Dispersed Mixture Research Articles

Production of Nanocarbon from Local Raw Materials

This research aims at extraction of nanocarbon from local raw materials through a detailed study of its characteristics. The research involves study of thermal properties of fruit kernels (apricots) and walnut kernels, determining the optimal modes of the carbonization process for each type of raw material, developing a method for the synthesis of spherical granules by liquid granulation and determining the optimum concentration of the sulfuric acid solution used in granulation. Analysis of the results on the dynamic sorption of petroleum products showed that maximum sorption is achieved when using a sorbent obtained at 400∘C for 30 minutes. Temperature regimes have been optimized for obtaining sorbent from walnut shells with different carbon content. The hydrophobicity and oleophilic of their surface are common to all these materials. The dynamic conditions of the adsorption capacity processes under the sorbents were studied. Sorption efficiency and the specific capacity of sorbents were determined. It has been shown that the technological cycle of the studied sorbents can be repeated by repeated purification. When activated charcoal is used to purify water from petroleum products, the process of leaching with colloidal and finely dispersed mixtures – it was found that deaeration is necessary. The individual composition of the ether fraction OV-1 has a fixed liquid phase, Connected to Finuigan 4023 Automated GC/MS System mass spectrometer, It was determined by chromato-mass spectrometry in a capillary column 40 m long and 0.25 mm in internal diameter. The results of the Fure-IR spectroscopy study of samples based on the apricot peel, walnut peel, and walnut peel showed that winning symmetrical bands (2920 and 2851 cm−1) were observed in them, these bands belong to the C-H-valence oscillation belonging to the methyl and methylene groups. In the spectrum taken from a sample of apricot peel, absorption bands belonging to cellulose (1377 cm−1 and 1069 cm−1 ) were observed.
 Thermogravimetric studies were performed on an STA 449C Jupiter synchronous thermal analysis instrument in the inert environment at a heating rate of 10∘ C/min in the temperature range of 25–1000∘C. Analysis of the porous structure parameters of carbon sorbents were carried out using the high-speed analyzer of gas sorption NOVA-1200e by the method of imaging nitrogen adsorption isotherms at a temperature of 77K.

Thermal Analysis in the Pre-formulation of Amorphous Solid Dispersion for Poorly Water-soluble Drugs

This study is unique in studying the thermogravimetric analysis (TGA) of poorly water-soluble drugs before their formulation. Three selected drugs atorvastatin, albendazole and diclofenac were mixed with three different polymers hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP) and soluplus (SOL). The pure drugs and physical mixtures were subjected to solvent evaporation and milling techniques to obtain solid dispersions. All, as received and TGA analyzed solid dispersion mixtures to evaluate their thermal behavior at a temperature that ranged from 0–300°C. The results showed that the addition of polymer either in physical mixtures or solid dispersions of the drugs has resulted in either increase or decrease of the thermal stability of the drugs depending on the method of preparation and the type of the polymer and the nature of the drug.

Method for determining homogeneity of fine dispersed mixtures based on the software analysis of photo cross-cut of the sample

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Experimental Study on the Impact of Clay Distribution and Mineralogy on NMR T2 and Internal Gradient: Insights From Well-Controlled Physical Samples

