教学课程资源库 更多>>

关键词： Clay characterizations   Fired clay bricks   Firing behavior   Construction materials suitability   Thermal properties   Mechanical properties  

摘要： This study aims at the valorization of unexploited clay from a rural village called Bensmim by investigating its potential suitability as a construction material. Two clays samples (Babmansour and Extrabrick) used in the clay brick manufacturing were also considered as a reference. The followed methodology consists of identifying the physicochemical properties of the raw materials and examining its influence on the final products properties (linear shrinkage, thermal conductivity, and compressive strength). The firing characteristics of the samples under study at different temperatures (650 degrees C, 850 degrees C, and 950 degrees C) were determined by linear shrinkage, compressive strength, and thermal conductivity. The results show that the clayey fraction of Bensmim consists mainly of illite and kaolinite. However, Extrabrick and Babmansour contain kaolinite with moderate amounts of smectite. The major oxides presented in all clays samples are SiO2 (57-59.6 wt%), Al2O3 (10.38-23.29 wt%), and Fe2O3 (3.78-6.58 wt%). The amount of CaO in Extrabrick clay is about of 10.61% and 11.14% for Babmansour, whereas it is almost absent in Bensmim clay. Extrabrick and Babmansour clays samples are considered as calcareous clay (CaO > 10%) characterized by a moderate specific surface and high plasticity due to their high clay fraction and moderate smectite content. While Bensmim has a weak specific surface and low plasticity due to the absence of swelling phase in its clay fraction and the excessive amount of sand. The performed tests attest high thermal properties of Bensmim clay, with good linear shrinkage. Unfortunately, under 950 degrees C, Bensmim clay presents low compressive strength. However, this can be adjusted by a small addition of the plastic clays. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Oxides   Metal to ligand charge transfer   Ligands   Layers   Solar cells  

摘要： Heteroleptic ruthenium (II) complexes were used for sensitizing ZnO surfaces in organic solar cells (OSCs) as mediators with photoactive layers. The complexes [Ru(4,4'-X-2-bpy)(Mebpy-CN)(2)](2+) (with X = -CH3, -OCH3 and -N(CH3)(2);bpy = 2,2'-bipyridine;Mebpy-CN = 4-methyl-2,2'-bipyridine-4'-carbonitrile) were synthesized and studied by analytical and spectroscopical techniques. Spectroscopic, photophysical, and electrochemical properties were tuned by changing the electron-donating ability of the -X substituents at the 4,4'-positions of the bpy ring and rationalized by quantum mechanical calculations. These complexes were attached through nitrile groups to ZnO as interfacial layer in an OSC device with a PBDB-T:ITIC photoactive layer. This modified inorganic electron transport layer generates enhancement in photo-conversion of the solar cells, reaching up to a 23% increase with respect to the unsensitized OSCs. The introduction of these dyes suppresses some degradative reactions of the nonfullerene acceptor due to the photocatalytic activity of zinc oxide, which was maintained stable for about 11 months. Improving OSC efficiencies and stabilities can thus be achieved by a judicious combination of new inorganic and organic materials.

关键词： Postharvest storage   Common bean   Glycosylated kaempferol   Antioxidant capacity   Phenolic compounds  

摘要： Carioca beans contribute to health maintenance around the world, and the evaluation of commercial postharvest storage (CPS) ensures their quality. This study aimed to evaluate the effect of CPS on technological, physicochemical and functional properties of carioca beans. Two genotypes (Pontal-PO and Madreperola-MP beans) were stored under CPS or controlled conditions and were evaluated after harvest and after threeand six-months storage. PO and MP hardened with time, but the cooking time did not differ. PO is darker than MP and both darkened over time. Storage time affected pH and acidity of the beans and MP presented better physicochemical properties than PO, with lower activity of peroxidase (p = 0.004) and polyphenoloxidase (p = 0.001) enzymes. Glycosylated kaempferol was suggested as a possible chemical marker to differentiate the aging of PO and MP beans. In conclusion, besides the technological differences, the storage was able to prevent physicochemical and functional alterations of beans.

关键词： Physicochemical   Leaching properties   Coal ashes   Toxicity characteristic leaching procedure   Synthetic precipitation leaching procedure   Heavy metals  

摘要： Coal ash (fly (FA) and bottom (BA) ashes) contain heavy metals. This research presents physicochemical and leaching properties of coal ashes (FA, BA and FA + BA) from a Malaysian power plant. The physicochemical (X-ray fluorescence (XRF) and scanning electron microscopy (SEM)) and leaching properties (toxicity characteristic leaching (TCLP) and synthetic precipitation leaching (SPLP) procedures) of ash samples were determined. Heavy metals like lead (Pb), zinc (Zn), copper (Cu) and arsenic (As) were quantified using atomic absorption spectrometer (AAS). Leaching properties were found to complied to the standard guidelines for heavy metals. Further investigation on leaching properties is recommended for construction industry applications.

