Search Results (67)

The search for effective and reliable methods of photosensitization of oxide-based semiconductor materials is of great significance for their use in photocatalytic reactions of hydrogen production and environmental remediation under natural sunlight. The present study is focused on partial substitution of titanium with manganese in the structure of layered perovskite-like titanate Na₂La₂Ti₃O₁₀, which was employed to yield a series of photocatalytically active materials, Na₂La₂Mn_xTi_3−xO₁₀ (x = 0.002–1.0), as well as their protonated forms H₂La₂Mn_xTi_3−xO₁₀ and nanosheets. It was established that the manganese cations Mn⁴⁺ are embedded in the middle sublayer of oxygen octahedra in the perovskite slabs La₂Mn_xTi_3−xO₁₀²⁻ and that the maximum achievable manganese content x in the products is ≈0.9. The partial cationic substitution in the perovskite sublattice led to a pronounced contraction of the optical band gap from 3.20 to 1.35 eV (depending on x) and, therefore, allowed the corresponding photocatalysts to utilize not only ultraviolet, but also visible and near-infrared light with wavelengths up to ≈920 nm. The materials obtained were tested as photocatalysts of hydrogen evolution from aqueous methanol, and the greatest activity in this reaction was demonstrated by the samples with low manganese contents (x = 0.002–0.01). However, the materials with greater substitution degrees may be of high interest for use in other photocatalytic processes and, especially, in thermophotocatalysis due to their improved ability to absorb the near-infrared part of solar radiation. Full article

Stiffened panels are extensively used in aerospace applications, particularly in wing and fuselage sections, due to their favorable strength-to-weight ratio under in-plane loading conditions. This research employs the commercial finite element software Ansys-19 to analysis the critical buckling and ultimate collapse load of an aluminum stiffened panel having a dimension of 1244 mm (Length) × 957 mm (width) × 3.5 mm (thickness), with three stiffener blades located 280 mm away from each other. Both the critical buckling load and post-buckling ultimate failure load of the panel are validated against the experimental data found in the available literature, where the edges towards the length are clamped and simply supported, and the other two edges are free. For nonlinear buckling analysis, a plasticity power law is adopted with a small geometric imperfection of 0.4% at the middle of the panel. After the numerical validation, the investigation is further carried out considering four different lateral pressures, specifically 0.013 MPa, 0.065 MPa, 0.085 MPa, and 0.13 MPa, along with the compressive loading boundary conditions. It was found that even though the pressure application of 0.013 MPa did not significantly impact the critical buckling load of the panel, the ultimate collapse load was reduced by 18.5%. In general, the ultimate collapse load of the panel was severely affected by the presence of lateral pressure while edge compressing. Three opening shapes—namely, square, circular, and rectangular/hemispherical—were also investigated to understand the behavior of the panel with openings. It was found that the openings significantly affected the critical buckling load and ultimate collapse load of the stiffened panel, with the lateral pressure also contributing to this effect. Finally, in critical areas with higher lateral pressure load, a titanium panel can be a good alternative to the aluminum panel since it can provide almost twice to thrice better buckling stability and ultimate collapse load to the panels with a weight nearly 1.6 times higher than aluminum. These findings highlight the significance of precision manufacturing, particularly in improving and optimizing the structural efficiency of stiffened panels in aerospace industries. Full article

