High Ti Research Articles

Corrosion resistance and tribological behavior of WS2-Ti coatings by Ti cathode power changes in magnetron co-sputtering

Titanium-doped tungsten disulfide thin films (WS2-Ti) were deposited using a DC magnetron co-sputtering on AISI 304 stainless steel and silicon substrates. Different Ti cathode power densities between 0 and 1.25 W/cm2 were used for coating deposition. Energy-dispersive spectroscopy evidenced an increase in Ti percentage at the expense of W, as well as a sulfur deficiency. Raman spectroscopy was used to identify bands corresponding to W-S for undoped WS2. As the material was doped, changes in crystalline structure caused W-S main bands to separate. Scratch adhesion testing showed that Ti percentage increased along with the critical load (Lc). Furthermore, adhesive failure type changed from plastic to elastic. Finally, corrosion resistance analysis using electrochemical impedance spectroscopy (EIS) showed that, at high Ti concentrations, corrosion resistance was enhanced as Ti facilitates coating densification and generates a protective layer.

Zircon ages and geochemistry of amphibolitic rocks from the Paleoproterozoic Erdaowa Group in the Khondalite Belt, North China Craton and their tectonic implications

A currently popular model regards the Khondalite Belt in the North China Craton as a typical continent–continent collisional belt along which the Yinshan and Ordos blocks amalgamated to form the Western Block at ∼1.95 Ga. Although this model is fully supported by the geological data of high-grade metamorphic rocks from the belt, it remains unknown whether it is consistent with the low- to medium-grade units in the belt. One of such low- to medium-grade units from the Khondalite Belt is the Paleoproterozoic Erdaowa Group that consists of low-grade schists, quartzites, amphibolitic rocks, calc-silicate rocks, marbles and minor meta-conglomerates, of which amphibolitic rocks can provide important insights into understanding the tectonic setting and timing of collision of the Yinshan and Ordos blocks along the Khondalite Belt. The Erdaowa amphibolitic rocks can be divided into two groups of which Group1 is assigned to tholeiitic basalts, whereas Group 2 belongs to basaltic andesites, but they both experienced the fractional crystallization of the primary magma that was derived from the partial melting of the lithospheric mantle with minor crustal contamination. Such partial melting of the lithospheric mantle most likely occurred in a subduction zone as evidenced by their REEs and trace elements characterized by depletions in high field strength element (HFSE), Ti, P, Nb and Ta, suggesting that their igneous protoliths have affinities to continental marginal arcs. Metamorphic zircons from two amphibolitic rock samples yield Pb/Pb ages of 1941 + 14 Ma and 1910 + 9 Ma, similar to those metamorphic ages obtained for high-grade pelitic granulites from the Khondalite Belt. This confirms that the Yinshan-Ordos collision occurred at 1.95–1.90 Ga, and provides direct evidence for the involvement of low- and medium-grade rocks during the collision.

Genesis of the Xianghualing Sn–Pb–Zn deposit, South China: A multi-method zircon study

