Search

Quasi-two-dimensional (quasi-2D) perovskites are emerging as promising materials for highly stable light-emitting diodes (LEDs). However, their lower charge transport mobilities and higher defect densities may constrain their light-emitting efficiency. Here, we combine an excessive-salt-assisted (ESA) process with antisolvent treatments to inhibit the defects in Dion-Jacobson-type perovskite LEDs. Such a method could improve the film quality and recombination efficiency. By further investigation, we found that artificially building a bulk junction interface and enhancing surface polarization could play a more important role in promoting the ability of charge carrier injection and recombination for high-performance LED devices. Accordingly, the DJ-type quasi-2D perovskite LED can achieve a high external quantum efficiency (EQE) of 7.1%.

We report a transition metal such as manganese doped methylammonium lead halide perovskite (MA(Pb:Mn)I3) solar cell with an power conversion efficiency (PCE) over 20%. The rational design and fabrication of MA(Pb:Mn)I3 lead to the enhancements of all the photovoltaic parameters. To incorporate Mn can effectively eliminate the trap-assist and bi-molecular recombination. The photo-absorption ability at shorter wavelengths (i.e., less than 500 nm) and charge carrier lifetime can be elaborated. More importantly, the existence of the Mn2+-I−-Mn3+ motif contributes for the double exchange effect, giving rise to the charge/spin transport. By a combination of linearly and circularly polarized photo-excitations, we have explicitly determined the role of intrinsic spin–orbit coupling (SOC) in MA(Pb:Mn)I3. More dark states are expected to be available for the photocurrent generation. This study may pave the way for deep understandings of transition metals doped hybrid perovskites for highly efficient solar cell applications.

It is essential to release annealing induced strain during the crystallization process to realize efficient and stable perovskite solar cells (PSCs), which does not seem achievable using the conventional annealing process. Here we report a novel and facile thermal gradient assisted crystallization strategy by simply introducing a slant angle between the preheated hot plate and the substrate. A distinct crystallization sequence resulted along the in-plane direction pointing from the hot side to the cool side, which effectively reduced the crystallization rate, controlled the perovskite grain growth, and released the in-plane tensile strain. Moreover, this strategy enabled uniform strain distribution in the vertical direction and assisted in reducing the defects and aligning the energy bands. The corresponding device demonstrated champion power conversion efficiencies (PCEs) of 23.70% and 21.04% on the rigid and flexible substrates, respectively. These highly stable rigid devices retained 97% of the initial PCE after 1097 h of storage and more than 80% of the initial PCE after 1000 h of continuous operation at the maximum power point. This novel strategy opens a simple and effective avenue to improve the quality of perovskite films and photovoltaic devices via strain modulation and defect passivation.

The organic modification of three-dimensional porous diatom frustules (biosilica) and their fossils (diatomite) is promising in heavy metal adsorption. However, the preparation of such materials involves complex processes, high costs, and environmental hazards. In this study, organic-biosilica composites based on in situ self-modification of diatoms were prepared by freeze-drying pretreatment. Freeze-drying resulted in the release of the intercellular organic components of diatoms, followed by loading on the surface of their diatom frustules. The bio-adsorbent exhibits outstanding Cd

Quasi-2D Ruddlesden–Popper (RP) perovskite films have been widely used in fabricating high-performance perovskite light-emitting diodes (PeLEDs) and solar cells because of their environmental stabi...

Realization of remote wearable health monitoring (RWHM) technology for the flexible photodiodes is highly desirable in remote-sensing healthcare systems used in space stations, oceans, and forecasting warning, which demands high external quantum efficiency (EQE) and detectivity in NIR region. Traditional inorganic photodetectors (PDs) are mechanically rigid and expensive while the widely reported solution-processed mixed tin-lead (MSP) perovskite photodetectors (PPDs) exhibit a trade-off between EQE and detectivity in the NIR region. Herein, a novel functional passivating antioxidant (FPA) strategy has been introduced for the first time to simultaneously improve crystallization, restrain Sn

