Effect of annealing on the microstructure,ordering and microhardness of ball milled cubic (L12) titanium trialuminide intermetallic powder

Ball milled powders of cubic (L1₂) titanium trialuminide modified with Mn, possessing nanocrystalline structure, were annealed at 600°C and 1000–1100°C. The best results for the calculation of the nanocrystalline grain size upon annealing from the X-ray diffraction (XRD) patterns, were obtained using the Cauchy/Gaussian approximation for both the instrumental broadening and nanocrystallite size/lattice strain separation. The nanocrystallite size increased upon annealing from 1 to 240 min at 600°C, from the initial several nanometers for the as-milled powders, to 30–140 nm for the annealed powders. This nanocrystalline grain growth is accompanied by a continuous increase of the long-range order (LRO) parameter, from zero to ∼0.8–0.9 after annealing at 600°C for 240 min. However, a phenomenal thermal stability of nanocrystalline grains is manifested in the fact that only very few powder particles exhibited the formation of micrometer-sized grains after annealing at the 1000–1100°C range. The observed differential thermal analysis (DTA) exothermic peaks around 410–430°C (peak I) and 570°C (peak II) are interpreted as the atomic re-ordering and the phase restoration peak, respectively. The observed hardening of the “outer layer” and “no core” particles upon annealing at 600°C is discussed in terms of nanograin boundaries age-hardening mechanism due to the pick-up of interstitials (carbon and/or nitrogen) and their preferential segregation at the nanograin boundaries. The reversal of the process, i.e. desegregation, might be responsible for the observed softening of the “outer layer” and “no core” particles upon annealing at the 1000–1100°C range, without any apparent microstructural changes observable under optical/scanning microscope.     

机械合金化及热压烧结制备Fe-Cr-Mn基超细晶奥氏体不锈钢研究

采用高能研磨诱导的机械合金化方法制备了Fe-Cr-Mn基不锈钢合金粉末;对机械合金化粉末分别进行了退火和热压烧结,分析了退火过程中的相变规律,并对热压烧结获得的奥氏体不锈钢进行了组织和耐蚀性能研究。结果表明:机械合金化获得的不锈钢合金粉由亚稳态的纳米晶铁素体构成;退火/热压烧结处理后,铁素体逐渐转变为热力学上更加稳定的奥氏体,相变温度介于498℃到730℃之间;对机械合金化16 h的合金粉末在900℃、200 MPa条件下热压烧结1h获得了Fe-Cr-Mn基奥氏体不锈钢,其平均晶粒尺寸为亚微米级且表现出高硬度和良好的耐蚀性能,其HV硬度值约为5350 MPa、自腐蚀电位和自腐蚀电流密度分别为–0.28 V和1.43×10^-9A·cm^-2。     

Giant dielectric response in (Li,Ti)-doped NiO ceramics synthesized by the polymerized complex method

This paper reports on the synthesis of nanocrystalline (Li, Ti)-doped NiO powders (i.e., Li_0.3Ti_0.02Ni_0.68O, abbreviated as LTNO) by the polymerized complex (PC) method. The synthesized LTNO powders were characterized by thermogravimetric–differential thermal analysis (TG–DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The powders, with particle sizes of 39, 65 and 72 nm as estimated from XRD, were sintered in air at 1280 °C for 4 h to obtain bulk LTNO ceramics. A giant dielectric constant of 10⁴–10⁵ at low frequency with weak temperature dependence over the measured temperature range (−30 to 160 °C) was observed in the sintered LTNO ceramics. The origin of the high permittivity observed in these LTNO ceramics is attributed to the Maxwell–Wagner polarization mechanism and a thermally activated mechanism.     

