Fly ash immobilization with vitrification

Raziskali smo možnost imobilizacije letečega pepela iz sežiga komunalnih odpadkov. Leteči pepel smo skupaj s slovenskim odpadnim steklom stalili in ulili v kovinske kokile, da je nastal pretežno amorfen produkt, tj. steklo, ki smo ga toplotno obdelali, da se je tvorila steklokeramika. Leteči pepel je bil sestavljen iz delcev velikosti <1 m, ki se povezujejo v aglomerate velikosti okrog 180 m. Tali se pri temperaturi okoli 1300 °C in se v tekočem stanju dobro meša z odpadnim steklom. Steklo, nastalo pri litju, se pretvori v steklokeramiko pri žarjenju v temperaturnem območju med 700 °C in 950 °C, pri čemer se tlačna trdnost poveča za dvakrat. Vrednosti izluževanja težkih kovin iz vzorčnega letečega pepela prekoračujejo predpisane mejne vrednosti za odlaganje na odlagališčih za nevarne odpadke, medtem ko so vrednosti za nastalo steklo in steklokeramiko pod predpisanimi vrednostmi. Zasteklen leteči pepel lahko odložimo kot stabiliziran in nereaktiven odpadek na odlagališčih nenevarnih odpadkov, mogoče pa bi ga bilo tudi predelati in uporabiti v koristne namene.The possibility of fly ash immobilization was investigated. Municipal solid waste fly ash mixed with waste glass cullet was melted and poured into metal moulds. Mainly amorphous glass product was formed, which was then heat treated to obtain glass- ceramics. Fly ash consisted of particles with size <1m, normally joined to larger agglomerates (r180 m). Its melting temperature was around 1300 °C and it mixed well with the glass cullet in the liquid state. Glass formed during solidification was transformed into the glass-ceramics after heat treatment in the temperature range between 700 °C in 950 °C, that doubled the compressive strength. Leaching of heavy metals from fly ash exceeded the allowed values for dumping dangerous waste in landfill, whereas the values for the produced glass and glass-ceramics were under the allowed values. The produced glass and glass-ceramics can be landfilled as a stabilised and unreactive waste in landfills for nonhazardous wastes. Their properties also offer the possibility for manufacturing useful products

Sestava in morfologija diboridov v zlitinah Al-Ti-B po žarjenju na 1873 K

In the investigation, Al-Ti-B alloys with different Ti/B ratios were annealed at 1873 K for 10 hours. Under this condition diboride particles were in contact with molten aluminium. During annealing considerable growth of remaining unmelted diboride particles took place. The composition of diboride particles shifted extremely close to the composition of pure TiB2 regardless of the Ti/B ratios in the alloys, indicating that in equilibrium almost pure TiB2 coexisted with a melt. Diboride particles were bound with well-defined crystal facets. Types and relative size of the facets depended on the Ti/B ratio. It is strongly indicated that an excess of Ti (B) in the melt over that needed to form TiB2 stabilizes crystal planes having planar arrangement of Ti (B) atoms.V tej raziskavi smo več zlitin Al-Ti-B, ki so imele različna razmerja Ti/B, žarili 10 ur pri 1873 K. V teh razmerah so bili delci diborida v kontaktu z aluminijevo talino. Med žarjenjem so diboridni delci močno zrasli. Njihova sestava se je v vseh raziskanih zlitinah močno približala sestavi čistega TiB2, kar kaže, da je v termodinamskem ravnotežju s talino praktično čisti TiB2. Diboridni delci so bili obdani s kristalnimi fasetami. Vrsta in relativna velikost faset je bila močno odvisna od razmerja Ti/B. Obstajajo trdni dokazi, da presežek Ti (B) nad vrednostjo, ki je potrebna za tvorbo TiB2, stabilizira kristalne ravnine, ki imajo ravninsko razporeditev Ti (B) atomov

The Solidification Path of the Complex Metallic Al-Mn-Be Alloy

The solidification paths of the Al86.1Mn2.5Be11.4 and Al84Mn5.1Be10.9 alloys, melt spun, cast into a copper mould and controlled cooled (during DSC) were investigated by means of light-optical microscopy (LOM), differential scanning calorimetry (DSC) combined with thermogravimetry (TG) or simultaneous thermal analysis (STA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and the X-ray diffraction (XRD) line in Elletra Trieste, Italy. The constitutions of samples from both alloys were examined in all three states, i.e., after melt spinning, after casting into a copper mould and after differential scanning calorimetry. It was established that in the cast and controlled-cooled specimens the alloys consisted of an aluminium-rich αAl-matrix, and the Al4Mn and Be4AlMn phases. In the case of casting and DSC the primary crystallization began with the precipitation of the Be4AlMn phase, followed by what can most likely be characterized as a uni-variant binary eutectic reaction L → (Be4AlMn + Al4Mn). The solidification process continued with an invariant ternary eutectic reaction, where the remaining melt (L) formed the heterogeneous structure (αAl + Al4Mn + Be4AlMn) or a ternary eutectic. When extremely high cooling rates were employed, as is the case with melt-spinning, the constituting phases of both alloys were precipitated in a very small form and the Be4AlMn phase was completely absent in the form of primary polygonal particles and replaced by the icosahedral quasicrystalline phase or the i-phase. There was also no evidence of the Al4Mn phase. The distribution, size and shape of all the constituents in the melt-spun alloys also varied from the contact surface towards the free surface of the ribbons. The smallest constituents were established at the contact surface, measuring less than 0.1 μm, to 0.5 μm at the free surface. The grains of the aluminium-rich matrix had mean diameters of less than 20 μm, close to the free surface, down to 1 μm at the contact surface.</p

