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1

Coupled action of ozone and UV radiation towards obtaining adipic acid from cyclohexane/one

Marek Adam A., Lisicki Dawid

Polish Journal of Chemical Technology

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2024

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Vol. 26, nr 1

97--101

EN

A lot of research is constantly underway in the world to develop new or improve the current processes of the chemical industry to make them more effective and environmentally friendly. The described research on the oxidation of cyclohexane or cyclohexanone to adipic acid with a coupled action of UV radiation and oxygen–ozone mixture, instead of the currently used oxidation with HNO3, is part of this trend. Gas chromatography was used to determine process indicators, such as cyclohexane conversion and selectivity to AA, which exceeded 50% at 25°C, after 16 h. This method can also be used for the preparation of other dicarboxylic acids from cycloalkanes, which proves its universal character.

2

Odzysk kobaltu i manganu ze strumieni odpadowych przemysłu petrochemicznego na przykładzie procesu produkcji kwasu tereftalowego

Kura Łukasz, Jurczakowski Rafał, Wiśniewski Piotr

Przemysł Chemiczny

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2023

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T. 102, nr 6

600--605

PL

Stwierdzono ilościowe wytrącanie szczawianów kobaltu(II) i manganu(II) (stężenia metali poniżej LOD: Co < 0,35 ppm, Mn < 0,27 ppm) w stężonym roztworze kwasu octowego (90% mas.), powszechnie stosowanym jako rozpuszczalnik w przemysłowych procesach utleniania p-ksylenu do kwasu tereftalowego. Obecność zanieczyszczeń typowych dla procesu utleniania p-ksylenu, czyli kwasu benzoesowego, kwasu bromowodorowego oraz jonów sodu nie miała negatywnego wpływu na powstawanie osadów. Obecność stałego kwasu tereftalowego w mieszaninie reakcyjnej miała pozytywny wpływ na proces odzyskiwania katalizatora. Zaobserwowano, że szczawiany tworzą aglomeraty na powierzchni stałego kwasu tereftalowego, co ułatwia oddzielenie osadu od cieczy macierzystej. Ponadto potwierdzono wysoką efektywność wytrącania w szerokim zakresie stężeń metali (50-1600 ppm). Wyniki pokazują, że strącanie kwasem szczawiowym jest skuteczną metodą odzyskiwania katalizatorów homogenicznych zawierających związki kobaltu(II) i manganu(II).

EN

A 1% soln. of (COOH)₂ in 90% MeCOOH was added to a 90% MeCOOH soln. contg. Co and Mn ions at concns. of 500 and 300 ppm, resp., and impurities typical of the oxidn. of p-xylene to C₆H₄(COOH)₂ (BzOH, HBr and Na ions) in amts. simulating the mother liquor compn. of a real industrial process. After mixing, the Co and Mn contents of the decanted liq. were detd. by AAS. Presence of impurities had no neg. impact on the ppt. formation. The presence of solid C₆H₄(COOH)₂ in the reaction mixt. had a pos. impact on the catalyst recovery process. Oxalates formed agglomerates on the surface of the solid C₆H₄(COOH)₂ which facilitated the sepn. of the ppt. from the mother liquor. The pptn. with (COOH)₂ is an efficient recovery method of spend Co(II) and Mn(II) homogeneous catalysts.

