Microstructure and Interfaces of Ultra-Thin Epitaxial AlN Films Grown by Plasma-Enhanced Atomic Layer Deposition at Relatively Low Temperatures

We demonstrate the growth of ultra-thin AlN films on Si (111) and on a GaN/sapphire (0001) substrate using atomic layer epitaxy in the temperature range of 360 to 420 °C. Transmission electron microscopy and X-ray diffraction were used to characterize the interfaces, fine scale microstructure, and the crystalline quality of thin films. Films were deposited epitaxily on Si (111) with a hexagonal structure, while on the GaN/sapphire (0001) substrate, the AlN film is epitaxial and has been deposited in a metastable zinc-blende cubic phase. Transmission electron microscopy reveals that the interface is not sharp, containing an intermixing layer with cubic AlN. We show that the substrate, particularly the strain, plays a major role in dictating the crystal structure of AlN. The strain, estimated in the observed orientation relation, is significantly lower for cubic AlN on hexagonal GaN as compared to the hexagonal AlN on hexagonal GaN. On the Si (111) substrate, on the other hand, the strain in the observed orientation relation is 0.8% for hexagonal AlN, which is substantially lower than the strain estimated for the cubic AlN on Si(111).

Anatomical study of the innervation of different parts of the posterior ligamentous region of the sacroiliac joint

Background and objectivesThe periarticular sacroiliac joint (SIJ) technique has become an important area of focus, and the quartering of the SIJ posterior ligamentous region has been proposed as a way to refine this technique. However, detailed nerve distribution combined with the division of the SIJ posterior ligamentous region is lacking. We aimed to explore the innervation of the SIJ posteriorly based on the quartering of the SIJ posterior ligamentous region.MethodsSixteen SIJs from eight embalmed cadavers were studied. Each SIJ posterior ligamentous region was equally divided into areas 0–3 from top to bottom. The origin, distribution, quantity, transverse diameter, spatial orientation, relation with bony structures, and the number of identifiable terminal nerve branches in each area were examined.ResultsAreas 0–1 were innervated by the lateral branches of the dorsal rami of L4−L5 directly in all specimens. Areas 2–3 were innervated by that of both lumbar and sacral nerves via the posterior sacral network (PSN), with L5 contributing to the PSN in all specimens and L4 in 68.75%. The number of identifiable terminal nerve branches were significantly higher in areas 2–3 than in areas 0–1.ConclusionsThe inferior part of the SIJ posterior ligamentous region seems to be the main source of SIJ-related pain and is innervated by lumbar and sacral nerves via the PSN. However, the superior part directly innervated by lumbar nerves should not be neglected, and further clinical verification is needed.

Структура межфазной границы alpha-beta в твердом растворе PdCu

In accordance with the orientation relation (110),<001>β || (111),<110> α, established by the fast electron diffraction method between ordered (β) and disordered (α) phases in the Pd – 57 at .% Cu solid solution foil , the atomic structure of the interface is modeled by molecular dynamics. It is found that the structural and dimensional mismatch is compensated by interfacial dislocations with Burgers vectors a / 2 <111> in β-phase coordinates.

Reversible epitaxial electrodeposition of metals in battery anodes

The propensity of metals to form irregular and nonplanar electrodeposits at liquid-solid interfaces has emerged as a fundamental barrier to high-energy, rechargeable batteries that use metal anodes. We report an epitaxial mechanism to regulate nucleation, growth, and reversibility of metal anodes. The crystallographic, surface texturing, and electrochemical criteria for reversible epitaxial electrodeposition of metals are defined and their effectiveness demonstrated by using zinc (Zn), a safe, low-cost, and energy-dense battery anode material. Graphene, with a low lattice mismatch for Zn, is shown to be effective in driving deposition of Zn with a locked crystallographic orientation relation. The resultant epitaxial Zn anodes achieve exceptional reversibility over thousands of cycles at moderate and high rates. Reversible electrochemical epitaxy of metals provides a general pathway toward energy-dense batteries with high reversibility.

