scholarly journals Isotropic microscale mechanical properties of coral skeletons

2015 ◽  
Vol 12 (106) ◽  
pp. 20150168 ◽  
Author(s):  
Luca Pasquini ◽  
Alan Molinari ◽  
Paola Fantazzini ◽  
Yannicke Dauphen ◽  
Jean-Pierre Cuif ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Nacreous Layer ◽  
X Ray Diffraction ◽  
Stylophora Pistillata ◽  
Force Microscopy ◽  
Coral Skeletons ◽  
Atomic Force ◽  
Diffraction Patterns ◽  
The Relationship ◽  
Atrina Rigida

Scleractinian corals are a major source of biogenic calcium carbonate, yet the relationship between their skeletal microstructure and mechanical properties has been scarcely studied. In this work, the skeletons of two coral species: solitary Balanophyllia europaea and colonial Stylophora pistillata , were investigated by nanoindentation. The hardness H IT and Young's modulus E IT were determined from the analysis of several load–depth data on two perpendicular sections of the skeletons: longitudinal (parallel to the main growth axis) and transverse. Within the experimental and statistical uncertainty, the average values of the mechanical parameters are independent on the section's orientation. The hydration state of the skeletons did not affect the mechanical properties. The measured values, E IT in the 76–77 GPa range, and H IT in the 4.9–5.1 GPa range, are close to the ones expected for polycrystalline pure aragonite. Notably, a small difference in H IT is observed between the species. Different from corals, single-crystal aragonite and the nacreous layer of the seashell Atrina rigida exhibit clearly orientation-dependent mechanical properties. The homogeneous and isotropic mechanical behaviour of the coral skeletons at the microscale is correlated with the microstructure, observed by electron microscopy and atomic force microscopy, and with the X-ray diffraction patterns of the longitudinal and transverse sections.

Growth and Characterization of bulk GaN by Ga Vapor Transport

2004 ◽  
Vol 831 ◽  
Author(s):  
Phanikumar Konkapaka ◽  
Huaqiang Wu ◽  
Yuri Makarov ◽  
Michael G. Spencer
Keyword(s):  
Growth Rates ◽  
Vapor Transport ◽  
Spiral Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Bulk Gan ◽  
Diffraction Patterns

ABSTRACTBulk GaN crystals of dimensions 8.5 mm × 8.5 mm were grown at growth rates greater than 200μm/hr using Gallium Vapor Transport technique. GaN powder and Ammonia were used as the precursors for growing bulk GaN. Nitrogen is used as the carrier gas to transport the Ga vapor that was obtained from the decomposition of GaN powder. During the process, the source GaN powder was kept at 1155°C and the seed at 1180°C. Using this process, it was possible to achieve growth rates of above 200 microns/hr. The GaN layers thus obtained were characterized using X-Ray diffraction [XRD], scanning electron microscopy [SEM], and atomic force microscopy [AFM]. X-ray diffraction patterns showed that the grown GaN layers are single crystals oriented along c direction. AFM studies indicated that the dominant growth mode was dislocation mediated spiral growth. Electrical and Optical characterization were also performed on these samples. Hall mobility measurements indicated a mobility of 550 cm2/V.s and a carrier concentration of 6.67 × 1018/cm3

Investigation of Structural and Mechanical Properties of Laser Deposited Microlaminate Hard Coatings

2001 ◽  
Vol 697 ◽  
Author(s):  
Manoj Radder ◽  
A.K. Sikder ◽  
Ashok Kumar
Keyword(s):  
Mechanical Properties ◽  
Boron Carbide ◽  
Composite Coatings ◽  
Bottom Layer ◽  
Hard Coatings ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Substrate Temperatures

Nitride and carbide are superhard material with a high potential for applications in different fields. A new group of coatings are the multilayered/microlaminate coatings, which have shown very interesting properties. Single and microlaminate films were coated on Silicon (Si) substrates using pulsed laser deposition (PLD) technique. Films were deposited at different substrate temperatures in order to study the microstructure evolution and their effect on the mechanical properties of these microlaminate films. Structure of the films was characterized by x-ray diffraction (XRD) technique. Surface morphology and roughness of the films were investigated using atomic force microscopy (AFM). Hardness and modulus of the films were investigated using nanoindentation technique. It has been demonstrated that using boron carbide as a bottom layer increases the hardness and Young's modulus values of carbide composite coatings. Microlaminates of boron carbide/titanium carbides have shown higher hardness and modulus as compared to the microlaminates of nitride coatings.

