The effect of the refractory material on the phase transformation parameteres during forming of the Al-8wt%Si-3wt%Cu structure

Očvršćavanje legura aluminijuma se najčešće odvija u termootpornim oblogama sačinjenim ili od metala ili od oksida koji su stabilni na visokim temperaturama. Značajno različita toplotna provodljivost između metala i termootpornih oksida prouzrokuje očvršćavanje sa različitim brzinama hlađenja. U ovom radu smo formirali sekundarnu leguru Al-8wt%Si-3wt%Cu u kalupu od nerđajućeg čelika, tankozidnoj čaši od nerđajućeg čelika i debelozidnoj čaši od cirkonijum oksida. Tok formiranja očvrsle strukture je praćen zaronjenim termoparovima koji su omogućili kompjutersku analizu krive hlađenja. Parametri na koje je brzina hlađenja imala najznačajniji uticaj su vrednosti pothlađenja formiranja primarnih kristala aluminijuma, vreme rasta primarnih kristala aluminijuma i ukupno vreme očvršćavanja od pojave prvih čvrstih kristala do formiranja potpuno očvrsle strukture. Al-8wt%Si-3wt%Cu legura aluminijuma formirana u metalnim kalupima ima manju veličinu zrna i posledočno veću zateznu čvrstoću, manju makroporoznost i manje hrapavu površinu od legure formirane u oblogama od termootpornih oksida. Ispitivane termootporne obloge su uticale na formiranje tri osnovna mikrokonstituenta u Al-8wt%Si-3wt%Cu leguri u različitim vremenskim intervalima, što je dovelo do formiranja različite mikrostrukture, gde odluka o izboru materijala termootporne obloge zavisi od isplativosti celokupnog procesa, zahtevanog kvaliteta spoljnih površina i zahtevane minimalne čvrstoće konačnog proizvoda.Solidification of the aluminum alloys takes place in heat-resistant refractory materials made of either metal or oxides that are stable at high temperatures. The significantly different thermal conductivities between metals and heat-resistant oxides cause solidification with significantly different cooling rates. In this work, we formed a secondary Al-8wt%Si-3wt%Cu alloy in a stainless steel mould, a thin-walled stainless steel cup, and a thick-walled zirconium oxide cup. The course of the formation of the solidified structure was monitored by immersed thermocouples, which enabled the computer analysis of the cooling curves. The parameters on which the cooling rate had the most significant influence are the undercooling values of the formation of primary aluminum crystals, the time of the growth of primary aluminum crystals and the total solidification time from the formation of the first solid crystals to the formation of a fully solidified structure. The Al-8wt%Si-3wt%Cu aluminum alloy formed in metal mould has a smaller grain size and consequently higher tensile strength, lower macro-porosity and less rough surface than the alloy formed in refractory oxide coatings. The examined heat-resistant refractory material influenced the formation of three basic micro-constituents in the Al-8wt%Si-3wt%Cu alloy in different time intervals, which led to the formation of a different microstructure, where the decision on the choice of material for the heat-resistant refractory material depends on the profitability of the entire process, the required quality of the external surfaces and required minimum strength of the final product

Surface ionization study of the non- stoichiometric LnFn-1 (n = 4 – 6) clusters

In this study we are presenting the results of the surface ionization of LinFn-1 (n=4- 6) clusters on rhenium surface impregnated with fullerenes using the magnetic mass spectrometer. The Li5F4 nanocubic cluster was detected for the first time. We determined values of ionization energies for Li4F3 and Li6F5, they are 4,3±0,2 eV, 4,0±0,2eV, respectively. The ionization energies agreed with theoretical ionization energies obtained by ab initio method, which indicates the excess electron localized in a specific site for non-stoichiometric clusters. The first ionization energy value for the Li4F3 was in accordance with earlier results obtained experimentally using photoionization time-of-flight mass spectrometer. There are currently no reliable experimental data for the ionization energy of Li6F5 cluster.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Modeling of Impurities Evaporation Reaction Order in Aluminum Alloys by the Parametric Fitting of the Logistic Function

Advancements in computer capabilities enable predicting process outcomes that earlier could only be assessed after post-process analyses. In aerospace and automotive industries it is important to predict parts properties before their formation from liquid alloys. In this work, the logistic function was used to predict the evaporation rates of the most detrimental impurities, if the temperature of the liquid aluminum alloy was known. Then, parameters of the logistic function were used to determine the transition points where the reaction order was changing. Samples were heated to 610 °C, 660 °C, 710 °C, and 760 °C for one hour, after which the chemical analyses were performed and evaporation rates were calculated for Cd, Hg, Pb and Zn elements. The pressure inside the encapsulated area was maintained at 0.97 kPa. Whereas parameters that define the evaporation rate increase with the temperature increase, the maximum evaporation rates were deduced from the experimental data and fitted into the logistic function. The elemental evaporation in liquid-aluminum alloys is the best defined by the logistic function, since transitions from the first to zero-order-governed evaporation reactions have nonsymmetrical evaporation rate slopes between the lowest and the highest evaporation rate point

