obvious advantages of TEM.

We have developed 100-kV, 200-kV, and 350-kV cold-field-emission transmission electron microscopes (FE-TEMs) successively up to this time. Using these instruments, we have been studying the magnetic structure of materials, high-resolution imaging by electron holography, and dynamic observation of the vortex in superconductors by Lorentz microscopy. To make more progress in our research, we need a better electron beam in terms of coherency, beam brightness, and penetration. Here, we report a new lMV-cold-field-emission transmission electron microscope we have developed. Historically, the pioneering projects on a lMV-field-emission scanning transmission electron microscope (FE-STEM) (Zeitler and Crewe, 1974) and a 1.6MV FE-STEM (Jouffrey et al., 1984) have been reported. In 1988, Maruse and Shimoyama obtained a lMV-field-emission beam using their 1.25MV-STEM connected to a field-emission gun. Since then, continuous improvements in beam brightness has been made.

The target specifications of our 1 MV-cold-field-emission TEM (H-1000FT) are as follows: Acceleration voltage: 1MV, high-voltage stability :

The development of increasingly coherent and penetrating electron beams in electron microscopy will hasten progress in such fields as high resolution imaging, electron holography, and material structure investigation. Now that we have completed the development of the 1MV-FE- TEM (H-1000FT), we report its performance from the viewpoint of coherent illumination.

We observed thin films of gold in testing the high-resolution performance of H-1000FT.Crystal lattice fringes are formed from the interference between Bragg diffracted electron waves. In TEM observation of the films, the visibility of the fringes depends on the coherence of the electron wave and the overall stability of the microscope. Here, we calculated chromatic aberration-limited resolution d, given by ∼-(Δ ƛ)1/2, to be ∼ 0.6 Å (Δ:focus spread). We then slightly tilted the illumination to partially escape from the chromatic effect and to enable us to a shorter spacing lattice image. Figure 1 shows a lattice fringe image we obtained for a Au thin film, in which lattice fringes of 0.498 Å are clearly visible.

Bright and coherent electron beams have been opening new frontiers in science and technology. So far, we have developed several field-emission transmission electron microscopes (FE-TEM) with increasing accelerating voltages to provide higher beam brightness. By using a 200-kV FE-TEM and electron holography techniques, we directly confirmed the Aharonov-Bohm effect. A 350-kV FE-TEM equipped with a low-temperature specimen stage enabled us to observe moving vortices in superconductors.2 Most Recently, we have developed a new 1-MV FE-TEM with a newly designed FE gun to obtain an even brighter and more coherent electron beam.

Electron beam brightness, Br, defined in Figure 1, is suitable for measuring the performance of electron guns, since both lens aberrations and mechanical/electrical vibrations contribute to a decrease in beam brightness, and beam coherency is proportional to (Br)1/2. Therefore, we optimized design of the illuminating system and its operation by maximizing the electron beam brightness.

Introduction

For the nano-area analysis of materials, it is necessary to evaluate all data obtained by HRTEM, EDS, EELS, and/or Energy Filter. Up till now, each analytical/imaging instrument required its original computer control system. Thus, the total operational environment for the nano-area analysis was not convenient for us. Recent progress of computer technology provides the ability to build a high performance environment for seamless operation by Client/Server design.

We have developed computer controlled high-throughput integration system based on PC, called FasTEM system, having seamless integration function and real-time remote control function of all instruments related to nano-area analysis. The FasTEM system is composed of Windows NT based Server PC System that is connected to the target TEM via RS232C for integrated operation, and Client PC SYSTEM connected to the Server PC via TCP/IP for remote operation (Fig.l).

Seamless Integration Function

All user interfaces of the analytical/imaging instruments, such as HRTEM, STEM BF/DF, EDS, PEELS and GIF can be seamlessly integrated into the Server PC.

Advances in internetwork data transmission rates and reductions in the cost of imaging components and applications have facilitated real-time sharing of video, still images, and microscope operating systems with collaborators or observers at remote locations. Specialized direct and web-based systems for transmission electron microscopy have been described previously. However, in order to develop a generic and flexible means of sharing live images and data from light, scanning electron, and transmission electron microscope instruments, a telemicroscopy system was configured using readily available components and software that can be adapted for use with most common computer operating and networking systems.

Figure 1 diagrams the general configuration used in our laboratory. Input devices can include inexpensive desktop digital or analog video cameras, specialized fast or slow scan CCD cameras, and the analog video-screen signal generated by scanning electron microscopes. For transmission through TCP/IP networks, analog signals must be digitized with a frame grabber card.

Electron tomography is a three-dimensional (3D) imaging method with transmission electron microscopy (TEM) that provides high-resolution 3D images of structural arrangements. Conventional TEM images are in first approximation mere 2D-projections of a 3D sample under investigation. With electron tomographya series of images is acquired of a sample that is tilted over a large angular range (±70°) with small angular tilt increments (so called tilt-series). For the subsequent 3D-reconstruction, the images of the tilt series are aligned relative to each other and the 3D-reconstruction is computed. Electron tomography is the only technique that can provide true 3D information with nm-scale resolution of individual and unique samples. For (cell) biology and material science applications the availability of high-resolution 3D images of structural arrangements within individual samples provides unique architectural information that cannot be obtained otherwise. Routine application of electron tomography will comprise a major revolutionary step forward in the characterization of complex materials and cellular arrangements.

