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The nonuniform plasma caused by plasma diffusion and the incomplete plasma recovery during short pulse-off time have great influences on the sheath dynamics and the implantation efficiency in plasma-based ion implantation (PBII). In this paper, a magnetized plasma diffusion fluid model is established to describe the plasma diffusion in PBII process. Together with a magnetized sheath fluid model, the full pulse period including sheath dynamics during pulse-on time and plasma recovery during pulse-off time can be described, and the models are verified to be accurate by comparing with experimentally measured electron density profiles. The influence of process parameters on sheath dynamics, the influence of incomplete plasma recovery under multi-pulse bias on implantation efficiency are investigated by solving the presented models with considering plasma diffusion. It is found that the variations of process parameters which accelerate the plasma diffusion reduce the steady-state sheath thickness and increase the ion implantation current, and vice versa. Change the pulse frequency from 1 kHz to 100 kHz under typical PBII process parameters significantly increases the average ion implantation current density, and the limiting factor which affects the implantation efficiency is converted from duty cycle to plasma diffusion. Increasing the plasma density and decreasing the transverse magnetic field are the effective methods to improve the implantation efficiency as well. The results reported here help to provide a theoretical guidance for the parameters optimization in PBII process. [ABSTRACT FROM AUTHOR]

• TiAlN thin films were deposited by deep oscillation magnetron sputtering. • Low deposition temperature was adjusted in oscillation voltage on-time and off-time. • Microstructure of TiAlN thin films changed from Zone I to Zone T with peak power. • Fracture toughness of TiAlN thin films in Zone T was optimized at a peak power. • Bombarding energy E bi and mobility D of species were discussed in deposition process. TiAlN thin films were deposited on Si(100) and AISI 304 austenitic stainless steel substrates at the low deposition temperature below 250℃ by the deep oscillation magnetron sputtering (DOMS), respectively. The peak sputtering power changed from 58.7 kW to 129.9 kW by adjusting the oscillation voltage on-time (τ on) / off-time (τ off) ratio with 6–12 μs to 30 μs. All TiAlN thin films have a face centered cubic structure with a composition of Ti 0.22 Al 0.28 N 0.50. With increasing the peak powers, a transit of the columnar morphology in Zone I with the preferred orientation of c-TiAlN(111) to a compact morphology in Zone T with c-TiAlN(200) was characterized. The hardness, residual stress, and H/E and H3/E2 ratios of TiAlN thin films increased with the maximal values obtained at the peak power of 90.2 kW, and then slightly decreased. Correspondently, the fracture toughness (K IC) of TiAlN thin films on Si(100) and AISI 304 stainless steel increased firstly from 0.56 MPa∙m1/2 to 1.10 MPa∙m1/2 and from 0.58 MPa∙m1/2 to 1.08 MPa∙m1/2 as the structure from Zone I with c-TiAlN(111) to Zone T with c-TiAlN(200), and then decreased to 0.94 MPa∙m1/2 and 0.71 MPa∙m1/2 at the structure of Zone T with c-TiAlN(200), respectively. The higher K IC values of Ti 0.22 Al 0.28 N 0.50 thin films in Zone T were achieved on Si(100) and AISI 304 stainless steel at 90.2 kW. The excellent mechanical properties of TiAlN thin films on Si(100) and AISI 304 stainless steel substrates were carried out by using DOMS at the low deposition temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] The energy state of nitrogen atoms was quantitatively studied by DFT. [•] Interaction energy between nitrogen atoms was obtained. [•] Relationship between energy and nitrogen concentration was obtained. [ABSTRACT FROM AUTHOR]

Abstract: Plasma-based low-energy nitrogen ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion enhanced deposition, has emerged as a low-temperature surface engineering technique for metal and alloy. In this paper, the pure metal Ti samples have been modified by the plasma source ion nitriding process at a process temperature of 700°C for a processing time of 4h. The nitrided Ti surfaces were constructed of a continuous and dense Ti2N compound layer about 2μm thick and a 7–8μm diffused layer. During tribological test on a ball on disk tribometer against the Si3N4 ceramic counterface, a low friction coefficient of about 0.3 and the faint wear volume were obtained for the nitrided Ti samples. The cyclic polarization curves of the nitrided Ti samples in 3.5% and 6.0% NaCl solutions showed that the improved pitting corrosion resistance with an increase of corrosion potential and a decrease of passive current, compared with that of the unnitrided Ti sample. The plasma source ion nitriding of the Ti samples provided the engineering surfaces for the functional applications with the combined improvement in wear and corrosion resistance. [Copyright &y& Elsevier]

Abstract: High-intensity pulsed ion beam (HIPIB) irradiation of AZ31 magnesium alloy is performed and electrochemical corrosion experiment of irradiated samples is carried out by using potentiodynamic polarization technology in order to explore the effect of HIPIB irradiation on corrosion resistance of magnesium alloy. The surface composition, cross-sectional morphology and microstructure are characterized by using electron probe microanalyzer, optical microscope and transmission electron microscope, respectively. The results indicated that HIPIB irradiation leads to a significant improvement in corrosion resistance of magnesium alloy, in terms of the considerable increase in both corrosion potential and pitting breakdown potential. The microstructural refinement and surface purification induced by HIPIB irradiation are responsible for the improved corrosion resistance. [Copyright &y& Elsevier]

Abstract: Poly(ethylene terephthalate) (PET) film was modified by using oxygen combined inductively coupled radio-frequency plasma (ICP) and capacitively coupled radio-frequency plasma (CCP) at the radio-frequency (RF) power of 200W and 100W, respectively, for a treatment time up to 300s. The RF plasma modification under the combined ICP and CCP mode with the controllable oxygen plasma density and oxygen ion-flux energy significantly improved the wettability of PET film, due to the creation of the polar functional groups containing oxygen, such as C–O and O–Ce increase of the surface roughness. At a low surface roughness, the polar functional groups on the PET film affected both the advancing contact angles and receding contact angles. When the surface roughness increased over a threshold, the advancing contact angles mainly depended on the polar functional groups, and the receding contact angles were particularly dependent on the surface roughness. Therefore, the controllable advancing contact angles and receding contact angles on the plasma-modified PET film were independently determined by plasma functionalization and plasma etching under the combined ICP and CCP mode. [Copyright &y& Elsevier]

Abstract: The dry sliding tribological behavior of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at energy density of 3.4J/cm2 with 10 shots is investigated by dry sliding wear tests in order to explore the effect of HIPIB irradiation on tribological property of magnesium alloy. Surface morphologies, composition and structure of the irradiated AZ31 magnesium alloys are examined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results indicated that HIPIB irradiation led to the increase in surface microhardness and the reduction in friction coefficient and wear rate. Wear rate for both the original and the irradiated samples increased with increasing sliding load from 0.1 to 0.5N. The transition from severe metallic wear to mild oxidative wear induced by HIPIB irradiation was observed by a combined analysis in surface morphology and chemical composition of wear tracks, mechanically mixed materials and wear debris, which is mainly attributed to the significant increase in microhardness resulting from grain refinement on the irradiated surface. In addition, defects induced by HIPIB irradiation promoted the diffusion of oxygen during sliding wear and therefore led to the formation of compact mixed materials and protective films on the wear tracks surface, which also contributes to the transition in wear mechanism of AZ31 magnesium alloy induced by HIPIB irradiation. [ABSTRACT FROM AUTHOR]

Abstract: The wear resistance and wear mechanism of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at an ion current density of 100A/cm2 with shot number from one to ten are investigated by dry sliding wear tests. The cross-sectional microstructure and surface microhardness of the irradiated AZ31 magnesium alloys are examined by optical microscopy (OM) and Vickers tester, respectively. It is found that surface hardness increased with increasing shot number, from an original value of 570MPa to a maximal value of 820MPa with ten shots, and the wear rate of the samples irradiated with five and ten shots was about one order of magnitude less than that of the original sample. The transition from severe metallic wear to mild oxidative wear induced by HIPIB irradiation was identified through a combined analysis in surface morphology and chemical composition of wear tracks, mechanically mixed materials, wear debris and wear scars of counterface steel ball by using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), which is mainly attributed to the significant increase in microhardness resulting from grain refinement on the irradiated surface. [Copyright &y& Elsevier]

