Vk x250

The surface morphology of the CA film deposited on the Ti substrate was observed under a scanning electron microscope (SEM; JSM-5600LV, JOEL Ltd., Tokyo, Japan) at an accelerating voltage of 15 kV after sputter coating with Au using an ion coater (QUICK COATER SC-701, Sanyu Electron, Tokyo, Japan). Three-dimensional observations of surface morphology were performed by a shape analyzer laser microscope (VK-X250, KEYENCE, Osaka, Japan). Images were acquired in three-dimensional ranges of decreasing size of 25 × 25 μm². Two surface parameters, three-dimensional arithmetic height (Sa) and surface deployment area rate (Sdr), were obtained.

The static and dynamic shear testing of the hybrid materials was performed according to the relevant standards [59 ,60 ,61 ]. The dimensions of the shear test specimens are shown in Figure 1.
Furthermore, the influence of artificial aging (0.5 MPa, 70 °C, 14 days [62 ]) on the static shear strength was evaluated. Accordingly, six different groups (Table 1) were characterized, and each group contained n = 5 specimens.
The static shear tests were conducted using a universal testing machine (Zwick 50kN RetroLine, Zwick Roell, Ulm, Germany). The specimens were loaded until fracture at a rate of 2.5 mm × min⁻¹. The fatigue tests were performed using an electro-dynamic testing machine (ElectroForce 3510, TA Instruments—Waters LLC, Eden Prairie, MN, USA) with a sinusoidal load between 1 MPa and 10 MPa and a frequency of 10 Hz [63 ]. Furthermore, 10⁷ cycles were defined as a successful test [59 ].
After mechanical testing, the fractured surfaces of all specimens were analyzed with a digital microscope (VHX-6000) and laser scanning microscope (VK-X250) (both obtained from Keyence Corporation, Osaka, Japan) to determine the causes of fracture.

The biological characterization was performed with both densely and open porous lattice–structured specimens. Cylindrical dense specimens (d = 12 mm, h = 2 mm) were fabricated in 0° and 90° build orientation, leading to six different groups [Ti–20Nb–6Ta, Ti–27Nb–6Ta, Ti–35Nb–6Ta] × [0°, 90°] with n = 38 specimens each. Additionally, specimens made of Ti–6Al–4V serving as a reference were manufactured in 0° and 90° build orientations. The surfaces were not further processed and are referred to as “as-printed” in the following. Open porous lattice-structured specimens were manufactured consisting of one layer of the above-described face-centered cubic unit cells (Figure 1D). Accordingly, the specimens were 12 mm in diameter and 2 mm in height, i.e., 1 mm of dense structure and 1 mm of open porous lattice structure. Prior to their biological testing, all specimens were cleaned in an ultrasonic bath to remove residual powder and heat-sterilized at 180 °C for 135 min.
The surface roughness of the dense specimens was analyzed with a laser-scanning microscope (VK-X250, Keyence Germany GmbH, Neu-Isenburg, Germany) with 20 times magnification, λ_S = 8, and λ_C = 25. The roughness values are summarized in Table 3, and light microscopic images are shown in Figure 1E. The light microscopic images demonstrated melt tracks and partly melted particles on the surface.