Construction of Zn–Co–Ni–Se nanosheet arrays on nickel foam for hybrid supercapacitors

The polymetallic selenides exhibit rich redox reactions and high conductivity, making them promising electroactive materials for hybrid supercapacitors (HSCs). Herein, a two-step hydrothermal strategy was developed to grow ternary metal selenides (Zn–Co–Ni–Se) nanosheet arrays on Ni foam (NF) for HSCs. The Zn–Co–Ni–Se nanosheets uniformly covered on NF are favorable to boosting the energy storage activity because they can afford abundant pores, which is beneficial to increase the contact areas and promote ion transport. The binder-free feature can further improve the rate and cyclic performance. As an innovative binder-free electrode, the Zn–Co–Ni–Se NA@NF can deliver 2.5 C cm^–2 at 3.1 mA cm^–2. Strikingly, the Zn–Co–Ni–Se NA@NF//AC HSC can afford 0.13 mWh cm^–2 at 1.27 mW cm^–2. The capacity retention of Zn–Co–Ni–Se NA@NF//AC HSC is 92.9% after 5000 cycles at 6.4 mA cm^–2. A Zn–Co–Ni–Se NA@NF//AC HSC device could successfully drive a small fan for about 150 s, displaying the bright application prospect of Zn–Co–Ni–Se@NF. Therefore, the present work demonstrates that Zn–Co–Ni–Se NA@NF is an excellent electroactive material for HSCs.     

New composites of spherical bridged polysilsesquioxanes and aggregates of Pd nanoparticles with POSS via ionic interactions

Spherical bridged polysilsesquioxane (BPS) particles with sulfonic groups (BPS–SO₃ ^?) were prepared by the subsequent reduction and oxidation of BPS with disulfide groups (BPS–S–S) after the hydrolysis and condensation reaction of silane monomers with disulfide groups under ammonia and alcoholic solutions. Spherical aggregates of Pd nanoparticles (Pd–polyhedral oligomeric silsesquioxanes, Pd–POSS) were produced by the mixing of POSS and palladium (II) acetate in methanol solution. The average size of BPS–SO₃ ^? and Pd–POSS was about 200–400 and 30–50 nm, respectively. New BPS–SO₃ ^?/Pd–POSS composites with the shape of BPS–SO₃ ^? covered with Pd–POSS nanoparticles were fabricated by ionic interactions between negatively charged BPS–SO₃ ^? and positively charged Pd–POSS. Pd–POSS nanoparticles were more effectively attached to BPS–SO₃ ^? than BPS–S–S, which resulted from the difference of zeta potential between BPS–SO₃ ^? and BPS–S–S. That is, ionic interactions in BPS–SO₃ ^?/Pd–POSS composites were stronger than those in BPS–S–S/Pd–POSS composites. As the storage time was increased, the precipitation of BPS–SO₃ ^?/Pd–POSS composites in methanol solution resulted from the strong complex between BPS–SO₃ ^? and Pd–POSS unlike BPS–S–S/Pd–POSS composites. New particle composites were characterized by Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy.     

Influence of sintering atmosphere on the phase,microstructure, and lithium-ion conductivity of the Al-doped Li7La3Zr2O12 solid electrolyte

Al-doped Li₇La₃Zr₂O₁₂ (Al–LLZO) solid electrolytes were sintered at 1150 ^°C for 8 h in atmosphere of oxygen, argon and air (named as Al–LLZO–O₂, Al–LLZO–Ar and Al–LLZO–Air, respectively). All the Al–LLZO samples exhibited a single cubic garnet-type structure. The sample of Al–LLZO–O₂ possessed the highest relative density (95.60%) and the largest average grain size among the three Al–LLZO samples. Furthermore, owing to its high relative density and small number of grain boundaries, Al–LLZO–O₂ demonstrated a higher lithium-ion conductivity than Al–LLZO–Ar and Al–LLZO–Air.     

