Ograniczanie wyników
Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 159

Liczba wyników na stronie
first rewind previous Strona / 8 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  cobalt
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 8 next fast forward last
PL
Wiele pierwiastków chemicznych oraz ich związków ma szerokie zastosowanie w produktach dostępnych na rynku. Są obecne zarówno w produktach żywnościowych, preparatach leczniczych, jak i w kosmetykach. Na podstawie przeglądu literatury i danych producenta dokonano analizy ich aktywności oraz potencjalnych korzyści i zagrożeń wynikających z ich stosowania. Przeanalizowano też wpływ tych substancji na środowisko naturalne.
EN
A review, with 35 refs., of chem. elements and their comps. used in foods, drugs and cosmetics. Their activity, potential benefits and risks as well as environmental impacts were taken into consideration.
EN
The article examines the ability of natural clays to extract heavy metal ions from aqueous solutions by ion exchange. The process of extracting metal ions was considered on the example of the absorption of manganese, nickel and cobalt from natural waters. In order to study the chemical and mineralogical composition of natural kaolin, the following were used in the work: X-ray diffraction and X-ray phase methods, as well as IR spectroscopy. The article presents a comparative analysis of the adsorption of manganese, cobalt and nickel ions on natural kaolin under different temperature conditions. The nature of the interaction of the studied metal ions with kaolin was established. The results obtained on the adsorption of the ions under study show the efficiency of using natural kaolin clay for water purification.
EN
The olefin polymerization catalysts constitute a large group of various compounds. Metallocene complexes are the largest part of this group. However, due to the instability at industrial plastics temperatures and the decomposition of complexes after MAO (or MMAO) activation, they have been partly replaced by non-metallocene compounds. This article concerns the studies on new non- metallocene precatalysts for the olefin polymerization and oligomerization. The report focuses on the structure and the catalytic activities of the complexes of chromium(III), vanadium(IV) and cobalt(II) with the following ligands: dipicolinate, 2-pyridinecarboxylate, oxalate, oxydiacetate, iminodiacetate, 2,2’- bipyridine, 4,4’-dimethoxy-2,2’-bipyridine, 1,10-phenantroline. These complex compounds are highly active precatalysts for olefin polymerization and oligomerization. The complexes: [Cr(dipic)2][Cr(bipy)(dipic)H20]-2H20 and [Cr(dipic) 2]Hdmbipy2.5H20 deserve special attention because they are new type of the precatalysts i.e. organic salt type complexes composed both of organic cations and anions. These compounds are not only interesting because of their structure but also because of their high catalytic activity.
4
Content available remote Gazy osłonowe do spawania niklu, kobaltu i ich stopów
PL
W artykule omówiono rodzaj i skład gazów używanych podczas spawania niklu, kobaltu i ich stopów, jak również opisano wpływ poszczególnych gazów na proces spawania i jakość złączy spawanych.
EN
The type and composition of gases used in welding of nickel, cobalt and their alloys are discussed, as well as the influence of shielding gases on welding process and quality of welded joints are described.
EN
The use of commercial sponges in materials science has gained much recent attention. Their unique properties, namely a fibrous, rigid skeleton, thermal stability and resistance to acid and basic hydrolysis, have been the primary motivation to use them in the development of new composites. In this work, a simple method of immobilization of cobalt and silver cations, followed by their reduction using sodium borohydride, was successfully applied for the first time to obtain functionalized spongin scaffolds. Three different materials, labeled Co_spongin, Ag_spongin and Co-Ag_spongin, were prepared. Their morphological and physicochemical properties were explored using various techniques (SEM+EDS, TG/DTA, FTIR). The focal point of the research was the application of the resulting materials in the reaction of 4-nitrophenol reduction with sodium borohydride in water. It was found that all of the composites possess superior activity in the reduction of 4-nitrophenol, achieving high rate constants of 0.31 min-1 for Ag_spongin, 0.52 min-1 for Co_spongin and 0.86 min-1 for Co-Ag_spongin. Reusability tests showed that all of the composites could be reused five times. Additional structural analysis after catalytic application showed no visible changes in the morphology of the catalysts. The results indicate that spongin can be considered as a facile, cost-effective, renewable and environmentally friendly three-dimensional support for use in heterogeneous catalysis.
