Impregnation Of Materials Research Articles

Antimicrobial Cellulose Nanofibril Porous Materials Obtained by Supercritical Impregnation of Thymol.

This study presents the impregnation in supercritical carbon dioxide (scCO2) of nanocellulose-based structures with thymol as a natural antimicrobial molecule to prepare bioactive, biosourced materials. First, cellulose nanofibrils (CNFs) were used to produce four types of materials (nanopapers, cryogels from water or tert-butyl alcohol suspensions, and aerogels) of increasing specific surface area up to 160 m2·g-1, thanks to the use of different processes, namely, vacuum filtration, freeze-drying, and supercritical drying. Second, these CNF-based structures were impregnated with thymol in the scCO2 medium using a relatively low temperature and pressure of 40 °C and 100 bar during 1 h. The amount of impregnated thymol in the different CNF materials was investigated by fluorescence spectroscopy, 13C NMR analysis, and gas chromatography. All three methods consistently showed that the amount of impregnated thymol increases with the specific surface area of the material. The antimicrobial activity of the impregnated CNF-based materials was then measured against three reference strains of microorganisms: the Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis bacteria, and the yeast Candida albicans using the disk diffusion test method. The latter revealed the leaching of thymol in sufficient amounts to generate antimicrobial activity against the three strains in the case of the cryogel derived from a tert-butyl alcohol suspension and the aerogel, which are the two materials exhibiting the highest specific surface areas. The proposed strategy, therefore, enabled us to precisely steer the amount of active molecule loading and the related antimicrobial activity by adjusting the specific surface area of the biosourced material impregnated in green supercritical conditions. These results are very promising and confirm that supercritical impregnation of active molecules onto nanocellulose three-dimensional (3D) structures can be an interesting solution for the design of active medical devices such as wound dressings.

General Strategy to Prepare Single-Layered Ag-Au-Pt Nanocrystal Ternary-Coated Biomass Textiles through Polymer-Driven Self-Assembly.

Current metal nanomaterials for developing nanofunctional textiles are mostly based on metal nanoparticles (NPs) that show aqueous instability, a tendency to aggregate, and low chemical affinity to biomass textiles, leading to low nano-metal uptake during finishing, significant declines in function, and nano-pollution. Herein, we demonstrate a strategy to transform metal (Ag, Au, and Pt) NPs into homogenous hyperbranched poly(amide-amine) (HBPAA)-encapsulated NPs showing high water solubility, oxidative resistance, and affinity to biomass materials upon surface capping with HBPAA. The proposed method represents a universal, simple, clean, and efficient self-assembly technology to produce monolayered Ag–Au–Pt ternary-coated biomass textiles. The combination of Ag, Au, and Pt NPs yields a positive potential of approximately +37.12 mV depending on the metal concentration and could simultaneously self-assemble onto natural fibers, including cotton, silk, and wool, through the one-step impregnation of textiles. Increasing the temperature and concentration of the mixture favors the self-assembly process. A mixture of 30–110 mg/L Ag, Au, and Pt NPs could nearly completely anchor onto cotton, silk, and wool textiles after impregnation at 100 °C for 1 h without chemical assistance, thereby indicating the possibility of clean production. As-prepared functional cotton, silk, and wool possessed similarly high antibacterial activities, and a mixture containing over 1500 mg/g NPs inhibited 99% of the Escherichia coli and Staphylococcus aureus in the sample textiles. The developed coating technology is simple, clean, controllable, and broadly applicable; thus, it could be potentially applied in functional textiles.

Using piezoresistive pressure sensors for resin flow monitoring in wind turbine blades

The production of large wind turbine blades is a costly and time-consuming process. In order to obtain high-quality products and to avoid dry spots, it is necessary to monitor the resin flow during the resin infusion process. Using piezoresistive pressure sensors to perform in-situ measurement of the pressure gradient gives live information about the textile impregnation status during the manufacturing process and enables instant reaction if some anomalies are discovered. In this work, the effects of the used sensors on the static mechanical properties and the fatigue behaviour of the used glass fibre composites were investigated. The sensors were used during the manufacturing of large sandwich panels similar to that used in wind turbine blades. It was found, that the used sensors do not degrade the mechanical performance of the used materials and they are able to measure the pressure gradient during the manufacturing of wind turbine blades and to give information about the progress of the resin front.

