Joaquı́n Lira-Olivares

• AB, MA, MS, PhD, HD
• Professor Emeritus at Simón Bolívar University

Glasses in the Fe2O3–SiO2–CaO system are potential candidates for many technological applications due to their ferrimagnetic and semiconductive properties, which have been extensively studied; in this sense, the effect of adding different melting additives like Li2O, B2O3, in this glass system on frits and glazes with 30–40 mass-% of Fe2O3 was stud...

This work studied the microstructure and tribological behavior of Al 2O3/TiO2/ZrO2 nanocomposites to be used in hip joint replacements. To increase the fracture toughness of alumina and enhance the tribological properties, nanometer sized particles of TiO 2 and ZrO2 were added. The specimens contained 10 mol% of TiO2, different percentages of ZrO2...

The Center for Surface Engineering was conceived with the idea of conducting research in the area of materials aimed at industrial applications and also dedicated to the promotion of young talents by providing tools and links to the achievement of their specialized training, both functions with the ultimate aim of contributing to national developme...

In this study, different frit compositions were prepared in the SiO 2-CaO-Fe 2O 3 system. The amounts of Fe 2O 3 were varied between 10 mass-% and 40 mass-%. The frits were melted and characterized using several different techniques in order to study the crystalline composition of the frits and glazes and assess their suitability for tile productio...

Collagen type I was obtained from rat tail tendons using a H3PO4, the direct nucleation of inorganic phase (hydroxyapatite- HA) inside collagen fibers consist of a neutralization synthesiswith an aqueous suspension of Ca(OH)2 until a hydrogel was formed. After 1 week of drying at 50�C a white dust was obtained, Genipin was added as a crosslinked ag...

A treatment study evaluates glass and glass-ceramics of the Na2O center dot CaO center dot K2O center dot MgO center dot SiO2 center dot P2O5 system, modified with B2O3, Al2O3 or B2O3/Al2O3 up to 0.66. Both, bioactivity using simulated body fluid (SBF) immersion and mineral nodule formation using calvaria derived osteoblasts, were tested. The surfa...

A treatment study evaluates glass and glass-ceramics of the Na2O·CaO·K2O·MgO· SiO2·P2O5 system, modified with B2O3, Al2O3 or B2O3/Al2O3 up to 0.66. Both, bioactivity using simulated body fluid (SBF) immersion and mineral nodule formation using calvaria derived osteoblasts, were tested. The surface structure changes were examined by SEM-EDX line sca...

Bone tissue is characterized by its mineral structure, showing unique properties as mechanical resistance, toughness and elasticity. These are due to its composite nature of collagen (the most important constituent protein in the bone matrix), with hydroxyapatite crystals. The place of collagen in the organization and growth promotion of mineral bo...

Bone is the only tissue able to undergo spontaneous regeneration and to remodel its micro and macro-structure (Wolf’s law, 1862). This is accomplished through a delicate balance between bone formation (osteogenesis) and bone degradation (osteoclastogenesis) (Brighton, 1984) -See figure A-. Nevertheless the piezoelectric characteristics of the bone...

Removal of fine particles from some gas-product effluents from motors and industries, using filters, is an important subject in the field of public health and environment. In the present work, a porous silicon filter was produced, which is able to capture most of the particles undesirable for the environment (transported by gases), larger than the...

Yasuda was the fisrt

Bone healing and growth are controlled by the rate of deposition of hydroxyapatite (HA). This process have been so far accredited to the work of osteoblasts, which are attracted by the electrical dipoles produced either by piezo-electricity, due to deformation of the bone, specially the colla-gen in it, or due to outside electrical stimuli. The mai...

The brittleness of ceramics has been their weak spot when considering them for total hip replacements. There are several situations from which concentrated stresses can develop and induce failure of the components. It is not a problem of the material’s properties in particular but also its design. This means that even proof tested-third generation-...

In the present work, we have studied the effect of the piezoelectricity of elastically deformed cortical bone collagen on surface using a biomimetic approach. The mineralization process induced as a consequence of the piezoelectricity effect was evaluated using scanning electron microscopy (SEM), thermally stimulated depolarization current (TSDC),...

