Field-emission Scanning Transmission Electron Microscopy Research Articles

Preparation, transport and Na-storage properties of monoclinic – Na2FeSiO4 for Na-ion batteries

Na2FeSiO4 (NFS) is considered one of the promising cathode materials for rechargeable sodium-ion batteries (SIBs). In this work, the monoclinic phase of NFS is prepared for the first time by a polymer-assisted synthesis technique. The nano-sized NFS particles and pores/voids are characterized by field-emission scanning transmission electron microscopy (FE-SEM) and N2-adsorption/desorption analysis, respectively. The temperature-dependent transport properties of monoclinic (Pn) NFS are also studied by AC electrochemical impedance spectroscopy (EIS). Monoclinic NFS exhibits electrical conductivity of 2.2 (±0.01) × 10−6 S cm−1. The I-V measurement technique further verifies these results. Moreover, the activation energy obtained for this crystallographic phase is found to be 1.57 eV. The initial charge capacity is found to be 225 mAhg−1 at a current rate of 0.1C (13.5 mAg−1) in the voltage range of 1.5–4.2 V, which is closer to the theoretical capacity (∼276 mAhg−1) of NFS. Despite the better-conducting properties along with less activation energy, the monoclinic phase of NFS is not found to be cyclable for long-term cycling. The plausible reason for capacity fading in this phase of the NFS is discussed in detail.

One-Put Ferula-Mediated Synthesis of Biogenic Silver Nanoparticles with More Antimicrobial Effect and Promising Human Cell Biocompatibility

The biogenic synthesis of silver nanoparticles has recently attracted more attention to counter microbial resistance, which has been one of the medical concerns in the last decade. This research expresses the biogenic synthesis of silver nanoparticles utilizing Ferula assafoetida aqueous extract (Fer@AgNP) as a reducing and capping agent. The total parts of the plant were extracted from an aqueous solution (FerEX) and characterized using GC/MS apparatus. The Fer@AgNP and chemically synthesized silver nanoparticles (AgNPs) were characterized using UV-vis, Fourier transform infrared (FTIR) spectroscopies, field emission-scanning transmission electron microscopy, powder X-ray diffraction analysis, and energy-dispersive X-ray spectroscopy. The impacts of nanoparticles and FerEX were evaluated against four pathogenic bacterial strains, including Staphylococcus aureus, Escherichia coli, Salmonella typhi, and Enterococcus faecalis, using the microdilution method. The biocompatibility of compounds was also evaluated on human cell line L-929 using MTT and human blood cells using the hemolytic assay. The major compounds found in FerEX were sulfur-containing compounds such as butyl disulfides (45.36%) and monoterpenes such as α-pinene (25.66%), β-pinene (16.31%), and ocimene (7.26%). The characterizations of materials confirmed the hexagonal structure of AgNPs. The sizes of cAgNP and Fer@AgNP were about 42.7 nm and 22.5 nm. The antimicrobial activity of Fer@AgNP was considerably developed and reached MIC values ranging from 10 to 50 μg/mL compared to AgNP, which showed MIC values ranging from 50 to 100 μg/mL. The biocompatibility assessment showed that the Fer@AgNP was improved compared to AgNP and had a minimal toxic impact on the normal fibroblast cell line. The Fer@AgNP also indicated outstanding compatibility with human RBCs. The results illustrated that biosynthesized Fer@AgNPs have improved antimicrobial efficacy against Gram-negative and Gram-positive pathogenic bacteria with promising biocompatibility and can be used as potential antibacterial agents.

Characterizing the spectral, microstructural, and chemical effects of solar wind irradiation on the Murchison carbonaceous chondrite through coordinated analyses