Design of Radiation Hard Spare Units for the Orbit Corrector Dipoles of LHC

Due to the High Luminosity upgrade of the Large Hadron Collider (HL-LHC), the orbit corrector dipoles located just before the interaction points of the accelerator will receive significantly increased gamma radiation doses, i.e., up to 20 MGy over the HL-LHC lifetime. Since these magnets were not designed to withstand such high gamma doses, new MCBC and MCBY magnets have to be designed and produced using radiation hard impregnation insulation and materials. In this paper, we describe both the gamma radiation campaign we are performing to determine the radiation hardness of the present MCBC and MCBY magnets and the new design and technologies that we have selected for the manufacturing of radiation hard spare units. We also discuss the impact of failing MCBC and MCBY magnets on the LHC and the foreseen alternative solutions.

Cinnamyl Alcohol Oxidation Using Supported Bimetallic Au\u2013Pd Nanoparticles: An Optimization of Metal Ratio and Investigation of the Deactivation Mechanism Under Autoxidation Conditions

The aerobic oxidation of cinnamyl alcohol in toluene under autoxidation conditions has been studied using a range of 1 wt% Au–Pd/TiO2 catalysts. The catalysts have been studied to determine the effect of preparation method (impregnation and sol immobilisation) and metal ratio on the conversion of cinnamyl alcohol and the selectivity to cinnamaldehyde. The catalysts prepared by sol-immobilisation demonstrate higher selectivity to the desired aldehyde than the analogous impregnation materials. The most active catalyst was found to be 0.75 wt% Au–0.25 wt% Pd/TiO2 prepared by sol-immobilisation and this demonstrates the importance of metal ratio optimisation in this catalytic process. Furthermore, this metal ratio was found to be most stable under the reactions conditions with little change observed over multiple uses.

Combustion Properties of Impregnated and Heat-Treated Wood Material

The use of heat-treated wood material and eco-friendly impregnation chemicals are steadily increasing in the woodworking industry over the last decades. In this study, the effects of applications of impregnation and heat treatment on combustion properties of Hornbeam (Carpinus betulus L.) wood were investigated. The test specimens were impregnated with Imersol-aqua (Ia) and Timbercare-aqua (Ta) impregnation material according to ASTM D 1413-76 standards. Impregnated specimens were subjected to heat treatment at 150, 170 and 190 °C for 2 h. The temperature of flame source combustion, the temperature of without flame source combustion and varying light intensities (Lux) depending on the smoke production in these combustion stages were determined according to ASTM E 160-50. According to the test results, the highest combustion temperature of flame source combustion was determined in unimpregnated and heat-treated samples at 190 °C, while the highest combustion temperature of without flame source combustion was determined in impregnated with Ta and heat-treated samples at 170 °C. The highest light density in flame source combustion phase was determined in unimpregnated and heat-treated samples at 190°C, while in without flame source combustion was in unimpregnated and heat-treated samples at 170°C. As a result, as the heat treatment temperature increase, the combustion temperature increased and the smoke density decreased. In addition to impregnation materials increased the smoke density while reduced the combustion temperatures of test specimens.

Desarrollo de Zeolitas Sn-ZSM-11 para la Síntesis de Lactatos de Alquilo

En el presente trabajo se exponen distintas alternativas de incorporación de Sn en la zeolita ZSM-11 (estructura MEL): impregnación por vía húmeda, tratamiento alcalino y síntesis hidrotérmica con estaño como heteroátomo; así como diferente contenido de catión metálico (~2-10% p/p). La estructura ZSM-11 se confirmó por DRX para todas las muestras, en tanto que en los materiales impregnados la cristalinidad disminuyó a medida que se incrementó la cantidad del metal incorporado al catalizador. El estudio por TPR señaló la reducción de las especies superficiales vecinas a los enlaces Sn-O y la reducción de Sn+4 a Sn+2. Por el método BET se analizó el área superficial y se encontró que la misma disminuye al aumentar el contenido de Sn incorporado por impregnación húmeda y por síntesis hidrotérmica. Mediante FTIR con adsorción de piridina se determinó la cantidad, fuerza y relación de sitios ácidos. Dichos materiales exhibieron un buen desempeño catalítico en la conversión de dihidroxiacetona (DHA) a alquil lactatos de cadena corta, éstos últimos representan solventes verdes prometedores.

