In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in har...In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.展开更多
Layered assembled membranes of 2D leaf-like zeolitic imidazolate frameworks(ZIF-L)nanosheets have received great attention in the field of water treatment due to the porous structure and excellent antibacterial abilit...Layered assembled membranes of 2D leaf-like zeolitic imidazolate frameworks(ZIF-L)nanosheets have received great attention in the field of water treatment due to the porous structure and excellent antibacterial ability,but the dense accumulation on the membrane surface and the low permeate flux greatly hinder their application.Herein,we synthesized m HNTs(modified halloysite nanotubes)/ZIF-L nanocomposites on modified m HNTs by in situ growth method.Interestingly,due to the different size of m HNTs and ZIF-L,m HNTs were packed in ZIF-L nanosheets.The hollow m HNTs provided additional transport channels for water molecules,and the accumulation of the ZIF-L nanosheets was decreased after assembling m HNTs/ZIF-L nanocomposites into membrane by filtration.The prepared m HNTs/ZIF-L membrane presented high permeate flux(59.6 L·m^(-2)·h^(-1)),which is 2-4 times of the ZIF-L membranes(14.8 L·m^(-2)·h^(-1)).Moreover,m HNTs/ZIF-L membranes are intrinsically antimicrobial,which exhibit extremely high bacterial resistance.We provide a controllable strategy to improve 2D ZIF-L assembles,and develops novel membranes using 2D package structure as building units.展开更多
Introducing inorganic nanomaterials into a polymer matrix greatly improves the anticorrosion performance of epoxy coatings(EP);however,poor compatibility between the materials can limit the improvement in properties.I...Introducing inorganic nanomaterials into a polymer matrix greatly improves the anticorrosion performance of epoxy coatings(EP);however,poor compatibility between the materials can limit the improvement in properties.In this work,based on the high interface compatibility of two-dimensional(2D)Co_(2)(OH)_(2)BDC(BDC=1,4-benzenedicarboxylate)in the epoxy coating that we reported in previous work,we fabricated a 2D Co_(2)(OH)_(2)BDC-halloysite nanotube(HNT)nanocomposite have a structure consisting of alternating of nanosheets and nanotube by in situ synthesis.The nanocomposite was characterized by Fourier transform infrared spectroscopy,X-ray diffraction,and scanning electron microscopy.The mechanical and anticorrosion performance of the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was evaluated by mechanical tests and electrochemical impedance spectroscopy spectra.Compared with a conventional unreinforced epoxy coating,the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating had higher mechanical strength and toughness,and the low-frequency impedance modulus of 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was increased by three orders of magnitude,demonstrating the high corrosion resistance of our reinforced coating.展开更多
On the basis of analysis of structure and properties, halloysite, a natural tubular mineral, was developed for an environmental treatment. TiO2 was mounted into halloysite by using hydrolysis of tetrabutyl titanate at...On the basis of analysis of structure and properties, halloysite, a natural tubular mineral, was developed for an environmental treatment. TiO2 was mounted into halloysite by using hydrolysis of tetrabutyl titanate at room temperature. The adsorption and photocatalytic performance of halloysite and TiO2-mounted halloysite have been examined in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Their performance of adsorption and photodecomposition was evaluated from the adsorbed and degraded amounts of methylene blue (MB). Due to the mixture of adsorption and photodecomposition, the concentration of MB, organic pollution, in water decreased rapidly with TiO2-mounted halloysite powder, which is a faster reaction than that with halloysite-only adsorption. This new use of halloysite is leading to many interesting applications in the decomposition and elimination of various pollutants in air and water.展开更多
The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent...The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent-free route.The properties of the HNT–ZnO nanofillers were characterized using zeta-potential measurement,X-ray diffraction(XRD),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),and thermogravimetric analysis(TGA).The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO.The TGA results indicate that the thermal stability of the HNT–ZnO nanofillers is higher than that of the HNT.Furthermore,UV?Vis diffuse reflectance spectroscopy(UV-DRS)results show that the HNT–ZnO achieve a total reflectance as high as approximately 87.5%in the UV region,as compare with 66.9%for the HNT.In summary,the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.展开更多