We performed H+ and He+ irradiation experiments on slabs of the Murchison CM2 meteorite to simulate solar wind irradiation of carbonaceous asteroids. Two separate 6 mm × 6 mm regions were irradiated with 1 keV H+ and 4 keV He+, respectively, to fluences of 8.1 × 1017 ions/cm2 for H+ and 1 × 1018 ions/cm2 for He+. Unirradiated and irradiated surfaces were analyzed using X-ray photoelectron spectroscopy (XPS), visible to near-infrared spectroscopy (VNIR; 0.35–2.5 μm), and microprobe two-step laser-desorption mass spectrometry (μL2MS). We also performed analytical field-emission scanning transmission electron microscopy (FE-STEM) on focused ion beam (FIB) cross-sections extracted from olivine grains and matrix material within the H+- and He+-irradiated regions. In situ XPS analyses suggest that ion irradiation results in the removal of most surface carbon and the partial reduction of surface iron to lower oxidation states. In response to He+-irradiation, we observe brightening (longward of ~0.75 μm) and reddening of reflectance spectra, which is a departure from typical lunar-style space weathering. Additionally, H+- and He+-irradiation have opposing effects on organic carbon content: H+-irradiation increases the abundance of some low-molecular-weight free organic species by breaking down macromolecular material while He+-irradiation causes a decrease in overall organic content by cleaving bonds and sputtering constituent atoms. This suggests that solar wind H+-irradiation and solar wind He+-irradiation change the organic functional group chemistry of asteroidal regolith in different ways. In contrast to some previous experimental space weathering studies, we observe an increase in H2O and OH− abundances in our sample in response to both types of ion irradiation. FE-STEM and energy dispersive X-ray spectroscopy (EDX) analyses show complete amorphization of matrix phyllosilicates in ion-affected rims, partial amorphization of olivine, and changes in Si and Mg concentrations at and/or near the surface. We discuss the implications of these results for understanding the complex nature of space weathering on primitive, carbon-rich asteroids and for analyzing future returned samples from carbonaceous asteroids Bennu and Ryugu.

Study of Ni/Al-Fe Catalyst Stability in the Aqueous Phase Hydrogenolysis of Glycerol

The present work studied the stability and reusability of Ni/Al-Fe catalyst in the aqueous phase hydrogenolysis of glycerol without external hydrogen addition. The catalyst based on 28 molar % of Ni with 3/1 molar ratio of Al/Fe was prepared through co-precipitation. This catalyst presented the best performance in our last study which compares several Ni/Al-Fe catalysts with different molar ratios of Al/Fe. To see the influence of the pressurized water on the physicochemical characteristics of Ni/Al-Fe catalyst, a test of up to 9 h has been carried out. Fresh and used catalysts were characterized by various techniques: X-ray Diffraction (XRD), N2-physisorption, field emission scanning electron microscopy (FESEM) and STEM. Glycerol conversion and carbon yield to gases and liquids did not vary significantly when compared at 3 h and 9 h. Furthermore, the morphology of the catalyst remains stable after continuous recycling under severe hydrothermal conditions. The nickel rich phase of the catalyst, which was determined by XRD and scanning transmission electron microscopy (STEM) techniques, showed a stable size after 9 h under reaction.

Investigating Variations in Water Abundances in Lunar Felsite Clasts Using Coordinated Field-Emission STEM and NanoSIMS Analyses

As representatives of petrochemically-evolved igneous rocks on the Moon, the granitic felsite clasts in lunar breccias have come under renewed focus as part of new efforts to use feldspars for assessing the inventory of lunar water and other volatiles. Previous petrologic studies of these clasts were tilted towards finding those assemblages and relationships most likely to be direct products of magmatic processes. In support of our on-going NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) measurements of trace water contents in the feldspars in these clasts, we are using coordinated analytical SEM (Scanning Electron Microscopy), electron probe microanalyzer (EPMA) and analytical field emission scanning transmission electron microscopy (FE-STEM) techniques to re-evaluate the full diversity of processes under which the feldspar-bearing assemblages in these clasts formed. Here we report a comparison of FE-STEM imaging and microanalysis results obtained on focused ion beam (FIB) sections extracted from felsite (alkali feldspar plus SiO2 plus or minus plagioclase) clasts in lunar breccias 15405 and 12013. The feldspars in these clasts have water contents which, although relatively low (7-18 ppm) by terrestrial standards, still show values significantly higher than measurements (approximately 0.5 ppm) of nominally anhydrous NanoSIMS standards.

Characterization of Lithium in Batteries with EDS and EELS

This paper will present start of the art characterization of Lithium in battery materials using energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) at 30 keV with the state of the art field emission scanning transmission electron microscope (FE-STEM) Hitachi SU-9000EA. This microscope has a resolution of 0,22 nm in bright field imaging at 30 keV. It has the extreme EDS detector from Oxford that allows the detection of the Ka line of Lithium. It has a EELS system with 0.5 eV resolution that allows to map the chemical state of Li in various materials. Examples of applications of these techniques will be presented as well as the challenges and limitations for Lithium characterization.