Effect of Applied Compressive Stress and Impregnation Material on Internal Strain and Stress State in Nb3Sn Rutherford Cable Stacks

The Nb3Sn superconductor in accelerator magnets must resist high mechanical stresses. In order to better understand the effect of the coil impregnation system on the stresses exerted on the strain-sensitive Nb3Sn superconductor, we have measured the elastic strain evolution in the conductor constituents under externally applied loads. For this purpose, a dedicated load frame that enables rotation of the sample load axis with respect to the neutron scattering geometry was installed in the Stress-Spec beamline at the neutron source Heinz Maier-Leibnitz FRM II. The Nb3Sn- and Cu-loading strains were measured in situ by neutron diffraction under monotonic and cyclic compressive loading. So-called ten-stack samples composed of Nb3Sn Rutherford type cables with different impregnation and coil blocks extracted from an 11 T dipole short model coil were investigated.

Kolofan reçinesi katkılı borlu bileşiklerle emprenye edilen Sarıçam (Pinus Sylvestris Lipsky) odununun yanma özellikleri

The aim of this study was to investigate the combustion properties of Scots pine (Pinus sylvestris Lipsky) wood impregnated with boron compound (borax (Na2B4O710H2O), boric acid (H3BO3) w/w 50:50%) doped colophony (C19H29COOH). For this aim, Scots pine wood samples were impregnated with boron compound doped colophony by the method of medium-term dipping according to ASTM D 1413 and producers’ definition. Combustion properties of samples after impregnated process were determined according to ASTM E 160. As a part of the research, 6 different combination and contents of impregnation materials have been used in order to especially investigate resistance against combustion of wood material treated with boron compounds in different concentrations. Consequently, retention performance and leaching resistance of boron compounds can be increased through colophony addition. Impregnation materials with colophony decreased the flame sourced combustion (Fsc) temperatures depending on kind of impregnation material, combustion period and weight loss ratio of the test samples decreased in comparison to the control samples. Colophony can be preferred in impregnation with boron compounds depending on kind of wood and using area.

Mathematical model of heat transfer in PCM incorporated fabrics subjected to different thermal loads

Impregnation of textiles (fabrics) by phase change materials (PCMs) changes their thermal properties. High thermal capacity of PCMs, due to large enthalpy of phase change (latent heat), increase the potential of these materials for heat accumulation, but also modifies heat transfer in transient states what improves their insulating characteristics. The paper presents selected results of the research that was focused on the development of mathematical and numerical models of heat transfer in the fabrics laminated by the layers containing phase change materials. Different modes of interaction with the environment were taken into account, including radiative heating, cooling in natural convection and direct contact of the fabric with a solid body of large thermal capacity. The models were validated with the use of experimental measurement of thermal performance characteristics of the fabrics with PCM incorporated. Validation allowed also quantitative identification of some parameters characterizing heat transfer both inside the fabrics and interaction with the environment, such as absorption an transmission coefficient for radiation. In the study the real thermal characteristics of the fabrics were used, e.g. enthalpy vs. temperature determined with the use of DSC. Overall thermal characteristics of the textiles, i.e. temperature variations under different thermal loads, are also presented in the paper.

Carbon Fibre Reinforced Concrete: Dependency of Bond Strength on T<sub>g</sub> of Yarn Impregnating Polymer

In this paper, a method for the evaluation of the influence of different polymer suspensions and environmental conditions on adhesion between an impregnated carbon fibre heavy tow and concrete for reinforcement will be proposed. For this purpose, the impregnation material itself was investigated as a polymer film before and after incubation in water and aqueous suspensions, such as NaOH and a cementitious solution, in terms of its thermal properties, swelling behaviour and morphology. Thin polymer films were manufactured and subsequently investigated with quantification of the swelling for 28 d by thermal and scanning electron microscope analysis. The effect of pull-out shear stress was evaluated to investigate parameters such as high temperature and moisture on adhesion to concrete. Contact angle measurements were used to determine the surface energy of the polymer films. All incubated polymer films yielded a change in both surface morphology and specific residues on the polymer film surface, e.g. in the form of calcium carbonate, but no change in glass-transition temperature. A high correlation between glass-transition temperature and measured shear stress was shown during single yarn pull-out tests. Furthermore, the water treatment of pull-out samples strengthened the influence for the glass-transition temperature during the adhesion test. No influence of the surface energy of the used polymer impregnation for carbon fibres on the pull-out test was detected.

