pH Value Of Sol Research Articles

Structural and optical properties of ZnO thin films as a function of pH value and its effect on photoelectrochemical water splitting

ZnO nanoparticles were synthesised via sol–gel method, and then, deposited on a glass substrate using the spin-coating procedure to hand in ZnO thin films. In order to study the effect of alkaline sol on different properties of ZnO thin films, the pH value of sol was adjusted with ammonia. Then, the structural, optical, and photoelectrochemical properties of the prepared samples were analysed. According to XRD analyses, by increasing pH values, the size of ZnO particles increases and the films’ crystallinity improves. In addition, SEM micrographs affirm the uniformity of thin films. According to AFM findings, the morphology and roughness of the samples’ surface are affected by pH values in such a way that with increasing the pH, the roughness of the surface decreases, and the crystallinity improves. Also, both UV–vis peaks shift towards lower wavelengths with increasing pH value of ZnO sol. This means that the more the pH values of ZnO sol, the more the excitation energy of electrons. On the other hand, the numerical values of the energy bandgap decrease by increasing pH. According to PL results, the increase of pH causes the separated electrons and holes to have more energy and can move away from each other. So, the recombination process rate decreases; this result affirms by EIS findings. Increasing the optical absorption and reducing charge recombination are in favour of the photocatalytic reactions. Clearly, increasing the pH value causes the stable photocurrent to increase and the threshold voltage of (J-V) diagram to decrease. Also, the samples show recognisable sensitivity to light. As a final result, the best suggested amount of pH to fabricate ZnO photoanods for water splitting is 10.5.

An efficient amine-modified silica aerogel sorbent for CO2 capture enhancement: Facile synthesis, adsorption mechanism and kinetics

At present, how to develop an economical and efficient solid adsorbent for CO2 capture at low temperature still remains a challenge. In this work, amine-modified silica (SiO2) aerogels were achieved by grafting with 3-(Aminopropyl) triethoxysilane (APTES) through a simple ambient pressure drying process, and verified as efficient adsorbents for CO2 capture. The effects of sol pH value and APTES concentration on the microstructure and CO2 adsorption property of as-prepared amine-modified silica aerogels (AMSAs) were investigated in detail. A double exponential model was proposed to reveal the kinetics adsorption mechanism of the AMSAs for the first time. It demonstrated that the as-prepared AMSAs were amorphous with a three-dimensional network structure composed of nanoparticles. And the AMSAs presented a high CO2 adsorption capacity of 3.37 mmol·g−1 at 70 °C. After 10 adsorption-desorption cycles, the AMSAs still kept 87.6% of the original capacity, exhibiting long cycle stability. Moreover, the kinetic adsorption behavior could be well simulated by the double exponential model, and the CO2 diffusion process was the speed-controlling step in the whole CO2 adsorption process. The diffusion active energy of AMSAs on CO2 capture was also calculated. This synthesis method is facile and environmental-friendly, which is of great significance to the large-scale production of SiO2 aerogel, and may provide a novel reference for the preparation of CO2 low-temperature adsorbents with high adsorption performance and good cycle stability.

Preparation and characterization of building insulation material based on SiO2 aerogel and its composite with expanded perlite

This article aims to complement the advantages of SiO2 aerogel and expanded perlite (EP) to prepare high-performance building insulation materials. SiO2 aerogels were prepared via acid/base two-step catalytic process followed by ambient pressure drying (APD) process. The two-step surface modification method is used to improve hydrophobicity of aerogel. And SiO2 aerogel/EP thermal insulation composites were obtained via introducing wet gel into EP. The effects of the amount of water, the amount of anhydrous alcohol and the pH value of sol on the properties of aerogels were analyzed. And the effects of vacuum degree and adsorption time on the thermal conductivity and compressive strength of SiO2/EP composite were studied. The pore size distribution and chemical structure of SiO2 aerogel were characterized by N2 adsorption-desorption test and Fourier transform infrared spectroscopy (FTIR). The micromorphology, crystal structure of SiO2 aerogel and SiO2/EP composite were characterized by scanning electron microscope, X-Ray diffraction. The results show that the thermal conductivity of SiO2 aerogel prepared with tetraethoxysilane (TEOS): methyltriethoxysilane (MTES): ethanol (EtOH):H2O = 1:0.3:14:6 (mole ratio) was as low as 0.0212 W/(m·K), the aerogel had high porosity (95.05%) and super hydrophobicity(the contact angle is 158.7°). Meanwhile, it was found that SiO2 aerogel is stably distributed in the pores of the EP and effectively reduces its thermal conductivity and water absorption. The minimum thermal conductivity of SiO2/EP composite was 0.036 W/(m·K), the minimum water absorption was 9.2% and the compressive strength was 214.35 kPa. Hence, SiO2 aerogel/EP with good performance and low cost has great potential in the field of building insulation.