Phase relations of the MgO–SiO2–CrOx system at 1600°C in air and reducing atmospheres

The equilibrium phase relations of the MgO–SiO₂–CrO_x system were investigated at 1600°C in air and at pO₂ of 10^–10 to 10^–11 atm using a high-temperature isothermal equilibration technique followed by rapid quenching and direct phase composition analyses with electron probe X-ray microanalysis. Two-phase equilibria (liquid–cristobalite, liquid–spinel, liquid–corundum, and liquid–olivine) and three-phase equilibria (liquid–cristobalite–spinel, liquid–olivine–spinel, liquid–spinel–corundum, and cristobalite–spinel–corundum) were observed. The 1600°C isothermal sections at various oxygen partial pressures were constructed for the MgO–SiO₂–CrO_x system based on the experimentally determined liquid and solid compositions. Data from the literature and the predictions by FactSage and MTDATA software were compared with the present experimental results.     

Raman and X-ray photoelectron spectroscopy study on the influence of La2O3 on the melt structure of SiO2–CaO–Al2O3–MgO

In order to gain more insights into the influence of rare earth elements on the melt structure of SiO₂–CaO–Al₂O₃–MgO glass ceramics, Raman and X-ray photoelectron spectroscopy techniques were used to study the influence of La₂O₃ on the Si–O/Al–O tetrahedron structure within SiO₂–CaO–Al₂O₃–MgO–quenched glass samples in this study. Results showed that some Raman peak shapes at low frequencies (200–840 cm^?1) changed significantly after the addition of La₂O₃, compared to the high frequency (840–1200 cm^?1) region that corresponds to the [SiO₄] structure, suggesting that the depolymerization of the low-frequency T–O–T (T=Si or Al) structure was more prevalent with La³⁺ addition. Besides, the depolymerization extent of the Si–O/Al–O tetrahedral network varied when the melt composition altered. Most notably, depolymerization is the most significant at a low CaO/SiO₂ ratio (0.25) and a high Al₂O₃ content (8%). Meanwhile, La³⁺ can promote the transformation of Si–O–Si and Al–O–Al bonds to the Si–O–Al ones, thereby forming a complex ionic cluster network interwoven with Si–O and Al–O tetrahedrons.     

M1 to M2 Phase Transformation and Phase Cooperation in Bulk Mixed Metal Mo–V–M–O (M=Te, Nb) Catalysts for Selective Ammoxidation of Propane

In the present study we systematically explored hydrothermal synthesis of bulk mixed metal Mo–V–(Te–Nb)–O catalysts and investigated the bulk characteristics of the resulting M1 and M2 phases as well as their roles in the selective ammoxidation of propane. It was found that unlike Mo–V–Te–Nb–O M1 phases, the Mo–V–Te–O M1 phases may be quantitatively transformed into M2 phases of the same chemical composition indicating that Nb stabilizes the M1 structure. The stabilizing role of Nb and Te was further observed in high resolution TEM studies of Mo–V–(Te–Nb)–O catalysts which indicated that structural order and the M1 phase domain size progressively decreased in this order: Mo–V–Te–Nb–O > Mo–V–Te–O > Mo–V–O. The cooperation between the M1 and M2 phases in propane ammoxidation to acrylonitrile was observed only at low propane conversions suggesting that the M1 phase is the only crystalline phase required for the activity and selectivity of the Mo–V–Te–Nb–O catalysts in propane ammoxidation to acrylonitrile at practical propane conversions.     

New insight into design of highly ordered calcium silicate hydrate with graphene oxide

Calcium silicate hydrate (C–S–H) is the main hydration product of cement and the most important binder that plays a pivotal role in the mechanical properties of concrete. However, one of the major drawbacks of C–S–H is its high brittleness and low flexural strength due to its disordered structure at the nano- and micro-scales. Therefore, this study adopts graphene oxide (GO) to modify the structure of C–S–H, and investigates the effects of synthetic methods on the structure of C–S–H–GO composites. In this study, the highly ordered C–S–H–GO composite is successfully synthesized and exhibits itself the high toughness. Moreover, the formation mechanism of the highly ordered C–S–H–GO composite is explored and discussed, which provides a new insight into the design of high-toughness cement-based materials.     

Cyclopropenoids and Fatty Acid Composition of Five Varieties of Cotton Seed Oils

Five varieties of cotton seed oils from Jayadhar, Bhagya, Mysore Vijaya, Hampi and 170 CO₂ have been analysed for their fatty acid content and the results (Wt.%) are in the following range: Myristic 0.8–1.1; Palmitic 23.0–23.9; Stearic 2.7–4.2; Arachidic 0.3–0.7; Behenic 0.3–1.4; Oleic 11.9–22.8; Linoleic 47.5–58.1; and Cyclopropenoid acids 0.6–2.1. The oil content and iodine value from 20.2–22.5 percent and 104.3–115.3 respectively. Protein content ranges from 24.8–48.4 percent.     