A natural nanotubular material,halloysite nanotubes(HNTs),was introduced to prepare styrene-butadiene rubber/modified halloysite nanotube(SBR/m-HNT) nanocomposites.Complex of resorcinol and hexamethylenetetramine (RH)...A natural nanotubular material,halloysite nanotubes(HNTs),was introduced to prepare styrene-butadiene rubber/modified halloysite nanotube(SBR/m-HNT) nanocomposites.Complex of resorcinol and hexamethylenetetramine (RH) was used as the interfacial modifier.The structure,morphology and mechanical properties of SBR/m-HNT nanocomposites,especially the interfacial interactions,were investigated.SEM and TEM observations showed that RH can not only facilitate the dispersion and orientation of HNTs in SBR matrix at ...展开更多
Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to theienvironmental friendliness,low cost,and high specific energy densities.However,the low electrical conductivity of...Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to theienvironmental friendliness,low cost,and high specific energy densities.However,the low electrical conductivity of sulfur,shuttling of soluble intermediate polysulfides between electrodes,and low capacitretention have hampered their commercial use.To address these issues,we use a halloysitemodulated(H-M)separator in a lithium–sulfur battery to mitigate the shuttling problem.The H-M separator acts as a mutual Coulombic repulsion in lithium-sulfur batteries,thereby selectively permitting Lions and efficiently suppressing the transfer of undesired lithium polysulfides to the Li anode sideMoreover,the use of halloysite switches the surface of the separator from hydrophobic to hydrophilicconsequently improving the electrolyte wettability and adhesion between the separator and cathodeWhen sulfur-multi-walled carbon nanotube(S-MWCNT)composites are used as cathode active materialsa lithium–sulfur battery with an H-M separator exhibits first discharge and charge capacities of 1587 an1527 m Ah g-1,respectively.Moreover,there is a consistent capacity retention up to 100 cyclesAccordingly,our approach demonstrates an economical and easily accessible strategy for commercialization of lithium–sulfur batteries.展开更多
Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce^(3+)-Zr^(4+),2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen.An acid assisted etching of the nanotubes was carried...Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce^(3+)-Zr^(4+),2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen.An acid assisted etching of the nanotubes was carried out with a view to increase the lumen diameter and thereby,increase the amount of loading of the corrosion inhibitor.The morphology of as-received and etched halloysite nanotubes was ob-served using TEM analysis.The loading of corrosion inhibitors was confirmed using SEM-EDS and BET analysis.Polymeric microcapsules were used as capping agents for the ends of the loaded HNTs following which,they were dispersed into a hybrid sol-gel silica matrix.Dip coating method was used to generate coatings on AZ91D substrates followed by heat treatment at 130℃ for 1 h.The release rate kinetics of corrosion inhibitors from as-received and etched nanotubes was investigated in buffer solutions of 3.5 wt%NaCl at different pH.The release mechanism of corrosion inhibitors from the HNT lumen was validated using various semi-empirical models.Coatings were also evaluated for their corrosion protection ability using electrochemical techniques after exposure to 3.5 wt%NaCl solution for 120 h.Coatings generated using Ce^(3+)-Zr^(4+)loaded into as-received halloysite nanotubes have shown more effective corrosion protection when compared to other corrosion inhibitors after 120 h exposure to the corrosive medium.展开更多
The linear and nonlinear torsional free vibration analyses of functionMly graded micro/nuno-tubes (FGMTs) are analytically investigated based on the couple stress theory. The employed non-classical continuum theory ...The linear and nonlinear torsional free vibration analyses of functionMly graded micro/nuno-tubes (FGMTs) are analytically investigated based on the couple stress theory. The employed non-classical continuum theory contains one material length scale parameter, which can capture the small scale effect. The FGMT model accounts for the through-radius power-law variation of a two-constituent material. Hamilton's principle is used to develop the non-classical nonlinear governing equation. To study the effect of the boundary conditions, two types of end conditions, i.e., fixed-fixed and fixed-free, are considered. The derived boundary value governing equation is of the fourthorder, and is solved by the homotopy analysis method (HAM). This method is based on the Taylor series with an embedded parameter and is capable of providing very good approximations by means of only a few terms, if the initial guess and the auxiliary linear operator are properly selected. The analytical expressions are developed for the linear and nonlinear natural frequencies, which can be conveniently used to investigate the effects of the dimensionless length scale parameter, the material gradient index, and the vibration amplitude on the natural frequencies of FGMTs.展开更多