Background/Objectives: Surgical removal is the treatment of choice for cholesteatoma control. Depending on the size, the surgery involves partial resection of the ossicular chain and, if necessary, the bony skull base. Titanium foreign materials (prostheses, meshes) can be used to restore sound transmission and to cover larger defects of the skull base. After the operation, recurrence and residual control are necessary. This can be achieved by means of second-look surgery or an MRI examination with a non-EPI DWI sequence. Similarly to other metal implants, artifacts may occur in the image due to the titanium used. In this study, we assessed the magnitude of the MRI hardware differences induced by titanium prostheses and meshes and whether these differences could obscure cholesteatoma detection. Methods: 28 MRI examinations (T1-, T2-, non-EPI DWI sequences) in 14 males and 14 females (5.2–92.4 years) after cholesteatoma surgery and single-staged implantation of a PORP, TORP, or titanium mesh were considered. The size of the respective artifacts was measured, and the mean artifact sizes of the respective prosthesis types were compared. A second look surgery was performed in all cases due to the MRI result or clinical findings. Both were also compared. Results: Artifacts occurred in all titanium foreign bodies depending on the used MRI sequence (PORP, TORP, Mesh). We found a positive association between the size of the prosthesis and the size of the artifact. All subsequent second-look surgeries confirmed the MRI examinations according to a positive control for the presence of cholesteatoma. The detection rate was 82.1%. All false results were false negatives, and there were no positive results. Conclusions: Titanium material-related artifacts might influence the MRI detectability of recurrent cholesteatoma. Small cholesteatoma might be missed by an MRI-based follow-up. This finding supports the reevaluation of single-stage versus staged reconstruction modern approaches. Full article

The Bijigou layered intrusion is located in the northern margin of the Yangtze block. Based on cumulus mineral assemblages, the intrusion is divided into three major units from the base upwards: the lower zone (LZ), dominated by olivine gabbro; the middle zone (MZ), composed of gabbro and Fe-Ti oxide ore layers; and the upper zone (UZ), characterized by (quartz) diorite. Previous studies reported various vermicular symplectite textures in layered intrusions, which are thought to be related to the magmatic evolution of the layered intrusions and the mineralization of vanadium–titanium magnetite. However, detailed studies on the specific reaction mechanism of those symplectites are lacking. In this study, the characteristics, mineral compositions, and crystal orientation relationships of minerals in symplectites from Fe-Ti oxide Fe-Ti oxide-rich gabbro are in the Bijigou layered intrusion investigated by an Electron Probe Microanalyzer (EPMA) and Electron Backscattered Diffraction (EBSD) to reveal the formation process of symplectites in gabbros. In the Fe-Ti oxide-rich gabbro, abundant amphibole + spinel (Amp₁ + Spl) symplectite and amphibole + plagioclase (Pl₂ + Amp₂) symplectite are developed between the primocryst plagioclase (Pl₁) and Fe-Ti oxide; Pl₂ had significantly higher An contents (An_92–97) relative to Pl₁. The Mg # for Amp₁ and Amp₂ was 0.78–1 and 0.6–0.84, respectively. Amphibole geothermometer calculations show Amp₁ and Amp₂ at 934–953 °C and 834–914 °C, suggesting that these symplectites crystallized at a late stage of magmatic evolution. The crystallographic orientation relationship between Amp₁ and Spl varies in different areas, and Spl has a particular orientation relationship with the external Ilm. Pl₂ and Amp₂ inherit the crystallographic orientation of Amp₁ and Pl₁, respectively. We speculate that in the Bijigou layered intrusions, Amp₁ + Spl and Pl₂ + Amp₂ were formed in two stages: Amp₁ + Spl symplectite due to Ilm epitaxial growth as a result of supersaturation and rapid nucleation; and Pl₂ + Amp₂ symplectite due to dissolution–precipitation. Full article

The adaptation of restorations to the titanium base (TiBase) abutments varies depending on the materials and methods used, playing a crucial role in implant and prosthetic success. This in vitro study aims to compare the internal and marginal fit of a titanium interface among three different milled materials: doped graphene PMMA, single-density zirconia, and dual-density zirconia, used for the rehabilitation of CAD-CAM implant-supported single crowns. A digital method based on the silicone replica technique was employed. The silicone reproduction of each fabricated restoration’s inner and basal parts was digitally aligned to the titanium base, measuring the space between them at three predetermined planes: basal, middle, and superior. The material with the worst overall adaptation was dual-density zirconia (0.1 ± 0.03 mm), followed by single-density zirconia (0.09 ± 0.03 mm), and doped graphene PMMA (0.06 ± 0.02 mm). No statistical differences were found in the internal fit, represented by the measurements made at the middle and superior plane, among the materials used (p > 0.05). However, the marginal fit of doped graphene PMMA restorations was statistically better than zirconia restorations (p < 0.05). No significant differences were observed between the marginal fit of both types of zirconia (p > 0.05). Across all three materials, the superior plane showed the best fit, while the marginal plane exhibited the worst. Full article

