The electrical properties of sulfur-implanted cubic boron nitride thin films

Cubic boron nitride （c-BN） thin films are deposited on p-type Si wafers using radio frequency （RF） sputtering and then doped by implanting S ions. Wile implantation energy of the ions is 19 keV, and the implantation dose is between 1015 ions/cm2 and 1016 ions/cm2. The doped c-BN thin films are then annealed at a temperature between 400℃ and 800℃. The results show that the surface resistivity of doped and annealed c-BN thin films is lowered by two to three orders, and the activation energy of c-BN thin films is 0.18 eV.

In situ infrared spectroscopic study of cubic boron nitride thin film delamination

This paper investigates the procedure of cubic boron nitride （cBN） thin film delamination by Fourier-transform infrared （IR） spectroscopy. It finds that the apparent IR absorption peak area near 1380cm^-1 and 1073 cm^-1 attributed to the B-N stretching vibration of sp2-bonded BN and the transverse optical phonon of cBN, respectively, increased up to 195% and 175% of the original peak area after film delamination induced compressive stress relaxation. The increase of IR absorption of sp2-bonded BN is found to be non-linear and hysteretic to film delamination, which suggests that the relaxation of the turbostratic BN （tBN） layer from the compressed condition is also hysteretic to film delamination. Moreover, cross-sectional transmission electron microscopic observations revealed that cBN film delamination is possible from near the aBN（amorphous BN）/tBN interface at least for films prepared by plasma-enhanced chemical vapour deposition.

The Adhesion Improvement of Cubic Boron Nitride Film on High Speed Steel Substrate Implanted by Boron Element

Cubic boron nitride(c-BN) films were deposited on W6Mo5Cr4V2 high speed steel(HSS) substrate implanted with boron ion by RF-magnetron sputtering. The films were analyzed by the bending beam method, scratch test, XPS and AFM. The experimental results show that the implantation of boron atom can reduce the internal stress and improve the adhesion strength of the films. The critical load of scratch test rises to 27.45 N, compared to 1.75 N of c-BN film on the unimplanted HSS. The AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. Then the composition of the boron implanted layer was analyzed by the XPS. And the influence of the boron implanted layer on the internal stress and adhesion strength of c-BN films were investigated.

Influence of oxygen on the growth of cubic boron nitride thin films by plasma-enhanced chemical vapour deposition

Cubic boron nitride thin films were deposited on silicon substrates by low-pressure inductively coupled plasmaenhanced chemical vapour deposition. It was found that the introduction of 02 into the deposition system suppresses both nucleation and growth of cubic boron nitride. At a B2H6 concentration of 2.5% during film deposition, the critical O2 concentration allowed for the nucleation of cubic boron nitride was found to be less than 1.4%, while that for the growth of cubic boron nitride was higher than 2.1%. Moreover, the infrared absorption peak observed at around 1230- 1280 cm^-1, frequently detected for cubic boron nitride films prepared using non-ultrahigh vacuum systems, appears to be due to the absorption of boron oxide, a contaminant formed as a result of the oxygen impurity. Therefore, the existence of trace oxygen contamination in boron nitride films can be evaluated qualitatively by this infrared absorption peak.

Recension of boron nitride phase diagram based on high-pressure and high-temperature experiments

Cubic boron nitride and hexagonal boron nitride are the two predominant crystalline structures of boron nitride.They can interconvert under varying pressure and temperature conditions.However,this transformation requires overcoming significant potential barriers in dynamics,which poses great difficulty in determining the c-BN/h-BN phase boundary.This study used high-pressure in situ differential thermal measurements to ascertain the temperature of h-BN/c-BN conversion within the commonly used pressure range(3-6 GPa)for the industrial synthesis of c-BN to constrain the P-T phase boundary of h-BN/c-BN in the pressure-temperature range as much as possible.Based on the analysis of the experimental data,it is determined that the relationship between pressure and temperature conforms to the following equation:P=a+1/bT.Here,P denotes the pressure(GPa)and T is the temperature(K).The coefficients are a=-3.8±0.8 GPa and b=229.8±17.1 GPa/K.These findings call into question existing high-pressure and high-temperature phase diagrams of boron nitride,which seem to overstate the phase boundary temperature between c-BN and h-BN.The BN phase diagram obtained from this study can provide critical temperature and pressure condition guidance for the industrial synthesis of c-BN,thus optimizing synthesis efficiency and product performance.