EN
The improved TiB2 ceramics were obtained in sintering process at the pressure of 5.5 GPa and temperature of 1550 °C in presence of metallic Co powder. The effect of Co content (ranging from 0 wt.% to 10.0 wt.%) on the phase composition, density, microstructure, Vickers hardness and thermal conductivity of TiB2 ceramics was analyzed. A small amount of new phase Co2 B has been created in the reaction of TiB2 and Co. The relative density of sintered TiB2 ceramics reached 98.1 %. When the mass fraction of Co increased, the porosity increased, while the hardness first increased and then decreased. The maximal Vickers hardness values were equal to 33.3 GPa or 28.2 GPa when the used load was of 4.9 N or 9.8 N, respectively. The highest reached value of thermal conductivity was 88.9 W∙m-1∙K-1. The dense TiB2 ceramics with improved hardness and thermal conductivity were ascribed to the high pressure sintering method and Co sintering aid. High pressure sintering method provides a new way for the preparation of ceramics materials.
EN
In this paper, the sorption capacity of Norit SX2 activated carbon, ground rice husks and C‑160 ion exchange resin in relation to the Cu2+ and Co2+ ions was compared. The studied sorption processes were described using the Langmuir adsorption model. The C‑160 ion exchange resin was characterized by the highest affinity for both Cu2+ and Co2+ ions. It was shown that rice husk and active carbon are efficient sorbents in diluted solutions. The copper recovery for activated carbon, ion exchanger and rice husk was high. The efficiency of this process was 98.1%; 92.3% and 88.9%, respectively. Reducing the volume of acid used for regeneration allowed the solution to be concentrated and facilitated element recovery. Regeneration for cobalt occurred to a lesser extent.
EN
The main objective of this study was to quantitatively and qualitatively idenify trace metal admixtures in ore mineralsfrom Fe-Ti-V ore deposits within the Suwałki Anorthosite Massifin NE Poland. Chemical composition of ore minerals was determined using the CAMECA SX-100 electron microprobe and scanning electron microscope. The most abundant trace elements were Ti and Vhosted in oxides and Co, Ni, Cu, Zn contained in sulphides such aspentlandite, pyrrhotite, chalcopyrite, pyrite, siegenite, millerite. Scarce occurrences of native Bi, hessite and greenockite were identified. Samples, which were depleted in iron oxides were enriched in REE due to the presence ofzircon, apatite and monazite.
EN
Magnesite ore with a low chalcopyrite – cobaltite mineralization was subjected to a series of separations designed to evaluate the possible concentration of the two accessory minerals. Although the Cu-Co grade in the ore (> 0.01% Co, > 0.1% Cu) is significantly lower than the typical economic grades, content of the main valuable mineral for which the ore is mined and processed in combination with a listing of cobalt as a critical raw material, coupled with their higher price might compensate for the additional beneficiation stages. The ore was first crushed and subsequently classified to -100 μm and +100 -400 μm size fractions. The fine fraction was upgraded by froth flotation processing in laboratory froth flotation cell. The coarser fraction was processed in several separation stages including gravity separation on shaking table, magnetic separation and corona electrostatic separation. The same procedure was also repeated with a higher-grade sample as a verification of the procedures. Preliminary results suggest that the accessory minerals can be separated from the talc-magnesite ore and individual mineral concentrates with about 19% Co and 28% Cu were prepared. However, further work must be done to achieve desirable recoveries for the processing to be economically viable.