The zygomatic bone area experiences frequent mechanical damage in the middle craniofacial region, including the orbital floor. The orbital floor bone is very thin, ranging from 0.74 mm to 1.5 mm. Enhancing digitization, reconstruction, and CAD modeling procedures is essential to improving the visualization of this structure. Achieving a homogeneous surface with high manufacturing accuracy is crucial for developing precise surgical models and tools for creating titanium mesh implants to reconstruct the orbital floor geometry. This article improved the accuracy of reconstruction and CAD modeling using the example of the development of a prototype implant to replace the zygomatic bone and a tool to form the geometry of the titanium mesh within the geometry of the orbital floor. The masked stereolithography (mSLA) method was used in the model manufacturing process because it is low-cost and highly accurate. Two manufacturing modes (standard and ultra-light) were tested on an Anycubic Photon M3 Premium 3D printer to determine which mode produced a more accurate representation of the geometry. To verify the geometric accuracy of the manufactured models, a GOM Scan1 structured light scanner was used. In the process of evaluating the accuracy of the model preparation, the maximum deviation, mean deviation, range and standard deviation were determined. The maximum deviations for anatomical structures created using the normal mode ranged from ±0.6 mm to ±0.7 mm. In contrast, models produced with the ultra-light mode showed deviations of ±0.5 mm to ±0.6 mm. Furthermore, the results indicate that the ultra-light mode offers better surface accuracy for die and stamp models. More than 70% of the surface of the models is within the deviation range of ±0.3 mm, which is sufficient for planning surgical procedures. However, the guidelines developed in the presented publication need to optimize the CAD process and select 3D-printing parameters to minimize deviations, especially at the edges of manufactured models. Full article

Background and Objectives: The manufacturing of single crowns using hybrid abutments is an alternative that may be interesting in clinical practice, combining the advantages of the different materials used in a personalized design for each case. The purpose of this in vitro study was to evaluate the torque loss, survival, reliability, failure mode, and strain distribution of implant-supported prostheses with zirconia (Zir) and cobalt–chromium (Co-Cr) hybrid abutments. Materials and Methods: Abutments were milled by CAD/CAM and divided into two groups according to the materials used, Zir and Co-Cr, and cemented on titanium bases screwed to dental implants. Monolithic zirconia crowns were cemented on the abutments. The implant/abutment/crown sets were subjected to thermomechanical cycling (n = 10) (2 Hz, 140 N, 1 × 10⁶ cycles, immersed in water at 5–55 °C) to evaluate the torque loss. The single load to fracture test (SLF) was performed to design the loading profiles (light, moderate, and aggressive) of the step-stress accelerated life testing (SSALT) (n = 21) to evaluate the survival and reliability. The representative fractured specimens were analyzed under optical and scanning electron microscopy. The digital image correlation (DIC) (n = 1) was performed using specimens embedded in polyurethane resin models that received static point loading, and the strain distribution was analyzed. Results: There was no difference in torque loss, survival, or reliability between zirconia and Co-Cr abutments. An analysis of the fractured surfaces showed that the abutments presented the same failure mode, where the fracture probably started in the titanium base/screw. The zirconia abutment model presented only compressive strains around the implant, while the Co-Cr abutment model showed tensile and compressive strains in the middle of the implant; however, all strains were within the clinically acceptable limits. There was a strain concentration in the titanium base close to the implant platform for both groups. Conclusions: Zirconia and Co-Cr hybrid abutments presented similar torque loss, survival, reliability, and failure modes, but the abutment material influenced the strain distribution around the implant. The titanium base screw was the weakest link in the system. Full article