Tribological and anti-corrosion performance of epoxy resin composite coatings reinforced with differently sized cubic boron nitride(CBN)particles

A series of high solid content(30 wt%)epoxy resin(EP)composite coatings reinforced with differently sized cubic boron nitride(CBN)particles were fabricated successfully on 304 L stainless steel.Polydopamine(PDA)was used to improve the dispersibility of CBN particles in EP.The structural and morphological features of the CBN particles and the composite coatings were characterized by Raman spectroscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM).Moreover,a UMT-3 tribometer and surface profiler were used to investigate the tribological behaviors of the as-prepared composite coatings.Electrochemical impedance spectroscopy(EIS)and Tafel analysis were used to investigate the coatings'anti-corrosion performance.The results demonstrated that the CBN fillers could effectively enhance the tribological and anti-corrosion properties of the EP composite coatings.In addition,when the additive proportion of the microsized(5μm)and nanosized(550 nm)CBN particles was 1:1,the tribological property of the EP composite coatings was optimal for dry sliding,which was attributed to the load carrying capability of the microsized CBN particles and the toughening effect of the nanosized CBN particles.However,when the additive proportion of the microsized and nanosized CBN particles was 2:1,the tribology and corrosion resistance performance were optimal in seawater conditions.We ascribed this to the load-carrying capacity of the microparticles,which played a more important role under the seawater lubrication condition,and the more compact structure,which improved the electrolyte barrier ability for the composite coatings.

Detailing interfacial reaction layer products between cubic boron nitride and Cu-Sn-Ti active filler metal

In the present study,we offer an in-depth analysis over the microstructure,thickness and product composition of the interfacial reaction layer generated upon CBN/Cu-Sn-Ti active filler metal at 1223 K.Current findings demonstrate that adequate wettability and satisfactory bonding have been achieved via chemical reactions between Ti and N,B.More importantly,we report,for the first time,the formation of a three-layer juxtaposition of reaction products,namely,TiN,TiB2 and TiB,along the diffusion path of Ti.Meanwhile,we determine the average layer thickness to be 1.24 μm.Through deep etching,we unambiguously present morphologies of the newly formed TiN and TiB2,which are columnar and bulky,re spectively,and constitute the formation of a high strength metallu rgical interfacial bonding layer,and is crucial towards gaining enhanced grinding performance.Finally,we propose a possible reaction sequence and mechanism that govern the nucleation and growth of corre s ponding crystals.

In situ synthesis of polycrystalline cubic boron nitride in cBN-Al-Ti system with different Gd_(2)O_(3) additions

Polycrystalline cubic boron nitride was sintered under high temperature(1400℃)and high pressure(5.5 GPa)using an in situ synthesis method.The composition,microstructure,relative density and mechanical properties of the polycrystalline cubic boron nitride(PcBN)with different contents of Gd_(2)O_(3) were studied by means of X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS).The results show that the phases of TiB_(2),TiN,AIN,AlTi_(2)N and GdB_(6) are formed through in situ synthesis of cBN-Al-Ti-Gd_(2)O_(3) system.With the Gd_(2)O_(3) content increasing,the relative density increases and mechanical properties of PcBN begin to increase and then decrease.Proper amount of Gd_(2)O_(3) can advance the formation of TiB_(2) and improve the aspect ratio of TiB_(2).When Gd_(2)O_(3) content is 1.0 wt%,the PcBN exhibits optimal comprehensive mechanical properties,with a microhardness of 33.35 GPa and a flexural strength of 972.37 MPa.

Growth kinetics of interfacial reaction layer products between cubic boron nitride and Cu-Sn-Ti active filler metal

In the present investigation,the growth kinetics of interfacial reaction layer products between cubic boron nitride(CBN) and Cu-Sn-Ti filler metal has been thoroughly investigated.Detailed morphological and compositional features of respective compounds have been demonstrated for a wide brazing temperature ranging from 1153 K to 1223 K.It is found that within 30 minutes brazing holding time,the reaction layer growth is largely determined by the population of Ti N via effective Ti diffusion with an activation energy of 223.51 k J/mol,leading to parabolic growth patterns.It is further revealed that TiN grows both in axial and length dimensions,which eventually extends to the forefront and covers the reaction layer.

Low pressure synthesis of boron nitride with (C_2H_5)_2O·BF_3 and Li_3N precursor

Cubic boron nitride（c-BN） was synthesized through benzene thermal method at a lower temperature of （300℃） by selecting liquid（（C2H5）2O·）BF3 and Li3N as reactants. Hexagonal boron nitride（h-BN） and orthorhombic boron nitride（o-BN） were also obtained. The samples were characterized by X-ray powder diffractometry and Fourier transformation infrared spectroscopy. The results show that all the BF3, BCl3 and BBr3 in the same family compounds can react with Li3N to synthesize BN since the strongest bond of B—F can be broken. Compared with BBr3, liquid （C2H5）2O·BF3 is cheaper, less toxic and more convenient to operate. Li3N not only provides nitrogen source but also has catalytic effect on accelerating the formation of c-BN at low temperature and pressure.

