Function Of Synthesis Parameters Research Articles

Effects of activation temperature and time on porosity features of activated carbons derived from lemon peel and preliminary hydrogen adsorption tests

Lemon peels, a common biomass waste, have an interesting composition in terms of cellulose and mineral salts that makes them good precursors for activated carbon production processes. From a circular economy perspective, this work highlights the possibility of turning a waste material into a new resource. The resulting nanostructures show interesting performance in terms of specific surface area and total pore volume, with excellent grade of microporosity, that make them suitable for various applications ranging from supercapacitors, sensors, gases separation and storage, etc. The last, and in particular hydrogen storage, represents the most interesting one. In this study the development of activated carbon through pyrolysis method, consisting of carbonization in inert ambient and subsequent physical activation in oxidizing atmosphere is reported. Influence of synthesis parameters on the porosity formation was investigated with the aim of textural properties optimization. All produced samples were initially characterized both morphologically and crystallographycally. Then, textural and adsorption properties were evaluated through volumetric apparatus. The experimental results show improvement of both textural and adsorption properties as function of synthesis parameters, developing adsorbent materials with high fraction of micropores (≃84 %), specific surface area (≃500 m2/g) and hydrogen uptake of 0.93 wt% at 77 K and 1 bar.

Studying the mechanism and kinetics of fuel desulfurization using CexOy/NiOx piezo-catalysts as a new low-temperature method

In order to advance desulfurization technology, a new method for excellent oxidative desulfurization of fuel at room temperature will be of paramount importance. As a novel desulfurization method, we developed piezo-catalysts that do not require adding any oxidants and can be performed at room temperature. A microwave method was used to prepare CeO2/Ce2O3/NiOx nanocomposites. Model and real fuel desulfurization rates were examined as a function of synthesis parameters, such as microwave power and time, and operation conditions, such as pH and ultrasonic power. The results showed that CeO2/Ce2O3/NiOx nanocomposites demonstrated outstanding piezo-desulfurization at room temperature for both model and real fuels. Furthermore, CeO2/Ce2O3/NiOx nanocomposites exhibited remarkable reusability, maintaining 79% of their piezo-catalytic activity even after 17 repetitions for desulfurization of real fuel. An investigation of the mechanism of sulfur oxidation revealed that superoxide radicals and holes played a major role. Additionally, the kinetic study revealed that sulfur removal by piezo-catalyst follows a second-order reaction kinetic model.

Thermophysical Characteristics of Novel Biomass-Derived Activated Carbon as a Function of Synthesis Parameters

Activated carbon signifies extensive carbonized materials of a high degree of porosity and has a wide range of applications. The porous and thermal properties of activated carbon (AC) are primarily dependent on the chosen raw material and synthesis conditions. In this article, the thermophysical properties of twelve waste biomass-derived AC samples are investigated and correlated. These AC samples are synthesized from mangrove and waste palm trunk. The samples are different in terms of carbonization temperature (500 and 600°C), activation temperature (600 to 900°C), and the mixing ratio (4 or 6) of the activation chemical, which is potassium hydroxide. The specific heat capacity of W-AC-C600-A900-K6 is found to have the lowest (0.843 to 1.14 kJ kg−1 K−1), and M-AC-C500-A900-K4 shows the highest (1.18 to 1.86 kJ kg−1 K−1) among the studied samples. Experimental data are fitted with the Green-Perry model with an error of less than 2%. This study also accounts for the comparison of specific heat capacity of studied samples and other adsorbents such as AC obtained from different precursors, silica gels, carbon-based consolidated composites, and metal-organic frameworks found in the literature. Moreover, this study gives the insight to synthesize high-quality AC from unknown biomass sources for a particular application.

