Increase In Interlayer Distance Research Articles

Similar Material Simulation Study on Protection Effect of Steeply Inclined Upper Protective Layer Mining with Varying Interlayer Distances

Protective layer mining, as a dominating regional prevention measure, is generally adopted to prevent and control gas disasters in highly gassy or outburst mines of China. Interlayer distance is one of the most important factors that influences protection effect. However, how does interlayer distance affect the protection effect of steeply inclined upper protective layer mining is not understood fully. According to the engineering practice in Nantong mining district, a new method for similar material simulation experiment of steeply inclined upper protective layer mining is proposed, in which an orthogonal test of similar materials comprising of sand, cement (containing gypsum and fly ash), and water mixture is conducted to obtain relations between proportioning parameters and mechanical properties using a multiple regression method. And then the method is applied to study the protection effect of steeply inclined upper protective layer mining with varying interlayer distances. The results show the following. (1) The proportioning parameters of similar material have strong linear relations with its mechanical properties, and mechanical behaviors of such similar material denote that it can simulate most coal‐rock lithologies in coal mine. (2) Both pressure‐relief curves and swelling strain curves for protected layer present convex shapes; protection angles at lower excavation boundary are greater than those of upper excavation boundary; with the increase of interlayer distance, the pressure‐relief curve evolves from pattern “∩” to pattern “∧” and corresponding pressure‐relief region becomes narrower, the center of pressure‐relief region tends to transfer to the corresponding center of upper protective layer excavation region, the stress concentration coefficient decreases, the protection angles change little, and the length of the protection region reduces dramatically. (3) The protection region and protection angle calculated based on swelling strain of 3‰ are less than the empirical values based on the dip angle in Provisions, denoting that the method proposed in this study is safer than that in Provisions. The research results provide a useful guide for layouts of roadway and gas drainage boreholes to prevent gas disaster in Nantong coal mine district.

MODIFICATION TECHNOLOGY OF MONTMORILLONITE BY POLYIONENES

Technology of obtaining montmorillonite modified by polyionenes is developed. Macromolecular polymer intercalation of a quaternary ammonium salt of montmorillonite intercrystalline space is shown to be accompanied with increased interlayer distances from 1.08 nm to 1.67 nm. The technique of synthesis of montmorillonite modified by polyionenes is suggested. Optimal conditions for sorption of polyionenes molecules with montmorillonite are found to be: the concentration of aqueous dispersion of montmorillonite is 1 %, the temperature of the reaction medium is 40 °C, the montmorillonite-polyionene ratio is 3 : 1, the processing time is 24 hours. The mechanism of montmorillonite modification is suggested to involve the next steps: connection of organic cations to montmorillonite surface determined by attachment of organic cations to exchange position during ion-exchange adsorption and adsorption of organic cations with acid sylanol groups, i.e. torn bonds on crystal faces. These processes are shown to result in more perfect structure by organic cations adsorption with acid sylanol groups (torn bonds on crystal faces).

Promising electrode material using Ni-doped layered manganese dioxide for sodium-ion batteries

Birnessite MnO2, a hydrated layered manganese dioxide with a layered structure, is a promising candidate for sodium-ion batteries because of a significant interlayer distance for the reversible insertion of sodium ions. This work proposes to improve the electrochemical performance of layered manganese dioxide by metal cation doping. Nickel-doped layered MnO2 (0.05–0.15 wt%) prepared by a sol–gel method using a chelate agent of fumaric acid showed a gradual increase of interlayer distance with an increase of Ni-doping amount. Moreover, ex situ XRD results during the first cycle confirmed a stabilization of the layered structure during the sodium insertion. During the charge–discharge test, the initial capacity of 15% Ni layered MnO2 was 140 mAh/g, with small capacity fade over 20 cycles. Layered structure of MnO2 and sodium diffusion along [001] and [010] direction.

