Low energy implantation to inhibit wear in N+ ions implanted WC–Co composite

This work discusses the influence of nitrogen ion (N⁺) implantation on wear resistance of WC–Co composite. The WC–Co samples were bombarded at low N⁺ ions energies of 20 and 30 keV and doses of 10¹⁷ and 2 × 10¹⁷ ions cm⁻². Tribological tests were conducted against cylindrical 100Cr6 pin at 200 N load and 180 mm s⁻¹ speed. The tests use water lubrication and four sample types with Co binder content ranging in 6.5–25%. The X-ray spectra reveal that implantation is able to transform the original [CFC] Co structure of virgin surface to harder amorphous phase. However, it was found that excessive low binder content alters the wear behavior on non-implanted samples since it causes wear rate transition from 0.59 × 10⁻⁷ to 2.1 × 10⁻⁷ mm³/(mm² s) imposing hence instable wear regime. The SEM micrographs confirm the formation of transferred film within the implanted worn surface owing to (i) an enhancement in Co flow and (ii) a generation of oxides (Fe₂O₃, Fe₃O₄, Co₂O₃, WO₂). While the formed film acts to inhibit severe abrasion, the material removal process combining cobalt flow and carbide grains pull-out seems to be associated with oxidation mechanisms to be accentuated with energy increase. The most improvements in wear resistance were observed on samples with the highest Co content and the results were found more sensitive to N⁺ ions implantation energy than dose.     

Thermal properties of manganin dynamic high-pressure sensor after complex Ti–Kr high fluence implantation,modelling and interpretation

Manganin gauge produced by Dynasen Corp (USA) in the form of planar structure of 2.5 μm thick and the nominal resistance of 20 Ω was investigated. The open surface of the gauge was implanted with 60 keV Ti ions at the fluence of 10¹⁶ ion/cm² and then with 250 MeV Kr ions at the ion fluence of 10¹³ Kr ion/cm². For Ti implantation the TRIM computer program (Transport of Ions in Matter) gives the maximum penetration range of about 50 nm. For high energy Kr ion implantation a special protection foil of 13 μm thick was used. The TRIM method of calculation gives information that Kr ions are located with the approximately constant density of 0.4 × 10¹⁹ Kr ions/cm³ all over the volume of the samples. The authors assumed that during Kr implantation Ti atoms moved into manganin up to a 0.5 μm depth. The temperature dependencies of electrical resistance of pure and implanted gauges were studied in the temperature range 20–220 °C. Using the modelling procedure for deeper interpretation of implanted foils with a layered structure, described in detail earlier by authors [5], one can calculate that the resistivity of mixed ion implantation volume decreases by about 40%. That means strong influence of Ti ions on conductivity of manganin. One can see that R–T (resistance–temperature) characteristic of gauge in the room temperature vicinity is improved in large measure. According to our data concentration of Ti ions in manganin is of the order of 2 × 10²² Ti ions/cm³.     

Transmission electron microscopy study of carbon nanophases produced by ion beam implantation

The formation of carbon nanocrystals, produced by ion implantation of carbon ions into fused SiO₂ substrates, followed by 1 h thermal annealing at 1000 °C, in an Ar + 5% H atmosphere has been studied. Combined high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) have been employed for structural characterization of carbon nanophases embedded in the quartz substrate. The dependence of grain size and sample morphology of the carbon nanophases on implantation dose was studied. The carbon nanocrystals formed by the implantation for a dose of 1 × 10¹⁶ C/cm² at 320 keV have been identified as a mixture of c-diamond nanophase and a modified diamond nanophase known as n-diamond. For a higher implantation dose, 5 × 10¹⁶ C/cm², besides n-diamond, another solid carbon nanophase was observed, with a structure known as i-carbon. Following the highest implantation dose 1 × 10¹⁷ C/cm² the sample contained the i-carbon nanophase only. A least-square refinement of SAED patterns was employed for the calculation of unit-cell parameters of identified carbon nanophases.     