Diamond/c-BN van der Waals heterostructure with modulated electronic structures

The structural and electronic properties of(100),(110), and(111) diamond/cubic boron nitride(c-BN) heterostructures are systematically investigated by first principles calculation. The interface between diamond and c-BN shows the weak van der Waals interactions, which is confirmed by the interface distance and interface binding energy. The diamond/cBN structures are the direct bandgap semiconductors with moderate bandgap values ranging from 0.647 e V to 2.948 e V.This work helps to promote the application of diamond in electronic and optoelectronic devices.

BONDING INTERFACE AND WEAR BEHAVIOR OF CBN GRAINS BRAZED USING NANO-TiC POWDER MODIFIED FILLER

A new kind of composite fillers,composed of Ag-Cu-Ti alloy and nano-TiC powders,is utilized to braze cubic boron nitride （CBN） grains and tool substrate. The bonding system,including the interfacial microstructure and reactive products between CBN grains and filler layer,is observed by optical microscope and scanning electron microscope （SEM）. Resistant-to-wear experiments of the brazed grains are performed. Results show that the nano-TiC powders evenly distribute in the filler layer so that the resultants grow compactly and uniformly on the surface of CBN grain. This indicates that the chemical bond is established between CBN grains and nano-TiC modified filler. Accordingly,the bonding strength of the grains is ensured. The CBN grains are worn smoothly without grain pull-out.

Fabrication of TiN/cBN and TiC/diamond coated particles by titanium deposition process

Cubic boron nitride particles coated by titanium nitride (TiN/cBN) as well as diamond particles coated by titanium carbide (TiC/diamond) were prepared by Ti molten salt deposition followed by heat-treatment process. cBN or diamond particles were mixed separately with Ti powders and molten salts (KCl, NaCl and K2TiF6). The mixture was heated at 900 °C under argon atmosphere. The produced particles were heat-treated under hydrogen at 1000 °C. The morphologies and chemical compositions of the produced particles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and focused ion beam (FIB). The results show that the cBN and the diamond particles are coated by nano-sized Ti layers. By heat-treatment of the Ti/cBN and TiC/diamond coated particles under hydrogen atmosphere, the deposited Ti layers were interacted by the in-situ transformation reaction with the surfaces of cBN and diamond particles and converted to titanium compounds (TiN and TiC), respectively.

Cutting Temperature and Tool Wear of Hard Turning Hardened Bearing Steel

A study was undertaken to investigate the performan ce of PCBN tool in the finish turning GCr15 bearing steel with different hardness between 30～64 HRC. The natural thermocouple was used to measure the cutting tem p erature, tool life and cutting temperature were investigated and compared. The m aterial can be heated by this instrument which using low voltage and high elec trical current, while PCBN can’t be heated by electrifying directly, so the ke ntanium layer coating over the PCBN is heated, so the PCBN is heated and its th ermoelectric property is got by this method. [TPP129,+60mm88mm,Y,PZ#] Fig.1 Effect of cutting depth and workpiec hardness on. the cutting temperatureThe objective was to determine the influence of the workpiece hardness on change s in cutting temperature and tool wear characterize. It can be found from Fig.1 that the cutting temperature show an increasing tendency with the improvement of workpiece hardness within the cutting speed scope when the workpiece hardness i s under HRC50. And on the other hand, it is found that the cutting temperature s how the downtrend with the improvement of workpiece hardness when the workpiece hardness is over HRC50. According to experimental results, the critical hard ness when turning hardened GCr15 bearing steel with PCBN tool is about HRC50. Th e wear causes of PCBN tool have been found out through taking photos on the micr o-shape of PCBN poly-laminate initial surface as well as face and flank of wea r tool and analysis on chemical elements. It is discovered that the PCBN tools a re not suitable for cutting the workpiece at nearly critical hardness, because n ear the critical hardness, PCBN wear at the highest speed. For researching the w ear rule of PCBN tool, the tool wear experiments have been carried on by using b earing steel GCr15 at hardness HRC40 and HRC60 with changing cutting speed. The indexes of tool life equations is gained under two kinds of conditions w hich are bigger than 0.6, so the effects of cutting speed on the PCBN tool are m uch less than that of carbide tool and ceramic tool.