PL
Ruda magnezu o niskiej mineralizacji chalkopirytu – kobaltytu została poddana serii separacji mających na celu ocenę możliwego uzysku dwóch minerałów towarzyszących. Chociaż zawartość Cu-Co w rudzie (> 0,01% Co,> 0,1% Cu) jest znacznie niższy niż wartości opłacalne ekonomicznie, zawartość głównego cennego minerału (magnezytu) , dla którego ruda jest wydobywana i przetwarzana w połączeniu z zawartością kobaltu jako surowca krytycznego może zrekompensować koszt dodatkowych etapów wzbogacania. W pierwszym etapie rudę kruszono, a następnie klasyfikowano do frakcji o wielkości -100 μm i +100 -400 μm. Drobną frakcję poddawano flotacji pianowej w laboratoryjnej maszynce flotacyjnej. Grubsza frakcja była przetwarzana w kilku etapach, w tym separacja grawitacyjna na stole wstrząsanym, separacja magnetyczna i separacja elektrostatyczna. Ta sama procedura została powtórzona z próbką o wyższych zawartościach. Wstępne wyniki sugerują, że minerały towarzyszące można oddzielić od rudy talku i magnezytu i zyskano koncentraty mineralne z zawartością około 19% Co i 28% Cu. Jednakże konieczne są dalsze prace w celu osiągnięcia pożądanych uzysków, aby przetwarzanie było opłacalne ekonomicznie.
EN
The influence of the electrode geometry on the microstructure and corrosion behaviour of Co-Mo nano-crystalline coatings elaborated by electrodeposition is studied. The corrosion behaviour was determined in the Ringer’s solution at 25°C. Electrodeposition mechanisms are also discussed as a function of the electrode geometry. The electrode geometry was found to affect the growth rate and, under certain conditions, the microstructure (existence of channels and pores). It does not have influence on the corrosion behaviour.
EN
The influence on the corrosion behaviour of Co-Mo nano-crystalline coatings of dissolved oxygen is studied in the Ringer’s solution and artificial saliva at 25°C. This was done by means of potentiodynamic tests and surface observations. It was shown that dissolved oxygen has no influence on passivity, oxidation of the coating and selective dissolution of cobalt. By contrast, dissolved oxygen affects corrosion. General corrosion was observed in the Ringer’s solution whereas pitting corrosion was found in artificial saliva.
EN
The study of the possibility of removing organic compounds from wastewater originating from the biodiesel purification stage by two catalytic processes, HSO5-/transition metal and Fenton method has been presented. The source of the ion HSO5-is potassium monopersulphate (2KHSO5∙KHSO4∙K5SO4) (Oxone) that may be decomposed into radicals (OH., SO4-., SO5-.) by means of transition metal as Co(II). Different concentrations were used for both compounds and the combination ([Co2+] = 1.00μM/[HSO5-] = 5.00·10-2 M) achieved the highest COD removal (60%) and complete decomposition of the oxidant was verified for contact times of 45 min. This process has some advantages comparing to the conventional Fenton method such as the absence of the costly pH adjustment and the Fe(III) hydroxide sludge which characterize this treatment process. The Fenton process showed that the combination of [H2O2] = 2.00M/[Fe2+] = 0.70 M was the best and archived COD removal of 80%. The treatments studied in this research have achieved high COD removal, but the wastewater from the biodiesel purification stage presents very high parametric values of Chemical Oxygen Demand (667,000 mgO2/L), so the final COD concentration reached is still above the emission limit of discharge in surface water, according the Portuguese Law (Decree-Law 236/98). However, both treatments have proved to be feasible techniques for the pre-oxidation of the wastewater under study and can be considered as a suitable pre-treatment for this type of wastewaters. A rough economic analysis of both processes was, also, made.
EN
Three types of sintered alloys were fabricated based on cobalt, nickel and high-temperature alloy ZhS32-VI matrix with titanium carbide strengthening phase. TiC content was in a range of 30–50 vol. %. The melting temperatures of alloys are higher than 1320°C, and they may undergo undamaged through all technological procedures together with turbine blades, including soldering and outgassing. DSC analyses indicates no additional thermal effects until melting, which confirms their structural stability. The examinations of microstructure revealed three types of constituents – TiC particles, matrix solid solution and blow outs – structural defects having negative effects on all the studied properties. It was found that heat resistance of nickel based sintered alloys at the temperature of 1100°C is superior as compared with the alloys based on cobalt and alloy ZhS32-VI. It has been established that wear resistance in conditions of fretting wear at temperatures of 20, 850, 950 and 1050°C of sintered alloy with ZhS32-VI matrix is mostly superior as compared with the other alloys. The properties of produced alloys allow to use them for manufacturing of components of friction couples operating in conditions of high temperature fretting wear, including protective pads of turbine blades top shrouds contact faces.