Investigation of UV-photon induced hydrophilicity of titanium ion-implanted soda-lime silicate glasses

The UV-induced wetting effect on titanium oxide surface is well-known; however, the UV-induced hydrophilicity of titanium implanted soda-lime silicate glass has not been investigated. Hence the contact angle of water droplet under the indoor fluorescent lights on titanium-ion implanted soda-lime silicate glasses was investigated. The silicate glasses were implanted by MEVVA ion implanter by 40 keV titanium ions with a fluence of 10¹⁵ ions cm^?2. The contact angle, the chemical bonding environment, and surface morphologies were examined. Results show the formation of TiO₂, the increase of surface roughness, and the reduction of the contact angle after the ion implantation. Further enhancement of hydrophilicity after the 254 nm pre-UV irradiation for 1 h on the implanted sample surface was observed. The enhancement of the wetting effect after ion implantation could be attributed to rougher TiO₂ content surface. However, according to the mechanisms of UV photo-induced hydrophilicity on TiO₂ proposed previously, the enhancement of hydrophilicity of titanium implanted surface with and without 254 nm pre-photon radiation can be attributed to not only the reduction of hydrocarbon on surface during the UV radiation but also to the oxygen vacancies produced by 254 nm UV photon irradiation.     

Surface characterization and wear behavior of ion implanted NiTi shape memory alloy

The aim of this study was investigation of changes in the modified near-surface layer on the NiTi shape memory alloy, caused by ion implantation as well as their influence on the mechanical and shape memory properties of this material. Surface of NiTi has been modified by nitrogen ion beam at several fluences 1 × 10¹⁷ cm^?2, 1 × 10¹⁸ cm^?2 and 2 × 10¹⁸ cm^?2 at the energy 50 keV. The effect of implantation parameters on surface characteristics and wear properties was investigated using dry-sliding-wear test, depth sensing indentation test and scanning profilometry method. The experimental results have shown how the ion implantation treatment can change the original surface: reducing Ni content in the surface, increasing the surface hardness (furthermore, the hardness improvement extended to the regions much deeper than the implanted layer), and improving the sliding wear resistance. The experimental results of surface treatment conditions and mechanical properties of the modified NiTi alloys are compared, analyzed and discussed in this paper.     

Temperature dependent work hardening in Ti–6Al–4V alloy over large temperature and strain rate ranges: Experiments and constitutive modeling

The plastic deformation behaviors of Ti–6Al–4V alloy over wide ranges of strain rate (from 10⁻⁴ to 10⁴ s⁻¹) and temperature (from 20 to 900 °C) are investigated by the quasi-static and dynamic uniaxial compression tests. The microstructure evolution of Ti–6Al–4V alloy at different temperatures is discussed. Material generates higher ductility and formability when temperature is higher than 500 °C, which leads to the decrease of work hardening rate. The true stress–strain responses are modeled with the JC, modified JC, KHL and modified KHL models. In detail, a temperature dependent work hardening function is introduced into the original JC and KHL models. The parameters of the four models for Ti–6Al–4V alloy are calculated by GA optimization method. The average standard deviations between the experimental and calculated flow stresses range from 4% to 13%, which validates the accuracy of the models. In addition, comparison of flow stresses at dynamic (10,000 s⁻¹), the work hardening rates at dynamic (7500 s⁻¹), as well as the quasi-static jump experiments were proposed to further validate the models. The modified JC and modified KHL models could characterize the temperature dependent work hardening effect for Ti–6Al–4V alloy over large strain rate and temperature ranges.     

Extremely high surface area of ordered mesoporous MCM-41 by atrane route

Silatrane synthesized from inexpensive oxide precursor, silica and TEA was used as the precursor for MCM-41 synthesis at low temperature because of its stability in aqueous solutions. Using cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB) as a template, the resulting meso-structure mimics the liquid crystal phase. Varying the surfactant concentration, ion concentration and temperature of the system, changes the structure of the liquid crystal phase, resulting in different pore structures and surface area. After heat treatment, very high surface area mesoporous silica was obtained and characterized using XRD, BET and TEM. XRD and TEM results show a clear picture of hexagonal structure. The surface area is extraordinarily high, up to more than 2400 m² g⁻¹ at a pore volume of 1.29 cm³ g⁻¹. However, the pore volume is up to 1.72 cm³ g⁻¹ when the surface area is greater than 2100 m² g⁻¹.     

