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The corrosion behavior of the sputter-deposited amorphous or/and nanocrystalline W-Ni alloys is studied in neutral 0.5 M NaCl solution at 25ºC, open to air using immersion tests, electrochemical measurements and confocal scanning laser microscopic (CSLM) techniques. In general, the corrosion rates of the W-Ni alloys containing less than 20 at% nickel content are slightly lower than that of tungsten metal whereas the corrosion rates of the alloys containing 20 at% nickel or more increased with the addition of nickel in the alloys. The pitting corrosion is observed in the nickel-rich W-69Ni alloy from CSLM studies. The open circuit corrosion potentials of all the examined W-Ni alloys are shifted to noble direction with the addition of nickel content in the alloys.Keywords: W-Ni alloys, passivation, NaCl, electrochemical measurement, pitting.DOI: 10.3126/jncs.v23i0.2096J. Nepal Chem. Soc., Vol. 23, 2008/2009 Page : 45-53

The relationship between the surface area of a catalyst and the crystallite size determined by X-ray measurements is examined. It is shown that simple methods of line-profile analysis may lead to gross errors when there is a wide distribution of crystallite sizes, and that Fourier methods are necessary to establish the correct size-data suitable for surface area determination.

Ternary amorphous or/and nanocrystalline Zr-(12–18)Cr–W alloys were successfully prepared by direct current (DC) magnetron sputtering. The corrosion rates of Zr-(12- 18)Cr-W alloys are in the range of 1-2 x 10 -3 mm/y which are even lower than those of the sputter-deposited binary W-Zr and W-Cr alloys, and are nearly one order of magnitude lower corrosion rate than those of the alloy-constituting elements in 12 M HCl at 30°C, open to air. All the examined sputter-deposited amorphous or/and nanocrystalline Zr-(12- 18)Cr–W alloys are passivated spontaneously. The zirconium addition suppresses the anodic dissolution current, and hence the anodic current densities of the alloys decreased with increasing the zirconium content in the alloys. It is, therefore, considered that the simultaneous additions of zirconium and tungsten with 12-18 at% of chromium enhance synergistically the corrosion-resistant and pitting corrosion of the sputter-deposited Zr-(12-18)Cr-W alloys in 12 M HCl. Keywords: Corrosion-resistant; Zr-Cr-W alloys; Electrochemical measurement; Pitting corrosion DOI: 10.3126/jncs.v26i0.3625 Journal of Nepal Chemical Society Vol. 26, 2010 Page: 13-21

The corrosion behavior of the sputter-deposited nanocrystalline W-Cr alloys was studied in 0.5 M NaCl and alkaline 1 M NaOH solutions at 25°C, open to air using immersion tests and electrochemical measurements. Chromium metal acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited W-Cr alloys so as to show higher corrosion resistance than those of alloy-constituting elements in both 0.5 M NaCl and 1 M NaOH solutions. In particular, the nanocrystalline W-Cr alloys containing 25-91 at% chromium showed about one order of magnitude lower corrosion rates (that is, about 1-2 × 10 -3 mm.y -1 ) than those of tungsten and chromium metals even for prolonged immersion in 0.5 M NaCl solution at 25°C. On the other hand, the corrosion rate of the sputter-deposited W-Cr alloys containing 25-75 at % chromium was decreased significantly with increasing chromium content and showed lowest corrosion rates (that is, 1.5-2.0 × 10 -3 mm.y -1 ) after immersed for prolonged immersion in 1 M NaOH solution. The corrosion rates of these nanocrystalline W-(25-75)Cr alloys are nearly two orders of magnitude lower than that of tungsten and more than one order of magnitude lower corrosion rate than that of sputter-deposited chromium metal in 1 M NaOH solution. The corrosion-resistant of all the examined sputter-deposited W-Cr alloys in 0.5 M NaCl solution is higher than in alkaline 1 M NaOH solution at 25°C. Open circuit potentials of all the examined W-Cr alloys are shifted to more noble direction with increasing the chromium content in the alloys after immersion for 72 h in both 0.5 M NaCl and 1 M NaOH solutions at 25°C, open to air. Keywords: Sputter deposition, nanocrystalline W-Cr alloys, corrosion test, electrochemical measurement, NaCl and NaOH solutions. DOI: 10.3126/jncs.v25i0.3300 Journal of Nepal Chemical Society Volume 25, 2010 pp 53-61

