Green Nanocoatings Based on the Deposition of Zirconium Oxide: The Role of the Substrate

Herein, the influence of the substrate in the formation of zirconium oxide monolayer, from an aqueous hexafluorozirconic acid solution, by chemical conversion and by electro-assisted deposition, has been approached. The nanoscale dimensions of the ZrO₂ film is affected by the substrate nature and roughness. This study evidenced that the mechanism of Zr-EAD is dependent on the potential applied and on the substrate composition, whereas conversion coating is uniquely dependent on the adsorption reaction time. The zirconium oxide based nanofilms were more homogenous in AA2024 substrates if compared to pure Al grade (AA1100). It was justified by the high content of Cu alloying element present in the grain boundaries of the latter. Such intermetallic active sites favor the obtaining of ZrO₂ films, as demonstrated by XPS and AFM results. From a mechanistic point of view, the electrochemical reactions take place simultaneously with the conventional chemical conversion process driven by ions diffusion. Such findings will bring new perspectives for the generation of controlled oxide coatings in modified electrodes used, as for example, in the construction of battery cells; in automotive and in aerospace industries, to replace micrometric layers of zinc phosphate by light-weight zirconium oxide nanometric ones. This study is particularly addressed for the reduction of industrial waste by applying green bath solutions without the need of auxiliary compounds and using lightweight ceramic materials.     

Human gingival fibroblasts function is stimulated on machined hydrided titanium zirconium dental implants

Objectives

The aim of this study was to evaluate the influence of different titanium zirconium (TiZr) alloy surfaces on primary human gingival fibroblasts (HGF) for improved soft tissue integration of dental implants.

Methods

TiZr polished, machined and machined + HCl/H₂SO₄ acid-etched surfaces were modified by cathodic polarization and/or HNO₃/HF acid etching. Contact angle of surfaces was measured. The influence of modified TiZr surfaces on HGF was evaluated through the analysis of cell number, morphology, recovery after a wound (wound healing assay) and the expression of several genes, including matrix metalloproteinase-1 (MMP1) and metallopeptidase inhibitor-1 (TIMP1).

Results

Modification of TiZr surfaces decreased its hydrophilicity. Hydride implementation on TiZr surfaces via cathodic polarization increased TIMP1 expression and decreased MMP1/TIMP1 mRNA ratio. Cathodic polarization of machined surfaces promoted cell attachment. Cells on machined and machined + cathodic polarization surfaces grew aligned to the microgrooves whereas on all polished surfaces they grew randomly. Acid etching of polished and machined surfaces did not improve HGF function.

Conclusions

Hydride implementation on TiZr machined surfaces may be used as new dental implant material for improved soft tissue integration.

Clinical significance

Enhancing dental implant surfaces’ bioactivity by hydride implementation may promote soft tissue attachment and sealing around the implant and reduce peri-implantitis related to ECM-destruction compared with conventional machined surfaces.     

Laser Structured Dental Zirconium for Soft Tissue Cell Occupation—Importance of Wettability Modulation

Various approaches are being pursued to physico-chemically modify the zirconia neck region of dental implants to improve the integration into the surrounding soft tissue. In this study, polished zirconia discs were laser microstructured with periodic cavities and convex waves. These zirconia samples were additionally activated by argon plasma using the kINPen^®09. The surface topography was characterized by scanning electron microscopy and the surface wettability by water contact angle. The in vitro study with human gingival fibroblasts (HGF-1) was focused on cell spreading, morphology, and actin cytoskeleton organization within the first 24 h. The laser-induced microstructures were originally hydrophobic (e.g., 60 µm cavities 138.4°), but after argon plasma activation, the surfaces switched to the hydrophilic state (60 µm cavities 13.7°). HGF-1 cells adhered flatly on the polished zirconia. Spreading is hampered on cavity structures, and cells avoid the holes. However, cells on laser-induced waves spread well. Interestingly, argon plasma activation for only 1 min promoted adhesion and spreading of HGF-1 cells even after 2 h cultivation. The cells crawl and grow into the depth of the cavities. Thus, a combination of both laser microstructuring and argon plasma activation of zirconia seems to be optimal for a strong gingival cell attachment.     