Abstract: Enhanced photoluminescence (PL) mechanism of Er3+-doped Al2O3 powders by Y3+ codoping at wavelength 1.53μm has been investigated through PL measurements of 0.1mol% Er3+- and 0–20mol% Y3+-codoped Al2O3 powders prepared at a sintering temperature of 900°C in a non-aqueous sol–gel method. PL intensity and lifetime of Er3+–Y3+-codoped Al2O3 powders composed of γ-(Al,Er,Y)2O3 and θ-(Al,Er,Y)2O3 phases increased with increasing Y3+-codoping concentration. The 10–20mol% Y3+ codoping in 0.1mol% Er3+-doped Al2O3 powders intensified the PL intensity by about 20 times, with a PL lifetime prolonged from 3.5 to 5.8ms. A maximal increase of the optical activity of Er3+ in 0.1mol% Er3+–Y3+-codoped Al2O3 powders about one order was achieved by 10–20mol% Y3+ codoping. It is found that the improved PL properties for Er3+–Y3+-codoped Al2O3 powders are mainly attributed to enhanced optical activation of Er3+ in the Al2O3 by Y3+ codoping, and to the slightly increased radiative quantum efficiency of Er3+ in the Al2O3. [Copyright &y& Elsevier]

Abstract: The concentration profile in binary A–B nanometer-scale multilayers submitted to thermal annealing was calculated based on the Martin''s kinetic discrete model for one-dimension nonlinear interdiffusion by a diffusion asymmetry coefficient m′ and an ordering energy V between A and B atoms. With decreasing the diffusion asymmetry coefficient m′ from 0 to − 6, the concentration profile of the multilayers deviated from symmetrical distribution, and their interfaces became sharp and shifted towards the side of the sublayer with lower pair interaction energy. The difference of diffusion coefficient of A and B atoms caused by the diffusion asymmetry coefficient m′ led to the difference of net fluxes of A and B atoms in the multilayers. When the ordering energy V changed from − 0.001 eV to − 0.05 eV, change in the concentration profile and interface structure was same for the multilayers with a given diffusion asymmetry coefficient m′, but the calculated diffusion time decreased correspondently. The lower ordering energy V makes the A and B atoms aggregating more easily during the interdiffusion. It is found that the nonlinear interdiffusion of a series of binary nanometer-scale multilayers can be characterized by the diffusion asymmetry coefficient m′ and the ordering energy V, to explore the solid state reaction between the sublayers of nanometer-scale multilayers. [Copyright &y& Elsevier]

Abstract: A high nitrogen face-centered-cubic phase (γN) was obtained on the nitrided surface of 1Cr18Ni9Ti austenitic stainless steel by plasma-based low-energy nitrogen ion implantation. No pitting corrosion for the γN phase was confirmed by electrochemical polarization measurement in 3% NaCl solution. The protective passive film with a duplex character, iron hydroxide/oxides in the outer region and chromium hydroxide/oxides and iron oxides accompanying chromium and iron nitrides in the inner region, was by 2–3 times thicker than that of original stainless steel. The thick iron hydroxide/oxides region formed on the chromium hydroxide/oxides region due to the increase of alkalinity in the solution, leading to barrier against penetration of localized attack of the aggressive ions. The equivalent general corrosion resistance for the γN phase was observed in 0.5 mol/l H2SO4 solution relative to the original stainless steel. The passive film formed on the γN phase in 0.5 mol/l H2SO4 solution was similar to that of original stainless steel. The different role of nitrogen was proposed in pitting corrosion resistance and general corrosion resistance of austenitic stainless steel. [Copyright &y& Elsevier]

Abstract: Al ions with ion energy of 120 keV are implanted into Fe under ion current density of 3.18 μA/cm2 to implantation doses of 5×1016 and 1×1017 ions/cm2 at room temperature and elevated temperatures of 250 and 500 °C, respectively. At 250 °C, the distribution depth of implanted Al reaches 160 nm with a peak concentration of 6 at.% at the dose of 5×1016 ions/cm2, and 180 nm with 10 at.% at 1×1017 ions/cm2, analyzed by Rutherford backscattering spectroscopy, respectively. At 500 °C, the implantation depth is 200 nm and the maximum concentration of Al is 10 at.% at the dose of 1×1017 ions/cm2. With 5×1016 ions/cm2, the intermetallics Al13Fe4 is formed in the Fe samples at 500 °C, revealed by X-ray diffraction. With 1×1017 ions/cm2, the phase is also detected at 250 °C. The concentration-depth profiles of implanted Al in Fe samples at the room temperature, 250 °C and 500 °C are calculated by a mass transfer model that is built based on the transport of ions in matter and the irradiation enhanced diffusion. The calculated concentration-depth profiles are in reasonable agreement with those obtained from the experiments. [Copyright &y& Elsevier]

Abstract: The surface of 316L stainless steel was irradiated by high-intensity pulsed ion beams (HIPIB) at ion current density of 100, 200 and 300 A/cm2 with 10 shots. The surface morphology and the phase structure in the near surface region of original and treated samples were analyzed with scanning electron microscope (SEM) and X-ray diffraction (XRD). Electron probe microanalysis (EPMA) was used to study the distribution of elements on the irradiated surfaces. It is found that the HIPIB irradiation can smooth the surface of the targets, and a preferred orientation presents in the surface layer of the treated samples. Otherwise, selective ablation of impurities occurs during the interaction between HIPIB and the targets. Due to the compress stress wave induced by the bombardment, the microhardness is increased significantly in a depth range of up to 200 μm, which reduces the friction coefficient of the treated surfaces and improves the wear resistance of them. Because the grain size reduces and the impurities content decreases in the irradiated surface layer, the electrochemical corrosion resistance is enhanced. In addition, HIPIB irradiation prolongates the fatigue life of 316L at room temperature due to a combination of the smooth surface and the high dislocation density in the surface layer of the treated samples. [Copyright &y& Elsevier]

Abstract: The high-intensity pulsed ion beam (HIPIB) technique has emerged as an efficient tool for surface engineering of materials. In this work, the Ti6Al4V alloy is irradiated by HIPIB at an accelerating pulse voltage of 300 kV in a pulse width of 75 ns (FWHM) with an ion current density ranging from 60 A/cm2 to 250 A/cm2 under one shot. The X-ray diffraction (XRD) analysis shows that the irradiated surface composed of α-Ti phase and β-Ti phase in minor amount retains the original structure of the Ti6Al4V alloy. The irradiated surfaces have an increased microhardness of about HV0.25 N 4.1 GPa in the modified layers 150–750 μm thick, which depend on the ion current density of 60–250 A/cm2. The wear tests are performed on a pin-on-disc tribometer in which the irradiated samples are rubbed against a hardened Cr12MoV high alloy steel disc (HRC 62–63) under a normal load of 18 N using machine oil as the lubricant media. The wear rate of the irradiated Ti6Al4V alloy is approximately reduced by 50–70%, compared with that of the non-irradiated alloy. The electrochemical polarization measurement shows that improved corrosion resistance of the irradiated Ti6Al4V alloy is obtained in 1 mol l−1 HCl test solution. We proved that the HIPIB irradiation onto the Ti6Al4V alloy results in combined improvement in wear and corrosion resistance. [Copyright &y& Elsevier]

