Nitrogen Absorption Method Research Articles

Effects of Biological and Chemical Degradation on the Properties of Scots Pine Wood-Part I: Chemical Composition and Microstructure of the Cell Wall.

Research on new conservation treatment for archaeological wood requires large amounts of wooden material. For this purpose, artificial wood degradation (biological—using brown-rot fungus Coniophora puteana, and chemical—using NaOH solution) under laboratory conditions was conducted to obtain an abundance of similar samples that mimic naturally degraded wood and can serve for comparative studies. However, knowledge about its properties is necessary to use this material for further study. In this study, the chemical composition and microstructure of degraded cell walls were investigated using FT-IR, XRD, helium pycnometry and nitrogen absorption methods. The results show that biological degradation caused the loss of hemicelluloses and celluloses, including the reduction in cellulose crystallinity, and led to lignin modification, while chemical degradation mainly depleted the amount of hemicelluloses and lignin, but also affected crystalline cellulose. These changes affected the cell wall microstructure, increasing both surface area and total pore volume. However, the chemical degradation produced a greater number of mesopores of smaller size compared to fungal decomposition. Both degradation processes weakened the cell wall’s mechanical strength, resulting in high shrinkage of degraded wood during air-drying. The results of the study suggest that degraded wood obtained under laboratory conditions can be a useful material for studies on new consolidants for archaeological wood.

Interfacial self-assembly of porphyrin-based SURMOF/graphene oxide hybrids with tunable pore size: An approach toward size-selective ambivalent heterogeneous photocatalysts

New photocatalysts were synthesized from graphene oxide (GO) and zinc porphyrins via non-covalent self-assembly in Pickering emulsions. The formation of surface-attached metal organic frameworks (SURMOFs) with different size of mesopores (1.1. and 1.6 nm) was confirmed by X-ray powder diffraction and BET nitrogen absorption methods. The activity of the SURMOF/GO materials in photodegradation of rhodamine 6G (Rh6G) and 1,5-dihydroxynaphtalene (DHN) were studied spectroscopically. The photocatalysts initiate aerobic oxidative photodestruction with k up to 2.3 × 10−1 min−1 through generation of singlet oxygen on porphyrin centers. Under anaerobic conditions, these materials assist photoreduction of the same dyes in the SURMOF micropores. The mechanisms of photodegradation assisted by SURMOF/GO hybrids were confirmed by a combination of MALDI-TOF spectroscopy, Sensor Green and terephthalic acid probing. The size of the SURMOF pores controls the reduction, which occur due to the effective charge separation between porphyrin SURMOFs and GO. The photocatalyst with larger pores can transform both Rh6G and DHN, whereas that one with smaller pores is active only with respect to small DHN molecules. The ability of as-formed SURMOF/GOs to exploit two mechanisms yielding different products of photodestruction provides a basis for creating novel ambivalent photocatalysts for selective transformations of targeted compounds in molecular mixtures.

Effect of KyAl4(Si8-y) O20(OH)4 Calcined Based-Clay on the Microstructure and Mechanical Performances of High-Performance Concrete

The work described in this paper has been performed to determine the potential use of meta-illite (KyAl4(Si8-y) O20(OH)4) calcined clay (MCC) as a supplementary cementitious material (SCM) in a binary Portland cement (PC) for high-performance concrete (HPC) production. To obtain the properties of the cementitious materials, the chemical composition, mineral phases, morphology, calcination efficiency and physical properties were quantitatively analysed using the advanced techniques of X-ray fluorescence (XRF), scanning electron microscopy/energy dispersive X-ray (SEM/EDX), X-ray diffraction (XRD), Fourier transform infrared/attenuated total reflection (FTIR/ATR), thermogravimetric analysis (TGA), laser particle sizing and Brunauer–Emmett–Teller (BET) nitrogen absorption method. The MCC’s effect on the workability and mechanical properties (compressive, splitting tensile and flexural strengths) and microstructure (morphology and crystalline phases) of hardened MCC-based HPCs were determined. The XRF result shows that the oxide composition of MCC confirmed the pozzolanic material requirements with recorded high useful oxides content. At the same time, the SEM image presents particles of broad, solid masses with a wider surface area of irregular shape. The XRD results show that the MCC was majorly an illite-based clay mineral calcined at a maximum temperature of 650 °C, as revealed by the TGA. The MCC addition increases the slump flow of HPCs at 5–15% cement replacement. The MCC incorporation at 10% cement replacement best improved the porosity of HPCs at a later age resulting in increased mechanical and microstructural properties of tested samples. Therefore, it is recommended that MCC addition within 10% cement replacement be adopted for low W/B Class I HPC at no deleterious results on mechanical and microstructural properties of the concrete.

