Nanocomposite Materials

Nanotechnology and the Environment ◽

10.5772/intechopen.93047 ◽

2020 ◽

Author(s):

Mousumi Sen

Keyword(s):

Food Packaging ◽

Advanced Materials ◽

Small Scale ◽

Individual Property ◽

Inorganic Solids ◽

Industrial Sectors ◽

Automobile Construction ◽

Electronics And Electrical ◽

Inorganic Matrix

Nanocomposites are the heterogeneous/hybrid materials that are produced by the mixtures of polymers with inorganic solids (clays to oxides) at the nanometric scale. Their structures are found to be more complicated than that of microcomposites. They are highly influenced by the structure, composition, interfacial interactions, and components of individual property. Most popularly, nanocomposites are prepared by the process within in situ growth and polymerization of biopolymer and inorganic matrix. With the rapid estimated demand of these striking potentially advanced materials, make them very much useful in various industries ranging from small scale to large to very large manufacturing units. With a great deal to mankind with environmental friendly, these offer advanced technologies in addition to the enhanced business opportunities to several industrial sectors like automobile, construction, electronics and electrical, food packaging, and technology transfer.

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Upscaling THM modeling from small-scale to full-scale in-situ experiments in the Callovo-Oxfordian claystone

International Journal of Rock Mechanics and Mining Sciences ◽

10.1016/j.ijrmms.2020.104582 ◽

2021 ◽

Vol 144 ◽

pp. 104582

Author(s):

D.M. Seyedi ◽

C. Plúa ◽

M. Vitel ◽

G. Armand ◽

J. Rutqvist ◽

...

Keyword(s):

Full Scale ◽

Small Scale ◽

In Situ Experiments

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Understanding ion-induced assembly of cellulose nanofibrilllar gels through shear-free mixing and in situ scanning-SAXS

Nanoscale Advances ◽

10.1039/d1na00236h ◽

2021 ◽

Author(s):

Tomas Rosén ◽

Ruifu Wang ◽

HongRui He ◽

Chengbo Zhan ◽

Shirish Chodankar ◽

...

Keyword(s):

Mechanical Properties ◽

Building Block ◽

Cellulose Nanofibrils ◽

Advanced Materials ◽

The Past

During the past decade, cellulose nanofibrils (CNFs) have shown tremendous potential as a building block to fabricate new advanced materials that are both biocompatible and biodegradable. The excellent mechanical properties...

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Effect of Na- and Organo-Modified Montmorillonite/Essential Oil Nanohybrids on the Kinetics of the In Situ Radical Polymerization of Styrene

Nanomaterials ◽

10.3390/nano11020474 ◽

2021 ◽

Vol 11 (2) ◽

pp. 474

Author(s):

Ioannis S. Tsagkalias ◽

Alexandra Loukidi ◽

Stella Chatzimichailidou ◽

Constantinos E. Salmas ◽

Aris E. Giannakas ◽

...

Keyword(s):

Essential Oil ◽

Radical Polymerization ◽

Food Packaging ◽

In Situ Polymerization ◽

Average Molecular Weight ◽

Monomer Conversion ◽

Hydroxyl Groups ◽

Modified Montmorillonite ◽

Kinetics Of

The great concern about the use of hazardous additives in food packaging materials has shown the way to new bio-based materials, such as nanoclays incorporating bioactive essential oils (EO). One of the still unresolved issues is the proper incorporation of these materials into a polymeric matrix. The in situ polymerization seems to be a promising technique, not requiring high temperatures or toxic solvents. Therefore, in this study, the bulk radical polymerization of styrene was investigated in the presence of sodium montmorillonite (NaMMT) and organo-modified montmorillonite (orgMMT) including thyme (TO), oregano (OO), and basil (BO) essential oil. It was found that the hydroxyl groups present in the main ingredients of TO and OO may participate in side retardation reactions leading to lower polymerization rates (measured gravimetrically by the variation of monomer conversion with time) accompanied by higher polymer average molecular weight (measured via GPC). The use of BO did not seem to affect significantly the polymerization kinetics and polymer MWD. These results were verified from independent experiments using model compounds, thymol, carvacrol and estragol instead of the clays. Partially intercalated structures were revealed from XRD scans. The glass transition temperature (from DSC) and the thermal stability (from TGA) of the nanocomposites formed were slightly increased from 95 to 98 °C and from 435 to 445 °C, respectively. Finally, better dispersion was observed when orgMMT was added instead of NaMMT.

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Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

MRS Proceedings ◽

10.1557/proc-663-561 ◽

2000 ◽

Vol 663 ◽

Cited By ~ 2

Author(s):

J. Samper ◽

R. Juncosa ◽

V. Navarro ◽

J. Delgado ◽

L. Montenegro ◽

...

