KINETICS OF YELLOW IRON OXIDE THERMODESTRUCTION

У статті викладено результати кінетичних досліджень терморозкладання оксигідроксиду заліза α-FeOOH (гетиту) термогравіметричним методом. Визначено, що процес сушки має проводитись при температурі не вище 130 °C, бо підвищення температури призводить до хімічних перетворень зразка α-FeOOH → α-Fe 2 O 3 та зміни кольору з жовтого на червоний, що може бути небажаним у виробництві пігментів. Процес одержання червоного оксиду заліза рекомендовано проводити при температурах 160-170°С. Процес терморозкладання протікає в кінетичній області і описується рівнянням, зазначеним як модель з фронтальним переміщенням зони реакції, енергія активації 55 кДж/моль. Результати досліджень можуть бути використані при розрахунках обладнання для проведення процесів сушки та прожарювання у виробництві пігментів та каталізаторів.В статье изложены результаты кинетических исследований терморазложения оксигидроксида железа α-FeOOH (гетита) термогравиметрическим методом. Определено, что процесс сушки должен проводиться при температуре не выше 130 °C, так как повышение температуры приводит к химическим превращениям образца α-FeOOH → α-Fe 2 O 3 и изменению цвета с желтого на красный, что может быть нежелательным в производстве пигментов. Процесс получения красного оксида железа рекомендуется проводить при температурах 160-170 °С. Процесс терморазложения протекает в кинетической области и описывается уравнением, указанным как модель с фронтальным перемещением зоны реакции, энергия активации 55 кДж/моль. Результаты исследований могут быть использованы при расчетах оборудования для проведения процессов сушки и прокаливания в производстве пигментов и катализаторов.The article presents the results of iron oxyhydroxide α- FeOOH (goethite) thermodestruction kinetic studies by thermogravimetric method. It is determined that the drying process has to be conducted at temperatures above 130 °C, because the temperature increasing leads to chemical reactions like α-FeOOH → α-Fe 2 O 3 and to color changes from yellow to red, which may not be desirable in the pigments production. The process of red iron oxides obtaining is recommended to at temperatures 160-170 °C. The thermodestruction process takes place in the kinetic region and described by the specified model with a front reaction zone moving, the activation energy is 55 KJ/mol. The research results can be used in the calculation of equipment for drying and calcining processes in pigments and catalysts production

FEATURES OF OUTFLOW OF INTRAOCULAR LIQUID AFTER AN EKSIMERLAZER SKLEREKTOMY (PILOT STUDY)

Modern approaches to surgical glaucoma treatment is based on the safe and effective methods. In recent years, great attention is paid to the techniques of stimulating uveoscleral path outtake aqueous humor from the eye. Uveoscleral space in the extended outflow pathways is dominant and constitutes about 72%. Sclera is a field of the greatest interest, as the end stages of the outflow of aqueous humor via the uveoscleral path. The aim of the study was to investigate the influence of excimer laser sclerectomy on the drainage function of the eye and development of a mathematical model based on the permeability of the sclera of the amount of laser ablation at a defined area of laser exposure and the level of IOP. Studies were conducted on 12 human cadaver eyes isolated person. The domestic excimer laser “MicroScan Vizum” with a wavelength of 193нм (0,193 µm) was used for the thinning of sclera. In the experiment used a special computer program provided ablation of scleral tissue, the scleral bed forming a rectangular shape with a size 7,0x5,0 mm. the Depth of influence started from 100 microns to 600 microns in increments of 50 µn. The exposure was carried out at a constant perfusion pressure of 25 mm Hg After each impact was measured of the coefficient ease the outflow. A correlation was established between the factor and effective features, i.e., between the excimer laser deep sclerectomy (µm) and ratio of lightness outflow (mm3/min/mm Hg.St). Thinning of the sclera leads to an improvement of its permeability and increasing the coefficient ease the outflow. A mathematical model, allowing to achieve the desired ratio of lightness outflow experiment by excimer laser sclerectomy was developed. The mathematical model has the form of the regression equation.The sclera is a promising object for further developments in the surgical treatment of glaucoma. Laser ablation of the sclera leads to an improvement of outflow via the uveoscleral path and reduce intraocular pressure