PL
Ekosystemy leśne dzięki piętrowemu ułożeniu roślinności stanowią naturalny filtr zatrzymujący pyły zawieszone w powietrzu. Zanieczyszczenia deponowane w wyniku depozycji mokrej są zatrzymywane w ekosystemie leśnym dzięki dużym zdolnościom sorpcyjnym. Organizmami, które są często wykorzystywana w bioindykacji są grzyby wielkozarodnikowe oraz drzewa ze względu na dużą zdolność do akumulacji pierwiastków śladowych oraz powszechność występowania. Na podstawie zawartości pierwiastków śladowych w biomasie grzybów oraz liściach drzew można ocenić stopień przyswajalności pierwiastków śladowych co jest związane z ich włączaniem do bioobiegu. Grzyby leśne są powszechnie cenionym składnikiem diety, dlatego też wysoka w nich zawartość pierwiastków śladowych stwarza zagrożenie dla ich konsumentów. Celem przeprowadzonych badań była ocena zawartości Fe, Mn, B, Li, Co w glebie, w mleczaju jodłowym oraz igliwiu jodły pospolitej zebranych na terenie pasma Przedbabiogórskiego w 2015 r. z 17 punktów pobrano próbki gleby, grzybów oraz igliwia jodły pospolitej. Wszystkie pobrane próbki wysuszono i zhomogenizowano. Próbki laboratoryjne grzybów oraz igieł poddano mineralizacji na sucho w systemie otwartym. Naważka analityczna wynosiła 3 g. Materiał roztwarzano w mieszaninie HNO3 i H2O2 w stosunku 5:1, v/v. Próbki gleby poddano mineralizacji w wodzie królewskiej. Stężenie pierwiastków w uzyskanych roztworach oznaczono metodą atomowej spektrometrii emisyjnej, w aparacie Optima 7600 DV firmy Perkin Elmer. Na podstawie uzyskanych wyników obliczono współczynniki bioakumulacji poszczególnych pierwiastków. Współczynnik bioakumulacji obliczano dzieląc stężenie pierwiastka w suchej masie grzybów i igieł wykorzystanych w badaniach przez zawartość tych pierwiastków w glebie. Ponadto obliczono współczynnik korelacji, pomiędzy zawartością badanych pierwiastków w glebie, grzybach i igłach. Zawartość badanych pierwiastków w glebach leśnych wskazuje na brak antropogenicznego ich wzbogacenia. Stężenie badanych pierwiastków w mleczaju jodłowym (Lactarius salmonicolor L) kształtowało się w kolejności od największego: Fe>Mn>B>Li> Co, natomiast w igliwiu jodły pospolitej (Abies alba M.) Mn>Fe>B>Li>Co. Nie stwierdzono istotnej statystycznie zależności pomiędzy odczynem oraz zawartością węgla organicznego w glebie i poziomem akumulacji badanych pierwiastków w wybranych organizmach z wyjątkiem wpływu odczynu na zawartość żelaza w igliwiu. Na podstawie przeprowadzonych badań stwierdzono, że w warunkach niskich zawartości Fe, Mn, B, Li i Co glebie, Mleczaj jodłowy (Lactarius salmonicolor L) oraz igliwie jodły pospolitej (Abies alba M.) nie są dobrymi wskaźnikami poziomu tych pierwiastków w biotopie.
