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This study emphasizes the comparative cutting performance evaluation of CVD- and PVD-coated carbide inserts in hard turning of AISI D2 steel. The cutting factors, namely cutting speed (100m/min), tool feed rate (0.08mm/rev), and depth of cut 0.2mm, have been fixed for the entire study. The comparative study is based on the analysis of the obtained test results of flank wear, tool life, auxiliary flank wear, surface roughness, and surface texture. Both tools are catastrophically failed when tool wear reached limiting flank wear ($\mathrm{\text{VBc}}=0.3$mm) criteria. SEM and EDS analysis of both the tools (at their end of tool life) are carried. Diffusion followed by adhesion is found to be the prime mechanism at the end of tool life. Based on limiting flank wear criteria, the tool life of CVD and PVD tools was estimated as 65 and 57min, respectively, i.e. the tool life of the CVD tool is 14% longer than that of the PVD tool. Considering the limiting criteria of surface roughness ($\mathrm{\text{Ra}}=1.6\mu$m), the tool life of the CVD tool was estimated as 63min while for the PVD tool, it was found as 54min i.e. about 14.3% higher tool life was found for the CVD tool relative to the PVD tool. The auxiliary flank wear was observed to be lower for the CVD tool relative to the PVD tool. Surface roughness for both the tools increased with cutting time and the relatively larger rough surface was obtained with the PVD tool. The machining cost of one pass of the CVD tool is 2.5% less than that of the PVD tool. However, for mass production, the CVD tool is more efficient than the PVD tool for machining hard D2 steel ($57\pm 1$ HRC).

Equal channel angular pressing (ECAP) processed materials have higher grain refinement and strength, and they exhibit more surface roughness when they are machined. This enhancement in the properties highly influences the surface roughness and material removal rate of the materials. The commercial pure aluminum has a wide variety of applications when it is enhanced with high strength properties. In this paper, the machinability of commercially pure aluminum processed through ECAP is investigated in turning operations. Different ECAP processes are carried out to study the microstructural characterization and mechanical properties of the material. The material removal rate and surface roughness are tested by performing the turning operation in the CNC lathe with chemical vapor deposited carbide tool such that the feed rate, spindle speed and depth of cut are considered as the machining variables. To create a hypothesis for the experimentation, the empirical models are developed for the objective functions using the statistical technique response surface methodology (RSM) such that the response models are the objective functions and the model variables are the machining parameters. The response models are verified for the adequacy through ANOVA and $p$-test, and also verified for the closeness with the experimental results. Artificial neural network (ANN)-based empirical equations are also developed for the objective functions using the RSM design matrix and the results of both the RSM and ANN are compared for the suitability.

Single crystal graphene has been getting lots of attention due to the lack of grain boundaries which ensures its distinguished intrinsic properties and good performance in graphene-based devices. Hence, the realization of single crystal graphene growth with tunable size and high crystallinity will be of great importance in commercial production and widespread applications. Recently, numerous studies have focussed on the controlled single crystal graphene growth, and great advancements have been made in the synthesis of large-sized single-crystal graphene (LSSG) by chemical vapor deposition (CVD). In this review, current developments of CVD-grown LSSG and its future prospects are presented and discussed. We emphasize on growth methods and growth mechanisms over transition-metal Cu and Cu alloys for deeper insights in control of size and crystallinity.