High-Performance Asymmetric Supercapacitors Based on the Surfactant/Ionic Liquid Complex Intercalated Reduced Graphene Oxide Composites

In this paper, ionic surfactants are employed to intercalate thermally-reduced graphene oxide (TRG). The ionic interaction between the intercalated surfactant and the ionic liquid could lead to the formation of large-sized ionic aggregates and, hence, enlarge the interlayer distance between the TRG sheets. The morphology and vibration modes of these composites were systematically characterized using XRD (X-ray diffraction), SAXS (small-angle X-ray scattering), and FTIR (Fourier transform infrared spectroscopy). An asymmetric supercapacitor, which consisted of a cationic surfactant-intercalated electrode on one side and an anionic surfactant-intercalated electrode on the other, was examined. It was found that, with the increased interlayer distance, the energy density and capacitance of the cells were improved. It seems that the cell with a cationic surfactant as the cathode had the best energy density of 67.8 Wh/kg, which is 4.4-fold higher than that of the TRG cell.

The Influence of the Interlayer Distance on the Performance of Thermally Reduced Graphene Oxide Supercapacitors.

In this paper, cationic surfactant cetyltrimethylammonium bromide (CTAB) was employed to prevent the restack of the thermally reduce graphene oxide (TRG) sheets. A facile approach was demonstrated to effectively enlarge the interlayer distance of the TRG sheets through the ionic interaction between the intercalated CTAB and ionic liquids (ILs). The morphology of the composites and the interaction between the intercalated ionic species were systematically characterized by SEM, SAXS, XRD, TGA, and FTIR. In addition, the performance of the EDLC cells based on these TRG composites was evaluated. It was found that due to the increased interlayer distance (0.41 nm to 2.51 nm) that enlarges the accessible surface area for the IL electrolyte, the energy density of the cell can be significantly improved (23.1 Wh/kg to 62.5 Wh/kg).

Carbon fiber paper supported interlayer space enlarged Ni2Fe-LDHs improved OER electrocatalytic activity

Herein, a series of three-dimensional Ni2Fe-SDS-LDH/CFP non-precious metal electrocatalysts in a simple hydrothermal route using sodium dodecyl sulfonate (SDS) as an interlayer spacer agent, and carbon fiber paper (CFP) as a conductive substrate was tailored. The electrocatalytic performance towards oxygen evolution reaction (OER) in alkaline medium was investigated. The results demonstrate that the OER activity improvement is mainly related to the increased interlayer distance from 0.76 nm to 2.49 nm depending on the intercalated amount of SDS in Ni2Fe-LDH, and resulting in the enhanced superior surface characteristics (e.g., larger specific surface area, bigger pore size and pore volume). Among all the samples, the Ni2Fe-SDS-LDH/CFP (molar ratio SDS/Fe = 1.5) showed the best OER performance (η@10 mA cm−2 = 289 mV, Tafel slope = 39 mV dec−1) comparable with the commercial IrO2 catalyst, which corresponded to the largest interlayer space of 2.49 nm.

Suppression of O3/P3 Phase Transition for Nanosize NaCrO2 with Enriched Domain Boundaries in Individual Particle

Rechargeable Na batteries are promising to realize sustainable energy development in the future because of the material abundance, and many electrode materials have been actively researched in the world. O3-type NaCrO2 1, 2 is known to show excellent cycle performance and thermal stability3. Additionally, O3 NaCrO2 shows second highest operating voltage among O3-type layered oxides, next to O3 NaFeO2. O3-type layered oxides translate into P3-type layered structure after removing Na from the layered structure. Such phase transitions result in large volume changes associated with increase in interlayer distance because of large repulsive interaction between MeO2 layers. The deterioration of cyclability associated with O3/P3 transitions is, therefore, anticipated as electrode materials. In this study, nanosize NaCrO2 with enriched domain boundaries in individual particle was synthesized from nanosize cation-disordered rocksalt-type NaCrO2 prepared by mechanical milling. The sample delivers large reversible capacity without voltage plateaus associated with phase transitions as shown in Figure 1a. Ex-situ XRD data clearly indicates that the O3/P3 phase transition is effectively suppressed on charge/discharge processes. High-resolution TEM imaging shows that micrometer-size secondary particles consist of highly crystalline nanosize NaCrO2 particles. These nanosize domains are randomly aligned in the individual particle. We propose that randomly aligned particles with many grain boundaries cancel and suppress gliding of transition metal layers. Moreover, nanosize NaCrO2 shows better capacity retention in Na cells (Figure 1b) on the long-term cycle test. From these results, we will further discuss the factors affecting phase transitions for O3-type layered structure as positive electrode materials of rechargeable Na batteries for more details. Acknowledgements This study was in part granted by MEXT program “Elements Strategy Initiative to Form Core Research Center”, MEXT; Ministry of Education Culture, Sports, Science and Technology, Japan. High-resolution TEM work was carried out with the support from Deakin Advanced Characterization Facility. A.M.G. acknowledges the funding support from Australian Research Council Discovery grant DP160101178.