Deposition and characterization of spin-coated n-type ZnO thin film for potential window layer of solar cell

Spin-coating technique has been utilized to deposit ZnO thin films on ITO substrates. The dependence of the structural, optical, and electrical properties of the prepared films on both the sol–pH values and annealing temperatures has been investigated. X-ray diffraction analysis has revealed that the optimal sol–pH value was found to be 8 at annealing temperature 450 °C. At these conditions, the optical transmission and reflection data have also shown a clear enhancement in both the morphology and the grain size of the films. In addition, the analysis of I–V and C–V measurements of the Schottky Au/ZnO diode has shown a high agreement with both the investigated structural and optical properties. Furthermore, a new empirical method based on the calculated electrical parameters in the context of both the thermionic emission and Mott–Schottky models has been proposed to evaluate the approximate value of the electron effective mass in the conduction band of the ZnO (m* = 0.224 mo).

Removal of Low-concentration Ammonia from Ambient Air by Aluminophosphates

A series of aluminumphosphate materials was prepared and used as adsorbents for the removal of ammonia at low concentrations. The influence of various preparation parameters, including the pH value of sol, calcination temperature and molar ratio of P/Al, on the structure and surface properties as well as adsorption capacity were investigated. The results showed that large amount of P—OH present on the surface of aluminophosphates was suitable for the removal of ammonia. They were the major source of weak Bronsted acid sites and acted as the main active centers for capturing ammonia.

A low cost and facile preparation of hydrophobic silica films and powders by a solution-based process

Super-hydrophobic surfaces with water contact angle (WCA) higher than 150° generated a lot of interests both in academic and in industry because of their self-cleaning functionality. Emphasis was given to the effect of pH value on the hydrophobic behavior of the obtained films or powders. At first, SiO2 sols were prepared by diluted ammonia. We found that following the increase of pH value of sol from 8 to 9, WCAs of the obtained films increased from 121.8° to 131.8°. Following the continued increase of the pH value of sol, precipitates began to appear and smooth film could not be obtained. The WCAs of the obtained powders could reach 121.7°, and through modifying by TMCS could further increase to as high as 165° and the water sliding angle (WSA) was 2°. The results of SEM indicate that the hydrophobic properties of the powders without modifying by TMCS should be originated from the formation of nano/micron binary structure, i e, a micron-scale diameter and a nano-scale surface roughness. In this work we provide a better solution to fabricate super-hydrophobic silica coating surface with a simple method at low cost.

Effects of pH Value and Water Content of Sol on TiO2 Photocatalytic Activity Prepared by SAS

To investigate the effects of sol pH value and water content on photocatalytic activity of TiO2 prepared with sol-gel auto-igniting synthesis (SAS) method, TiO(NO3)2 was prepared with TiCl4 as raw material and used as precursor of TiO2. By changing sol pH value and water content, different TiO2 powders were prepared and characterized with XRD, SEM and photodegradation of methylene blue (MB). Results indicated that TiO2 presented the highest photocatalytic activity while sol pH value and mass fraction of water were adjusted to 7 and 50% respectively while the mole ratio of n (TiCl4): n (citric acid): n (ammonium nitrate) was fixed as 1: 1: 3. The TiO2 powders were confirmed as loose and porous anatase type with particle size of 15 nm by SEM and XRD.

Influence of Parameters on Alumina Particles Size and Morphology

The sol - gel method is the effective technique to prepare high purity ultrafine alumina powder. Laser particle size analyzer and scanning electron microscopy were used to study the inflence of pH, leaching of precursor sol, surface modification of alumina powder on the secondary particle size. The impact of leaching sol on powder crystal was tested with X-ray diffraction. The results show that: aluminum nitrate solution showed different appearance with different pH values during titration aluminum nitrate solution with ammonia. When pH=3~5.5, the solution occur through no precipitation to the white precipitate, then the solution becomes relatively thin paste; when the pH was from 6.0 to 6.5, the solution becomes more thick paste. When the pH increased from 7.0 to 8.0, the solution has turned into a more dilute paste. The impact of pH on the particle size is: When the pH increased from 5.5 to 7.0, aluminum powder particle size gradually become thicker and larger. When the pH continues to rise, powder particle size is reduced, when the sol pH value is 8.0, it can get the smallest particle size for alumina powder, up to 548nm. Powder average particle size when adding TEA surfactant to sol is less than the sol without any surfactant particle size from the micrograph. Moreover, particle size is more uniform with TEA surfactant, but powder particle size which did not add surfactant to the sol is clear size differences and the dispersion is poor. When the sol containing surfactant, the effect of surface modification is not obvious. In the case of sol without surfactant powder particle size reduced after the surface modification, then powder surface modification is necessary, it can prevent the powder from congregating. The crystal type is relatively perfect and single α-Al2O3 after filtration, the crystal type without leaching is α-Al2O3 and γ-Al2O3, with a smaller particle size, crystal grain size is relatively smaller. If alumina sol isn’t be leached it contains ammonium nitrate, ammonium nitrate will decompose and release various gases during sintering, the gas emission has an crushed effect on the sintered powder.

