Combination Of Chemical Pretreatments Research Articles

Characteristics of In0.7Ga0.3As MOS Capacitors Obtained using Hydrochloric Acid Treatment, Ammonium Sulfide Passivation, Methanol Treatment, and Forming Gas Annealing

This paper proposes a chemical pre-treatment process to reduce sulfate prior to atomic layer deposition of Al2O3 gate dielectrics on n-doped In0.7Ga0.3As layers to form metal oxide semiconductor capacitors (MOSCAPs). Cleaning with methanol was done after hydrogen chloride etching and ammonium sulfide passivation. X-ray photoelectron spectroscopy performed on the sample with methanol cleaning indicated that its native oxide regrowth was effectively prevented on the sulfur-passivated In0.7Ga0.3As surface under air exposure. By analysis using atomic force microscopy of the sample cleaned using methanol, no further increase of surface roughness was observed after 5 months of air exposure. In addition, a mid-gap interface defect density (Dit) of 1.3 × 1012 cm−2 eV−1 was obtained from this sample. After forming gas annealing (FGA), the Dit was improved significantly, to a value below 1012 cm−2 eV−1. The obtained data indicate that the combination of chemical pre-treatment and FGA is advantageous to passivating the trap states on In0.7Ga0.3As MOSCAPs.

Natural cellulose nanofiber extracted from cell wall of bamboo leaf and its derived multifunctional aerogel

In the current research, high‐purity natural cellulose nanofiber (CNF) from bamboo leaf (BL) was successfully obtained via a combination of chemical pretreatment and ultrasonic technique. The as‐prepared CNF was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), thermogravimetric and differential thermal analysis (TGA−DTG). The as‐obtained CNF had an average diameter of 53.2 nm and a high aspect ratio of about 5600. The crystallinity of CNF was 55%, which increased by 27% compared to that of the raw BL. With further modification by methyltrimethoxysilane (MTMS), the aerogel derived from the obtained CNF through a freeze‐drying process showed superior multifunctions of superabsorbent performance, thermal insulation, and sound absorption. The study might provide a new family of nature‐based nanocellulose. POLYM. COMPOS., 39:3869–3876, 2018. © 2017 Society of Plastics Engineers

Poly(vinyl alcohol) films reinforced with nanofibrillated cellulose (NFC) isolated from corn husk by high intensity ultrasonication

This work was aimed at fabricating and characterizing poly(vinyl alcohol) films that were reinforced by nanofibrillated corn husk celluloses using a combination of chemical pretreatments and ultrasonication. The obtained nanofibrillated celluloses (NFCs) possessed a narrow width ranging from 50 to 250nm and a high aspect ratio (394). The crystalline type of NFC was cellulose I type. Compared with the original corn husks, the NCF crystallinity and thermal stability increased due to the removal of the hemicelluloses and lignin. PVA films containing different NFC concentrations (0.5%, 1%, 3%, 5%, 7% and 9%, w/w, dry basis) were examined. The 1% PVA/NFC reinforced films exhibited a highly visible light transmittance of 80%, and its tensile strength and the tensile strain at break were increased by 1.47 and 1.80 times compared to that of the pure PVA film, respectively. The NFC with high aspect ratio and high crystallinity is beneficial to the improvement of the mechanical strength and thermal stability.

Fabrication and characterization of nanofibrillated cellulose and its aerogels from natural pine needles.

To obtain the nanofibriled cellulose from natural pine needles, a combination of chemical pretreatments and subsequently ultrasonic treatments was employed for removing the hemicelluloses and lignins and splitting the bundled cellulose into pine needle nanofibers. Using SEM and diameter distribution method, it was confirmed that the obtained pine needle nanofibers had a narrow diameter from 30 to 70 nm. The crystalline type of the pine needle nanofibers was the cellulose I type. The crystallinity reached 66.19%, which was increased by 7.61% as compared with the raw material pine needles. The TGA and DTG results showed that the degradation temperature of the nanofibers was increased to approximately 267 and 352°C compared with 221 and 343°C of the raw material fibers, respectively. Furthermore, the highly flexible and ultralight pine needle nanofibers aerogels were prepared from the aqueous pine needle nanofibers solution using the freezing-drying technique. Aerogels were studied by SEM observation and nitrogen gas adsorption. The mechanical properties were measured in compression for aerogels. This study provides a new opportunity to fabricate novel nanomaterials from waste biomass materials, which is crucial for the fully utilizing of abundant biomass resources.

