The field of bone tissue engineering has experienced an increase in prevalence due to the inherent challenge of the natural regeneration of significant bone deformities.This investigation focused on the preparation of...The field of bone tissue engineering has experienced an increase in prevalence due to the inherent challenge of the natural regeneration of significant bone deformities.This investigation focused on the preparation of Three-Dimensional(3D)-printed Polycaprolactone(PCL)scaffolds with varying proportions of Nanohydroxyapatite(NHA)and Nanoclay(NC),and their physiochemical and biological properties were assessed.The mechanical properties of PCL are satisfactory;however,its hydrophobic nature and long-term degradation hinder its use in scaffold fabrication.NHA and NC have been employed to improve the hydrophilic characteristics,mechanical strength,adhesive properties,biocompatibility,biodegradability,and osteoconductive behavior of PCL.The morphology results demonstrated 3D-printed structures with interconnected rectangular macropores and proper nanoparticle distribution.The sample containing 70 wt%NC showed the highest porosity(65.98±2.54%),leading to an increased degradation rate.The compressive strength ranged from 10.65±1.90 to 84.93±9.93 MPa,which is directly proportional to the compressive strength of cancellous bone(2–12 MPa).The wettability,water uptake,and biodegradability of PCL scaffolds considerably improved as the amount of NC increased.The results of the cellular assays exhibited increased proliferation,viability,and adhesion of MG-63 cells due to the addition of NHA and NC to the scaffolds.Finally,according to the in vitro results,it can be concluded that 3D-printed samples with higher amounts of NC can be regarded as a suitable scaffold for expediting the regeneration process of bone defects.展开更多
This research explores the water uptake behavior of glass fiber/epoxy composites filled with nanoclay and establishes an Artificial Neural Network(ANN)to predict water uptake percentage fromexperimental parameters.Com...This research explores the water uptake behavior of glass fiber/epoxy composites filled with nanoclay and establishes an Artificial Neural Network(ANN)to predict water uptake percentage fromexperimental parameters.Composite laminates are fabricated with varying glass fiber(40-60 wt.%)and nanoclay(0-4 wt.%)contents.Water absorption is evaluated for 70 days of immersion following ASTM D570-98 standards.The inclusion of nanoclay reduces water uptake by creating a tortuous path for moisture diffusion due to its high aspect ratio and platelet morphology,thereby enhancing the composite’s barrier properties.The ANN model is developed with a 3-4-1 feedforward structure and learned through the Levenberg-Marquardt algorithm with soaking time(7 to 70 days),fiber content(40,50,and 60 wt.%)and nanoclay content(0,2,and 4 wt.%)as input parameters.The model’s output is the water uptake percentage.The model has high prediction efficiency,with a correlation coefficient(R)of 0.998 and a mean squared error of 1.38×10^(-4).Experimental and predicted values are in excellent agreement,ensuring the reliability of the ANN for the simulation of nonlinear water absorption behavior.The results identify the synergistic capability of nanoclay and fiber concentration to reduce water absorption and prove the feasibility of ANN as a substitute for time-consuming testing in composite durability estimation.展开更多
Nanoclays have large specific surface area,good adsorption properties,and biocompatibility that have great potential for drug delivery applications[1].Evaluating the in vivo metabolic pathways of nanoclays can help to...Nanoclays have large specific surface area,good adsorption properties,and biocompatibility that have great potential for drug delivery applications[1].Evaluating the in vivo metabolic pathways of nanoclays can help to understand their pharmacodynamic sites and the toxicological effects caused by their in vivo retention time[2].展开更多
This study emphasizes on the evaluation and comparison of the anticorrosive properties of sol-gel coatings with and without inhibitor loaded nanocontainers.In this case,naturally available clay nanotubes(halloysite)we...This study emphasizes on the evaluation and comparison of the anticorrosive properties of sol-gel coatings with and without inhibitor loaded nanocontainers.In this case,naturally available clay nanotubes(halloysite)were loaded with cationic corrosion inhibitors Ce 3+/Zr 4+.These nanocontainers were dispersed in hybrid organic-inorganic sol-gel matrix sol.Coating was applied on magnesium alloy AZ91D using the sols containing modified and unmodified nanocontainers employing the dip coating method and cured at 130℃for 1 h in air.Corrosion resistance of coated/uncoated substrates were analyzed using electrochemical impedance spectroscopy,potentiodynamic polarization and weight loss measurements after exposure to 3.5 wt%NaCl solution for varying time durations between 24 h to 120 h.Self-healing ability of coatings was evaluated by micro-Raman spectroscopy after 120 h exposure to 3.5 wt%NaCl solution.Coatings generated after dispersion of corrosion inhibitor loaded clay in hybrid sol-gel matrix have shown more promising corrosion resistance when compared to just the sol-gel matrix coatings,after prolonged exposure to corrosive environment.展开更多
Tuning microstructures by adding nanoparticles is a promising way of improving the performance of cementitious composites.In this study,nanoclay was introduced to polyvinyl alcohol(PVA)fiber reinforced ultra high toug...Tuning microstructures by adding nanoparticles is a promising way of improving the performance of cementitious composites.In this study,nanoclay was introduced to polyvinyl alcohol(PVA)fiber reinforced ultra high toughness cementitious composites(UHTCCs).The mechanical properties,crack patterns,water permeation resistance,and microstructures of UHTCCs with different dosages of nanoclay were studied.The addition of a proper dosage of nanoclay shows few effects on the compressive strength of UHTCCs,however,the compressive strength is decreased when an excessive amount of nanoclay is added.The flexural deformation capacity of UHTCCs is independent of nanoclay dosage,whereas the flexural strength generally decreases with an increasing dosage of nanoclay.Different cracking patterns were observed in the ultra high toughness cementitious composites containing nanoclay(NC-UHTCC)specimens subject to bending tests.A UHTCC with 1%(in weight)nanoclay shows the best water permeation resistance and the lowest water permeability.Variations in the mechanical properties and the water permeation resistance of UHTCCs containing different dosages of nanoclay could be ascribed to the synthetic effects of filling and heterogeneous nucleation of nanoclay at low dosages and the agglomeration effect of nanoclay at high dosages.This study is to optimize the water permeation resistance of UHTCCs,paving a path for the future application of UHTCCs in the fields of construction,decoration,and repair.展开更多