The synergistic effect of the simultaneous additions of tungsten and zirconium in the sputter-deposited amorphous or nanocrystalline Zr-(12-21)Cr-W alloys is studied in 0.5 M NaCl solution open to air at 25°C using corrosion tests and open circuit potential measurements. Corrosion rates of the sputter-deposited Zr-(12-21)Cr-W alloys containing 10-80 at % tungsten (that is, 0.95-1.85 x 10 -2 mm.y -1 ) are more than one order of magnitude lower than that of the sputter-deposited tungsten and even lower than those of zirconium as well as chromium in 0.5 M NaCl solution. The addition of 8-73 at % zirconium content in the sputter-deposited binary W-(12-21)Cr alloys seems to be more effective to improve the corrosion-resistant properties of the sputter-deposited ternary Zr-Cr-W alloys containing 12-21 at % chromium in 0.5 M NaCl solution. The sputter-deposited Zr-(17-21)Cr-W alloys containing an adequate amounts of zirconium metal showed the more stable passivity and showed higher corrosion resistance than those of alloy-constituting elements in 0.5 M NaCl solution open to air at 25°C. Keywords: Zr-(12-21)Cr-W alloys, sputter deposition, corrosion test, open circuit potential, 0.5 M NaCl. DOI: 10.3126/jncs.v25i0.3305 Journal of Nepal Chemical Society Volume 25, 2010 pp 75-82

This paper describes the effect crystallite size has on the coercive force Hc of thin ferromagnetic films. Crystallite size was determined by the use of x‐ray diffraction using a small angle between the x‐ray beam and film samples. Films in this study ranged in thickness from 150 to 1750 A with crystallite size from 50 to 950 A and Hc values of 2.1 to 8.4 Oe.It was found that Hc is dependent on the crystallite size for films that have domain wall widths larger than the crystallite size. The data exhibits a decreasing Hc as the crystallite size increases for films with Neel or crosstie domain walls. For films with Bloch walls and crystallite size greater than the domain wall width, there is no apparent dependence on crystallite size of Hc.To a first approximation, the results of this study are shown to agree with the anisotropy constant variation term from Middelhoek's semiquantitative theory for coercive force of thin magnetic films. For films with domain wall widths larger than the crystallite size, this...

Structural and magnetic measurements have been performed on the FINEMET type of ribbons with nominal composition of Fe 74 Cu 0.5 Nb 3 Si 13.5 B 9 synthesized by rapid solidification technique. The crystallization behavior and the nanocrystal formation have been studied by differential thermal analysis (DTA) and X-ray diffraction (XRD). The crystallization onset temperatures determined by XRD are in good agreement with DTA results. Magnetic permeability and magnetization measurements have been carried out using inductance analyzer and vibrating sample magnetometer (VSM). Magnetic permeability sensitively depends on the annealing temperature which increases sharply with the increase of annealing temperature. Maximum permeability corresponding to optimum annealing temperature (T a ) was observed at T a = 575°C. Saturation magnetization, Ms, increases with T a for the sample and finally decreases for annealing at a temperature much higher than peak crystallization temperature. The results show that the amounts of Cu and Nb are very important for the soft magnetic properties of FINEMET alloys. Key words: FINEMET; XRD; Grain size; Permeability; Saturation; Magnetization DOI: http://dx.doi.org/10.3329/jbas.v35i2.9423 JBAS 2011; 35(2): 187-195

Crystallinity and crystallite size determinations have been carried out on a number of samples of swollen, hydrolyzed, and swollen and hydrolyzed cotton fibers, employing x-ray diffraction techniques and a Geiger counter recording spectrometer. A new hi variate analysis technique has been developed in order to determine the crystalline con tent of samples in which two crystalline phases are present, namely cellulose I and II. In the determination of crystallite dimensions the tilted fiber technique has been adopted for measuring crystallite lengths. A new method of resolving superposed line profiles for the measurement of crystallite width has also been developed. The results of these studies seem to suggest that there is a very close relationship between crystallinity and crystallite volume for all the types of chemical treatment studied, and that increasing crystallinity is a measure of increasing crystallite volume. On the other hand, no unique relationship between crystallinity and any one crystallite dimension has emerged for all the treatments studied. However, there are relationships which are specific to different kinds of chemical treatment of cotton.