The Xianghualing Sn–Pb–Zn deposit is situated near the center of the world-class Nanling W–Sn ore belt, associated with the highly evolved Laiziling granite of Jurassic age. Previous studies focused mainly on geochemical and geochronological features of the mineralization-related granite, whereas research on the source, evolution and geochronology of the ore-forming fluids has been limited. We carried out precise U–Pb dating, trace element, and Hf isotopic analyses on magmatic and hydrothermally-altered zircons from the skarn-stage and sulfide-stage ores in the Xianghualing deposit. Zircon U–Pb dating results from the two ore-forming stages show distinct geochronological populations: the skarn stage ores contain mainly magmatic and hydrothermally-altered zircons in three age clusters (∼150 Ma, ∼220 Ma, and ∼ 420 Ma), whereas the sulfide-stage ores are characterized by abundant old detrital zircons ranging from 497 to 3409 Ma, with a peak at 800–1000 Ma. This pattern may indicate that magmatic–hydrothermal events in the Silurian and Triassic were precursors to the main Sn mineralization event in the Jurassic, when circulation of evolved fluids through older sedimentary rocks led to Pb–Zn mineralization. The Jurassic zircons exhibit high trace-element contents (e.g., Hf, P, Y, Nb, Ta, Th, U) and low Ti contents, Eu anomalies, Nb/Ta and Th/U ratios, which imply that the Laiziling magma experienced significant plagioclase, biotite and muscovite fractional crystallization, and that it interacted extensively with post-emplacement F-rich hydrothermal fluids. The positive Ce anomalies of these zircons (Ce/Ce∗ = 1.0–226) indicate that the magmatic–hydrothermal fluids that led to the Jurassic Sn mineralization event were reducing. The less negative εHf(t) values of Triassic zircons (−18.7 to −2.6) compared to the Silurian zircons (−14.6 to 2.3) suggest more limited interaction between the mantle and the magma source region. The Jurassic magmatic zircons in the skarns exhibit even more negative εHf(t) values (−30.7 to −6.7), along with TDMC model ages ranging from 1627 to 3134 Ma, indicating that the Jurassic magma was derived from partial melting of old continental crustal basement. Based on the combined study of zircons in the skarns and sulfide ores, we propose a three-stage ore genetic model for the Xianghualing Sn–Pb–Zn deposit.

Effects of Ti and Nb on the Grain Refinement and Mechanical Properties of AISI 4145 Steel

In this study, we investigated the effects of Ti and Nb additions on the grain size of prior austenite and mechanical properties such as yield strength, yield ratio, and impact toughness in quenched and tempered AISI 4145 steel. It was found that the grain size of prior austenite directly influenced the mechanical properties. Thermodynamic calculations were carried out to find the characteristics of the precipitates such as dissolution temperature of precipitates, the average size of precipitate particles, precipitate fraction, and mean distance among precipitate particles, quantitatively. A specimen with low Ti content had a smaller Ti/N ratio than the stoichiometric ratio of 3.42 and showed an effective inhibition of grain growth of prior austenite, whereas a specimen with high Ti content showed a little effect to prevent the austenite grain growth compared with a Ti-free sample. Based on the thermodynamic simulation, the (Nb, Ti) (C, N) complex was precipitated and contributed to the inhibition of austenite grain growth, resulting in not only higher yield strength and yield strength/tensile strength ratio but also improved toughness.

The 920–900 Ma Bahia-Gangila LIP of the São Francisco and Congo cratons and link with Dashigou-Chulan LIP of North China craton: New insights from U-Pb geochronology and geochemistry

A widespread mafic sill and dyke unit (the Pedro Lessa suite) adjacent to the southeastern São Francisco (SF) craton (eastern South America) is dated as 940 ± 42 Ma, 912 ± 17 Ma, and 986 ± 64 Ma (based on combined ID-TIMS and LA-ICPMS analyses on baddeleyite grains) on the Santa Maria de Itabira gabbroic intrusion. These ages suggest membership in the previously defined ca. 920–900 Ma Large Igneous Province (LIP) (herein referred to as the Bahia-Gangila LIP) of the reconstructed São Francisco and formerly adjacent Congo craton (Africa). Additional mafic and felsic units throughout the SF craton are also linked (based on a literature review), thus expanding the size of the reconstructed LIP to ca. 1,500,000 km2. Geochemistry reveals high Ti OIB signature for most units and low Ti E-MORB composition for the Gangila flood basalts, marking the initiation of attempted ocean opening. Geochemistry of the Bahia-Gangila LIP is also compared with the ca. 920–900 Ma Dashigou-Chulan LIP of the North China craton, and implications for three possible reconstructions of SF/Congo craton with the North China craton are considered.