Summary Nuclear magnetic resonance (NMR) is a reliable tool for petrophysical evaluation and the characterization of pore structures. Compared to conventional carbonate reservoirs, sandstone reservoirs contain higher amounts of ferromagnetic and paramagnetic ions (such as iron, nickel, or manganese) usually found in microporous clay aggregates. The interpretation of petrophysical data in sandstone formations can be complicated by variations in clay mineralogy and distribution patterns (laminated, structural, and dispersed). Nevertheless, the impact of clay distribution patterns on NMR signals is not well understood. This study aims to investigate the impact of clay mineralogy and distribution patterns on the T2 relaxation times and internal gradient (i.e., inhomogeneity in the magnetic field). Glass beads were mixed with three different clay minerals characterized by no iron content (kaolinite) to higher iron content (illite and nontronite). The bead-clay mixtures were prepared at a fixed clay content but with variable clay distribution patterns to examine the impact of clay distribution alone. NMR T2 measurements at several echo times were performed on the pure glass beads and the mixtures to evaluate how clay mineralogy and distribution patterns affect the T2 and the internal gradient of the host glass beads. At a given clay distribution pattern, a more significant decrease in T2 relaxation times and a larger increase in the internal gradient of glass beads were observed when adding clays with higher iron content. This is explained by the higher surface relaxivity, and magnetic susceptibility caused when introducing clay with higher iron content. Such an impact can complicate the characterization of NMR-derived pore sizes as similar pore size distribution (PSD) can have very different T2 distribution and the logarithmic mean of T2 relaxation time distribution (T2LM) values. Micro-computed tomography (µCT) images were acquired to compute the PSD to compare it with ones obtained from the NMR measurements. The PSD for the three clay minerals showed almost the same distribution using µCT; however, they showed totally different T2 relaxation times distributions. That is due to the significant impact of the internal gradient causing a distortion in the magnetic field. Thus, careful consideration must be taken before converting the NMR data into PSD. The introduction of iron-free kaolinite resulted in a negligible impact on the internal gradient of glass beads regardless of the clay distribution pattern. On the other hand, the addition of dispersed iron-rich clays (illite and nontronite) results in up to two orders of magnitude increase in internal gradients, compared to mixtures with laminated and structural clays (at the same clay mineralogy and content). Moreover, dispersed clay mixtures display larger changes in T2LM and porosity as a function of increasing echo time. The results from this study suggest that changes in T2LM and the logarithmic mean of the effective internal gradient distribution geff,LM, compared to the clean host sand, can provide insight into iron-rich clay distribution. Larger changes in any given clay content and mineralogy would suggest a more dominant dispersed clay distribution while negligible changes would suggest a laminated distribution.

Ecotoxicity of Natural Nanocolloids in Aquatic Environment

Nanocolloids (Ncs) are highly dispersed mixtures of nanoscale (1–100 nm) heterogeneous systems, which are ubiquitous in aquatic environments. Ncs are considered a vital pollutant carrier due to their special surface properties and unique hydrodynamic characteristics. They play an essential role in the process of promoting pollutant migration and transformation. In recent years, with the increase in chemicals in the environment and the complexity of environmental pollution, the health threats of Ncs in ecological systems are arousing great concerning. Therefore, recent work to characterize the ecotoxicity of Ncs has focused on the potential environmental health implications, including exploration of toxicity to aquatic organisms from a wide range of the ecosystem food webs. Herein, we summarize the formation, distribution, and characterization of natural Ncs in the marine environments. Moreover, we highlight the adverse impacts of Ncs on representatives of various trophic levels aquatic organisms (e.g., algae, bacteria, invertebrates, and fish). The mechanisms of Ncs ecotoxicity at the cellular level are reviewed, and the remaining unclear points on toxic tools such as oxidative damage and metabolic disorder are presented. We also discuss the research challenges and future developments within the field of ecotoxicity. This study will bridge our knowledge gap on the ecotoxicity of Ncs.

Structure and properties of powder gas-plasma coatings based on nickel

Problem. The development of modern technology requires a constant increase in reliability and durability of products. Widely used in the practice of domestic and foreign engineering coatings from electrolytic chromium for several hundred hours are triggered, they are unsatisfactorily working on friction and wear at high temperatures. The subject of the study were powder materials based on nickel PG-SR 3 and PG-SR 4. The work is devoted to the study of the formation of gas-plasma coatings on parts of the cylinder-piston group of internal combustion engines using self-fluxing powders based on nickel, as well as the structure and properties change after coating sputtering, its reflow, subsequent hardening. Goal. The purpose of this work is to study powder materials applied to the working surfaces of piston rings by gas-thermal spraying. The object of the study are processes of formation of the structure and properties of coatings from powder materials. Methodology. Plasma sputtering modes were carried out with the following constant parameters: sample rotation speed - 45 rpm, linear speed of sample movement relative to the plasma jet - 18.4 m/min; the diameter of the charge line in the anode nozzle is 2 mm; the distance from the place of introduction of the powder to the cut of the nozzle is 4 mm; the axis of the plasma jet is perpendicular to the axis of rotation of the sample. Radiographically, a multiphase structure is registered in the initial powder. The most fully presented solid solution lines based on nickel and carbide phase Cr23С6 type. But many lines cannot be clearly identified. A match can be found with the main lines of chromium and nickel borides, chromium silicides. The X-ray pattern of the fused layer quite completely coincides with the X-ray pattern of the powder. Chromium carbide lines and the strongest lines of other phases are preserved on the radiograph of the unmelted layer. Preservation of phase lines in the deposited layer without reflow and the layer after quenching indicates that these phases are formed during primary crystallization. This is confirmed by the metallography of the original powder and the original layer. In the structure of the powder, crystals are visible, as well as a dispersed mixture of phases between them. Electron microscopic studies show that in the area of coarse mixtures, oriented areas are observed, in the area of fine mixtures - non-oriented, less dispersed. Results. The presence in the deposited layer of a solid solution based on nickel, carbide phase, borides of chromium and nickel, chromium silicides is established. The greatest macro- and microhardness is possessed by fused layers containing the greatest number of strengthening phases. Originality. Gas-thermal sputtering of powder materials applied to the working surfaces of piston rings is used, which significantly increases their operational properties in comparison with other methods. Practical value. The conducted researches and industrial tests allowed to introduce the coating into production. Conclusions. As a result of the conducted researches on surfacing and heat treatment of coatings made of PG-SR powders, it was confirmed that the best properties have fused coatings. For coatings made of PG-SR powders, heat treatment is undesirable, as it deteriorates the structure and properties of the coating.