As 3D printing technology expands rapidly in medical disciplines, the accuracy evaluation of 3D-printed medical models is required. However, no established guidelines to assess the dimensional error of anatomical models exist. This study aims to evaluate the dimensional accuracy of medical models 3D-printed using a hospital-based Fused Deposition Modeling (FDM) 3D printer. Two dissected cadaveric right hands were marked with Titanium Kirshner wires to identify landmarks on the heads and bases of all metacarpals and proximal and middle phalanges. Both hands were scanned using a Cone Beam Computed Tomography scanner. Image post-processing and segmentation were performed on 3D Slicer software. Hand models were 3D-printed using a professional hospital-based FDM 3D printer. Manual measurements of all landmarks marked on both pairs of cadaveric and 3D-printed hands were taken by two independent observers using a digital caliper. The Mean Absolute Difference (MAD) and Mean Dimensional Error (MDE) were calculated. Our results showed an acceptable level of dimensional accuracy. The overall study’s MAD was 0.32 mm (±0.34), and its MDE was 1.03% (±0.83). These values fall within the recommended range of errors. A high level of dimensional accuracy of the 3D-printed anatomical models was achieved, suggesting their reliability and suitability for medical applications. Full article

Background/Objectives: The purpose of this in vitro study was to evaluate and compare the internal adaptation and cement film thickness of cast-gold custom post and core (CPC), three-dimensionally (3D)-printed titanium (Ti) CPC, and milled Ti CPC. Methods: Forty-eight 3D printed resin models, simulating a tooth prepared to receive a CPC, were fabricated. Models were randomly assigned to one of three groups (n = 16 per group): (A) cast-gold CPC (control group), (B) 3D-printed Ti CPC, and (C) milled Ti CPC. Following the manufacturing of CPCs, each CPC was cemented using dual-cure polymerizing resin cement. Then, each model/post-and-core assembly was sectioned at the coronal, middle, and apical thirds of the post at a specific point. Each section was photographed using a microscope in a standardized setting (25×). The pixel count for cement surface area was calculated for each image using Adobe Photoshop software. Descriptive statistics of the mean and standard deviation of the cement film thickness around posts were calculated. Kruskal–Wallis and Dwass–Steel–Critchlow–Fligner tests were used for statistical analysis, with a significance level of α = 0.05. Results: Pairwise comparisons in the coronal section revealed a statistically significant difference (p < 0.05) between groups A and B and groups B and C. In the middle section, there was a statistically significant difference (p < 0.05) between groups A and B only. In the apical section, there was a statistically significant difference (p < 0.05) between all groups. Conclusions: Within the limitation of the present study, neither 3D printed nor milled Ti CPC could achieve comparable cement film thickness to cast-gold CPC in all three sections. Cast-gold CPC cement film thickness was found to be more reduced and consistent, thus having superior internal adaptation to 3D-printed and milled Ti CPCs. Full article

The titanium nitride (TiN) columnar structure results in a rapid diffusion of copper atoms into the substrate along a vertical path. In this paper, the TiN columnar growth process was modified, which resulted in the deposition of amorphous-like films. The amorphous-like TiN layer demonstrated a low resistivity of 75.3 μΩ·cm. For the test structure of Cu/TiN/SiO₂, the Cu diffusion depth in the 3 nm TiN middle layer was only approximately 1 nm after annealing at 750 °C for 30 min. Excellent copper diffusion barrier due to high density and complex diffusion pathways. The results of this study suggest that conventional barrier materials can still be used in ultra-narrow copper interconnects. Full article

