Dr Tong Deng BSc, BEng, MSc, PhD

Industrial consultancies and research

Key areas of research interests

Currently Dr Deng's research mainly focuses on distinctive studies of bulk solids and powders in material handling process and relative areas. The research can be multiple or cross disciplines including physics, chemistry, material science, mechanical and chemical engineering. The specific areas of his research are:

• Erosive wear and mechanisms by solid particle impacts;

Characterisation of wear in bulk solids handling processes, determining material failures due solid particle impacts, improving surface protection by surface modification, finding solutions for industrial wear problems including abrasive and adhesive wear.

• Dynamics of solid particles in bulk solids handling process;

Particle dynamics in wear testing, pneumatic conveying, powder segregation in process, particle degradation due to high-speed impacts, dust generation and evaluation, breakage of solids in pneumatic conveyor, prediction of solids degradation using bench scale tester.

• Electrostatic charging of powders and inductive sensing technique;

Electrostatic charging of particles, charge evaluation of solids, inductive sensing of solid particles, electrostatic charging in solids handling process, effect of electrostatic charging on bulk behaviour of solids, applications of inductive charge sensor.

• Particle adhesion and its influence on powder flow;

Sensing of particle adhesion, powder cohesiveness, prediction of powder flow using particle adhesion and cohesiveness, powder caking and agglomeration, prediction of powder segregation, powder characterisation of material properties.

• Industrial and innovative services for bulk solids handling processes;

Innovative ideas testing and development, trouble shooting and solutions, material characterisations, powder material modifications, engineering design and novel solution, testing and evaluation of solid materials, novel applications for handling processes.

Key recent funded projects

Abrasion index of different battery materials - funded by Northvolt AB, 2023

Tribological property of solids is important in manufacturing, which include abrasiveness of the solids. However, the aggressive of solids subject to many factors including hardness, size and shape of the solids. When the solids are small in term of particle size, the abrasiveness of solids is hard to be determined. For battery materials, the severe damage to the equipment such as screw feeders has been reported , which caused the process had to be shut down. Because the particle sizes of the battery materials are very small, a novel study was undertaken to assess the abrasiveness of the battery powders.

The abrasion tests were developed at the Wolfson Centre by using an ASTM standard rubber-wheel abrasion testing. A standard stainless steel surface material was used for targets with known surface hardness. Any surface damage indicated the aggressiveness of the battery powders. If the battery powder is harder than the stainless steel, the target surface can be damaged by the solid particles. For battery powders, there is another challenge that the powder used to be polymer-based, which heat generated in the abrasion wear testing can caused the powder melt and therefore influence the test results. In the project, the study successfully demonstrated the ability of determination of powder abrasion using a rubber-wheel abrasion tester with advanced test control, which can be used for other similar industrial applications.

Micro sample characterisation of biopharmaceuticals to support digital formulations towards manufacturing - funded by Merck KGaA, 2022.

In pharmaceutical process, powder flow can be a serious problem if the powder is too cohesive or free-flowing. The challenge is that any flow problem cannot be discovered before entering manufacturing process. In formulation stage where the drug is developed, sample of powders available is limited, which will not be sufficient for any manufacturing design, although some basic bulk properties of the powder can be characterised. The characterisation of powder flow properties is impossible.

To solve the challenge, this project tended to develop a digital prediction tool for powder flow properties using a small sample of powders (less than 50 mg) by using particle adhesion to represent powder cohesiveness for the prediction of powder flow properties. This work was sponsored by a world-lead pharmaceutical company (Merck) by using their products. This research delivered a feasibility study for practical applications and revealed  that electrostatic charge on powders and environmental conditions can have an influence on the particle adhesion measurement and alternatively affect the prediction of  the powder flow properties.

Assuring powder-machine compatibility of direct compression formulations for continuous manufacturing processes in relation to segregation and blend flowability – funded by Roche AG, 2020

Flow and segregation problems are common issues in pharmaceutical process and are subject to both the process equipment and the properties of the powders being processed. An assessment of a new continuous direct compression manufacturing line is important with respect to its capability of ensuring robust processing of formulations of low risks of powder flow and segregation.

