With the decreased sizes of microelectronic devices, the excess heat has become one of the most important factors that shorten the lifetime of electronic components. As a result, developing materials ...with high-thermal conductivity is an urgent issue. In this study, we combine an ultrasonic exfoliation and evaporated self-assembly methods to prepare boron nitride nanosheets (BNNS)/thermoplastic polyurethane (TPU) composites with small (S) and large (L) sizes connected BNNS as additives. Our results indicate that BNNS/TPU nanocomposites have better thermal conductivity than TPU, and the optimum performance is achieved at 10 wt% BNNS(S/L-1/9)/TPU. This enhanced thermal conductivity is ascribed to the successful construction of effective thermal conductive pathway. The S-BNNS is connected to the adjacent L-BNNS in TPU, which can also form a dense structure. The formation of the continuous thermal conductive pathways and networks structure facilitate the heat diffusion throughout the composites, which are the key to achieving high thermal conductivity in polymer composites. Furthermore, these results may be helpful to the deeper understanding for the combined structure of fillers in polymer matrix, which will expand the scope of applications for these materials.
In this work, the M/MoS
2
and M/BN/MoS
2
(M = Ag or Mo) nanolaminate films were prepared by RF magnetron sputtering via successive layer-by-layer deposition at room temperature, followed by annealing ...at 500 °C. And then, the BN/MoS
2
heterostructure with clean and tight interface were successfully prepared on different metal electrode layers. The results show that the first deposited metal (Mo or Ag) layer strongly influences the morphology of the top MoS
2
layer, while inserting a BN layer promotes its influence. The results of electric property test indicate the resistivity of the Mo/BN/MoS
2
film at the linear part of
E
–
J
curve is higher than that of Ag/BN/MoS
2
film but the Mo/MoS
2
film is lower than the Ag/MoS
2
film in total resistivity, confirming Mo is more suitable than Ag as the electrode material for the MoS
2
-BN based two-dimensional (2D) electronic devices. This work supplies a simple way for the low-temperature continuous fabrication of 2D MoS
2
-BN-based integrated devices.
BNNTs are synthesized by the nitridation of the mixture of B2O3 and boron with stainless steel as a catalyst.
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•BNNTs can be synthesized by nitridation of the mixture of B2O3 and ...boron.•The B2O3/B precursor can avoid the introduction of metal impurities.•The concentration of B2O3 has a significant influence on the formation of BNNTs.
Boron nitride nanotubes (BNNTs) can be grown on stainless steel by annealing a mixture of diboron trioxide (B2O3) and boron (B) at 1200–1300°C under ammonia (NH3). In previously reported boron oxide chemical vapor deposition methods for the synthesis of BNNTs, diboron dioxide (B2O2) is generated in situ by the reaction of boron and metal oxides. In this study, we directly used a mixture of B2O3 and boron as boron sources, thereby, avoiding the use of metal containing species in the starting material. The concentration of B2O3 significantly influenced the formation, quality and quantity of BNNTs.
The chemically inert surface and strong ionic bonds make exfoliation and functionalization of hexagonal boron nitride (h-BN) difficult. This inevitably increases the interface thermal resistance and ...hinders phonon transfer. Herein, polydopamine (PDA)-coated exfoliated h-BN, denoted as exfoliated h-BN@PDA, was prepared by a one-step ball milling route. During the ball milling process, dopamine self-polymerized into PDA on the surface of the exfoliated h-BN@PDA in an alkaline aqueous solution. The coated PDA contents were estimated to be about 3 wt %. Meanwhile, exfoliation of h-BN occurred due to the hydrolysis of h-BN in water and the shear force introduced by ball milling. The results reveal that the exfoliated h-BN generally composed of <20 layers. The resulting exfoliated h-BN@PDA was further added to cellulose nanocrystal (CNC) and improved thermal conductivity up to 40 W m–1 K–1 with 94 wt % h-BN. By controlling the feed ratio, exfoliated h-BN@PDA/CNC composites with different h-BN contents were fabricated. The corresponding thermal conductivity increased with increasing h-BN contents. A facile, highly efficient, and moderate route to prepare modified few-layered two-dimensional layered materials was provided. These composites have great potential in thermal management applications.
•Four strategies are integrated to fabricate soluble BNNSs.•Synergistic effects of multi-steps fabrication are responsible for the high yield.•Ball-milling and annealing make the main contributions ...to the final yield.•The good dispersity is derived from the organic modification and the nanohybrids.•The Gly-gly-BNNSs can enhance the thermal conductivity of neat TPU.
In this contribution we report an integrated method to obtain soluble boron nitride nanosheets (BNNSs) by combing ball-mill, chemical vapor deposition (CVD) growth, Lewis acid-base interaction, and ultrasonic exfoliation. This simple and inexpensive method can achieve a high yield of 40% few layer BNNSs. Based on the excellent dispersity in water and dimethylformamide (DMF), we introduced these nanosheets into thermoplastic polyurethane (TPU) to fabricate composite films, which display good uniformity and high thermal conductivity. The high-yield can be attributed to the synergistic effects of the multi-steps processing, while the good dispersity may be derived from the chemical functionalization and the formation of nanohybrids. The present method can promote the practical applications of BNNSs in many fields, especially the polymer-based nanocomposites.
