The processes of mechanical activation of a hexagonal boron nitride (h-BN) and its reactivity upon interaction with hydrogen and water were investigated using X-ray, TEM, Microdiffraction, Dynamic Light Scattering, FTIR-spectroscopy, adsorption (BET). Initial h-BN samples were monocrystalline plates 70–80 nm thick. Mechanical treatment of h-BN is accompanied by plate splitting and formation of crystallographically oriented “rods.” The rod thickness gradually diminishes to less than 5 nm. Specific surface area of the rods (400 m2/g), is found to be equal to the outer geometrical surface of rods. As nanocrystallites form “c” parameter of h-BN increases. When nanocrystallites are less than several nanometers in size, mechanical treatment results in BN amorphization; in this case specific surface of the system begins to decrease. Splitting of BN plates in the atmosphere of hydrogen is accompanied by the material hydrogenation and formation of BH and NH bonds. The amount of adsorbed hydrogen corresponds to monolayer filling. The amorphous part of activated BN interacts with water even at room temperature

Berestetskaya, I. V.

Bokhonov, B. B.

Kolbanev, I. V.

Leonov, A. V.

Permenov, D. G.

Streletskii, A. N.

Streletzky, Kiril A.

English

EngagedScholarship @ Cleveland State University

Destruction, Amorphization and Reactivity of Nano-BN Under Ball Milling

Cleveland-Marshall College of Law

Cleveland State UniversityEngagedScholarship@CSUPhysics Faculty Publications Physics Department8-26-2009Destruction, Amorphization and Reactivity ofNano-BN Under Ball MillingA. N. StreletskiiRussian Academy of SciencesD. G. PermenovFederal State Unitary EnterpriseB. B. BokhonovRussian Academy of SciencesI. V. KolbanevRussian Academy of SciencesA. V. LeonovMoscow State UniversitySee next page for additional authorsFollow this and additional works at: https://engagedscholarship.csuohio.edu/sciphysics_facpubPart of the Physics CommonsH w does acces  to this work benefit you? Let us know!Publisher's StatementNOTICE: this is the author’s version of a work that was accepted for publication in Journal of Alloysand Compounds. Changes resulting from the publishing process, such as peer review, editing,corrections, structural formatting, and other quality control mechanisms may not be reflected in thisdocument. Changes may have been made to this work since it was submitted for publication. Adefinitive version was subsequently published in Journal of Alloys and Compounds, 483, 1-2, August26, 2009 DOI#10.1016/j.jallcom.2008.08.088This Article is brought to you for free and open access by the Physics Department at EngagedScholarship@CSU. It has been accepted for inclusion inPhysics Faculty Publications by an authorized administrator of EngagedScholarship@CSU. For more information, please contactlibrary.es@csuohio.edu.Repository CitationStreletskii, A. N.; Permenov, D. G.; Bokhonov, B. B.; Kolbanev, I. V.; Leonov, A. V.; Berestetskaya, I. V.; and Streletzky, Kiril A.,"Destruction, Amorphization and Reactivity of Nano-BN Under Ball Milling" (2009). Physics Faculty Publications. 253.https://engagedscholarship.csuohio.edu/sciphysics_facpub/253AuthorsA. N. Streletskii, D. G. Permenov, B. B. Bokhonov, I. V. Kolbanev, A. V. Leonov, I. V. Berestetskaya, and Kiril A.StreletzkyThis article is available at EngagedScholarship@CSU: https://engagedscholarship.csuohio.edu/sciphysics_facpub/253Fig. 1. TEM image and selected area electron diffraction for initial h-BN.The reﬂection on selected area electron diffraction pattern cor-responds to h-BN (Fig. 1) and suggests that the tablets aremonocrystalline. The original h-BN XRD pattern indicates that theintensity of lines 0 0 2 and 0 0 4 is essentially higher than in thestandard spectrum (texturing). In addition, lines 0 0 2 and 0 0 4 arenoticeably widened. The line widening is due only to reductionin size of L of CSR: L(0 0 2/0 0 4) = 84 ± 15 nm, ε (0 0 2/0 0 4) = 0. Thelines in the direction of [1 0 0] are not widened, allowing to concludethat L(1 0 0) > 150 nm.The value of speciﬁc surface area (S) measured