Visualization of silver-decorated poly (DL-lactide-co-glycolide) nanoparticles and their efficacy against Staphylococcus epidermidis

Understanding of self-protection activity of the bacteria and interaction with drug substances has significant importance for designing of effective drug delivery system for treatment of biofilm infections. Recently silver nanoparticle has attracted attention as antibacterial substance for drug delivery system because of its high antibacterial activity. Here, efflux of silver nanoparticles obtained from within the prepared silver-decorated poly (DL-lactide-co-glycolide) (Ag PLGA) nanoparticles derived from Staphylococcus epidermidis bacterial cell was successfully visualized using scanning transmission electron microscopy (STEM). We also revealed the interaction between prepared Ag PLGA nanoparticles and the bacterial cells at the nanoscale level using field emission scanning electron microscopy and STEM, after a pretreatment process by an ionic liquid. This finding is significant to understand a fundamental function of S. epidermidis bacterial cells, which is not explored previously. The results suggest that Ag PLGA nanoparticles could demonstrate high efficacy against biofilm infections.

Eco-friendly nitrogen-containing carbon encapsulated LiMn2O4 cathodes to enhance the electrochemical properties in rechargeable Li-ion batteries.

This study describes the synthesis of nitrogen-containing carbon (N-C) and an approach to apply the N-C material as a surface encapsulant of LiMn2O4 (LMO) cathode material. The N heteroatoms in the N-C material improve the electrochemical performance of LMO. A low-cost wet coating method was used to prepare N-C@LMO particles. The N-C@LMO was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), high-resolution Raman spectroscopy (HR-Raman), field emission scanning electron microscopy (FE-SEM), and field emission scanning transmission electron microscopy (FE-TEM) with elemental mapping. Furthermore, the prepared samples were electrochemically studied using the AC electrochemical impedance spectroscopy (EIS) and the electrochemical cycler. XPS suggested that the N-C coating greatly reduced the dissolution of Mn and EIS showed that the coating greatly suppressed the charge transfer resistance, even after long-term cycling. The control of Mn dissolution and inner resistance allowed faster Li-ion transport between the two electrodes resulting in improved discharge capacity and cycling stability.

Effect of the gelation on the properties of precipitated silica powder produced by acidizing sodium silicate solution at the pilot scale

Controlling the properties of precipitated silica (PS) synthesized by acidizing sodium silicate solution is a significant challenge. Here, we report the effect of gelation on the BET surface area and pore volume of the PS produced at the pilot scale. H2SO4 was added to a mixture of sodium silicate and sodium chloride in two stages: the first stage ends before the gelation point and the second one ends as pH of solution reached to 5. The interval (Δt) from the end of the first stage to the gelation point was recorded to evaluate its effect on the properties of the resulting PS. The obtained samples were characterized by nitrogen adsorption–desorption method, field emission scanning electron microscopy (FE-SEM), and field emission scanning transmission electron microscopy (FE-STEM). The results revealed that the BET surface area and pore volume of the prepared PS decreases with the increase of Δt and temperature, while the pore size is not affected. The variations in the properties of the PS were successfully explained by the application of a percolation model to the flocculation and bridging of the primary particles.

Growth kinetics of vanadium pentoxide nanostructures under hydrothermal conditions

The work reported here involved a study of the growth kinetics of V 2O 5 nH 2O nanostructures under hydrothermal conditions. The coarsening process of V 2O 5 nH 2O nanoribbons was followed by subjecting the as-prepared suspensions to hydrothermal treatments at 80 °C for periods ranging from 0 to 7200 min. X-ray diffraction (XRD) confirms that the hydrothermal treatments at 80 °C caused no significant modification of the long-range order structure of samples subjected to different periods of hydrothermal treatment. Field emission scanning transmission electron microscope (FE-STEM) was used to analyze the morphology and width distribution of the nanostructures. The results indicated that the crystal growth mechanism in the [1 0 0] direction of vanadium pentoxide 1D nanostructure under hydrothermal conditions is well described by the oriented attachment (OA) mechanism. This evidence was supported by HRTEM images showing the existence of defects at the interface between nanostructures, which is characteristic of the oriented attachment (OA) mechanism.