Calcium carbide residue (CCR) is a solid waste resulting from acetylene gas production. In this study, CCR was used as an alkali activator to prepare fly ash (FA)-based geopolymers without any alkali supplementation. We studied the factors (FA/CCR ratio, curing temperature, and water/binder ratio) influencing the mechanical property of FA/CCR-based geopolymers. The compressive strength results showed that, by optimizing these three factors, the FA/CCR mixture has great potential for use as a cementitious material and geopolymer with a dense microstructure having a maximal compressive strength of 17.5 MPa. The geopolymers’ chemical structure, microstructure, and chemical composition were characterized and determined by a combination of techniques. All these results revealed that amorphous C-(A)-S-H (calcium (aluminate) silicate hydrate) gels mainly formed after geopolymerization resulting from the reaction of FA and CCR. In addition, some crystallines, such as ettringite and monosulfate, were also formed. Further, geopolymers prepared with a suitable FA/CCR ratio (1:1 or 1:2) possessed a compact microstructure because of their sufficient reactive SiO2 and Al2O3 and high-enough alkalinity, responsible for higher content of C-(A)-S-H formation and better mechanical property. Too high curing temperature or water content induced the formation of a loosely bound geopolymer matrix that strongly weakens its mechanical property.

The Cyber-Physical System (CPS), which combines computing units and physical entities, is an extremely complex distributed real-time cyber-physical system. Aiming at the problems and challenges faced by its system modeling, this paper will focus on analyzing the time-space characteristic model of CPS, and propose to analyze and study CPS from the perspective of time and space. The physical entities in the model are abstracted into objects, then the objects in the model and their running processes are analyzed from the two dimensions of the attributes and operations of the objects. Combine CPS, Petri nets, spatiotemporal characteristics and object-oriented to form a new modeling idea-object-oriented spatiotemporal Petri nets (OOSPN). V2V technology vehicle dynamic analysis and optimization cases will be used to verify the effectiveness of the object-oriented spatiotemporal Petri net model. And draw the object model diagram of the Petri net of the case, which provides new ideas for the development of time-space characteristics analysis.

In this work, Al2O3–MnO2@diatomite composite (AM-Dt) was prepared by a simple hydrothermal method. This composite was formed by using diatomite as a porous substrate to support Al2O3 and MnO2 nanop...

The occurrence of minor elements in the structure of biogenic diatomaceous opal-A is an important issue because it is closely related to biogeochemical processes driven by the precipitation, sedimentation, and storage of diatoms, as well as to the properties and applications of diatomite, which is the sedimentary rock composed of diatomaceous opal-A. However, to date, there is no direct microscopic evidence for the existence of minor elements, such as Al, Fe, and Mg, in the structure of diatomaceous opal-A, because such evidence requires observation of the internal structure of frustules to exclude the disturbance of impurity minerals, which is technically challenging using conventional techniques. In this work, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) mapping analysis were performed on diatomaceous opal-A from three typical diatomite specimens that were pretreated using focused ion beam (FIB) thinning. This technique produces a slice of a diatom frustule for direct TEM observation of the internal structure of the diatomaceous opal-A. The results of this work clearly indicate that minor elements, such as Al, Fe, Ca, and Mg, conclusively exist within the siliceous framework of diatomaceous opal-A. The contents of these minor elements are at atomic ratio levels of 1 (minor element)/10 000 (Si) – 1/100, regardless of the genus of the diatoms. The occurrence of minor elements in the internal structure is likely through biological uptake during biosynthesis by living diatoms. Moreover, surface coatings composed of aluminosilicates on diatom frustules are common, and the contents of elements such as Al and Fe are tens or hundreds of times higher in the coatings than in the internal siliceous structure of diatomaceous opal-A. The discovery of the incorporation of the above-mentioned minor elements in the diatomaceous opal-A structure, both in the internal Si-O framework and on the surface, updates the knowledge about the properties of diatomite.