Effect of Increased Powder-Binder Adhesion by Backbone Grafting on the Properties of Feedstocks for Ceramic Injection Molding.

The good interaction between the ceramic powder and the binder system is vital for ceramic injection molding and prevents the phase separation during processing. Due to the non-polar structure of polyolefins such as high-density polyethylene (HDPE) and the polar surface of ceramics such as zirconia, there is not appropriate adhesion between them. In this study, the effect of adding high-density polyethylene grafted with acrylic acid (AAHDPE), with high polarity and strong adhesion to the powder, on the rheological, thermal and chemical properties of polymer composites highly filled with zirconia and feedstocks was evaluated. To gain a deeper understanding of the effect of each component, formulations containing different amounts of HDPE and or AAHDPE, zirconia and paraffin wax (PW) were prepared. Attenuated total reflection spectroscopy (ATR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and rotational and capillary rheology were used for the characterization of the different formulations. The ATR analysis revealed the formation of hydrogen bonds between the hydroxyl groups on the zirconia surface and AAHDPE. The improved powder-binder adhesion in the formulations with more AAHDPE resulted in a better powder dispersion and homogeneous mixtures, as observed by SEM. DSC results revealed that the addition of AAHDPE, PW and zirconia effect the melting and crystallization temperature and crystallinity of the binder, the polymer-filled system and feedstocks. The better powder--binder adhesion and powder dispersion effectively decreased the viscosity of the highly filled polymer composites and feedstocks with AAHDPE; this showed the potential of grafted polymers as binders for ceramic injection molding.

Binary or ternary mixture of solid dispersion: Meloxicam case

The present work was carried out to assess the value of adding water insoluble polymer to meloxicam amorphous solid formulation (ASD). Meloxicam was mixed with polyvinylpyrrolidone (PVP) (1:1 ratio) as a binary mixture and with PVP and ethyl cellulose (1:1:1 ratio) as a ternary mixture. Solvent evaporation method was used to prepare ASD formulations. The differential scanning calorimetry, powder X-Ray diffraction, Cambridge Structural Database and in-vitro dissolution were performed to assess the formulas. The results showed that the addition of insoluble polymer could prevent the recrystallization process during ASD formation. However, the binary mixture showed higher drug release percentage than the ternary mixture. Therefore, a rational amount of insoluble polymer could be considered to control recrystallization and manipulate drug release from ASD formulations.

Thermo-acoustical studies of zinc oxide nano particles dispersed nematic liquid crystals mixtures in the temperatures range 283.15 K318.15K

ABSTRACT In the present work, coefficient of volume expansion is estimated using ultrasonic velocity and density of 8CB, 8CB + 0.5% ZnO, 8CB + 2.0% ZnO and 8CB + 5.0% ZnO mixtures in the temperature range of 283.15K–318.15K. The coefficient of volume expansion is used to evaluate numerous thermo-acoustic parameters viz; Moelwyn-Hughes parameter (C 1 ), Beyer’s nonlinear parameter (B/A), reduced volume (V*), reduced bulk modulus (B*), isochoric acoustical parameter (Δ), fractional free volume (f), repulsive exponent (n), isobaric (Γ), isochoric (Γ′′), and isothermal (Γ′) Gruneisen parameters, Anderson-Gruneisen parameter (δ) and Sharma’s constant (S 0 ). Present study reveals that Sharma constant can be treated as molecular constant for 8CB and ZnO dispersed 8CB mixtures. A relationship between Δ≅B* +0.1 and C 1 ≅δ +1 has been established for all the samples under investigation. The effect of increase of ZnO NPs concentration on the intermolecular interactions has been explained in terms of temperature variation of thermo-acoustical parameters.