Multi-walled carbon nanotubes (MWCNTs) were synthesized onto a series of individual and bimetallic catalysts by the chemical vapor deposition (CVD) of acetylene at low temperature (600${}^{\circ }$C). The catalysts were prepared by two methods, i.e., precipitation and sol–gel, with two different carriers – MgO and Al₂O₃. The catalysts were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric (TG) analysis, low-temperature adsorption of nitrogen. The yield of the MWCNTs was calculated in two ways, while the highest yield of 800% was achieved onto the two-component NiO/Co₂O₃/MgO catalyst, SEM and transmission electron microscopy (TEM) results confirm that uniform tube-like structure MWCNTs with the yield of 410% were obtained onto Co₂O₃/Al₂O₃ catalyst. These MWCNTs are smooth and pointing in the same direction. Their tube diameter is about 20nm, which is the smallest around all observed MWCNTs. Moreover, nonuniform curved bamboo-like MWCNTs with nozzles in the yield of 760% were obtained onto NiO/V₂O₃/MgO catalyst. Their diameter ranges from 25nm to 50nm. Results show that single-component catalyst promotes the growth of uniform and smaller nanotubes. Among the as-grown nanotubes, their specific surface area increases and average pores diameter reduces after the treatment with concentrated nitric acid at reflux and washing condition. The largest specific surface area (305m²/g) and average pores diameter (26m²/g) are processed to MWCNTs grown onto the NiO/Co₂O₃/MgO catalyst. MWCNTs with such large structural adsorption characteristics and purity of more than 99% obtained with yield 800% show potential use for preparation of nanocomposites as anode materials in lithium ion batteries.

The hard part turning process used to finish the cylindrical surfaces has some critical machining responses like tool wear with the lower quality of the machined surfaces. Minimum quantity lubrication (MQL)-based machining environment is currently considered an advanced cooling and lubrication technique. Cutting speed, feed rate, and cutting depth are considered input parameters, and the TaguchiL₂₇ orthogonal array (OA) has been adopted as the design of the experiment. In this context, average surface roughness ($R_a$), tool flank wear (VBc), cutting temperature ($T^{\circ }$C), and chip morphology have been selected as measured outputs. To improve the machining performance of hardened steel, a sustainable MQL ($\mathrm{\text{flank}}+\mathrm{\text{rake}}$ directions) cooling system has been employed at the cutting zone. Iron–aluminum LRT 30 was considered as the base fluid for the hard turning of AISI 4340 steel by PVD (AlTiN) and CVD (TiN/TiCN/Al₂O₃) coating cutting inserts. The primary effects of process parameters and their influences on the measured outputs have been discussed. The dual jet MQL-based hard turning was performed at three levels of cutting speeds (80, 170, and 260m/min), feed rate (0.5, 0.1, and 0.15mm/rev), and cutting depth (0.2, 0.3, and 0.4mm) with an air pressure of 5bar and mist flow rate 50ml/h. The findings showed that PVD-coated carbide tools outperformed CVD-coated tools. The model of the measured outputs of both tools has been developed using second-order regression analysis. Utilizing ANOVA analysis, all the predictive models were observed to be significant and acceptable with larger than 90% of $R^2$ value.

A numerical study is needed to gain insight into the growth mechanism and improve the reactor design or optimize the deposition condition in chemical vapor deposition (CVD). In this study, we have performed a numerical analysis of the deposition of gallium arsenide (GaAs) from trimethyl gallium (TMG) and arsine in a vertical CVD reactor. The effects of operating parameters, such as the rotation velocity of susceptor, inlet velocity, and inlet TMG fraction, are investigated and presented. The three-dimensional model which is used in this investigation includes complete coupling between the thermal-fluid transport and species transport with chemical reaction.

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7J/cm², at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84nm to 31.88nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7J/cm², large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

Direct growth of large-area uniform graphene films on insulating materials could facilitate the applications of graphene in optoelectronic devices. The ultrafast photocarrier relaxation and saturable absorption of direct chemical vapor deposition-grown graphene glasses, with lots of defects, are studied by using femtosecond time-resolved pump–probe and Z-scan techniques at 800 nm. We find that both the relaxation times associated with hot carrier cooling and the hot phonon effect are greatly suppressed in these defect-rich graphene glasses, which further leads to the increase of both saturation intensity and anisotropy in transient optical response for graphene glasses as compared with defect-free graphene. And, both the suppression effect and saturation intensity increase with the thickness of graphene film. The dominance of defect-assisted carrier-acoustic phonon scattering (i.e., supercollision, the collision of a carrier with both an acoustic phonon and defects) in the cooling process of hot carriers is responsible for the suppression of relaxation time.