Redox Active Cation Intercalation/Deintercalation in Two-Dimensional Layered MnO2 Nanostructures for High-Rate Electrochemical Energy Storage.

Two-dimensional (2D) layered materials with a high intercalation pseudocapacitance have long been investigated for Li+-ion-based electrochemical energy storage. By contrast, the exploration of guest ions other than Li+ has been limited, although promising. The present study investigates intercalation/deintercalation behaviors of various metal ions in 2D layered MnO2 with various interlayer distances, K-birnessite nanobelt (K-MnO2), its protonated form (H-MnO2), and a freeze-dried sample of exfoliated nanosheets. Series of metal ions, such as monovalent Li+, Na+, and K+ and divalent Mg2+, exhibit reversible intercalation during charge/discharge cycling, delivering high-rate pseudocapacitances. In particular, the freeze-dried MnO2 of exfoliated nanosheets restacked with the largest interlayer spacing and a less compact 3D network exhibits the best rate capability and a stable cyclability over 5000 cycles. Both theoretical calculation and kinetic analysis reveal that the increased interlayer distance facilitates the fast diffusion of cations in layered MnO2 hosts. The results presented herein provide a basis for the controllable synthesis of layered nanostructures for high-rate electrochemical energy storage using various single- and multivalent ions.

Aptamer-graphene oxide for highly sensitive dual electrochemical detection of Plasmodium lactate dehydrogenase

A 90 mer ssDNA aptamer (P38) enriched against Plasmodium falciparum lactate dehydrogenase (PfLDH) through SELEX process was immobilized over glassy carbon electrode (GCE) using graphene oxide (GO) as an immobilization matrix, and the modified electrode was investigated for detection of PfLDH. The GO was synthesized from powdered pencil graphite and characterized by XRD based on the increased interlayer distance between graphitic layers from 0.345 nm for graphite to 0.829 nm for GO. The immobilization of P38 on GO was confirmed by ID/IG intensity ratio in Raman spectra where, the ratio were 0.67, 0.915, and 1.35 for graphite, GO and P38-GO, respectively. The formation of the P38 layer over GO-GCE was evident from an increase in the surface height in AFM analysis of the electrode from ∼3.5 nm for GO-GCE to ∼27 nm for P38-GO-GCE. The developed aptasensor when challenged with the target, a detection of as low as 0.5 fM of PfLDH was demonstrated. The specificity of the aptasensor was confirmed through a voltametric measurement at 0.65 V of the reduced co-factor generated from the PfLDH catalysis. Studies on interference from some common proteins, storage stability, repeatability and analysis of real samples demonstrated the practical application potential of the aptasensor.

Facile synthesis of Mo0.91W0.09S2 ultrathin nanosheets/amorphous carbon composites for lithium-ion battery anode

We report a facile process to synthesize Mo0.91W0.09S2/amorphous carbon composites with mean thickness of only 5nm ultrathin nanosheets and their improved electrochemical performance as anode materials for lithium ion batteries (LIBs). Structural and morphological characterizations of the nanocomposite have been investigated by XRD, SEM and TEM. It was found the amorphous carbon to be well dispersed on the ultrathin nanosheets surface. Due to the increased interlayer distance and the synergistic effects between Mo0.91W0.09S2 nanosheets and amorphous carbon, the as-prepared Mo0.91W0.09S2/C electrode deliveres exhibit a high Li capacity, an excellent rate capability, and a stable cycling performance, which suggests the Mo0.91W0.09S2/C composites as promising electrode material for LIBs.

