scholarly journals The scalable production of high-quality nanographite by organic radical-assisted electrochemical exfoliation.

2021 ◽  
Vol 2086 (1) ◽  
pp. 012014
Author(s):  
E Grushevski ◽  
D Savelev ◽  
L Mazaletski ◽  
N Savinski ◽  
D Puhov

Abstract One of the promising ways to produce graphene is the technology of graphite splitting or exfoliation, both by physical or mechanical and chemical, including electrochemical methods. The product of electro exfoliation is nanographite, which is transformed into multigraphene at the subsequent stage of liquid-phase mechanical and ultrasonic disintegration. This approach demonstrates a successful method of obtaining multigraphene from available graphite raw materials. Since, already at a potential of 1.23V, during the electrolysis of water on a graphite anode, the hydroxyl anion is discharged with the formation of a very active hydroxyl radical oxidizer, it is not surprising that when the graphite electro exfoliation process is overvolted at 10V, graphite oxidation products are formed. In order to control the defectiveness of the graphene lattice by oxidation products, we carried out processes of graphite exfoliation in the presence of both a number of reducing agents ascorbic acid, sodium borohydride, hydrazine hydrate, and in the presence of industrial antioxidants radical traps (2,2,6,6-tetramethylpiperidine-1-il)oxyl (TEMPO), (2,2,6,6-tetramethyl-4 oxo-piperidine-1-yl)oxyl (IPON), a mixture of 5,8,9-bis isomers[(2,2,6,6-tetramethyl - 4 oxo-piperidine-1-yl)]-{5,8,9-[1,1’- bi(cyclopentylidene)]-2,2’,4,4’- tetraene}(YARSIM-0215). It should be noted, that the best result of preventing the oxidation of nanographite in electro exfoliation technology in our studies is the ratio of carbon to oxygen (C/O) about 69.

2015 ◽  
Vol 137 (43) ◽  
pp. 13927-13932 ◽  
Author(s):  
Sheng Yang ◽  
Sebastian Brüller ◽  
Zhong-Shuai Wu ◽  
Zhaoyang Liu ◽  
Khaled Parvez ◽  
...  

2013 ◽  
Vol 13 (17) ◽  
pp. 8651-8667 ◽  
Author(s):  
Y. B. Lim ◽  
Y. Tan ◽  
B. J. Turpin

Abstract. Atmospherically abundant, volatile water-soluble organic compounds formed through gas-phase chemistry (e.g., glyoxal (C2), methylglyoxal (C3), and acetic acid) have great potential to form secondary organic aerosol (SOA) via aqueous chemistry in clouds, fogs, and wet aerosols. This paper (1) provides chemical insights into aqueous-phase OH-radical-initiated reactions leading to SOA formation from methylglyoxal and (2) uses this and a previously published glyoxal mechanism (Lim et al., 2010) to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012). This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010), and is used to simulate the profiles of products and to estimate SOA yields. At cloud-relevant concentrations (~ 10−6 − ~ 10−3 M; Munger et al., 1995) of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass) are ~ 120% for glyoxal and ~ 80% for methylglyoxal. During droplet evaporation oligomerization of unreacted methylglyoxal/glyoxal that did not undergo aqueous photooxidation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (~ 10 M), the major oxidation products are oligomers formed via organic radical–radical reactions, and simulated SOA yields (by mass) are ~ 90% for both glyoxal and methylglyoxal. Non-radical reactions (e.g., with ammonium) could enhance yields.


2021 ◽  
Vol 12 (2) ◽  
Author(s):  
N Нolembovska ◽  
◽  
N Slobodianiuk ◽  
V Israelian ◽  
◽  
...  

Taking into account the results of scientific literature research concerning the nutritional value and biological efficiency of cranberry and goji berry, we found that the development of the technology of semi-finished products with their use is relevant and has practical significance for the technology of production of fish products. The article presents the results of studying chemical composition, organoleptic evaluation, and physicochemical changes in semi-finished products with the addition of non-traditional raw materials and determining their shelf life. The study illustrates the feasibility of combining freshwater fish with plant raw materials to expand the range of biologically valuable food products. The obtained positive general impressions, harmonious, fishy and sweet and salty taste proved the feasibility of combining cranberries and goji berries with freshwater fish, as evidenced by the high indicators of appearance, taste, and odor. By consistency, the fish sticks are plastic and tight in section. It was found that in the control sample, there are processes of hydrolytic spoilage after 90 days of storage that testify to the intensive lipid hydrolysis and the accumulation of free fatty acids in this sample. In the experimental samples, the hydrolytic spoilage gradually increases and only reaches the critical point by the end of the shelf life. Oxidative processes in the lipids of semi-finished products were determined by changes in the accumulation of primary oxidation products – peroxides and secondary products – carbonyl compounds. According to the dynamics of changes in the peroxide value of lipids in semi-finished products, we found that the control sample is not subject to storage for 60–135 days, and the fat quality deteriorates in the experimental samples after 135 days and is characterized as not subject to storage. It has been experimentally established that the addition of non-traditional raw materials allows not only to improve the technology of production of chopped semi-finished products but also to solve the problem of obtaining a product with increased nutritional value. We found that the developed technology of fish semi-finished products will significantly expand the range of functional products based on natural components, which will to some extent expand the current problem of raw material processing from inland water bodies of Ukraine.


1984 ◽  
Vol 78 (1-3) ◽  
pp. 113-122 ◽  
Author(s):  
A.Martín Rodríguez ◽  
Pedro Valerga Jiménez

2020 ◽  
Vol 27 (09) ◽  
pp. 1950211
Author(s):  
XINQIANG LU ◽  
SHOUREN WANG ◽  
TIANYING XIONG ◽  
DAOSHENG WEN ◽  
GAOQI WANG ◽  
...  

