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Vascularization in interconnected 3D printed Ti-6Al-4V foams with hydrogel matrix for biomedical bone replacement implants

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Science China Materials 2018年第4期61卷 565-578页

作者： Victor L.Correa Kristine M.Garza Lawrence E.Murr Department of Metallurgical Materials and Biomedical Engineering University of Texas at El Paso Department of Biological Sciences University of Texas at El Paso

Vascularization on newly implanted metal orthopedic implants has remained a challenge in the field of tissue engineering. To address this challenge, in this research,an interconnected foam structure of Ti-6 Al-4 V was microfabricated by electron beam melting(EBM) technique. The foam in question has a density of 1.77 g cm-3 with 60% porosity and a tensile strength of 18 GPa. An extracellular matrix based hydrogel was added as an aqueous matrix to the *** mimetic stress has been closely related to many wound healing biomedical applications as it increases survival and proliferation molecular signals. To that end, increased expression of hypoxia-inducible factor-1α(Hif-1α) and vascular endothelial growth factor(VEGF) in the aqueous hydrogel matrix was achieved by the addition of a hypoxia mimetic deferoxamine mesylate(DFM). In this study, the formation of an endothelial network was achieved in a hydrogel matrix in the presence of the before mentioned 3 D printed metal foam. Cellular viability, fluorescent microscopy and scanning electron microscopy imaging analysis demonstrate that pre-osteoblasts undergo proliferation and also attach efficiently to the foam when exposed to DFM. Human umbilical vascular endothelial cells(HUVECs) were grown in an extracellular matrix-like 3 D hydrogel and a hypoxia-like stress was achieved. This research demonstrates that pre-osteoblast cells undergo cell differentiation and increase the production of hydroxyapatite on exposure to the hypoxia mimetic molecule. This proposed approach encompasses an ideal prototype for a completely living implanted structure for future orthopedic implants.

关键词： Ti-6Al-4V electron beam melting angiogenesis deferoxamine mesylate hydrogel vascularization

Gauge Inverse Monoids

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Algebra Colloquium 2020年第2期27卷 181-192页

作者： Emil Daniel Schwab Department of Mathematical Sciences The University of Texas at El Paso El PasoTexas 79968USA

The paper introduces a class of inverse(sub)monoids which contains Jones-Lawson’s gauge inverse(sub)*** aim is to give examples and the basic properties of these ***-Lawson’s gauge inverse monoid,as an inverse submonoid of the polycyclic monoid,is the prototype in our development *** generalization leads also to Mea-kin-Sapir type results involving bijections between special congruences and special wide inverse submonoids.

关键词： inverse semigroup gauge inverse monoid polycyclic monoid

Static and cyclic oxidation of Nb-Cr-V-W-Ta high entropy alloy in air from 600 to 1400℃

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Journal of Materials Science & Technology 2020年第3期38卷 189-196页

作者： S.K.Varma Francelia Sanchez Sabastian Moncayo C.V.Ramana Department Metallurgical Materials and Biomaterials EngineeringThe University of Texas at El PasoEl PasoTX79968-0520USA Center for Advanced Materials Research(CMR) The University of Texas at El PasoEl PasoTX79968-0520USA

An oxidation resistance study has been made on Nb-Cr-V-W-Ta high entropy alloy in a range of temperature from 600 to 1400℃in *** oxidation study has been performed for either(a)12 or 24 h of heating time or(b)3 or 10℃/min heating rates to the desired oxidation *** oxidation study conducted for three and a half days has been conducted at 600,700,and 800℃using 12 h of heating *** alloy can withstand the cyclic oxidation process with only a reasonable loss of *** identification of oxides indicates crystals of W and Ta oxides in cylindrical form while Nb and Cr oxides show a nodular or granular morphology at both 1000 and 1200℃while and additional of oxide of V in whisker forms at 1200℃.

关键词： High entropy alloys Nb-Cr-V-W-Ta Microstructures Oxidation

Grain boundary and microstructure engineering of Inconel 690 cladding on stainless-steel 316L using electron-beam powder bed fusion additive manufacturing

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Journal of Materials Science & Technology 2019年第2期35卷 351-367页

作者： I.A.Segura L.E.Murr C.A.Terrazas D.Bermudez J.Mireles V.S.V.Injeti K.Li B.Yu R.D.K.Misra R.B.Wicker W.M.Keck Center for 3D Innovation The University of Texas at El Paso Department of Mechanical Engineering The University of Texas at El Paso Department of Metallurgical Materials and Biomedical Engineering The University of Texas at El Paso