Halloysite template, a ceramic substrate, is of a hollow cylindric structure, on which the fine Pd nanoparticles are uniformly formed by the reduction of palldate chloride to initiate electroless deposition. The elect...Halloysite template, a ceramic substrate, is of a hollow cylindric structure, on which the fine Pd nanoparticles are uniformly formed by the reduction of palldate chloride to initiate electroless deposition. The electroless deposition of Ni is catalyzed by the Pd particles, which results in a uniform layer of Ni-P alloy on halloysite. The alloy is of a nanocrystalline structure, of which the average diameter is about 6 nm. After being heat-treated at 400 ℃, it contains both Ni and Ni12P5 crystal, meanwhile, the Ni crystal gets larger with an average size of 51.9 nm.The content of phosphorous in the Ni layer has a great influence on crystal structure. The metallized halloysite has a higher inherent coercive force, and a much lower saturation magnetization in its as-plated state, while after heattreatment, the inherent coercive force decreases drastically. These magnetic properties have great relationship with the superparamagnetism of Ni nanocrystalline and the stress anisotropy in Ni layer.展开更多
1 Introduction The weathered crust rare earth deposits is one of the most significant rare earth deposits,which are mostly distributed in southern China,especially in the south of Jiangxi province(Chi et al.,2007).The...1 Introduction The weathered crust rare earth deposits is one of the most significant rare earth deposits,which are mostly distributed in southern China,especially in the south of Jiangxi province(Chi et al.,2007).The compositions of these deposits,which are weathered from igneous rocks such as granite through biological,physical or chemical展开更多
The N-doped TiO2-loaded halloysite nanotubes(N-Ti O2/HNTs) nanocomposites were prepared by using chemical vapor deposition method which was realized in autoclave. The photocatalytic activity of nanocomposites was eval...The N-doped TiO2-loaded halloysite nanotubes(N-Ti O2/HNTs) nanocomposites were prepared by using chemical vapor deposition method which was realized in autoclave. The photocatalytic activity of nanocomposites was evaluated by virtue of the decomposition of formaldehyde gas under solar-light irradiation. The XRD patterns verified that the anatase structured TiO2 was deposited on HNTs. The TEM images showed that the surface of HNTs was covered with nanosized TiO2 with a particle size of ca. 20 nm. The UV-vis spectra indicated that the N-Ti O2/HNTs presented a significant absorption band in the visible region between 400 nm and 600 nm. Under solar-light irradiation, the highest degradation rate of formaldehyde gas attained 90% after 100 min of solar-light irradiation. The combination of the photocatalytic property of TiO2 and the unique structure of halloysite would assert a promising perspective in degradation of organic pollutants.展开更多
Naturally occurring tubular halloysite is a potential drug carrier because of the significant deposit, unique mesoscopic (2-50 nm) or even macroscopic (>50 nm) lumen, and excellent biocompatibility. The drugs loade...Naturally occurring tubular halloysite is a potential drug carrier because of the significant deposit, unique mesoscopic (2-50 nm) or even macroscopic (>50 nm) lumen, and excellent biocompatibility. The drugs loaded on halloysite exhibited slow release under the diffusion limitation by the halloysite nanotube. However, due to the weak interaction between halloysite and guest, the loading capacity of halloysite was relatively low. This drawback severely limits the application of halloysite as carrier in pharmaceutics. In this study, the performance of halloysite as carrier for ibuprofen (IBU) loading was investigated for the first time. The effects of 3-aminopropyltriethoxysilane (APTES) modification and thermal treatment of halloysite on the loading and release of IBU were also studied. The purified halloysites were heated at 120 ℃ and 400 ℃ (labeled as Hal/120 and Hal/400), and then modified with APTES (labeled as Hal/120-A and Hal/400-A). The loading of IBU was achieved by soaking method (labeled as IBU-Hal/120, IBU-Hal/400, IBU-Hal/120-A, and IBU-Hal/400-A.). The in vitro drug delivery assays were performed in phosphate buffer solution. IBU was loaded mainly into the lumen and partially on the external surface of halloysite. The order of IBU contents was as follows: IBU-Hal/400-A (14.8wt%) > IBU-Hal/120-A (12.7wt%) > IBU-Hal/400 (11.8wt%) > IBU-Hal/120 (11.7wt%). The IBU was initially anchored to the surface hydroxyl groups of halloysite by hydrogen bonding, followed by further bonding of IBU with the anchored IBU to form hydrogen-bonded aggregates. The APTES modification of halloysite promoted the loading of IBU by introducing a strong affinity through electrostatic attraction between the introduced aminopropyl groups of APTES and the carboxyl groups of IBU. Thermal treatment at 400°C did not destroy the tubular morphology or the crystal structure of halloysite and had little effect on IBU loading in unmodified halloysite. However, thermal treatment by reducing water content in halloysite