Keyword(s):

Large Scale ◽

Reference Model ◽

Numerical Models ◽

Full Scale ◽

Small Scale ◽

Model Parameters ◽

In Situ Test ◽

Wide Range ◽

Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

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On the short-term variability of turbulence and temperature in the winter mesosphere

Annales Geophysicae ◽

10.5194/angeo-36-1099-2018 ◽

2018 ◽

Vol 36 (4) ◽

pp. 1099-1116

Author(s):

Gerald A. Lehmacher ◽

Miguel F. Larsen ◽

Richard L. Collins ◽

Aroh Barjatya ◽

Boris Strelnikov

Keyword(s):

Attitude Control ◽

Large Scale ◽

Lower Thermosphere ◽

Density Fluctuations ◽

Large Temperature ◽

Small Scale ◽

Spatial And Temporal Variability ◽

Temperature Structure ◽

Wind Shears

Abstract. Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (<0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0<Ri<0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (Kp∼5).

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Low Environmental Impact Machining Processes of Composite Materials Applied to the Aerospace Sector

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.107.15 ◽

2010 ◽

Vol 107 ◽

pp. 15-19 ◽

Cited By ~ 3

Author(s):

Miguel Álvarez ◽

Moisés Batista ◽

Jorge Salguero ◽

Manuel Sánchez-Carrilero ◽

Mariano Marcos Bárcena

Keyword(s):

Evaluation Process ◽

Advanced Materials ◽

Surface Finishing ◽

Matrix Composites ◽

Machining Processes ◽

Tool Materials ◽

Industrial Sectors ◽

Aerospace Sector ◽

Aeronautical Industry

In the last decades, technologically innovative processes performed in advanced materials such as Carbon Fibre (CF) and Metal Matrix Composites (MMC) have continuously increased because of these materials find increasingly applications in the most of the industrial sectors, particularly in aeronautical industry. This is caused by their excellent relationship weight/mechanical properties. Although there is a high trend to apply and develop non-conventional technologies and methods for machining CF and MMC, other common machining processes are commonly applied for working these materials. Thus, in aeronautical industry, mechanical drilling processes are usually applied for preparing the manufactured elements to be assembled. However, drilling of CF based materials can carry on troubles related to a loss of surface finishing quality and/or quick and high tool wear. This work reports on the results about an evaluation process of the surface quality of drilled CF samples as a function of the cutting conditions and the tool materials.

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Microwave snow emission modeling uncertainties in boreal and subarctic environments

The Cryosphere Discussions ◽

10.5194/tcd-9-5719-2015 ◽

2015 ◽

Vol 9 (5) ◽

pp. 5719-5773

Author(s):

A. Roy ◽

A. Royer ◽

O. St-Jean-Rondeau ◽

B. Montpetit ◽

G. Picard ◽

...

Keyword(s):

Grain Size ◽

Spatial Variability ◽

Boreal Forest ◽

Frozen Soil ◽

Microwave Emission ◽

Small Scale ◽

Radiometric Measurements ◽

Snow Properties ◽

Modeling Uncertainties

Abstract. This study aims to better understand and quantify the uncertainties in microwave snow emission models using the Dense Media Radiative Theory-Multilayer model (DMRT-ML) with in situ measurements of snow properties. We use surface-based radiometric measurements at 10.67, 19 and 37 GHz in boreal forest and subarctic environments and a new in situ dataset of measurements of snow properties (profiles of density, snow grain size and temperature, soil characterization and ice lens detection) acquired in the James Bay and Umijuaq regions of Northern Québec, Canada. A snow excavation experiment – where snow was removed from the ground to measure the microwave emission of bare frozen ground – shows that small-scale spatial variability in the emission of frozen soil is small. Hence, variability in the emission of frozen soil has a small effect on snow-covered brightness temperature (TB). Grain size and density measurement errors can explain the errors at 37 GHz, while the sensitivity of TB at 19 GHz to snow increases during the winter because of the snow grain growth that leads to scattering. Furthermore, the inclusion of observed ice lenses in DMRT-ML leads to significant improvements in the simulations at horizontal polarization (H-pol) for the three frequencies (up to 20 K of root mean square error). However, the representation of the spatial variability of TB remains poor at 10.67 and 19 GHz at H-pol given the spatial variability of ice lens characteristics and the difficulty in simulating snowpack stratigraphy related to the snow crust. The results also show that for ground-based radiometric measurements, forest emission reflected by the surface leads to TB underestimation of up to 40 K if neglected. We perform a comprehensive analysis of the components that contribute to the snow-covered microwave signal, which will help to develop DMRT-ML and to improve the required field measurements. The analysis shows that a better consideration of ice lenses and snow crusts is essential to improve TB simulations in boreal forest and subarctic environments.