Energy Dispersive X-Ray Microanalysis of Elemental Distribution in Raw and Germinated Brown Rice Varieties

In this study, the mineral composition of germinated brown rice, brown rice, and white rice was evaluated. Brown rice grain was processed through a combination of chemical pretreatment and low oxygen treatment, after which germination was confirmed through imaging under a microscope. Using energy dispersive X-ray analysis, Mg, Al, and Cl were found to be slightly higher in germinated brown rice than in brown rice and white rice. These variations in the mineral content of germinated brown rice were attributed to the joint effect of the germination process and the prior soaking. The inability of energy dispersive X-ray to detect other minerals suggested that it was not sensitive and, hence, it was not suitable for studying elemental distribution in rice grains, or maybe the elements were not present in the rice grains studied.

Chemical Pretreatment Methods for the Production of Cellulosic Ethanol: Technologies and Innovations

Pretreatment of lignocellulose has received considerable research globally due to its influence on the technical, economic and environmental sustainability of cellulosic ethanol production. Some of the most promising pretreatment methods require the application of chemicals such as acids, alkali, salts, oxidants, and solvents. Thus, advances in research have enabled the development and integration of chemical-based pretreatment into proprietary ethanol production technologies in several pilot and demonstration plants globally, with potential to scale-up to commercial levels. This paper reviews known and emerging chemical pretreatment methods, highlighting recent findings and process innovations developed to offset inherent challenges via a range of interventions, notably, the combination of chemical pretreatment with other methods to improve carbohydrate preservation, reduce formation of degradation products, achieve high sugar yields at mild reaction conditions, reduce solvent loads and enzyme dose, reduce waste generation, and improve recovery of biomass components in pure forms. The use of chemicals such as ionic liquids, NMMO, and sulphite are promising once challenges in solvent recovery are overcome. For developing countries, alkali-based methods are relatively easy to deploy in decentralized, low-tech systems owing to advantages such as the requirement of simple reactors and the ease of operation.

Bioethanol Production from Rice Straw

Problem statement: Rice straw has been treated with different chemical (acid, alkali) and physical (subcritical water, ultrasound) methods to convert lignocellulose material to sugar. In addition enzyme treatment of pretreated samples has been applied to improve the conversion of lignocellulose material in sugar. Approach: Sulfuric acid at concentration of 1-9% was applied for acid treatment. For alkali treatment was sodium hydroxide solution at concentration of 1-5% used. Subcritical water treatment carried out at 160°C (5 bar) and 200°C (15 bar) for 10 min. Ultrasound was applied as combination method after acid pretreatment. The condition during ultrasound treatment was 40 W at 50°C and 10 min. Finally the pretreated sample was fermented using Saccharomyces cerevisiae yeast and the amount of produced ethanol was measured. Results: Acid treatment at 121°C, 15 min is an effective pretreatment method for converting lignocellulose to sugar. Up to 21.45% sugar w/w could be measure after acid treatment. Combination of chemical pretreatment and subsequent enzyme treatment increased the sugar yield drastically. Up to 37 and 28% sugar w/w could be achieved for acid and alkali pretreated samples respectively. Subcritical Water (SCW) treatment method is an effective physical method. SCW treatment at 200°C and 10 min followed by enzyme treatment yielded up to 17% sugar w/w. Combination of acid pretreatment with ultrasonic before enzyme treatment increased the conversion of lignocelluloses to sugar. Sugar yield up to 44% w/w after combination of acid and ultrasonic pretreatment and subsequent enzyme treatment could be achieved. Fermentation of pretreated rice straw shown that after 3 days fermentation most of sugar (55-65%) will be converted to bioethanol. The remaining sugar could not be converted in ethanol even after 6 days fermentation. Under these conditions, the maximum ethanol of 1.69% (v/v) was obtained. Conclusion: The combination method of acid pretreatment combined with ultrasound and subsequent enzyme treatment result the highest conversion of lignocelluse in rice straw to sugar and consequently, highest ethanol concentration after 6 days fermentation with S. cerevisae yeast.