Molecular engineering of aromatic amine spacers for high-performance graphene-based supercapacitors

In this work, chemical compounds of graphene oxide (GO) and amine molecules as spacers were synthesized by one-step hydrothermal reactions. The products of the reactions, referred to as rGO-Spacers samples, were fabricated into electrodes for supercapacitors. By engineering the molecular structures of the spacers, the specific capacitance (Cs) of the rGO-Spacers can reach up to 612F/g at 2mV/s in cyclic voltammetry (CV) measurement, 597F/g at 0.5A/g and 512F/g at 10A/g in galvanostatic charge–discharge measurement using two-electrode setup with 1M sulfuric acid aqueous solution at the electrolyte. 97% of the high Cs was retained after 10 000 charge–discharge cycles. In comparison, the control sample without spacers presents a Cs of 194F/g measured in CV measurement under the same conditions. The increased interlayer distance up to 1.9nm between graphene sheets caused by addition of the amine spacers was confirmed by X-ray diffraction. The morphology of rGO-Spacers samples was characterized by scanning electron microscope, transmission electron microscope and atomic force microscope, where crumpled thin sheets were observed. The spacer molecules were found to disperse uniformly on the sheets by energy dispersive spectroscope mapping. Chemical reactions and covalent bonding between GO and the spacers are evidenced by thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, Fourier-transform infrared spectroscope and Raman spectroscopy. Based on the characterization results, the amide formation reactions and epoxide ring opening reactions between amine spacers and GO are proposed. The weight measurement and the atomic ratio information from XPS further reveal different reactivity of the spacers to GO, which could account for the different Cs of the samples with spacers of different molecular structures. From the results of these comparative studies, the engineering of the molecular structures was found to play a pivotal role in determining the value of Cs. The findings also provide guidance to achieve even higher Cs by optimization of the molecular structures of the spacers, as well as other experimental parameters which can facilitate the reaction between the spacers and GO.

Interlayer expansion of the layered zeolite precursor COK-5 with Sn(acac)2Cl2

In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis(2,4-pentanedionate)-dichlorotin [Sn(acac)2Cl2], instead of a silylating agent was used to link the layers at 180 °C. The obtained material, which is designed as Sn-COE-5, shows a shift of the first XRD reflection, which is very similar to that of COK-5 interlayer expanded with dichlorodimethylsilane (DCDMS), indicating an increase in interlayer distance. X-ray diffraction (XRD), N2 sorption isotherms, inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS) support the incorporation of isolated Sn sites in the sample. In the conversion of glucose to levulinic acid, Sn-COE-5 exhibits much higher activity than COK-5, which is due to the presence of Lewis acidic sites in the Sn-COE-5.

Using Mg‐Al‐layered double hydroxide intercalated with chiral dicarboxylic acid for the reinforcement of isoleucine amino acid containing poly(amide‐imide)

A series of bionanocomposite (BNC) materials based on isoleucine containing poly(amide‐imide) (PAI) and modified MgAl‐layered double hydroxide (LDH) were prepared by solution intercalation method for the first time. An optically active PAI was synthesized by direct polycondensation reaction of N,N'‐(pyromellitoyl)‐bis‐isoleucine with 3,5‐diamino‐N‐(thiazol‐2‐yl)benzamide under green conditions. Organically modified LDH was prepared via ion exchange reaction of MgAl‐LDH in a solution of N,N'‐(pyromellitoyl)‐bis‐l‐isoleucine in distilled water. X‐ray diffraction (XRD) results of modified LDH show an increase in interlayer distance as compared to the unmodified one. The obtained polymer and modified LDH were used to prepare chiral and high‐performance hybrid materials. Fourier transform infrared spectroscopy, XRD, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis (TGA) techniques were used to study the morphology and thermal properties of the obtained hybrid materials. TGA data indicated an increase in thermal stability of the BNCs as compared to the pure polymer. POLYM. COMPOS., 37:3288–3295, 2016. © 2015 Society of Plastics Engineers

