THE HEAT REQUIRED TO FIRE CERAMIC BODIES1

A differential thermal method for determining interval specific heats of ceramic materials is described. The specific heat of the unknown is determined by comparing its temperature to that of quartz after each sample has been subjected to a definite heat treatment. This method shows the number of calories required to heat one gram of the material in question from 0 to t°C, accounting for all thermal processes which the material may undergo during the heating process. It shows the temperatures at which the various thermal processes begin and end as well as the quantitative figures for the more pronounced of these thermal processes. The kaolin, ball, flint, and diaspore clays undergo an endothermic reaction at about 575°C which amounts to “60 to 130” calories per gram of the air dried material. They undergo an exothermic reaction at about 960°C which amounts to about 25 calories per gram of the air dried material. About 510 calories are required to heat one gram of any firebrick body from 25 to 1200°C, the specific heat over this interval being about 43. About 500 calories are required to heat one gram of any kaolin or ball clay from 0–1000°C, the specific heat over this interval being about 5. About 290 calories are required to heat one gram of flint or feldspar from 0–1050°C, the specific heat over this interval being about 28. Instead of the kiln efficiencies being about 22% as was previously believed, this work proved them to be about 35%.     

Swelling and dye sorption studies of AAm/SA hydrogels crosslinked by glutaraldehyde and divinylbenzene

Highly swollen acrylamide (AAm)/sodium acrylate (SA) hydrogels were prepared by free radical solution polymerization in aqueous solution of AAm with SA as comonomer and two multifunctional crosslinkers such as glutaraldehyde (GL) and divinylbenzene (DVB). Water absorption and percentage swelling were determined gravimetrically. The influence of SA content in hydrogels was examined. Percentage swelling ratio of AAm/SA hydrogels was increased up to 2946–12,533%, while AAm hydrogels swelled up to 1326–1618%. The values of equilibrium water content of the hydrogels are between 0.9297–0.9921. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non‐Fickian in character. Adsorption properties of AAm/SA hydrogels in aqueous thionin solution have been investigated. Finally, the amount of sorbed thionin per gram of dry hydrogel (q_e) was calculated to be 4.81 × 10^?6?11.69 × 10^?6 mol thionin per gram for hydrogels. Removal efficiency (RE%) of the AAm/SA hydrogels was changed range 37.03–68.82%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Tailoring doping locations and types for high-performance CuFeO2-based photocatalysts

Doping engineering has been recognized as an effective strategy for improving the solar-to-hydrogen conversion efficiency of delafossite CuFeO₂-based photocatalysts. However, a comprehensive and systematic study on the doping effect in CuFeO₂ is still needed to establish a universal law. To address this, we utilized density functional theory calculations to scrutinize the doping effects of various dopants at different lattice positions. Our findings revealed that Mn replacing Fe and N replacing O are the most readily achievable doping methods under oxygen-rich and oxygen-poor conditions, respectively, with a maximum doping concentration of 10²⁰ cm⁻³ achievable at 900 K. Interestingly, we found that doping with N for O, F for O, and Ni for Cu generates impurity levels capable of capturing photogenerated holes at the top of the valence band, while Zn for Cu and Co for Fe engender impurity levels capable of capturing photogenerated electrons at the bottom of the conduction band, thereby facilitating the separation of photogenerated electron–hole pairs. However, it is worth highlighting that Mn replacing Fe results in impurity levels forming in the middle of the bandgap, acting as a recombination center for photogenerated electron–hole pairs. Furthermore, we discovered that Mg replacing Cu or Fe serves as an example of heterovalent doping capable of promoting the solar-to-hydrogen conversion efficiency of CuFeO₂. In isovalent doping, dopants with more valence electrons than Cu, dopants with the same valence electron as Fe, and dopants with less valence electron than O can enhance the solar-to-hydrogen conversion efficiency of CuFeO₂. Overall, this study provides a systematic analysis of the doping effects on CuFeO₂-based photocatalysts and can be applied to doping engineering of ABO₂-type delafossite photocatalytic materials.     

Testing of electrochemical capacitors: Capacitance, resistance, energy density, and power capability

DC testing of electrochemical capacitors has been reviewed with emphasis on the test procedures used by the USABC, IEC, and the University of California-Davis (USA). Differences in the test procedures are identified and the effect of the differences on the inferred characteristics of various carbon/carbon and hybrid (pseudo-capacitive) electrochemical devices evaluated from test data. The effect of the test procedures is greater for hybrid devices than carbon/carbon capacitors.It was found that the differences in the test procedures have a minor effect on capacitance, but larger effects on resistance and energy density. The pulse power capability of devices is calculated from the rated voltage of the device and its measured resistance. The inferred power capability of a device based on the matched impedance value (V²/4R) is nearly a factor of ten higher than that corresponding to an efficiency of 95% as required in the USABC and IEC test procedures.     