EN
Forest ecosystems, thanks to the layering of vegetation, constitute a natural filter that catches airborne particulate matter. Wet-deposited pollutants are caught in the forest ecosystem thanks to substantial sorption capacities. Large spore mushrooms and trees are organisms frequently used in bioindication. This is due to their substantial capacity to accumulate trace elements and because they are common. Based on the content of trace elements in biomass of mushrooms as well as in tree leaves, one can assess the degree of their availability, which is associated with trace element incorporation into the biological cycle. Forest mushrooms are a part of diet that is widely held in high regard; that is why a high content of trace elements in them poses a risk to their consumers. The aim of the conducted study was to determine the content of Fe, Mn, B, Li, Co in the soil, in Lactarius salmonicolor, and in Abies alba needles, all of which were collected in the Przedbabiogórski Range. In 2015, samples of soil, mushrooms and Abies alba needles were collected from 17 sites. All the collected samples were dried and homogenized. The laboratory samples of the mushrooms and needles were subjected to dry mineralization in an open system. The analytical sample was 3 g. The material was digested in a mixture of HNO3 and H2O2 (5:1 v/v ratio). The soil samples were mineralized in aqua regia. Concentration of elements in the obtained solutions was determined by atomic emission spectrometry, on an Optima 7600 DV spectrometer manufactured by PerkinElmer. Based on the obtained results, bioaccumulation factors of individual elements were calculated. The bioaccumulation factors were calculated by dividing the concentration of the elements in dry matter of mushrooms and needles used in the study by the content of these elements in the soil. In addition, the correlation coefficient between the content of the studied elements in the soil, mushrooms and needles was computed. The content of the investigated elements in forest soils indicates the lack of their anthropogenic enrichment. Concentration of the studied elements in Lactarius salmonicolor L. was arranged in the order from the highest: Fe>Mn>B>Li> Co, whereas in case of Abies alba needles – Mn>Fe>B>Li>Co. No statistically significant relationship between reaction as well as the organic carbon content in the soil, and the level of accumulation of the studied elements in selected organisms was observed (except the effect of reaction on iron content in needles). Based on the study that was carried out it was found that at a low content of Fe, Mn, B, Li and Co in soil, neither Lactarius salmonicolor nor Abies alba needles are good indicators of the level of these elements in the biotope.
PL
Wydzielano struwit w sposób ciągły z wodnych roztworów fosforanów zawierających także charakterystyczne składniki obecne w gnojowicy: bor, kobalt, mangan i molibden. Wykazano, że bor, kobalt i molibden, w przeciwieństwie do manganu, sprzyjały otrzymywaniu dobrze wykształconych kryształów struwitu. Kobalt i molibden nie zmieniały standardowego pokroju kryształów struwitu (La/Lb ok. 6), ale mangan i bor (obecne w układzie procesowym) zwiększały te proporcje geometryczne odpowiednio do 7,7, a nawet do 9,1. Krystalizacja struwitu przebiegała najlepiej w obecności boru. Liniowa szybkość wzrostu wyniosła ponad 2·10-8 m/s, a szybkość zarodkowania była mniejsza niż 2·108 1/(s·m3). Kobalt i mangan wydzieliły się jako wodorotlenki, a ich zawartość w fazie stałej wynosiła odpowiednio 393 mg/kg i 749 mg/kg.
EN
Struvite was continuously pptd. from aq. solns. of phosphates in presence of B, Co, Mn and Mo salts contained in liq. manure. The B, Co and Mo compds. (in contrast to Mn compds.) favored well-formed struvite crystals. Neither Co nor Mo changed the std. geometrical proportions of struvite crystals, while Mn and B increased the proportions. Struvite crystn. run well in the presence of B. The linear growth rate was more than 2·10-8 m/s, and the nucleation rate was less than 2·108 1/(s·m3). Co and Mn were sepd. as hydroxides and their content in solid phase was 393 mg/kg and 749 mg/kg Mn, resp.
16
PL
Przedstawiono wyniki badań usuwania jonów Co2+ z roztworów wodnych za pomocą węgla aktywnego Norit SX2, zmielonych łusek ryżu oraz żywicy jonowymiennej C-160. Proces sorpcji opisano za pomocą modelu Langmuira. Największym powinowactwem do jonów Co2+ charakteryzował się jonit C-160. Wykazano, że łuska ryżowa i węgiel aktywny są skutecznymi sorbentami tylko w roztworach rozcieńczonych. Morfologię powierzchni sorbentów badano za pomocą skaningowego mikroskopu elektronowego.
