Debris Generation Research Articles

Strategic disposal of flood debris via CO2-assisted catalytic pyrolysis

Recent abnormal climate changes resulted in the dramatic alternation of rainfall and flood patterns in many countries. The massive generation of flood debris, a mixture of soil (sediment), biomass, plastic, metal, and various hazardous materials, poses various environmental and public health problems. This study suggests a sustainable technical platform to convert the hazardous materials into value-added products. CO2-assisted pyrolysis was used to thermally convert flood debris into syngas (H2 and CO). CO2 enhanced the syngas production due to gas phase homogeneous reactions (HRs) between CO2 and volatile hydrocarbons evolved from pyrolysis of flood debris. For improvement of HRs in line with enhancement of syngas production, additional thermal energy and earth abundant catalyst were used. In particular, Ni/SiO2 catalyst increased more than one order of magnitude higher syngas production, comparing to non-catalytic pyrolysis. Synergistic effect of CO2 and Ni catalyst showed nearly 50% more production of syngas in reference to catalytic pyrolysis under N2. During flood debris pyrolysis, compositional matrix of flood debris was also determined by detecting index chemicals of waste materials that cannot be identified by naked eyes. Thus, this study confirmed that CO2-assisted pyrolysis is a useful tool for conversion of flood debris into value-added chemicals.

Implementation of a Cryogenic Facility for Space Debris Analysis

This paper has resulted from a continued study of spacecraft material degradation and space debris formation. The design and implementation of a thermal vacuum cycling cryogenic facility for the evaluation of space debris generation at a low Earth orbit (LEO) is presented. The facility used for spacecraft external material evaluation is described, and some of the obtained results are presented. The infrastructure was developed in the framework of a study for the European Space Agency (ESA). The main purpose of the cryogenic facility is to simulate the LEO spacecraft environment, namely thermal cycling and vacuum ultraviolet (VUV) irradiation to simulate the spacecraft material degradation and the generation of space debris. In a previous work, some results under LEO test conditions showed the effectiveness of the cryogenic facility for material evaluation, namely: the degradation of satellite paints with a change in their thermo-optical properties, leading to the emission of cover flakes; the degradation of the pressure-sensitive adhesive (PSA) used to glue Velcro’s to the spacecraft, and to glue multilayer insulation (MLI) to the spacecraft’s. The paint flakes generated are space debris. Hence, in a scenario of space missions where a spacecraft has lost the thermal shielding capability, the failure of PSA tape and the loss of Velcro properties may contribute to the release of the full MLI blanket, contributing to the generation of space debris that presents a growing threat to space missions in the main Earth orbits.

The role of surface roughness during fretting corrosion of 316L stainless steel

Abstract Fretting corrosion is a synergistic process between the mechanical events and the chemical attack of two contacted surfaces for similar or different alloys. Since implant devices are designed to slide or rotate to perform their function, implant devices may subject to mechanical interaction such as friction, wear damage, together with a corrosive attack as it in contact with human body fluids. The current study focuses on assessing the fretting corrosion resistance of 316L stainless steel (SS) under several applied load (0.5–10) N and grinded surface (400, 600, and mirror finish) grit. The experiment was performed by using a pin on disc technique surrounded by 25 °C Phosphate buffer saline. The morphology, elemental analysis, and resistance to fretting corrosion are investigated by using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) as well as the Tafel extrapolation method. The results demonstrate that the mirror surface finish gives a lower average fretting corrosion current density value with less debris generation as compared with rougher surface (400 and 600) grit. However, when a high load is applied, the current density seems to be struggling in recovering to the baseline due to the initiation of localized corrosion. The SEM scan clarified the arising of fretting islands. The EDS analysis indicated a high accumulation of chromium and oxygen elements on the fretted area border as compared to the center.