Tims and maldi tof of endohedral 99mTc@C60 metallofullerene

Mass spectral studies (both TIMS – thermal ionization and MALDI TOF – matrixassisted laser desorption time-of-flight mass spectrometry) of the endohedral metallofullerenes, 99mTc@C60 and 99mTc@C70, provided detailed structural and reactivity information about these unusual species. MS experiment revealed that both fullerenes and endohedral metallofullerenes fragment by multiple C2 loss. However, a difference in the terminal fragmentation products was observed for metallofullerene relative to C60, suggesting that the encapsulation metal strongly impacts the fragmentation product. Singly charged cations of the metallofullerenes (M@Cn + ) were completely unreactive in the gas phase with oxygenated compounds such as ethylene oxide: however, the corresponding neutral species appear to react readily with oxygenated species. Collisional dissociation of the ionized endohedral fullerenes listed above revealed multiple C2 loss (either as sequential C2 loss or larger C2n eliminations) to generate similar terminal fragmentation products, which might be predicted due to the similar ionic radii of the encapsulated metals. The observed ionization energies of endohedral molecules were, 5.1 ± 0.1 eV and 5.3 ± 0.1 eV, respectively.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Monitoring the amount of formed solid phase in aluminum alloy under free cooling conditions

Jedan od najefikasnijih načina za buduće projektovanje, proizvodnju, analizu i optimizaciju novih procesa koji uključuju faznu promenu materijala je razvoj visokoosetljivih kvantitativnih metoda zasnovanih na detekciji temperaturnih promena tokom trajanja procesa i korelaciji tih promena sa promenama u tretiranom materijalu. U ovom radu, sekundarna legura Al-8wt%Si-3wt%Cu je formirana iz tečnog stanja u uslovima slobodnog hlađenja. Identifikovane su karakteristične temperature transformacija i formalizovan je metod za praćenje količine čvrste faze tokom procesa očvršćavanja. Iz snimljene krive hlađenja određene su vrednosti prvog izvoda i formirana je odgovarajuća referentna kriva. Površina između prvog izvoda krive hlađenja i referentne krive je korišćena za praćenje količine očvrslog dela materijala tokom procesa očvršćavanja. Dobijeni rezultati su pokazali da je predložena metoda efikasna u dobijanju podataka o količini očvrslog dela materijala u svakom trenutku procesa očvršćavanja, kao i da se mogu dalje koristiti za detekciju broja faza i mikrokonstituenata u formiranoj strukturi i eksperimentalnu potvrdu latentne toplote očvršćavanja novih materijala. Metoda praćenja količine formirane čvrste faze u uslovima slobodnog hlađenja ne zahteva posebnu pripremu uzoraka niti kompleksnu laboratorijsku opremu, pa shodno tome, u praktičnoj primeni efikasno zamenjuje standardne metode za detekciju termofizičkih osobina materijala, kao što su diferencijalna termijska analiza ili diferencijalna skenirajuća kalorimetrija.One of the most effective ways for the future design, production, analysis and optimization of new processes, involving phase change of materials, is the development of highly sensitive quantitative methods based on the detection of temperature changes during the solidification process and the correlation of these changes with changes in the treated material. In this work, the secondary Al-8wt%Si3wt%Cu alloy was formed from the liquid state under free cooling conditions. Characteristic transformation temperatures were identified and a method for monitoring the amount of solid phase during the solidification process was formalized. From the recorded cooling curve, the values of the first derivative were determined and the corresponding reference curve was formed. The area between the first derivative of the cooling curve and the reference curve was used to assess the amount of solidified part of the material during the solidification process. The obtained results showed that the proposed method is effective in obtaining data of the fraction solid at every moment of the solidifcation process, as well as that it can be further used to detect the number of phases and microconstituents in the formed structure, as well as an experimental examination of the latent heat of solidification of new materials. The method of monitoring the amount of solid phase, formed under free cooling conditions, does not require specific preparation of samples or complex laboratory equipment, and accordingly, in practical application it effectively replaces standard methods for detecting thermophysical properties of materials, such as differential thermal analysis or differential scanning calorimetry