Structural and Magnetotransport Properties of NiMnSb/Cu and NiMnSb/Ag Multilayers

1997 ◽  
Vol 475 ◽  
Author(s):  
J.A. Caballero ◽  
F. Petroff ◽  
A. Cabbibo ◽  
Y.D. Park ◽  
J.R. Childress
Keyword(s):  
Layer Thickness ◽  
Thin Layers ◽  
Crystalline Quality ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Spacer Layer ◽  
Spin Polarized ◽  
The Relationship ◽  
Substrate Temperatures

ABSTRACTWe report on the integration of the predicted half-metallic (100% spin-polarized) ferromagnetic Heusler alloy NiMnSb into NiMnSb/Cu and NiMnSb/Ag multilayer structures, and on their magnetic, microstructural and magnetotransport properties. The NiMnSb layer thickness was fixed at 30Å and those of Cu and Ag were varied from 5 to 60Å. The multilayers were characterized using x-ray diffraction (XRD), four-wire resistivity measurements, atomic force microscopy, SQUID magnetometry and magnetotransport measurements. Moderate substrate temperatures (250°C) are shown to be sufficient to produce stochiometric Clb-structured NiMnSb. XRD data confirm that the NiMnSb ultra-thin layers retain their crystalline quality and texture. SQUID measurements shows that the bulk saturation magnetization (∼740 emu/cm3) is maintained and that it is strongly sensitive to interlayer diffusion and roughness. AFM studies show that the surface roughness, which can be as low as 4Å, depends on the choice of spacer layer, layer thickness and substrate temperature. The relationship between the measured magnetoresistance, NiMnSb crystalline quality, magnetic properties and interfacial roughness are discussed.

Synthesis and Characterization of Amorphous Metallic Alloy Thin Films for MEMS Applications

2003 ◽  
Vol 806 ◽  
Author(s):  
Senthil N Sambandam ◽  
Shekhar Bhansali ◽  
Venkat R. Bhethanabotla
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Surface Morphology ◽  
X Ray Diffraction ◽  
Micro Electro Mechanical Systems ◽  
Force Microscopy ◽  
Target Composition ◽  
Atomic Force ◽  
Deposition Parameters ◽  
Afm Analysis

ABSTRACTMicrostructures of multi-component amorphous metallic glass alloys are becoming increasingly important due to their excellent mechanical properties and low coefficient of friction. In this work, thin films of Zr-Ti-Cu-Ni-Be have been deposited by DC magnetron sputtering in view of exploring their potential technological applications in fields such as Micro Electro Mechanical Systems (MEMS). Their structure, composition, surface morphology, mechanical properties viz., hardness and Young's modulus were analyzed using X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Nanoindentation. Influence of the deposition parameters of sputtering pressure and power upon the composition and surface morphology of these films has been evidenced by SEM, and AFM analysis, showing that such a process yields very smooth films with target composition at low sputtering pressures. These studies are useful in understanding the multicomponent sputtering process.

scholarly journals Tribo-Mechanical Properties of the Antimicrobial Low-Density Polyethylene (LDPE) Nanocomposite with Hybrid ZnO–Vermiculite–Chlorhexidine Nanofillers

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2811
Author(s):  
Karla Čech Barabaszová ◽  
Sylva Holešová ◽  
Marianna Hundáková ◽  
Alena Kalendová
Keyword(s):  
Mechanical Properties ◽  
Zinc Oxide ◽  
Xrd Analysis ◽  
Surface Topology ◽  
Low Density Polyethylene ◽  
Indentation Hardness ◽  
Low Density ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force

Materials made from low-density polyethylene (LDPE) in the form of packages or catheters are currently commonly applied medical devices. Antimicrobial LDPE nanocomposite materials with two types of nanofillers, zinc oxide/vermiculite (ZnO/V) and zinc oxide/vermiculite_chlorhexidine (ZnO/V_CH), were prepared by a melt-compounded procedure to enrich their controllable antimicrobial, microstructural, topographical and tribo-mechanical properties. X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FTIR) revealed that the ZnO/V and ZnO/V_CH nanofillers and LDPE interacted well with each other. The influence of the nanofiller concentrations on the LDPE nanocomposite surface changes was studied through scanning electron microscopy (SEM), and the surface topology and roughness were studied using atomic force microscopy (AFM). The effect of the ZnO/V nanofiller on the increase in indentation hardness (HIT) was evaluated by AFM measurements and the Vickers microhardness (HV), which showed that as the concentration of the ZnO/V nanofiller increased, these values decreased. The ZnO/V and ZnO/V_CH nanofillers, regardless of the concentration in the LDPE matrix, slightly increased the average values of the friction coefficient (COF). The abrasion depths of the wear indicated that the LDPE_ZnO/V nanocomposite plates exhibited better wear resistance than LDPE_ZnO/V_CH. Higher HV and HIT microhardness values were measured for both nanofillers than the natural LDPE nanocomposite plate. Very positive antimicrobial activity against S. aureus and P. aeruginosa after 72 h was found for both nanofiller types.

Measurement of Mechanical Properties of Single and Multilayered Nitride thin Films Prepared by Cathodic Arc Deposition

2001 ◽  
Vol 697 ◽  
Author(s):  
A.K. Sikder ◽  
I. M. Irfan ◽  
Ashok Kumar ◽  
Robert Durvin ◽  
Mark McDonough ◽  
...  
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
X Ray Diffraction ◽  
Thin Coatings ◽  
Force Microscopy ◽  
Atomic Force ◽  
Cathodic Arc Deposition ◽  
Steel Substrates ◽  
Cathodic Arc ◽  
Arc Deposition

Mechanical properties of thin films differ significantly from those of bulk materials due to the effects of interfaces, microstructure and thick underlying substrates. In this study we will present the results of nanoindentation tests to evaluate mechanical properties of nitride (TiN, ZrN, CrN, TiCN and TiAlN) thin films. Films were coated on steel substrates using cathodic arc deposition technique. Surface morphology and roughness of the samples are investigated using atomic force microscopy (AFM). Films were also characterized by x-ray diffraction (XRD) technique. Nanoindentation technique along with AFM and XRD methods are very useful for characterizing hard thin coatings.

