Structure, phase content and mechanical properties of aluminium with hard particles after shock-wave compaction

The possibilities to combine metal and metal oxide powders in various compositions open a broad range of mechanical and thermal behavior. When using in nanostructured components the resulting materials might exhibit even more interesting properties, like product effectiveness, tensile strength, wear resistance, endurance and corrosion resistance. Intermetallics like TiAl could be obtained as TiAlx in a quality similar to that obtained from melting where only eutectic mixture can be produced. Similar effects are possible when compacting nanoceramic powders whereas these can be combined with intermetallics. Currently, it is very difficult to produce wires and special shaped parts from high temperature superconducting materials. The compacting by explosives could solve this problem.The present paper uses explosion compacting of Al nanoparticles to create nanocomposite with increased physico-mechanical properties. Russian civil explosive Uglenit was chosen as high energy material (HEM) for shock-wave compaction. The different schemes and conditions were suggested to run the explosion process. Al nanoparticles as produced by electric wire explosion contain 8-10% of aluminum oxide. That aluminum oxide can serve as strengthening material in the final nanocomposite which may be generated in various compositions by explosive compacting. Further modifications of nanocomposites were obtained when including nanodiamonds into the mixture with aluminum nanoparticles with different percentages. The addition of nanodiamonds results in a substantial strengthening effect

Influence of static tensile testing on the deformation behavior of Al–4% Cu alloy containing micro- and nanoparticles

At present, aluminum alloys reinforced with nonmetallic particles are of great interest in various fields of science and technology due to their high specific strength, hardness, wear resistance, and other properties. At the same time there is a great interest in the study of processes occurring during plastic deformation of such materials under static tensile loading. Plastic flow of metals occurs through the creation and movement of linear defects (dislocations), in which there is a phenomenon of discontinuous yielding. An introduction of particles into aluminum alloy promotes a considerable increase of stiffness and specific strength of alloys, and the study of the deformation behavior of such alloys is of great interest. The objective of this research is to analyze mechanical properties and the deformation behavior of aluminum alloy with the identification of mechanisms of plastic deformation when introducing solid nonmetallic micro- and nanoparticles into the soft aluminum matrix. An analysis of the microstructure of the obtained alloys shows that the introduction of particles (Al2O3, TiB2, TiC) leads to a reduction of the alloy grain size from 350 to 170 µm while residual porosity does not exceed 2%. Tensile tests performed show that the change in the type and quantity of particles also changes characteristics of discontinuous yielding, thus resulting in an increase of yield strength (from 18 to 40 MPa), reduction of ductility (from 15 to 2%), and moreover a significant increase of tensile strength (from 77 to 130 MPa), as compared to the initial Al–4 wt % Cu alloy

Damage formation, fatigue behavior and strength properties of ZrO[2]-based ceramics

It is suggested that a non-destructive testing technique using a three-dimensional X-raytomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO[2]-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical propertiesof the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{5} stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material

Damage formation, fatigue behavior and strength properties of ZrO[2]-based ceramics

It is suggested that a non-destructive testing technique using a three-dimensional X-raytomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO[2]-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical propertiesof the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{5} stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material

A study of the influence of soft particle size and concentration on strength and strain properties of ceramic composites

In the paper a theoretical study of the influence of particle distribution of soft inclusions-agglomerates in a ceramic composite sample on its strength and deformation characteristics was carried out. A movable cellular automaton method was used to simulate a uniaxial compression test of two-dimensional rectangle composite samples. It was found that the average size of inclusions agglomerate-while maintaining the volume fraction of the particles of the soft phase has little effect on the strength and deformation properties of the simulated samples. The simulation results can help to understand the mechanical properties of such objects within any generalized model

Numerical simulation of mechanical behaviour and prediction of effective properties of metal matrix composites with consideration for structural evolution under shock wave loading

Mechanical behaviour of stochastic metal-ceramic composite materials under shock wave loading was numerically simulated on mesoscopic scale level. Deformation of mesoscopic volumes of composites whose structure consisted of a metal matrix and randomly distributed ceramic inclusions was simulated. The results of numerical simulation were used for numerical evaluation of effective elastic and strength properties of metal-ceramic materials with different values of volume concentration of ceramic inclusions. The values of the effective mechanical characteristics of investigated materials were obtained, and the character of the dependence of the effective elastic and strength properties on the structure of composites was determined. It is shown that the dependence of the values of the effective elastic moduli on the volume concentration of ceramic inclusions is nonlinear and monotonically increasing. The values of the effective elastic limits increase with increasing concentration of the inclusions, however, for the considered composites, this dependence is not monotonic

Rheology and porosity effect on the proliferation of preosteoblast on zirconia ceramics

It has been studied ZrO2(MexOy) based porous ceramics, obtained from the powders consisting of hollow spherical particles. It was shown that the structure is represented as a cellular carcass with a bimodal porosity, formed of a large pore close to a spherical shape and the pores that were not filled with the powder particles during the compaction. For such ceramics the increase of pore volume is accompanied by an increase in strain in an elastic area. It was also shown that the porous ZrO2 ceramics had no acute or chronic cytotoxicity. At the same time, ceramics possess the osteoconductive properties: adhesion support, spreading, proliferation and osteogenic differentiation of MSCs