Biodegradable Hydrogels: Evaluation of Degradation as a Function of Synthesis Parameters and Environmental Conditions

The development of functional materials that promote the infiltration and retention of water and the controlled release of fertilizers and nutrients in soil is of interest in agriculture. In this context, hydrogels, three-dimensional polymeric structures able to absorb high amounts of water in their swelling process, play an important role. The swelling ability of hydrogels depends on their crosslinking: the higher the crosslinking degree, the higher the number of interactions in the structure, the lower the swelling response. In this work, we describe biodegradable hydrogels composed of natural feedstocks: cellulose, clay minerals, and humic acids, designed to (i) protect, hydrate, and help germinating seedlings to root even in unfavorable conditions; (ii) sustainably contribute to soil fertility in terms of moisture and nutrients; and (iii) act as a nutritive and protective coating for the seeds. Upon assessing the correlations between curing process and swelling degree (SW), we evaluated the degradation of new biodegradable hydrogels as a function of the synthesis parameters (swelling degree and composition) and environmental conditions (type of soil and water amount for the hydration of the hydrogels). The term curing is hereafter referred to the operation of baking the ingredients at given combinations of time and temperature to obtain a dry hydrogel. The results show that the environmental parameters considered, i.e., amount of hydration water and physical and chemical properties of the soil, play a more decisive role in determining the stability of these hydrogels in soil than their synthesis parameters, such as the composition and the swelling degree.

A graphene oxide Cookbook: Exploring chemical and colloidal properties as a function of synthesis parameters

Herein, we describe the synthesis of graphene oxide (GO) over a large range of conditions, exploring the effects of reaction temperature, reaction time, oxidant ratio, and sonication time on the chemical and colloidal properties of the product. As a function of reaction parameters, modified from Hummers’ method, GO products were characterized and described via a suite of spectroscopic, structural, and morphological techniques, including TEM, UV–vis spectroscopy, XPS, Raman spectroscopy, FTIR, and DLS. Average carbon oxidation state and the yield (upon sonication) were chosen as the two criteria to evaluate synthesized GO materials. It was observed that as reaction temperature increased, GO oxidation state and yield of the sonication step both increased. Further, increasing reaction time and oxidant ratio not only increased the oxidation state, but also had a pronounced effect on the final yield. As synthesized, GO with higher degrees of oxidization exhibited higher negative ζ-potential, slightly smaller hydrodynamic diameter, and higher critical coagulation concentration(s). Data sets collectively demonstrate that carbon oxidation state, functional group ratios, and the aggregation kinetics of GO products can be readily controlled by varying processing time and conditions with expected changes in aqueous behavior(s), including stability/aggregation.

Biodegradable cationic nanogels with tunable size, swelling and pKa for drug delivery.

Cationic polymers have garnered significant interest for their utility in intracellular drug delivery and gene therapy. However, due to their associated toxicities, novel synthesis approaches must be explored to develop materials that are biocompatible. The novel library of nanoparticles synthesized in this study exhibit tunable hydrodynamic diameters, composition and pH-responsive properties as a function of synthesis parameters. In addition, differences in the responsiveness of these nanoparticles under different pH conditions affords greater control over intracellular drug release.

Indentation creep of superelastic hard carbon

Instrumented indentation methods have been used to study the effect of the loading rate and holding time at different maximum loads on the indentation characteristics of superelastic hard carbon particles reinforcing metal matrix composite materials. The properties of the carbon particles prepared in fullerite-metal powder mixtures by high-pressure synthesis substantially differ as a function of synthesis parameters (P, T) and the initial fullerite characteristics (C60 in crystalline or amorphous state). The indentation creep CIT decreases with increasing Fmax (500-2000 mN) and increases with holding time (60-600 s). The harder carbon particles formed from amorphous fullerite are characterized by higher indentation creep CIT and deeper penetration at constant load. Such creep behavior correlates with different elastic recovery characteristics of the particles upon indentation.

From Batch to Continuous Precipitation Polymerization of Thermoresponsive Microgels.

Microgels are commonly synthesized in batch experiments, yielding quantities sufficient to perform characterization experiments for physical property studies. With increasing attention on the application potential of microgels, little attention is yet paid to the questions (a) whether they can be produced continuously on a larger scale, (b) whether synthesis routes can be easily transferred from batch to continuous synthesis, and (c) whether their properties can be precisely controlled as a function of synthesis parameters under continuous flow reaction conditions. We present a new continuous synthesis process of two typical but different microgel systems. Their size, size distribution, and temperature-responsive behavior are compared in depth to those of microgels synthesized using batch processes, and the influence of premixing and surfactant is also investigated. For the surfactant-free poly( N-vinylcaprolactam) and poly( N-isopropylacrylamide) systems, microgels are systematically smaller, while the actual size is depending on the premixing of the reaction solutions. However, by the use of a surfactant, the size difference between batch and continuous preparation diminishes, resulting in equal-sized microgels. Temperature-induced swelling-deswelling of microgels synthesized under continuous flow conditions was similar to that of their analogues synthesized using the batch polymerization process. Additionally, investigation of the internal microgel structure using static light scattering showed no significant changes between microgels prepared under batch and continuous conditions. The work encourages synthesis concepts of sequential chemical conditions in continuous flow reactors to prepare precisely tuned new microgel systems.

