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14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

Miyoshi, K.↗
NASA NTRS1983

Surface chemistry, friction, and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to the surfaces of the ferrites in sliding. Previously announced in STAR as N83-19901

Miyoshi, K.↗
NASA NTRS1987

Effect of abrasive grit size on wear of manganese-zinc ferrite under three-body abrasion

Wear experiments were conducted using replication electron microscopy and reflection electron diffraction to study abrasion and deformed layers produced in single-crystal Mn-Zn ferrites under three-body abrasion. The abrasion mechanism of Mn-Zn ferrite changes drastically with the size of abrasive grits. With 15-micron (1000-mesh) SiC grits, abrasion of Mn-Zn ferrite is due principally to brittle fracture; while with 4- and 2-micron (4000- and 6000-mesh) SiC grits, abrasion is due to plastic deformation and fracture. Both microcracking and plastic flow produce polycrystalline states on the wear surfaces of single-crystal Mn-Zn ferrites. Coefficient of wear, total thickness of the deformed layers, and surface roughness of the wear surfaces increase markedly with an increase in abrasive grit size. The total thicknesses of the deformed layers are 3 microns for the ferrite abraded by 15-micron SiC, 0.9 microns for the ferrite abraded by 4-micron SiC, and 0.8 microns for the ferrite abraded by 1-micron SiC.

Miyoshi, Kazuhisa↗
NASA NTRS1983

X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces.

Miyoshi, K.↗
NASA NTRS1986

Abrasion and deformed layer formation of manganese-zinc ferrite in sliding contact with lapping tapes

Wear experiments were conducted using replication electron microscopy and reflection electron diffraction to study abrasion and the deformed layers produced in single-crystal Mn-Zn ferrite simulated heads during contact with lapping tapes. The crystaline state of the head is changed drastically during the abrasion process. Crystalline states ranging from nearly amorphous to highly textured polycrystalline can be produced on the wear surface of a single-crystal Mn-Zn ferrite head. The total thickness of the deformed layer was approximately 0.8 microns. This thickness increased as the load and abrasive grit size increased. The anisotropic wear of the ferrite was found to be inversely proportional to the hardness of the wear surface. The wear was lower in the order 211 111 10 0110. The wear of the ferrite increased markedly with an increase in sliding velocity and abrasive grit size.

Miyoshi, K.↗
NASA NTRS1986

Effect of crystallographical and geometrical changes of a ferrite head on magnetic signals during the sliding process with magnetic tape

This paper reviews changes in the crystalline structure and geometry of lapped Mn-Zn ferrite heads in sliding contact with magnetic tape and the effects of these changes on magnetic signals. A highly textured, polycrystalline structure was produced on the surface of a single-crystal Mn-Zn ferrite head when it was finished with an aluminum oxide lapping tape. Sliding this lapped surface against a magnetic tape produced a nearly amorphous structure. The sliding process led to a degradation in readback signal of 1 to 2 dB (short-wavelength recording). Furthermore, wear of the magnetic head caused geometrical changes in the head surface. The signal read back with the worn magnetic head was sensitive to operating parameters such as head displacement and tape tension. A change in operating parameters created head-to-tape spacings and, consequently, excessive gains or losses in the readback signal.

Miyoshi, K.↗
NASA NTRS1984

Ceramic wear in indentation and sliding

The various wear mechanisms involved with single-crystal ceramic materials in indentation and in sliding contacts. Experiments simulating interfacial events have been conducted with hemispherical, conical and pyramidal indenters (riders). With spherical riders, under either abrasive or adhesive conditions, two types of fracture pits have been observed. First, spherical-shaped fracture pits and wear particles are found as a result of either indenting or sliding. These are shown to be due to a spherical-shaped fracture along the circular or spherical stress trajectories. Second, polyhedral fracture pits and debris, produced by anisotropic fracture, and also found both during indenting and sliding. These are primarily controlled by surface and subsurface cracking along cleavage planes. Several quantitative results have also been obtained from this work. For example, using a pyramidal diamond, crack length of Mn-Zn ferrite in the indentation process grows linearly with increasing normal load. Moreover, the critical load to fracture both in indentation and sliding is essentially isotropic and is found to be directly proportional to the indenter radius.

Miyoshi, K.↗
NASA NTRS1985

Effects of wear on structure-sensitive magnetic properties of ceramic ferrite in contact with magnetic tape

Wear experiments and electron microscopy and diffraction studies were conducted to examine the wear and deformed layers in single-crystal Mn-Zn (ceramic) ferrite magnetic head material in contact with magnetic tape and the effects of that contact on magnetic properties. The crystalline state of the single-crystal magnetic head was changed drastically during the sliding process. A nearly amorphous structure was produced on its wear surface. Deformation in the surficial layer of the magnetic head was a critical factor in readback signal loss above 2.5 dB. The signal output level was reduced as applied normal load was increased. Considerable plastic flow occurred on the magnetic tape surface with sliding, and the signal loss due to the tape wear was approximately 1 dB.

Miyoshi, K.↗
NASA NTRS1985

Ceramic wear in indentation and sliding contact

The various wear mechanisms involved with single-crystal ceramic materials in indentation and in sliding contacts. Experiments simulating interfacial events have been conducted with hemispherical, conical and pyramidal indenters (riders). With spherical riders, under either abrasive or adhesive conditions, two types of fracture pits have been observed. First, spherical-shaped fracture pits and wear particles are found as a result of either indenting or sliding. These are shown to be due to a spherical-shaped fracture along the circular or spherical stress trajectories. Second, polyhedral fracture pits and debris, produced by anisotropic fracture, and also found both during indenting and sliding. These are primarily controlled by surface and subsurface cracking along cleavage planes. Several quantitative results have also been obtained from this work. For example, using a pyramidal diamond, crack length of Mn-Zn ferrite in the indentation process grows linearly with increasing normal load. Moreover, the critical load to fracture both in indentation and sliding is essentially isotropic and is found to be directly proportional to the indenter radius.