Allophane/diatomite (Allo/Dt) nanocomposite with a hierarchically porous structure was prepared via an in situ hydrothermal method. This hierarchically porous structure consists of i) micropores remaining from the initial stacked coating allophane particles; ii) mesopores formed by the transformation of the macropores of diatom frustules due to the filling of allophane particles in the inner walls, and iii) preserved macropores of diatom frustules. The coating amount of allophane particles in Allo/Dt nanocomposite was 59.1%, leading to a specific surface area of 155.9 m2/g, which was substantially higher than that of diatomite (17.9 m2/g). The benzene adsorption performance and related adsorption mechanisms of Allo/Dt nanocomposite were investigated. The larger benzene dynamic adsorption capacity of 121.6 mg/g, compared to that of the synthetic allophane (105.9 mg/g), resulted from the adequate adsorption space provided by the hierarchically porous structure. Moreover, Allo/Dt nanocomposite displayed a higher efficiency for benzene adsorption in mesopores of the coating allophane particles because of their improved dispersity. These results demonstrated that the fabrication process of Allo/Dt nanocomposite can overcome not only the aggregation of allophane but also diatomite's shortcoming of low specific surface area, making the nanocomposite to be a promising adsorbent for the treatment of volatile organic compounds.

Organic-inorganic hybrid perovskites have attracted great attentions for photovoltaic applications due to impressive energy conversion efficiency and low cost fabrication. This article reports the effect of photogenerated dipoles in the electron transport layer (ETL) on the photovoltaic actions in perovskite solar cells (PSCs). A nonfullerene material ITIC with optically induced dipoles was doped into PCBM acting as ETL in inverted planar structure PSCs (ITO/PEDOT:PSS/MAPbI3-xClx/ETL/PEI/Ag). The power conversion efficiency (PCE) of PSCs increases from 13.48% to 14.52% with introducing ITIC into ETL. The capacitance measurements indicate that optically induced dipoles can decrease interfacial charge accumulation. Furthermore, impedance spectroscopy suggests the charge recombination as well as ionic migration are reduced with ITIC doped ETL. Steady and transient PL spectra reveal that the electron extraction is more efficient with optically induced dipoles in the ETL. These results provide unique design of ETL in perovskite solar cells.

This work investigated changes in the chemical composition, structure and porosity of hollow spherical allophane under alkaline conditions, which are significant not only for understanding its fate in natural environment but also for its functional applications. Hollow spherical allophane with a silicon/aluminium (Si/Al) molar ratio of 0.77 was hydrothermally synthesised followed by treatment with dilute sodium hydroxide (NaOH) solutions with different concentrations (indicated by pH values). The allophane and its alkali-treated products were then characterized using a combination of techniques, such as Fourier-transform infrared spectroscopy, nuclear magnetic resonance and nitrogen physisorption analysis. Allophane showed a weak structural stability in alkaline conditions. At pH ≤ 11.0, the framework of allophane particles was almost intact; its polymerised silicates showed only slight dissolution. At a higher pH (> 11.0), desilication and dealumination enhanced, resulting in the destruction of the imogolite local structure (ImoLS) along the edges of defect pores and the formation of amorphous materials. Most of the defect pores increased in size, becoming accessible to nitrogen and the textural parameters of the micropores reached their maximum values at a pH of 12.5. However, the damage to some secondary pores and the collapse of some hollow spherules reduced total pore volume (Vtotal). At a pH of 13.0, most of the hollow spherules were observed to have collapsed, resulting in remarkable decrease in the textural parameters. However, some unbroken and/or mildly broken allophane particles might remain, deduced from the relatively high BET specific surface area (SSA) and Vtotal and the considerable proportion of micropores for Allo13.0. These results reveal the dissolution behaviour of allophane in alkaline conditions and the mechanism underlying this behaviour, providing essential insights into the mineral's potential applications.