Effects of two fretting damage modes on the dental implant–abutment interface and the generation of metal wear debris: An in vitro study

AbstractFretting damage at the dental implant–abutment interface (IAI) is a critical factor of dental implant failure, and it has been investigated using fatigue cycle (FC) loading tests. For the first time, we applied chewing cycle (CC) loading onto the IAI to simulate masticatory movements. It was found that more serious furrow wear was induced by the sliding forces present under CC loading. Furthermore, four types of metal wear debris and a markedly higher torque loss rate were observed after undergoing both cyclic loadings. Such debris can aggravate the resulting fretting damage, and an increased amount of large‐grain wear debris was generated under CC loading. Therefore, CC loading can be an effective approach for exploring the fretting damage at the IAI to improve implant‐supported prostheses.

A promising laser nitriding method for the design of next generation orthopaedic implants: Cytotoxicity and antibacterial performance of titanium nitride (TiN) wear nano-particles, and enhanced wear properties of laser-nitrided Ti6Al4V surfaces

In this study, fibre laser nitriding in open air was applied to the Ti6Al4V alloy in order to improve the wear resistance, thus minimising the generation of wear debris from the surfaces for load-bearing applications. The recent technological advancement to perform the laser nitriding process in open air allows the opportunity to surface-harden any curved and/or specific areas in the hip implants. The laser nitriding process was modulated between the pulsed mode and continuous wave (CW) mode by varying the duty cycle between 60% (pulsed) and 100% (CW). Our experimental investigations were divided into two stages in sequential order: Firstly, to create crack-free, homogenous and golden laser-nitrided surfaces by the proper selection of duty cycle. Secondly, it was to analyse the properties (both physical and chemical) of the wear debris as well as to evaluate their cytotoxicity and antibacterial performance. The laser-nitrided surfaces were characterized and tested using a variety of techniques, incl. Optical microscopy, SEM-EDX, XRD, surface roughness and Vickers hardness measurements, as well as tribological tests (i.e. ball-on-disk wear tests and DLS). The wear debris from the laser-nitrided surfaces (collected in the wear tests) were analysed using TEM, XPS and SEM-EDX. Their toxicity was evaluated using in-vitro cell culture with macrophages at two time points (24 h and 48 h). The antibacterial performance was tested in vitro against two of the most commonly implicated pathogens in orthopaedic infection, namely Staphylococcus aureus and Escherichia coli for 24 h. Our findings indicated that the wear resistance of the surfaces after laser nitriding was significantly improved and the amount of wear debris generated was also significantly reduced. The wear particles from the laser-nitrided surfaces were in the nano-sized scale range (0.01 μm to 0.04 μm or 10 nm to 40 nm). They were found to be less toxic towards RAW 264.7 macrophages, yet display antimicrobial properties against Staphylococcus aureus, when compared with the larger particles (1.5 μm in size) from the untreated surfaces. It is envisioned that successful fabrication of the non-toxic and highly wear-resistant TiN layer in Ti6Al4V using the open-air laser nitriding technique can enable progress towards the development of metal-on-metal (MoM) hip implants fully made of Ti-based alloys.

Polyethylene-Based Knee Spacer for Infection Control: Design Concept and Pre-Clinical In Vitro Validations.

Antibiotic-loaded polymethyl methacrylate (PMMA) has been widely applied in the treatment of knee periprosthetic joint infections. However, problems with antibiotic-loaded PMMA-based spacers, such as structural fracture and implant dislocation, remain unresolved. A novel polyethylene-based spacer, designed with an ultra-congruent articulating surface and multiple fenestrations, was introduced in the current study. Validation tests for biomechanical safety, wear performance, and efficacy of antibiotic cement were reported. During cycle fatigue testing, no tibial spacer failures were observed, and less wear debris generation was reported compared to commercial PMMA-based spacers. The volumetric wear of the novel spacer was within the safety threshold for osteolysis-free volumetric wear. An effective infection control was demonstrated despite the application of lesser antibiotic cement in the 30-day antibiotic elution test. The tube dilution test confirmed adequate inhibitory capabilities against pathogens with the loaded antibiotic option utilized in the current study. The novel polyethylene-based knee spacer may offer sufficient biomechanical safety and serve as an adequate carrier of antibiotic-loaded cement for infection control. Further clinical trials shall be conducted for more comprehensive validation of the novel spacer for practical application.

