Ultrasonic synthesis of graphene via graphite exfoliation is the most reliable and advantageous method to produce high-quality graphene sheets on industrial scale. Hielscher high-performance ultrasonic processors are precisely controllable and can generate very high amplitudes in 24/7 operation. This allows to prepare high volumes of pristine graphene in a facile and size-controllable way.

Ultrazvučno Priprema grafena

Kako su poznate izuzetne karakteristike grafita, razvijene su nekoliko metoda za njegovu pripremu. Pored hemijske proizvodnje grafena iz grafena oksida u višestepenim procesima, za koje su potrebni veoma jaki oksidanti i reducirajući agensi. Pored toga, grafen pripremljen pod ovim oštrim hemijskim uslovima često sadrži i veliku količinu defekata čak i nakon smanjenja u poređenju sa grafenima dobijenim iz drugih metoda. Međutim, ultrazvuk je dokazana alternativa za proizvodnju visokokvalitetnog grafena, takođe u velikim količinama. Istraživači su razvili nešto drugačije načine korišćenja ultrazvuka, ali uopšte grafena je jednostavan proces u jednom koraku.

Sekvenca velike brzine (od a do f) okvira koji ilustruju sono-mehaničku eksfolijaciju grafitne pahuljice u vodi UP200S, ultrazvučni sistem od 200W sa 3-mm sonotrodom. Strelice pokazuju mjesto cijepanja (pilinga) sa mjehurićima kavitacije koji prodiru u cijepanje.
(studije i slike: © Tyurnina et al. 2020)

Advantages of Ultrasonic Graphene Exfoliation

Hielscher probe-type ultrasonicators and reactors turn graphene exfoliation into a highly efficient process used to produce graphene from graphite through the application of powerful ultrasound waves. This technique offers several advantages over other methods of graphene production. Major benefits of ultrasonic graphene exfoliation are the following:

• High efficiency: Graphene exfoliation via probe-type ultrasonication is a very efficient method of graphene production. It can produce large amounts of high-quality graphene in a short period of time.
• Niska cijena: The equipment required for ultrasonic exfoliation in industrial graphene production is relatively inexpensive compared to other methods of graphene production, such as chemical vapor deposition (CVD) and mechanical exfoliation.
• Skalabilnost: Exfoliating graphene via ultrasonicator can be easily scaled up for large-scale production of graphene. Ultrasonic exfoliation and dispersion of graphene can be run in batch as well as in continuous inline process. This makes it a viable option for industrial-scale applications.
• Control over graphene properties: Graphene exfoliation and delamination using probe-type ultrasonication allows for precise control over the properties of the graphene produced. This includes its size, thickness, and number of layers.
• Minimal environmental impact: Graphene exfoliation using an ultrasonic proven is a green method of graphene production, as it can be used with non-toxic, environmentally benign solvents such as water or ethanol. This means that ultrasonic graphene delamination allows to avoid or reduce the use of harsh chemicals or high temperatures. This makes it an environmentally friendly alternative to other graphene production methods.

Overall, graphene exfoliation using Hielscher probe-type ultrasonicators and reactors offers a cost-effective, scalable, and environmentally friendly method of graphene production with precise control over the properties of the resulting material.

Example for the Simple Production of Graphene using Sonication

Graphite is added in a mixture of dilute organic acid, alcohol, and water, and then the mixture is exposed to ultrasonic irradiation. The acid works as a “molekularne klin” koji razdvaja listova grafena od matične grafita. Ovaj jednostavan proces, velike količine neoštećene, kvalitetne grafen raspršeni u vodi se stvara. (An et al. 2010.)
 

Grafen Direktni Piling

Ultrazvuk omogućava pripremu graphenes u organskim otapalima, tenzidi / voda rješenja, ili jonske tečnosti. To znači da je upotreba jakim sredstvima ili smanjenje agenti mogu se izbjeći. Stanković i dr. (2007) proizvela grafena po piling pod ultrasonication.
The AFM images of graphene oxide exfoliated by the ultrasonic treatment at concentrations of 1 mg/mL in water always revealed the presence of sheets with uniform thickness (~1 nm; example is shown in the picture below). These well-exfoliated samples of graphene oxide contained no sheets either thicker or thinner than 1nm, leading to a conclusion that complete exfoliation of graphene oxide down to individual graphene oxide sheets was indeed achieved under these conditions. (Stankovich et al. 2007)

AFM image of exfoliated GO sheets with three height profiles acquired in different locations
(picture and study: ©Stankovich et al., 2007)

Priprema grafena listovi

Stengl et al. have shown the successful preparation of pure graphene sheets in large quantities during the production of nonstoichiometric TiO2 graphene nanocomposit by thermal hydrolysis of suspension with graphene nanosheets and titania peroxo complex. The pure graphene nanosheets were produced from natural graphite using a high intensity cavitation field generated by Hielscher ultrasonic processor UIP1000hd in a pressurized ultrasonic reactor at 5 bar. The graphene sheets obtained, with high specific surface area and unique electronic properties, can be used as a good support for TiO2 to enhance the photocatalytic activity. The research group claims that the quality of the ultrasonically prepared graphene is much higher than graphene obtained by Hummer’s method, where graphite is exfoliated and oxidized. As the physical conditions in the ultrasonic reactor can be precisely controlled and by the assumption that the concentration of graphene as a dopant will vary in the range of 1 – 0.001%, the production of graphene in a continuous system on commercial scale is easily installed. Industrial ultrasonicators and inline reactors for efficient exfoliation of high-quality graphene are readily available.

