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EN
Poly(L-lactic acid) (PLLA) as an important biodegradable polymer suffers from slow crystallization rate and poor heat resistance. An organic compound N,N’-dodecanedioic bis(3-phenylpropionic acid) dihydrazide (BHADD) was synthesized to evaluate its general influences on the physical properties of PLLA. The melt-crystallization process indicated that BHADD could serve as a heterogeneous nucleating agent for improving the crystallization of PLLA, and PLLA/1%BHADD exhibited the sharpest melt-crystallization peak located at the highest temperature, as well as an increase of cooling rate weakened the crystallization ability of BHADD-nucleated PLLA. And the final melting temperature also displayed the significant effect on the crystallization process of PLLA. For the cold-crystallization process, both BHADD concentration and heating rate affected the cold-crystallization behavior of PLLA/BHADD, the increasing of BHADD concentration caused the cold-crystallization peak to shift to the lower temperature; in contrast, a higher heating rate during heating leaded to the peak’s shift toward the higher temperature because of the thermal inertia. The melting behavior of PLLA/BHADD depended on the crystallization temperatures and heating rates, and the double melting peaks were attributed to the melting-recrystallization. Thermal decomposition experiment showed all PLLA/BHADD samples as the pure PLLA only exhibited one thermal decomposition stage, but PLLA/BHADD had a lower thermal stability than the pure PLLA. Additionally, the addition of BHADD seriously decreased the light transmittance of PLLA.
PL
Poli(kwas L-mlekowy) (PLLA) to ważny biodegradowalny polimer charakteryzujący się małą szybkością krystalizacji i słabą odpornością na ciepło. Dihydrazyd kwasu bis(3-fenylopropiono) N,N'-dodekanodiowego (BHADD) zsyntetyzowano w celu oceny jego wpływu na właściwości fizyczne PLLA. Przebieg procesu krystalizacji ze stopu świadczy o tym, że BHADD może służyć jako heterogeniczny środek zarodkujący zwiększający szybkość krystalizacji PLLA. Mieszanina PLLA/1% mas. BHADD wykazywała najostrzejszy pik krystalizacji ze stopu zlokalizowany w zakresie najwyższej temperatury, a jednocześnie większą szybkość chłodzenia osłabiającą zdolność krystalizacji PLLA zarodkowanej BHADD. Również końcowa temperatura topnienia w istotnym stopniu wpływała na proces krystalizacji PLLA. W procesie krystalizacji na zimno zarówno stężenie BHADD, jak i szybkość ogrzewania oddziaływały na zachowanie PLLA/BHADD podczas krystalizacji, zwiększenie stężenia BHADD powodowało przesunięcie piku krystalizacji na zimno w kierunku niższej temperatury, natomiast większa szybkość ogrzewania prowadziła do, spowodowanego bezwładnością cieplną, przesunięcia piku krystalizacji na zimno w kierunku wyższej temperatury. Zachowanie PLLA/BHADD podczas topnienia zależało od temperatury krystalizacji i szybkości ogrzewania, a drugi pik topnienia przypisano procesowi rekrystalizacji. Badany przebieg rozkładu termicznego świadczy, że wszystkie próbki PLLA/BHADD, tak jak czysty PLLA, wykazywały tylko jeden etap rozkładu termicznego, mieszanina PLLA/BHADD charakteryzowała się jednak mniejszą stabilnością termiczną niż czysty PLLA. Dodatek BHADD w znacznym stopniu zmniejszył przepuszczalność światła PLLA.
EN
The presented paper deals with the measurement methodologies of the structural properties of porous anodic alumina (PAA) films filled with YalO3:Tb3+ composite using X-ray diffraction, atomic force microscopy and scanning electron microscopy. It shows that the deposited material does not uniformly fill the porous volume of the anodic alumina film and the part of it forms a thick layer on the PAA surface. The aim of this work is to show the differences in the XRD response obtained at different angles of incidence of the excitation beam for the PAA/YalO3:Tb3+ system. Furthermore, this simple approach enables separation of the signal from both regions on the surface and inside the PAA pores, providing more accurate data interpretation. It reveals that the crystallization of the material on the PAA surface and within the pores is different.