The synergistic effect of chromium addition in the sputter-deposited amorphous or nanocrystalline W-Cr-(4-15)Ni alloys is studied in alkaline NaOH solutions at 25°C, open to air using immersion tests and electrochemical measurements. In 1 M NaOH solution, the addition of chromium to W-Cr-(4-15)Ni alloys containing 42-75 at % chromium increased the corrosion resistance and shifted the open circuit potential more noble so as to show higher corrosion resistance than those of alloy-constituting elements (that is, tungsten, chromium and nickel). The corrosion rates (that is, about 2-5 x 10 -3 mm.y -1 ) of all the examined W-Cr-(4-15)Ni alloys are about two orders of magnitude lower than that of tungsten and nearly one order of magnitude lower than that of chromium metal. The open circuit potential of the W-Cr-(4-15)Ni alloys is generally increased with increasing chromium content in different concentrations of NaOH solutions. The passivity of the WCr-(4-15)Ni alloys is increased with decreasing the concentration of NaOH solutions at 25°C. Keywords : Corrosion resistance; Sputter deposition; W-Cr-Ni alloy; NaOH solution; Open Circuit potential. DOI: 10.3126/jncs.v24i0.2380 Journal of Nepal Chemical Society, Vol. 24, 2009 Page: 3-11

The corrosion and electrochemical properties of sputter-deposited nanocrystalline binary W-Mo alloys were studied after immersion for 2429 h in different concentrations of NaOH solutions open to air at 25°C using corrosion tests and open circuit potential measurements. Molybdenum acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited binary W-Mo alloys so as to show higher corrosion resistance than those of alloy-constituting elements (i.e. tungsten and molybdenum) after immersion for 24 h in NaOH solutions. Open circuit potentials of all the examined sputter-deposited W-Mo alloys are shifted to the more positive (noble) direction with increasing molybdenum content in the alloys. The stability of the spontaneously passivated films formed on the binary W-Mo alloys is decreased with increasing concentrations of NaOH solutions. In spite of these facts, the corrosion rates of all the examined W-Mo alloys are almost independent of concentrations of NaOH solutions after immersion for 24 h at 25°C.Key words: nanocrystalline W-Mo alloys; sputter deposition; corrosion resistance; open circuit potential; NaOH solutions DOI: 10.3126/njst.v11i0.4137Nepal Journal of Science and Technology 11 (2010) 147-152

x-ray line broadening techniques have been used to determine both a- and c-direction crystallite sizes for a range of pyrolytic graphite samples whose effective formation temperature lay between 2330 and 3020°C. x-ray line profiles were analysed using the variance method. It is shown that if the proper allowance is made for the stacking fault contribution to the 110 line, the x-ray determination gives results for the a-direction crystallite size in good agreement with estimates obtained from the mobility and thermal conductivity of the samples. The a-direction crystallite sizes ranged from 0·01 to 3 μm and gave a thermal activation energy of 5·9 eV for a-direction crystallite growth. The crystallite size ratio La/Lc increased linearly with formation temperature in the range 2500 to 3020°C reaching a value of 36 at 3020°C.

An attempt was made to enhance the oxygen evolution efficiency in seawater electrolysis by additions of antimony and molybdenum to manganese–tin–tungsten oxide electrocatalyst prepared by anodic deposition on the intermediate Ir 1–x–y Sn x Sb y O 2+0.5y /Ti electrode. Ir 1–x–y Sn x Sb y O 2+0.5y /Ti supported nanocrystalline g–MnO 2 type Mn–Sn–W–X(X=Sb or/and Mo)–O electrocatalysts with grain size of about 4-8 nm were tailored by anodic deposition and these anodes showed almost 100 % oxygen evolution efficiency at current density of 1000 A.m -2 in 0.5 M NaCl solution of pH 1 at 25°C. They guaranteed the stable anode performance of 99.60-99.85% oxygen evolution efficiency for more than 5 months at current density of 1000 A.m -2 in 0.5 M NaCl solution of pH 1 at 25°C. Keywords: Oxygen evolution anodes, electrocatalyst, CO 2 recycle, XRD, SCLM. DOI: 10.3126/jncs.v25i0.3277 Journal of Nepal Chemical Society Volume 25, 2010 pp 9-18

Thin Ni-Fe films were electrodeposited onto Cu-substrates which had been evaporated onto glass microscope slides. The coercive force of the as-plated films increased with increasing crystallite size. The coercive force of films stripped from their substrates was determined after increasingly severe anneals. The results obtained suggest that for crystallite sizes in the approximate range 300 to 800 A the coercive force does not depend appreciably on crystallite size as such. The observed increase of coercive force with annealing may be explained in terms of surface roughness.