Observation of three-dimensional elemental distributions of a Si device using a 360°-tilt FIB and the cold field-emission STEM system

A technique for preparation of a pillar-shaped specimen and its multidirectional observation using a combination of a scanning transmission electron microscope (STEM) and a focused ion beam (FIB) instrument has been developed. The system employs an FIB/STEM compatible holder with a specially designed tilt mechanism, which allows the specimen to be tilted through 360° [T. Yaguchi, M. Konno, T. Kamino, T. Hashimoto, T. Ohnishi, K. Umemura, K. Asayama, Microsc. Microanal. 9 (Suppl. 2) (2003) 118; T. Yaguchi, M. Konno, T. Kamino, T. Hashimoto, T. Ohnishi, M. Watanabe, Microsc. Microanal. 10 (Suppl. 2) (2004) 1030]. This technique was applied to obtain the three-dimensional (3D) elemental distributions around a contact plug of a Si device used in a 90-nm technology. A specimen containing only one contact plug was prepared in the shape of a pillar with a diameter of 200 nm and a length of 5 μm. Elemental maps were obtained from the pillar specimen using a 200-kV cold-field emission gun (FEG) STEM model HD-2300C equipped with the EDAX genesis X-ray energy-dispersive spectrometry (XEDS) system through a spectrum imaging technique. In this study, elemental distributions of minor elements with weak signals were enhanced by applying principal component analysis (PCA), which is a superior technique to extract weak signals from a large dataset. The distributions of elements, especially the metallization component Ti and minor dopant As in this particular device, were successfully extracted by PCA. Finally, the 3D elemental distributions around the contact plug could be visualized by reconstruction from the tilt series of maps.

Whisker Initiation Behavior from Electrodeposited Sn/Cu Coating on Cu Leadframe

Tin/copper (Sn/Cu) coatings on Cu leadframes (CUFE), in which Fe atoms are doped as a minor element, showed whisker initiation at room temperature over a long period of 47 months. By means of the planar slice method and electron back scattering pattern (EBSP) measurement, the whisker roots were consistently found to be located at the intersections of grain boundaries in the coating. Whisker roots were also located above the peaks and ridge lines of intermetallic compound (IMC) Cu6Sn5, which was formed with a pyramid-shaped configuration between the Sn/Cu coating and Cu leadframe. Using finite element analysis (FEA), we calculated stress distribution in the coating. The results indicated that compressive stress normal to the grain boundary was induced with a gradient toward the surface in the coating. Therefore, the compressive stress gradient induced by the pyramid-shaped IMC is thought to be the root cause of whisker initiation in Sn/Cu coatings on Cu leadframes. When the Cu leadframe with a minor doped element of Cr atoms (CUCR) was used as the substrate with the same Sn/Cu coating, no whisker initiation was observed even after a longer storage time of 65 months. Through field-emission scanning transmission electron microscopy (FE-STEM) and field-emission transmission electron microscopy (FE-TEM) microstructural observations of vertical sections of each sample, the shape of the IMCs formed between the coating and the leadframe in the Sn/Cu-CUFE sample was found to be different from that in the Sn/Cu-CUCR sample. The difference in whisker initiation tendency can therefore be explained by the difference in compressive stress depending on the shape of the Cu-Sn IMCs, because stress distribution in the coating of the Sn/Cu-CUCR sample calculated using FEA revealed a smaller stress gradient than that in the Sn/Cu-CUFE sample.

First experimental test of a new monochromated and aberration-corrected 200 kV field-emission scanning transmission electron microscope

The first 200 kV scanning transmission electron microscope (STEM) with an imaging energy filter, a monochromator and a corrector for the spherical aberration ( C s-corrector) of the illumination system has been built and tested. The STEM/TEM concept with Koehler illumination allows to switch easily between STEM mode for analytical and TEM mode for high-resolution or in situ studies. The C s-corrector allows the use of large illumination angles for retaining a sufficiently high beam current despite the intensity loss in the monochromator. With the monochromator on and a 3 μm slit in the dispersion plane that gives 0.26 eV full-width at half-maximum (FWHM) energy resolution we have obtained so far an electron beam smaller than 0.20 nm in diameter (FWHM as measured by scanning the spot quickly over the CCD) which contains 7 pA current and, according to simulations, should be around 0.12 nm in true size. A high-angle annular dark field (ADF) image with isotropic resolution better than 0.28 nm has been recorded with the monochromator in the above configuration and the C s-corrector on. The beam current is still somewhat low for electron energy-loss spectroscopy (EELS) but is expected to increase substantially by optimising the condenser set-up and using a somewhat larger condenser aperture.