Thick c-BN films deposited by radio frequency magnetron sputtering in argon/nitrogen gas mixture with additional hydrogen gas

The excellent physical and chemical properties of cubic boron nitride(c-BN) film make it a promising candidate for various industry applications. However, the c-BN film thickness restricts its practical applications in many cases. Thus, it is indispensable to develop an economic, simple and environment-friend way to synthesize high-quality thick, stable c-BN films. High-cubic-content BN films are prepared on silicon(100) substrates by radio frequency(RF) magnetron sputtering from an h-BN target at low substrate temperature. Adhesions of the c-BN films are greatly improved by adding hydrogen to the argon/nitrogen gas mixture, allowing the deposition of a film up to 5-μm thick. The compositions and the microstructure morphologies of the c-BN films grown at different substrate temperatures are systematically investigated with respect to the ratio of Hgas content to total working gas. In addition, a primary mechanism for the deposition of thick c-BN film is proposed.

Preparation of Porous Ceramic Bond cBN Composites Using cBN Micro-particles as Additive

Ceramic bond cBN composites with large pores were prepared by firing at 740 ℃ for 1 h using Na2O -Al2O3-B2O3 -SiO2 gluss and cBN abrasives （particles size 0. 150 mm/0. 124 mm） as main starting materials, eBN micro-particles （particles size O. 014 mm ） as the additive, and NH4HCO3 as the pore forming agent. The effect of NH4HCO3 and cBN micro-particles on the microstructure and properties of cBN composites was studied. The results show that for the cBN composite without cBN micro-particles the porosity obviously increases when the NH4HCO3 addition increases from 0 to 21 mass% , and increases slightly when the NH4HCO, addition increuses from 28 muss% to 42 muss% ; and the bending strength decreases with the NH4HCO3 addition increasing. For the cBN composite with 14 mass% cBN micro- particles, the porosity increases continuously with the NH4HCO3 addition increasing, achieving 56. 14% for the NH4HCO3 addition of 42 mass% , while, an obvious decrease of the bending strength is obtained. It is clearly indicated that the cBN micro-particles contribute to the high porosity and high strength of the porous ceram, ic bond cBN composites.

Brazed joints of CBN grains and AISI 1045 steel with AgCuTi-TiC mixed powder as filler materials

The brazing process of cubic boron nitride （CBN） grains and AISI 1045 steel with AgCuTi-TiC mixed powder as a filler material was carried out.The joining strength and the interfacial microstructure were investigated.The experimental results indicate that the spreading of the molten filler material on AISI 1045 steel is decreased with the increase of TiC content.A good interface is formed between the TiC particulates and AgCuTi alloy through the wetting behavior.In the case of AgCuTi＋16wt% TiC,the strength of the brazed steel-to-steel joints reached the highest value of 95MPa dependent upon the reinforcement effect of TiC particles within the filler layer.Brazing resultants of TiB2,TiB,and TiN are produced at the interface of the CBN grains and the AgCuTi-TiC filler layer by virtue of the interdiffusion of B,N,and Ti atoms.

Effect of PCBN cutting tools wear on surface integrality in high-speed hard turning

In this paper, the effect of of flank wear polycrystalline cubic boron nitride （PCBN） tools on residual stresses, white layer and roughness of machined workpiece surfaces is studied. Experimental results indicate that with the increase of the tool wear, the surface of the machined workpiece tends to generate tensile residual stresses, and white layer becomes clearly thicker and uneven on the workpiece surface. The effect of the flank wear on the surface roughness is less within some range of flank wear value. The results show that it is possible to produce ideal surface integrality levels by controlling the tool flank wear.

Hydrochloric Acid-Promoted Synthesis of cBN via Hydrothermal Route

Single phase crystalline cubic boron nitride （cBN） with high yield was prepared by hydrothermal route at low temperature, using hydrochloric acid （HCI） as the promoter. The promotion effect of HCI on the synthesis of cBN is briefly discussed.

DEPOSITION OF c-BN FILMS AND ADHESION IMPROVEMENT

Cubic boron nitride (c-BN) films were successfully grown on Si(100)substrates by a helicon wave plasma-assisted chemical vapor deposition technique.The lower limits of rf substrated bias voltage and plasma density for formation of a single phase c-BN film were 350V and 4.5×10￣(10) cm￣(3),respectively. The grown c-BN films demonstrated a poor adhesion to the substrates. A postannealing treatment at 800℃ C in N_2 atmosphere was found very effective in relieving the compressive stress in the films which were thereby stabilized to improve the adhesion.