Novel chemically synthesized polyaniline electrodes containing a fluoroboric acid dopant for supercapacitors

The performance of chemically synthesized dual‐acid‐doped polyaniline (PANI) electrode material was investigated for supercapacitors for the first time. Three different grades of PANI‐containing fluoroboric acid (HBF₄) as one of the dopants were prepared by a chemical polymerization method. PANI–dodecylhydrogen sulfate–HBF₄ salt was synthesized by an emulsion polymerization pathway. A PANI–HBF₄–sodium tetrafluoroborate composite and PANI–HBF₄ salt were prepared from different modifications of dopants by a dedoping–redoping process. Capacitative behaviors of the three grades of PANI electrode materials were investigated. Among the three different grades of PANI, PANI–HBF₄ electrode showed the best performance in terms of conductivity (2.3 × 10^?1 S/cm), specific capacitance of the supercapacitor (140 F/g), specific energy (9.6 W h/kg), and specific power (58.8 W/kg). An increase in the capacitance of PANI–HBF₄ was achieved, which identified the significant contribution of the dedoping–redoping processes in the PANI system for supercapacitors. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Diffusion of cyclic hydrocarbons in benzene-swollen,divinylbenzene-crosslinked polystyrene beads

Diffusion of cyclic hydrocarbons within benzene-swollen, polystyrene-divinylbenzene gel-type beads were studied at 25°C. Solute concentrations less than 6.3 × 10^?2M and volume fractions of polymer less than 0.6 were used. Diffusion coefficients were calculated assuming Fick's law diffusion, and were found to depend upon the volume fraction of polymer. The dependence suggests that the swollen polymer network acts as a physical obstruction to diffusion. Studies indicated that the solute–solvent interactions affecting diffusion were the same in the solvent-swollen polymer as in the pure benzene solvent.     

Comparison of high voltage and high temperature performances of wide bandgap semiconductors for vertical power devices

Temperature dependent properties of wide bandgap semiconductors have been used to calculate theoretical specific on-resistance, breakdown voltage, and thermal run-away temperature in SiC, GaN, diamond, and Si vertical power devices for comparison. It appears mainly that diamond is interesting for high power devices for high temperature applications. At room temperature, diamond power devices should be superior to SiC only for voltage higher than 30–40 kV, due to the high energy activation of the dopants.     

Freezing and nonfreezing water in cellulose acetate membranes

The relative amounts of freezing and nonfreezing water in various cellulose acetate (CA) membranes were determined by differential scanning calorimetry. It was found that: (1) A significant fraction (17–40%) of the water (1.0–3.1 g H₂O per gram dry CA) in any membrane does not freeze at temperatures as low as ?60°C. (2) The amount of nonfreezing bound water (0.4–0.7 g nonfreezing water per gram dry CA) depends upon the nature of the membrane and is significantly higher than the total amount of water (all of which is nonfreezing) absorbed from liquid water by a dense film of the same polymer (～0.18 g water per gram dry CA). The structures of the membranes were studied by scanning electron microscopy. The results suggest that the amounts of nonfreezing water in cellulose acetate membranes decrease with the increase in the packing density (compactness) of the polymer within the membrane. In dense films, the extent of polymer–polymer interactions within the polymeric matrix is high, and therefore the macromolecular chains are less accessible to bind water.     

Performance Evaluation of Doped Titanium Oxide for Low‐Voltage Applications

Varistors are the electronic devices which are used in various industries to protect the electrical and electronic systems from sudden surges. In this research, the electrical properties of titanium dioxide (TiO₂) doped with tantalum pentoxide (Ta₂O₅), tungsten trioxide (WO₃), cobalt oxide (Co₃O₄), and bismuth oxide (Bi₂O₃) and fired at different temperatures were investigated for low‐voltage applications. The adequate amount of dopants at suitable sintering temperature had beneficial effect in improving the properties of TiO₂. The relative density was found to be more than 97% of theoretical density when samples sintered between 1300°C and 1400°C for all composition compared to undoped samples. On the other hand, the addition of dopants enhanced hardness and compressive strength of varistor disks. The average grain size was also increased with the dopants system, making it suitable for low‐voltage application. Furthermore, the current–voltage characteristic of the TiO₂ revealed a significantly high value of nonlinearity of 19.6. A high dielectric constant of 10⁴ with minimum dissipation factor of 0.002852 at 1 kHz was also obtained, thereby making it suitable for low‐voltage application.     

