A New Approach for the Leaching of Palladium from Spent Pd/C Catalyst in HCl–H2O2 System

Protection of Metals and Physical Chemistry of Surfaces - Recovery of the spent precious metal catalysts by suitable methods is very important for chemical industries. This work introduces a new...     

Investigation of the Possibility of the Insecticide Diagnosis Using Infrared Thermography

Russian Journal of Nondestructive Testing -     

A novel double Ag@AgCl/Cu@Cu2O plasmonic nanostructure: Experimental design and LC-Mass detection of tetracycline degradation intermediates

Here a novel sunlight-driven double-plasmonic Ag^@AgCl/Cu^@Cu₂O nanophotocatalyst was constructed via photochemical-conversion and photoreduction methods for the first time. The as-prepared Ag^@AgCl/Cu^@Cu₂O was characterized by several characterizations techniques. The Scherrer equation showed the crystallite sizes of 37, 25, and 40 nm for the as-prepared Ag^@AgCl, Cu^@Cu₂O and Ag^@AgCl/Cu^@Cu₂O catalysts, while their band gap energies were 3.36, 2.51, and 3.04 eV (DRS results), respectively. TC (tetracycline) served as a probe to study its photocatalytic activity under sunlight. It was found that the as-prepared nanophotocatalyst with suitable Ag^@AgCl and Cu^@Cu₂O content not only demonstrated superior photocatalytic activity to both Ag^@AgCl and Cu^@Cu₂O plasmonic nanoparticles, but also had remarkable photostability due to the presence of two simultaneous surface plasmon resonance (SPR) in metallic Ag and Cu NPs and the hetero-junction structure formed at the interface between Ag^@AgCl and Cu^@Cu₂O. The main active species were detected through a trapping experiment which confirmed that ^?O₂^? and ^?OH were the main active species in the photocatalytic system. Central composite design (CCD) was used for the modeling and optimization of the photodegradation process. The possible photocatalytic degradation pathway of TC was proposed based on the identified intermediates. The photodegradation rate constant of TC was about 0.043 min^?1 (t_1/2 = 0.910 min) (in the range of 5–60 min). The optimum RSM run had the conditions the TC concentration of 2.0 (mg/L), Ag^@AgCl/Cu^@Cu₂O dosage of 0.53 (g/L), irradiation time 18 (min), and pH value of 6.5.     

Polyacrylamide-induced coagulation process removing suspended solids from palm oil mill effluent

Palm oil mill effluent (POME) is a colloidal suspension with 2–4% suspended solids. About 50% of the suspended solids are cellulosic compounds, which are not degraded in the typical biological treatment systems. Chemical (polymer-induced coagulation) and physical (settling) pretreatment methods were examined to remove the suspended solids in this study. A novel physicochemical treatment with high water recovery and sludge compressibility including three cationic polyacrylamides (C-PAM; as coagulant) and three anionic polyacrylamides (A-PAM; as flocculant) with different molecular weights and charge densities was used. The coagulants used were biodegradable. The combination of a C-PAM (Chemfloc1515C) with medium molecular weight and charge density and an A-PAM (Chemfloc 430A) with high molecular weight and charge density at doses of 300 and 50 mg/dm³ showed the best total suspended solids (TSS) and chemical oxygen demand (COD) removal (96.4 and 70.9%, respectively). The optimal condition was found at pH 5, rapid mixing at 150 rpm for 1 min, and slow mixing at 40 rpm for 30 s. As a conclusion, the physiochemical pretreatment using biodegradable coagulants was a promising alternative to effectively separate TSS (96.4%) with high water recovery (76%).     

Enhancement-mode metal/(Al,Ga)As/GaAs buried-interface field-effect transistor (BIFET)

Undoped Al0.5Ga0.5As is used as an insulator layer in the fabrication of MIS-type buried-interface field-effect transistors (BIFETs). The devices had a 2.5 ?m-long gate and an insulator layer 1000 ? thick. When operated in an accumulation mode the transconductance and maximum current increased from 21 mS/mm and 77 mA/mm at 300 K to 40 mS/mm and 138 mA/mm at 77 K, respectively. The maximum possible 77 K transconductance is calculated as approximately 130 mS/mm. These preliminary experimental results are the best yet reported for a GaAs MIS-type device and represent the first report of enhanced device performance at cryogenic temperatures as a result of an increased electron saturation velocity.     