3

Klimat i oceanografia przełomu jury i kredy zachodniej Tetydy

Lodowski Damian Gerard

Przegląd Geologiczny

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2023

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Vol. 71. nr 10

514--522

EN

The key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controlson one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term coThe key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controlson one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term consequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition; amongst them, the best documented so far are: long term marine regression during the Tithonian-early Berriasian, climate aridization during the late Tithonian-early Berriasian, and tectonic activity in western parts of the Neo Tethys Ocean during the late Berriasian-Valanginian. This study, which is based on the Ph Ddissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic-earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pośrednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms ofpaleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providinga consistent scenario of the Tithonian-Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian-lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena cooccurred with elevated accumulations of nutrient-type elements (i. e. enrichment factor of Zn). Besides, collected data document the late Tithonian-early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian-early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced sea water stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the Neo Tethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the Neo Tethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings). nsequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition; amongst them, the best documented so far are: long term marine regression during the Tithonian-early Berriasian, climate aridization during the late Tithonian-early Berriasian, and tectonic activity in western parts of the Neo Tethys Ocean during the late Berriasian-Valanginian. This study, which is based on the Ph Ddissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic-earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pośrednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms ofpaleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providinga consistent scenario of the Tithonian-Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian-lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena cooccurred with elevated accumulations of nutrient-type elements (i. e. enrichment factor of Zn). Besides, collected data document the late Tithonian-early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian-early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced sea water stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the Neo Tethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the Neo Tethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings).

4

Modern materials used for environmental barrier coatings – a review

Mokrzycka Magdalena, Jopek Jakub, Słyś Anita, Góral Marek, Ochał Kamil

Ochrona przed Korozją

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2023

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nr 4

104--112

EN

In this article, the materials used for EBC coatings, representing next stage in the development of heat-resistant layers, and thermal barrier coatings are reviewed. In the introduction, the design of gas turbine is characterized, as well as the materials used for the hot part components and the requirements for protective coatings. Ceramic materials that can be an alternative to currently used nickel superalloys for turbine blades are also described. The requirements for EBC coatings were analyzed and then the various types of EBC coatings were characterized, as well as their degradation mechanisms.

PL

W artykule dokonano krótkiego przeglądu materiałów stosowanych na powłoki EBC (environmental barrier coatings) reprezentujących kolejny etap zaawansowania warstw żaroodpornych i powłokowych barier cieplnych (TBC – thermal barrier coatings). Opisano konstrukcję turbiny gazowej i materiały stosowane do produkcji elementów części gorącej oraz wymagania w zakresie powłok ochronnych. Opisane zostały również materiały ceramiczne, które mogą być alternatywą dla obecnie stosowanych nadstopów niklu używanych do wytwarzania łopatek turbin. Przeprowadzono analizę wymagań dotyczących powłok EBC, a następnie scharakteryzowano poszczególne rodzaje tych powłok, a także mechanizmy ich degradacji.

5

Manufacturing Cu-Pb alloys and studying efficiency in resisting oxidation

Sufian Amina, Hamood Mahmood Ahmad Al- Jiboori

Ochrona przed Korozją

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2023

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nr 12

388--392

EN

Binary alloys of copper and lead were produced by casting these elements in specially designed moulds with dimensions appropriate to the tests to be carried out on them. The effectiveness of these alloys in resisting oxidation was then studied in an atmosphere of a mixture of sodium chloride vapour and sodium sulphate at specific concentrations and heating the mixture to 180°C. Recently, corrosion has become a major problem in the overall performance of many engineering devices due to automotive exhaust gases produced by the internal combustion engine, which leads to corrosion of materials that make up some components of engineering industries. Copper also has good corrosion performance due to the formation of a copper oxide layer, which has made it the most important material in industrial applications. Through this research, we have achieved the desired goal as the alloys produced have shown their efficiency in resisting saline and acidic conditions and at high levels. The best sample is Cu95Pb5 and Cu90Pb10 with little difference between them in terms of efficiency. The aim of this work is to produce alloys and study their efficiency in resisting oxidation at high temperatures.