Due to outstanding mechanical properties, heat resistance, and relatively facile production,nanoclay reinforced epoxy composites(NCRE composites) have been suggested as candidate materials for use on external surfaces...Due to outstanding mechanical properties, heat resistance, and relatively facile production,nanoclay reinforced epoxy composites(NCRE composites) have been suggested as candidate materials for use on external surfaces of spacecraft residing in the low Earth orbit(LEO) environment. The resistance of the NCRE composites to bombardment by atomic oxygen(AO), a dominant component of the LEO environment, has been investigated. Four types of samples were used in this study. They were pure epoxy(0 wt% nanoclay content), and NCRE composites with different loadings of nanoclay—1 wt%, 2 wt%, and 4 wt%. Etch depths decreased with increasing nanoclay content, and for the 4 wt% samples it ranged from 28% to 37% compared to that of pure epoxy. X-ray photoelectron spectroscopy(XPS) indicates that after AO bombardment, relative area of C-C/C-H peak decreased,while the area of the C-O, ketones peaks increased, and the oxidation degree of surfaces increased. New carbon-related component carbonates were detected on nanoclay containing composite surfaces. Scanning electron microscopy indicates that aggregates formed on nanoclay-containing surfaces after AO bombardment. The sizes and densities of aggregates increased with nanoclay content. The combined erosion depths, XPS and SEM results indicate that although all the studied surfaces got eroded and oxidized after AO bombardment,the nanoclay containing composites showed better AO resistance compared to pure epoxy,because the produced aggregates on surface potentially act as a physical "shield", effectively retarding parts of the surface from further AO etching.展开更多
The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally....The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally.Ball milling was used to disperse different weight(wt)percentages(0,1,2,4,6 wt.%)of nanoclay into phenolic resin.Viscosity changes to resin due to nanoclay was studied.On the other hand,nanoclay added phenolic matrix composites(Type-II)were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser(TGA).This data was used to understand the mechanical,thermal and ablation properties of Type-I composites.Inter laminar shear strength(ILSS),flexural strength and flexural modulus of Type I composites increased by about 29%,12%and 7%respectively at2 wt.%addition of nanoclay beyond which these properties decreased.This was attributed to reduced fiber volume fraction(%Vf)of Type-I composites due to nanoclay addition at such high loadings.Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux(125 W/cm^(2))and high heat flux levels(500 W/cm^(2)).Mass ablation rates have increased at both flux levels marginally up to 2 wt.%addition of nanoclay beyond which it has increased significantly.This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.%addition of nanoclay.Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay,which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.展开更多
The main objective of this study is to investigate the effects of the nanoclay mixed with recycled polyester fiber on the mechanical behavior of soil as a new stabilizer material.To meet this objective,a series of dra...The main objective of this study is to investigate the effects of the nanoclay mixed with recycled polyester fiber on the mechanical behavior of soil as a new stabilizer material.To meet this objective,a series of drained direct shear and compaction tests were performed on unreinforced and reinforced soil specimens with three different combinations of the fiber-soil ratios ranging between 0.1%and 0.5%,as well as three different combinations of nanoclay soil ratios ranging between 0.5%and 1.5%of the soil dry weight.Results indicated that composition of the nanoclay recycled polyester fiber with the soil improved the friction angle(Φ)by 41%and cohesion(c)by 174%.The soil particles stick together through viscose gel produced by nanoclay.In addition,the rough and wavy surface of the fibers creates a bond and friction between the soil particles and prevents the movement of soil particles,and as a result,the soil strength is increased.展开更多
Studies on the behavior of molecular transport properties such as thermal conductivity, gas permeability, volume and surface resistivity have been carried out for the naturally woven coconut sheath （CS） fiber reinfo...Studies on the behavior of molecular transport properties such as thermal conductivity, gas permeability, volume and surface resistivity have been carried out for the naturally woven coconut sheath （CS） fiber reinforced composites with the addition of nanoclay and chemical treatment of fiber. The compression molding technique was used to fabricate the coconut sheath/clay reinforced hybrid composites. The morphological studies such as X-ray diffractogram （XRD）, transmission electron microscopy （TEM） and scanning electron microscopy （SEM） have been carried out for polyester nanocomposites and coconut sheath fiber. The decreased gas permeability, thermal conductivity and volume and surface resistivity have been observed with increasing the weight percentage of nanoclay in polyester matrix. In chemical modifications, the alkali and silane treated coconut sheath reinforced composites have shown great influence on the transport properties due to the increasing hydrophilic nature by the topographical changes at the fiber surface. Dielectric strength has also been reported in this paper for all types of composites. Infra-red （IR） spectra have also been taken to study the physical and chemical structural changes of treated coconut sheath.展开更多