Realization of high Ti plasmas and confinement characteristics of ITB plasmas in the LHD deuterium experiments

The deuterium (D) operation was initiated in the LHD in 2017. In the first campaign of the D experiments, we successfully extended the high temperature regime in the LHD. The new record of the ion temperature (Ti) of 10 keV associated with the ion internal transport barrier (ITB) was achieved due to several operational optimization. The thermal confinement characteristics of ITB plasmas were compared between hydrogen and D discharges. The effective ion thermal diffusivity of the ion-ITB plasmas was found to be smaller in the D discharges than that in the H discharges. The profiles of the Ti, the electron density, and the impurity of the high Ti plasmas strongly depended on the magnetic configuration and these profiles tended to peaked in the inward-shifted configuration. It was also found that the electron thermal confinement of the electron-ITB plasmas was clearly improved in the deuterium case. The GKV simulation showed the linear growth rate of TEM/ITG reduced in the plasmas with D both for the ion ITB and the electron ITB plasmas and qualitatively agreed with the tendency of the change in the thermal diffusivity obtained from the power balance analysis.

Experimental study of variable thermal lens in a two-stage chirped-pulse high-power Ti:sapphire amplifier at 1kHz

In general, misalignment, surface quality of optical components, thermal and nonlinear properties, doping level and inhomogeneity in the gain material can induce unexpected pulse propagation effects on intnese femtosecond laser pulses. Among them, the thermal lens in a thermally loaded material is more serious since it limits power scaling and degrades maximum achievable intensity at the focus by introducing distortion into the wavefront. Thereby, an understanding of thermally distortion wavefront is of great importance for optimum design of high power laser amplifiers and efficient serving femtosecond lasers in various specific applications. In this paper, we experimentally studied beam quality and wavefront distortion in a longitudinally pumped two-stage chirped pulse high power Ti:sapphire amplifier laser at 1 kHz operation in terms of pump power. The amplifier crystals are cooled thermoelectrically to below −10 °C. A simple formula for coupling the thermal lens in a two-stage amplifier consists of a regenerative amplifier followed by a single-pass amplifier pumped equally by the Nd:YLF laser at 527 nm with maximum average output power of 44 W and 130 ns pulse duration at 1 kHz is presented. The wavefront curvature of the compressed laser pulses with ∼40 fs pulse duration and center wavelength of 800 nm is evaluated directly by Shack-Hartmann Wavefront Sensor (SHWS) with help of the Zernike polynomials. While the beam radius and spatial beam quality M2 factor are estimated by knife-edge testing. Also, the optical wavefront distortion caused by an iris inserted into the beam path of a high power laser for quick spot size adjustment has been presented. When diameter of the iris is about 75% of the laser beam size (corresponding to 67% fraction transmission), laser beam distortion associated with the iris is negligible.

Pre-infiltration and brazing behaviors of Cf/C composites with high temperature Ti[sbnd]Si eutectic alloy

A novel method is developed to join carbon fiber reinforced carbon composites (Cf/C composites) via a two-step approach using Ti14Si86 metal foil as the joining material. The infiltration behavior, joint microstructure, interface reaction, fracture characteristics and joining mechanism are investigated. The preparation of the almost compact deposit layer and the infiltration carbide can immediately heal the pores of Cf/C composites and form the gradient composite structure, which can effectively minimize the impact of the coefficient of thermal expansion (CTE) mismatch between the outer reaction layer and the carbon matrix and avoid the excessive filler infiltration in the brazing step. The brazing process reveals that the growing SiC interface and TiSi eutectic structure in the seam also behave as a graded CTE composite structure, which is beneficial for strengthening the joint. Compared with direct brazing, this method can obtain more reliable Cf/C composites joints due to strong interfacial bonding and the gradient structure. As a result, a favorable shear strength of 26 MPa is achieved within 10 min at a brazing temperature of 1400 °C.