Influence of specific surface area on sulfate attack–induced expansion of cement-treated aggregates

Sulfate attack–induced expansion of cement-treated aggregates is a well-known problem to be addressed causing remarkable heave in road and railway subgrades. The specific surface area (SSA) of the materials influences chemical reactions significantly. In this study, cement, sodium sulfate, and basalt powder were ground in a ball mill for 0 (without grinding), 5, 10, 30, and 60 min respectively to achieve different SSA gradients. Under the curing condition of a constant temperature of 10 °C and humidity of 70%, with 5% cement, the effects of sodium sulfate contents and SSA gradients on the expansion of sulfate attack in cement-treated aggregate (SACA) were investigated during 60 days in laboratory. Based on nitrogen absorption methods, microscopic tests, and swelling tests, the results show that, grinding within 60 min, the respective peak value of SSAs of cement, mixture of 3% (or 8%) sodium sulfate and basalt powder, and mixture of 3% (or 8%) sodium sulfate, cement, and basalt powder was 1.867 m2/g, 1.109 m2/g (or 1.393 m2/g), and 1.128 m2/g (or 1.404 m2/g), respectively. The SSAs increase as the aggregates refined, then decrease as the aggregates gathered. The strain variation can be generally divided into four stages with 3% sodium sulfate attack in cement-treated aggregate (3% SACA): rapid strain increase, short stagnation, continuous heave, and constant strain. Two stages of strain variation have been observed with 8% sodium sulfate attack in cement-treated aggregate (8% SACA): rapid strain increase, and a constant strain. Finer needle-like ettringite crystals (average length: 0.5–1 μm) filling in the smaller holes produce the greater expansion induced by SACA. Based on grey incidence analysis, the SSAs of cement, mixture of sodium sulfate and basalt powder (S+B), and the whole mixture of cement, sodium sulfate, and basalt powder (C+S+B) have a significant effect on strain. This work provides theoretical support for amending SACA at the SSA level.

METHOD FOR OBTAINING BIOSORBENT AND STUDY OF ITS PROPERTIES

The problem of surface waters pollution with heavy metals and their accumulation in the sediments of wastewaters that are formed on the cleaning installations of municipal enterprises is the top priority in the area of environmental protection and resource saving. The absence of wastewaters sediments disposal and increase in their quantity in the active sludge banks lead to the expropriation of the new land sites for storage areas, pollution of underground waters and air while wastewaters sediments can be used as a secondary raw material after the additional processing aimed at reducing the toxic influence of heavy metals. The author of article proposes the methods for obtaining biosorbent from wastewaters sediments using thermal pyrolysis and the methodology of its specific surface area study. For this purpose, the wastewaters sediments, after the previous processing by dehydration and grinding, are subjected to pyrolysis in the hermetically sealed container, which is isolated from air and connected hydraulically with pyrolysis process control block. In the process of pyrolysis, the wastewaters sediments are transformed into metals oxides which can be used as biosorbents. The biosorbent specific surface area was studied using the low temperature nitrogen absorption method.

Intercalation of Porphyrin‐Based SURMOF in Layered Eu(III) Hydroxide: An Approach Toward Symbimetic Hybrid Materials

