ISSN:1059-910X    

DOI:10.1002/jemt.1070250502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractAn outline is presented of the first commercial environmental scanning electron microscope (ESEM). A concise description of this instrument and its operation, from a user's perspective, is given. More specifically, the description includes the electron optics, pressure stages and control, detection modes, resolution, and ancillary equipment. © 1993 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070250503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWith the ability to perform dynamic experiments in the environmental scanning electron microscope (ESEM), the evaluation of microporous polymer membranes via a scanning electron microscope has advanced beyond morphological and elemental analysis. By adjusting sample temperature and environmental chamber pressure, the process of condensing water onto the porous membrane surface can be achieved. In doing so, assessments about the uniformity of wetting in hydrophilic membranes can be obtained based on how the liquid water spreads. Variations in the shape of condensed water droplets formed on non‐water wetting structures will reflect the degree of hydrophobicity. This technique has proven useful in the characterization of hydrophobic spots on chemically modified hydrophilic structures and the dynamic examination of irregular wetting patterns in naturally hydrophilic membranes. © 1993 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070250504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe preservation of nineteenth‐century albumen prints is of great concern to collection managers and to conservators of photographic materials. In the field of art conservation, preservation techniques incorporating aqueous treatments are often used to enhance the long‐ and short‐term stability of historical artifacts or art objects. In a study of the interaction of water with albumen photographs, experiments were carried out in the ESEM to follow the real time effects of water on the prints. The experiments were designed to observe the effects of a range of relative humidities and liquid water on samples of expendable historic albumen prints, utilizing the advantages of imaging in the presence of water vapor. All albumen photographs exhibit a fine network of cracks in the albumen protein layer. Average crack width is approximately 10 μm. As observed in the ESEM, a 4.25‐fold increase in the width of a single crack (at 50% RH), viewed normal to the surface, resulted from a single controlled excursion to high relative humidity and immersion. In an extraordinary series of images, a print viewed in cross‐section exhibited a 22% swelling and shrinkage in thickness, and a 5% and 9% swelling and shrinkage along the width of a fragment of the albumen/image layer when the sample was immersed in water and dried. The visual information gained through the use of the ESEM helped to focus a materials investigation and served as a foundation for a study which shows that aqueous treatment causes increased cracking of both unsupported albumen and the albumen/image layer in prints. © 1993 Wile