Graded Inconel 625 coatings with in-situ processing of Ni3Al

Ni superalloys have been widely used to process coatings due to a bouquet of attractive properties in a wide range of temperature. However, higher performance Ni alloys are typically those that offer larger processing challenges. Materials systems have been studied to mitigate this challenge. In hardfacing coatings multilayers have been processed both to reduce the detrimental effects of dilution with the substrate and to enhance the resistance to crack propagation, the latter of particularly relevance when depositing alloys reinforced with hard particles with a reduced weldability but that offer enhanced performance at the surface. The present study addressed the effects of customizing a commercial Inconel 625 atomized alloy, with increasing additions of Ni and Al elemental powder mixtures, to obtain multilayered coatings with a composition and property gradient. The gradual additions of Ni + Al powder mixture to the IN 625 atomized alloy allow for the in-situ synthesis of aluminides while maintaining good weldability, increasing mechanical properties and oxidation resistance. Results show a continuous solidification microstructure, crack-free multilayer coatings with smooth chemical composition profiles and property gradient. A gradual change on the strengthening mechanisms is identified, from solid solution on the first layer of IN 625 to a mixture of solid solution and Ni3Al precipitate dispersion on the top layer processed with the feedstock richer in the Ni + Al powder mixture. These changes induced increasing elastic modulus, hardness and oxidation resistance at 1300 °C following the chemical composition gradient in coatings.

Solubility enhancement of lornoxicam with poloxamer 188 by solvent evaporation method

This investigation aimed to enhance the solubility and bioavailability of the BCS class II poorly water-soluble drug Lornoxicam by solid dispersion (SD) techniques using Polaxomer 188 as a hydrophilic carrier. Solid dispersion of Lornoxicam was made through physical mixing (kneading method) and solvent Evaporation technique via different drug: carrier ratios. Prepared solid dispersion was characterized for solubility, drug content, percentage yield, and in vitro dissolution study. Solid-state characterization was performed by differential scanning calorimetry and Fourier-transform infrared spectroscopy. Lornoxicam’s apparent solubility increased with an increasing level of carrier. A solid dispersion study revealed a better dissolution of lornoxicam than physical blends. In the phase solubility study, the drug demonstrated a higher solubility over phosphate buffer pH range 6.8 compared to distilled water. Solid Dispersion of Lornoxicam: Polaxomer188 solvent evaporation (1:3) showed maximum dissolving effectiveness between all solid dispersion and physical mixture. IR spectra showed no clear interaction between the drug and the polymer. Solubility increases with Solvent Evaporation than with physical mixing and alongside use of water-soluble polymer Polaxomer 188.

The creep performance of bio-based and synthetic lining adhesives at different environmental conditions

Canvas paintings are prone to environmental ageing. Hence, the structural conservation of canvas paintings may require lining, a process in which a secondary canvas is adhered to the reverse of the damaged original canvas to provide additional support. Choosing the optimum adhesive in combination with a lining method is crucial and yet challenging, as they should preferably be mechanically and chemically stable and reversible for at least 100 years. Comprehensive data on thermal and long term mechanical behaviour of prevalently used adhesives and their bonded assemblies to canvas is scarce and yet necessary to enable conservators for a proper choice of the materials in terms of durability. In this study, four prevalently used adhesives in the conservation of canvas paintings are investigated and their creep performance is evaluated and benchmarked at three different temperatures and environmental relative humidities (RHs). These adhesives are either bio-based (animal glue-starch paste and beeswax-dammar resin mixtures), or synthetic (BEVA® 371 and an aqueous Plextol™ D540/K360 dispersion mixture). Differential Scanning Calorimetry (DSC) technique is used to study the thermal transitions at different RHs. T-peel and lap shear tests are performed to determine the fracture behaviour and shear strength respectively. An in-house built creep set-up equipped with environmental control is developed which allows investigation of the mechanical creep for different canvas bonded assemblies. The results demonstrate the effects of temperature and relative humidity on the creep behaviour of lined canvases, which are related to their physical response. Moreover, the animal glue-starch paste shows the best creep mechanical performance for this application, while the Plextol TM acrylic dispersion mixture in combination with Mist-Lining is a better alternative when both environment and reversibility are considered.

