Obtaining of nanostructured powders for production of new dispersion strengthened sintered material in the system Cu-Al2O3

U doktorskoj disertaciji je ispitivana mogućnost sinteze nanostrukturnih kompozitnih materijala na bazi bakra i glinice novom metodom, koja predstavlja kombinaciju termo-hemijskog postupka sinteze i mehaničkog legiranja. Termohemijska sinteza se odvija kroz tri faze i to: sušenje raspršivanjem rastvora nitrata, oksidaciono žarenje i redukcija. Metoda sinteze je razvijena sa ciljem dobijanja materijala sa superiornijim osobinama u odnosu na konvencionalne. U toku rada određeni su optimalni parametri procesa za svaku od faza sinteze, kao i karkaterizacija praha prekursora dobijenog hemijskim putem i finalnog praha dobijenog mehaničkim legiranjem različitim instrumentalnim metodama (SEM, XRD i AEM). Prahovi sa 1; 1,5 i 2% Al2O3 su sinterovani na različitim temperaturama u opsegu od 725-925°C u toku 15-120 min sa ciljem optimizacije parametara procesa sinterovanja dobijenih prahova. Određena je optimalna temperatura od 875°C i vreme od 1h. U cilju potvrđivanja upotrebnih osobina materijala, sinterovani uzorci su dalje mehanički i termički tretirani. Dokazano je da termo-mehanički tretman ima pozitivan uticaj na karakteristike materijala i kombinaciju električnih i mehaničkih svojstava koja se zahteva od ove vrste materijala. Vrednosti električne provodljivosti nakon termomehaničkog tretmana su na nivou od 61%IACS, a tvrdoće od 57HRF. Na osnovu mikrostrukturnih analiza i merenja električne provodljivosti i tvrdoće materijala, ojačavanje do kog dolazi u ispitivanom sistemu može biti objašenjeno mehanizmom koji čine disperzno, deformaciono i ojačavanje granicama zrna. Ojačavanje granicom zrna se postiže ne samo disperzoidom već i novoformiranom trećom fazom koja je detektovana u strukturi, čime se sprečava proces rasta zrna i povećava stabilnost materijala na povišenim temperaturama. Prednost predložene metode dobijanja se ogleda u velikom potencijalu za industrijsku proizvodnju i dobijanja značajnih količina prahova po relativno niskoj ceni, zbog jednostavnosti procesa sinteze i korišćenja sirovina sa niskom cenom za dobijanje materijala sa unapređenim osobinama. Ova doktorska disertacija je urađena u okviru realizacije projekta tehnološkog razvoja koje je finansiralo Ministarstvo za nauku i tehnološki razvoj Republike Srbije evidencioni broj 19032 ”Dobijanje nanostrukturnih prahova u cilju proizvodnje novih disperzno ojačanih sinterovanih materijala u sistemu Cu-Al2O3” (2008-2010).This PhD thesis presents the possibility of nanostructured composite materials based on copper and alumina synthesis trough a new method, which is a combination of thermo-chemical synthesis and mechanical alloying. Thermochemical synthesis is carried out through three stages: spray drying of nitrate solutions, oxidation and reduction. Synthesis method was developed with the aim of obtaining materials with superior properties compared to conventional ones. For each phase of synthesis process parameters were optimized. Characterization of powder precursors obtained by chemical means and the final powder obtained by mechanical alloying was carried out by different instrumental methods (SEM, XRD and AEM). Powders with 1, 1.5 and 2% Al2O3 were sintered at different temperatures in the range of 725-925°C during 15-120min in order to optimize sintering process parameters obtained. Optimal sintering temperature at 875°C was determined and sintering time of 1h. In order to confirm utility properties, sintered samples were further mechanically and thermally treated. It is proven that the thermo-mechanical treatment has a positive influence on the properties of materials and a combination of electrical and mechanical properties that is required for this type of material. The values of electrical conductivity after thermo-mechanical treatment on the level of 61% IACS, and the hardness of 57HRF. Based on microstructural analysis and measurements of electrical conductivity and hardness of materials, reinforcement that appears in the examined system can be explained by complex mechanism involving dispersive, deformation and grain boundary strengthening. Grain boundary strengthening is achieved not only by dispersoide, but by the newly formed third phase detected in the structure, which prevents the process of grain growth and increases the stability of the material at elevated temperatures. The advantage of the proposed method is in it’s the great potential for industrial production and production of significant amounts of powders at relatively low cost because of the simplicity of the synthesis process and use of low cost raw materials for production of materials with improved properties. This PhD thesis is part of the technological development project funded by the Ministry of Science and Technological Development of Serbia, No. 19032 ”Obtaining of nanostructured powders for production of new dispersion strengthened sintered material in the system Cu-Al2O3” (2008-2010)