Comorbidades psiquiátricas em adolescentes internados com transtorno de uso de substâncias

Orientador: Prof. Dr. Gustavo Manoel S. DóriaDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências da Saúde, Programa de Pós-Graduação em Saúde da Criança e do Adolescente. Defesa : Curitiba, 25/11/2016Inclui referências: p. 74-88Resumo: O objetivo desse estudo é avaliar as comorbidades psiquiátricas em adolescentes com Transtorno de Uso de Substâncias (TUS) internados na cidade de Curitiba. O abuso de substâncias e a presença de comorbidades psiquiátricas na adolescência, aumenta o comportamento disfuncional do adolescente, o coloca em riscos (evasão escolar, gestações indesejadas, criminalidade, homicídio, suicídio), chegando a ser um problema de saúde pública. O TUS na adolescência se tornou um grande problema social e de saúde. A idade da primeira experimentação tem diminuido e a precocidade do uso aumenta o risco para desenvolver dependência e outros transtornos psiquiátricos. Espera-se que grande parte dos adolescentes dependentes de substâncias apresentem comorbidades psiquiátricas. A versão brasileira do Schedule for Affective Disorders and Schizophrenia for School Aged-Children (K-SADS-PL) foi aplicada a 35 adolescentes do sexo masculino que foram hospitalizados por TUS na cidade de Curitiba. Verificou-se que 92% dos adolescentes tinham alguma comorbidade psiquiátrica. As comorbidades mais frequentemente observadas foram o Transtorno de Conduta (TC) (57,1%), Transtorno de Déficit de Atenção e Hiperatividade (TDAH) (48,6%) e Transtorno opositor desafiante (TOD) (40,0%). A maconha (94,2%) e o crack (40,0%) foram as principais substâncias utilizadas pelos adolescentes. O uso de maconha esteve mais frequentemente associada a efeitos negativos sobre o comportamento e vida dos adolescentes. É de extrema importância avaliar os fatores que podem prevenir a progressão de um transtorno e/ou comorbidade para diminuir os prejuízos do desenvolvimento do adolescente e o custo gerado para o tratamento tardio. Desta forma, é necessária a implantação de serviços que atendam essa população. Palavras-chave: Transtornos Relacionados ao Uso de Substâncias. Psiquiatria Infantil. Psiquiatria do Adolescente. Transtornos Mentais.Abstract: The aim of this study is to evaluate psychiatric comorbidity in hospitalized adolescents with Substance Use Disorder (SUD) in the city of Curitiba. Substance abuse and the presence of psychiatric comorbidities in adolescence increases the dysfunctional behavior, puts him at risk (school dropout, unexpected pregnancies, criminality, homicide, suicide), becoming a public health problem. Substance Use Disorder in adolescence has become an important social and health problem. The age of first experimentation has decreased and the precocity of use increases the risk for dependence and other psychiatric disorders.It is expected that most of the adolescents with substance dependence have psychiatric comorbidities. The Brazilian version of the Schedule for Affective Disorders and Schizophrenia for School Aged-Children (K-SADS-PL) was applied to 35 male adolescents with SUD who were hospitalized in the city of Curitiba. It was found that 92% of adolescents had some psychiatric comorbidity. The most frequent comorbidities among adolescents of this present study were Conduct disorder (CD) (57.1%), Attention deficit hyperactivity disorder (ADHD) (48.6%) and Oppositional defiant disorder (ODD) (40.0%). Marijuana (94.2%) and crack (40.0) were the main substances used by adolescents. The use of marijuana was the most frequently associated with negative effects on the behavior and lives of adolescents. It is very important to assess the factors that can prevent the natural progression of a disorder and/or comorbidity to reduce the impairment of the adolescent development and the cost for late treatment. Thus, the development of services that support this population is needed. Keyword: Substance-Related Disorders. Child Psychiatry. Adolescent Psychiatry. Mental Disorders

Microstructure, mechanical properties and machining performance of hot-pressed Al[2]O[3]-ZrO[2]-TiC composites

The effect of adding nanocrystalline ZrO[2] and submicron TiC to ultrafine Al[2]O[3] on mechanical properties and the microstructure of the composites developed by hot pressing was investigated. It was shown that by means of hot pressing in an argon atmosphere at a sintering temperature of 1500 °С one can obtain the composites Al[2]O[3] - ZrO[2] - TiC with a fine structure and minimal porosity. It has been shown that in material a multi-scale hierarchical structure is formed, which possesses high physical and mechanical properties: the hardness and fracture toughness was 21.5 GPa and 5.2 MPa*m{1/2} respectively, the modulus of elasticity was 500 GPa and bending strength was 390 MPa. Tests on composites' cutting properties were carried out on interrupted cutting of hardened steel. All samples had wear of the cutting edge in the form of chips of the grain rear working surface of the tool, but the cutting tool which was made by Al2O3 - 10% ZrO2 - 10% TiC had a minimum width of wear