Novel nanocomposites of poly(vinyl alcohol) and Mg–Al layered double hydroxide intercalated with diacid N-tetrabromophthaloyl-aspartic

In this work, organic diacid was synthesized from tetrabromophthalic anhydrides and l-aspartic acid in refluxed acetic acid at the presence of pyridine. The interlayer basal spacing of LDH was modified with organic diacid via co-precipitation method using ultrasonic irradiation. The intercalated Mg–Al LDH (mLDH) materials showed an increase in interlayer distance as compared to the unmodified Mg–Al LDH by X-ray diffraction. Transmission electron microscopy images showed plate-like nature for intercalated diacid LDH. Poly(vinyl alcohol) (PVA)/mLDH nanocomposites (NCs) with different composition of mLDH were prepared through ultrasound-assisted technique in the deionized water by solution intercalation method. Field emission scanning electron microscopy image results show that mLDH was dispersed homogeneously in PVA matrix. Optical clarity of obtained NCs was investigated using UV–visible transmission spectra. Thermogravimetry showed improvement in thermal properties of PVA/mLDH NCs. Mechanical data showed improvement in the tensile strength and modulus with increasing of the mLDH loading.

Exploring the role of stearic acid in modified zinc aluminum layered double hydroxides and their acrylonitrile butadiene rubber nanocomposites

ABSTRACTThe proposed study attempted to explore the role of stearic acid modification on the properties of zinc‐aluminum based layered double hydroxides (LDH) and their composites with acrylonitrile butadiene rubber (NBR). Three distinctive LDH systems were adapted for such comparison; an unmodified LDH and two stearic acid modified LDH. The use of zinc oxide and stearic acid in the rubber formulation was avoided as the modified LDH would be able to deliver the necessary activators for the vulcanization process. Emphasis was predominantly given to reconnoiter the merits of stearic acid modification on the increase in interlayer distance of the LDH. X‐ray diffraction studies and transmission electron microscope morphological investigations of LDH powders indicated that modification with stearic acid increased the interlayer spacing which would favor the intercalation of NBR polymer chains into the layered space. However, stress–strain studies indicated better mechanical properties for composites with unmodified LDH. Composites with LDH showed higher crosslinking densities than conventionally sulfur cured control compounds using zinc oxide/stearic acid as activators. This was evident from equilibrium swelling method as well as statistical theory of rubber elasticity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41539.

Intercalation study of low-molecular-weight hyperbranched polyethyleneimine into graphite oxide.

We report for the first time the intercalation of low-molecular-weight hyperbranched polyethyleneimine (PEI) into graphite oxide (GO) for the facile, bulk synthesis of novel graphene-based hybrid (GO-PEI) materials exhibiting tailored interlayer galleries. The size of the intercalant as well as the loading in GO were systematically investigated to determine their contribution to the basal spacing of the resulting materials. Powder X-ray diffraction measurements demonstrated the generation of constrained hybrid systems along the c axis that exhibit considerably increased interlayer distances compared with the starting, pristine GO. The results of X-ray photoelectron and FTIR studies are consistent with a "grafting-to" process of the intercalated PEI with the oxygen functional groups present along the GO framework. Furthermore, it was found that a great number of the nitrogen-containing groups in PEI still remain available within the newly formed, confined micro-environment of intercalated GO galleries. The increased surface area of the GO-PEI hybrids in conjunction with the remaining available active groups of intercalated PEI render the synthesised hybrids very attractive candidates as nanostructured adsorbents.