AbstractA strategy for rational design of synergetic hybrid materials exploiting stabilization of intercalated layered matrices via coordination bonding is described. A new hybrid material is assembled through subsequent intercalation of the surface‐anchored metal–organic framework (SURMOF) components, zinc acetate and 5,10,15,20‐tetrakis(4‐carboxyphenyl)‐porphyrin‐zinc(II) (ZnTCPP), into the layered europium(III) hydroxychloride (LEuH). The formation of the SURMOF clusters intercalated in LEuH is confirmed by X‐ray diffraction, FTIR and Raman spectroscopy, and BET nitrogen absorption methods. The catalytic function of the SURMOF/LEuH hybrid and its components in the model reaction of hydrolysis of bis(4‐nitrophenyl) phosphate in the acidic solution is studied by UV–vis and MALDI‐TOF spectroscopy. Both the non‐intercalated matrix and the MOF powder are inactive and unstable in the substrate solution. Unlike its components, the SURMOF/LEuH hybrid exhibits synergetic catalytic activity increasing with the amount of the intercalated compounds because of the mutual stabilization of the components through coordination interactions. The results provide a basis for symbimetic (mimicking the symbiotic behavior in biological systems) hybrid materials, in which stabilization of functional units in the intercalated structure translates into a synergy of useful properties.

Facile Preparation of Porous Microfiber from Poly-3-(R)-Hydroxybutyrate and Its Application.

In this study, we described the development of a simplified wet spinning method of the production of a novel type of porous continuous fiber based on poly-3-(R)-hydroxybutyrate (PHB). The principle of this method is precipitation of PHB dissolved in chloroform solution into the ethanol precipitation bath. The influence of various PHB concentrations and feed rates on specific surface area (measured by nitrogen absorption method) was studied. Materials were also characterized by SEM. Surface areas of fibers achieved by wet spinning were in the range of tens of m2.g−1, and the biggest surface area value was 55 m2.g–1. The average diameter of fibers was in the range of 20–120 μm and was dependent on both PHB concentration and feed rate. Optimum conditions for reaching stable fibers of high surface area were 3–5 % w.t. of PHB and feed rate 0.5–3 ml.h−1. Fibers were functionalized by adsorption of some natural plant extracts. The incorporation of active substances into fibers was confirmed by infrared spectroscopy. High antioxidant and antimicrobial effect of PHB-fibers with cloves extract was found, as well as excellent long-term stability and optimal dynamics of the release of active compounds. The newly produced material would be applicable in pharmacy, cosmetics, and wound healing.

Exploration of effect of delignification on the mesopore structure in poplar cell wall by nitrogen absorption method

As an important commodity wood material, poplar has porous structure, which is worthy of being investigated. Especially, the lignin concentration is closely related to the formation and change of pores. Although a few studies reported the relation between the pore volume and the lignin removal of the ground wood (Stone and Scallan in J Polym Sci C Polym Symp 11(1):13–25, 1965), no information of the distribution of pore sizes versus the whole delignification process steps was reported. This study initially explored the effect of delignification level on the pore size distribution and pore structure in poplar cell walls using nitrogen absorption measurement. It was found that delignification increased the N2 adsorption amount and specific surface area of poplar. It also caused a large number of mesopores in the cell wall, mainly in the 2–10 nm pore size range, and decreased the average pore size. The whole delignification process can be roughly divided into three major phases, namely, the initial phase, the transitional phase and the stable phase, in which, the change process was not completely uniform. During the delignification, the size of poplar cell wall pores continued reducing, and finally a large number of uniform pores of about 2.1 nm was formed.

Pure ultrafine magnetite from carbon steel wastes

This paper proposes a straightforward air-aqueous oxidation of St3 steel wastes for mass production of pure ultrafine magnetite. The characterization of the obtained product has been made by X-ray fluorescence analysis, X-ray diffraction, impedance spectroscopy, low-temperature nitrogen absorption method, Mössbauer spectroscopy and optical microscopy. The investigation results have shown high purity of the obtained product, wide range of particle sizes and strongly pronounced magnetic properties

Irregular micro-sized Li1.2Mn0.54Ni0.13Co0.13O2 particles as cathode material with a high volumetric capacity for Li-ion batteries

A high tap density for cathode active material is desirable because it is beneficial to the improvement of volumetric energy density of Li-ion battery. However, a high tap density for lithium rich layered cathode material was hardly achieved because of the low tap density of spherical precursors with a loose packing of the plate-shaped long rectangular primary particles prepared by the conventional NH3-bearing co-precipitation method in atmosphere of flowing nitrogen. In this article, irregular Li1.2Mn0.54Ni0.13Co0.13O2 particles with a high tap density were prepared using irregular precursors with a tight packing of the spherical primary particles synthesized by a NH3-free co-precipitation method in atmosphere of flowing air. The galvanostatic charge/discharge measurement indicates that the irregular Li1.2Mn0.54Ni0.13Co0.13O2 particles possess a high gravimetric capacity of 259 mAh g−1 and a volumetric capacity of 926 mAh cm−3. The superior electrochemical performance of as-prepared material can be attributed to that the irregular secondary particle have a large specific surface area and small pore volume detected by both nitrogen absorption method and mercury intrusion method and that the primary particle possesses more active planes exposure observed through HR-TEM images.