Abstract: The Al ion implantation into AZ31 magnesium alloy is carried out in a MEVVA 80-10 ion implantation system with an ion implantation dose ranging from 2×1016 ions/cm2 to 1×1017 ions/cm2 at an ion energy of 40–50 keV. The concentration–depth profile of implanted Al in AZ31 magnesium alloy was a Gaussian-type distribution in the depth up to about 840 nm with the maximum Al concentration up to about 10 at.% measured by using Rutherford backscattering spectrometry (RBS). The microstructure, which is composed of α-Mg phase, intermetallic β-Mg17Al12 and MgO phases is observed on the ion implanted samples by X-ray diffraction (XRD). Potentiodynamic anodic polarization curves in 0.01 M NaCl solution with pH=12 showed that the increase of corrosion potential and pitting breakdown potential and the decrease of the passive current density are obtained for the Al ion implanted samples. The Al ion implanted AZ31 magnesium alloy with the ion implantation dose of 2×1016 ions/cm2 achieved the high pitting breakdown potential to about −1000 mV(SCE). The wear rate of the Al ion implanted AZ31 magnesium alloy is approximately reduced by 30–40%, compared with that of the unimplanted sample. [Copyright &y& Elsevier]

Abstract: The Fe/Ti multilayers of nominal bilayer thickness of 4.0, 8.0 and 18.0 nm with alternating Fe and Ti sublayers thickness ratio of 1:1 were deposited by direct current magnetron sputtering on Si(100) substrates. The bilayer thickness of as-deposited Fe/Ti multilayers was measured as a modulation wavelength of 4.8, 8.5 and 19.0 nm, respectively, by small angle X-ray diffraction and cross-sectional transmission electron microscopy (XTEM). The three Fe/Ti multilayers were composed of pure metallic α-Fe and α-Ti according to wide angle X-ray diffraction and selected area diffraction. The Fe/Ti multilayers were in situ submitted to thermal vacuum annealing at the temperatures ranging from 523 K to 723 K for the annealing time of 3 h. With annealing at the lower temperature of 523 K, the intermetallic FeTi appeared in the Fe/Ti multilayers with small modulation wavelength of 4.8 nm. At 623 K, the intermetallic FeTi was formed with modulation wavelength of 8.5 nm. At the higher temperature of 723 K, the intermetallic FeTi was detected with modulation wavelength of 19.0 nm. The modulation wavelength of the Fe/Ti multilayers remained during the thermal annealing. The mixture of intermetallic FeTi and α-Fe phase was observed in the extended Fe sublayer of the Fe/Ti multilayers annealed at 723 K by XTEM, correspondingly the remaining Ti sublayer was obtained as a thinned sublayer. Coexistence of the intermetallic FeTi, α-Fe and α-Ti phases indicated that the dynamic factors have control of the intermixing between the Fe and Ti sublayers in the Fe/Ti multilayers during the thermal annealing. [Copyright &y& Elsevier]

Abstract: The Er3+-doped Al2O3 films were prepared by sintering Er-ion-implanted γ-AlOOH xerogel films on SiO2/Si(100) substrates. In a cycle, the γ-AlOOH xerogel films about 50 nm thick were dip-coated using aluminium isopropoxide-derived γ-AlOOH sols; the Er ions were then implanted into the γ-AlOOH xerogel films using an ion energy of 45 keV with different doses of 5×1014 to 1×1016 ions cm−2. Er3+-doped Al2O3 films were formed after 1, 2, and 4 cycles of dip-coating and implantation at different sintering temperatures of 800–1200 °C. The photoluminescence (PL) spectra were observed with a main peak at 1.533 μm and a side peak at 1.549 μm for all the Er3+-doped Al2O3 films. The intensity of PL peak of the Er3+-doped Al2O3 film obtained after 4 cycles with 5×1015 ions cm−2 dose at every cycle and sintered at 900 °C for 5 h, increased by about 10 and 3 times compared with that of the films obtained after 1 and 2 cycles. At the same sintering temperature of 900 °C, the intensity of PL peak of the Er3+-doped Al2O3 films first increased with the increase of dose from 5×1014 to 5×1015 ions cm−2 at every cycle, and then a saturation tendency was observed when the dose further was increased to 1×1016 ions cm−2. For the samples using 5×1015 ions cm−2 dose at every cycle, the PL intensity increased with the increase of sintering temperature from 800 to 1200 °C. [Copyright &y& Elsevier]

Abstract: The ablated surface morphology feature of plasma sprayed Cr2O3 coatings on heat-resistant steel irradiated by high-intensity pulsed ion beam (HIPIB) at an ion current density of 300–500A/cm2 with a shot number of 1–10 was investigated by using scanning electron microscopy, X-ray diffractometry, microhardness testers, respectively, in order to explore the modification mechanism of HIPIB onto coatings. HIPIB irradiation caused a melting and ablating of Cr2O3 coating surface and formed a thin remelted Cr2O3 layer with compact structure. At the low ion current density of 300A/cm2, the splat melting and cavity sealing caused a partially compact surface with several microcracks. And a discontinuous remelted Cr2O3 layer on the compact matrix coating was obtained. With increasing the ion current density to 500A/cm2, the reformed splats by serious splat melting and sufficient cavity sealing induced a more compact surface with a continuous and thicker remelted layer, companying with a slight increase of microcracks. The enlarged splats reformed by serious splats remelting and sufficient cavities sealing induced a gradually compact and smooth surface on the irradiated Cr2O3 coatings with increasing the shot number and a more uniform and smooth surface with compact structure was obtained by the agglomeration of the enlarged splats after 10 shots. It is found that the change in microhardness of the compact remelted layer was consistent with the sealing feature on the irradiated surface. [Copyright &y& Elsevier]

Abstract: Plasma-based low-energy ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion enhanced deposition of thin films, for surface engineering of metallic materials was emerged as low-temperature, low-pressure surface modification technique. Plasma source ion nitriding onto AISI 316L austenitic stainless steel produced a high nitrogen face-centered-cubic phase (γN) layer about 10μm thick at the temperature of 380°C during 4h with the high microhardness of HK0.1N 22.0GPa. The microhardness of the nitrided surface from the titanium nitride phase [(Ti,Al,V)N] layer on Ti6Al4V alloy at 750°C during 4 h achieved up to about HK0.1N 15.5GPa. No pitting corrosion in the Ringer’s solution at 37°C was detected by electrochemical polarization measurement for the nitrided AISI 316L stainless steel and Ti6Al4V alloy, respectively. Plasma source ion nitriding of the metallic materials provided the engineering surfaces with combined improvement in hardness and corrosion resistance. [Copyright &y& Elsevier]

Abstract: A mass transfer model for metal ion implantation into a metal target at elevated temperatures has been built up based on transport of ions in matter and radiation enhanced diffusion. It is used to calculate concentration-depth profiles and compositional changes of the implanted species. The ion implantation at elevated temperatures was simulated by a dynamic Monte Carlo (MC) method, which takes into account a local saturation in the crystalline target by using a maximum atomic fraction allowed in the matrix. For the diffusion process, the transport of the implanted species was obtained from the diffusion equations for the implanted species and nonequilibrium vacancies. The radiation enhanced diffusion coefficient was obtained by taking into account linear annealing of the defects. A nonequilibrium vacancy source function and surface sputtering were introduced into the diffusion equations. Concentration-depth profiles of Cr, Fe and Ni ions implanted into Al at a temperature range from 200 to 510°C were calculated. The calculated results principally were consistent with measured concentration-depth profiles obtained by Rutherford backscattering spectroscopy (RBS). In some cases deviations occur, which are discussed. [Copyright &y& Elsevier]