As a new kind of highly efficient luminescent materials, quasi-two-dimensional (quasi-2D) perovskites show great potential in industrial display applications. In this work, the poling methods are used in modulating the phase arrangement in quasi-2D perovskite light-emitting diodes (PeLEDs). We find the effective modulation of different phase components in uniform arrangement can enhance both brightness and current efficiency to 30 810 cd/m

These days, organic-inorganic hybrid perovskites (OIHP) and non-fullerene acceptor (NFA) molecules are all at the frontiers of research and development in the domain of photovoltaics. A careful design and use of inorganic transparent metal oxides with wide band gaps as electron and hole transport layers are critically important for highly efficient and stable solar cells. As one of the most favorable electron transport materials, tin oxide (SnO

Recent studies have shown that introductions of some organic additives are beneficial for optimizing organic–inorganic hybrid perovskite (OIHP) optoelectronic properties to promote their industrial...

Recent studies have shown that organic-inorganic hybrid perovskites (OIHPs) exhibit unprecedented optoelectronic properties for photovoltaic applications. Complete realizations of photo- and electrically induced surface polarization and recombination are critically important for extensively upgrading solar cell performance. We have explored such effects in a planar solar cell comprising ITO(glass)/PEDOT:PSS/CH3NH3PbI3-xClx/PC60BM/PEI/Ag with a maximum power conversion efficiency (PCE) of 15.4%. A remarkable frequency-dependence of surface polarization was observed for the operating device under illumination (i.e. short-circuit current J s c condition) and at steady state (i.e. open-circuit voltage V o c condition). A sign reversal of the capacitance (i.e. negative capacitance) associated with the surface polarization and recombination was detected at some specific steady states. Based on capacitance-voltage (C-V) spectroscopic measurements and theoretical fittings, they can be understood that, (i) a naturally formed surface depletion region due to energy mismatch can be fully suppressed at a very low fluence and moderate forward bias voltage; (ii) a surface capacitance ( C s ) appears at lower ac-modulation frequencies only; (iii) remarkable trap-assist and band to band surface recombination may play the dominant roles for generating the negative capacitive effect in the CH3NH3PbI3-xClx based photovoltaic system.

Despite the focus of many studies on the preparation, characterization, and potential applications of solvent-free nanofluids based on diverse nanomaterials, fewer studies have focused on how to control the macroscopic liquid-like behaviour of solvent-free nanofluids. The present study prepared a halloysite-based solvent-free nanofluid and developed a facile method of tuning the fluidity of this nanofluid by preheating halloysite (Hal) at different temperatures. The effects of preheating on the structure and surface functional groups of halloysite and further on the fluidity of the obtained nanofluids were explored. Heating Hal at 110 °C resulted in little changes to its surface functional moieties, and the obtained nanofluid (Hal110-F) did not exhibit a markedly different fluidity compared with Hal-F at room temperature, though Hal-F and Hal110-F had different melting temperatures and exhibited different fluidities at a lower temperature. While for Hal heated at 700 °C, the corresponding nanofluid (Hal700-F) exhibited a lower fluidity than Hal-F and Hal110-F due to the remarkable calcination-induced changes in the species/amount of surface functional moieties of Hal700. This method for controlling the fluidity of the nanofluids via a facile core pretreatment was believed to be versatile for most, if not all, solvent-free nanofluids.

The quantification of clay minerals is essential for the evaluation of clay-rich rock and soil, but it remains challenging due to the unique structures and various element compositions of clay minerals. In this article, several quantification methods for clay minerals sourced from X-ray diffraction (XRD) analysis, mainly recommending the reference intensity ratio (RIR), mineral intensity factor (MIF), Rietveld, and full pattern summation methods are reviewed. Principles and applications of these methods are focused upon in addition to related differences in the analysis of clay minerals (i.e., sample preparation, the selection of characteristic reflections for quantification and standards added during analysis). This critical review also provides a proposal for selection of an adaptive XRD quantification method to be applied to various clay-rich samples.