PL

Binarne stopy miedzi i ołowiu zostały wytworzone metodą odlewania w specjalnie zaprojektowanych formach o wymiarach dostosowanych do badań. Odporność stopów na utlenianie została zbadana w atmosferze mieszaniny oparów chlorku sodu i siarczanu sodu w określonych stężeniach i po podgrzaniu mieszaniny do 180°C. Korozja jest poważnym problemem, zaburza funkcjonowanie wielu urządzeń inżynieryjnych. Jej źródłem są m.in. spaliny wytwarzane przez silniki spalinowe. Miedź ma dobre właściwości antykorozyjne ze względu na warstwę tlenku miedzi, tworzącą się na jej powierzchni w wyniku utleniania. Z tego względu jest głównym materiałem stosowanym w przemyśle. Badane stopy miedzi i ołowiu wykazały wysoką odporność na działanie soli i kwasów w dużych stężeniach. Najlepsze wyniki uzyskano dla stopów Cu95Pb5 i Cu90Pb10 (różnica między nimi była niewielka). Celem pracy było zbadanie odporności wytworzonych stopów na utlenianie w wysokich temperaturach.

6

Removal of Organic Pollutants from Wastewater Using Different Oxidation Strategies

Fajri Nibras Raad, Mohammed Rusul Naseer

Journal of Ecological Engineering

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2023

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Vol. 24, nr 10

351--359

EN

Many countries use nontraditional methods to treat wastewater, especially those with water lacks. Among these methods, heterogeneous photocatalysis is more commonly widely used since it converts organic molecules into carbon dioxide and water. In this study, the photocatalytic degradation process of total organic carbon was investigated by TIO2/UV technique (TUT). This treatment is carried out in a batch recycle reactor using a UV light and catalyst TIO2. The optimum operating parameters were investigated regarding the best organic removal including, total organic carbon concentration, flow rate, pH, irradiation time, and photocatalysis dosage. The result showed that the TUT is affected by reducing total organic carbon (TOC) from synthetic wastewater (SW) by 61% at 50 ml/min of flow rate, 250 mg of catalyst concentration TIO2, and a concentration of TOC of 25 mg/l. Then the result of TUT was compared with a process of combining TIO2/UV and an oxidizing agent (Hydrogen peroxide H2O2). It was found that 73% of organic removal was obtained which is best than TUT when using an H2O2 dosage of 100 mg/l. Experimentally, Ozone was also added to the process of TUT and the result showed that the removal percentage increased to 80%.

7

The formation of Al-Si aluminide coatings by pack cementation method on TNM-B1 intermetallic alloy

Woźniak Mateusz, Góral Marek, Kościelniak Barbara

Advances in Mechanical and Materials Engineering

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2023

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Vol. 40, nr 1

79--86

EN

The TiAl intermetallics are the promising material for aerospace application. According to its insufficient oxidation resistance above 900°C the using of protective coatings is necessary. The diffusion aluminide coatings based on TiAl2 or TiAl3 phases permits to formation of alumina scale on the surface of TiAl alloys. The pack cementation with Si doping is one of the most popular method of this type of coatings production. In present article the influence of Si content in the pack, process time and temperature during pack cementation process were investigated. The thickness of obtained coating was in range 20-50 μm. When Si content was higher the formation of titanium silicides was observed using almost all analysed values of process parameters. The results showed that using of 24 wt. % Si containing pack and process parameters: 4h/950°C enables to obtain the coating characterized by optimal thickness and structure. The porosity and cracks in coatings according to TiAl phases brittleness was observed.

PL

Fazy międzymetaliczne TiAl są obiecującym materiałem do zastosowań w lotnictwie. Ze względu na niedostateczną odporność na utlenianie powyżej 900°C konieczne jest stosowanie powłok ochronnych. Dyfuzyjne powłoki aluminidkowe na bazie faz TiAl2 lub TiAl3 pozwalają na tworzenie się zgorzeliny tlenku aluminium na powierzchni stopów TiAl. Aluminiowanie metodą kontaktowo gazową z wprowadzaniem Si jest jedną z najpopularniejszych technik wytwarzania tego typu powłok. W niniejszym artykule zbadano wpływ zawartości Si w powłoce w zależności od czasu trwania procesu oraz temperatury. Grubość otrzymanej powłoki zawierała się w przedziale 20-50 μm. Gdy zawartość Si była wyższa, obserwowano powstawanie krzemków tytanu przy prawie wszystkich analizowanych wartościach parametrów procesu. Wyniki pokazały, że użycie proszku zawierającego 24% wag. % Si oraz czasu i temperatury 4h/950°C pozwala na uzyskanie powłoki charakteryzującej się optymalną grubością i strukturą. Zaobserwowano porowatość i spękania powłok.

