The Influence of Hydrogen on the Frangibility of Modern Structural Steels Processed at a CSP-plant

Mehaničkim, metalografskim i SEM ispitivanjima proučavan je utjecaj vodika na krhkost modernih visokočvrstih dvofaznih DP- i višefaznih TRIP-čelika. Rezultati proučavanja mikrostrukturnih i mehaničkih svojstava termomehanički obrađenih TMCP-čelika prije i nakon navodičenja ukazali su na činjenicu da je TRIP-čelik otporniji na vodikovu krhkost, o čemu svjedoči njegova sitnozrnata mikrostruktura bez pukotina te nepromijenjene vrijednosti za mehanička svojstva nakon navodičenja.By mechanical testing, metallographic and SEM analyses, the influence of hydrogen on the frangibility of modern high-strength dual phase DP- and multiphase TRIP-steels was studied. Results of studying of microstructural and mechanical properties of thermomechanically controlled processed TMCP-steels before and after hydrogenation indicate that TRIP-steel has higher resistance to HE, which can be seen from its fine-grained microstructure with no cracks and also from unchanged mechanical performances after hydrogenation

PROPERTIES OF THE CHEMICALLY ACTIVATED CARBON ANODE DUST

Ugljična anodna prašina (UAP) otpadni je materijal pri proizvodnji aluminija. Kemijski sastav UAP određen je metodom apsorpcijske spektrometrije (AAS), a mineraloški sastav metodom difrakcije rendgenskog zračenja (XRD). Površinska svojstva (specifična površina, prosječni promjer pora i ukupni volumen pora) određeni su Brunauer Emmett Telleorovom (BET) metodom i Barrett-Joyner-Halendainom (BJH) metodom. Mikroskopska ispitivanja provedena su pretražnom elektronskom mikroskopijom (SEM). Sva su ispitivanja provedena prije i nakon kemijske aktivacije UAP s KOH, ZnCl2 i organskim kiselinama (octenom i limunskom). Dobiveni rezultati pokazali su pozitivan utjecaj kemijske aktivacije na kemijska i strukturna svojstva ugljične anodne prašine kao potencijalnoga jeftinog adsorbensa.The carbon anode dust (CAD) is waste material of the aluminium production industry. The chemical and mineralogical composition of CAD was examined by atomic absorption spectroscopy (AAS) and the X-ray diffraction method (XRD), respectively. Surface area properties (specific surface area, average pore diameter, total pore volume) are determined by the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. Microscopic observation was conducted using scanning electron microscopy (SEM method). All of investigations were performed before and after chemical activation of CAD by KOH, ZnCl2 and by organic acids (acetic and citric). The results obtained suggest the positive effect of chemical activation on the chemical and structural properties of carbon anode dust as a potentially low-cost adsorbent

The change in surface area properties of blast furnace sludge treated by citric acid

The blast furnace sludge (BFS) is a waste material of pig iron production. The chemical and mineralogical composition of BFS was examined by Proton Induced X-ray Emission (PIXE) and X-ray Diffraction (XRD) methods. Surface area properties (specific surface area, average pore diameter, total pore volume) are determined by the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) method. The microscopic observation was conducted using a scanning electron microscopy (SEM method). Chemical treatment of BFS was performed by adsorbed citric acid. Thermal treatment was done by heating at 700°C. The surface properties of the blast furnace sludge are compared to those obtained after treatment. The results have shown that this successfully performed experiment modified the surface of BFS as a potentially low-cost adsorbent

Passivity of Some Dental Materials in Ringer’s Solution

U ovome radu ispitana je korozijska otpornost dviju eksperimentalnih zubnih slitina, Co-Cr-Mo i Co-Cr-Ni, jedne komercijalne Co-Cr-Mo (Wironit®) slitine, titana i Ag-amalgama (Permite®) u Ringerovoj otopini. Na osnovi elektrokemijskih mjerenja određen je relevantni pokazatelj lokalne korozije - piting potencijal Epit, pri kojem nastaje proboj pasivnoga sloja i pojava lokalne korozije. Vrjednovanjem materijala prema piting potencijalu pokazalo se da je korozijski najstabilniji čist titan, slijede ga komercijalna slitina Wironit®, te Co Cr-Mo i Co-Cr-Ni slitine, a amalgam se je pokazao najmanje otpornim u ispitnim uvjetima koji oponašaju medij usne šupljine.In this paper corrosion resistance of two experimental dental alloys, Co-Cr-Mo and Co-Cr-Ni, one commercial Co-Cr-Mo (Wironit®) alloy, high purity titanium and Ag-amalgam (Permite®) was studied in Ringer’s solution. On the basis of electrochemical measurements, the relevant indicator of local corrosion - pitting potential Epitt , at which the breakdown of passive layer and the effects of local corrosion start, was determined. By ranking of materials according to pitting potential, it was found that pure titanium is the most stable material followed by commercial alloy Wironit®, Co-Cr-Mo and Co-Cr-Ni alloys, while amalgam showed the lowest resistance in the experimental conditions of model oral cavity medium