To date, the functional application of the flexible organic single-crystal devices in strain sensors has not been studied. In this letter, the excellent flexibility of the beltlike rubrene single crystals enables the rubrene single-crystal field-effect transistors to be bent inward and outward, and their electrical properties under compressive and tensile strain are demonstrated. The current and mobility of the device show the nearly linear changes under the tensile and compressive strain of

Commercial adsorbents were tested for removing the dibenzothiophene sulfone (DBTO) from a model diesel fuel and organosulfur oxidized products (sulfones) from a real diesel fuel under ambient conditions. Activated carbons treated by concentrated H2SO4 at high temperature showed increasing adsorption capacity and affinity towards DBTO. On the basis of adsorption tests and the characterization by BET, base titration, SEM, XPS, Visible-Raman and FTIR, the acidic-oxygenated groups incorporated to the surface act as adsorption sites for selective adsorption of sulfone. The specific interaction may be formed through the acid-base interaction involving the SO group. Activated carbon treated by steam at 900 °C and followed by concentrated H2SO4 at 250 °C displayed significantly enhanced DBTO adsorption performance and a sulfur capacity of 5.8 mg S/g adsorbent for removing organosulfur compound from a real diesel to less than 10 ppmw.

Montmorillonite (Mt), kaolinite (Kaol) and halloysite (Hal) are commonly investigated porous clay minerals, but their performance for the adsorption of volatile organic compounds (VOC) was rarely studied. In this work, the dynamic adsorption of benzene, as a model VOC, on Mt, Kaol and Hal was investigated. The effect of the microstructures of the above-mentioned clay minerals on benzene adsorption were explored by comparing the benzene adsorption of the different derivates of these clay minerals, which were obtained by adjusting the interlayer space and the porosity of the clay minerals through heating treatment. Calcium-based montmorillonite (Ca2 +-Mt) heated at 120 °C exhibited higher benzene adsorption capacity (141.2 mg/g) than sodium-based montmorillonite (Na+-Mt) heated at 120 °C (87.1 mg/g), because the interlayer distance of Ca2 +-Mt was sufficiently large to accommodate the adsorption of benzene. However, for calcined Ca2 +-Mt and Na+-Mt, the collapse of their interlayer space resulted in that the interlayer micropores no longer existed and reduced benzene adsorption. Kaol exhibited the lowest benzene adsorption capacity (56.7 mg/g) among the studied clay minerals because its interlayer space was not available for adsorption and because its specific surface area (SSA) was relatively small. As a polymorph of Kaol but with a tubular morphology, Hal showed a higher benzene adsorption capacity than Kaol owing to its larger SSA. In particular, heating at 120 °C resulted in the increase of the benzene adsorption of Hal, which was ascribed to the exposure of the adsorption sites initially occupied by water molecules. These results demonstrate that the benzene adsorption capacity of the above-mentioned clay minerals was not only highly related to their SSA but also strongly affected by their porosity features.

Activated carbons chemically treated by steam and concentrated H2SO4, were used as adsorbents for removing organic sulfur compounds from a model diesel. The modified activated carbon was characterized by N2 sorption, base titration and FTIR spectroscopy. As compared with the untreated activated carbon, the treatment by a steam at 900 °C increased the mesoporous volumes from 0.248 to 0.856 cm3/g and sulfur adsorption capacity for dibenzothiophene from 10.9 to 20.6 mg/g and the treatment by a concentrated H2SO4 at 250 °C increased the amount of surface acidic-oxygenated groups from 0.05 to 1.95 mmol/g, and total adsorption capacity for dibenzothiophene from 10.9 to 33.3 mg/g. The total adsorption capacity for dibenzothiophene is found to be proportional to the mesoporous volume and the amount of surface oxygen-containing groups. It is proposed that direct interaction between the sulfur atom and surface oxygen-containing groups plays an important role in the adsorption of organic sulfur compound.

The dehydration of fructose in aqueous and biphasic system was studied using heteropolyacids, immobilized in silica, as catalyst. The catalysts were characterized by ICP-AES, nitrogen sorption, NH3-TPD, TEM, FT-IR, XRD, and TGA. The effect of different parameters, such as reaction temperature, reaction time, catalyst loading and volume ratio of water with methyl isobutyl ketone (MIBK) was studied. Silica included tungstosilisic acid (HSiW) was found to function as an efficient catalyst for the transformation of fructose into 5-hydroxymethylfurfural in aqueous phase. Addition of MIBK into the reaction system can increase both of fructose conversion and HMF selectivity. Besides, MIBK showed a positive effect in increasing the stability of the catalyst by suppressing the formation and deposition of humins over catalyst surface. After the third catalysis cycles, a stabilization of the catalytic activity was observed.

Diatoms play an important role in marine biogeochemical cycle of aluminum (Al), as dissolved Al is taken up by diatoms to build their siliceous frustules and is involved in the sedimentation of diatomaceous biogenic silica (BSi). The Al incorporation in BSi facilitates decreasing the dissolution of marine BSi and thus substantially influences the biochemical processes driven by diatoms, such as CO2 sequestration. However, the role of lake BSi in the terrestrial biochemical Al cycle has not been explored, though lakes represent the second-largest sink for BSi. By identifying the previously unexplored high Al/Si atomic ratios (up to 0.052) in lake BSi, here we show lake BSi is a large terrestrial Al pool due to its high Al content, and lake sedimentary BSi constitutes a significant global sink for Al, which is on the same magnitude as the Al sink in global oceans., Diatoms drive biogeochemical cycling of aluminum by incorporating this element into their shells, but this process has not been quantified in freshwater systems. Here the authors quantify diatom-mediated aluminum fluxes in lakes and determine that they rival the aluminum sink in the global ocean.

Silico-aluminophosphate (SAP) geopolymers were synthesized by using metakaolin (MK) and a high content of fly ash (FA) for the first time. With the increase in the FA mass fraction in the raw materials from 50% to 100%, the setting time of the SAP geopolymers was shortened and their compressive strength was decreased. The effects of the FA content on the SAP geopolymers composition and microstructure were investigated. The results showed that a high FA proportion caused the lack of active aluminum, which led to excess phosphate acid reacting with the calcium from FA. The fast formation of amorphous calcium phosphate (ACP) shortened the initial setting time through the consumption of water. However, after long-term aging, ACP transformed into needle- and slice-like nanoparticles, which decreased the compressive strength of the resulting geopolymers. Moreover, MK supplied active aluminum to increase the water-containing -Si-O-Al-O-P- network (SAP gel). The SAP gel contributed to the compressive strength enhancement and prevented the ACP transformation; however, it prolonged the final setting time, due to the slow polycondensation of SAP gel. These results indicate that a desirable setting time and compressive strength of the SAP geopolymers can be achieved by adjusting the FA and MK contents.

This study focuses on using fly ash to prepare phosphoric acid-activated metakaolin geopolymer, in which the replacement of metakaolin by a high percentage (up to 30%) of fly ash was achieved. The effects of the addition of fly ash on the compressive strength of the resulting geopolymer were tested and statistically analyzed, and the related mechanism was explored through using X-ray diffraction, field emission scanning electron microscope, Fourier-transform infrared, and magic angle spinning nuclear magnetic resonance analysis. The results indicated that the compressive strength of geopolymer maintained at a high level even as a high percentage of fly ash was used to replace metakaolin. The key reason is that fly ash cenospheres effectively optimized the acid-activated geopolymerization of metakaolin. On one hand, cenospheres prevented the plate-like metakaolin particles from being bonded by the aluminum phosphate rapidly generating on the particle surface, which promoted the geopolymerization degree of metakaolin. On the other hand, the three-dimensional network of Si–O–Al–O–P became stronger with the increase of the crosslinking degree of Si, Al, and P under the influence of fly ash cenospheres. These findings demonstrate the feasibility of using fly ash as raw materials for the preparation of high strength phosphoric acid-activated geopolymer, which shows potential for the proper disposal and effective recycling of fly ash.

As a natural clay mineral, halloysite possesses a distinctive nanotubular structure and surface reactivity. Effects of curing temperatures and curing environments on the microstructure and the development of compressive strength of alkali-activated halloysite-based geopolymers were investigated in this study. Fourier-transform infrared spectroscopy, X-ray diffraction, and nuclear magnetic resonance were used to characterize the chemical structure of obtained geopolymer products, while N2 physisorption and scanning electron microscopy were used to characterize the microstructure of obtained geopolymers. Halloysite-based geopolymers cured at ambient temperatures had a compacted and homogeneous microstructure, and thus exhibited high compressive strength. However, elevating the curing temperature produced geopolymers containing more unreacted halloysite and larger pores, due to more rapid polymerization, water evaporation, and zeolite formation, which decreased the compressive strength of the final product. In addition, curing at certain temperatures (60–80 °C) in a moist environment favored the early compressive strength of halloysite-based geopolymers. The results showed that owing to the high geopolymerization reactivity of halloysite, alkali-activated halloysite-based geopolymers are sensitive to the curing conditions, and that curing at ambient temperature in a moist environment was beneficial to the development of geopolymeric compressive strength.

This paper is concerned with propagation phenomena for an epidemic model describing the circulation of a disease within two populations or two subgroups in periodic media, where the susceptible individuals are assumed to be motionless. The spatial dynamics for the cooperative system obtained by a classical transformation are investigated, including spatially periodic steady state, spreading speeds and pulsating travelling fronts. It is proved that the minimal wave speed is linearly determined and given by a variational formula involving linear eigenvalue problem. Further, we prove that the existence and non-existence of travelling wave solutions of the model are entirely determined by the basic reproduction ratio \begin{document}$ \mathcal{R}_{0} $\end{document} . As an application, we prove that if the localized amount of infectious individuals are introduced at the beginning, then the solution of such a system has an asymptotic spreading speed in large time and that is exactly coincident with the minimal wave speed.

This work focuses on the geopolymerization of undehydrated kaolinite in place of the more commonly used dehydrated kaolinite via phosphoric acid-activation. The results showed that the compressive strength, microstructure, and chemical composition of acid-activated undehydrated kaolinite were greatly affected by the concentration of phosphoric acid. When kaolinite was acid-activated by 10 mol/L and 12 mol/L phosphoric acid, metavariscite and geopolymer with P–O–Al network were obtained; but the products possessed porous and inhomogeneous microstructure, which exhibited low compressive strength. When kaolinite was acid-activated by 14 mol/L phosphoric acid, geopolymer dominant with Si–O–P–O–Al networks was synthesized, which had compact and dense microstructure. The compressive strength of the geopolymer product was greatly improved. These results demonstrate the feasibility of using undehydrated kaolinite as the starting material for the preparation of phosphoric acid-based geopolymer. The findings of this study have meaning not only for extending the application field of kaolinite but for reducing the energy input in geopolymer preparation.

In this study, Al was incorporated into the structure of diatomite by loading tridecameric aluminium polymer and subsequently heating to improve the solid acidity of diatomite. The results show that Al incorporation increased the number of Bronsted (B) and Lewis (L) acid sites of diatomite by implanting Al-OHs and unsaturated Al3+ ions, respectively. L acid sites increased with the increment of preparation temperatures of Al-incorporated diatomite, whereas the B acid sites decreased. Moreover, L acid sites have stronger acidity than B acid sites. Al-incorporated diatomite exhibits high catalytic activity and considerably decreases the degradation temperature of 12-aminolauric acid (ALA). Large quantities of NH3 and CO2 were generated, which was sourced from ALA decomposition with the catalysis of B and L acid sites, respectively; and CO2 was obtained at a lower temperature than NH3. The manufactured Al13-diatomite composite shows promise as a solid acid catalyst.

A novel, hierarchically porous diatomite/silicalite-1 composite with a high benzene removal efficiency was prepared via a facile coating process. Silicalite-1 nanoparticles (Sil-1nano) were synthesized in situ on the surface of the pre-modified diatomite support by using a mild, low-temperature reflux reaction method. The obtained composite possessed a hierarchically porous structure, involving micropores and stacking mesopores from the silicalite-1 nanoparticles, and it retained the macropores from the diatomite support. The specific surface area and micropore volume of the composite were 348.7 m2/g and 0.127 cm3/g, respectively, with a zeolite loading amount of up to 60.2%. The diatomite/silicalite-1 composite exhibited considerably higher static and dynamic benzene adsorption capacities (94.9 mg/g (Sil-1nano) and 246.0 mg/g (Sil-1nano) respectively) per unit mass of zeolite than did the synthesized Sil-1nano and commercial ZSM-5. Moreover, the introduced macroporosity of the diatomite reduced the mass transfer resistance of the nanoparticles because of their improved dispersity, and it provided more possible entryways for benzene molecules, leading to better penetration of benzene than for Sil-1nano or commercial ZSM-5. The composite showed steady reversibility after 4 adsorption cycles, further demonstrating the promise of such a novel synthesized adsorbent for the removal of volatile organic compounds in industrial applications.

The commercialized, low-cost, and lightweight glass fiber microwires have been shown as a new mask to simplify the fabrication of organic single-crystal nanowire transistors based on copper phthalocyanine (CuPc). The glass fiber is light weight so that the van der Waals force is capable of resisting the effect of gravity when the substrate is flipped over. In this case, the glass fiber mask need not be artificially fixed onto the substrate during metal deposition for electrode fabrication, so the device fabrication process can be simplified. With such a facile method, multiple organic single-crystal nanowire transistors can be fabricated at the same time, and the high mobility up to 0.7 cm $^{2}\text{V}^{{-1}}\text{s}^{{-1}}$ has been realized for CuPc nanowire transistors. Good stability has been also demonstrated. This method effectively improves the efficiency of devices preparation, showing the potential in large-scale fabrication of organic nanowire transistors. Meanwhile, it is favorable for the fundamental electrical studies of 1-D organic nanomaterials.

Acidification of allophanic Andosols has significant effects on their physicochemical properties and productivity. Understanding of the acidification and related effects is limited by the structural changes of allophane – the major mineral composition of allophanic Andosols. In this work, we systematically investigated the structural stability of allophane and the mechanisms of structural changes under different acidic conditions (initial pH 4.0–2.0) by using chemical analysis, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, solid-state magic-angle-spinning nuclear magnetic resonance, and N2 physisorption analysis. The results indicated that the structure of allophane was readily altered in acidic conditions. Acid leaching in conditions with initial pH > 3.0 only dissolved some polymerized silicates from allophane, enlarging the defect pores. By contrast, the dissolution of the imogolite-like local structure was observed in strongly acidic conditions (initial pH

Halloysite is a hydrated polymorph of kaolinite but possesses a distinctive nanosized tubular structure and surface reactivity. The microstructure and mechanical performance of geopolymers derived from calcined halloysite via acid-activation were investigated in this study. The acid-activation products were characterized using a combination of techniques including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Acid-activation of halloysite calcined at 450 °C by 6 mol/L and 10 mol/L phosphoric acid solution produced metavariscite crystals. When the phosphoric acid concentration was increased to 14 mol/L, the acid-activation product became more compact due to the formation of geopolymer that were mainly composed of Al–O–P networks. Calcination of halloysite at 750 °C led to an active form of halloysite, which was favored by geopolymerization. Higher phosphoric acid concentration led to the incorporation of more Si and P in the geopolymer matrix with Si–O–P–O–Al networks, and thus greater compressive strength. Halloysites calcined at 1000 °C barely reacted with phosphoric acid, due to the nanocrystalline formation and the decreased Si–OH content in the calcined halloysite, which had low reactivity unfavorable for geopolymerization. These results indicated that the microstructure and mechanical performance of halloysite-based geopolymers are highly dependent on the precalcination temperature of halloysite and the phosphoric acid concentration. Suitable precalcination temperature and high concentration of phosphoric acid facilitate high degree of geopolymerization, which is conducive to the formation of an acid-activated halloysite-based geopolymer with excellent mechanical performance.