restricted the grafting of APTES in the lumen space, and further increased IBU loading. All IBU-loaded samples exhibit a burst release with a following slow release. However, owing to the strong electrostatic attraction in modified samples, the burst release was much more suppressed and the release rate was also lower than that in unmodified ones. The in vitro release profiles of the IBU-loaded samples were well fitted with the modified Korsmeyer-Peppas model. The IBU release mechanism of the unmodified samples was Fickian diffusion; however it was non-Fickian diffusion for the modified samples. The findings are of significance for broadening the use of halloysite as carrier for drugs and other active molecules in the pharmaceutical, pesticides, and coating industries.展开更多
Novel cobalt Fischer-Tropsch synthesis (FTS) catalysts were prepared from natural halloysite nanotubes (HNT) by double-solvent and wet- impregnation methods, and characterized by TEM, XRD, TPR and N2 adsorption-de...Novel cobalt Fischer-Tropsch synthesis (FTS) catalysts were prepared from natural halloysite nanotubes (HNT) by double-solvent and wet- impregnation methods, and characterized by TEM, XRD, TPR and N2 adsorption-desorption. Comparing with the catalyst prepared by wet- impregnation method, the catalyst prepared by double-solvent method reduces Co3O4 particle migration and agglomeration due to size-induced effect, thus showing higher catalytic activity for Fischer-Tropsch synthesis.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
The diffusion permeability through new hybrid materials based on a Nafion-type membrane (MF- 4SC) and nanotubes of halloysite is investigated using the Nernst-Planck approach. A method of quantitative evaluation of ph...The diffusion permeability through new hybrid materials based on a Nafion-type membrane (MF- 4SC) and nanotubes of halloysite is investigated using the Nernst-Planck approach. A method of quantitative evaluation of physicochemical parameters (averaged and individual diffusion coefficients and averaged distribution coefficients of ion pairs in the membrane) of system “electrolyte solution—ion-exchange membrane—water”, which was proposed earlier, is further developed. The parameters of hybrid membranes on the base of MF-4SC and nanotubes of halloysite (5% wt and 8% wt) are obtained from experimental data on diffusion permeability of NaCl solutions using theoretical calculations. New model of three-layer membrane system can be used for refining calculated results with taking into account both diffusive layers. It is shown that adding of halloysite nanotubes into the membrane volume noticeably affects exchange capacity as well as structural and transport characteristics of original perfluorinated membranes. Hybrid membranes on the base of MF-4SC and halloysite nanotubes can be used in fuel cells and catalysis.展开更多
In this work a three-dimensional, time-quantified Monte Carlo model that efficiently describes diffusion through and from nanotubes is implemented. Controlled delivery from Halloysite Nano-tubes (HNT) is modeled based...In this work a three-dimensional, time-quantified Monte Carlo model that efficiently describes diffusion through and from nanotubes is implemented. Controlled delivery from Halloysite Nano-tubes (HNT) is modeled based on interactions between the HNT’s inner wall and the nanoparticles (NPs) and among NPs themselves. The model was validated using published experimental data. The validated model is then used to study the effect of multiples parameter like HNT diameter and length, particle charge, and ambient temperature on the release of encapsulated NPs. The results show that release profiles depend on the size distribution of the HNT batch used for the experiment, as delivery is sensitive to HNT lumen and length. A very good agreement with the experiment is observed when a weighted average release profile is compared to the experimental profile. Although the NP dynamics is temperature-dependent, the effect is minimum within the range of temperatures relevant to biomedical applications, but will be relevant for other applications at temperatures significantly different from room temperature. This model can be used to predict the best conditions for a particular delivery need.展开更多
Tubular halloysite is a hydrated polymorph of kaolinite, commonly considered as its associated mineral. Due to its unique mesoscopic (2–50 nm) tubular structure, it has attracted great interest in the field of adsorp...Tubular halloysite is a hydrated polymorph of kaolinite, commonly considered as its associated mineral. Due to its unique mesoscopic (2–50 nm) tubular structure, it has attracted great interest in the field of adsorption, catalysis, and nanocarrier. The halloysites in different deposits present various morphological properties which significantly affect the interface reactions with functional guests. These scattered properties in addition to their low purity severely limit the actual applications of halloysite in industry.展开更多
文摘In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.
