Synthesis of Ti5Si3-x Nb composites by the field-activated combustion method

The influence of an electric field on the combustion synthesis of Ti₅Si₃-x Nb composites (0≤ x ≤0.8) was investigated. Composites where x ≥ 0.8 can only be synthesized in the presence of a field. In the absence of a field, those systems where x=0.8 can result in a non-steady combustion wave causing an incomplete reaction. That is, an unstable wave propagates to the middle of the sample and then becomes extinguished. The wave velocity of the Ti₅Si₃-x Nb composites slightly increases with the imposition of an external electric field across the sample.     

Consolidation and properties of binderless sub-micron tungsten carbide by field-activated sintering

The rapid sintering of nano-structured WC hard materials in a short time is introduced with a focus on the manufacturing potential of this spark plasma sintering process. The advantage of this process allows very quick densification to near theoretical density and prohibition of grain growth in nano-structured materials. A dense pure WC hard material with a relative density of up to 97.6% was produced with simultaneous application of 60 MPa pressure and electric current of 2800 A within 2 min. A larger current caused a higher rate of temperature increase and therefore a higher densification rate of the WC powder. The finer the initial WC powder size the higher is the density and the better are the mechanical properties. The fracture toughness and hardness values obtained were 6.6 MPa m^1/2 and 2480 kg/mm², respectively under 60 MPa pressure and 2800 A using 0.4 μm WC powder.     

Smooth cutting pattern generation technique for membrane structures using geodesic line on subplane and spline interpolation

Practical techniques for smooth geodesic patterning of membrane structures were investigated, For the geodesic search, adjustment of the subplane of the extracted elements series was proposed, and various spline approximation methods were used to flatten the strip for the generation of a smooth pattern. This search approach is very simple, and the geodesic line could be easily attained by the proposed method without the need for a difficult computation method. Smooth cutting patterning can also be generated by spline approximation without the noise in discrete nodal information. Additionally, the geodesic cutting pattern saved about 21% of the required area for the catenary model due to the reduction of the curvature of the planar pattern seam line.     

Simultaneous pulsed current activated combustion synthesis and densification of NbSi2–SiC composite

Dense ultrafine NbSi₂–SiC composite was synthesized by the pulsed current activated combustion synthesis (PCACS) method within 3 min in one step from mechanically activated powders of NbC and 3Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense NbSi₂–SiC composite with relative density of up to 97% was produced under simultaneous application of a 60 MPa pressure and the electric current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.     

Synthesis of TiC, TiC-Cu Composites, and TiC-Cu Functionally Graded Materials by Electrothermal Combustion

Titanium carbide and composites and functionally graded materials (FGMs) of TiC– x Cu were synthesized by an electrothermal combustion (ETC) method. TiC synthesized by ETC showed small amounts of porosity relative to those synthesized by ignition using radiative heating. Composites and FGMs with higher copper content can be synthesized by ETC. In the FGM products a nearly linear change in composition in the graded region was observed in samples with 0 ≤ x (wt%) ≤ 75.     

Sintering of ultra-fine tetragonal yttria-stabilized zirconia ceramics

High-frequency induction heated sintering (HFIHS) is utilized to consolidate ultra-fine grain tetragonal zirconia stabilized with 3 mol%Y₂O₃ (3Y-SZ) ceramics. Densification to near theoretical density in a relatively short time can be accomplished using this method. Samples of 3Y-SZ with a relative density of up to 99.5% and an average grain size of about 170 nm could be obtained by sintering at 950 °C for 5 min under a pressure of 100 MPa pressure. The influence of sintering temperature and mechanical pressure on the final density and grain size of the sintered products was investigated. The sintered materials had fracture toughness and hardness values of 4.4 MPa m^1/2 and 10.7 GPa, respectively.     

Antioxidative ability of native and thermized sour whey in oxidation‐catalysed model systems†

Antioxidative properties of sour (cottage) were evaluated with (thermized) and without (native) heat treatment (80°C for 30 min). A model system comprising a Tween 20 stabilized peanut oil in phosphate buffer (pH 7.0) emulsion containing lipid oxidation catalysts, FeCl ₃, H₂O₂ and ascorbate was used. Native sour whey powder (SWP) was significantly better than thermized whey in terms of limiting the formation of thiobarbituric acid‐reactive substances and peroxide value. Antioxidative ability was best at pH 3.0 and decreased with increasing pH. SWP (20%, w/v) was significantly better than all commonly used antioxidants tested after 96 h of incubation at 40°C.     

场激活加压燃烧合成WC-Ni复合材料的工艺参数研究

以钨、碳和镍为原料,在电场激活下,材料的燃烧合成和致密化同时进行,短时间内完成了碳化钨镍复合材料的制备。研究了场激活 加压燃烧合成中的工艺参数,如脉冲电流、能量控制模式、升温速率、最高温度和压力对反应的影响。测量了在反应合成和致密化前后的样品 收缩率。所制备的复合材料的相对密度,490N载荷下Vickers硬度和断裂韧性分别为99.2%,13.965GPa和5.9MP·m1/2。     

Properties and fast low-temperature consolidation of nanocrystalline Ni-ZrO2 composites by high-frequency induction heated sintering

Nanopowders of Ni and ZrO₂ (11 nm and 90 nm, respectively) were synthesized from NiO and Zr by high energy ball milling. A highly dense nanostructured 2Ni-ZrO₂ composite was consolidated at low temperature by high-frequency induction heat sintering within 2 min of the mechanical synthesis of the powders (Ni-ZrO₂) with horizontal milled NiO + Zr powders under 500 MPa pressure. This process allows very quick densification to near theoretical density and prohibits grain growth in nano-structured materials. The grain sizes of Ni and ZrO₂ in the composite were calculated. Finally, the average hardness and fracture toughness values of nanostructured 2Ni-ZrO₂ composites were investigated.     

Properties and rapid consolidation of nanostructured NiTi by pulsed current activated sintering

Highly dense nanostructured TiNi with a relative density of up to 99 % was obtained within two minutes by pulsed current activated sintering under a pressure of 80 MPa. The advantage of this process is that it allows very quick densification to near theoretical density and prohibits grain growth in nano-structured materials. The microstructural and mechanical properties of the dense TiNi produced by PCAS were investigated.