Influência da adição de defloculante, ligante e partículas de alumina no comportamento reológico de suspensões a base de frita e caulim

Hotza, Dachamir; Fredel, Márcio C.; Neto, João Batista Rodrigues; Alarcon, Orestes Estevam

doi:10.1590/s0100-40421998000400029

Cited by 3 publications

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“…Por sua vez, a alta concentração de óxidos em suspensão leva a diversos problemas, como alta viscosidade e envelhecimento. Esses problemas de processamento podem ser drasticamente reduzidos com o uso de polieletrólitos como defloculantes 1,2 . Dois polieletrólitos bastante usados são o poliacrilato e o polimetaacrilato de sódio ou amônio [3][4][5][6] .…”

Section: Introductionunclassified

Influência do pH sobre a estabilidade de suspensões de alumina estabilizadas eletroestericamente

Sales¹,

Souza²,

Soledade³

et al. 2007

Quím. Nova

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Recebido em 6/12/05; aceito em 11/4/06; publicado na web em 22/8/06INFLUENCE OF pH ON THE STABILITY OF ALUMINA SUSPENSIONS ELECTROSTERICALLY STABILIZED. In this work, aqueous suspensions of aluminas with different particle sizes were evaluated. The effect of pH on the electrosteric stabilization using PMAA-NH 4 (ammonium polymethacrylate) as deflocculant was studied. The amount of deflocculant was optimized and rheologic properties were determined at four different pH values. Sedimentation was also evaluated. For suspensions with pH 4, an electrostatic mechanism of stabilization was observed, probably due to a flat adsorption of PMMA -on the alumina surface, leading to a small efficiency in relation to steric stabilization. For a suspension with pH 12, the steric mechanism of stabilization prevails. Suspensions with pH 7 and 9 present a higher flocculation degree. In relation to particle size, A-1000 samples present a smaller particle size, leading to a smaller interparticle distance (IPS), making stabilization more difficult.Keywords: pH; polymethylmethacrylate; alumina. INTRODUÇÃONo processamento de materiais cerâmicos, a maior parte dos processos de fabricação envolve, em pelo menos uma de suas etapas, um sistema líquido -partícula. Por sua vez, a alta concentração de óxidos em suspensão leva a diversos problemas, como alta viscosidade e envelhecimento. Esses problemas de processamento podem ser drasticamente reduzidos com o uso de polieletrólitos como defloculantes 1,2 . Dois polieletrólitos bastante usados são o poliacrilato e o polimetaacrilato de sódio ou amônio [3][4][5][6] . As reações de dissociação do PMAA-NH 4 são as seguintesO PMAA -pode adsorver na superfície da alumina, reduzindo seu potencial de superfície e alterando o pH da suspensão, até um ponto de saturação. Neste ponto, o polímero em solução engloba toda a partícula até atingir o ponto em que fica em solução, sendo que, neste momento, a suspensão tende a aumentar sua força iônica 8 . Um aspecto importante é a conformação do PMAA. Diversos trabalhos mostram que o pH controla o sinal e a densidade de carga na superfície, e o grau de dissociação e deformação do polieletrólito livre na suspensão 3,4,6,9 . Segundo Biggs e Healy 10 , a conformação adotada pelo polímero na interface será determinada primeiramente pela afinidade da ligação polímero-superfície e pela repulsão polímero-polímero. Em pH ácido, o polieletrólito adsorve na conformação plana, devido à ausência de carga na cadeia polimérica. De acordo com Saravanan e Subramanian, este processo ocorre com a formação de uma ligação de hidrogênio 4 . Por sua vez, a superfície da alumina está positivamente carregada e o mecanismo de estabilização é principalmente eletrostático. Com o aumento do pH, a conformação estendida predomina, devido à carga negativa ao longo da cadeia, levando a uma repulsão. A superfície também está negativamente carregada, de modo que a adsorção ocorre em alguns pontos de defeitos na superfície. Dessa forma, há um aumento da espessura da camada absorvente, havendo est...