Abstract: The 0–1.5 mol% Er3+-doped Al2O3 films have been prepared on the thermally oxidized SiO2/Si(100) substrate in the dip-coating process by the sol–gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived γ-AlOOH sols with the addition of erbium nitrate [Er(NO3)3·5H2O]. The continuous Er3+-doped Al2O3 films with the thickness of about 1.2 μm were obtained for nine coating cycles at a sintering temperature of 900 °C. The aggregate size for the Er3+-doped Al2O3 films increased with increasing the Er3+ doping concentration from 0 to 1.5 mol%. The root-mean-square roughness of the films was independent on the Er3+ doping, which was about 1.8 nm for the 0–1.5 mol% Er3+-doped Al2O3 films. The γ-Al2O3 phase with a (110) preferred orientation was produced for the Al2O3 film. The photoluminescence (PL) spectra of 0.1–1.5 mol% Er3+-doped Al2O3 films were observed at the measurement temperature of 10 K. There was no significant change for the PL peak intensity with the increase of Er3+ doping concentration from 0.1 to 1.5 mol%, and similar full width at half maximum of about 40 nm was detected for the 0.1–1.5 mol% Er3+-doped Al2O3 thin films. The Er3+-doped Al2O3 films possess the available PL properties for use in planar optical waveguides. [Copyright &y& Elsevier]

Abstract: Plasma-based low-energy ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion-enhanced deposition, has emerged as a low-temperature surface engineering technique for steel and alloys. In this work, the effects of nitrogen alloying on the wear and corrosion resistance of the plasma source ion nitrided 1Cr18Ni9Ti austenitic stainless steel have been investigated in order to produce a combined improvement in wear and corrosion resistance. A high-nitrogen face-centered-cubic (f.c.c.) phase (γN) with the different nitrogen contents formed on the nitrided stainless steel was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing-angle X-ray diffraction and transmission electron microscopy. The wear tests were performed on a pin-on-disc tribometer in which the γN-phase samples were rubbed against a hardened Cr12MoV high-alloy steel disc (HRC 62–63) under a normal load from 2.2 to 39 N using Cr2O3 powders in machine oil as the abrasive media. The corrosion resistance was analyzed in 1% NaCl and 0.5 mol l−1 H2SO4 solutions by the electrochemical polarization technology. The γN-phase samples have a high microhardness of about HK0.1N 22 GPa and a high load-bearing capability, leading to significant improvement in wear resistance, especially under the high normal loads. The high nitrogen content in the γN phase resulted in higher wear resistance through the formation of a thicker hardened layer. The γN-phase samples have a high pitting corrosion resistance and a similar general corrosion resistance compared with those of the original stainless steel. The nitrogen content in the γN phase mainly affected the pitting corrosion resistance and slightly affected the general corrosion resistance. [Copyright &y& Elsevier]

The Er3+–Yb3+ co-doped Al2O3 powders have been prepared by the sol–gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with the addition of erbium nitrate [Er(NO3)3 · 5H2O] and ytterbium nitrate [Yb(NO3)3 · 5H2O]. The phase structure, including only two crystalline types of Al2O3 phases, γ and θ, was obtained for the 0–1 mol% Er3+ and 0–2 mol% Yb3+ co-doped Al2O3 powders at the different sintering temperature of 800–1000 °C. The evidence for indirect pumping of Er3+ through transfer of energy from Yb3+ was found in the Al2O3 matrix material. For the 0.5 mol% Er3+ and 0.5 mol% Yb3+, the 1.0 mol% Er3+ and 1.0 mol% Yb3+ co-doped Al2O3 powders, the photoluminescence (PL) peak intensity at 1.533 μm in the spectra increased by a factor of about 2, and the corresponding full widths at half maximum (FWHM) was increased to about 59 nm, compared with that of the 0.5 and 1 mol% Er3+-doped Al2O3 powders, respectively. At the same Er3+–Yb3+ co-doping concentration, the PL intensity increased with increasing the sintering temperature from 800 to 1000 °C. Coherent effect of Er3+–Yb3+ co-doping on enhanced PL properties of Al2O3 powders was observed. A proper molar ratio of 1:1 for Yb3+ and Er3+ led to the maximum PL intensity at the same sintering temperature. [Copyright &y& Elsevier]

The Er3+-doped Al2O3 powders have been prepared by the sol–gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3 · 5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er–Al–O phases, ErAlO3 and Al10Er6O24, was obtained with the 0–5 mol% Er3+-doped Al2O3 powders at the different sintering temperature of 600–1200 °C. The phase structure has an evident influence on the photoluminescence (PL) properties for the Er3+-doped Al2O3 powders. For the phase mixture of γ-(Al,Er)2O3 and θ-(Al,Er)2O3 in minor amounts with the different Er3+ doping concentration sintered at 900 °C, the PL spectra of the full widths at half maximum (FWHM) of about 55 nm were observed with a main peak at λ=1.533 μm and a side peak at λ=1.549 μm. The stronger PL intensity was detected with the 0.5 and 1 mol% Er3+ doping concentration, and decreased with further increasing the Er3+ doping concentration. The dramatic concentration quenching effect took place above the 1.5 mol% Er3+ doping concentration. At the 1 mol% Er3+ doping concentration, the PL intensity of the Er3+-doped Al2O3 powders increased with the phase structure changed from γ-(Al,Er)2O3 → θ-(Al,Er)2O3 → α-(Al,Er)2O3, corresponding to the increase of sintering temperature from 600 to 1200 °C. The PL spectrum was observed with the main sharp peak at λ=1.533 μm and many sharp side peaks at the different wavelengths for the α-(Al,Er)2 O3, ErAlO3 and Al10Er6O24 phases prepared at 1200 °C. [Copyright &y& Elsevier]

Surface morphology of pure Ti irradiated by high-intensity pulsed ion beam (HIPIB) with ion current density of 60–250 A/cm2 and shot number of 1–30 at 220 kV has been investigated by using profilometer, scanning electron microscopy and atomic force microscopy to explore the interaction mechanism between HIPIB and metallic materials. Two kinds of samples were prepared with different initial surface roughness (Ra), i.e. high-roughness and low-roughness Ti, respectively. A similar change trend of Ra was found on the irradiated surfaces for both the two kinds of samples that increase of the Ra was obtained with few shot number and then continuous decrease of the Ra to a surface smoothing was with multi-shot irradiation. However, the increase of Ra on the irradiated low-roughness Ti was greatly limited as compared to the high-roughness case. It is demonstrated that surface smoothing and roughening of irradiated Ti can be realized under optimization of the parameters by combining adjustments of ion current density and shot number. The morphology features on the irradiated high-roughness Ti were craters and waviness for roughened surfaces and some vague or apparent texture with disappearance of the craters for smoothed surfaces. For the low-roughness Ti, no distinct craters were formed except for some obvious texture. The micro-non-uniformity (micro-protrusions) on the irradiated surfaces causes the cratering on pure Ti by inducing a selective ablation under HIPIB irradiation. The locally more intense liquid evaporation and droplet ejection from the irradiated surfaces of different morphologies led to disturbance of the molten surface layer in the different scales, resulting in the surface roughening and smoothing. [Copyright &y& Elsevier]

Surface morphology and roughness of pure Ti irradiated by a high-intensity pulsed ion beam (HIPIB) have been investigated by using scanning electronic microscopy and profilometry in order to explore the interaction mechanism between HIPIB and metallic materials. Two groups of Ti samples of different initial surface roughness (Ra) were prepared to determine the effect of original surface states on the crater formation as a result of HIPIB irradiation. Particularly, the cratering behavior under various irradiation intensities was clarified by examining large Ti samples of high initial roughness with Ra of 0.18 μm. It is noted that no obvious cratering took place on Ti of low initial roughness. For high-roughness Ti, the Ra significantly increased from an initial value of 0.18 μm to the maximal 0.43 μm at 250 A/cm2 with 1 shot, and then decreased continuously to a final 0.06 μm with 30 shots presenting a planar ablated surface. The similar trend for Ra was also found for the low-roughness Ti, but the maximal value was limited to 0.18 μm from the initial 0.07 μm. The micro non-uniformity of the original surfaces resulted in the cratering on pure Ti by inducing a selective ablation and disturbance of the molten surfaces under HIPIB irradiation. A more uniform ablated Ti surface without crater formation was obtained by multi-shot irradiation due to the gradually decreased non-uniformity at the repetitive ablation. [Copyright &y& Elsevier]