8

Microstructural Evolution and Oxidation Behavior of Fe-4Cr-6Ti Ferritic Alloy with Fe2Ti Laves Phase Precipitates

Demirel Ahmet, Çetin Emre Can, Karakuş Ali, Ataş Mehmet Şahin, Yildirim Mehmet

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 3

827--836

EN

The microstructural properties and hardness of a model ternary Fe-4Cr-6Ti ferritic alloy aged at 800°C for 8, 16 and 24 h are investigated in detail. Fine Fe2Ti Laves phase particles precipitate in the α-Fe (ferrite) matrix phase after solutionizing and subsequent aging treatments. The size and amount of Fe2Ti precipitates gradually increase with increasing aging time. The magnetic measurements of the aged samples confirm the variations in the microstructural properties including the volume fraction of the constituent phases, and Ti content of the α-Fe matrix phase. The mean Vickers microhardness value also increases from 203.5 to 238.4 with increasing aging time from 8 to 24 h. In addition, the cyclic oxidation behavior of 24 h aged sample, which contains maximum amount of Fe2Ti precipitates, is also investigated in detail. X-ray diffraction analysis reveals that scale product is α-Fe2O3 (hematite). Significant scale spallation and void formation is observed on the surfaces of 24 h aged Fe-4Cr-6Ti sample oxidized at 500°C.

9

Metody utleniania aldehydu 2-etyloheksanowego do kwasu 2-etyloheksanowego o potencjale aplikacyjnym

Czieszowic Łukasz, Orlińska Beata, Pankalla Ewa

Przemysł Chemiczny

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2021

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T. 100, nr 8

770--774

PL

Kwas 2-etyloheksanowy (2-EHA) znajduje szerokie zastosowanie m.in. w przemyśle chemicznym, farmaceutycznym i kosmetycznym. Na skalę przemysłową jest otrzymywany w procesie utleniania aldehydu 2-etyloheksanowego (2-EHAL). W pracy dokonano przeglądu literaturowego i przedstawiono dane dotyczące metod utleniania 2-EHAL z uwzględnieniem tych o potencjalnym zastosowaniu przemysłowym.

EN

A review, with 46 refs., of BuEtCCHO oxidn. methods using greener catalysts, solvents and oxidizing agents, including those with potential industrial application. An alternative to the processes currently used in the chem. industry may be reaction systems using N-hydroxyphthalimide as a catalyst.

10

Selective flotation separation of chalcopyrite and sphalerite by thermal pretreatment under air atmosphere

Zhou Hepeng, Geng Liang, Zhang Yongbing, Yang Zhizhao, He Kunzhong, Xie Fanxin

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 1

305--314

EN

Thermal pretreatment was performed to enhance the flotation separation of chalcopyrite and sphalerite under the air atmosphere for the first time. Microflotation experiment showed that the floatability of chalcopyrite vanished after thermal pretreatment at above 170℃. By contrast, the floatability of sphalerite was well maintained with a flotation recovery of 90%. In artificial mixed mineral flotation experiments, the separation of sphalerite and chalcopyrite was successfully realized by thermal pretreatment. Results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses indicated that the chalcopyrite surface was oxidized dramatically at 170℃, and hydrophilic species such as sulfate (SO42-), oxides (CuO and Fe2O3), and hydroxyl species (Fe(OH)3) were formed on the surface. Hence, the adsorption of potassium butyl xanthate on chalcopyrite decreased significantly after thermal pretreatment. The reason for the higher oxidation speed of chalcopyrite than that of sphalerite was also analyzed.