关键词： Rice bran   Dietary fiber   Crystalline structure   Thermal stability   Micro-structure   Chemical composition   Cellulase  

摘要： Rice bran dietary fiber (ERBDF) subjected to pre-water-washing and complex enzyme treatment using heat stable alpha-amylase, alcalase, and glucoamylase had significantly higher (p < 0.05) proportions of cellulose, hemicellulose, lignin, and lower proportions of lipid, protein, and starch than rice bran dietary fiber subjected to complex enzyme treatment without pre-water-washing. Cellulase modification of ERBDF significantly decreased (p < 0.05) cellulose, hemicellulose, starch, and protein contents while the relative lignin content increased. Cellulase modification significantly improved (p < 0.05) water-holding capacity, oil-holding capacity, swelling capacity, cholesterol absorption capacity, and glucose adsorption capacity, while decreasing the emulsifying capacity and glucose dialysis retardation index. The changes of physicochemical and functional properties of fiber samples after cellulase modification were attributed to the increased porosity of the fiber surface, greater exposure of binding sites caused by reduced crystallinity, and changes to the chemical composition.

关键词： Ionic liquid   Anionic surfactants   Micellization behavior   Human serum albumin   Fluorescence   FTIR  

摘要： The physicochemical properties on micellization of anionic surfactant, sodium dodecyl sulphate (SDS) and lithium dodecyl sulphate (LDS) in the presence of imidazolium-based ionic liquid 1-decyl-3-methylimidazolium tetrafluoroborate [Dmim][BF4] have been studied using surface tension and conductivity techniques. The interfacial and thermodynamic parameters have also been determined. FTIR has studied the aggregation behavior while aggregation number and Stern-Volmer constant is determined by fluorescence measurement. The current results indicate that the addition of [Dmim][BF4] to the anionic surfactant leads to a dramatic decrease in the CMC. The interaction of human serum albumin with micellar solution of SDS and LDS have been examined.

关键词： Imidazolium-based ionic liquids   Physicochemical properties   Temperature-Dependence   Scavengers  

摘要： Three types of imidazolium-based ionic liquids (IMILs) were synthesized and characterized by C-13 and H-1 NMR, FT-IR, and elemental analysis. Thermal stability and physicochemical properties of prepared IMILs were measured in the temperature range of 283.15 to 363.15 K. The physicochemical results revealed the entirely temperature-dependent properties and quietly decreasing through increasing the temperature. Electrochemical studies of the IMILs were also performed at the surface of screen-printed electrode cells. Consideration of these properties and determining the unique abilities of IMILs will help researchers through modern applications like liquid-liquid extraction, particular tasks of scavenging and removal of hydrogen sulfide and thiols from petroleum matrices. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Physicochemical properties  

摘要： The functionality and property of pectin are correlated with its structure which is affected by the extraction method used. In this study, three different methods of extracting pectin, the microwave-assisted extraction (MAE), the ultrasonic-assisted extraction (UAE) and the conventional heating extraction (CHE), were used at three different temperatures with both an acid and alkali extraction solution. It was found that temperature mainly influenced pectin yield, while pectin structures and physicochemical properties were affected by the pH condition and extraction technology. The alkali-extraction with MAE and UAE at short time promoted the yield of low-ester pectin. Monosaccharide composition analysis showed a high galacturonic acid (GalA) content in the pectin derived from MAE and UAE. The high viscosity and desirable viscoelastic properties of the acid-MAE pectin were due to its large molecular weight and particle size. The results contribute to our understanding of the association among pectin extraction, structure and properties. © 2021 Elsevier Ltd

关键词： Aromatization   Pyridin FTIR   Zn-modified ZSM-5 zeolite   Boron promoter  

摘要： The characterization and catalytic performance of Zn/ZSM-5 and Zn-B/ZSM-5 catalysts in the n-hexane aromatization was reported. Catalysts were prepared by post-synthesis ion exchange and thoroughly characterized by means of XRD, Py-FTIR, N-2 adsorption, Al-27 and B-11 MAS NMR spectroscopy and electron microscopy techniques. The incorporation of zinc reduces the Bronsted acid site density and increases the Lewis acidic sites of the final ZSM-5 based catalysts. The presence of boron slightly reduces the initial activity of the catalyst but slows down its deactivation rate.

关键词： crop rotation   no till   soil cover   soil quality   soil organic matter  

摘要： Maize (Zea mays L.) is Mexico's primary staple food, but the Country's degrading soils and climate variability limit its productivity. Conservation agriculture (CA), a management technique that combines minimal tillage, permanent soil cover, and crop diversification, could reduce soil degradation and help improve soil health. There is however a lack of information about the effects of CA on soil health in the diverse agroecological conditions in Mexico. This study reports results of a field trial network established to adapt CA to Mexico's diverse cropping systems and local conditions. Physicochemical soil health, also referred to as soil quality, was studied in 20 trials in agro-ecologies ranging from handplanted traditional systems to intensive irrigated systems, initiated between 1991 and 2016. Soil in CA was compared to the local conventional practice (CP), which commonly involves tillage, residue removal, and continuous maize production. Across the sites, organic matter and nitrates were higher in the top (0-5 cm) layer of soil and soil aggregate stability was greater under CA than under CPs. For other soil health parameters, such as nutrient content, pH or penetration resistance, the effects of management varied widely across sites and soil types and most were determined more by local soil type than by management. CA increased maize yields at most sites and on average by 0.85 +/- 1.80 t ha(-1). Given the significant variation across agro-ecologies, local adaptive trials are important to assess the effects of CA on soil health and fit the practice to local conditions.