EN
Purpose: The aim of the proposed research is to investigate the influence of temperature and duration of isothermal melt processing on structural characteristics of castings in connection with technological background of charge metal. Design/methodology/approach: Ferrous and non-ferrous alloys were obtained by remelting a charge with a dispersion-structured structure (which was ensured by high- speed crystallization). Remelting was carried out at different temperatures of overheating of the melt over the liquidus with different isothermal exposure at these temperatures. Experimental castings were crystallized under normal conditions. It was studied a change of structure formation and mechanical characteristics depending on the temperature and duration of thermal treatment of the melt before crystallization. Findings: It is established that isothermal treatment of the melt at the overheating of the liquid metal above a certain equilibrium temperature of the micro-inhomogeneous melt (Te) causes a gradual loss of hereditary characteristics of the original charge metal, increase of the chemical homogeneity of the melt and the formation of crystallization and formation a corresponding change in the mechanical properties of castings. Research limitations/implications: The results can be complemented by studies of the effect of thermal treatment in the temperature range of crystallization. Practical implications: The results can be used to select the optimal heat treatment during remelting and, accordingly, the mechanical properties of the resulting casting. Originality/value: The obtained results testify to the predominant influence of temperature on the dispersion of the cast structure of steels, given the duration of technological operations of preparation and casting of steels in the manufacture of castings in industrial conditions.
EN
This article presents a study of the crystallization and microstructure of the AlSi9 alloy (EN AC-AlSi9) used for the alfin processing of iron ring supports in castings of silumin pistons. Alfin processing in brief is based on submerging an iron casting in an Al-Si bath, maintaining it there for a defined time period, placing it in a chill mould casting machine and immersing it in the alloy. This technology is used for iron ring supports in the pistons of internal combustion engines, among others. Thermal analysis shows that when the AlSi9 alloy contains a minimal content of iron, nucleation and increase in the triple α (Al)+Fe+(Si) eutectic containing the α -Al8Fe2Si phase takes place at the end of the crystallization of the double α (Al)+ß(Si) eutectic. Due to the morphology of the ”Chinese script” the -Al8Fe2Si phase is beneficial and does not reduce the alloy’s brittleness. After approx. 5 hours of alfin processing, the -Al5FeSi phase crystallizes as a component of the α+Al5FeSi+(Si) eutectic. Its disadvantageous morphology is ”platelike” with sharp corners, and in a microsection of the surface, ”needles” with pointed corners are visible, with increases the fragility of the AlSi9 alloys.
EN
The paper presents research of metallic glass based on a Mg72Zn24Ca4 alloy. Metallic glass was prepared using induction melting and further injection on a spinning copper wheel. The X-ray diffractometer and differential scanning calorimeter (DSC) were used to investigate the phase transformation of the amorphous ribbon. The heat released in the crystallization process, during isothermal annealing, based on the differential scanning calorimeter investigation, was determined to be 166.18 Jg-1. The effect of isothermal annealing temperature on the kinetics of the amorphous alloy crystallization process using differential scanning calorimeter was investigated. For this purpose, two isothermal annealing temperatures were selected. The incubation time decreases as the temperature of the isothermal annealing increases from 300 to 252 seconds. The same relationship is visible in the case of duration of the phase transformation, which also decreases as the temperature of the isothermal annealing increases from 360 to 228 seconds. The obtained results show a significant influence of isothermal annealing temperature on the degree of phase transformation.