Damage Mechanisms of Polymer Impregnated Carbon Textiles Used as Anode Material for Cathodic Protection

Carbon textiles as anode material for cathodic corrosion protection (CP) have been used in several reinforced steel structures. However, experience with durability is limited. To date, various influencing factors have been discovered and systematic tests on different carbon textiles with different impregnation materials in various environmental media have been carried out and considered the degradation of the impregnation materials. In this work the boundary potentials are determined at which the impregnation and sizing is destroyed under anodic polarization and the damage mechanisms are described.

Evaluation of a solid nitrogen impregnated MgB2 racetrack coil

To develop powerful wind turbine generators using superconducting technology, high-performance superconducting racetrack coils are essential. Herein, we report an evaluation of a multifilamentary magnesium diboride (MgB2) conductor-based racetrack coil cooled and impregnated simultaneously by solid nitrogen (SN2). The coil was wound on a copper former with 13 mm winding width, an inner diameter of 124 mm at the curvature, and 130 mm length of the straight section. An in situ processed S-glass-insulated 36-filament MgB2 wire was wound on the former in two layers with 19.5 turns, and heat treated via the wind and react method without any epoxy resin. The coil was evaluated for critical temperature and transport critical current in the SN2 environment at different temperatures up to 31.3 K in self-field. The coil was able to carry 200 A transport current at 28.8 K in self-field. During coil charging and operation, SN2 effectively acted as an impregnation material. The test results demonstrate the viability to use MgB2 racetrack coil potentially with SN2 impregnation in advanced rotating machine applications.

Development of flexible particle-laden elastomeric textiles with improved penetration resistance to hypodermic needles

Needle stick injuries are a major concern for workers in hospitals, service and hospitality sectors. Current prevention strategies include double/triple gloving reduce flexibility significantly and also do not provide a significant reduction in injuries as desired. Here, we develop a new particle-laden elastomer using colloidal silica (CS) and polydimethylsiloxane (PDMS) which when coated onto high-density polyethylene (HDPE) woven fabric shows a remarkable 90% increase in specific penetration resistance force (SPRF) to hypodermic needles as compared to the neat fabric. We show that the resistance to penetration is dependent on the concentration of the hard silica particles and hypothesize that a percolation network of connected particles form upon impact that distributes the load and provides high resistance. We term this phenomenon as elastic jamming. Furthermore, we also show that by adding silicon carbide nanoparticles to CS increases the SPRF to 110% of neat fabric. A two-layer stack of the same treated fabric was able to completely prevent the penetration of a 21 G needle at a speed of 50 cm/min in about one-third of the performed experiments. These results demonstrate that impregnation of textiles with these nanocomposites can be an attractive method for the manufacture of needle stick penetration resistant garments.

Experimental Analysis of Critical Current and Alternating Current Losses of High-Temperature Superconductor Tape with Resin and Gallium-Indium-Tin.

This paper experimentally analyzes the critical current degradation and AC (alternating current) losses of second-generation (2G) high-temperature superconductor (HTS) tape during the impregnation process. Two impregnation materials were utilized: Gallium-Indium-Tin (GaInSn), and an epoxy resin, Araldite. The critical current of the impregnation materials was measured after different thermal cycles and compared with the tape with no impregnation process. The experimental results show that the critical current of Yttrium Barium Copper Oxide (YBCO) short samples varies between differently impregnated materials. The resin, Araldite, degraded the critical current; however, the GaInSn showed no degradation. Two degradation patterns with Araldite were identified due to the impregnation process, and the corresponding causes were analyzed. We further measured the AC losses of tapes impregnated with liquid metal at different frequencies, up to 600 Hz. Based on the experimental results, GaInSn liquid metal should be the most suitable impregnation material in terms of critical current degradation.

Selective propylene epoxidation in liquid phase using highly dispersed Nb catalysts incorporated in mesoporous silicates

Selective propylene epoxidation to propylene oxide (PO) with hydrogen peroxide (H 2 O 2 ) was carried out in a catalytic semi-batch reactor. High propylene epoxidation activity (44 h − 1 ) was observed over Nb based mesoporous silicate materials Nb-TUD-1 under mild operating conditions. The physical and chemical properties of the Nb based silicates characterized using BET, FTIR, TPD, TEM and UV–Vis revealed that the site isolation and surface acidity are crucial for PO production. Catalyst synthesis methods were investigated for their effects on PO productivity, PO selectivity and H 2 O 2 utilization efficiency. It is found that Nb-TUD-1 material synthesized by the sol–gel method is more active and selective than impregnated materials for liquid phase propylene epoxidation. Surface characterization confirms that thus synthesized Nb-TUD-1 catalysts have more Lewis acidity and less Bronsted acidity compared to the catalysts by impregnation.