Ultrasound-assisted one-pot preparation of organo-modified nano-sized layered double hydroxide and its nanocomposites with polyvinylpyrrolidone

In this contribution, polyvinylpyrrolidone (PVP) nanocomposites (NCs) with novel chiral diacid intercalated layered double hydroxides (LDHs) as nanofillers were prepared via ultrasonic irradiation. Chiral LDH was synthesized in one step via a co-precipitation reaction in aqueous solution under ultrasonic irradiation. The modified Mg-Al LDH shows an increase in interlayer distance as compared to the unmodified Mg-Al LDH by X-ray diffraction (XRD). Different NCs of organo-modified chiral LDHs and PVP were constructed by means of an ultrasonic process. The structures of these new materials were investigated by XRD, Fourier transform infrared, field emission scanning electron microscopy and transmission electron microscopy techniques. XRD and electron microscopy results confirmed the delaminated state of the LDH in the PVP matrix. Furthermore, thermal analysis was evaluated and the prepared NCs show significantly improved thermal stability at higher temperature because of the homogeneous and good dispersion of modified LDH in polymeric matrix.

Novel bionanocomposites of poly(vinyl alcohol) and modified chiral layered double hydroxides: Synthesis, properties and a morphological study

a b s t r a c t The effect of novel modified layered double hydroxides (LDHs) on thermal and structural properties of poly(vinyl alcohol) (PVA) was investigated. Organically modified chiral LDH was prepared via ion exchange reaction of LDH in a solution of N,N� -(pyromellitoyl)-bis-l-phenylalanine diacid in distilled water. The modified Mg-Al LDH materials showed an increase in interlayer distance as compared to the unmodified Mg-Al LDH by X-ray diffraction (XRD). Bionanocomposites of PVA with the modified chi- ral LDH were prepared with different compositions of LDH by solution-intercalation method using the ultrasound-assisted technique. The effect of LDH contents on thermal, physicomechanical, and morpho- logical properties of PVA films was investigated using XRD, Fourier transform infrared, thermogravimetric analysis (TGA), field emission scanning electron microscopy and transmission electron microscopy tech- niques. The TGA of the obtained bionanocomposites showed an increase in thermal stability. The uniform distribution of clay due to the intimate interaction between clay and polymer appeared to be the reason for the improved properties.

P-Xylylenediamine intercalation of graphene oxide for the production of stitched nanostructures with a tailored interlayer spacing

The p-xylylenediamine intercalation reaction of graphene oxide (GO) has been investigated as a convenient and simple approach to the preparation of pillared-type graphene-based materials with a tailored interlayer spacing. Powder X-ray diffraction studies in combination with thermo-gravimetric analyses and swelling tests have demonstrated the generation of a constrained system (covalently “stitched”) along the c-axis exhibiting a considerably increased interlayer distance compared to the starting, pristine GO. X-ray photoelectron spectroscopy measurements were consistent with a cross-linking process involving oxygen functional groups (basically epoxides) typically present at the GO basal plane. Finally, nitrogen adsorption–desorption isotherms (BET plots), transmission electron microscopy and scanning electron microscopy micrographs have been used to underline the increased specific surface area and porosity of the amine intercalated material, as well as to emphasize the morphological differences between the two samples (pristine GO and intercalated material). The production of tailored GO-based nanostructures with improved chemico-physical properties paves the way towards the multigram synthesis of porous carbon-based nanomaterials.

Synthesis and Properties of Oval-Shaped Iron Oxide/Ethylene Glycol Mesostructured Nanosheets

We have demonstrated a new and facile bottom-up protocol for the effective synthesis of oval-shaped iron oxide/ethylene glycol (FeOx /EG) mesostructured nanosheets. Deprotonated ethylene glycol molecules are intercalated into iron oxide layers to form an interlayer distance of 10.6 Å. These materials display some peculiar magnetic properties, such as the low Morin temperature T(M) and ferromagnetism below this T(M) value. CdSe/ZnS nanoparticles can be loaded onto these mesostructured nanosheets to produce nanocomposites that combine both magnetic and fluorescence functions. In addition, iron oxide/propanediol (or butanediol) mesostructured materials with increased interlayer distances can also be synthesized. The developed synthetic strategy may be extended toward the creation of other ultrathin mesostructured nanosheets.