Evolution of microstructure in advanced ferritic-martensitic steels under irradiation : the origin of low temperature radiation embrittlement

Advanced reduced activation ferritic/martensitic steels and oxide dispersion-strengthened steels exhibit significant radiation embrittlement under low temperature neutron irradiation. In this study we focused on atom probe tomography (APT) of Eurofer97 and ODS Eurofer steels irradiated with neutrons and heavy ions at low temperatures. Previous TEM studies revealed dislocation loops in the neutron-irradiated f\m steels. At the same time, our APT showed early stages of solid solution decomposition. High density (10$^{24}$ m$^{-3}$) of ∼3–5 nm clusters enriched in chromium, manganese, and silicon atoms were found in Eurofer 97 irradiated in BOR-60 reactor to 32 dpa at 332°C. In this steel irradiated with Fe ions up to the dose of 24 dpa, pair correlation functions calculated using APT data showed the presence of Cr-enriched pre-phases. APT study of ODS Eurofer found a significant change in the nanocluster composition after neutron irradiation to 32 dpa at 330 °C and an increase in cluster number density. APT of ODS steels irradiated with Fe ions at low temperatures revealed similar changes in nanoclusters. These results suggest that irradiation-induced nucleation and evolution of very small precipitates may be the origin of low temperature radiation embrittlement of f\m steels

Enucleaton of the right eye due to large choroidal melanoma with simultaneous penetrating cornea transplantation from OD to OS (Case report).

There is presentation case report of 75‑year old woman with choroidal melanoma (T3N0M0) on the right eye and failed graft on the left pseudophakic eye with far advanced glaucoma and ARMD. No treatment was given to the leading eye with VA 0,2. VA of OS = 1 / ∞ pr.l.certa; PKP OS in 2008 for pseudophakic bullous keratopathy on the eye with far advanced glaucoma. IOP was normal after previous filtering surgery. After PKP VA = 0,04; clear graft during 2 years; then gradually opacification and vascularization occurred. VA dropped to light perception. Echography OD — tumor h 8,29 mm, d 21,77 mm. No ingrowth of tumor into anterior segment of the eye; VA OD = 0 (no light perception). Concerning the need to enucleate the right eye with large choroidal melanoma, the advantage of using corneal autograft from OD to OS, location of tumor in the posterior pole with no ingrowth in anterior segment, the decision was made to perform the following operation — to enucleate the right eye and transplant simultaneously corneal graft from OD on OS. Patient was discharged from the Ophthalmology Hospital with VA OS = 0,01, during next week VA improved to 0,02. 8,0 mm graft isclear, fixed with 8 interruptured and continious suture 10 / 0‑nylon. Anterior chamber — normal depth, atrophic iris, stable position of PC IOL. Optic nerve head is pale with subtotal deep glaucomatous excavation. Conclusion: presented case report demonstrates the rarepossibility to use cornea after enucleation the eye with large malignant tumor (located in the posterior pole) for grafting in the only eye with failed vascularised graft. It was the only possibility for this patient to restore some vision

Carbides in Co Re Cr based high temperature alloys

Co Re base alloys with very high melting point are being developed to supplement Ni superalloys in future gas turbines in which much higher gas entry temperatures are expected. The microstructure of Co 17Re 23Cr 2.6C and Co 17Re 23Cr 1.2Ta 2.6C alloys has been investigated by scanning and transmission electron microscopy. These alloys are mainly strengthened by carbides of Cr and or Ta, but it is not trivial to accurately quantify the composition of the carbides. The compositions of the various carbides in Co Re base alloys were quantified with near atomic resolution using atom probe tomography. The Cr as well as Ta carbides exists in the alloys with different morphologies, ranging from extremely fine nm scale to large lm scale sizes. The composition and the crystal structure of the investigated phases were measured and reported. It is shown that both types of carbides are stable up to 1000 C but the Ta carbides are more stable than the Cr carbides at 1200 C after long time ageing. They are also effective as strengthening precipitate