Positive synergistic effect of the reuse and the treatment of hazardous waste on pyrometallurgical process of lead recovery from waste lead-acid batteries

Modification and optimization of the pyrometallurgical process of lead recovering from the waste lead-acid batteries have been studied in this paper. The aim of this research is to develop a cleaner production in the field of the secondary lead metallurgy. Lead smelting process with the addition of flux (sodium(I)-carbonate) and reducing agents (coke, iron) has been followed. The modified smelting process with the addition of hazardous waste (activated carbon) as alternative reducing agents has shown positive results on the quality of the secondary lead, the generated slag and the process gases. Filtration efficiency of the gases, the return of baghouse dust to the process and use of oxygen burners have positive effect on the environment protection and energy efficiency. Optimization of the recycling process has been based on the properties of the slag. Stabilization of slag is proposed in the furnace with addition of waste dust from the recycling of cathode ray tube (CRT) monitors. Phosphorus compounds from dust reduce leachability of toxic elements from the generated slag. Reduction the slag amount and its hazardous character through the elimination of migratory heavy metals and valorization of useful components have been proposed in the patented innovative device - cylindrical rotating washer/separator.  http://dx.doi.org/10.5937/metmateng1403171

Synthesis and Characterization of Dispersion Reinforced Sintered System Based on Ultra Fine and Nanocomposite Cu-Al2O3 Powders

Characterization of the obtained powder indicates a possibility of the synthesis of nanocomposite Cu-Al2O3 system by the thermochemical procedure, starting from water solutions Cu(NO3)2 and Al(NO3)3. AEM analysis indicates the presence of individual particles of 20-50 nm size. The shape of particles is irregular, with the presence of individual particles of nodular shape. The surface morphology is rough. Apart from that, the presence of an agglomerate with the magnitude of >100nm and of a sponge shape is noticeable. The obtained nanocomposite powders, with the structure basically preserved together with the final product, provided a significant reinforcement effect in the obtained sintered system. This is a consequence of the homogenous distribution of the elements in the structure, accomplished during the synthesis of powder and presence of the third phase which causes stabilization of dislocation substructure and achieves the relevant reinforcing effect. The analysis of the mechanical and electric properties of the sintered Cu-Al2O3 systems based on powders obtained by the thermochemical method shows that in the system with 3wt.%Al2O3, sintered at 900ºC, structural stabilisation occurs only after 30 minutes with considerable reinforcement effects. Since in other systems, the structural stabilisation process was not completed even after 120 minutes, the system with 3wt.% of dispersoids sintered at 900ºC for 30 minutes seems to be the optimum solution for the production of dispersively reinforced Cu-Al2O3 systems. This statement is confirmed by the corresponding analysis of the microstructure. In accordance with the previous statements, the EDS analysis of the sintered systems surface as well as FIB analysis show a homogenous distribution of elements, i.e. present phases. FIB analysis also indicates the size of microstructural constituents within the range of 50-250nm. TEM analysis of the sintered systems reveals the presence of copper crystals of 100 nm in size exposed to twinning, thus pointing to stabilization of the dislocation substructure. SADP of the examined nanocomposite Cu–Al2O3 sintered system shows spots and rings, where spots refer to the individual crystals of copper, and sharp circles (rings) originate from nanocrystals of alumina dispersed in the copper matrix. HRTEM analysis indicates the changes in the lattice parameter, which leads to the conclusion that the eutectic reaction occurred and the third, CuxAlyOz phase was formed on the grain boundary, which will be the subject of future studies based on a more precise approach to physical chemistry of system surfaces and of thermodynamic examinations of the influences of finely dispersed Al2O3 on the formation of the third phase and the increase in the system surface energy. In the end, all the above-mentioned examinations show that the reinforcement of Cu-Al2O3 system occurs via two mechanisms, which are: dispersion and reinforcement mechanism due to the homogenous dispersion of fine particles of Al2O3 in the matrix, and the mechanism of grain boundary reinforcement due to the appearance of the third phase