DETERMINATION OF RATIONAL PARAMETERS OF PSEUDOMIXING BY COMPLEX MODELLING OF WORK PROCESSES

The area of improving the quality of the formation of mixtures upon mixing in the food industry is relevant since the improvement of technology and equipment for processing components by various methods, nature, and degree of influence is practically achievable for their improvement. The purpose of this study was to improve the design parameters and increase the efficiency of the mixer by creating conditions that will ensure the optimisation of the dissolution kinetics of a dispersed mixture of flour and liquid components during their pseudo-mixing in a suspended state. This study considered the properties of raw materials based on methods for determining their quality, laboratory methods and tools for conducting research were proposed with the established planning methodology with analysis of the results obtained, and the Flow Vision software package was used in plotting based on the laws of thermodynamics. The experimental data set was processed using a mathematical description of the process of forming the liquid flow and the dispersed flow of flour particles. The study used an incomplete multivariate model of the approximation of the experimental data of the function of three variables in the form of polynomials according to the three-level Box-Behnken plan with 13 experiments performed in 5-fold repetition. Periodic mixers were analysed, and the redistribution and transformation of deformations under optimal mixing modes was considered. The interaction of components and their flow dynamics while minimising energy consumption was established. The authors determined the influence of fluidisation and vibration during the dosing period of the components on the intensification of the interaction of the dispersed phase according to the principle of discrete-pulse energy input, which creates rapid changes in the movement of the components. The functional dependence of the uniformity of the formation of bubbles of the medium on three factors υt=f(h, V, υс) was obtained with the verification of the homogeneity of dispersions, the adequacy of the obtained functional dependence and the search for its optimum. The materials considered in this paper represent the practical value of the effective process of uniform distribution of recipe components in the working chamber of the mixer design under study, with the creation of favourable conditions for the formation of the foam structure

Physico-Mechanical Properties of Thermoplastic Composite Reinforced with Kelempayan, Oil Palm Trunk and Bamboo as Fillers

Thermoplastic composite panel can be used for a variety of applications. The wide distribution, renewability and recyclability of lignocelluloses can expand the market for low-cost thermoplastic composites. Lignocellulosic materials from fast growing and plantation species such as lesser-known timber, bamboo and palm tree are promising materials for particulate filler for the production of thermoplastic composite panel due to its accessibility, great substrate behaviour and high yield resources. This study was to determine the physico-mechanical properties of thermoplastic composite panel reinforced with particulate fillers from kelempayan (Neolamarckia cadamba), oil palm (Elaeis guineensis) and betong bamboo (Dendrocalamus asper). This study focused on the effect of particle size and three percent additive to dimensional stability and strength properties of a panel. The polypropylene plastic has been blended with the particulate fillers in a dispersion mixture at the temperature of 180 °C. Then, it was hot pressed for five to nine minutes and the mold was cold pressed for three minutes before the panel was conditioned for testing performance. Statistical analysis has proven that different particle sizes and the supplementary of three percent additive significantly influenced the physico-mechanical properties of the thermoplastic composite panel.

Synthesis of CdS nanomaterials and their photocatalytic activity under visible light

CdS nanomaterial was hydrothermally synthesized at 160 oC for 6 hours from a dispersed mixture of Cd(NO3)2.4H2O and CH3CSNH2 in 50 mL ethylenediamine and denoted as Cw-m, where w-m is the weight ratio of Cd(NO3)2.4H2O/CH3CSNH2 and equals to 1-2, 1-1 and 3-2. The obtained materials were characterized by X-Ray Diffraction (XRD), Infrared spectra (IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray (EDX), and Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The UV-vis DRS showed that the CdS materials possess bandgap of around 2.24 eV. The photocatalytic activity of the CdS was assessed by degradation of methylene blue (MB) under visible light. The experiments indicated that CdS semiconductor materials can be active under visible light. The MB degradation over the CdS was mainly attributed to the photoreduction process induced by the superoxide radical anions (O2• -) and hydroxyl radicals (•OH).