Herein, we fabricated a low-melting-point Zr-16Ti-6Cu-8Ni-6Co eutectic filler based on a Zr-Ti-Cu-Ni filler to achieve effective joining of a Ti6Al4V (TC4) titanium alloy. The temperature at which the brittle intermetallic compound (IMC) layer in the seam completely disappeared was reduced from 920 °C to 900 °C, which broadened the temperature range of the Zr-based filler, brazing the TC4 without a brittle IMC layer. The shear strength of the Zr-16Ti-6Cu-8Ni-6Co brazed joint increased by 113% more than that of the Zr-16Ti-9Cu-11Ni brazed joint at 900 °C. The proportion of β-Ti in the seam of the Zr-16Ti-6Cu-8Ni-6Co brazed joint increased by 21.31% compared with that of the Zr-16Ti-9Cu-11Ni brazed joint. The nano-indentation results show that the elastic modulus of the β-Ti (143 GPa) in the interface is lower than that of the α-Ti (169 GPa) and (Ti,Zr)₂(Ni,Cu,Co) (203 GPa). As a result, the β-Ti is subjected to a greater strain under the same stress state compared with the α-Ti and (Ti,Zr)₂(Ni,Cu,Co), and the Zr-16Ti-6Cu-8Ni-6Co brazed joint can maintain a higher strength than the Zr-16Ti-9Cu-11Ni brazed joint under a middle–low erosion area of the TC4 base metal. This provides valuable insights into the use of high-strength, fatigue-resistant TC4 brazed joints in engineering applications. Full article

A 6-year-old castrated male mixed dog presented with a rapidly growing mass at the right chest wall two weeks after initial detection. A mesenchymal origin of the malignancy was suspected based on fine-needle aspiration. Computed tomography (CT) revealed that the mass originated from the right chest wall and protruded externally (6.74 × 5.51 × 4.13 cm³) and internally (1.82 × 1.69 × 1.50 cm³). The patient revisited the hospital because of breathing difficulties. Radiography confirmed pleural effusion, and ultrasonography-guided thoracocentesis was performed. The effusion was hemorrhagic, and microscopic evaluation showed no malignant cells. Before surgery, CT without anesthesia was performed to evaluate the status of the patient. The 7–10th ribs were en bloc resected at a 3-cm margin dorsally and ventrally, and two ribs cranially and caudally from the mass. After recovering the collapsed right middle lobe of the lung due to compression from the internal mass with positive-pressure ventilation, a 3D-printed bone model contoured titanium mesh was tied to each covering rib and surrounding muscles using 2-0 blue nylon and closed routinely. The thoracic cavity was successfully reconstructed, and no flail chest was observed. The patient was histo-pathologically diagnosed with extraskeletal osteosarcoma. A CT scan performed 8 months after surgery showed no evident recurrence, metastasis, or implant failure. This is the first case report of chest wall reconstruction using titanium mesh in a dog. The use of a titanium mesh allows for the reconstruction of extensive chest wall defects, regardless of location, without major postoperative complications. Full article

Background: Orbital floor fractures (OFFs) represent an interesting chapter in maxillofacial surgery, and one of the main challenges in orbit reconstruction is shaping and cutting the precise contour of the implants due to its complex anatomy. Objective: The aim of the retrospective study was to demonstrate, through pre- and postoperative volumetric measurements of the orbit, how the use of a preformed titanium mesh based on the stereolithographic model produced with 3D printers (“In-House” reconstruction) provides a better reconstruction volumetric compared to the intraoperatively shaped titanium mesh. Materials and Methods: The patients with OFF enrolled in this study were divided into two groups according to the inclusion criteria. In Group 1 (G1), patients surgically treated for OFF were divided into two subgroups: G1a, patients undergoing orbital floor reconstruction with an intraoperatively shaped mesh, and G1b, patients undergoing orbital floor reconstruction with a preoperative mesh shaped on a 3D-printed stereolithographic model. Group 2 (G2) consisted of patients treated for other traumatic pathologies (mandible fractures and middle face fractures not involving orbit). Pre- and postoperative orbital volumetric measurements were performed on both G1 and G2. The patients of both groups were subjected to the measurement of orbital volume using Osirix software (Pixmeo SARL, CH-1233 Bernex, Switzerland) on the new CT examination. Both descriptive (using central tendency indices such as mean and range) and regressive (using the Bravais–Pearson index, calculated using the GraphPad program) statistical analyses were performed on the recorded data. Results: From 1 January 2017 to 31 December 2021, of the 176 patients treated for OFF at the “Magna Graecia” University Hospital of Catanzaro 10 fulfilled the study’s inclusion criteria: 5 were assigned to G1a and 5 to G1b, with a total of 30 volumetric measurements. In G2, we included 10 patients, with a total of 20 volumetric measurements. From the volumetric measurements and statistical analysis carried out, it emerged that the average of the volumetric differences of the healthy orbits was ±0.6351 cm³, the standard deviation of the volumetric differences was ±0.3383, and the relationship between the treated orbit and the healthy orbit was linear; therefore, the treated orbital volumes tend to approach the healthy ones after surgical treatment. Conclusion: This study demonstrates that if the volume is restored within the range of the standardized mean, the diplopia is completely recovered already after surgery or after one month. For orbital volumes that do not fall within this range, functional recovery could occur within 6 months or be lacking. The restoration of the orbital volume using pre-modeled networks on the patient’s anatomical model, printed internally in 3D, allows for more accurate reconstructions of the orbital floor in less time, with clinical advantages also in terms of surgical timing. Full article