Synthesis of nanocomposites of difference architectures and applications based on copper, nickel and alumina

Considering that nanostructural materials are expected to have special physical and mechanical properties, in the recent years the examinations of synthesis and characterization of the nanocomposite system attracts even greater scientific interest. This paper presents production of sintered contacts materials produced from nanocomposite powders obtained by combination of thermochemical synthesis of Cu-Al2O3 powder and mechanical alloying of atomized copper powder with previously sinthetized Cu-Al2O3 powder. Produced powders were characterized by X-ray diffraction and Analytical Electron Microscopy. Characterization of sintered samples included Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), measurement of hardness and specific electrical conductivity. By thermochemical method of Cu-Al2O3 nanocomposite synthesis, i.e. deposition from aqueous solutions, in combination with mechanical alloying, significant effects of reinforcement were achieved as a result of homogenous distribution of alumina in the nanocomposite system. In combination with conventional methods, thermochemical process of nanocomposite powders synthesis could be successfully applied for synthesis of new nanocomposite catalysts, which are characterized by a high degree of dispersion of the catalytically active component, respectively the catalyst with high activity and selectivity. The high degree of dispersion is the result of uniform distribution of the catalytically active component into alumina suspension, realized during the thermochemical treatment in the synthesis of nanocomposite catalysts. In accordance with this, the paper shows the synthesis of Ni/Al2O3 and Ni-Pd/Al2O3 nanocomposite catalysts with homogeneously dispersed Ni particles, as catalytically active component, and Pd, as activity modifier, supported on ceramic Al2O3 based foam. Namely, the previous synthesized monolith was soaked in a mixed alumina suspension with NiCl2, PdCl2 and appropriate organic additives in order to obtain a nanocomposite catalysts with homogeneous distribution of catalytically active components. Characterization of obtained Al2O3 foam, as the active catalytic components primary carrier, and synthesized nanocomposite catalysts included SEM, EDS, gas permeability and mechanical properties. Synthesis of nanocomposite materials with homogeneous distribution of particles on the nanometer level may lead to formation of new materials with improved or even unexpected properties

Innovative solutions for the extraction of technology metals from complex primary a nd secondary raw materials

Technological evolution and growing demand for various high-tech devices have increased need for metals, both in terms of their diversity and quantities, resulting in more intense use of natural resources and generation of huge amounts of various waste materials. In contrast to base metals, advances in material science have given rise to a new group of metals, which are used in small or trace amounts to alter drastically the properties of matter. Whether in composite materials, like semiconductors or minor elements in alloys, these trace metals shape modern-day technology and, hence, are termed as Technology Metals (TM). Metals such as Sb, Co, Ga, Ge, In, Ta, the Platinum Group Metals (PGMs) and the Rare Earth Elements (REEs) are among the TM in which Europe is 100% import dependent. Development of the novel processing technologies will aim not only in securing raw material supply, but will rather aim to establish sustainable metallurgical processing, meaning establishing technologies for de-complexing the advanced material products with the minimum environmental footprint. Hydro and electro metallurgical steps make essential base with synergy to primary production route, advanced mechanical and minor pyro pretreatment step. However, absence of such extraction technologies, successfully applied on industrial scale, is still notable. To secure a reliable and sustainable supply of critical materials, innovative solutions need to be developed along the entire value chain. This transition requires multi-stakeholder partnerships that foster innovation and entrepreneurship, which can be obtained by applying the Triple Helix concept. Presented compilation of scientific, theoretical and experimental results, promotes an innovative synergy of various metals and industrial activities in metallurgy, resulting in profitable transformation of by-products and waste materials into resources. Focusing on treatment of specific by-products from zinc and copper primary production, as well on specific waste streams like WEEE and waste automotive catalysts, group is actively contribute to the EU sustainability policies