Mg ion implantation on SLA-treated titanium surface and its effects on the behavior of mesenchymal stem cell

Magnesium (Mg) is one of the most important ions associated with bone osseointegration. The aim of this study was to evaluate the cellular effects of Mg implantation in titanium (Ti) surfaces treated with sand blast using large grit and acid etching (SLA). Mg ions were implanted into the surface via vacuum arc source ion implantation. The surface morphology, chemical properties, and the amount of Mg ion release were evaluated by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), and inductively coupled plasma-optical emission spectrometer (ICP-OES). Human mesenchymal stem cells (hMSCs) were used to evaluate cellular parameters such as proliferation, cytotoxicity, and adhesion morphology by MTS assay, live/dead assay, and SEM. Furthermore, osteoblast differentiation was determined on the basis of alkaline phosphatase (ALP) activity and the degree of calcium accumulation. In the Mg ion-implanted disk, 2.3 × 10¹⁶ ions/cm² was retained. However, after Mg ion implantation, the surface morphology did not change. Implanted Mg ions were rapidly released during the first 7 days in vitro. The MTS assay, live/dead assay, and SEM demonstrated increased cell attachment and growth on the Mg ion-implanted surface. In particular, Mg ion implantation increased the initial cell adhesion, and in an osteoblast differentiation assay, ALP activity and calcium accumulation. These findings suggest that Mg ion implantation using the plasma source ion implantation (PSII) technique may be useful for SLA-treated Ti dental implants to improve their osseointegration capacity.     

Development of an inconel self powered neutron detector for in-core reactor monitoring

The paper describes the development and testing of an Inconel600 (2 mm diameter×21 cm long) self-powered neutron detector for in-core neutron monitoring. The detector has 3.5 mm overall diameter and 22 cm length and is integrally coupled to a 12 m long mineral insulated cable. The performance of the detector was compared with cobalt and platinum detectors of similar dimensions. Gamma sensitivity measurements performed at the ⁶⁰Co irradiation facility in 14 MR/h gamma field showed values of −4.4×10⁻¹⁸ A/R/h/cm (−9.3×10⁻²⁴ A/γ/cm²-s/cm), −5.2×10⁻¹⁸ A/R/h/cm (−1.133×10⁻²³ A/γ/cm²-s/cm) and 34×10⁻¹⁸ A/R/h/cm (7.14×10⁻²³ A/γ/cm²-s/cm) for the Inconel, Co and Pt detectors, respectively. The detectors together with a miniature gamma ion chamber and fission chamber were tested in the in-core Apsara Swimming Pool type reactor. The ion chambers were used to estimate the neutron and gamma fields. With an effective neutron cross-section of 4b, the Inconel detector has a total sensitivity of 6×10⁻²³ A/nv/cm while the corresponding sensitivities for the platinum and cobalt detectors were 1.69×10⁻²² and 2.64×10⁻²² A/nv/cm. The linearity of the detector responses at power levels ranging from 100 to 200 kW was within ±5%. The response of the detectors to reactor scram showed that the prompt response of the Inconel detector was 0.95 while it was 0.7 and 0.95 for the platinum and cobalt self-powered detectors, respectively. The detector was also installed in the horizontal flux unit of 540 MW Pressurised Heavy Water Reactor (PHWR). The neutron flux at the detector location was calculated by Triveni code. The detector response was measured from 0.02% to 0.07% of full power and showed good correlation between power level and detector signals. Long-term tests and the dynamic response of the detector to shut down in PHWR are in progress.     

Entrapment of enzyme within organic and inorganic materials for biosensor applications: Comparative study

In order to determine the best kind of matrix that enables preservation of the enzymatic and electro-enzymatic activity of immobilized enzyme and provides accessibility towards substrate, various host materials (electropolymerized polypyrrole films, alginate polysaccharide, biocompatible synthetic latex and inorganic clays (laponite and layered double hydroxides LDHs), differing in permeability, ion exchange properties and hydrophobic–hydrophilic character, were compared for the fabrication of amperometric glucose biosensors. The electrochemical assays were performed by potentiostating the enzyme electrodes at 0.6 V vs. Ag/AgCl in order to oxidize the hydrogen peroxide enzymatically generated in the presence of glucose and oxygen. The highest sensitivity and maximum current density were recorded for laponite (82.3 mA M^− 1 cm^− 2 and 410 μA cm^− 2 respectively) and LDHs (55 mA M^− 1 cm^− 2 and 417 μA cm^− 2, respectively).     