Titanium alloys are widely used in aerospace applications due to their high specific strength and exceptional corrosion resistance. In this study, a silicide coating with a multi-layer structure was designed and prepared via a pack cementation process to improve the high-temperature oxidation resistance of titanium alloy. A new theory based on the Le Chatelier’s principle is proposed to explain the generation mechanism of active Si atoms. Taking the chemical potential as a bridge, a functional model of the relationship between the diffusion driving force and the change in the Gibbs free energy of reaction diffusion is established. Experimental results indicate that the depth of the silicide coating increases with the siliconization temperature (1000–1100 °C) and time (0–5 h). The multi-layer coating prepared at 1075 °C for 3 h exhibits a thick and dense structure with a thickness of 23.52 μm. This coating consists of an outer layer of TiSi₂ (9.40 μm), a middle layer of TiSi (3.36 μm), and an inner layer of Ti₅Si₃ (10.76 μm). Under this preparation parameter, increasing the temperature or prolonging the holding time will cause the outward diffusion flux of atoms in the substrate to be much larger than the diffusion flux of silicon atoms to the substrate, thus forming pores in the coating. The calculated value of the diffusion driving force F_TiSi = 2.012S is significantly smaller than that of ${\mathrm{F}}_{{\mathrm{TiSi}}_2}$ = 13.120S and ${\mathrm{F}}_{{\mathrm{Ti}}_5{\mathrm{Si}}_3}$ = 14.552S, which perfectly reveals the relationship between the thickness of each layer in the Ti–Si multi-layer coating. Full article

Laser welding of the near α-phase titanium alloy Ti-4Al-2V, used for complex components in the nuclear industry, has been rarely reported. In this study, butt weld joints made of Ti-4Al-2V alloy plates under different parameters, including the laser power, the welding speed, and the defocus distance, were manufactured and analyzed. The results showed that adjusting the combination of 4.2 kW of laser power, a 20 mm/s welding speed, and a −2 mm defocus distance could achieve a penetration depth exceeding 6 mm. Porosity defects were prone to forming in the middle and bottom parts of the fusion zone, due to rapid cooling. The microstructure of the fusion zone was mainly needle-like α martensite, which precipitated in the form of specific clusters. The interior of a cluster was composed of three types of variants with <11−20>/60° phase interfaces to achieve the lower boundary’s energy. Affected by the microstructure and welding defects, the strength of the weld joint was basically similar under different welding conditions, namely about 720 MPa, slightly higher than that of the base metal, while the rupture elongation at breaking decreased by more than 50%. The micro-Vickers hardness of the weld joints was about 50–60 HV higher than that of the base metal, while the impact toughness was about 40 KJ, almost half that of the base metal. This research lays a solid foundation for the engineering application of laser welding of Ti-4Al-2V alloys. Full article