REMOVAL OF Ni(II) FROM AQUEOUS SOLUTION BY LOW-COST ADSORBENTS

The use of low-cost adsorbents has been investigated as a replacement for costly adsorbents and methods of removing nickel ions from aqueous solution. The purpose of this review article is to provide the scattered available information on various aspects of utilization of low-cost adsorbents derived from agricultural waste, industrial by-products and waste material or natural material. To highlight their technical applicability, selected information on initial nickel concentration, pH level, dose required, adsorption capacity, temperature, thermodynamic data, adsorption isotherm, adsorption kinetics is presented. In generall, technical applicability and cost-effectiveness are the key factors in the selection of the most suitable adsorbent to treat aqueous solution contain nickel ions

Characterization of Ladle Furnace Slag from Carbon Steel Production as a Potential Adsorbent

A promising type of steel slag for applications is the ladle furnace (LF) slag, which is also known as the basic slag, the reducing slag, the white slag, and the secondary refining slag. The LF slag is a byproduct from further refining molten steel after coming out of a basic oxygen furnace (BOF) or an electric arc furnace (EAF). The use of the LF slag in further applications requires knowledge of its characteristics. The LF slag characterization in this paper has been performed using the following analytical methods: chemical analysis by energy dispersive spectrometry (EDS), mineralogical composition by X-ray diffraction (XRD), surface area properties by the Brunauer-Emmett-Teller (BET) and the Barrett-Joyner-Halenda (BJH) methods, surface chemistry by infrared absorption (FTIR) spectroscopy, and morphological analysis by scanning electron microscopy (SEM). The results showed that the main compounds are calcium, silicon, magnesium, and aluminium oxides, and calcium silicates under their various allotropic forms are the major compounds in the LF slag. Surface area properties have shown that the LF slag is a mesoporous material with relatively great BET surface area. The ladle furnace slag is a nonhazardous industrial waste because the ecotoxicity evaluation by its eluate has shown that the LF slag does not contain constituents which might in any way affect the environment harmfully

Pit nucleation on as-cast aluminiuim alloy AW-5083 in 0.01M NaCl

The use of aluminium alloys in a wide range of technical applications is related mostly to the two facts: they facilitate weight saving of final products (if compared to the steel) and they are prone to spontaneous passivity due to the coherent surface oxide layer which impedes further reaction of aluminium with the environment. Among the commercial Al alloys, EN AW-5083 alloy is a representative non-heat treatable Al-Mg based alloy which possesses many interesting characteristics as a structural material, such as low price, moderately high strength, high formability in conjunction with superplasticity and good corrosion resistance in marine atmospheres. Aiming to enhance the knowledge of possible interactions of studied alloy EN AW-5083 in as-cast condition with chloride media, electrochemical measurements were used to follow the pitting behaviour in 0.01 M NaCl. The results of tests have shown that susceptibility of alloy to pitting corrosion is strongly influenced by the microstructural constituents of the alloy in as-cast condition

Surface properties of carbon black treated by inorganic acids

Cilj je ovog rada ispitati utjecaj kemijske obrade čađe anorganskim oksidirajućim kiselinama (H2SO4 i HNO3) na njezina površinska svojstva. Specifična površina, prosječni promjer pora i raspodjela veličina pora analizirani su metodama Brunauer-Emmett-Teller (BET) i Barrett-Joyner-Halenda (BJH). Mikroskopska opažanja provedena su pretražnom elektronskom mikroskopijom (SEM). Za identifi ciranje površinskih skupina prije i nakon obrade čađe upotrijebljena je Fourierova pretvorna infracrvena spektrometrija (FTIR). Rezultati su pokazali da je kemijska obrada s H2SO4 modifi cirala površinu čađe. Istodobno, nisu uočene znatnije promjene specifi čne površine, veličine pora i raspodjele veličina pora nakon obrade objema kiselinama. Dobiveni rezultati omogućuju procjenu upotrebe čađe kao adsorbenta, čime se proširuje područje njezine primjene.The aim of this work is to investigate the infl uence of chemical treatment by inorganic acids (H2SO4 and HNO3) as oxidizing agents on the surface properties of carbon black. The specifi c surface area, average pore diameter, total pore volume were analyzed by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. Fourier transform infrared spectroscopy (FTIR) analysis was used to identify the changes in the sample surface groups before and after chemical treatment. Microscopic observation was conducted using scanning electron microscopy (SEM) method. The results have shown that chemical treatment by H2SO4 modified the carbon black surface. At the same time there were no significant changes in the specific surface area, average pore diameter, total pore volume after treatment with both acids. The obtained results allow assessment of the use of carbon black as an adsorbent thereby extending the scope of its application