Disperzno ojačani materijali na bazi nanostrukturnih prahova u sistemu bakar-glinica

U okviru monografije, polazeći od teorijskog prikaza sinteze, strukture, svojstava i primene nanostrukturnih materijala, dati su originalni eksperimentalni rezultati uporedne analize različitim postupcima sintetisanih disperzno ojačanih nanostrukturnih kompozitnih Cu-Al2O3 materijala sledećih sistema: - nanokompozitnog Cu-Al2O3 sistema dobijenog mehaničkim legiranjem komercijalnog praha bakra dobijenog elektrolitičkim postupkom i glinice sintetisane sol-gel metodom, - nanokompozitnog Cu-Al2O3 sistema na bazi praha dobijenog termohemijskim postupkom, taloženjem iz tečne faze, - nanokompozitnog Cu-Al2O3 sistema dobijenog kombinacijom hemijskog postupka sinteze i mehaničkog legiranja

Postupak prerade otpadne olovne alkalne šljake u korisne proizvode

Postupkom prerade otpadne olovne alkalne šljake u korisne proizvode, dobijaju se frakcija +1mm, koja sadrži korisne komponente (metalno sulfidne, čvrste, nerastvorne) i koja se vraća u proces topljenja u cilju valorizacije korisnih komponenti. Postupkom se takođe dobija frakcija -1mm (jalovinska oksidno – sulfatna), optimalnog sastava i strukture, pogodna za postupak stabilizacije i solidifikacije u cementnoj matrici betona radi primene u građevinarstvu. Postupak obuhvata ispiranje u cilindričnom rotirajućem ispiraču – odvajaču (temperatura 22-43oC, brzina mešanja 6-25min-1, odnos čvrsto tečno 10-28% čvrstog), pri čemu se uklanjaju u vodi rastvorne komponente iz šljake, dobija stabilnija šljaka (frakcija -1mm) i izdvaja povratni metal i kamenac (frakcija +1mm) sa sadržajem korisnih komponenata, koje se valorizuju vraćanjem u proces topljenja. Koristan proizvod je i rastvor nakon tretmana sodnog sadržaja, koji se koristi u procesu proizvodnje natrijum(I) – sulfata, zajedno sa rastvorom iz faze desumporizacije olovne paste prerade otpadnih olovnih akumulatora, u cilju dobijanja komercijalnog proizvoda Na2SO4

Positive synergistic effect of the reuse and the treatment of hazardous waste on pyrometallurgical process of lead recovery from waste lead-acid batteries

Modification and optimization of the pyrometallurgical process of lead recovering from the waste lead-acid batteries have been studied in this paper. The aim of this research is to develop a cleaner production in the field of the secondary lead metallurgy. Lead smelting process with the addition of flux (sodium(I)-carbonate) and reducing agents (coke, iron) has been followed. The modified smelting process with the addition of hazardous waste (activated carbon) as alternative reducing agents has shown positive results on the quality of the secondary lead, the generated slag and the process gases. Filtration efficiency of the gases, the return of baghouse dust to the process and use of oxygen burners have positive effect on the environment protection and energy efficiency. Optimization of the recycling process has been based on the properties of the slag. Stabilization of slag is proposed in the furnace with addition of waste dust from the recycling of cathode ray tube (CRT) monitors. Phosphorus compounds from dust reduce leachability of toxic elements from the generated slag. Reduction the slag amount and its hazardous character through the elimination of migratory heavy metals and valorization of useful components have been proposed in the patented innovative device - cylindrical rotating washer/separator. http://dx.doi.org/10.5937/metmateng1403171