Catalytic behaviour of four different supported noble metals in the crude glycerol oxidation

The activity of four different noble metals (Ag, Au, Pd and Pt) in the liquid phase oxidation of pure glycerol was confronted with the results obtained with a crude glycerol fraction, received from a large-scale biodiesel production plant. The catalysts were characterized by numerous techniques, giving insight into actual metal loading (elemental analysis by ICP and XRF), surface morphology (nitrogen absorption methods—BET and porosity), chemical state of both the support and the metal (XRD and XPS), and, finally, the metal particle size distribution (TEM microscopy). A good dispersion of totally reduced noble metal particles of a nanometric size (an average metal diameters were equal 3.5nm, 4.2nm, 4.7nm and 21.2nm for respectively Pd, Pt, Au and Ag) was accompanied with a comparable values of total metal loadings on the alumina support (from 0.95 and 0.96wt.% for Pt and Pd, up to 0.98 and 1.13wt.% for Au and Ag supported catalysts, respectively). In terms of initial reaction rate, the most active sample was the Au/Al2O3 catalyst, both using pure (12976molh−1molAu−1) or crude glycerol (1230molh−1molAu−1). However, comparison of the selectivities and conversions after 1–2h shows that the most robust and resistant catalyst – toward the impurities present in crude glycerol – is Pd/Al2O3, with a loss of conversion less than 50% (in respect to analogous reaction using pure glycerol) and almost unchanged high selectivity to glyceric acid (close to 80–90%). Ag/Al2O3 also showed a relatively high resistance to impurities in terms of glycerol conversion, but with a drastic modification of its selectivity. The activity of the two other catalysts was dramatically affected with a conversion divided by ca. 4 and even 10 for the Pt and the Au catalysts, respectively, when using crude glycerol instead of pure glycerol. Finally, the effect of each main impurity (MONG-NM, i.e., matter organic non-glycerol and non-methanol; ash; methanol; sulphur compounds) was independently studied. In any case, the sulphur compounds and MONG-NM were the impurities the most detrimental for the performances of catalysts. Thus, they should be removed in priority from crude glycerol fractions before reaction, while ashes and methanol should not be considered as completely undesirable.

A facile hydrothermal synthesis, characterization and magnetic properties of mesoporous CoFe2O4 nanospheres

Mesoporous CoFe2O4 nanospheres with an average size of 180nm were fabricated via a facile hydrothermal process using ethylene glycol as solvent and sodium acetate (NaAc) as electrostatic stabilizer. In this method, ethylene glycol plays a vital role in the formation of cobalt nanoospheres as a solvent and reducing agent. The structure and morphology of the prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The nanospheres exhibited ferromagnetic properties with high saturation magnetization value of about 60.19emu/g at room temperature. The BET surface area of the nanospheres was determined using the nitrogen absorption method. The porous CoFe2O4 nanospheres displayed good magnetic properties, which may provide a very promising candidate for their applications in target drug delivery.

In-situ ellipsometric characterization of the growth of porous anisotropic nanocrystalline ZnO layers

ZnO films have increasingly been in the spotlight due to their largely varied electro-physical and optical properties. For several applications, porous anisotropic nanocrystalline layers are especially interesting. To study the growth kinetics of such films during different fabrication processes, a powerful non-destructive in-situ technique is required. In this work, both ex-situ and in-situ spectroscopic ellipsometry are used along with advanced modelling techniques that are able to take both the anisotropy and the porosity of the films into account. Scanning electron microscopy, along with nitrogen absorption methods for measuring porosity, validated the ellipsometric data and proposed model. The film, grown by chemical bath deposition, was monitored from around 700 to 1800 nm in thickness. This same principle can now be used to monitor any other porous and/or anisotropic structure in an effective in-situ manner, e.g., growth of porous anodic aluminium oxides, nano-porous silica films, etc.