Multilayer formation via spinodal decomposition in TiO2-VO2 epitaxial films on sapphire substrates

We present multilayer formation via spinodal decomposition in rutile TiO2-VO2 (TVO) epitaxial films on sapphire substrates. (001)- and (101)-oriented TVO solid-solution films are grown epitaxially on TiO2/Al2O3 using a pulsed laser deposition technique and annealed inside the spinodal region. X-ray diffraction measurements and scanning transmission electron microscopy (STEM) observations show that the films are phase-separated along the [001] direction and lamellar structures are formed in a parallel or slanted direction to the sapphire substrates depending on the film orientation. The results indicate the multilayer formation via spinodal decomposition in the TVO films. STEM investigations also reveal a relatively high Ti concentration in the decomposed phases, reflecting the influence of lattice deformation on the phase decomposition in the films. Our work shows that spinodal decomposition is a promising approach for the formation of a multilayer structure in TVO films and helps deepen understanding the spinodal decomposition in TVO system.

Role of Ti Content on the Occurrence of the 3309-cm–1 Peak in FTIR Absorption Spectra of Ruby Samples

The study is based on the determination of trace elements in ruby samples, Ti in particular, using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS). The samples were then divided into three groups: high (≥ 200 ppma), moderate (100–200 ppma), and low (≤ 50 ppma) Ti content. In addition, X-ray absorption spectroscopy (XAS) was employed to confirm that the Ti oxidation state was Ti4+. The heat experiment conditions were set at 800, 1200, and 1650°C to investigate the transformation of the –OH vibration in the FTIR spectra of ruby samples. The FTIR spectra showed that samples containing a low Ti concentration did not show the 3309-cm–1 absorption peak either before or after heating at any of the designed temperatures. An obvious 3309-cm–1 peak appeared only in samples with a moderate to high Ti content after heating at ≥ 1200°C. The results also suggest that, in addition of Ti4+, the occurrence of the 3309-cm–1 peak in the FTIR spectra is strongly affected by the charge compensation of –OH in Al sites, i.e., the structural –OH; thus, the structural –Ti–OH stretching in the ruby samples. Hence, for gemological identification, the 3309-cm–1 peak can be applied to indicate whether a ruby has undergone heat treatment if those samples contain enough Ti ions in their structure, i.e., Ti ≥ 100 ppma. This condition is usually found in ruby samples from major deposits such as Mong Hsu and Mogok, Myanmar; Luc Yen, Vietnam; and Montopuez, Mozambique.

Importance of solvents in preparing highly active Ti-SBA-15 catalysts by grafting method

The importance of solvents in preparing Ti-incorporated SBA-15 mesoporous silica (Ti-SBA-15) of highly catalytic activities in epoxidation of bulky alkenes using titanium alkoxides as grafting agents was disclosed. Solvents were found to markedly affect the coordination environment of Ti incorporated on SBA-15. Among the common solvents examined, best dispersion of tetrahedrally coordinated Ti(IV) on silica surface was obtained by grafting in 1-butanol and the second was in 1-hexanol. It is attributed to that the hydrolysis of titanium alkoxides in these alcohols is slower than in other studied solvents, including short-chain alcohols and non-polar hydrocarbons. Detailed studies on the hydrolysis rates of titanium alkoxide in different solvents were examined. In contrast, titanium alkoxides of different alkyl groups as titanium sources were found to have little influences on the structures and catalytic activities of resultant Ti-SBA-15 materials. Ti-SBA-15 of high Ti loading (ca. 4.2% Ti/Si ratio) prepared by grafting with TBOT in 1-butanol was found to have optimal catalytic activities in epoxidation of cycloalkenes, including cyclohexene and dicyclopentadiene, using tert-butylhydroperoxide as the oxidant.

Iodine-stabilized high resolution dual-frequency Ti: sapphire laser.

