scholarly journals Mineralogical, Textural and Physical Characterisation to Determine Deterioration Susceptibility of Irulegi Castle Lime Mortars (Navarre, Spain)

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 584 ◽  
Author(s):  
Graciela Ponce-Antón ◽  
Anna Arizzi ◽  
Maria Zuluaga ◽  
Giuseppe Cultrone ◽  
Luis Ortega ◽  
...  
Keyword(s):  
Size Range ◽  
Local Environment ◽  
High Water ◽  
Absorption Capacity ◽  
Annual Rainfall ◽  
High Porosity ◽  
Repair Mortar ◽  
Lime Mortars ◽  
Historical Heritage ◽  
High Degree

Archaeological lime mortars from the Tower Keep and West perimeter wall of Irulegi Castle (Navarre, Spain) were analysed to determine susceptibility to deterioration. Chemical, mineralogical, textural and physical characterisation was performed by different tests and multianalysis techniques in order to determine the intrinsic features of the original historical mortars at the castle. Samples from the Tower Keep are more prone to deteriorate compared with the West perimeter wall due to high water absorption capacity and high porosity. A high degree of pore interconnection, high desorption index and the presence of high pore volume in the 0.01 to 1 µm size range affect the mortar durability since pores retain water longer inside the mortar. Local environment conditions with persistent annual rainfall, high humidity and temperature variations contribute to the decay process of the original mortar. Characterisation of historical mortars not only allows better understanding of susceptibility to deterioration but also helps the design of compatible and durable repair mortar for future interventions on historical heritage. Compatibility of new materials with the historical mortar will be ensured by studying mortar characteristics and properties.

scholarly journals Preparation and Characterization of Nanocellulose/Chitosan Aerogel Scaffolds Using Chemical-Free Approach

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 246
Author(s):  
Samsul Rizal ◽  
Esam Bashir Yahya ◽  
Abdul Khalil H.P.S. ◽  
C. K. Abdullah ◽  
Marwan Marwan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Uptake ◽  
High Surface ◽  
Cellulose Nanofibers ◽  
High Surface Area ◽  
Three Dimensional ◽  
High Water ◽  
Absorption Capacity ◽  
Mechanical And Thermal Properties ◽  
High Porosity

Biopolymer-based aerogels are open three-dimensional porous materials that are characterized by outstanding properties, such as a low density, high porosity and high surface area, in addition to their biocompatibility and non-cytotoxicity. Here we fabricated pure and binary blended aerogels from cellulose nanofibers (CNFs) and chitosan (CS), using a chemical-free approach that consists of high-pressure homogenization and freeze-drying. The prepared aerogels showed a different porosity and density, depending on the material and mixing ratio. The porosity and density of the aerogels ranged from 99.1 to 90.8% and from 0.0081 to 0.141 g/cm3, respectively. Pure CNFs aerogel had the highest porosity and lightest density, but it showed poor mechanical properties and a high water absorption capacity. Mixing CS with CNFs significantly enhance the mechanical properties and reduce its water uptake. The two investigated ratios of aerogel blends had superior mechanical and thermal properties over the single-material aerogels, in addition to reduced water uptake and 2-log antibacterial activity. This green fabrication and chemical-free approach could have great potential in the preparation of biopolymeric scaffolds for different biomedical applications, such as tissue-engineering scaffolds.

Enhanced Hydrolytic Stability of Porous Boron Nitride via the Control of Crystallinity, Porosity and Chemical Composition

2018 ◽  
Author(s):  
Ravi Shankar ◽  
Sofia Marchesini ◽  
Camille Petit
Keyword(s):  
Boron Nitride ◽  
Hydrolytic Stability ◽  
Chemical Properties ◽  
Spectroscopic Techniques ◽  
High Porosity ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Treated Sample ◽  
Molecular Separations ◽  
High Degree