Some Physical and Mechanical Properties of Impregnated Chestnut Wood with Natural and Chemical Agent Exposed to Outdoor Conditions

Wood preservatives have been widely used to extend the service life of wood. The most objectionable environment for wood is outdoor conditions. In this study, test specimens prepared from chestnut wood (Castanea sativa Mill) were impregnated with natural and chemical impregnation agent. It was aimed to determine the effect of outdoor conditions on physical and mechanical properties of wood material by keeping them under these conditions for one year. As natural impregnation material pine tannin and acorn tannins, as chemical impregnation material imersol aqua and timbercare aqua were used. The retention amount, air-dried density, bending strength, modulus of elasticity, compression strength parallel to fibers, adhesion strength parallel to fibers, screw withdrawal strength were determined. As a result, it can be said that the physical and mechanical test values can compare wood impregnated with natural impregnation materials to wood impregnated with chemical impregnation materials after one year exposed to outdoor conditions.

Addition of a Second Metal (Co) to Molybdenum Carbide: Effect of the Doping Route

Molybdenum carbide is an interesting and versatile material, which has important applications in the metal matrix industry as a reinforcement material, as well as in the catalytic field. Though many papers suggest different methodologies for adding cobalt to the carbide structure aiming either to increase catalytic activity or enhancing mechanical proprieties such as ductility, etc. no straightforward evaluation is available. In the present paper two doping methodologies were studied: via solid state mixture of powders and via wet impregnation. Ammonium molybdate [(NH4)2MoO4] and cobalt nitrate [Co(NO3)2·6H2O] were used as starting materials and the doping process was carried out before carburization reaction. Those materials were characterized by FT-IR, SEM, XRF and XRD. The carbo-reduction products' were evaluated on XRD and XRF basis. Doped precursors' evaluation showed that the wet impregnated doped materials presented smaller particle sizes, were more homogeneous and retained more cobalt than the solid state doped ones. However, final products' assessment indicated that the solid state methodology was able to retain a greater dopant percentage according to XRF evaluation, and XRD data indicated a more intrinsic addition of the dopant to the carbide structure. In addition, no significant changes on particle size could be attributed to any of the methodologies, both producing Mo2C of approximately 30 nm.

Characterization of microencapsulated and impregnated porous host materials based on calcium chloride for thermochemical energy storage

Thermochemical heat storage in salt hydrates is a promising method to improve the solar fraction in the built environment. The major concern at this stage is liquefaction followed by washing out of active material and agglomeration into large chunks of salt, thus deteriorating the diffusive properties of the porous salt hydrate structure. In this work, specific attention is given to the methods to stabilize a sample salt hydrate. Attempts have been made to stabilize calcium chloride by impregnation in expanded natural graphite and vermiculite, and by microencapsulation with ethyl cellulose. The effect of these stabilization methods on the performance of the material, such as kinetics and energy density, is investigated. Characterization of the materials is carried out with combined Thermo-Gravitational Analysis (TGA) and Differential Scanning Calorimetry (DSC) methods and microscopic observation, in order to evaluate the improvements on the basis of three subjects: reaction kinetics, heat storage density and stability. Within the boundary conditions for thermochemical energy storage as presented in this work, microencapsulated calcium chloride showed high multicyclic stability, compared with pure and impregnated materials, that liquefy upon hydration under the given conditions. Microencapsulated material remains stable over multiple cycles and at the same time shows the faster kinetics, but has a lower volumetric energy storage density.

Mechanical Properties of Composite Materials Based on Latex-Impregnated Needle-Punched Nonwoven Fabrics from Fibers of Different Nature

The influence of the chemical nature of fibers on mechanical properties of nonwoven needlepunched fabrics impregnated with latex-based copolymer based on butadiene and methyl-acrylic acid (SKD-1) was studied. Fabrics made of traditional polyester and polypropylene fibers and polyacetal fiber were used for impregnation. Application of fabrics made of polyacetal fiber provides impregnated materials with maximum tensile strength. The chemical nature of fibers does not influence the strength of the impregnated materials.