Thermodynamic modeling of Al–Ce–Mg phase equilibria coupled with key experiments

The ternary Al–Ce–Mg phase diagram was calculated using the Calphad method and investigated with selected key experiments. Arc melted alloys were annealed at 400 °C for 500 h and the phases were analyzed using quantitative X-ray powder diffraction (XRD). Differential thermal analysis (DTA) was also performed on an alloy with a composition near the ternary phase Al₁₃CeMg₆ (τ). Temperatures above 1000 °C could be attained due to a special sealing of the sample under argon by welding in a tantalum crucible to avoid evaporation and oxidation. Only with this procedure could reproducible and reliable DTA signals be obtained. The present experimental investigation and the consistent thermodynamic calculation show that the “ternary phase” Ce(Mg,Al)₂, seemingly isolated in the ternary at 400 °C, can be rationalized as a single solid solution phase between the binary end members if a larger temperature range and a solid state miscibility gap is considered. It is demonstrated that previously reported low values of ternary liquidus temperatures must be related to other phase equilibria. The actually found ternary liquidus temperatures are much higher and widely governed by the high melting compound Ce(Al,Mg)₂ and also by Al₁₁Ce₃ with primary solidification fields stretching far into the ternary system.     

Mechanochemical reaction between ilmenite (FeTiO3) and aluminium

A natural ilmenite (FeTiO₃) and aluminium powder have been mechanically milled together for 100 h in a laboratory ball mill. The as-milled powder and an unmilled powder of identical composition were annealed at up to 1200°C and examined by X-ray diffraction and differential thermal analysis (DTA). The unmilled sample showed aluminium melted prior to an exothermic reaction starting at 850°C. The milled powder showed no thermal activity, other than a reversible phase transition at 1067±4°C, indicating that reaction occurred within the mill. The products of both powders were the same, TiAl₃, Fe₄Al₁₃ and Al₂O₃, although in the milled powder these phases were nanocrystalline until annealing caused crystallite growth. The thermal reaction seemed to occur in two stages, formation of TiAl₃, Al₂O₃ and elemental iron followed by a slower, diffusion controlled reaction between the elemental iron and residual aluminium to form Fe₄Al₁₃. The reaction during milling was attributed to increased intermixing between the ilmenite and aluminium causing a change in the rate determining step from solid-state diffusion to another, unknown, controlling mechanism.     

Superelastic properties of nanocrystalline NiTi shape memory alloy produced by thermomechanical processing

Effects of thermomechanical treatment of cold rolling followed by annealing on microstructure and superelastic behavior of the Ni₅₀Ti₅₀ shape memory alloy were studied. Several specimens were produced by copper boat vacuum induction melting. The homogenized specimens were hot rolled and annealed at 900 °C. Thereafter, annealed specimens were subjected to cold rolling with different thickness reductions up to 70%. Transmission electron microscopy revealed that the severe cold rolling led to the formation of a mixed microstructure consisting of nanocrystalline and amorphous phases in Ni₅₀Ti₅₀ alloy. After annealing at 400 °C for 1 h, the amorphous phase formed in the cold-rolled specimens was crystallized and a nanocrystalline structure formed. Results showed that with increasing thickness reduction during cold rolling, the recoverable strain of Ni₅₀Ti₅₀ alloy was increased during superelastic experiments such that the 70% cold rolled–annealed specimen exhibited about 12% of recoverable strain. Moreover, with increasing thickness reduction, the critical stress for stress-induced martensitic transformation was increased. It is noteworthy that in the 70% cold rolled–annealed specimen, the damping capacity was measured to be 28 J/cm³ that is significantly higher than that of commercial NiTi alloys.     

Properties of nickel-cobalt composite silicides by thermal annealing of Ni<Subscript>1−x</Subscript>Co<Subscript>x</Subscript> (x=0.2, 0.5, and 0.8) alloy thin films on silicon and polysilicon substrates