The breadth of an x-ray diffraction line has been calculated for a grain having a finite absorption coefficient and divided by reflecting planes into parallel crystallite slabs whose thickness varies in a non-random manner with depth below the surface. The predicted `apparent' crystallite size is a function of the Bragg angle θ. Qualitative support is given to the theory by the results of x-ray and hardness measurements on lightly abraded nickel.

The corrosion behavior of the sputter-deposited amorphous or nanocrystalline W-Ti alloys was studied in neutral 0.5 MNaCl solution at 25°C, open to air by immersion tests, electrochemical measurements and confocal scanning laser microscopic(CSLM) techniques. Titanium metal acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited W-Ti alloys so as to show higher corrosion resistance than those of alloy-constituting elements (that is, tungsten and titanium) in neutral 0.5 M NaCl solution. In particular, the amorphous W-Ti alloys containing 30-53 at% titanium showed lowest corrosion rates (that is, about 1 × 10-3 mm.y-1). Open circuit potentials of all the examined W-Ti alloys were shifted to more noble direction than those of the open circuit potentials of alloyconstituting elements in 0.5 M NaCl solution.Key words: Sputter deposition; W-Ti alloys; Corrosion-resistant; CSLM; NaCl solution.DOI: 10.3126/njst.v10i0.2899Nepal Journal of Science and Technology Volume 10, 2009 December Page:109-113

Radial distribution functions obtained from polycrystalline materials are influenced by both the atomic bonding and the crystallite size. A modified radial distribution function has been deduced which is independent of crystallite size and a function solely of the bonding within the crystallite. This modified radial distribution function has been computed for various samples of carbon fibre material, produced by pyrolysis at different temperatures, and the materials have been shown to be almost identical in atomic structure although differing considerably in crystallite size. For the particular ease of a layer structure a planar distribution function has been derived which has certain advantages over the radial distribution function at large atomic separations. The agreement between the measured planar distribution function for the carbon fibre material and that calculated for graphite is good.

The passivation behavior of the sputter-deposited amorphous or nanocrystalline W-Ti alloys is studied in alkaline 1 M NaOH solution at 25oC, open to air using corrosion tests, electrochemical measurements and confocal scanning laser microscopic (CSLM) techniques. The corrosion rates of the W-Ti alloys decreased with increasing titanium content and the corrosion rates of the alloys containing 53 at % (atomic percentage) or more titanium as well as the sputter-deposited titanium metal are nearly two orders of magnitude lower than that of the sputter-deposited tungsten in 1 M NaOH solution. The pitting corrosion is clearly observed in the W-Ti alloys containing 30-53 at % titanium from CSLM studies. The open circuit potentials of all the examined W-Ti alloys are located between those of tungsten and titanium metals. DOI: 10.3126/jncs.v22i0.518Journal of Nepal Chemical Society Vol. 22, 2007 pp.17-25

An attempt is made to reduce the use of IrO 2 by the IrO 2 -SnO 2 -Sb 2 O 5 intermediate layer which is necessary to avoid the growth of insulating titanium oxide on the titanium substrate for oxygen evolution a-MnO 2 type nanocrystalline Mn-Mo-Sn-O/Ir 1-x-y Sn x Sb y O 2+0.5y /Ti anodes in 0.5 M NaCl solution of pH 1 at 25°C. These electrodeposited Mn-Mo-Sn-based triple oxide anodes showed about 97.2-98.6 % oxygen evolution efficiency at high current density of 1000 A.m -2 in 0.5 M NaCl solution of pH 1 at 25°C. The high oxygen evolution efficiency of these triple oxide electrocatalysts maintained during prolonged electrolysis and even after the electrolysis for about two months. Key-words: Oxygen evolution efficiency; electrocatalyst; seawater electrolysis; CO 2 recycling; XRD DOI: 10.3126/botor.v7i0.4387 Botanica Orientalis - Journal of Plant Science (2010) 7: 79-84

Nanocrystalline, single bcc solid solutions of W-Mo alloys have been successfully prepared by D. C. magnetron sputtering in a wide composition. The corrosion behavior of the sputter-deposited W-Mo alloys was studied. The W-Mo alloys showed significantly high corrosion resistance in 12 M HCl at 30o C. Their corrosion rates are about one and half orders of magnitude lower than that of sputter-deposited tungsten and lower than that of the sputter-deposited molybdenum even after prolonged immersion.DOI: 10.3126/jncs.v21i0.217Journal of Nepal Chemical Society Vol.21 2006 pp.19-25