Influence of Laser Beam Power on Microstructure and Microhardness of Fe/ZrC Coatings Produced on Steel Using Laser Processing—Preliminary Study on the Single Laser Tracks

This paper presents preliminary tests of the parameter analysis of the Fe/ZrC coatings production process and the obtained properties. The effects of laser beam power on the obtained microstructure, chemical composition and microhardness were investigated. The tests consisted of the production of composite coatings by laser processing of initial coatings made in the form of a paste on a steel substrate. During the tests, a diode laser with a rated power of 3 kW was used. The laser processing process was carried out using a constant scanning speed laser beam of 3 m/min and four different powers of the laser beam: 500 W, 700 W, 900 W, 1100 W. It was found that it is possible to create composite coatings on a steel surface, where the matrix is made of iron-based alloy and the reinforcing phase is ZrC carbide. It was also found that reinforcing phase content decreased as laser beam power increased. A similar relationship was found for microhardness. As laser beam power increases, the microhardness of the iron-based matrix decreases, finally reaching a value lower than the heat-affected zone. It was found that the amount of hard carbide phases in the iron-based matrix affects the total hardness of the coatings. Presented study concern Fe/ZrC coatings that have not previously been produced on steel by laser processing of precoating, which may be a new contribution in the field of metal surface engineering.     

新形势下体育教育专业球类技术学科现状及思考

通过对高师体育教育专业球类技术学科现状的反思,并对照新形势下素质教育的要求,发现在传统的教学模式下培养的体育教师不能适应今后中学的球类课教学,存在着很多的问题,并对此提出了改善的措施.     

Combustion Synthesis of High Density ZrN/ZrSi2 Composite: Influence of ZrO2 Addition on the Microstructure and Mechanical Properties

In this study, a high-density ZrN/ZrSi₂ composite reinforced with ZrO₂ as an inert phase was synthesized under vacuum starting with a Zr-Si₄N₃-ZrO₂ blend using combustion-synthesis methodology accompanied by compaction. The effects of ZrO₂ additions (10–30 wt%) and compression loads (117–327 MPa) on the microstructure, porosity and hardness of the samples were studied. The process was monitored using XRD, SEM, EDS, porosity, density and hardness measurements. Thermodynamic calculations of the effect of ZrO₂ addition on the combustion reaction were performed including the calculation of the adiabatic temperatures and the estimation of the fractions of the liquid phase. The addition of up to 20 wt% ZrO₂ improved the hardness and reduced the porosity of the samples. Using 20 wt% ZrO₂, the sample porosity was reduced to 1.66 vol%, and the sample hardness was improved to 1165 ± 40.5 HV at 234 MPa.     

Radiation-Induced Sharpening in Cr-Coated Zirconium Alloy

To improve the safety of nuclear power plants, a Cr protective layer is deposited on zirconium alloys to enhance oxidation resistance of the nuclear fuel cladding during both in-service and hypothetical accidental transients at High Temperature (HT) in Light Water Reactors. The formation of the Cr₂O₃ film on the coating surface considerably helps in reducing the oxidation kinetics of the zirconium alloy, especially during hypothetic Loss of Coolant Accident (LOCA). However, if the Cr coating is successful to increase the oxidation resistance at HT of the zirconium substrate, for in-service conditions, under neutron irradiation, Cr desquamation has to be avoided to guarantee a safe use of the Cr-coated zirconium alloys. Therefore, the adhesion properties have to be maintained despite the structural defects created by sustained neutron irradiation in the reactor environment. This paper proposes to study the behavior of the Zircaloy-Cr interface of a first generation Cr-coated material during a specific in situ ion irradiation. As deposited, the Cr-coated sample presents a f.c.c. C15 Laves-type intermetallic phase at the interface with off-stoichiometric composition. After irradiation and for the specific conditions applied, this interfacial phase has significantly dissolved. Energy Dispersion Spectroscopy revealed that the dissolution was accompanied by a counterintuitive “sharpening” effect.     

