Catalytic synthesis of graphite-like boron nitride

Abstract

It is well-known [1, 2] that lithium compounds have a strong effect on the process of formation of boron nitride by the carbothermal method from highly dispersed charges produced by the dissolution method. It is therefore interesting to examine the effect of these compounds on the formation and ordering of the structure of boron nitride in other methods of preparation.Investigations were carried out into the process of nitriding boron and a mixture of boric acid with soot in the presence of lithium compounds. Initial substances were amorphous boron with a purity of 98.6, boric acid of ChDA grade, grade 514 soot, grade ChDA lithium carbonate and hydroxyl, and dried nitrogen and ammonia. Charges were prepared by mixing the components by the dried method. The ratio of the boric acid and soot in the charges was constant (7:2), and the concentration of the addition was varied in the range from 1 to 58% (by mass). Nitriding was carried out in the temperature range 800-1500°C in a gas flow with an optimum speed of 2 litres/h. Temperature was measured with a platinum-platinum/rhodium thermocouple and regulated using an Sh-4501 device. Nitriding products were examined by chemical and x-ray analysis and also electron microscopy.

Atomically Thin Boron Nitride: Unique Properties and Applications

“…[ 88 ] www.afm-journal.de www.MaterialsViews.com not included), indicating that it has the standard AA′ stacking. [ 93,94 ] More importantly, the Li and NH 3 helped to in situ unzip the BN nanotubes to nanoribbons. It refl ects that the BN nanoribbon has a wellordered stacking.…”

Effect of calcium carbonate addition on carbothermic formation of hexagonal boron nitride

“…al. 11,12 found in their study on h-BN formation from boric acid + carbamide mixtures that more C remains present at a given temperature while more h-BN forms when Li 2 CO 3 is added to the reaction mechanism. This result may also be taken as an indication that some h-BN forms without use of C when Li 2 CO 3 is added to the reaction mixture when a lithium borate is expected to form.…”

“…studied the effect of Li 2 CO 3 addition to h-BN formation by different methods like subjecting B 2 O 3 -C mixtures, boric acid-carbamide mixtures to N 2 (g) or ammonia gas. 11,12 They have found Li 2 CO 3 to favorably affect h-BN formation and h-BN crystallinity and have suggested h-BN to crystallize from the lithium borate melt. A similar mechanism may apply in formation of h-BN from B 2 O 3 + C + CaO mixtures subjected to N 2 gas.…”

“…For this purpose catalytic effect of some lithium compounds such as Li 2 CO 3 and LiOH on the yield and three-dimensional crystallographic ordering of h-BN was investigated. 11,12 It was found from the experiments conducted at 1500 • C for 3 h in nitrogen atmosphere that when Li 2 CO 3 was added to boric acid-carbon black mixture at an amount of 12%, the amount of h-BN formed was about twice the amount formed in the experiments without Li 2 CO 3 . The crystal structure of the formed h-BN was also seen to be improved by the addition of Li 2 CO 3 .…”

Catalyzed synthesis of rhombohedral boron nitride in sodium chloride molten salt

“…Thomas firstly found that the pure t-BN can be thermally transformed into h-BN at a temperature above 1500°C by a process which proceeded analogously to the carbon graphitization process [12]. Moreover, in the presence of boric oxide [13,14], alkali metal borate or alkaline earth borate [15][16][17][18], the rate of the transformation could be increased obviously, while the transformation temperature could be lower. The raw materials such as B 2 O 3 and borate [19,20] are often used in the chemical synthesis of BN, therefore most of the BN synthesized by these methods are t-BN (low temperature) or h-BN (high temperature) [15][16][17][18][19][20][21][22][23].…”