Quantitative Analysis of Work Hardening and Dynamic Softening Behavior of low carbon alloy Steel Based on the Flow Stress

In this study, the constitutive equation and DRX(Dynamic recrystallization) model of Nuclear Pressure Vessel Material 20MnNiMo steel were established to study the work hardening and dynamic softening behavior based on the flow behavior, which was investigated by hot compression experiment at temperature of 950 °C, 1050 °C, 1150 °C and 1250 °C with strain rate of 0.01 s⁻¹, 0.1 s⁻¹ and 10 s⁻¹ on a thermo-mechanical simulator THE RMECMASTOR-Z. The critical conditions for the occurence of dynamic recrystallization were determined based on the strain hardening rate curves of 20MnNiMo steel. Then the model of volume fraction of DRX was established to analyze the DRX behavior based on flow curves. At last, the strain rate sensitivity and activation volume V^* of 20MnNiMo steel were calculated to discuss the mechanisms of work hardening and dynamic softening during the hot forming process. The results show that the volume fraction of DRX is lower with the higher value of Z (Zener–Hollomon parameter), which indicated that the DRX fraction curves can accurately predicte the DRX behavior of 20MnNiMo steel. The storage and annihilation of dislocation at off-equilibrium saturation situation is the main reason that the strain has significant effects on SRS(Strain rate sensitivity) at the low strain rate of 0.01 s⁻¹ and 0.1 s⁻¹. While, the effects of temperature on the SRS are caused by the uniformity of microstructure distribution. And the cross-slip caused by dislocation piled up which beyond the grain boundaries or obstacles is related to the low activation volume under the high Z deformation conditions. Otherwise, the coarsening of DRX grains is the main reason for the high activation volume at low Z under the same strain conditions.     

Anomalous activation of shallow B+ implants in Ge

The electrical activation of B⁺ implantation at 2 keV to doses of 5.0 × 10¹³–5.0 × 10¹⁵ cm^?2 in crystalline and pre-amorphized Ge following annealing at 400 °C for 1.0 h was studied using micro Hall effect measurements. Preamorphization improved activation for all samples with the samples implanted to a dose of 5.0 × 10¹⁵ cm^?2 displaying an estimated maximum active B concentration of 4.0 × 10²⁰ cm^?3 as compared to 2.0 × 10²⁰ cm^?3 for the crystalline sample. However, incomplete activation was observed for all samples across the investigated dose range. For the sample implanted to a dose of 5.0 × 10¹³ cm^?2, activation values were 7% and 30%, for c-Ge and PA-Ge, respectively. The results suggest the presence of an anomalous clustering phenomenon of shallow B⁺ implants in Ge.     

Refractive index profiles of planar optical waveguides in β-BBO produced by silicon ion implantation

The planar waveguides have been fabricated in z-cut beta barium metaborate crystals by 2.8 MeV Si⁺ ion implantation with doses of 1 × 10¹⁵ and 3 × 10¹⁵ ions/cm² at room temperature. The waveguides were characterized by the prism-coupling method. The refractive index profiles were reconstructed using reflectivity calculation method. It is found that relatively large positive changes of extraordinary refractive indices happen in the guiding regions, and the negative changes of ordinary refractive indices happen at the end of the track. TRIM’98 (transport of ions in matter) code was used to simulate the damage profile in β-BBO by 2.8 MeV Si⁺ ion implantation.     

Microstructure characteristic for high temperature deformation of powder metallurgy Ti–47Al–2Cr–0.2Mo alloy

Hot compression tests of a powder metallurgy (P/M) Ti–47Al–2Cr–0.2Mo (at. pct) alloy were carried out on a Gleeble-3500 simulator at the temperatures ranging from 1000 °C to 1150 °C with low strain rates ranging from 1 × 10⁻³ s⁻¹ to 1 s⁻¹. Electron back scattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to investigate the microstructure characteristic and nucleation mechanisms of dynamic recrystallization. The stress–strain curves show the typical characteristic of working hardening and flow softening. The working hardening is attributed to the dislocation movement. The flow softening is attributed to the dynamic recrystallization (DRX). The number of β phase decreases with increasing of deformation temperature and decreasing of strain rate. The ratio of dynamic recrystallization grain increases with the increasing of temperature and decreasing of strain rate. High temperature deformation mechanism of powder metallurgy Ti–47Al–2Cr–0.2Mo alloy mainly refers to twinning, dislocations motion, bending and reorientation of lamellae.     