EN
Understanding the influence of iron impurity on the formation of the structure and the properties of hypereutectic aluminum-silicon alloys are important for achieving the required quality of castings, especially those obtained from secondary materials. In the present work, the influence of different iron contents (0.3, 1.1, and 2.0 wt.%) on the crystallization process, microstructure and mechanical properties of the Al-15% Si alloy was studied. It is shown that the presence of iron impurity in the Al-15% Si alloy leads to increasing the eutectic crystallization time from 6.2 to 7.6 s at increasing the iron content from 0.3 wt.% to 1.1 wt.%, changing the structure of the alloy eutectic in the solid state. The primary silicon and β-Al5SiFe phase coexist in the structure of the Al-15% Si alloys at a temperature below 575°C in the range of iron concentrations from 0 to 2 wt.% in equilibrium conditions. In the experimental alloys structure, the primary crystals of the β-phase were metallographically detected only in the alloys containing 1.1 and 2 wt.% of iron impurity. Increase of the iron content up to 2 wt.% significantly reduces the mechanical properties of the Al-15% Si alloy due to the formation of large platelet-like inclusions of β-Al5SiFe phase.
7
Content available Compacted Graphite Iron with the Addition of Tin
EN
The paper presents the effect of tin on the crystallization process, microstructure and hardness of cast iron with compacted (vermicular) graphite. The compacted graphite was obtained with the use of magnesium treatment process (Inmold technology). The lack of significant effect of tin on the temperature of the eutectic transformation has been demonstrated. On the other hand, a significant decrease in the eutectoid transformation temperature with increasing tin concentration has been shown. It was demonstrated that tin narrows the temperature range of the austenite transformation. The effect of tin on the microstructure of cast iron with compacted graphite considering casting wall thickness has been investigated and described. The carbide-forming effect of tin in thin-walled (3 mm) castings has been demonstrated. The nomograms describing the microstructure of compacted graphite iron versus tin concentration have been developed. The effect of tin on the hardness of cast iron was given.
EN
This article discusses the effects of surfacing with the introduction of mechanical vibrations into the material using shot blasting. It does not require a rigid attachment of the vibrating system to the base material, and vibrations are introduced as a result of supplying energy of collision of the shot with the parent material. The effect of introducing mechanical vibrations through shot blasting during welding of P235GH steel on the structure and hardness of obtained structures was described. Comparative results of tests revealing the basic differences in the structural structure and hardness of reached welds without shot blasting and with its participation were presented. As a result of the conducted research, differences in the structural structure of the welds were shown and it was shown that shot blasting is an effective and alternative method of introducing mechanical vibrations supporting welding processes.
PL
W niniejszym artykule omówiono efekty napawania z wprowadzaniem drgań mechanicznych do materiału z wykorzystaniem śrutowania. Nie wymaga ona sztywnego zamocowania układu drgającego do materiału podstawowego, a drgania wprowadzane są w wyniku dostarczania energii zderzenia śrutu z podłożem. Opisano wpływ wprowadzania drgań mechanicznych poprzez śrutowanie w czasie napawania stali P235GH na strukturę i twardość uzyskanych struktur. Zaprezentowano porównawcze wyniki badań ujawniających podstawowe różnice w budowie strukturalnej i twardości uzyskanych napoin bez śrutowania oraz z jego udziałem. W wyniku przeprowadzonych badań wykazano różnice w budowie strukturalnej napoin i pokazano, że śrutowanie stanowi efektywną i alternatywną metodę wprowadzania drgań mechanicznych wspomagających procesy spawalnicze.
PL
W pracy przedstawiono badania wpływu dodatku manganu (0,6 i 1,2%mas.) na przebieg procesu krystalizacji i kształtowanie struktury okołoeutektycznego siluminu EN AC-43000. Stwierdzono, iż dodatek Mn powoduje zanik niekorzystnej kruchej fazy β-Al5FeSi na korzyść fazy α-Al15(FeMn)3Si2, która krystalizuje w postaci zwartych, równomiernie rozłożonych w osnowie roztworu stałego a(Al) wielościennych wydzieleń o wymiarach ok. 7–8 mm. Zmiana niekorzystnej morfologii kruchych eutektyk zawierających żelazo przekłada się na niewielki wzrost właściwości mechanicznych, bez pogorszenia plastyczności stopów Al-Si-Mg-Mn.