基金supported by the Excellent Youth Foundation of Henan Scientific Committee,China(222300420018)Key Scientific Research Projects in Universities of Henan Province,China(21zx006)。
文摘Layered assembled membranes of 2D leaf-like zeolitic imidazolate frameworks(ZIF-L)nanosheets have received great attention in the field of water treatment due to the porous structure and excellent antibacterial ability,but the dense accumulation on the membrane surface and the low permeate flux greatly hinder their application.Herein,we synthesized m HNTs(modified halloysite nanotubes)/ZIF-L nanocomposites on modified m HNTs by in situ growth method.Interestingly,due to the different size of m HNTs and ZIF-L,m HNTs were packed in ZIF-L nanosheets.The hollow m HNTs provided additional transport channels for water molecules,and the accumulation of the ZIF-L nanosheets was decreased after assembling m HNTs/ZIF-L nanocomposites into membrane by filtration.The prepared m HNTs/ZIF-L membrane presented high permeate flux(59.6 L·m^(-2)·h^(-1)),which is 2-4 times of the ZIF-L membranes(14.8 L·m^(-2)·h^(-1)).Moreover,m HNTs/ZIF-L membranes are intrinsically antimicrobial,which exhibit extremely high bacterial resistance.We provide a controllable strategy to improve 2D ZIF-L assembles,and develops novel membranes using 2D package structure as building units.
文摘Introducing inorganic nanomaterials into a polymer matrix greatly improves the anticorrosion performance of epoxy coatings(EP);however,poor compatibility between the materials can limit the improvement in properties.In this work,based on the high interface compatibility of two-dimensional(2D)Co_(2)(OH)_(2)BDC(BDC=1,4-benzenedicarboxylate)in the epoxy coating that we reported in previous work,we fabricated a 2D Co_(2)(OH)_(2)BDC-halloysite nanotube(HNT)nanocomposite have a structure consisting of alternating of nanosheets and nanotube by in situ synthesis.The nanocomposite was characterized by Fourier transform infrared spectroscopy,X-ray diffraction,and scanning electron microscopy.The mechanical and anticorrosion performance of the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was evaluated by mechanical tests and electrochemical impedance spectroscopy spectra.Compared with a conventional unreinforced epoxy coating,the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating had higher mechanical strength and toughness,and the low-frequency impedance modulus of 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was increased by three orders of magnitude,demonstrating the high corrosion resistance of our reinforced coating.
基金a project sponsored by the Scientific Research Foundation for Returned 0verseas Chinese Scholarsthe State Education Ministry+1 种基金and in part by the National Natural Science Foundation of China(No.50272005)the Analysis Foundation of Peking University
文摘On the basis of analysis of structure and properties, halloysite, a natural tubular mineral, was developed for an environmental treatment. TiO2 was mounted into halloysite by using hydrolysis of tetrabutyl titanate at room temperature. The adsorption and photocatalytic performance of halloysite and TiO2-mounted halloysite have been examined in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Their performance of adsorption and photodecomposition was evaluated from the adsorbed and degraded amounts of methylene blue (MB). Due to the mixture of adsorption and photodecomposition, the concentration of MB, organic pollution, in water decreased rapidly with TiO2-mounted halloysite powder, which is a faster reaction than that with halloysite-only adsorption. This new use of halloysite is leading to many interesting applications in the decomposition and elimination of various pollutants in air and water.