Permalloy films of composition 83% Ni 17% Fe ranging from polycrystalline to monocrystalline were prepared by evaporation. Conventional electron micrographs, selected area diffraction patterns, and Lorentz electron micrographs were taken to study the average magnetic ripple wavelength (λ0) as a function of the average crystallite size (a) of the film. Below a critical crystallite size, polycrystalline films showed a linear increase of the ripple wavelength with increase in crystallite size. It was found that λ0=4a in agreement with the maximum probable wavelength predicted theoretically by Rother. Films with preferred orientation showed similar behavior with λ0=10a. A plateau was reached (λ0=9000 A, a=2000 A, λ0=12 000 A, a=1160 A, respectively) after which an increase in crystallite size had no effect on the ripple wavelength. Monocrystalline films did not exhibit ripple structure and it is concluded that in these films λ0=∞.

Crystallite sizes have been obtained from the breadth of equatorial x-ray reflections from polypropylene samples subjected to a draw ratio of 6 at 21°C and then annealed at 155°C, 140°C, and 120°C, respectively. For all samples it was found that the ratio of the dimension of the crystallite perpendicular to the {110} planes to that perpendicular to the (040) plane is a constant. The ratio of the lateral crystallite size to the meridional long period was also found to be constant, independent of annealing temperature. In contrast, the thickness of the crystallites in the direction parallel to the draw direction, as calculated from the meridonal long period and density data, was not proportional to the lateral crystallite size.

As part of a detailed study of the sintering behavior of thoria gel, the crystallite size distribution in the gel was measured by electron microscopy. The distribution is in quantitative agreement with BET surface area and X-ray crystallite size measurement, and X-ray diffraction line profiles calculated using the measured size distribution agree with experiment. The relative accuracies of the integral and half-maximum intensity breadth techniques, and the relation between the size distribution and the crystallite size measured by each technique are discussed. Some implications of this work to the sintering study are mentioned.

The passivity of sputter-deposited ternary W-Cr-Ni alloys is investigated by immersion tests and electrochemical measurements in 12 M HCl solution at 30°C, open to air. Particular attention is paid to the effects of alloying elements to the corrosion behavior. All the examined amorphous or/and nanocrystalline W-Cr-Ni alloys are passivated spontaneously even in an aggressive environment of 12 M HCl, and hence these alloys showed higher corrosion resistance than those of alloyconstituting elements. The chromium addition suppresses the anodic dissolution current because of the formation of tetravalent chromium oxyhydroxide having a relatively high activity for both cathodic oxygen and hydrogen reduction with a consequent ennoblement of the open circuit potential. The ennoblement of the open circuit potential leads to the formation of the passive chromium oxyhydroxide film. It is, therefore, considered that the addition of chromium improves synergistically the corrosion resistance and passivating abilities of the sputter-deposited binary W-Ni alloys in 12 M HCl solution. Keywords: Sputter-deposition; Ternary W-Cr-Ni alloys; Corrosion-resistant; Electrochemical measurements. DOI: 10.3126/sw.v7i7.3819 Scientific World Vol.7(7) 2009 pp.24-28

The passivation behavior of the sputter-deposited amorphous or/and nanocrystalline W-Ni alloys is studied in different concentrations of NaOH solutions at 25°C, open to air using corrosion tests, electrochemical measurements and confocal scanning laser microscopic (CSLM) techniques. The corrosion rates of the W-Ni alloys containing about 60-80 at% nickel are nearly two orders of magnitude lower than that of tungsten and even lower than that of nickel metal in 1 M NaOH solution at 25°C. The pitting corrosion is observed in the tungsten-rich W-9Ni alloy from CSLM studies. The open circuit potentials of all the examined W-Ni alloys are located between those of tungsten and nickel metals in 0.01, 0.1 and 1 M NaOH solutions. The stability of the passive films formed on the sputter-deposited W-Ni alloys increased with decreasing the concentrations of NaOH solutions. DOI: 10.3126/jncs.v22i0.517Journal of Nepal Chemical Society Vol. 22, 2007 pp. 7-16

Different experimental techniques and measures of line breadth have been employed to estimate the average crystallite size of magnesium oxide powders over a range of values. The limitations of these methods of crystallite size determination are outlined and, in particular, the validity of assumptions commonly made in line profile analysis is discussed. From a comparison of data obtained using Stokes′ correction with values given by less rigorous methods, the best correction function for the elimination of instrumental broadening is determined. Data from x-ray diffraction, electron microscope and nitrogen adsorption studies of the powders are compared and their usefulness considered.