Mineral Carriers for Nanoscale Additives in Bituminous Concrete

To prolong the lifetime and to improve the quality of pavements made of bituminous concretes it is necessary to apply innovative solutions during design of such building materials. The common way to increase the values of operational properties is to admix various modifying additives during production. Nanoscale additives currently constitute the big group of advanced modifiers. The known difficulty limiting the widespread practical use of nanotechnology is the necessity to ensure uniform distribution of nanoscale objects in the volume of material. Thus, to realize nanotechnology in construction it is necessary to use the various carriers for nanoscale modifiers. Several mineral materials (dolomite- and silica-based) were examined and results are presented in this paper. The optimal grain size is determined and optimal modes of grinding were identified to provide conformity of structural parameters for carriers. It is shown that total surface area of diatomite obtained by means of nitrogen absorption method is quite high due to structure of its pore space. It is stated that for structure with numerous contacts between grains, rheological properties of mixture are mostly determined by the thickness and properties of solvation shells on the grains. High surface activity of diatomite is confirmed by the rheology data. It is shown that there is the formation of adsorption layer during interaction between bitumen and surface of diatomite, and thickness of this layer is relatively high for the wide range of temperatures. It is found by means of IR spectroscopy that there is only physical sorption of bitumen on the diatomite and no new chemical compounds are forming.

Synthesis of composites SBA-15 mesoporous particles carrying oxytocin and evaluation of their properties, functions, and in vitro biological activities.

Using the organic template method, we have synthesized mesoporous SBA-15 particles and characterized them by scanning electron microscopy and transmission electron microscopy. The bone metabolism regulating hormone oxytocin (OT) was selected as a model for preparation of drug/SBA-15 complexes. The process of drug loading was studied using X-ray diffraction and nitrogen absorption methods. Optimal drug loading parameters were experimentally investigated. The kinetics of drug release from the carrier was evaluated. Finally, the extractions of SBA-15 particles were tested for cytotoxicity, in vitro hemolysis, and the direct attachment toxicity. Our findings suggest that SBA-15 materials have good biocompatibility. Moreover, we demonstrated that OT/SBA-15 complex can stimulate alkaline phosphatase activity in osteoblast cells. The study provides fundamental information for further in vivo drug-carrier testing.

Influence of sodium aluminate on cement hydration and concrete properties

The influences of sodium aluminate (SA) on cement hydration were studied. Heat evolution of cement pastes with and without SA was monitored by a differential scanning calorimeter (DSC). Hydration products were identified using scanning electron microscope (SEM), X-ray diffraction (XRD), thermal analysis (TG–DSC), and mass spectrum (MS). Pore structures of cement pastes were analyzed using nitrogen absorption method. Concrete strength and chloride penetration resistance were also evaluated. The mechanisms by which SA contributes to cement hydration and microstructure development were explored. The results indicate that addition of SA resulted in changed calcium sulfoaluminate morphology, form acicular AFt to tabular AFm. Adding of SA increased the volume of small capillary pores (5–30nm) and reduced the volume of larger pores (>30nm). Cement setting time reduced significantly as SA addition reached up to 4%. 1.5% SA addition can enhance concrete strength at early age but reduce it at later age. Addition of SA also improved chloride penetration resistance of concrete.

Research on variability characteristics of micropore of Zhanjiang clay under ambient temperature and pressure, normal atmospheric