EN
Activated C, com. ion exchange resin and shredded rice husks (grain size ≤ 150 μm) were used as sorbents (2 g to 200 mL of CoSO4·7H2O soln. with concns. 10-10 000 mg/L). The contact time of each sorbent with adsorbate soln. was 60 min. Concns. of Co2+ ions in adsorbate soln. were detd. using visible and near-ultraviolet light spectroscopy. The sorption was described by the Langmuir model. The tested materials were effective sorbents only in dild. solns., and a sorption capacity depended on the pH of the solns. In addn., the surface morphol. of the sorbents was examd. by scanning electron microscopy.
17
Content available remote Badanie transportu jonów metali w wybranych układach separacyjnych
PL
Przedstawiono ługowanie, ekstrakcję ciecz-ciecz i ultrafiltrację micelarną jako skuteczne sposoby wydzielania takich pożądanych jonów metali, jak platynowce i kobalt z odpadowych katalizatorów samochodowych i z roztworów wodnych.
EN
Pulverized spent automobile catalyst was leached with acidic solns. (optionally with H₂O₂). The leachates were liq.-liq. extd. with com. org. phase-contg. complexants to remove Fe(III), Mg(II) and Zn(II) ions and to sep. them from Pt group ions present in the raffinate. Co(II) ions were also recovered by using a com. complexant. The ultrafiltration in presence of surface active agents resulted in sepn. of Co(II) ions from Zn(II) ions.
EN
A fast, simple, and economical method for extraction, preconcentration and determination of cobalt, nickel and copper as their 1-(2-pyridilazo) 2-naphthol (PAN) complexes based on ultrasound-assisted emulsification–microextraction (USAEME) and multivariate calibration of spectrophotometric data is presented. Various parameters affecting the extraction efficiency were optimized both with univariate and Box–Behnken design. The resolution of ternary mixtures of these metallic ions was accomplished by using partial least-squares regression (PLS), orthogonal signal correction-partial least-squares regression (OSC-PLS), and orthogonal signal correction-genetic algorithmspartial least-squares regression (OSC-GA-PLS). Under the optimum conditions, the calibration graphs were linear in the range of 2.0–150.0, 2.0–120.0 and 2.0–150.0 ng mL−1  for Co2+ , Ni2+ , and Cu2+ , respectively, with a limit of detection of 0.14 (Co2+ ), 0.13 (Ni2+ ) and 0.14 ng mL−1  (Cu2+ ) and the relative standard deviation was <2.5%. The method was successfully applied to the simultaneous determination of these cations in different samples.
EN
In this work, multi-walled carbon nanotubes (MWCNTs) with significantly different mean diameters were produced by catalytic CVD over Ni and Co-based supported catalysts. Our results indicate that Ni nanoparticles in the Ni/MgO catalyst are responsible for controlling the inner diameters of the carbon nanotubes. Contrary, Co nanoparticles in the Co/MgO catalyst control the outer diameters of MWCNTs. The "base-growth" mechanism and smaller diameters of the MWCNTs grown on the Ni/MgO catalyst are associated with a strong metal-support interaction (SMSI) resulting from NixMg1−xO mixed oxide formation. The concept of the weak metal-support interaction (WMSI) between Co nanoparticles and MgO for the Co/MgO catalyst confirms the "tip-growth" mechanism of the MWCNTs.
EN
The machining of titanium has been understood to be challenging and costly due to its material properties such as low thermal conductivity, low modulus of elasticity, high strength at elevated temperatures and chemical reactivity. This work aims to study the effect of iron as a partial substitution along with cobalt binder as the tool material for machining of titanium alloy. In this work, iron-rich binder tool (WC-Co-Fe) and cobalt binder tool (WC-Co) samples were produced by powder metallurgy route using powders with a mean particle size of less than 0.5 µm. Next, the evaluation of mechanical properties and phase analysis were performed. Turning experiments were conducted at various cutting speeds, feed and depth of cut (DOC), to evaluate the effects of iron-rich binder on flank wear, cutting forces and cutting temperature. The obtained results of turning experiments reveal that iron-rich binder tends to increase cutting performance in comparison to conventional WC-Co composite cutting tools.
first rewind previous Strona / 8 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.