The precise methods of obtaining X-ray line profile and broadening in crystalline high polymer using X-ray diffractometer are discussed in detail, and the causes of X-ray line broadening in highly oriented linear polyethylene `Marlex 50' are investigated. It is found that the main causes are crystallite size effect and lattice-distortion, and the strain distribution function is approximated by Cauchy-form 1/(1+ k 2 x 2 ). Therefore, the separation of two effects can be made by means of Hall's equation. Using 110 and 220 reflections on the equator, recrystallization of crystallite by annealing, break-up of crystallite with elongation and change in lattice-distortion are observed. The obtained values of strain (1∼2%) are larger by one order of magnitude than those of cold-worked metals, and not changed so greatly by annealing and deformation, whereas crystallite size varies widely (100A∼larger than 700A).

The passivation behavior of the sputter-deposited amorphous or/and nanocrystalline W-Zr alloys is studied in 0.5 M NaCl and 1 M NaOH solutions at 25°C, open to air using corrosion tests and electrochemical measurements. Zirconium metal acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited W-Zr alloys so as to show lower corrosion rates than those of alloy-constituting elements (that is, tungsten and zirconium) in 0.5 M NaCl solution. In particular, corrosion rates of the binary W-Zr alloys containing 23-76 at % zirconium are more than one order of magnitude lower than that of tungsten (that is, about 0.8-1.1 × 10 -3 mm.y -1 ) and even lower than that of the sputterdeposited zirconium. On the other hand, the corrosion rates of the W-Zr alloys containing 54-76 at% zirconium are nearly two orders of magnitude lower than that of tungsten and even about one order of magnitude lower corrosion rate than that of sputter-deposited zirconium metal in alkaline 1 M NaOH solution. These results clearly revealed that the simultaneous additions of both tungsten and zirconium metals to the sputter-deposited amorphous or nanocrystalline W-Zr alloys are effective in enhancing the corrosion resistance of the alloys in both 0.5 M NaCl and alkaline 1 M NaOH solutions at 25°C, open to air. The corrosion-resistant of all the examined binary W-Zr alloys in 0.5 M NaCl solution is higher than in 1 M NaOH solution at 25°C. In general, the open circuit potentials of all the examined W-Zr alloys are shifted to more noble direction with increasing the alloy zirconium content in both 0.5 M NaCl and 1 M NaOH solutions. Keywords: Sputter-deposited W-Zr alloys, amorphous, corrosion test, electrochemical measurement, NaCl and NaOH solutions. DOI: 10.3126/jncs.v25i0.3283 Journal of Nepal Chemical Society Volume 25, 2010 pp 37-45

Magnetic properties have been measured for a number of samples of acicular γ‐Fe2O3 particles of the type used in magnetic recording tapes. The average particle size and shape were approximately the same for all samples. However, the average crystallite sizes of the samples, as determined from x‐ray line broadening, ranged from 50 to 700 A. All magnetic properties measured showed a strong dependence on average crystallite size. Saturation magnetization at room temperature, σ, decreased sharply with decreasing crystallite size. An excellent fit to the σ vs crystallite size data was made by assuming that the crystallites were separated by a nonmagnetic grain boundary on the order of 6 A wide. Room‐temperature coercive force decreased with decreasing crystallite size, and the ratio Hc(83°K)/Hc(293°K) increased sharply with decreasing crystallite size.The data support a particle model in which the constituent crystallites interact magnetostatically across nonmagnetic grain boundaries. A critical crystallite diameter of order 400 A may be inferred. Below this crystallite size, superparamagnetic behavior is observed; above this size, noncoherent magnetization reversals in the crystallites are suggested. This model is quite consistent with the ``fanning'' mode of reversal based on a ``chain‐of‐spheres'' model which has been considered by several authors to be most compatible with their data on γ‐Fe2O3 particle assemblies.

Determination of crystallite size and strain in permalloy films is being undertaken as part of a research program to relate the magnetic properties of electroplated films to their structural properties.

The correlation between crystallite size and carrier mobility of indium antimonide films deposited in a vacuum on glass substrates was studied. The crystallite size was determined from the X-ray diffraction profile, while the carrier mobility was deduced from a d.c. measurement of the transverse magnetoresistance effect. The data obtained from 50 specimens revealed the existence of a threshold crystallite size for a high mobility film and that the threshold value of this dimension is of the same order of magnitude as the mean free path of the electrons, i.e., 1000Å, Some effects of annealing the film on the crystallite size were also investigated.