EN
The paper presents studies on the effect of manganese addition (0.6 and 1.2% by mass) on the course of the crystallization process and shaping the approximate structure of the silicone EN AC-43000. It was found that the addition of Mn causes the disappearance of the disadvantageous fragile β-Al5FeSi phase in favor of the α-Al15(FeMn)3Si2phase, which crystallizes in the form of compact, uniformly distributed solid matrix a(Al) polyhedral particles with dimensions of approx. 7–8 mm. A change in the unfavorable morphology of brittle iron-containing eutectics translates into a small increase in mechanical properties without deterioration of the Al-Si-Mg-Mn alloys.
PL
W artykule skoncentrowano się na słabo rozpoznane zjawisko opadania w kąpieli metalowej heterogenicznych zarodków pierwotnej krystalizacji podeutektycznych stopów Al-Si, którymi są borki tytanu TiB2 pochodzące z zapraw AlTi5B. Badaniami objęto pięć zapraw rynkowych. Wykazano, iż w przypadku pozostawienia metalu w bezruchu w dłuższym okresie (np. ~ 2godzin) następuje wyraźne zubożenie górnych warstw kąpieli metalowej w cząstki pochodzące z AlTi5B i wzbogacenie w nie dolnych warstw kąpieli. Równolegle w warstwach zubożonych obserwuje się wyraźnie zmniejszenie zdolności do zarodkowania, co prowadzi do tworzenia się struktury gruboziarnistej w odlewach. Do oceny zdolności do zarodkowania wykorzystano próbę zwaną testem pierścienia (ang. Ring Test). Wykazano, iż szybkość procesu opadania cząstek nie jest jednakowa dla badanych zapraw, i może ona stanowić jedno z kryteriów oceny ich przydatności do technologii odlewania, w której są zastosowane podgrzewane kadzie. Ma to m.in. miejsce przy zalewaniu form metalowych sposobem odlewania pod niskim ciśnieniem. Prace realizowano we współpracy trzech jednostek Wydziału Odlewnictwa Akademii Górniczo Hutniczej oraz firm: Technologia i Technika Aluminium Z. Smorawiński (Konin) i firmy Royal Polska sp. z o.o. w Jelczu.
EN
The paper is focused on weakly recognised effect of heterogeneous nuclei of the primary crystallisation of hypoeutectic Al-Si alloys, falling in the metal bath. These nuclei are titanium borides TiB2, originated from AITi5B foundry alloys. Five foundry alloys, available in the market, were tested. It was revealed, that in case of leaving the motionless metal for a longer time (e.g. ~ 2 hours), the upper layers of the metal bath were significantly impoverished of particles originated from AITi5B, while the lower layers were enriched in them. Simultaneously a significant decrease of the nucleation ability was observed in impoverished layers, which led to forming coarse-grained structures in castings. The test, called the Ring Test, was applied for assessing the nucleation ability. It was demonstrated that particles falling rates were not the same for the investigated foundry alloys and could constitute one of the assessment criterion of their suitability in the casting technology, in which heated ladles are applied. This occurs, among others at pouring metal moulds by means of the low pressure die casting. Works were realized in cooperation of three units of the Faculty of Foundry Engineering of AGH University of Science and Technology and Companies: Technology and Aluminium Technique Z. Smorawiński (Konin) and Royal Polska I.I.c. in Jelcz.