Utilization of Lime-softening Sludge to Obtain Calcium Nitrate

The given research is devoted to the development of the technology of utilization of lime-softening sludge to obtain calcium nitrate.Water treatment waste by chemical composition differs from natural raw materials such as limestone, which is traditionally used to obtain calcium nitrate. Sludge obtained at the stage of lime-softening contains about 70% calcium carbonate, a fairly large amount of iron, which enters the precipitate with solutions of coagulants, as well as organic impurities. Organic impurities come from river water and precipitate as a result of coagulation.The process of extracting calcium by the acid solution is stable. The results are well reproduced on two kinds of waste from different enterprises. This is explained both by the high dissolution rate of calcium carbonate in nitric acid, and the similar chemical composition of the waste.Not only calcium compounds, but also iron ones together with the organic component of liming sludge fall into the solution. A process scheme is proposed for cleaning the solution, which should include the stages of oxidation of the solution and subsequent precipitation of iron.The concentration of iron in the experimental solutions was up to 6 g/l. With the help of the calculations of the precipitate-solution equilibrium, it has been stated that iron in the area of low concentrations of nitric acid precipitates in the solution, and calcium stays in it. The decrease of the acid concentration was carried out by the addition of pure calcium carbonate.Kinetic studies of the process of iron precipitation on model solutions of iron (III) nitrate have been carried out. The second-order kinetic equation is obtained. The calculation of the process activation energy is available in the paper. The value of the energy is ~37 kJ/ mole, which is the evidence of the precipitation process in the transition area. The undissolved residue contains about 40% iron and can be used to obtain coagulants.Thus, the application of the proposed method will allow the best use of water treatment wast

Pinning of nanocrystals growth at Fe-Ni-B amorphous alloy crystallization: Atom probe investigations

The crystallization processes in Fe<inf>50</inf>Ni<inf>33</inf>B<inf>17</inf> amorphous alloy have been investigated by transmission electron microscopy (TEM) and a three dimensional atom probe (3DAP). The γ-Fe,Ni FCC crystals, 25 nm in size, were found in the amorphous alloy annealed at temperatures ranging 360-400 °C for 1 h. TEM demonstrates that the nanocrystals growth stops as the temperature rises. The formation of an amorphous layer enriched in boron at the border of γ-Fe,Ni nanocrystals responsible for the pinning of nanocrystals size was observed by 3DAP. The composition of an amorphous barrier by 3DAP was found to be Fe<inf>50</inf>Ni<inf>29</inf>B<inf>21</inf>. It was proposed that this composition reveals higher crystallization temperature, which is the reason of pinning nanocrystals growth

Nanostructure evolution in ODS steels under ion irradiation

Excellent mechanical properties of ODS steels are directly related to the high density of homogeneously distributed, well-formed oxide particles (such as Y2O3, or Y-Ti-O). However, atom probe tomography study of ODS steels revealed that in addition they contain almost a hundred times more nanoclusters enriched in Y, O and V/Ti (if present in the alloy composition) than larger oxide particles. In this work, we carried out atom probe tomography (APT) and transmission electron microscopy (TEM) studies of three different ODS steels produced by mechanical alloying: ODS Eurofer, 13.5Cr ODS and 13.5Cr-0.3Ti ODS. These materials were investigated after irradiation with Fe (5.6MeV) or Ti (4.8MeV) ions up to 1015ion/cm2 and part of them up to 3×1015ion/cm2. In all cases, areas for TEM investigation were cut at a depth of ∼ 1.3µm from the irradiated surface corresponding to the peak of the radiation damage dose. It was shown that after irradiation at RT and at 300°С the number density of oxide particles in all the samples grew up. Meanwhile, the fraction of small particles in the size distribution has increased. APT revealed an essential increase in nanoclusters number and a change of their chemical composition at the same depth. The nanostructure was the most stable in 13.5Cr-0.3Ti ODS irradiated at 300°С: the increase of the fraction of small oxides was minimal and no change of nanocluster chemical composition was detected