Interface microstructure and mechanical properties of Ni–Co–P alloy coatings modified carbon fibres reinforced 7075Al matrix composites

To optimize interface microstructure between 7075Al matrix and CFs, Ni–Co–P multi-component alloy coatings coated carbon fibres were prepared by electroless plating firstly and then Ni–Co–P coated CFs reinforced 7075Al matrix composites (CF/Al(Ni–Co–P)) with high relative density were fabricated by hot pressing sintering process. After modification of Ni–Co–P coatings, Al–Co–Ni Intermetallic compounds were formed stably between matrix and reinforcement because of the smaller mixing enthalpy values of Al–Co, Al–Ni and Co–Ni, which not only restrained the generation of Al₄C₃ but also improved interfacial bonding strength. Yield strength and ultimate tensile strength of CF/Al(Ni–Co–P) composites with 30 vol% CFs had maximum improvement compared with CF/Al(U) composites than other composites reinforced by 10 vol%, 20 vol% and 30 vol%CFs, which is up to 305.8 MPa and 668.7 MPa respectively, and the fracture mode of composites from accumulation fracture to non-accumulation fracture as the existence of Ni–Co–P coatings.     

Effect of Ti–Si–Fe alloys on microstructure and properties of nitride/oxynitride bonded SiC ceramics sintered under CO/N2 atmosphere

Ti–Si–Fe alloys extracted from high-titanium blast furnace slag were utilized to replace part of the silicon powders, and then nitride/oxynitride bonded SiC ceramics were prepared by reactive sintering in graphite bed. Ti–Si–Fe alloys could react with CO/N₂ at a low temperature (1200 °C), and the addition of Ti–Si–Fe alloys could reduce the nitriding temperature of Si. Density functional theory calculations suggested that Ti–Si–Fe alloys enhanced reaction activity via weakening the strength of CO and NN bonds. The regional equilibrium phase diagrams of Si–C–N–O and Ti–Si–C–N–O under CO/N₂ atmosphere were calculated by thermodynamics. The change of whiskers morphology was observed by scanning electron microscope. Furthermore, the bulk density, the cold modulus of rupture, and the cold compressive strength improved with Ti–Si–Fe alloys content. The results showed that the addition of Ti–Si–Fe alloys not only significantly promoted nitriding of Si and formation of Si₃N₄ whiskers, but also improved the mechanical properties of the samples.     

Understanding the adsorption behavior of oxygen on the 3C–SiC(1 1 0) surface: A first-principles study

The adsorption behavior of atomic oxygen and molecular O₂ on the 3C–SiC(1 1 0) surface is investigated by first-principles calculations. The atomic O prefers to be adsorbed at the C top site (C–O) with adsorption energy of −1.95 eV after zero-point energy correction, followed by the C–O–Si bridge site, Si–O–Si bridge site, and the Si top site (Si–O) with adsorption energies of −1.46, −1.36, and −1.13 eV, respectively. The molecular O₂ separately trapped by the second nearest neighboring C and Si atoms (C–O–O–Si, M4 type) is the most stable configuration with the adsorption energy of −2.46 eV, which is followed by the Si–O–O–Si (M5 type), C–O–O–Si (M3 type), O–Si–O (M2 type), and Si–O=O (M1 type) configurations with the adsorption energies of −2.24, −1.87, −1.07, and −0.75 eV, respectively. All these molecular O₂ adsorption configurations exhibit high tendency to dissociate with the dissociation barriers range of 0.09–0.19 eV. The adsorbed atomic O seems to be easily trapped at the C–O site due to the extremely low diffusion barrier. In addition, the infrared spectra of all the atomic O and molecular O₂ adsorption configurations are predicted and compared with available experimental observations.     