基金Universiti Sains Malaysia for Bridging Fund(grant No.304.PBAHAN.6316090)
文摘The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent-free route.The properties of the HNT–ZnO nanofillers were characterized using zeta-potential measurement,X-ray diffraction(XRD),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),and thermogravimetric analysis(TGA).The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO.The TGA results indicate that the thermal stability of the HNT–ZnO nanofillers is higher than that of the HNT.Furthermore,UV?Vis diffuse reflectance spectroscopy(UV-DRS)results show that the HNT–ZnO achieve a total reflectance as high as approximately 87.5%in the UV region,as compare with 66.9%for the HNT.In summary,the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.
基金supported by the National Natural Science Foundation of China(Nos.50573021 and 50603005)
文摘A natural nanotubular material,halloysite nanotubes(HNTs),was introduced to prepare styrene-butadiene rubber/modified halloysite nanotube(SBR/m-HNT) nanocomposites.Complex of resorcinol and hexamethylenetetramine (RH) was used as the interfacial modifier.The structure,morphology and mechanical properties of SBR/m-HNT nanocomposites,especially the interfacial interactions,were investigated.SEM and TEM observations showed that RH can not only facilitate the dispersion and orientation of HNTs in SBR matrix at ...
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(No.2018R1C1B6004689)the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2020R1I1A306182111)the Electronics and Telecommunications Research Institute(ETRI)grant funded by the Korean government(21ZB1200,Development of ICT Materials,Components and Equipment Technologies)。
文摘Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to theienvironmental friendliness,low cost,and high specific energy densities.However,the low electrical conductivity of sulfur,shuttling of soluble intermediate polysulfides between electrodes,and low capacitretention have hampered their commercial use.To address these issues,we use a halloysitemodulated(H-M)separator in a lithium–sulfur battery to mitigate the shuttling problem.The H-M separator acts as a mutual Coulombic repulsion in lithium-sulfur batteries,thereby selectively permitting Lions and efficiently suppressing the transfer of undesired lithium polysulfides to the Li anode sideMoreover,the use of halloysite switches the surface of the separator from hydrophobic to hydrophilicconsequently improving the electrolyte wettability and adhesion between the separator and cathodeWhen sulfur-multi-walled carbon nanotube(S-MWCNT)composites are used as cathode active materialsa lithium–sulfur battery with an H-M separator exhibits first discharge and charge capacities of 1587 an1527 m Ah g-1,respectively.Moreover,there is a consistent capacity retention up to 100 cyclesAccordingly,our approach demonstrates an economical and easily accessible strategy for commercialization of lithium–sulfur batteries.
文摘Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce^(3+)-Zr^(4+),2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen.An acid assisted etching of the nanotubes was carried out with a view to increase the lumen diameter and thereby,increase the amount of loading of the corrosion inhibitor.The morphology of as-received and etched halloysite nanotubes was ob-served using TEM analysis.The loading of corrosion inhibitors was confirmed using SEM-EDS and BET analysis.Polymeric microcapsules were used as capping agents for the ends of the loaded HNTs following which,they were dispersed into a hybrid sol-gel silica matrix.Dip coating method was used to generate coatings on AZ91D substrates followed by heat treatment at 130℃ for 1 h.The release rate kinetics of corrosion inhibitors from as-received and etched nanotubes was investigated in buffer solutions of 3.5 wt%NaCl at different pH.The release mechanism of corrosion inhibitors from the HNT lumen was validated using various semi-empirical models.Coatings were also evaluated for their corrosion protection ability using electrochemical techniques after exposure to 3.5 wt%NaCl solution for 120 h.Coatings generated using Ce^(3+)-Zr^(4+)loaded into as-received halloysite nanotubes have shown more effective corrosion protection when compared to other corrosion inhibitors after 120 h exposure to the corrosive medium.
文摘The linear and nonlinear torsional free vibration analyses of functionMly graded micro/nuno-tubes (FGMTs) are analytically investigated based on the couple stress theory. The employed non-classical continuum theory contains one material length scale parameter, which can capture the small scale effect. The FGMT model accounts for the through-radius power-law variation of a two-constituent material. Hamilton's principle is used to develop the non-classical nonlinear governing equation. To study the effect of the boundary conditions, two types of end conditions, i.e., fixed-fixed and fixed-free, are considered. The derived boundary value governing equation is of the fourthorder, and is solved by the homotopy analysis method (HAM). This method is based on the Taylor series with an embedded parameter and is capable of providing very good approximations by means of only a few terms, if the initial guess and the auxiliary linear operator are properly selected. The analytical expressions are developed for the linear and nonlinear natural frequencies, which can be conveniently used to investigate the effects of the dimensionless length scale parameter, the material gradient index, and the vibration amplitude on the natural frequencies of FGMTs.
