RESUMO
With the aim of introducing permanent prostheses with main properties equivalent to cortical human bone, Ti-diamond composites were processed through powder metallurgy. Grade 1 titanium and mixtures of Ti powder with 2%, 5% and 10 wt% diamond were compacted at 100MPa, and then sintered at 1250°C/2hr/10-6mbar. Sintered samples were studied in the point of view of their microstructures, structures, yield strength and elastic modulus. The results showed that the best addition of diamonds was 2 wt%, which led to a uniform porosity, yield strength of 370MPa and elastic modulus of 13.9 GPa. Samples of Ti and Ti-2% diamond were subjected to in vitro cytotoxicity test, using cultures of VERO cells, and it resulted in a biocompatible and nontoxic composite material.
Assuntos
Materiais Biocompatíveis/análise , Diamante/análise , Teste de Materiais/métodos , Titânio/análise , Animais , Chlorocebus aethiops , Humanos , Porosidade , Propriedades de Superfície , Resistência à Tração , Células VeroRESUMO
ABSTRACT With the aim of introducing permanent prostheses with main properties equivalent to cortical human bone, Ti-diamond composites were processed through powder metallurgy. Grade 1 titanium and mixtures of Ti powder with 2%, 5% and 10 wt% diamond were compacted at 100MPa, and then sintered at 1250°C/2hr/10-6mbar. Sintered samples were studied in the point of view of their microstructures, structures, yield strength and elastic modulus. The results showed that the best addition of diamonds was 2 wt%, which led to a uniform porosity, yield strength of 370MPa and elastic modulus of 13.9 GPa. Samples of Ti and Ti-2% diamond were subjected to in vitro cytotoxicity test, using cultures of VERO cells, and it resulted in a biocompatible and nontoxic composite material.
Assuntos
Humanos , Animais , Titânio/análise , Materiais Biocompatíveis/análise , Teste de Materiais/métodos , Diamante/análise , Propriedades de Superfície , Resistência à Tração , Células Vero , Chlorocebus aethiops , PorosidadeRESUMO
A CVD based radiation detector has recently become commercially available from the manufacturer PTW-Freiburg (Germany). This detector has a sensitive volume of 0.004 mm(3), a nominal sensitivity of 1 nC Gy(-1) and operates at 0 V. Unlike natural diamond based detectors, the CVD diamond detector reports a low dose rate dependence. The dosimetric properties investigated in this work were dose rate, angular dependence and detector sensitivity and linearity. Also, percentage depth dose, off-axis dose profiles and total scatter ratios were measured and compared against equivalent measurements performed with a stereotactic diode. A Monte Carlo simulation was carried out to estimate the CVD small beam correction factors for a 6 MV photon beam. The small beam correction factors were compared with those obtained from stereotactic diode and ionization chambers in the same irradiation conditions The experimental measurements were performed in 6 and 15 MV photon beams with the following square field sizes: 10 × 10, 5 × 5, 4 × 4, 3 × 3, 2 × 2, 1.5 × 1.5, 1 × 1 and 0.5 × 0.5 cm. The CVD detector showed an excellent signal stability (<0.2%) and linearity, negligible dose rate dependence (<0.2%) and lower response angular dependence. The percentage depth dose and off-axis dose profiles measurements were comparable (within 1%) to the measurements performed with ionization chamber and diode in both conventional and small radiotherapy beams. For the 0.5 × 0.5 cm, the measurements performed with the CVD detector showed a partial volume effect for all the dosimetric quantities measured. The Monte Carlo simulation showed that the small beam correction factors were close to unity (within 1.0%) for field sizes ≥1 cm. The synthetic diamond detector had high linearity, low angular and negligible dose rate dependence, and its response was energy independent within 1% for field sizes from 1.0 to 5.0 cm. This work provides new data showing the performance of the CVD detector compared against a high spatial resolution diode. It also presents a comparison of the CVD small beam correction factors with those of diode and ionization chamber for a 6 MV photon beam.
Assuntos
Diamante/análise , Diamante/química , Fótons/uso terapêutico , Radiometria/instrumentação , Radiometria/métodos , Radioterapia/instrumentação , Radioterapia/métodos , Humanos , Método de Monte Carlo , Aceleradores de PartículasRESUMO
Foi utilizado um método inédito para a avaliaçäo do desempenho (tempo de vida útil) de pontas diamantadas, especialmente confeccionadas com 8 tipos de gräos (naturais e sintéticos), cortando-se substrato constituído por vidro, o qual era movimentado contra a ponta em açäo. Estabelecida uma série de necessárias condiçöes operatórias, os valores de tensäo e corrente elétrica no motor da caneta (a qual prendia a ponta em ensaio) eram basicamente transferidos para um microcomputador, onde em tempo real era calculado o valor da respectiva força tangencial de corte, através de um programa de computaçäo especialmente desenvolvido, o qual efetuava uma série de cálculos matemáticos, criando gráficos e mantendo o registro de todos os valores verificados. Nas condiçöes estabelecidas, em ordem decrescente de magnitude da vida útil, os gräos de diamante avaliados assim se comportaram: PDA 433, DMB-T, DMB-G, PDA 555, PDA 665, PDA 768, TED-II e PDA 878