Wear and corrosion in medical applications

Abstract Biomaterials applied to replace or restore body functions are exposed to different mechanical forces and corrosion processes due to body fluids, which might result in the generation of corrosion products, wear debris and particles potentially leading to inflammation and inhibition or loss of function. This brief review will give a short overview about the processes of wear generation and corrosion, the occurrence of the respective wear products in different medical applications and their biological influences. Wear and corrosion are important factors that control and determine the long-term clinical performance of a biomaterial.

In vitro fretting crevice corrosion damage of CoCrMo alloys in phosphate buffered saline: Debris generation, chemistry and distribution

Fretting crevice corrosion in modular tapers of total hip replacements has become a major concern in orthopedic medical devices. Solid and ionic debris arising from fretting crevice corrosion have been implicated in device failure and revision surgery. This study aims to use a 2D pin-on-disk fretting corrosion test system to visualize damage progression and debris generation during fretting corrosion of CoCrMo alloys in phosphate buffered saline (PBS). The results provide direct evidence of rapid debris generation during fretting corrosion (after only 12 min of testing). Debris was generated and either extruded from the contact region or impacted into adjacent crevice sites as long as fretting continued. After testing, the fretting region consisted of a damaged and plastically deformed contact region surrounded by a halo of fretting debris consisting entirely of oxides and phosphates within the crevice region. Evidence of pitting corrosion and grain boundary corrosion was observed. Solid debris consisted of chromium (Cr), phosphate (P) and oxygen (O). X-ray photoelectron spectroscopy analysis of the near-fretted metal surface area showed a thicker oxygen (O1s) containing film with the depth profile of O1s above 10% penetrating up to 5.75 nm while the O1s concentration on the unfretted area fell to below 10% after 1 nm depth. Ion concentration in the PBS, measured using inductively coupled mass spectrometry, showed cobalt (Co) ions were most prevalent (1.46 ppm) compared to chromium (Cr) (0.07 ppm) and molybdenum (Mo) (0.05 ppm) (p <0.05). All of these results are consistent with the analysis of in vivo modular taper corrosion processes. Statement of SignificanceCoCrMo alloys has been widely used as a metallic biomaterial for implant devices and can lose their durability and reliability due to wear, corrosion and tribocorrosion. Debris, as one of the major products of these reactions, is associated with implant device failure. In the first time, we developed a fretting corrosion testing system to visualize the debris generation process in real-time between CoCrMo alloy pin and disk samples. Debris was generated rapidly during fretting corrosion and some of the debris egressed from the crevice site while also accumulating within the crevice area as fretting continued. Our study opens a new method for future studies to advance understanding of debris generation processes during wear and tribocorrosion phenomenon.

Measuring Demisability of Bulk Metallic Glasses for Potential Satellite Applications through Ablation Experiments

Bulk metallic glasses (BMGs) exhibit attractive properties for spacecraft applications. When low Earth‐orbiting satellites reenter the atmosphere at end of mission, a measure to mitigate the generation of space debris, operators must limit the number of satellite components that reach the ground to ensure public safety. Inductively coupled plasma using an argon/air mixture to simulate reentry conditions is used to study ablation of BMG and conventional spacecraft alloys. Differential scanning calorimetry is used to determine the thermal properties of the alloys. BMGs are shown to ablate similarly to aluminum alloys (Al7075) and dramatically faster than titanium alloys (Ti‐6Al‐4V).