In this work, 40+ formulations have been studied by combining 4 active pharmaceutical ingredients (APIs) and five excipients in different proportions. In total, 120+ experiments were conducted on a pilot simulation rig and 36 tests on bench-scale testers, providing extensive test data for developing a segregation predictive toolkit based on segregation indices (SIs) calculated for all experiments. A strong correlation between the segregation tendency and the powder flowability was discovered, which was used for development of a predictive segregation model. On the other hand, flow risks of the formulations were predicted by an existing toolkit developed in the Virtual Formulation Laboratory (VFL) project at the Wolfson Centre. The new segregation model developed can be incorporated with the existing VFL toolkit to predict both of flow and segregation risks at the formulation stage, which will be significant for manufacturing design at an early stage.

Micro to manufacturing: advanced measurement and characterisation of inter-particle forces with application to the design and control of flow behaviour in pharmaceutical continuous manufacturing – funded by EPSRC CMAC, 2020

This feasibility study was to use a novel technique of mechanical surface energy tester developed at the Wolfson Centre for characterisation of particle adhesion forces, which was used to characterise powder cohesiveness and predict powder flow properties at the manufacturing-scale.

The work was designed and undertaken using 16 materials which were widely used in pharmaceutical industry. In the study, material properties were characterised including particle size, shape, and solid density. Using a mechanical surface energy tester developed at the Wolfson Centre, Bond numbers for the powders were detected using a few grams of samples to represent powder cohesiveness, which was defined as a ratio of particle adhesion to its gravitational force at median particle size. The Bond number and the particle physical properties were used for assessing powder flowability, which typically requires hundreds of grams of samples in conventional tests but impossible to have such a quantity of samples at an early formulation stage in the pharmaceutical industry. The outcomes of this feasibility study demonstrated that the prediction tool of powder flow using particle adhesion had strong potentials for evaluation of powder flow properties at manufacturing levels.

Key funded projects

Investigation of Wear and Tribological Properties of Nano-Carbon Fabrics (NCF) Reinforced Ceramic Materials

VC-Scholarship in collaboration with University of Cambridge.

Tribological interactions of solid surfaces' exposed faces with interfacing materials and environment may result in loss of material from the surface. Therefore many studies on surface engineering have been carried out by using techniques such as heat treatment, surface hardening, surface coating or lubricants. These methods have had limited success to date and challenges remain. Nano-carbon tube polymer composites developed in Cambridge and tested in Greenwich have shown some potential in wear resistance improvement of such materials. These polymer composites have shown strong potential in aerospace applications, such as helicopter blades protection. However because polymer materials are soft, it limits the application for hard solids impact.

A research idea has been proposed that nano-carbon fabrics (NCF) reinforced ceramic materials will be developed with applications of carbon nanotube structures. If successful, this material will provide extremely high wear resistance and could be used as a high profile coating material for many applications in material handling processes and other industrial applications. However, there are still many unknowns in relation to material manufacturing and tribological study of materials.

This study has focused on investigation of wear and tribological properties of carbon nanotubes reinforced ceramic polymer composite materials. In the future, the wear mechanisms of nano-structured composites will be a major research area, although this research can be easily extended to other application areas.

Novel Approaches to Signal Acquisition and Processing in relation to Sensing Electrostatic Behaviour of Particulate Materials in Motion.

PhD project funded by the School of Engineering, University of Greenwich,

Serious problems with cohesive pharmaceutical powders balling and building up in powder handling and sieving processes has been reported by the University of Greenwich's industrial clients. These difficulties affect the quality of the batch, particularly the levels of the active ingredient across the sample range. Recent test work has illustrated different levels in electrostatic behaviour and this is starting to indicate the root of the behaviour. The research therefore proposes to develop and build upon the previous success of the use of the charge probes in order to allow the detection and monitoring of a number of pharmaceutical powders in motion.

Charge detection of solid particle is not easy because millions of particles are involved. Charge on particles will have change when particles have contact with different surface materials. This study focused on the development of an inductive sensing method and using this method to study the effect of various relevant variables, especially change in the surface material, environmental conditions, etc. The results of this research have provided a new charging sensing method for fine cohesive particulates, which can provide recommendations for alternative process changes.