ISSN:1059-910X    

DOI:10.1002/jemt.1070250505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis article describes two cases in which the advantages of the ESEM have been exploited in unanticipated ways. First, we have found that etching occurs as the electron beam scans the surface of uncoated polymers in the ESEM. The surface topography caused by this etching, as seen in ESEM images, reflects the morphology of crystalline structures in the polymers. This technique has been valuable in the study of such textures in polymers. The second application is related to our use of the ESEM in support of research on the deinking of paper. In this effort we have learned that an unconventional contrast mechanism can be used during ESEM imaging to distinguish between inked and non‐inked areas of newsprint. Under usual operating conditions, ESEM imaging does not distinguish between inked and non‐inked areas. However, at relatively low sample chamber pressures the non‐inked areas appear brighter than inked areas in ESEM images. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070250506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis work provides examples of some of the imaging capabilities of environmental scanning electron microscopy applied to easily charged samples relevant to particle analysis. Environmental SEM (also referred to as high pressure or low vacuum SEM) can address uncoated samples that are known to be difficult to image. Most of these specimens are difficult to image by conventional SEM even when coated with a conductive layer. Another area where environmental SEM is particularly applicable is for specimens not compatible with high vacuum, such as volatile specimens. Samples from which images were obtained that otherwise may not have been possible by conventional methods included fly ash particles on an oiled plastic membrane impactor substrate, a one micrometer diameter fiber mounted on the end of a wire, uranium oxide particles embedded in oil‐bearing cellulose nitrate, teflon and polycarbonate filter materials with collected air particulate matter, polystryene latex spheres on cellulosic filter paper, polystyrene latex spheres “loosely” sitting on a glass slide, and subsurface tracks in an etched nuclear track‐etch detector. Surface charging problems experienced in high vacuum SEMs are virtually eliminated in the low vacuum SEM, extending imaging capabilities to samples previously difficult to use or incompatible with conventional methods. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070250507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractMicroorganisms, including bacteria, fungi, protozoa, and microalgae, are composed predominantly of water which prohibits direct observation in a traditional scanning electron microscope (SEM). Preparation for SEM requires that microorganisms be fixed, frozen or dehydrated, and coated with a conductive film before observation in a high vacuum environment. Sample preparation may mechanically disturb delicate samples, compromise morphological information, and introduce other artifacts. The environmental scanning electron microscope (ESEM) provides a technology for imaging hydrated or dehydrated biological samples with minimal manipulation and without the need for conductive coatings.Sporulating cultures of three fungi,Aspergillussp.,Cunninghamellasp., andMucorsp., were imaged in the ESEM to assess usefulness of the instrument in the direct observation of delicate, uncoated, biological specimens. Asexual sporophores showed no evidence of conidial displacement or disruption of sporangia.Uncoated algal cells ofEuglena gracilisandSpirogyrasp. were examined using the backscatter electron detector (BSE) and the environmental secondary electron detector (ESD) of the ESEM. BSE images had more clearly defined intracellular structures, whereas ESD gave a clearer view of the surface.E. graciliscells fixed with potassium permanganate,Spirogyrasp. stained with Lugol's solution, andSaprolegniasp. fixed with osmium tetroxide were compared using BSE and ESD to demonstrate that cellular details could be enhanced by the introduction of heavy metals. The effect of cellular water on signal quality was evaluated by comparing hydrated to critical point dried specimens. © 1993 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070250508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe presence and distribution of Al and Mn in floral and seed tissues of eucalypts from Al‐contaminated soils was analyzed using energy‐dispersive X‐ray microanalysis (EDS) in an environmental scanning electron microscope (ESEM). EDS by ESEM determined the distribution of elements between tissue types was suitable for intact samples or those with lower available moisture or intact specimens. The analytical technique was not appropriate for highly vascular samples. Other factors influencing the detection of elements by ESEM‐EDS were electron scattering and the relative concentration and localization of elements within the tissues. EDS‐detectable levels were significantly correlated with tissue concentrations determined by atomic absorption spectrophotometry for Mn but not for Al. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070250509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractFour common scanning electron microscope (SEM) processing techniques involving freeze‐substitution and chemical fixation were compared with fresh unprocessed samples imaged in an environmental scanning electron microscope (ESEM) using small pieces of potato tubers as test specimens. Potato tubers were chosen for this investigation because of their high moisture content and, consequently, the common need for extensive processing for conventional, high vacuum SEM imaging. ESEM results showed that the fresh unprocessed specimens were essentially unaltered, showing clear potato cell structure, morphology, and cell content. However, processed samples showed strong differences to the fresh samples: freeze‐substituted specimens showed fine networks of material stretching across the surface of cells. These structures may represent fibrillar material or may be artifact caused during processing. Chemical fixation almost entirely destroyed the microstructure of these potato samples. © 1993 Wiley‐Lis

ISSN:1059-910X    

DOI:10.1002/jemt.1070250510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA comparison of four dentinal conditioners was performed utilizing a traditional scanning electron microscope (SEM) and a new technology, the ElectroScan™ environmental scanning electron microscope (ESEM). Both ESEM and SEM analysis verified current theorized mechanisms of adhesion to dentin surfaces. ESEM images appeared to more closely approximate what one would expect cut and treated dentin surfaces look like. Increases in information from the “surfaces” of uncoated specimens and the reduction in specimen preparation time were associated with ESEM analysis. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070250511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY