Synthesis of mesoporous silicon directly from silicalite-1 single crystals and its response to thermal diffusion of ZnO clusters

This article describes the preparation of mesoporous silicon granules with a layered structure directly from silicalite-1 single crystals. The silicalite-1 single crystals were thermally reduced in vacuum at 630 °C, with the original shape retained. The samples are confirmed as crystalline silicon by X-ray diffraction and transmission electron microscope. The silicon granule is composed of a monocrystalline surface and polycrystalline layered interior. A surface area of around 66 m² g⁻¹ and the pore size centered at 3.7 nm were obtained from nitrogen porosimetry, BET and BJH analysis. The ZnO clusters have been loaded into the porous silicon granule by thermal diffusion method. The photoluminescence emission centered at 3.44 eV originates from the small particles of ZnO and the band at 2.81 eV may be due to both an oxidized surface and quantum confinement effects. The microstructure in this silicon granule is very different from those in etched samples. The synthetic design demonstrates an interesting way from the microporous zeolite to mesoporous silicon and enlarges the structural diversity of porous silicon crystal.     

Synthesis of nanocrystalline sodalite with organic additives

Ethanol, urea and acetone were used as organic additives in the synthesis of nanocrystalline sodalite. The sodalite crystals with sizes of less than 100 nm were produced when ethanol was introduced in the synthesis solution. When both ethanol and urea were present, the resultant sodalites exhibited even smaller crystal sizes, and showed a nitrogen sorption capability as high as around 170-180 cm³/g and a BET surface area of over 78.3 m²/g. However, the addition of acetone in the synthesis solution yielded sodalite with sizes of ca. 200 nm and a trace amount of zeolite A.     

Effects of macropore size on structural and electrochemical properties of hierarchical porous carbons

Hierarchical porous carbons (HPCs) were synthesized by a colloid crystal template method with phenolic resin as carbon source and triblock copolymer Pluronic F127 as a soft template. The obtained HPCs with tunable macropore size of 242–420 nm exhibit large BET surface areas (~900 m² g⁻¹) and large pore volumes (~1.2 cm³ g⁻¹). With an increase in the diameters of silica template, the BET surface areas and pore volumes of HPCs decrease. The electrochemical properties of the HPCs with various macropore sizes used as supercapacitor electrodes materials were evaluated using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. The results show the HPC with the macropore size of 242 nm possesses the largest specific capacitance among the HPCs. The excellent capacitive behavior of HPC-242 can be attributed to its faster ion transport behavior and better ion-accessible surface area.     

The synthesis of mesoporous Ce1?xZrxO2 by modified evaporation-induced self-assembly method

Mesoporous Ce_1−x Zr _x O₂ with high surface area was synthesized using a modified evaporation-induced self-assembly method that combined citric acid as complexing agent and cetyltrimethyl ammonium bromide as surfactant. The samples with different Ce/Zr molar ratio were characterized by thermogravimetry and differential thermal analysis, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, Brunauer–Emmett–Teller (BET), and Barrett–Joyner–Halenda methods. It was found that when the Zr molar fraction was larger than 0.3, a mixture of cubic phase and tetragonal phase was formed. Ce_0.7Zr_0.3O₂ solid solution had the largest BET surface area (217 m² g⁻¹) and mesoporous structure. The catalytic performances of mesoporous Ce_1−x Zr _x O₂ for CO oxidation were examined. Mesoporous Ce_0.7Zr_0.3O₂ solid solution demonstrated the best catalytic activity due to the high surface area and an enhanced redox property caused by appropriate Zr⁴⁺ incorporation.     

Sol-gel synthesis of alumina,titania and mixed alumina/titania in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulphonyl) amide

In this paper we report on the synthesis of alumina, titania and mixed alumina–titania in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulphonyl) amide [Py_1,4]TFSA via sol-gel methods using aluminium isopropoxide and titanium isopropoxide as precursors. Our results show that the as-synthesized alumina is mainly mesoporous boehmite with an average pore diameter of 3.8 nm. The obtained boehmite is subject to a phase transformation into γ-Al₂O₃ and δ-Al₂O₃ after calcinations at 800 and 1,000 °C, respectively. The as-synthesized TiO₂ shows amorphous behaviour and calcination at 400 °C yields anatase which undergoes a further transformation to rutile at 800 °C. The as-prepared alumina–titania powders are amorphous and transformed to rutile and α-Al₂O₃ after calcination at 1,000 °C TiO₂. The obtained alumina–titania has a higher surface area than those of alumina or titania. The surface area of the as-synthesized alumina–titania was found to exceed 486 m² g⁻¹, whereas the surface areas of the as-synthesized boehmite and titania were around 100 m² g⁻¹, respectively.     

Defect formation in silicon implanted with ∼1 MeV/nucleon ions

Defect formation processes in silicon implanted with ∼1 MeV/nucleon boron, oxygen, and argon ions have been studied using microhardness and Hall effect measurements. The results indicate that ion implantation increases the surface strength of silicon single crystals owing to the formation of electrically inactive interstitials through the diffusion of self-interstitials from the implantation-damaged layer to the silicon surface. The radiation-induced surface hardening depends significantly on the nature of the ion, its energy, and the implant dose. In the case of low-Z (boron) ion implantation, the effect had a maximum at an implant dose of ∼5 × 10¹⁴ cm⁻², whereas that for O⁺ and Ar⁺ ions showed no saturation even at the highest dose reached, 1 × 10¹⁶ cm⁻². When the ion energy was increased to ∼3 MeV/nucleon (210-MeV Kr⁺ ion implantation), we observed an opposite effect, surface strength loss, due to the predominant generation of vacancy-type defects.     

Silicalite-1 zeolite membranes on unmodified and modified surfaces of ceramic supports: A comparative study

Silicalite-1 zeolite membranes were prepared hydrothermally on the porous ceramic supports, both unmodified and modified with 3-aminopropyl triethoxysilane (APTES) as a coupling agent following ex situ (secondary) crystal growth process. The microstructure of the membranes was examined by scanning electron microscopy (SEM). The permeation study with a single gas, nitrogen (N₂) was performed through the membranes. For the surface modified support, a more surface coverage of the seed crystals on the porous support was observed resulting in a relatively higher dense packing of the crystals during secondary crystal growth process compared to that obtained from the unmodified support. The membrane developed on surface modified support rendered lower permeance value i.e. 9 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ of N₂ compared to that formed on the unmodified support which gave permeance value of 20 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ of N₂.     

Synthesis of copper oxide vegetable sponges and their antibacterial,electrochemical and photocatalytic performance

Copper oxide (CuO) vegetable sponges with mesoporous structure were successfully prepared from pine tree needles cellulose as templates. The sample was characterized by X-ray diffraction, scanning electron microscopy and nitrogen absorption–desorption. In the performance test, the obtained CuO vegetable sponges showed great antibacterial activities, as good as penicillin and kanamycin, especially towards Streptococcus faecalis. They also displayed active photocatalytic degradation of rhodamine B molecules in aqueous solution. Electrochemical data demonstrated that the CuO vegetable sponges were capable of delivering a specific capacitance of 440 F g⁻¹ at a current density of 1 A g⁻¹ and offered good specific capacitance retention of 95.1% after 1,000 continuous charge–discharge cycles even at 5 A g⁻¹.     

Extremely high surface area of ordered mesoporous MCM-41 by atrane route

Silatrane synthesized from inexpensive oxide precursor, silica and TEA was used as the precursor for MCM-41 synthesis at low temperature because of its stability in aqueous solutions. Using cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB) as a template, the resulting meso-structure mimics the liquid crystal phase. Varying the surfactant concentration, ion concentration and temperature of the system, changes the structure of the liquid crystal phase, resulting in different pore structures and surface area. After heat treatment, very high surface area mesoporous silica was obtained and characterized using XRD, BET and TEM. XRD and TEM results show a clear picture of hexagonal structure. The surface area is extraordinarily high, up to more than 2400 m² g⁻¹ at a pore volume of 1.29 cm³ g⁻¹. However, the pore volume is up to 1.72 cm³ g⁻¹ when the surface area is greater than 2100 m² g⁻¹.     

Sponge-like β-Ni(OH)<Subscript>2</Subscript> nanoparticles: synthesis,characterization and electrochemical properties

The present investigation describes the synthesis of uniform sponge-like Ni(OH)₂ nanoparticles on stainless steel substrates by a two-step successive ionic layer adsorption and reaction method; the study also explores electrochemical properties. The formation of the β-phase Ni(OH)₂ and it’s nanocrystallinity are confirmed by X-ray diffraction and X-ray photoelectron spectroscopy studies. Scanning electron microscopy revealed the formation and random distributions of porous and sponge-like nanoparticles with high Brunauer–Emmett–Teller surface area of 56.4 m² g⁻¹. The maximum specific capacitance of 428 F g⁻¹ was obtained at 5 mV s⁻¹ in a 2 M KOH electrolyte, indicating promising supercapacitor applications with remarkable rate capability. These results suggest the importance of rational design and synthesis of thin nanomaterials for high-performance energy applications.     

Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>/worm-like mesoporous carbon synthesized via a microwave method for supercapacitors

A quick and facile microwave method has been employed to prepare Mn₃O₄/worm-like mesoporous carbon (Mn₃O₄–MC) composites. Structural and morphological characterizations of worm-like mesoporous carbon and Mn₃O₄–MC composites have been carried out using X-ray diffraction, transmission electron microscopy, N₂ adsorption–desorption, and electrochemical measurement. Cyclic voltammograms demonstrate that the Mn₃O₄–MC composites perform improved capacitive behavior at the range of −0.8~0.2 V (vs. Hg/HgO electrode) with reversibility. The Mn₃O₄–MC composite electrode possesses an enhanced specific capacitance of 266 F g⁻¹ at a sweep rate of 1 mV s⁻¹.     