Nanoclay-enabled self-supporting printing has been emerging as a promising filament-based extrusion fabrication approach for different biomedical and engineering applications including tissue engineering. With the add...Nanoclay-enabled self-supporting printing has been emerging as a promising filament-based extrusion fabrication approach for different biomedical and engineering applications including tissue engineering. With the addition of nanoclay powders, liquid build materials may exhibit solid-like behavior upon extrusion and can be directly printed in air into complex three-dimensional structures. The objective of this study is to investigate the effect of nanoclay on the extrudability of N-isopropylacrylamide （NIPAAm） and the effect of standoff distance on the print quality during nanoclay-enabled direct printing. It is found that the addition of nanoclay can significantly improve the NIPAAm extrudability and effectively eliminate die swelling in material extrusion. In addition, with the increase of standoff distance, deposited filaments change from over-deposited to well-defined to stretched to broken, the filament width decreases, and the print fidelity deteriorates. A mathematical model is further proposed to determine the optimal standoff distance to achieve better print fidelity during nanoclay-enabled direct printing. Based on the extrudability and standoff distance knowledge from this study, NIPAAm-Laponite nanoclay and NIPAAm-Laponite nanoclay-graphene oxide nanocomposite hydrogel precursors are successfully printed into a three-layered one-dimensional responsive pattern, demonstrating the good extrudability and print quality during nanoclay-enabled printing under optimal printing conditions.展开更多
The incorporation of commercial flame retardants into fiber-reinforced polymer(FRP)composites has been proposed as a potential solution to improve the latter’s poor flame resistance.However,this approach often poses ...The incorporation of commercial flame retardants into fiber-reinforced polymer(FRP)composites has been proposed as a potential solution to improve the latter’s poor flame resistance.However,this approach often poses a challenge,as it can adversely affect the mechanical properties of the FRP.Thus,balancing the need for improved flame resistance with the preservation of mechanical integrity remains a complex issue in FRP research.Addressing this critical concern,this study introduces a novel additive system featuring a combination of one-dimensional(1D)hollow tubular structured halloysite nanotubes(HNTs)and two-dimensional(2D)polygonal flake-shaped nano kaolinite(NKN).By employing a 1D/2D hybrid kaolinite nanoclay system,this research aims to simultaneously improve the flame retardancy and mechanical properties.This innovative approach offers several advantages.During combustion and pyrolysis processes,the 1D/2D hybrid kaolinite nanoclay system proves effective in reducing heat release and volatile leaching.Furthermore,the system facilitates the formation of reinforcing skeletons through a crosslinking mechanism during pyrolysis,resulting in the development of a compact char layer.This char layer acts as a protective barrier,enhancing the material’s resistance to heat and flames.In terms of mechanical properties,the multilayered polygonal flake-shaped 2D NKN plays a crucial role by impeding the formation of cracks that typically arise from vulnerable areas,such as adhesive phase particles.Simultaneously,the 1D HNT bridges these cracks within the matrix,ensuring the structural integrity of the composite material.In an optimal scenario,the homogeneously distributed 1D/2D hybrid kaolinite nanoclays exhibit remarkable results,with a 51.0%improvement in mode II fracture toughness(GIIC),indicating increased resistance to crack propagation.In addition,there is a 34.5%reduction in total heat release,signifying improved flame retardancy.This study represents a significant step forward in the field of composite materials.The innovative use of hybrid low-dimensional nanomaterials offers a promising avenue for the development of multifunctional composites.By carefully designing and incorporating these nanoclays,researchers can potentially create a new generation of FRP composites that excel in both flame resistance and mechanical strength.展开更多
The environmental stress cracking resistance of halloysite nanoclay-polyester nanocomposites was investigated using fracture mechanics approach. The incorporation of halloysite nanoclay was found to improve the enviro...The environmental stress cracking resistance of halloysite nanoclay-polyester nanocomposites was investigated using fracture mechanics approach. The incorporation of halloysite nanoclay was found to improve the environmental stress cracking resistance of the nano-composites. The storage modulus of nano-composites measured by dynamic mechanical analysis increased remarkably as a function of halloysite nanoclay content. At 0.7 wt% nanoclay, the Tg improved from 72°C to 76°C. The fracture toughness increased up to 33% and time to failure improved 155% with the addition of 0.7 wt% of halloysite nanoclay. The maximum microhardness was found 119% higher for the same nano-filler concentration compared to monolithic polyester. The reinforcement with 1 wt% showed lower fracture toughness due to agglomerations of nanoclay which act as flaws. The presence of agglomerates weakened the bond between nano-particles and matrix hence reduces the environmental stress cracking resistance by halloysite nanoclay reinforcement.展开更多
PMMA/reactive nanoclay nanocomposites were prepared by emulsion polymerization using two different reactive nanoclays. X-ray diffraction（XRD） and thermogravimetric analysis（TGA） results confirmed that the reactive...PMMA/reactive nanoclay nanocomposites were prepared by emulsion polymerization using two different reactive nanoclays. X-ray diffraction（XRD） and thermogravimetric analysis（TGA） results confirmed that the reactive nanoclays, kaolinite and montmorillonite, were obtained by the silylation reaction and the double bonds were grafted onto the edges and surfaces of the nanoclays. The presence of reactive nanoclays could increase the average molecular weights, the glass transition temperatures（Tg） and improve the thermal properties of nanocomposite. The tensile properties, Young＇s modulus, and the aging properties of the nanocomposite films were also enhanced while the light transmittance decreased. Furthermore, the nanocomposites with the reactive kaolinite presented better performances than that with the reactive montmorillonite. Finally, the action mechanism of the reactive nanoclays to the performances of PMMA/reactive nanoclay nanocomposites was proposed.展开更多