Sol–gel synthesis and characterization of lithium aluminate (L–A–H) and lithium aluminosilicate (L–A–S–H) gels

Hydrous lithium aluminosilicate (L–A–S–H) and lithium aluminate (L–A–H) gels are candidate precursors for glass-ceramics and ceramics with potential advantages over conventional processing routes. However, their structure before calcination remained largely unknown, despite the importance of precursor structure on the properties of the resulting materials. In the present study, it is demonstrated that L–A–S–H and L–A–H gels with Li/Al ≤ 1 can be produced via an organic steric entrapment route, while higher Li/Al ratios lead to crystallization of gibbsite or nordstrandite. The composition and the structure of the gels was studied by thermogravimetric analysis, X-ray diffraction, ²⁷Al and ²⁹Si magic-angle spinning nuclear magnetic resonance, and Raman spectroscopy. Aluminium was found to be almost exclusively in six-fold coordination in both the L–A–H and the L–A–S–H gels. Silicon in the L–A–S–H gels was mainly in Q⁴ sites and to a lesser extent in Q³ sites (four-fold coordination with no Si–O–Al bonds). The results thus indicate that silica-rich and aluminium-rich domains formed in these gels.     

Study of curative interactions in cis-1,4-polyisoprene. XII. The cis-1,4-polyisoprene–sulfur–tetramethylthiuram disulphide–ZnO–stearic acid vulcanization system

Several aspects on the mechanism of vulcanization in the synthetic cis-1,4-polyisoprene (IR)-sulfur-tetramethylthiuram disulphide (TMTD)–ZnO system were harmonized. The differential scanning calorimetry (DSC) thermograms showed that the vulcanization processes became better resolved on increasing the curative loading in the compound. Two major crosslinking reactions occurred consecutively in the IR (100)–sulfur (9.46)–TMTD (8.86)–ZnO (3.00) mixture, viz the IR–sulfur–TMTD–ZnO and IR–sulfur–zinc dimethyldithiocarbamate (ZDMC) (or IR–sulfur–ZDMC–ZnO) reactions. In the first process poly-and disulfidic pendent groups RS_xSX (R = polyisoprenyl, X = Me₂NC (S), x ≥ 1) formed via the IR–XSS_xSX reaction, and in the second via the IR–XSS_xZnSSX reaction. Thermogravimetric analysis (TGA) and high-pressure liquid chromatography (HPLC) data showed that dimethyldithiocarbamic acid liberated during the IR–sulfur–TMTD–ZnO reaction was trapped by ZnO to yield ZDMC. Hence ZDMC was a product, and not precursor, of this crosslinking process. A comparison of reactions in IR–sulfur–TMTD–ZnO and poly(ethylene-co-propylene)–sulfur–TMTD–ZnO mixtures showed that the participation of IR molecules was essential for ZDMC formation. The ZDMC concentration remained constant at ～ 38.4 mol % during the later stages of cure, showing that it did not participate in the desulfuration reactions of polysulfidic links. In the presence of stearic acid the stearic acid–ZnO reaction occurred at 87°C as was manifested by an intense crystallization peak of zinc stearate. The vulcanization processes were the same both in the presence and absence of stearic acid.     

Modification of styrene–divinylbenzene copolymer by anchoring ferric–dipyridylamine complex

Polystyrene–divinylbenzene (PS–DVB) copolymer was modified by anchoring dipyridylamine (DPA) on it followed by complexation with Fe(III). Under the experimental conditions followed, 9% incorporation of Fe(III) was achieved. PS–DVB–DPA and PS–DVB–DPA–Fe(III) were characterized by IR spectra. Diffuse reflectance spectra for PS–DVB–DPA–Fe(III) and DPA–Fe(III) revealed λ_max at ～ 360 and ～ 310, respectively. This difference could be due to a difference in the nature of the coordinating moieties complexing with Fe(III) in these two systems. Scanning electron micrographs of PS–DVB, PS–DVB–DPA–Fe(III), and heat-treated PS–DVB–DPA–Fe(III) revealed some typical surface features. Thermal stability varied in the order PS–DVB–DPA–Fe(III) > PS–DVB–DPA ?PS–DVB, and DTA showed characteristic exotherms. © 1992 John Wiley & Sons, Inc.     