文摘Halloysite template, a ceramic substrate, is of a hollow cylindric structure, on which the fine Pd nanoparticles are uniformly formed by the reduction of palldate chloride to initiate electroless deposition. The electroless deposition of Ni is catalyzed by the Pd particles, which results in a uniform layer of Ni-P alloy on halloysite. The alloy is of a nanocrystalline structure, of which the average diameter is about 6 nm. After being heat-treated at 400 ℃, it contains both Ni and Ni12P5 crystal, meanwhile, the Ni crystal gets larger with an average size of 51.9 nm.The content of phosphorous in the Ni layer has a great influence on crystal structure. The metallized halloysite has a higher inherent coercive force, and a much lower saturation magnetization in its as-plated state, while after heattreatment, the inherent coercive force decreases drastically. These magnetic properties have great relationship with the superparamagnetism of Ni nanocrystalline and the stress anisotropy in Ni layer.
基金supported by the National Natural Science Foundation of China (Grant No. 41302030)Fundamental Research Project of Chinese Academy of Geological Sciences (Grant No. YYWF201619)+1 种基金National Key R&D Program of China (Grant No.2016YFC0600605)China Geological Survey Program (DD20179152)
文摘1 Introduction The weathered crust rare earth deposits is one of the most significant rare earth deposits,which are mostly distributed in southern China,especially in the south of Jiangxi province(Chi et al.,2007).The compositions of these deposits,which are weathered from igneous rocks such as granite through biological,physical or chemical
基金Supported by the National ]qatural Science Foundation of China (20906064), the National Basic Research Program of China (2009CB623407), the Program for Changjiang Scholars and Innovative Research Team in University (IRTl163), and the Foundation for the Author of National Excellent Doctoral Dissertation of China (201163).
基金supported by the Talent Introduction Fund of Yangzhou Universitythe Jiangsu Social Development Project(BE2014613)the Six Talent Peaks of Jiangsu province(2014-XCL-013)
文摘The N-doped TiO2-loaded halloysite nanotubes(N-Ti O2/HNTs) nanocomposites were prepared by using chemical vapor deposition method which was realized in autoclave. The photocatalytic activity of nanocomposites was evaluated by virtue of the decomposition of formaldehyde gas under solar-light irradiation. The XRD patterns verified that the anatase structured TiO2 was deposited on HNTs. The TEM images showed that the surface of HNTs was covered with nanosized TiO2 with a particle size of ca. 20 nm. The UV-vis spectra indicated that the N-Ti O2/HNTs presented a significant absorption band in the visible region between 400 nm and 600 nm. Under solar-light irradiation, the highest degradation rate of formaldehyde gas attained 90% after 100 min of solar-light irradiation. The combination of the photocatalytic property of TiO2 and the unique structure of halloysite would assert a promising perspective in degradation of organic pollutants.