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Section: Introductionunclassified

Influência do pH sobre a estabilidade de suspensões de alumina estabilizadas eletroestericamente

Sales¹,

Souza²,

Soledade³

et al. 2007

Quím. Nova

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“…At the end of this period, it was noticed the suspension inside the jar was more viscous than desired. Following, more 100 ml of isopropyl alcohol and 0.02% of PVB were added in order to decrease the shear stress and thus optimize the milling process (HOTZA et al, 1998). A sample of the obtained suspension was removed for particle size characterization.…”

Section: Biosilicate® Millingmentioning

confidence: 99%

Biocompósitos eletrofiados e microfabricação 3D em engenharia do tecido ósseo

Bellani¹

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Bone tissue regeneration is still an important challenge in orthopedics and traumatology.Despite the natural ability of bone repair, a trauma beyond the critical limit (critical fracture) cannot be regenerated. Tissue Engineering is a multidisciplinary field that applies the principles of engineering and biological sciences to the development of biological substitutes that restore, maintain or improve the tissue function or of an organ as a whole. The aim of this work was to develop osteogenic and mechanically improved biomimetic scaffolds for bone tissue engineering; to improve the vascularization of a bone tissue engineered implant by the design and development of a suturable vessel graft embedded in hydrogels for 3D biofabrication. Biodegradable PCL membranes for guided bone regeneration, obtained by electrospinning, reinforced with various ratios of natural nanocomposites obtained from cellulose nanocrystals (CNCs) were produced.Results showed an improvement of mechanical properties, in the degree of crystallinity and in the melting temperature according to the ratio of cellulose nanocrystals. I employed Biosilicate® as bioactive phase into these membranes. The Biosilicate®, combined with the cellulose nanocrystals, considerably improved their mechanical properties. Osteoblasts were able to proliferate and biomineralize in these membranes. Thus, a biomimetic and biodegradable membranes, with osteogenicity and improved mechanical properties for guided bone regeneration and bone tissue engineering were developed. In order to improve the vascularization of bone tissue engineering constructs, new GelMA-CNC composites were developed. Cell-laden GelMA-CNC hydrogels with endothelial cells were biofabricated. Endothelial cells were able sprout and to organize in tubules. As rapid vascularization strategy, a rapid degrading biomimetic suturable graft obtained from electrospun membranes fusing, in order to allow endothelial cell migration from the vascular graft to the bone-like grafts and, following, new capillary formation, was manufactured. A porous pattern over the suturable grafts was fabricated by laser micromachining.The obtained elastic scaffolds were suturable and supported stress and recoil. The scaffolds are autoclavable and possess no in vitro toxicity. The porous patterned created on the suturable grafts allowed the endothelial cell towards the 3D culture of osteoblasts in GelMA, and 3D structures formed from the interaction of endothelial cells and osteoblasts were observed. Therefore, this strategy can potentially be employed to enhance the size and the survival biofabricated bone implants, accelerating the clinical translation of bone tissue engineering.

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Rheological Study of Iron Oxide Reinforced by Ceramic Nanoparticles

Vieira

Neto

Hotza

2012

MSF

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The aim of this work is to produce a stable suspension of iron oxide reinforced by different ceramic nanoparticles like SiO2, TiO2. Measurements of mean particle size, zeta potential and flow curves have been done. Additionally deflocculation curves and sedimentation were drawn to complement the study. The results showed that nanoparticles helped suspensions to maintain a deflocculated stable condition for longer periods of time.

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Influência da adição de defloculante, ligante e partículas de alumina no comportamento reológico de suspensões a base de frita e caulim

Cited by 3 publications

References 0 publications

Influência do pH sobre a estabilidade de suspensões de alumina estabilizadas eletroestericamente

Influência do pH sobre a estabilidade de suspensões de alumina estabilizadas eletroestericamente

Biocompósitos eletrofiados e microfabricação 3D em engenharia do tecido ósseo

Rheological Study of Iron Oxide Reinforced by Ceramic Nanoparticles

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