Porous boron nitride is gaining significant attention for applications in molecular separations, photocatalysis, and drug delivery. All these areas call for a high degree of stability (or a controlled stability) over a range of chemical environments, and particularly under humid conditions. The hydrolytic stability of the various forms of boron nitride, including porous boron nitride, has been sparingly addressed in the literature. Here, we map the physical-chemical properties of the material to its hydrolytic stability for a range of conditions. Using analytical, imaging and spectroscopic techniques, we identify the links between the hydrolytic instability of porous boron nitride and its limited crystallinity, high porosity as well as the presence of oxygen atoms. To address this instability issue, we demonstrate that subjecting the material to a thermal treatment leads to the formation of crystalline domains of h-BN exhibiting a hydrophobic character. The heat-treated sample exhibits enhanced hydrolytic stability, while maintaining a high porosity. This work provides an effective and simple approach to producing stable porous boron nitride structures, and will progress the implementation of the material in applications involving interfacial phenomena.<br>

scholarly journals Nucleation of Ga droplets self-assembly on GaAs(111)A substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Artur Tuktamyshev ◽  
Alexey Fedorov ◽  
Sergio Bietti ◽  
Stefano Vichi ◽  
Riccardo Tambone ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Size Distribution ◽  
Self Assembly ◽  
Cluster Size ◽  
Droplet Size Distribution ◽  
Local Environment ◽  
The Self ◽  
Critical Cluster ◽  
Droplet Nucleation ◽  
High Degree

AbstractWe investigated the nucleation of Ga droplets on singular GaAs(111)A substrates in the view of their use as the seeds for the self-assembled droplet epitaxial quantum dots. A small critical cluster size of 1–2 atoms characterizes the droplet nucleation. Low values of the Hopkins-Skellam index (as low as 0.35) demonstrate a high degree of a spatial order of the droplet ensemble. Around $$350\,^{\circ }\hbox {C}$$ 350 ∘ C the droplet size distribution becomes bimodal. We attribute this observation to the interplay between the local environment and the limitation to the adatom surface diffusion introduced by the Ehrlich–Schwöbel barrier at the terrace edges.

scholarly journals Cellulose Nanofibrils/Xyloglucan Bio-Based Aerogels with Shape Recovery

Gels ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 5
Author(s):  
Samuel Mandin ◽  
Samuel Moreau ◽  
Malika Talantikite ◽  
Bruno Novalès ◽  
Jean-Eudes Maigret ◽  
...  
Keyword(s):  
Water Absorption ◽  
Shape Recovery ◽  
Cellulose Nanofibrils ◽  
High Water ◽  
Absorption Capacity ◽  
Absorption Properties ◽  
High Affinity ◽  
High Water Absorption ◽  
Freezing Procedure ◽  
The Impact

Bio-based aerogels containing cellulose nanofibrils (CNFs) are promising materials due to the inherent physical properties of CNF. The high affinity of cellulose to plant hemicelluloses (xyloglucan, xylan, pectin) is also an opportunity to develop biomaterials with new properties. Here, we prepared aerogels from gelled dispersions of CNFs and xyloglucan (XG) at different ratios by using a freeze-casting procedure in unidirectional (UD) and non-directional (ND) manners. As showed by rheology analysis, CNF and CNF/XG dispersions behave as true gels. We investigated the impact of the freezing procedure and the gel’s composition on the microstructure and the water absorption properties. The introduction of XG greatly affects the microstructure of the aerogel from lamellar to cellular morphology. Bio-based aerogels showed high water absorption capacity with shape recovery after compression. The relation between morphology and aerogel compositions is discussed.

Wind blown sediment mass budget of Sahelian village land units in Niger

2001 ◽  
Vol 172 (5) ◽  
pp. 523-531 ◽  
Author(s):  
Jean-Louis Rajot
Keyword(s):  
Wind Erosion ◽  
Size Range ◽  
Arable Land ◽  
Annual Rainfall ◽  
Complete Disappearance ◽  
Mass Budget ◽  
Sediment Mass ◽  
Aeolian Sediments ◽  
Average Annual Rainfall ◽  
The Village

Abstract To assess the mass budget of aeolian sediments transported by wind (erosion vs. deposition) at the scale of village land units (25 kmX25 km), measurements were carried out during 3 years (from 1996 to 1998) in a cultivated field and in a fallow area simultaneously. These were located in the Sahelian zone of Niger with an average annual rainfall of 560 mm. The vertical upward fluxes of particles &lt;20 mu m exported from the study area were estimated from the horizontal sediment fluxes measured using BSNE sand catchers. This mass of exported dust was compared with the vertical downward fluxes of particles of the same size range (&lt;20 mu m) measured using passive CAPYR collectors. Values of deposition recorded in the field and in the fallow were similar. In the field, wind erosion reached its maximum in May and June when the vegetation cover was minimal. In the fallow area, wind erosion was always very low in comparison with the field. It occurred during the strongest storms when the grass cover was minimal. Nevertheless, the net balance between deposition and erosion was highly positive in the fallow areas. These results have been extrapolated at the scale of the village land units based on the current land use. At this scale, the balance was positive for the arable land, indicating a net deposition of aeolian sediments of +0.36 t ha (super -1) yr (super -1) . However, the complete disappearance of fallow land would result in a balanced budget for the arable land.

