scholarly journals The ice–vapour interface during growth and sublimation

2021 ◽  
Vol 21 (24) ◽  
pp. 18629-18640
Author(s):  
Maria Cascajo-Castresana ◽  
Sylvie Morin ◽  
Alexander M. Bittner
Keyword(s):  
Grain Boundaries ◽  
Surface Defects ◽  
Environmental Scanning Electron Microscopy ◽  
Decisive Role ◽  
Inorganic Materials ◽  
Environmental Scanning ◽  
Biological Origin ◽  
Effect Of Impurities ◽  
Low Humidity ◽  
Extensive Information

Abstract. We employed environmental scanning electron microscopy (ESEM) in low-humidity atmosphere to study the ice growth, coalescence of crystallites, polycrystalline film morphology, and sublimation, in the temperature range of −10 to −20 ∘C. First, individual ice crystals grow in the shape of micron-sized hexagonal columns with stable basal faces. Their coalescence during further growth results in substantial surface defects and forms thick polycrystalline films, consisting of large grains separated by grain boundaries. The latter are composed of 1 to 3 µm wide pores, which are attributed to the coalescence of defective crystallite surfaces. Sublimation of isolated crystals and of films is defect-driven, and grain boundaries play a decisive role. A scallop-like concave structure forms, limited by sharp ridges, which are terminated by nanoscale asperities. The motivation for this work is also to evaluate ESEM's ability to provide a clean and reproducible environment for future study of nucleation and growth on atmospherically relevant nucleators such as materials of biological origin and inorganic materials. Hence, extensive information regarding potential ESEM beam damage and effect of impurities are discussed.

scholarly journals The ice-vapor interface during growth and sublimation

2021 ◽  
Author(s):  
Maria Cascajo-Castresana ◽  
Sylvie Morin ◽  
Alexander Bittner
Keyword(s):  
Grain Boundaries ◽  
Environmental Scanning Electron Microscopy ◽  
Decisive Role ◽  
Ice Crystals ◽  
Environmental Scanning ◽  
Film Morphology ◽  
Growth Forms ◽  
Vapor Interface ◽  
Low Humidity ◽  
Scanning Electron

Abstract. We employed Environmental Scanning Electron Microscopy (ESEM) in low humidity atmosphere to study the complete scenario of ice growth, coalescence of crystallites, polycrystalline film morphology and sublimation, in the temperature range of −10 ºC to −20 ºC. First, individual ice crystals grow in the shape of micron-sized hexagonal columns with stable basal faces. Their coalescence during further growth forms thick polycrystalline films, consisting of large grains separated by grain boundaries. The latter are composed of 1 to 3 µm wide pores, which are attributed to the coalescence of defective crystallite surfaces. Sublimation of isolated crystals and of films is defect-driven, and grain boundaries play a decisive role. A scallop-like concave structure forms, limited by sharp ridges, which are terminated by nanoscale asperities.

Developments in characterizing soft matter

MRS Bulletin ◽  
2010 ◽  
Vol 35 (9) ◽  
pp. 702-707 ◽  
Author(s):  
Athene M. Donald
Keyword(s):  
Soft Matter ◽  
Complex Fluids ◽  
High Vacuum ◽  
Environmental Scanning Electron Microscopy ◽  
Microstructural Characterization ◽  
Inorganic Materials ◽  
Environmental Scanning ◽  
Conductive Material ◽  
Scanning Electron

Soft matter—also known as complex fluids—is a field of growing interest and importance, spanning many classes of materials, including polymers, biopolymers, colloids, and liquid crystals. Different approaches for microstructural characterization are more appropriate than those used for hard (and usually fully crystallized) materials such as metals and inorganic materials because of the time and length scales involved. This article discusses a range of techniques applicable to the characterization of soft matter, including environmental scanning electron microscopy (SEM) and microrheology. The former offers two key advantages for this class of material over conventional SEM because it requires neither a high vacuum—which is a problem for hydrated samples—nor that an insulator be coated with a conductive material. Microrheology is well suited to small volumes of fluid with low moduli that may be heterogeneous; it is capable of measuring gelation in real time.

scholarly journals Wet-STEM Tomography: Principles, Potentialities and Limitations

2014 ◽  
Vol 20 (2) ◽  
pp. 366-375 ◽  
Author(s):  
Karine Masenelli-Varlot ◽  
Annie Malchère ◽  
José Ferreira ◽  
Hamed Heidari Mezerji ◽  
Sara Bals ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Three Dimensional ◽  
Environmental Scanning Electron Microscopy ◽  
Inorganic Materials ◽  
Dimensional Structure ◽  
Environmental Scanning ◽  
Minimum Thickness ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Specific Device

AbstractThe characterization of biological and inorganic materials by determining their three-dimensional structure in conditions closer to their native state is a major challenge of technological research. Environmental scanning electron microscopy (ESEM) provides access to the observation of hydrated samples in water environments. Here, we present a specific device for ESEM in the scanning transmission electron microscopy mode, allowing the acquisition of tilt-series suitable for tomographic reconstructions. The resolution which can be obtained with this device is first determined. Then, we demonstrate the feasibility of tomography on wet materials. The example studied here is hydrophilic mesoporous silica (MCM-41). Finally, the minimum thickness of water which can be detected is calculated from Monte Carlo simulations and compared with the resolution expected in the tomograms.