This work presents the effect of synthetic procedures (extrusion and casting) on the dispersion characteristics of nano layered silicate clay particles in the polypropylene (PP) polymer matrix. Three different molecul...This work presents the effect of synthetic procedures (extrusion and casting) on the dispersion characteristics of nano layered silicate clay particles in the polypropylene (PP) polymer matrix. Three different molecular weights PP samples are taken and filled with nanoclay of 1 wt% and 3 wt%, and these nanocomposites were synthesized by using an extrusion or casting methods. The X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) is used to characterize the structure and morphology of nanocomposites. Rheological and mechanical results show that the extruded products are better than that of cast products. The outcome of this work is discussed in this paper.展开更多
This study presents the modification of surfaces of nanoclays, halloysite nanotubes (HNT) and sepiolite (SEP), with styrene-maleic anhydride copolymers (SMA) via esterification reaction between hydroxyl groups of the ...This study presents the modification of surfaces of nanoclays, halloysite nanotubes (HNT) and sepiolite (SEP), with styrene-maleic anhydride copolymers (SMA) via esterification reaction between hydroxyl groups of the nanoclays and anhydride groups of SMA. The structural, thermal, and morphological analyses of the modified nanoclays were performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). All of these results suggested that the expected modification of HNT and SEP surfaces were performed. Although XRD patterns of HNT containing samples showed that the basal spacing shifted to higher distances, it was found that those of the crystalline structure of SEP remained unchanged. Thermal gravimetric analysis exhibited that SMA copolymers were grafted onto the surfaces of nanoclays varying amounts between 15 and 43 wt. % depending on the types of nanoclays and SMA copolymers. This modification indicates that these nanoclays can be added to the polystyrene matrix without any compatibilizers.展开更多
Bone morphogenetic protein 2(BMP2)is clinically applied for treating intractable fractures and promoting spinal fusion because of its osteogenic potency.However,adverse effects following the release of supraphysiologi...Bone morphogenetic protein 2(BMP2)is clinically applied for treating intractable fractures and promoting spinal fusion because of its osteogenic potency.However,adverse effects following the release of supraphysiological doses of BMP2 from collagen carriers are widely reported.Nanoclay gel(NC)is attracting attention as a biomaterial,given the potential for localized efficacy of administered agents.However,the efficacy and mech-anism of action of NC/BMP2 remain unclear.This study explored the efficacy of NC as a BMP2 carrier in bone regeneration and the enhancement mechanism.Subfascial implantation of NC containing BMP2 elicited superior bone formation compared with collagen sponge(CS).Cartilage was uniformly formed inside the NC,whereas CS formed cartilage only on the perimeter.Additionally,CS induced a dose-dependent inflammatory response around the implantation site,whereas NC induced a minor response,and inflammatory cells were observed inside the NC.In a rat spinal fusion model,NC promoted high-quality bony fusion compared to CS.In vitro,NC enhanced chondrogenic and osteogenic differentiation of hBMSCs and ATDC5 cells while inhibiting osteoclas-togenesis.Overall,NC/BMP2 facilitates spatially controlled,high-quality endochondral bone formation without BMP2-induced inflammation and promotes high-density new bone,functioning as a next-generation BMP2 carrier.展开更多
Natural two-dimensional （2D） kaolinite nanoclay has been incorporated into an emerging drug delivery system. The basal spacing of the kaolinite nanoclay was expanded from 0.72 to 4.16 nm through the intercalation of...Natural two-dimensional （2D） kaolinite nanoclay has been incorporated into an emerging drug delivery system. The basal spacing of the kaolinite nanoclay was expanded from 0.72 to 4.16 nm through the intercalation of various organic vip species of different chain lengths, which can increase the efficiency in drug delivery and reduce the toxicity of doxorubicin （DOX）. Original kaolinite （Kaolin） and the Kaolin intercalation compounds exhibited a high level of biocompatibility and very low toxicity towards cells of pancreatic cancer, gastric cancer, prostate cancer, breast cancer, colorectal cancer, esophageal cancer, and differentiated thyroid cancer. However, lung cancer and hepatocellular cancer cells need more strict compositional, structural, and morphological modulations for drug delivery carriers. DOX-Kaolin and the DOX-Kaolin intercalation compounds showed dramatically faster drug release in moderately acidic solution than in neutral condition, and exhibited enhanced therapeutic effects against ten model cancer cell cultures in a dose-dependent manner. The use of 2D nanoclay materials for a novel drug delivery system could feasibly pave a way towards high-performance nanotherapeutics, with superior antitumor efficacy and significantly reduced side effects.展开更多
The dispersion of montmorillonite （MMT） in vinylester for preparing nanoclay/vinylester gel coat was reported. Two sets of MMT/vinylester specimens, namely Type I and Type 2, were prepared for comparative studies. T...The dispersion of montmorillonite （MMT） in vinylester for preparing nanoclay/vinylester gel coat was reported. Two sets of MMT/vinylester specimens, namely Type I and Type 2, were prepared for comparative studies. Type I specimens were prepared using ultrasonication only, and Type 2 specimens were prepared using both ultrasonication and twin-screw extrusion. According to XRD and TEM results, Type 2 specimens showed lower levels of nanoclay agglomeration and higher levels o! exfoliation. DSC results showed that the glass transition temperatures of Type 2 specimens are higher than those of Type 1 specimens. TGA results showed that the residual weight of 4 wt.% MMT/vinylester of Type 1 was 7.38%, while the corresponding value of Type 2 was 13,5%, indicating lower thermal degradation in the latter. MMTt vinylester/glass and MMT/vinylester/carbon specimens were fabricated and tested for mechanical and fire retardation behaviours. Type 2 based nanocomposite laminates showed greater values of ultimate tensile strength, flexural strength, interlaminar shear strength, impact strength, horizontal burning rate, and vertical burning rate than Type 1 based laminates. SEM images of tensile fractured surfaces revealed that Type 2 based laminates have no or less agglomeration of nanoclay than Type 1 based laminates.展开更多