A Study on the Nucleation Mechanism of Nano-Scale Precipitates of 7055 Aluminum Alloy

7055 aluminum alloy is a typical age-hardening alloy whose properties change with microstructural evolution as a result of heat treatment. In this paper, the microstructural evolution of the alloy after solid solution treatment and manual aging is examined using SEM, TEM and HADDF. The precipitation, nucleation and growth mechanisms of [Formula: see text] and [Formula: see text] phases are also analyzed. Results show that, as aging proceeds, the Al–Cu phase gradually enlarges and thickens the following precipitation sequence of supersaturated solid solution (SSSS) [Formula: see text] GPI zone [Formula: see text] GPII zone [Formula: see text] phase [Formula: see text] phase; some [Formula: see text] phases formed during aging, which have two different nucleation mechanisms: homogeneous nucleation and heterogeneous nucleation, the [Formula: see text] phases of the latter being marginally larger in size than those of the former. There is a transition in the transformation of (Al3Cu) in GPII zone into [Formula: see text]-phase (Al2Cu). The orientation relation between [Formula: see text] phase and Al matrix is (100)Al//(100)[Formula: see text], (010)Al//(010)[Formula: see text], (001)Al//(001)[Formula: see text]. According to this relationship, [Formula: see text] phase has three variants in the matrix: Variants 1, 2, and 3, which represent the [Formula: see text] phase along {100}Al, {010}Al and {001}Al. As [Formula: see text] phase has a special orientation relation with Al matrix (100)Al//(100)[Formula: see text], (010)Al//(010)[Formula: see text], (001)Al//(001)[Formula: see text], [Formula: see text] phase is distributed in disc form on {001}Al. Significantly larger [Formula: see text] phase can be observed. The orientation relation between S phase and Al matrix is [100]Al//[100]S, [021]Al//[010]S, [012]Al//[001]S. [Formula: see text] phase grows in step form for a period equaling to 1.75-fold unit cell of [Formula: see text]. As [Formula: see text] phase grows, the Cu atoms segregated on the edge of [Formula: see text] phase are gradually consumed.

A Study to Evaluate and Compare Right and Left Condylar Discrepancy between Centric Relation and Maximum Intercuspation in Three Age Groups

<strong><em>Background</em>:</strong>Since discrepancy between centric relation and maximum intercuspation has been an area of interest for dental fraternity for decades, the study was conducted to expand the concepts of the same when age is taken into consideration.<p><strong>Objective:</strong> This study was conducted to assess and measure the discrepancy between centric relation (CR) and maximum intercuspation (MI) at right and left condyles in three age groups, compare the discrepancy at right and left condyles between three age groups and right and left side condyles within the same age group.</p><p><strong>Methods:</strong> Sixty healthy subjects were selected and divided into three groups of twenty subjects each. Group I: 18-25 years, Group II: 30-45 years and Group III: more than fifty years. Preliminary impressions were made. Orientation relation was transferred to a semi-adjustable arcon articulator. Subjects were guided into centric relation using Dawson's bimanual manipulation technique and centric interocclusal record was made. The mandibular cast was related to the maxillary cast using centric interocclusal record. The casts were then allowed to fall into maximum intercuspation and the distance that the condylar analogues had moved was measured using Feeler gauge.</p><p><strong><em>Results:</em></strong> The mean CR-MI discrepancy in Group I was 0.417±0.137 mm and 0.364±0.123 mm, Group II was 0.528±0.160 mm and 0.512±0.158 mm and Group III was 0.873±0.228 mm and 0.815±0.172 mm at the right and left condyles respectively.</p><p><strong><em>Conclusion:</em></strong> Within the limitations of the study it was concluded that all the sixty subjects had a CR-MI discrepancy in both left and right condyles. The variation in discrepancy between the three age groups was found to be very highly significant.</p>

Localized dissolution of grain boundary T1 precipitates in Al-3Cu-2Li

Transmission electron microscopy (TEM) was employed to investigate the dissolution behavior of nanocrystalline grain boundary T1 precipitates in Al-3Cu-2Li. These grain boundary T1 plates exhibit an orientation relation with matrix, with the (1-11)α-Al parallel to (0001)T1 and [022]α-Al parallel to [10-10]T1, which is similar to the orientation relationship of T1 plates formed within grains. TEM studies showed that these grain boundary T1 plates react readily in moist air. As a result of the localized dissolution, the Cu-rich clusters form onto T1, which is consistent with the localized dissolution behavior observed in nanocrystalline S phase in Al-Cu-Mg.