EN
Glasses in the Na2O–B2O3–SiO2–Fe2O3 system with a constant SiO2 content 70 mol% were synthesized using conventional melting in platinum crucibles in SiC-furnace in air. After synthesis and annealing, glasses were heat treated at 550°C for 96–144 hrs to promote phase separation. A tentative region of phase separation for this temperature was outlined. X-ray powder diffractometry results showed three iron-containing phases (Fe3O4, FeSiO3 and β-Fe2O3) forming in the investigated glasses with magnetite being the main phase as it is observed in most of the glasses. Chemical durability studies showed that compositions of phase-separated glasses suitable for synthesis of porous glasses, both iron-free and iron-containing lie in between 4 and 8 mol% of Na2O. Bulk samples of porous glasses were obtained within the chosen region having the following parameters: specific surface area 40–185 m2/g, porosity 30%–45%, pore diameter 3–14 nm. The parameters of porous structure of iron-containing porous glasses are of the same order of magnitude as the porous glass used for the multiferroic nanocomposite synthesis.
EN
Purpose: The aim of the proposed research is to investigate the mutual influence of the temperature of an overheated melt and its cooling rate during crystallization on the formation of the cast structure and mechanical properties of structural steels. Design/methodology/approach: Two structural medium-carbon steels were melted in induction furnace and poured from temperatures 1520-1670°C into casting moulds with different heat removal ability. This ensured the crystallization and structure formation of the studied steel castings at cooling rates (Vc) of 5°C/sec (sand-clay mould), 45°C/sec (steel mould), 350°C/sec (water cooled copper mould). It was studied a change of structure formation, mechanical characteristics depending on the temperature-kinetic conditions of the processing of the melt. Based on the processing of the array of obtained experimental data using linear regression analysis and a software package, interpolation models and their graphic images obtained allow a quantitative assessment of the established patterns of structural characteristics and mechanical properties of the studied steels depending on melt temperature (T, °C) and its cooling rate (Vc, °C/sec) during crystallization and structure formation. Findings: Among the technological factors that determine the formation of the cast structure and the mechanical properties of steels, the dominant role is played by the intensity of heat removal during the solidification of castings. The high cooling rate of the melt during crystallization determines an increase in the number of crystallization nuclei due to an increase in the degree of supercooling of the melt, eliminates the negative effect of the high overheating temperature of the metal before casting. Research limitations/implications: In the future, the results can be complemented by studies of the influence of the duration of isothermal exposure of the melt at different temperatures of superheating and cooling conditions. Practical implications: The obtained mathematical models (regression equations) that determine the mutual influence of the cooling rate and the temperature of the melt overheating on the structure and mechanical properties of the studied steels make it possible to obtain steel castings with predetermined properties at the level of properties of wrought steel of similar chemical composition. Originality/value: Interpolation models that allow a quantitative assessment of the established patterns of structural characteristics and mechanical properties of the studied steels depending on the melt temperature (T, °C) and its cooling rate (Vc, °C/sec) during crystallization and structure formation are obtained.
PL
Mikrostruktura złącza spawanego cechuje się bardzo dużą niejednorodnością na jego przekroju, a ponadto jest zależna od materiału spawanego, użytego spoiwa oraz od zastosowanej metody i warunków spawania. Ze względu na dużą różnorodność materiałów spawanych oraz parametrów spawania w artykule przedyskutowano tylko podstawowe zasady tworzenia się mikrostruktury spoiny. Szczególną uwagę zwrócono na redystrybucję pierwiastków rozpuszczonych oraz na kształt i stabilność frontu krystalizacji podczas krzepnięcia spoin. Scharakteryzowano poszczególne strefy złącza spawanego oraz omówiono szczegółowo czynniki wpływające na mikrostrukturę spoiny oraz strefy wpływu ciepła.
EN
Weld microstructure observed on the weld cross-section is highly inhomogeneous and depends on joined materials, filler metals, welding methods as well welding conditions. Due to large variety of welded materials and applied welding parameters the paper discusses only the basic principles that govern the evolution of microstructure during welding. In particular, the redistribution of alloying elements during solidification as well as the shape and stability of the crystallization front were addressed in detail. Also, particular regions of weld were described in a thorough manner with an emphasis on factors influencing the weld microstructure.