In this paper the suitability of a graft polymer nanocomposite hydrogel system for enhanced oil recovery was examined using polyacrylamide graft starch/clay nanocomposite(a laboratory synthesized product) and chromium...In this paper the suitability of a graft polymer nanocomposite hydrogel system for enhanced oil recovery was examined using polyacrylamide graft starch/clay nanocomposite(a laboratory synthesized product) and chromium(III) acetate(crosslinker). X-ray diffraction analysis,Fourier transform infrared spectrometry analysis, field-emission scanning electron microscopy and transmission electron microscopy were carried out to reveal the laboratory synthesized product as a nanocomposite. The effects of various parameters like salt concentration, p H, temperature, polymer concentration and crosslinker concentration on the properties of the developed gel system were systematically evaluated.The thermal stability of the nanocomposite gel and the conventional gel system were also determined by thermogravimetric analysis. The graft polymer nanocomposite gel system exhibited acceptable gel strength, gelation time and gel stability compared with the conventional gel system. The nanocomposite gels prepared using a low crosslinker concentration showed higher gel strength and required longer gelation time than the conventional gel which is more desirable properties for the effective placement of gel during enhanced oil recovery operations. In addition, sand pack flooding experiments show that the graft polymer nanocomposite gels had better plugging capacity than the conventional gel systems under reservoir conditions. Hence, this gel system may be suitable in the water shutoff treatments required for enhanced oil recovery from oilfields.展开更多
文摘The field of bone tissue engineering has experienced an increase in prevalence due to the inherent challenge of the natural regeneration of significant bone deformities.This investigation focused on the preparation of Three-Dimensional(3D)-printed Polycaprolactone(PCL)scaffolds with varying proportions of Nanohydroxyapatite(NHA)and Nanoclay(NC),and their physiochemical and biological properties were assessed.The mechanical properties of PCL are satisfactory;however,its hydrophobic nature and long-term degradation hinder its use in scaffold fabrication.NHA and NC have been employed to improve the hydrophilic characteristics,mechanical strength,adhesive properties,biocompatibility,biodegradability,and osteoconductive behavior of PCL.The morphology results demonstrated 3D-printed structures with interconnected rectangular macropores and proper nanoparticle distribution.The sample containing 70 wt%NC showed the highest porosity(65.98±2.54%),leading to an increased degradation rate.The compressive strength ranged from 10.65±1.90 to 84.93±9.93 MPa,which is directly proportional to the compressive strength of cancellous bone(2–12 MPa).The wettability,water uptake,and biodegradability of PCL scaffolds considerably improved as the amount of NC increased.The results of the cellular assays exhibited increased proliferation,viability,and adhesion of MG-63 cells due to the addition of NHA and NC to the scaffolds.Finally,according to the in vitro results,it can be concluded that 3D-printed samples with higher amounts of NC can be regarded as a suitable scaffold for expediting the regeneration process of bone defects.
文摘This research explores the water uptake behavior of glass fiber/epoxy composites filled with nanoclay and establishes an Artificial Neural Network(ANN)to predict water uptake percentage fromexperimental parameters.Composite laminates are fabricated with varying glass fiber(40-60 wt.%)and nanoclay(0-4 wt.%)contents.Water absorption is evaluated for 70 days of immersion following ASTM D570-98 standards.The inclusion of nanoclay reduces water uptake by creating a tortuous path for moisture diffusion due to its high aspect ratio and platelet morphology,thereby enhancing the composite’s barrier properties.The ANN model is developed with a 3-4-1 feedforward structure and learned through the Levenberg-Marquardt algorithm with soaking time(7 to 70 days),fiber content(40,50,and 60 wt.%)and nanoclay content(0,2,and 4 wt.%)as input parameters.The model’s output is the water uptake percentage.The model has high prediction efficiency,with a correlation coefficient(R)of 0.998 and a mean squared error of 1.38×10^(-4).Experimental and predicted values are in excellent agreement,ensuring the reliability of the ANN for the simulation of nonlinear water absorption behavior.The results identify the synergistic capability of nanoclay and fiber concentration to reduce water absorption and prove the feasibility of ANN as a substitute for time-consuming testing in composite durability estimation.
基金supported by National Key Research and Development Program of China(Grant No.:2023YFF0716000)National Natural Science Foundation of China(Grant No.:82071965)+1 种基金Major plan of Jointly Constructed Project by the Science and Technology Department of the State Administration of Traditional Chinese Medicine and the Zhejiang Provincial Administration of Traditional Chinese Medicine,China(Grant No.:GZY-ZJ-KJ-24025)Zhejiang Provincial Natural Science Foundation of China(Grant No.:LQ23H180005).
文摘Nanoclays have large specific surface area,good adsorption properties,and biocompatibility that have great potential for drug delivery applications[1].Evaluating the in vivo metabolic pathways of nanoclays can help to understand their pharmacodynamic sites and the toxicological effects caused by their in vivo retention time[2].
基金financial sup-port from SERB,DST for the funding provided through grant number SB/S3/ME/007/2014.
文摘This study emphasizes on the evaluation and comparison of the anticorrosive properties of sol-gel coatings with and without inhibitor loaded nanocontainers.In this case,naturally available clay nanotubes(halloysite)were loaded with cationic corrosion inhibitors Ce 3+/Zr 4+.These nanocontainers were dispersed in hybrid organic-inorganic sol-gel matrix sol.Coating was applied on magnesium alloy AZ91D using the sols containing modified and unmodified nanocontainers employing the dip coating method and cured at 130℃for 1 h in air.Corrosion resistance of coated/uncoated substrates were analyzed using electrochemical impedance spectroscopy,potentiodynamic polarization and weight loss measurements after exposure to 3.5 wt%NaCl solution for varying time durations between 24 h to 120 h.Self-healing ability of coatings was evaluated by micro-Raman spectroscopy after 120 h exposure to 3.5 wt%NaCl solution.Coatings generated after dispersion of corrosion inhibitor loaded clay in hybrid sol-gel matrix have shown more promising corrosion resistance when compared to just the sol-gel matrix coatings,after prolonged exposure to corrosive environment.