The analytical transmission electron microscope is one of the most powerful instruments today for materials characterization. The interaction of the electron beam with the specimen provides immediate visual and compositional information of the structure of materials. Improvements in optics, vacuum technology, emitter and goniometer design have made sub-2Å compositional imaging a standard technique.

Side-entry, multifunctional specimen holders compatible with new goniometer designs have been developed to provide an extended tilt range for tomographic applications. Planar features within a TEM specimen are most easily studied if the specimen is first rotated until the planar feature is aligned parallel to the main tilt axis of the specimen holder. Typically this requires manual removal of the specimen for reorientation, subjecting it to potential damage, or the use of motorized specimen rotation in a single tilt holder. Ideally all degrees of freedom of specimen movement should be available to the microscopist through the specimen holder and goniometer.

The West Greene School District (WGSD) in partnership with RJ Lee Group (RJLG) has been designing and developing innovative programs as part of the Schoolhouse Project to provide exceptional educational and business opportunities to its students. The objective of the educational/business partnership are multiple including motivating students to pursue advanced education, especially in mathematics, computer sciences, engineering, and the basic sciences; enriching the educational experience beyond that commonly available to students in rural communities; and improving the general attractiveness of the region for business growth. Access to remote analytical instrumentation is a key component of the Schoolhouse Project. To encourage remote access, RJLG has recently developed microscopy-at-a-distance Web-based technologies which enable control and operation of a scanning electron microscope (SEM) over the internet.

The SEM was chosen as the initial advanced analytical instrumentation because 1) its imaging and elemental composition functions have made it a standard analytical tool throughout research and industry, 2) it can be applied to many disciplines, and 3) students find it easy and fun to operate.

Wright-Patterson Air Force Base (near Dayton, OH) continues to offer a unique educational outreach program, Scanning Electron Microscopy EDucatorS (SEMEDS; pronounced sem-eds). This ten year old motivational science program provides an opportunity for students and educators to visit the Materials and Manufacturing Directorate's research laboratories, where scanning electron microscopes (SEMs) are used by scientists and engineers working in diverse areas of materials research.

As a favorite motivational science program, SEMEDS serves surrounding communities by bringing students and educators on-site to Wright-Patterson Air Force Base's Air Force Research Laboratory (AFRL) to operate state-of-the-art SEMs in a real life research laboratory setting. The special features of this program include: exposure to a world-class facility, introductions to the elite researchers who work there, and an opportunity for students to operate the same equipment used by the facility researchers.

SEMEDS is an after school program intended for middle school and high school students.

The capabilities of the scanning electron microscope (SEM continue to grow. An understanding of and competency in operating the SEM is a vital asset to researchers in many fields. Acquiring the practical knowledge demands considerable training, which is expensive in terms of instrument time and personnel resources. Moreover confined laboratory environments severely limit the number of operators who can be trained simultaneously.

An alternative training approach is to develop software simulations. For example, the Interactive Microscope Laboratory simulates the optical microscope as part of a computer-based teaching resource for school-level biology courses. The VSEM (Virtual Scanning Electron Microscope) project extends our earlier work on emulating the operation and behaviour of the SEM and combines it with a virtual reality model of the instrument. The aim of the VSEM project has been to develop a microscopy teaching application which can be deployed on multiple platforms without the need for expensive hardware or software support facilities.

Wright-Patterson Air Force Base (near Dayton, OH) continues to expand their local community educational outreach programs with the new mobile science research laboratory, Tech Trek - Mobile Research Laboratory. Tech Trek serves surrounding communities using a 40-foot customized Blue Bird bus equipped with an R.J. Lee Instruments Limited portable scanning electron microscope (SEM). The microscope is on loan from the Materials and Manufacturing Directorate of the Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base.

The purpose of the Tech Trek program is to stimulate school science programs by making state-of-the-art, usually cost-prohibitive scientific equipment and experienced support staff accessible to schools. The program is focussed on providing opportunities for students currently in the grades six through twelve, our future scientists and engineers, to interact with role models in science and technology while being engaged in interesting scientific research. Using this mobile format combination classroom and laboratory,

Bugscope is a second generation educational project in the World Wide Laboratory that provides web browser based control of scientific imaging instrumentation using the Internet. We had previously demonstrated web based remote access to sophisticated scientific imaging systems several years ago in the Chickscope project. The primary goal of the Bugscope project is to demonstrate that relatively low cost, sustainable access to an environmental scanning electron microscope (ESEM) can be made available to K-12 classrooms.

Methods: To participate in the project, a classroom submits a web based application that describes how they plan to use the microscope. If the application is accepted, a one hour session on the ESEM is scheduled and the classroom mails in their chosen specimen. During their access time, classrooms use a standard web browser over the Internet to control and acquire images from the ESEM (Philips/FEI XL-30FEG).

The intense use of computers to operate electron microscopes as well as the ability to control microscopes remotely over the Internet, is increasingly changing the way electron microscopes are being used and how microscopy is being taught. Practically all of the top-of-the-line electron microscopes offered by the microscope vendors today are fully computer controllable, and provide for digital imaging. The combination of both features with the ever increasing speed of computers has created a situation that has and will continue to change the way electron microscopists work.

Lehigh University together with Oak Ridge National Laboratory have collaborated since 1996 to make the instrumentation in the High Temperature Materials Laboratory at ORNL available for teaching purposes. The primary instrument being used is the Hitachi HF-2000 field emission TEM, which is controlled by Gatan's DigitalMicrograph™ (DM) software and uses a Ik by Ik CCD camera for digital imaging.