A dual frequency Ti: sapphire laser is presented in which two lines operate simultaneously with the same intensity on two TM00 longitudinal modes. This operation is obtained by means of the 127I2 molecules contained in an intra-cavity cell, pumped by a low-power laser. Its properties are interesting: the two lines lase simultaneously, they overlap spatially, their spectral width could be very narrow, their frequency is automatically locked to molecular frequencies and can serve as a frequency reference, the frequency difference is adjustable over the thousands of rotational or vibrational molecular energy gaps in the 0.1-0.9 THz and 3-6 THz domains, and it is computable with high precision. THz wave production is demonstrated as a first application.

Iron dissolution and speciation in atmospheric mineral dust: Metal-metal synergistic and antagonistic effects

Under acidic atmospheric conditions, iron leached from atmospheric mineral dust may influence the distribution of bioavailable iron at a global scale. However, the effects of non-Fe-containing minerals on iron dissolution remain unknown. This work describes metal-metal synergistic and antagonistic effects on iron dissolution that go beyond aggregation and ionic strength effects in mineral dust mixtures. In this study, we investigated iron mobilization by proton-promoted dissolution in natural mineral dust samples from the Kalahari Desert (SZ1) and Australian Red Dawn event (RO), along with one iron oxide proxy, hematite. The total iron dissolution in natural dust samples highly corresponds with the respective amount of Ti, rather than their particle sizes or Fe contents. The dust sample with high Ti content, SZ1, also showed a higher fraction of dissolved Fe(II), under dark conditions. These observations are in good agreement with the dissolution data for hematite artificially mixed with metal oxides. Total iron dissolution in hematite, mixed with TiO2, is 1.5- and 2-fold higher compared to that of just hematite under dark and light conditions, respectively. However, dissolution of hematite is suppressed when mixed with Al2O3 and CaO. Under dark conditions, furthermore, dissolved Fe(II) fraction is enhanced for hematite when mixed with TiO2 compared to that of other mixtures or hematite alone. Yet, dissolved Fe(II) is lower in hematite mixed with TiO2 under light conditions compared to that of hematite alone, suggesting photo-oxidation of Fe(II) by reactive oxygen species, such as OH radicals.

Investigation of the complete power conversion chain for small vertical- and horizontal-axis wind turbines in turbulent winds

The study of wind turbines requires a multidisciplinary approach that covers the electrical, mechanical and aerodynamic aspects. Most wind turbine studies focus their modelization effort on a single aspect and rely on simplified models for the other ones. The present paper aims at a complete modelization and investigation of the energy conversion chain of small wind turbines (up to 100kW), going from the turbulent wind resource to the electrical power injected into the grid. For that purpose, the following computational chain is set up: a synthetic turbulence is used as inflow to a Vortex Particle-Mesh method which computes the wind turbine coarse scale aerodynamics taking into account the rotor dynamics; the aero-mechanical results are used to feed an electrical simulation and the consistency of both simulations is ensured by using a common Maximum Power Point Tracking algorithm. We apply this methodology to compare the behavior of horizontal- and vertical-axis machines in a turbulent wind with two different turbulent intensities (low TI = 8.3% and high TI = 16%).

Melanite-bearing nepheline syenite fragments and 40Ar/39Ar age of phlogopite megacrysts in conduit breccia from the Poços de Caldas Alkaline Massif (MG/SP), and implications