Priprema ultrazvučnim Tretman grafena oksid

Oh et al. (2010) su pokazali put priprema pomoću ultrazvučnog zračenje za proizvodnju grafen oksida (GO) slojeva. Dakle, oni suspendovan dvadeset pet miligrama grafena oksida praha u 200 ml dejonizovana vode. Do miješajući se dobila nehomogene smeđa suspenzija. Rezultirajući obustave sonicated (30 min, 1,3 × 105J), a nakon sušenja (pri 373 K) je ultrazvučno tretiranih grafen oksida je proizveden. A FTIR spektroskopije pokazala da ultrazvučni tretman nije promijenilo funkcionalne grupe grafena oksida.

SEM image of graphene pristine nanosheets obtained by ultrasonication (Oh et al., 2010)

Funkcionisanje grafena listovi

Xu i Suslick (2011) opisuju pogodnom metodom jedan korak za pripremu polistirena funkcionalna grafita. U svojoj studiji, koristili su grafit pahuljica i stirena kao osnovnu sirovinu. Do upotrebe sonikatora grafita pahuljice u stirena (reaktivno monomer), ultrazvuk zračenje je rezultiralo mehanohemijske piling grafita pahuljica u jednoslojni i nekoliko sloja grafen listova. Istovremeno, ostvaren je funkcionisanje od grafena listova sa stiropora lancima.
Isti proces od funkcionisanje se može izvesti s drugim vinil monomera za kompozite na osnovu grafen.

grafen disperzije

Raspon disperzije grafena i grafena oksida je izuzetno važan za korišćenje pun potencijala grafena sa svojim specifičnostima. Ako grafen nije dispergovan pod kontrolisanim uslovima, polidisperznost grafene disperzije može dovesti do nepredvidivog ili neidealnog ponašanja nakon ugrađivanja u uređaje, jer se svojstva grafena razlikuju u funkciji njegovih strukturnih parametara. Sonikacija je dokazano tretiranje da oslabi sile međuslase i omogućava tačnu kontrolu važnih parametara obrade.
"Za grafena oksid (GO), koji se obično ekspandiranog kao jednim slojem listova, jedan od glavnih polidisperznosti izazove proizlazi iz razlike u lateralni području pahuljice. Dokazano je da je srednja lateralne veličine GO može biti pomaknut od 400 nm do od 20 mikrometara promjenom grafit početni materijal i uslove sonication. "(Green et al. 2010.)
The ultrasonic dispersing of graphene resulting in fine and even colloidal slurries has been demonstrated in various other studies. (Liu et al. 2011/ Baby et al. 2011/ Choi et al. 2010)
Zhang et al. (2010) su pokazali da je upotreba ultrasonication stabilne grafena disperzija sa visokom koncentracijom od 1 mg · mL-1 i relativno čisti grafen listovi su ostvareni, a kao pripremljeni grafen listova pokazuju visok električni vodljivosti 712 S · m^-1. Rezultati Fourier transformiše infracrvenih spektara i Raman spektar ispitivanje pokazuje da je način pripreme ultrazvučnog ima manje štete na kemijske i kristalne strukture grafena.

High Performance Ultrasonicators for Graphene Exfoliation

Za proizvodnju visokokvalitetnih grafica, pouzdana visokozvučna oprema je potrebna. Amplituda, pritisak i temperatura su osnovni parametri, koji su presudni za reproducivost i dosljedan kvalitet proizvoda. Hielscher Ultrasonics’ ultrasonic processors are powerful and precisely controllable systems, which allow for the exact setting of process parameters and continuous high-power ultrasound output. Hielscher Ultrasonics industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.
Our customers are satisfied by the outstanding robustness and reliability of Hielscher Ultrasonics systems. The installation in fields of heavy-duty application, demanding environments and 24/7 operation ensure efficient and economical processing. Ultrasonic process intensification reduces processing time and achieves better results, i.e. higher quality, higher yields, innovative products.
Tabela u nastavku daje naznaku približan kapacitet prerade naših ultrasonicators:

Priprema Carbon Nanoscrolls

Carbon Nanoscrolls are similar to multi-walled carbon nanotubes. The difference to MWCNTs is the open tips and the full accessibility of the inner surfaces to other molecules. They can be synthesized wet-chemically by intercalating graphite with potassium, exfoliating in water and sonicating the colloidal suspension. (cf. Viculis et al. 2003) The ultrasonication assists the scrolling up of the graphene monolayers into carbon nanoscrolls (see graphic below). A high conversion efficiency of 80% has been achieved, that makes the production of nanoscrolls interesting for commercial applications.

Ultrasonic synthesis of Carbon Nanoscrolls (Viculis et al. 2003)

Priprema Nanoribbons

Istraživačka grupa Hongjie Dai i njegove kolege sa Univerziteta Stanford pronašli su tehniku ​​pripreme nanobibona. Grafene trake su tanke trake grafena koje mogu imati još korisne karakteristike od grafena. Kod širina od oko 10 nm ili manje, ponašanje grafenskih traka slično je poluprovodniku jer su elektroni prisiljeni da se pomeraju dužinom. Zbog toga bi moglo biti zanimljivo koristiti nanoribone sa poluprovodničkim funkcijama u elektronici (npr. Za manje, brže računarske čipove).
Dai et al. priprema grafena nanoribbons baza na dva koraka: prvo, oni popustio slojeva grafena od grafita po termičku obradu 1000ºC za jednu minutu u 3% hidrogen u argon plin. Zatim, grafen je razbijena u trake koristeći ultrasonication. Je nanoribbons dobiveni ovom tehnikom se odlikuju puno 'glađe’ trake od onih koje je konvencionalnim litografski sredstvima. (Jiao et al. 2009.)