Bone healing and growth are controlled by the rate of deposition of hydroxyapatite (HA). This process have been so far accredited to the work of osteoblasts, which are attracted by the electrical dipoles produced either by piezoelectricity, due to deformation of the bone, specially the collagen in it or due to outside electrical stimuli.The main pu...

Bone healing and growth are controlled by the rate of deposition of hidroxiapatite (HA). This process have been so far accredited to the work of osteoblasts, which are attracted by the electrical dipoles produced either by piezoelectricity, due to deformation of the bone, specially the collagen in it, or due to outside electrical stimuli. The prese...

Bone healing and growth are controlled by the rate of deposition of hydroxyapatite (HA). This process have been so far accredited to the work of osteoblasts, which are attracted by the electrical dipoles produced either by piezoelectricity, due to deformation of the bone, specially the collagen in it, or due to outside electrical stimuli. The main...

This work studied the microstructure and tribological behavior of Al 2O3/TiO2/ZrO2 nanocomposites to be used in hip joint replacements. To increase the fracture toughness of alumina and enhance the tribological properties, nanometer sized particles of TiO 2 and ZrO2 were added. The specimens contained 10 mol% of TiO2, different percentages of ZrO2(...

Numerical simulations based on Finite Element Analysis (FEA) are widely used to predict and evaluate the forming parameters before performing the physical processes. In the sheet metal industry, there are basically two types of FE programs: the inverse (one-step) programs and the incremental programs. In the present paper, the forming process of th...

Alumina ceramics as well as zirconia ceramics have been used to manufacture hip replacement components since the 1990's. These materials have been used for the ceramic balls and cups in the replacements for the following reasons: in the case of alumina for its excellent wear behavior; and in the case of zirconia, for its good wear behavior but with...

This work studied the microstructure and tribological behavior of Al2O3/TiO2/ZrO2 nanocomposites to be used in hip joint replacements. To increase the fracture toughness of alumina and enhance the tribological properties, nanometer sized particles of TiO2 and ZrO2 were added. The specimens contained 10 mol% of TiO2, different percentages of ZrO2 (0...

Microstructure and mechanical properties of Al2O 3-TÍO2-SÍC nanocomposites were studied. To improve the mechanical and tribological properties of alumina, nano-sized TiO2 and SiC powders were dispersed. Spark Plasma Sintering (SPS) technique, at 1400°C, 50 MPa for 5 minutes, was applied for the densification of Al 2O3-TiO2-SiC nanocomposites. Chara...

The Basel Convention (1989) and Rio Summit (1992) were two major instances to tackle with the main issues on Hazardous Waste. The first one is the mechanism to control the illegal traffic of hazardous waste, and to promote an Environmental Sound Management for the overall waste cycle. On the other hand, Rio Summit launched a renewed interest on reg...

One of the most revolutionary trends of the past four decades should be named the innovative use of specials ceramics designed to reproduce different function of living organisms. Ceramics used for these purposes are defined as bioceramics. In this category we find bioactive glasses of SiO2.Na2O.CaO.K2O.MgO.P2O5 system that show the capacity of che...

Se ha estudiado la factibilidad de la formación de recubrimientos protectores de aluminio por deposición química en fase vapor por reactor de lecho fluidizado (CVD-FBR) sobre la aleación de titanio Ti-15Mo-3Al. Antes de realizar los experimentos, se utilizaron los cálculos termoquímicos del sistema usando el método de minimización de energía libre...

Total hip joint replacement is the major achievement in orthopedic surgery; zirconia and alumina have been widely used in the medical field due to their biocompatibility, excellent corrosion resistance, low friction, high wear resistance, high strength, and low cost. Fracture toughness of alumina is enhanced with dispersion of nanometer sized parti...

A recovery system for silver in the plating rinse waters using electrowinning process was developed. The target of this work was checking the system characteristics and recovery capacity, as well as determining the best combination of equipment parameters that allows a good silver recovery efficiency. The equipment function parameters are current (...