Soils are generally used as building material and foundation, are normally under the atmospheric with ambient temperature and pressure, nevertheless, effect of oxidation of soil proceeding so slowly that it is no easy to perceive, long-term deterioration of soil properties, cannot be ignored. Zhanjiang Clay was taken as the object of study, studied the reformation effect on the micro-structures under the influence of the atmospheric and its impacting mechanism to soil properties, by scanning electron microscopy, mercury intrusion porosimetry and nitrogen absorption method. Research shows, after oxidized, the color of soil changes from grayish green and light grayish green to yellow and yellowish brown; while aggregation of soil particles increases, not only Swelling-shrinkage properties, but also plasticity of soil particles decreases, as for the sensitivity and structure yield strength reduced. Furthermore, atmospheric environment has an effect of shrinkage and closure on pores (<italic>d</italic><0.1 μm), and enlargement and dispersion on pores (<italic>d</italic>>1 μm), which results in a decrease of total pores volume of oxidized clay. As far as pores (<italic>d</italic>>1 μm) are concerned, pores volume increases remarking, with appearance of fracture porosity and reduction of ink-bottle type pores, as well as conversion from open pores to close ones. The transformation of soil properties by the influence of atmospheric is not caused by inherent changes of mineral, but the remodeling effect of micro-structures because of motion effects and chemical reactions of water-soil-electrolytes- atmosphere leading to coupling and transforming of soil particles. It is the variation of ultra-micro-structure that generates this phenomenon. Prolonged influence with comparatively large potential harmful impact on soil stability caused by damage effects on structural strength during oxidation, it turns out to be necessary to strengthen monitoring the effect on geotechnical engineering of physical and chemical factors in environment.

An Evaluation of Shrinkage Model Based upon Microstructure of Blended Cement Pastes

As shrinkage in concrete leading to the subsequent cracking and reducing durability, the study on shrinkage is quite important. Based on microstructure of pores obtained from Nitrogen absorption method and mechanical testing, a numerical shrinkage model was built. The standard shrinkage test results show consistent in the blended cement pastes with different water-to-cement ratioand admixture content to predict shrinkage values, which confirmes the shrinkage model based upon microstructure of blended cement pastes.

Preparation and Characterization of Inorganic Silica-Organic Polymer Mixture Based C16 Capillary Monolithic Column

Abstract A novel inorganic silica-organic polymer mixed-based capillary electrochromatography monolithic column was prepared by using precursor 3-(trimethoxysilyl) propyl methacrylate with double-functional group hydrolysis/polycondensation in acidic aqueous solution, followed by double-bond co-polymerization with organic monomer hexadecyl mathacrylate under the thermal initiated condition, and the combination of preparation of silica-based monolithic column and organic polymer monolithic column was suggested. A simple operation of controlling sol mixture using mercury infusion when the mixture infused into capillary was raised to acquire smooth interface of stationary phase. The preparation conditions of monolithic column were optimized. The structure of the monolithic columns was characterized by SEM images and nitrogen absorption method, and the results showed that the median pore diameter of the materials was in the range of 3 to 7 nm with average surface area of 103.4 M2 g−1. The influence of buffer concentration, pH value, and organic modifier content on electroosmotic flow (EOF) velocity has been investigated. Seven neutral aromatic hydrocarbons were baseline separated with column efficiency of naphthalene up to 54000 plates m−1. The reproducibility for separation time and retention factor was given in terms of RSD values at 0.9% and 0.6% (n = 5) for run-to-run injections and 1.2% and 0.8% (n = 3) for day-to-day operations. The RSD values of separation time and capacity factor of different columns (n = 3) were 8.7 and 5.7%, respectively. The studies on performance of columns indicated that the columns possess typical reverse retention mechanism.

Mechanical Properties of Ni-Free High-Nitrogen Austenitic Stainless Steel Made by Metal Injection Molding with Nitrogen Absorption Method

Microstructure and mechanical properties of high nitrogen steels containing 17Cr-12Mn-3Mo produced by means of metal injection moulding and nitrogen absorption methods were examined. The compacts were sintered at 1300°C, then furnace-cooled to 1200°C and were held at that temperature for 2 to 20 hrs. Subsequently, they were furnace-cooled. Thereafter, solution treatment was done at 1200°C. The solution treated compacts held at 1200°C for above 5 hrs had homogeneous microstructure. Increasing the holding time at 1200°C, ferrite phase disappeared due to the increment of nitrogen content and grain size became larger. Lattice constant of austenite phase also increased. Yield and tensile strength increased with increasing nitrogen content. Yield and tensile strength of the compact held at 1200°C for 10 hrs were 758 MPa, 1172 MPa respectively and elongation was 41 %. However, ductile-brittle transition (DBT) behaviour was seen, and the DBT temperature of every compact was about -20°C. From the fracture surface analysis, brittle fracture surface was identified as (111).