Comparison of Bio and Eco-technologies with Chemical Methods for Pre-treatment of Flax Fibers: Impact on Fiber Properties

2014 ◽  
Vol 9 (4) ◽  
pp. 155892501400900 ◽  
Author(s):  
Sabela Camano ◽  
Nemeshwaree Behary ◽  
Philippe Vroman ◽  
Christine Campagne
Keyword(s):  
Water Absorption ◽  
Fiber Bundle ◽  
Glass Fibers ◽  
Fiber Surface ◽  
Pectate Lyase ◽  
High Water ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Flax Fibers ◽  
The Impact

Flax fibers, available as fiber bundles, are commonly used as fiber reinforcement in composite materials as a substitute for glass fibers. Pre-treatments are often necessary for improving fiber-resin adhesion, and also to facilitate fiber elementarization, and to improve fiber ability to be implemented in mechanical processes limiting fiber damages. This paper focuses on the impact of biotechnologies (effect of 2 different enzymes: a pectate lyase and a laccase) and of an ecotechnology (ultrasound with ethanol), compared to classical chemical pre-treatments (using aqueous NaOH and ammonia) on the final flax fiber bundle properties, before and after a carding process. Fiber surface properties (wettability and/or zeta potential values), fiber elementarization and mechanical properties vary with the type of treatment (chemical nature of product and conditions used). Fibers elementarised using pectate lyase and ultrasound/ethanol have a hydrophilic surface and a high water absorption capacity, and are also of highest quality in terms of increased fineness. Treatment with NaOH yields the poorest fiber bundle tenacity. Laccase enzyme yields long thick hydrophobic fibers having very low water absorption capacity, and the most neutral surface charge. Properties of flax fibers can be easily monitored using different pre-treatments resulting in fibers which would be suited for various final applications.

scholarly journals Fresh contact: Youth, migration, and atmospheres in India

2018 ◽  
Vol 37 (2) ◽  
pp. 313-330 ◽  
Author(s):  
Jane Dyson
Keyword(s):  
Young People ◽  
Word Meaning ◽  
Local Environment ◽  
Social Nature ◽  
Environmental Setting ◽  
The Social ◽  
Youth Agency ◽  
Indian Village ◽  
High Degree

This paper uses long-term research in an Indian village to develop Karl Mannheim’s notion of each generation’s ‘fresh contact’ with their inherited social and environmental setting. I examine how a generation of young people re-apprehend their local environment following a period of migration. I argue that young people aged between 25 and 34 who have lived outside their locality re-appraise their village economically and spiritually when they return home. I point to the social nature of this ‘fresh contact’, its spatial character, and the high degree of reflexivity that young men display in discussing their own agency as a generation – a point that emerged especially clearly in their discussion of the term ‘ mahaul,’ a Hindi word meaning ‘atmosphere’. The paper contributes to geographical and anthropological work on youth agency by highlighting the utility of notions of fresh contact in specific social conjunctures, such as the migration of a particular cohort. At the same time, it suggests the importance of placing alongside Mannheim’s work an explicit focus on the spatial nature of fresh contact, the sociality that constitutes cohorts as generations, and young people’s reflexive capacity to theorise their generational agency.

scholarly journals China's water sustainability in the 21st century: a climate-informed water risk assessment covering multi-sector water demands

2014 ◽  
Vol 18 (5) ◽  
pp. 1653-1662 ◽  
Author(s):  
X. Chen ◽  
D. Naresh ◽  
L. Upmanu ◽  
Z. Hao ◽  
L. Dong ◽  
...  
Keyword(s):  
Water Stress ◽  
Risk Measures ◽  
Rainfall Variability ◽  
Political Process ◽  
Temporal Distribution ◽  
High Water ◽  
Annual Rainfall ◽  
Water Sustainability ◽  
Domestic Water ◽  
Water Demands