Miyoshi, K.↗
NASA NTRS1995

Improved L-C resonant decay technique for Q measurement of quasilinear power inductors: New results for MPP and ferrite powdered cores

The L-C resonant decay technique for measuring circuit Q or losses is improved by eliminating the switch from the inductor-capacitor loop. A MOSFET switch is used instead to momentarily connect the resonant circuit to an existing voltage source, which itself is gated off during the decay transient. Very reproducible, low duty cycle data could be taken this way over a dynamic voltage range of at least 10:1. Circuit Q is computed from a polynomial fit to the sequence of the decaying voltage maxima. This method was applied to measure the losses at 60 kHz in inductors having loose powder cores of moly permalloy and an Mn-Zn power ferrite. After the copper and capacitor losses are separated out, the resulting specific core loss is shown to be roughly as expected for the MPP powder, but anomalously high for the ferrite powder. Possible causes are mentioned.

Niedra, Janis M.↗
DOE OSTI2020

Materials Data on MnZn by Materials Project

MnZn is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Mn is bonded in a body-centered cubic geometry to eight equivalent Zn atoms. All Mn–Zn bond lengths are 2.60 Å. Zn is bonded in a body-centered cubic geometry to eight equivalent Mn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn3Zn by Materials Project

Mn3Zn is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Mn sites. In the first Mn site, Mn is bonded to eight Mn and four equivalent Zn atoms to form MnMn8Zn4 cuboctahedra that share corners with twelve equivalent MnMn8Zn4 cuboctahedra, edges with eight equivalent ZnMn12 cuboctahedra, edges with sixteen MnMn8Zn4 cuboctahedra, faces with four equivalent ZnMn12 cuboctahedra, and faces with fourteen MnMn8Zn4 cuboctahedra. There are four shorter (2.48 Å) and four longer (2.59 Å) Mn–Mn bond lengths. All Mn–Zn bond lengths are 2.59 Å. In the second Mn site, Mn is bonded to eight equivalent Mn and four equivalent Zn atoms to form MnMn8Zn4 cuboctahedra that share corners with four equivalent MnMn8Zn4 cuboctahedra, corners with eight equivalent ZnMn12 cuboctahedra, edges with twenty-four MnMn8Zn4 cuboctahedra, faces with six equivalent ZnMn12 cuboctahedra, and faces with twelve MnMn8Zn4 cuboctahedra. All Mn–Zn bond lengths are 2.48 Å. Zn is bonded to twelve Mn atoms to form ZnMn12 cuboctahedra that share corners with four equivalent ZnMn12 cuboctahedra, corners with eight equivalent MnMn8Zn4 cuboctahedra, edges with eight equivalent ZnMn12 cuboctahedra, edges with sixteen equivalent MnMn8Zn4 cuboctahedra, faces with four equivalent ZnMn12 cuboctahedra, and faces with fourteen MnMn8Zn4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnZn3 by Materials Project

MnZn3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mn is bonded to twelve equivalent Zn atoms to form MnZn12 cuboctahedra that share corners with six equivalent MnZn12 cuboctahedra, corners with twelve equivalent ZnMn4Zn8 cuboctahedra, edges with eighteen equivalent ZnMn4Zn8 cuboctahedra, faces with eight equivalent MnZn12 cuboctahedra, and faces with twelve equivalent ZnMn4Zn8 cuboctahedra. There are six shorter (2.68 Å) and six longer (2.74 Å) Mn–Zn bond lengths. Zn is bonded to four equivalent Mn and eight equivalent Zn atoms to form ZnMn4Zn8 cuboctahedra that share corners with four equivalent MnZn12 cuboctahedra, corners with fourteen equivalent ZnMn4Zn8 cuboctahedra, edges with six equivalent MnZn12 cuboctahedra, edges with twelve equivalent ZnMn4Zn8 cuboctahedra, faces with four equivalent MnZn12 cuboctahedra, and faces with sixteen equivalent ZnMn4Zn8 cuboctahedra. There are a spread of Zn–Zn bond distances ranging from 2.70–2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnZn by Materials Project

MnZn is Magnesium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Mn is bonded to six equivalent Mn and six equivalent Zn atoms to form MnMn6Zn6 cuboctahedra that share corners with eighteen equivalent MnMn6Zn6 cuboctahedra, edges with six equivalent MnMn6Zn6 cuboctahedra, edges with twelve equivalent ZnMn6Zn6 cuboctahedra, faces with eight equivalent MnMn6Zn6 cuboctahedra, and faces with twelve equivalent ZnMn6Zn6 cuboctahedra. All Mn–Mn bond lengths are 2.64 Å. All Mn–Zn bond lengths are 2.68 Å. Zn is bonded to six equivalent Mn and six equivalent Zn atoms to form ZnMn6Zn6 cuboctahedra that share corners with eighteen equivalent ZnMn6Zn6 cuboctahedra, edges with six equivalent ZnMn6Zn6 cuboctahedra, edges with twelve equivalent MnMn6Zn6 cuboctahedra, faces with eight equivalent ZnMn6Zn6 cuboctahedra, and faces with twelve equivalent MnMn6Zn6 cuboctahedra. All Zn–Zn bond lengths are 2.64 Å.

36 MATERIALS SCIENCE↗