The influence of dipolar interaction in a frozen ferrofluid has been experimentally studied. consisted particles $\ensuremath{\gamma}$- ${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$ with mean diameter 70 \AA{}. Four samples volume concentration magnetic ranging from 0.03% to 17% have investigated. relaxation the most concentrated particle system shows typical spin glass dynamics at low temperature, e.g., depends on time spent constant temperature before applying field---the ages. diluted sample...

Breakaway oxidation of alloy 304L at 600 °C was studied in four environments (O2 + H2O KCl, O2 SO2 H2 Ar, K2CO3) for up to 168 h. The resulting scales were investigated by FIB/SEM, SEM/EDX, STEM/EELS, STEM/EDS and elucidated thermodynamic calculations (Thermo-Calc). initial thin protective scale broke down all cases. After breakaway, the consisted two layers, i.e. an inward growing spinel/reaction zone outward iron-rich layer. general features microstructure after breakaway similar explained...

The effects of a dipole-dipole interaction on the magnetic relaxation in nanoparticle system have been investigated using ac-susceptibility, relaxation, and noise measurements, which altogether cover time window nine decades. In experimental window, it is possible to distinguish two temperature regimes: low-temperature regime where collective dynamics probed, as evidenced by appearance aging significantly broadened high-temperature best described single-particle dynamics. Moreover,...

The field dependence of the ac susceptibility a concentrated frozen ferrofluid containing ultrafine Fe-C particles monodisperse nature has been analyzed using static scaling. For first time, divergent behavior nonlinear dipole-dipole interacting system is demonstrated. From analysis, critical exponents $\ensuremath{\gamma}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4.0\ifmmode\pm\else\textpm\fi{}0.2$ and...

The influence of the dipole-dipole interaction on dynamics monodispersive ensembles magnetic nanoparticles have been studied by Monte Carlo simulations. An increased strength drives system from a state with only individual particle relaxation at all temperatures to where collective phenomena govern low temperatures. nature is reflected in appearance ageing and dramatically broadened function.

The dynamic scaling behavior of the Ising spin glass F${\mathrm{e}}_{0.5}$M${\mathrm{n}}_{0.5}$Ti${\mathrm{O}}_{3}$ in superimposed dc magnetic fields has been studied. freezing temperatures ${T}_{f}\left(\ensuremath{\omega},H\right)$ were determined as a function field $0\ensuremath{\le}H\ensuremath{\le}3.1$ T and frequency $0.017\ensuremath{\le}\ensuremath{\omega}/2\ensuremath{\pi}\ensuremath{\le}5100$ Hz. in-field is strikingly different from zero-field well described by activated...

Abstract This paper reports the oxidation behaviour of a low‐alloyed steel (Fe‐2.25Cr‐1Mo) in presence small amounts KCl(s) at 400 and 500°C. Cleaned polished sample coupons were exposed horizontal tube furnace with exposure times ranging from one hour to week. The flue gas composition was 5% O 2 40% H N , 0.1 mg KCl/cm deposited on samples prior exposure. X‐ray diffraction (XRD) scanning electron microscopy (SEM) energy dispersive (EDX) analysis used characterize samples. Cross sections...

The present study investigates the influence of Si on high temperature corrosion behaviour FeCrAl model alloys in O2, O2+H2O and + KCl at 600 °C for up to 168 h. investigation by SEM/EDX showed that all displayed a protective dry O2. In more corrosive environments (O2+H2O KCl) addition affected oxidation properties two ways; Alloys containing resisted breakaway caused Cr-evaporation (O2+H2O) thickness oxide formed after decreased with increasing amount KCl).

The corrosion behaviour of a FeCrAl alloy was investigated at 600 °C in O2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that accelerates potassium chromate formation depletes the protective scale Cr, thus triggering fast-growing iron-rich scale. Iron oxide found to grow both inward outward, on either side initial oxide. chromia layer is formed time underneath iron It although does not form continuous pure alumina temperature, aluminium is, however, always...

Breakaway corrosion remains a challenge for many high temperature applications. The oxide formed after breakaway is commonly considered non-protective. This study investigates the protective properties on wide set of (Fe,Cr,Al/Ni)-model alloys by thermogravimertric analysis, ion/electron microscopy and X-ray spectroscopy. results show that scales exhibit similar microstructural features all FeCr(Ni/Al)-alloys, growth rate greatly influenced alloy composition some while has little influence...

This study investigates the intergranular corrosion of a stainless steel (304 L) in presence KCl(g)/KCl(s) at 600 °C by using FIB/SEM to perform 3D reconstruction/tomography grain boundary attacks combination with TEM. The investigation shows that FIB/TEM offers great potential for complex features, i.e. corrosion. initiation and propagation attack occurred very rapidly below an intact secondary protection. No large accumulations metal chlorides were observed regions. Instead, indications...

The corrosion behavior of Fe(5−20)Cr3Al2Si model alloys and the underlying mechanisms after breakaway oxidation was investigated at 600 °C. Rapid triggered for all in presence KCl(s). Thermogravimetric analysis showed that with a Cr content ≥ 10 wt% transitioned into sub-parabolic kinetics an early stage process oxidation. Through advanced electron/ion microscopy, this attributed to high Cr-enrichment bottom part inward-growing scale, indicating formation healing layer. Additionally,...

The long-term corrosion behavior of three FeCrAl(Si) alloys has been investigated in two environments (K2CO3 and KCl+H2O) at 600 °C. FeCrAl alloy experienced breakaway oxidation both but displayed a higher rate KCl+H2O. FeCrAlSi retained the primary protection presence K2CO3 underwent considerably reduced rates, suggested to be an effect prevention internal formation non-continuous corundum-type oxide dispersed within inward-growing scale.

The oxidation of an austenitic FeCr(Ni) steel at 600 °C in H2O + KCl O2/H2 Ar environments is studied up to 168 h. behaviour after “breakaway” investigated by microstructural investigations, and thermodynamic calculations (Thermo-Calc) on the FeCr(Ni)–O system are used interpret results. characteristic scale morphology exhibits outward-growing iron oxide a bottom layer consisting inward-growing spinel reaction zones containing Cr-rich precipitates Cr-depleted metal. equilibrium show that...

The effect of SO2(g) on the initial oxidation stainless-steel 304L, sprayed with 0.1 mg/cm2 KCl and exposed in 5% O2 40% H2O at 600 °C, was investigated. In absence SO2(g), accelerates corrosion attack by formation K2CrO4. reaction depletes oxide chromium converts it into an iron-rich, poorly protective oxide. When introduced to gas flow, rapidly transformed K2SO4. contrast KCl, K2SO4 does not form Hence, accelerate rate. Although conversion is fast, rate samples presence higher than It...