基金Project supported by the National Natural Science Foundation of China(No.51978624)the Zhejiang Provincial Natural Science Foundation of China(No.LY19E080030)+3 种基金the Production and Construction Group’s Programs for Science and Technology Development(No.2019AB016)the Zhejiang Cultural Relics Protection Science and Technology Project(No.2014009)the 2017 Hangzhou Transportation Society Scientific Research Project(No.14)the First-class Disciplines Project of Civil Engineering in Zhejiang Province,China。
文摘Tuning microstructures by adding nanoparticles is a promising way of improving the performance of cementitious composites.In this study,nanoclay was introduced to polyvinyl alcohol(PVA)fiber reinforced ultra high toughness cementitious composites(UHTCCs).The mechanical properties,crack patterns,water permeation resistance,and microstructures of UHTCCs with different dosages of nanoclay were studied.The addition of a proper dosage of nanoclay shows few effects on the compressive strength of UHTCCs,however,the compressive strength is decreased when an excessive amount of nanoclay is added.The flexural deformation capacity of UHTCCs is independent of nanoclay dosage,whereas the flexural strength generally decreases with an increasing dosage of nanoclay.Different cracking patterns were observed in the ultra high toughness cementitious composites containing nanoclay(NC-UHTCC)specimens subject to bending tests.A UHTCC with 1%(in weight)nanoclay shows the best water permeation resistance and the lowest water permeability.Variations in the mechanical properties and the water permeation resistance of UHTCCs containing different dosages of nanoclay could be ascribed to the synthetic effects of filling and heterogeneous nucleation of nanoclay at low dosages and the agglomeration effect of nanoclay at high dosages.This study is to optimize the water permeation resistance of UHTCCs,paving a path for the future application of UHTCCs in the fields of construction,decoration,and repair.
基金the National Natu- ral Science Foundation of China (No.21473015 and No.41574101)the Fundamental Research Funds for the Central Universities (No.3132018233).
文摘Due to outstanding mechanical properties, heat resistance, and relatively facile production,nanoclay reinforced epoxy composites(NCRE composites) have been suggested as candidate materials for use on external surfaces of spacecraft residing in the low Earth orbit(LEO) environment. The resistance of the NCRE composites to bombardment by atomic oxygen(AO), a dominant component of the LEO environment, has been investigated. Four types of samples were used in this study. They were pure epoxy(0 wt% nanoclay content), and NCRE composites with different loadings of nanoclay—1 wt%, 2 wt%, and 4 wt%. Etch depths decreased with increasing nanoclay content, and for the 4 wt% samples it ranged from 28% to 37% compared to that of pure epoxy. X-ray photoelectron spectroscopy(XPS) indicates that after AO bombardment, relative area of C-C/C-H peak decreased,while the area of the C-O, ketones peaks increased, and the oxidation degree of surfaces increased. New carbon-related component carbonates were detected on nanoclay containing composite surfaces. Scanning electron microscopy indicates that aggregates formed on nanoclay-containing surfaces after AO bombardment. The sizes and densities of aggregates increased with nanoclay content. The combined erosion depths, XPS and SEM results indicate that although all the studied surfaces got eroded and oxidized after AO bombardment,the nanoclay containing composites showed better AO resistance compared to pure epoxy,because the produced aggregates on surface potentially act as a physical "shield", effectively retarding parts of the surface from further AO etching.
文摘The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally.Ball milling was used to disperse different weight(wt)percentages(0,1,2,4,6 wt.%)of nanoclay into phenolic resin.Viscosity changes to resin due to nanoclay was studied.On the other hand,nanoclay added phenolic matrix composites(Type-II)were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser(TGA).This data was used to understand the mechanical,thermal and ablation properties of Type-I composites.Inter laminar shear strength(ILSS),flexural strength and flexural modulus of Type I composites increased by about 29%,12%and 7%respectively at2 wt.%addition of nanoclay beyond which these properties decreased.This was attributed to reduced fiber volume fraction(%Vf)of Type-I composites due to nanoclay addition at such high loadings.Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux(125 W/cm^(2))and high heat flux levels(500 W/cm^(2)).Mass ablation rates have increased at both flux levels marginally up to 2 wt.%addition of nanoclay beyond which it has increased significantly.This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.%addition of nanoclay.Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay,which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.
文摘The main objective of this study is to investigate the effects of the nanoclay mixed with recycled polyester fiber on the mechanical behavior of soil as a new stabilizer material.To meet this objective,a series of drained direct shear and compaction tests were performed on unreinforced and reinforced soil specimens with three different combinations of the fiber-soil ratios ranging between 0.1%and 0.5%,as well as three different combinations of nanoclay soil ratios ranging between 0.5%and 1.5%of the soil dry weight.Results indicated that composition of the nanoclay recycled polyester fiber with the soil improved the friction angle(Φ)by 41%and cohesion(c)by 174%.The soil particles stick together through viscose gel produced by nanoclay.In addition,the rough and wavy surface of the fibers creates a bond and friction between the soil particles and prevents the movement of soil particles,and as a result,the soil strength is increased.
基金financially supported by the Department of Science and Technology,India for the funding through SR/FTP/ETA-92/2009 project
文摘Studies on the behavior of molecular transport properties such as thermal conductivity, gas permeability, volume and surface resistivity have been carried out for the naturally woven coconut sheath （CS） fiber reinforced composites with the addition of nanoclay and chemical treatment of fiber. The compression molding technique was used to fabricate the coconut sheath/clay reinforced hybrid composites. The morphological studies such as X-ray diffractogram （XRD）, transmission electron microscopy （TEM） and scanning electron microscopy （SEM） have been carried out for polyester nanocomposites and coconut sheath fiber. The decreased gas permeability, thermal conductivity and volume and surface resistivity have been observed with increasing the weight percentage of nanoclay in polyester matrix. In chemical modifications, the alkali and silane treated coconut sheath reinforced composites have shown great influence on the transport properties due to the increasing hydrophilic nature by the topographical changes at the fiber surface. Dielectric strength has also been reported in this paper for all types of composites. Infra-red （IR） spectra have also been taken to study the physical and chemical structural changes of treated coconut sheath.
基金This study was partially supported by the U.S. National Science Foundation （NSF CMMI-1634755）.