11

Use of Metal Oxide-Modified Aerated Concrete for Cleaning Flue Gases from Carbon Monoxide

Ivanenko Olena, Gomelya Nikolai, Shabliy Tetyana, Trypolskyi Andrii, Nosachova Yuliia, Leleka Serhii, Trus Inna, Strizhak Peter

Journal of Ecological Engineering

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2021

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Vol. 22, nr 5

104--113

EN

The necessity of development of technical solutions that will allow to reduce carbon monoxide emissions of flue gases of industrial productions is substantiated. It is shown that the most rational design solution to the problem of carbon monoxide pollution during the firing of electrode blanks is the use of aerated concrete blocks with a catalyst, which can be quickly and conveniently located directly on the carbon material of the “green” electrodes pouring in the subfloor space of the firing furnaces. Modified by oxides of Mn4+, Fe2+, Fe3+, Cu2+, Cr3+ -catalysts based on aerated concrete were obtained. It is shown that in an empty reactor in the temperature range 200–400 °С the degree of conversion of carbon monoxide in the absence of a catalyst is zero. It is established that on the investigated catalysts based on aerated concrete 100% oxidation of carbon monoxide is achieved at a temperature of 390 °C in the case of using a mixture of catalyst powders 30% CuO + 70% MnO2, 40% CuO + 60% MnO2, 50% Fe (FexCr1-x) 2O4 + 50% MnO2; 50% Fe3O4 + 50 % MnO2. It is determined that the addition of ferrite catalyst powder in aerated concrete in a mixture or without manganese dioxide does not critically affect the mechanical properties of the products.

12

Usage of Sorbent-Catalyst to Accelerate the Oxidation of Manganese

Gomelya Mykola, Tverdokhlib Mariia, Shabliy Tetyana, Linyucheva Olga

Journal of Ecological Engineering

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2021

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Vol. 22, nr 4

232--239

EN

The processes of manganese (II) ions removal from water using sorbent catalysts and ion exchange materials modified with iron oxides were studied. It was shown that manganese ions oxidize very slowly in artesian water, even when the pH is adjusted to 9.0. Intensive aeration of solutions due to stirring also does not promote the oxidation of manganese (II) ions. The degree of manganese extraction due to oxidation is reduced from 20–30% for solutions with a concentration of manganese ions of 1 and 5 mg/dm3 to 11–15% for solutions with a concentration of 15 and 30 mg/dm3. A significant increase in the oxidation efficiency of manganese ions was achieved by using magnetite as a sorbent catalyst. The efficiency of water demanganization increases along with the intensity of water aeration when mixing solutions. It was established that strongly acid cation exchangers provide efficient extraction of manganese ions from water. At the same time, a high exchange capacity of strong acid cation exchange resin KU-2–8 in acid and salt form was noted. It was shown that the capacity of manganese ions of this cation exchange resin in the Ca2+-form is slightly lower. When using the KU-2–8 in Ca2+-form of cation exchange resin to remove manganese ions from the solution already in the first samples, the leakage of manganese ions at the level of 10 mg/dm3 and above was observed. This indicates that this form of ion exchanger is not suitable for deep purification of water from manganese (II) ions. In order to increase the efficiency of manganese ion extraction from water, increase the duration of the filter cycle, magnetite and magnetite-modified KU-2–8 cation exchange resin were used as a sorbent-catalyst. It was shown that the cation exchange resin modified with magnetite provides the removal of a significant part of manganese ions due to catalytic oxidation on magnetite. The conditions of effective manganese extraction under static and dynamic conditions are determined.