A series of alloy elements, including the detrimental neutral and beneficial elements for bulk alloying into γ-TiAl base intermetallics, i.e., V, Cr, Y, Er, Nb, and W, has been implanted into a γ-Ti-50Al intermetallic in order to explore the mechanism of high-temperature oxidation resistance for the ionimplanted intermetallic. The oxidation resistance was investigated under cyclic-oxidation conditions at oxidation temperatures from 800 to 1000°C for 200 hr in air. At a lower oxidation temperature of 800°C, the V-ion implantation has a detrimental effect on the oxidation resistance of Ti-50Al, while a neutral and beneficial effect was observed for Er-, Y- and Cr-, Nb-, W-ion implantation, respectively. At 900°C, V-, Er-, Y-, and Cr-ion implantation all showed a neutral effect, whereas Nb- and W-ion implantation apparently improved the oxidation resistance. With increasing oxidation temperature to 1000°C, Y- and Cr-ion implantation kept the neutral effect, and the beneficial effect of Nb-ion implantation disappeared gradually. The oxidation behavior of ion-implanted γ-TiAl base intermetallics is different from that of bulk- alloyed materials due to the two alloying methods, although the effect of the alloy elements on the oxidation resistance has not essentially changed in the γ-TiAl base intermetallics. [ABSTRACT FROM AUTHOR]

The mechanical properties of WC-Ni coatings by HVOF thermal spraying were comprehensively evaluated by indentation tests at a wide load range of 10−1-103 N, i.e. nano-, micro- and macro-indentations. The correlation between process parameters and coating microstructure and mechanical properties was characterized via particle deposition temperature. The coating microstructure changes in reduced porosity, enhanced WC phase decomposition and better splats flattening were correlated to the particle deposition temperature rising. A porosity divergence between coating surface and cross-section was found as a quantitative anisotropy indicator to coating intrinsic lamellar microstructure formed by the splats flattening and piling up. Considering the lamellar microstructure, indentation responses on coating surface and cross-section were compared for hardness and elastic modulus evaluation below 3 N. The surface hardness is higher than that of cross-section, and both increased correlatively to the particle deposition temperature rising except for the almost constant surface hardness below 1 N. An analogous particle temperature-dependent behavior was also manifested for the elastic modulus by nano-indentation below 1 N. Interestingly, the elastic modulus by coating surface micro-indentation at 30 N presented identical particle temperature dependence to that by coating cross-section nano-indentation, both consistently representing the overall coating elastic modulus change trend verified by non-destructive ultrasonic test. Indentation fracture toughness on coating surface under 1.96 kN and on coating cross-section under 49 N was comparatively evaluated, and the values had a reverse trend of dependence on the particle deposition temperature. The particle-deposition-temperature dependent mechanical properties were interpreted by the coating intra-splats and inter-splats defects reduction with enhanced carbide-metal bonding essentially determined by the melting state of the metal binder phase, providing an insight to utilize indentation tests for characterizing thermal spray coatings. • WC-12Ni coatings with laminate microstructure are indented in a wide load range. • Surface and cross-section porosity divergence is a quantitative laminate indicator. • Metal binder phase melting state controls intra-splats/inter-splats defects reduction. • Indentation depth effect of hardness and elastic modulus is clarified with laminate. • Microstructure and mechanical properties correlate to particle deposition temperature. [ABSTRACT FROM AUTHOR]

In present work, a perfect nitrogen-expanded austenite free from the deformation defect is prepared by the plasma-based low-energy nitrogen ion implanted (also named plasma source ion nitriding) TEM foil of Fe-Cr-Ni austenitic alloys under an unconstrained condition. The effective area in nano-scale, which is constructed by the perfect nitrogen-expanded austenite without stress and plastic strain, is obtained for TEM observation. The electron diffraction directly proves that the Fe 4 N-like long-rang ordered transformation is the nature of nitrogen-expanded austenite only dependent on nitrogen concentration, and independent on stress or defect. Moreover, the intrinsic microstructure of the nitrogen-expanded austenite is confirmed without twins and ε-martensite, which were formed from the constrained deformation of the nitrided layer depending on the stacking fault energy. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Experimentally and theoretically, the basic structures of disordered expanded austenite, γ N , and ordered expanded austenite, γ' N , have been confirmed to consist of Cr-N short-range ordering (SRO) and Fe 4 N-like long-range ordering (LRO) in addition to Cr-N SRO, respectively. So far, the transition from γ N to γ' N during low temperature nitriding has not been elucidated. In present work, four f.c.c. Fe-Cr-Ni alloys with 0, 6, 12 and about 18 wt.% Cr in low-temperature nitrided condition were investigated with transmission electron microscopy (TEM) to explore the evolution from γ N to γ' N. The Fe 4 N-like LRO is present as small ordered domains separated by antiphase boundaries. Ordering of the interstitial nitrogen involves nucleation, growth and, after impingement, coarsening of the ordered domains. The domain size decreases with Cr content and increases with N content in the investigated alloys. A 3-dimensional Cellular Automaton (CA) was developed to simulate nucleation and growth until impingement into full LRO was reached; also the subsequent coarsening stage was simulated. The simulated distributions of ordered domains for the range of Cr contents are consistent with the TEM results. Cr-N SRO plays both a role of promoting nucleation and limiting growth of the ordered domains. Diffraction simulation by Fourier transforming the CA-simulated nitrogen distribution is consistent with the diffraction data and clarifies the different roles of high-density antiphase boundaries and Cr-N SRO on the superlattice reflections. The simulation is further validated by comparison of the predicted distributions of occupied interstices to literature data for Mössbauer spectroscopy and Extended X-ray Absorption Fine Structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Surface characterization of WC-13Ni cemented carbide irradiated by high intensity pulsed electron beam (HIPEB) at energy density of 3–34 J/cm 2 with 10 pulse was investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and Vickers tester. The surface tribological properties were measured by a block-on-ring tribometer. It was found that the HIPEB irradiation induced surface remelting and Ni selective ablation, resulting in the phase transformation from hexagonal α -WC to metastable phases, i.e. face centered cubic β- WC 1- x and hexagonal α -W 2 C, and the formation of some defects such as microcracks and blow holes, and then the microstructural changes provided hardening and softening in different degree on the irradiated surface. The friction coefficient of irradiated samples reduced from 0.8 of the original WC-13Ni cemented carbide to 0.5, and the specific wear rate decreased to 3.8 × 10 −7 mm 3 /Nm from 1.2 × 10 −6 mm 3 /Nm, showing the surface tribological properties of HIPEB irradiated WC-13Ni cemented carbide is not only related to the surface hardening, but also with the surface microstructure. [ABSTRACT FROM AUTHOR]

AISI 304 L austenitic stainless steel was modified by using the plasma-based low-energy nitrogen ion implantation (PBLEII) at a process temperature of 400 °C for a processing time of 4 h in order to improve the corrosion-fatigue resistance of the austenitic stainless steel. A single high-nitrogen face-centered-cubic phase (γ N ) layer with a maximal nitrogen concentration of about 25 at.% was formed on the nitrogen-modified austenitic stainless steel. Compared with the original austenitic stainless steel, the γ N phase layer on the austenitic stainless steel possessed a significant improvement in corrosion resistance in the borate buffer solution with a pH value of 8.4. The corrosion-fatigue properties of the γ N phase layer on the austenitic stainless steel were examined by the push–pull fatigue experiments with a ratio R of tensile and compression of − 1 in the borate buffer solution. The γ N phase layer has an increased corrosion-fatigue strength up to 230 MPa from 180 MPa of the original austenitic stainless steel with an apparent increase of about 28%. The corrosion-fatigue crack initiation in the γ N phase layer was found as a controllable stage in the fracture process at the interface between the γ N phase layer and the austenitic stainless steel matrix with the arc corrosion-fatigue source. Some tiny corrosion-fatigue striations were obtained on the corrosion-fracture surfaces of the γ N phase layer. The high density of slip bands and dislocations in the γ N phase layer was able to prevent the crack initiation and propagation, leading to improvement of the corrosion-fatigue properties in the borate buffer solution. [ABSTRACT FROM AUTHOR]