This research explores the prospect of fabricating a face-centered cubic(fcc) Ni-base alloy cladding(Inconel 690) on an fcc Fe-base alloy(316 L stainless-steel) having improved mechanical properties and reduced sensitivity to corrosion through grain boundary and microstructure engineering concepts enabled by additive manufacturing(AM) utilizing electron-beam powder bed fusion(EPBF). The unique solidification and associated constitutional supercooling phenomena characteristic of EPBF promotes[100] textured and extended columnar grains having lower energy grain boundaries as opposed to random, high-angle grain boundaries, but no coherent {111} twin boundaries characteristic of conventional thermo-mechanically processed fcc metals and alloys, including Inconel 690 and 316 L *** addition to [100] textured grains, columnar grains were produced by EPBF fabrication of Inconel 690 claddings on 316 L stainless-steel substrates. Also, irregular 2–3 μm diameter, low energy subgrains were formed along with dislocation densities varying from 108 to 109 cm^2, and a homogeneous distribution of Cr_(23)C_6 precipitates. Precipitates were formed within the grains(with ~3 μm interparticle spacing),but not in the subgrain or columnar grain boundaries. These inclusive, hierarchical microstructures produced a tensile yield strength of 0.527 GPa, elongation of 21%, and Vickers microindentation hardness of 2.33 GPa for the Inconel 690 cladding in contrast to a tensile yield strength of 0.327 GPa, elongation of 53%, and Vickers microindentation hardness of 1.78 GPa, respectively for the wrought 316 L stainlesssteel substrate. Aging of both the Inconel 690 cladding and the 316 L stainless-steel substrate at 685?C for50 h precipitated Cr_(23)C_6 carbides in the Inconel 690 columnar grain boundaries, but not in the low-angle(and low energy) subgrain boundaries. In contrast, Cr_(23)C_6 carbides precipitated in the 316 L stainless-steel grain boundaries, but not in the low energy

关键词： Additive manufacturing electron-beam powder bed fusion (EPBF) Inconel 690 cladding 316L stainless steel Grain boundary engineering Materials characterization Mechanical properties

Metal Fabrication by Additive Manufacturing Using Laser and electron Beam Melting Technologies

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Journal of Materials Science & Technology 2012年第1期28卷 1-14页

作者： Lawrence E. Murr Sara M. Gaytan Diana A. Ramirez Edwin Martinez Jennifer Hernandez Krista N. Amato Patrick W. Shindo Francisco R. Medina Ryan B. Wicker Department of Metallurgical and Materials Engineering The University of Texas at El PasoEl Paso TX 79968 USA W.M. Keck Center for 3D Innovation The University of Texas at El PasoEl Paso TX 79968 USA

Lawrence E. Murr is Mr.J Mrs. Macintosh Murehison Professor and Chairman of the Department of Metallurgical and Materials Engineering and Ph.D. Program Director in the Materials Research Technology Institute at the university of texas at el paso. Dr. Murr received his ***. in physical science from Albright College, and his B.S.E.E. in electronics, his M.S. in engineering mechanics, and his Ph.D. in solidstate science, all from the Pennsylvania State university. Dr. Murr has published 20 books, over 750 scientific and technical articles in a wide range of research areas in materials science and engineering, environmental science and engineering, manufacturing science and engineering （especially rapid prototype/layered manufacturing）,

关键词： Selective laser melting electron beam melting Additive manufacturing Microstructures Microstructural architecture

Effect of sintering temperature on the chemical bonding,electronic structure and electrical transport properties of β-Ga_(1.9)Fe_(0.1)O_(3) compounds

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Journal of Materials Science & Technology 2021年第8期67卷 135-144页

作者： Swadipta Roy C.V.Ramana Center for Advanced Materials Research(CMR) University of Texas at El PasoEl Paso500 W University AveEl PasoTX79968United States

A model system,which is based on iron(Fe)doped gallium oxide(Ga_(2)O_(3))(Ga_(1.9)Fe_(0.1)O_(3)),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the chemistry,local structure and chemical bonding,and electrical transport properties of a wide band gap oxide(Ga_(2)O_(3)).The Ga_(1.9)Fe_(0.1)O_(3) compounds were synthesized using standard high-temperature solid state reaction *** effect of processing conditions in terms of different calcination and sintering environments on the structural and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds is studied in *** characterization by Raman spectroscopy revealed that Ga_(1.9)Fe_(0.1)O_(3) compounds exhibit monoclinic crystal symmetry,which is quite similar to the intrinsic parental crystal structure,though Fedoping induces lattice *** temperature(T_(sint))which was varied in the range of 900-1200℃,has significant impact on the structure,chemical bonding,and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) *** spectroscopic measurements indicate the proper densification of the Ga_(1.9)Fe_(0.1)O_(3) compounds achieved through complete Fe diffusion into the parent Ga_(2)O_(3) lattice which is evident at the highest sintering *** X-ray photoelectron spectroscopy validates the chemical states of the constituent elements in Ga_(1.9)Fe_(0.1)O_(3) *** electrical properties of Ga_(1.9)Fe_(0.1)O_(3) fully controlled by T_(sint),which governed the grain size and microstructural *** temperature and frequency dependent electrical measurements demonstrated the salient features of the Fe doped Ga_(2)O_(3) *** activation energy determined from Arrhenius equation is 0.5 e *** results demonstrate that control over structure,morphology,chemistry and electrical properties of the Ga_(1.9)Fe_(0.1)O_(3) compounds can be achieved by optimizing T_(sint).