Decomposition behaviour of amorphous Fe89−xZr7B3Cu1Gex alloys

The decomposition behaviour and the effect of Ge on the microstructural evolution in Fe89−xZr7B3Cu1Gex (x = 0 and 3 at%) alloys were examined using differential scanning calorimetry, x-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning TEM with nanoprobe energy-dispersive x-ray spectroscopy (NanoEDXS). The onset temperatures of primary crystallization for amorphous Fe89−xZr7B3Cu1Gex alloys were found to be independent of the Ge content. The XRD and TEM results showed that the crystallization takes place through two stages of amorphous→bcc Fe+residual amorphous → α−Fe+Fe3Zr, regardless of Ge content. The addition of Ge has an effect on reducing the grain size of the Fe89Zr7B3Cu1 alloy by 10–15%. The NanoEDXS results confirmed that Ge is enriched in the residual amorphous matrix together with Zr, resulting in enhanced Curie temperature and the exchange stiffness of the intergranular region. The refined grain size and the partitioning of Ge into the intergranular region together resulted in improved soft magnetic properties. Further, the NanoEDXS results implied that unlike Cu, Ge does not assist in the heterogeneous nucleation of the bcc Fe phase during the primary crystallization reaction.

FABRICATION OF 2- AND 3-DIMENSIONAL NANOSTRUCTURES

Amongst tools for fabricating periodic and aperiodic nanostructures and nanodevices, electron beam-induced organometallic chemical vapor deposition (E-OMCVD) offers a highly flexible and controllable one-step deposition process. E-OMCVD enables maskless fabrication of nanoscale research and custom structures that have least dimensions near or below 10nm – a scale at which other methods prove difficult or costly. Using the focused electron beam in a modified HB501 field-emission scanning transmission electron microscope (STEM), pads and wires with uniform thickness and well-defined shapes have been defined and deposited. Although conditions for fabricating the smallest deposits have not yet been optimized, the edge acuity (sharpness) of the deposits is consistently as low as 4nm or less and the corresponding smallest wire width is 8nm. Under different deposition conditions, three-dimensional open structured nanonetworks have been fabricated. Results of an investigation of E-OMCVD parameters are presented for the metallocene compound, nickelocene (Ni(C5H5 )2), as source organometallic.

Implications of specimen preparation and of surface contamination for the measurement of the grain boundary carbon concentration of steels using x-ray microanalysis in an UHV FESTEM

The purpose of the present investigation was to gain an understanding of the nature of the carbon contamination on the surface of standard steel transmission electron spectroscopy (TEM) specimens, the effect of exposure of a clean specimen to normal laboratory air, and the efficacy of plasma-cleaning treatments. This knowledge is a necessary prerequisite to the development of appropriate specimen preparation and/or specimen cleaning methods. X-ray photoelectron spectroscopy in combination with argon ion beam profiling was used to characterize the specimen surfaces of X65 steel and 316 stainless steel. The only clean carbon-free surface obtained was that during argon etching of the sample in the surface analysis chamber. Any exposure of a previously cleaned sample to laboratory air resulted in a rapid carbon (hydrocarbon) contamination of the sample surface and the development of surface oxidation, Plasma cleaning with subsequent exposure of the specimen to the laboratory air also resulted in a carbon-contaminated surface. This suggests that procedures of preparation of TEM specimens of steels outside an ultrahigh vacuum chamber are unlikely to result in the lowering of contamination rates on specimens to levels where measurements for carbon in the grain boundaries are possible. What is needed is a cleaning system as an integral part of the specimen insertion system into the field-emission scanning transmission electron microscope. This cleaning could be carried out by argon ion etching. Copyright (C) 2000 John Wiley & Sons, Ltd.