Endohedral fullerenes of different elements

In this work we have studied the Li/C-60, Li/C-70, (99)mTc/C-60, (TC)-T-99/C-70, Gd/C-60, Gd/C-70, Nd/C-60, Nd/C-70, Y/C-60 and Y/C-70 systems by surface ionization mass spectrometry and investigated a possibility of the formation of endohedral fullerenes. Using the ion implantation technique (introducing negatively charged fullerene into a low temperature lithium, technetium, gadolinium, neodymium or yttrium plasma column by a strong axial magnetic field), the endohedral fullerenes Li congruent to C-60, Li congruent to C-70, Li-2 congruent to C-70, Tc-99m congruent to C-60, Tc-99m congruent to C-70, Gd congruent to C-60, Nd congruent to C-60, Y congruent to C-60, Gd congruent to C-70, Nd congruent to C-70 and Y congruent to C-70 have been produced and ionization energies were measured. Their existence was demonstrated through the high sensitivity, magnetic mass spectrometer (TIMS- thermal ionization mass spectrometer). These metallofullerenes were identified as stable molecules. The reaction of the obtained endohedral fullerenes with oxygen compounds (H2O, O-2 and N2O) has also been investigated. The result showed that these metallofullerenes are very inert to all of these gas phase oxygen-rich molecules, leading support to the endohedral structure of the metallofullerenes. Observed ionization energies for Li congruent to C-60, Li congruent to C-70, Li-2 congruent to C-70, Tc-99m congruent to C-60, Tc-99m congruent to C-70, Gd congruent to C-60, Nd congruent to C-60, Y congruent to C-60, Gd congruent to C-70, Nd congruent to C-70 and Y congruent to C-70 were 5.9eV, 5.1eV, 5.3eV, 5.1eV, 5.3ev, 6.2eV, 6.5eV, 6.6eV, 6.4eV, 6.5eV and 6.7eV, respectively

The role of radiotherapy in combined treatment for locally advanced breast cancer with ipsilateral supraclavicular metastases

Background: Locally advanced breast cancer (LABC) includes a heterogeneous group of breast neoplasms classified from stage IIB, IIIA to IIIB. LABC with ipsilateral supraclavicular adenopathy without evidence of distant disease is included in the stage IV (but regional stage IV). Purpose of this study was to assess the role of radiotherapy (RT) in combined treatment with systemic therapy (chemotherapy and hormonotherapy) in LABC with ipsilateral supraclavicular adenopathy. Methods: In 5-year period 45 patients with LABC and ipsilateral supraclavicular metastases were treated with radiotherapy and chemo- or hormonotherapy depending on the physical condition, age and steroid receptors (ER, PGR) content. Twenty patients received TD 30 Gy in 10 fractions on breast and regional lymph nodes and 25 patients received TD 51 Gy in 15 fractions on the breast and TD 45 Gy in 15 fractions on regional lymph nodes. Twenty-three patients received chemotherapy (CMF or FAC), 10 received hormonotherapy, and 12 received both chemo- and hormonotherapy. Results: After finishing complete treatment the overall response rate was 93.3%. Complete response was 20% and partial response was 73.3%. Locoregional relapse occurred in 5 patients and distant metastases occurred in 10 patients. Conclusion: Treatment of LABC with ipsilateral supraclavicular lymph node involvement should be aggressive, what means combined radiotherapy and systemic chemo-hormonotherapy. Such treatment provides for these patients maximum chance of long-term disease - free and overall survival

Ionization energies of the non-stoichiometric LinFn-1 (n=3, 4, 6) clusters

Ionization energies of non-stoichiometric LinFn-1 (n =3,4, 6) clusters determined by a thermal ionization mass spectrometry (TIMS) were 4.2 +/- 0.2 eV for Li3F2, 4.3 +/- 0.2 eV for Li4F3 and 4.1 +/- 0.2 eV for Li6F5. The ionization energy of Li6F5 cluster was obtained experimentally for the first time. The ionization energies of Li3F2 and Li4F3 are in correlation with the results obtained by photoionization time-of-flight mass spectrometry. The determined ionization energies are comparable with theoretical ionization energies calculated by ab initio method. The theoretical predictions supported that the most stable isomers of a non-stoichiometric cluster LinFn-1 (n = 3 and n = 4) in which the excess electron localizes on a specific site have a segregated electronic structure composed of the metallic part and ionic part. (C) 2008 Elsevier Ltd. All rights reserved

Ionization energies of LinX(n=2,3; X=Cl,Br,I) molecules

Molecules of LinX (n = 2,3; X = Cl, Br, I) were examined with a magnetic sector mass spectrometer by surface ionization using a triple rhenium filament impregnated with fullerene (C-60). The ionization energies obtained for Li2Cl, Li2Br and Li2I Molecules are 3.8 +/- 0.1, 3.9 +/- 0.1 and 4.0 +/- 0.1 eV. respectively. The first ionization energy of Li2Cl is documented, while there are no literature data for the ionization energies of Li2Br and Li2I. The molecules of Li3Cl, Li3Br and Li3I were detected experimentally for the first time with ionization energies of 4.0 +/- 0.1, 4.1 +/- 0.1 and 4.1 +/- 0.1 eV, respectively. The ionization energies of LinX (n = 2, 3; X = Cl, Br, I) are in correlation with the theoretical prediction of their hyperlithiated configurations. Copyright (c) 2006 John Wiley and Sons, Ltd