Effect of acid treatment on the composition and structure of a natural aluminosilicate and on its catalytic properties in α-pinene isomerization

The article deals with the effect of the conditions of modification of a natural aluminosilicate catalyst with a 10% HCl solution on the chemical and phase compositions, porous and crystal structures, and acidity of the material and on its catalytic properties in α-pinene isomerization. Treatment of the aluminosilicate with 10% HCl (25–250 mL per gram of solid) causes cation exchange, increases the concentration of protonic sites on the aluminosilicate surface, and removes impurity calcite and dolomite. The specific surface area of the aluminosilicate increases from 52 to 68–82 m²/g. Treatment of the aluminosilicate with 175.0 or 250.0 mL/g of HCl removes a considerable amount framework Al³⁺, Fe^2+/3+, and Mg²⁺ cations, leading to a partial disruption of its structure and to a decrease in its acidity, specific surface area, and, as a consequence, catalytic activity relative to the same parameters of the samples treated with 50 or 100 mL/g of HCl. The highest catalytic activity is displayed by the aluminosilicate treated with 50 mL/g of HCl. The camphene and dipentene selectivity of the reaction (at 85% α-pinene conversion) with the original catalyst is 55 and 30%, respectively; modifying the aluminosilicate with HCl raises the camphene selectivity and reduces the dipentene selectivity by 5–6%. The catalyst considered here is more active than the commercial titanium catalyst.     

A facile synthesis strategy of fungi-derived porous carbon-based iron oxides composite for asymmetric supercapacitors

Transition metal oxides (TMOs) have been considered as potential anode materials for asymmetric supercapacitors due to their high theoretical capacities. However, undesirable electric conductivity limits the further application in future energy storage. Here, a honeycomb-like architecture of FeOx embedded in the fungi-derived porous carbon-based material (FeOx/C) for asymmetric supercapacitor was reported. The facile synthesis strategy of fungi-derived porous carbon-based iron oxides was using the carbon derived from fungi and the process of carbothermal reduction to form the iron oxide compound. This carbon-encapsulated iron oxide compound provides highly specific surface area (The specific surface area of Fe–O–C-650 was largest (up to 219.0905 m²/g) compared with samples of Fe–O–C-550(144.0304 m²/g), Fe–O–C-750(201.7352 m²/g), Fe–O–C-850(163.2206 m²/g).), an abundance of redox sites, sufficient efficient channels for fast transportation of ions, excellent electrical conductivity, and stable skeleton. Under the three-electrode test system, the FeOx/C electrode delivers excellent specific capacitance of 565F/g at 1 mV/s and impressive cycling performance with capacitance retention of 100% after 3000 cycles. And the NiO electrode delivers a high specific capacitance of 425 F/g at a high current density of 5 mV/s. In addition, the FeOx/C//NiO asymmetric supercapacitor was assembled which exhibits remarkable specific capacitance of 111F/g at 10 mV/s and gravimetric energy density of 36 Wh/kg as well as gravimetric power density of 800W/kg with capacitance retention of 100% after 20,000 cycles, approaching those of ions capacitors.     

The influence of dopants on the catalytic activity of hematite in the ethylbenzene dehydrogenation

The effect of neodymium, lanthanum, aluminum and zirconium on the textural and catalytic properties of hematite was studied in this work, which aimed to develop catalysts to ethylbenzene dehydrogenation, in the presence of steam, the main commercial route to obtain styrene. Hematite and magnetite were found in fresh and spent catalysts, respectively. All dopants increased the specific surface area of the fresh and spent catalysts and made them more resistant against reduction, but only aluminum avoided sintering during reaction. The dopants increased the catalytic activity per area of hematite, except aluminum which acted only as a textural promoter. The selectivity was decreased due to zirconium and lanthanum while the other dopants did not change this parameter. The neodymium-containing catalyst showed high levels of activity and selectivity and was able to work up to 530 °C, without deactivation, being the most promising with regard to styrene production.     