The Pocos de Caldas Alkaline Massif, located in southeast Brazil, is composed of tinguaites, as well as phonolites and nepheline syenites (NeS), together with assorted pyroclastic rocks. The latter constitute deposits within the Vale do Quartel, and show fragments of alkaline rocks (NeS, tinguaites), basaltic and ultramafic volcanics/subvolvanics, sandstones, and quartz-feldspathic rocks from the crystalline basement. NeS fragments with melanite, previously unknown, and cm-sized fragments of phlogopite megacrysts from related conduit breccia were chosen for detailed studies. The NeS fragments are medium-to coarse grained and contain K-feldspar (Or 95-83), secondary albite (Ab 97), altered nepheline, clinopyroxene (diopside, minor hedenbergite) and partially altered, zoned, idiomorphic melanite. These NeS fragments are typically metaluminous, and point to the existence of similar intrusions hidden at depth, an important input to the massif's petrology. The phlogopite megacrysts are compositionally homogeneous, with high Ti, Mg and Al contents; Ba and F are minor components. Two phlogopite aliquots were dated and yielded identical Ar-40/Ar-39 plateau ages of 87.1(+/- 0.5) Ma and 86.6(+/- 0.5) Ma, which represent minimum and maximum values for phlogopite crystallization and breccia emplacement, respectively. Previously obtained ages for the Pocos de Caldas rocks are concentrated in the 75-86 Ma range interval.

Effects of Ti addition on corrosion behavior of Zr-based metallic glass in chloride medium

The effects of Ti element on the corrosion resistance of the metallic glass Zr51.3Al10Ni6Cu31.8Ag0.1Y0.8 in aqueous solution with various chloride concentrations were investigated, and the effect mechanism was discussed. X-ray diffraction confirmed that Ti-added Zr51.3Al10Ni6Cu31.8Ag0.1Y0.8 metallic glasses with diameter of 3 mm were all metallic glasses. Weight loss and electrochemical method were introduced to characterize their corrosion resistance, and X-ray photoelectron spectroscopy study was used to characterize the passive film composition. The results show that the corrosion resistance of metallic glass is significantly improved with Ti addition, and Zr dioxides dominate in passive film during corrosion when Ti content is low. High Ti addition can lead to an obvious accumulation of Ti dioxides, which results in a thicker, Ti-enriched protective passive film.

Magnetoresistance of oxygen concentration-modulated Co–Ti–O films

Co–Ti–O films have been prepared by a sputtering method in an Ar- and O2-mixed atmosphere. The O2 flow rate was modulated during the deposition to optimize the oxygen concentration and the microstructure of the films. For the as-deposited film, negligible magnetization and magnetoresistance (MR) were observed. The structure of the layers with lower O2 flow rate is basically amorphous alloy with Ti–O and Co–Ti bonds. On the other hand, in the layers with high O2 flow rate, both Ti and Co are oxidized. Upon thermal annealing in a vacuum, significant enhancements in both magnetization and MR in Co–Ti–O films were observed. It is found that granular structure of Co particles embedded in insulating TiO2 matrix is formed due to the oxygen diffusion and further oxidization of Ti as a result of the heat treatment. The significantly enhanced magnetization and MR ratio have been ascribed to the formation of nano-sized Co particles and the tunneling conduction between these Co particles across the TiO2 interlayers, respectively.

Preparation of Multi-components TiAl Based Alloy by Aluminothermic Reduction of Acid Soluble Titanium Bearing Slag

The aluminothermic reduction of high Ti acid soluble Ti bearing slag (ASTS) was carried out to prepare the multi-components TiAl based alloy. In order to control and understand the preparation of TiAl alloy, the effects of the addition of Al and CaO, and temperature were discussed. By considering materials proportioning calculations it could successfully make TiAl alloy with sound slag-alloy separation. The recovery rates of most reduced elements are high, about 95% in the all experimental conditions. The Al addition can mainly affect the composition of TiAl alloy, while CaO addition influences the slag-metal separation by varying composition of slag system. Besides, the temperature of system can increase the recovery rate and distribution ratio for most reduced elements.

