There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Nanotechnology in concrete – A review

In this manuscript we review experimental constraints for the viscosity of the upper mantle. We first analyze experimental data to provide a critical review of flow law parameters for olivine aggregates and single crystals deformed in the diffusion creep and dislocation creep regimes under both wet and dry conditions. Using reasonable values for the physical state of the upper mantle, the viscosities predicted by extrapolation of the experimental flow laws compare well with independent estimates for the viscosity of the oceanic mantle, which is approximately 10 19 Pa s at a depth of ∼100 km. The viscosity of the mantle wedge of subduction zones could be even lower if the flux of water through it can result in olivine water contents greater than those estimated for the oceanic asthenosphere and promote the onset of melting. Calculations of the partitioning of water between hydrous melt and mantle peridotite suggest that the water content of the residue of arc melting is similar to that estimated for the asthenosphere. Thus, transport of water from the slab into the mantle wedge can continually replenish the water content of the upper mantle and facilitate the existence of a low viscosity asthenosphere.

Rheology of the Upper Mantle and the Mantle Wedge: A View from the Experimentalists

New microproducts need the utilization of a diversity of materials and have complicated three-dimensional (3D) microstructures with high aspect ratios. To date, many micromanufacturing processes have been developed but specific class of such processes are applicable for fabrication of functional and true 3D microcomponents/assemblies. The aptitude to process a broad range of materials and the ability to fabricate functional and geometrically complicated 3D microstructures provides the additive manufacturing (AM) processes some profits over traditional methods, such as lithography-based or micromachining approaches investigated widely in the past. In this paper, 3D micro-AM processes have been classified into three main groups, including scalable micro-AM systems, 3D direct writing, and hybrid processes, and the key processes have been reviewed comprehensively. Principle and recent progress of each 3D micro-AM process has been described, and the advantages and disadvantages of each process have been presented.

/pdf/a-review-on-3d-micro-additive-manufacturing-technologies-1kbpeb2xb5.pdf

A review on 3D micro-additive manufacturing technologies

[1] The relationship between diffusion of individual species and creep of silicates is unclear and has long been debated, factually anchored by the central observation that the activation energies for creep are higher than the activation energy for diffusion of any species. There have been numerous attempts to explain this difference. New advances in experimental technology enable us to demonstrate that this difference does not exist and was an artefact of the limited experimental resolution of earlier studies – the activation energies of creep and diffusion of Si in olivine are identical, 530 kJ/mol. This allows the creep mechanism in olivine to be understood as one of simple climb (consistent with microstructural observations) and opens possibilities of estimating, understanding and predicting the (much simplified) creep behavior of diverse silicates under a wide range of P-T-X conditions through the use of diffusion data–measured or computed.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2002GL015480

Si and O diffusion in olivine and implications for characterizing plastic flow in the mantle

We have determined Fe–Mg diffusion coefficients in olivines from different sources (Nanga Parbat, Pakistan and San Carlos, Arizona, USA) at atmospheric pressure as a function of composition, oxygen fugacity (10−5–10−12 Pa) and temperature (700–1200°C) using thin films produced by pulsed laser deposition and RBS to analyze the concentration profiles. We have characterized the nano-scale structure and composition of the thin films annealed at various conditions and shown that the nature of the film (e.g. crystallinity, wetting behavior) depends strongly on the annealing conditions. If these variations are not taken into account in the form of boundary conditions for modeling the diffusion profiles, artifacts would result in the diffusion data. The diffusion coefficients obtained from 75 experiments reveal that (i) between fO2 of 10−5 and 10−10 Pa, diffusion along all three principal crystallographic directions in olivine, [100], [010] and [001], are described by a constant activation energy of ∼200 kJ/mol, precluding any temperature dependence of diffusion anisotropy and change of mechanism of diffusion at temperatures between 950 and 1200°C, (ii) diffusion coefficients increase with oxygen fugacity at fO2 > 10−10 Pa, with an fO2 exponent that lies between 1/4 and 1/7, and (iii) at fO2 below 10−10 Pa, and consequently at temperatures below ∼900°C, diffusion becomes weakly dependent/independent of fO2, indicating a change of diffusion mechanism. Activation energy of diffusion at these conditions is slightly higher, ∼220 kJ/mol. The data, including the change of mechanism, are analyzed in terms of point defect chemistry in Part II of this work to derive an equation that allows calculation of diffusivities in olivine over its entire field of stability. Availability of directly measured data at temperatures down to 700°C imply that for the first time diffusion coefficients can be interpolated, rather than extrapolated, for modeling most natural systems.

Fe–Mg diffusion in olivine I: experimental determination between 700 and 1,200°C as a function of composition, crystal orientation and oxygen fugacity

In this paper we describe a setup to efficiently deposit thin films (up to several micrometers) of complex silicate and oxide compositions. We describe the production and characterization of thin films of a variety of natural mineral compositions ( e.g. olivine, garnet, pyroxene and plagioclase solid solutions). The films have been characterized using different techniques ( e.g. RBS, TEM, SEM and white light interference microscopy) and are found to be amorphous, highly uniform (± 1nm) in thickness and of the desired solid solution stoichiometries, as deposited. Small amounts of excess oxygen after deposition can be readjusted by subsequent annealing and such anneals may crystallize the films in some cases ( e.g. several hours at 900°C for olivine). The films have an excellent contact with the substrate even at the HRTEM scale and open the possibility for a variety of studies in mineral kinetic and surface sciences, which are outlined. Some examples of the production of diffusion couples in minerals for measurements that were difficult or impossible before are illustrated. These include Fe-Mg diffusion in olivine at low temperatures, Si and O diffusion in olivine and diffusion of Lu in garnets.