NewSpace and its implications for space debris models

Until two decades ago, the dominance of the space industry by national governments shaped the key characteristics of the spacecraft population and hence the space debris models used to anticipate future orbital populations. The rise of `NewSpace’ with the growth of private sector involvement has brought innovations, disrupting the status quo and changing to the physical characteristics and mission orbits of commercial spacecraft. Analysis of shifts in mass and launch traffic for spacecraft launched between 1980 and 2019 (source: ESA's DISCOS database) suggests significant impacts for debris modelling. Results emphasised the ongoing change towards a more commercially focused space sector. 742 spacecraft were launched in the 1980s, of which 34 were labelled as commercial. By contrast, there were 1292 commercial missions out of 2325 launched in the 2010s - an increase from 4.6% to 55.6%. These increases correlate with a rise in the number of different organisations operating spacecraft and a clear trend can be seen towards smaller, lower mass spacecraft. This is likely to alter the distributions of fragments generated in collisions compared with the distributions obtained from empirical methods, such as the NASA Standard Breakup model, derived from the fragmentation of larger spacecraft in the 600-1,000 kg range. A study of observed breakup events indicates that the NASA Standard Breakup Model over-estimates the number of large debris released during fragmentations due to collisions or explosion of satellites while also under-estimating the number of small debris. It is believed that this will have a significant impact on the outcomes of simulations of the future debris environment where these fragmentation modes are expected to dominate the generation of new debris over the propulsion based explosions which have been historically prevalent.

The economics of orbital debris generation, accumulation, mitigation, and remediation

We explore how economic forces contribute to the generation and accumulation of orbital debris. The current structure of economic incentives for using orbital space may result in an economic Kessler Syndrome, in which orbital space becomes economically unprofitable for commercial exploration. We use simulations of an economic model to compare the effectiveness of various policy choices in slowing the accumulation rate and reducing levels of orbital debris. These findings provide useful guidance for policymakers.

Tribological properties of bronze surface with dimple textures fabricated by the indentation method

Surface texturing is an effective approach to improve the tribological properties of mechanical components. An indentation method is presented to fabricate dimple textures on bronze specimen surfaces. Graphite was selected as the mating balls in ball-on-disc wear tests. The worn surfaces and the indented dimples heaped with the thin ribbon debris were observed by microscope. The morphology and evolution of wear debris were employed to explain the influence of indented dimple textures. The experimental results indicate that the generation of thin ribbon debris is due to the edge hardening of indented dimple. The thin ribbon debris and the indented conical dimple are conducive to the debris heaping on slopes of dimples, which can facilitate the formation of the graphite-rich transfer layers on indented dimple surface. Compared with nontextured surface, indented dimple surface has lower coefficients of friction and slighter wear. The tribological properties of indented dimple surface are improved because of the edge hardening, the debris heaping and the formation of transfer layers.

A lubricated wear model for determining wear surface geometry on journal-bearing surfaces

In this study, the friction fatigue mechanism is employed to describe the quantitative information concerning characterization of the steady-state wear process in journal bearings, which combined with the load sharing notion in mixed lubrication. For this approach, the asperity stress cycle number is estimated by combining the statistical dynamic contact model with the mixed elasto-hydrodynamic lubrication (EHL) simulation model. The maximum shear stress theory is applied together with the subsurface stress distribution of contact asperities to predict the average volume of wear fragment for asperity. Quantitative analysis of steady-state wear profiles for the bearing reveals that the maximum wear depth appears at both ends of the bearing. With the increase of running time, the wear gradually extends to the bearing centre, and the wear rate rapidly decreases to a certain value and then tends to be stable. With this lubricated wear model, the influences of surface roughness, external load, and shaft speed are also discussed. The proposed wear simulation method is based on the interdisciplinary theory, which includes the description of surface micro-morphology (Gaussian rough surfaces), the friction fatigue theory for explaining the generation of wear debris, and the coupling effect of wear and lubrication that is expressed by considering the wear surface geometry in oil film thickness equation. Additionally, the simulation results and available experiment data are compared to demonstrate the fatigue wear modeling scheme.