10 nm-Ni_1−xCo_x (x=0.2, 0.5, and 0.8)/p-Si(100)(or poly crystalline Si) was thermally annealed using rapid thermal annealing for 40 s at 600–1100°C. The annealed film structures developed into NiCoSi_x, and the resulting changes in sheet resistance, microstructure, and composition were investigated using a four-point probe, a scanning electron microscope, a field ion beam, an X-ray diffractometer, and an Auger electron spectroscope. The final thickness of NiCoSi_x formed on single-crystal silicon was approximately 12.64nm, and it maintained its sheet resistance below 20 Ω/sq. during the silicidation annealing at 1100°C. The NiCoSi_x formed on polysilicon had a thickness of 35.04nm, and its low resistance was maintained up to 900°C. Additional annealing of silicides at the given RTA temperature for 30 min resulted in a drastic increase in sheet resistance. We identified Ni₃Si₂ and a NiSi phase at 700°C and 1000°C for single-crystal silicon substrates. Moreover, Ni₃Si₂, NiSi, and CoSi₂ phases were stable at 700°C, and then NiSi₂ and Ni₃Si₂ became stable for polycrystalline silicon substrates at 1000°C. When the amount of Co was 80%, only a Ni₃Si₂ phase was confirmed at 700°C and 1000°C in both the single and polycrystalline substrates. With less Co (Co=0.2, 0.5), Ni₃Si₂, NiSi, and CoSi₂ phases were observed at 700, and Ni₃Si₂ and NiSi₂ phases were observed at 1000°C. Cobalt also improved thermal stability of the silicides formed on the polysilicon gate, but this enhancement was lessened due to the silicon mixing during high temperature diffusion. In conclusion, the proposed nickel cobalt composite silicides formed from the nano-thick alloy films may be superior to conventional nickel monosilicides due to improved thermal stability.     

Synthesis of titanium carbide by thermo-chemical methods with TiH2 and carbon black powders

A new synthesizing method for producing submicron TiC powders was studied by using TiH₂ and carbon black powders. It is well known that hydrogen absorption transforms titanium from metal (h.c.p.) to brittle hydride (f.c.c.) powders by ball-milling. This research focused on obtaining submicron-sized TiC powders from the ball-milled mixture of TiH₂ and carbon black by thermal treatment. The hydrogen, carbon, iron, and oxygen composition changes in the mixed powders were analyzed. Thereafter, a differential thermal analysis (DTA) test was performed to observe change of phase with ball-milling time. The TiC powders were obtained by heat treating the powders milled for 5h at various temperatures (600–1200°C). The phase microstructure was investigated via DTA, X-ray diffraction (XRD), and scanning electron microscope (SEM). The mixture milled for 2h had an f.c.t. structure containing 66.73 at. %H transformed to f.c.c. by milling for 4h. After 5h of ball-milling, submicron-sized particles of 273 nm were obtained. At the isothermal heat-treating temperature of 500°C, the Ti single phase was formed completely, and the TiC phase of lattice parameter 0.310 nm was completely formed over the temperature of 1000°C.     

Phase transformations and phase equilibria in a Ti–37% Al–20% Mn alloy

The solid-state phase transformations and phase equilibria in a Ti–37 at% Al–20 at% Mn alloy have been investigated. The alloy was prepared by plasma-arc melting and the microstructures of high-temperature-annealed and water-quenched or furnace-cooled samples were studied. The results show that at 1235°C β-phase and (Mn,Al)₂Ti (Laves phase) are present whereas below 1000°C the phases (γ+α/α₂+(Mn,Al)₂Ti) are formed. A comparison between calculated equilibrium phase compositions and values measured by EDXA shows reasonable agreement for the β, γ and α/α₂ phases over a range of temperatures but agreement for the (Mn,Al)₂Ti phase is less good, particularly at the higher temperatures. The transformation kinetics in this system appear to be sluggish and true equilibrium does not appear to have been achieved in all samples annealed below 1145°C. DTA analysis was also undertaken and the heating thermogram obtained is interpreted with the aid of the calculated phase equilibria.     