Studying dispersed phase holdup in a pilot plant agitated liquid–liquid mixer by developing online expanded laser beam based technique

Expanded Laser Transmission Technique (E-LTT), where a laser beam is used in conjunction with a beam expander large enough to cover the average drop size up to a few millimeters in the path of the laser in a liquid–liquid dispersion mixture, has been applied for online continuous measurement and investigation in a non-invasive manner of the drop phase volume fraction in an agitated flow mixer of a pilot plant scale. The limitations of beam scattering by the drops through the dispersion path were overcome by having liquids of matching refractive indices enabled by the temperature control system. This study reports for the first time the continuous measurements of the line averaged dispersed phase holdup for a pilot plant scale liquid–liquid mixer equipped with a commercial design mixer, where the measurements have no limitations to the geometrical aspects. Experimental results from a cubic mixing tank with a dispersion depth of 30cm were discussed. Online measurements were carried out in the presence of a revolving impeller and transmission of the expanded laser beam. The net volume of the mixer was 20.42liter, and the dispersed phase holdup that was successfully measured ranged between 0.15 and 0.75. In this work, arrangement of the laser setup was made to scan and measure continuously the line average dispersed phase holdup along the height of the pilot plant scale of the flow agitated liquid–liquid mixer. The E-LTT measurements were validated by comparing their results with those obtained from the mixer by shut-down procedure.

Aggregation Turns BODIPY Fluorophores into Photosensitizers: Reversibly Switching Intersystem Crossing On and Off for Smart Photodynamic Therapy

Aggregation Turns BODIPY Fluorophores into Photosensitizers: Reversibly Switching Intersystem Crossing On and Off for Smart Photodynamic Therapy

Alignment of carbon nanotubes under the influences of nematic liquid crystals and electric fields — an analytical study

Carbon nanotubes (CNTs) have benefits in various fields, they are disadvantageous due to their tendency to form aggregates and poorly controlled alignment of the CNT molecules (characterized by order parameters). These deficiencies can be overcome by dispersing the CNTs in nematic liquid crystal (LC) and placing the mixture under the influence of an electric field. In this study, Doi and Landau–de Gennes free energy density equations are used to analytically confirm that an electric field increases the order parameters of CNTs and LCs in a dispersion mixture. The anchoring strength of the nematic LC is also found to affect the order parameters of the CNTs and LC. Further, increasing the length-to-diameter ratio of the CNTs increases their alignment without affecting the LC alignment. These findings indicate that CNT molecular alignment can be controlled by adjusting the CNT length-to-diameter ratio, anchoring the LCs, and adjusting the electric field strength.

Investigation of dispersion methodologies of microcrystalline and nano-fibrillated cellulose on cement pastes

The objective of this investigation was to find a suitable methodology to disperse and mix two different types of cellulose-based materials, microcrystalline cellulose (MCC) and nano-fibrillated cellulose (NFC), into cement pastes. To achieve this, six different dispersion strategies were explored, including mechanical means, i.e., mechanical and magnetic stirring, ultrasonication, and chemical methods, i.e., addition of polaxamer and superplasticizer, and TEMPO oxidation. Their dispersion capacity and mixture feasibility were assessed using flow table and compression tests. Then the selected methods were applied to each type of fiber to enhance the resulting flexural properties at the optimal fiber content. Both MCC and NFC were characterized in terms of morphology by means of light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), in addition to the water retention value. The reinforcement characteristics and the microstructure of the composites were correlated with their mechanical performance using thermo-gravimetric analysis and porosity evaluation. Ultrasonication and the use of superplasticizer were found to be the most suitable for MCC and NFC, respectively. The optimal content of MCC was 0.75% by wt., and that of NFC was 1% by wt. These mixtures resulted in increases in both strength and flexural modulus by more than 5 and 8 times, for MCC and by more than 3 and 7 times for NFC, respectively. The analyses indicated that the enhanced response on NFC addition is probably associated with its intrinsic properties and bridging capacity, and for the inclusion of MCC the filler effect may have also influenced the mechanical behavior.

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite with sulfonic acid for acid-catalyzed reactions

Abstract Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite was performed with sulfonic acid functional groups to achieve new solid acid materials. The sulfonic acid functional groups were created through the ring opening nucleophilic reaction of amine groups of chitosan with 1,4-butane sultone. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopies (XPS) verified the successful sulfonic acid functionalization of chitosan. The obtained sulfonic acid functionalized chitosan-magnetite nanocomposite showed superparamagnetic properties according to the vibrating sample magnetometry analysis and exhibited magnetic separation feature from dispersed mixtures. Nitrogen adsorption-desorption analysis indicated the increase in surface area after formation of chitosan-magnetite nanocomposite and functionalization with sulfonic acid. Both of the prepared solid acids exhibited high catalytic activities in the acid-catalyzed acetic acid esterification with n-butanol and benzaldehyde acetalization with ethylene glycol as model reactions. Furthermore, they can be reused several times without considerable loss of their activities.