by BET of origi-nal h-BN sample is S = 12 m2/g. For ﬂat tablets of thickness h, whichis considerably smaller than the tablet diameter, the geometricalspeciﬁc surface area is S ≈ 2/h (here  is density). The thicknessestimate based on this formula gives the value of h = 71 nm. Thus,the results on the tablet thickness are conﬁrmed by three indepen-dent methods.Therefore, we can conclude that the original h-BN samples aremicrocrystalline and have the shape of tablets with diameter of300–500 nm and thickness of 70–80 nm. The ﬂat side of tabletscorresponds to the basal plane [0 0 1].The BN destruction and amorphization under ball millingFig. 2 shows the dependence of speciﬁc surface area measuredby BET on the dose of mechanical treatment. At the initial stage ofmechanical treatment speciﬁc surface area increases with increaseof the dose, reaches maximum of about 400 m2/g (at the dose of6–8 kJ/g), and then decreases as the dose continues to increase.Adsorption measurements in the broad interval of pressure haveshown no microporosity at the initial stage of mechanical treat-ment.Fig. 3a shows a microphotograph and microdiffraction patternfor the BN sample activated under the dose of 2.2 kJ/g. Apparently,the activated sample consists of long “rods” with 5–25 nm thick-ness. Selected area electron diffraction (SAD) patterns of the phase,formed during the ball milling (Fig. 3a), is characterized by the pres-ence of the diffraction rings of polycrystalline boron nitride. Thecalculated interstitial distances for ring-type reﬂections are: 3.33,2.16, 2.07 and 1.82 Å, which is in good agreement with the hexag-onal boron nitride parameters. For the sample under the dose ofFig. 2. Speciﬁc surface area of BN under ball milling.4.3 kJ/g, the rods are signiﬁcantly smaller (most rods are thinnerthan 5 nm). For this dose the SAD patterns show reﬂexes of poly-crystalline boron nitride and an amorphous halo (primary data arenot shown). Finally, for the sample under the dose of about 22 kJ/g(Fig. 3b) SAD corresponds to almost completely amorphous mate-rial.Fig. 3. TEM image and selected area electron diffraction for mechanically activatedBN under the dose of 2.2 (a) and 22 (b) kJ/g.Table 1Comparison of the rod thickness obtained by TEM, BET and DLS techniques.N Dose (kJ/g) TEM BET DLS1 2.2 5–25 nm 10 nm –2 4.3 <5 nm 6 nm 5.5 nmIt is natural to assume that, in the absence of micropores, spe-ciﬁc surface area is the external surface of the rods. Under theassumption that rods length considerably exceeds their thicknessthe speciﬁc surface area S is found to be about 4/h. Table 1 com-pares h values, calculated using this formula with the data of TEM.Clearly a satisfactory agreement is observed.XRD patterns of mechanically activated BN under various dosesare presented in Fig. 4. As doses of mechanical treatment increase,the BN lines widen. The lines 0 0 2 and 0 0 4 are widened much morethan the line 100. For the dose of 2.2 kJ/g the CSR size estimatedusing Sherrer’s formula for the line 0 0 2 was L(0 0 2) ∼ 30 nm and forthe line 100 it was L(1 0 0) > 130 nm. The anisotropy of roentgen linewidening could indicate that rods are crystallographically orientedand their long side has a direction [1 0 0].Under higher doses of mechanical activation, at the stage ofreduction of speciﬁc surface two broad maxima are observed ondiffractograms. The CSR formal estimation for diffractogram 7 inFig. 4 results in L(0 0 2) ∼ 1.2–1.5 nm.Additional conﬁrmation that the entire activated material at lowdoses consists of long rods is obtained from the Dynamic Light Scat-tering (DLS) spectroscopy. This method yields the translational andthe rotational diffusion coefﬁcients (Dtr, , respectively) of parti-cles in solution (and/or suspension) from which the distribution ofthe apparent hydrodynamic radius and the shape of particles canbe deduced. The shape of the size distribution function at differ-ent scattering angles for activated sample with the dose of 4.3 kJ/greveals that: (1) BN particles have strongly anisotropic shape, (2)Dtr = 3.97 × 10−12 m2/s and  = 289.4 