Structure and the physical and mechanical properties of dental hybrid composite materials
Struktura i fizičko-mehanička svojstva stomatoloških hibridnih kompozitnih materijala
Докторанд
Ben Hassan, Somaya AhmedМентор
Aleksić, RadoslavЧланови комисије
Uskoković, PetarRadojević, Vesna
Jančić-Heinemann, Radmila
Obradović Đuričić, Kosovka
Метаподаци
Приказ свих података о дисертацијиСажетак
Kompoziti sa dodatkom nanočestica pokazuju poboljšanje mehaničkih svojstava.
PMMA polimer korišćen je kao matrica u kombinaciji sa dva različita ojačanja, koja
imaju izrazito različite oblike, kada su dodati u kompozit. Ojačanja napravljena od
aluminijum oksidnih čestica imaju sferičan oblik a viskersi imaju odnos dužina prema
prečniku od 200. Uticaj veličine čestica, njihov oblik i udeo, na mehanička svojstva
proučavani su pomoću nanoindentacionih merenja i dinamičko-mehaničke analize.
Utvrdjeno je da i ćestice i viskersi poboljšavaju mehanićka svojstva, ali poboljšanje je
mnogo više izraženo u slučaju viskersa. Koncentracija ojačavajućih čestica varira do 5
mas. %. Najbolja svojstva dobijena su sa dodatkom 3 mas. % viskersa u pogledu
mehaničkih svojstava dobijenog kompozita.
U disertaciji su prikazani rezultati istraživanja uticaja procesnih parametara
elektropredenja na uniformnost, morfologiju i sastav nanokompozitnih vlakana u obliku
mata (PVB/Sep). Suspenzija sepiolita ima tiksot...ropna svojstva zbog svoje vlaknaste
prirode, velike specifićne površine i prisustva silanolnih grupa na površini.
Funkcionalizacija sepiolitnih vlakana uradjena je u vodenom tiksotropnom gel stanju
korišćenjem silana kao vezivnog agensa. Ispitano je ponašanje pri elektropredenju
suspenzije tri različite koncentracije sepiolita (3 mas. %, 30 mas. % i 59 mas. %) u
rastvoru PVB u etanolu sa i bez modifikacije silanima vlakana sepiolita. Utvrdjeno je da
pod istim uslovima kompozitna vlakna PVB/Sep imaju nižu vrednost srednjeg prečnika
vlakana nego čista PVB vlakna. Optimalni uslovi dobijanja najravnomernijih
nanokompozitnih vlakana se postižu pri protoku suspenzije od 0,5 mL/h, rastojanju
dizne od kolektora 15 cm i naponu od 24 kV.
Composites with the addition of alumina nanofillers show improvement in mechanical
properties. The PMMA polymer was used as a matrix and two different types of
nanofillers, added as reinforcement in the matrix, having extremely different shapes
were added to form the composite. Reinforcements were made of alumina spherical
nanoparticles having spherical shape and whiskers having the length to diameter ratio of
200. The influence of alumina fillers size, shape and fillers loading on mechanical
properties of obtained composite were studied using the nanoindentation measurements
and dynamic mechanical analysis. It was observed that both alumina whiskers and
alumina spherical nanoparticles added in the PMMA matrix improved the mechanical
properties of obtained composite samples but the improvement was significantly higher
with alumina whisker reinforcement. The concentration of the reinforcing alumina
spherical nanoparticles and alumina whiskers in PMMA matrix varied up to 5 wt. %.
The bes...t performance was obtained by the addition of 3 wt. % of alumina whiskers in
the PMMA matrix with regard to mechanical properties of the obtained composite.
This study presents investigation of processing conditions on the uniformity,
morphology and structure of patterned nanofibrous mats for poly (vinyl
butyral)/sepiolite (PVB/Sep) nanocomposite fibers obtained by electrospinning process.
Sepiolite aqueous suspensions show a thixotropic behavior because of their fibrous
structure, porosity, large specific surface area and the presence of silanol groups on the
surface. Functionalization of the sepiolite fibers in aqueous thixotropic gel was made on
the surface of individual fibers using amino silanes as coupling agents. Different
contents (3 wt. %, 30 wt. % and 50 wt. %) of neat and modified sepiolite fibers were
dispersed by ultrasonic irradiation in the solution of PVB in ethanol and were used to
obtain nanocomposite fibers by electrospinning. The PVB/Sep nanocomposite fibers
showed lower mean fiber diameter than of the neat PVB fibers. Uniform nanofibers
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were obtained using the lower flow rate (0.5 mL/h), high collector distance (15 cm) and
a constant applied voltage of 24 kV.