A recent investigation of the nitriding response of austenitic Fe-Cr-Ni alloys with various compositions showed that the surface adjacent zone generally identified as expanded austenite consists of a duplex structure. In the near-surface part, with the highest N content, long-range ordering (LRO) among the nitrogen atoms occurs in addition to short-range ordering (SRO) of N and Cr atoms; and in the near-matrix part, with a lower N content, only SRO of N and Cr atoms is encountered. These zones are dubbed γ' N and γ N , respectively. In the present contribution, a pragmatic model is presented to effectively describe the nitrogen arrangements in γ N and γ' N and the transition of one into the other by changing the Cr and N contents. The model considers the occupancy of octahedral interstices surrounded by more than one Cr atom and, depending on the number of Cr atoms constituting the octahedron, distinguishes between strong and weak interactions between the octahedral sites and N atoms. In order to account for the competition between Cr-N SRO and Fe 4 N-like LRO, the occupancy of neighboring interstices with N surrounding a central metal atom is taken into consideration. The distribution of N atoms over differently coordinated interstices is obtained by pragmatically fitting the model to experimental data. The model is validated by comparison of the predicted distributions of occupied interstices to literature data for Mössbauer spectroscopy and Extended X-ray Absorption Fine Structure, respectively. Furthermore, the model provides a consistent interpretation of thermodynamics and diffusion data for nitrogen-stabilized expanded austenite. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Modification of WC-Ni cemented carbides was studied by using high-intensity pulsed ion beam (HIPIB) irradiation. Surface hardening can be achieved for all the HIPIB-irradiated surfaces but of different degree at ion current density of 50–300A/cm2 up to 10 shots. Thermal and dynamic process of remelting and ablation under HIPIB irradiation led to significant changes in surface morphology, phase structures and composition of the irradiated surfaces. Gradual transitions to remelting densification, selective ablation of Ni binder and phase transformation from hexagonal α-WC to cubic non-stoichiometric β-WC1−x were found by adjusting the irradiation intensity and shot number, explaining the hardness enhancement of cemented carbides. It is revealed that the densification with defects healing and the lower binder content can significantly enhance the hardness whereas occurrence of the metastable non-stoichiometric phase and limited surface cracking may slightly lower the hardness. The parameter-dependent variation of surface hardening degree is thus attributed to single or multiple contributions from remelting densification, binder removal and phase transformation. It is demonstrated by the HIPIB processing that mechanical properties of WC based cemented carbides may be effectively improved by decreasing the binder phase content and enhancing the bonding strength between carbide grain and binder with less defect density. [Copyright &y& Elsevier]

Abstract: In order to apply the inner surface modification of the tube component by plasma-based ion implantation (PBII) technique, the tube size has been characterized by introducing a characteristic parameter – the critical radius of tube (CRT) to optimize the process parameters of a grid-enhanced PBII technique for the nitrogen ion implantation onto the inner surface of an Fe–Cr–Ni stainless steel tube under the process conditions, including the plasma density of central plasma source, the steady pulse voltage, the grid electrode radius, and the processing pressure. The temporal sheath dynamics of the ion matrix sheath on the inner surface of the tube component modified by PBII were demonstrated by the collisional fluid model using the equations of ion continuity and ion motion, Poisson’s equation, and Boltzmann’s relationship of electron to determine the effective range of the process parameters. The optimum process parameters were found by the effect factors of the CRT which was bounded by the two important process parameters, i.e. the ion implantation dose and the processing time, for the engineering practice due to the available dependence on the surface modification effect in suitable costs. [Copyright &y& Elsevier]

Abstract: Microarc oxidation (MAO) films on AZ31 magnesium alloy were treated by high-intensity pulsed ion beam (HIPIB) irradiation with ion energy of 300keV at ion current density of 200A/cm2. A remelted layer of a few micrometers was produced on irradiated MAO films. The corrosion resistance of MAO films was characterized by potentiodynamic electrochemical test in 3.5% NaCl solution. The anodic polarization behavior of MAO samples exhibited a transition from the active anodic dissolution for the original one to the passivation–pitting breakdown for the modified films. The passivation–pitting breakdown voltage of modified films increased with multi-shot irradiation, i.e. from a value of −1420mV(SCE) at 1 shot to −800mV(SCE) at 5 shots, and the corresponding passivation current density decreased by two orders of magnitude. The irradiated MAO films have a higher corrosion potential than the original one, reaching a maximal value of −1350mV(SCE) at 5 shots from the original −1580mV(SCE). The electrochemical impedance spectrum (EIS) of modified MAO films was measured with varying the immersion time in 3.5% NaCl solution. The Nyquist impedance plots from modified films may show only a capacitive loop at the immersion time of 5h, and the inductive loop occur at longer immersion time, whereas original films presenting both capacitive and inductive loops at all the immersion time. Bode plots of MAO films before and after irradiation were obviously distinguished in shape at low frequency range, especially at short immersion time. The evolution of Nyquist and Bode plots with immersion time was discussed in association with the processes of electrolyte penetration into the MAO structure and resultant reaction at the film-substrate interface. It is concluded that the improvement in the continuity and compaction of MAO films accounts for the enhanced corrosion resistance of the films irradiated by HIPIB. [Copyright &y& Elsevier]

Abstract: The energy deposition of high-intensity pulsed ion beam (HIPIB) into a titanium target was studied in TEMP-6 apparatus of bipolar-pulse mode using a self-magnetic field magnetically insulated ion diode (MID), where anode plasma was pre-generated by a first negative voltage and then mixed carbon ions and proton beam was extracted during the positive stage of the bipolar pulse. According with the time-of-flight (TOF) of ions, C+ arriving at the target 14cm downstream from the MID was delayed by 55ns relative to H+ at a peak accelerating voltage of 250kV and the ion energy spectrum varied greatly, starting with a Gaussian profile at exit of MID and arriving with a multi-energy complex distribution. The TOF ion energy deposition of HIPIB showed that the energy deposition proceeded firstly in a deeper depth delivered by H+ and then moved towards a top layer dominated by C+. It is found that, the contribution of H+ to the energy deposition is negligible at the beam composition of 70%C+ and 30%H+. As a result, the gradient of energy deposition profile in target is negative by C+ deposition through the whole pulse. This unique feature of HIPIB energy deposition can lead to different thermal and dynamic effects as compared to previous studies of H+-abundant HIPIB, electron or laser beam, especially limiting subsurface heating that is concerned as a major cause of droplet ejection and surface cratering and waviness formation. [Copyright &y& Elsevier]

Abstract: 1 mol%Er3+–10 mol%Yb3+ codoped Al2O3 thin films have been prepared on thermally oxidized SiO2/Si(110) substrates by a dip-coating process in the non-aqueous sol–gel method from the hydrolysis of aluminum isopropoxide [Al(OC3H7)3] under isopropanol environment. Addition of N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA) into the sol suppresses formation of the cracks in the Er3+–Yb3+ codoped Al2O3 thin films when the rare-earth ion is doped with a high doping concentration. Homogeneous, smooth and crack-free Er3+–Yb3+ codoped Al2O3 thin films form at the conditions by a molar ratio of 1:1 for DMF:Al(OC3H7)3. A strong photoluminescence spectrum with a broadband extending from 1.400 to 1.700 µm centered at 1.533 µm is obtained for the Er3+–Yb3+ codoped Al2O3 thin films, which is unrelated to the addition of DMF. Controllable formation of the Er3+–Yb3+ codoped Al2O3 thin films may be explained by the fact that the DMF assisted the deprotonation process of ;OH at the surfaces of gel particles, resulting in enhancement of the degree of polymerization of sols and improvement of the mechanical properties of gel thin films. [Copyright &y& Elsevier]