Environmental scanning electron microscopy of fresh human gallstones reveals new morphologies of precipitated calcium salts

1992 ◽  
Vol 50 (2) ◽  
pp. 1322-1323
Author(s):  
Howard S. Kaufman ◽  
Keith D. Lillemoe ◽  
John T. Mastovich ◽  
Henry A. Pitt
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
X Ray Diffraction ◽  
Calcium Salts ◽  
Cholesterol Gallstones ◽  
X Ray ◽  
Ca Carbonate ◽  
Scanning Electron

Gallstones contain precipitated cholesterol, calcium salts, and proteins. Calcium (Ca) bilirubinate, palmitate, phosphate, and carbonate occurring in gallstones have variable morphologies but characteristic windowless energy dispersive x-ray (EDX) spectra. Previous studies of gallstone microstructure and composition using scanning electron microscopy (SEM) with EDX have been limited to dehydrated samples. In this state, Ca bilirubinates appear as either glassy masses, which predominate in black pigment stones, or as clusters, which are found mostly in cholesterol gallstones. The three polymorphs of Ca carbonate, calcite, vaterite, and aragonite, have been identified in gallstones by x-ray diffraction, however; the morphologies of these crystals vary in the literature. The purpose of this experiment was to study fresh gallstones by environmental SEM (ESEM) to determine if dehydration affects gallstone Ca salt morphology.Gallstones and bile were obtained fresh at cholecystectomy from 6 patients. To prevent dehydration, stones were stored in bile at 37°C. All samples were studied within 4 days of procurement.

Detector strategies for environmental scanning electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1296-1297
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Vacuum ◽  
Environmental Scanning Electron Microscopy ◽  
Charge Carriers ◽  
Environmental Scanning ◽  
Surface Information ◽  
X Ray ◽  
Detector Electrode ◽  
Electrons And Ions ◽  
Low Energy Electrons ◽  
Environmental Sem

Environmental SEM operate at specimen chamber pressures of ∼20 torr (2.7 kPa) allowing stabilization of liquid water at room temperature, working on rugged insulators, and generation of an environmental secondary electron (ESE) signal. All signals available in conventional high vacuum instruments are also utilized in the environmental SEM, including BSE, SE, absorbed current, CL, and X-ray. In addition, the ESEM allows utilization of the flux of charge carriers as information, providing exciting new signal modes not available to BSE imaging or to conventional high vacuum SEM.In the ESEM, at low vacuum, SE electrons are collected with a “gaseous detector”. This detector collects low energy electrons (and ions) with biased wires or plates similar to those used in early high vacuum SEM for SE detection. The detector electrode can be integrated into the first PLA or positioned at any other place resulting in a versatile system that provides a variety of surface information.

scholarly journals 616 Preventing Biofilms on BACTIGON® Coated Camstent Urinary Catheters in Patients Undergoing Elective Colorectal Surgery: A Single Centre Pilot Study

2021 ◽  
Vol 108 (Supplement_2) ◽  
Author(s):  
C Lewis-Lloyd ◽  
J Dubern ◽  
K Kalenderski ◽  
N Halliday ◽  
M Alexander ◽  
...  
Keyword(s):  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
Bacterial Cells ◽  
Urinary Catheters ◽  
Elective Colorectal Surgery ◽  
Mineral Compositions ◽  
Microscopy Data ◽  
Tract Infections ◽  
Biofilm Development ◽  
Hospital Acquired

Abstract Introduction Catheter associated urinary tract infections account for 40% of hospital acquired infections. They are associated with biofilms consisting of bacterial cells enmeshed in a self-generated extracellular matrix adhering to catheter surfaces. We have developed a novel polymer family that, coated onto urinary catheters, creates a “non-stick” surface preventing biofilm development. Method Prospective cohort of elective colorectal patients recruited pre-operatively, received a standard silicone (SS) or Camstent (BACTIGON®) coated urinary catheter. After removal, catheters were cut longitudinally into 3 segments. Biomass and biomineralisation were analysed using confocal fluorescence microscopy. Data were normalised by square rooting the catheter indwelling duration. Environmental scanning electron microscopy and energy dispersive x-ray spectroscopy was performed. Results Of 40 patients, 20 each received a SS or coated catheter. Between SS and coated catheters, average indwelling duration was similar and biofilm biomass was 32.068µg/cm2 (95%CI ±21.950) vs. 1.948µg/cm2 (95%CI ±2.595) (P = 0.0111). Confocal microscopy suggested a 93.93% reduction in biofilm biomass on coated catheters. Mineral compositions were different with biofilm and struvite/apatite on SS and calcium oxalate, endogenously derived, on coated catheters. Conclusions Inert BACTIGON® coated catheters appear superior at preventing biofilm formation than SS catheters. Clinical trials are needed to determine the clinical and health economic benefit of this intervention.

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