The large-scale manufacture of inexpensive boron nitride nanotubes (BNNTs) has proven difficult in recent decades. In this study, BNNTs are fabricated on a massive scale by ball-milling a mixture of ...boron oxide (B2O3), amorphous boron powder (B), and magnesium diboride (MgB2) and then annealing the resulting product in NH3, which follows a vapor-liquid-solid growth mechanism. MgB2 serves as a catalyst in the growth process, and the vaporous B2O3 and diboron dioxide (B2O2) produced from the reaction of B2O3 and B are efficient sources of boron. The obtained BNNTs can be dispersed well in dimethyl formamide, possibly as a result of some cracked structures in the BNNTs and impurities that form during the synthesis process. Taking advantage of the good dispersity, the uniform BNNT/thermoplastic polyurethane composite films are prepared via solution blending. The incorporation of BNNTs apparently enhances the thermal conductivity of the neat thermoplastic polyurethane. This article contributes to the low-cost fabrication of BNNTs and their potential application as fillers in polymers.
Low blank value analytical method for analysis of PAEs in the foodstuff.
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•We established a novel PAE analysis method.•The method can overcome the problems of the blank value in PAE ...analysis.•Contents and profiles of PAEs were analysed in 78 foodstuffs.•PAEs exposure was estimated from foodstuffs sold in the Chinese market.
Phthalate esters (PAEs) are commonly used as nonreactive plasticisers in vinyl plastics to increase the flexibility of plastic polymers. Numerous studies have indicated that the PAEs as a class of endocrine-disrupting chemicals. In addition, the studies have also shown that a major source of human exposure to phthalates is the diet. To date, the largest problem in PAEs analysis is the high blank value because PAEs are widely used in various applications and products. To overcome this shortcoming, gas purge microsyringe extraction (GP-MSE) was applied, which established a new and low-blank-value analytical method for PAE analysis to analyse PAEs in foodstuffs. In this study, GP-MSE was used as a clean-up method, and the overall recoveries ranged from 85.7 to 102.6%, and the RSD was less than 10%. More importantly, this method can overcome the problem of the high blank value in PAE analysis. This method was applied for measuring PAEs in 78 foodstuffs. The results showed that a wide variety of PAE concentrations were found in the different groups, and the content of PAEs (varies from 658 to 1610ngg−1 fresh weight) is greatest in seafood. The concentrations were in the following order: DEHP>DBP>DEP≈DMP>BBP≈DNOP. Finally, the daily intake of PAEs was estimated for adults based on the levels of PAEs in foodstuffs. The total EDIdiet values of 3.2 and 12.9μgkg−1 bw d−1 were calculated for DEHP based on the mean and highest concentrations in foodstuffs, respectively.
The difficulty in synthesizing boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace by chemical vapor deposition (CVD) may be ascribed to the failure to identify suitable ...catalysts and nucleation particles. This report demonstrates that magnesium diboride (MgB
) can effectively catalyze the growth of BNNTs in such a tube furnace from various boron sources, including boron oxide (B
O
), boric acid (H
BO
), and a mixture of boron (B) and calcium oxide (CaO). This catalyst is more efficient than the possible magnesium oxide (MgO) or magnesium nitride (Mg
N
) catalysts. MgB
efficiently catalyzes the formation of BNNTs by maintaining a liquid state and showing a dissolving capacity for B
O
at the growth temperature, thus satisfying the criteria for the vapor-liquid-solid (VLS) mechanisms of one-dimensional nanomaterials. First-principles simulations demonstrate that B
O
can be dissolved into the MgB
nanoparticle. We believe that the strong catalytic behavior of MgB
can be attributed to its robust nucleation for BNNTs and dissolubility for B
O
.
Boron nitride nanosheets (BNNSs) are a structural analogue of graphene that are thought to exhibit good tribological performances, due to their typical laminated structure. However, the tribological ...properties of pure solid BNNSs have not been thoroughly researched, which may be resulted from the lack of knowledge regarding the synthesis of this special two-dimensional (2D) material. In this work, BNNSs were deposited on silicon wafers via nitridation of magnesium diboride (MgB2) in a chemical vapor deposition system. The ammonia (NH3) was used as the nitrogen source. The tribological behaviors of the synthesized BNNSs, including friction and wear resistance, were evaluated with a CSM tribometer. The results indicated that the BNNSs can decrease the friction of bare silicon wafer. The average value of the friction coefficients had no obvious change with the changes in load and frequency. The wear rate increased when the load and frequency increased. The results suggested that the BNNSs had good potential applications in industrial lubrication, after they were modified by small molecules or polymers.
•BNNSs were deposited on silicon wafers via MgB2 nitridation.•The BNNSs decreased the friction of bare silicon wafer.•The wear rate of the BNNSs increased alongside the load and the frequency.
The difficulty in synthesizing boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace by chemical vapor deposition (CVD) may be ascribed to the failure to identify suitable ...catalysts and nucleation particles. This report demonstrates that magnesium diboride (MgB
2
) can effectively catalyze the growth of BNNTs in such a tube furnace from various boron sources, including boron oxide (B
2
O
3
), boric acid (H
3
BO
3
), and a mixture of boron (B) and calcium oxide (CaO). This catalyst is more efficient than the possible magnesium oxide (MgO) or magnesium nitride (Mg
3
N
2
) catalysts. MgB
2
efficiently catalyzes the formation of BNNTs by maintaining a liquid state and showing a dissolving capacity for B
2
O
3
at the growth temperature, thus satisfying the criteria for the vapor-liquid-solid (VLS) mechanisms of one-dimensional nanomaterials. First-principles simulations demonstrate that B
2
O
3
can be dissolved into the MgB
2
nanoparticle. We believe that the strong catalytic behavior of MgB
2
can be attributed to its robust nucleation for BNNTs and dissolubility for B
2
O
3
.
MgB
2
can serve as an efficient catalyst for BNNT growth because of satisfying the criteria for the VLS mechanisms.