Electrochemical capacitance study on Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanowires for super capacitors application

One-dimensional Co₃O₄ nanowires have been prepared by utilizing the ordered mesoporous silica material SBA-15 as template. The results of transmission electron microscope (TEM) and N₂ adsorption–desorption characterizations show that the Co₃O₄ nanowires possess a uniform size and a large Brunauer-Emmett-Teller (BET) surface area. Its electrochemical performance was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques in various concentration of KOH solution. This nanomaterial shows a small resistance, a high specific capacitance (SC), and a strong cyclic stability. The maximal SC value of 373 F·g⁻¹ was obtained in 6 M electrolyte under the scan speed of 3 mV·s⁻¹ at the first CV cycle. After 500 CV cycles, the SC value is about 90% of the original value. It is considered that the short path of ion transfer given by nanomaterial brought on the great pseudo capacitance performance.     

Calcium carbonate crystallization in the presence of taurine

The kinetics of calcite (CaCO₃) crystallization on calcite seed crystals in the presence of taurine was investigated by the constant composition method. The presence of taurine (4× 10^{− 5}− 4× 10⁻⁴M) in the supersaturated solutions lead to calcite crystals with a characteristic discontinuous planes of growth and poor habit, as compared to the hombohedral morphology of the seed crystals. The acceleration effect of taurine on the crystal growth rate was 17–96%. The apparent order of the crystal growth was found to be 2.0± 0.2 typical for a surface diffusion-controlled spiral growth processes.     

Utilization of ball clay adsorbents for the removal of crystal violet dye from aqueous solution

In this work, an attempt has been made to find the adsorption characteristics of crystal violet (CV) dye on calcined and uncalcined ball clay using batch adsorption technique. The ball clay adsorbents are characterized using thermo gravimetric analysis (TGA), particle size analysis, X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm, and Fourier transform infrared (FT-IR) spectroscopy. The influence of pH and temperature on the adsorption of CV dye is examined. The experimental results of adsorption isotherms are fitted with Langmuir, Freundlich, and Redlich–Perterson models. Adsorption mechanisms of the CV dye on both the ball clays are investigated using thermodynamic parameters and analytical techniques. The results indicate that the Langmuir and Redlich–Peterson models are found to be the more appropriate model to explain the adsorption of CV dye on ball clays than that of Freundlich model. The maximum adsorption capacity of the calcined and uncalcined ball clay is found to be 1.6 × 10⁻⁴ and 1.9 × 10⁻⁴ mol g⁻¹, respectively. The lower adsorption capacity of the calcined ball clay is due to the reduction in the surface hydroxyl group and surface area. Adsorption capacity and percentage removal of the CV dye on calcined and uncalcined ball clay increase with an increase in the temperature and pH, respectively. The obtained negative ΔG ⁰ values indicate that the adsorption of CV dye on ball clay is feasible and spontaneous in nature at temperatures studied. The energy supplied for calcining the ball clay did not bring any improvement in the adsorption capacity. Rather, a reduction in the adsorption capacity of the CV dye on calcined ball clay suggests that the uncalcined ball clay would be more economic and efficient adsorbent for the removal of CV dye than the calcined ball clay. In conclusion, uncalcined ball clay could be used as a low cost alternate for the expensive activated carbon.     

Detector-grade CdZnTe:In crystals obtained by annealing

A method for successfully obtaining detector-grade CdZnTe:In (CZT:In) crystals by annealing is described in this article. Pure Te is used as annealing source, which can provide sufficient deep-level Te antisites. Characterizations reveal that the resistivity is greatly enhanced by more than five orders after this annealing, thus the crystals can be use for radiation detectors. This is due to introduce efficient Te antisites to pin the Fermi level to the middle of the band gap. The EPD of dislocation reduces because the star-like Cd inclusions are eliminated by annealing. Investigation of annealing time shows that 240 h annealed CZT:In crystal with 7.8% energy resolution and 2.01×10⁻³ cm²/V μτ value has the best detector performance.     