Occurrence, characterisation and fate of (nano)particulate Ti and Ag in two Norwegian wastewater treatment plants

Due to their widespread application in consumer products, elemental titanium (e.g., titanium dioxide, TiO2) and silver (Ag), also in nanoparticulate form, are increasingly released from households and industrial facilities to urban wastewater treatment plants (WWTPs). A seven-day sampling campaign was conducted in two full-scale WWTPs in Trondheim (Norway) employing only primary treatment. We assessed the occurrence and elimination of Ti and Ag, and conducted size-based fractionation using sequential filtration of influent samples to separate particulate, colloidal and dissolved fractions. Eight-hour composite influent samples were collected to assess diurnal variations in total Ti and Ag influx. Measured influent Ti concentrations (up to 290 μg L−1) were significantly higher than Ag (<0.15–2.1 μg L−1), being mostly associated with suspended solids (>0.7 μm). Removal efficiencies ≥70% were observed for both elements, requiring for one WWTP to account for the high Ti content (∼2 g L−1) in the flocculant. Nano- and micron-sized Ti particles were observed with scanning transmission electron microscopy (STEM) in influent, effluent and biosolids, while Ag nanoparticles were detected in biosolids only. Diurnal profiles of influent Ti were correlated to flow and pollutant concentration patterns (especially total suspended solids), with peaks during the morning and/or evening and minima at night, indicating household discharges as predominant source. Irregular profiles were exhibited by influent Ag, with periodic concentration spikes suggesting short-term discharges from one or few point sources (e.g., industry). Influent Ti and Ag dynamics were reproduced using a disturbance scenario generator model, and we estimated per capita loads of Ti (42–45 mg cap−1 d−1) and Ag (0.11 mg cap−1 d−1) from households as well as additional Ag load (14–22 g d−1) from point discharge. This is the first study to experimentally and mathematically describe short-term release dynamics and dry-weather sources of emissions of Ti and Ag in municipal WWTPs and receiving environments.

A new type of oxidized and pre-irradiated micrometeorite

This paper investigates the mineralogy and noble gas composition of a unique micrometeorite from the Transantarctic Mountains, #45c.29. The magnetite rim and the particle interior with olivine, pyroxene and magnetite relict grains (30–250 µm in size) set in a vesicular mesostasis are typical features of coarse-grained, partially melted micrometeorites. Particle #45c.29 stands out from other micrometeorites of this type by the texture of the mesostasis made of abundant plagioclase and augite laths, the remarkably high Ni contents in magnetite and olivine relict grains, and by the similarly high abundance of cosmogenic noble gases (21Necos up to 1.62 × 10−7 cm3 STP/g and 38Ar up to 7.2 × 10−8 cm3 STP/g). The high Ni content of Fa26 olivine relict grains (NiO ∼ 0.65 wt%), the high Ni (NiO ∼ 0.8 wt%) and Ti (TiO2 ∼ 0.3 wt%) contents of magnetite relicts, and the oxygen isotope composition of a sample of the particle (δ18O ∼ 2.3‰, δ17O ∼ −1.5‰), suggest a parentage with rare equilibrated CK chondrites. Pyroxene and plagioclase are not expected to crystallize during atmospheric entry of micrometeoroids. Their occurrence in #45c.29 may be explained by the Ca-, Al- and Na- rich composition of its precursor – in agreement with the high abundance of plagioclase reported in the matrix of CK chondrites – if combined with a relatively low cooling rate and, therefore, unusual atmospheric entry parameters (velocity/angle) of the micrometeoroid. Given these specific entry parameters, the particle has recorded unique information on mineralogical and textural transformations of micrometeoroids during atmospheric entry, with solid-state oxidation of the olivine relict grains in the igneous rim, and partial melting of relict mineral phases and relict/melt reactions in the particle interior. The cosmogenic 21Ne/22Ne ratio of 0.94 ± 0.02 is incompatible with major production by cosmogenic ray irradiation of a small particle in space. We propose that micrometeorite #45c.29 mostly records an earlier irradiation stage, in a meteoroid or more likely near the surface (<20 cm in depth) of an asteroid. In contrast, most of the other unmelted and scoriaceous micrometeorites analyzed for noble gases – if coming from asteroidal sources of the Main Belt – seem to have sampled deeper parts of their parent body, where they were shielded from cosmic rays and from where they were excavated during high-energy disruptive processes.