Synthesis of nano-structured La0.8Ba0.2MnO3 perovskite via a mechano-thermal route

In this study, barium-doped lanthanum manganite, La_0.8Ba_0.2MnO₃, was synthesized via a mechano-thermal route employing high energy ball milling and subsequent heat treatment. The structural evolution, morphology and thermal behaviour of the powders were evaluated using XRD, FESEM, and DTA/TGA, respectively. DTA/TGA results showed that the calcination temperature of the carbonates significantly decreased by increasing the milling time. The results revealed that single phase perovskite was formed at 900 °C in a milled sample for 2 h and this temperature decreased to 600 °C by increasing the milling time to 30 h. The mean crystallite size also decreased from 32 to 20 nm by increasing the milling time from 2 to 30 h. The reaction sequence of La_0.8Ba_0.2MnO₃ formation via the mechano-thermal route is proposed using XRD and DTA/TGA results. FESEM micrographs showed that the mean particle size of the perovskite phase is increased slightly from 30 to 40 nm by increasing the heat treatment temperature from 600 to 900 °C.     

A study on the microstructure of D023 Al3Zr and L12 (Al+12.5 at.% Cu)3Zr intermetallic compounds synthesized by PBM and SPS

The spark plasma sintering (SPS) of L1₂ phase Al₃Zr and (Al+12.5 at.% Cu)₃Zr powders with a nanocrystalline microstructure has been studied to produce bulk intermetallic compounds which maintain metastable structures such as L1₂ structure and nanocrystalline microstructure. The powders were prepared by 10 h planetary ball milling (PBM). Full-density L1₂ (Al+12.5 at.% Cu)₃Zr intermetallic compounds were obtained by SPS for 0 min at 600 °C. The specimens prepared with a longer holding time than 0 min at 600 °C or a higher temperature than 600 °C had local melting areas where micro-cracks were found. They had a lower relative density than the specimen SPS sintered at 600 °C for 0 min. The smallest grain size was obtained in the specimen prepared at 600 °C for 0 min, which was 20–30 nm as confirmed by TEM observation. This was the smallest grain size ever reported in the trialuminide specimens processed by various consolidations of nanocrystalline powders. Accordingly, the highest micro-hardness, 989.5 H_V, was obtained in the specimen and this value was three times higher than those of the specimens with micro grain sizes. Full density Al₃Zr intermetallics were prepared by SPS at 700 °C for 0 min. However, their crystal structure was D0₂₃ and micro-hardness was 778.1 H_V. By using SPS, the sintering time can be reduced within 10 min. It was thought that the decrease in sintering temperature for the PBM Al₃Zr and (Al+12.5 at.% Cu)₃Zr powders by 200–300 °C compared with the conventional sintering temperature resulted in the refinement of microstructure to the nano-size level.     

Phase Evolution and Thermal Analysis of Nanocrystalline AlCrCuFeNiZn High Entropy Alloy Produced by Mechanical Alloying

A multi-component nanocrystalline AlCrCuFeNiZn high entropy alloy with 12 nm crystallite size was successfully synthesized using high energy ball milling. The progress of solid solution formation during milling was analyzed using XRD. A major portion of the HEA is observed to be BCC in crystal structure after 30 h of milling. Thermal analysis showed that HEA powders exhibited exponential oxidation characteristics. Thermal analysis showed that low activation energy was sufficient to start recrystallization because of high energy stored in the milled powders. The crystallite size after consolidation is in nanocrystalline range due to the sluggish diffusion of atoms and nanotwinning. After consolidation, the crystallite size is around 79 nm. Samples sintered at 850 °C for 2 h exhibited high hardness values of 700 ± 15 HV_1.0, major volume fraction of the phases are having FCC crystal structure along with a minor phase having BCC crystal structure. Due to positive enthalpy mixing of Cu with other elements, decomposition of BCC to new FCC phases occurs.     

Microstructure,Mechanical Properties,and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.     