s−1, (3) the rigid rod scatter-ing model [11] suggests that the rods of the 450 nm in length and5.5 nm in diameter is one possible solution that produces the val-ues of  and Dtr that are similar to experimental values. The valueof 5.5 nm for sample 2 in Table 1 is similar to the values obtainedfrom other methods.In summary, mechanical treatment in the ball mill can bedivided into two stages: under doses up to 6–8 kJ/g monocrystallinetablets of h-BN are cleaved to nanocrystalline rods, speciﬁc sur-face of which reaches hundreds of m2/g; under higher doses theamorphization processes start to appear and reduction of speciﬁcFig. 4. X-ray diffraction patterns of BN after mechanical activation. Diffractogramscorrespond to doses: 0(1), 2.2 (2), 4.3(3), 6(4), 8.6 (5), 25 (6) and 32(7) kJ/g.Fig. 5. FTIR spectra of initial h-BN sample (1) and ball milled samples with doses of6.5 (2) and 22 (3) kJ/g as compared with the model FTIR pattern for B2O3 (4).surface begins. By the moment when amorphization processes aredominant transversal dimension of “nanorods” is less than severalnanometers.It was found that the mechanical treatment causes a shift of XRDlines 0 0 2 and 0 0 4 towards small angles in addition to their widen-ing. Also, the lines become anisotropic in shape (Fig. 4) under thetreatment. The shift of lines 0 0 2 and 0 0 4 towards small anglespoints to the increase in the d002 distance between basal planesin BN. By the dose of 10 kJ/g, the distance estimated by position ofline 0 0 2 maximum, d002, increases from 0.3343 to 0.3365 nm. Theanisotropy of the line 0 0 2 indicates possible formation of severalfractions, differing by the extent of lattice “swelling”. It appearedthat the shape of line 0 0 2 can be described satisfactory with theassumption of three or four fractions present. The more pronouncedthe lattice “swelling” is in a fraction, the wider the line in thisfraction is.“Swelling” of the mechanically activated BN lattice has also beenconﬁrmed by FTIR spectroscopy. The FTIR spectra of original h-BNsample have two bands at ∼820 and ∼1370 cm−1 (Fig. 5). Accordingto [12], the band with the maximum at 1370 cm−1 corresponds toin plane vibration and the band at 817 cm−1 corresponds to out-of-plane vibrations. Fig. 5 shows that the mechanical activation resultsin a shift of the band from 820 cm−1 towards low frequencies byabout 20 cm−1. The shift of this band is indicative of the increase inthe interlayer distance d002 [13].Mechanical activation also results in appearance of new bandsin FTIR spectra at 1030, 1500, and 3150 cm−1. Control experimentsFig. 6. Consumption of H2 during ball milling of BN. H2 pressure is (3–5) 104 Pa.Table 2The depth (˛, %) of BN + H2O reaction at different temperatures.Dose (kJ/g) ˛1 (T = 20 ◦C) ˛2 (T = 70–90 ◦C)2.2 3 –6.5 5 1322 3 3632 17 56have shown that the appearance of new bands at 1500 and∼3200 cm−1 may be attributed to B2O3. Boron oxide emerges inthe samples, probably, as a result of the activated BN hydrolysis bywater vapors from atmosphere during storage (see Section 3.4).Mechanochemical hydrogenation of BNFig. 6 shows the dependence of the amount of absorbed hydro-gen molecules on the dose of mechanical treatment. The rate ofhydrogen absorption is nearly constant up to the doses of about8 kJ/g and then it slightly decreases with the increase of the dose.Maximum amount of absorbed hydrogen under experimental con-ditions is 0.8 wt%.Under the dose of 8 kJ/g the speciﬁc surface area appears tobe equal to S = 250 m2/g and the amount of absorbed hydro-gen molecules is N = 1.3 × 1021 molecules/g. This corresponds tothe surface ﬁlling N/S with about 1 × 1015 hydrogen atoms percm2, i.e. the ﬁlling is close to monolayer type of ﬁlling. Afterhydrogen chemosorption, the BN (band 2600 cm−1) and NH (band3086 cm−1) groups formation was observed by FTIR method. Itcan be assumed that hydrogen interacts with disrupted bonds of–B· · ·N–, that inevitably appear upon cleavage of boron nitride par-ticles with formation of “nanorods” according to the reaction–B—N- → - B· · ·N - + H2 → -BH + HN– (1)Upon heating