EN
The thermoplastic polymers present amorphous or semi-crystalline structures which are very important factors in describing volumetric shrinkage. The thermoplastic materials are commonly used for production of daily life products, industrial or as the prototypes. Different techniques of manufacturing polymer structures are considered like: injection molding, extrusion, milling, additive manufacturing (AM). AM is a very fast developing field in the manufacturing and research. Unfortunately, components or prototypes made using the thermoplastic semi-crystalline materials in 3D techniques have quite low mechanical strength compared to the parts made by injection molding processes. It is caused by porosity obtained during the processing, as well as by fraction of crystallinity in the volume of the components. Additionally, the volumetric shrinkage is hard to predict without knowledge of its origin. Therefore, it is necessary to consider crystallization kinetics and the melting of the analysed materials. The investigations presented in this work concern the crystallization and melting model to be implemented in the finite element (FE) analyses. With use of the model, one can predict development of the structure during the real processes and, in the future, to control the warpage of the manufactured components.
EN
The paper presents the effect of manganese on the crystallization process, microstructure and selected properties: cast iron hardness as well as ferrite and pearlite microhardness. The compacted graphite was obtained by Inmold technology. The lack of significant effect on the temperature of the eutectic transformation was demonstrated. On the other hand, a significant reduction in the eutectoid transformation temperature with increasing manganese concentration has been shown. The effect of manganese on microstructure of cast iron with compacted graphite considering casting wall thickness was investigated and described. The nomograms describing the microstructure of compacted graphite iron versus manganese concentration were developed. The effect of manganese on the hardness of cast iron and microhardness of ferrite and pearlite were given.
EN
Mechanical properties of aluminum-silicon alloys are defined by condition of alloying components in the structure, i.e. plastic metallic matrix created from solid solution &alpha on the basis of Al, as well as hard and brittle precipitations of silicon. Size and distribution of silicon crystals are the main factors having effect on field of practical applications of such alloys. Registration of crystallization processes of the alloys on stage of their preparation is directly connected with practical implementation of crystallization theory to controlling technological processes, enabling obtainment of suitable structure of the material and determining its usage for specific requirements. An attempt to evaluate correlation between values of characteristic points laying on crystallization curves and recorded with use of developed by the author TVDA method (commonly denominated as ATND method) is presented in the paper together with assessment of hardness of tested alloy. Basing on characteristic points from the TVDA method, hardness of EN AC-AlSi9Mg alloy modified with strontium has been described in the paper in a significant way by the first order polynomial.
EN
The complexity and uncontrolled formation of struvite (MgNH4PO4·6H2O) and its deposition in the technological equipment of wastewater treatment plants (WWTPs) are still the subject of research aimed at understanding the causes and proposing a remedial action. In order to reduce the intensity of the precipitation of struvite in wastewater treatment plants, it is recommended, among others, to limit flow velocity to below 1.5 m·s-1. Literature analysis showed that there are no studies on the precipitation of struvite deposits in pipelines. Most studies focus on the deliberate precipitation of struvite, for example phosphorus recovery, resulting in a molar ratio of 1:1:1 (NH4+:PO4 3-:Mg2+). In fact, in WWTPs, such concentrations do not occur, but there have been cases of the precipitation of this mineral (and its mixtures) in the sludge parts. In this paper, the study aimed at determining conditions for the precipitation of deposits with a significant participation of struvite on the inner walls of steel pipes. The study was conducted at a non-stoichiometric concentration of ingredients at different pH values, as well as under dynamic conditions with flow velocity below 1.5 m·s-1. A mathematical formula (ANOVA) that can be used to determine the mass of deposits in relation to the concentration of ammonium, phosphate, pH and flow velocity was developed. Computational models were developed on to investigate struvite precipitation under different pH levels (8.0–9.5) and ionic concentrations. The studies were carried out on solutions containing ammonium (NH4 +), phosphate (PO4 3-), and magnesium (Mg2+), at a flow velocities of 0.4, 0.9 and 1.4 m·s-1. In order to determine the mathematical formula thanks to which the mass of precipitates can be determined, a special pilot study installation was constructed. The XPS surface analysis of sludge from sewage treatment plants showed a similar composition of compounds with sediments obtained in own research. The presence of struvite was suggested, but the share of atomic percentage of bonds to which struvite was classified is small and amounts to less than 4%. This means that sediments precipitated in the technological installations are a mixture of various compounds of which pure struvite may constitute only a small part.
