A Long-Term Study on the Bactericidal Effect of ZrN-Cu Nanostructured Coatings Deposited by an Industrial Physical Vapor Deposition System.

ZrN-Cu coatings containing two different amounts of Cu (~11 at.% and ~25 at.%) were deposited using an industrial physical vapor deposition (PVD) system. The as-deposited coatings exhibited 100% bactericidal efficiency against Escherichia coli CCM 3988 for an exposure time of 40 min. Subsequently, the samples were attached onto our faculty's door handles for six months to study the coatings' long-term effectiveness and durability under actual operational conditions. The samples were periodically evaluated and it was observed that the coatings with 25 at.% Cu performed better than the ones with 11 at.% Cu. For example, following 15 days of being touched, the bactericidal effectiveness of the sample containing 25 at.% Cu dropped to 65% while it fell to 42% for the sample containing 11 at.%. After 6 months, however, both samples showed bactericidal efficiency of ~16-20%. The bactericidal efficiency of the samples touched for 6 months was successfully restored by polishing them. Furthermore, a group of samples was kept untouched and was also evaluated. The untouched samples with Cu content of ~25 at.% did not show any drop in their bactericidal properties after 6 months. ZrN-Cu coatings were concluded to be promising materials for self-sanitizing application on high-touch surfaces.

Geometrical Selection of GaN Nanowires Grown by Plasma-Assisted MBE on Polycrystalline ZrN Layers.

GaN nanowires grown on metal substrates have attracted increasing interest for a wide range of applications. Herein, we report GaN nanowires grown by plasma-assisted molecular beam epitaxy on thin polycrystalline ZrN buffer layers, sputtered onto Si(111) substrates. The nanowire orientation was studied by X-ray diffraction and scanning electron microscopy, and then described within a model as a function of the Ga beam angle, nanowire tilt angle, and substrate rotation. We show that vertically aligned nanowires grow faster than inclined nanowires, which leads to an interesting effect of geometrical selection of the nanowire orientation in the directional molecular beam epitaxy technique. After a given growth time, this effect depends on the nanowire surface density. At low density, the nanowires continue to grow with random orientations as nucleated. At high density, the effect of preferential growth induced by the unidirectional supply of the material in MBE starts to dominate. Faster growing nanowires with smaller tilt angles shadow more inclined nanowires that grow slower. This helps to obtain more regular ensembles of vertically oriented GaN nanowires despite their random position induced by the metallic grains at nucleation. The obtained dense ensembles of vertically aligned GaN nanowires on ZrN/Si(111) surfaces are highly relevant for device applications. Importantly, our results are not specific for GaN nanowires on ZrN buffers, and should be relevant for any nanowires that are epitaxially linked to the randomly oriented surface grains in the directional molecular beam epitaxy.

Enhanced Mechanical Properties of Yellow ZrN Ceramic with Addition of Solid Solution of TiN.

As a superhard ceramic with a yellow color and excellent electrical conductivity, ZrN has potential applications in the field of decoration, but it is limited by its poor mechanical properties. In this work, the mechanical properties of ZrN ceramic were improved by forming a (Zr, Ti)N solid solution via spark plasma sintering of a ZrN and TiN powder mixture. The influences of the amount of TiN additive on the sinterability, microstructure, color, and mechanical properties of ZrN ceramic were investigated. X-ray diffraction analysis, energy-dispersive spectroscopy, and microstructural images indicated that Ti atoms dissolved into a ZrN lattice, and a (Zr, Ti)N solid solution was formed during the sintering process. When the content of TiN was 10 vol%, the obtained (Zr, Ti)N composite exhibited the best comprehensive mechanical properties; the Vickers hardness, flexural strength, and fracture toughness were 15.17 GPa, 520 MPa, and 6.03 MPa·m1/2, respectively. The color coordinates and color temperature diagram revealed the addition of TiN hardly impacted the color performance of the ZrN ceramic.