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A Case Study of Clear-Air Turbulence at Upper Levels

10.5194/ems2021-182 ◽

2021 ◽

Author(s):

Léo Rogel ◽

Didier Ricard ◽

Eric Bazile ◽

Irina Sandu

Keyword(s):

Turbulent Flow ◽

Partial Information ◽

Weather Prediction ◽

Turbulent Fluxes ◽

Small Scale ◽

Mixing Length ◽

Vertical Resolution ◽

Stable Conditions ◽

Study Results

Because of the technical difficulties of achieving measurements at high altitudes, it is not clear how well turbulent phenomena are represented in the upper levels of current Numerical Weather Prediction (NWP) operational models. Indeed, turbulence in strongly stable conditions near the tropopause is known to be particularly difficult to correctly parameterize. The constraining buoyancy forces on the vertical lead to anisotropic turbulence, potentially inhibiting turbulent production in NWP models. Partial information for high altitude turbulence events is nonetheless available in the form of in-situ measurements from aircrafts. However, it only allows for qualitative comparisons with model outputs. This study focuses on a turbulent episode induced by a winter upper-level jet above east Belgium on January 27, 2018, for which in-situ EDR (Eddy Dissipation Rate) reports indicate moderate-or-greater turbulence levels. Numerical simulations are performed with the M&#233;t&#233;o-France operational model AROME, and with the mesoscale research model MesoNH (Laero/CNRM), at the same horizontal grid resolution (1.3km). These two models also use the eddy-diffusivity turbulence scheme of Cuxart et al (2000), a 1.5 order closure scheme based on a prognostic Turbulent Kinetic Energy (TKE) evolution equation, with a diagnostic computation of the mixing length. TKE budgets, as well as stability indices and gradient-based quantities (Richardson number, vertical wind shear) are computed from the model outputs, and qualitative comparison with in-situ data is presented. Time evolution of the turbulent event over Belgium is well captured by both models, agreeing with EDR data. Several sensitivity tests on the vertical resolution, on the mixing length formulation and on the parameters of the TKE equation are then performed. Most notably, the use of an increased vertical resolution near the tropopause greatly enhances the turbulent fluxes in both operational and research models. Secondly, comparison of various expressions of the mixing length shows that the Bougeault and Lacarrere (1989) formulation produces the higher amount of subgrid TKE and turbulent mixing. A decreased turbulent dissipation parameter also significantly increases the amount of subgrid TKE. On the contrary, the use of a 3D turbulence scheme appears to have very limited impacts on the turbulent flow at this kilometer-scale horizontal resolution. On a second part of this study, results from ongoing Large Eddy Simulations (LES) will be presented. These simulations aim at representing small-scale features of the turbulent flow. They will be used as a reference for the computation of turbulent fluxes at kilometer-scale resolution using a coarse-graining method, allowing for a comparison with the parameterized fluxes from the turbulence scheme. In particular, the dissipation term of the TKE equation will be examined. These results are expected to give insight on the leading turbulent mechanisms for which the current turbulence parameterization can be improved in stable conditions.

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The standard characterization of the Romanian onion landrace ‘Roșie de Făgăraș’

Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca Horticulture ◽

10.15835/buasvmcn-hort:12227 ◽

2016 ◽

Vol 73 (2) ◽

pp. 101

Author(s):

Mihaela Antofie ◽

Camelia Sand Sava

Keyword(s):

In Situ Conservation ◽

Political Support ◽

Medium Size ◽

Small Scale ◽

The European Union ◽

Market Place ◽

Food And Agriculture ◽

Land Cultivation

‘Roșie de Făgăraș’ is a red onion landrace originating from the old region Făgăraș Country situated in South East Transylvania. It was officially included in the National Official Catalogue for cultivars and hybrids in 1952, for almost 50 years, and erased before 2004 without applying in situ conservation measures. However, food security depends on the appropriate management of all genetic resources for food and agriculture (PGRFA). Thus they have to be conserved and sustainable used and efforts have to be done for the recognition of this landrace as a PGRFA and therefore to be maintained "under conservation" into the Official Catalogue. The study focused on analysing data from three localities recognized for cultivating ‘Roșie de Făgăraș’, in order to evaluate morphometric characteristics of mature onion bulbs according to the UPOV Standard TG/46/7, productivity, land cultivation and socio-economic vulnerabilities. The analysis of morphometric measurements results support that ‘Roșie de Făgăraș’ is a medium size red onion that may have the chance to enter the market place, at least at the small scale, according to the current regulatory framework of the European Union regarding the conservation of landraces and provided by: Directive 2008/62/EC, Directive 2009/145/EC and Directive 2010/60/EU. The analysis of productivity, and land cultivation revealed dramatic land use change associated with the decline of cultivated area as following: 76.27% in Mândra, 50% in Recea and 33.34% in Beclean. With an increasing aging population, lack of political support for entering the market place, decrease of landowners cultivating ‘Roșie de Făgăraș’ for trade will increase vulnerability of traditional knowledge related to the conservation of this landrace.

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