关键词： Ga_(2)O_(3)compounds Fe-doping Raman spectroscopy Chemical bonding electrical properties

Evaluation of behaviors of earth and rockfill dams during construction and initial impounding using instrumentation data and numerical modeling

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 709-725页

作者： Mohammad Rashidi S. Mohsen Haeri university of texas at el paso El Paso USA Sharif university of Technology Tehran Iran

In this study,the behavior of Gavoshan dam was evaluated during construction and the first impounding.A two-dimensional（2D） numerical analysis was conducted based on a finite difference method on the largest cross-section of the dam using the results of instrument measurements and back *** evaluations will be completed in the case that back analysis is carried out in order to control the degree of the accuracy and the level of confidence of the measured behavior since each of the measurements could be controlled by comparing it to the result obtained from the numerical *** that,by comparing the results of the numerical analysis with the measured values,it is indicated that there is a proper consistency between these two ***,it was observed that the dam performance was suitable regarding the induced pore water pressure,the pore water pressure ratio r;,settlement,induced stresses,arching degree,and hydraulic fracturing probability during the construction and initial impounding *** results demonstrated that the maximum settlement of the core was 238 cm at the end of *** the following 6 years after construction（initial impounding and exploitation period）,the accumulative settlement of the dam was 270 *** is clear that 88% of the total settlement of the dam took place during dam *** reason is that the clay core was smashed in the wet side,*** optimum moisture *** the average curving ratio was 0.64 during dam construction; at the end of the initial impounding,the maximum amount of curving ratio in the upstream was 0.81,and the minimum（critical） amount in the downstream was *** was also concluded that this dam is safe in comparison with the behaviors of other similar dams in the world.

关键词： Earth and rockfill dams Initial impounding Numerical modeling Instrumentation Settlement Pore pressure

Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

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Journal of Materials Science & Technology 2019年第2期35卷 309-321页

作者： César A.Terrazas Lawrence E.Murr Diego Bermudez Edel Arrieta David A.Roberson Ryan B.Wicker W.M.Keck Center for 3D Innovation The University of Texas at El PasoEl PasoTX 79968USA Department of Mechanical Engineering The University of Texas at El PasoTX 79968USA Department of Metallurgical Materials and Biomedical EngineeringThe University of Texas at El PasoTX 79968USA

A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPBF) additive manufacturing(AM): specifically, the commercial electron beam melting(EBM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm^3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the EPBF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illu

关键词： Hydroxyapatite (HA) Metal-matrix ceramic composites Open-cellular (mesh) structures electron-beam powder bed fusion (EPBF) Additive manufacturing (AM) Mechanical properties Microstructure characterization

Effect of an electron gas on a neutron-rich nuclear pasta

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Nuclear Science and Techniques 2015年第2期26卷 75-82页

作者： Jorge Alberto Lopez Enrique Ramirez-Homs Department of Physics University of Texas at El Paso

We studied the role that electron gas has on the formation of nuclear structures at subsaturation densities and low temperatures(T<1 Me V).Using a classical molecular dynamics model we studied isospin symmetric and as... 详细信息

We studied the role that electron gas has on the formation of nuclear structures at subsaturation densities and low temperatures(Tel we studied isospin symmetric and asymmetric matter at subsaturation densities and low temperatures varying the Coulomb interaction *** effect of such variation was quantified on the fragment size multiplicity,the inter-particle distance,the isospin content of the clusters,the nucleon mobility and cluster persistence,and on the nuclear structure *** found that the presence of an electron gas distributes matter more evenly,disrupts the formation of larger objects,reduces the isospin content,and modifies the nucleon average displacement,but does not affect the inter-nucleon distance in *** nuclear structures are also found to change shapes by different degrees depending on their isospin content,temperature and density.

关键词：电子气体分子动力学模型面食中子相互作用强度核结构同位旋平均位移