Functionalized titania nanotube composite membranes for high temperature proton exchange membrane fuel cells

In this study, functionalized titania nanotubes (F-TiO₂-NT) were synthesized by using 3-mercaptopropyl-tri-methoxysilane (MPTMS) as a sulfonic acid functionalization agent. These F-TiO₂-NT were investigated for potential application in high temperature hydrogen polymer electrolyte membrane fuel cells (PEMFCs), specifically as an additive to the proton exchange membrane. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results confirmed that the sulfonic acid groups were successfully grafted onto the titania nanotubes (TiO₂-NT). F-TiO₂-NT showed a much higher conductivity than non-functionalized titania nanotubes. At 80 °C, the conductivity of F-TiO₂-NT was 0.08 S/cm, superior to that of 0.0011 S/cm for the non-functionalized TiO₂-NT. The F-TiO₂-NT/Nafion composite membrane shows good proton conductivity at high temperature and low humidity, where at 120 °C and 30% relative humidity, the proton conductivity of the composite membrane is 0.067 S/cm, a great improvement over 0.012 S/cm for a recast Nafion membrane. Based on the results of this study, F-TiO₂-NT has great potential for membrane applications in high temperature PEMFCs.     

High performance porous polybenzimidazole membrane for alkaline fuel cells

In this study, a highly ion-conductive and durable porous polymer electrolyte membrane based on ion solvating polybenzimidazole (PBI) was developed for anion exchange membrane fuel cells (AEMFCs). The introduction of porosity can increase the attraction of electrolytic solutions (e.g., potassium hydroxide (KOH)) and ion solvation, which results in the enhancement of PBI's ionic conductivity. The morphology, thermo-physico-chemical properties, ionic conductivity, alkaline stability, and the AEMFC performance of KOH-doped PBI membranes with different porosities were characterized. The ionic conductivity and AEMFC performance of 70 wt.% porous PBI was about 2 times higher than that of the commercially available Fumapem^® FAA. All KOH-doped porous PBI membranes maintained their ionic conductivity after accelerated alkaline stability testing over a period of 14 days, while the commercial FAA degraded just after 3 h. The excellent performance and good durability of KOH-doped porous PBI membrane makes it a promising candidate for AEMFCs.     

Exciton localization in vertically and laterally coupled GaN/AlN quantum dots

Near-field and time-resolved photoluminescence measurements show evidence of exciton localization in vertically and laterally coupled GaN quantum dots (QDs). The binding energies in multiple period QDs (MQDs) are observed to be stronger by more than six times compared to single period QDs (SQDs). Excitons in MQDs have a short (450 ps) lifetime and persist at room temperature, while SQDs exhibit extraordinarily long (>5 ns) lifetime at 10 K due to reduced spatial overlap of electron and hole wave functions in strained QDs.     

III-Nitride semiconductor growth by MBE: Recent issues

Semiconductor III-Nitrides, such as GaN, AlN, InN and their ternaries, have recently gained considerable attention after an uneven effort around the first half of the 1970s which paved the way to intense activity in the preceding decade. This is in part due to early obstacles achieving high quality layers, particularly those with p-type conductivity. With marketing of blue LEDs, the interest and consequently the effort grew to the point that CW lasers, high power amplifiers, and UV detectors have been added to the list of devices made in this material system. GaN and its allied semiconductors are grown with a variety of techniques. Generally, thick GaN layers are grown with hydride vapor phase epitaxy whereas the thin ones and heterojunctions formed by the above mentioned binaries and their ternaries are grown by organometallic vapor phase epitaxy and molecular beam epitaxy. OMVPE uses ammonia and metalorganics for group V and III elements whereas MBE uses either ammonia or RF activated , and metal for group III elements. Among the above mentioned thin-film growth methods, only the issues pertaining to MBE will be reviewed in this paper.