of hydrogenated samples to 800 ◦C the gases of H2and NH3 are released.Hydrolysis of mechanically activated h-BNOriginal boron nitride is chemically inert, including its zero sen-sitivity to oxidation up to 1000 ◦C. After mechanical activation BNacquires the ability to interact with water at room temperatureaccording to the reaction2BN + 3H2O → B2O3 + 2NH3↑, (2)Ammonia formation was registered organoleptically and bychemical analysis. The appearance of B2O3 was conﬁrmed by obser-vation of absorption bands in FTIR spectrum at 1500 cm−1 and in theregion of 3000–3500 cm−1. The depth of the reaction 2 (determinedby gravimetric technique) increases as the dose of mechanical treat-ment increases. It reaches 56% at the dose of 32 kJ/g (Table 2). Thedifference between results obtained with cold and hot water inTable 2 is probably due to formation of the glass-like modiﬁcationof boron oxide, which is practically insoluble in cold water and issoluble upon heating above 60 ◦C.The most disordered part of activated boron nitride is involvedin the reaction 2 with water. The XRD line of BN observed beforethe hydrolysis does not disappear after interaction with water, butbecomes narrower.ConclusionsTwo processes take place during mechanical treatment of h-BNmonocrystals. At the initial stage of mechanical treatment, the mainprocess is cleavage of boron nitride plates in the plane (0 0 1) andformation of crystallographically oriented nanodimensional rods.The external speciﬁc surface of the rods reaches 400 m2/g.The particle cleavage stimulates boron nitride hydrogenation(reaction 1) with formation of –BH and HN– groups in a concen-tration similar to monolayer. The detailed mechanism of amazingprocesses of “oriented” cleavage requires further investigation.The second process happening during the mechanical treatmentis disordering of the BN crystalline structure. This is revealed inthe increase of interlayer distance d002, registered by XRD and FTIRtechniques. It is possible that the lattice “swelling” is due to theprocesses of shifting along the plane (0 0 1), resulting in the loss ofmutual orientation of these planes and boron nitride transition tothe turbostratic and amorphous structures. Amorphization of BN isaccompanied by the emergence of chemical activity during interac-tion with water (reaction 2). As a result of mechanical activation thedepth of reaction 2 is near 60% even at 100 ◦C, whereas for hydratingof non-activated BN the temperature has to be raised to 1000 ◦C.AcknowledgementsThe work was carried out under ﬁnancial support of PresidiumRAS Program (no. 08-P), RFBR (grant 07-03-00610) and INTAS (grant05-1000005-7672).References[1] J. Tomas Jr., N.E. Weston, T.E. O’Connor, J. Am. Chem. Soc 84 (1963) 4619.[2] Z.P. Xia, Z.Q. Li, J. Alloys Compd. 436 (2006) 170.[3] Y. Chen, L.T. Chadderton, J.F. Gerald, J.S. Williams, Appl. Phys. Let. 74 (1999) 2960.[4] A.N. Streletskii, D.G. Permenov, I.V. Povstugar, S.N. Mudretsona, I.V. Berestet-skaya, Chem. Sustainable Dev. 15 (2007) 175 (in Russian).[5] J.Y. Huang, H. Yasuda, H. Mori, J. Am. Ceram. Soc. 83 (2000) 403.[6] X.J. Du, F.Q. Guo, K. Lu, Nanostruct. Mater. 5 (1996) 579.[7] P.Yu. Butygin, I.K. Pavlichev, Reactivity Solids 1 (1986) 361.[8] P.Yu. Butyagin, A.N. Streletskii, I.V. Berestetskaya, et al., Colloid J. 63 (2001) 639.[9] E.V. Shelekhov, Proceeding of National Conference on X-ray, SR, Neutrons andElectrons Application for Mat. Sci. Investigation, Dubna, V.3, 1997, p. 316 (inRussian).[10] K.M. Zero, R. Recora, Macromolecules 15 (1982) 87.[11] B.J. Berne, R. Pecora, Dynamic Light Scattering, Wiley, New York, 1976.[12] R.J. Nemanich, S.A. Solin, R.M. Martin, Phys. Rev. B23 (1981) 6348.[13] A.S. Rozenberg, Yu.A. Sinenko, N.V. Chukanov, J. Mater. Sci. 28 (1993) 567.

https://engagedscholarship.csuohio.edu/cgi/viewcontent.cgi?article=1255&amp;context=sciphysics_facpub

Destruction, Amorphization and Reactivity of Nano-BN Under Ball Milling

Abstract

Similar works

Full text

Available Versions

EngagedScholarship @ Cleveland State University

Cleveland-Marshall College of Law