13

Development of a Catalyst for Flue Gas Purification from Carbon Monoxide of Multi-Chamber Furnaces for Baking Electrode Blanks

Ivanenko Olena, Trypolskyi Andrii, Gomelya Nikolai, Karvatskii Anton, Vahin Andrii, Didenko Olga, Konovalova Viktoria, Strizhak Peter

Journal of Ecological Engineering

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2021

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Vol. 22, nr 1

174--187

EN

The catalysts based on natural zeolite-clinoptilolite of Sokyrnytsia deposit modified with oxides of Mn4+, Fe2+, Fe3+, Cu2+, Cr3+ were synthesized. It was determined that 100% conversion of carbon monoxide was achieved at a temperature of 390°C when using the copper-manganese-oxide catalyst (30% CuO + 70% MnO2). It was shown that although the use of the manganese-oxide catalyst provided 92.8% of CO conversion degree, this catalyst had the most advantages for application compared to the other studied solids. The structural parameters of the manganese-oxide catalyst were determined using XRD, SEM, and nitrogen adsorption. The composition of the main elements of the catalyst samples was determined by micro-X-ray spectral analysis. It was shown that using the catalyst containers in chambers heated by flue gases in the fire channels of a multi-chamber furnace for baking of electrode blanks can be one of the constructive solutions to the problem of flue gas purification from carbon monoxide. The environmental safety of the copper-manganese-oxide catalyst application for the treatment of the flue gases of electrode production is justified by obtaining a catalyst from spent sorbents for purification of the manganese-containing natural water and its non-toxicity in the case of burial or storage in landfills.

14

Scaling Behaviour of Si-alloyed Steel Slabs under Reheating Conditions

Mikl Gregor, Höfler Thomas, Gierl-Mayer Christian, Danninger Herbert, Linder Bernhard, Angeli Gerhard

Journal of Casting & Materials Engineering

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2021

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Vol. 5, no. 4

71--74

EN

Reheating of steel slabs for further processing such as hot rolling usually takes place in gas-fired pusher furnaces. Temperatures well above 1000°C, combined with an atmosphere containing H2O, CO2, and O2, lead to substantial oxidation of most steel grades. Newly developed advanced steels often contain significant amounts of Si. This element plays a dominant role in the scaling behaviour near the steel-scale-interface, since fayalite (Fe2SiO4) forms a eutectic with wuestite (Fe1–xO) that melts as low as 1177°C. To better understand the high temperature oxidation behaviour, lab-scale trials were performed with different steel grades containing up to 3 wt.% Si. Possible interactions of Si with other alloying elements present in the samples such as Cr, Mn and Al were also of interest. The atmosphere contained 20% H2O, 7% CO2, and 3% O2, resembling reheating conditions in pusher furnaces, and temperatures ranged from 1100 to 1240°C. For metallographic investigation, the oxidised samples were cold mounted under vacuum using taper section angles. After preparation, the sections were examined through light microscopy, SEM/EDS, XRD, and TEM. The local distribution of the alloying elements could be mapped efficiently, and phase identification was successful in most parts. Under the applied experimental conditions, the elements of interest were present in their oxidic form either as pure or as mixed oxides. Higher Si-contents led to an increased build-up of eutectic melting phase at the steel-scale-interface at temperatures above 1177°C, which in turn further accelerated the oxidation.

15

Influence of Si Addition on Oxide Growth of Al-6 mass%Mg Alloy Melts

Yoon Young-Ok, Ha Seong-Ho, Shah Abdul Wahid, Kim Bong-Hwan, Lim Hyun-Kyu, Kim Shae K.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

695--698

EN

Influence of Si addition on oxide layer growth of Al-6 mass%Mg alloys in molten state was investigated in this study. After melt holding for 24 h, the melt surface of only Si-free alloy became significantly bumpy, while no considerably oxidized surface was observed even with 1 mass%Si addition. There was no visible change on the appearance of melt surfaces with increasing Si content. As a result of compositional analysis on the melt samples between before and after melt holding, the Si-added alloys nearly maintained their Mg contents even after the melt holding for 24 h. On the other hand, the Mg content in the Si-free alloy showed a great reduction. The bumpy surface on Si-free alloy melt showed a large amount of pores and oxide clusters in its cross-section, while the Si-added alloy had no significantly grown oxide clusters on the surfaces. As a result of compositional analysis on the surfaces, the oxide clusters in Si-free alloy contained a great amount of Mg and oxygen. The oxide layer on the Si-added alloy was divided into Mg-rich and Mg-poor areas and contained certain amounts of Si. Such a mixed oxide layer containing Si would act as a protective layer during the melt holding for a long duration.