In this paper, the effect of hydrogen embrittlement in High-strength low-alloy steel (HSLA) material was studied. HSLA steels are known for their susceptibility to hydrogen induced failure especially when subjected to hydrogen rich environment. In this research, samples from HSLAS were surface-treated using chemical vapor deposition (CVD) techniques, followed by direct Zinc coating using physical vapor deposition (PVD). Other samples were additionally post-heat treated at a temperature of 260^∘C for 4h to optimize the coating process. The hydrogen embrittlement test was performed by immersing the tensile samples in a solution containing H₂SO₄ diluted with water for 24h. Hardness, and mechanical properties were evaluated using tensile testing. XRD and SEM were used for microstructural and topographical features’ examination of the treated samples. The results indicate that the samples of combined $\mathrm{\text{PVD}}+\mathrm{\text{CVD}}$ coating that was backed at 260^∘C show superior resistance to hydrogen embrittlement compared to other conditions. This could be attributed to the buildup of a strong outer layer that prevents hydrogen from diffusing towards the base HSLAS material. The greater mechanical properties are possibly due to the reduction of hydrogen amount generated by the surface reaction associated by the formation of Zn(N${}_3{)}_2$ phase and the reduction of hydrogen amount passed through Zn and C₃N₄ layers.

Unlike synthesis of nanowires (1D nano-objects) the synthesis of nanoplatelets (2D nano-objects) has not been performed frequently. Herein, we report on the synthesis of Cu–Ge based on nanoplatelets with a high surface-to-volume ratio prepared by low pressure chemical vapor deposition (LPCVD) of Ge₂Me₆ and a mixture of Ge₂Me₆/PbEt₄. Nanostructured deposits are composed of Cu_1-xGe_x nanoplatelets, Ge nanowires and Ge nanoparticles. The nanoplatelets, which have the lateral size up to several tens of micrometers and thickness of 100–400 nm, belong to the cubic α phase of Cu₉₁Ge₉ alloy (Ge admixture in cubic Cu) and hexagonal ζ phase of Cu₈₅Ge₁₅ alloy. Nanowires composed of cubic Ge have a diameter of about 30 nm and length of several tens of micrometers. Lead does not enter any of these phases due to Pb–Cu and Pb–Ge immiscibility; therefore, it was observed as separate nanoparticles.

Multi-walled carbon nanotubes (MWCNTs) produced by chemical vapor deposition (CVD) are the most common commercial products at extremely low price in the market. However, due to the inherent drawbacks of CVD surroundings at temperature below $\sim$1000${}^{\circ }$C, CVD-grown nanotubes usually have very disordered structure, resulting in most of their properties being much below expectations. Herein, we present a simple and energy-efficient method for improving rapidly the structure of CVD-grown MWCNTs via a drastic thermite reaction process. Direct observations from scan electron microscope (SEM) and transmission electron microscope (TEM) images, decrease of $I_D∕I_G$ ratios in Raman spectra, increase of the starting oxidation temperatures observed in thermogravimetric analysis (TGA), decrease of the volumetric electrical resistivity and decrease of the turn-on electric fields from 3.64 to 2.88V/$\mu$m in field emission measurements suggest that the graphitization of MWCNTs can be effectively enhanced and the structure of nanotubes becomes more ordered after the drastic thermite reaction process.

The h-BN and graphene films on Si substrates were prepared by RF magnetron sputtering and CVD techniques, respectively. Structures and morphologies of these films were analyzed by IR and Raman spectroscopies and scanning electronic microscopy. Thermal conductivities of bulk Si and Si substrate with h-BN or graphene grown were measured and compared. Results indicate that both h-BN and graphene films have an enhancement effect on the TC of the Si substrate even if they are not single-layer. Our findings imply that the h-BN and graphene films may have good applications as a thermal management material to help heat dissipation in semiconductor devices.