Impact of high dose krypton ion irradiation on corrosion behavior of laser beam welded zircaloy-4

In order to study the effect of krypton ion irradiation on the aqueous corrosion behavior of laser beam welded zircaloy-4 (LBWZr4), the butt weld joint of zircaloy-4 was made by means of a carbon dioxide laser, subsequently the LBWZr4 samples were irradiated with Kr ions using an accelerator at an energy of 300 keV, with a dose range from 1 × 10¹⁵ to 3 × 10¹⁶ ions/cm² at about 150 °C. Three-sweep potentiodynamic polarization measurement was employed to evaluate the aqueous corrosion behavior of Kr-irradiated LBWZr4 in a 0.5 M H₂SO₄ solution. Scanning electron microscopy (SEM) was used to examine the surface topography of the Kr-irradiated LBWZr4 after the potentiodynamic polarization measurement. Transmission electron microscopy was employed to examine the change of microstructures in the irradiated surface. The polarization tests showed that compared with the passive current density of the as-received LBWZr4, the Kr-irradiated LBWZr4 is much lower; however, with the irradiation dose increasing from 1 × 10¹⁵ to 3 × 10¹⁶ ions/cm², the passive current density, closely related to the surface corrosion resistance, increased remarkably. The mechanism of the corrosion behavior transformation was due to the recrystallization of the amorphous phase induced by the lower ion irradiation.     

Determination of residual stresses in SiC monofilament reinforced metal-matrix composites using Raman spectroscopy

Raman spectroscopy has been used to follow the deformation of chemical vapour deposition type SCS-6 and Sigma 1140+ SiC monofilaments and to determine residual stresses in these SiC monofilaments reinforced metal-matrix composites. Raman bands at 1330 and 1600 cm⁻¹ due to carbon have been observed on the monofilament surface and it has been shown that both bands shift linearly to lower wavenumbers during tensile deformation. The residual stresses in SiC monofilament reinforced composites arising from thermal expansion mismatch have also been determined by measuring the shifts of carbon bands from the same monofilaments embedded in a Ti–6Al–4V matrix. The axial residual stresses in the carbon coating are found to be around −850 MPa for the SCS-6 composite and −540 MPa for the Sigma 1140+ composite.     

Synthesis of carbon nanostructures with unique morphologies via a reduction-catalysis reaction route

Large-scale carbon nanostructures with unique morphologies were successfully synthesized by a reduction-catalysis reaction route. The as-synthesized products, characterized by XRD, SEM and TEM, revealed that hollow carbon nanospheres with diameters in the range of 100–200 nm can be formed at 500 °C while the tetrapod-like carbon nanotubes with bamboo structure can be synthesized with the typical diameters of about 100 nm and length of over 1 μm. Two strong and wide Raman peaks at 1600 cm⁻¹ (G-band) and at 1347 cm⁻¹ (D-band) are observed at room temperature and their mechanism of formation is discussed. These unique carbon nanostructures offer potential applications, such as nanoscale transistors, amplifiers, switches and ballistic rectifiers and so on.     

Synthesis of ytterbium bisphthalocyanines: Photophysicochemical properties and nonlinear absorption behavior

Herein we report on the syntheses, photophysico-chemical properties and nonlinear absorption parameters of bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-2-yloxy phthalocyaninato)} ytterbium (III) (3) and bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium (III) (4). The fluorescence and singlet oxygen quantum yields obtained for complexes 3 and 4 are low. The triplet quantum yield obtained for complex 3 is high at Φ_T = 0.89 whereas for complex 4 Φ_T = 0.48. The third order optical susceptibility values are of the order: 10⁻¹¹ esu (for complex 3), and 10⁻¹³ esu (for complex 4) while the hyperpolarizability values are of the order: 10⁻²⁸ esu (for complex 3) and 10⁻³¹ esu (for complex 4). Complexes 3 and 4 show two-photon absorption coefficients of the order of 10⁻⁴⁶ cm⁴ s/photon and 10⁻⁴⁸ cm⁴ s/photon, and threshold intensities as low as 0.3 J cm⁻² and 0.0045 J cm⁻², respectively.     

Photoluminescence enhancement in Si+ implanted PMMA

Silicon ion implantation effects on the optical and photoluminescence (PL) properties of polymethyl–methacrylate (PMMA) have been studied. Low-energy ion implantation (E = 30–50 keV) was carried out over a range of different ion fluences (D = 10¹³–10¹⁷ cm^?2). Visible PL and optical transmission spectra in the range (330–800 nm) have been measured. The existing visible range PL emission in the unimplanted PMMA samples is clearly affected by the Si⁺ ion implantation and the observed modification effect of photoluminescence enhancement (PLE) is essentially dependent on the implantation fluence. For certain fluences, dependent on the ion energy, the overall amplitude of the PL emission has a several times (～5 times) increase. Optical absorption also gradually increases with the fluence.