Argamassa de revestimento externo em obras verticais na cidade de Juazeiro do Norte, Ceará

Na execução de revestimentos externos verticais observa-se grande geração de resíduos e entulhos espalhados pelo canteiro de obras. Na execução desta etapa, dificilmente possui supervisão e gerenciamento do processo, causando desperdício de materiais e aumentando o custo da obra. Assim, o presente trabalho consiste em quantificar e analisar as perdas geradas durante à execução do revestimento externo em obras verticais na cidade de Juazeiro do Norte/CE, buscando quantificar através de indicadores as perdas durante o serviço, verificando também a forma de trabalho dos funcionários e propor soluções. Foram realizadas visitas periódicas em 3 canteiros de obras, reunindo os dados de argamassa produzida na central de argamassa e perdida após o serviço, verificando as espessuras das camadas de revestimento e coletando o material desperdiçado que gera o entulho do serviço. Calculou-se o valor teórico para as camadas de massa única, indicando o índice de perdas. Os resultados demonstram índices elevados de perdas e entulhos gerados, especialmente na Obra B, motivado pela utilização de métodos tradicionais. Observou-se ausência de chapiscos em uma das obras, erro de prumo em outra obra e na terceira adotou-se maior rigor, implicando em menores índices de desperdício. Assim, com maior controle na execução de alvenarias e revestimentos tendem a reduzir a geração de resíduos de argamassas.

Debris Evolution Analysis of Breakup Events Based on Modified Space Debris Evolution Model and Collision Factor

Breakup events are crucial source of space debris. It is important to focus on the effect of breakup model on space environment. In order to reveal the evolutionary mechanism of space debris environment based on breakup events, in this paper, elliptical orbits and solar radiation pressure perturbation are firstly considered to modify the altitude distribution model and orbit decay model in space debris evolution model (SDEM). Then based on the modified SDEM, the debris generation, evolution and the effects on collision probability of space environment caused by different altitude break up events are analyzed in detail. Furthermore, considering the volume that the debris sweep per unit time, collision factor is introduced to describe the effects of breakup events on collision probability, and a large value means a great influence. The results show that when breakup events happen on the low orbits, the number of debris decrease rapidly, while the high orbits break up events would cause long-term influence on space environment and the influence of collision events are more significant than explosion events. Moreover, the generation of space debris is related to the original space environment, the influence of collision events on space environment is larger than explosion events and non-functional spacecraft.

Tribocorrosion behaviour of Ti6Al4V under various normal loads in phosphate buffered saline solution

Abstract Tribocorrosion tests were conducted on Ti6Al4V against alumina in phosphate buffered saline solution under normal loads of 3−30 N (corresponding to the maximum Hertzian contact pressures of 816−1758 MPa) using a ball-on-disk tribometer. Nano-hardness measurements revealed the formation of work-hardened layers on the pure wear and tribocorrosion surfaces. As the normal load increased from 15 to 30 N during the pure wear, the surface hardness was increased by about 100%. However, a lower generation of wear debris resulted in a lower wear rate under a normal load of 30 N. The presence of corrosion caused an increase in the wear rates by 28%−245% under various normal loads. The corrosion current density acquired from polarization curves was increased by three orders of magnitude and the open circuit potential (OCP) shifted to more negative potentials during tribocorrosion compared with the stagnant condition. The successive formation and removal of tribofilms, which consisted of oxygen and phosphorous compounds, resulted in peaks in the OCP trend and lower fluctuations in coefficient of friction under normal loads higher than 3 N.

CMM‐based method for assessing the volume change of retrieved polyethylene cups in MoP total hip replacements

Wear occurring at the bearing surface and the consequent generation of wear debris has been identified as the primary cause of aseptic loosening in metal-on-polyethylene (MoP) hip joint replacements. The accurate estimation of volume change in polyethylene cups due to creep and wear is, therefore, an important step for identifying the cause of failure and improving the longevity of MoP prosthesis. The purposes of this study were to present and apply a co-ordinate measuring machine (CMM)-based method for assessing the volume change of retrieved components due to wear and creep by using a combination of CMM data and a bespoke computer programme. The method was firstly validated against the standard gravimetric technique, and then applied to four retrieved polyethylene cups for wear assessment and analysis. The results show that the volume changes calculated using the present method match well with those assessed through the gravimetric technique. The CMM-based method presented in the study is capable of effectively and reliably determining the volume change and characterising the wear patch of retrieved components from MoP hip joint replacements.