Towards single atom analysis of biological structures

Mapping single atoms in biological structures is now becoming within the reach of analytical electron microscopy. Electron energy-loss spectroscopy (EELS) in the field-emission scanning transmission electron microscope (STEM) provides a particularly high sensitivity for detecting the biologically important element, phosphorus. Imaging can be performed at low dose with dark-field STEM prior to analysis at high dose, so that structures of macromolecular assemblies can be correlated with the numbers of specific atoms that they contain. Measurements confirm theoretical predictions that single atom detection requires a nanometer-sized probe. Although phosphorus atoms may have moved several nanometers from their original positions by beam-induced structural degradation at the high required dose of ∼10 9 e/nm 2, damaged molecules are nevertheless stable enough to be analyzed at 1 or 2 nm resolution. Such analyses can only be achieved by means of spectrum-imaging with correction for specimen drift. Optimal strategies for mapping small numbers of phosphorus atoms have been investigated using well-characterized specimens of DNA plasmids and tobacco mosaic virus.

Electronic structure analysis of (In, Ga, Al) N heterostructures on the nanometre scale using EELS.

In this work the local electronic structure of MOVPE-grown (In, Ga, Al) N heterostructures has been investigated by electron energy loss spectroscopy (EELS). The cold field-emission scanning transmission electron microscope (VG HB501) used was equipped with a dedicated parallel EELS system which provides high dispersions at an energy resolution of 0.35 eV with the use of subnanometre electron probes the spatial resolution of the measurements depends on the physical localization of the scattering process itself and thus is in the order of nanometres. The low-loss region of the energy spectra gives information on plasmon excitations and transitions across the bandgap. The main problem on looking at the bandgap region of EELS spectra is to separate the bandgap signal from the fading tail of the zero-loss peak. High energy resolution and application of suitable deconvolution routines for removal of the zero-loss peak extract improved information from this energy region. Thus the EEL spectra of different group III nitrides reveal the onset of the bandgap itself and the characteristic shape of the joint density of states. From these results the local optical properties can be deduced via a Kramers-Kronig transformation. The data obtained show detailed structure on the energy scale and are in excellent agreement with optical ellipsometric results. In comparison with these techniques EELS methods yield a superior spatial resolution of better than 10 nm which enables detailed investigation of the effect of local defects and boundaries on the optical properties.

In Situ Stem Technique for Characterization of Nanoscale Interconnects During Electromigration Testing

AbstractA technique for observing microstructure and morphology changes during annealing or electromigration of 100 nm-scale and smaller interconnects is presented. The technique is based on dynamic in situ characterization using a UHV field-emission scanning transmission electron microscope (STEM) and can enable full microstructural characterization (images, diffraction patterns and compositions) during electromigration testing. Initial steps in the validation of the approach include in situ electron-beam OMCVD of Al-containing wires and observation of these wires. Although the deposition conditions were not optimized, Al-containing wires, with high edge acuity, thickness uniformity, and with minimum interconnect widths as small as 15 nm have successfully been deposited. In situ imaging of the annealing of 100 nm Al films on 25 nm Si3N4 substrates at 350°C demonstrates that an image resolution of 10 nm should readily be attainable in passivated nanoscale interconnects during electromigration.

Microscopic and Mesoscopic Evaluations of Materials. Miscibility and Fracture Toughness of SMI/SAN Polymer Blends.

The relationship between miscibility and fracture toughness for poly (styrene-co-N-phenyl-male-imide) (SMI) and poly (styrene-co-acrylonitrile) (SAN) blends was studied as a function of acrlonitrile (AN) content in SAN. Miscibility and blend morphology were characterized using differential scanning calorimetry (DSC) and field emission scanning transmission electron microscopy (FE-STEM) respectively. Stress intensity factor at crack initiation, Kli, was obtained to evaluate fracture toughness. DSC results showed that SMI/SAN blends changed from a miscible to an immiscible state with an increase of AN content in SAN. FE-STEM provided excellent phase contrast for morphology of immiscible SMI/SAN blends. Generally speaking, Kn of miscible blends was higher than that of immiscible blends. It has been shown that toughness enhancement can be achieved with increases of AN content in SAN and molecular weight of SMI and SAN in a miscible blend.