Karakterizacija hitrostrjenih trakov zlitine Cu-Al-Ni z uporabo fokusiranega ionskega curka

This work investigates the possibilities for applying a focussed ion beam (FIB) for the metallographic preparation and characterization of Cu-Al-Ni melt-spun ribbons. Two alloys were selected for this reason: CuAl13Ni4 and CuAl15Ni4. The microstructure of the first alloy was fully martensitic and the microstructure of the second consisted of two phases: martensite and ▫$gamma_2$▫. It was discovered that with FIB-etching the microstructures of both alloys can be clearly revealed on polished cross-sections of the melt-spun ribbons, as well as on their wheel-side and air-side surfaces. However, better results were obtained when the etched surface was smoother, and finer details were visible when using smaller ion currents. In addition, a study was made into the influence of platinum deposition on the quality of 3D-cross sections. It was found that Pt-deposition is necessary when the edge of the trench should be straight and sharp, and the surface of the 3D cross-section smooth. However, in this case, the microstructure of the ribbons free surface cannot be seen.V tem delu smo raziskali mo.nosti uporabe fokusiranega ionskega curka (FIB) pri metalografski pripravi in karakterizaciji hitro strjenih zlitin Cu-Al- Ni. Izbrali smo dve zlitini: CuAl13Ni4 in CuAl15Ni4. Mikrostruktura prve zlitine je bila v celoti martenzitna, medtem ko je bila mikrostruktura druge zlitine sestavljena iz dveh faz: martenzita in ▫$gamma_2$▫. Ugotovljeno je bilo, da lahko pri jedkanju z ionskim curkom odkrijemo mikrostrukturo tako na poliranih prečnih prerezih trakov, kot tudi na obeh prostih površinah hitrostrjenih trakov. Mikrostruktura se je boljše odkrila, če je bila raziskana površina bolj gladka, medtem ko smo lahko razločili drobnejše mikrostrukturne sestavine pri uporabi manjših ionskih tokov. Poleg tega smo študirali tudi vpliv nanosa platine na kakovost 3D-prečnih prerezov. Ugotovili smo, da je nanos platine smiselno uporabiti, če želimo zelo ravne in ostre robove reza ter gladko površino prečnega reza, vendar pa v tem primeru ne moremo videti mikrostrukture proste površine

Plasmonic Refractive Index Sensing Based on Interference in Disordered Composite Films

The strong dispersion in the effective optical constants of plasmonic nanocomposite films is used to generate interference effects that are highly sensitive to changes in the dielectric environment of particles. Numerical simulations show that reflectance measurements on metal nanoparticle systems close to a metallic substrate have larger sensitivities to changes in the surrounding refractive index than the standard transmittance measurements of the same system when placed on a transparent substrate. The scheme is particularly advantageous in case of disordered nanoparticle systems, where the difference between reflectance and transmittance‐based sensing approaches is enhanced due to local‐field fluctuations that modify the effective optical constants dispersion. Exceptional to most plasmonic applications, in the present case, a disordered system provides larger sensitivity and figure of merit than its ordered counterpart. The key concepts suggested from numerical calculations are verified by the fabrication of metal island films coated with different dielectric layers, that confirm the superiority of the reflectance‐based sensing scheme. Overall, the present approach profits from the disorder to improve refractive index sensitivity in metal nanoparticle systems that are produced with industrially appealing techniques. Thus, the proposed scheme may be valuable for the broad implementation of low‐cost and highly efficient plasmonic sensors

Microstructure and Indentation Properties of Single-Roll and Twin-Roll Casting of a Quasicrystal-Forming Al-Mn-Cu-Be Alloy

In this investigation, strips of an experimental Al-Mn-Cu-Be alloy were manufactured by high-speed single-roll and twin-roll casting to stimulate the formation of a quasicrystalline phase during solidification. The strips were characterised by light microscopy, scanning and transmission electron microscopy, microchemical analysis, and X-ray diffraction. Indentation testing was used to determine the mechanical responses of the strips in different areas. A smooth surface was achieved on both sides of the twin-roll-cast strip, while the free surface of the single-roll-cast strip was rough. The microstructures in both strips consisted of an Al-rich solid solution matrix embedding several intermetallic phases &Theta;-Al2Cu, Be4Al (Mn, Cu), Al15Mn3Be2 and icosahedral quasicrystalline phase (IQC). The microstructure of the single-roll-cast strip was more uniform than that of the twin-roll-cast strip. Coarse Al15Mn3Be2 particles appeared in both alloys, especially at the centre of the twin-roll strip. These coarse particles adversely affected the strength and ductility. Nevertheless, both casting methods provided high-cooling rates, enabling the formation of metastable phases, such as quasicrystals. However, improvements in alloy composition and casting procedure are required to obtain enhanced microstructures and properties

In situ TEM study of precipitation in a quasicrystal-strengthened Al-alloy

Precipitation kinetics and mechanisms within an Al-Mn-Be-Cu quasicrystal strengthened alloy at 300°C were studied using in-situ transmission electron microscopy. The alloy was cast into a copper mould. Quasicrystalline precipitates formed throughout the Al-rich solid solution, whilst heterogeneous formations of Al2Cu and T-phase occurred on icosahedral quasicrystalline particles formed during solidification. The formation of quasicrystalline particles and T-phase was limited by manganese diffusivity, whilst that of Al2Cu by copper diffusivity. The precipitation produced only a small hardening effect