16

Effect of Cu Addition on Oxide Growth of Al-7 mass%Mg Alloy at High Temperature

Ha Seong-Ho, Shah Abdul Wahid, Kim Bong-Hwan, Yoon Young-Ok, Lim Hyun-Kyu, Kim Shae K.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

699--702

EN

Effect of Cu addition on oxide growth of Al-7 mass%Mg alloy at high temperature was investigated. As-cast microstructures of Al-7 mass%Mg and Al-7 mass%Mg-1 mass%Cu alloys showed α-Al dendrites and area of secondary particles. The 1 mass%Cu addition into Al-7 mass%Mg alloy formed Mg32(Al, Cu)49 ternary phase with β-Al3Mg2. The total fraction of two Mg-containing phases in Cu-added alloy was higher than the β-Al3Mg2 fraction in Cu-free alloy. From measured weight gains depending on time at 500°C under an air atmosphere, it was shown that all samples exhibited significant weight gains depending on time. Al-7mass%Mg1mass%Cu alloy showed the relatively increased oxidation rate when compared with Cu-free alloy. All the oxidized cross-sections throughout the entire oxidation time showed coarse and dark areas regarded as oxides grown from the surface to inside, but bigger oxidized areas were formed in the Al-7mass%Mg-1mass%Cu alloy containing higher fraction of Mg-based phases in the as-cast microstructure. As a result of compositional analysis on the oxide clusters, it was found that the oxide clusters contained Mg-based oxides formed through internal oxidation during a long time exposure to oxidizing environments.

17

Consolidation and Oxidation of Ultra Fine WC-Co-HfB2 Hard Materials by Spark Plasma Sintering

Park Hyun-Kuk, Oh Ik-Hyun, Kim Ju-Hun, Hong Sung-Kil, Lee Jeong-Han

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

997--1000

EN

In this study, a novel composite was fabricated by adding the Hafnium diboride (HfB2) to conventional WC-Co cemented carbides to enhance the high-temperature properties while retaining the intrinsic high hardness. Using spark plasma sintering, high density (up to 99.4%) WC-6Co-(1, 2.5, 4, and 5.5 wt. %) HfB2 composites were consolidated at 1300°C (100°C/min) under 60 MPa pressure. The microstructural evolution, oxidation layer, and phase constitution of WC-Co-HfB2 were investigated in the distribution of WC grain and solid solution phases by X-ray diffraction and FE-SEM. The WC-Co-HfB2 composite exhibited improved mechanical properties (approximately 2,180.7 kg/mm2) than those of conventional WC-Co cemented carbides. The high strength of the fabricated composites was caused by the fine-grade HfB2 precipitate and the solid solution, which enabled the tailoring of mechanical properties.

18

Oxide Layer Evolution of Cast Fe24Cr12NiXNb Heat-Resistant Cast Steels at 900°C in Atmospheric Air

Ramos P. A., Coelho R. S., Pinto H. C., Soldera F., Mücklich F., Brito P. P.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 1

125--131

EN

The austenitic stainless steels are a group of alloys normally used under high mechanical and thermal requests, in which high temperature oxidation is normally present due to oxygen presence. This study examines the oxide layer evolution for Fe24Cr12NiXNb modified austenitic stainless steel A297 HH with 0,09%Nb and 0,77%Nb content at 900°C under atmospheric air and isothermal oxidation. The modifiers elements such as Mo, Co and Ti, added to provide high mechanical strength, varied due to the casting procedure, however main elements such as Cr, Ni, Mn and Si were kept at balanced levels to avoid microstructure changing. The oxide layer analysis was performed by confocal laser scanning microscopy (CLS) and scanning electron microscopy (SEM). The elemental analysis of the different phases was measured with energy dispersive X-ray spectroscopy (EDX). The Nb-alloyed steel generated a thicker Cr oxide layer. Generally elemental Nb did not provide any noticeable difference in oxide scale growth, for the specific range of Nb amount and temperature studied. High temperature oxidation up to 120h was characterized by protective Cr oxidation, after this period a non-protective Fe-based oxidation took place. Cr, Fe and Ni oxides were observed in the multilayer oxide scale.