Abstract: The 1mol% Er3+- and 0–20mol% Yb3+-codoped Al2O3 powders have been prepared by the nonaqueous sol–gel process using aluminum isopropoxide as precursor, acetylacetone as chelating agent, nitric acid as catalyzer, and hydrated erbium and ytterbium nitrate as dopant under isopropanol environment. The two crystalline types of doped Al2O3, γ and θ, and a stoichiometric compound, (Yb,Er)3Al5O12, were obtained for all the Er3+–Yb3+-codoped Al2O3 powders at the sintering temperature of 1000°C. The maximal intensity of both the green and red up-conversion emissions centered at about 523, 545, and 660nm was observed for the 1mol% Er3+- and 10mol% Yb3+-codoped Al2O3 powders. The intensity ratio of the red to green up-conversion emission (I red/I green) increased with increasing the Yb3+ doping concentration for the Er3+–Yb3+-codoped Al2O3 powders. Furthermore, the intensity ratio of the green up-conversion emission at about 523 to 545nm (I 523/I 545) was proportional to the Yb3+ doping concentration and pump electric current, which was associated with the elevated temperature of powders. [Copyright &y& Elsevier]

Abstract: High-intensity pulsed ion beam (HIPIB) treatment is a promising technology of surface modification. In this paper, the creep property of 316L stainless steel irradiated by HIPIB at incident energy fluence per shot of 1.1–3.4J/cm2 with 1–10 shots at 700°C have been studied. It is found that the creep property of the treated specimens after 10 shots fluctuates greatly with increasing energy density per shot. HIPIB irradiation at energy density of 1.1J/cm2 and 2.3J/cm2 prolong the creep rupture life and reduce the steady creep rate with respect to the original specimen. In contrast, HIPIB irradiation at 3.4J/cm2 proves to be detrimental, causing a shorter rupture life and a faster steady creep rate. Otherwise, at a fixed irradiation intensity of 2.3J/cm2 per shot, the number of shots has little effect on the creep property of the treated specimens. The specimens irradiated with 1, 5 and 10 shots all have better creep property compared to the control one and the difference between them is not big. The surface morphology and phase structure in the near surface region of the specimens before and after irradiation were analyzed by using scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. It is shown that the HIPIB irradiation can smooth the surface of the specimens, which can restrain the production of the surface crack. And the presence of a preferred orientation implies the treatment creates an intense compression wave and high dislocation density in the surface layer of the irradiated specimens, which hinders the dislocations movement. [Copyright &y& Elsevier]

Abstract: High-intensity pulsed ion beam (HIPIB) treatment is a new technology for surface modification of materials. In this paper, the surface of 316L stainless steel was irradiated by high-intensity pulsed ion beams at ion current density of 100, 200 and 300A/cm2 with 1, 5 and 10 shots. The surface morphology and the phase structure in the near surface region of original and treated samples were analyzed with scanning electron microscope (SEM) and X-ray diffraction (XRD). Electron probe microanalysis (EPMA) was used to study the distribution of elements on the irradiated surfaces. It is found that the HIPIB irradiation can smooth the surface of the targets, and a preferred orientation presents in the surface layer of the treated samples. Otherwise, selective ablation of impurities occurs during the interaction between HIPIB and the targets. The influence of HIPIB irradiation on the electrochemical corrosion resistance of 316L stainless steel in 0.5mol/L H2SO4 was investigated. The polarization curves show that under the cooperation of the smooth surface and the grain refinement with the selective ablation of impurities, the corrosion resistance of the irradiated samples was improved significantly. [Copyright &y& Elsevier]

Abstract: Er3+ doped Al2O3 has been prepared by a non-aqueous sol–gel method using aluminum isopropoxide as precursor, acetylacetone as chelating agent, nitric acid as catalyzer, and hydrated erbium nitrate as a dopant in an isopropanol environment. The fluorescence intensity ratio (FIR) of the green up-conversion emissions at the wavelengths of about 523 and 545nm in the Er3+ doped Al2O3 was studied as a function of temperature over a wide temperature range of 295–773K, using a 978nm semiconductor laser diode (LD) as an excitation source. The maximum sensitivity and the temperature resolution derived form the FIR of the green up-conversion emissions are approximately 0.0052K−1 and 0.3K, respectively. It is demonstrated that the prototype optical high temperature sensor based on the FIR technique from the green up-conversion emissions in the Er3+ doped Al2O3 is promising for applications in high temperature measurement. [Copyright &y& Elsevier]

Abstract: The Al ion implantation into AZ31 magnesium alloy was carried out in a MEVVA 80–10 ion implantation system at an ion energy of 40–50 keV with an ion implantation dose ranging from 2×1016 to 1×1017 ions/cm2 at an elevated temperature of 300 °C induced by an ion current density of 26 μA/cm2. The concentration–depth profile of implanted Al in AZ31 alloy measured by Rutherford backscattering spectrometry (RBS) is a Gaussian-type-like distribution in a depth up to about 1200 nm with the maximum Al concentration of about 8 at.%. The X-ray diffraction (XRD) analysis revealed the formation of α-Mg(Al) phase, intermetallic β-Mg17Al12, and MgO phase on the Al ion implanted samples. The potentiodynamic anodic polarization curves of the Al ion implanted samples in the 0.01 mol/l NaCl solution with a pH value of 12 showed increases of the corrosion potential and the pitting breakdown potential, and a decrease of the passive current density, respectively. The Al ion implanted samples with 6×1016 ions/cm2 achieved the high pitting breakdown potential to about −480 mV (SCE). In the 0.08 mol/l NaCl solution with pH=12, the Al ion implanted samples with 1×1017 ions/cm2 showed an increased pitting breakdown potential to about −1290 mV (SCE), from around −1540 mV (SCE) of unimplanted samples. It is indicated that different corrosion mechanisms are responsible for improvement in corrosion resistance of the AZ31 magnesium alloy in the NaCl solutions with the varied concentrations. [Copyright &y& Elsevier]

Abstract: The Er3+-doped Al2O3 powders have been prepared by the non-aqueous sol–gel method using the aluminum isopropoxide as precursor, acetylacetone as chelating agent, nitric acid as catalyzer, and hydrated erbium nitrate, as dopant under isopropanol environment. The phase structure and phase transition of the Er3+-doped Al2O3 powders were investigated by using thermogravimetry/differential thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The phase contents diagram for the Er-doped Al–O system with the doping concentration up to 5mol% was described at the sintering temperature from 550 to 1250°C. There were the three crystalline types of Er3+-doped Al2O3 phases, γ-, θ- and α-(Al, Er)2O3, and the two relative stoichiometric compounds composed of Al, Er, and O, ErAlO3 and Al10Er6O24 phases in the Er–Al–O phase contents diagram. The Er3+ doping suppressed crystallization of the γ and θ phases and delayed phase transition of the γ→θ and θ→α. The increased Er3+ doping concentration and the elevated sintering temperature enhanced the precipitation of the ErAlO3 and Al10Er6O24 phases. The preparation procedure for the Er3+-doped Al2O3 powders in the non-aqueous sol–gel process, including chelating, hydrolysis, peptization, doping and gelation, has a significant effect on the phase formation and its transition for the Er3+-doped Al2O3 powders. [Copyright &y& Elsevier]