Residual Stress and Tribological Performance of ZrN Coatings Produced by Reactive Bipolar Pulsed Magnetron Sputtering.

In the past few decades, ZrN thin films have been identified as wear resistant coatings for tribological applications. The mechanical and tribological properties of ZrN thin layers depend on internal stress induced by the adopted deposition techniques and deposition parameters such as pressure, temperature, and growth rate. In sputtering deposition processes, the selected target voltage waveform and the plasma characteristics also play a crucial influence on physical properties of produced coatings. In present work, ZrN thin films, obtained setting different values of duty cycle in a reactive bipolar pulsed dual magnetron sputtering plant, were investigated to evaluate their residual stress through the substrate curvature method. A considerable progressive increase of residual stress values was measured at decreasing duty cycle, attesting the significant role of voltage waveform in stress development. An evident correlation was also highlighted between the values of the duty cycle and those of wear factor. The performed analysis attested an advantageous effect of internal stress, having the samples with high compressive stress, higher wear resistance. A downward trend for wear rate with the increase of internal residual stress was observed. The choice of suitable values of duty cycle allowed to produce ceramic coatings with improved tribological performance.

Synthesis, microstructural characterization and nanoindentation of Zr, Zr-nitride and Zr-carbonitride coatings deposited using magnetron sputtering.

INTRODUCTION: Hard coatings are primarily based on carbides, nitrides and carbonitrides of transition metal elements such as W, Ti, Zr, etc. Zr-based hard coatings show good resistance to wear, erosion, and corrosion as well as exhibit high hardness, high temperature stability, and biocompatibility, making them suitable candidates for tribological, biomedical, and electrical applications. OBJECTIVES: The present study aims to synthesize uniform and adherent hard Zr-based coatings that demonstrate sound mechanical integrity. METHODS: Stainless steel (SS316) samples were coated with single layers of Zr, Zr-nitride, and Zr-carbonitride using magnetron sputter deposition technique. Deposition conditions were controlled to produce each coating with two different thickness i.e., 2 and 3 µm. Calotest was employed to confirm coatings thickness. Scanning electron microscope fitted with energy dispersive x-ray spectrometer was used to ascertain the morphology and elemental constitution of coatings. Cross-sectional samples were examined to ascertain coatings thickness and adhesion. X-ray diffractometer was employed for structural analysis. Instrumented nanoindentation hardness and elastic modulus were determined with nanoindenter. Ratio of nanohardness to elastic modulus was evaluated to observe the effect of coatings thickness on tribological behavior. RESULTS: Three coating compositions were produced namely hcp-Zr, fcc-ZrN and fcc-Zr2CN. The highest hardness and elastic modulus were shown by ZrN coatings while pure Zr coatings showed the lowest values. CONCLUSION: All coating compositions were found to be relatively uniform, continuous and adherent with no evidence of decohesion at the coating-substrate interface. Coatings produced in this study are thought to be suitable for tribological applications.

Measurements of formation cross-sections of short-lived nuclei around the 14 MeV neutron induced reactions on 180Hf and 90Zr and theoretical calculation of excitation functions.

The cross sections of the 180Hf(n,p)180Lu and 90Zr(n,2n)89mZr reactions were measured around the neutron energies of 13.5-14.8 MeV by using the activation technique. The excitation functions of the above reactions in the neutron energies from the threshold to 20 MeV were calculated by using the nuclear theoretical model program system Talys-1.9 with the adjusted relevant parameters. The measured results were discussed and compared with previous experiments by other researchers and with the evaluated data of ENDF/B-VIII.0, CENDL-3.1, JEFF-3.3, JENDL-4.0u2, BROND-3.1 as well as the theoretical values based on Talys-1.9. The obtained experimental values at some neutron energies, within experimental error, are consistent with those of the fitting line of the results of previous experiments and are also consistent with those of theoretical excitation curve at the corresponding energies. The obtained theoretical excitation curves match well with most of the experimental data.