19

The oxidation of WC-Co knives in wood extract

Barlak Marek, Wilkowski Jacek, Ostrowski Krzysztof, Werner Zbigniew, Zagórski Jerzy

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2021

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No. 114

15--25

EN

The oxidation of WC-Co knives in wood extract. The virgin WC-Co knives for wood machining and those implanted with Mg, Cr, Zn and Ni were corroded in pH 4 wood extract. A change of oxygen content throughout the experiment was determined using EDS method. The obtained results suggest a passivation of the corroded WC-Co material implanted with selected elements.

PL

Utlenianie noży WC-Co w ekstrakcie drzewnym. Wyjściowe noże WC-Co do obróbki drewna oraz noże implantowane jonami Mg, Cr, Zn i Ni zostały poddane korozji w ekstrakcie drzewnym o wartości pH 4. Zmianę zawartości tlenu w trakcie eksperymentu oznaczono metodą EDS. Uzyskane wyniki sugerują wystąpienie zjawiska pasywacji utlenianego materiału WC-Co implantowanego wybranymi pierwiastkami.

20

Influence of environment, temperature and time of the thermal modification of ash wood (Fraxinus excelsior L.) on the cellulose weight average degree of polymerization

Gawron Jakub

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2021

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No. 116

39--45

EN

Influence of environment, temperature and time of the thermal modification of ash wood (Fraxinus excelsior L.) on the cellulose weight average degree of polymerization . Using the size-exclusion chromatography (HPLC SEC) method, the weight average degree of cellulose polymerization was determined. The polymer was isolated by the Kürschner-Hoffer method from ash wood (Fraxinus excelsior L.). The wood was thermally modified in different environments (nitrogen, steam and air) at 190°C and modification times of 2, 6 and 10 hours. Depending on the anaerobic atmosphere used, the highest values of the weight average degree of cellulose polymerization were obtained for the nitrogen environment, followed by steam and air. The effect of modification time on the weight average degree of polymerization was observed. The highest values were obtained for wood modified at 2 hours, then 6 and 10 hours of modification. The native wood showed the highest degree of polymerization. On the basis of the results obtained, it can be concluded that for the material studied the oxidation and degradation reactions occurring depend on the environment and time for a given temperature of wood modification.

PL

Wpływ środowiska, temperatury i czasu modyfikacji termicznej drewna jesionu wyniosłego (Fraxinus excelsior L.) na wagowo średni stopień polimeryzacji celulozy. Wykorzystując metodę chromatografii wykluczania przestrzennego (HPLC SEC), wyznaczono wagowo średni stopień polimeryzacji celulozy. Polimer wyodrębniono metodą Kürschnera-Hoffera z drewna jesionu wyniosłego (Fraxinus excelsior L.). Drewno poddano modyfikacji termicznej w różnym środowisku (azot, para wodna i powietrze) w temperaturze 190°C i czasach modyfikacji wynoszących 2, 6 i 10 godzin. W zależności od zastosowanej atmosfery beztlenowej uzyskano największe wartości wagowo średniego stopnia polimeryzacji celulozy dla środowiska azotu, następnie pary wodnej i powietrza. Zaobserwowano wpływ czasu modyfikacji na wagowo średni stopień polimeryzacji. Największe jego wartości uzyskano dla drewna modyfikowanego w czasie 2 godzin następnie 6 i 10 godzin modyfikacji. Drewno natywne wykazuje największy stopień polimeryzacji. Na podstawie uzyskanych wyników można stwierdzić, że dla badanego materiału zachodzące reakcje utlenienia i degradacji są zależne od środowiska i czasu dla zadanej temperatury modyfikacji drewna.