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Characteristic Polynomial
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Lorentz Jäntschi, Sorana D. Bolboacă
Let’s take a chemical compound, namely hexamine (Pubchem CID: 4101). Hexamine (C6H12N4) it uses in the production of powdery or liquid preparations of phenolic resins and phenolic resin molding compounds. It has been proposed that hexamethylenetetramine could work as a molecular building block for self-assembled molecular crystals (Markle, 2000). It has a cage-like structure similar to adamantine and its representation is given in Figure 7.3.
The chemical process for materials deposition in aqueous solution: a review
Published in Surface Engineering, 2022
A. I. Oliva, I. J. González-Chan, P. E. Várguez, A. I. Trejo-Ramos, A. I. Oliva-Avilés
The core of the CBD technique is the chemical reagents, which are hosted by water (oxygen provider). The reagents conforming the deposition medium are: (i) a metallic salt, (ii) a precursor for the chalcogenide, and (iii) a complexing agent. The salts and chalcogenide precursor (thiourea, selenourea, selenosulphate, tellurosulphate) are mixed to form the desired compound. The main roles of the complexing agent are to avoid fast precipitation of metals by forming chemical bonds and to regulate the pH of the solution through the control of the concentrations of salts ions [28] which strongly governs the material deposition rate. Common complexing agents are ammonia, hydrazine, hexamine, among others [28,30]. Several authors confirm that the parameters with a major contribution on the physicochemical properties of the deposited films are the deposition rate, bath composition, bath temperature, stirring speed, pH value, and type of substrates [4,28,32]. Table 1 shows some chemical reagents used for CBD deposition of some sulphides and selenides.
Mass fabrication of 2D nanostructure (ZnO) in chemical growth solution using tip induced lithography
Published in Materials and Manufacturing Processes, 2022
Deepak Kumar, Ravi Shankar Rai, Vivek Bajpai, Nirmal Kumar Singh
In current work, deliberation of OH− ions significantly influence the growth direction of ZnO nanostructure. The tetrahedral coordination of Zn2+ and O2- poses a stacked-layer along the c-axis during growth.[48] Here, Hexamine reacts with water molecules to develop formaldehyde (HCHO) and ammonia (NH3) at retarded rate. The slow release of ammonia (NH3) generates fewer numbers of OH− ions which affects the nucleation rate of Zn+ ions during hydrolysis.[49] Moreover, the existence of ammonia (NH3) limited the growth of zinc hydroxide ions along c-axis by absorbing the amine molecules on the surface.[50] The zincate ions combine with hydroxyl ions (OH−) to form the Zn(OH)2 colloids and growth unit as tetrahedral zincate ions Zn(OH)42- radicals. This tetrahedral zincate ion was finally dehydrated to form zinc oxide (ZnO) under heated conditions.[51] To understand the morphological evolution and growth mechanics, the spontaneous chemical reaction associated with the fabrication of 2D ZnO nanosheet is elaborated below.
An overview of simultaneous saccharification and fermentation of starchy and lignocellulosic biomass for bio-ethanol production
Published in Biofuels, 2019
Fuel can be present in different forms like liquid, solid or gaseous form such as hydrogen fuel (for automotive uses). Examples of different forms of fuels are liquefied petroleum gas (propane + butane), non-petroleum fossil fuels, ammonia, wood, charcoal, peat, coal, and hexamine fuel tablets [24,25]. Non-petroleum fossil fuels are synthetic fuels which are normally used when petroleum is not easily available. Chemical processes such as the Fischer-Tropsch process can be used to produce liquid fuels from coal or natural gas [26]. Liquid fuels are much more advantageous than solid fuels. In an industrial process, especially for maritime industry, solid fuels become increasingly difficult to work with. Compared to liquid and gas fuels, solid fuels require a much larger area to store. Combustion of fossil fuels generates sulfuric, carbonic, and nitric acids, which generally fall back to earth in the form of acid rain. From 2009 to 2013 in United States, nearly 36% of the total CO2 emissions were due to the burning of solid fuels [27]. Burning coal also generates large amounts of bottom ash and fly ash. Fossil fuel plays a major role in global warming. Moreover, fossil fuels lead to environment pollutions which impacts on the human population because particles of fossil fuel in the air cause negative health effects when inhaled. These health effects include premature death, acute respiratory illness, aggravated asthma, chronic bronchitis and decreased lung function [28].