Gelatin-assisted porous expansion of mesoporous silica

In this study, we report the pore expansion effect of gelatin, a common amphoteric biological protein, on the hexagonal mesoporous silica materials. Tetraethyl orthosilicate (TEOS) was used as silica source and the nonionic surfactant P123 (EO₂₀PO₇₀EO₂₀) as template. The microstructure characters of products were investigated by low-angle X-ray diffraction (LAXRD), transmission electron microscope (TEM), and N₂ adsorption–desorption measurements. The results show that the products prepared with gelatin have the mild expansion ratios of 29–39% and 5–22% in pore diameter and pore volume, respectively. The specific surface area of products ranges from 445 to 590 m² g⁻¹. Moreover, it is revealed that the presence of gelatin did not change the intact 2D-hexagonal mesoporous structure of materials. The ultraviolet–visible absorption spectroscopy (UV–Vis) analysis indicates that there is an interaction between the oxygen atoms of P123 and gelatin molecules. The pore expansion may be because the gelatin can interact with the hydrophilic sides of P123 micelles via hydrogen bonds interaction, which is different from the reported pore expansion mechanisms for other systems.     

Preparation and gases storage capacities of N-doped porous activated carbon materials derived from mesoporous polymer

In this report, the chemical activation of mesoporous carbon derived from mesoporous polymer is used to prepare N-doped carbon materials with high surface area and narrow pores size distribution. The porous carbons derived from the activation of mesoporous carbon generally possess high surface area up to 2400 m² g⁻¹ and narrow micropores/super-micropore size distribution and exhibit H₂ uptake capacity of up to 4.8 wt% at −196 °C and 20 bar and CO₂ sorption capacity of up to 3.7 mmol g⁻¹ at 25 °C and 1 bar. The measured isosteric heat of adsorption for H₂ sorption is 10 kJ mol⁻¹ and 58 kJ mol⁻¹ for CO₂ sorption, indicating a strong interaction between the carbon surface and adsorbed hydrogen and carbon dioxide respectively.     

Synthesis and capacitive property of δ-MnO2 with large surface area

δ-MnO₂ with layered structure is synthesized in a mixed system of KMnO₄ and C₃H₆O (epoxypropane) by a facile low-temperature hydrothermal method at 90 °C for 24 h. The obtained product is characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and N₂ adsorption–desorption, and its electrochemical property was investigated by cyclic voltammetry method. Experiment results show that the as-synthesized product has a layered structure and a high specific surface area of 188 m² g⁻¹, and C₃H₆O existing in the reaction system plays a crucial role for the formation of δ-MnO₂ particles. Electrochemical characterization indicates that the prepared material exhibits an ideal capacitive behavior with the initial capacitance value of 296 F g⁻¹ in 1 mol L⁻¹ Na₂SO₄ aqueous solution at a scan rate of 5 mV s⁻¹ and good cycling behavior.     

Synthesized silicon-substituted hydroxyapatite coating on titanium substrate by electrochemical deposition

Silicon-substituted hydroxyapaptite (Si-HA) coatings were prepared on titanium substrates by electrolytic deposition technique in electrolytes containing Ca²⁺, PO₄ ³⁻ and SiO₃ ²⁻ ions with various SiO₃ ²⁻/(PO₄ ³⁻ + SiO₃ ²⁻) molar ratios(η_si). The deposition was all conducted at a constant voltage of 3.0 V, with titanium substrate as cathode and platinum as anode, for 1 h at 85°C. The coatings thus prepared were characterized with inductively coupled plasma (ICP), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), field-emission-type scanning electron microscope (FSEM). The results show that the silicon amount in the coatings increases linearly to about 0.48 wt% at first with increasing η_si between 0 and 0.03, then increases slowly to about 0.55 wt% between 0.03 and 0.10 and finally maintains almost at a level around 0.55 wt% between 0.10 and 0.30. The tree-like Si-HA crystals are observed in the coatings prepared in the electrolyte of η_si = 0.20. And the presence of silicon in electrolytes decreases the thickness of the coatings, with effect being more significant as η_si increased. Additionally, the substitution of Si causes some OH⁻ loss and changes the lattice parameters of hydroxyapatite (HA).     

Effect of humidity treatment on the structure and photocatalytic properties of titania mesoporous powder

In the work presented here, mesoporous titania (MT) powders is synthesized by sol–gel method using amphiphilic triblock copolymer as a template at two different levels of relative humidity (RH); 20 and 80%. Various techniques such as small angle X-ray diffraction (SAXRD), wide angle X-ray diffraction (XRD), UV–visible spectroscopy, high resolution transmission electron microscopy (HRTEM), Fourier transformed infra red (FTIR) spectroscopy and N₂-adsorption/desorption analysis were utilized to study the prepared samples. Further, the photocatalytic activities of the prepared samples were evaluated from the photo-degradation analysis of methylene blue (MB). For the sample treated with 80%RH the formation of an ordered mesoporous structure with a high specific surface area (172 m²g⁻¹), mesoporosity (48%) and enhanced photocatalytic activity were obtained compared to those of the sample subjected to 20%RH. The observed increased MB degradation for the latter is mainly attributed to the formation of higher specific surface area and mesoporosity. The availability of highly ordered open pore channels could provide increased contacts between reactants in the solution and the active sites on the surfaces of MT particles.