Abstract: The model of effective heat of formation in metal-Al binary system proposed by Pretorius et al. was developed based on characteristics of the solid-state reaction at interface to predict the formation of intermetallics during metal ion implantation into Al substrate at elevated temperature. For the Fe, Hf, Mo, Nb, Ni, Ta and Zr ion implantation with the ion energy of 50–140keV under the ion current density of 10–60μA/cm2 into Al substrate to the implantation dose of 1017–1018 ions/cm2 at the elevated temperature ranging from 300°C to 600°C, the model of effective heat of formation predicted the formation of intermetallics Al13Fe4, HfAl3, MoAl12, NbAl3, NiAl3, TaAl3 and ZrAl3, which were consistent with the experimental results. Taking the kinetic factors and the limitation of thermodynamic data into account, the model of effective heat of formation explained the formation of metastable intermetallics Cr14Al86 at the lower temperature of 400°C and of the stable intermetallics Cr2Al13 at the higher temperature of 510°C, and the formation of simple intermetallics VAl3 relative to complex intermetallics V4Al23, VAl7, and VAl10, for the Cr and V ion implantation into Al substrate, respectively, at the elevated temperature up to 510°C. [Copyright &y& Elsevier]

Abstract: The axisymmetric model of heat transfer in materials irradiated by high-intensity pulsed ion beam (HIPIB) was constructed based on the temporal and spatial distribution of the HIPIB. The ablated behaviors on titanium irradiated by HIPIB during a pulse width of 120ns with the shots up to 10 was investigated using the enthalpy formulation under an energy density range from 0.1 to 120J/cm2, considering the HIPIB energy absorption coefficient of materials. At the first shot, the critical energy density for melting and ablating on the irradiated titanium was 0.2 and 0.7J/cm2, respectively, and as the energy density increased up to 120J/cm2, the onset times for melting and ablating were shorten and their interval was also decreased. After 2 shots, both the onset times were delayed and the time interval was increased, whereas following the shots up to 10, both the onset times were kept at constant. As the energy density increased from 0.7 to 120J/cm2, the melting and ablating depths at the center of sample surface increased, the thickness of liquid layer in initial stage increased and then decreased after the first shot. During the pulse, both the melting and ablating depths increased monotonically, while the thickness of liquid layer initially increased, then decreased, and finally increased again. For the shots up to 10, both the depths increased with the constant thickness of liquid layer. The ablation mass of titanium irradiated by HIPIB with the shots up to 10 under an energy density from 0.7 to 120J/cm2 was obtained from the calculated ablating depth. The calculated ablation mass of irradiated Ti sample with 10 shots under the energy density of 70J/cm2 was consistent with that measured by HIPIB irradiation experiments. [Copyright &y& Elsevier]

• Real-time nanostructure of passive film on γ N phase is characterized by TEM/EDS. • All passive films composed of defect spinels are epitaxially growing on γ N phase. • n -type inner (Fe,Cr) 3 (N,O) 4 and p -type outer γ -Fe 2 (N,O) 3 region in passive films. • Low-defective passive film inhibits absorption of aggressive ion. • Nanostructure of dense passive film limits migration of Cr3+ ion and anion vacancy. The real-time composition and structure of the passive film formed on a high nitrogen face-centered-cubic phase (γ N) layer at the characterized transient corrosion currents from the electrochemical noise analyses in the borate buffer solution with the pH = 7.7 are investigated by the transmission electron microscope (TEM) with energy dispersion X-ray spectrum (EDS) using the focused ion beam (FIB) sampling. The thicker passive film of the γ N phase layer on the nitrided AISI 304L in the borate buffer solutions is observed as two regions structure of O enriched n -type defect spinel γ -Fe 2 (N,O) 3 and hydroxides in the outer region and Cr and N enriched p -type defect spinel (Fe,Cr) 3 (N,O) 4 in the inner region, although few β -(Fe,Cr)OOH compounds are detected due to dehydration. The defect spinel in directions of < 112 >, < 213 > and < 110 > is epitaxially growing on the γ N phase matrix during the passivation up to 8 h with a decreasing lattice mismatch from 5.9 to 1%, which is attributed to lattice expansion of the γ N phase and the defect spinel. The lattice expansion of the γ N phase at the interface with growing passive film is affected by dissolving nitrogen outward to the borate buffer solution. The dissolving nitrogen in the defect spinel induces its lattice expansion by hydrolysis at the interface. The dense and low-defective passive films on the γ N phase layer have a significant effect on the corrosion resistance due to inhibition of the absorption of aggressive ion and limitation of the carrier density. [Display omitted] [ABSTRACT FROM AUTHOR]

The fracture toughness of TiAlN thin films on AISI 304 austenitic stainless steel was inversely investigated by combining nanoindentation experiment with finite element method (FEM) and extended FEM (XFEM) simulation. The TiAlN thin films were deposited by deep oscillation magnetron sputtering (DOMS) with the oscillation pulse on and off times of 12 μs and 30 μs at a peak power of 136.1 kW. A completely dense TiAlN thin film with the thickness of 1500 nm has a face-centered-cubic microstructure with (200) preferred orientation. The displacements of the nanoindenter were intentionally interrupted by 1200 nm and 1800 nm, latter is thin film-crossing to induce an apparently cracking. The cross-sectional samples of TiAlN thin films with the cracks were fabricated by focused ion beam. The experimental crack number and position in the cross-sectional samples were observed by scanning electron microscopy. The maximum damage initiating stress (σ max) and corresponding crack separation distance (δ c) in the Griffith–Irwin relationships were fitted using the XFEM calculation based on the crack morphology to match the crack number and position of TiAlN thin films. The fracture toughness of TiAlN thin films on AISI 304 austenitic stainless steel was calculated to be 1.09 MPa m1/2 according to the fitted parameters of 5.5 GPa for σ max and 1.5 nm for δ c. Therefore, an alternative method by the nanoindentation morphology and the inversely calculation fitting was developed to estimate the fracture toughness of thin films. 1. TiAlN thin films were deposited on steel by deep oscillation magnetron sputtering. 2. Fracture toughness was evaluated by extended finite element method and experiments. 3. Key fracture parameters of TiAlN thin films were solved as an inverse problem. 4. Crack separation distance and maximum damage initiating stress were key parameters. 5. Experimental and calculated similarity in crack number and position was established. [ABSTRACT FROM AUTHOR]

Thermodynamic numerical model is established for high-intensity pulsed ion beam (HIPIB) processing of metallic components. The HIPIB delivers a thermal energy input typically of several J/cm2 per pulse of 100 ns range. Incorporation of material constraints is emphasized in the modelling to predict residual surface stresses formation as a result of material loading, i.e. the coupled thermal-mechanical material responses of processed components. Taking tungsten as an example, five sets of material constraints were comparatively studied, including temperature-dependent thermophysical properties, Zerilli-Armstrong and Johnson-Cook constitutive equations, and simplified ones adopted in other studies by assuming constant specific heat C p and/or thermal conductivity k , or ignoring the material yield strength, respectively. The highest surface temperature with the largest rising rate is observed at constant C p due to the less thermal energy for the temperature increment, while the lowest surface temperature for constant k due to more thermal energy diffused. The transient temperature field evolutions induced large temperature gradients that simultaneously caused high thermal stresses. Residual surface stresses formed only if plastic strain occurred, where the model of ignoring yield strength predicted no residual stresses formation having the largest error among the five models. The models with comprehensively incorporated material constraints, particularly for incorporation of Z-A constitutive equation considering dislocation behaviors during plastic deformation, have a higher accuracy in residual surface stresses prediction. Comprehensive incorporation of material constraints in the thermodynamic model facilitates an accurate elucidation of coupled thermal-mechanical responses for resultant residual stresses under the processing load of thermal energy input. [ABSTRACT FROM AUTHOR]