Understanding structure and porosity of nanodiamond-derived carbon onions

Carbon onions derived by thermal annealing of nanodiamonds are an intriguing material for various applications that capitalize the nanoscopic size, high electrical conductivity, or moderately high external surface area. Yet, the impact on synthesis conditions and possible post-synthesis treatment on the pore characteristics lacks a detailed parametric understanding. We present a comprehensive model describing the change of structure, morphology, specific surface area (SSA), and pore size distribution (PSD) of carbon onions derived via thermal annealing of nanodiamonds as a function of synthesis parameters and the effect of physical activation in air. Different heating rates, temperatures, holding times, as well as two different nanodiamond precursors were used. During thermal annealing the increase in SSA occurs along with a loss of surface functional groups and volatile impurities. The sp3-to-sp2 conversion results in a much lower density and an increase in SSA of up to ∼160%. At high temperatures, a sintering and carbon redistribution process limits the increase in SSA and leading to the formation of micrometer-sized graphitic particles with a very low SSA. Oxidation in air is a facile way for the effective removal of predominately amorphous carbon between carbon onion particles and the removal of outer carbon shells.

Preferred Orientation in Sputtered TiO2 Thin Films and Its Effect on the Photo-Oxidation of Acetaldehyde

Crystal orientation is not typically considered when investigating the reactivity of thin films. We propose that accounting for the preferred crystallographic orientation may serve as an indirect measure of the active sites along the solid–solid interface that are difficult to measure with direct techniques. The goal of this work is to identify the preferred orientation, examine its evolution as a function of synthesis parameters, and determine its effect on photoreactivity. We examine the effect of substrate radio frequency (RF) bias and reactive gas partial pressure on the structure and photoreactivity of TiO2 films synthesized by reactive direct current (DC) magnetron sputtering. We characterize these films using ellipsometry, scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), and pole figure scans, and test their photoreactivity with the degradation of acetaldehyde under 365 nm UV light. We find that, in the parameter space investigated, changes in RF bias strongly influence both film texture and reactivity, and that the orientation of the crystallites is the best predictor of photoreactivity. Under the synthesis conditions tested, we observe an optimum RF bias of −50 V at which the films exhibit biaxial texture with the c-axis parallel to the surface with maximum crystallinity and degree of orientation, corresponding to a maximum in the reactivity as well. Beyond this point a change in the preferred orientation is observed, and the films transition to a fiber texture with the c-axis normal to the film surface and the appearance of small amounts of rutile. The effect of texture on reactivity is discussed.

High quality biodiesel production from pork lard by high solvent additive

Large scale biodiesel production by using low cost and abundant feedstock as waste animal fat is becoming more important due to petroleum reserves crisis and adverse environmental problems. This paper has experimentally developed a new method for lard synthesis by using suitable conditions of production with high solvent blending. A polynomial equation was obtained for lard biodiesel yields as a function of synthesis parameters. The validity of the predictive model was confirmed by validation experiments. The suitable combination for high quality biodiesel production from lard was less than 2.0 wt.% catalyst with 10:1 methanol/lard molar ratio and 65.0 wt.% solvent additive. The significant point of this method was to use high solvent blending ratios for lard synthesis to overcome poor solubility problem between highly concentrated free fatty acid pork lard and catalyst. Using this method, gave high yields of biodiesel in short reaction time. The evaluation of the synthesis was made using gas chromatography. The final products fulfilled all of the requirements of ASTM D6751-09 and EN 14214 standards. Overall, this process can be useful for larger scale industrial process with low energy consumption.

Superconducting properties of strontium copper oxyfluoride, Sr 2CuO 2F 2+δ

Superconducting properties of Sr 2CuO 2F 2+δ have been measured as a function of synthesis parameters. Fluorination initiates above 160°C, appears optimum near 180°C and is difficult to control above 250°C in forming superconducting samples. Optimum T c values are nominally 47 K; however, Meissner data show fluctuations extending to 60 K.