Pulse Plasma Sintering of NiAl-Al2O3 Composite Powder Produced by Mechanical Alloying with Contribution of Nanometric Al2O3 Powder

NiAl-Al2O3 composites, fabricated from the prepared composite powders by mechanical alloying and then consolidated by pulse plasma sintering, were presented. The use of nanometric alumina powder for reinforcement of a synthetized intermetallic matrix was the innovative concept of this work. Moreover, this is the first reported attempt to use the Pulse Plasma Sintering (PPS) method to consolidate composite powder with the contribution of nanometric alumina powder. The composite powders consisting of the intermetallic phase NiAl and Al2O3 were prepared by mechanical alloying from powder mixtures containing Ni-50at.%Al with the contribution of 10 wt.% or 20 wt.% nanometric aluminum oxide. A nanocrystalline NiAl matrix was formed, with uniformly distributed Al2O3 inclusions as reinforcement. The PPS method successfully consolidated NiAl-Al2O3 composite powders with limited grain growth in the NiAl matrix. The appropriate sintering temperature for composite powder was selected based on analysis of the grain growth and hardness of Al2O3 subjected to PPS consolidation at various temperatures. As a result of these tests, sintering of the NiAl-Al2O3 powders was carried out at temperatures of 1200 °C, 1300 °C, and 1400 °C. The microstructure and properties of the initial powders, composite powders, and consolidated bulk composite materials were characterized by SEM, EDS, XRD, density, and hardness measurements. The hardness of the ultrafine-grained NiAl-Al2O3 composites obtained via PPS depends on the Al2O3 content in the composite, as well as the sintering temperature applied. The highest values of the hardness of the composites were obtained after sintering at the lowest temperature (1200 °C), reaching 7.2 ± 0.29 GPa and 8.4 ± 0.07 GPa for 10 wt.% Al2O3 and 20 wt.% Al2O3, respectively, and exceeding the hardness values reported in the literature. From a technological point of view, the possibility to use sintering temperatures as low as 1200 °C is crucial for the production of fully dense, ultrafine-grained composites with high hardness.

Preparation of ZnO/Brucite Functional Composite Powder by the Mechanochemical Method

In this experiment, ZnO/brucite composite powder was prepared through the mechanochemical method; further, the properties, particle morphology, and structure of the composite powder were characterized. The results show that mechanical grinding action can promote the production of a large number of surface ions with unsaturated coordination number on the surface of brucite and ZnO particles, thereby promoting hydroxylation of the particle surfaces. The addition of NaOH to the composite system can also aid the further activation of the surface of the brucite and ZnO particles and the formation of more associated hydroxyl groups. Finally, a core–shell composite powder is formed with weak forces such as hydrogen bonds and van der Waals forces as the connecting bonds.

Collagen-Chitosan Composite Powder as a Novel Biomaterial for Chronic Wounds in Hansen Disease-A Clinical Study

Aims: Natural biomaterials are more suitable than synthetic biomaterials for in vivo applications for treating damaged tissues. Collagen and chitosan are abundantly available natural biomaterials for wound dressings for tissue/wound repair. In this context, collagen-chitosan composite powder has been used to treat chronic wounds in Hansen disease (HD) patients. Place and Duration of Study: CSIR Central Leather Research Institute, Sardar Patel Road, Adyar, Chennai 600021, Southern Railway Headquarters Hospital, Constable Road, Ayanavaram, Chennai 600023, and Gremaltes Hospital, India between June 2013 and July 2020. Methodology: Collagen extracted from bovine rumen, a waste product of meat industry, and a commercially available chitosan were prepared as a composite powder (COL/CS) and applied to chronic wounds in HD patients after debridement and the wound contours were measured by planimetry. Biochemical parameters in blood samples were periodically assessed. Histopathology of wound tissue with Hematoxylin and Eosin and Masson’s Trichrome staining was studied. Matrix Metalloproteinase-9 (MMP9) levels before and after treatment were estimated. Results: Wound healing of 64.2% was obtained with COL/CS treatment and formation of granulation cells was observed early. Hemogram studies have been reported in a regression model with 95% confidence intervals. Histopathology revealed dense collagen fibres and continuity of sub-epithelial layer on 8th day. MMP-9 levels showed collagen integrity after treatment. Conclusion: The novel biocompatible, biodegradable COL/CS wound dressing is a promising biomaterial for management of chronic wounds in Hansen disease patients.

The Use of ZrO2 Waste for the Electrolytic Production of Composite Ni–P–ZrO2 Powder

Ni–P–ZrO2 composite powder was obtained from a galvanic nickel bath with ZrO2 powder. Production was conducted under galvanostatic conditions. The Ni–P–ZrO2 composite powder was characterized by the presence of ZrO2 particles covered with electrolytical nanocrystalline Ni–P coating. The chemical composition (XRF method), phase structure (XRD method) and morphology (SEM) of Ni–P–ZrO2 and the distribution of elements in the powder were all investigated. Based on the analyses, it was found that the obtained powder contained about 50 weight % Zr and 40 weight % Ni. Phase structure analysis showed that the basic crystalline component of the tested powder is a mixed oxide of zirconium and yttrium Zr0.92Y0.08O1.96. In addition, the sample contains very large amounts of amorphous compounds (Ni–P). The mechanism to produce the composite powder particles is explained on the basis of Ni2+ ions adsorption process on the metal oxide particles. Current flow through the cell forces the movement of particles in the bath. Oxide grains with adsorbed nickel ions were transported to the cathode surface. Ni2+ ions were discharged. The oxide particles were covered with a Ni–P layer and the heavy composite grains of Ni–P–ZrO2 flowed down to the bottom of the cell.