PL
Złożoność i niekontrolowane powstawanie struwitu (MgNH4PO4·62O) oraz jego osadzanie w urządzeniach technologicznych oczyszczalni ścieków jest nadal przedmiotem badań mających na celu zrozumienie przyczyn i zaproponowanie działań zaradczych. W celu zmniejszenia intensywności wytrącania struwitu w oczyszczalniach ścieków zalecano między innymi ograniczenie prędkości przepływu poniżej 1,5 m·s-1. Analiza literatury wykazała, że nie ma badań dotyczących wytrącania struwitu w rurociągach stalowych. Większość badań koncentruje się na umyślnym wytrącaniu struwitu, na przykład w celu odzysku fosforu, doprowadzając do stosunku molowego 1:1:1 (NH4:PO4:Mg). W rzeczywistości w oczyszczalniach ścieków takie stężenia nie występują, ale zdarzały się przypadki wytrącania tego minerału (i jego mieszanin) w częściach osadowych. W pracy podjęto próbę określenia warunków występowania osadów z udziałem struwitu na wewnętrznych ścianach rur stalowych. Badanie przeprowadzono przy niestechiometrycznym stężeniu składników przy różnych wartościach pH, a także w warunkach dynamicznych z prędkością przepływu poniżej 1,5 m·s-1. Opracowano wzór matematyczny (ANOVA), który można wykorzystać do określenia masy osadów w zależności od stężenia amonu, fosforanu, pH i prędkości przepływu. Opracowano modele obliczeniowe do badania wytrącania struwitu i jego mieszanin przy różnych poziomach pH (8,0–9,5) i stężeniach jonowych. Badania prowadzono na roztworach zawierających jony, w tym amonu (NH4+), fosforanu (PO43-), magnezu (Mg2+) oraz prędkości przepływu (0,4; 0,9 i 1,4 m·s-1). Następnie wyznaczono formułę matematyczną w oparciu o badania wyzyskane w warunkach przepływowych na specjalnie skonstruowanej instalacji. Analiza powierzchniowe osadów mineralnych z oczyszczalni ścieków wykazała podobny skład z osadem uzyskanym w badaniach własnych. Sugerowano istnienie struwitu, ale procent udziału atomowego połączeń, do których sklasyfikowano struwite jest mały i wynosi mniej niż 4%. Oznacza to, że osady powstające w obiektach technologicznych oczyszczalni ścieków są mieszaniną różnych związków, w których czysty struwit może stanowić tylko niewielką część.