Nano-Structured CrN/CNx Multilayer Films

2007 ◽  
Vol 334-335 ◽  
pp. 893-896 ◽  
Author(s):  
A. Vyas ◽  
Yao Gen Shen ◽  
Zhi Feng Zhou ◽  
K.Y. Li
Keyword(s):  
Mechanical Properties ◽  
Multilayer Films ◽  
Closed Field ◽  
X Ray Diffraction ◽  
Substrate Bias Voltage ◽  
Force Microscopy ◽  
Unbalanced Magnetron Sputtering ◽  
Atomic Force ◽  
Transmission Electron ◽  
Unbalanced Magnetron

CrN/CNx nano-scale multilayered films were deposited on Si (100) substrate by closed-field unbalanced magnetron sputtering. Designed experimental parameters enabled an evaluation of the effects of negative substrate bias voltage (Vb), and bi-layer thickness λ (by changing substrate rotation rate) during deposition on the structural and mechanical properties of multilayer films. These multilayers were characterized and analyzed by transmission electron microscope (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation measurements. In all cases, the CNx layers were amorphous and independent of Vb, while the microstructures of the CrN layers were dependent primarily on Vb. The CrN layers showed a mixed structure phase consisting of CrN, Cr2N, and Cr at Vb = -(40-120) V. At higher Vb values (-140 V or above), the Cr2N phase was dominant along with low CrN phase content. AFM measurements revealed that the root-mean-square (rms) surface roughness of the CrN/CNx film was 2 nm at Vb= -200 V whereas the rms values were about 9.5-3.3 nm for lower Vb values of -(40-180 V). By nanoindentation measurements, a maximum hardness of about 36 GPa was observed at Vb= -140 V. The improved mechanical properties of the films are correlated to the phase formation during deposition.

Depth dependent osmotic and swelling properties of cartilage

2012 ◽  
Vol 1418 ◽  
Author(s):  
Candida Silva ◽  
Iren Horkayne-Szakaly ◽  
Preethi Chandran ◽  
Emilios K. Dimitriadis ◽  
David Lin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Articular Surface ◽  
Swelling Pressure ◽  
Osmotic Swelling ◽  
Swelling Properties ◽  
Force Microscopy ◽  
Atomic Force ◽  
Joint Surfaces ◽  
And Function ◽  
The Relationship

ABSTRACTArticular cartilage is a low-friction, load-bearing tissue located at joint surfaces. It experiences static and dynamic forces including shear, compression and tension. We investigate the relationship between structure and function by measuring the osmotic and mechanical properties in cartilage layers as a function of the distance from the articular surface. Atomic force microscopy is used to probe the mechanical properties at high spatial resolution. The mechanical measurements are complemented by osmotic swelling pressure observations made on the same samples using a novel tissue osmometer. The results show that the osmotic modulus significantly depends on the distance from the articular surface. Its value is highest in the deep zone and lowest in the middle zone.

HIV infection changes glomerular podocyte cytoskeletal composition and results in distinct cellular mechanical properties

2007 ◽  
Vol 292 (2) ◽  
pp. F701-F710 ◽  
Author(s):  
R. Tandon ◽  
I. Levental ◽  
C. Huang ◽  
F. J. Byfield ◽  
J. Ziembicki ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Characteristics ◽  
Stress Fibers ◽  
Wild Type ◽  
Force Microscopy ◽  
Hemodynamic Forces ◽  
Filtration Barrier ◽  
Atomic Force ◽  
Relationship Of ◽  
The Relationship

In addition to forming the selective filtration barrier for the renal glomerulus, podocytes maintain glomerular capillary architecture by opposing distending hemodynamic forces. To understand the relationship of cytoskeletal properties and the mechanical characteristics of podocytes, we studied filamin expression and distribution and measured cell membrane deformability in conditionally immortalized wild-type (WT) mouse podocytes, and in podocytes derived from a mouse model of HIV-associated nephropathy (HIVAN). In the WT cells, filamin and F-actin were localized at the periphery and in prominent stress fibers. In the HIVAN cells, filamin expression was reduced, and stress fibers were sparse. In a microaspiration assay, HIVAN cells ruptured under minimal negative pressure. Atomic force microscopy demonstrated that the WT cells had a stiffness of 17 kPa, whereas the value for the HIVAN cells was 4 kPa. These results demonstrate that the mechanical properties of WT and HIVAN podocytes are markedly different in a manner that is consistent with differences in the composition and arrangement of their cytoskeletons. The mechanical properties of the WT podocytes suggest that these cells can better maintain capillary integrity than the HIVAN podocytes and implicate pathological assembly of the cytoskeleton as a mechanism of HIVAN.

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