In this review article, the latest developments of the four most common additive manufacturing methods for metallic materials are reviewed, including powder bed fusion, direct energy deposition, binder jetting, and sheet lamination. In addition to the process principles, the microstructures and mechanical properties of AM-fabricated parts are comprehensively compared and evaluated. Finally, several future research directions are suggested.
Novel soybean-oil-based
(SBO-based) epoxy acrylate (EA) resins
were developed via ring-opening reaction of epoxidized soybean oil
(ESO) with hydroxyethyl methacrylated maleate (HEMAMA) precursor,
a synthesized unsaturated carboxylic acid having two active CC
groups and a side methyl group. Experimental conditions for the synthesis
of the precursor and the SBO-based EA (ESO-HEMAMA) product were studied,
and their chemical structures were confirmed by FT-IR, 1H NMR, 13C NMR, and gel permeation chromatography. Subsequently,
the volatility of HEMAMA was studied and compared with acrylic acid
(AA). Furthermore, gel contents and ultimate properties of the UV-cured
ESO-HEMAMA resins were investigated and compared with a commercial
acrylated ESO (AESO) resin. At last, UV-curing behaviors of the SBO-based
EA resins were determined by real-time IR. It was found that the HEMAMA
precursor showed much lower volatility than AA, and the optimal pure
ESO-HEMAMA resin possessed a CC functionality up to 6.02 per
ESO and biobased content of 65.4%. Meanwhile, the obtained ESO-HEMAMA
biomaterials exhibited much superior properties as compared to the
AESO resin. For instance, the obtained pure ESO-HEMAMA material possessed
a storage modulus at 25 °C of 1.00 GPa, glass transition temperature
(T
g) of 70.1 °C, and tensile strength
and modulus of 13.4 and 592.1 MPa, which were 9.4, 3.6, 6.9, and 15.7
times the values of the pure AESO material, respectively. The resulting
biomaterial with 30% of hydroxyethyl methacrylate diluent even reached
a tensile strength of 28.4 MPa and T
g of
89.0 °C. Therefore, the developed SBO-based EA resins are very
promising for applications in UV-curable coatings.
By taking advantage of cellulose, graphene oxide sheets
(GOSs),
and the process of freeze-drying, we propose a simple and effective
method to prepare green cellulose aerogels with significant mechanical
improvements. The addition of GOSs could accelerate the gelation of
cellulose solution, which was confirmed by differential scanning calorimetry
and rheology. Detailed investigations including dynamic light scattering
and ultraviolet spectroscopy revealed the existence of interaction
between GOSs and cellulose chains, which might be responsible for
the promotion of the gelation process. With the incorporation of only
0.1 wt % GOSs, the compression strength and Young’s modulus
of the composite aerogels were dramatically improved by about 30 and
90% compared to with those of pristine cellulose aerogels, respectively.
This method is believed to provide possibilities to combine the extraordinary
performances of GOSs with the multifunctional properties of environmentally
friendly cellulose-based aerogels, thus holding great potential for
biological applications in the future.
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