文摘Nanoclay-enabled self-supporting printing has been emerging as a promising filament-based extrusion fabrication approach for different biomedical and engineering applications including tissue engineering. With the addition of nanoclay powders, liquid build materials may exhibit solid-like behavior upon extrusion and can be directly printed in air into complex three-dimensional structures. The objective of this study is to investigate the effect of nanoclay on the extrudability of N-isopropylacrylamide （NIPAAm） and the effect of standoff distance on the print quality during nanoclay-enabled direct printing. It is found that the addition of nanoclay can significantly improve the NIPAAm extrudability and effectively eliminate die swelling in material extrusion. In addition, with the increase of standoff distance, deposited filaments change from over-deposited to well-defined to stretched to broken, the filament width decreases, and the print fidelity deteriorates. A mathematical model is further proposed to determine the optimal standoff distance to achieve better print fidelity during nanoclay-enabled direct printing. Based on the extrudability and standoff distance knowledge from this study, NIPAAm-Laponite nanoclay and NIPAAm-Laponite nanoclay-graphene oxide nanocomposite hydrogel precursors are successfully printed into a three-layered one-dimensional responsive pattern, demonstrating the good extrudability and print quality during nanoclay-enabled printing under optimal printing conditions.
基金supported by the National Natural Science Foundation of China(11872279,12172258,and 11625210).
文摘The incorporation of commercial flame retardants into fiber-reinforced polymer(FRP)composites has been proposed as a potential solution to improve the latter’s poor flame resistance.However,this approach often poses a challenge,as it can adversely affect the mechanical properties of the FRP.Thus,balancing the need for improved flame resistance with the preservation of mechanical integrity remains a complex issue in FRP research.Addressing this critical concern,this study introduces a novel additive system featuring a combination of one-dimensional(1D)hollow tubular structured halloysite nanotubes(HNTs)and two-dimensional(2D)polygonal flake-shaped nano kaolinite(NKN).By employing a 1D/2D hybrid kaolinite nanoclay system,this research aims to simultaneously improve the flame retardancy and mechanical properties.This innovative approach offers several advantages.During combustion and pyrolysis processes,the 1D/2D hybrid kaolinite nanoclay system proves effective in reducing heat release and volatile leaching.Furthermore,the system facilitates the formation of reinforcing skeletons through a crosslinking mechanism during pyrolysis,resulting in the development of a compact char layer.This char layer acts as a protective barrier,enhancing the material’s resistance to heat and flames.In terms of mechanical properties,the multilayered polygonal flake-shaped 2D NKN plays a crucial role by impeding the formation of cracks that typically arise from vulnerable areas,such as adhesive phase particles.Simultaneously,the 1D HNT bridges these cracks within the matrix,ensuring the structural integrity of the composite material.In an optimal scenario,the homogeneously distributed 1D/2D hybrid kaolinite nanoclays exhibit remarkable results,with a 51.0%improvement in mode II fracture toughness(GIIC),indicating increased resistance to crack propagation.In addition,there is a 34.5%reduction in total heat release,signifying improved flame retardancy.This study represents a significant step forward in the field of composite materials.The innovative use of hybrid low-dimensional nanomaterials offers a promising avenue for the development of multifunctional composites.By carefully designing and incorporating these nanoclays,researchers can potentially create a new generation of FRP composites that excel in both flame resistance and mechanical strength.
文摘The environmental stress cracking resistance of halloysite nanoclay-polyester nanocomposites was investigated using fracture mechanics approach. The incorporation of halloysite nanoclay was found to improve the environmental stress cracking resistance of the nano-composites. The storage modulus of nano-composites measured by dynamic mechanical analysis increased remarkably as a function of halloysite nanoclay content. At 0.7 wt% nanoclay, the Tg improved from 72°C to 76°C. The fracture toughness increased up to 33% and time to failure improved 155% with the addition of 0.7 wt% of halloysite nanoclay. The maximum microhardness was found 119% higher for the same nano-filler concentration compared to monolithic polyester. The reinforcement with 1 wt% showed lower fracture toughness due to agglomerations of nanoclay which act as flaws. The presence of agglomerates weakened the bond between nano-particles and matrix hence reduces the environmental stress cracking resistance by halloysite nanoclay reinforcement.
基金Funded by the National Youth Natural Science Foundation of China(No.21406247)
文摘PMMA/reactive nanoclay nanocomposites were prepared by emulsion polymerization using two different reactive nanoclays. X-ray diffraction（XRD） and thermogravimetric analysis（TGA） results confirmed that the reactive nanoclays, kaolinite and montmorillonite, were obtained by the silylation reaction and the double bonds were grafted onto the edges and surfaces of the nanoclays. The presence of reactive nanoclays could increase the average molecular weights, the glass transition temperatures（Tg） and improve the thermal properties of nanocomposite. The tensile properties, Young＇s modulus, and the aging properties of the nanocomposite films were also enhanced while the light transmittance decreased. Furthermore, the nanocomposites with the reactive kaolinite presented better performances than that with the reactive montmorillonite. Finally, the action mechanism of the reactive nanoclays to the performances of PMMA/reactive nanoclay nanocomposites was proposed.
文摘This work presents the effect of synthetic procedures (extrusion and casting) on the dispersion characteristics of nano layered silicate clay particles in the polypropylene (PP) polymer matrix. Three different molecular weights PP samples are taken and filled with nanoclay of 1 wt% and 3 wt%, and these nanocomposites were synthesized by using an extrusion or casting methods. The X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) is used to characterize the structure and morphology of nanocomposites. Rheological and mechanical results show that the extruded products are better than that of cast products. The outcome of this work is discussed in this paper.