Improving fretting corrosion resistance of CoCrMo alloy with TiSiN and ZrN coatings for orthopedic applications.

Total hip replacement is the most effective treatment for late stage osteoarthritis. However, adverse local tissue reactions (ALTRs) have been observed in patients with modular total hip implants. Although the detailed mechanisms of ALTRs are still unknown, fretting corrosion and the associated metal ion release from the CoCrMo femoral head at the modular junction has been reported to be a major factor. The purpose of this study is to increase the fretting corrosion resistance of the CoCrMo alloy and the associated metal ion release by applying hard coatings to the surface. Cathodic arc evaporation technique (arc-PVD) was used to deposit TiSiN and ZrN hard coatings on CoCrMo substrates. The morphology, chemical composition, crystal structures and residual stress of the coatings were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry. Hardness, elastic modulus, and adhesion of the coatings were measured by nano-indentation, nano-scratch test, and the Rockwell C test. Fretting corrosion resistance tests of coated and uncoated CoCrMo discs against Ti6Al4V spheres were conducted on a four-station fretting testing machine in simulated body fluid at 1Hz for 1 million cycles. Post-fretting samples were analyzed for morphological changes, volume loss and metal ion release. Our analyses showed better surface finish and lower residual stress for ZrN coating, but higher hardness and better scratch resistance for TiSiN coating. Fretting results demonstrated substantial improvement in fretting corrosion resistance of CoCrMo with both coatings. ZrN and TiSiN decreased fretting volume loss by more than 10 times and 1000 times, respectively. Both coatings showed close to 90% decrease of Co ion release during fretting corrosion tests. Our results suggest that hard coating deposition on CoCrMo alloy can significantly improve its fretting corrosion resistance and could thus potentially alleviate ALTRs in metal hip implants.

Cell-cargo mediated ZrN nanoparticle for the synergetic phototherapy on both of mice and rabbits.

Realization of phototherapy on the big animal modal with orthotopic tumor is of considerable significance in view of its great clinical relevance to the human deep tumor treatment. Herein, near infrared (NIR)-active ZrN nanoparticles were chosen for both of photothermal and photodynamic purposes to achieve the synergetic phototherapy on mice with subcutaneous tumor and even rabbits bearing with orthotopic tumor. Broad and strong photoabsorption, photosensitive ROS generation and photothermal effect of ZrN nanoparticles together made it to be ideal candidate for the effective tumor photoablation. Meanwhile, cell-cargo of macrophage enables targeted delivery of ZrN nanoparticles without influence on its photophysical properties. Resultantly, macrophage loaded ZrN could efficiently mediate synergetic phototherapeutic outcome as proved by complete removal of solid tumor from mice and rabbits. In this work, we also introduced B-mode ultrasonography and contrast-enhanced ultrasound technique for monitoring the evolution process of deep orthotopic tumor on rabbits post-treatment and confirmed the pathological changes of vascular degeneration and liquefaction necrosis post phototherapy.

TiN, ZrN and DLC nanocoatings - a comparison of the effects on animals, in-vivo study.

The paper presents a comparative study of the impact that TiN, ZrN and DLC nanocoatings on titanium implants have on animal organisms. The experiment lasted 602 days and used 15 laboratory animals (rabbits from the Lagomorph species). Implants, eight of each type, were implanted subcutaneously in the cervical region. The control group consisted of three animals. Over the course of the experiment, at the beginning and subsequently every 7 days, the animals had their blood drawn and analysed for parameters indicating inflammation. Once the experiment ended, a histopathological evaluation of the animals' internal organs was conducted, and the places where the implants came into contact with the tissue were also assessed. The results of the laboratory tests did not indicate any characteristics of inflammation for any of the coatings. The histopathological examination confirmed biocompatibility in all cases. This is of great importance in the case of the DLC coating, which, due to its tribological properties - a low friction coefficient - has a very high potential for application in various areas of medicine.