Abstract. China is facing a water resources crisis with growing concerns as to the reliable supply of water for agricultural, industrial and domestic needs. High inter-annual rainfall variability and increasing consumptive use across the country exacerbates the situation further and is a constraint on future development. For water sustainability, it is necessary to examine the differences in water demand and supply and their spatio-temporal distribution in order to quantify the dimensions of the water risk. Here, a detailed quantitative assessment of water risk as measured by the spatial distribution of cumulated deficits for China is presented. Considering daily precipitation and temperature variability over fifty years and the current water demands, risk measures are developed to inform county level water deficits that account for both within-year and across-year variations in climate. We choose political rather than watershed boundaries since economic activity and water use are organized by county and the political process is best informed through that unit. As expected, the risk measures highlight North China Plain counties as highly water stressed. Regions with high water stress have high inter-annual variability in rainfall and now have depleted groundwater aquifers. The stress components due to agricultural, industrial and domestic water demands are illustrated separately to assess the vulnerability of particular sectors within the country to provide a basis for targeted policy analysis for reducing water stress.

scholarly journals OPTIMUM PERFORMANCE OF STABILIZED EDE LATERITE AS AN ALTERNATIVE CONSTRUCTION MATERIAL

2020 ◽  
Vol 3 (8) ◽  
pp. 1-8
Author(s):  
Adegbenle Bukunmi O
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Construction Material ◽  
High Water ◽  
Good Alternative ◽  
Linear Shrinkage ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Optimum Performance ◽  
High Water Absorption

Laterite samples from Ede area with particle components of 19.7% clay, 32.8% silt and 47.5% sand was stabilized with combined cement, lime and bitumen and test for Compressive strength, Linear Shrinkage, Permeability and Water Absorption. The stabilizers were mixed with laterite soil in different ratios and percentage. The laterite carried 90% which is constant while the three stabilizers shared the remaining 10% in varying form. After 28 days of curing, laterite stabilizer with 90% of laterite, 8% of cement, 1% lime and 1% bitumen (LCLB1) possessed compressive strength of 2.01N/mm2. It Water Absorption Capacity was 3.05%. LCLB4 stabilizer (90% laterite, 6% cement, 2% lime and 2% bitumen) has the same compressive strength with LCLB1 stabilizer but with a high Water Absorption Capacity of 4.2%. The stabilizer of 90% laterite, 3.33% cement, 3.33% lime and 3.33% of bitumen (LCLB8) has the lowest compressive strength of 0.74N/mm2 and the highest Water Absorption Capacity of 5.39%. The results shows that LCLB1 stabilizer is a better stabilizer for strength and blocks made from laterite stabilized with it stand a good alternative to sand Crete blocks in building constructions. The combination of these stabilizers in order to determine a most economical volume combination for optimum performance is highly possible and economical.

Pineapple shell fiber as reinforcement in cassava starch foam trays

2019 ◽  
Vol 27 (8) ◽  
pp. 496-506
Author(s):  
Arnold Cabanillas ◽  
Julio Nuñez ◽  
JP Cruz-Tirado ◽  
R Vejarano ◽  
Delia R Tapia-Blácido ◽  
...  
Keyword(s):  
Food Packaging ◽  
Physical And Mechanical Properties ◽  
Crystallinity Index ◽  
High Water ◽  
Cassava Starch ◽  
Absorption Capacity ◽  
Expanded Polystyrene ◽  
Molding Process ◽  
Dry Food ◽  
Physicochemical And Structural Properties

Pineapple shell, considered a waste in the juice industry, was used as a reinforcement material to produce biodegradable foam trays (FTs) based on cassava starch by a compression molding process. These foams were prepared with different starch/fiber ratios and then were characterized according to their microstructure and physical and mechanical properties. The starch/fiber ratio of 95/5 showed the lowest values of thickness and density (2.58 mm and 367 kg m−3, respectively). There was a good distribution of the pineapple shell fiber throughout the polymeric matrix. All FTs showed a semicrystalline structure and 95/5 ratio showed the highest crystallinity index (CI) value (39%). In addition, this ratio improved the tensile strength of the FTs, obtaining similar values to expanded polystyrene (EPS) samples, used as the reference material. Nevertheless, all FTs reinforced with pineapple shell fiber showed high water absorption capacity (WAC); therefore, future studies should focus on to improve the physicochemical and structural properties of the cassava starch-based foams, considering the promising potential of this novel biodegradable material for dry food packaging, such as a viable alternative to reduce the use of petroleum-based materials such as commercial EPS trays.

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