Preparation and Characterization of BaTiO<sub>3</sub> Powders by Sol-Gel and BaTiO<sub>3</sub> Ferroelectric Films by Electrophoretic Deposition Technique

The clear and transparent sols of BaTi acetate were prepared from tetrabutyltitanate, barium acetate aqueous solution, ethanol and acetic acid. The BaTi acetate sols were transferred into gels by sol-gel process, and the gels were dried and calcined to nanostructured BaTiO3 powders. Pure barium titanate powders added in mixtures of acetone and iodine and water or acetylacetone (Acac) and ethanol (EtOH) as suspension systems, the aim of this study was to use the electrophoretic deposition technique (EPD) to fabrication the BaTiO3 ferroelectric films with high dielectric constant. During sol-gel transition process, it is found that the initial PH value of sol affected not only the sol-gel transition, but also the particles size of the final calcined BaTiO3 powders. The effects of the EPD process parameters such as the suspension, powder concentration, electrical field strength on the specific EPD deposited weight were investigated. The films sintered at 1050°C for 2h were crystallized into the tetragonal phase at room temperature, which were sufficiently dense and had uniform microstructure and excellent dielectric properties.

The Sonogel-Carbon electrode as a sol-gel graphite-based electrode.

In this work, a novel sol-gel-based procedure to obtain solid carbon composite electrodes is proposed. The procedure is based on the use of sonocatalysis to apply high-energy ultrasound directly to the precursors; this way, ultrasonic cavitation is achieved so that hydrolysis with acidic water is promoted in the absence of any additional solvent and the time needed to get a unique phase is reduced drastically. The mix of sonogel with spectroscopic grade graphite leads to a new type of sol-gel electrode: the Sonogel-Carbon electrode. The amount of water, necessary for hydrolysis to occur, has been studied, as well as the sol pH value and the electrochemical behavior of the Sonogel-Carbon electrode in Britton-Robinson buffer. Mechanical renewal of the electrodes surfaces and background signal stability for at least 42 days have been also tested. We have carried out some tests to check the ability of the synthesized material to give electrochemical response when redox species are present in the background electrolyte. Mechanical and electrochemical studies indicate that the Sonogel-Carbon electrode shows good properties for use as an electrochemical sensor.

Lead phthalocyanine incorporated in sol and gel

Lead phthalocyanine (PbPc) was first successfully doped in organic-inorganic matrix by choosing proper alkoxy-silane containing amino-group by sol-gel processing. The characteristics of PbPc in sol and gel were studied using optical absorption spectroscopy. The results show that the presence of PbPc monomer in the sol and gel is strongly controlled by the pH value of sol, and the action of amino-group is an important factor for PbPc monomer able to exist in gel.

かまぼこの足について-XIII

In this study, we have investigated the influence of heating on the viscosity of a fish muscle sol. Sols were prepared by extracting lizard fish muscle with 10vol. of 0.6M NaCl (pH 6.8) overnight at a temperature between 3° and 5°C. All the vicosity measurements were carried out at 5° ± 0.5°C by using a Brooksfield type viscometer after heating at different temperatures for various periods. Changes in viscosity values during heating occurred in two steps; a remarkable increase at a temperature range between 30° and 40°C, and a sudden fall accompanied by a coagulation of proteins and also a release of water between 40° and 50°C, which temperature was known as the coagulation temperature of myosin-B (Fig. 1). However, the rise and fall in the viscosity were dependent on both temperature and period of heating. After prolonged heating, the viscosity-increase were obsevued even at a lower temperature (e. g. 20°C), and the gradual decrease occurred below 40°C. (e. g. 35°C.) after the stage of the viscosity-increase (Fig. 2). The occurrence of such a viscosity-increase was found to be independent of the pH value of sol (Fig. 4), but the rate of the increase was a function of the consistency of the sol (Fig. 3). The first step, an increase in the viscosity of the fish muscle sols during heating, may be interpreted in terms of the unfolding and the hydration of actomyosin chains, and the second step, fall in the viscosity, may probably be due to the formation of cross-linkages between the unfolded chains.