High-Temperature Oxidation-Resistant ZrN0.4B0.6/SiC Nanohybrid for Enhanced Microwave Absorption.

Most microwave absorbers lose their function under harsh working conditions, such as a high temperature and an oxidative environment. Here, we developed a heterogeneous ZrN0.4B0.6/SiC nanohybrid via combined catalytic chemical vapor deposition (CCVD) and chemical vapor infiltration (CVI) processes using ZrB2 as the starting material. The composition and structure of the ZrN0.4B0.6/SiC nanohybrid were controlled by tuning the CCVD and CVI parameters, such as reaction temperature, time, and reactant concentration. The optimal heterogeneous ZrN0.4B0.6/SiC nanohybrids were obtained initially by preparing ZrB2@C via the CCVD process at 650 °C for 30 min and the subsequent CVI at 1500 °C, where the ZrB2@C reacted with Si under N2. The ZrN0.4B0.6/SiC nanohybrid exhibited enhanced microwave absorption ability with a minimum reflection loss value of approximately -50.8 dB at 7.7 GHz, a thickness of ∼3.05 mm, and antioxidation features at a high temperature of 600 °C. The heterogeneous ZrN0.4B0.6/SiC nanohybrid possessed reasonable conductivity, leading to dielectric loss, whereas SiC nanofibers formed a three-dimensional network that brought higher dipole moments, whereas a small part of the ZrN0.4B0.6/SiC nanohybrid structure generated an effective interface for higher attenuation of microwaves. Therefore, these material features synergistically resulted in a well-defined Debye relaxation, Maxwell-Wagner relaxation, dipole polarization, and the quarter-wavelength cancellation, which accounted for the enhanced microwave absorption.

Influence of Alloy Substrate Treatment on Microstructure and Surface Performances of Arc-Ion Plated Gold-Like Film.

Three typical surface pretreatment strategies (grind, drawing, polishing) are employed to explore the influence of alloy substrate treatment on microstructure and surface performances of arc-ion plated TiN and ZrN films. The luminance and color of the films are measured by the color coordinate value of CIELab system (a color system which is defined by the International Commission on illumination). The crystal phases, morphology and microstructure are characterized and analyzed by scanning electron microscope (SEM) and X-ray powder diffraction (XRD). In addition, the anti-alkali, salt corrosion and anti-oxidation performances of films are systematically researched. The results show that the films with grinding pretreatment are more like gold color, "L" values are 77.27 cd/m² and 80.30 cd/m². The "b" value of TiN film is 29.96, which is the same as that of pure gold. The "a" value of ZrN film is 0.31, which is the same as pure silver. The density of TiN and ZrN films is the best, and both TiN and ZrN films were crystalline. They have the best anti-alkali and anti-oxidation performance. The films with drawing pretreatment show slant red color and have medium brightness values (74.07⁻76.37 cd/m²), worse compactness, obvious furrows and holes in their microstructures and worse salt corrosion and anti-oxidation performances. However, the TiN films are in amorphous states. The films with polishing pretreatment have the lowest brightness (72.66 cd/m²), gold-like color, superior compactness and best salt corrosion performance, which have a small number of holes. The TiN films with polishing pretreatment are also in amorphous state. Above all, alloy substrate pretreatment by grinding has the best gold-like color, brightness, compactness and corrosion resistance performance. This work exclusively sheds new light on surface pretreatment of alloy substrate by arc-ion plated films and also provides a reference for corrosion resistance performance of gold-like films.

Validation of zirconium isotopes (n,g) and (n,2n) cross sections in a comprehensive LR-0 reactor operative parameters set.