Syntheses and characterization of a chelating resin containing ONNO donor quadridentate Schiff base and its coordination complexes with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), molybdenum(VI) and uranium(VI),

A new mixed Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine) has been synthesized by the condensation of equimolar quantities of ethylenediamine, salicylaldehyde and 3-formylsalicylic acid. A polymer supported Schiff base (PS–CH₂–LH₂) has been synthesized by the reaction of chloromethylated polystyrene (containing 3.9 mmol of chlorine per g of resin and 2% cross-linked with divinylbenzene) and the Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine). The polymer-anchored Schiff base reacts with metal salt/metal complex and forms polymer-anchored complexes having the formulae PS–CH₂–LCu, PS–CH₂–LNi, PS–CH₂–LCo, PS–CH₂–LFeCl·DMF, PS–CH₂–LZn, PS–CH₂–LCd, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂. The polymer-anchored complexes have been characterized on the basis of elemental analysis, infrared and electronic spectra and magnetic susceptibility measurements. The shifts of the ν(CN) (azomethine) stretch to lower energy and ν(CO) (carboxylic) to higher energy in the polymer-anchored complexes indicate the ONNO donor behaviour of the chelating resin. The metal ions in the metal bound polymers can be leached by hot dilute formic acid, acetic acid or hydrochloric acid. The coordinated dimethylformamide is completely lost on heating the complexes in air. The complexes PS–CH₂–LCu and PS–CH₂–LCo are paramagnetic with square planar structure, PS–CH₂–LNi is diamagnetic with square planar structure and PS–CH₂–LFeCl·DMF is paramagnetic and octahedral, PS–CH₂–LZn and PS–CH₂–LCd are diamagnetic and tetrahedral, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂ are diamagnetic and have octahedral structure. The stoichiometry and the structure of the metal bound polymers are comparable with those of metal complexes of N,N′-ethylenebis(salicylideneimine). This is the first report of the syntheses of a mixed Schiff base and its coordination complexes.     

Effects of sintering method and BiFeO3 dopant on the dielectric and ferroelectric properties of BaTiO3–BiYbO3 based solid solution ceramics

(0.95–x) BaTiO₃–0.05 BiYbO₃–x BiFeO₃ (x?=?0, 0.01, 0.02, and 0.04) (abbreviated as (0.95–x) BT–0.05 BY–x BFO) ceramics were fabricated by conventional sintering (CS) and microwave sintering (WS) methods. Effects of sintering method and BFO dopant on the microstructure and electric properties of (0.95–x) BT–0.05 BY–x BFO ceramics were comparatively investigated. X-ray diffraction showed that all CS and WS samples presented a single perovskite phase. It was also found that WS ceramics possessed denser microstructure and finer grains compared to CS samples as indicated by the surface morphology characterization. Dielectric measurements revealed that all samples exhibited the weak relaxation behavior; however, the degree of relaxation behavior of BT–BY based ceramic could be strengthened by addition of BFO and by WS method. Moreover, the temperature and frequency stability could be improved with doped BFO. The density of 0.93BT–0.05BY–0.02BFO ceramic was found to be the largest while that of 0.94BT–0.05BY–0.01BFO ceramic was the smallest, thus, the dielectric constant of 0.93BT–0.05BY–0.02BFO was significantly larger than that of 0.94BT–0.05BY–0.01BFO and 0.94BT–0.05BY–0.04 BFO ceramics. minimum dielectric constant of (0.95–x) BT–0.05 BY–x BFO ceramic was obtained at x?=?0.01. Ferroelectric measurements indicated that all samples showed the slim hysteresis loop. The remnant polarization (P_r) and coercive field (E_C) of (0.95–x) BT–0.05 BY–x BFO ceramics first decreased and then increased with increasing x，the minimum values were obtained at x?=?0.01. Moreover, P_r and E_C of WS ceramics were slightly larger than those of CS ceramics, indicating that higher density and larger grain sizes contributed to enhancing the ferroelectric characteristic. These findings indicate that addition of moderate amount of BFO and use of WS technique can strengthen the degree of relaxation behavior and improve the ferroelectric properties of BT–BY based ceramics.     