Nanocrystalline LiMn2O4 thin film cathode material prepared by polymer spray pyrolysis method for Li-ion battery

Nanocrystalline cubic spinel lithium manganese oxide thin film was prepared by a polymer spray pyrolysis method using lithium acetate and manganese acetate precursor solution and polyethylene glycol-4000 as a polymeric binder. The substrate temperature was selected from the thermogravimetric analysis by finding the complete crystallization temperature of LiMn₂O₄ precursor sample. The deposited LiMn₂O₄ thin films were annealed at 450, 500 and 600 °C for 30 min. The thin film annealed at 600 °C was found to be the sufficient temperature to form high phase pure nanocrystalline LiMn₂O₄ thin film. The formation of cubic spinel thin film was confirmed by X-ray diffraction study. Scanning electron microscopy and atomic force microscopy analysis revealed that the thin film annealed at 600 °C was found to be nanocrystalline in nature and the surface of the films were uniform without any crack. The electrochemical charge/discharge studies of the prepared LiMn₂O₄ film was found to be better compared to the conventional spray pyrolysed thin film material.     

Low-temperature perovskite-type cadmium titanate thin films derived from a simple particulate sol–gel process

Low-temperature perovskite-type cadmium titanate (CdTiO₃) with a nanocrystalline and mesoporous structure was prepared at various Ti:Cd molar ratios by a straightforward particulate sol–gel route. The prepared sols had a narrow particle size distribution, in the range 23–26 nm. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the powders contained a mixture of ilmenite-CdTiO₃, perovskite-CdTiO₃, anatase and rutile phases, depending on the annealing temperature and the Ti:Cd molar ratio. Perovskite-CdTiO₃ was the major type obtained from cadmium-prominent powders at low temperature, whereas ilmenite-CdTiO₃ was the major type obtained from titanium-prominent powders at high temperature. It was observed that the anatase-to-rutile phase transformation accelerated with decreasing Ti:Cd molar ratio. Furthermore, the ilmenite-to-perovskite phase transformation accelerated with a decrease in both the Ti:Cd molar ratio and the annealing temperature. The crystallite sizes of the ilmenite- and perovskite-CdTiO₃ phases reduced with increasing the Ti:Cd molar ratio. Field emission scanning electron microscopic analysis revealed that the average grain size of the thin films decreased with an increase in the Ti:Cd molar ratio. Moreover, atomic force microscope images showed that CdTiO₃ thin films had a columnar-like morphology. Based on Brunauer–Emmett–Taylor analysis, cadmium titanate powder containing Ti:Cd = 75:25 showed the greatest surface area and roughness and the smallest pore size among all the powders annealed at 500 °C. This is one of the smallest crystallite sizes and largest surface areas reported in the literature, and can be used in many applications in areas from optical electronics to gas sensors.     

Characterization and Synthesis of Co(ss)/WSi2-CoWSi Nanocomposite by Mechanical Alloying and Subsequent Sintering

In this study, Co_(ss)/WSi₂-CoWSi nanocomposite was synthesized via mechanical alloying and heat treatment. In order to fabricate bulk composite, 50-h-milled powders were cold pressed and subsequently sintered at 1150 °C for 4 h in Ar atmosphere. Phase development and structural changes were investigated by x-ray diffraction technique and scanning electron microscopy. After various milling times, the powders were investigated by differential thermal analysis and microhardness measurements. The starting powder mixture has two allotropic structures of Co (fcc and hcp). After 10-h milling, an allotropic transformation takes place in Co (fcc to hcp), and a composite microstructure consisting of cold-welded Co, W, and Si phases is formed. After 20 h, new peaks related to WSi₂ appeared in x-ray diffractograms. Increasing milling time to 50 h caused the formation of (Co, W, and Si) solid solution, WSi₂, and CoWSi phases. DTA analysis of 30- and 50-h-milled powders confirmed an increase in the degree of ordering. The 50-h-milled powders exhibited high microhardness value of about 1050 HV_0.1. XRD result of sintered material demonstrated that only ordered Co_(ss)/WSi₂-CoWSi nanostructured composite is present. Consolidated sample showed 12% porosity. Nanoindentation results showed that the sintered composite an exhibited a high hardness of 700 HV_0.1 with an elastic modulus of 107 GPa.     