Zirconium is an important material used in most of reactor concepts for fuel cladding. Thus the knowledge of its cross section is important for reliable prediction of fuel operation. Also 90Zr(n,2n) reaction, is included in IRDFF files as dosimetry cross section standard. Due to its very high threshold, 12.1MeV, it is suitable for measurement of high energy neutrons. One of possible interesting applications is also evaluation of prompt fission neutron spectra in 235U and 238U what is under auspices of the International Atomic Energy Agency in CIELO project. The experimental values - obtained with the LR-0 nuclear reactor - of various zirconium cross sections were compared with calculations with the MCNP6 code using IAEA CIELO, ENDF/B-VII.0, JEFF-3.1, JEFF-3.2, JENDL-3.3, JENDL-4, ROSFOND- 2010, and CENDL-3.1 transport libraries combined with the dosimetry cross sections extracted from the IRDFF library. Generally, the best C/E agreement for 90Zr(n,2n) cross section, was found with the IAEA CIELO 235U evaluation that includes an updated prompt fission neutron spectra in the evaluated data file. The cross section of this reaction averaged over LR-0 spectra was determined being 28.9 ± 1.2 µb, corrected to spectral shift, spectral averaged cross section in 235U was determined to be 0.107 ± 0.005mb. Notable discrepancies were reported in both 94Zr(n,g) and 96Zr(n,g).

Optical properties of Ar ions irradiated nanocrystalline ZrC and ZrN thin films.

Thin nanocrystalline ZrC and ZrN films (<400 nm), grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique, were irradiated by 800 keV Ar ion irradiation with fluences from 1 × 1014 at/cm2 up to 2 × 1015 at/cm2. Optical reflectance data, acquired from as-deposited and irradiated films, in the range of 500 - 50000 cm-1 (0.06 - 6 eV), was used to assess the effect of irradiation on the optical and electronic properties. Both in ZrC and ZrN films we observed that irradiation affects the optical properties of the films mostly at low frequencies, which is dominated by the free carriers response. In both materials, we found a significant reduction in the free carriers scattering rate, i.e. possible increase in mobility, at higher irradiation flux. This is consistent with our previous findings that irradiation affects the crystallite size and the micro-strain, but it does not induce major structural changes.

Evaluation of antibacterial activity and osteoblast-like cell viability of TiN, ZrN and (Ti1-xZrx)N coating on titanium.

PURPOSE: The aim of this study was to evaluate antibacterial activity and osteoblast-like cell viability according to the ratio of titanium nitride and zirconium nitride coating on commercially pure titanium using an arc ion plating system. MATERIALS AND METHODS: Polished titanium surfaces were used as controls. Surface topography was observed by scanning electron microscopy, and surface roughness was measured using a two-dimensional contact stylus profilometer. Antibacterial activity was evaluated against Streptococcus mutans and Porphyromonas gingivalis with the colony-forming unit assay. Cell compatibility, mRNA expression, and morphology related to human osteoblast-like cells (MG-63) on the coated specimens were determined by the XTT assay and reverse transcriptase-polymerase chain reaction. RESULTS: The number of S. mutans colonies on the TiN, ZrN and (Ti1-xZrx)N coated surface decreased significantly compared to those on the non-coated titanium surface (P<0.05). CONCLUSION: The number of P. gingivalis colonies on all surfaces showed no significant differences. TiN, ZrN and (Ti1-xZrx)N coated titanium showed antibacterial activity against S. mutans related to initial biofilm formation but not P. gingivalis associated with advanced periimplantitis, and did not influence osteoblast-like cell viability.

Ab initio calculations of the ground and excited states of the ZrN molecule including spin-orbit effects.

The electronic structures with spin-orbit effects of the zirconium nitride ZrN molecule are investigated by the methods of multireference single and double configuration interaction. The potential energy curves are calculated along with the spectroscopic constants for the lowest-lying 34 spin-orbit states Ω in ZrN. A good agreement is displayed by comparing the calculated spectroscopic constants with those available experimentally. The permanent dipole moments are calculated along with the vibrational energies. New results are obtained in this work for 29 spin-orbit states and their spectroscopic constants calculated.