文摘Naturally occurring tubular halloysite is a potential drug carrier because of the significant deposit, unique mesoscopic (2-50 nm) or even macroscopic (>50 nm) lumen, and excellent biocompatibility. The drugs loaded on halloysite exhibited slow release under the diffusion limitation by the halloysite nanotube. However, due to the weak interaction between halloysite and guest, the loading capacity of halloysite was relatively low. This drawback severely limits the application of halloysite as carrier in pharmaceutics. In this study, the performance of halloysite as carrier for ibuprofen (IBU) loading was investigated for the first time. The effects of 3-aminopropyltriethoxysilane (APTES) modification and thermal treatment of halloysite on the loading and release of IBU were also studied. The purified halloysites were heated at 120 ℃ and 400 ℃ (labeled as Hal/120 and Hal/400), and then modified with APTES (labeled as Hal/120-A and Hal/400-A). The loading of IBU was achieved by soaking method (labeled as IBU-Hal/120, IBU-Hal/400, IBU-Hal/120-A, and IBU-Hal/400-A.). The in vitro drug delivery assays were performed in phosphate buffer solution. IBU was loaded mainly into the lumen and partially on the external surface of halloysite. The order of IBU contents was as follows: IBU-Hal/400-A (14.8wt%) > IBU-Hal/120-A (12.7wt%) > IBU-Hal/400 (11.8wt%) > IBU-Hal/120 (11.7wt%). The IBU was initially anchored to the surface hydroxyl groups of halloysite by hydrogen bonding, followed by further bonding of IBU with the anchored IBU to form hydrogen-bonded aggregates. The APTES modification of halloysite promoted the loading of IBU by introducing a strong affinity through electrostatic attraction between the introduced aminopropyl groups of APTES and the carboxyl groups of IBU. Thermal treatment at 400°C did not destroy the tubular morphology or the crystal structure of halloysite and had little effect on IBU loading in unmodified halloysite. However, thermal treatment by reducing water content in halloysite restricted the grafting of APTES in the lumen space, and further increased IBU loading. All IBU-loaded samples exhibit a burst release with a following slow release. However, owing to the strong electrostatic attraction in modified samples, the burst release was much more suppressed and the release rate was also lower than that in unmodified ones. The in vitro release profiles of the IBU-loaded samples were well fitted with the modified Korsmeyer-Peppas model. The IBU release mechanism of the unmodified samples was Fickian diffusion; however it was non-Fickian diffusion for the modified samples. The findings are of significance for broadening the use of halloysite as carrier for drugs and other active molecules in the pharmaceutical, pesticides, and coating industries.
基金supported by the National Natural Science foundation of China (21073238)the National Basic Research Program of China(2011CB211704)the Special Fund for Basic Scientific Research of Central Colleges,South-Central University for Nationalities
文摘Novel cobalt Fischer-Tropsch synthesis (FTS) catalysts were prepared from natural halloysite nanotubes (HNT) by double-solvent and wet- impregnation methods, and characterized by TEM, XRD, TPR and N2 adsorption-desorption. Comparing with the catalyst prepared by wet- impregnation method, the catalyst prepared by double-solvent method reduces Co3O4 particle migration and agglomeration due to size-induced effect, thus showing higher catalytic activity for Fischer-Tropsch synthesis.
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.
文摘The diffusion permeability through new hybrid materials based on a Nafion-type membrane (MF- 4SC) and nanotubes of halloysite is investigated using the Nernst-Planck approach. A method of quantitative evaluation of physicochemical parameters (averaged and individual diffusion coefficients and averaged distribution coefficients of ion pairs in the membrane) of system “electrolyte solution—ion-exchange membrane—water”, which was proposed earlier, is further developed. The parameters of hybrid membranes on the base of MF-4SC and nanotubes of halloysite (5% wt and 8% wt) are obtained from experimental data on diffusion permeability of NaCl solutions using theoretical calculations. New model of three-layer membrane system can be used for refining calculated results with taking into account both diffusive layers. It is shown that adding of halloysite nanotubes into the membrane volume noticeably affects exchange capacity as well as structural and transport characteristics of original perfluorinated membranes. Hybrid membranes on the base of MF-4SC and halloysite nanotubes can be used in fuel cells and catalysis.
文摘In this work a three-dimensional, time-quantified Monte Carlo model that efficiently describes diffusion through and from nanotubes is implemented. Controlled delivery from Halloysite Nano-tubes (HNT) is modeled based on interactions between the HNT’s inner wall and the nanoparticles (NPs) and among NPs themselves. The model was validated using published experimental data. The validated model is then used to study the effect of multiples parameter like HNT diameter and length, particle charge, and ambient temperature on the release of encapsulated NPs. The results show that release profiles depend on the size distribution of the HNT batch used for the experiment, as delivery is sensitive to HNT lumen and length. A very good agreement with the experiment is observed when a weighted average release profile is compared to the experimental profile. Although the NP dynamics is temperature-dependent, the effect is minimum within the range of temperatures relevant to biomedical applications, but will be relevant for other applications at temperatures significantly different from room temperature. This model can be used to predict the best conditions for a particular delivery need.
文摘Tubular halloysite is a hydrated polymorph of kaolinite, commonly considered as its associated mineral. Due to its unique mesoscopic (2–50 nm) tubular structure, it has attracted great interest in the field of adsorption, catalysis, and nanocarrier. The halloysites in different deposits present various morphological properties which significantly affect the interface reactions with functional guests. These scattered properties in addition to their low purity severely limit the actual applications of halloysite in industry.