PL
Twardość wody, powodowana obecnością jonów wapnia i magnezu, nie jest czynnikiem stanowiącym zagrożenie zdrowia konsumentów. Jednakże woda o podwyższonej twardości może nie być akceptowana przez odbiorców z powodu wytrącania się osadów i wówczas zmniejszenie twardości wody staje się koniecznym warunkiem komfortu jej użytkowania. Zmiękczanie wody może być prowadzone na drodze chemicznej lub fizycznej, w takich procesach jak wymiana jonowa, procesy membranowe, strącanie chemiczne czy krystalizacja. Możliwości zmiękczania wody podziemnej metodą krystalizacji heterogenicznej, łącznie z usuwaniem związków żelaza i manganu, określono doświadczalnie w stacji pilotowej, której podstawowym elementem był reaktor ze złożem fluidalnym z piasku kwarcowego, pełniącego rolę zarodków krystalizacji węglanu wapnia. Twardość ogólna wody podziemnej wynosiła 160÷166 gCaCO3/m3, zawartość żelaza – 0,44÷0,66 gFe/m3, a manganu – 0,16÷0,23 gMn/m3. Do zmiękczania wody zastosowano ług sodowy (NaOH), dawkowany w ilości odpowiadającej w przybliżeniu dawce stechiometrycznej wymaganej do usunięcia jonów wapnia. W badaniach pilotowych nad zmiękczaniem wody podziemnej w procesie krystalizacji heterogenicznej z użyciem ługu sodowego wykazano możliwość zmniejszenia twardości ogólnej wody o 40% przy użyciu dawki NaOH o połowę mniejszej od stechiometrycznej. Stwierdzono selektywne usuwanie jonów wapnia, przy stosunkowo niewielkim zmniejszeniu zawartości jonów magnezu, a także jednoczesne usunięcie z wody związków żelaza i manganu. Przeprowadzona analiza porównawcza procesu krystalizacji heterogenicznej i nanofiltracji potwierdziła przydatność obu procesów do zmniejszania twardości wody wprowadzanej do systemu dystrybucji oraz jej negatywnych skutków.
EN
Hardness of water caused by calcium and magnesium salts does not pose any health risk to consumers. However, harder water may not be widely accepted due to the build-up of scale deposits. Hence, hardness reduction becomes a critical factor of water usage comfort. Water hardness may be reduced via chemical or physical processes, such as ion exchange, membrane processes, stripping or crystallization. Potential application of heterogeneous crystallization to groundwater hardness reduction, including iron and manganese removal, was determined empirically at the pilot station with fluidized bed reactor of arenaceous quartz, serving as a nuclei of crystallization for calcium carbonate. Total hardness of groundwater was ranging from 160 to 166 gCaCO3/m3, the iron content – from 0.44 to 0.66 gFe/m3, while the manganese – from 0.16 to 0.23 gMn/m3. Sodium hydroxide (NaOH) was used for the purpose of water softening, at the amount close to the stoichiometric dose required for the calcium ion removal. Pilot studies on groundwater softening using the heterogeneous crystallization with sodium hydroxide revealed a possibility to reduce the total water hardness by 40% at the half stoichiometric point. Selective calcium ion removal was demonstrated with relatively small reduction in magnesium content. Iron and manganese cations were co-removed. A comparative analysis of heterogeneous crystallization and nanofiltration confirmed suitability of the both processes for hardness reduction of water entering the distribution system and elimination of its adverse effects.
19
Content available remote Partial crystallization of the erbium/ytterbium co-doped oxyfluoride glass
EN
Erbium/Ytterbium co-doped oxyfluoride glass-ceramics can be applied as the optical fiber core. For that reason its crystallization kinetics is described in terms of the JMAK model (Johnson-Mehl-Avrami-Kolmogorov) with later updates. Differential Thermal Analysis (DTA) measurements of glass and glassceramics powders (with size comparable to the diameter of multimode optical fiber core) combined with X-ray diffraction (XRD) measurements enables both the identification of growing nanocrystals structure and determination of the specific annealing parameters. This specific glass powder annealing results in the desired microstructure of glass-ceramics fibers (nanocrystals embedded in the glassy host).
PL
Zamiarem autorów było precyzyjne określenie warunków wygrzewania włókien optycznych ze szkieł tlenofluorkowych, współdomieszkowanych erbem i iterbem, przeznaczonych na rdzenie aktywnych światłowodów wielodomowych. Pożądana, finalna mikrostruktura włókien to jednorodnie rozłożone w matrycy szklistej nanokryształy wzbogacone w erb i iterb. Ponieważ średnica rdzeni włókien wielodomowych jest standaryzowana (50, 62,5 lub 100 μm), do badań użyto frakcji proszków szkieł o rozmiarach 45÷100 μm.
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