Synthesis of Ni,N co-doped TiO<Subscript>2</Subscript> using microwave-assisted method for sodium lauryl sulfate degradation by photocatalyst

A titanium dioxide (TiO₂) photocatalyst was modified with nickel (Ni) and nitrogen (N) in titanium tetra-isopropoxide (TTIP) as a precursor through a microwave-assisted method. The Ni and N dopants led to a decrease in the TiO₂ band gap and made it able to function with visible light irradiation. The results of X-ray diffraction analysis demonstrated that the crystalline size of Ni–N–TiO₂ was 13.275 nm in anatase form with a specific peak in 2θ = 25.32°. Ni–N–TiO₂ was analyzed by scanning electron microscopy, which showed the smaller morphology and thin particles, and this was further supported by energy-dispersive X-ray data regarding the elemental composition of Ni and N being 4.50 and 2.39%, respectively. Fourier transform infrared spectroscopy results demonstrated the absorption spectrum in wavenumbers of 1197 and 1149 cm^?1, indicating an N–TiO₂ bond, a Ti–O bond at 648 cm^?1, and an Ni–O bond at 469 cm^?1. TiO₂ modified by Ni and N exhibited a decrease in the band gap at 1.95 eV, suggesting the Ni and N dopants successfully inserted onto the TiO₂ crystalline surface to be visualized with visible light. Photoactivity testing was carried out to degrade sodium lauryl sulfate surfactants under visible irradiation, where the degradation efficiency was 93.75%.     

Arsenic (V) removal from aqueous solutions using natural clay ceramic monoliths

Abstract

An adsorbent material arranged in a ceramic monolith (CM) obtained by extrusion technique using natural bentonite and alumina (as raw materials) is presented. Ceramic and raw materials were characterized by X-ray fluorescence, thermal analysis, X-ray diffraction, and textural analysis (with N₂ adsorption–desorption at 77?K and Hg intrusion–extrusion porosimetry) to determine their chemical and physical properties. Then, As (V) adsorption capacity of the CM at different pH (3–9) using arsenic aqueous solution (with 2000?µg As (V) L^?1) was evaluated. Additionally, studies of kinetics and equilibrium of As (V) adsorption on CM were performed. It was found that: (i) the As (V) removal capacity is favored at acidic pH, reaching an average value of 15?µg As (V) per gram of CM; (ii) from kinetic studies, As (V) adsorption on CM occur in two stages, the first of them reaching a lower As uptake in a short time period, followed by an slow second stage with a subsequent higher As uptake, which continued for a longer time period, reaching equilibrium conditions in approximately 24?h; and (iii) the As (V) adsorption isotherm is a type-Langmuir, indicating that the CM present an homo quantity of fixed sites to adsorb the As (V).     

Polyelectrolyte CASA hydrogels for uptake of uranyl ions from aqueous solutions

In this study, uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked acrylamide/sodium acrylate (CASA) hydrogels. Adsorption studies were investigated by the spectroscopic method. CASA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), sodium acrylate (SA), and water by free radical polymerization in aqueous solution, using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA). Uranyl ion adsorption from aqueous solutions was studied by the batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In experiments of sorption, L‐type sorption in the Giles classification system was found. Some binding parameters, such as initial binding constant (K_i), equilibrium constant (K), monolayer coverage (n), site‐size (u), and maximum fractional occupancy (Ô) for the CASA hydrogel–uranyl ion binding system, were calculated using the Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 4.44 × 10^?4–14.86 × 10^?4 mol uranyl ion per gram for CASA hydrogels. Adsorption of uranyl ion (percentage) was changed within a range of 12.86–46.71%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 200–204, 2007     

Ultrasonic degradation of polysiloxane solutions

Fractions of dimethylsiloxane polymer with viscosity-average molecular weights from 2.4 × 10⁵ to 1.3 × 10⁶ were dissolved in toluene in concentrations from 0.01 to 1.0 g./dl. These solutions were subjected to ultrasonic degradation at 20,000 cps for periods extending to as much as 960 min. in a water-cooled reaction vessel. Gel permeation chromatography shows that samples with different initial distributions approach the same distribution after 120 min. of degradation. Dilution of the polymer from 1.0 to 0.01 g./dl. more than triples the degradation per gram of polymer but requires 10 times as much energy per gram of polymer to degrade from a number-average molecular weight of 10⁶ to 10⁵. Increasing the power input from 36 to 72 w. almost doubles the degradation rate per gram of polymer.     