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目的评价4种黏结剂对氧化锆全瓷嵌体边缘微渗漏的影响。方法选取2012年8月佛山市禅城区向阳医院口腔科新鲜拔除的上颌第三磨牙40颗,随机分为A、B、C、D组,每组10颗,制备V类洞形。4组离体牙分别采用全酸蚀黏结剂AdperSinglebond2（A组）及自酸蚀黏结荆ClearFilSEBond（B组）、MultilinkSpnnt（C组）和AdperEasyOne（D组）黏结氧化锆全瓷嵌体,修复后离体牙经冷热循环后行2％亚甲基蓝染色,根管显微镜下观察各组微渗漏程度并进行比较。结果在铪壁,c组微渗漏明显高于A和B组,差异均有统计学意义（P〈0．05）;但与D组差异无统计学意义（P〉0．05）。在龈壁,c组微渗漏明显高于其他3组,差异均有统计学意义（P〈0．05）;而其他3组之间差异均无统计学意义（P〉0．05）。结论自酸蚀黏结剂ClearFilSEBond和AdperEasyOne的封闭能力较好,且较全酸蚀黏结剂操作简单方便,推荐临床使用。     

不同材料桩核对IPS-Empress 2全瓷冠颜色的影响

目的研究不同材料桩核对IPS- Empress 2全瓷冠不同部位颜色的影响规律。方法制作全瓷桩核、氧化锆桩树脂核、金合金桩核、镀金镍铬合金桩核和镍铬合金桩核各3个,用PR- 650光谱扫描色度仪测量不同桩核背景下IPS- Empress 2全瓷冠唇面切1/3、中1/3和颈1/3的L*、a*、b*颜色参数,研究不同材料桩核对全瓷冠颜色的影响。结果全瓷桩核和镀金镍铬合金桩核背景的L*、a*、b*值均高于其他桩核背景,氧化锆桩树脂核背景的L*、a*值较高,b*值较低,金合金桩核背景的L*、a*、b*值较低,镍铬合金背景的L*、a*、b*值最低。结论应用IPS- Empress2全瓷冠修复根管治疗后的上前牙时,推荐使用全瓷桩核和氧化锆桩树脂核,也可以考虑使用镀金镍铬合金桩核或金合金桩核,不推荐使用镍铬合金桩核。     

Custom-Made Zirconium Dioxide Implants for Craniofacial Bone Reconstruction

Reconstruction of the facial skeleton is challenging for surgeons because of difficulties in proper shape restoration and maintenance of the proper long-term effect. ZrO₂ implant application can be a solution with many advantages (e.g., osseointegration, stability, and radio-opaqueness) and lacks the disadvantages of other biomaterials (e.g., metalosis, radiotransparency, and no osseointegration) or autologous bone (e.g., morbidity, resorption, and low accuracy). We aimed to evaluate the possibility of using ZrO₂ implants as a new application of this material for craniofacial bone defect reconstruction. First, osteoblast (skeleton-related cell) cytotoxicity and genotoxicity were determined in vitro by comparing ZrO₂ implants and alumina particle air-abraded ZrO₂ implants to the following: 1. a titanium alloy (standard material); 2. ultrahigh-molecular-weight polyethylene (a modern material used in orbital surgery); 3. a negative control (minimally cytotoxic or genotoxic agent action); 4. a positive control (maximally cytotoxic or genotoxic agent action). Next, 14 custom in vivo clinical ZrO₂ implants were manufactured for post-traumatologic periorbital region reconstruction. The soft tissue position improvement in photogrammetry was recorded, and clinical follow-up was conducted at least 6 years postoperatively. All the investigated materials revealed no cytotoxicity. Alumina particle air-abraded ZrO2 implants showed genotoxicity compared to those without subjection to air abrasion ZrO₂, which were not genotoxic. The 6-month and 6- to 8-year clinical results were aesthetic and stable. Skeleton reconstructions using osseointegrated, radio-opaque, personalized implants comprising ZrO₂ material are the next option for craniofacial surgery.