Two kinds of composite coatings, Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] and Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text], were prepared on steel matrix (Q235) by cold spraying. The Zn, Al, Mg, and ZnO in raw materials were calculated by percentage of mass. The morphology of the original coating was observed by scanning electron microscopy (SEM) and characterized by energy dispersive spectroscopy (EDS). It was found that the microstructures of Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] and Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] composite coatings prepared by cold spraying were compact without oxidation products, and the plastic deformation of powder particles was significant. The friction and wear test data of the two coatings showed that the Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] coating had longer-lasting protective properties and wear resistance under the same conditions. Neutral salt spray test (NSS) and electrochemical accelerated corrosion test were carried out on samples at different time periods. The results of samples’ corrosion microstructure and electrochemical curves showed that Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] and Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] have good electrochemical protection performance, and Zn[Formula: see text]Al[Formula: see text]Mg5ZnO[Formula: see text] coating has better protection effect.


2021 ◽  
Vol 6 (4) ◽  
pp. 267-278
Author(s):  
Yulian A. Khan ◽  
Tatyana P. Dyachkova ◽  
Evgeny S. Bakunin ◽  
Elena Yu. Obraztsova ◽  
Artyom V. Rukhov ◽  
...  

The paper presents a generalized analysis of the results of scanning electron microscopy, energy dispersive spectroscopy, and TG/DSC analysis of electrochemical exfoliation products from two types of initial graphite raw materials at different process temperatures in solutions of potassium hydroxide (KOH) and sulfuric acid (H2SO4). It is shown that an increase in the concentration of an alkaline electrolyte in the range from 0.1 to 1.0 molL–1 promotes the intensification of the process of separation and splitting of graphite into fragments. In the case of the formation of large fragments, the product contains a significant amount of intercalated potassium ions, which are not removed when the material is washed off. The products of electrochemical exfoliation of the spent electrocontact graphite material demonstrate structural heterogeneity, contain a significant amount of functional groups and impurities of the amorphous phase. Thermogravimetric curves have several sections of sample weight reduction. After heating these materials in an inert atmosphere to 900 °C, the total weight loss reaches 66 %. From a thermally expanded graphite foil, samples of nanographites, extremely homogeneous in chemical composition, with increased thermal stability and a minimum number of surface defects were obtained. The total weight loss of the samples when heated in an inert atmosphere to 900 °C does not exceed 17 %. It was shown that the replacement of an alkaline electrolyte with a sulfuric acid solution leads to an increase in the number of defects in the product.


1893 ◽  
Vol 184 ◽  
pp. 505-639 ◽  

The present investigation was commenced three years ago, in order to throw further light on the mode of action of the paraffinic nitrites when introduced into the animal organism, and particularly to determine in what manner this action is conditioned by the different chemical constitution of the various nitrites employed. Since the chemical constitution of these compounds is well established and their molecules are comparatively simple in structure, and moreover as their principal physiological effects are capable of accurate quantitative study, it seemed likely that the inquiry would furnish valuable pharmacological results. Although the investigation, both on its chemical and physiological sides, has proved to be far more laborious and difficult than was anticipated, unexpected difficulties having arisen which have rendered necessary the employment of specially-devised apparatus, and the execution of several series of experiments in order to control the accuracy of the results first obtained, yet the conclusions we have finally reached will serve, we think, not only to elucidate the modes of action of these compounds, and to establish the manner of their dependence on the presence of certain groups in the respective molecules, but we hope may also be of some importance in their bearings on the treatment of disease. It is already known that the physiological action of amyl and ethyl nitrites closely resembles in its important features that of the metallic nitrites, and that the characteristic effect is due to the presence in both series of compounds of the nitroxyl group NO 2 , the nitrogen of this group not being directly united to the metal or organic radical, but indirectly by means of an atom of oxygen (R’ONO). Our knowledge of the physiological behaviour of the organic nitrites has been almost wholly derived from the study of amyl nitrite, which has been observed to produce a similar, but far greater, effect than its lower homologue, ethyl nitrite, whose action, however, has not hitherto been so closely examined as that of the amyl compound. Both these organic nitrites are therapeutically employed, the amyl compound at the suggestion of Lauder Brunton , who proposed to use it in the treatment of certain diseases on account of its known physiological action. Unfortunately, however, it seems likely that most of the results which have been obtained with amyl nitrite are to a large extent vitiated by the circumstance that, as a rule, sufficient pains have not been taken to procure the nitrite in a chemically pure state. One of us has already shown that the material usually employed in medicine under the name of amyl nitrite is highly impure, containing a large proportion of other nitrites (ethyl, propyl, butyl), as well as their oxidation products. The redistilled amyl nitrite which has been employed by some investigators is a mixture of two amyl nitrites with a variable proportion of iso-butyl nitrite. In the present investigation special precautions were taken to obtain the various nitrites in a pure state. The compounds selected for examination were: methyl nitrite, ethyl nitrite, primary propyl nitrite, secondary propyl nitrite, primary butyl nitrite, iso-butyl nitrite, secondary butyl nitrite, tertiary butyl nitrite, α -iso-amyl nitrite, β -iso-amyl nitrite, tertiary amyl nitrite. These nitrites were chosen because they contain nitroxyl united to typical and differently constituted radicals. Their examination would, therefore, enable us to determine the modifying influence exerted by these radicals upon the characteristic action of nitroxyl.


Sign in / Sign up

Export Citation Format

Share Document