文摘This study presents the modification of surfaces of nanoclays, halloysite nanotubes (HNT) and sepiolite (SEP), with styrene-maleic anhydride copolymers (SMA) via esterification reaction between hydroxyl groups of the nanoclays and anhydride groups of SMA. The structural, thermal, and morphological analyses of the modified nanoclays were performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). All of these results suggested that the expected modification of HNT and SEP surfaces were performed. Although XRD patterns of HNT containing samples showed that the basal spacing shifted to higher distances, it was found that those of the crystalline structure of SEP remained unchanged. Thermal gravimetric analysis exhibited that SMA copolymers were grafted onto the surfaces of nanoclays varying amounts between 15 and 43 wt. % depending on the types of nanoclays and SMA copolymers. This modification indicates that these nanoclays can be added to the polystyrene matrix without any compatibilizers.
基金financially supported by the JSPS Grant-in-Aid C(20K09479)to TKresearch grant(J210701148)by Biosciencepartners Inc.
文摘Bone morphogenetic protein 2(BMP2)is clinically applied for treating intractable fractures and promoting spinal fusion because of its osteogenic potency.However,adverse effects following the release of supraphysiological doses of BMP2 from collagen carriers are widely reported.Nanoclay gel(NC)is attracting attention as a biomaterial,given the potential for localized efficacy of administered agents.However,the efficacy and mech-anism of action of NC/BMP2 remain unclear.This study explored the efficacy of NC as a BMP2 carrier in bone regeneration and the enhancement mechanism.Subfascial implantation of NC containing BMP2 elicited superior bone formation compared with collagen sponge(CS).Cartilage was uniformly formed inside the NC,whereas CS formed cartilage only on the perimeter.Additionally,CS induced a dose-dependent inflammatory response around the implantation site,whereas NC induced a minor response,and inflammatory cells were observed inside the NC.In a rat spinal fusion model,NC promoted high-quality bony fusion compared to CS.In vitro,NC enhanced chondrogenic and osteogenic differentiation of hBMSCs and ATDC5 cells while inhibiting osteoclas-togenesis.Overall,NC/BMP2 facilitates spatially controlled,high-quality endochondral bone formation without BMP2-induced inflammation and promotes high-density new bone,functioning as a next-generation BMP2 carrier.
基金This work was supported by the National Natural Science Foundation of China （Nos. 51225403 and 41572036）, the Hunan Provincial Science and Technology Project （Nos. 2016RS2004 and 2015TP1006）, the Postdoctoral Science Foundation of Central South University （No. 155219） and the China Postdoctoral Science Foundation （No. 2015M582346）.
文摘Natural two-dimensional （2D） kaolinite nanoclay has been incorporated into an emerging drug delivery system. The basal spacing of the kaolinite nanoclay was expanded from 0.72 to 4.16 nm through the intercalation of various organic vip species of different chain lengths, which can increase the efficiency in drug delivery and reduce the toxicity of doxorubicin （DOX）. Original kaolinite （Kaolin） and the Kaolin intercalation compounds exhibited a high level of biocompatibility and very low toxicity towards cells of pancreatic cancer, gastric cancer, prostate cancer, breast cancer, colorectal cancer, esophageal cancer, and differentiated thyroid cancer. However, lung cancer and hepatocellular cancer cells need more strict compositional, structural, and morphological modulations for drug delivery carriers. DOX-Kaolin and the DOX-Kaolin intercalation compounds showed dramatically faster drug release in moderately acidic solution than in neutral condition, and exhibited enhanced therapeutic effects against ten model cancer cell cultures in a dose-dependent manner. The use of 2D nanoclay materials for a novel drug delivery system could feasibly pave a way towards high-performance nanotherapeutics, with superior antitumor efficacy and significantly reduced side effects.
文摘The dispersion of montmorillonite （MMT） in vinylester for preparing nanoclay/vinylester gel coat was reported. Two sets of MMT/vinylester specimens, namely Type I and Type 2, were prepared for comparative studies. Type I specimens were prepared using ultrasonication only, and Type 2 specimens were prepared using both ultrasonication and twin-screw extrusion. According to XRD and TEM results, Type 2 specimens showed lower levels of nanoclay agglomeration and higher levels o! exfoliation. DSC results showed that the glass transition temperatures of Type 2 specimens are higher than those of Type 1 specimens. TGA results showed that the residual weight of 4 wt.% MMT/vinylester of Type 1 was 7.38%, while the corresponding value of Type 2 was 13,5%, indicating lower thermal degradation in the latter. MMTt vinylester/glass and MMT/vinylester/carbon specimens were fabricated and tested for mechanical and fire retardation behaviours. Type 2 based nanocomposite laminates showed greater values of ultimate tensile strength, flexural strength, interlaminar shear strength, impact strength, horizontal burning rate, and vertical burning rate than Type 1 based laminates. SEM images of tensile fractured surfaces revealed that Type 2 based laminates have no or less agglomeration of nanoclay than Type 1 based laminates.
基金the Indian Institute of Technology(Indian School of Mines),Dhanbad,India,for providing financial support
文摘In this paper the suitability of a graft polymer nanocomposite hydrogel system for enhanced oil recovery was examined using polyacrylamide graft starch/clay nanocomposite(a laboratory synthesized product) and chromium(III) acetate(crosslinker). X-ray diffraction analysis,Fourier transform infrared spectrometry analysis, field-emission scanning electron microscopy and transmission electron microscopy were carried out to reveal the laboratory synthesized product as a nanocomposite. The effects of various parameters like salt concentration, p H, temperature, polymer concentration and crosslinker concentration on the properties of the developed gel system were systematically evaluated.The thermal stability of the nanocomposite gel and the conventional gel system were also determined by thermogravimetric analysis. The graft polymer nanocomposite gel system exhibited acceptable gel strength, gelation time and gel stability compared with the conventional gel system. The nanocomposite gels prepared using a low crosslinker concentration showed higher gel strength and required longer gelation time than the conventional gel which is more desirable properties for the effective placement of gel during enhanced oil recovery operations. In addition, sand pack flooding experiments show that the graft polymer nanocomposite gels had better plugging capacity than the conventional gel systems under reservoir conditions. Hence, this gel system may be suitable in the water shutoff treatments required for enhanced oil recovery from oilfields.