Production of silicate thin films using pulsed laser deposition (PLD) and applications to studies in mineral kinetics

Pure copper metal thin films were grown on SiO 2 /Si(100) substrates by metal-organic (MO)CVD in a horizontal cold-wall reactor employing the two metal-organic compounds, Cu(OCHMeCH 2 NR 2 ) 2 , where R = Et (1) and R = Me (2) as precursors. Thermogravimetric analyses proved them to be convenient compounds for the deposition of copper without a reducing agent. Depositions were carried out at various substrate temperatures in the range 230-350°C. X-ray diffraction (XRD) indicated that the resulting films were highly crystalline and showed a strong (111) preferred orientation, which increased with increasing deposition temperature. Photoelectron spectroscopy (XPS) revealed that copper films deposited at 230°C and 260°C consisted solely of metallic copper with no detectable carbon, nitrogen, or oxygen contamination. Copper films obtained from 1 at 260°C had a resistivity of 2.16 μΩ cm.

A Study on the Metal Organic CVD of Pure Copper Films from Low Cost Copper(II) Dialkylamino-2-propoxides: Tuning the Thermal Properties of the Precursor by Small Variations of the Ligand

We have measured Fe-Mg interdiffusion coefficients, D Fe-Mg , parallel to the three main crystallographic axes in two natural orthopyroxene single crystals [approximately En 98 Fs 1 ( X Fs = X Fe = 0.01) and En 91 Fs 9 ] using diffusion couples consisting of a 20–90 nm thick silicate thin film deposited under vacuum on polished and oriented pyroxene single crystals. The thin films were prepared using pulsed laser ablation of polycrystalline olivine pellets (composition: Fo 30 Fa 70 ). Samples were annealed for 4–337 h at 870–1100 °C under atmospheric pressure in a continuous flow of CO + CO 2 to control the oxygen fugacity, f O 2 , between 10 −11 and 10 −7 Pa within the stability field of pyroxene. Film thickness and compositional profiles were measured using Rutherford backscattering spectroscopy (RBS) on reference and annealed samples, and Fe concentration depth profiles were extracted from the RBS spectra and fitted numerically considering a compositional dependence of D Fe-Mg in orthopyroxene. We obtain an Arrhenius relationship for both types of crystals, but only for the more Fe-rich composition a dependence on f O 2 could be clearly identified. For diffusion along [001] in the composition Fs 9 , least-squares regression of the log D Fe-Mg vs. reciprocal temperature yields the following Arrhenius equation:
 D Fe - Mg [ m 2 / s ] = 1 . 12 × 10 − 6 ( f o 2 [ Pa ] ) 0 . 053 ± 0 . 027 exp [ – 308 ± 23 [ kJ / mol ] / ( R T ) ] . D Fe-Mg in Opx with X Fe = 0.01 obeys a relationship that does not depend on f O 2 :
 D Fe - Mg [ m 2 / s ] = 1 . 66 × 10 − 4 exp [ – 377 ± 30 [ kJ / mol ] / ( R T ) ] . Diffusion along [001] is faster than diffusion along [100] by a factor of 3.5, while diffusion along [010] is similar to that along [001]. Comparison of D Fe-Mg and rates of order-disorder kinetics indicates that for f O 2 around the IW buffer and lower, diffusion in natural orthopyroxene becomes insensitive to f O 2 , which could be related to a transition in the diffusion mechanism from a transition metal extrinsic (TaMED) domain to a pure extrinsic (PED) domain. This behavior is analogous to that observed for Fe-Mg diffusion in olivine and this complexity precludes the formulation of a closed form expression for the composition and f O 2 dependence of D Fe-Mg in orthopyroxene at present. We were not able to quantitatively constrain the dependence of D Fe-Mg on the X Fs content from the profile shapes, but consideration of the experimentally measured diffusion coefficients along with the data for order-disorder kinetics suggests that the compositional dependence is weaker than previously estimated, at least for orthopyroxene with X Fe T and f O 2 range of available experimental data, Fe-Mg interdiffusion in orthopyroxene is slower than in olivine and aluminous spinel, comparable to garnet, and faster than in clinopyroxene.

Hans-Werner Becker

Papers

Si and O diffusion in olivine and implications for characterizing plastic flow in the mantle

Fe–Mg diffusion in olivine I: experimental determination between 700 and 1,200°C as a function of composition, crystal orientation and oxygen fugacity

Production of silicate thin films using pulsed laser deposition (PLD) and applications to studies in mineral kinetics

A Study on the Metal Organic CVD of Pure Copper Films from Low Cost Copper(II) Dialkylamino-2-propoxides: Tuning the Thermal Properties of the Precursor by Small Variations of the Ligand

Fe-Mg interdiffusion in orthopyroxene