Boron Doped Diamond for Real-Time Wireless Cutting Temperature Monitoring of Diamond Coated Carbide Tools.

Among the unique opportunities and developments that are currently being triggered by the fourth industrial revolution, developments in cutting tools have been following the trend of an ever more holistic control of manufacturing processes. Sustainable manufacturing is at the forefront of tools development, encompassing environmental, economic, and technological goals. The integrated use of sensors, data processing, and smart algorithms for fast optimization or real time adjustment of cutting processes can lead to a significant impact on productivity and energy uptake, as well as less usage of cutting fluids. Diamond is the material of choice for machining of non-ferrous alloys, composites, and ultrahard materials. While the extreme hardness, thermal conductivity, and wear resistance of CVD diamond coatings are well-known, these also exhibit highly auspicious sensing properties through doping with boron and other elements. The present study focuses on the thermal response of boron-doped diamond (BDD) coatings. BDD coatings have been shown to have a negative temperature coefficient (NTC). Several approaches have been adopted for monitoring cutting temperature, including thin film thermocouples and infrared thermography. Although these are good solutions, they can be costly and become impractical for certain finishing cutting operations, tool geometries such as rotary tools, as well as during material removal in intricate spaces. In the scope of this study, diamond/WC-Co substrates were coated with BDD by hot filament chemical vapor deposition (HFCVD). Scanning electron microscopy, Raman spectroscopy, and the van der Pauw method were used for morphological, structural, and electrical characterization, respectively. The thermal response of the thin diamond thermistors was characterized in the temperature interval of 20-400 °C. Compared to state-of-the-art temperature monitoring solutions, this is a one-step approach that improves the wear properties and heat dissipation of carbide tools while providing real-time and in-situ temperature monitoring.

Multilayer Diamond Coatings Applied to Micro-End-Milling of Cemented Carbide.

Cobalt-cemented carbide micro-end mills were coated with diamond grown by chemical vapor deposition (CVD), with the purpose of micro-machining cemented carbides. The diamond coatings were designed with a multilayer architecture, alternating between sub-microcrystalline and nanocrystalline diamond layers. The structure of the coatings was studied by transmission electron microscopy. High adhesion to the chemically pre-treated WC-7Co tool substrates was observed by Rockwell C indentation, with the diamond coatings withstanding a critical load of 1250 N. The coated tools were tested for micro-end-milling of WC-15Co under air-cooling conditions, being able to cut more than 6500 m over a period of 120 min, after which a flank wear of 47.8 µm was attained. The machining performance and wear behavior of the micro-cutters was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Crystallographic analysis through cross-sectional selected area electron diffraction patterns, along with characterization in dark-field and HRTEM modes, provided a possible correlation between interfacial stress relaxation and wear properties of the coatings. Overall, this work demonstrates that high adhesion of diamond coatings can be achieved by proper combination of chemical attack and coating architecture. By preventing catastrophic delamination, multilayer CVD diamond coatings are central towards the enhancement of the wear properties and mechanical robustness of carbide tools used for micro-machining of ultra-hard materials.

A representative metalloprotease induces PGE2 synthesis in fibroblast-like synoviocytes via the NF-κB/COX-2 pathway with amplification by IL-1ß and the EP4 receptor.

Inflammatory joint conditions are characterized by synovial inflammation, which involves activation of fibroblast-like synoviocytes (FLSs) and production of inflammatory mediators and matrix metalloproteases (MMPs) in joints. This study showed that the snake venom metalloprotease (SVMP) BaP1 activates FLSs to produce PGE2 by a mechanism dependent on COX-2, mPGES-1 and iPLA2s. BaP1 also induces IL-1ß release, which up-regulates the production of PGE2 at a late stage of the stimulation. Expression of COX-2 and mPGES-1 are induced by BaP1 via activation of NF-κB pathway. While NF-κB p50 and p65 subunits are involved in up-regulation of COX-2 expression, only p65 is involved in BaP1-induced mPGES-1 expression. In addition, BaP1 up-regulates EP4 receptor expression. Engagement of this receptor by PGE2 triggers a positive feedback loop for its production by up-regulating expression of key components of the PGE2 biosynthetic cascade (COX-2, mPGES-1 and the EP4 receptor), thus contributing to amplification of BaP1-induced effects in FLSs. These data highlight the importance of FLS as a target for metalloproteases in joint inflammation and provide new insights into the roles of MMPs in inflammatory joint diseases. Moreover, our results may give insights into the importance of the catalytic domain, of MMPs for the inflammatory activity of these enzymes.

Effects of neutrophil depletion in the local pathological alterations and muscle regeneration in mice injected with Bothrops jararaca snake venom.

In order to study the role of neutrophils in the acute local pathological alterations induced by Bothrops jararaca snake venom, and in the process of skeletal muscle regeneration that follows, an experimental model was developed in mice pretreated with either an anti-mouse granulocyte rat monoclonal immunoglobulin G, which induces a profound neutropenia, or an isotype-matched control antibody. B. jararaca venom induced prominent haemorrhage and oedema, but only a moderate myonecrosis. No significant differences were observed in the extent of local haemorrhage, oedema and myonecrosis between neutropenic and control mice, suggesting that neutrophils do not play a determinant role in the acute pathological alterations induced by B. jararaca venom in this experimental model. Moreover, no differences were observed in skeletal muscle regeneration between these two experimental groups. In both the cases, limited areas of myonecrosis were associated with a drastic damage to the microvasculature and a scarce inflammatory infiltrate, with the consequent lack of removal of necrotic debris during the first week, resulting in a poor regenerative response at this time interval. Subsequently, a similar regenerative process occurred in both groups, and by 30 days, necrotic areas were substituted by groups of small regenerating muscle fibres. It is suggested that the drastic effect exerted by B. jararaca venom in the microvasculature precludes an effective access of inflammatory cells to necrotic areas, thereby compromising an effective removal of necrotic debris; this explains the poor regenerative response observed during the first week and the fact that there were no differences between neutropenic and control mice. As neutropenia in this model lasted only 7 days, the successful regenerative process observed at 30 days is associated with revascularization of necrotic regions and with a successful removal by phagocytes of necrotic debris in both groups.

Inflammatory events induced by Lys-49 and Asp-49 phospholipases A2 isolated from Bothrops asper snake venom: role of catalytic activity.

The inflammatory events induced in the peritoneal cavity of mice by two PLA2s isolated from Bothrops asper snake venom were investigated. MT-III, an Asp-49 catalytically active enzyme and MT-II, a catalytically inactive Lys-49 variant induced increase in vascular permeability. Inhibition of enzymatic activity of MT-III with p-bromophenacyl bromide reduced this effect. MT-III induced a larger neutrophil infiltrate than MT-II. This activity was significantly reduced after inhibition of catalytic activity. Reduction in the number of neutrophils was observed when antibodies against L-selectin, CD18 or LFA-1 were used, suggesting the involvement of these adhesion molecules in the effects of both PLA2s. There was no effect with antibodies against ICAM-1 and PECAM-1. Increase in the levels of LTB4 and TXA2, as well as of IL-1, IL-6 and TNF-alpha, were observed in the peritoneal exudates induced by MT-III. MT-II did not enhance levels of eicosanoids but increased those of cytokines. It is concluded that both PLA2s induce inflammatory events in this model. Since MT-III exerts a stronger proinflammatory effect, the enzymatic phospholipid hydrolysis may be relevant for these phenomena. However, the fact that MT-II induced inflammation suggests that molecular regions distinct from the catalytic site elicit inflammatory events perhaps by interacting with specific cell membrane acceptors.