Attachment of ZnO nanoparticles onto layered double hydroxides microspheres for high performance photocatalysis

In this study, ZnO nanoparticles were successfully deposited on the surface of ZnMgAl–CO₃–LDHs microspheres to form ZnO/ZnMgAl–CO₃–LDHs heterojunction photocatalysts by coprecipitation process. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The results show that ZnO nanoparticles with diameters about 10–80 nm are tightly grown on the nanosheets of the ZnMgAl–CO₃–LDHs microspheres. Compared with the pristine ZnMgAl–CO₃–LDHs microspheres and pure ZnO, the photocatalytic activity of the heterojunction ZnO/ZnMgAl–CO₃–LDHs photocatalyst is significantly enhanced towards the degradation of phenol under UV light irradiation. The enhancement of the photocatalytic activity of the heterojunction catalysts can be ascribed to their improved light absorption property and the lower recombination rate of the photoexcited electrons and holes during the photocatalytic reaction. The optimal molar ratio of ZnO/ZnMgAl–CO₃–LDHs for the photocatalysis is 3. The heterojunction photocatalyst ZnO/ZnMgAl–CO₃–LDHs may be a promising photocatalyst for future application in water treatment due to its excellent performance in degradation of phenol.     

Effects of Mo addition on tribological performance of plasma-sprayed Ti–Si–C coatings

Ti–Si–C–Mo composite coatings were fabricated by plasma spraying using Ti, Si, graphite and Mo powders. The effect of Mo on microstructure and tribological performance of the Ti–Si–C coatings were investigated. The results showed that the Ti–Si–C coating consisted of TiC, Ti₃SiC₂, Ti₅Si₃, and residual graphite. The Ti–Si–C–Mo coatings consisted of TiC, Ti₃SiC₂, Ti₅Si₃, residual graphite, Mo and Mo₅Si₃ phases. With increasing Mo contents, the fractions of Mo and Mo₅Si₃ phases increased, and the fractions of Ti₃SiC₂ and Ti₅Si₃ phases decreased. All the coatings existed a typical lamellar structure. The addition of Mo enhanced the hardness and fracture toughness of Ti–Si–C coating by 16% and 52%, respectively. The coating porosity decreased by 57.6%. The wear resistance of the Ti–Si–C coating was also improved and the mass loss decreased by 83%. The wear mechanism of the Ti–Si–C–Mo coatings was the combination of abrasive wear, adhesive wear, and tribo-oxidation wear.     

Microstructure and properties of niobium carbide composite coatings prepared by plasma spraying

Niobium carbide composite coatings were prepared on titanium alloy surface by plasma spraying NbC–Al₂O₃, Nb–SiC and Nb–SiC–Al composite powders, respectively. The phase composition, microstructure and formation mechanism of the three composite coatings were analyzed and their microhardness, toughness and scratch resistance were compared. The phases of the NbC–Al₂O₃ system did not change during the plasma spraying process, and new phases (Nb₂C, NbC and Nb₃Si) were formed in the Nb–SiC and Nb–SiC–Al systems. TEM results of the Nb–SiC composite coating indicate that the new phases nanocrystalline Nb₂C, submicron NbC and nanocrystalline Nb₃Si were formed during the plasma spraying process. Compared with the NbC–Al₂O₃ composite coating, the microstructure of the Nb–SiC and the Nb–SiC–Al composite coatings were uniform, and the porosity were relatively low, and the hardness was higher. The Nb–SiC–Al composite coating was denser than the Nb–SiC composite coating, the lamellar structure was obvious and the number of pores in the coating was the least, which is attributed to the better molten state of the composite powder by the addition of the Al to the Nb–SiC system. The Nb–SiC–Al composite coating had better toughness and scratch resistance.     

A molecular dynamics study of N–A–S–H gel with various Si/Al ratios

In this paper, the atomic structures of sodium aluminosilicate hydrate (N–A–S–H) gels with different Si/Al ratios are studied by molecular dynamics simulation. An N–A–S–H gel model was obtained from the polymerization of Si(OH)₄ and Al(OH)₃ monomers with the use of a reactive force field (ReaxFF). The simulated atomic structural features, such as the bond length, bond angle, and simulated X-ray diffraction pattern of the gel structure are in good accordance with the experimental results in the literature. Si–O–Al is found to be preferred over Si–O–Si in the N–A–S–H gel structure according to the amount of T–O–T bond angles and distribution of Si⁴(mAl). Pentacoordinate Al is identified in all simulated N–A–S–H models. It provides strong support to current knowledge that pentacoordinate Al in geopolymer does not only come from raw material. Furthermore, the structural analysis results also show that N–A–S–H gel with lower Si/Al ratios has a more cross-linked and compacted structure.