Preparation of micron-sized flake copper powder for base-metal-electrode multi-layer ceramic capacitor

The preparation of flake micron-sized copper powders with the chemical–mechanical method was investigated. Reaction of [Cu(NH₃)₄]²⁺ complex with hydrazine hydrate at 85 °C produced monodispersed fine spherical copper powders, which were used as precursor to synthesize flake copper powders by the ball milling process. The flake copper powders having an excellent dispersibility and a uniform size of 9 ± 2 μm could be achieved. Thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA) of the flake copper were investigated with thermal analyzer. The results showed that the oxidizing temperature increased with a decreasing specific area. The flake copper powder particles were employed as functional conductive materials in copper thick film paste for base-metal-electrode multi-layer ceramic capacitors (BME-MLCCs). Excellent connection between internal and terminal electrode and even distribution of glass in copper thick film can be observed by polarized light photograph. The dense thick films were also found by scanning electron microscopy (SEM) analysis, and the high densification of the fired films could be attributed to the “framework” effects.     

Synthesis of nanocrystalline Bi2Te3 via mechanical alloying

Bi₄₀Te₆₀ thermoelectric compound was fabricated via mechanical milling of bismuth and tellurium as starting materials. Effect of the milling time and heat treatment temperatures were investigated. In order to characterize the ball milled powders, the X-ray diffraction (XRD) was used. Thermal behavior of the mechanically alloyed powders was studied by differential thermal analysis (DTA). The morphological evolutions were studied by scanning electron microscopy (SEM). Results showed that the nanocrystalline Bi₂Te₃ compound was formed after 5 h of milling. Further milling (25 h) and heating to 500 °C showed that the synthesized phase was stable during these conditions. Nanocrystalline Bi₂Te₃ with 9–10 nm mean grain size and flaky morphology (lamellar structure) was obtained at the end of milling.     

The antimony-niobium (Sb-Nb) system

A constitutional diagram was established for the Nb-Sb system in the region with more than 30 at. % Sb and below 1450 °C. Investigation of the phase relations was based on differential thermal analysis (DTA), light optical microscopy, electron probe microanalysis, and X-ray diffraction experiments on argon arc melted bulk alloys, which were annealed at 600 °C in vacuum-sealed silica capsules up to 1400 h. Differential thermal analysis runs (5 to 20 K/min, T _max=1450 °C) were performed on alloys vacuum sealed in Ta crucibles with an inner lining of W. In contrast to earlier claims for the existence of five binary phases, Nb₃Sb, Nb₃Sb₂, NbSb, Nb₅Sb₄ (or Nb₄Sb₃), and NbSb₂, the authors observed only three binary compounds: Nb₃Sb, Nb₅Sb₄, and NbSb₂. These compounds are essentially line compounds at their stoichiometric composition and without a significant homogeneity region at 600 °C. All compounds are formed by peritectic reactions: L+(Nb)↔Nb₃Sb (1750±25 °C, (L℞55 at.% Sb), L+Nb₃Sb↔Nb₅Sb₄ (1320±10 °C, L℞71 at.% Sb), and L+Nb₅Sb₄↔NbSb₂ (1180±10 °C, L℞88 at.% Sb). The system is characterized by a depleted eutectic reaction L↔(Sb)+NbSb₂ at 618±8 °C and L℞99 at.% Sb.     

Phase equilibria in the Al–Mo–Si system

The ternary Al–Mo–Si phase diagram was investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA), electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). Ternary phase equilibria were investigated within two isothermal sections at 600 °C for the Mo-poor part and 1400 °C for the Mo-rich part of the phase diagram. The solubility ranges of several phases including MoSi₂ (C11_b) as well as Mo(Si,Al)₂ with C40 and C54 structure were determined. The binary high temperature phase Al₄Mo was found to be stabilized at 600 °C by addition of Si. DTA was used to identify 9 invariant reactions and thus constructing a ternary reaction scheme (Scheil diagram) in the whole composition range. A liquidus surface projection was constructed on basis of the reaction scheme in combination with data for primary crystallization from as-cast samples determined by SEM measurements.