The regulation of ferroelectric photovoltaics by non–compensated doping engineering

By absorbing and transferring the photons (nearby bandgap) to photoelectrons, non–compensated (Ce⁴⁺ dopants) doping Bi₅Ti₃FeO₁₅ ferroelectric films present switchable and stable photovoltaics. The defect dipole attraction in non–compensated doping films not only narrows the bandgap effectively by the creation of tunable intermediate sub–band (gap state), but enhances separation of electron–hole pairs in the visible–light region. The concept is proved by dramatic redshift of optical absorbance and intense photovoltaics. Subsequently, contrast investigations of equivalent–compensated doping films offer solid experimental evidences. Furthermore, the intensity of Coulomb attraction between defect dipoles can be destroyed by thermal perturbation, which is empirically supported by the abrupt drop of temperature dependent photovoltage at 340 K. These results demonstrate that non–compensated doping can be a promising route to construct more efficient energy transfer devices.     

Studies on the Structural,Morphological, Optical,Electro Chemical and Antimicrobial Activity of Bare,Cu and Ag @ WO<Subscript>3</Subscript> Nanoplates by Hydrothermal Method

Hydrothermal synthesis eases the lopsided growth of monoclinic bare, Cu and Ag @ WO₃ nanoplates that exhibit good physic-chemical, optical and electro chemical properties. The powder X-ray diffraction patterns reveals that the synthesized samples WO₃ samples are in monoclinic structure. The 2 mol% of Cu and Ag dopants were increases the crystallinity and the predominant peaks are shifted to higher glancing angles. The variations observed in lattice parameter values indicate the incorporation of dopants in the WO₃ crystal lattice. The FESEM and HRTEM images revealed nanoplate morphology with the particle size range 100–200 nm of diameter and 200–300 nm of thickness. The prominent absorption peak of bare, Cu and Ag @ WO₃ nanoplates were observed in visible region at 332, 326 and 323 nm respectively. The strong continuous from luminescence emission peaks were observed in blue to yellow region with optimal intensity. The electro chemical property was studied using cyclic voltammetry which reveals quick electron transfer accessed in Cu and Ag doped materials. The antimicrobial activity of synthesized bare, Cu and Ag @ WO₃ was investigated on the gram positive, gram negative and fungus strains and observed efficiency of inhibition is exclusively explained.     

New method for the preparation of solid polymer electrolyte based on poly(vinylidene fluoride-co-hexafluoropropylene)

A novel solid polymer electrolyte (pore-gel SPE) has been found to provide superior SPE having a high conductivity, good mechanical strength and low solution leakage. This pore-gel SPE was prepared from gelation in pores of polymer membrane with electrolyte solution including solvent. The conductivity of pore-gel type PVDF-HFP/ TEABF₄ (Tetraethylammomium tetrafluoroborate) membrane can reach 1.6×10^-1 Scm^-1. The tensile strength of this membrane was 4,000 kPa, which is about 23 times larger than that of gel-type SPE with the same composition. Poregel SPE reduced solution leakage to 0%, compared with 2% of hybrid-type SPE after 2.0 hr leakage test in PVDFHFP/ TEABF₄ membrane.     

R&D considerations for the performance and application of electrochemical capacitors

Research and development (R&D) of electrochemical capacitors is discussed in terms of material characteristics and device performance and testing. Various chemistries and technologies being developed are identified and the status of and problems associated with each of the technologies are discussed. The technologies considered include those using various types of carbon and pseudo-capacitive materials such as metal oxides. What is needed to make the various electrochemical capacitor technologies cost competitive with batteries for different applications and markets is also considered.Electrochemical capacitors (especially double-layer capacitors) are intrinsically high power devices of limited energy storage capability and long cycle life; batteries are basically energy storage devices, which can be designed and used as relatively high power devices with a sacrifice in useable energy storage capacity. Both electrochemical capacitors and high power batteries are designed with thin electrodes, materials having nano-scale characteristics, and a minimum resistance. Much of the research on electrochemical capacitors is concerned with increasing their energy density with the minimum sacrifice in power capability and cycle life for deep discharges. Of special interest has been the development of advanced carbons with specific capacitance (F/g) significantly greater than the present values of 150-200 F/g in aqueous electrolytes and 80-120 F/g in organic electrolytes. Cost continues to be a major obstacle to the development of large markets for electrochemical capacitors particularly for vehicle applications. The development of lower cost carbons appropriate for use in electrochemical capacitors is underway by several speciality carbon suppliers. The goal is to reduce the cost of the carbon to $10-15/kg.