In the production of uniaxially pressed components, the powder size, distribution and pressure used are key factors to obtain a high quality product. Several models have been reported to correlate the packing and sintered densities as a function of the compaction pressure but, most of them for spherical-like and wide particle size distributions, In...

Two new techniques that have proved useful in preparation of field ion microscope specimens are described. These techniques allow for continuous microscopic observation of the electrochemical etching process, even when nontransparent electrolytes are utilized.

Composite precursor powders for liquid phase sintering were obtained by coating WC and VC particles. The Ni–B coating was deposited onto the carbide nucleus by electroless processes in alkaline and acid bath, both based on nickel chloride. In order to observe structural modifications, the composite powders were heated in an argon atmosphere, during...

Introduction, Definition of Pore, Fractal Geometry and Porosity, Polarization and Dielectric Permittivity, Dielectric Permittivity of a Mixture, Sample Preparation and Dielectric Properties, Measurements, Experimental Results, Conclusions

The paper asks whether recent debates in Britain concerning the compact city have fully explored the relevant issues, including crucial questions of the environmental benefits accruing to compaction, and its acceptability to local communities. Major doubts are raised about the economic, political and technical dimensions of compaction and particula...

Electroless deposition is a very simple process which can be used to obtain amorphous metallic coatings of uniform thickness on metallic or non-metallic substrates. In this work, nickel-boron coatings were deposited by electroless plating on WC and VC powders and sintered substrates. Two electrolyte solutions for the deposition of Ni-B coatings wer...

Zirconia coatings were obtained with the spray pyrolysis process, using a precursor solution of zirconium n-propoxide in 1-propanol. An investigation was undertaken into the influence of carrier gas (air, He, N2 and Ar), temperature (450 and 600 °C), time (1 and 2 h) and substrate composition (borosilicate glass, alumina, stainless steel and carbon...

Nickel alloy matrix/dispersed carbide (VC, NbC, WC) composites were prepared by either flame-spray, liquid phase sintering, or solid state sintering. A commercial Ni-B-Si alloy was mixed with 15% vol. of carbide particles and used to prepare composite coatings by flame-spray, bulk composite materials by solid state sintering (below 1045C) or liquid...

Ni-based alloys containing low amounts of boron and silicon, reinforced with hard carbides, are extensively used for wear-resistant coatings. A powdered alloy of NiBSi and two of NiCrBSi (with 10.5 and 15 wt.% Cr, respectively) were mixed with VC and WC in proportions of 15 and 50 vol.% and then processed by either thermal spraying or liquid phase...

Sol-gel aluminosilicate coatings were deposited on a carbon steel substrate. Three application methods were compared: wet deposition techniques as dipping and spraying of the sol and xerogel thermal spraying with flame torch. Characterization by X-ray diffraction and scanning electron microscopy shows that amorphous thick coatings (> 5 μm) were obt...

The wear and corrosion of carbon steel parts can be reduced by-coating them with an appropriate alloy. It would be even more desirable to design a cermet with toughness imparted by the metal matrix and hardness or strength by the ceramic reinforcement thus more closely approximating the industrial requirement for the sintered or coated parts. Inves...

Four types of nichrome-WC sprayed coatings (85%, 55%, 15% and 5% WC) were studied by means of Falex dry friction and wear tests. Significant sudden drops in the friction force were recorded; from the morphological study of the worn surfaces it was determined that these friction force variations correspond to the removal of WC particles. This interp...

The electron emission from cold, NI4W specimens was studied using a field ion-field emission microscope and a Jarrell-Ash recording microphotometer. Small current variations were observed on azimuthal intensity measurements on the alpha phase. These were interpreted as produced by different densities of solute at the surface of the emitter. The ele...

RESUMEN En este trabajo se presenta preliminarmente un prototipo de implante intervertebral para ser usado en sustitución total del mismo, constituido en base a dos materiales comerciales biotolerables, como son el caso de la hidroxiapatita porosa, aprovechando sus propiedad osteoconductora, propiedades químicas, físicas y mecánicas similares al hu...