TRUNNIONOSIS- What we should know as an Orthopaedic Surgeon

The main question is what is Trunnionosis and what do we need to know as a surgeon. So trunnionosis is basically metallosis. It is the generation of metallic debris from a combination of motion at head on neck junction and an electrochemical corrosion [1,2]. Trunnion is part of the femoral stem where head gets engaged [1]; Corrosion of this part is called Trunnionosis. Taper is the slotted part of head which fits into trunnion of stem; corrosion of this part is called Taperosis (Figure 1).

System for space materials evaluation in LEO environment

This paper describes the conception and experimental setup of a new concept for a Vacuum Ultraviolet with extreme Thermal Vacuum Cycle system and the evaluation of LEO satellites materials with the equipment. The system was developed in the framework of a study of spacecraft debris generation due to satellites materials degradation, when exposed to space environment. The study was developed in the framework of an ESA project. Its main purpose was to evaluate the characteristics and the quantity of debris resulting from surface of satellites due spacecraft materials degradation and provide input to space debris models. The experimental setup developed partially simulates the space environment, on an accelerated mode, as endured by a spaceship in Low Earth Orbit, allows the testing of materials to a Vacuum, Ultraviolet and thermal cycles. This thermal cycling provided to the sample holder was implemented using an innovative mechanical thermal switching architecture. This architecture allows temperature cycling of +200 °C to −200 °C without the use of LN2. The experimental setup design, manufacture and final characterization is presented.

Stimulation of Resolution of Inflammation via Pro‐Resolving Lipid Mediators Prevents Ethanol‐Induced Tumor Growth

Alcohol consumption is a common cause of various cancers such as hepatocellular carcinoma (HCC) by inducing inflammation. Alcohol is oxidized in the body to aldehydes, mostly acetyldehyde which is a group 1 carcinogen. However, effective therapies to stimulate the resolution of inflammation to prevent alcohol‐induced cancers have not been elucidated. Ethanol and acetyldehyde generate apoptotic cell (“debris”) which may stimulate inflammation and tumor growth via an inflammatory response. Thus, controlling ethanol‐stimulated inflammation will be critical to prevent HCC and other tumor‐types caused by ethanol. This could be addressed with specialized pro‐resolving lipid mediators (SPMs), such as maresins and protectins, which are derived from essential fatty acids and stimulate the resolution of tumor‐promoting inflammation by activating macrophage clearance of cellular debris. In contrast to traditional anti‐inflammatories (e.g. NSAIDs and steroids), SPMs are not immunosuppressive and are active at nanomolar concentrations. SPMs are currently being evaluated in clinical trials for various inflammatory diseases. Here, we demonstrate that ethanol‐generated cell debris stimulates primary tumor growth in vivo by stimulating the release of pro‐inflammatory cytokines and bioactive lipid mediators. Aldehyde‐generated debris also stimulated tumor growth via oxidative stress and reactive oxygen species. Systemic administration of SPMs prevent ethanol‐induced cancers in mice via resolution of inflammation. Cytokine array analysis demonstrated that ethanol‐generated tumor and non‐tumor cell debris of multiple tumor types each triggered human or murine macrophages to release a storm of pro‐inflammatory and pro‐angiogenic cytokines. Maresins, maresin conjugates, and protectin conjugates stimulated macrophage phagocytosis of ethanol‐generated and aldehyde‐generated cell debris and suppressed the release of pro‐inflammatory, tumor‐promoting cytokines by debris‐activated macrophages. Thus, ethanol‐generated cell debris triggers a cytokine storm providing a potential mechanism whereby ethanol harbors the potential to stimulate or induce tumor initiation, growth, and/or metastasis. Uncovering the mechanism of ethanol‐induced cell death and debris‐induced tumor progression is paramount to preventing cancer induced by ethanol‐generated inflammation. Dead cells generated by cytotoxic ethanol or aldehyde exposure may inadvertently stimulate proliferation of dormant tumor cells in patients. While generation of cell debris may explain risk of alcohol causing cancer, enhancing endogenous clearance of cell debris via SPMs, such as maresin conjugates and protectin conjugates, represents a novel approach to prevent ethanol‐induced cancer.